WO2018003268A1 - Elastic wave filter device, multiplexer, high-frequency front end circuit, and communication device - Google Patents

Abstract

Provided is a ladder-type elastic wave filter device (21) comprising parallel resonators (151-154) and series resonators (101-105) configured from an IDT electrode (22) that is formed on a substrate (220) having a piezoelectric layer (227). In the parallel resonators (152 and 153) excluding the parallel resonator (151) connected closest to an input power terminal (100) and the parallel resonator (154) connected closet to an output power terminal (120) among the parallel resonators (151-154), the anti-resonance frequency fap152 of the parallel resonator (152) is lower than the anti-resonances frequencies fap151 and fap154 of the parallel resonators (151 and 154), and the anti-resonance frequency fap153 of the parallel resonator (153) is higher than the anti-resonance frequencies fap151 and fap154 of the parallel resonators (151 and 154).

Description

Elastic wave filter device, multiplexer, high-frequency front-end circuit, and communication device

The present invention relates to an elastic wave filter device having a ladder-type resonator structure, a multiplexer including the elastic wave filter device, a high-frequency front-end circuit, and a communication device.

From the viewpoint of effectively using frequency resources for wireless communication, various frequency bands are allocated as communication bands for mobile terminals and the like. In addition, in recent years, due to an increase in data communication amount and multi-functionality of mobile terminals, RF (Radio Frequency) circuits having close frequency bands are often used simultaneously for one mobile terminal. For example, in the case of 2.4 GHz band WiFi (2400-2483 MHz), Band 40 (2300-2400 MHz) exists on the low frequency side, and Band 7 (transmission band: 2500-2570 MHz, reception band: 2620-2690 MHz) on the high frequency side. Therefore, the 2.4 GHz band WiFi filter requires steepness on both the low frequency side and the high frequency side.

Patent Document 1 discloses a surface acoustic wave device that can suppress an increase in insertion loss while narrowing the band.

FIG. 8 is a diagram showing a resonator structure and resonance characteristics of the surface acoustic wave device described in Patent Document 1. In the surface acoustic wave device described in Patent Document 1, as shown in FIG. 6A, series resonators 511a, 511b and 511c, and parallel resonators 512a, 512b, 512c and 512d are arranged in a ladder shape. Has been. As shown in FIG. 5B, the resonance frequencies of the series resonators 511a and 511b among the series resonators 511a to 511c are set lower than the anti-resonance frequencies of the parallel resonators 512a to 512d. As a result, the capacitive region of the series resonator 511c is set in the inductive region formed by the parallel resonators 512a to 512d and the series resonators 511a and 511b that form the pass band. It is said that a lossy surface acoustic wave device can be realized.

JP 2005-045475 A

However, as in the conventional ladder-type surface acoustic wave device described in Patent Document 1, the design method for matching the antiresonance frequencies of the parallel resonators 512a to 512d makes the filter passband width and the steepness of both ends of the passband. It becomes difficult to adjust the characteristics. For example, if the anti-resonance frequencies of all the parallel resonators are arranged in the vicinity of the center of the pass band, the bandwidth may be excessively widened. For example, when a narrow passband is required, such as a 2.4 GHz band WiFi filter, it is not possible to secure a sufficient amount of attenuation on the low frequency side outside the passband. For this reason, it is difficult to realize a narrow band filter having steepness on both the low frequency side and the high frequency side of the pass band while ensuring low loss of the pass band.

Therefore, the present invention has been made to solve the above-described problem, and has a narrow band filter characteristic with good steepness on both the low frequency side and the high frequency side while ensuring low loss in the pass band. It is an object of the present invention to provide an elastic wave filter device, a multiplexer, a high frequency front end circuit, and a communication device.

In order to achieve the above object, an elastic wave filter device according to an aspect of the present invention is a ladder-type elastic wave filter device having a series resonator and a parallel resonator, and includes a first input / output terminal and a second input. Three or more series resonators connected in series between output terminals, a connection node between the first input / output terminal, the second input / output terminal, and the three or more series resonators and a reference terminal 4 or more parallel resonators connected in between, and among the 4 or more parallel resonators, a first parallel resonator connected closest to the first input / output terminal, and the second input / output terminal In the two or more parallel resonators except for the second parallel resonator connected closest to the first parallel resonator, the anti-resonance frequency of the third parallel resonator that is one of the two or more parallel resonators is Antiresonance of the parallel resonator and the second parallel resonator The resonance frequency of the third parallel resonator is lower than the wave number and lower than the resonance frequency of the first parallel resonator and the second parallel resonator, and is one of the two or more parallel resonators. The anti-resonance frequency of the fourth parallel resonator is higher than the anti-resonance frequencies of the first parallel resonator and the second parallel resonator, and the resonance frequency of the fourth parallel resonator is the first resonance frequency of the first parallel resonator. The resonance frequency is higher than that of the parallel resonator and the second parallel resonator.

When the anti-resonance frequencies of all parallel resonators are arranged near the center of the passband as in the conventional ladder-type elastic wave filter, the bandwidth becomes too wide even if an attempt is made to obtain a narrowband filter characteristic, for example, The attenuation on the low frequency side outside the passband cannot be secured.

In contrast, the anti-resonance frequency of the fourth parallel resonator is set to the anti-resonance frequency of the first parallel resonator closest to the first input / output terminal and the second parallel resonator closest to the second input / output terminal. Shift to a higher frequency side than the anti-resonance frequency. As a result, the pass band width on the low pass band side can be narrowed, and the attenuation on the low frequency side outside the pass band can be secured. At this time, because the impedance matching on the low frequency side of the passband is shifted due to the effect of shifting the antiresonance frequency of the fourth parallel resonator to the high frequency side, the antiresonance frequency of the third parallel resonator is changed to the first parallel resonator. And the antiresonance frequency of the second parallel resonator. Thereby, the impedance matching can be adjusted. The anti-resonance frequency of the first parallel resonator and the second parallel resonator is between the anti-resonance frequency of the third parallel resonator and the anti-resonance frequency of the fourth parallel resonator, and near the center of the passband. Therefore, impedance matching does not occur in the first input / output terminal and the second input / output terminal. As described above, it is possible to obtain a narrow-band ladder-type filter having good steepness on both the low frequency side and high frequency side of the pass band while ensuring low loss of the pass band.

An elastic wave filter device according to one embodiment of the present invention is a ladder-type elastic wave filter device having a series resonator and a parallel resonator formed of IDT electrodes formed on a substrate having a piezoelectric layer. And three or more series resonators connected in series between the first input / output terminal and the second input / output terminal, the first input / output terminal, the second input / output terminal, and the three or more series resonances. 4 or more parallel resonators connected between one of the connection nodes of the child and the reference terminal, and the first of the four or more parallel resonators connected closest to the first input / output terminal. In two or more parallel resonators excluding a parallel resonator and a second parallel resonator connected closest to the second input / output terminal, a third parallel resonance which is one of the two or more parallel resonators The electrode pitch of the child is the first parallel The electrode pitch of the fourth parallel resonator, which is larger than the electrode pitch of the pendulum and the second parallel resonator and is one of the two or more parallel resonators, is the first parallel resonator and the second parallel resonator. It is smaller than the electrode pitch of the resonator.

