JP3180055B2 - Surface acoustic wave filter and multi-stage surface acoustic wave filter - Google Patents

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 and a multistage surface acoustic wave filter which can be used, for example, for a high-frequency circuit in a radio communication device.

[0002]

2. Description of the Related Art An electromechanical functional component using a surface acoustic wave (SAW) has a property that the sound speed of a wave is several km / s and the energy of the wave is concentrated on the surface of a propagation medium. With the development of interdigital transducer (IDT electrode) electrodes and the development of thin film preparation technology and surface processing technology that enabled its deformation and development, attention has been paid to the trend toward higher densification.
It has been put to practical use in band filters for television receivers, etc.
At present, it is widely used as a filter in the RF and IF stages of a wireless communication device transmission / reception circuit.

In recent years, with the digitization of mobile communication devices, the development of digital mobile phones, digital cordless phones, and the like has been strongly advanced. Since the communication system used for these devices has information on the amplitude and phase of the signal, the filter used in the IF stage is required to have flat amplitude characteristics and group delay deviation characteristics. Also,
Since a characteristic excellent in selectivity for distinguishing a signal of an adjacent channel from a desired signal is required, a sharp cutoff characteristic having a narrow transition bandwidth is also a necessary condition. Also recently, IF
Balanced input / output of IC elements before and after the filter is progressing, and IF
A balanced input / output type filter is also required.

Conventionally, as a surface acoustic wave filter suitable for the IF stage, a transversal type surface acoustic wave filter,
Also, two types of mode-coupled surface acoustic wave filters of a longitudinal mode coupling type and a transverse mode coupling type are known. Although the transversal surface acoustic wave filter has excellent group delay deviation characteristics, it has a large insertion loss, poor blocking characteristics, and a large element size. On the other hand, the mode-coupled surface acoustic wave filter exhibits a sharp cutoff characteristic, has a small insertion loss,
Although the element size is small, the group delay deviation characteristic is inferior to that of the transversal surface acoustic wave filter. Further, the longitudinal mode surface acoustic wave filter is characterized in that a relatively large spurious component exists on the high frequency side near the pass band, and the transverse mode surface acoustic wave filter has a very narrow band pass characteristic. . Due to the above characteristics, a transverse mode coupling type surface acoustic wave filter having a small size and excellent cutoff characteristics has been widely used as an IF filter for a mobile communication device.

Hereinafter, a conventional transverse mode coupled surface acoustic wave filter will be described.

FIG. 24 is a configuration diagram showing a transverse mode coupled resonator type surface acoustic wave filter according to the prior art. In FIG. 24, reference numeral 241 denotes a single-crystal piezoelectric substrate. By forming an electrode pattern on the piezoelectric substrate 241, surface acoustic waves can be excited. Reference numeral 242a denotes an IDT electrode formed on the piezoelectric substrate 241, and an energy trap type surface acoustic wave resonator is formed by disposing reflector electrodes 242b and 242c on both sides of the IDT electrode. A similar surface acoustic wave resonator is formed on the piezoelectric substrate 241 by the IDT electrode 243a and the reflector electrodes 243b and 243c. These two resonators are arranged close to each other, and acoustic coupling occurs between them to form a surface acoustic wave filter.

The surface acoustic wave filter configured as described above has two types of excitation on the piezoelectric substrate depending on the width of the electrode finger crossing the IDT electrode and the distance between the two surface acoustic wave resonators arranged close to each other. The mode frequency of the surface acoustic wave is determined,
The pass bandwidth of the filter is determined.

[0008]

However, in the surface acoustic wave filter configured as described above, the achievable bandwidth is very narrow, and the specific bandwidth of the realized filter (normally determined by the center frequency of the filter). Bandwidth) is at most about 0.1%. In order to cope with recent digitization, it is required to widen the bandpass characteristic of the filter and widen the flat band of the group delay deviation characteristic.

Recently, the balance of input and output of IC elements in the stage before and after the IF filter has been advanced, and therefore,
There is also a strong demand for balanced input / output filters. However, as shown in FIG. 24, in the conventional surface acoustic wave filter, the IDT electrodes 242a,
Since one side of the electrode finger 43a is grounded, there is a problem that it cannot be a balanced input / output type.

Further, there is a demand for impedance matching between the IF filter and the IC elements before and after the IF filter, and the input / output impedance of the conventional filter is the number of pairs of electrode fingers included in the IDT electrode, which is closely related to the filter characteristics. Therefore, it is difficult to obtain a desired impedance value at the same time as obtaining a desired filter characteristic.

The present invention solves the above-mentioned problems in the prior art. (1) It is possible to realize a balanced input / output configuration, improve the balance of the balanced type input / output terminals, and reduce insertion loss. (2) To provide a surface acoustic wave filter having a desired input / output impedance, which can achieve a broader passband and flatten phase and amplitude characteristics.

[0012]

In order to achieve the above object, the present invention according to claim 1 comprises first and second elastic members having reflector electrodes on both sides of an IDT electrode as an interdigital transducer electrode. A surface acoustic wave filter on a piezoelectric substrate, wherein the surface acoustic wave resonators are arranged close to each other and acoustically coupled at positions where propagation directions of the respective surface acoustic waves are parallel to each other, wherein the first surface acoustic wave resonator First
And the inner bus bar electrode included in the second IDT electrode of the second surface acoustic wave resonator is electrically separated from each other;
The first IDT electrode is connected to a balanced input terminal, the second IDT electrode is connected to a balanced output terminal, and one terminal of the balanced input terminal is connected to the first input terminal. At least two of the busbar electrodes inside the IDT electrode
And one of the balanced output terminals is connected to at least two of the bus bar electrodes inside the second IDT electrode. is directly or indirectly drawn-out lead electrode electrically connected to balanced operation, the
An extraction electrode is provided between the IDT electrode and the reflector electrode.
This is a surface acoustic wave filter formed in the gap .

With this configuration, for example, a basic electrode pattern of a surface acoustic wave filter having balanced input / output terminals having low insertion loss and good balance can be obtained.

According to a twenty-second aspect of the present invention, the first and third surface acoustic wave resonators having reflector electrodes on both sides of an IDT electrode as an interdigital transducer electrode are respectively provided on a piezoelectric substrate. Are formed at positions where the propagation directions of the surface acoustic waves are parallel to each other, and a plurality of stripline electrodes are provided between the first and third surface acoustic wave resonators. A second surface acoustic wave resonator is disposed in parallel with the surface acoustic wave resonator at the same electrode period, and has a periodic structure electrode row in which the plurality of strip line electrodes are connected to each other by a bus bar electrode. The first and third surface acoustic wave resonators and the second surface acoustic wave resonator are disposed close to each other and acoustically coupled, and an adjacent bus bar electrode between the surface acoustic wave resonators is electrically connected. A surface acoustic wave filter in which the periodic structure electrodes of the second surface acoustic wave resonator are all grounded, and wherein the IDTs constituting the first and third surface acoustic wave resonators are provided. Assuming that the electrode finger intersection width of the electrode is W1 and the strip line length of the periodic structure electrode row constituting the second surface acoustic wave resonator is W2, the relative dimension of W1 and W2 is 1 <W2 // W1 ≦ 1.
3 is a surface acoustic wave filter set to 3 .

According to this configuration, the intervals between the three resonance frequencies are equalized, and when the input and output are matched, the ripple in the pass band is reduced, and excellent pass characteristics are obtained. As a result, a surface acoustic wave filter having a wide band and flat pass characteristics and a steep cutoff characteristic can be obtained.

According to a twenty-eighth aspect of the present invention, a surface acoustic wave resonator having reflector electrodes on both sides of an IDT electrode as an interdigital transducer electrode is provided so that the propagation directions of the respective surface acoustic waves are parallel to each other. A surface acoustic wave filter on a piezoelectric substrate, at least two of which are acoustically coupled in close proximity to at least one of a plurality of electrode fingers included in at least one of the IDT electrodes. The plurality of electrode fingers are surface acoustic wave filters that are connected in such a way that the fingers are in an opposite phase relationship and their charges do not cancel each other.

With this configuration, for example, a surface acoustic wave filter having a desired input / output impedance can be obtained.

As described above, according to the present invention, for example, the insertion loss is further reduced as compared with the related art, the degree of balance at the balanced input / output terminal is improved, or the flatness of the filter passing characteristic is improved. An out-of-band attenuation characteristic can be realized, or a compact surface acoustic wave filter having a desired input / output impedance can be provided.

[0019]

Embodiments of the present invention will be described below with reference to the drawings.

(Embodiment 1) FIG. 1 is an electrode pattern configuration diagram showing a first embodiment of a surface acoustic wave filter according to the present invention.

A surface acoustic wave can be excited by forming a strip line electrode pattern having a periodic structure on the single crystal piezoelectric substrate 11 shown in FIG. On the piezoelectric substrate 11, the IDT electrode 12a and the reflector electrode 1
An energy trap type first surface acoustic wave resonator constituted by 2b and 12c is formed. Also,
On the piezoelectric substrate 11, a second surface acoustic wave resonator including an IDT electrode 13a and reflector electrodes 13b and 13c is formed. These two surface acoustic wave resonators are arranged close to each other, and acoustic coupling occurs between them to form a surface acoustic wave filter.

The first embodiment of the present invention shown in FIG.
A significant difference in the electrode pattern configuration from the surface acoustic wave filter of the prior art shown in FIG. 4 is that the bus bar electrode 244 common to the two resonators arranged close to each other in the conventional example of FIG.
However, in the embodiment of the present invention shown in FIG. 1, the first bus bar 14 and the second bus bar 15 located inside the IDT electrode portion are electrically separated. The first bus bar 14 belongs to a first surface acoustic wave resonator, and the second bus bar 15 belongs to a second surface acoustic wave resonator. With this busbar separation configuration, the first and second surface acoustic wave resonators can have completely electrically independent input and output stages. That is, the balanced input stage of the first surface acoustic wave resonator is constituted by an IDT electrode 12a composed of an electrode finger formed by being connected by the first bus bar electrode 14, and an electrode finger paired with the electrode finger. Is done. Similarly, the second
The balanced output stage of the surface acoustic wave resonator described above is composed of an IDT electrode 13a composed of an electrode finger formed by being connected by the second bus bar electrode 15, and an electrode finger paired with the electrode finger. Here, the first IDT electrode of the present invention is an IDT electrode.
Corresponds to electrode 12a. Further, the second IDT electrode of the present invention corresponds to the IDT electrode 13a.

The connection of the signal line to the balanced circuit thus configured is made between the first bus bar electrode 14 and the third bus bar electrode 14a which is paired with the third bus bar electrode and is located outside the IDT electrode. The connection may be made so as to apply an input signal, and the connection may be made so as to take out an output signal between the second bus bar electrode 15 and the fourth bus bar electrode 15a located outside the IDT electrode paired with the second bus bar electrode. With this, the purpose of the input / output terminal balancing has been achieved, but from the viewpoint of insertion loss, the above connection was about 3.2 dB.

For one of the above-mentioned balanced input terminals, a connection line is drawn out from one place of the first bus bar electrode 14, and for one of the balanced output terminals, the connection line is connected to the second bus bar electrode 14. The case where the connection line is extended from one location of the bus bar electrode 15 has been described. On the other hand, the first and second bus bar electrodes 14 and 15
The case of a configuration in which connection lines are drawn from the two locations will be described.

This insertion loss is caused by the first bus bar electrode 14.
From the two locations (lead electrode fingers 16a, 16b)
To form one terminal on the input side, and connect the connection lines (lead electrode fingers 17a, 17a) from two places of the second bus bar electrode 15.
b) to make one terminal on the output side,
At the same time as the improvement of the degree of balance in the balanced input / output terminals was realized, the difference in loss occurring in each terminal was reduced, and the above-described insertion loss was significantly reduced to about 2.8 dB. This is an important value in a small portable communication device that has a problem of minute loss and the degree of balance at the balanced input / output terminal. That is, in FIG.
Outer electrode fingers 16a and 16b are formed from both ends of the bus bar electrode 14 in the gap between the IDT electrode 12a and the reflector electrodes 12b and 12c, and the ends of these electrode fingers are connected as shown in the figure. The above effect can be obtained. Extraction electrode fingers 17 at both ends of second bus bar electrode 15
a and 17b exhibit the same effect. The extraction electrode finger 1
Reference numerals 6a and 16b denote electrode fingers connected to both ends of the first bus bar electrode 14 and having the same length as the other electrode fingers, and a short lead connected to the tips of both electrode fingers. It can be seen that it is composed of electrodes. or,
The same applies to the extraction electrode fingers 17a and 17b.

