Bandpass filter circuit and module comprising the bandpass filter circuit

Abstract

A band-pass filter circuit includes an elastic wave resonator connected in series between an input terminal and an output terminal, a first element which is a capacitor connected at one end to a first node between the input terminal and the elastic wave resonator, a second element which is a capacitor connected at one end to a second node between the elastic wave resonator and the output terminal, a third element which is an inductor connected at one end to a third node between the other end of the first element and the other end of the second element and connected at the other end to a ground terminal, three capacitors connected in series between the first node and the second node, a first inductor connected at one end to a node between two adjacent ones of the three capacitors and connected at the other end to the ground terminal, and a second inductor connected at one end to a node between the other two adjacent ones of the three capacitors and connected at the other end to the ground terminal. With this, a band-pass filter circuit and module which is steep on the high frequency side and has a wide frequency band can be provided with a simple configuration.

Description

Technical Field

[0001] This disclosure relates to a bandpass filter circuit and a module including the bandpass filter circuit. Background Technology

[0002] Patent document 1 (Japanese Patent Application Publication No. 2018-129680) illustrates a filter circuit, multiplexer, and module that can improve the steepness of blocking characteristics. For example... Figure 18 As shown in Patent Document 1, an LC series resonant circuit is provided between node N1 between terminal T1 and elastic wave resonators R1a and R1b, and between node N2 between terminal T2 and elastic wave resonators R1a and R1b. The LC series resonant circuit is composed of an inductor and two capacitors connected in series. Summary of the Invention

[0003] [The problem the invention aims to solve]

[0004] Bandpass filters require improved steepness of the blocking characteristics between the passband and the bandgap. A bandpass filter circuit is needed that can achieve both a steep high-frequency side of the passband and wide-band blocking characteristics on that high-frequency side. Furthermore, the aforementioned bandpass filter circuit needs to be implemented with a simple configuration of fewer components.

[0005] To address the aforementioned problems, this disclosure aims to provide a bandpass filter circuit with a steep high-frequency side and a wide bandwidth, and a module including the bandpass filter circuit, through a simple configuration of fewer components.

[0006] [Methods used to solve problems]

[0007] The bandpass filter circuit disclosed herein includes:

[0008] An elastic wave resonator connected in series between the input and output terminals;

[0009] One end is connected to the first node between the input terminal and the elastic wave resonator and is the first element of the capacitor;

[0010] One end is connected to the second node between the elastic wave resonator and the output terminal, and is the second element of the capacitor;

[0011] A third element, which is an inductor, has one end connected to a third node between the other end of the first element and the other end of the second element, and the other end connected to a ground terminal.

[0012] A fourth element, connected at one end to the first node and serving as a capacitor;

[0013] One end is connected to the second node and is the fifth element of the capacitor;

[0014] A sixth element, which is a capacitor, is connected at one end between the other end of the fourth element and the other end of the fifth element;

[0015] A seventh element, which is an inductor, has one end connected to the fourth node between the fourth and sixth elements and the other end connected to the ground terminal; and

[0016] The eighth element is an inductor, with one end connected to the fifth node between the fifth and sixth elements and the other end connected to the ground terminal.

[0017] In one embodiment of this disclosure, a ninth element, which is a capacitor, is provided in parallel with the third element between the third node and the grounding terminal.

[0018] In one embodiment of this disclosure, the anti-resonance frequency of the elastic wave resonator is higher than the upper passband of the bandpass filter circuit.

[0019] In one embodiment of this disclosure, at least one of the input terminal and the first node and the output terminal and the second node are provided with a matching circuit.

[0020] In one embodiment of the present invention, an inductor is provided between the first node and the grounding terminal and between the second node and the grounding terminal.

[0021] In one embodiment of the present invention, the elastic wave resonator is an IDT.

[0022] In one embodiment of this disclosure, the elastic wave resonator is a piezoelectric thin film resonator.

[0023] One embodiment of this disclosure includes a module comprising the bandpass filter circuit.

[0024] [The effects of the invention]

[0025] The beneficial effects of the present invention are as follows: According to this disclosure, a bandpass filter circuit with a steep high-frequency side and a wide bandwidth, and a module including the bandpass filter circuit, can be provided by simply configuring fewer components. Attached Figure Description

[0026] Figure 1 This is a circuit diagram of the bandpass filter circuit of the first embodiment.

