阅读说明：本技术 滤波器装置以及具备该滤波器装置的双工器和多工器 (Filter device, and duplexer and multiplexer provided with same ) 是由 近藤清磨 于 2020-09-24 设计创作，主要内容包括：本发明提供一种滤波器装置、双工器以及多工器。滤波器装置具备设置在滤波器芯片的多个串联臂谐振器和多个并联臂谐振器、以及与多个并联臂谐振器包含的一部分并联臂谐振器各自串联地连接的多个电感器,在多个并联臂谐振器中的反谐振频率最大的第1并联臂谐振器串联地连接有多个电感器中的电感最大的第1电感器,第1并联臂谐振器的一端和多个并联臂谐振器中的另一部分并联臂谐振器包含的第2并联臂谐振器的一端与连结滤波器芯片的输入端子和输出端子的线路上的、被多个串联臂谐振器隔开的多个布线中的同一布线连接,第1并联臂谐振器的另一端与滤波器芯片的第1接地端子连接,第2并联臂谐振器的另一端与滤波器芯片的第2接地端子连接。(The invention provides a filter device, a duplexer and a multiplexer. The filter device comprises a plurality of series arm resonators and a plurality of parallel arm resonators provided on a filter chip, and a plurality of inductors connected in series to each of some of the parallel arm resonators included in the plurality of parallel arm resonators, a1 st inductor having the largest inductance among the plurality of inductors is connected in series to a 1 st parallel arm resonator having the largest anti-resonance frequency among the plurality of parallel arm resonators, one end of the 1 st parallel arm resonator and one end of a 2 nd parallel arm resonator included in another part of the plurality of parallel arm resonators are connected to the same one of a plurality of wirings separated by the plurality of series arm resonators on a line connecting an input terminal and an output terminal of the filter chip, the other end of the 1 st parallel arm resonator is connected to a 1 st ground terminal of the filter chip, and the other end of the 2 nd parallel arm resonator is connected to a 2 nd ground terminal of the filter chip.)

1. A filter device is provided with:

a plurality of series arm resonators provided on the filter chip;

a plurality of parallel arm resonators provided on the filter chip; and

a plurality of inductors each connected in series with a part of the parallel arm resonators included in the plurality of parallel arm resonators,

in the filter means in question, it is,

a 1 st inductor having the largest inductance among the plurality of inductors is connected in series to a 1 st parallel arm resonator having the largest anti-resonance frequency among the plurality of parallel arm resonators,

one end of the 1 st parallel arm resonator and one end of the 2 nd parallel arm resonator are connected to the same one of a plurality of wirings separated by the plurality of series arm resonators on a line connecting the input terminal and the output terminal of the filter chip, the 2 nd parallel arm resonator is included in another part of the plurality of parallel arm resonators which is different from the part of the parallel arm resonators,

the other end of the 1 st parallel arm resonator is connected to the 1 st ground terminal of the filter chip,

the other end of the 2 nd parallel arm resonator is connected to a 2 nd ground terminal of the filter chip different from the 1 st ground terminal.

2. The filter arrangement of claim 1,

the another part of the parallel arm resonators includes a 3 rd parallel arm resonator,

one end of the 3 rd parallel arm resonator is connected to a wiring different from the wiring to which the one end of the 1 st parallel arm resonator and the one end of the 2 nd parallel arm resonator are connected among the plurality of wirings, and the other end of the 3 rd parallel arm resonator is connected to the 2 nd ground terminal of the filter chip.

3. The filter arrangement according to claim 1 or 2,

the plurality of parallel arm resonators includes:

a 4 th parallel arm resonator connected to a wiring closest to the input terminal among the plurality of wirings; and

and a 5 th parallel arm resonator connected to a wiring closest to the output terminal among the plurality of wirings.

4. The filter arrangement according to any one of claims 1 to 3,

the anti-resonance frequency of the 2 nd parallel arm resonator is higher than each of the anti-resonance frequencies of the parallel arm resonators other than the 2 nd parallel arm resonator in the another part of the parallel arm resonators.