FIG. 2 shows an example of a variation of the first embodiment of the present invention shown in FIG. The parts performing the same functions as those in FIG. 1 are denoted by the same reference numerals, and description thereof will be omitted.

A wiring pattern 21 connecting between the extraction electrode fingers 16a and 16b is formed on the piezoelectric substrate 11 and has a line width wider than the resonator electrode width. A part thereof is further expanded as shown in FIG. 2 to connect one of the connection lands 21 for connection between the balanced input terminal and the external wiring body 25a.
a is formed.

The wiring pattern 22 connecting between the extraction electrode fingers 17a and 17b is formed on the piezoelectric substrate 11 and has a line width wider than the resonator electrode width. A part thereof is further expanded to form one connection land 22a for connection between the balanced output terminal and the external wiring body 26a, as shown in FIG.

The bus bar electrode 14a is extended outward, and is used for connection between the balanced input terminal and the external wiring body 25b.
The other connection land 23 is formed. The bus bar electrode 15a is also extended outward, and forms the other connection land 24 for connection between the balanced output terminal and the external wiring body 26b.

The above configuration ensures the characteristics of low insertion loss and good balance of the surface acoustic wave filter having the above-mentioned low insertion loss balanced type input / output terminal, and is effective for stabilizing the filter characteristics.

With reference to FIGS. 1 and 2, a one-stage surface acoustic wave filter has been described as an example. Such a surface acoustic wave filter can be used in a multi-stage configuration.

FIG. 3 shows an example of the same piezoelectric substrate 3.
When a plurality of surface acoustic wave filters are cascaded on 1 to form a multi-stage connected surface acoustic wave filter, the insertion loss can be slightly increased, but the characteristics of the stop band and the transition region can be greatly improved. The two-stage cascade filter in FIG. 3 includes the IDT electrode 12a and the reflector electrode 12b described in FIG.
A first surface acoustic wave resonator composed of
A surface acoustic wave filter 32 in which an electrode 13a and a second surface acoustic wave resonator composed of reflector electrodes 13b and 13c are disposed close to each other, and a surface acoustic wave filter 33 having the same configuration as the surface acoustic wave filter 33 are placed on a piezoelectric substrate 31. And both are connected by a connection line.

In FIG. 3, the extraction electrodes 17a and 17b on the output side of the surface acoustic wave filter 32 of the first stage are connected to the extraction electrode 16 on the input side of the surface acoustic wave filter 33 of the next stage.
a and 16b are connected by connection lines 39a and 39b, respectively. The busbar electrode 15a of the IDT electrode, which is another output of the first stage, is connected to the IDT electrode 14a, which is another input of the next stage, by a connection line 40.

As described above, even between the filter stages, the ID
By connecting one of the T electrodes at two places 39a and 39b, it is possible to reduce the increase in insertion loss when cascading in multiple stages and to improve the degree of balance of the balanced input / output terminals.

The connections on the input and output sides of the multi-stage filter shown in FIG. 3 are the same as those in FIG. 1 and exhibit the same functions and effects.

FIG. 4 shows the connection between the stages and the input / output wiring on the substrate 41.
An example performed by using the wiring pattern formed above will be described.

On the piezoelectric substrate 41, a first surface acoustic wave filter 42 and a second surface acoustic wave filter 43 having the same configuration as the surface acoustic wave filters shown in FIGS. 1, 2 and 3 are provided. Is formed.

The extraction electrodes 17a and 17b on the output side of the first surface acoustic wave filter 42 are connected to the extraction electrodes 16a and 16b on the input side of the second filter 43 by a first electrode wider than the electrode width of the resonator. The connection is made by forming the inter-stage connection electrodes 44 a and 44 b on the piezoelectric substrate 41. Also,
Another output 15a of the first filter 42 and another input 14a of the second filter 43 form on the piezoelectric substrate 41 a second interstage connection electrode 45 wider than the electrode width of the resonator. Connected by

The extraction electrodes 16a and 16b on the input side of the first filter 42 are connected by a wiring pattern 46 having a line width wider than the width of the resonator electrode formed on the piezoelectric substrate 41. Further, a part of the wiring pattern 46 is further expanded to provide an external wiring body 47 of a balanced input terminal.
a connection land 46a with the outer IDT.
The bus bar electrode 14a of the electrode is extended outward to form a connection land 48 with the external wiring body 47b of the balanced input terminal.

On the other hand, the extraction electrodes 17a and 17b on the second filter output side are connected by a wiring pattern 46b having a line width wider than the width of the resonator electrode formed on the piezoelectric substrate 41. Further, a part of the wiring pattern is further extended to form a connection land 46c with the external wiring body 47c of the balanced output terminal, and the bus bar electrode 15a is extended outward to extend the external wiring body 47d of the balanced output terminal. To form a connection land 48a.

With such a pattern configuration, it is possible to provide a balanced multistage surface acoustic wave filter having low insertion loss and good balance.

The external wiring lands 44c and 45a provided on the inter-stage connection electrodes 44b and 45 in FIG . 4 are useful for connecting an external circuit element for adjusting filter characteristics.

By simply cascading the surface acoustic wave filters, the desired good transmission characteristics may not be obtained due to the mismatch of the input / output impedance of each stage.

In such a case, a reactance element such as an inductor may be connected to the inter-stage connection electrode as a matching element for adjustment. The external wiring lands 44c and 45a serve for this purpose. In addition, if a reactance element such as a spiral inductor is formed on the same piezoelectric substrate 41 or another substrate and is connected to the inter-stage connection electrode, no extra space is required, Circuit size can be easily reduced. The adjustment reactance element may be connected to one of the first inter-stage connection lands 44c and 45a, and the other lands may be grounded. However, according to experiments, it is better to connect the reactance element to the first connection land 44c. An improvement in the symmetry of the transmission characteristics was obtained.

(Embodiment 2) FIG. 5 is an electrode pattern configuration diagram showing a surface acoustic wave filter according to a second embodiment of the present invention.

In FIG. 5, a surface acoustic wave can be excited by forming a strip line electrode pattern having a periodic structure on a piezoelectric substrate 51. On the piezoelectric substrate 51, an IDT electrode 52a and a reflector electrode 52
The first surface acoustic wave resonator of the energy confinement type constituted by b and 52c is formed. On the piezoelectric substrate 51, an IDT electrode 54a and a reflector electrode 5 are provided.
4b and 54c form a third surface acoustic wave resonator.

The point to be noted here is that the reflector electrode 53
b, 53c, the IDT electrode portion of the second surface acoustic wave resonator formed between the first surface acoustic wave resonator and the third surface acoustic wave resonator has the same structure as the reflector electrode. IDT in the first and third surface acoustic wave resonators
The point is that it is constituted by a strip electrode line 53a having a periodic structure having a length substantially equal to the width of the electrode fingers of the electrodes 52a and 54a.

That is, as described above, the structure of the electrode portion of the second surface acoustic wave resonator is the same as that of the above-described IDT electrodes 52a and 54a.
If the electrode period is the same even if the structure is not the same as that of FIG.
Since the surface acoustic wave can propagate in exactly the same way, the acoustic behavior of the central second surface acoustic wave resonator is
It is not different from the case of the electrode structure.

The three surface acoustic wave resonators are arranged close to each other and acoustically coupled, and the bus bar electrodes adjacent to each other are electrically independent. One end of the bus bar electrode 55 adjacent to the second surface acoustic wave resonator of the IDT electrode in the first surface acoustic wave resonator is connected to a gap between the IDT electrode 52a and the reflector electrodes 52b and 52c by one of the balanced input terminals. The first and second electrode fingers 57a and 57b forming the portion are formed outward. Further, balanced output terminals are formed at both ends of the bus bar electrode 56 of the third surface acoustic wave resonator adjacent to the second surface acoustic wave resonator, between the IDT electrode 54a and the reflector electrodes 54b and 54c. The third and fourth electrode fingers 58a and 58b forming a part of the first electrode are formed outward. The above-described electrode configuration is a basic configuration of a triple mode surface acoustic wave filter having a low insertion loss balanced input / output terminal according to the present invention.

FIG. 6 shows an example of connection of the balanced type input / output terminal of the present invention to the triple mode surface acoustic wave filter described with reference to FIG.

As shown in the drawing, the first electrode finger 57a and the second electrode finger 57b of the first surface acoustic wave resonator are connected by connection lines 61a and 61b, and one of the balanced input terminals is connected. Bus bar electrode 55 of the outer IDT electrode as an input terminal
A connection line 62 is drawn out from a to be the other input terminal of the balanced input terminal. Then, the third surface acoustic wave resonator
Connecting the third electrode finger 58a and the fourth electrode finger 58b to the connection line 63.
a, 63b to form one of the balanced input terminals as an output terminal, and the connection wire 64 is drawn out from the bus bar electrode 56a of the outer IDT electrode to constitute the other output terminal of the balanced output terminal.

FIG. 7 shows another example of the balanced input / output terminal configuration of the triple mode surface acoustic wave filter.

As shown in the drawing, the space between the first electrode finger 57a and the second electrode finger 57b of the first surface acoustic wave resonator is wider than the width of the resonator electrode formed on the piezoelectric substrate 51. The connection is made with a wiring pattern 71 having a line width, and the pattern 71 is further expanded to connect with an external wiring body 75a.
Are formed, the bus bar electrode 55a of the IDT electrode is extended outward to form a connection land 73 with the external wiring body 75, and the third and fourth electrode fingers 58a and 5a of the third surface acoustic wave resonator are formed.
8b are connected by a wiring pattern 72 having a line width wider than the resonator electrode width formed on the piezoelectric substrate 51, and the pattern 72 is further expanded to form a connection land 72a with the external wiring body 76a. An external wiring body 76 and a connection land 74 are formed by extending the bus bar electrode 56a of the electrode outward. According to this configuration, as described in the first embodiment, the insertion loss can be further reduced, and a triple mode surface acoustic wave filter that can be easily connected to an external circuit can be provided.

FIG. 8 shows an example in which the triple mode surface acoustic wave filter described in FIG. 5 is cascaded in a plurality of stages.

As shown in the figure, a first triple mode surface acoustic wave filter 82 and a second triple mode surface acoustic wave filter 83 are formed on a piezoelectric substrate 81. Output side third and fourth electrode fingers 58a,
58b and the output side bus bar electrode 56a are connected to the input side first and second electrode fingers 57a and 57b of the second filter 83 and the input side bus bar electrode 55a by connection lines 83a and 83a.
b and 84 are interstage connected. The balanced connection of the input circuit and the output circuit is exactly the same as that of the single-stage filter shown in FIG.

FIG. 9 shows another example of the input / output configuration and interstage configuration of the cascade triple mode surface acoustic wave filter shown in FIG.

As shown in the drawing, a first triple mode surface acoustic wave filter 92 and a second triple mode surface acoustic wave filter 93 are formed on a piezoelectric substrate 91. Both filters are the third output of the first filter 92,
Fourth electrode fingers 58a, 58b and output-side bus bar electrode 56a, input first and second electrode fingers 57a and 57b of second filter 93, and input-side bus bar electrode 55
are connected to each other by interstage connection electrodes 94a, 94b, and 95 wider than the resonator electrode width formed on the piezoelectric substrate 91. The lands 94c and 95a formed on a part of each connection electrode are convenient for connecting an external element for adjusting a filter characteristic. The connection patterns of the input circuit and the output circuit are exactly the same as those of the single-stage filter shown in FIG.

As described above, according to the first and second embodiments, since the bus bar electrode of the IDT electrode is electrically independent, balanced input / output can be realized, and therefore, the filter characteristic is reduced to the ground state of the electrode. The characteristics of the stop band and the transition region are improved because they are no longer affected by stray capacitance due to
Further, the extraction electrode structure, which is a feature of the present invention, can realize a great improvement in insertion loss and an improvement in the degree of balance in the balanced input / output terminal.

