JP2001308672A - Surface acoustic wave filter device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a surface acoustic wave filter device which has a wide band, good balancing, and the conversion function of balanced-unbalanced input and output. SOLUTION: The surface acoustic wave filter device includes the following devices. The first through the third surface acoustic wave filter elements 1-3 are put on the piezoelectric substrate. The transmission amplitude characteristic of both the second and the third surface acoustic wave filter elements 2, 3 is almost the same but the transmitting phase characteristic of those is quite different within the band. At least one IDT2b, 2c of the second surface acoustic wave filter elements and at least one IDT3b, 3c of the third surface acoustic wave filter elements 3 are connected to one IDT1b, 1c at least one of the first surface acoustic wave filter elements 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface acoustic wave filter device, and more particularly to a surface acoustic wave filter device having different input / output characteristic impedances and having an unbalanced-balanced conversion function. About.

[0002]

2. Description of the Related Art In recent years, miniaturization and weight reduction of mobile phones have been progressing, and not only reduction of each component and miniaturization, but also development of a component having a plurality of functions has been advanced.

[0003] In view of the above situation, the R
A surface acoustic wave filter used in the F stage having a balanced-unbalanced conversion function, that is, a so-called balun function, has been studied, and has been used mainly in GSM and the like.

[0004] The portion from the antenna of the portable telephone to the bandpass filter is unbalanced and generally has a characteristic impedance of 50 Ω. In an amplifier or the like used at the subsequent stage of the filter, a balanced terminal of 150 to 200 Ω is used. Often has impedance. Therefore, there has been proposed a filter using a surface acoustic wave filter as a band-pass filter and having the function of converting the 50 Ω unbalance into a 150 to 200 Ω balance.

For example, in Japanese Unexamined Patent Publication No. Hei 10-117123, an unbalanced input-balanced output is realized by using four surface acoustic wave filter elements. FIG. 28 shows a configuration of the surface acoustic wave filter device described in the prior art. Here, two surface acoustic wave filter elements 20
A first surface acoustic wave filter unit 203, a surface acoustic wave filter element 204, and a surface acoustic wave filter element 204 formed by cascade-connecting the first and second components 1, 202 differ in transmission phase characteristics by approximately 180 °. A second surface acoustic wave filter unit 206 formed by cascade-connecting the surface acoustic wave filter element 205 is configured. One of the input / output terminals of each of the surface acoustic wave filter units 203 and 206 is connected in parallel, the other is connected in series, the parallel connection terminal is an unbalanced terminal, and the series connection terminal is a balanced terminal.

Japanese Unexamined Patent Publication No. Hei 6-204781 discloses a surface acoustic wave filter device 211 having three IDTs as shown in FIG. In this surface acoustic wave filter device 211, two output-side IDs on both sides are used.
The IDTs 212 and 213 are arranged so that the phases thereof are inverted, and the output terminals of the IDTs 212 and 213 constitute balanced terminals. One end of the central input-side IDT 214 is an unbalanced terminal. Also in this configuration, the input impedance is 50Ω and the output impedance is 15Ω.
It can be 0 to 200Ω.

[0007]

The surface acoustic wave filter having the above-mentioned balanced-unbalanced input / output is required to have a wider band with the expansion of the band of the portable telephone system. However, in a surface acoustic wave filter having a balanced-unbalanced input / output, the transmission characteristics in the pass band between the unbalanced terminal and the balanced terminal have equal amplitudes and inverted phases by 180 °. That is, it is required to improve the so-called equilibrium degree.

However, Japanese Patent Application Laid-Open No. 10-117123
In the surface acoustic wave filter device disclosed in
As the band is widened, the impedance of the surface acoustic wave filter element becomes capacitive. Therefore, in addition to the capacitive property, a parasitic capacitance is added between the two cascade-connected stages, which tends to cause impedance mismatch between the surface acoustic wave filter portions, and it has been difficult to broaden the band.

Further, since four surface acoustic wave filter elements are used, the wiring is complicated, and the complicated wiring increases the parasitic capacitance and degrades the degree of balance. Further, there has been a problem that the element size is increased, it is difficult to reduce the size of the device itself, and the number of surface acoustic wave filter devices that can be obtained from one wafer is reduced.

On the other hand, in the surface acoustic wave filter device described in Japanese Patent Laid-Open No. 6-204781, the structure of two IDTs 212 and 213 for forming a balanced terminal is made different, or the center IDT 214 of the IDTs 116 and 117 is made different. , The equilibrium degree tends to deteriorate because the positional relationship with respect to is different. Also, the IDTs 212 and 21 on the balanced terminal side
3 are electrically connected in series, there is a problem that the loss due to the resistance value of the electrode finger increases and the insertion loss in the pass band increases.

An object of the present invention is to overcome the above-mentioned disadvantages of the prior art, to provide a wide band, a good balance, and a balance.
An object of the present invention is to provide a surface acoustic wave filter device having unbalanced input and output.

[0012]

A surface acoustic wave filter device according to a first aspect of the present invention comprises a piezoelectric substrate and first to third surface acoustic wave filter elements formed on the piezoelectric substrate. Each of the surface acoustic wave filter elements has a plurality of IDTs formed along the propagation direction of the surface acoustic wave, and the second and third surface acoustic wave filter elements have substantially the same transmission amplitude characteristics in the band. And transmission phase characteristics are approximately 18
0 °, at least one IDT of the second surface acoustic wave filter element and at least one IDT of the third surface acoustic wave filter element,
At least one ID of the first surface acoustic wave filter element
T is connected.

A surface acoustic wave filter device according to a second aspect of the present invention includes a piezoelectric substrate and a first substrate formed on the piezoelectric substrate.
To a third surface acoustic wave filter element, wherein the first surface acoustic wave filter element includes a first IDT formed along the propagation direction of the surface acoustic wave, and a surface wave propagation direction of the first IDT. And second and third IDTs disposed on both sides, wherein the second and third surface acoustic wave filter elements have a plurality of IDTs disposed along a surface acoustic wave propagation direction, The transmission amplitude characteristics in the bands of the second and third surface acoustic wave filter elements substantially match, and the transmission phase characteristics are approximately 180 °.
The first surface acoustic wave filter element is configured differently, the second IDT of the first surface acoustic wave filter element is connected to the second surface acoustic wave filter element, and the third IDT of the first surface acoustic wave filter element is It is characterized in that it is connected to the IDT of the third surface acoustic wave filter element.

In a specific aspect of the surface acoustic wave filter device according to the second invention, each of the first to third surface acoustic wave filter elements includes one input side IDT and one input side IDT.
Two output sides I arranged on both sides of the DT in the surface wave propagation direction
IDT having the DT and connected to the first surface acoustic wave filter element of the second surface acoustic wave filter element
And a first distance between the IDT connected to the output terminal and the IDT connected to the first surface acoustic wave filter element of the third surface acoustic wave filter element and an output terminal connected to the output terminal. When the wavelength of the surface acoustic wave is λ, the second interval between the IDT and the IDT is 0.48 λ to 0.5.
It is configured to differ by 25λ.

In a more specific aspect of the surface acoustic wave filter device according to the second invention, the first interval is

[0016]

[Equation 17]

Wherein the second interval is:

[0018]

(Equation 18)

## EQU1 ## More preferably, the first interval is

[0020]

[Equation 19]

Wherein the second interval is

[0022]

(Equation 20)

## EQU1 ## More preferably, the first interval is in the range of 1.72λ to 1.83λ, and the second interval is
Are in the range of 2.22λ to 2.33λ.

In another specific aspect of the surface acoustic wave filter device according to the second invention, the piezoelectric substrate is made of LiTaO _3.
Single crystal is 36-44 ° from Y axis to Z axis centering on X axis
A LiTaO ₃ substrate which is rotated in a range of, the electrode covering ratio in at least one interval of the first interval and a second interval in the first surface acoustic wave filter element is 50% or more .

More preferably, the electrode coverage is 63%.
It is above. In still another specific aspect of the surface acoustic wave filter device according to the second invention, the first and second reflections are disposed on both sides of the plurality of IDTs of the second surface acoustic wave filter element in the surface wave propagation direction. Vessels are further provided,
In the third surface acoustic wave filter element, a plurality of IDs
The third and the third are located on both sides of the region where T is provided in the surface wave propagation direction.
Fourth reflectors are provided, and the distance between the first reflector and the second reflector is substantially equal to the distance between the third reflector and the fourth reflector.

A surface acoustic wave filter device according to a third aspect of the present invention includes a piezoelectric substrate, and first to third surface acoustic wave filter elements formed on the piezoelectric substrate.
Has a first IDT, and second and third IDTs arranged on both sides of the first IDT in the surface wave propagation direction, and the second surface acoustic wave filter element has a first IDT. 1
The third surface acoustic wave filter element is connected to the third IDT of the first surface acoustic wave filter element, and the third surface acoustic wave filter element is connected to the third IDT of the first surface acoustic wave filter element. The phase difference between the input and output of the second IDT of the surface acoustic wave filter element and the input or output of the third IDT is different by about 180 ° in the pass band.

[0027] In a specific aspect of the surface acoustic wave filter device according to the third invention, the first space between the first and second IDTs of the first surface acoustic wave filter element and the first space between the first and second IDTs are provided. First IDT and third IDT of surface acoustic wave filter element
Is different from 0.48λ to 0.525λ when the wavelength of the surface acoustic wave filter is λ, whereby the distance between the input terminal of the first surface acoustic wave filter element and The phase difference in the band is different by about 180 °.

Preferably, the first interval is:

[0029]

(Equation 21)

Wherein the second interval is:

[0031]

(Equation 22)

More preferably, the first interval is:

[0033]

(Equation 23)

Wherein the second interval is

[0035]

(Equation 24)

More preferably, the first interval is in the range of 1.72λ to 1.88λ, and the second interval is in the range of 2.22λ to 2.33λ. In still another specific aspect of the surface acoustic wave filter device of the third invention, the piezoelectric substrate is formed by rotating the LiTaO ₃ single crystal in the range of 36 to 44 ° from the Y axis to the Z axis around the X axis. and has a LiTaO ₃ substrate, the electrode covering ratio is 50% or more in at least one interval of the first interval and a second interval in the first surface acoustic wave filter element.

Preferably, the electrode coverage is 63% or more. In another specific aspect of the surface acoustic wave filter device according to the third invention, the first surface acoustic wave filter element is disposed on both sides of the region where the plurality of IDTs are provided in the surface acoustic wave propagation direction. 1, further comprising a second reflector,
The distance from the center of the first IDT to the first reflector is substantially equal to the distance from the center of the first IDT to the second reflector.

In a specific aspect of the surface acoustic wave filter device according to the first to third aspects of the present invention, the electrode finger intersecting width of the IDT constituting the first surface acoustic wave filter element is equal to the second surface acoustic wave filter element. 1.5 to less than the electrode finger intersection width of each IDT constituting the wave filter element and the third surface acoustic wave filter element
It is in the range of 3.5 times.

A surface acoustic wave filter device according to a fourth aspect of the present invention includes a piezoelectric substrate, and first and second surface acoustic wave filter elements formed on the piezoelectric substrate.
Has a plurality of IDTs arranged along the surface acoustic wave propagation direction, and the second surface acoustic wave filter element has a plurality of IDTs arranged along the surface acoustic wave propagation direction. And the transmission amplitude characteristic in the pass band of the second surface acoustic wave filter element substantially matches the transmission amplitude characteristic of the first surface acoustic wave filter element, and the transmission phase characteristic is Wave filter element is approximately 180
° are configured to be different, one terminal of the first and second surface acoustic wave filter elements are electrically connected in parallel, the other terminal is electrically connected in series,
The terminal connected in parallel constitutes an unbalanced terminal, and the terminal connected in series constitutes a balanced terminal.

In a specific aspect of the surface acoustic wave filter device according to the fourth invention, the first and second surface acoustic wave filter elements each have three IDTs, and the first surface acoustic wave filter An IDT located at the center of the element;
As compared with the first interval between the IDTs arranged on both sides,
When the second interval between the IDT connected to the unbalanced terminal and the IDT connected to the balanced terminal in the second surface acoustic wave filter element is λ where the wavelength of the surface acoustic wave is λ,
0.48 to 0.525λ.

In the surface acoustic wave filter device according to the fourth invention, preferably, the first interval is

[0042]

(Equation 25)

Wherein the second interval is

[0044]

(Equation 26)

More preferably, the first interval is:

[0046]

[Equation 27]

Wherein the second interval is

[0048]

[Equation 28]

More preferably, the first interval is in the range of 1.72λ to 1.88λ, and the second interval is
Are in the range of 2.22λ to 2.33λ. In another specific aspect of the surface acoustic wave filter device according to the fourth invention, the piezoelectric substrate is such that the LiTaO ₃ single crystal is rotated in the range of 36 to 44 ° from the Y axis to the Z axis around the X axis. 36-44 ° rotated Y-cut LiTaO ₃ substrate, wherein the electrode coverage in at least one of the first interval and the second interval in the first surface acoustic wave filter element is 50% or more. ing. The electrode coverage is more preferably 63% or more.