The electrode pitch of the fourth parallel resonator is smaller than the electrode pitch of the first parallel resonator closest to the first input / output terminal and the electrode pitch of the second parallel resonator closest to the second input / output terminal. By doing so, the anti-resonance frequency of the fourth parallel resonator is shifted to a higher frequency side than the vicinity of the center in the pass band. As a result, the pass band width on the low pass band side can be narrowed, and the attenuation on the low frequency side outside the pass band can be secured. At this time, because the impedance matching on the low frequency side of the passband is shifted due to the effect of shifting the anti-resonance frequency of the fourth parallel resonator to the high frequency side, the electrode pitch of the third parallel resonator is changed to that of the first parallel resonator. By making it larger than the electrode pitch and the electrode pitch of the second parallel resonator, the anti-resonance frequency of the third parallel resonator is shifted to the lower frequency side from the vicinity of the center in the pass band. Thereby, the impedance matching can be adjusted. The electrode pitch of the first parallel resonator and the second parallel resonator is between the electrode pitch of the third parallel resonator and the electrode pitch of the fourth parallel resonator, and is the first parallel resonator and the second parallel resonator. Since the antiresonance frequency of the parallel resonator is set near the center of the pass band, impedance matching at the first input / output terminal and the second input / output terminal does not go away. As described above, it is possible to obtain a narrow-band ladder-type filter having good steepness on both the low frequency side and high frequency side of the pass band while ensuring low loss of the pass band.

An elastic wave filter device according to one embodiment of the present invention is a ladder-type elastic wave filter device having a series resonator and a parallel resonator formed of IDT electrodes formed on a substrate having a piezoelectric layer. And three or more series resonators connected in series between the first input / output terminal and the second input / output terminal, the first input / output terminal, the second input / output terminal, and the three or more series resonances. 4 or more parallel resonators connected between one of the connection nodes of the child and the reference terminal, and the first of the four or more parallel resonators connected closest to the first input / output terminal. In two or more parallel resonators excluding a parallel resonator and a second parallel resonator connected closest to the second input / output terminal, a third parallel resonance which is one of the two or more parallel resonators The electrode duty of the child is The electrode duty of the fourth parallel resonator, which is larger than the electrode duty of the parallel resonator and the second parallel resonator and is one of the two or more parallel resonators, is the first parallel resonator and the second parallel resonator. It is smaller than the electrode duty of the two parallel resonators.

The electrode duty of the fourth parallel resonator is smaller than the electrode duty of the first parallel resonator closest to the first input / output terminal and the electrode duty of the second parallel resonator closest to the second input / output terminal. By doing so, the anti-resonance frequency of the fourth parallel resonator is shifted to a higher frequency side than the vicinity of the center in the pass band. As a result, the pass band width on the low pass band side can be narrowed, and the attenuation on the low frequency side outside the pass band can be secured. At this time, because the impedance matching on the low frequency side of the passband is shifted due to the effect of shifting the antiresonance frequency of the fourth parallel resonator to the high frequency side, the electrode duty of the third parallel resonator is set to the electrode of the first parallel resonator. By making the duty and the electrode duty of the second parallel resonator larger, the anti-resonance frequency of the third parallel resonator is shifted to the lower frequency side than the vicinity of the center in the pass band. Thereby, the impedance matching can be adjusted. The electrode duty of the first parallel resonator and the second parallel resonator is between the electrode duty of the third parallel resonator and the electrode duty of the fourth parallel resonator, and is the first parallel resonator and the second parallel resonator. Since the antiresonance frequency of the parallel resonator is set near the center of the pass band, impedance matching at the first input / output terminal and the second input / output terminal does not go away. As described above, it is possible to obtain a narrow-band ladder-type filter having good steepness on both the low frequency side and high frequency side of the pass band while ensuring low loss of the pass band.

The substrate includes a piezoelectric layer in which the IDT electrode is formed on one main surface, and a high-sonic velocity supporting substrate whose bulk wave velocity is higher than an acoustic wave velocity that propagates through the piezoelectric layer. And a low sound velocity film disposed between the high sound velocity support substrate and the piezoelectric layer and having a bulk wave sound velocity propagating at a lower speed than an elastic wave sound velocity propagating through the piezoelectric layer. .

Thereby, the Q value of each resonator including the IDT electrode formed on the substrate having the piezoelectric layer can be maintained at a high value.

The multiplexer according to one aspect of the present invention is a multiplexer that demultiplexes an input signal by including a plurality of bandpass filters that selectively pass a predetermined frequency band, and the plurality of bandpass filters pass through the multiplexer. Each of the frequency bands is different, one end of each of the plurality of band pass filters is connected to a common terminal, and at least one of the plurality of band pass filters is any one of the elastic wave filter devices. .

Thereby, it is possible to provide a multiplexer having a narrow band filter characteristic with good steepness on both the low frequency side and high frequency side of the pass band while ensuring low loss of the pass band.

A high-frequency front-end circuit according to an aspect of the present invention includes any one of the elastic wave filter devices or the multiplexer and an amplifier circuit that is connected to the elastic wave filter device and amplifies a high-frequency signal.

Thus, it is possible to provide a high-frequency front-end circuit having a narrow-band filter with good steepness on both the low-frequency side and high-frequency side while ensuring a low loss in the pass band.

Also, a communication device according to an aspect of the present invention includes the high-frequency front end circuit and an RF signal processing circuit that processes a high-frequency signal.

Thereby, it is possible to provide a communication apparatus having a narrow band filter with good steepness on both the low frequency side and the high frequency side while ensuring a low loss in the pass band.

According to the present invention, an elastic wave filter device, a multiplexer, a high-frequency front-end circuit, and a communication having a narrow-band filter characteristic with good steepness on both the low-frequency side and the high-frequency side while ensuring a low loss in the pass band An apparatus can be provided.

FIG. 1 is a circuit configuration diagram of an acoustic wave filter device according to an embodiment. FIG. 2 is a plan view and a cross-sectional view schematically illustrating a resonator of the acoustic wave filter device according to the embodiment. FIG. 3 is a circuit configuration diagram illustrating a principle of operation of a ladder-type elastic wave filter and a graph showing frequency characteristics. FIG. 4 is a cross-sectional view illustrating a mounting configuration of the acoustic wave filter device according to the embodiment. FIG. 5 is a graph showing filter pass characteristics and resonance characteristics of the acoustic wave filter device according to the example. FIG. 6 is a graph comparing the filter pass characteristics of the elastic wave filter devices according to the example and the comparative example. FIG. 7 is a circuit configuration diagram of a high-frequency front-end circuit and a communication device having an elastic wave filter device according to an embodiment. FIG. 8 is a diagram showing a resonator structure and resonance characteristics of the surface acoustic wave device described in Patent Document 1. In FIG.