In the third embodiment, the balanced triple mode filter is provided with a central resonator I as shown in FIG.
The example in which the DT electrode has the same periodic structure as the reflector electrode was used, but this part is the same as the conventional IDT.
Even with the electrode structure, the effect of improving the filter characteristics by the balanced connection in the present invention can be obtained in exactly the same manner.

(Embodiment 3) FIG. 10 is a configuration diagram showing a surface acoustic wave filter according to a third embodiment of the present invention.

In FIG. 10, reference numeral 101 denotes a single crystal piezoelectric substrate. By forming an electrode pattern on the piezoelectric substrate 101, surface acoustic waves can be excited. On the piezoelectric substrate 101, an energy trap type first surface acoustic wave resonator constituted by an IDT electrode 102a and reflector electrodes 102b and 102c is formed. An IDT electrode 104 is provided on the piezoelectric substrate 101.
a and a third surface acoustic wave resonator constituted by the reflector electrodes 104b and 104c. With the reflector electrodes 103b and 103c, an electrode portion 103a of the second surface acoustic wave resonator formed between the first surface acoustic wave resonator and the third surface acoustic wave resonator is connected to the reflector electrode. It has a similar structure.

As described above, even if the structure of the electrode portion 103a of the second surface acoustic wave resonator is not the same as that of the above-described IDT electrode, and the periodic structure of the strip line electrode array, the electrode period is the same. Then, since the surface acoustic wave can propagate in exactly the same way, the acoustic behavior of the second surface acoustic wave resonator disposed at the center is the same as that of the IDT electrode structure.

Further, the width of the electrode finger intersection of the IDT electrodes 102a and 104a in the first and third surface acoustic wave resonators is W1, the IDT electrode portion 103 of the second surface acoustic wave resonator.
Assuming that the length of the strip line constituting a is W2, the relative dimensions of W1 and W2 are set such that W1 ≦ W2.

The three surface acoustic wave resonators are arranged close to each other, and the bus bar electrodes in adjacent portions are electrically independent. The electrode finger of the IDT electrode 102a in the first surface acoustic wave resonator is connected to the balanced input terminal IN,
The electrode finger of the IDT electrode 104a in the third surface acoustic wave resonator is connected to the balanced output terminal OUT. The periodic structure stripline electrode array 103a in the second surface acoustic wave resonator is grounded.

The operation of the surface acoustic wave filter configured as described above will be described below.

FIG. 11 is an excitation mode distribution diagram of the surface acoustic wave filter according to the present embodiment, and portions corresponding to FIG. 10 are denoted by the same reference numerals. In FIG.
11A is an electrode configuration diagram of the surface acoustic wave filter shown in FIG. When the first to third surface acoustic wave resonators are arranged close to each other, acoustic coupling occurs therebetween, and FIG.
A first order having a potential distribution as shown in FIG.
The second and third modes are excited. Here, since the electrode portion 103a of the third surface acoustic wave resonator disposed at the center is electrically grounded, the polarity of the potential distribution of the second mode can be inverted at the center.
Strong excitation intensity at the same level as in the second and third modes can be obtained. Therefore, a multi-mode filter that effectively utilizes the three excitation modes can be configured, and a surface acoustic wave filter having a wide band and steep cutoff characteristics is realized.

FIG. 12 shows the change in the resonance frequency of each mode with respect to the value of W normalized by the wavelength λ of the surface acoustic wave when W1 = W2 = W, obtained by waveguide mode analysis. Curves 121, 122, and 123 are primary and secondary, respectively.
Next, changes in the resonance frequency of the third and third modes are shown. FIG.
As shown in FIG. 2, for a given W, the frequency difference Δ1 between the primary mode and the secondary mode and the frequency difference Δ2 between the secondary mode and the tertiary mode have different values. That is, 50Ω
As seen from the system, as shown in FIG. 13, in the pass characteristic of the surface acoustic wave filter, peaks of the three resonance modes are not equally spaced as shown by a curve 131. Therefore, even if the input and output are matched, ripples remain in the band as shown by the curve 132,
Filter characteristics deteriorate.

Here, the electrode portion 103 of the second surface acoustic wave resonator with respect to the electrode finger intersection width W1 of the IDT electrodes 102a and 104a in the first and third surface acoustic wave resonators.
a ratio (W2
/ W1) is shown in FIG. FIG.
FIG. 11 shows normalized values of the measured values of the frequency difference (Δ1, Δ2 in FIG. 13) of the resonance mode with respect to W2 / W1 in the surface acoustic wave filter according to the present invention having the configuration of FIG. FIG. 14 shows the electrode portions of the second surface acoustic wave resonator when the IDT electrode finger intersection width W1 of the first and third surface acoustic wave resonators is 6.5 wavelengths and the coupling gap length G is 1 wavelength. The values when the length W2 of the strip line constituting the line 103a is changed are shown. As shown in FIG.
When the value of W1 is about 1.13, Δ1 = Δ2. That is, the intervals between the three resonance frequencies are equal. As the allowable range, the relative dimensions of W1 and W2 may be determined so as to fall within the range of 1 <W2 / W1 ≦ 1.3. actually,
In consideration of manufacturing variations, it is desirable to determine the values of W1 and W2 in the range of 1 <W2 / W1 ≦ 1.16.

FIG. 15 shows that W1 = 6.5 wavelengths and W2 = 7.
5 shows the pass characteristics of the surface acoustic wave filter when five wavelengths are satisfied, that is, when W2 / W1 = 1.15. In FIG.
Reference numeral 1 denotes a characteristic when viewed in a 50Ω system, and 152 denotes a characteristic when matching is performed. It can be seen that the ripple in the pass band is clearly reduced as compared with the case of FIG. 13, and that excellent pass characteristics are obtained.

As described above, according to the third embodiment, 3
Pieces of the surface acoustic wave resonators are arranged close to each other, and the electrode portion of the central surface acoustic wave resonator has the same structure as the reflector electrode, and has IDT electrode fingers of the first and third surface acoustic wave resonators. A surface acoustic wave filter having a wide band, flat pass characteristics, and a steep cutoff characteristic can be obtained by forming a strip line electrode array having a periodic structure slightly longer than the intersection width and grounding all of them.

Further, since the bus bar at the center of the IDT electrode is electrically independent, the IDT electrode 102a of the first surface acoustic wave resonator and the bus bar of the third surface acoustic wave resonator are electrically isolated.
Since all the wires 4a can be independently wired, the balanced input / output of the surface acoustic wave filter can be realized. Therefore, since the filter characteristics are not affected by the stray capacitance or the like due to the grounding state of the electrodes, the characteristics of the stop band and the transition region are further improved. In addition, since it becomes possible to connect a balanced element such as an IC to the front and rear stages of the filter without using an external circuit such as a balun, noise characteristics of the entire circuit are also improved.

In FIG. 10, the electrode portion 103a of the second surface acoustic wave resonator has an electrode pattern existing in the gap between the IDT electrode 104a and the reflector electrode 104c of the third surface acoustic wave resonator. Although it is grounded via the electrode section 103, it is not necessarily limited to this configuration.
a may be grounded via the reflector electrodes 103b and 103c on both sides.

In the third embodiment, the surface acoustic wave filter having a single-stage configuration is described as an example.
As shown in FIG. 16, when a plurality of surface acoustic wave filters 162 and 163 are cascaded on the same piezoelectric substrate 161 to form a multi-stage connected surface acoustic wave filter, the insertion loss is slightly increased, but the stop band is increased. And the characteristics of the transition region are greatly improved, and further excellent filter characteristics can be obtained. In this case, the first surface acoustic wave resonator electrode of the preceding surface acoustic wave filter is connected to the balanced input terminal, and the third surface acoustic wave resonator electrode of the subsequent surface acoustic wave resonator is connected to the balanced surface acoustic wave filter. Preferably it is connected to an output terminal. This is because it can be easily connected to a peripheral circuit such as a balanced front-end IC, and it is not necessary to secure the ground for the wiring, so that the effect of the stray capacitance is small and stable filter characteristics can be obtained.

By simply connecting the surface acoustic wave filters in cascade, good transmission characteristics may not be obtained due to a mismatch between input and output impedances at each stage. In this case, the connection electrode pattern 16 between the steps is used.
4 and 165, a reactance element such as an inductor may be connected as a matching element. In this case, the electrode patterns 164 and 165 are required to completely support the balanced input / output circuit.
It is necessary to connect a matching element between them. However, in practice, the inter-stage portion has no electrical connection with the input / output terminal and is only acoustically coupled, so that one electrode pattern (for example, the electrode pattern 165) is directly grounded, and the other electrode pattern is connected. If the electrode pattern 164 (for example, the electrode pattern 164) is grounded via the reactance element 166, the same operation as when a reactance element is connected therebetween can be performed. If such a configuration is adopted, the ground wiring can be provided on the electrode pattern, so that the number of bonding wires can be reduced. As a result, the characteristics can be improved with a simple structure.

(Embodiment 4) FIG. 17 is a block diagram showing a surface acoustic wave filter according to a fourth embodiment of the present invention.

In FIG. 17, reference numeral 171 denotes a single crystal piezoelectric substrate. By forming an electrode pattern on the piezoelectric substrate 171, a surface acoustic wave can be excited as in the third embodiment. On the piezoelectric substrate 171, I
An energy trap type first surface acoustic wave resonator constituted by the DT electrode 172a and the reflector electrodes 172b and 172c is formed. Further, on the piezoelectric substrate 171, an IDT electrode 173a and reflector electrodes 173b, 173b are provided.
3c, and an energy trapping type third surface acoustic wave resonator formed by the IDT electrode 174a and the reflector electrodes 174b, 174c. Have been.
These three surface acoustic wave resonators are arranged close to each other, and the bus bar electrodes of the adjacent IDT electrodes are electrically independent. The reflector electrodes are connected by a common bus bar. The electrode finger of the IDT electrode 172a in the first surface acoustic wave resonator is a balanced input terminal IN.
And the electrode finger of the IDT electrode 174a in the third surface acoustic wave resonator is connected to the balanced output terminal OUT. The IDT in the second surface acoustic wave resonator
The electrode fingers of the electrode 173a are all grounded. Further, when the electrode finger intersection width of the IDT electrodes 172a and 174a in the first and third surface acoustic wave resonators is W1, and the electrode finger intersection width of the IDT electrode 173a of the second surface acoustic wave resonator is W2, The relative dimensions of W1 and W2 are set so that W1 ≦ W2.

In the surface acoustic wave filter having the above configuration, the electrode structure of the second surface acoustic wave resonator at the center is changed from the periodic structure strip line electrode array of the third embodiment to the IDT electrode 173a. However, since the surface acoustic wave propagates in exactly the same way, the basic operation is shown in FIG.
This is the same as the case of the third embodiment shown in FIG. Therefore,
Flattening of the pass characteristics of the surface acoustic wave filter and suppression of spurious in the stop band are realized in the same manner as in the third embodiment.

According to the fourth embodiment, three surface acoustic wave resonators are arranged close to each other, all of the IDT electrodes 173a constituting the central second surface acoustic wave resonator are grounded, and their intersections are formed. By making the width slightly longer than the IDT electrode finger intersection width of the first and third surface acoustic wave resonators, it is possible to obtain a surface acoustic wave filter having a wideband and flat pass characteristic and a steep cutoff characteristic. . Further, since the bus bar at the center of the IDT electrode is electrically independent, the IDT electrode 172a of the first surface acoustic wave resonator and the IDT electrode 174a of the second surface acoustic wave resonator are all independently wired. Thus, balanced input / output of the surface acoustic wave filter can be realized. As a result, the characteristics of the filter are not affected by the stray capacitance due to the grounding state of the electrode.
The characteristics of the stop and transition zones are improved. In addition, since it becomes possible to connect a balanced element such as an IC to the front and rear stages of the filter without using an external circuit such as a balun, the noise characteristics of the entire circuit are also improved.

