Bandpass filter circuit, module

Abstract

To provide a band-pass filter circuit which is simply structured and in which a high region side is steeply formed and has a wide band, and provide a module.SOLUTION: A band-pass filter circuit comprises: an acoustic wave resonator elastic which is serially connected to an input terminal and an output terminal; a first element that is a capacitor of which one end is connected to a first node between the input terminal and the acoustic wave resonator; a second element that is a capacitor of which one end is connected to a second node between the acoustic wave resonator and the output terminal; a third element that is an inductor of which one end is connected to a third node connecting the other end of the first element and the other end of the second element; three capacitors which are serially connected to the first node and the second node; a first inductor of which one end is connected to between the two capacitors in which the three capacitors are adjacent, and the other end is connected to a ground terminal; and a second inductor of which one end is connected to another two capacitors in which the three capacitors are adjacent, and the other end is connected to the ground terminal.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to bandpass filter circuits and modules. [Background technology]

[0002] Patent Document 1 discloses a filter circuit, a multiplexer, and a module that improve the steepness of cutoff characteristics. Figure 6 of Patent Document 1 shows that an LC series resonant circuit is provided between a node N1 between a terminal T1 and elastic wave resonators R1a and R1b, and a node N2 between a terminal T2 and elastic wave resonators R1a and R1b. This LC series resonant circuit is an inductor and two capacitors connected in series. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2018-129680 A Summary of the Invention [Problem to be solved by the invention]

[0004] In a bandpass filter, it is required to increase the steepness of the cutoff characteristic between the passband and the stopband. There has been a demand for a bandpass filter circuit that has a steep high-frequency side of the passband and realizes a wide-band stop characteristic on the high-frequency side. There has also been a demand for realizing such a bandpass filter circuit with a simple configuration using a small number of elements.

[0005] The present disclosure has been made to solve the above-mentioned problems. An object of the present disclosure is to provide a bandpass filter circuit and module that has a simple configuration using a small number of elements and has a steep and wide band on the high-frequency side. [Means for solving the problem]

[0006] The bandpass filter circuit according to the present disclosure comprises: an elastic wave resonator connected in series between an input terminal and an output terminal; a first element which is a capacitor having one end connected to a first node between the input terminal and the acoustic wave resonator; a second element which is a capacitor having one end connected to a second node between the acoustic wave resonator and the output terminal; a third element which is an inductor having one end connected to a third node to which the other end of the first element and the other end of the second element are connected and the other end connected to a ground terminal; a fourth element which is a capacitor having one end connected to the first node; a fifth element which is a capacitor having one end connected to the second node; a sixth element which is a capacitor connected between the other end of the fourth element and the other end of the fifth element; a seventh element which is an inductor having one end connected to a fourth node to which the fourth element and the sixth element are connected and the other end connected to a ground terminal; and an eighth element which is an inductor having one end connected to a fifth node to which the fifth element and the sixth element are connected and the other end connected to a ground terminal.

[0007] According to one aspect of the present disclosure, a ninth element which is a capacitor provided in parallel with the third element is provided between the third node and a ground terminal.

[0008] In one aspect of the present disclosure, an anti-resonant frequency of the acoustic wave resonator is higher than an upper end of a pass band of the band-pass filter circuit.

[0009] According to one aspect of the present disclosure, the amplifier further includes a matching circuit provided at least one between the input terminal and the first node and between the output terminal and the second node.

[0010] According to one aspect of the present disclosure, the semiconductor device further includes an inductor connected at least one of between the first node and a ground terminal and between the second node and a ground terminal.

[0011] In one aspect of the present disclosure, the acoustic wave resonator includes an IDT.

[0012] In one aspect of the present disclosure, the acoustic wave resonator includes a film bulk acoustic resonator.