Hereinafter, embodiments of the present invention will be described in detail with reference to examples and drawings. It should be noted that any of the embodiments described below is a comprehensive or specific example. Numerical values, shapes, materials, constituent elements, arrangement of constituent elements, connection forms, and the like shown in the following examples are merely examples, and are not intended to limit the present invention. Among the constituent elements in the following embodiments, constituent elements not described in the independent claims are described as arbitrary constituent elements. In addition, the size or size ratio of the components shown in the drawings is not necessarily strict.

(Example)
[1. Basic configuration of elastic wave filter device]
A basic configuration of an elastic wave filter device according to an embodiment of the present invention will be described. In this embodiment, a band-pass surface acoustic wave filter applied to a 2.4 GHz band WiFi (2400-2483 MHz) is illustrated.

FIG. 1 is a circuit configuration diagram of an elastic wave filter device 21 according to an embodiment. As shown in the figure, the acoustic wave filter device 21 includes series resonators 101, 102, 103, 104, and 105, parallel resonators 151, 152, 153, and 154, input / output terminals 100 and 120, Is provided.

The series resonators 101 to 105 are connected in series between the input / output terminal 100 and the input / output terminal 120. The parallel resonators 151 to 154 are connected in parallel between connection points of the input / output terminal 100, the input / output terminal 120, and the series resonators 101 to 105, and a reference terminal (ground). Due to the above-described connection configuration of the series resonators 101 to 105 and the parallel resonators 151 to 154, the acoustic wave filter device 21 constitutes a ladder type band pass filter.

The number of series resonators and parallel resonators of the acoustic wave filter device according to the present invention is not limited to 5 and 4, respectively, and there may be 2 or more series resonators and 4 or more parallel resonators. That's fine. Further, for a ladder structure composed of two or more series resonators and four or more parallel resonators, for example, a longitudinally coupled resonance is provided between the input / output terminal 100 and the input / output terminal 120. A child or the like may be connected.

In this embodiment, the reference terminal (ground) to which the parallel resonators 152 to 154 are connected is shared, but the reference terminal (ground) to which the parallel resonators 151 to 154 are connected is shared. Or may be individualized.

Further, circuit elements such as inductors and capacitors may be inserted or connected to connection points of the input / output terminals 100 and 120, the series resonators 101 to 105, and the parallel resonators 151 to 154.

In this embodiment, an example in which the elastic wave filter device 21 is applied to the 2.4 GHz band WiFi will be described. However, the elastic wave filter device according to the present invention is not limited to WiFi and can be applied to other frequency bands. It is.

[2. Resonator structure of acoustic wave filter device]
The structure of each resonator that is a component of the acoustic wave filter device 21 will be described. The series resonator and the parallel resonator constituting the acoustic wave filter device 21 according to the present embodiment are surface acoustic wave (SAW) resonators.

FIG. 2 is a plan view and a cross-sectional view schematically showing a resonator of the acoustic wave filter device 21 according to the embodiment. In the figure, a schematic plan view and a schematic cross-sectional view showing the structure of the series resonator 101 among a plurality of resonators constituting the acoustic wave filter device 21 are illustrated. Note that the series resonator 101 shown in FIG. 2 is for explaining a typical structure of the plurality of resonators, and the number and length of electrode fingers constituting the electrode are the same. It is not limited.

Each resonator of the acoustic wave filter device 21 includes a substrate 220 having a piezoelectric layer 227 and IDT (InterDigital Transducer) electrodes 22a and 22b having a comb shape.

As shown in the plan view of FIG. 2, a pair of IDT electrodes 22a and 22b facing each other are formed on the piezoelectric layer 227. The IDT electrode 22a includes a plurality of electrode fingers 222a that are parallel to each other and a bus bar electrode 221a that connects the plurality of electrode fingers 222a. The IDT electrode 22b includes a plurality of electrode fingers 222b that are parallel to each other and a bus bar electrode 221b that connects the plurality of electrode fingers 222b. The plurality of electrode fingers 222a and 222b are formed along a direction orthogonal to the X-axis direction.

Further, the IDT electrode 22 composed of the plurality of electrode fingers 222a and 222b and the bus bar electrodes 221a and 221b has a laminated structure of the adhesion layer 223 and the main electrode layer 224 as shown in the cross-sectional view of FIG. ing.

The adhesion layer 223 is a layer for improving adhesion between the piezoelectric layer 227 and the main electrode layer 224, and Ti is used as a material, for example. The film thickness of the adhesion layer 223 is 12 nm, for example.

The main electrode layer 224 is made of, for example, Al containing 1% Cu. The film thickness of the main electrode layer 224 is, for example, 131 nm.

The protective layer 225 is formed so as to cover the IDT electrodes 22a and 22b. The protective layer 225 is a layer for the purpose of protecting the main electrode layer 224 from the external environment, adjusting frequency temperature characteristics, and improving moisture resistance, for example, a film mainly composed of silicon dioxide. . The film thickness of the protective layer 225 is, for example, 30 nm.

Note that the materials constituting the adhesion layer 223, the main electrode layer 224, and the protective layer 225 are not limited to the materials described above. Furthermore, the IDT electrode 22 may not have the above-described laminated structure. The IDT electrode 22 may be made of, for example, a metal or alloy such as Ti, Al, Cu, Pt, Au, Ag, or Pd, or may be made of a plurality of laminates made of the above metal or alloy. May be. Further, the protective layer 225 may not be formed.

Next, the laminated structure of the substrate 220 will be described.

As shown in the lower part of FIG. 2, the substrate 220 includes a high sound speed support substrate 228, a low sound speed film 226, and a piezoelectric layer 227. The high sound speed support substrate 228, the low sound speed film 226, and the piezoelectric layer 227 are provided. It has a laminated structure in this order.

The piezoelectric layer 227 is formed of, for example, a 50 ° Y-cut X-propagating LiTaO ₃ piezoelectric single crystal or a piezoelectric ceramic (lithium tantalate unit cut along a plane whose normal is an axis rotated by 50 ° from the Y axis with the X axis as the central axis. A single crystal or ceramics in which a surface acoustic wave propagates in the X-axis direction). The thickness of the piezoelectric layer 227 is 3.5λ or less, for example, 450 nm when the wavelength of the elastic wave determined by the electrode pitch of the IDT electrode 22 is λ. The electrode pitch of the IDT electrode 22 refers to the distance between the centers of adjacent electrode fingers in the IDT electrode 22.