[0027] Figure 2 This is an equivalent circuit diagram illustrating an example of the construction of an elastic wave resonator.

[0028] Figure 3 A is a schematic diagram illustrating a construction example of an elastic wave resonator.

[0029] Figure 3B is a schematic diagram illustrating other structural examples of an elastic wave resonator.

[0030] Figure 4 This is a circuit diagram of a bandpass filter circuit with a matching circuit added.

[0031] Figure 5 This is a schematic diagram of the frequency characteristics of S21.

[0032] Figure 6 yes Figure 5 A magnified view of a portion of the image.

[0033] Figure 7 This is a schematic diagram of the frequency characteristics of S11.

[0034] Figure 8 This is a schematic diagram of the frequency characteristics of S22.

[0035] Figure 9 This is a circuit diagram of a comparative bandpass filter circuit.

[0036] Figure 10 This is a schematic diagram of the frequency characteristics of the comparative example S21.

[0037] Figure 11 This is a circuit diagram of the bandpass filter circuit in the second embodiment.

[0038] Figure 12 This is a schematic diagram of the frequency characteristics of S21.

[0039] Figure 13 yes Figure 12 A magnified view of a portion of the image.

[0040] Figure 14 This is a schematic diagram of the frequency characteristics of S11.

[0041] Figure 15 This is a schematic diagram of the frequency characteristics of S22.

[0042] Figure 16 This is a circuit diagram of the bandpass filter circuit in the third embodiment.

[0043] Figure 17 A is a cross-sectional view of the module.

[0044] Figure 17 B is a cross-sectional view of another example module.

[0045] Figure 17 C is a cross-sectional view of a module from another example.

[0046] Figure 17 D is a cross-sectional view of another example module.

[0047] Figure 18It is an example of an existing LC series resonant circuit as described in Japanese Patent Application Publication No. 2018-129680. Detailed Implementation

[0048] The specific embodiments of the present invention will be described below with reference to the accompanying drawings. Similar or identical parts in each drawing are referred to by the same reference numerals. Repeated descriptions of similar or identical parts will be simplified or omitted.

[0049] (First Embodiment)

[0050] Figure 1 This is a circuit diagram of the bandpass filter circuit of the first embodiment. The bandpass filter circuit includes an input terminal T1 and an output terminal T2. An elastic wave resonator Y1 is connected in series between the input terminal T1 and the output terminal T2. Figure 2 , 3 The elastic wave resonator Y1 described in examples A and 3B.

[0051] Figure 2 This is an equivalent circuit diagram illustrating the elastic wave resonator Y1. The elastic wave resonator Y1 includes a resistor RS connected to the input terminal T1. A series circuit having an inductor L1, a capacitor C1, and a resistor R1, and a series circuit having a capacitor C0 and a resistor R0, are connected in parallel between the resistor RS and the output terminal T2.

[0052] Figure 3 A is a schematic diagram illustrating a construction example of the elastic wave resonator Y1. Figure 3 A is a plan view of a surface wave resonator. The surface wave resonator has an interdigital transducer (IDT) 51 and a reflector 52 disposed on a piezoelectric substrate 50. The IDT 51 has a pair of opposing comb-shaped electrodes 51a. According to one example, the comb-shaped electrodes 51a have a plurality of electrode fingers 51b and a busbar 51c connecting the electrode fingers 51b. The reflector 52 is disposed on both sides of the IDT 51, sandwiching the IDT 51. The IDT 51 excites surface waves on the piezoelectric substrate 50. According to one example, the piezoelectric substrate 50 is a lithium tantalate substrate or a lithium niobate substrate. According to one example, the IDT 51 and the reflector 52 are formed of an aluminum thin film or a copper thin film. According to one example, the piezoelectric substrate 50 may also be bonded to the lower surface of a support substrate such as a sapphire substrate, an alumina substrate, a spinel substrate, or a silicon substrate. Furthermore, a protective film or temperature compensation film may be provided to cover the IDT 51 and the reflector 52.