[0013] A module having the above-described bandpass filter circuit is one aspect of the present disclosure. Effect of the Invention

[0014] According to the present disclosure, it is possible to provide a bandpass filter circuit and module that has a steep and wide band on the high frequency side with a simple configuration using a small number of elements. [Brief description of the drawings]

[0015] [Figure 1] 1 is a circuit diagram of a bandpass filter circuit according to a first embodiment. [Diagram 2] FIG. 2 is an equivalent circuit diagram illustrating a configuration example of an elastic wave resonator. [Diagram 3] Fig. 3A is a diagram illustrating an example of the structure of an acoustic wave resonator, and Fig. 3B is a diagram illustrating another example of the structure of an acoustic wave resonator. [Figure 4] FIG. 1 is a circuit diagram of a bandpass filter circuit including a matching circuit. [Diagram 5] FIG. 13 is a diagram showing the frequency characteristics of S21. [Figure 6] FIG. 6 is a partially enlarged view of FIG. 5. [Figure 7] FIG. 11 is a diagram showing the frequency characteristics of S11. [Figure 8] FIG. 13 is a diagram showing the frequency characteristics of S22. [Figure 9] FIG. 1 is a circuit diagram of a band-pass filter circuit according to a comparative example. [Figure 10] FIG. 13 is a diagram showing frequency characteristics of S21 in the comparative example. [Figure 11] FIG. 11 is a circuit diagram of a bandpass filter circuit according to a second embodiment. [Figure 12] FIG. 13 is a diagram showing the frequency characteristics of S21. [Figure 13]FIG. 13 is a partially enlarged view of FIG. [Figure 14] FIG. 11 is a diagram showing the frequency characteristics of S11. [Figure 15] FIG. 13 is a diagram showing the frequency characteristics of S22. [Figure 16] FIG. 11 is a circuit diagram of a bandpass filter circuit according to a third embodiment. [Figure 17] Fig. 17A is a cross-sectional view of a module, Fig. 17B is a cross-sectional view of a module according to another example, Fig. 17C is a cross-sectional view of a module according to another example, and Fig. 17D is a cross-sectional view of a module according to another example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] The embodiments will be described with reference to the accompanying drawings. In each drawing, the same or corresponding parts are denoted by the same reference numerals. Duplicate descriptions of the parts may be simplified or omitted.

[0017] Embodiment 1 Fig. 1 is a circuit diagram of a bandpass filter circuit according to a first embodiment. The bandpass filter circuit has an input terminal T1 and an output terminal T2. An acoustic wave resonator Y1 is connected in series between the input terminal T1 and the output terminal T2. Figs. 2, 3A, and 3B show examples of the acoustic wave resonator Y1.

[0018] 2 is a diagram showing an equivalent circuit of an acoustic wave resonator Y1. This acoustic wave resonator has a resistor RS connected to an 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 an output terminal T2.

[0019] FIG. 3A is a diagram showing another example of the configuration of the surface acoustic wave resonator Y1. FIG. 3A is a plan view of the surface acoustic wave resonator. This surface acoustic wave resonator includes an interdigital transducer (IDT) 51 and a reflector 52 on a piezoelectric substrate 50. The IDT 51 has a pair of comb electrodes 51a arranged opposite to each other. According to one example, the comb electrode 51a includes a plurality of electrode fingers 51b and a bus bar 51c connecting the plurality of electrode fingers 51b. The reflectors 52 are provided on both sides of the IDT 51 so as to sandwich the IDT 51. The IDT 51 excites a surface acoustic wave in 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 film or a copper film. According to one example, the piezoelectric substrate 50 may be bonded to the bottom surface of a supporting substrate such as a sapphire substrate, an alumina substrate, a spinel substrate, or a silicon substrate. A protective film or a temperature compensation film covering the IDT 50 and the reflector 52 may be provided.

[0020] FIG. 3B is a diagram showing another example of the acoustic wave resonator Y1. FIG. 3B is a cross-sectional view of a piezoelectric thin film resonator. This piezoelectric thin film resonator includes a piezoelectric film 57 on a substrate 55. A lower electrode 56 and an upper electrode 58 are provided to sandwich the piezoelectric film 57. A gap 59 is formed between the lower electrode 56 and the substrate 55. The lower electrode 56 and the upper electrode 58 excite an acoustic wave in a thickness longitudinal vibration mode in the piezoelectric film 57. In one example, the lower electrode 56 and the upper electrode 58 are metal films such as a ruthenium film. In one example, the piezoelectric film 57 is an aluminum nitride film. In one example, the substrate 55 is a silicon substrate, a sapphire substrate, an alumina substrate, a spinel substrate, or a glass substrate. In another example, the acoustic wave resonator Y1 may have a configuration different from that shown in FIGS. 2, 3A, and 3B.

