Filter device

Abstract

The present application provides a filter device capable of suppressing 3rd order distortion due to an interference wave. The filter device (1) has a first filter (2A) having a first passband, which is commonly connected to a common terminal (3), and a second filter (2B) having a second passband located on a higher frequency side than the first passband. In the first filter (2A), a plurality of parallel arm resonators constitute a parallel connection portion (5) in which the plurality of parallel arm resonators are connected in parallel to each other without passing through series arm resonators. The plurality of parallel arm resonators in the parallel connection portion (5) include first and second parallel arm resonators whose anti-resonance frequencies are different from each other. When the first passband is set to f 1min ~ f 1max , the second passband is set to f 2min ~ f 2max , in the combined impedance frequency characteristic of the plurality of parallel arm resonators in the parallel connection portion, at least one of the anti-resonance frequencies other than the highest anti-resonance frequency is 2f 1min ~ f 2min , and 2f 1max ~ f 2max .

Description

TECHNICAL FIELD

[0001] The present application relates to a filter device. BACKGROUND

[0002] Conventionally, a filter device utilizing an elastic wave resonator is widely used for a portable telephone and the like. An example of a multiplexer utilizing an elastic wave resonator is described in Patent Literature 1 described below. In this multiplexer, a plurality of bandpass type filters including elastic wave resonators are commonly connected to a common terminal. The plurality of bandpass type filters are a transmission filter and a reception filter of Band 66, a transmission filter and a reception filter of Band 25, and a transmission filter and a reception filter of Band 30.

[0003] PRIOR ART DOCUMENTS

[0004] PATENT LITERATURE

[0005] Patent Literature 1: Japanese Patent Application Publication No. 2019-022164 SUMMARY

[0006] PROBLEMS TO BE SOLVED BY THE INVENTION

[0007] However, in the filter device described in Patent Literature 1, in a case where an interference wave flows into the common terminal, a signal of 3rd order distortion can be generated in the bandpass type filters in the filter device, and the filter characteristics can be deteriorated.

[0008] An object of the present application is to provide a filter device capable of suppressing 3rd order distortion due to an interference wave.

[0009] TECHNICAL SOLUTION FOR SOLVING THE PROBLEM

[0010] A filter device according to the present application includes a common terminal, a first filter connected to the common terminal and having a first passband, and a second filter connected to the common terminal and having a second passband located on a higher frequency side than the first passband, the first filter having a series arm resonator and a plurality of parallel arm resonators, the plurality of parallel arm resonators constituting a parallel connection portion in which the plurality of parallel arm resonators are connected in parallel to each other without passing through the series arm resonator, the plurality of parallel arm resonators in the parallel connection portion including a first parallel arm resonator and a second parallel arm resonator having different anti-resonance frequencies from each other, a frequency of an end portion on a high frequency side of the first passband being f 1max and a frequency of an end portion on a low frequency side being f 1min , a frequency of an end portion on a high frequency side of the second passband being f 2max and a frequency of an end portion on a low frequency side being f 2minAt least one of the anti-resonance frequencies other than the highest anti-resonance frequency in the composite impedance frequency characteristic of the plurality of shunt arm resonators in the shunt connection section is located at 2f 1min -f 2min The above and 2f 1max -f 2max The following frequency band.

[0011] Inventive Effects

[0012] According to the filter device related to the present application, 3rd order distortion due to an interference wave can be suppressed. BRIEF DESCRIPTION OF DRAWINGS

[0013] Figure 1 is a schematic circuit diagram of the filter device related to the 1st embodiment of the present application.

[0014] Figure 2 is a graph showing the impedance frequency characteristic of each shunt arm resonator in the shunt connection section in the 1st embodiment of the present application and the composite impedance frequency characteristic of the plurality of shunt arm resonators in the shunt connection section.

[0015] Figure 3 is a graph showing the return loss of each shunt arm resonator in the shunt connection section in the 1st embodiment of the present application and the return loss as the reflection characteristic of the composite of the plurality of shunt arm resonators in the shunt connection section.

[0016] Figure 4 is a circuit diagram of an equivalent circuit of a shunt arm resonator.

[0017] Figure 5 is a schematic circuit diagram of the filter device related to the 2nd embodiment of the present application.