In another specific aspect of the surface acoustic wave filter device according to the fourth invention, the first and second surface acoustic wave filter elements are arranged on both sides of a plurality of IDTs in the direction of surface acoustic wave propagation. And a reflector of the third type.
In the surface acoustic wave filter element, the third and fourth reflectors are respectively provided on both sides of the region where the plurality of IDTs are provided in the surface wave propagation direction, and the first and second reflectors are provided. Is substantially equal to the distance between the third reflector and the fourth reflector.

In still another specific aspect of the surface acoustic wave filter device according to the fourth invention, a terminal connected to the unbalanced side of the first surface acoustic wave filter element and a second surface acoustic wave filter The terminal connected to the unbalanced side of the element
They are connected by an electrode pattern on the piezoelectric substrate.

A surface acoustic wave filter device according to a fifth aspect of the present invention is provided with a piezoelectric substrate, a first IDT, and a second IDT disposed on both sides of the first IDT. , A third surface acoustic wave filter element having an IDT, and a first IDT between the first IDT and the second IDT.
When the second interval between the first IDT and the third IDT is set to be the wavelength of the surface acoustic wave,
0.48λ to 0.525λ, the first interval is

[0053]

(Equation 29)

And the second interval is:

[0055]

[Equation 30]

The IDT of the first SAW filter element constitutes an unbalanced terminal, and the second and third IDTs of the second SAW filter element constitute balanced terminals. And

In the fifth invention, preferably, the first interval is

[0058]

(Equation 31)

And the second interval is:

[0060]

(Equation 32)

It is assumed that More preferably, the first interval is between 1.72λ and 1.83λ, and the second interval is between 2.22λ and 2.33λ.

In another specific aspect of the fifth invention, the first,
The electrode coverage in at least one of the second intervals is 50% or more. Preferably, the electrode coverage is 63% or more.

In another specific aspect of the surface acoustic wave filter device according to the fifth invention, first and second reflectors are arranged outside the second and third IDTs, respectively.
The distance from the first IDT to the first reflector and the first I
The distance from DT to the second reflector is substantially equal.

In a specific aspect of the surface acoustic wave filter device according to the fourth or fifth aspect, a series resonator connected to the unbalanced terminal side is further provided. In another specific aspect of the surface acoustic wave filter device according to the fourth to fifth aspects, the surface acoustic wave resonator further includes a surface acoustic wave resonator connected in series to each terminal on the balanced terminal side.

In a specific aspect of the surface acoustic wave filter device according to the first to fifth aspects of the present invention, the surface acoustic wave filter further includes a ladder-type surface acoustic wave filter cascaded to the balanced terminal side. First to first
The surface acoustic wave filter device according to the fifth invention can be configured as a surface acoustic wave filter device having an appropriate package structure. For example, a chip in which a surface acoustic wave filter element is formed on the piezoelectric substrate is used. A case material for housing, and a conductive portion for electrically connecting the electrode pattern on the chip and the package are further provided, and at least one of the electrode pattern, the package, and the conductive portion formed on the piezoelectric substrate is provided. It is configured to have a substantially line-symmetric structure.

In this case, it is preferable that at least two of the electrode pattern, the package and the conductive portion have a structure substantially line-symmetric with respect to the same axis of symmetry. In another specific aspect of the surface acoustic wave filter device according to the first to fifth inventions, a case material in which a chip including the surface acoustic wave filter element is mounted on the piezoelectric substrate by a flip chip bonding method The case material is provided with one external input terminal or external output terminal used as an unbalanced signal terminal, and two external output terminals or external input terminals used as a balanced signal terminal, These two external output terminals or external input terminals are arranged substantially line-symmetrically with respect to one external input terminal or external output terminal.

In still another specific aspect of the surface acoustic wave filter device according to the first to fifth inventions, a chip having the surface acoustic wave filter element is mounted on the piezoelectric substrate by flip chip bonding. The case material further includes one external input terminal or external output terminal used as an unbalanced signal terminal, and two external output terminals or external input terminals used as balanced signal terminals. The two external output terminals or external input terminals are electrically substantially symmetric with respect to one external input terminal or external output terminal. Note that the term “electrically symmetric” refers to a structure in which the electrical length is substantially symmetric due to wiring or the like, even if it is physically somewhat asymmetric.

In still another specific aspect of the surface acoustic wave filter device according to the first to fifth aspects, at least one ground terminal is arranged between the external input terminal and the external output terminal.

[0069] In another specific aspect of the surface acoustic wave filter device according to the first to fifth inventions, at least one ground terminal is provided between two external output terminals or external input terminals used as the balanced signal terminal. Is arranged.

Further, a duplexer such as an antenna duplexer can be configured using the surface acoustic wave filter device according to the present invention, and various communication devices can be configured using the duplexer according to the present invention. can do.

[0071]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be clarified by describing specific embodiments of a surface acoustic wave filter device according to the present invention with reference to the drawings.

Referring to FIG. 1, a surface acoustic wave filter device according to a first embodiment of the present invention will be described. The surface acoustic wave filter device according to the first embodiment corresponds to an embodiment of the surface acoustic wave filter device according to the first and second aspects of the present invention.

FIG. 1 is a plan view showing the electrode structure of the surface acoustic wave filter device according to the first embodiment. In the surface acoustic wave filter device of the present embodiment, three surface acoustic wave filter elements 1 to 3 are formed on a piezoelectric substrate. As the piezoelectric substrate, an appropriate piezoelectric substrate such as LiTaO ₃ or quartz can be used, but in this embodiment, 36 ° Y-XL
An iTaO ₃ substrate is used.

The first surface acoustic wave filter element 1 comprises three IDTs 1a to 1c arranged along the surface wave propagation direction.
Having. On both sides in the surface wave propagation direction of the region where the IDTs 1a to 1c are provided, grating-type reflectors 1d,
1e is arranged.

Similarly, each of the second and third surface acoustic wave filter elements 2 and 3 has a structure in which three IDTs 2a to 2c and 3a to 3c are arranged along the surface acoustic wave propagation direction. Also, in the second and third surface acoustic wave filter elements 2 and 3, the grating type reflector 2 is located outside the region where the IDTs 2a to 2c and 3a to 3c are provided in the surface wave propagation direction.
IDTs 1a to 2d where d, 2e, 3d, and 3e are arranged
Each of 1c, 2a to 2c, and 3a to 3c has a pair of comb electrodes.

One of the IDTs 1 a at the center of the first surface acoustic wave filter element 1 is connected to the input terminal 4. Also, one of the comb-shaped electrodes of the second and third IDTs 1b arranged outside the central first IDT 1a is connected to the second and third IDTs arranged outside the second surface acoustic wave filter element.
Are electrically connected to one of the IDTs 2b and 2c. Similarly, one comb electrode of the outer IDTs 3b and 3c of the third surface acoustic wave filter element 3 is electrically connected to one comb electrode of the outer IDT 1c of the first surface acoustic wave filter element. . One of the IDTs 2a and 3a at the center of the second and third surface acoustic wave filter elements is electrically connected to the output terminals 5 and 6, respectively. Of the comb electrodes of the IDTs 1a to 1c, 2a to 2c, and 3a to 3c, the comb electrodes other than the comb electrodes described above are connected to the ground potential.

The input terminal 4 is an unbalanced terminal, and the output terminals 5 and 6 are balanced terminals. Note that the transmission phase characteristic of the third surface acoustic wave filter element 103 differs from the transmission phase characteristic of the second surface acoustic wave filter element 102 by approximately 180 °.

Next, a specific structure example of the first to third surface acoustic wave filter elements 1 to 3 will be described. In this embodiment,
In the first surface acoustic wave filter element 1, the IDTs 1a to 1a
The electrode finger intersection width W at c is 52λ. Here, λ indicates the wavelength of the surface acoustic wave. The number of pairs of electrode fingers of the first IDT 1a arranged at the center is 16, and the number of pairs of electrode fingers of the outer IDT, that is, the second and third IDTs 1b and 1c is 11, respectively. The wavelength λI of the surface wave in the IDTs 1a to 1c is 4.2 μm. In addition, reflector 1
The number of electrode fingers in d and 1e is 120, and the wavelength λR is 4.3 μm. In addition, adjacent IDT1a ~
The interval GI between 1c is 1.77λR. Note that the interval between adjacent IDTs refers to, for example, the pitch between the closest electrode fingers on the hot side of the IDTs 1a and 1b, for example, between the IDTs 1a and 1b.

In the second surface acoustic wave filter element 2, I
The electrode finger intersection width W in the DTs 2a to 2c is set to 31λ. The number of pairs of electrode fingers of the first IDT 2a disposed at the center is 16, and the outer IDT, that is, the second and third IDTs.
The number of pairs of electrode fingers in each of 2b and 2c is 11. The wavelength λI of the surface wave in the IDTs 2a to 2c is 4.
2 μm. The number of electrode fingers in the reflectors 2d and 2e is 120, and the wavelength λ is 4.3 μm.
The interval GI between adjacent IDTs 2a to 2c is 1.7.
7λR.

The third surface acoustic wave filter element 103 has the same configuration as that of the second surface acoustic wave filter element 2 except that the interval GI between adjacent IDTs is 2.27λR. I have.

The second surface acoustic wave filter element 2 and the third surface acoustic wave filter element 3 have transmission phase characteristics of about 18
The intervals GI between adjacent IDTs are different so as to differ by 0 °. The configuration in which the transmission phase characteristics of the second and third surface acoustic wave filter elements 2 and 3 are different by 180 ° is not limited to the above-described structure in which the intervals between the IDTs are different.

In the present embodiment and the following embodiments, since the number of electrode fingers of the surface acoustic wave filter element and the number of electrode fingers of the reflector are very large, they are schematically shown in the drawings.

The operation of the surface acoustic wave filter device of this embodiment when the input terminal 4 is used as an unbalanced input terminal and the output terminals 5 and 6 are used as balanced output terminals will be described. When an electric signal is input to the input terminal 4, the electric signal filtered by the first surface acoustic wave filter element 1 is provided to the second and third surface acoustic wave filter elements 2 and 3. At this time, the IDT of the surface acoustic wave filter element 1
1b and 1c have the same structure, and the IDT 1a
If the distances from to IDTs 1b and 1c are equal,
The electric signals applied to the second and third surface acoustic wave filter elements 2 and 3 are the same.

The electric signals input to the surface acoustic wave filter element 2 and the surface acoustic wave filter element 3 are filtered again and led out to balanced output terminals 5 and 6. Here, in the surface acoustic wave filter element 2 and the surface acoustic wave filter element 3, only the interval GI between adjacent IDTs is different as described above. Therefore, the filtered amplitude characteristic is the same and the transmission phase characteristic is about 180 °
Will be different. Therefore, the electric signals derived from the output terminals 5 and 6 are completely balanced signals having the same amplitude characteristics and different transmission phase characteristics by about 180 °.

Further, in the surface acoustic wave filter element 1,
Parameters such as an intersection width are set so as to match an unbalanced circuit connected to the input terminal 4, for example, 50Ω which is a characteristic impedance of the antenna circuit. In the surface acoustic wave filter elements 2 and 3, the characteristic impedance 1 of a balanced circuit such as an amplifier circuit connected to the output terminals 5 and 6 is obtained.
Parameters such as the width of the intersection are set so as to match １ ／ of 50Ω. This is because when the respective terminals 5 and 6 of the balanced circuit are regarded as independent unbalanced terminals, the characteristic impedance becomes equal to 特性 of the characteristic impedance of the balanced circuit.

The surface acoustic wave filter device having a balanced-to-unbalanced conversion function disclosed in Japanese Patent Laid-Open No. Hei 10-117123 requires two surface acoustic wave filter elements on the input side (unbalanced side). there were.

On the other hand, in this embodiment, the input side (unbalanced side) can be constituted by one surface acoustic wave filter element as described above. Therefore, when compared with the above prior art, according to the present embodiment, the parasitic capacitance formed between the bus bars of the adjacent IDTs and the connection between the input surface acoustic wave filter element and the output surface acoustic wave filter element are connected. It is possible to greatly reduce the parasitic capacitance of a chip-like lead-out electrode connecting the terminal of the package, the terminal of the package and the surface acoustic wave filter device, or a bonding pad. Such a parasitic capacitance has been a major obstacle in realizing a wider surface acoustic wave filter device.

In the surface acoustic wave filter device of this embodiment,
As described above, these parasitic capacitances can be reduced,
Without deteriorating the flatness and VSWR in the pass band,
Broadband filter characteristics can be realized.

