JP7298543B2 - Filters and multiplexers - Google Patents

Description

The present invention relates to filters and multiplexers.

Conventionally, there has been known a band-pass filter in which a ladder-type filter including a first parallel-arm resonator and a second parallel-arm resonator and a longitudinally-coupled resonator-type filter are connected in series on a piezoelectric substrate. (For example, Patent Document 1).

The filter of Patent Document 1 has a first ground terminal connected to the first parallel arm resonator, a second ground terminal connected to the second parallel arm resonator, and a third ground connected to the longitudinally coupled resonator type filter. have terminals.

The first ground terminal and the second ground terminal are not connected to each other on the piezoelectric substrate, and the second ground terminal and the third ground terminal are connected to each other on the piezoelectric substrate. In other words, on the piezoelectric substrate, the first ground terminal and the second ground terminal are independent, and the second ground terminal and the third ground terminal are shared.

According to the filter of Patent Document 1, the influence of parasitic inductance is reduced by making the first ground terminal and the second ground terminal independent, so that the attenuation characteristic at the low end of the passband can be sharpened. In addition, by sharing the second ground terminal and the third ground terminal, the ground potential of the longitudinally coupled resonator type filter is stabilized. isolation) can be increased.

JP 2017-85262 A

However, conventional filters may not provide sufficient attenuation outside the passband.

Accordingly, the present invention provides a band-pass filter in which a ladder-type filter and a longitudinally-coupled resonator-type filter are connected in series, and which is excellent in attenuation outside the passband.

To achieve the above object, a filter according to an aspect of the present invention includes a ladder-type filter including a first parallel-arm resonator and a second parallel-arm resonator, and the second parallel-arm resonator of the ladder- type filter. a longitudinally coupled resonator-type filter connected to a node connected to a first parallel arm resonator; a first ground terminal connected to the first parallel arm resonator; on a first signal path connecting a second ground terminal connected to an arm resonator, a third ground terminal connected to the longitudinally coupled resonator type filter, the second parallel arm resonator and the second ground terminal; a third signal path connected to a first node of and a second node on a second signal path connecting the longitudinally coupled resonator filter and a third ground terminal; and the first signal path on the first signal path. At least one of a first inductor connected between a node and the second ground terminal or a second inductor connected between the second node and the third ground terminal on the second signal path and an inductor , wherein the one inductor is composed of wiring having a meandering portion .

Further, a multiplexer according to an aspect of the present invention includes a first filter and a second filter whose ends are connected to each other, the first filter being the filter described above, and the center of the passband of the first filter The frequency is higher than the center frequency of the passband of said second filter.

According to the above filter, since the first ground terminal is provided independently of the second ground terminal and the third ground terminal, it is possible to sharpen the attenuation characteristic at the low end of the passband as in the conventional filter.

Also, the second parallel arm resonator and the longitudinally coupled resonator filter are connected to each other via an inductor on the ground side. Here, the inductor is an equivalent representation of the inductance component of the signal path connecting the first node and the second node, and may be so small that it can be substantially ignored.

As a result, series resonance is generated by the combined capacitance of the second parallel arm resonator and the longitudinally coupled resonator filter and the second inductor. The attenuation pole generated by the series resonance shifts to the low frequency side compared to the case where the second inductor is not provided. As a result, the attenuation in the target frequency band on the low frequency side outside the passband is effectively improved.

Since the second inductor is commonly connected to the second parallel arm resonator and the longitudinally coupled resonator-type filter, compared to the case where individual inductors are connected to the second parallel arm resonator and the longitudinally coupled resonator-type filter, , the miniaturization of the device becomes possible.

Further, since the second inductor is connected between the first node and the second ground terminal, compared to the case where the second inductor is connected between the second node and the third ground terminal, the longitudinally coupled resonator type The ground potential of the filter is less likely to become unstable. As a result, the attenuation in the target frequency band is stably improved.

According to the filter described above, the attenuation in the target frequency band on the low-frequency side outside the passband is improved, along with the sharp attenuation characteristic at the low-frequency end of the passband. Therefore, by configuring a multiplexer by combining the above filter with another filter having a lower passband center frequency, a multiplexer with excellent isolation between bands can be obtained.