[0018] Figure 6 is a graph showing the impedance frequency characteristic of each shunt arm resonator in the shunt connection section in the 2nd embodiment of the present application and the composite impedance frequency characteristic of the plurality of shunt arm resonators in the shunt connection section.

[0019] Figure 7 is a graph showing the return loss as the reflection characteristic of the composite of the plurality of shunt arm resonators in the shunt connection section in the 2nd embodiment of the present application.

[0020] Figure 8 is a schematic diagram of the filter device related to the 3rd embodiment of the present application. DETAILED DESCRIPTION

[0021] Hereinafter, specific embodiments of the present application will be described with reference to the accompanying drawings, thereby clarifying the present application.

[0022] Note that each of the embodiments described in this specification is illustrative, and a part of a structure can be substituted or combined between different embodiments.

[0023] Figure 1 is a schematic circuit diagram of a filter device according to a first embodiment of the present application.

[0024] The filter device 1 has a common terminal 3 and a first filter 2A and a second filter 2B. In the present embodiment, the common terminal 3 is connected to an antenna. The first filter 2A and the second filter 2B are commonly connected to the common terminal 3. The first filter 2A is a transmission filter, and the second filter 2B is a reception filter. The filter device 1 is a duplexer. Note that the first filter 2A and the second filter 2B can each be a transmission filter or a reception filter. Both the first filter 2A and the second filter 2B can be a transmission filter or a reception filter.

[0025] The first filter 2A has a first passband. The first passband is a transmission frequency band of Band 25, and is 1850 to 1915 MHz. The second filter 2B has a second passband. The second passband is a reception frequency band of Band 25, and is 1930 to 1995 MHz. Note that the first passband and the second passband are not limited to the above. As long as the second passband is located on a higher frequency side than the first passband. In the present embodiment, the first passband and the second passband are passbands of the same communication band, but can be passbands of different communication bands.

[0026] The first filter 2A has a plurality of series arm resonators and a plurality of parallel arm resonators. The first filter 2A is a ladder-type filter. As shown in FIG. 1, the first filter 2A has a signal terminal 4. Note that the signal terminal 4 and the common terminal 3 can be configured as electrode pads or as wiring. Figure 1

[0027] Between the signal terminal 4 and the common terminal 3, a series arm resonator S1, a series arm resonator S2, a series arm resonator S3, and a series arm resonator S4 are connected. Between a connection point between the series arm resonator S1 and the series arm resonator S2 and a ground potential, a parallel arm resonator P1 is connected. Between a connection point between the series arm resonator S2 and the series arm resonator S3 and the ground potential, a parallel arm resonator P2 is connected. Between a connection point between the series arm resonator S3 and the series arm resonator S4 and the ground potential, a parallel arm resonator P3 is connected.

[0028] ​The parallel arm resonator P4 and the parallel arm resonator P5 are connected in parallel to each other between a connection point between the series arm resonator S4 and the common terminal 3 and a ground potential. The parallel arm resonator P4 is an example of the "first parallel arm resonator" in the present application, and the parallel arm resonator P5 is an example of the "second parallel arm resonator" in the present application. In addition, the parallel arm resonator P4 can be the "second parallel arm resonator" in the present application, and the parallel arm resonator P5 can be the "first parallel arm resonator" in the present application. It is only necessary that the anti-resonance frequency of the first parallel arm resonator and the anti-resonance frequency of the second parallel arm resonator be different from each other.

[0029] The parallel arm resonator P4 and the parallel arm resonator P5 are connected in parallel to each other without passing through the series arm resonator. More specifically, no series arm resonator is disposed between the parallel arm resonator P4 and the parallel arm resonator P5. In the present embodiment, the resonators closest to the common terminal 3 in the first filter 2A are the parallel arm resonator P4 and the parallel arm resonator P5. In addition, the resonator closest to the common terminal 3 is the resonator closest to the common terminal 3 in terms of electrical connection.