[0053] Figure 3 B is a schematic diagram illustrating other structural examples of the elastic wave resonator Y1. Figure 3B is a cross-sectional view of the piezoelectric thin-film resonator. The piezoelectric thin-film resonator has a piezoelectric film 57 located on a substrate 55. A lower electrode 56 and an upper electrode 58 are designed to enclose the piezoelectric film 57. A gap 59 is formed between the lower electrode 56 and the substrate 55. Therefore, the lower electrode 56 and the upper electrode 58 can excite elastic waves within the piezoelectric film 57 in a thickness-longitudinal vibration mode. According to one example, the lower electrode 56 and the upper electrode 58 are metal films such as ruthenium thin films. According to one example, the piezoelectric film 57 is an aluminum nitride thin film. According to one example, the substrate 55 is a silicon substrate, a sapphire substrate, an alumina substrate, a spinel substrate, or a glass substrate. According to other examples, the elastic wave resonator Y1 may also be made of different materials. Figure 2 , 3 The structures shown in A and 3B.

[0054] like Figure 1 As shown, the bandpass filter circuit includes a first element C11, one end of which is connected to a first node N1 between the input terminal T1 and the elastic wave resonator Y1. The first element C11 is a capacitor. A second element C12, one end of which is connected to a second node N2 between the elastic wave resonator Y1 and the output terminal T2. The second element C12 is also a capacitor.

[0055] One end of the third element L11 is connected to the third node N3, which connects the other end of the first element C11 and the other end of the second element C12. The other end of the third element L11 is connected to the ground terminal. The third element L11 is an inductor. One end of the fourth element C21 is connected to the first node N1. The fourth element C21 is a capacitor. One end of the fifth element C23 is connected to the second node N2. The fifth element C23 is a capacitor.

[0056] The sixth element C22 is connected between the other end of the fourth element C21 and the other end of the fifth element C23. The sixth element C22 is a capacitor. One end of the seventh element L21 is connected to the fourth node N4 connecting the fourth element C21 and the sixth element C22. The other end of the seventh element L21 is connected to the ground terminal. The seventh element L21 is an inductor. One end of the eighth element L22 is connected to the fifth node N5 connecting the fifth element C23 and the sixth element C22. The other end of the eighth element L22 is connected to the ground terminal. The eighth element L22 is an inductor.

[0057] Figure 4 These are circuit diagrams of other example bandpass filter circuits. The bandpass filter circuits are compatible with matching circuits C31 and C32. Figure 1The bandpass filter circuits are different. Matching circuit C31 is disposed between the input terminal T1 and the first node N1. Matching circuit C32 is disposed between the output terminal T2 and the second node N2. According to other examples, only one of the matching circuits C31 and C32 may be disposed.

[0058] Figure 5-8 show Figure 4 The frequency characteristics of the S-parameters of the bandpass filter circuit are obtained under the following simulation conditions.

[0059] Input terminal T1, output terminal T2: 50Ω termination

[0060] Elastic wave resonator Y1 ( Figure 2 Resonant frequency fr = 5.003 GHz

[0061] Elastic wave resonator Y1 ( Figure 2 The Q value (Qr) of the resonant frequency is 500.

[0062] Elastic wave resonator Y1 ( Figure 2 The anti-resonance frequency fa = 5.176 GHz

[0063] Elastic wave resonator Y1 ( Figure 2 The Q value (Qa) of the anti-resonance frequency is 500.

[0064] The capacitance of capacitor C0 is 0.194pF.

[0065] The characteristics of each component were optimized using numerical methods employing design tools incorporating Agilent's Advanced Design System (ADS), and specifically optimized for the n79 in the new radio band for 5G mobile communication systems. Furthermore, the n79 has a passband of 4.4 GHz to 5.0 GHz.

[0066] Figure 5 This is a schematic diagram of the passband characteristics (S21) from input terminal T1 to output terminal T2 with respect to frequency. Frequency below the frequency indicated by marker m1 must be attenuated. In this example, the frequency of m1 is 2.69 GHz (referred to as 2.7 GHz for convenience). Markers m2 and m3 indicate the lower and upper ends of the passband, respectively. The frequency of m2 is, for example, 4.4 GHz. The frequency of m3 is, for example, 5.0 GHz. Frequency above the frequency indicated by marker m4 must be attenuated. In this example, the frequency of m4 is 5.15 GHz.

[0067] The S21 values ​​for m1, m2, m3, and m4 are as follows.