1 is a circuit diagram showing an example of a configuration of a multiplexer according to an embodiment; FIG. FIG. 2 is a plan view and a cross-sectional view schematically showing an example of the structure of an IDT (InterDigital Transducer) electrode. FIG. 3 is a plan view schematically showing an example of electrode arrangement on the piezoelectric substrate of the multiplexer according to the embodiment. 4 is a plan view schematically showing an example of electrode arrangement on a piezoelectric substrate of a multiplexer according to Comparative Example 1. FIG. FIG. 5 is a circuit diagram showing an example of the configuration of a multiplexer according to Comparative Example 2. As shown in FIG. 6 is a plan view schematically showing an example of electrode arrangement on a piezoelectric substrate of a multiplexer according to Comparative Example 2. FIG. FIG. 7 is a circuit diagram showing an example of the configuration of a multiplexer according to Comparative Example 3. As shown in FIG. 8 is a plan view schematically showing an example of electrode arrangement on a piezoelectric substrate of a multiplexer according to Comparative Example 3. FIG. FIG. 9 is a plan view schematically showing an example of electrode arrangement on the piezoelectric substrate of the multiplexer according to the modification. FIG. 10 is a graph showing an example of isolation characteristics between terminals Tx and Rx of the multiplexer.

EMBODIMENT OF THE INVENTION Hereinafter, embodiment of this invention is described in detail using embodiment and drawing. It should be noted that the embodiments described below are all comprehensive or specific examples. Numerical values, shapes, materials, constituent elements, arrangement of constituent elements, connection forms, and the like shown in the following embodiments are examples, and are not intended to limit the present invention. In the following embodiments, "connected" includes not only direct connection via wiring conductors, but also electrical connection via other circuit elements.

A multiplexer according to an embodiment will be described with an example of a duplexer including a transmission filter and a reception filter.

FIG. 1 is a circuit diagram showing an example configuration of a multiplexer 1 according to an embodiment. As shown in FIG. 1, multiplexer 1 comprises terminals Ant, Tx, Rx, receive filter 10 and transmit filter 20 . Terminal Ant is connected to antenna element 30 .

The reception filter 10 is a filter circuit that passes a predetermined reception frequency band, and is connected to a terminal Ant and a terminal Rx. One end and the other end of receive filter 10 may be directly connected to terminals Ant and Rx, respectively, or may be connected via other circuit elements (not shown).

In receive filter 10, series arm resonators 13 and 14 and parallel arm resonators 15 and 16 form a ladder type resonator filter. The resonator groups 17 and 18 connected in parallel constitute a longitudinally coupled resonator type filter. Each of the resonator groups 17 and 18 has five IDT electrodes juxtaposed in the elastic wave propagation direction. The ladder type resonator filter and the longitudinally coupled resonator type filter are connected in series.

One end of the parallel arm resonator 15 is connected to the ground B1. A node N1 on the signal path R1 connecting the parallel arm resonator 16 and the ground B2 and a node N2 on the signal path R2 connecting the resonator groups 17 and 18 and the ground B3 are connected by a signal path R3.

An inductor L1 is arranged between the node N1 on the signal path R1 and the ground B2, and an inductor L2 is arranged between the node N2 on the signal path R2 and the ground B3. The ground-side ends of all IDT electrodes included in resonator groups 17 and 18 are connected to ground B3 via inductor L2. Grounds B1, B2 and B3 are terminals for external connection and have parasitic inductance.

Inductors L1 and L2 may be equivalent inductance components of corresponding wirings, or may be inductance components of discrete components. The inductance of inductor L1 is greater than the inductance of inductor L2. The inductance of inductor L2 may be so small as to be substantially negligible. Although other wirings also have inductance components, they are not shown in the figure because they are not essential parts of the present invention.

The transmission filter 20 is a ladder type resonator filter composed of series arm resonators 21 , 22 , 23 , 24 and 25 and parallel arm resonators 26 , 27 , 28 and 29 . The ground side end of the parallel arm resonator 26 is connected to the ground B4, and the ground side ends of the parallel arm resonators 27, 28 and 29 are connected to the ground B5. The grounds B4 and B5 are terminals for external connection and have parasitic inductance components.

Next, the basic structure of the IDT electrode will be described.

2A and 2B are a plan view and a cross-sectional view schematically showing an example of the basic structure of the IDT electrode 50. FIG. The structure of the IDT electrode 50 shown in FIG. 2 is applied to each IDT electrode constituting the series arm resonators 13 and 14, the parallel arm resonators 15 and 16, and the resonator groups 17 and 18 in the receive filter 10. FIG. Note that the example in FIG. 2 is for explaining the basic structure of the IDT electrode 50, and the number and length of electrode fingers constituting the electrode are not limited to the example in FIG.