[0021] 1, the bandpass filter circuit includes a first element C11 having one end connected to a first node N1 between an input terminal T1 and an acoustic wave resonator Y1. The first element C11 is a capacitor. One end of a second element C12 is connected to a second node N2 between the acoustic wave resonator Y1 and an output terminal T2. The second element C12 is a capacitor.

[0022] One end of the third element L11 is connected to a third node N3 to which the other end of the first element C11 and the other end of the second element C12 are connected. The other end of the third element L11 is connected to a 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.

[0023] 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 a fourth node N4 to which the fourth element C21 and the sixth element C22 are connected. The other end of the seventh element L21 is connected to a ground terminal. The seventh element L21 is an inductor. One end of the eighth element L22 is connected to a fifth node N5 to which the fifth element C23 and the sixth element C22 are connected. The other end of the eighth element L22 is connected to a ground terminal. The eighth element L22 is an inductor.

[0024] Fig. 4 is a circuit diagram of a bandpass filter circuit according to another example. This bandpass filter circuit differs from the bandpass filter circuit of Fig. 1 in that it includes matching circuits C31 and C32. The matching circuit C31 is provided between the input terminal T1 and the first node N1. The matching circuit C32 is provided between the output terminal T2 and the second node N2. According to another example, only one of the matching circuits C31 and C32 can be provided.

[0025] Figures 5-8 are diagrams showing the frequency characteristics of the S parameters in the bandpass filter circuit of Figure 4. These frequency characteristics were obtained under the following simulation conditions. Input terminal T1, output terminal: 50 Ω termination Elastic wave resonator Y1 (Figure 2): Resonant frequency fr = 5.003 GHz Elastic wave resonator Y1 (Figure 2): Q value (Qr) at resonant frequency = 500 Elastic wave resonator Y1 (Figure 2): Anti-resonant frequency fa = 5.176 GHz Elastic wave resonator Y1 (Figure 2): Q value (Qa) at anti-resonance frequency = 500 Capacitor C0 capacitance: 0.194pF The characteristics of each element were optimized for n79, one of the new radio frequency bands for the fifth generation mobile communication system (5G), using numerical optimization methods with design tools including Agilent's Advanced Design System (ADS). The passband of n79 is from 4.4 GHz to 5.0 GHz.

[0026] FIG. 5 is a diagram showing the frequency dependence of the pass characteristic (S21) from input terminal T1 to output terminal T2. Attenuation is required at frequencies below the frequency indicated by marker m1. In this example, the frequency of m1 is set to 2.69 GHz (2.7 GHz for convenience). Markers m2 and m3 indicate the frequencies at 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. Attenuation is required at frequencies above the frequency indicated by marker m4. In this example, the frequency of m4 is 5.15 GHz. The S21 values ​​for m1, m2, m3, and m4 were as follows: S21 at m1 = -45.049 S21 in m2 = -1.220 S21 in m3 = -1.121 S21 in m4 = -24.015

[0027] FIG. 6 is an enlarged view of the passband in FIG. 5. Frequencies m5, m6, and m7 are the same as the frequencies m2, m3, and m4 described above. From FIG. 5 and FIG. 6, it can be seen that the passband with small loss is relatively wide due to the large value of S21. Moreover, the cutoff characteristics between the passband and the stopband can be made steep on the high frequency side from m3. Furthermore, such excellent effects can be achieved with a simple circuit having one acoustic wave resonator, three inductor elements, and a small number of capacitors, as shown in FIG. 4.

[0028] Fig. 7 is a diagram showing the frequency dependence of the input reflection coefficient (S11), which indicates the ratio of a signal reflected to the input terminal T1 relative to a signal input to the input terminal T1. Fig. 7 also shows a Smith chart showing the reflection characteristics.