[0068] At m1, S21 = -45.049

[0069] In m2, S21 = -1.220

[0070] In m3, S21 = -1.121

[0071] At m4, S21 = -24.015

[0072] Figure 6 yes Figure 5 A magnified view of the passband. Frequencies m5, m6, and m7 are the same as m2, m3, and m4. From... Figure 5 , 6 It is understandable that a larger S21 value results in a wider bandwidth by sacrificing a smaller passband. Furthermore, it allows for a steeper cutoff characteristic between the passband and bandgap on the high-frequency side of m3. Moreover, this superior effect can be achieved simply by using... Figure 4 The simple circuit shown can achieve this with one elastic wave resonator, three inductors and several capacitors.

[0073] Figure 7 This is a schematic diagram showing the relationship between the input reflection coefficient (S11) and frequency, expressed as the ratio of the reflected signal from the input terminal T1 to the signal input from the input terminal T1. Figure 7 Also shown is the Smith chart, which displays the reflective properties.

[0074] Figure 8 This is a schematic diagram showing the relationship between the output reflection coefficient (S22) and frequency, which is expressed as the ratio of the reflected signal at output terminal T2 to the signal input from output terminal T2. Figure 8 Also shown is the Smith chart, which displays the reflective properties.

[0075] At frequencies m2 and m3, i.e., 4.4 GHz and 5.0 GHz, the reflection coefficient of S21 is small. Therefore, most of the high-frequency signals input from the input terminal T1 will not be reflected or attenuated in the bandpass filter circuit and can be output from the output terminal T2. On the other hand, at frequencies m1 and m4, i.e., 2.7 GHz and 5.15 GHz, the reflection coefficient of S21 is large. Therefore, most of the high-frequency signals input from the input terminal T1 will be reflected or attenuated in the bandpass filter circuit, and most of them cannot be output from the output terminal T2. Furthermore, the difference between m3 and m4 is small, which enables a bandpass filter characteristic with a steep blocking characteristic between the passband and the band gap to be achieved on the high-frequency side of the passband.

[0076] Then cooperate Figure 9 , 10 Explain the comparative examples. Figure 9This is a circuit diagram of a comparative bandpass filter circuit. The bandpass filter circuit includes an inductor L21' with one end connected to the first node N1 and the other end connected to a ground terminal. Furthermore, the bandpass filter circuit also includes an inductor L22' with one end connected to the second node N2 and the other end connected to a ground terminal.

[0077] Figure 10 This is a schematic diagram of the frequency characteristics of S21 in the comparative example bandpass filter circuit.

[0078] Figure 10 The charts were obtained under the following simulated conditions.

[0079] Input terminal T1, output terminal T2: 50Ω termination

[0080] Elastic wave resonator Y1 ( Figure 2 Resonant frequency fr = 5.119 GHz

[0081] Elastic wave resonator Y1 ( Figure 2 The Q value (Qr) of the resonant frequency is 500.

[0082] Elastic wave resonator Y1 ( Figure 2 Anti-resonance frequency fa = 5.296 GHz

[0083] Elastic wave resonator Y1 ( Figure 2 The Q value (Qa) of the anti-resonance frequency is 500.

[0084] The capacitance of capacitor C0 is 0.159pF.

[0085] The characteristics of each component are optimized using numerical optimization methods with the design tools that include Agilent's Advanced Design System (ADS), and optimized for n79.

[0086] and Figure 5 The frequencies m1, m2, m3, and m4 shown are also marked in... Figure 10 middle. Figure 10 The S21 values ​​for m1, m2, m3, and m4 are shown below. (The values ​​are referenced in parentheses.) Figure 5 The S21 values ​​of m1-m4.

[0087] m1: S21 = -29.723(-45.049)

[0088] m2:S21=-1.377(-1.220)

[0089] m3: S21 = -0.915(-1.121)

[0090] m4: S21 = -20.093(-24.015)

[0091] Figure 10 In the frequency characteristics, it is impossible to make the blocking characteristics between the passband and the bandgap on the high-frequency side of m3 steep. In other words, although it is possible to ensure that the bandwidth of S21 is wide enough above the upper end of the passband, Figure 10 The area enclosed by the dotted line cannot allow S21 to be reduced sufficiently.

[0092] The filter characteristics obtained by the circuit structure of the first embodiment described above can make the high-frequency side of the passband steeper, and because the high-frequency side has broadband blocking characteristics, it is quite superior in all aspects compared to the bandpass filter of the comparative example.