The IDT electrode 50 is composed of a pair of comb-shaped electrodes 50a and 50b facing each other. The comb-shaped electrode 50a is composed of a plurality of parallel electrode fingers 51a and busbar electrodes 52a connecting the plurality of electrode fingers 51a. The comb-shaped electrode 50b is composed of a plurality of parallel electrode fingers 51b and a busbar electrode 52b connecting the plurality of electrode fingers 51b. The electrode fingers 51a and 51b are formed to extend in a direction orthogonal to the X-axis direction, which is the propagation direction of elastic waves, and are arranged so as to be inserted into each other.

Parameters that define the shape and size of the IDT electrode 50 are called electrode parameters. Examples of electrode parameters include a wavelength λ that is a repetition period of the electrode fingers 51a or 51b in the X-axis direction, an intersection width L that is a length of overlap between the electrode fingers 51a and 51b when viewed in the X-axis direction, and an electrode finger 51a. , 51b, and the space width S between adjacent electrode fingers 51a and 51b.

A logarithm that is 1/2 of the total number of electrode fingers of the electrode fingers 51a and 51b, a pitch (W+S) that is the repetition period of the electrode fingers that are the total of the electrode fingers 51a and 51b, and a duty that is the ratio of the line width to the pitch. The ratio W/(W+S) is also an example of an electrode parameter.

Electrode fingers 51 a and 51 b and bus bar electrodes 52 a and 52 b are composed of electrode layers 53 formed on piezoelectric substrate 59 .

As an example, the electrode layer 53 may be made of a metal such as copper or aluminum or an alloy thereof, and the piezoelectric substrate 59 may be made of a piezoelectric layer containing lithium tantalate or lithium niobate. The electrode layer 53 may be formed on the piezoelectric substrate 59 with an adhesion layer (not shown) interposed therebetween. The electrode layer 53 may be covered with a protective layer 54 .

The piezoelectric substrate 59 may be composed of a single piezoelectric layer, or may be a laminated substrate having piezoelectricity at least partially. The laminated substrate having piezoelectricity at least in part includes a supporting substrate, a high acoustic velocity film formed on the supporting substrate and having a bulk wave acoustic velocity that propagates faster than an elastic wave acoustic velocity propagating through the piezoelectric thin film, and a high acoustic velocity film. A lamination composed of a low acoustic velocity film laminated on a sound velocity film and having a bulk wave acoustic velocity slower than the acoustic velocity of an elastic bulk wave propagating through the piezoelectric thin film, and a piezoelectric thin film laminated on the low acoustic velocity film. It can be a body. Also, the support substrate may be a high acoustic velocity support substrate such as a silicon substrate that serves as both the high acoustic velocity film and the support substrate.

Next, an example of electrode arrangement of the multiplexer 1 formed on the piezoelectric substrate will be described.

FIG. 3 is a plan view schematically showing an example of electrode arrangement on the piezoelectric substrate 59 of the multiplexer 1. As shown in FIG. As shown in FIG. 3, each resonator of multiplexer 1 consists of an IDT electrode formed in a correspondingly labeled area on piezoelectric substrate 59 . Further, on the piezoelectric substrate 59, terminals Ant, Tx, Rx, B1, B2, B3, B4 and B5, which are electrode structures for external connection, wiring for connecting the resonators and connecting the resonators and the terminals are provided. Electrodes functioning as wirings are formed.

The bus bar electrodes on the ground side of the IDT electrodes forming the resonator groups 17 and 18 and the ground terminal B3 are connected via a three-dimensional wiring 19 . The ground terminal B1 is provided independently of the ground terminals B2 and B3.

Inductors L1 and L2 are the inductance components of the corresponding wiring. Specifically, the inductor L1 is an inductance component of the wiring connecting the node N1 and the ground terminal B2. Inductor L2 is an inductance component of wiring connecting node N2 and ground terminal B3.

The inductance component of inductor L1 is greater than the inductance component of inductor L2. Specifically, since the wiring connecting the node N1 and the ground terminal B2 is intentionally routed in a meandering manner, the inductance component of the inductor L1 is large. On the other hand, since the wiring connecting the node N2 and the ground terminal B3 is composed of wiring having a planar pattern without a meandering portion, the inductance component of the inductor L2 is negligibly small.

The electrode parameters of the parallel arm resonators 15 and 16 are set as follows, for example. The parallel arm resonators 15 and 16 have a logarithm of 63 pairs and 67 pairs, respectively, and cross widths of 71 μm and 91 μm, respectively.