Further, also in the fourth embodiment, if a plurality of surface acoustic wave filters are connected in cascade to form a multi-stage connected surface acoustic wave filter, the characteristics of the transition region and the stop region are greatly improved. . The cascade connection method and the connection method of the reactance elements (matching elements) between the stages in this case are exactly the same as in the case of the third embodiment shown in FIG. This is the same as described in the embodiment.

In the third embodiment,
As shown in FIG. 10, ID of the first surface acoustic wave resonator
Although the T electrode 102a and the IDT electrode 104a of the second surface acoustic wave resonator have an electrode arrangement in opposite phases, they are not necessarily limited to this configuration, and may have an electrode arrangement in the same phase. Even in this case, the effect of the out-of-band spurious is slightly different, but the operation and effect are not changed. This is the same for the fourth embodiment.

In the third and fourth embodiments, the input / output terminals are of a balanced type. However, the present invention is not necessarily limited to this configuration, and one side of each of the input / output terminals is grounded. It is also possible to use an unbalanced type. When one of the input / output terminals is grounded, a surface acoustic wave filter having a balanced-unbalanced terminal can be configured. (Fifth Embodiment) FIG. 18 shows an electrode pattern configuration diagram of a surface acoustic wave filter according to a fifth embodiment of the present invention.

In FIG. 18, reference numeral 181 denotes a single crystal piezoelectric substrate. By forming a periodic strip electrode pattern on the piezoelectric substrate 181, surface acoustic waves can be excited. On the piezoelectric substrate 181, an IDT electrode 182a and a reflector electrode 182b,
82c to form an energy trap type first surface acoustic wave resonator. The IDT electrode 183a and the reflector electrode 1 are provided on the piezoelectric substrate 181.
An energy trap type second surface acoustic wave resonator constituted by 83b and 183c is formed.

As shown in FIG. 18, the IDT electrode 183a constituting the second surface acoustic wave resonator has first, second and third divided IDT electrodes 184a, 184b and 184c.
Of the three groups. Here, the first divided IDT electrode 184a and the second divided IDT
The electrode 184b is arranged in the opposite phase, and the second divided IDT electrode 184b and the third divided IDT electrode 184c are arranged in the same phase. The in-phase and out-of-phase will be described later.

The way of connecting these three groups is as follows.

That is, the lower electrode (outer busbar electrode) 1841o of the first divided IDT electrode 184a and the upper electrode (inner busbar electrode) of the second divided IDT electrode 184b.
1842i are connected to each other via a fifth electrode finger 184a5 included in the first divided IDT electrode 184a and a short connection electrode 184ab. Also, the second division ID
Lower electrode (outer busbar electrode) 18 of T electrode 184b
42o and the lower electrode (outer busbar electrode) 1843o of the third divided IDT electrode 184c are connected.

As a result, the IDT electrode 183a constituting the second surface acoustic wave resonator is formed.

Whether the groups are divided is based on the division of the inner bus bar electrodes and the division of the outer bus bar electrodes.

That is, the upper electrode 1843i and the upper electrode 18
42i is divided into third division IDs.
It is divided into a T electrode 184c and a second divided IDT electrode 184b. Also, the lower electrode 1842o and the lower electrode 18
41o and the second divided IDT
The electrode is divided into an electrode 184b and a first divided IDT electrode 184a.

The two first and second surface acoustic wave resonators are arranged close to each other, and acoustic coupling occurs between them to form a surface acoustic wave filter.

Further, the upper electrode and the lower electrode of the IDT electrode 182a are respectively connected to the balanced input terminal IN. Further, the lower electrode of the first divided IDT electrode 184a and the second divided ID which constitute the IDT electrode 183a.
The upper electrode of the T electrode 184b is connected to one of the balanced output terminals OUT, and the lower electrode of the second divided IDT electrode 184b and the lower electrode of the third divided IDT electrode 184c are connected to the other of the balanced output terminals OUT. , The first split ID
The upper electrode of the T electrode 184a and the upper electrode of the third divided IDT electrode 184c are grounded to form a balanced input / output terminal.

Here, the above-mentioned in-phase and out-of-phase will be described.

First, the structural arrangement of two adjacent electrode fingers (ie, a pair of adjacent electrode fingers) will be described.

That is, two adjacent electrode fingers having the same phase relationship means that one of the two electrode fingers is connected to the inner bus bar electrode and extends from the inside to the outside.
It means that the other is connected to the outer bus bar electrode and is in a connection relationship extending from the outside to the inside.
Further, two adjacent electrode fingers are in opposite phase relation, either of the two electrode fingers being connected to the inner bus bar electrode and extending from the inner side to the outer side, or the outer bus bar. It refers to a connection relationship that is connected to an electrode and extends from the outside to the inside. Here, the electric charges of the inner and outer bus bar electrodes are different. The pitch (center-to-center distance) between two adjacent electrode fingers is ｘ × λ. The pitch between the electrode fingers is (m + ／)
xλ may be used. In that case, if the pitch is (m +
1) If xλ, the meanings of the in-phase relationship and the anti-phase relationship are completely reversed from those described above. Here, λ is the wavelength of the excited surface acoustic wave, and m = 0, 1, 2, 3,
...

Specifically, the first divided IDT electrode 184
a, for example, as shown in FIG.
The electrode finger 184a1 and the second electrode finger 184a2 have an in-phase relationship, and the fourth electrode finger 184a4 and the fifth electrode finger 184a
a5 also has the same phase relationship. Therefore, all of the first to fifth electrode fingers included in the first divided IDT electrode 184a have an in-phase relationship. Similarly, the second and third divisions I
All the electrode fingers included in the DT electrodes 184b and 184c also have the same phase relationship in each divided IDT electrode.

Next, looking at two adjacent electrode fingers 184a5 and 184b1, as shown in FIG.
Since 84a5 is connected to the outer bus bar electrode 1841o and the electrode finger 184b1 is connected to the outer bus bar electrode 1842o, they are in opposite phase relationship. Also, these 2
One electrode finger is disposed at a division between the first divided IDT electrode 184a and the second IDT electrode 184b.

From the above, the meaning of the opposite phase or the same phase described in the arrangement relation of the above three groups is also as follows.
It goes without saying that it is based on the above-mentioned relationship between two adjacent electrode fingers. This point is the same in other embodiments.

The width of the fifth electrode finger 184a5 in the lateral direction will be further described. In FIG. 18, the fifth electrode finger 184a
5 shows a configuration in which the width of the other electrode fingers is the same as the width of the other electrode fingers, but is not limited thereto, and may be, for example, wider than the width of the other electrode fingers. By doing this,
The resistance value of the electrode finger is reduced, and therefore the ID including the electrode finger is reduced.
This has the effect of reducing the resistance value of the T electrode and reducing the insertion loss. This applies to the other embodiments.

The operation of the surface acoustic wave filter according to the fifth embodiment configured as described above will be described below.

FIG. 19 is a capacitance equivalent circuit diagram of the fifth embodiment. C ₁ denotes an ID constituting the first surface acoustic wave resonator.
This is the capacitance of the T electrode 182a. Ca, Cb, and Cc are the capacitances of the first, second, and third divided IDT electrodes 184a, 184b, and 184c, respectively.
b and Cc have the second surface acoustic wave resonator ID
It becomes the total capacitance C2 of the T electrode 183a. Here, the number of pairs of electrode fingers included in the IDT electrode 183a is n, and the first, second, and third divided IDT electrodes 184a, 184b, 1
Assuming that each logarithm of 84c is na, nb, nc,
The following equation holds. n = na + nb + nc In the surface acoustic wave filter described above, the IDT electrodes 182a, 18
The capacitance of 3a is governed by the logarithm of the electrodes. IDT electrode 18
Assuming that the logarithm of 2a is n and the electrode capacitance of the pair of IDT electrode fingers is C, C ₁ , Ca, Cb and Cc can be expressed as follows.

C ₁ = n × C Ca = na × C = C ₁ × na / n = C ₁ × na / (na +
nb + nc) Cb = nb × C = C 1 × nb / n = C 1 × nb / (na +
nb + nc) Cc = nc × C = C 1 × nc / n = C 1 × nc / (na +
nb + nc) Therefore, from the capacitance equivalent circuit diagram of FIG. 19, the total capacitance C ₂
Is expressed by (Equation 1) using Ca, Cb, and Cc.

[0101]

(Equation 1)

For example, the divided IDT electrodes 184a, 184
When the logarithms of b and 184c are equal, that is, na
= When a nb = nc = n / 3, C 2 = C 1 × 1/2 , and the capacitance of C ₂ is half of C _1. Split IDT electrode 1
84a, 184b, logarithmic na of 184 c, nb, by changing the nc, the total capacity C2 of the IDT electrode 183a varies from _{C 1 × 1/4 <C} 2 <C 1 in accordance with the equation (1). That is, the total capacity of the IDT electrode 183a is
It can be controlled by the division ratio of the DT electrodes 184a, 184b, 184c.

At this time, the electric charges on the electrodes of the first, second and third divided IDT electrodes 184a, 184b and 184c are not canceled each other, and the first, second and third divided IDT electrodes are not canceled out. Since the surface acoustic waves generated by 184a, 184b, and 184c have the same phase, the second surface acoustic wave resonator has the same resonance characteristics as the first surface acoustic wave resonator. Therefore, the first surface acoustic wave resonator and the second surface acoustic wave
By arranging the surface acoustic wave resonators in close proximity to each other, the filter operates as a transverse mode coupled resonator type filter as in the related art.

As described above, according to the fifth embodiment, the surface acoustic wave filter having the balanced type input / output has the characteristic that the band is excellent in the out-of-band selectivity in the narrow band, and the division characteristic of the present invention. The output impedance of the surface acoustic wave filter can be controlled by the electrode structure of the IDT electrode formed by the IDT electrode.

In the fifth embodiment, the IDT electrode 183a constituting the second surface acoustic wave resonator has
Although the case where the first, second, and third divided IDT electrodes 184a, 184b, and 184c constituting the DT electrode 183a are sequentially arranged from left to right in the drawing has been described,
Not limited to this, 184a, 184 sequentially from right to left
b, 184c. Further, the electrode pattern of the IDT electrode 183a may be turned upside down. In this case, as shown in FIG. 20, the IDT electrode 203a constituting the second surface acoustic wave resonator on the piezoelectric substrate 201
Are the first, second and third divided IDT electrodes 204a,
It is composed of connections of three groups 204b and 204c. The first divided IDT electrode 204a and the second
Are arranged in opposite phases, and the second divided IDT electrode 204b and the third divided IDT electrode 204c
Are arranged in the same phase, and the first divided IDT electrodes 2
04A is connected to the lower electrode of the second divided IDT electrode 204b, the upper electrode of the second divided IDT electrode 204b is connected to the upper electrode of the third divided IDT electrode 204c, and the second surface acoustic wave An IDT electrode 203a forming a resonator is formed. Also in FIG. 20, the divided IDT electrodes 204a, 204b, 204c are
Although 04a, 204b, and 204c are used, this may be from the right side. In these cases, only the electrode structure of the IDT electrode is different, and the characteristics of the surface acoustic wave filter can obtain the same effects as in FIG.

In the fifth embodiment, IDT
Logarithm of electrode 182a and first, second and third divided IDTs
Although the sum of the respective logarithms of the electrodes 184a, 184b, 184c is assumed to be equal, it is not necessary that the sum of the logarithms is exactly the same.
Also, the first, second and third divided IDT electrodes 184a,
The log ratios of 184b and 184c can also be set arbitrarily. In addition, the number of divisions of the IDT electrode 183a is set to three, but may be any other number. Also, the IDT electrode 182
Although the electrical terminal a is of a balanced type, it may be an unbalanced electrical terminal by grounding either the upper electrode or the lower electrode. In that case, a surface acoustic wave filter having a balanced-unbalanced terminal can be configured. Reflector electrode 182
b and 183b, and 182c and 183c are electrically separated, but both may be connected and grounded. Further, the divided IDT electrodes 184a, 184b and 1
Although the IDT electrode 183a constituted by 84c constitutes the second surface acoustic wave resonator, this may constitute the first surface acoustic wave resonator, or both may constitute the first surface acoustic wave resonator. In that case, a surface acoustic wave filter capable of controlling both input and output impedances can be realized. (Sixth Embodiment) FIG. 21 shows an electrode pattern configuration diagram of a surface acoustic wave filter according to a sixth embodiment of the present invention.