The high sound velocity support substrate 228 is a substrate that supports the low sound velocity film 226, the piezoelectric layer 227, and the IDT electrode 22. The high-sonic support substrate 228 is a substrate in which the acoustic velocity of the bulk wave in the high-sonic support substrate 228 is higher than that of the surface wave or boundary wave that propagates through the piezoelectric layer 227. The piezoelectric layer 227 and the low acoustic velocity film 226 are confined in a laminated portion and function so as not to leak downward from the high acoustic velocity support substrate 228. The high sound speed support substrate 228 is, for example, a silicon substrate and has a thickness of, for example, 200 μm. Note that the high sound velocity support substrate 228 includes (1) a piezoelectric body such as aluminum nitride, aluminum oxide, silicon carbide, silicon nitride, silicon, sapphire, lithium tantalate, lithium niobate, or quartz, (2) alumina, zirconia, Various ceramics such as cordierite, mullite, steatite, or forsterite, (3) magnesia diamond, (4) materials containing the above materials as main components, and (5) mixtures of the above materials as main components. You may be comprised with either of materials.

The low acoustic velocity film 226 is a membrane in which the acoustic velocity of the bulk wave in the low acoustic velocity film 226 is lower than the acoustic velocity of the elastic wave propagating through the piezoelectric layer 227. The low acoustic velocity membrane 226 is formed between the piezoelectric layer 227 and the high acoustic velocity support substrate 228. Arranged between. Due to this structure and the property that energy is concentrated in a medium where acoustic waves are essentially low in sound velocity, leakage of surface acoustic wave energy to the outside of the IDT electrode is suppressed. The low acoustic velocity film 226 is, for example, a film mainly composed of silicon dioxide. The thickness of the low acoustic velocity film 226 is 2λ or less, for example, 505 nm, where λ is the wavelength of the elastic wave determined by the electrode pitch of the IDT electrode 22.

According to the laminated structure of the substrate 220, the Q value at the resonance frequency and the anti-resonance frequency can be significantly increased as compared with the conventional structure in which the piezoelectric substrate is used as a single layer. That is, since a surface acoustic wave resonator having a high Q value can be configured, a filter with a small insertion loss can be configured using the surface acoustic wave resonator.

Note that the high sound velocity support substrate 228 has a structure in which a support substrate and a high sound velocity film in which the sound velocity of a propagating bulk wave is higher than that of a surface wave or boundary wave propagating in the piezoelectric layer 227 is laminated. You may have. In this case, the support substrate is a piezoelectric material such as sapphire, lithium tantalate, lithium niobate, crystal, alumina, magnesia, silicon nitride, aluminum nitride, silicon carbide, zirconia, cordierite, mullite, steatite, forsterite, etc. Various ceramics, dielectrics such as glass, semiconductors such as silicon and gallium nitride, resin substrates, and the like can be used. In addition, the high sound velocity film includes various materials such as aluminum nitride, aluminum oxide, silicon carbide, silicon nitride, silicon oxynitride, DLC film or diamond, a medium mainly composed of the above materials, and a medium mainly composed of a mixture of the above materials. High sound velocity material can be used.

In the present embodiment, the IDT electrode 22 constituting the acoustic wave filter device 21 is formed on the substrate 220 having the piezoelectric layer 227. However, the substrate on which the IDT electrode 22 is formed is piezoelectric. A piezoelectric substrate made of a single layer of the body layer 227 may be used. The piezoelectric substrate in this case is composed of, for example, a LiTaO ₃ piezoelectric single crystal or another piezoelectric single crystal such as LiNbO ₃ .

In addition, the substrate on which the IDT electrode 22 is formed may have a structure in which a piezoelectric layer is laminated on a support substrate in addition to a piezoelectric layer as a whole as long as it has a piezoelectric layer.

Moreover, the piezoelectric layer 227 according to the embodiment is obtained by using a 50 ° Y-cut X-propagation LiTaO ₃ single crystal, cut angles of single crystal material is not limited thereto. In other words, the laminated structure, material, and thickness may be appropriately changed according to the required pass characteristics of the acoustic wave filter device, and a LiTaO ₃ piezoelectric substrate or a LiNbO ₃ piezoelectric substrate having a cut angle other than the above is used. The same effect can be achieved even with the conventional surface acoustic wave filter.

Here, the design parameters of the IDT electrode 22 will be described. The wavelength of the surface acoustic wave resonator is defined by a wavelength λ that is a repetition period of the plurality of electrode fingers 222a or 222b constituting the IDT electrode 22 shown in the middle stage of FIG. The electrode pitch is ½ of the wavelength λ, the line width of the electrode fingers 222a and 222b constituting the IDT electrodes 22a and 22b is W, and the space width between the adjacent electrode fingers 222a and 222b Is defined as (W + S). Further, as shown in the upper part of FIG. 2, the crossing width L of the IDT electrode is an overlapping electrode finger length when viewed from the X-axis direction of the electrode finger 222a of the IDT electrode 22a and the electrode finger 222b of the IDT electrode 22b. It is. The electrode duty of each resonator is the line width occupation ratio of the plurality of electrode fingers 222a and 222b, and is the ratio of the line width to the sum of the line width and the space width of the plurality of electrode fingers 222a and 222b. , W / (W + S).

[3. Principle of operation of elastic wave filter]
Here, the operation principle of the ladder-type elastic wave filter according to the present embodiment will be described.

FIG. 3 is a circuit configuration diagram illustrating a principle of operation of a ladder-type elastic wave filter and a graph showing frequency characteristics.

The elastic wave filter shown in FIG. 3 (a) is a basic ladder type filter composed of one series resonator 50s and one parallel resonator 50p. As shown in FIG. 3B, the parallel resonator 50p has a resonance frequency frp and an anti-resonance frequency fap (> frp) in resonance characteristics. The series resonator 50s has a resonance frequency frs and an anti-resonance frequency fas (> frs> frp) in resonance characteristics.

In configuring a band-pass filter with ladder-type resonators, the anti-resonance frequency fap of the parallel resonator 50p and the resonance frequency frs of the series resonator 50s are brought close to each other. As a result, the vicinity of the resonance frequency frp in which the impedance of the parallel resonator 50p approaches 0 becomes a low-frequency side stop band. As the frequency increases, the impedance of the parallel resonator 50p increases near the antiresonance frequency fap, and the impedance of the series resonator 50s approaches 0 near the resonance frequency frs. As a result, in the vicinity of the anti-resonance frequency fap to the resonance frequency frs, the signal path from the input / output terminals 100 to 120 becomes a signal pass band. Further, when the frequency becomes high and near the anti-resonance frequency fas, the impedance of the series resonator 50s becomes high, which becomes a high-frequency side blocking region.

Note that the number of resonance stages composed of parallel resonators and series resonators is appropriately optimized according to the required specifications. In general, when an elastic wave filter is configured with a plurality of resonance stages, the anti-resonance frequencies fap of the plurality of parallel resonators are substantially matched, and the anti-resonance frequencies fas of the plurality of series resonators are substantially matched.