[0029] Fig. 8 is a diagram showing the frequency dependence of the output reflection coefficient (S22), which indicates the ratio of a signal reflected to the output terminal T2 to a signal input from the output terminal T2. Fig. 8 also shows a Smith chart showing the reflection characteristics.

[0030] At frequencies m2 and m3, i.e., 4.4 GHz and 5.0 GHz, S21 is large and the reflection coefficient is small. Therefore, the high-frequency signal input from input terminal T1 is hardly reflected or attenuated by the band-pass filter circuit, and is output from output terminal T2. On the other hand, at frequencies m1 and m4, i.e., 2.7 GHz and 5.15 GHz, S21 is small and the reflection coefficient is large. Therefore, the high-frequency signal input from input terminal T1 is hardly reflected or attenuated by the band-pass filter circuit, and is hardly output from output terminal T2. Furthermore, the difference between m3 and m4 is small, and a band-pass filter characteristic with a steep cutoff characteristic between the pass band and the stop band is realized on the high-frequency side of the pass band.

[0031] Here, a comparative example will be described with reference to Figs. 9 and 10. Fig. 9 is a circuit diagram of a bandpass filter circuit according to the comparative example. This bandpass filter circuit includes an inductor L21' having one end connected to a first node N1 and the other end connected to a ground terminal. Furthermore, this bandpass filter circuit includes an inductor L22' having one end connected to a second node N2 and the other end connected to the ground terminal.

[0032] Fig. 10 is a diagram showing the frequency characteristics of S21 of the bandpass filter circuit according to the comparative example. The graph of Fig. 10 was obtained under the following simulation conditions. Input terminal T1, output terminal: 50 Ω termination Elastic wave resonator Y1 (Figure 2): Resonant frequency fr = 5.119 GHz Elastic wave resonator Y1 (Figure 2): Q value (Qr) at resonant frequency = 500 Elastic wave resonator Y1 (Figure 2): Anti-resonant frequency fa = 5.296 GHz Elastic wave resonator Y1 (Figure 2): Q value (Qa) at anti-resonance frequency = 500 Capacitor C0 capacitance: 0.159pF The characteristics of each element were optimized for n79 using numerical optimization methods with design tools including Agilent ADS.

[0033] The same frequencies m1, m2, m3, and m4 shown in Figure 5 are also shown in Figure 10. The S21 values ​​of m1, m2, m3, and m4 in Figure 10 are as follows. Note that the S21 values ​​of m1-m4 in Figure 5 are quoted in parentheses. m1:S21=-29.723(-45.049) m2:S21=-1.377(-1.220) m3:S21=-0.915(-1.121) m4:S21=-20.093(-24.015)

[0034] In the frequency characteristics of Fig. 10, the cutoff characteristics between the passband and the stopband cannot be made steep on the high frequency side from m3. In other words, the band where S21 is low at frequencies higher than the upper end of the passband should be wide, but S21 is not sufficiently low in the region enclosed by the dashed line in Fig. 10.

[0035] The filter characteristics obtained with the circuit configuration of the above-mentioned embodiment 1 have a steeper higher frequency side of the pass band and a wideband rejection characteristic on the higher frequency side, and are therefore far superior to the bandpass filters of the comparative examples.

[0036] Embodiment 2 Fig. 11 is a diagram showing a circuit diagram of a bandpass filter circuit according to embodiment 2. This bandpass filter circuit differs from the configuration in Fig. 4 in that it includes a ninth element C13. The ninth element C13 is a capacitor provided in parallel with the third element L11 between the third node N3 and the ground terminal.

[0037] Figures 12-15 are diagrams showing frequency characteristics of the S parameters in the bandpass filter circuit of Figure 11. These frequency characteristics were obtained under the following simulation conditions. Input terminal T1, output terminal: 50 Ω termination Elastic wave resonator Y1 (Figure 2): Resonant frequency fr = 4.967 GHz Elastic wave resonator Y1 (Figure 2): Q value (Qr) at resonant frequency = 500 Elastic wave resonator Y1 (Figure 2): Anti-resonant frequency fa = 5.139 GHz Elastic wave resonator Y1 (Figure 2): Q value (Qa) at anti-resonance frequency = 500 Capacitor C0 capacitance: 0.286pF The characteristics of each element were optimized for n79 using numerical optimization methods with design tools including Agilent ADS.