FIG. 2 shows the filter characteristics of this embodiment by solid lines. Further, for comparison, Japanese Patent Application Laid-Open No. HEI 1 (1996) -1995 configured to have the same band as the surface acoustic wave filter device of the embodiment.
The broken line shows the filter characteristics of the surface acoustic wave filter device manufactured based on the description in JP-A-117123.

As is apparent from FIG. 2, it is understood that the use of the surface acoustic wave filter device of this embodiment can provide a wide band filter characteristic. 3 and 4 show the VSWR characteristics of the surface acoustic wave filter device of the present embodiment and the unbalanced terminal side and the balanced terminal side of the surface acoustic wave filter device prepared based on the description of the above prior art. Is shown. The solid line shows the characteristics of the surface acoustic wave filter device of the embodiment, and the broken line shows the characteristics of the conventional example. As is clear from FIGS. 3 and 4, according to the present embodiment, it is found that the deterioration of the VSWR can be suppressed.

Further, in the surface acoustic wave filter device of this embodiment, only three surface acoustic wave filter elements need to be used, so that the chip size can be reduced. Further, the size of the entire surface acoustic wave filter device can be reduced, and the number of surface acoustic wave filter devices to be obtained per wafer prepared for manufacturing the surface acoustic wave filter device can be increased, thereby reducing costs. Can be planned.

FIGS. 5 and 6 show that the intervals GI between adjacent IDTs of the second surface acoustic wave filter element are 1.77.
λ, the difference between the intervals between the IDTs of the surface acoustic wave filter elements 2 and 3 when the intervals GI and GI between the adjacent IDTs of the third surface acoustic wave filter element 3 are changed,
It is a figure which shows the relationship of a balance. Here, the interval between the IDTs is defined as the distance between the center of the electrode finger closest to the adjacent IDT and the other IDT among the electrode fingers connected to the signal line of one of the adjacent IDTs that are not grounded. Of the electrode fingers connected to the signal line without being grounded to the center of the electrode finger closest to the adjacent IDT. The difference between the intervals on the horizontal axis in FIGS. 5 and 6 is a value normalized by λ.

The amplitude balance and the phase balance are defined as the three-port surface acoustic wave filter device of the present embodiment, and the unbalanced input terminal is port 1 and the balanced output terminals 5 and 6 are respectively defined. When port 2 and port 3 are used
The amplitude balance | A | is A = | S21 | − | S31 |, and the phase balance | B−180 | is B = | ∠S21−.
∠S31 |.

Ideally, the amplitude balance is 0 dB and the phase balance is 0 °. However, as a practically usable range, the amplitude balance is 1.5 dB or less and the phase balance is 0 dB. 2
0 ° or less.

According to FIG. 5, the amplitude balance degree satisfies such a value because the surface acoustic wave filter elements 2 and 3
According to FIG. 6, the difference between the IDTs of the surface acoustic wave filter elements 2 and 3 is such that the phase difference satisfies the above value. Should be set in the range of 0.48λ to 0.525λ. Therefore, in order to satisfy both the ranges of the amplitude balance and the phase balance, the distance between the IDTs in the surface acoustic wave filter element 2 and the distance between the adjacent IDTs in the surface acoustic wave filter element 3 are satisfied. The difference is 0.48λ
It is understood that it is only necessary to be within the range of 0.525λ.

In the case of a longitudinally coupled resonator type surface acoustic wave filter element having three IDTs, the interval between adjacent IDTs is (0.72 + n / 2) × λ to (0.83 + n / 2).
It is already known that a wideband filter characteristic can be realized by setting xλ in the range of n = 0, 1, 2, and 6. Therefore, various ranges are conceivable as combinations for setting the difference between the adjacent IDTs of the surface acoustic wave filter element 2 and the surface acoustic wave filter element 3 to the above value.

However, when the value of n in the above equation is increased, the following problem occurs. That is, FIG. 7 shows that the distance between adjacent IDTs in the surface acoustic wave filter element 2 of the surface acoustic wave filter device of the present embodiment is
(N / 2 + 0.77) × λ, where n is 0, 1, 2, 6
The relationship between the spacing between adjacent IDTs and the bandwidth of the surface acoustic wave filter device in the case of the above is shown. As is apparent from FIG. 7, in order to secure a minimum bandwidth of 35 MHz required for a surface acoustic wave filter device for a mobile phone, n is 6
It is understood that the following must be performed.

On the other hand, there is a problem caused by reducing n. FIG. 9 shows the distance GI between adjacent IDTs in the second surface acoustic wave filter element 2 in the surface acoustic wave filter device of the present embodiment, which is (0.77 + m / 2) ×
λ, where m is 0 and a natural number, and the interval GI between adjacent IDTs of the surface acoustic wave filter element 3 is (1.27 + m
The relationship between the amplitude GI and the interval GI between adjacent IDTs in the second surface acoustic wave filter element 2 when (/ 2) × λ is shown.

FIG. 10 shows that the distance GI between adjacent IDTs of the second surface acoustic wave filter element 2 in the surface acoustic wave filter device of this embodiment is (0.77 + m / 2).
× λ, and the interval GI between adjacent IDTs in the third surface acoustic wave filter element 3 is (1.27 + m / 2) ×
The relationship between the interval GI between IDTs and the phase balance when λ is shown.

From FIG. 9 and FIG. 10, the amplitude balance degree is 1.5
It can be seen that the interval between IDTs must be set to 1.77λ or more, that is, the value of m must be set to 1 or more in order to satisfy dB or less and to satisfy the phase balance of 20 ° or less. The phenomenon in which the degree of equilibrium is degraded when the interval between adjacent IDTs is reduced can be considered as follows.

In the case of the longitudinally coupled resonator type surface acoustic wave filter, not only adjacent IDTs are acoustically coupled but also,
They may also be coupled electromagnetically. The transmission characteristic by acoustic coupling is changed by changing the interval between adjacent IDTs by 0.5λ, so that the phase is inverted by the surface acoustic wave filter elements 2 and 3, whereas the transmission characteristic by electromagnetic coupling is adjacent. It does not depend on the interval between matching IDTs, and therefore has the same phase and the same amplitude. The transmission component having the same phase and the same amplitude is a factor for deteriorating the degree of balance. Therefore, in a structure in which the distance between IDTs is reduced and electromagnetic coupling is increased, the degree of balance is deteriorated.

From the above results, the interval GI between the adjacent IDTs of the surface acoustic wave filter element 2 is set to (0.77 + n /
2) × λ, n = 1, 2, 3, 4, 5 and the interval GI between adjacent IDTs of the surface acoustic wave filter element 3 is (1.2
7 + n / 2) × λ, where n is a natural number in the range of 1 to 5, so that a filter characteristic can be obtained in which both the degree of balance and the bandwidth are practically acceptable.

Further, when considering the frequency fluctuation due to the temperature change, a bandwidth of 39 MHz is required. In this case, an interval GI between adjacent IDTs of the surface acoustic wave filter element 2 is (0.77 + n / 2) × λ, where n is a natural number of 1 to 3, and the adjacent surface acoustic wave filter elements 3 are adjacent to each other. The interval GI between IDTs is (1.27 + n / 2) × λ,
However, n may be a natural number of 1 to 3.

Furthermore, in order to obtain the widest bandwidth without deteriorating the balance, the interval GI between adjacent IDTs of the surface acoustic wave filter element 2 should be set to (0.77 + n / 2).
× λ, where n = 2, and the interval GI between adjacent IDTs of the surface acoustic wave filter element 3 is (1.27 + n / 2) ×
λ, where n = 2.

On a piezoelectric substrate formed by rotating a LiTaO ₃ single crystal in the range of 36 ° to 44 ° from the Y axis to the Z axis around the X axis, two types of surface acoustic waves are excited and propagated. You. One surface acoustic wave is a leaky wave, that is, a pseudo surface acoustic wave, and the other is a bulk wave called SSBW. Of these, leaky waves are mainly used to form resonators and filters, and SS
When the BW is mainly propagated, the propagation loss increases, and the Q of the resonator deteriorates and the insertion loss as a filter increases. The above two types of surface acoustic waves are excited and propagated together. However, when the surface state is closer to an electrical short circuit, that is, when the electrode coverage is large, leaky waves are mainly propagated, and when the surface state is closer to electrical opening,
That is, when the electrode coverage is small, SSBW is mainly propagated.

Therefore, the first distance between the center IDT in the second surface acoustic wave filter element and the outer second and third IDTs, and the first distance between the center IDT in the third surface acoustic wave filter element. If at least one electrode finger is inserted in the second interval between the IDT and the outer second and third IDTs and the electrode coverage is increased, leaky waves can be mainly propagated, Excitation and propagation of the SSBW can be suppressed, and insertion loss can be reduced.

FIG. 8 shows the relationship between the electrode coverage at the first interval and the in-band insertion loss. It can be seen that the electrode coverage must be 0.5 or more, that is, 50% or more in order to realize a practical insertion loss in the band of 3.0 dB or less. Further, it is understood that, in an application in which the loss is required to be further reduced, in order to reduce the insertion loss to 2.5 dB or less, the electrode coverage should be 0.63 or more, that is, 63% or more. The same can be said for the second interval.

The signal input to the second surface acoustic wave filter element 2 excites a surface acoustic wave by the IDTs 2b and 2c. This surface acoustic wave propagates in a predetermined propagation direction and is reflected by the reflectors 2d and 2e. The reflected surface acoustic wave is a standing wave between the reflectors 2d and 2e due to buffering of the excited surface acoustic wave. Occurs. Due to the standing wave, the Q has a very high resonance, and when the excited standing wave is received by the IDT 2a, the standing wave is converted into an electric signal in the IDT 2a to perform a function as a filter. The same operation is performed in the third surface acoustic wave filter element 3. However, the output signal is determined by the positional relationship between the excited standing wave and the output side IDT 3a, but the phase relationship is changed to the second by shifting the position of the IDT 3b by 0.5 times the wavelength λ of the surface acoustic wave. It is inverted as compared with the case of the surface acoustic wave filter element.

Here, if the distance C between the two reflectors 2d and 2e of the surface acoustic wave filter element 2 and the distance D between the two reflectors 3d and 3e of the surface acoustic wave filter element 3 are different, In this case, the intensity distribution of the standing wave in the element will be different. Therefore, the resonance characteristics also change, and the characteristics as a filter also change. Therefore, by setting the distance C between the two reflectors 2d and 2e of the surface acoustic wave filter element 2 and the distance D between the two reflectors 3d and 3e of the surface acoustic wave filter element 3 to be substantially equal, the elasticity is improved. It is possible to suppress the deterioration of the degree of balance without causing a difference in the filter characteristics between the surface acoustic wave filter elements 2 and 3.

In this embodiment, the reflectors 1d, 1e,
Although grating type reflectors are used as 2d, 2e, 3d and 3e, the present invention is not limited to this.
For example, it may use reflection at the end face of the piezoelectric substrate.

In this embodiment, the input terminal (unbalanced terminal) 4
Has a characteristic impedance of 50Ω, and the output terminals 5, 6
The characteristic impedance of the (balanced terminal) is 150Ω. In order to match with such input / output impedance, in this embodiment, the surface acoustic wave filter element 1 is adjusted as described above so as to match with 50Ω which is the characteristic impedance of the unbalanced circuit connected to the input side. Intersection width is 51
is set to λ. The electrode finger intersection width of each of the surface acoustic wave filter elements 2 and 3 is set to 31λ so as to match the characteristic impedance of the balanced circuit connected to the output side to 1/2 of 150Ω. this is,
This is because when the respective terminals 5 and 6 of the balanced circuit are regarded as independent unbalanced terminals, the characteristic impedance is equal to 特性 of the characteristic impedance of the balanced circuit.

As described above, the impedance matching with the unbalanced circuit connected to the input side is achieved by the surface acoustic wave filter element 1, and the impedance matching with the balanced circuit connected to the output side by the surface acoustic wave filter elements 2 and 3. By matching, the input / output impedance ratio can be set freely.

FIG. 11 shows the ratio of the intersection width of the surface acoustic wave filter element 1 connected to the unbalanced terminal 4 to the electrode finger intersection width of the surface acoustic wave filter elements 2 and 3 connected to the balanced terminal. This shows the relationship with the bandwidth. FIG. 11 shows that the widest bandwidth can be obtained when the intersection width ratio is 2.0. On the other hand, if the cross width ratio exceeds 3.5, the decrease in bandwidth exceeds 5%, and the yield rate decreases.

FIG. 12 shows the electrode finger intersection width of the surface acoustic wave filter element 1 connected to the unbalanced terminal 4 and the balanced terminals 5 and 5.
6 shows the relationship between the ratio to the electrode finger intersection width in the surface acoustic wave filter elements 2 and 3 connected to 6 and the value of VSWR within the pass band. When the cross width ratio is 2.5, VSW
R is the best value, and when it is 1.5 or less, VSWR
Is significantly deteriorated, causing a practical problem. Therefore, it is desirable to set the electrode finger cross width ratio in the range of 1.5 to 3.5.