In FIG. 21, reference numeral 211 denotes a single-crystal piezoelectric substrate. A surface acoustic wave can be excited by forming an electrode pattern in the form of a periodic strip line on the piezoelectric substrate 211. On the piezoelectric substrate 211, an IDT electrode 212a and a reflector electrode 212b,
12c to form an energy trap type first surface acoustic wave resonator. The IDT electrode 213a and the reflector electrode 2 are provided on the piezoelectric substrate 211.
An energy trap type second surface acoustic wave resonator constituted by 13b and 213c is formed. IDT electrode 213a constituting second surface acoustic wave resonator
Are the first, second and third divided IDT electrodes 214a,
It is configured by connection of three groups 214b and 214c. The first, second, and third divided IDT electrodes 214a, 214b, and 214c are all arranged in the same phase, and the upper electrode of the first divided IDT electrode 214a is connected to the upper electrode of the second divided IDT electrode 214b. And the lower electrode of the second divided IDT electrode 214b and the third
The IDT electrode 213a constituting the second surface acoustic wave resonator is formed by connecting the lower electrode of the divided IDT electrode 214c. These two first and second surface acoustic wave resonators are arranged close to each other,
Acoustic coupling occurs during this time, thereby forming a surface acoustic wave filter.

Further, the upper electrode and the lower electrode of the IDT electrode 212a are respectively connected to the balanced input terminal IN. Further, the upper electrode of the first divided IDT electrode 214a and the second divided ID which constitute the IDT electrode 213a.
The upper electrode of the T electrode 214b is connected to one of the balanced output terminals OUT, and the lower electrode of the second divided IDT electrode 214b and the lower electrode of the third divided IDT electrode 214c are connected to the other of the balanced output terminals OUT. , The first split ID
The lower electrode of the T electrode 214a and the upper electrode of the third divided IDT electrode 214c are grounded to form a balanced input / output terminal.

In the surface acoustic wave filter configured as described above, the first surface acoustic wave resonator has the same structure as the surface acoustic wave resonator of the fifth embodiment, and the second surface acoustic wave In the resonator, the IDT electrode 213a differs from the IDT 183a of the fifth embodiment only in the electrode pattern and the connection method. Also in this case, the divided IDT electrodes 214a, 21a
The electric charges on the electrodes 4b, 214c are not canceled each other, and the divided IDT electrodes 214a, 214b, 214c
Since the surface acoustic waves generated by the first surface acoustic wave resonator have the same phase, the second surface acoustic wave resonator has the same resonance characteristics as the first surface acoustic wave resonator, and the first surface acoustic wave resonator and the second surface acoustic wave resonator have the same resonance characteristics. By disposing the wave resonator in close proximity, the sixth embodiment
Operates as a conventional transverse mode coupled resonator type filter as in the fifth embodiment.
Further, the surface acoustic wave filter having balanced input / output has excellent characteristics in a narrow band and out-of-band selectivity, and can control the input / output impedance of the surface acoustic wave filter according to the fifth embodiment. An effect similar to that of the wave filter can be obtained.

Note that in the sixth embodiment, the divided IDT electrodes 214a, 214b,
Although 214b and 214c are used, the number of divisions may be from the right side, and the number of divisions of the IDT electrode 213a is three, but other numbers may be used. In addition, the IDT electrode 212
Although the electric terminal a is of a balanced type, either one of the upper electrode or the lower electrode may be grounded to be an unbalanced electric terminal. In that case, a surface acoustic wave filter having a balanced-unbalanced terminal can be configured. Although the reflector electrodes 212b and 213b and the reflector electrodes 212c and 213c are electrically separated, both may be connected and grounded. Further, the divided IDT electrodes 214a, 214
IDT electrode 213a composed of b and 214c
Constitutes the second surface acoustic wave resonator. However, this may constitute the first surface acoustic wave resonator, or both may constitute the first surface acoustic wave resonator. A surface acoustic wave filter capable of controlling both output impedances can be realized. (Seventh Embodiment) In the fifth and sixth embodiments, the description has been given by taking the one-stage surface acoustic wave filter as an example. Such a surface acoustic wave filter can be used in a multi-stage configuration.

FIG. 22 shows an example of this, and shows a configuration diagram of an electrode pattern of a surface acoustic wave filter according to Embodiment 7 of the present invention. In FIG. 22, reference numeral 221 denotes a single-crystal piezoelectric substrate. When a plurality of surface acoustic wave filters are cascaded on the piezoelectric substrate 221 to form a multi-stage connected surface acoustic wave filter, the insertion loss slightly increases. However, a significant improvement in the properties of the stop and transition zones is obtained.

The two-stage cascade filter in FIG.
A first surface acoustic wave resonator including a T electrode 222a and reflector electrodes 222b and 222c, and an IDT electrode 223a.
A first surface acoustic wave filter in which a second surface acoustic wave resonator composed of a reflector electrode 223b and a reflector electrode 223c are disposed in close proximity; an IDT electrode 224a and a reflector electrode 224;
b, 224c, a third surface acoustic wave resonator;
A second surface acoustic wave filter in which an IDT electrode 225a and a fourth surface acoustic wave resonator constituted by reflector electrodes 225b and 225c are arranged close to each other is formed on a piezoelectric substrate 221. The IDT electrodes 225a that constitute the fourth surface acoustic wave resonator in the second surface acoustic wave filter include first, second, and third divided IDT electrodes 226a, 226.
b and 226c. First divided IDT electrode 226a and second divided I
The DT electrode 226b is arranged in the opposite phase, and the second divided IDT
The electrode 226b and the third divided IDT electrode 226c are arranged in the same phase, the lower electrode of the first divided IDT electrode 226a is connected to the upper electrode of the second divided IDT electrode 226b, and the second divided IDT electrode 226b is connected. Is connected to the lower electrode of the third divided IDT electrode 226c to form the IDT constituting the fourth surface acoustic wave resonator.
An electrode 225a is formed. One of the extraction electrodes on the output side of the first-stage surface acoustic wave filter is connected to the corresponding extraction electrode on the input side of the next-stage surface acoustic wave filter by an inter-stage connection electrode pattern 227a.
A second-stage surface acoustic wave filter is formed by connecting another output-side IDT electrode of the next stage to another input-side IDT electrode of the next stage by an inter-stage connection electrode pattern 227b.

Further, the IDT electrode 222 constituting the first surface acoustic wave resonator in the first surface acoustic wave filter
The upper electrode and lower electrode a are connected to the balanced input terminal IN. Further, in the IDT electrode 225a forming the fourth surface acoustic wave resonator in the second surface acoustic wave filter, the first
The lower electrode of the divided IDT electrode 226a and the upper electrode of the second divided IDT electrode 226b are connected to the balanced output terminal OUT.
And the lower electrode of the second divided IDT electrode 226b and the lower electrode of the third divided IDT electrode 225c are connected to the other of the balanced output terminals OUT, and the upper electrode of the first divided IDT electrode 226a and Third split IDT
The upper electrode of the electrode 226c is grounded to form a balanced input / output terminal.

However, simply cascading the surface acoustic wave filters may not be able to achieve the desired good transmission characteristics due to the mismatch between the input and output impedances of each stage. In this case, a reactance element such as an inductor may be connected to the inter-stage connection electrode as a matching element for adjustment. In addition, if a reactance element such as a spiral inductor is formed on the same piezoelectric substrate 221 or another substrate, and the reactance element is connected to the inter-stage connection electrode, no extra space is required. Circuit size can be easily reduced. The reactance element for adjustment is the first
22 can be connected to one of the inter-stage connection electrode patterns 227a and 227b and the other inter-stage electrode connection pattern can be grounded. According to an experiment, as shown in FIG. 22, the reactance element 228 is connected to the inter-stage connection electrode pattern. The connection to 227a improved the symmetry of the filter transmission characteristics.

With the above configuration, the surface acoustic wave filter having balanced inputs and outputs according to the seventh embodiment has a narrow band characteristic, and the two surface acoustic wave filters are connected by the inter-stage connection electrode patterns 227a and 227b. By connecting, the out-of-band selectivity becomes steeper than in the case of one stage, and the output impedance of the surface acoustic wave filter can be controlled.

In the seventh embodiment, in the IDT electrode 225a constituting the fourth surface acoustic wave resonator in the second surface acoustic wave filter, the first, second and third parts constituting the IDT electrode 225a are formed. Divided IDT electrode 226
a, 226b and 226c are 22
6a, 226b and 226c, but this may be from the right side. Further, the electrode pattern of the IDT electrode 225a may be turned upside down.

Also, in the seventh embodiment, the ID
Although the number of divisions of the T electrode 225a is set to 3, other values may be used. Although the electric terminals of the IDT electrode 222a are of a balanced type, either the upper electrode or the lower electrode may be grounded to form an unbalanced electric terminal. In that case, a surface acoustic wave filter having a balanced-unbalanced terminal can be configured. The IDT electrode 225a may be the IDT electrode 213a having the configuration shown in the sixth embodiment. In these cases, only the electrode structure of the IDT electrode 234a is different, and the characteristics of the surface acoustic wave filter can obtain the same effects as in FIG. Reflector electrodes 222b and 223
b, and 222c and 223c are electrically separated, but both may be connected and grounded. Further, the IDT electrode 225a constituted by the divided IDT electrodes 226a, 226b and 226c constitutes the fourth surface acoustic wave resonator, but this constitutes the first surface acoustic wave resonator. It may be either or both. In that case, a surface acoustic wave filter capable of controlling both input and output impedances can be realized. In addition, although the number of stages of the surface acoustic wave is set to two, the number may be more than that, and in this case, a steep filter characteristic having more excellent out-of-band selectivity is obtained. (Eighth Embodiment) FIG. 23 is a diagram showing an electrode pattern configuration of a surface acoustic wave filter according to an eighth embodiment of the present invention. In FIG. 23, reference numeral 231 denotes a single-crystal piezoelectric substrate. By forming an electrode pattern on the piezoelectric substrate 231, surface acoustic waves can be excited. On the piezoelectric substrate 231, the IDT electrode 232a and the reflector electrodes 232b, 23
An energy trap type first surface acoustic wave resonator constituted by 2c is formed. Also, the piezoelectric substrate 23
1 above, an IDT electrode 234a and a reflector electrode 234
b, 234c to form a third surface acoustic wave resonator. With the reflector electrodes 233b and 233c, the electrode portion 233a of the second surface acoustic wave resonator formed between the first surface acoustic wave resonator and the third surface acoustic wave resonator is connected to the reflector electrode. It has a similar structure. Thus, even if the structure of the electrode portion 233a of the second surface acoustic wave resonator is not the IDT electrode structure but a periodic strip line electrode array, the surface acoustic waves are exactly the same if the electrode period is the same. The acoustic behavior of the second surface acoustic wave resonator located in the center is ID
It is not different from the case of the T electrode structure.

Further, the IDT electrode 234a constituting the third surface acoustic wave resonator is formed by connecting three groups of first, second and third divided IDT electrodes 235a, 235b and 235c. First split IDT
The electrode 235a and the second divided IDT electrode 235b are arranged in opposite phases, the second divided IDT electrode 235b and the third divided IDT electrode 235c are arranged in phase, and
Lower electrode of the divided IDT electrode 235a and the second divided ID
The upper electrode of the T electrode 235b is connected to the second divided ID.
Lower electrode of T electrode 235b and third divided IDT electrode 23
By connecting the lower electrode 5a, the IDT electrode 234a constituting the third surface acoustic wave resonator is formed.