The resonator capacitance is primarily proportional to the product of the logarithm and the cross width. Parallel arm resonators 15 and 16 have capacitances of 2.1 pF and 2.8 pF, respectively, and parallel arm resonator 16 has a larger capacitance than parallel arm resonator 15 .

According to the multiplexer 1 configured as described above, since the ground terminal B1 is provided independently of the ground terminals B2 and B3, the attenuation characteristic at the low-frequency end of the passband can be sharpened as in the conventional filter.

Also, the parallel arm resonator 16 and the resonator groups 17 and 18 are connected to each other via a signal path R3 on the ground side.

As a result, series resonance occurs due to the combined capacitance of the parallel arm resonator 16 and the resonator groups 17 and 18 and the inductor L1. The attenuation pole generated by series resonance shifts to the low frequency side compared to the case where the inductor L1 is not provided. As a result, the attenuation in the transmission frequency band on the low frequency side outside the passband is effectively improved.

Since the inductor L1 is commonly connected to the parallel arm resonator 16 and the resonator groups 17 and 18, the device is more compact than the case where the parallel arm resonator 16 and the resonator groups 17 and 18 are individually connected. can be made smaller.

Further, since the attenuation pole is shifted using the inductor L1 connected between the node N1 and the ground terminal B2, there is no need to increase the inductance of the inductor L2 connected between the node N2 and the ground terminal B3. . Since the inductance of inductor L2 is not increased, the ground potential of resonator groups 17 and 18 is less likely to become unstable. As a result, attenuation in the transmission frequency band is stably improved.

In addition, since the ground-side ends of all the IDT electrodes of the resonator groups 17 and 18 are shared, the ground potential of the resonator groups 17 and 18 is further stabilized, and the parasitic inductance component is reduced. The effect of improving attenuation in the frequency band increases.

Moreover, the capacitance of the parallel arm resonator 16 is the largest among the capacitances of the parallel arm resonators 15 and 16 . As a result, the combined capacitance of the parallel arm resonator 16 and the resonator groups 17 and 18 is increased, and the inductance component necessary for shifting the attenuation pole to the low frequency side can be reduced. As a result, it can contribute to miniaturization of the chip.

According to the reception filter 10, the attenuation in the transmission frequency band is improved as well as the steep attenuation characteristic at the low end of the passband. Therefore, by configuring the multiplexer 1 by combining the reception filter 10 and the transmission filter 20, the multiplexer 1 excellent in isolation between transmission and reception can be obtained.

Effects of the multiplexer 1 and the modified example described above will be described in comparison with a comparative example.

FIG. 4 is a plan view schematically showing an example of electrode arrangement on the piezoelectric substrate 59 of the multiplexer 2 according to Comparative Example 1. FIG.

Multiplexer 2 has the same circuit configuration as multiplexer 1, but differs in that the inductance component of inductor L1 is smaller.

As shown in FIG. 4, in the multiplexer 2, the wiring connecting the node N1 and the ground terminal B2 is composed of electrodes having a planar pattern. Almost the same and small enough to be ignored.

FIG. 5 is a circuit diagram showing an example of the configuration of the multiplexer 3 according to Comparative Example 2. As shown in FIG.

FIG. 6 is a plan view schematically showing an example of electrode arrangement on the piezoelectric substrate 59 of the multiplexer 3. As shown in FIG.

Multiplexer 3 differs from multiplexer 1 in that it has inductor L3 between parallel arm resonator 16 and node N1.

As shown in FIGS. 5 and 6, in the multiplexer 3, the receive filter 11 is provided with an inductor L3, which is an intentionally meandering wiring between the parallel arm resonator 16 and the node N1. . The length of the wiring corresponding to the inductor L1 is substantially 0, and the wiring corresponding to the inductor L2 is composed of electrodes having a planar pattern, so the inductance components of the inductors L1 and L2 can be ignored. small to some extent.

FIG. 7 is a circuit diagram showing an example of the configuration of the multiplexer 4 according to Comparative Example 3. As shown in FIG.

FIG. 8 is a plan view schematically showing an example of electrode arrangement on the piezoelectric substrate 59 of the multiplexer 4. As shown in FIG.

Multiplexer 4 differs from multiplexer 1 in that it does not have a signal path connecting node N1 and node N2.