(Second Embodiment) FIG. 13 shows a second embodiment of the present invention.
FIG. 5 is a plan view showing an electrode structure of the surface acoustic wave filter device according to the example. In this embodiment, three surface acoustic wave filter elements 11 to 13 are formed on a piezoelectric substrate (not shown). As the piezoelectric substrate, an appropriate piezoelectric substrate such as LiTaO ₃ or quartz can be used. In this embodiment, 36 ° YX LiTaO ₃ is used. Since the basic structure and connection structure of the first to third surface acoustic wave filter elements 1 to 13 are the same as those of the first embodiment, the same parts are given the same reference numerals. Therefore, the description of the first embodiment will be omitted by using the description of the first embodiment.

The surface acoustic wave filter device of the second embodiment differs from the surface acoustic wave filter device of the first embodiment in the electrode structure of the first to third surface acoustic wave filter elements 11 to 13. .

As will be apparent from the operation described below, in this embodiment, the first surface acoustic wave filter element 11 is used.
IDT, that is, the second and third IDTs 11b, 1
1c has a transmission phase characteristic of approximately 18
The surface acoustic wave filter elements 11 and 12 are different from each other by 0 ° so that electric signals having the same amplitude and a phase difference of about 180 ° are provided to the second and third surface acoustic wave filter elements 12 and 13. It is configured.

In this embodiment, in the first surface acoustic wave filter element 11, the electrode finger intersection width W in the IDTs 11a to 11c is 52λ. Here, λ indicates the wavelength of the surface acoustic wave.

In the first surface acoustic wave filter element 11, the number of pairs of electrode fingers of the first IDT 11a disposed at the center is 16, the outer IDT, that is, the second and third IDTs.
The number of pairs of electrode fingers in each of 11b and 11c is eleven. Further, the wavelength λI in the IDTs 11a to 11c
Is 4.2 μm. The number of electrode fingers in the reflectors 11d and 11e is 120, and the wavelength λR is 4.
3 μm. Also, the first IDT 11a and the second IDT 11a
First spacing A ₁ between the DT11b is 1.77Ramudaaru, second distance B ₁ between the first IDT11a and third IDT11c is a 2.27Ramudaaru.

In the second surface acoustic wave filter element 12,
The electrode finger intersection width is 31λ, the logarithm of the electrode finger of the first IDT 12a arranged at the center is 16, and the logarithm of the electrode finger of the outer IDT, ie, the second and third IDTs 12b and 12c is 11, respectively. is there. In addition, IDT12a ~
The wavelength λI at 12c is 4.2 μm. Also,
The number of electrode fingers in the reflectors 12d and 12e is 120, and the wavelength λR is 4.3 μm. Also, the first I
An interval A ₂ between the DT 12a and the second IDT 12b is 1.77λR, and the first IDT 12a and the third ID
Distance B ₂ between the T12c is as 1.77Ramudaaru.

Further, the third surface acoustic wave filter element 13
Are configured similarly to the second surface acoustic wave filter element 12. The operation of the surface acoustic wave filter device according to the second embodiment when the input terminal 4 is used as an unbalanced input terminal and the output terminals 5 and 6 are used as balanced output terminals will be described.

When an electric signal is input to the input terminal 4,
The surface acoustic wave is excited by the first IDT 11a of the first surface acoustic wave filter element. This surface acoustic wave propagates in a direction orthogonal to the direction in which the electrode fingers extend, and
d, 11e, the reflected surface acoustic waves interfere with the surface acoustic waves to be excited, and the two reflectors 11d, 1d
A standing wave is generated during 1e. The occurrence of this standing wave results in a resonance having a very high Q, and the excited standing wave is received by the IDTs 11b and 11c on the output side. Accordingly, the signal is converted into an electric signal, and the first surface acoustic wave filter element 11 operates as a filter.

In this case, the output signal is determined by the positional relationship between the standing wave to be formed and the IDTs 11b and 11c on the output side.
The phase relationship can be reversed by shifting either T11b or 11c. In the second embodiment, the ID
The first and second intervals A ₁ and B ₁ are determined as described above so that the electric signal output from the T11b and the electric signal output from the IDT 11c have a phase characteristic that differs by approximately 180 °. Therefore, the second and third surface acoustic wave filter elements 12 and 13 have the same amplitude and the same phase of 180.
° Different electrical signals are provided. Further, the output signal is filtered by the second and third surface acoustic wave filter elements 12 and 13, and the filtered signal is output to the output terminals 5 and 6 as a balanced signal.

[0124] From the results of FIGS. 5 and 6 described above, also in the second embodiment, the IDT 11a, and the first distance A ₁ between the IDT11b, and IDT 11a, IDT11c
The difference between the second distance B ₁ between the 0.48λ~0.52
It is presumed that it should be set within the range of 5λ.

The interval between the IDTs and the IDTs is
(N / 2 + 1.22) × λ to (n / 2 + 1.33) ×
λ, where n is an integer of 0 to 4, and (n / 2 + 1.7
2) × λ to (n / 2 + 1.83) × λ, where n is 0
Integer of ４4], the deterioration of the degree of equilibrium can be prevented, and a wide band characteristic can be obtained.

Further, as in the case of the first embodiment, the center IDT of the second surface acoustic wave
A first gap between the first and second outer third IDTs 12b and 12c and the center first IDT 13a in the third surface acoustic wave filter element;
If at least one electrode finger is inserted in the second interval between the IDTs 13b and 13c and the electrode coverage in the region of the interval is increased, leaky waves can be mainly propagated, and insertion loss can be reduced. Can be reduced. In the present embodiment, therefore, the electrode coverage at the first and second intervals is set to 63%, thereby reducing the insertion loss.

In the present embodiment, the first and second intervals are different from each other.
Different, which prevents the amplitude balance from deteriorating.
Have been. Also, the first surface acoustic wave filter element 11
From the first IDT 11a to the reflector 11d
P and the distance from the first IDT 11a to the reflector 11e
Q _TwoAnd the first elastic table
Excitation strength of standing wave formed in surface wave filter element
The asymmetry of the distribution has been eliminated. Therefore, IDT11
b, 11c have the same surface acoustic wave intensity
As a result, the deterioration of the degree of equilibrium is suppressed. The distance
The separations P and Q are respectively connected to the signal line of the IDT 11a.
The center of the outermost electrode finger and the reflector 1
The distance between the innermost electrode fingers of 1d and 11e
U.

(Third Embodiment) FIG. 14 is a schematic plan view showing an electrode structure of a surface acoustic wave filter device according to a third embodiment. Also in the third embodiment, first to third surface acoustic wave filter elements 31 to 33 are formed on a piezoelectric substrate. Each of the surface acoustic wave filter elements 31 to 33 has a second
The configuration is the same as that of the embodiment. Therefore, portions similar to those of the second embodiment will be omitted by using the description of the second embodiment.

In the third embodiment, however, the surface acoustic wave filter element 31 and the surface acoustic wave filter elements 32, 3
3 is different from that of the second embodiment. That is,
In the third embodiment, the outer IDTs of the first to third surface acoustic wave filter elements 31 to 33, that is, 31b, 31c,
2b, 32c, 33b, 33c are not grounded but are float-connected.

More specifically, one of the comb electrodes of the second IDT 31b of the first surface acoustic wave filter element 31 is connected to the second and third IDs of the second surface acoustic wave filter element 32.
It is connected to one end of T32b, 32c. On the other hand, I
The other end of the DT 31b is connected to the other ends of the IDTs 32b and 32c of the second surface acoustic wave filter element 32. Similarly, the third surface acoustic wave filter element 31
Are connected to the first ends of the second and third IDTs 33b and 33c of the third surface acoustic wave filter element 33, and the second end of the IDT 31c is It is connected to the second ends of the IDTs 33b and 33c.

Note that 31d, 31e, 32d, 32e,
33d and 33e indicate reflectors. Other points are the same as in the second embodiment. Therefore, the third surface acoustic wave filter device can be operated in the same manner as the surface acoustic wave filter device of the second embodiment, and the same effect can be obtained. In addition, because of having the above connection structure,
The number of ground bonding pads can be significantly reduced, the size of the surface acoustic wave filter device can be reduced, and the parasitic capacitance caused by the bonding pads and the connection wiring with the bonding pads can be reduced.

(Fourth Embodiment) FIG. 15 shows a fourth embodiment of the present invention.
It is a schematic plan view which shows the electrode structure of the surface acoustic wave filter device concerning Example of 1st.

In the surface acoustic wave filter device of this embodiment,
First and second surface acoustic wave filter elements 41 and 42 are formed on a piezoelectric substrate (not shown). As the piezoelectric substrate, a piezoelectric substrate made of a piezoelectric ceramic, a piezoelectric single crystal, or the like can be used.
A LiTaO ₃ substrate is used.

First and second surface acoustic wave filter elements 4
1, 42 are three IDTs 41a to 41c, 4
This is a resonator type surface acoustic wave filter element having 2a to 42c.

The first center part of the surface acoustic wave filter element 41
The first end of the IDT 41a and the first end of the first IDT 42a at the center of the second surface acoustic wave filter element 42 are commonly connected and connected to the input terminal 4.

The second IDT 41a, 42a
Is grounded. On the other hand, the outer IDT, that is, the IDTs 41b and 41c are connected to the output terminal 5, and the outer IDT, that is, one end of the second and third IDTs 42b and 42c is connected to the output terminal 6. Note that the second and third I
The other ends of the DTs 41b, 41c, 42b, 42c are grounded.

The IDTs 41a to 41c and 42a to 4
Reflectors 41d, 41e, 42d and 42e are arranged on both sides of the area where 2c is provided.
In this embodiment, the transmission phase characteristic of the first surface acoustic wave filter element 41 is different from the transmission phase characteristic of the second surface acoustic wave filter element 42 by approximately 180 °.

More specifically, the first surface acoustic wave filter element 41 has an electrode finger intersection width W of 31λ.
The IDT 41a has 16 pairs of electrode fingers, and the IDTs 41b and 4 have
The number of electrode fingers of 1c is eleven. Also, IDT41a
.Lambda.I of the reflectors 41d, 4c is 4.2 .mu.m.
The number of electrode fingers of 1e is 120, and the reflector 41d,
The wavelength λR at 41e is set to 4.3 μm. The first interval GI ₁ between the IDT 41a and the IDTs 41b and 41c is set to 1.75λR.

In the second surface acoustic wave filter element 42,
And IDT42a, IDT42b, second spacing GI ₂ between 42c is except that it is a 2.25Ramudaaru, is configured similarly to the first surface acoustic wave filter element 41. As described above, the first interval and the second interval are different, whereby the first surface acoustic wave filter element 41 and the second surface acoustic wave filter element 42 have substantially equal transmission amplitude characteristics, And the transmission phase characteristic is approximately 180
° Different.

The input terminal 4 of the surface acoustic wave filter device of this embodiment is an unbalanced terminal, and the input terminal 4 is used as an input.
The operation when the balanced output terminals 5 and 6 are used as output terminals will be described.

When an electric signal is input to the input terminal 4, signals having the same phase and the same amplitude are applied to the first and second surface acoustic wave filter elements 41 and 42. This signal is the IDT
41a and 42a are applied to excite a surface wave. This surface wave propagates in a direction orthogonal to the direction in which the electrode fingers extend, and is reflected by the reflectors 41d, 41e, 42d, and 42e. Therefore, the reflected surface acoustic wave is buffered with the excited surface acoustic wave, and the two reflectors 41d, 41e or 4
A standing wave is formed between 2d and 42e. Therefore, a very high Q resonance occurs, and the excited standing wave is output to the output terminals 5 and 5.
IDTs 41b, 41c, 42b, 42c connected to 6
And converted into an electrical signal. The standing waves excited at this time and the output-side IDTs 41b, 41c, 42
The output signal is determined by the positional relationship between b and 42c.

In this embodiment, the surface acoustic wave filter element 4
1, a first space between the IDT 41a and the IDTs 41b and 41c, and a second surface acoustic wave filter element 42.
The distance between the IDT 42a and the IDTs 42b and 42c differs by 0.50 times the wavelength of the surface acoustic wave. Therefore, the first surface acoustic wave filter element 41
And the signal output from the second surface acoustic wave filter element 42 have inverted phases.

Therefore, the surface acoustic wave filter elements 41, 4
2 has a characteristic that transmission phase characteristics are different by 180 °, and electric signals having the same amplitude and a different phase by 180 ° are derived from output terminals 5 and 6 which are balanced output terminals.

In this embodiment, since the filter has a single-stage configuration using two surface acoustic wave filter elements 41 and 42, the in-band insertion loss can be extremely reduced. FIG. 16 shows the filter characteristics of the surface acoustic wave device according to the fourth embodiment. As is clear from FIG. 16, it can be seen that the loss in the pass band can be reduced.