The three surface acoustic wave resonators are arranged close to each other, and the bus bar electrodes of the adjacent portions are electrically independent. The first in the first surface acoustic wave filter
The upper electrode and the lower electrode of the IDT electrode 232a constituting the surface acoustic wave resonator of the above are connected to the balanced input terminal IN, respectively. In the IDT electrode 234a constituting the third surface acoustic wave resonator, the IDT electrode 234a
The lower electrode of the first divided IDT electrode 235a and the upper electrode of the second divided IDT electrode 235b are connected to one of the balanced output terminals OUT, and the lower electrode of the second divided IDT electrode 235b and the third divided electrode are arranged. IDT electrode 235
The lower electrode c is connected to the other of the balanced output terminals OUT, and the upper electrode of the first divided IDT electrode 235a and the upper electrode of the third divided IDT electrode 235c are grounded to form a balanced input / output terminal. And the periodic structure strip line electrode array 233 in the second surface acoustic wave resonator.
a is grounded.

As described above, in the surface acoustic wave filter according to the eighth embodiment, three surface acoustic wave resonators are arranged close to each other in parallel with the propagation direction of the surface acoustic wave, and are acoustically coupled to each other. Is realized.

At this time, the surface acoustic wave filter uses the IDT electrode in the surface acoustic wave multimode filter disclosed in Japanese Patent Application Laid-Open No. Hei 8-51334 published by the present inventors and the second surface acoustic wave in the surface acoustic wave filter of the present invention. It is replaced with an IDT electrode 233a constituting a resonator, and performs the same operation as that described in JP-A-8-51334.
In other words, by using three stages of surface acoustic wave resonators, it is possible to have excellent characteristics in wideband and out-of-band selectivity, and to control the output impedance of the surface acoustic wave filter.

In the eighth embodiment, the IDT electrode 234a constituting the third surface acoustic wave resonator has
Although the first, second, and third divided IDT electrodes 235a, 235b, and 235c that constitute the DT electrode 234a are 235a, 235b, and 235c from the left side in the drawing,
This can be from the right side. Also, the IDT electrode 23
The electrode pattern 4a may be turned upside down. The IDT electrode 234a may be the IDT electrode 213a having the configuration shown in the sixth embodiment. In these cases, only the electrode structure of the IDT electrode 234a is different, and the characteristics of the surface acoustic wave filter can obtain the same effects as in FIG.

Although the number of divisions of the IDT electrode 234a is set to three, it may be other than three. IDT electrode 23
Although the electrical terminal 2a is of a balanced type, either the upper electrode or the lower electrode may be grounded to form an unbalanced electrical terminal. In that case, a surface acoustic wave filter having a balanced-unbalanced terminal can be configured. Reflector electrode 23
Although 2b and 233b and 232c and 233c are electrically separated, both may be connected and grounded. Further, the divided IDT electrodes 235a, 235b and 2
The IDT electrode 234a composed of
Of the surface acoustic wave resonator of
The first surface acoustic wave resonator may be formed, or both may be formed. In this case, a surface acoustic wave filter capable of controlling both input and output impedances can be realized.

In the eighth embodiment, the IDT electrode 23
3a is an IDT electrode 232a and a reflector electrode 23 on the right side thereof.
Although the grounding is performed through the electrode pattern provided in the gap 3c, the grounding may be performed through the electrode pattern provided in the gap between the IDT electrode 233a and the reflector electrode 233a on the left side. 234a and reflector electrode 2
It may be grounded via an electrode pattern provided in one of the gaps 34b and 234c. Reflector electrode 2
32b and 233b and 233c, and 232c and 233c
And 234c are electrically separated for each surface acoustic wave resonator. However, they may be connected and grounded. Further, the IDT electrode 233a is connected to the reflector electrodes 232b, 232c, 233b, 233c, 234
b, 234c. The IDT electrode 233a may have the same electrode structure as that of the IDT electrode 232a. In this case as well, the propagation of the surface acoustic wave is performed in the same manner, so that the same characteristics as the surface acoustic wave filter of the eighth embodiment are obtained. can get. Furthermore, the split ID
Although the T electrode 234a constitutes the third surface acoustic wave resonator, it may be constituted by the first surface acoustic wave resonator, or may be both, in which case the input side or the The impedance of both input and output can be controlled. Although the first to third surface acoustic wave resonators have the same configuration, they need not always be the same. Further, the surface acoustic wave filter according to the eighth embodiment may be configured to be cascaded in two stages, and in this case, the out-of-band selectivity characteristic becomes steeper.

The piezoelectric substrate according to the present invention includes:
Although it is preferable to use ST-cut quartz having excellent temperature characteristics, LiTaO ₃ , LiNbO ₃ , Li ₂ B ₄ O ₇ , La ₃
Ga ₃ SiO ₁₄ or the like can be used as the substrate.
Further, as the electrode material, it is preferable to use aluminum having a relatively small density for which the film thickness can be easily controlled, but it is also possible to use a gold electrode.

Further, according to the present invention, not only the above-described surface acoustic wave but also a slip wave (S
surface Skimming Balk Wave
e) and pseudo surface waves (Pseudo surface wa)
ves) and the like.

[0127]

As is apparent from the above description, the present invention has the advantages of realizing a balanced input / output configuration, improving the balance of the balanced type input / output terminals, and reducing insertion loss. Have.

The present invention has the advantage that the passband can be widened and the phase and amplitude characteristics can be flattened.

Further, the present invention has an advantage that a desired input / output impedance can be realized.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing a surface acoustic wave filter according to a first embodiment of the present invention.

FIG. 2 is a configuration diagram showing another example of the surface acoustic wave filter according to the first embodiment of the present invention.

FIG. 3 is a configuration diagram showing a multi-stage surface acoustic wave filter according to the first embodiment of the present invention.

FIG. 4 is a configuration diagram showing another example of the multi-stage surface acoustic wave filter according to the first embodiment of the present invention.

FIG. 5 is a configuration diagram showing a surface acoustic wave filter according to a second embodiment of the present invention.

FIG. 6 is a configuration diagram showing another example of the surface acoustic wave filter according to the second embodiment of the present invention.

FIG. 7 is a configuration diagram showing another example of the surface acoustic wave filter according to the second embodiment of the present invention.

FIG. 8 is a configuration diagram showing a multi-stage surface acoustic wave filter according to a second embodiment of the present invention.

FIG. 9 is a configuration diagram showing another example of the multi-stage surface acoustic wave filter according to the second embodiment of the present invention.

FIG. 10 is a configuration diagram showing a surface acoustic wave filter according to a third embodiment of the present invention.

FIGS. 11A and 11B are a diagram of a surface acoustic wave filter and an excitation mode distribution diagram for explaining the operation of the surface acoustic wave filter according to the third embodiment of the present invention.

FIG. 12 shows a third embodiment of the present invention in which W1 = W
FIG. 9 is a characteristic diagram of the resonance frequency of each mode with respect to the value of W normalized by the wavelength λ of the surface acoustic wave when 2 = W.

FIG. 13 is a representative measurement diagram showing a comparative example of the pass characteristics of the surface acoustic wave filter according to the third embodiment of the present invention.

FIG. 14 shows W2 / W in the third embodiment of the present invention.
FIG. 3 is an actual measurement diagram of a resonance mode frequency difference for 1;

FIG. 15 is an actual measurement diagram showing the pass characteristics of the surface acoustic wave filter according to the third embodiment of the present invention.

FIG. 16 is a configuration diagram showing another example of the surface acoustic wave filter according to the third embodiment of the present invention.

FIG. 17 is a configuration diagram showing a surface acoustic wave filter according to a fourth embodiment of the present invention.

FIG. 18 is a configuration diagram showing a surface acoustic wave filter according to a fifth embodiment of the present invention.

FIG. 19 is a capacitance equivalent circuit diagram of a surface acoustic wave filter according to a fifth embodiment of the present invention.

FIG. 20 is a configuration diagram showing another example of the surface acoustic wave filter according to the fifth embodiment of the present invention.

FIG. 21 is a configuration diagram showing a surface acoustic wave filter according to a sixth embodiment of the present invention.

FIG. 22 is a configuration diagram showing a surface acoustic wave filter according to a seventh embodiment of the present invention.

FIG. 23 is a configuration diagram showing a surface acoustic wave filter according to an eighth embodiment of the present invention.

FIG. 24 is an electrode pattern diagram of a conventional surface acoustic wave filter.

[Explanation of symbols]

11, 31, 41, 51, 101 Single crystal piezoelectric substrate 12a, 13a, 52a, 54a IDT electrode 12b, 12c, 13b, 13c Reflector 14 First bus bar electrode 14a Third bus bar electrode 15 Second bus bar electrode 15a Fourth bus bar electrode 16a, 16b, 17a, 17b Extraction electrode finger 103a Periodic structure strip line electrode array 166, 228 Reactance element 184a First divided IDT
Electrode 184b Second split IDT
Electrode 184c Third divided IDT
electrode

────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Toshio Ishizaki 1006 Kazuma Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (56) References JP-A-62-142409 (JP, A) JP-A 8- JP-A-3-3342013 (JP, A) JP-A-10-93388 (JP, A) JP-A-5-160669 (JP, A) JP-A-8-307191 (JP, A) JP-A-9-331232 (JP, A) JP-A-10-2463 (JP, A) JP-A-59-131213 (JP, A) European Patent Application Publication 709957 (EP, A1) International Publication 95/15614 ( WO, A1) Proc. Of the 1994 IEICE Autumn Meeting-Society Preceding Conference, Basics and Boundaries, published September 5, 1994, p. 299-300 1995 IEEE ULTRASONS S Symposium VOL. 1P. 67-70 IEEE TRANSACTIONS ON ULTRASONICS, FERROELECTRICS, AND F REQUENCY CONTROL, VOLUME 42, NUMBER 4, J ULY 1995, p. 717-725 (58) Field surveyed (Int.Cl. ⁷ , DB name) H03H 9/64 H03H 9/145 H03H 9/25

Claims (46)