[0093] (Second Embodiment)

[0094] Figure 11 A circuit diagram illustrating the bandpass filter circuit of the second embodiment is shown. The bandpass filter circuit includes a ninth element C13, and... Figure 4 The structures are different. The ninth element C13 and the third element L11 are connected in parallel between the third node N3 and the ground terminal, and it is a capacitor.

[0095] Figure 12-15 show Figure 11 The frequency characteristics of the S-parameters of the bandpass filter circuit are obtained under the following simulation conditions.

[0096] Input terminal T1, output terminal T2: 50Ω termination

[0097] Elastic wave resonator Y1 ( Figure 2 Resonant frequency fr = 4.967 GHz

[0098] Elastic wave resonator Y1 ( Figure 2 The Q value (Qr) of the resonant frequency is 500.

[0099] Elastic wave resonator Y1 ( Figure 2 Anti-resonance frequency fa = 5.139 GHz

[0100] Elastic wave resonator Y1 ( Figure 2 The Q value (Qa) of the anti-resonance frequency is 500.

[0101] The capacitance of capacitor C0 is 0.286pF.

[0102] The characteristics of each component are optimized using numerical optimization methods with the design tools that include Agilent's Advanced Design System (ADS), and optimized for n79.

[0103] Figure 12 The frequencies m1, m2, m3, and m4 shown are... Figure 5 The m1, m2, m3, and m4 are the same. Figure 12 The S21 values ​​for m1, m2, m3, and m4 are shown below. (The values ​​are referenced in parentheses.) Figure 5 The S21 values ​​of m1, m2, m3, and m4.

[0104] m1: S21 = -46.510(-45.049)

[0105] m2: S21 = -1.215(-1.220)

[0106] m3: S21 = -1.230(-1.121)

[0107] m4: S21 = -17.550(-24.015)

[0108] Figure 13 yes Figure 12 A partially enlarged view of the passband. Frequencies m5, m6, and m7 are the same as the previously mentioned frequencies m2, m3, and m4. From... Figure 12 , 13 It can be understood that a large S21 value and a small loss result in a wider passband. Furthermore, it allows for a steeper cutoff characteristic between the passband and bandgap on the high-frequency side of m3. Moreover, this superior effect can be achieved with a relatively small number of components.

[0109] Figure 14 This is a schematic diagram showing the relationship between S11 and frequency. Figure 14 Also shown is the Smith chart, which displays the reflective properties. Figure 15 This is a schematic diagram showing the relationship between S22 and frequency. Figure 15 The image also shows a Smith chart illustrating the reflective properties.

[0110] From the above simulation results, it can be understood that Figure 11 The bandpass filter circuit shown in the second embodiment is, with Figure 4 The bandpass filter circuits shown have the same characteristics.

[0111] According to the structure of the second embodiment, by adding the ninth element C13, the capacitance value of the capacitor C0 of the elastic wave resonator Y1 can be increased. According to one example, Figure 4 The capacitance of capacitor C0 in the bandpass filter circuit is 0.194pF, but Figure 11 The capacitance value of capacitor C0 in the bandpass filter circuit can be increased to 0.286pF. Increasing the capacitance value of capacitor C0 can increase the dielectric strength.

[0112] (Third Embodiment)

[0113] Figure 16 A circuit diagram of the bandpass filter circuit of the third embodiment is shown. The bandpass filter circuit also includes inductors L31 and L32, and... Figure 4 This differs from the bandpass filter circuit. Inductor L31 is connected to the first node N1 and the ground terminal. Inductor L32 is connected to the second node N2 and the ground terminal. According to other examples, only one of inductors L31 and L32 may be used. Based on this circuit structure, similar to the first and second embodiments, the steepness of the blocking characteristics between the passband and the bandgap on the high-frequency side of the passband can be improved, thus achieving broadband blocking characteristics on the high-frequency side.

[0114] (Example 4)

[0115] Figure 17 A, 17B, 17C, and 17D are cross-sectional views of the module in the fourth embodiment. The module includes at least one of the bandpass filter circuits.

[0116] Figure 17 The module shown in Figure A includes an elastic wave resonator 22 and an integrated passive device (IPD) 23 mounted on a printed circuit board 20. The IPD 23 is stacked on top of the circuitry in the bandpass filter circuit, excluding the elastic wave resonator. The printed circuit board 20 is provided with, for example, a resin seal 28. The resin seal 28 covers the elastic wave resonator 22 and the IPD 23. According to one example, the printed circuit board 20 is a substrate on which wiring is formed on an insulating substrate such as glass epoxy resin. The resin seal 28 is, for example, a molding resin such as epoxy resin.