Also in the fourth embodiment, from the results of FIGS. 5 and 6, the difference between the first interval and the second interval is 0.48.
It can be said that it is sufficient to set the range of λ to 0.525λ.

The first interval and the second interval are (n
/2+1.22)×λ to (n / 2 + 1.33) × λ,
[Where n is an integer of 0 to 4] and (n / 2 + 1.72)
× λ to (n / 2 + 1.83) × λ, where n is 0 to 4
Integer], it is possible to prevent deterioration of the degree of equilibrium and to obtain a wideband characteristic.

Also, in the fourth embodiment, as in the first embodiment, one or more electrode fingers are inserted between the first and second intervals to increase the electrode coverage. Waves can be mainly propagated, and excitation and propagation of SSBW can be suppressed. Therefore, by setting the electrode coverage at the first and second intervals to preferably 50% or more, more preferably 63% or more, a low-loss surface acoustic wave filter device can be provided.

In the present embodiment, in the second surface acoustic wave filter element 42, the positional relationship between the output side IDTs 42b and 42c is determined by the output side IDT in the first surface acoustic wave filter element.
Since the positions of the DTs 41b and 41c are shifted by 0.5 times the wavelength of the surface acoustic wave, the phase relationship is inverted as described above.

Here, the first surface acoustic wave filter element 4
The distance between the two reflectors 41d and 41e and the two reflectors 42d and 42 of the second surface acoustic wave filter element 42.
If the interval between e is different, the intensity distribution of the standing wave in each element changes. Therefore, it is expected that the resonance characteristics also change and the characteristics as a filter also change. Therefore, preferably, the reflectors 41d, the distance P ₁ between 41e, reflectors 4
2d, substantially equal intervals to Q ₁ between 42e, thereby inhibiting the balance of the degradation.

In the fourth embodiment, as for the reflectors 41d to 42e, grating type reflectors are shown. However, for example, other appropriate reflectors such as a reflector using reflection at a chip end face are used. A structured reflector can be used.

The central IDT 41a of the surface acoustic wave filter element 41 and the central IDT 42a of the surface acoustic wave filter element 42 are commonly connected by an electrode pattern on the piezoelectric substrate, and are connected to the unbalanced input terminal 4. Accordingly, the parasitic capacitance of the surface acoustic wave filter element 41 and
The parasitic capacitance of the surface acoustic wave filter element 42 is shared. Therefore, the degree of equilibrium is also improved thereby.

(Fifth Embodiment) FIG. 17 is a schematic plan view showing an electrode structure of a surface acoustic wave filter device according to a fifth embodiment.

In this embodiment, two resonator type surface acoustic wave filter elements are used as in the fourth embodiment. That is, the first and second surface acoustic wave filter elements 51 and 52 are formed on the piezoelectric substrate. Also,
In the first and second surface acoustic wave filter elements 51 and 52, floating electrode fingers 53a to 53d between the center IDTs 51a and 52a and the outer second and third IDTs 51b, 51c, 52b and 52c, respectively. Are inserted respectively. IDTs 51a to 51c and reflectors 51d and 51e
Is the ID of the surface acoustic wave filter element 41 of the fourth embodiment.
The configuration is almost the same as T41a to 41c and the reflectors 45d and 45e. Also, the IDTs 52a to 52c of the second surface acoustic wave filter element 52 and the reflectors 52d and 52d
e is the second surface acoustic wave filter element 4 of the fourth embodiment.
The two IDTs 42a to 42c and the reflectors 42d and 42e have substantially the same configuration.

As in the present embodiment, the floating electrode fingers 53a to 53a
3d may be formed independently of the IDT, so that the electrode coverage of the space between the IDTs can be 50% or more.

(Sixth Embodiment) FIG. 18 shows a sixth embodiment.
Schematic diagram for explaining a surface acoustic wave filter device according to
It is a top view. One elastic table on a piezoelectric substrate (not shown)
The surface wave filter element 61 is configured. As a piezoelectric substrate
In this embodiment, 36 ° YX LiTaO _ThreeThe board is
Used but other cuts each LiTaO_Threesubstrate
Alternatively, it is possible to use a piezoelectric substrate made of another piezoelectric material as appropriate.
it can.

In the surface acoustic wave filter element 61, three IDTs 61a to 61c are formed along the surface wave propagation direction. Reflectors 61d and 61e are formed on both sides of the area where the IDTs 61a to 61c are provided.

In this embodiment, the center first IDT 61a
Is connected to an input terminal 4 which is an unbalanced input terminal. The other end of the IDT 61a is grounded. One ends of the outer second and third IDTs 61b and 61c are connected to output terminals 5 and 6, which are balanced output terminals, and the other ends are grounded. The reflectors 61d and 61e are constituted by grating reflectors, but may be constituted by other reflectors.

The electrode finger intersection width W of the IDTs 61a to 61c is 31λ, and the number of pairs of electrode fingers of the IDT 61a is one.
6. The number of pairs of electrode fingers of IDTs 61b and 61c is 1
It is set to 1. The wavelength λI of the surface wave in the IDTs 61a to 61c is 4.2 μm.

The number of electrode fingers in each of the reflectors 61d and 61e is 120, and the wavelength λR is 4.3 μm.
First interval JI between IDT 61a and IDT 61b
₁ is 1.75λR, and IDT61a and IDT61
The second interval JI ₂ between the first and second c is 2.25λR.

In the surface acoustic wave filter device of this embodiment,
When an electric signal is input from the input terminal 4 to the IDT 61a, the reflector 61 is turned on, as in the first to fifth embodiments.
A standing wave is formed between d and 61e. Due to this standing wave, a very high resonance is obtained, and the excited standing wave has an ID
Waves are received at T61b and 61c and extracted from output terminals 5 and 6.

Also in this embodiment, the output signal is determined by the positional relationship between the standing wave to be excited and the output IDTs 61b and 61c. In this embodiment, the IDTs 61a and 6a
Since the first interval between the IDTs 1b and the IDT 61a, and the second interval between the IDT 61a and the IDT 61c are different by 0.50 times the wavelength of the surface acoustic wave, the phases of the output signals of the IDTs 61b and 61c are inverted. I have.

Therefore, since the electric signal output from the IDT 61b and the electric signal output from the IDT 61c have characteristics in which the transmission phase characteristics differ by 180 °, the output terminals 5 and 6 have the same amplitude and 180 ° phase. Different electrical signals are derived.

Also in this embodiment, from the results of FIGS. 5 and 6, the difference between the first and second intervals is 0.48λ to 0.525.
It can be seen that it is sufficient to set the range to λ. Also, IDT
The interval JI _1, JI ₂ between (n + 1.22) × λ− (n
+1.33) × λ, where n is an integer of 0 to 4;
By using a combination of (n + 0.72) × λ to (n + 0.83) × λ (where n is an integer of 0 to 4), deterioration of the degree of balance can be suppressed, and a wideband characteristic can be obtained. Can be

Further, in this embodiment, the IDT 61
b, the innermost electrode finger of 61c are wider, whereby the electrode covering ratio in intervals JI _1, JI ₂ between the IDT is 0.63. Therefore, the interval J between IDTs
The propagation loss at I _{1 and} JI ₂ is reduced. Therefore, deterioration of the amplitude balance due to the difference between the first and second intervals is prevented.

Also, the reflector 61 from the IDT 61a at the center is used.
By making the distances P and Q equal to d and 61e,
The asymmetry of the excitation intensity distribution of the standing wave is eliminated, and the deterioration of the degree of balance can be prevented.

(Seventh Embodiment) FIG. 19 shows a seventh embodiment of the present invention.
FIG. 3 is a schematic plan view of the surface acoustic wave filter device according to the example of FIG. In the seventh embodiment, the central first IDT 71a
And floating electrode fingers 72 and 73 are arranged at intervals between the second and third outer IDTs 71b and 71c, respectively. In other respects, the configuration is the same as that of the surface acoustic wave filter device of the sixth embodiment. Also in the present embodiment, each IDT 71a to 71c and the reflectors 71d and 71e are configured similarly to the surface acoustic wave filter device of the sixth embodiment, and thus are similar to the surface acoustic wave filter device of the sixth embodiment. The effect of can be obtained.

Since the floating electrode fingers 72 and 73 are provided, the electrode coverage at the first and second intervals can be increased, and the propagation loss can be reduced. Preferably,
The electrode coverage is at least 5%, more preferably at least 63%.

(Eighth Embodiment) FIG. 20 shows an eighth embodiment of the present invention.
FIG. 5 is a schematic plan view for explaining a surface acoustic wave filter device according to an example of the present invention. First and second surface acoustic wave filter elements 81 and 82 are formed on a piezoelectric substrate (not shown). The first and second surface acoustic wave filter elements 81,
Reference numeral 82 is the same as that of the surface acoustic wave filter device according to the fourth embodiment. The difference is that the first IDT 8 at the center of the first and second surface acoustic wave filter elements 81 and 82 is different.
The first surface acoustic wave resonator 83 is connected between the first and second surface acoustic wave resonators 81 and 82 and the input terminal 4. One terminal-pair surface acoustic wave resonators 84 and 85 are connected between the IDTs 81b, 81c, 82b and 82c and the output terminals 5 and 6, respectively. Note that 81
d, 81e, 82d and 82e indicate reflectors.

The first surface acoustic wave resonator 83 has one IDT 83a and grating-type reflectors (not shown) arranged on both sides of one IDT. Electrode finger intersection width W of IDT 83a of first surface acoustic wave resonator 83
Is 20λ, the logarithm N of the electrode fingers is 80, the wavelength λI of the IDT is 4.20 μm, and the number of electrode fingers of the reflector (not shown) is 120.

The second and third paired surface acoustic wave resonators 84 and 85 connected to the output terminals 5 and 6 have the same configuration as the first surface acoustic wave resonator 83. . In this embodiment, the first to third surface acoustic wave resonators 83 to 83 are used.
85 is connected, as shown in FIG.
As compared with the embodiment, the amount of attenuation outside the pass band can be increased. In FIG. 21, the solid line shows the filter characteristics of the surface acoustic wave filter device of the eighth embodiment, and the broken line shows the filter characteristics of the surface acoustic wave filter device of the fourth embodiment.

(Ninth Embodiment) FIG. 22 is a schematic plan view showing an electrode structure of a surface acoustic wave filter device according to a ninth embodiment. The surface acoustic wave filter device according to the ninth embodiment includes first to third surface acoustic waves on the input side and the output side of the surface acoustic wave filter device according to the sixth embodiment, similarly to the eighth embodiment. This corresponds to a structure in which the resonators 93 to 95 are connected.

The surface acoustic wave filter element 91 has substantially the same configuration as the surface acoustic wave filter element 61 of the sixth embodiment. In addition, the central first IDT 9
1a, the first surface acoustic wave resonator 93 connected between the input terminal 4 and the second and third IDTs 91b and 91c.
The second and third surface acoustic wave resonators 94 and 95 connected between the output terminals 5 and 6 are exactly the same as the surface acoustic wave resonators 83 to 85 used in the eighth embodiment. It is configured.

In this embodiment, as in the eighth embodiment, the first to third surface acoustic wave resonators are provided between the input side and the input terminal of the surface acoustic wave filter element and the surface acoustic wave resonance. Since it is connected between the output side of the amplifier and the output terminal, it is possible to increase the amount of attenuation near the pass band, particularly the amount of attenuation on the high frequency side.

(Tenth Embodiment) FIG. 23 is a schematic plan view showing an electrode structure of a surface acoustic wave filter device according to a tenth embodiment. This embodiment is different from the surface acoustic wave filter device of the eighth embodiment in that the second surface acoustic wave resonator 84
And a fourth surface acoustic wave resonator 101 between the
Are connected to each other. In other words, the fourth surface acoustic wave resonator 101 is connected to the output terminals 5 and 6 in parallel. The fourth surface acoustic wave resonator 101 has one IDT and grating type reflectors (not shown) arranged on both sides of the IDT. The fourth surface acoustic wave resonator 101 has an IDT electrode finger intersection width W of 15
λ, the number of pairs of electrode fingers is 50, and the wavelength λI of the IDT is 4.40.
μm, and the number of electrode fingers of the reflector is 120.

By connecting the fourth surface acoustic wave resonator 101 according to the present embodiment to the surface acoustic wave filter device of the eighth embodiment, the balanced output terminals 5 and 6 have
A ladder-type filter circuit is configured. By locating the attenuation poles of the ladder-type filter circuit on the low band side and the high band side of the pass band of the surface acoustic wave filter, the amount of attenuation can be further increased, and the selectivity can be increased. .

Further, since the surface acoustic wave resonator 101 is connected in a bridging manner between the balanced output terminals 5 and 6, the effects on the balanced terminals 5 and 6 are equal, and the factors that deteriorate the balance are canceled. I do. Therefore, the attenuation outside the pass band can be increased without deteriorating the balance.