(57) [Claims] A first electrode having reflector electrodes on both sides of an IDT electrode serving as an interdigital transducer electrode;
And a surface acoustic wave filter on a piezoelectric substrate, wherein the surface acoustic wave resonators are disposed close to each other and acoustically coupled at positions where the propagation directions of the respective surface acoustic waves are parallel to each other. An inner bus bar electrode included in the first IDT electrode of the surface acoustic wave resonator and an inner bus bar electrode included in the second IDT electrode of the second surface acoustic wave resonator are electrically separated from each other. Wherein the first IDT electrode is connected to a balanced input terminal, the second IDT electrode is connected to a balanced output terminal, and one terminal of the balanced input terminal is The first IDT
It is electrically connected to a lead electrode directly or indirectly drawn from at least two places of the bus bar electrode inside the electrode, and one terminal of the balanced type output terminal is connected to the second IDT electrode. directly from at least two places of the inside bus bar electrode, or indirectly pulled out electrically connected to the lead electrode and balanced operation, the extraction electrode, and the reflector electrode and the IDT electrode
A surface acoustic wave filter formed in a gap between the two. 2. An interdigital transducer electrode and
Table with reflector electrodes on both sides of the IDT electrode
When the propagation direction of each surface acoustic wave is
Acoustic coupling by arranging at least two in close proximity to the
A combined surface acoustic wave filter on a piezoelectric substrate , wherein the plurality of electrodes are included in at least one of the IDT electrodes.
Any adjacent pair of electrode fingers of the finger are in phase.
And the plurality of electrode fingers have respective electric charges
And at least one IDT electrode is connected to the first, second, and
And a third divided IDT electrode, and a bus bar electrode inside the first divided IDT electrode and the third divided IDT electrode.
The bus bar electrode inside the second divided IDT electrode is connected.
And the bus bar outside the second divided IDT electrode
A pole and a busbar electrode outside the third divided IDT electrode;
Are connected, and the inner electrode and the outer electrode of the second divided IDT electrode are connected to each other.
Are connected to balanced positive and negative electrical terminals, respectively.
In the first and third divided IDT electrodes,
One of the positive and negative electrical terminals
A surface acoustic wave filter comprising an electrode grounded . 3. A connection between two extraction electrodes formed in a gap between the IDT electrode and the reflector electrode, to connect one of the balanced input terminals or one of the balanced output terminals. and then, the outer bus bar electrode included in said IDT electrode, according to claim 1 Symbol, characterized in that the other terminal of said balanced type input terminal or said balanced type output terminal
SAW filter mounting. 4. A wiring having a line width wider than a width of the extraction electrode formed on the piezoelectric substrate, between two extraction electrodes formed in a gap between the IDT electrode and the reflector electrode. A portion further extended in the wiring pattern is a connection land as one terminal of the balanced input terminal or one terminal of the balanced output terminal, and is included in the IDT electrode. site where the outer bus bar electrode is extended outward is claimed in claim 1 or 3, characterized in that the other terminal or connection land as the other terminal of said balanced type output terminal of said balanced type input terminal Surface acoustic wave filter. 5. The surface acoustic wave filter according to claim 1 , wherein the surface acoustic wave filter is formed in a plurality of stages on the same piezoelectric substrate, and one of the extraction electrodes on the output side of the previous surface acoustic wave filter is opposed to the next surface acoustic wave. Connected to a corresponding extraction electrode on the input side of the filter, and connected the other of the extraction electrodes on the output side of the previous surface acoustic wave filter to a corresponding extraction electrode on the input side of the next surface acoustic wave filter; A multi-stage surface acoustic wave filter, wherein one remaining output-side electrode of the preceding surface acoustic wave filter is connected to one remaining input-side electrode of the next-stage surface acoustic wave filter. 6. The surface acoustic wave filter according to claim 1 , wherein the surface acoustic wave filter is formed in a plurality of stages on the same piezoelectric substrate, and the surface acoustic wave filter of the next stage is opposed to one of the output electrodes on the output side of the surface acoustic wave filter of the preceding stage. The opposite extraction electrode on the input side of the filter, and the other extraction electrode on the input side of the next surface acoustic wave filter and the other extraction electrode on the output side are wider than the width of the extraction electrode. A first output electrode of the previous surface acoustic wave filter and a remaining one input electrode of the next surface acoustic wave filter are connected to each other by the first inter-stage connection electrode of the first stage. A second inter-stage connection electrode wider than the first stage surface acoustic wave filter, and a space between the two extraction electrodes on the input side of the first surface acoustic wave filter is wider than a width of the extraction electrode formed on the piezoelectric substrate. Line Are connected by a wiring pattern having a width, further expanded portion in its wiring pattern is a connection land as one terminal of said balanced type input terminal, IDT of said first stage surface acoustic wave filter
A portion where the outer busbar electrode included in the electrode is extended outward is a connection land as the other terminal of the balanced input terminal, and two extraction electrodes on the output side of the final stage surface acoustic wave filter. Are connected by a wiring pattern having a line width wider than the width of the extraction electrode formed on the piezoelectric substrate, and a portion further expanded in the wiring pattern is one of the balanced output terminals. A connection land as a terminal, and a portion where the outer bus bar electrode included in the IDT electrode of the last-stage surface acoustic wave filter is extended outward is a connection land as the other terminal of the balanced output terminal. A multi-stage surface acoustic wave filter characterized by the above-mentioned. 7. The multi-stage surface acoustic wave filter according to claim 6, wherein the first and second inter-stage connection electrodes are connected via a reactance element. 8. The multi-stage surface acoustic wave filter according to claim 6, wherein one of the first and second inter-stage connection electrodes is grounded, and the other is grounded via a reactance element. 9. The multi-stage surface acoustic wave filter according to claim 6, wherein the first inter-stage connection electrode is grounded via a reactance element, and the second inter-stage connection electrode is grounded. 10. A first surface acoustic wave resonator having reflector electrodes on both sides of a first IDT electrode for exciting surface acoustic waves, and a second surface reflector having reflector electrodes on both sides of a second IDT electrode. A surface acoustic wave filter on a piezoelectric substrate, wherein the surface acoustic wave resonator is disposed close to and acoustically coupled to a position where the propagation directions of the surface acoustic waves are parallel to each other; The inner first busbar electrode included in the first IDT electrode and the inner second busbar electrode included in the second IDT electrode are separated from each other and disposed to face each other. One of the balanced input terminals, which is formed by using the electrical connection between the extraction electrodes extracted from at least two locations, and at least two locations on the inner second bus bar electrode. The balance operation is performed by using one of the balanced output terminals, which is configured by using the electrical connection between the extraction electrodes, and the balance operation is performed, and the extraction electrode includes the IDT electrode, the reflector electrode, and the like.
A surface acoustic wave filter formed in a gap between the two. 11. First and third surface acoustic wave resonators having reflector electrodes on both sides of an IDT electrode serving as an interdigital transducer electrode are formed at positions where the propagation directions of the respective surface acoustic waves are parallel. The ID is provided between the first and third surface acoustic wave resonators.
A plurality of strip line electrodes having substantially the same length as the electrode finger intersection width of the T electrode are arranged in parallel with the first and third surface acoustic wave resonators at the same electrode period, and the plurality of strip line electrodes are arranged in parallel. A second surface acoustic wave resonator composed of an electrode array having a periodic structure in which both end portions of the strip line electrode are connected to each other by a bus bar electrode is formed, and the first, second, and third surface acoustic wave resonators are formed. IDT of the first surface acoustic wave resonator which is disposed in close proximity and acoustically coupled
A first and a second extraction electrode forming a part of a balanced input terminal are formed in a gap between the reflector electrodes on both sides from both ends of the bus bar electrode inside the electrode toward the outside. The third surface acoustic wave resonator is configured such that a portion of a balanced output terminal is formed in a gap between the reflector electrodes on both sides from both ends of the bus bar electrode inside the IDT electrode to the outside.
And a fourth extraction electrode, and perform a balance operation. 12. The IDT of the first surface acoustic wave resonator, wherein the first and second extraction electrodes of the first surface acoustic wave resonator are connected to form one input terminal of a balanced input terminal. A bus bar electrode outside the electrode is used as the other input terminal of the balanced input terminal, and the third and fourth extraction electrodes of the third surface acoustic wave resonator are connected to one output terminal of a balanced output terminal. The surface acoustic wave filter according to claim 11, wherein the bus bar electrode outside the IDT electrode of the third surface acoustic wave resonator is the other output terminal of the balanced output terminals. 13. The first surface acoustic wave resonator is connected between the first and second extraction electrodes by a wiring pattern having a line width wider than the width of the extraction electrodes formed on a piezoelectric substrate. A part of the wiring pattern is further expanded to form one connection land of the balanced input terminal, and the bus bar electrode outside the IDT electrode of the first surface acoustic wave resonator is expanded outward to balance. Forming a second connection land of the mold input terminal; and providing a line width between the third and fourth extraction electrodes of the third surface acoustic wave resonator that is wider than the width of the extraction electrode formed on the piezoelectric substrate. Connected by a wiring pattern having
A part of the wiring pattern is further extended to form one connection land of the balanced output terminal, and a bus bar electrode outside the IDT electrode of the third surface acoustic wave resonator is extended outward to form a balanced type. 13. The surface acoustic wave filter according to claim 11, wherein another connection land of the output terminal is formed. 14. The surface acoustic wave filter according to claim 12, wherein the surface acoustic wave filter is formed in a plurality of stages on the same piezoelectric substrate, and the third and fourth extraction electrodes of the previous surface acoustic wave filter are opposed to the next stage of the surface acoustic wave filter. The first output electrode and the second output electrode of the surface acoustic wave filter are connected to each other, and the remaining output electrode of the previous surface acoustic wave filter and the remaining input electrode of the next surface acoustic wave filter are connected. A multi-stage surface acoustic wave filter. 15. The surface acoustic wave filter according to claim 12, wherein the surface acoustic wave filter is formed in a plurality of stages on the same piezoelectric substrate, and the next surface of the surface acoustic wave filter faces the third and fourth extraction electrodes of the previous surface acoustic wave filter. The first and second extraction electrodes of the wave filter are connected by a first inter-stage connection electrode on the piezoelectric substrate, which is wider than the width of the extraction electrode; An electrode and an input-side electrode are connected by a second inter-stage connection electrode on the piezoelectric substrate, the second inter-stage connection electrode being wider than the width of the extraction electrode; Are connected by a wiring pattern having a line width wider than the width of the lead electrode formed on the piezoelectric substrate,
A part of the wiring pattern is further extended to form one connection land of the balanced input terminal, and the bus bar electrode outside the IDT electrode of the first-stage surface acoustic wave filter is extended outward to obtain a balanced input. A wiring having a line width wider than the width of the extraction electrode formed on the piezoelectric substrate, between the third and fourth extraction electrodes of the surface acoustic wave filter at the last stage, forming the other connection land of the terminal; Connect by pattern,
A part of the wiring pattern is further expanded to form one connection land of the balanced type output terminal, and the bus bar electrode outside the IDT electrode of the last-stage surface acoustic wave filter is expanded outwardly to form a balanced type. A multi-stage surface acoustic wave filter, wherein the other connection land of the output terminal is formed. 16. The multi-stage surface acoustic wave filter according to claim 15, wherein the first and second inter-stage connection electrodes are connected via a reactance element. 17. The method according to claim 17, wherein the first and second inter-stage connection electrodes are:
16. The multi-stage surface acoustic wave filter according to claim 15, wherein one is grounded and the other is grounded via a reactance element. 18. The multi-stage surface acoustic wave filter according to claim 15, wherein the first inter-stage connection electrode is grounded via a reactance element, and the second inter-stage connection electrode is grounded. 19. The second surface acoustic wave resonator has substantially the same shape as the first and third surface acoustic wave resonators.
A structure having reflector electrodes on both sides of the IDT electrode,
The surface acoustic wave filter according to any one of claims 11 to 13, wherein the IDT electrode is grounded. 20. The second surface acoustic wave resonator has substantially the same shape as the first and third surface acoustic wave resonators.
A structure having reflector electrodes on both sides of the IDT electrode,