In the acoustic wave filter having the above operation principle, when a high-frequency signal is input from the input / output terminal 100, a potential difference is generated between the input / output terminal 100 and the reference terminal, which causes the piezoelectric layer to be distorted, thereby causing an X direction. Surface acoustic waves propagating to the surface are generated. Here, by making the pitch λ of the IDT electrodes 22a and 22b substantially coincide with the wavelength of the pass band, only a high-frequency signal having a frequency component to be passed passes through the elastic wave filter.

[4. Mounting configuration of elastic wave filter]
An example of the mounting configuration of the acoustic wave filter device 21 according to the present embodiment will be described.

FIG. 4 is a cross-sectional view showing a mounting configuration of the acoustic wave filter device 21 according to the embodiment. The acoustic wave filter device 21 shown in the figure includes a substrate 220 having a piezoelectric layer, an IDT electrode 22, an electrode pad 233, a support layer 231, a cover layer 232, an under bump metal 234, and a bump 235. And a mounting board 23 and a resin member 24. The acoustic wave filter device 21 according to the present embodiment has a so-called WLP (Wafer Level Package) structure in which a substrate 220 having an acoustic wave propagation function also serves as a package function, and realizes a reduction in size and height. Yes. Such a WLP structure is applied to a SAW filter such as the elastic wave filter device 21.

As shown in FIG. 2, the IDT electrode 22 is a functional electrode that converts an elastic wave propagating through the substrate 220 into an electric signal, or converts an electric signal into the elastic wave.

The electrode pad 233 is electrically connected to the IDT electrode 22, is formed on the surface of the substrate 220, extracts an electric signal converted by the IDT electrode 22, or supplies the electric signal to the IDT electrode 22. The electrode pad 233 is, for example, a stacked body of terminal electrodes 233a and wiring electrodes 233b. The terminal electrode 233 a is an electrode connected to the IDT electrode 22 and is provided around the IDT electrode 22. The terminal electrode 233a is made of the same material as the IDT electrode 22. The wiring electrode 233b is an electrode electrically connected to the terminal electrode 233a, and constitutes a part of a wiring path for connecting the IDT electrode 22 and the external wiring. The terminal electrode 233a and the wiring electrode 233b may be composed of a plurality of laminated bodies composed of metals or alloys.

The support layer 231 is a support member formed so as to surround the IDT electrode 22. The cover layer 232 is a cover member formed on the support layer 231.

With the above configuration, the substrate 220, the support layer 231 and the cover layer 232 seal the IDT electrode 22 in the hollow space 236.

In the cover layer 232 and the support layer 231, a via hole (through hole) reaching the electrode pad 233 is formed. This via hole is filled with an under bump metal 234. The under bump metal 234 penetrates the cover layer 232 and the support layer 231 and is formed above the substrate 220. A bump 235 exposed to the outside is formed on the under bump metal 234.

The bump 235 is formed so as to protrude from the cover layer 232. The bump 235 is a ball-shaped electrode made of a highly conductive metal, and examples thereof include a solder bump made of Sn / Ag / Cu and a bump mainly composed of Au.

The mounting board 23 is a board on which the acoustic wave filter is mounted, and is, for example, a printed board or a ceramic board. A land electrode 237 and wiring (not shown) are formed on one main surface of the mounting substrate 23. The substrate 220 and the IDT electrode 22 are flip-chip mounted (flip chip bonding) on the land electrode 237 of the mounting substrate 23 via bumps 235.

The resin member 24 is a sealing member that contacts the main surface of the mounting substrate 23 and covers the substrate 220, the IDT electrode 22, and the cover layer 232.

The arrangement of the resin member 24 enhances the reliability of the acoustic wave filter device 21 such as airtightness, heat resistance, water and moisture resistance, and insulation. The resin member 24 is made of a resin such as an epoxy resin, for example. Note that the resin member 24 may include a thermosetting epoxy resin containing an inorganic filler such as SiO ₂ . Here, the resin member 24 is not formed in the hollow space 236 but is filled between the cover layer 232 and the mounting substrate 23 and between the plurality of bumps 235.

According to the mounting configuration described above, it is possible to reduce the size and height of the elastic wave filter device 21 according to the embodiment.

Note that the mounting configuration of the elastic wave filter device 21 according to the present invention is not limited to the mounting configuration described above. For example, the main surface of the piezoelectric substrate on which the IDT electrodes are not formed may be mounted on a mounting substrate with gold bumps or may have a structure other than WLP.

[5. Circuit configuration of acoustic wave filter device]
As shown in FIG. 1, an elastic wave filter device 21 according to this embodiment includes series resonators 101 to 105, parallel resonators 151 to 154, and input / output terminals 100 and 120.

The series resonators 101 to 105 are connected in series between the input / output terminal 100 (first input / output terminal) and 120 (second input / output terminal). The parallel resonators 151 to 154 are connected in parallel to each other between the input / output terminals 100 and 120 and the connection points of the series resonators 101 to 105 and the reference terminal (ground). Due to the above-described connection configuration of the series resonators 101 to 105 and the parallel resonators 151 to 154, the acoustic wave filter device 21 constitutes a ladder type band pass filter.

Table 1 shows the design parameters (wavelength λ (electrode pitch × 2), cross width L, IDT logarithm N, electrode) of the series resonators 101 to 105 and the parallel resonators 151 to 154 of the elastic wave filter device 21 according to the present embodiment. Details of duty D) are shown.

In Table 1, among the parallel resonators 151 to 154, the parallel resonator 151 (first parallel resonator) connected closest to the input / output terminal 100 (first input / output terminal) and the input / output terminal 120 (first IDT electrodes of the parallel resonators 152 (third parallel resonators) and 153 (fourth parallel resonators) excluding the parallel resonator 154 (second parallel resonator) connected closest to the two input / output terminals) The following formula 1 is satisfied.

[Wavelength λ (electrode pitch) of parallel resonator 152> Wavelength λ (electrode pitch) of parallel resonator 151] and [Wavelength λ (electrode pitch) of parallel resonator 152> Wavelength λ (electrode pitch) of parallel resonator 154 ] And [wavelength λ (electrode pitch) of the parallel resonator 153 <wavelength λ (electrode pitch) of the parallel resonator 154] and [wavelength λ (electrode pitch) of the parallel resonator 153 <wavelength λ of the parallel resonator 151 (electrode) Pitch)] (Formula 1)
Although not described in Table 1, in this embodiment, the electrode duties of the series resonators 101 to 105 and the parallel resonators 151 to 154 are 50%.

FIG. 5 is a graph showing filter pass characteristics and resonance characteristics of the acoustic wave filter device 21 according to the embodiment. The upper part of the figure shows the pass characteristic (insertion loss) between the input / output terminals 100 and 120 of the elastic wave filter device 21 according to the example, and the lower part of the figure shows the elastic characteristic according to the example. The impedance characteristic of each parallel resonator constituting the wave filter device 21 is shown.