In the description of the surface acoustic wave filter devices according to the first to tenth embodiments, only the electrode structure formed on the piezoelectric substrate is shown. By adopting a simple package structure, it can be configured as a chip type surface acoustic wave filter device.

The eleventh embodiment relates to a surface acoustic wave filter device as a component built in such a package. As shown in FIG. 24, a surface acoustic wave filter element according to the present invention is formed by forming predetermined electrodes on a piezoelectric substrate 102. This surface acoustic wave filter element is housed in a package 103 having a concave portion 103a.

In this embodiment, the piezoelectric substrate 102 constituting the surface acoustic wave filter element has a rectangular plate shape, and has a symmetric axis X passing through the center. On the other hand, the package 103 also has a rectangular planar shape and has a symmetry axis Y passing through the center. In the present embodiment, the piezoelectric substrate 102 is set so that the symmetry axis X of the piezoelectric substrate 102 and the symmetry axis Y of the package 103 coincide.
Are fixed in the package 103. Further, although not shown in FIG. 24, the surface acoustic wave filter element and an electrode pad provided on the package 103 are connected by a bonding wire. The electrode pads and the bonding wires are also arranged symmetrically with respect to the symmetry axes X and Y.

As described above, the axis of symmetry X of the piezoelectric substrate 102
And the symmetry axis Y of the package 103, the electrical length and the parasitic capacitance of the wiring on the surface acoustic wave filter connected to each of the balanced output terminals can be equalized, and the degree of balance is deteriorated. Can be suppressed.

Further, by adopting a structure passing through the center of the package and being symmetrical with respect to the axis of symmetry Y, it is possible to equalize the electric length and the parasitic capacitance of the wiring in the package connected to the balanced terminal. Therefore, the deterioration of the degree of equilibrium can be suppressed. Therefore, it is possible to extremely reduce the factors that deteriorate the degree of balance, and as a result, it is possible to provide a surface acoustic wave filter device having an excellent balance and a balance-unbalance conversion function.

Further, as described above, the degree of balance can be further increased by arranging the electrode pads and the wire bonding in line symmetry with respect to the symmetry axes X and Y.

Note that the same effect can be obtained by arranging the bump bonding positions in line symmetry even when the electrical connection is performed by bump bonding instead of wire bonding. In particular, in the case of bump bonding, the degree of balance is better than in the case of wire bonding in which the wire length changes depending on the chip arrangement position.

FIG. 25 is a schematic plan view showing a surface acoustic wave filter in which unbalanced-balanced surface acoustic wave filters having different frequencies are formed on the same piezoelectric substrate as a twelfth embodiment of the present invention. is there. This surface acoustic wave filter 1
Reference numeral 11 denotes the same surface acoustic wave filter device as the surface acoustic wave filter device 1 shown in FIG.
13 and 114 are arranged. In this case, by forming the surface acoustic wave filter device 113 as, for example, a band filter of a 900 MHz band and the surface acoustic wave filter device 114 as a band filter of a 1900 MHz band, as described above, two unbalanced-balanced waves having different frequencies are obtained. The surface acoustic wave filter devices 113 and 114 can be configured using the same piezoelectric substrate 112, and the size of the bandpass filter can be reduced.

In FIG. 25, the connection between the electrode pad on the piezoelectric substrate and the electrode pattern in a package (not shown) or the electrode pattern connected to the ground potential is made by a bonding wire. May be electrically connected to each other.

FIG. 26 is a schematic configuration diagram showing an antenna duplexer in a communication device using the surface acoustic wave filter device 111 shown in FIG. Here, the input terminals of the surface acoustic wave filter devices 113 and 114 are commonly connected to the antenna ANT. And the surface acoustic wave filter device 1
13 and 114 are output terminals Tx on the transmission side, respectively.
And a receiving-side output terminal Rx.

In FIG. 25, filters having different frequencies are formed by using the same piezoelectric substrate 112.
As shown in FIG. 27, the surface acoustic wave filter devices 113 and 114 having different frequencies have different piezoelectric substrates 1 respectively.
12a and 112b may be used. here,
Surface acoustic wave filter devices 113 and 114 configured using different piezoelectric substrates 112a and 112b respectively
It is stored in a package 116.

FIGS. 30 to 32 are bottom views for explaining still another embodiment of the surface acoustic wave filter device according to the present invention. The surface acoustic wave filter device 301 shown in FIG. 30 has the case material 302 shown in the figure. The case member 302 is a plate-like case substrate in the present embodiment, and the surface acoustic wave filter device according to the present invention is mounted on a surface (not shown) by a flip chip bonding method.

On the lower surface 302a of the case member 302,
One external input terminal 303 electrically connected to the surface acoustic wave filter device and electrically connected to the outside
And two external output terminals 304 and 305. In this case, the external input terminal 303 is connected to the unbalanced signal terminal of the surface acoustic wave filter device, and the external output terminal 30 is connected to a pair of balanced signal terminals of the surface acoustic wave filter device.
4,305 are electrically connected. In this embodiment,
For the external input terminal 303, two external output terminals 30
4,305 are arranged substantially line-symmetrically via the axis of symmetry indicated by the broken line in the figure. Thus, by arranging the two external output terminals 304 and 305 substantially symmetrically with respect to the external input terminal 303, the degree of balance can be increased.

In addition, two external output terminals 304 and 30
A ground terminal 306 is arranged between the five, preferably in the center, thereby further increasing the degree of balance. Further, ground terminals 307 and 307 are provided between the external input terminal 303 and the external output terminal 304 and between the external input terminal 303 and the external output terminal 305, preferably at the center.
308 are arranged, whereby it is possible to suppress the direct achievement between the external input / output terminals.

The surface acoustic wave filter device 31 shown in FIG.
Similarly, in FIG. 1, the external output terminals 314 and 315 are arranged substantially line-symmetrically with respect to the external input terminal 313. Therefore, the surface acoustic wave filter device 3 shown in FIG.
As in the case of 01, the degree of equilibrium can be increased. here,
Ground terminals 316 and 317 are arranged between the external input terminal 313 and the external output terminals 314 and 315, thereby suppressing the direct achievement between the input and output terminals.

In FIGS. 30 and 31, plate-like case members 302 and 312 are used, but the shape of the case member is not limited to this, and the case member is formed by a package that seals the surface acoustic wave filter device. It may be configured.

In the surface acoustic wave filter device 321 shown in FIG. 32, the lower surface of the piezoelectric substrate 322 is shown.
A surface acoustic wave filter element is formed on the upper surface side of the piezoelectric substrate 322. On the lower surface of the piezoelectric substrate 322, an external input terminal 323 electrically connected to the surface acoustic wave filter element and used as an unbalanced signal terminal is formed by a conductive film. Further, two external output terminals 324 and 325 used as balanced signal terminals are provided so as to be located substantially line-symmetrically with respect to the external input terminal 323. Also in the surface acoustic wave filter device 321, the ground terminal 3 is provided at the center between the two external output terminals 324 and 325.
26 are provided, which further enhances the degree of equilibrium. Ground terminals 327 and 328 are provided between the external input terminal 323 and the external output terminal 324 and between the external input terminal 323 and the external output terminal 325, respectively.
Are arranged, thereby suppressing direct achievement.

FIG. 33 is a schematic block diagram for explaining a communication device 160 using the surface acoustic wave device according to the present invention. In FIG. 33, a duplexer 162 is connected to an antenna 161. Between the duplexer 162 and the reception-side mixer 163, a surface acoustic wave filter 164 and an amplifier 165 constituting an RF stage are connected.
Further, a surface acoustic wave filter 169 in the IF stage is connected to the mixer 163. Further, an amplifier 16 constituting an RF stage is provided between the duplexer 162 and the mixer 166 on the transmission side.
7 and the surface acoustic wave filter 168 are connected.

As the surface acoustic wave filters 164 and 168 in the communication device 160, a surface acoustic wave device configured according to the present invention can be suitably used.

[0196]

According to the surface acoustic wave filter device of the first invention, the transmission amplitude characteristics within the band of the second and third surface acoustic wave filter elements are substantially the same, and the transmission phase characteristics are substantially the same. At least one IDT of the second surface acoustic wave filter element,
At least one ID of the third surface acoustic wave filter element
T is at least one of the first surface acoustic wave filter elements.
Connected to one IDT, the terminals connected to the first surface acoustic wave filter element are unbalanced terminals,
When the terminal connected to the surface acoustic wave filter element is a balanced terminal, a surface acoustic wave filter device having a balance-unbalance conversion function can be configured. In this case, four surface acoustic wave filter elements are conventionally required, but according to the first invention, the balance-unbalance conversion function is realized by using three surface acoustic wave filter elements. You. Therefore, the size and cost of the surface acoustic wave filter device having the balance-unbalance conversion function can be reduced.

In addition, since the number of surface acoustic wave filter elements can be reduced, the parasitic capacitance can be reduced, and the balance is hardly deteriorated. Therefore, it is easy to increase the bandwidth.

In the surface acoustic wave filter device according to the second invention, the transmission amplitude characteristics in the band of the second and third surface acoustic wave filter elements substantially match, and the transmission phase characteristics are approximately 18
0 °, the second IDT of the first surface acoustic wave filter element is connected to the second surface acoustic wave filter element, and the third IDT of the first surface acoustic wave filter element is IDT of the third surface acoustic wave filter element
Since it is connected to the DT, the terminal connected to the first surface acoustic wave filter element is an unbalanced terminal, and the terminals connected to the second and third surface acoustic wave filter elements are balanced terminals. A surface acoustic wave filter device having a balance-unbalance conversion function can be configured. In this case, while conventionally four surface acoustic wave filter elements were required, according to the second invention, the balance-unbalance conversion function is realized by using three surface acoustic wave filter elements. You. Therefore, the size and cost of the surface acoustic wave filter device having the balance-unbalance conversion function can be reduced.

Further, since the number of surface acoustic wave filter elements can be reduced, the parasitic capacitance can be reduced, and the balance is hardly deteriorated. Therefore, it is easy to increase the bandwidth.

[0200] In the surface acoustic wave filter device according to the second aspect of the present invention, the first interval and the second interval are 0.48λ to 0.48λ.
In the case where the configuration is different by 0.525λ, the amplitude balance can be 1.5 dB or less and the phase balance can be 20 ° or less, and the deterioration of the balance can be reliably prevented. .

The first interval and the second interval are respectively
When Expressions 1 and 2 are satisfied, a sufficient bandwidth can be obtained, and deterioration of the degree of balance can be suppressed.
Further, in the surface acoustic wave filter device according to the second invention, when the first and second intervals are selected so as to satisfy Expressions 3 and 4, even if a frequency change due to a temperature change is considered. , A sufficient bandwidth can be obtained, and the deterioration of the degree of balance can be suppressed.

Further, the first interval is set between 1.72λ and 1.8.
When 3λ and the second interval are in the range from 2.22λ to 2.33λ, it is possible to more reliably suppress the deterioration of the degree of balance and to make the bandwidth sufficiently wide.

The surface acoustic wave filter device according to the second invention
In, LiTaO_ThreeSingle crystal from Y axis around X axis
LiT rotated in the range of 36 to 44 ° in the Z-axis direction
aO _ThreeUsing a substrate, at least one of the first and second intervals
At least one electrode finger is inserted in one interval.
The electrode coverage at the interval where the electrode finger is inserted is 5
If it is 0% or more, leaky waves propagate to the surroundings.
Transport, thereby reducing insertion loss
You. In particular, when the electrode coverage is 63% or more,
The insertion loss can be further reduced.

In the surface acoustic wave filter device according to the second invention, the distance between the first reflector and the second reflector is substantially equal to the distance between the third reflector and the fourth reflector. When equalized, the filter characteristics of the second surface acoustic wave filter element and the third surface acoustic wave filter element become substantially equal, and the deterioration of the degree of balance can be suppressed more reliably.

The surface acoustic wave filter device according to the third aspect of the present invention includes first to third surface acoustic wave filter elements, and the second surface acoustic wave filter element is the second surface acoustic wave filter element of the first surface acoustic wave filter element. And the third surface acoustic wave filter element is connected to the third IDT of the first surface acoustic wave filter element, and the second IDT of the first surface acoustic wave filter element is connected to the third surface acoustic wave filter element. And the phase difference between the input and output of the third IDT is about 180 ° in the pass band.
Since the terminals connected to the first surface acoustic wave filter element are unbalanced terminals and the terminals connected to the second and third surface acoustic wave filter elements are balanced terminals, the balanced-unbalanced conversion is achieved. A surface acoustic wave filter device having a function can be configured. In this case, conventionally, four surface acoustic wave filter elements were required, but according to the third aspect, the use of three surface acoustic wave filter elements realizes a balanced-unbalanced conversion function. You. Therefore, the size and cost of the surface acoustic wave filter device having the balance-unbalance conversion function can be reduced.