The multi-stage surface acoustic wave filter according to any one of claims 14 to 18, wherein the IDT electrode is grounded. 21. A first surface acoustic wave resonator having reflector electrodes on both sides of a first electrode for exciting surface acoustic waves, and a third elastic member having reflector electrodes on both sides of a third electrode. A surface acoustic wave filter, wherein a surface acoustic wave filter is disposed on a piezoelectric substrate at a position where propagation directions of the respective surface acoustic waves are parallel to each other, and a first electrode included in the first electrode The bus bar electrode and the third bus bar electrode included in the third electrode are separated from each other and arranged to face each other, and a plurality of bus bar electrodes are provided between the facing first bus bar electrode and the third bus bar electrode. A second surface acoustic wave resonator having a stripline electrode, an electrode connecting one end of the plurality of stripline electrodes, and an electrode connecting the other end is formed. The second elasticity The first surface acoustic wave resonator and the third surface acoustic wave resonator are disposed close to each other and acoustically coupled to the surface acoustic wave resonator, and at least on the first bus bar electrode One of the balanced input terminals, which is formed by using the electrical connection between the extraction electrodes extracted from two locations, and the extraction extracted from at least two locations on the third bus bar electrode A surface acoustic wave filter comprising a balanced output terminal and one of balanced output terminals formed by using electrical connection between electrodes. 22. First and third surface acoustic wave resonators each having a reflector electrode on both sides of an IDT electrode as an interdigital transducer electrode, and the direction of propagation of each surface acoustic wave is set on the piezoelectric substrate. A plurality of strip line electrodes are formed at positions parallel to each other and have the same electrode cycle as the first and third surface acoustic wave resonators between the first and third surface acoustic wave resonators. And a second surface acoustic wave resonator having a periodic structure electrode row in which the plurality of strip line electrodes are connected to each other by a bus bar electrode is formed, and the first and third elastic waves are formed. The surface acoustic wave resonator and the second surface acoustic wave resonator are disposed close to each other and acoustically coupled, and adjacent bus bar electrodes between the surface acoustic wave resonators are electrically separated from each other. A surface acoustic wave filter in which all of the periodic structure electrodes of the second surface acoustic wave resonator are grounded;
Assuming that the electrode finger intersection width of the DT electrode is W1 and the strip line length of the periodic structure electrode row constituting the second surface acoustic wave resonator is W2, the relative dimensions of W1 and W2 are 1 <W2. /W1≦1.3 , wherein a surface acoustic wave filter is set. 23. First, second, and third surface acoustic wave resonators having reflector electrodes on both sides of an IDT electrode serving as an interdigital transducer electrode are provided on a piezoelectric substrate to propagate respective surface acoustic waves. Acoustic coupling is performed by closely disposing them at positions where the directions are parallel to each other, and adjacent bus bar electrodes between the surface acoustic wave resonators are electrically separated and provided between the first and third surfaces. The second
A surface acoustic wave filter in which all of said IDT electrodes of said surface acoustic wave resonator are grounded, wherein said I and said third surface acoustic wave resonators are formed.
When the electrode finger intersection width of the DT electrode is W1 and the electrode finger intersection width of the IDT electrode of the second surface acoustic wave resonator is W2, the relative dimensions of W1 and W2 are 1 <W2 / W1 ≦
A surface acoustic wave filter characterized by being set to 1.3 . 24. The relative dimension of W1 and W2 is 1 <W2 / W
23. The condition is set to 1 ≦ 1.16.
Or a surface acoustic wave filter according to item 23. 25. A multi-stage surface acoustic wave filter according to claim 22, wherein a plurality of surface acoustic wave filters are cascaded by first and second inter-stage connection electrode patterns formed on a piezoelectric substrate. Surface wave filter. 26. The multi-stage surface acoustic wave filter according to claim 25, wherein one of the first and second inter-stage connection electrode patterns is directly grounded, and the other is grounded via a reactance element. . 27. The first surface acoustic wave filter of the preceding stage.
Surface acoustic wave resonator electrode is connected to the balanced input terminal,
26. The multi-stage surface acoustic wave filter according to claim 25, wherein a third surface acoustic wave resonator electrode of the subsequent surface acoustic wave filter is connected to a balanced output terminal. 28. A surface acoustic wave resonator having reflector electrodes on both sides of an IDT electrode serving as an interdigital transducer electrode, at least two surface acoustic wave resonators being arranged close to each other at positions where propagation directions of respective surface acoustic waves are parallel to each other. A surface acoustic wave filter on a piezoelectric substrate, which is acoustically coupled, wherein at least one pair of adjacent electrode fingers among a plurality of electrode fingers included in at least one of the IDT electrodes has an anti-phase relationship, and The surface acoustic wave filter, wherein the plurality of electrode fingers are connected so that their electric charges do not cancel each other. 29. The IDT electrode has an inner bus bar electrode and an outer bus bar electrode, and the phrase “the pair of electrode fingers has an opposite phase relationship” means that (1) the pitch between the pair of electrode fingers is ( m + 1/2) × λ (where m = 0, 1, 2, 3,..., λ is the wavelength of the excited surface acoustic wave), and any of those electrode fingers is Or (2) the pitch between the pair of electrode fingers is (m + 1 /
2) It is xλ and is connected to the outer bus bar electrode, or (3) the pitch between the pair of electrode fingers is (m + 1) xλ, and one of the electrode fingers is 29. The elastic surface according to claim 28, wherein one of the electrode fingers is connected to the inner bus bar electrode, and the other electrode finger is connected to the outer bus bar electrode. Wave filter. 30. The at least one IDT electrode,
The first, second, and third divided IDT electrodes are constituted by a pair of electrode fingers at a position where the first divided IDT electrode and the second divided IDT electrode are adjacent to each other, in the opposite phase relationship. And a pair of electrode fingers at a portion where the second divided IDT electrode and the third divided IDT electrode are adjacent to each other have an in-phase relationship, and further have a bus bar electrode outside the first divided IDT electrode. A bus bar electrode inside the second divided IDT electrode is connected, and a bus bar electrode outside the second divided IDT electrode and a bus bar electrode outside the third divided IDT electrode are connected. The surface acoustic wave filter according to claim 28, wherein: 31. The first, second and third split IDTs
The electrodes are grouped on the basis of the division of the bus bar electrode of the at least one IDT electrode, and the phrase “the pair of electrode fingers are in the same-phase relationship” means that (1) the pitch between the pair of electrode fingers is (M + 1/2) xλ (where m = 0, 1, 2, 3,..., Λ is the wavelength of the excited surface acoustic wave) and, of those electrode fingers,
One electrode finger is connected to the inner bus bar electrode, and the other electrode finger is connected to the outer bus bar electrode, or (2) between the pair of electrode fingers. The pitch is (m + 1) × λ, and all of the electrode fingers are connected to the inner bus bar electrode, or (3) the pitch between the pair of electrode fingers is (m + 1) × λ. 31. The surface acoustic wave filter according to claim 30, wherein the surface acoustic wave filter is provided so as to be connected to the outer bus bar electrode. 32. The at least one IDT electrode,
The first, second, and third divided IDT electrodes are constituted by a pair of electrode fingers at a position where the first divided IDT electrode and the second divided IDT electrode are adjacent to each other, in the opposite phase relationship. And a pair of electrode fingers at a portion where the second divided IDT electrode and the third divided IDT electrode are adjacent to each other have an in-phase relationship, and further have a bus bar electrode inside the first divided IDT electrode. A bus bar electrode outside the second divided IDT electrode is connected, and a bus bar electrode inside the second divided IDT electrode and a bus bar electrode inside the third divided IDT electrode are connected. The surface acoustic wave filter according to claim 28, wherein: 33. A surface acoustic wave resonator having reflector electrodes on both sides of an IDT electrode as an interdigital transducer electrode, at least two surface acoustic wave resonators being arranged close to each other at positions where propagation directions of respective surface acoustic waves are parallel to each other. A surface acoustic wave filter on a piezoelectric substrate, which is acoustically coupled by any one of a plurality of electrode fingers included in at least one of the IDT electrodes, wherein any adjacent pair of electrode fingers has an in-phase relationship, and The plurality of electrode fingers are connected such that respective charges do not cancel each other, and the at least one IDT electrode is configured by first, second, and third divided IDT electrodes , and ,
Electricity of IDT electrodes constituted by the divided IDT electrodes
A terminal is of a balanced type, a bus bar electrode inside the first divided IDT electrode and a bus bar electrode inside the second divided IDT electrode are connected, and a bus bar electrode outside the second divided IDT electrode is connected. A surface acoustic wave filter, wherein a bus bar electrode is connected to a bus bar electrode outside the third divided IDT electrode. 34. The phrase “the pair of electrode fingers has the same phase relationship” means that (1) the pitch between the pair of electrode fingers is (m + 1 /
2) xλ (where m = 0, 1, 2, 3,...)
·, Λ is the wavelength of the excited surface acoustic wave) and
And (2) one of the electrode fingers is connected to the inner bus bar electrode and the other electrode finger is connected to the outer bus bar electrode. The pitch between the pair of electrode fingers is (m + 1) x
λ, and all of the electrode fingers are connected to the inner bus bar electrode, or (3) the pitch between the pair of electrode fingers is (m + 1) × λ, and The surface acoustic wave filter according to claim 33, wherein the surface acoustic wave filter is connected to an outer bus bar electrode. 35. A surface acoustic wave filter according to any one of claims 30 to 32 in which the electrical terminal of IDT electrode constituted by said divided IDT electrodes, characterized in that it is a balanced. 36. The first and third divided IDTs, wherein the inner electrode and the outer electrode of the second divided IDT electrode are connected to balanced positive and negative electric terminals, respectively.
The surface acoustic wave filter according to any one of claims 30 to 32 , wherein an electrode of the electrode that is not connected to any of the positive and negative electric terminals is grounded. 37. By changing the division ratio of the divided IDT electrodes, claims wherein the total capacity of the IDT electrode is made variable, and controlling the impedance of the input and output
The surface acoustic wave filter according to any one of 30 to 36 . 38. A surface acoustic wave device comprising two surface acoustic wave resonators each having a reflector electrode on both sides of an IDT electrode and closely arranged at positions where propagation directions of respective surface acoustic waves are parallel to each other, and acoustically coupled. A multi-stage surface acoustic wave filter on a piezoelectric substrate, in which a plurality of wave filters are connected in cascade by an inter-stage connection electrode pattern, wherein the uppermost and lowermost IDTs of the multi-stage surface acoustic wave filter are provided.
Among a plurality of electrode fingers included in at least one of the IDT electrodes, at least a pair of adjacent electrode fingers are in a reverse phase relationship, and the plurality of electrode fingers are connected such that respective charges do not cancel each other. A multistage surface acoustic wave filter characterized in that: 39. The at least one IDT electrode,
The first, second, and third divided IDT electrodes are constituted by a pair of electrode fingers at a position where the first divided IDT electrode and the second divided IDT electrode are adjacent to each other, in the opposite phase relationship. And a pair of electrode fingers at a portion where the second divided IDT electrode and the third divided IDT electrode are adjacent to each other have an in-phase relationship, and further have a bus bar electrode outside the first divided IDT electrode. A bus bar electrode inside the second divided IDT electrode is connected, and a bus bar electrode outside the second divided IDT electrode and a bus bar electrode outside the third divided IDT electrode are connected. The multi-stage surface acoustic wave filter according to claim 38, wherein: 40. The at least one IDT electrode,
The first, second, and third divided IDT electrodes are constituted by a pair of electrode fingers at a position where the first divided IDT electrode and the second divided IDT electrode are adjacent to each other, in the opposite phase relationship. And a pair of electrode fingers at a portion where the second divided IDT electrode and the third divided IDT electrode are adjacent to each other have an in-phase relationship, and further have a bus bar electrode inside the first divided IDT electrode. A bus bar electrode outside the second divided IDT electrode is connected, and a bus bar electrode inside the second divided IDT electrode and a bus bar electrode inside the third divided IDT electrode are connected. The multi-stage surface acoustic wave filter according to claim 38, wherein: 41. A surface acoustic wave device comprising two surface acoustic wave resonators each having a reflector electrode on both sides of an IDT electrode and closely arranged at positions where the propagation directions of the respective surface acoustic waves are parallel to each other and acoustically coupled. A multi-stage surface acoustic wave filter on a piezoelectric substrate, in which a plurality of wave filters are connected in cascade by an inter-stage connection electrode pattern, wherein the uppermost and lowermost IDTs of the multi-stage surface acoustic wave filter are provided.
In a plurality of electrode fingers included in at least one IDT electrode of the electrodes, any adjacent pair of electrode fingers are in the same-phase relationship, and the plurality of electrode fingers are such that respective charges do not cancel each other. The at least one IDT electrode is constituted by first, second, and third divided IDT electrodes; and a bus bar electrode inside the first divided IDT electrode and the second divided IDT electrode. A multi-stage structure in which a bus bar electrode inside the IDT electrode is connected, and a bus bar electrode outside the second divided IDT electrode is connected to a bus bar electrode outside the third divided IDT electrode. Surface acoustic wave filter. 42. The multi-stage surface acoustic wave filter according to claim 39, wherein the electric terminals of the IDT electrodes constituted by the divided IDT electrodes are of a balanced type. 43. The first and third divided IDTs, wherein the inner electrode and the outer electrode of the second divided IDT electrode are respectively connected to balanced positive and negative electric terminals.
42. The multistage surface acoustic wave filter according to claim 39, wherein an electrode of the electrode that is not connected to any of the positive and negative electric terminals is grounded. 44. The multi-stage elastic surface according to claim 42, wherein a plurality of the inter-stage connection electrode patterns are provided, one of them is grounded, and the other is grounded via a reactance element. Wave filter. 45. On a piezoelectric substrate, three surface acoustic wave resonators having reflector electrodes on both sides of an IDT electrode are arranged close to each other at positions where propagation directions of respective surface acoustic waves are parallel to each other. A coupled surface acoustic wave filter, wherein among the three surface acoustic wave resonators, all IDT electrodes constituting the surface acoustic wave resonator disposed at the center are electrically grounded, and IDT electrodes constituting the arranged surface acoustic wave resonator are electrically independent, and further,
Among the plurality of electrode fingers included in the IDT electrode of at least one of the surface acoustic wave resonators disposed on the outside, at least one pair of adjacent electrode fingers has an anti-phase relationship, and Wherein the electrode fingers are connected so that their charges do not cancel each other. 46. A multi-stage surface acoustic wave filter according to claim 45, wherein the surface acoustic wave filter according to claim 45 is cascaded by a plurality of stages and a plurality of inter-stage connection electrode patterns formed on the piezoelectric substrate.