As shown in FIGS. 7 and 8, in multiplexer 4, ground terminals B1, B2 and B3 are all independently provided in receive filter 12. FIG. In addition, an inductor L4 is provided by wiring that is intentionally routed so as to meander between the parallel arm resonator 16 and the ground terminal B2.

FIG. 9 is a plan view schematically showing an example of electrode arrangement on the piezoelectric substrate 59 of the multiplexer 5 according to the modification.

Multiplexer 5 has the same circuit configuration as multiplexer 1 in FIG. 1, but differs in that inductor L1 has a smaller inductance component and inductor L2 has a larger inductance component.

As shown in FIG. 9, in the multiplexer 5, since the wiring between the node N2 and the ground terminal B3 is intentionally routed in a meandering manner, the inductance component of the inductor L2 is large. Further, since the wiring connecting the node N1 and the ground terminal B2 is composed of electrodes having a planar pattern, the inductance component of the inductor L1 is negligibly small. Accordingly, in the multiplexer 5, the inductance component of the inductor L2 is larger than the inductance component of the inductor L1.

Using the multiplexer 1 as an example, the isolation characteristics between the terminals Tx→Rx were obtained for the multiplexers 1, 2, 3, 4 and 5 according to the example, comparative examples 1, 2 and 3, and modifications. The uplink frequency band (814 MHz or more and 849 MHz or less) of Band 26 of LTE (Long Term Evolution) is the passband (hereinafter referred to as transmission band) of the transmission filter 20, and the downlink frequency band (859 MHz or more and 894 MHz or less) is the reception filter 10. , 11 and 12 (hereinafter referred to as reception bands).

FIG. 10 is a graph showing an example of isolation characteristics between terminals Tx→Rx of the multiplexer.

As can be seen in FIG. 10, the minimum value of insertion loss (worst value of isolation) in the transmission band is 60.7 dB in the example, 58.6 dB in the modified example, 57.2 dB in the comparative example 1, and 57.2 dB in the comparative example 1. Example 2 is 56.3 dB, and Comparative Example 3 is 53.8 dB.

In the embodiment, by connecting the node N1 and the node N2, the attenuation pole generated by the series resonance due to the combined capacitance of the parallel arm resonator 16 and the resonator groups 17 and 18 and the inductor L1 is spread over the reception band. is shifted to the low frequency side from the vicinity of . By using the combined capacitance to shift the attenuation pole to the low-frequency side, the required inductance component is reduced, and good isolation is achieved over the entire transmission band.

In Comparative Example 1, the node N1 and the node N2 are connected, but the inductor L1 is realized by an electrode having a planar pattern, and the inductance component is so small that it can be practically ignored. Inability to shift sufficiently to the side. Therefore, compared to the embodiment, the isolation in the middle to high frequencies (831.5 MHz or more and 849 MHz or less) of the transmission band is deteriorated.

In Comparative Example 2, an inductor L3 is provided between the parallel arm resonator 16 and the node N1, and the attenuation pole generated by the series resonance between the parallel arm resonator 16 and the inductor L3 is shifted from the vicinity of the reception band to the low frequency side. By shifting, the attenuation of the transmission band is improved.

In Comparative Example 2, in order to shift the attenuation pole, the required inductance component is increased as compared with the Example because the capacitance of the resonator groups 17 and 18 is not used. Therefore, it becomes an obstacle to miniaturization of the device. In addition, since the steepness of the attenuation characteristic deteriorates at the low-frequency end of the reception band, the isolation near the high-frequency end (849 MHz) of the transmission band deteriorates.

In Comparative Example 3, the ground of the parallel arm resonator 16 and the grounds of the resonator groups 17 and 18 are not shared, and an inductor L4 is provided between the parallel arm resonator 16 and the ground terminal B2. Attenuation in the transmission band is improved by shifting the attenuation pole generated by the series resonance of 16 and inductor L4 from the vicinity of the reception band to the low frequency side.

In Comparative Example 3, since the ground-side ends of the resonator groups 17 and 18 are not connected to the ground terminal B2, the parasitic inductance component generated in the ground of the resonator groups 17 and 18 increases. Normally, the more stable the ground potential of the resonator groups 17 and 18, the greater the attenuation in the transmission band. Isolation over the entire band deteriorates.

In the modified example, by connecting the node N1 and the node N2, the attenuation pole generated by the series resonance of the combined capacitance of the parallel arm resonator 16 and the resonator groups 17 and 18 and the inductor L2 is spread over the reception band. is shifted to the low frequency side from the vicinity of . In the modified example, the necessary inductance component is reduced by shifting the attenuation pole to the low frequency side using the combined capacitance, as in the embodiment.