[0030] The inductor L1 is connected between the signal terminal 4 and the series arm resonator S1. The inductor L2 is connected between the parallel arm resonator P1 and the parallel arm resonator P2 and a ground potential. In addition, the ends of the parallel arm resonator P1 and the parallel arm resonator P2 on the ground potential side are commonly connected to the inductor L2. The inductor L3 is connected between the parallel arm resonator P3 and a ground potential. The plurality of series arm resonators and the plurality of parallel arm resonators of the first filter 2A are elastic wave resonators. More specifically, the plurality of series arm resonators and the plurality of parallel arm resonators of the first filter 2A are surface acoustic wave resonators.

[0031] The first filter 2A has a parallel connection portion 5. The parallel connection portion 5 is a portion including a plurality of parallel arm resonators connected in parallel to each other without passing through a series arm resonator. More specifically, the parallel connection portion 5 in the present embodiment is a portion including the parallel arm resonator P4 and the parallel arm resonator P5. In addition, the parallel connection portion 5 can include three or more parallel arm resonators.

[0032] On the other hand, the circuit structure of the second filter 2B is not particularly limited.

[0033] The anti-resonance frequency of the parallel arm resonator P4 and the anti-resonance frequency of the parallel arm resonator P5 in the parallel connection portion 5 of the first filter 2A are different. More specifically, the anti-resonance frequency of the parallel arm resonator P4 is higher than the anti-resonance frequency of the parallel arm resonator P5.

[0034] Here, the frequency of the end of the high frequency side of the first passband is set to f 1maxand the frequency of the end on the low frequency side is set to f 1min and the frequency of the end on the low frequency side is set to f 2max and the frequency of the end on the low frequency side is set to f 2min . 2f 1min - f 2min 2f 1max - f 2max The frequency band below is set to W0.

[0035] In addition, when a filter device is used, an interference wave sometimes flows in from the outside. As described above, if an interference wave flows into a filter device, third-order distortion can occur in the first filter, for example. In the present specification, it is assumed that the frequency of the interference wave is within the frequency band W0.

[0036] In contrast, the filter device 1 of the present embodiment is characterized by having the following structure. 1) The first filter 2A has a parallel connection portion 5. 2) The plurality of parallel arm resonators in the parallel connection portion 5 include a first parallel arm resonator and a second parallel arm resonator whose anti-resonance frequencies are different from each other. 3) In the combined impedance frequency characteristic of the plurality of parallel arm resonators in the parallel connection portion 5, at least one of the anti-resonance frequencies other than the highest anti-resonance frequency is within the frequency band W0 of 2f 1mjn - f 2min 2f 1max - f 2max . Thus, third-order distortion due to an interference wave can be suppressed. Details thereof will be described below.

[0037] Figure 2 is a graph showing the impedance frequency characteristics of each parallel arm resonator of the parallel connection portion in the first embodiment and the combined impedance frequency characteristics of the plurality of parallel arm resonators of the parallel connection portion. Figure 3 is a graph showing the return loss of each parallel arm resonator of the parallel connection portion in the first embodiment and the return loss of the reflection characteristic of the combination of the plurality of parallel arm resonators of the parallel connection portion. In Figure 2 and Figure 3 , the frequency band W1 is the first passband. In Figure 2 and Figure 3 , the characteristics of the combination of the parallel arm resonator P4 and the parallel arm resonator P5 are shown by a solid line, the characteristics of the parallel arm resonator P4 are shown by a dashed line, and the characteristics of the parallel arm resonator P5 are shown by a single-dot chain line. The difference between the resonance frequencies and the difference between the anti-resonance frequencies of the parallel arm resonator P4 and the parallel arm resonator P5 are each 40 MHz.

[0038] In the Figure 2In the synthesized impedance frequency characteristics shown, there are two anti-resonant points indicated by arrows A1 and A2, and two resonant points indicated by arrows B1 and B2. The frequencies of the two resonant points indicated by arrows B1 and B2 are approximately the same as the resonant frequencies of the parallel arm resonators P4 and P5, respectively. On the other hand, the anti-resonant points indicated by arrows A1 and A2 are located at the same frequencies as the impedances of the parallel arm resonators P4 and P5, respectively.