5. The filter arrangement of claim 4,

each of anti-resonance frequencies of parallel arm resonators other than the 2 nd parallel arm resonator of the another part of parallel arm resonators is higher than about 99.5% of the anti-resonance frequency of the 2 nd parallel arm resonator.

6. The filter arrangement of claim 5,

the pitch of the 2 nd parallel arm resonator is greater than about 99.5% of the pitch of each of the parallel arm resonators other than the 2 nd parallel arm resonator in the another part of the parallel arm resonators.

7. The filter arrangement according to any one of claims 1 to 6,

the filter chip comprises LiTaO₃。

8. The filter arrangement according to any one of claims 1 to 7,

the plurality of inductors are disposed on a pattern layer on which the filter chip is laminated.

9. The filter arrangement according to any one of claims 1 to 8,

one end of a 2 nd inductor of the plurality of inductors is connected to the other end of the parallel arm resonator having one end connected to one of the plurality of wirings other than the wiring to which the 1 st parallel arm resonator is connected,

one end of a 3 rd inductor among the plurality of inductors is connected to the other end of the parallel arm resonator having one end connected to a wiring of the plurality of wirings that is farther from the wiring to which the 1 st parallel arm resonator is connected than the one wiring,

the distance between the 1 st inductor and the 2 nd inductor is smaller than the interval between the 1 st inductor and the 3 rd inductor.

10. A duplexer includes:

the filter arrangement of any one of claims 1 to 9.

11. A multiplexer includes:

the filter arrangement of any one of claims 1 to 9.

Technical Field

The present invention relates to a filter device.

Background

In mobile communication devices such as mobile phones, a common antenna is sometimes used for transmission of a transmission signal and reception of a reception signal in order to reduce the size of the terminal. A duplexer for separating a transmission signal and a reception signal is connected to such an antenna. As an example of the duplexer, a ladder filter circuit may be used in which a plurality of resonators having a specific resonance frequency and an antiresonance frequency are connected in a ladder-like manner to pass a signal of a given frequency band and attenuate signals of other frequency bands.

For example, patent document 1 describes a ladder filter including series arm resonators, parallel arm resonators, and inductors connected in series to the parallel arm resonators.

Prior art documents

Patent document

Patent document 1: international publication No. 2016/088680

As the frequency characteristics of the ladder filter circuit, generally, it is preferable that the input loss in the pass band is small and the attenuation characteristics of the attenuation band in the vicinity of the pass band are steep. However, for example, when an inductor is connected in series to the parallel arm resonator, the anti-resonance frequency of the parallel arm resonator remains substantially the same and the resonance frequency shifts to the low frequency side, so that the input loss of the passband decreases, but the steepness of the attenuation characteristic of the attenuation band deteriorates. On the other hand, for example, when a large number of parallel arm resonators are added to the ladder filter circuit, the input loss in the passband becomes large although the steepness of the attenuation characteristic in the attenuation band is improved.

Disclosure of Invention

Problems to be solved by the invention

An object of the present invention is to provide a filter device capable of reducing the input loss of the passband while maintaining the steepness of the attenuation characteristic of the attenuation band.

Means for solving the problems

In order to achieve the above object, a filter device according to an aspect of the present invention includes: a plurality of series arm resonators provided on the filter chip; a plurality of parallel arm resonators provided on the filter chip; and a plurality of inductors respectively connected in series with a part of the parallel arm resonators included in the plurality of parallel arm resonators, in the filter device, a 1 st inductor having the largest inductance among the plurality of inductors is connected in series to a 1 st parallel arm resonator having the largest anti-resonance frequency among the plurality of parallel arm resonators, one end of the 1 st parallel arm resonator and one end of a 2 nd parallel arm resonator are connected to the same one of the plurality of wires separated by the plurality of series arm resonators on a line connecting the input terminal and the output terminal of the filter chip, the 2 nd parallel arm resonator is included in another part of the plurality of parallel arm resonators than the part of the parallel arm resonators, the other end of the 1 st parallel arm resonator is connected to a 1 st ground terminal of the filter chip, and the other end of the 2 nd parallel arm resonator is connected to a 2 nd ground terminal of the filter chip different from the 1 st ground terminal.