[0117] Figure 17 The module shown in B includes an elastic wave resonator 22 and a chip component 26 mounted on the printed circuit board 20. The chip component 26 is an inductor or a capacitor.

[0118] Figure 17 The module shown in C includes an elastic wave resonator 22, an IPD 23, a stacked filter 24, and a chip component 26 mounted on the printed circuit board 20. The IPD 23 or the chip component 26 provides the structural elements of the bandpass filter circuit. The stacked filter 24 may also be configured as at least one of a diplexer and a duplexer. The chip component 26 may also be configured as at least one of a diplexer and a duplexer.

[0119] It can also be used Figure 17The ceramic substrate 20a in D is used to replace Figure 17 Printed substrates 20 of A, 17B, and 17C. The ceramic substrate 20a is, for example, a low-temperature co-fired ceramic (LTCC) or a high-temperature co-fired ceramic (HTCC).

[0120] While at least one embodiment has been described above, it should be understood that various changes, modifications, or improvements will readily occur to those skilled in the art. These changes, modifications, or improvements are also part of this disclosure and fall within the scope of this invention.

[0121] It should be understood that the embodiments of the methods or apparatus described herein are not limited to the architecture and arrangement of the constituent components described above or illustrated in the accompanying drawings. The methods and apparatus can be installed or performed in other embodiments.

[0122] The specific embodiments described herein are for illustrative purposes only and are not intended to be limiting. For example, while the embodiment exemplifies a single elastic wave resonator Y1 connected between the first node N1 and the second node N2, it also includes circuits connecting multiple identical elastic wave resonators between the first node N1 and the second node N2 in parallel, series, or both. Furthermore, the number of components mounted on the module is not limited to those shown in the figures.

[0123] The descriptions and terms used in this disclosure are for illustrative purposes only and are not intended to be limiting. The use of "including," "possessing," "having," "comprise," and variations thereof here means to include the items listed below, their equivalents, and additional items.

[0124] The word “or”, or any word used in a description, may be interpreted as one, more than one, or all of the descriptive words.

[0125] The references to front, back, left, right, top, bottom, upper, lower, and horizontal and vertical are for ease of description and are not intended to limit the position and spatial configuration of any component in this invention. Therefore, the above description and drawings are merely exemplary.

Claims

1. A bandpass filter circuit, characterized in that... Include: An elastic wave resonator connected in series between the input and output terminals; One end is connected to the first node between the input terminal and the elastic wave resonator and is the first element of the capacitor; One end is connected to the second node between the elastic wave resonator and the output terminal, and is the second element of the capacitor; A third element, which is an inductor, has one end connected to a third node that connects the other end of the first element and the other end of the second element, and the other end connected to a ground terminal. A fourth element, connected at one end to the first node and serving as a capacitor; One end is connected to the second node and is the fifth element of the capacitor; A sixth element, which is a capacitor, is connected between the other end of the fourth element and the other end of the fifth element; A seventh element, which is an inductor, has one end connected to the fourth node connecting the fourth element and the sixth element, and the other end connected to the ground terminal. and An eighth element, which is an inductor, is connected at one end to the fifth node connecting the fifth element and the sixth element, and at the other end to the ground terminal.

2. The bandpass filter circuit according to claim 1, characterized in that: A ninth element, which is a capacitor, is connected in parallel with the third element between the third node and the grounding terminal.

3. The bandpass filter circuit according to claim 1 or 2, characterized in that: The anti-resonance frequency of the elastic wave resonator is higher than the frequency at the upper end of the passband of the bandpass filter circuit.

4. The bandpass filter circuit according to claim 1, characterized in that: At least one of the input terminal and the first node, and the output terminal and the second node, is provided with a matching circuit.

5. The bandpass filter circuit according to claim 1, characterized in that: An inductor is provided between the first node and the grounding terminal, and between the second node and the grounding terminal.

6. The bandpass filter circuit according to claim 1, characterized in that: The elastic wave resonator is an IDT.

7. The bandpass filter circuit according to claim 1, characterized in that: The elastic wave resonator is a piezoelectric thin film resonator.

8. A module comprising the bandpass filter circuit according to any one of claims 1 to 7.

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