[0039] The reasoning is as follows. Generally, an elastic wave resonator exhibits inductive behavior within the frequency band between the resonant and anti-resonant frequencies, and capacitive behavior outside this band. Therefore, at the points indicated by arrows A1 and A2, where the impedances of the two parallel arm resonators are identical, the imaginary component of the impedance becomes 0. Moreover, at the point where the imaginary component of the impedance becomes 0, the impedance becomes an extreme value, which is the anti-resonance point, for this reason.

[0040] like Figure 2 As shown, the anti-resonance point indicated by arrow A1 is located between the resonant frequency and the anti-resonance frequency of the parallel arm resonator P4. The anti-resonance point indicated by arrow A2 is located between the resonant frequency and the anti-resonance frequency of the parallel arm resonator P5. Here, the anti-resonance point indicated by arrow A1 is located within the first passband, i.e., frequency band W1. Therefore, the parallel arm resonators of the parallel connection part 5 constitute the first passband. Furthermore, as... Figure 3 As shown, the absolute value of the return loss in the first passband is extremely small, so it has almost no effect on the filter characteristics of filter device 1.

[0041] On the other hand, such as Figure 2 As shown, the anti-resonance point indicated by arrow A2 is also located within frequency band W0. Therefore, as... Figure 3 As shown, the absolute value of the return loss, which is a composite reflection characteristic of the parallel arm resonators P4 and P5, increases within the frequency band W0. As described above, the frequency band W0 represents the range of frequencies of the interference wave. In the first embodiment, the absolute value of the return loss within the frequency band W0 is large, thus effectively suppressing the flow of interference waves into the parallel arm resonators in the parallel connection section 5. Therefore, the third-order distortion in the first filter 2A caused by the interference wave can be effectively suppressed. Consequently, the influence of the third-order distortion on the second filter 2B, which is connected to the common terminal 3 with the first filter 2A, can also be effectively suppressed.

[0042] Furthermore, the frequency of the anti-resonance point indicated by arrow A2 can be adjusted by the resonant frequency and capacitance of each parallel arm resonator in the parallel connection section 5. Therefore, at any frequency within the frequency band W0, the aforementioned inflow of interference waves can be effectively suppressed. Additionally, in this specification, the frequency of the anti-resonance point and the anti-resonance frequency refer to the same frequency.

[0043] However, the closer the parallel arm resonator is to the common terminal 3, the more easily an interfering wave from the outside flows into the parallel arm resonator, and the more easily 3rd order distortion is generated in the parallel arm resonator. In contrast, in the present embodiment, the parallel arm resonator P4 and the parallel arm resonator P5 of the parallel connection portion 5 are resonators closest to the common terminal 3 in the 1st filter 2A. Therefore, it is possible to further effectively suppress 3rd order distortion due to an interfering wave, and it is possible to further effectively suppress the influence of 3rd order distortion on the 2nd filter 2B.

[0044] In addition, in order to show the characteristics of the parallel arm resonator P4 in Figure 2 and Figure 3 , in detail, the equivalent circuit of the parallel arm resonator shown in Figure 4 is used. The same is true of the characteristics of the parallel arm resonator P5. In the equivalent circuit shown in Figure 4 , a 1st resistance element R1 is connected between the 1st terminal 6A and the 2nd terminal 6B. A 1st element group and a 2nd element group are connected in parallel to each other between the 1st resistance element R1 and the 2nd terminal 6B. In the 1st element group, from the 1st resistance element R1 side, an inductor L4, a 1st capacitance element C1, and a 2nd resistance element R2 are connected in series to each other in that order. In the 2nd element group, from the 1st resistance element R1 side, a 2nd capacitance element C2 and a 3rd resistance element R3 are connected in series to each other. The resistance of the 1st resistance element R1, the 2nd resistance element R2, and the 3rd resistance element R3 is 0.1 Ω. The inductance of the inductor L4 is 75 nH. The capacitance of the 1st capacitance element C1 is 0.1 pF. The capacitance of the 2nd capacitance element C2 is 2.2 pF. Note that the parameters of the elements are not limited to the above.

[0045] In addition, Figure 2 the measurement of the synthetic impedance frequency characteristics shown in may be performed, for example, by bringing probes for measurement into contact with both end portions of the parallel connection portion, respectively. The both end portions of the parallel connection portion are two nodes to which the plurality of parallel arm resonators of the parallel connection portion are commonly connected. However, the method of the measurement of the synthetic impedance frequency characteristics of the common connection portion is not limited to the above.