[0038] The frequencies m1, m2, m3, and m4 in Fig. 12 are the same as m1, m2, m3, and m4 in Fig. 5. The S21 values ​​of m1, m2, m3, and m4 in Fig. 12 are as follows. Note that the S21 values ​​of m1, m2, m3, and m4 in Fig. 5 are quoted in parentheses. m1:S21=-46.510(-45.049) m2:S21=-1.215(-1.220) m3:S21=-1.230(-1.121) m4:S21=-17.550(-24.015)

[0039] FIG. 13 is an enlarged view of the passband in FIG. 12. Frequencies m5, m6, and m7 are the same as the frequencies m2, m3, and m4 described above. From FIG. 12 and FIG. 13, it can be seen that the passband with small loss is relatively wide because S21 is a large value. Moreover, the cutoff characteristics between the passband and the stopband can be made steeper on the high frequency side from m3. Furthermore, such excellent effects can be achieved with a small number of components.

[0040] Fig. 14 is a diagram showing the frequency dependence of S11. Fig. 14 also shows a Smith chart showing the reflection characteristics. Fig. 15 is a diagram showing the frequency dependence of S22. Fig. 15 also shows a Smith chart showing the reflection characteristics.

[0041] These simulation results show that the bandpass filter circuit according to the second embodiment shown in FIG. 11 has characteristics equivalent to those of the bandpass filter circuit according to the first embodiment shown in FIG.

[0042] According to the configuration of the second embodiment, the capacitance value of the capacitor C0 of the acoustic wave resonator Y1 can be increased by adding the ninth element C13. As an example, the capacitance value of the capacitor C0 in the bandpass filter circuit of Fig. 4 is 0.194 pF, but in the bandpass filter circuit of Fig. 11, the capacitance value of the capacitor C0 can be set to a large value of 0.286 pF. Increasing the capacitance value of the capacitor C0 improves the power resistance.

[0043] Embodiment 3 FIG. 16 is a diagram showing a circuit diagram of a bandpass filter circuit according to a third embodiment. This bandpass filter circuit differs from the bandpass filter circuit of FIG. 4 in that it includes inductors L31 and L32. The inductor L31 connects the first node N1 and the ground terminal. The inductor L32 connects the second node N2 and the ground terminal. According to another example, only one of the inductors L31 and L32 may be included. With such a circuit configuration, as in the first and second embodiments, it is possible to improve the steepness of the cutoff characteristics between the passband and the stopband on the high-frequency side of the passband, while providing wideband stop characteristics on the high-frequency side.

[0044] Embodiment 4 17A, 17B, 17C and 17D are cross-sectional views of modules according to embodiment 4. These modules are provided with at least one of the bandpass filter circuits described above.

[0045] The module shown in FIG. 17A includes an acoustic wave resonator 22 and an integrated passive device (IPD) 23 mounted on a printed circuit board 20. The IPD 23 integrates circuits other than the acoustic wave resonator in the above-mentioned bandpass filter circuit. For example, a resin sealing portion 28 is provided on the printed circuit board 20. The resin sealing portion 28 covers the acoustic wave resonator 22 and the IPD 23. According to one example, the printed circuit board 20 is a board in which wiring is formed on an insulating substrate such as a glass epoxy resin. The resin sealing portion 28 is, for example, a molded resin such as an epoxy resin. 17B includes an acoustic wave resonator 22 and a chip component 26 mounted on a printed circuit board 20. The chip component 26 is an inductor or a capacitor.

[0046] 17C includes an acoustic wave resonator 22, an IPD 23, a laminated filter 24, and a chip component 26 mounted on a printed circuit board 20. The IPD 23 or the chip component 26 is provided with components of the bandpass filter circuit described above. The laminated filter 24 may be provided with at least a part of the filters of a diplexer and a duplexer. The chip component 26 may be provided with at least a part of the capacitors and inductors of the diplexer.