Further, since the number of surface acoustic wave filter elements can be reduced, the parasitic capacitance can be reduced, and the balance is hardly deteriorated. Therefore, it is easy to increase the bandwidth.

In the surface acoustic wave filter device according to the third invention, the first and second intervals are. 048λ ~ 0.525
When the difference is only λ, the amplitude balance can be 1.5 dB or less and the phase balance can be 20 ° or less, and the deterioration of the balance can be reliably prevented.

In the surface acoustic wave filter device according to the third aspect of the present invention, when the first and second intervals satisfy Expressions 1 and 2, a sufficient bandwidth can be obtained and the degree of balance can be reduced. Can be suppressed.

In the third aspect, when the first and second intervals satisfy Expressions 3 and 4, a sufficient bandwidth can be obtained even if frequency fluctuation due to temperature change is considered.
In addition, the deterioration of the equilibrium degree can be suppressed.

When the first interval is in the range of 1.72λ to 1.88λ and the second interval is in the range of 2.22λ to 2.33λ, deterioration of the degree of balance is more reliably suppressed. And the bandwidth can be made sufficiently large.

[0211] In the surface acoustic wave filter device according to the third invention, the distance from the center of the first IDT to the first reflector is equal to the distance from the center of the first IDT to the second reflector. In this case, the deterioration of the degree of equilibrium can be suppressed more reliably.

In the surface acoustic wave filter devices according to the first to third aspects of the present invention, the electrode finger crossing width of the IDT constituting the first surface acoustic wave filter element is equal to that of the second surface acoustic wave filter element and the third surface acoustic wave filter element. In the case where the electrode finger crossing width of each IDT constituting the surface acoustic wave filter element is in the range of 1.5 to 3.5 times, the deterioration of the VSWR value in the pass band can be suppressed.

[0213] In the surface acoustic wave filter device according to the fourth aspect of the invention, the transmission characteristics of the second surface acoustic wave filter element in the pass band substantially coincide with the transmission amplitude characteristics of the first surface acoustic wave filter element. The first and second surface acoustic wave filter elements are configured so that transmission phase characteristics are different from the first surface acoustic wave filter element by approximately 180 °, and one terminal of each of the first and second surface acoustic wave filter elements is electrically connected in parallel. The other terminal is electrically connected in series, the terminal connected in parallel constitutes an unbalanced terminal, and the terminal connected in series constitutes a balanced terminal. As in the case of the surface acoustic wave filter device according to the invention, a balanced-unbalanced conversion function is realized. In addition, since it is configured using two surface acoustic wave filter elements, further downsizing and cost reduction can be achieved.

Further, in the surface acoustic wave filter element according to the fourth invention, the first and second intervals are set to 0.48λ to 0.48λ.
If the difference is 0.525λ, the balance of the amplitude is set to 1.5d
B or less, the degree of phase balance can be 20 ° or less,
Deterioration of the degree of balance can be reliably prevented.

In the surface acoustic wave filter device according to the fourth aspect of the present invention, if the first and second intervals satisfy Expressions 1 and 2, a sufficient bandwidth can be obtained and the degree of balance is deteriorated. Can be suppressed.

Further, when the first and second intervals satisfy Expressions 3 and 4, a sufficient bandwidth can be obtained, and even if the frequency fluctuation due to the temperature change is taken into consideration, the deterioration of the degree of balance can be obtained. Can be suppressed.

In the fourth invention, when the first interval is in the range of 1.72λ to 1.88λ and the second interval is in the range of 2.22λ to 2.33λ, the degree of equilibrium is determined. Can be more reliably suppressed, and the bandwidth can be made sufficiently wide.

Also in the fourth invention, the piezoelectric substrate is made of LiT
The aO ₃ single crystal is moved from the Y axis around the X axis in the Z axis direction from 36 to
Using a LiTaO ₃ substrate rotated in a range of 44 °, at least one of the first and second intervals is
When at least one electrode finger is inserted and the electrode coverage at the interval where the electrode finger is inserted is 50% or more, leaky waves are propagated to the surroundings, thereby reducing insertion loss. Can be achieved. In particular, when the electrode coverage is 63% or more, the insertion loss can be further reduced.

In the surface acoustic wave filter device according to the fourth aspect, the distance between the first reflector and the second reflector is substantially equal to the distance between the third reflector and the fourth reflector. When equalized, the filter characteristics of the second surface acoustic wave filter element and the third surface acoustic wave filter element become substantially equal, and the deterioration of the degree of balance can be suppressed more reliably.

[0220] In the surface acoustic wave filter device according to the fourth invention, a terminal connected to the unbalanced side of the first surface acoustic wave filter element and a terminal connected to the unbalanced side of the second surface acoustic wave filter element. When the terminals are connected to each other by an electrode pattern on the piezoelectric substrate, the parasitic capacitance can be reduced, whereby the insertion loss can be further reduced.

A surface acoustic wave filter device according to a fifth aspect of the present invention includes one surface acoustic wave filter element having first to third IDTs, a first space between the first and second IDTs, Since the second interval between the first and third IDTs satisfies Equations 1 and 2, the first IDT constitutes an unbalanced terminal, and the second and third IDTs are connected to balanced terminals. A surface acoustic wave filter device having a balance-unbalance conversion function can be configured. In this case, while conventionally four surface acoustic wave filter elements were required, according to the fifth invention, the balance-unbalance conversion function is realized by using one surface acoustic wave filter element. You. Therefore, the size and cost of the surface acoustic wave filter device having the balance-unbalance conversion function can be reduced.

Further, since the number of surface acoustic wave filter elements can be reduced, the parasitic capacitance can be reduced, and the balance is hardly deteriorated. Therefore, it is easy to increase the bandwidth.

In the fifth aspect of the present invention, the first and the second
Is within the above-mentioned specific range, a sufficient bandwidth can be realized and the degree of balance can be improved as in the first aspect.

[0224] In the surface acoustic wave filter device according to the fifth aspect of the invention, at least one floating electrode finger is inserted between the first and second intervals, and the electrode coverage in the region is set to 50% or more. In this case, the insertion loss can be reduced.

Particularly, when the electrode coverage is 63% or more, the insertion loss can be further reduced.
In the present invention, when a surface acoustic wave resonator is connected in series to the unbalanced terminal side, the attenuation outside the pass band can be improved.

Similarly, by connecting a surface acoustic wave resonator to each terminal on the balanced terminal side in series, the out-of-band attenuation can be improved. When a surface acoustic wave filter having a ladder-type circuit configuration cascaded on the balanced terminal side is provided, the attenuation pole of the ladder-type surface acoustic wave filter is arranged on the low band side and the high band side of the pass band. , Attenuation and selectivity can be further increased. Furthermore, with the surface acoustic wave resonator connected in parallel between the balanced terminals,
The effects of the balanced terminals can be made equal, and the attenuation outside the passband can be increased without deteriorating the balance.

In a surface acoustic wave device according to the present invention, in a structure in which a chip having a surface acoustic wave filter element is housed in a package, at least one of an electrode pattern, a package, and a conductive portion formed on a piezoelectric substrate is provided. In the case of having a substantially line-symmetric structure, it is possible to suppress the deterioration of the degree of equilibrium.

In particular, when at least two of the electrode pattern, the package, and the conductive portion are substantially line-symmetric with respect to the same axis of symmetry, deterioration of the degree of balance can be further suppressed.

Further, the surface acoustic wave filter device according to the present invention includes a case material on which a chip having a surface acoustic wave filter element formed on a piezoelectric substrate is mounted by flip chip bonding. Two external input terminals or external output terminals and two external output terminals or external input terminals are provided, and two external output terminals or external input terminals are substantially connected to one external input terminal or external output terminal. When symmetrically arranged or electrically symmetrically arranged, the degree of balance can be further increased.

Further, in the surface acoustic wave filter device according to the present invention, when at least one ground terminal is disposed between the external input terminal and the external output terminal, the amount of direct achievement between the input and output terminals is reduced. Suppression can be achieved. Further, when at least one ground terminal is disposed between the two external output terminals or the external input terminals, the degree of balance can be increased by that.

Further, the surface acoustic wave filter device according to the present invention can be used for a duplexer and a communication device having the duplexer as described above, and the size of the duplexer and the communication device can be reduced.

[Brief description of the drawings]

FIG. 1 is a schematic plan view showing an electrode structure of a surface acoustic wave filter device according to a first embodiment.

FIG. 2 is a diagram illustrating filter characteristics of the surface acoustic wave filter device according to the first embodiment and a surface acoustic wave filter device according to a conventional example.

FIG. 3 is a diagram illustrating the V of the unbalanced terminal side in the surface acoustic wave filter device of the first embodiment and the conventional surface acoustic wave filter device.
The figure which shows SWR characteristic.

FIG. 4 is a diagram showing VSWR characteristics on the balanced terminal side of the first embodiment and the conventional surface acoustic wave filter device.

FIG. 5 is a diagram showing the relationship between the interval between adjacent IDTs and the degree of amplitude balance.

FIG. 6 is a diagram showing a relationship between an interval between adjacent IDTs and a degree of phase balance.

FIG. 7 is a diagram showing a relationship between an interval between adjacent IDTs and a bandwidth.

FIG. 8 is a diagram showing a relationship between an interval between adjacent IDTs and an insertion loss in a band.

FIG. 9 is a diagram showing a relationship between an interval between adjacent IDTs and an amplitude balance.

FIG. 10 is a diagram showing a relationship between an interval between adjacent IDTs and a degree of phase balance.

FIG. 11 is a diagram showing a relationship between an electrode finger cross width ratio and a bandwidth having an attenuation of 4.0 dB.

FIG. 12 is a diagram showing a relationship between an electrode finger cross width ratio and VSWR.

FIG. 13 is a schematic plan view showing an electrode structure of a surface acoustic wave filter device according to a second embodiment of the present invention.

FIG. 14 is a schematic plan view showing an electrode structure of a surface acoustic wave filter device according to a third embodiment of the present invention.

FIG. 15 is a schematic plan view showing an electrode structure of a surface acoustic wave filter device according to a fourth embodiment of the present invention.

FIG. 16 is a diagram illustrating filter characteristics of a surface acoustic wave filter device according to a fourth embodiment.

FIG. 17 is a schematic plan view showing an electrode structure of a surface acoustic wave filter device according to a fifth embodiment of the present invention.

FIG. 18 is a schematic plan view showing an electrode structure of a surface acoustic wave filter device according to a sixth embodiment of the present invention.

FIG. 19 is a schematic plan view showing an electrode structure of a surface acoustic wave filter device according to a seventh embodiment of the present invention.

FIG. 20 is a schematic plan view showing an electrode structure of a surface acoustic wave filter device according to an eighth embodiment of the present invention.

FIG. 21 is a diagram showing filter characteristics of the surface acoustic wave filter devices according to the fourth embodiment and the eighth embodiment.

FIG. 22 is a schematic plan view showing an electrode structure of a surface acoustic wave filter device according to a ninth embodiment of the present invention.

FIG. 23 is a schematic plan view showing an electrode structure of a surface acoustic wave filter device according to a tenth embodiment of the present invention.

FIG. 24 is an exploded perspective view for explaining a surface acoustic wave filter device according to an eleventh embodiment of the present invention.

FIG. 25 is a schematic plan view for explaining a surface acoustic wave filter device according to a twelfth embodiment of the present invention.

FIG. 26 is a schematic configuration diagram for describing an antenna duplexer configured using the surface acoustic wave filter device according to the twelfth embodiment.

FIG. 27 is a schematic configuration diagram for explaining a surface acoustic wave filter device according to a modification of the twelfth embodiment.

FIG. 28 is a schematic plan view for explaining an example of a conventional surface acoustic wave filter device.

FIG. 29 is a schematic plan view showing another example of the conventional surface acoustic wave filter device.

FIG. 30 is a view for explaining another embodiment of the surface acoustic wave filter device according to the present invention, and is a bottom view of a case member.

FIG. 31 is a view for explaining still another embodiment of the surface acoustic wave filter device of the present invention, and is a bottom view of a case material.

FIG. 32 is a view for explaining another embodiment of the surface acoustic wave filter device according to the present invention, and is a bottom view of the piezoelectric substrate.

FIG. 33 is a schematic block diagram for explaining a communication device using the surface acoustic wave device according to the present invention.