[0046] As described above, in the filter device 1, both the first passband and the second passband are passbands of Band 25. As such, in the present embodiment, the first passband and the second passband are passbands of the same communication frequency band, but are not limited thereto. The first passband and the second passband can also be passbands of different communication frequency bands. In this case, it is preferable that both the first passband and the second passband be passbands of a high frequency band, passbands of a middle frequency band, or passbands of a low frequency band. Thereby, the anti-resonance frequency of the parallel-arm resonator P5 in the parallel connection section 5 can be appropriately disposed within the frequency band W0. Thus, the third-order distortion due to an interference wave can be appropriately suppressed. In the present specification, the passband of the high frequency band refers to 2300 MHz or more and 2700 MHz or less. The passband of the middle frequency band refers to 1400 MHz or more and 2200 MHz or less. The passband of the low frequency band refers to 600 MHz or more and 1000 MHz or less.

[0047] Further, in the case where the first passband and the second passband are passbands of the same communication frequency band, the communication frequency band is not limited to Band 25. For example, it can also be a communication frequency band of Band 3, Band 7, Band 66, or the like.

[0048] Further, the parallel connection section can also include three or more parallel-arm resonators that are connected in parallel with each other without passing through the series-arm resonator. In this case, it is only necessary that the anti-resonance frequency of at least one of the parallel-arm resonators in the parallel connection section be different from the anti-resonance frequencies of the other parallel-arm resonators in the parallel connection section. Furthermore, in the combined impedance frequency characteristics of the plurality of parallel-arm resonators in the parallel connection section, it is only necessary that at least one of the anti-resonance frequencies other than the highest anti-resonance frequency be within the frequency band W0.

[0049] Figure 5 is a schematic circuit diagram of the filter device according to the second embodiment.

[0050] The present embodiment differs from the first embodiment in that the parallel connection section 15 includes three parallel-arm resonators. Other than the above point, the filter device 11 of the present embodiment has the same structure as the filter device 1 of the first embodiment.

[0051] In the parallel connection section 15, the parallel arm resonator P4, the parallel arm resonator P5, and the parallel arm resonator P16 are not connected in parallel with each other via the series arm resonator. The parallel arm resonator P16 is an example of the "third parallel arm resonator" in the present application. The anti-resonance frequency of the third parallel arm resonator is different from the anti-resonance frequency of the first parallel arm resonator and the anti-resonance frequency of the second parallel arm resonator. Here, as in the first embodiment, the parallel arm resonator P4 of the filter device 11 is an example of the first parallel arm resonator. The parallel arm resonator P5 is an example of the second parallel arm resonator. Therefore, the anti-resonance frequencies of the parallel arm resonator P4, the parallel arm resonator P5, and the parallel arm resonator P16 are different from each other. In the present embodiment, in the parallel connection section 15, the anti-resonance frequency of the parallel arm resonator P4 is the highest, and the anti-resonance frequency of the parallel arm resonator P16 is the lowest. The anti-resonance frequency of the parallel arm resonator P5 is a frequency between the anti-resonance frequency of the parallel arm resonator P4 and the anti-resonance frequency of the parallel arm resonator P16.

[0052] Figure 6 Fig. 12 is a graph showing the impedance frequency characteristics of each parallel arm resonator in the parallel connection section in the second embodiment and the resultant impedance frequency characteristics of the plurality of parallel arm resonators in the parallel connection section. Figure 7 Fig. 13 is a graph showing the return loss of the reflection characteristics of the resultant of the plurality of parallel arm resonators in the parallel connection section in the second embodiment. In Figure 6 and Figure 7 In Figs. 12 and 13, the characteristics of the resultant of the parallel arm resonator P4, the parallel arm resonator P5, and the parallel arm resonator P16 are shown by a solid line, the characteristics of the parallel arm resonator P4 are shown by a broken line, the characteristics of the parallel arm resonator P5 are shown by a single-dot chain line, and the characteristics of the parallel arm resonator P16 are shown by a double-dot chain line. The difference between the resonance frequency and the anti-resonance frequency of the parallel arm resonator P4 and the parallel arm resonator P5 is 30 MHz. The difference between the resonance frequency and the anti-resonance frequency of the parallel arm resonator P5 and the parallel arm resonator P16 is 30 MHz.