[0047] A ceramic substrate 20a shown in Fig. 17D may be used instead of the printed circuit board 20 in Fig. 17A, 17B, and 17C. The ceramic substrate 20a is, for example, low temperature co-fired ceramic (LTCC) or high temperature co-fired ceramic (HTCC).

[0048] Having described several aspects of at least one embodiment, it should be understood that various alterations, modifications, and improvements will readily occur to those skilled in the art and are intended to be part of this disclosure, and are intended to be within the scope of this disclosure.

[0049] It is to be understood that the embodiments of the method and apparatus described herein are not limited in their application to the details of construction and the arrangement of components set forth in the above description or illustrated in the accompanying drawings, and the method and apparatus can be implemented in other embodiments and practiced or carried out in various ways.

[0050] The specific implementation examples are provided here for illustrative purposes only and are not intended to be limiting. For example, in the embodiment, a circuit in which one acoustic wave resonator Y1 is connected between the first node N1 and the second node N2 is illustrated, but a circuit in which multiple equivalent acoustic wave resonators are connected between the first node N1 and the second node N2 in parallel, series, or both of these connection methods is also included. Also, for example, the number of components mounted on the module is not limited to the number shown in the figure.

[0051] The phraseology and terminology used in this disclosure are for the purpose of description and should not be regarded as limiting. The use of "including," "comprising," "having," "including" and variations thereof herein means the inclusion of the items listed thereafter and equivalents thereof as well as additional items.

[0052] References to "or" may be construed as meaning that any term described using "or" refers to one, more than one, and all of those described terms.

[0053] All references to front, back, left, right, top, bottom, up, down, horizontal, vertical, front and back are intended for convenience of description. Such references are not intended to limit the components of this disclosure to any one positional or spatial orientation. Accordingly, the foregoing description and drawings are by way of example only. [Explanation of symbols]

[0054] T1 input terminal, T2 output terminal, Y1 acoustic wave resonator, N1 first node, N2 second node, N3 third node, N4 fourth node, N5 fifth node, C11 first element, C12 second element, L11 third element, C21 fourth element, C22 sixth element, C23 fifth element, L21 seventh element, L22 eighth element

Claims

1. an elastic wave resonator connected in series between an input terminal and an output terminal; a first element which is a capacitor having one end connected to a first node between the input terminal and the acoustic wave resonator; a second element which is a capacitor having one end connected to a second node between the acoustic wave resonator and the output terminal; a third element which is an inductor having one end connected to a third node to which the other end of the first element and the other end of the second element are connected and the other end connected to a ground terminal; a fourth element which is a capacitor having one end connected to the first node; a fifth element which is a capacitor having one end connected to the second node; a sixth element which is a capacitor connected between the other end of the fourth element and the other end of the fifth element; a seventh element which is an inductor having one end connected to a fourth node to which the fourth element and the sixth element are connected and the other end connected to a ground terminal; an eighth element which is an inductor having one end connected to a fifth node to which the fifth element and the sixth element are connected and the other end connected to a ground terminal.

2. 2. The bandpass filter circuit according to claim 1, further comprising a ninth element which is a capacitor provided in parallel with the third element between the third node and a ground terminal.

3. 3. The bandpass filter circuit according to claim 1, wherein an anti-resonant frequency of the acoustic wave resonator is higher than an upper end of a passband of the bandpass filter circuit.

4. 4. The band-pass filter circuit according to claim 1, further comprising a matching circuit provided at least one between the input terminal and the first node and between the output terminal and the second node.

5. 5. The bandpass filter circuit according to claim 1, further comprising an inductor provided at least one between the first node and a ground terminal and between the second node and a ground terminal.

6. The bandpass filter circuit according to claim 1 , wherein the acoustic wave resonator includes an IDT.

7. 6. The bandpass filter circuit according to claim 1, wherein the acoustic wave resonator includes a thin film piezoelectric resonator.

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

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