[Explanation of symbols]

 1-3 first-third surface acoustic wave filter elements 1a, 2a, 3a first IDT 1b, 2b, 3b second IDT 1c, 2c, 3c third IDT 1d, 1e-3d , 3e ... reflector

Claims (44)

[Claims] 1. A piezoelectric substrate comprising: a piezoelectric substrate; and first to third surface acoustic wave filter elements formed on the piezoelectric substrate, wherein each of the surface acoustic wave filter elements is formed along a propagation direction of the surface acoustic wave. And the second and third surface acoustic wave filter elements are configured such that transmission amplitude characteristics in a band are substantially the same and transmission phase characteristics are different by approximately 180 °. At least one IDT of the second surface acoustic wave filter element and at least one IDT of the third surface acoustic wave filter element are connected to at least one IDT of the first surface acoustic wave filter element, respectively. A surface acoustic wave filter device. 2. A piezoelectric device comprising: a piezoelectric substrate; and first to third surface acoustic wave filter elements formed on the piezoelectric substrate, wherein the first surface acoustic wave filter element extends along a surface acoustic wave propagation direction. A first IDT formed, and second and third IDTs disposed on both sides of the first IDT in a surface wave propagation direction, wherein the second and third surface acoustic wave filter elements are provided with A plurality of IDTs arranged along the propagation direction of the surface acoustic wave, wherein the transmission amplitude characteristics in the bands of the second and third surface acoustic wave filter elements substantially match, and the transmission phase characteristics are approximately 180
The second IDT of the first surface acoustic wave filter element is connected to the second surface acoustic wave filter element, and the third IDT of the first surface acoustic wave filter element Is connected to the IDT of the third surface acoustic wave filter element. 3. The first to third surface acoustic wave filter elements each include one IDT and two IDTs disposed on both sides of the IDT in the surface wave propagation direction. As compared with the first space between the IDT connected to the first surface acoustic wave filter element in the surface acoustic wave filter element and the IDT adjacent to the IDT, the first space in the third surface acoustic wave filter element The second interval between the IDT connected to the surface acoustic wave filter element and the adjacent IDT is different from 0.48λ to 0.525λ when the wavelength of the surface acoustic wave is λ. The surface acoustic wave filter device according to claim 2, wherein: 4. The method according to claim 1, wherein the first interval is: And the second interval is: The surface acoustic wave filter device according to claim 3, wherein 5. The method according to claim 1, wherein the first interval is: And the second interval is: The surface acoustic wave filter device according to claim 4, wherein 6. The first interval is 1.72λ to 1.8.
3λ, and the second interval is 2.22λ to 2.2.
The surface acoustic wave filter device according to claim 5, wherein the surface acoustic wave filter device is in a range of 33λ. Wherein said piezoelectric substrate is a LiTaO ₃ substrate LiTaO ₃ single crystal is rotated within a range of the Z-axis direction to 36-44 ° from the Y axis about the X axis, and said first distance The surface acoustic wave filter device according to any one of claims 3 to 6, wherein the electrode coverage in at least one of the second intervals is 50% or more. 8. The electrode coverage is 63% or more.
A surface acoustic wave filter device according to claim 7. 9. The first surface acoustic wave filter element further comprises first and second reflectors provided on both sides of a region in which a plurality of IDTs are provided in a surface wave propagation direction, wherein the third and fourth reflectors are provided. Multiple IDs in a surface acoustic wave filter element
The third and the third are located on both sides of the region where T is provided in the surface wave propagation direction.
A fourth reflector is provided, and a distance between the first reflector and the second reflector is substantially equal to a distance between the third reflector and the fourth reflector. Item 9. A surface acoustic wave filter device according to any one of Items 3 to 8. 10. A piezoelectric substrate comprising: a piezoelectric substrate; and first to third surface acoustic wave filter elements formed on the piezoelectric substrate, wherein the first surface acoustic wave filter element is a first IDT.
And second and third IDTs disposed on both sides of the first IDT in the direction of propagation of the surface acoustic wave. The second surface acoustic wave filter element is a second IDT of the first surface acoustic wave filter element. A third surface acoustic wave filter element is connected to a third IDT of the first surface acoustic wave filter element; a second IDT of the first surface acoustic wave filter element; Third
Surface acoustic wave filter device, wherein a phase difference between an input and an output of the IDT differs by about 180 ° in a pass band. 11. A first interval between first and second IDTs of the first surface acoustic wave filter element, and a first IDT and a third IDT of the first surface acoustic wave filter element. Is between 0.48λ and 0.525λ, where λ is the wavelength of the surface acoustic wave filter.
And the phase difference between the input end of the first surface acoustic wave filter element and the input end in the pass band is about 180 °.
The surface acoustic wave filter device according to claim 10, wherein the surface acoustic wave filter device is different. 12. The method according to claim 1, wherein the first interval is: And the second interval is: The surface acoustic wave filter device according to claim 11, wherein: 13. The method according to claim 12, wherein the first interval is: And the second interval is: The surface acoustic wave filter device according to claim 12, wherein: 14. The method according to claim 1, wherein the first interval is from 1.72λ to 1.72.
88λ, and the second interval is 2.22λ-
14. The method according to claim 13, wherein the range is 2.33λ.
4. The surface acoustic wave filter device according to item 1. 15. The piezoelectric substrate is a LiTaO ₃ substrate LiTaO ₃ single crystal is rotated within a range of the Z-axis direction to 36-44 ° from the Y axis about the X axis, the first surface acoustic The surface acoustic wave filter device according to any one of claims 11 to 14, wherein an electrode coverage of at least one of the first interval and the second interval in the wave filter element is 50% or more. 16. The surface acoustic wave filter device according to claim 15, wherein the electrode coverage is 63% or more. 17. The first surface acoustic wave filter element further includes first and second reflectors disposed on both sides of a region where a plurality of IDTs are provided in a surface wave propagation direction. The distance from the IDT to the first reflector and the first I
The surface acoustic wave filter device according to any one of claims 10 to 16, wherein a distance from the DT to the second reflector is substantially equal. 18. The electrode finger crossing width of the IDT forming the first surface acoustic wave filter element is equal to the width of each of the IDTs forming the second surface acoustic wave filter element and the third surface acoustic wave filter element. The surface acoustic wave filter device according to any one of claims 1 to 17, wherein the surface acoustic wave filter device is in a range of 1.5 to 3.5 times the electrode finger intersection width of the IDT. 19. A piezoelectric substrate comprising: a piezoelectric substrate; and first and second surface acoustic wave filter elements formed on the piezoelectric substrate, wherein the first surface acoustic wave filter element extends along a surface acoustic wave propagation direction. A plurality of IDTs arranged, wherein the second surface acoustic wave filter element has a plurality of IDTs arranged along the surface acoustic wave propagation direction, and a pass band of the second surface acoustic wave filter element The transmission amplitude characteristic of the first surface acoustic wave filter element substantially coincides with the transmission amplitude characteristic of the first surface acoustic wave filter element, and the transmission phase characteristic is different from that of the first surface acoustic wave filter element by about 180 °. One terminal of each of the first and second surface acoustic wave filter elements is electrically connected in parallel, the other terminal is electrically connected in series, and the terminal connected in parallel is not connected. Balanced terminals, connected in series Serial terminal constitute a balanced terminal, the surface acoustic wave filter device. 20. The first and second surface acoustic wave filter elements each having three IDTs, an IDT disposed at the center of the first surface acoustic wave filter element, and disposed on both sides. Compared to the first distance between the IDT and the IDT, the second distance between the centrally located IDT and the IDTs disposed on both sides of the second surface acoustic wave filter element is larger than the first distance between the IDTs. When the wavelength is λ, 0.48λ
The surface acoustic wave filter device according to claim 19, wherein the surface acoustic wave filter device is different from the surface acoustic wave filter by 0.525? 21. The method according to claim 21, wherein the first interval is: And the second interval is: The surface acoustic wave filter device according to claim 20, wherein: 22. The method according to claim 19, wherein the first interval is: And the second interval is: The surface acoustic wave filter device according to claim 21, wherein: 23. The method according to claim 23, wherein the first interval is 1.72λ to 1.72.
88λ, and the second interval is 2.22λ-
23. The range of 2.33.lambda.
4. The surface acoustic wave filter device according to item 1. 24. The piezoelectric substrate according to claim 1, wherein the LiTaO ₃ single crystal is a Y-cut LiTaO that is rotated by 36 to 44 ° from the Y axis to the Z axis in a range of 36 to 44 ° about the X axis.
_The surface acoustic wave filter device according to any one of claims 20 to 23, wherein the surface acoustic wave filter device is a _three- substrate, and has an electrode coverage of 50% or more in at least one of the first interval and the second interval. 25. The surface acoustic wave filter device according to claim 24, wherein the electrode coverage is 63% or more. 26. First and second IDTs of the first surface acoustic wave filter element which are arranged on both sides in a surface wave propagation direction of the plurality of IDTs.
A second reflector; and a plurality of IDs in the second surface acoustic wave filter element.
The third and the third are located on both sides of the region where T is provided in the surface wave propagation direction.
A fourth reflector is provided, and a distance between the first reflector and the second reflector is substantially equal to a distance between the third reflector and the fourth reflector. Item 30. The surface acoustic wave filter device according to any one of Items 19 to 25. 27. A terminal connected to the unbalanced side of the first surface acoustic wave filter element and a terminal connected to the unbalanced side of the second surface acoustic wave filter element are electrodes on the piezoelectric substrate. The surface acoustic wave filter device according to any one of claims 19 to 26, wherein the surface acoustic wave filter device is connected by a pattern. 28. A surface acoustic wave filter element formed on a piezoelectric substrate, and having a first IDT and second and third IDTs disposed on both sides of the first IDT. And a second interval between the first IDT and the third IDT is smaller than a first interval between the first IDT and the second IDT. When the wavelength is λ, 0.48λ
０．５0.525λ, where the first interval is And the second interval is: And the first IDT is connected to the unbalanced terminal,
A surface acoustic wave filter device wherein a third IDT is connected to a balanced terminal. 29. The method according to claim 29, wherein the first interval is: And the second interval is: The surface acoustic wave filter device according to claim 28, wherein 30. The method according to claim 30, wherein the first interval is 1.72λ to 1.72.
83λ, and the second interval is 2.22λ to 2.3.
29. The surface acoustic wave filter device according to claim 28, which has a wavelength of 3λ. 31. The elastic surface according to claim 28, wherein an electrode coverage in at least one of the first and second intervals is 50% or more. Wave filter device. 32. The surface acoustic wave filter device according to claim 31, wherein the electrode coverage is 63% or more. 33. First and second reflectors are disposed outside the second and third IDTs, respectively, and a distance from the first IDT to the first reflector and a first and second reflectors are arranged. 33. The surface acoustic wave filter device according to claim 28, wherein the distance from the IDT to the second reflector is substantially equal. 34. The surface acoustic wave filter device according to claim 19, further comprising a series resonator connected to the unbalanced terminal side. 35. The apparatus according to claim 1, further comprising a surface acoustic wave resonator connected in series to each terminal on the balanced terminal side.
The surface acoustic wave filter device according to any one of 9 to 34. 36. The surface acoustic wave filter device according to claim 1, further comprising a ladder type surface acoustic wave filter cascade-connected to the balanced terminal side. 37. The semiconductor device according to claim 37, further comprising an electrode pattern formed on the piezoelectric substrate and electrically connected to the outside, wherein the chip on which the surface acoustic wave filter element and the electrode pattern are formed is formed on the piezoelectric substrate. A case material to be mounted, further comprising: a conductive portion for electrically connecting the electrode pattern on the chip with the electrode pattern and the package; the electrode pattern formed on the piezoelectric substrate, the package and the conductive portion. The surface acoustic wave filter device according to any one of claims 1 to 36, wherein at least one has a substantially line-symmetric structure. 38. The surface acoustic wave filter device according to claim 37, wherein at least two of the electrode pattern, the package, and the conductive portion have a structure substantially line-symmetric with respect to the same axis of symmetry. 39. A case material on which a chip on which the surface acoustic wave filter element is formed on the piezoelectric substrate is mounted by flip chip bonding, wherein one external input terminal or one external output terminal is provided on the case material. And two external output terminals or external input terminals are provided, and the two external output terminals or external input terminals are disposed substantially symmetrically with respect to one external input terminal or external output terminal. The surface acoustic wave filter device according to any one of claims 1 to 36. 40. A case material on which a chip on which the surface acoustic wave filter element is formed on the piezoelectric substrate is mounted by flip chip bonding, wherein one external input terminal or one external output terminal is provided on the case material. And two external output terminals or two external input terminals are provided. The two external output terminals or the external input terminals are arranged substantially symmetrically with respect to one external input terminal or the external output terminal. The surface acoustic wave filter device according to any one of claims 1 to 36. 41. The surface acoustic wave filter device according to claim 39, wherein at least one or more ground terminals are arranged between the external input terminal and the external output terminal. 42. The surface acoustic wave filter device according to claim 39, further comprising at least one ground terminal disposed between the two external output terminals or between the external input terminals. 43. A duplexer using the surface acoustic wave filter according to claim 1. Description: 44. A communication device using the surface acoustic wave filter device according to claim 1 or the duplexer according to claim 43.