[0053] As Figure 6As shown, the anti-resonance point indicated by arrow A11 in the synthesized impedance frequency characteristic lies between the resonant frequency and anti-resonant frequency of the parallel arm resonator P4. The anti-resonance point indicated by arrow A12 lies between the resonant frequency and anti-resonant frequency of the parallel arm resonator P5. The anti-resonance point indicated by arrow A13 lies between the resonant frequency and anti-resonant frequency of the parallel arm resonator P16. Furthermore, the frequency of the anti-resonance point indicated by A11 is the frequency at which the imaginary component of the impedance becomes 0 due to the inductive parallel arm resonator P4, the capacitive parallel arm resonator P5, and the parallel arm resonator P16. The frequency of the anti-resonance point indicated by A12 is the frequency at which the imaginary component of the impedance becomes 0 due to the inductive parallel arm resonator P5, the parallel arm resonator P16, and the capacitive parallel arm resonator P4. The frequency of the anti-resonance point indicated by A13 is the frequency at which the imaginary component of the impedance becomes 0 due to the inductive parallel arm resonator P16, the capacitive parallel arm resonator P4, and the parallel arm resonator P5.

[0054] Here, of the anti-resonance points indicated by arrows A11, A12, and A13, the anti-resonance point indicated by arrow A11 is located at the highest frequency. This anti-resonance point indicated by arrow A11 is located within the first passband, i.e., frequency band W1. Therefore, the parallel arm resonators of the parallel connection portion 15 constitute the first passband.

[0055] On the other hand, such as Figure 7 As shown, the absolute value of the return loss, which is a composite of the parallel arm resonators P4, P5, and P16, increases within the frequency band W0. More specifically, in this embodiment, within the frequency band W0, the absolute value of the return loss increases, with two frequencies exhibiting extreme values. Therefore, interference waves flowing into the parallel arm resonators in the parallel connection section 15 can be effectively suppressed over a wide frequency band. Consequently, third-order distortion caused by interference waves can be effectively suppressed over a wide frequency band, and the impact of third-order distortion on the second filter 2B can be effectively suppressed.

[0056] In this embodiment, the combined impedance frequency characteristics of the plurality of parallel arm resonators in the parallel connection section 15 have three anti-resonant frequencies. Alternatively, for example, the anti-resonant frequency of parallel arm resonator P16 may be the same as the anti-resonant frequency of parallel arm resonator P4 or parallel arm resonator P5. In this case, the combined impedance frequency characteristics of the plurality of parallel arm resonators in the parallel connection section 15 have two anti-resonant frequencies, similar to the first embodiment. Therefore, in this case, also similar to the first embodiment, the parallel arm resonators of the parallel connection section 15 constitute a first passband and are able to suppress third-order distortion caused by interference waves.

[0057] As described above, the parallel connection section can also include three or more parallel arm resonators connected in parallel with each other without passing through the series arm resonator. In this case, the parallel connection section preferably includes the above-described third parallel arm resonator. In addition, the anti-resonance frequency of the third parallel arm resonator is different from the anti-resonance frequency of the first parallel arm resonator and the anti-resonance frequency of the second parallel arm resonator. Furthermore, in the combined impedance frequency characteristics of the plurality of parallel arm resonators in the parallel connection section, at least two of the anti-resonance frequencies other than the highest anti-resonance frequency are preferably located within the frequency band W0. Thus, the third-order distortion due to the interference wave can be effectively suppressed within a wide range of frequency bands.

[0058] In the first and second embodiments, examples in which the filter device is a duplexer are shown, but the filter device to which the present application is applied can also be a multiplexer.

[0059] Figure 8 Fig. 7 is a schematic diagram of a filter device to which a third embodiment of the present application is applied.

[0060] The filter device 21 of the present embodiment is a multiplexer. The filter device 21 has a first filter 22A, a second filter 22B, and a third filter 22C. The first filter 22A, the second filter 22B, and the third filter 22C are commonly connected to the common terminal 3.