In the modified example, the inductor L2 connected between the node N2 and the ground terminal B3 is used to shift the attenuation pole to the low frequency side. The parasitic inductance component to be applied becomes large. Therefore, the isolation in the vicinity of the middle band (831.5 MHz) of the transmission band deteriorates compared to the embodiment.

It should be noted that the ground terminal B1 is independent of the ground terminals B2 and B3 in all of the multiplexers 1, 2, 3, 4 and 5 according to the embodiment, comparative examples 1, 2 and 3, and modifications. If the ground terminal B1 is shared with the ground terminals B2 and B3, the attenuation pole generated by the parallel arm resonator 15 will also shift to the low frequency side, and the steepness of the attenuation characteristic on the low frequency side of the reception band will be impaired. can occur. Multiplexers 1, 2, 3, 4 and 5 avoid this disadvantage.

Although filters and multiplexers according to embodiments of the present invention have been described above, the present invention is not limited to individual embodiments. As long as it does not depart from the spirit of the present invention, one or more modifications of the present embodiment that can be conceived by a person skilled in the art, or a form constructed by combining the components of different embodiments may be included within the scope of the embodiments.

For example, in the embodiments, an example of a duplexer has been described, but the present invention is not limited to a duplexer. etc. may be applied.

For example, in the embodiment, the second parallel arm resonator and the longitudinally coupled resonator filter are connected to each other via an inductor on the ground side, and this inductor is connected to the node N1 on the first signal path R1. Although an example of the inductor L1 between the ground terminal B2 has been shown, the present invention is not limited to this. The inductor may be inductor L2 between node N2 on signal path R2 and ground terminal B3. Like inductor L1, inductor L2 can also increase the amount of attenuation outside the passband.

INDUSTRIAL APPLICABILITY The present invention can be widely used as filters and multiplexers in communication equipment such as mobile phones.

1, 2, 3, 4, 5 multiplexer 10, 11, 12 reception filter 13, 14 serial arm resonator 15, 16 parallel arm resonator 17, 18 resonator group 19 three-dimensional wiring 20 transmission filter 21, 22, 23, 24 , 25 series arm resonators 26, 27, 28, 29 parallel arm resonators 30 antenna element 50 IDT electrodes 50a, 50b comb-like electrodes 51a, 51b electrode fingers 52a, 52b busbar electrodes 53 electrode layer 54 protective layer 59 piezoelectric substrate N1 , N2 Nodes R1, R2, R3 Signal Paths L1, L2, L3, L4 Inductors Ant, Tx, Rx, B1, B2, B3, B4, B5 Terminals

Claims (6)

a ladder filter including a first parallel arm resonator and a second parallel arm resonator;
a longitudinally coupled resonator filter connected to a node to which the second parallel arm resonator of the ladder filter is connected;
a first ground terminal connected to the first parallel arm resonator;
a second ground terminal provided independently of the first ground terminal and connected to the second parallel arm resonator and a third ground terminal connected to the longitudinally coupled resonator type filter;
A first node on a first signal path connecting the second parallel arm resonator and the second ground terminal, and a second node on a second signal path connecting the longitudinally coupled resonator type filter and a third ground terminal. a third signal path connected to
A first inductor connected between the first node on the first signal path and the second ground terminal, or between the second node on the second signal path and the third ground terminal at least one of the connected second inductors;
with
The one inductor is composed of wiring having a meandering portion,
filter. the filter comprises both the first inductor and the second inductor;
The other inductor of the first inductor or the second inductor is composed of wiring that does not have a meandering portion,
A filter according to claim 1 . the filter comprises both the first inductor and the second inductor;
the inductance of the first inductor is greater than the inductance of the second inductor;
3. A filter according to claim 1 or 2. The longitudinally coupled resonator-type filter has a plurality of IDT (InterDigital Transducer) electrodes arranged in parallel in a propagation direction of elastic waves, and one end of each of the plurality of IDT electrodes is connected to the third ground terminal. ,
4. A filter according to any one of claims 1-3. the capacitance of the second parallel arm resonator is the largest among the capacitances of all the parallel arm resonators included in the ladder filter;
5. A filter according to any one of claims 1-4. A first filter and a second filter having one ends connected to each other,
The first filter is the filter according to any one of claims 1 to 5,
the center frequency of the passband of the first filter is higher than the center frequency of the passband of the second filter;
multiplexer.

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