By satisfying the above equation 1, the antiresonance frequency fap152 of the parallel resonator 152 (third parallel resonator) is equal to the antiresonance of the parallel resonator 151 (first parallel resonator) as shown in the impedance characteristics of FIG. It is lower than the frequency fap 151 and the antiresonance frequency fap 154 of the parallel resonator 154 (second parallel resonator). The antiresonance frequency fap153 of the parallel resonator 153 (fourth parallel resonator) is equal to the antiresonance frequency fap154 of the parallel resonator 154 (second parallel resonator) and the antiresonance frequency fap154 of the parallel resonator 151 (first parallel resonator). It is higher than the resonance frequency fap151. Note that the antiresonance frequencies fap151 and fap154 of the parallel resonators 151 and 154 are set at substantially the center of the passband. The resonance frequency of the parallel resonator 152 is lower than the resonance frequency of the parallel resonator 151 and the parallel resonator 154. The resonance frequency of the parallel resonator 153 is higher than the resonance frequency of the parallel resonator 154 and the parallel resonator 151.

Thereby, as shown in the pass characteristic of FIG. 5, it is possible to realize a filter characteristic that satisfies the filter requirement specification of 2.4 GHz band WiFi (2400-2483 MHz). This will be described in detail below.

FIG. 6 is a graph comparing the filter pass characteristics of the elastic wave filter devices according to the example and the comparative example. Here, the acoustic wave filter device of the comparative example has the ladder-type resonance circuit configuration shown in FIG. 1, but the anti-resonance frequencies of the four parallel resonators are substantially the same frequency and pass band. It is set at almost the center.

When the anti-resonance frequency of all parallel resonators is arranged near the center of the pass band as in the ladder type elastic wave filter of the comparative example, the pass is narrower than the pass band determined by the electromechanical coupling coefficient of the piezoelectric layer. Even if it is intended to obtain the filter characteristics of the band, the bandwidth becomes too wide. For this reason, for example, as shown in FIG. 6 (broken line), it is not possible to secure an attenuation amount on the low frequency side outside the pass band, and the attenuation specification on the low frequency side defined by the relationship with the adjacent frequency band. Can not be satisfied.

On the other hand, in the acoustic wave filter device 21 according to the present embodiment, the electrode pitch of the parallel resonator 153 (fourth parallel resonator) is closest to the input / output terminal 120 as shown in the resonance characteristics of FIG. The electrode pitch of the parallel resonator 154 (second parallel resonator) and the electrode pitch of the parallel resonator 151 (first parallel resonator) closest to the input / output terminal 100 are made smaller. As a result, the antiresonance frequency fap153 of the parallel resonator 153 is shifted to a higher frequency side than the vicinity of the center in the passband. As a result, the pass band width on the low pass band side can be narrowed, and the attenuation on the low frequency side outside the pass band can be secured.

At this time, impedance matching (capacity and inductivity) on the low frequency side of the passband shifts due to the effect of shifting the anti-resonance frequency fap153 of the parallel resonator 153 to the high frequency side. The electrode pitch of the parallel resonator) is the electrode pitch of the parallel resonator 151 (first parallel resonator) closest to the input / output terminal 100 and the parallel resonator 154 (second parallel resonator) closest to the input / output terminal 120. It is larger than the electrode pitch. As a result, the anti-resonance frequency fap 152 of the parallel resonator 152 is shifted to the lower frequency side than the vicinity of the center in the pass band. As a result, the impedance matching (capacitive and inductive degree) can be adjusted.

With the above configuration, the electrode pitch of the parallel resonator 151 (first parallel resonator) and 154 (second parallel resonator) is equal to the electrode pitch of the parallel resonator 152 (third parallel resonator) and the parallel resonator 153. It is between the electrode pitches of (fourth parallel resonator). For this reason, the impedance matching at the input / output terminals 100 and 120 of the acoustic wave filter device 21 is not shifted, and an optimized state can be maintained. In other words, in the acoustic wave filter device 21 according to the embodiment of the present invention, a low-loss and narrow-band filter is realized without deteriorating impedance matching with an external circuit at the input / output terminals. The antiresonance frequencies of the other parallel resonators are shifted while the antiresonance frequencies of the closest parallel resonators 151 and 154 are fixed near the center of the pass band.

In the above embodiment, it has been described that the pass band width on the low pass band side can be narrowed and the attenuation on the low frequency side outside the pass band can be secured. The pass band width can be narrowed, and the attenuation amount on the high frequency side outside the pass band can be secured.

That is, the electrode pitch of the parallel resonator 152 (third parallel resonator) is set to the electrode pitch of the parallel resonator 151 (first parallel resonator) that is closest to the input / output terminal 100 and the parallel that is closest to the input / output terminal 120. It is larger than the electrode pitch of the resonator 154 (second parallel resonator). As a result, the anti-resonance frequency fap 152 of the parallel resonator 152 is shifted to the lower frequency side than the vicinity of the center in the pass band. As a result, the pass band width on the high pass band side can be narrowed, and the attenuation on the high frequency side outside the pass band can be secured.

At this time, the impedance matching (capacity and inductivity) on the high frequency side of the passband shifts due to the effect of shifting the anti-resonance frequency fap152 of the parallel resonator 152 to the low frequency side. The electrode pitch of the parallel resonator) is the electrode pitch of the parallel resonator 154 (second parallel resonator) closest to the input / output terminal 120 and the parallel resonator 151 (first parallel resonator) closest to the input / output terminal 100. It is made smaller than the electrode pitch. As a result, the antiresonance frequency fap153 of the parallel resonator 153 is shifted to a higher frequency side than the vicinity of the center in the passband. As a result, the impedance matching (capacitive and inductive degree) can be adjusted.

With the above-described configuration, the elastic wave filter device 21 according to the embodiment of the present invention obtains a narrow band ladder type filter with good steepness in both the low frequency side and the high frequency side while ensuring low loss in the pass band. It becomes possible.

In the case of having a ladder type filter structure in which five or more parallel resonators are arranged, at least of three or more parallel resonators excluding parallel resonators at both ends closest to the input / output terminal. The two parallel resonators only need to satisfy the relationship of the above formula 1 or formula 2.

In the above embodiment, as shown in the impedance characteristics of FIG. 5, the antiresonance frequency fap152 of the parallel resonator 152 (third parallel resonator) is the antiresonance frequency fap151 of the parallel resonator 151 (first parallel resonator). The parallel resonator 154 (second parallel resonator) is lower than the anti-resonance frequency fap 154, and the parallel resonator 153 (fourth parallel resonator) has an anti-resonance frequency fap 153 of the parallel resonator 154 (second parallel resonator). In order to satisfy the relationship that is higher than the anti-resonance frequency fap 154 and the anti-resonance frequency fap 151 of the parallel resonator 151 (first parallel resonator), the relationship between the electrode pitches of the parallel resonators is defined as in Equation 1. However, the elastic wave filter device according to the present invention is not limited to this.