[0061] The first filter 22A has the same structure as the first filter in the first or second embodiment. The circuit structure of the second filter 22B and the third filter 22C is not particularly limited. The first filter 22A, the second filter 22B, and the third filter 22C can each be a transmission filter or a reception filter.

[0062] In addition, the filter device 21 further has a plurality of filters other than the first filter 22A, the second filter 22B, and the third filter 22C. The plurality of filters are also commonly connected to the common terminal 3. In the case where the filter device 21 is a multiplexer, the number of filters commonly connected to the common terminal 3 is not particularly limited.

[0063] The filter device 21 of the present embodiment has the same first filter 22A as in the first or second embodiment, and thus can effectively suppress the third-order distortion due to the interference wave. Therefore, the third-order distortion can also effectively affect other filters commonly connected to the common terminal 3 with the first filter 22A.

[0064] Explanation of Reference Numerals

[0065] 1... filter device;

[0066] 2A, 2B... first and second filters;

[0067] 3…common terminal;

[0068] 4…signal terminal;

[0069] 5…parallel connection portion;

[0070] 6A, 6B…1st, 2nd terminal;

[0071] 11…filter device;

[0072] 12A…1st filter;

[0073] 15…parallel connection portion;

[0074] 21…filter device;

[0075] 22A to 22C…1st to 3rd filter;

[0076] C1, C2…1st, 2nd capacitive element;

[0077] L1 to L4…inductor;

[0078] P1 to P5, P16…parallel arm resonator;

[0079] R1 to R3…1st to 3rd resistive element;

[0080] S1 to S4…series arm resonator.

Claims

1. A filter device comprising: Common terminal; A first filter, connected to the common terminal, has a first passband; and The second filter, connected to the common terminal, has a second passband located at a higher frequency than the first passband. The first filter has a series arm resonator and multiple parallel arm resonators. The plurality of parallel-arm resonators constitute a parallel connection section, in which the plurality of parallel-arm resonators are connected in parallel to each other without passing through the series-arm resonators. The plurality of parallel arm resonators in the parallel connection section include a first parallel arm resonator and a second parallel arm resonator with different anti-resonance frequencies. The frequency of the high-frequency end of the first passband is set to f. 1max And set the frequency of the low-frequency end to f. 1min The frequency of the high-frequency end of the second passband is set to f. 2max And set the frequency of the low-frequency end to f. 2min At that time, in the combined impedance frequency characteristics of the plurality of parallel arm resonators in the parallel connection section, at least one of the anti-resonant frequencies other than the highest anti-resonant frequency is located at 2f. 1min -f 2min Above and 2f 1max -f 2max Within the following frequency bands.

2. The filter device according to claim 1, wherein, The plurality of parallel arm resonators of the parallel connection portion are included in the resonator closest to the common terminal in the first filter.

3. The filter device according to claim 1 or 2, wherein, In the combined impedance frequency characteristics of the plurality of parallel arm resonators in the parallel connection section of the first filter, the highest anti-resonance frequency is located within the first passband.

4. The filter device according to claim 1 or 2, wherein, The parallel connection portion of the first filter further includes a third parallel arm resonator, which has an anti-resonance frequency different from that of the first parallel arm resonator and the second parallel arm resonator. In the combined impedance frequency characteristics of the plurality of parallel arm resonators in the parallel connection section of the first filter, at least two of the anti-resonant frequencies other than the highest anti-resonant frequency are located at 2f. 1min -f 2min Above and 2f 1max -f 2max Within the following frequency bands.

5. The filter device according to claim 1 or 2, wherein, The first filter is a transmitting filter, and the second filter is a receiving filter.

6. The filter device according to claim 1 or 2, wherein, Both the first passband and the second passband are passbands above 2300MHz and below 2700MHz.

7. The filter device according to claim 1 or 2, wherein, Both the first passband and the second passband are passbands above 1400MHz and below 2200MHz.

8. The filter device according to claim 1 or 2, wherein, Both the first passband and the second passband are passbands above 600MHz and below 1000MHz.

9. The filter device according to claim 1 or 2, wherein, The first passband and the second passband are passbands of the same communication frequency band.

Images