The elastic wave filter device according to the present invention may define the electrode duty of each parallel resonator instead of defining the magnitude relation of the electrode pitch of each parallel resonator. That is, the relationship of the following formula 2 may be satisfied.

[Electrode duty D of parallel resonator 152> electrode duty D of parallel resonator 151] and [electrode duty D of parallel resonator 152> electrode duty D of parallel resonator 154] and [electrode duty D of parallel resonator 153> Electrode duty D of parallel resonator 154] and [electrode duty D of parallel resonator 153 <electrode duty D of parallel resonator 151] (Equation 2)
That is, the electrode duty of the parallel resonator 153 (fourth parallel resonator) is set closest to the electrode duty of the parallel resonator 151 (first parallel resonator) closest to the input / output terminal 100 and the input / output terminal 120. It is made smaller than the electrode duty of the parallel resonator 154 (second parallel resonator). As a result, the antiresonance frequency fap153 of the parallel resonator 153 is shifted to a higher frequency side than the vicinity of the center in the passband. As a result, the pass band width on the low pass band side can be narrowed, and the attenuation on the low frequency side outside the pass band can be secured.

At this time, impedance matching (capacity and inductivity) on the low frequency side of the passband shifts due to the effect of shifting the anti-resonance frequency fap153 of the parallel resonator 153 to the high frequency side. The electrode duty of the parallel resonator 151 (first parallel resonator) closest to the input / output terminal 100 and the parallel resonator 154 (second parallel resonator) closest to the input / output terminal 120 are set. It is larger than the electrode duty. As a result, the anti-resonance frequency fap 152 of the parallel resonator 152 is shifted to the lower frequency side than the vicinity of the center in the pass band. As a result, the impedance matching (capacitive and inductive degree) can be adjusted.

The electrode duty of the parallel resonator 151 (first parallel resonator) and 154 (second parallel resonator) is the same as that of the parallel resonator 152 (third parallel resonator) and the parallel resonator 153 (fourth parallel resonator). It is between the electrode duty of the resonator. For this reason, the impedance matching at the input / output terminals 100 and 120 of the acoustic wave filter device 21 is not shifted, and an optimized state can be maintained. In other words, in the acoustic wave filter device 21 according to the embodiment of the present invention, a low-loss and narrow-band filter is realized without deteriorating impedance matching with an external circuit at the input / output terminals. The antiresonance frequencies of the other parallel resonators are shifted while the antiresonance frequencies of the closest parallel resonators 151 and 154 are fixed near the center of the pass band.

Further, the electrode duty of the parallel resonator 152 (third parallel resonator) is set closest to the electrode duty of the parallel resonator 151 (first parallel resonator) closest to the input / output terminal 100 and the input / output terminal 120. The electrode duty of the parallel resonator 154 (second parallel resonator) is larger. As a result, the anti-resonance frequency fap 152 of the parallel resonator 152 is shifted to the lower frequency side than the vicinity of the center in the pass band. As a result, the pass band width on the high pass band side can be narrowed, and the attenuation on the high frequency side outside the pass band can be secured.

At this time, the impedance matching (capacity and inductivity) on the high frequency side of the passband shifts due to the effect of shifting the anti-resonance frequency fap152 of the parallel resonator 152 to the low frequency side. The electrode duty of the parallel resonator 154 (second parallel resonator) closest to the input / output terminal 120 and the parallel resonator 151 (first parallel resonance) closest to the input / output terminal 100 are set. Smaller than the electrode duty of the child). As a result, the antiresonance frequency fap153 of the parallel resonator 153 is shifted to a higher frequency side than the vicinity of the center in the passband. As a result, the impedance matching (capacitive and inductive degree) can be adjusted.

Even with the configuration in which the electrode duty is changed as described above, it is possible to obtain a narrow band ladder type filter with good steepness on both the low frequency side and the high frequency side while ensuring low loss in the pass band. . In this case, it is preferable that the electrode pitches of the parallel resonators 151 to 154 are substantially the same. As a result, by changing the electrode duty in accordance with the definition of Equation 2, it is possible to effectively obtain a narrow band ladder type filter with good steepness on both the low frequency side and the high frequency side of the pass band.

[6. Configuration of high-frequency front-end circuit and communication apparatus]
Here, a high-frequency front-end circuit and a communication device including the elastic wave filter device according to the above embodiment will be described.

FIG. 7 is a circuit configuration diagram of the high-frequency front-end circuit 10 and the communication device 1 having the elastic wave filter device 21 according to the embodiment. In the figure, a high frequency front end circuit 10, an antenna element 2, an impedance matching circuit 5, an RF signal processing circuit (RFIC) 3, and a baseband signal processing circuit (BBIC) 4 are shown.

The high-frequency front-end circuit 10, the RF signal processing circuit 3, and the baseband signal processing circuit 4 constitute the communication device 1.

The high frequency front end circuit 10 includes elastic wave filter devices 11 and 21, a power amplifier circuit 31, and a low noise amplifier circuit 41.

The power amplifier circuit 31 amplifies the high-frequency transmission signal output from the RF signal processing circuit 3 and outputs it to the antenna element 2 via the input / output terminal 110, the elastic wave filter device 11, and the impedance matching circuit 5. It is.

The low noise amplifier circuit 41 is a reception amplification circuit that amplifies a high-frequency signal that has passed through the antenna element 2, the impedance matching circuit 5, and the elastic wave filter device 21 and outputs the amplified signal to the RF signal processing circuit 3.

The acoustic wave filter device 11 is a filter that is connected to the antenna element 2 via the impedance matching circuit 5 and selectively passes, for example, a high-frequency signal in the Band A transmission band.

The acoustic wave filter device 21 is a filter that is connected to the antenna element 2 via the impedance matching circuit 5 and selectively passes, for example, a high-frequency signal in the Band A reception band.

The RF signal processing circuit 3 performs signal processing on the high-frequency reception signal input from the antenna element 2 via the reception signal path by down-conversion or the like, and the received signal generated by the signal processing is a baseband signal processing circuit 4. Output to. Further, the RF signal processing circuit 3 performs signal processing on the transmission signal input from the baseband signal processing circuit 4 by up-conversion or the like, and outputs the high-frequency transmission signal generated by the signal processing to the power amplifier circuit 31. The RF signal processing circuit 3 is, for example, an RFIC (Radio Frequency Integrated Circuit).

The signal processed by the baseband signal processing circuit 4 is used, for example, for displaying an image as an image signal or for a call as an audio signal.

The high-frequency front end circuit 10 may include other circuit elements between the elastic wave filter devices 11 and 21, the power amplifier circuit 31, and the low noise amplifier circuit 41.

Here, in the high-frequency front-end circuit 10, the elastic wave filter device according to the above embodiment can be applied to at least one of the elastic wave filter devices 11 and 21.

According to the above configuration, it is possible to provide the high-frequency front-end circuit 10 having a narrow-band filter having good steepness on both the low-frequency side and the high-frequency side while ensuring a low loss in the passband.

Further, according to the above configuration, it is possible to provide the communication device 1 having a narrow band filter with good steepness on both the low frequency side and the high frequency side while ensuring low loss of the pass band.

Further, the communication device 1 may not include the baseband signal processing circuit (BBIC) 4 according to the high-frequency signal processing method.

In the high-frequency front-end circuit 10 and the communication device 1, the elastic wave filter devices 11 and 21 may be duplexers for simultaneously transmitting and receiving the Band A transmission signal and the reception signal. The elastic wave filter devices 11 and 21 do not have to be transmission filters and reception filters in the same band, but may be transmission filters in different bands or reception filters in different bands. That is, the elastic wave filter device 21 according to the present embodiment may be applied to a filter constituting a duplexer or a multiplexer.

[7. Other variations]
As described above, the acoustic wave filter device, the multiplexer, the high-frequency front end circuit, and the communication device according to the embodiment of the present invention have been described with reference to the examples. However, the present invention is not limited to the above examples.

Moreover, in the said embodiment, although the surface acoustic wave filter which has an IDT electrode was illustrated, the acoustic wave filter apparatus which concerns on this invention is not limited to a surface acoustic wave filter, and is comprised with a series resonator and a parallel resonator. An elastic wave filter device using boundary acoustic waves or BAW (Bulk Acoustic Wave) may be used. Also by this, the same effect as the effect which the surface acoustic wave filter concerning the above-mentioned embodiment has is produced.

The present invention can be widely used in communication devices such as mobile phones as an elastic wave filter device, a multiplexer, a high-frequency front-end circuit, and a communication device that can be applied to a frequency standard with a narrow bandwidth and a narrow band interval.

DESCRIPTION OF SYMBOLS 1 Communication apparatus 2 Antenna element 3 RF signal processing circuit (RFIC)
4 Baseband signal processing circuit (BBIC)
DESCRIPTION OF SYMBOLS 5 Impedance matching circuit 10 High frequency front end circuit 11, 21 Elastic wave filter apparatus 22, 22a, 22b IDT electrode 23 Mounting board 24 Resin member 31 Power amplifier circuit 41 Low noise amplifier circuit 50s, 101, 102, 103, 104, 105, 511a 511b, 511c Series resonator 50p, 151, 152, 153, 154, 512a, 512b, 512c, 512d Parallel resonator 100, 110, 120 Input / output terminal 220 Substrate 221a, 221b Bus bar electrode 222a, 222b Electrode finger 223 Adhesion layer 224 Main electrode layer 225 Protective layer 226 Low sound velocity film 227 Piezoelectric layer 228 High sound velocity support substrate 231 Support layer 232 Cover layer 233 Electrode pad 233a Terminal electrode 233b Wiring electrode 234 Down Dah bump metal 235 bump 236 hollow space 237 land electrode

Claims (7)

A ladder-type elastic wave filter device having a series resonator and a parallel resonator,
Three or more series resonators connected in series between the first input / output terminal and the second input / output terminal;
Four or more parallel resonators connected between any of the first input / output terminal, the second input / output terminal, and the connection node of the three or more series resonators and a reference terminal;
Of the four or more parallel resonators, 2 excluding the first parallel resonator connected closest to the first input / output terminal and the second parallel resonator connected closest to the second input / output terminal. In the above parallel resonator,
An anti-resonance frequency of a third parallel resonator that is one of the two or more parallel resonators is lower than an anti-resonance frequency of the first parallel resonator and the second parallel resonator, and the first The resonant frequency of the three parallel resonators is lower than the resonant frequency of the first parallel resonator and the second parallel resonator,
An anti-resonance frequency of a fourth parallel resonator that is one of the two or more parallel resonators is higher than an anti-resonance frequency of the first parallel resonator and the second parallel resonator, and the first The resonance frequency of the four parallel resonators is higher than the resonance frequency of the first parallel resonator and the second parallel resonator.
Elastic wave filter device. A ladder-type acoustic wave filter device having a series resonator and a parallel resonator constituted by IDT electrodes formed on a substrate having a piezoelectric layer,
Three or more series resonators connected in series between the first input / output terminal and the second input / output terminal;
Four or more parallel resonators connected between any of the first input / output terminal, the second input / output terminal, and the connection node of the three or more series resonators and a reference terminal;
Of the four or more parallel resonators, two or more excluding the first parallel resonator connected closest to the first input / output terminal and the second parallel resonator connected closest to the second input / output terminal. In the parallel resonator of
The electrode pitch of the third parallel resonator that is one of the two or more parallel resonators is larger than the electrode pitch of the first parallel resonator and the second parallel resonator,
The electrode pitch of the fourth parallel resonator that is one of the two or more parallel resonators is smaller than the electrode pitch of the first parallel resonator and the second parallel resonator,
Elastic wave filter device. A ladder-type acoustic wave filter device having a series resonator and a parallel resonator constituted by IDT electrodes formed on a substrate having a piezoelectric layer,
Three or more series resonators connected in series between the first input / output terminal and the second input / output terminal;
Four or more parallel resonators connected between any of the first input / output terminal, the second input / output terminal, and the connection node of the three or more series resonators and a reference terminal;
Of the four or more parallel resonators, two or more excluding the first parallel resonator connected closest to the first input / output terminal and the second parallel resonator connected closest to the second input / output terminal. In the parallel resonator of
The electrode duty of the third parallel resonator that is one of the two or more parallel resonators is greater than the electrode duty of the first parallel resonator and the second parallel resonator,
The electrode duty of the fourth parallel resonator that is one of the two or more parallel resonators is smaller than the electrode duty of the first parallel resonator and the second parallel resonator,
Elastic wave filter device. The substrate is
A piezoelectric layer in which the IDT electrode is formed on one main surface;
A high sound velocity support substrate having a bulk wave sound velocity propagating higher than an elastic wave sound velocity propagating through the piezoelectric layer;
A low-sonic film disposed between the high-sonic speed support substrate and the piezoelectric layer and having a low acoustic wave velocity propagating through the piezoelectric layer and having a low bulk acoustic wave velocity.
The elastic wave filter device according to claim 2 or 3. A multiplexer that demultiplexes an input signal by having a plurality of bandpass filters that selectively pass a predetermined frequency band,
Each of the frequency bands through which the plurality of band pass filters pass is different, and one end of each of the plurality of band pass filters is connected to a common terminal,
At least one of the plurality of bandpass filters is the acoustic wave filter device according to any one of claims 1 to 4.
Multiplexer. The elastic wave filter device according to any one of claims 1 to 4, or the multiplexer according to claim 5,
An amplification circuit connected to the acoustic wave filter device for amplifying a high-frequency signal,
High frequency front end circuit. A high-frequency front-end circuit according to claim 6;
An RF signal processing circuit for processing a high-frequency signal;
Communication device.

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