Effects of the invention

According to the present invention, it is possible to provide a filter device capable of reducing the input loss of the passband while maintaining the steepness of the attenuation characteristic of the attenuation band.

Drawings

Fig. 1 is a diagram showing an example of the circuit configuration of the filter device 10.

Fig. 2 is a diagram showing an example of a top view of the filter chip 100.

Fig. 3A is a diagram showing an example of a top view of the layer 1 a of the pattern layer.

Fig. 3B is a diagram showing an example of a top view of the 2 nd layer 200B of the pattern layer.

Fig. 3C is a diagram showing an example of a top view of the 3 rd layer 200C of the pattern layer.

Fig. 3D is a diagram showing an example of a top view of the 4 th layer 200D of the pattern layer.

Fig. 3E is a diagram showing an example of a top view of the 5 th layer 200E of the pattern layer.

Fig. 3F is a diagram showing an example of a top view of the 6 th layer 200F of the pattern layer.

Fig. 4A is a graph showing simulation results of frequency characteristics (attenuation characteristics) in the filter device 10 according to embodiment 1 and comparative example.

Fig. 4B is another graph showing simulation results of frequency characteristics (attenuation characteristics) in the filter device 10 according to embodiment 1 and the comparative example.

Description of the reference numerals

10: filter device, S1 to S5: series-arm resonator, P1 to P6: parallel arm resonator, L1 to L3: inductor, IN: input terminal, OUT: output terminals, T1 to T4: ground terminal, 100: filter chip, 200A: layer 1 of the pattern layer, 200B: layer 2 of the pattern layer, 200C: layer 3 of the pattern layer, 200D: layer 4 of the pattern layer, 200E: layer 5 of the pattern layer, 200F: layer 6 of the pattern layer.

Detailed Description

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The same elements are denoted by the same reference numerals, and redundant description thereof is omitted.

Fig. 1 is a diagram showing an example of the circuit configuration of a filter device 10 according to embodiment 1. One antenna for transmitting and receiving a Radio Frequency (RF) signal is sometimes used in a mobile communication device, and in such a case, for example, a splitter for separating a transmission signal and a reception signal is used. The filter device 10 may constitute, for example, a transmission signal filter circuit and a reception signal filter circuit for constituting such a demultiplexer. The demultiplexer may be, for example, a composite filter device including a plurality of filter circuits and separating signals of a plurality of frequency bands. The composite filter device includes, for example, a duplexer in which two filter circuits are combined, a triplexer in which three filter circuits are combined, a quadplexer in which four filter circuits are combined, or an octaxer in which eight filter circuits are combined.

As shown in fig. 1, the filter device 10 according to the present embodiment is a ladder filter in which a plurality of resonators are connected in series and in parallel. The filter device 10 includes five series-arm resonators S1 to S5, six parallel-arm resonators P1 to P6, and three inductors L1 to L3. Series-arm resonators S1 to S5 and parallel-arm resonators P1 to P6 are provided on the filter chip 100. The filter chip 100 is further provided with an input terminal IN, an output terminal OUT, and terminals T1 to T4. Inductors L1 to L3 are provided in the pattern layer.

When the filter device 10 is configured as a transmission signal filter circuit, a transmission signal is supplied from the input terminal IN to a front-end module including a power amplifier, for example, and a filtered transmission signal is supplied from the output terminal OUT to an antenna, for example. IN the case where the filter device 10 is configured as a received signal filter circuit, a received signal is supplied from the antenna, for example, to the input terminal IN, and a filtered received signal is supplied from the output terminal OUT, for example, to a front-end module or the like.

The terminals T1 to T4 are terminals for grounding connected to the parallel arm resonators, respectively. Here, the terminal T3 is an example of the 1 st ground terminal. The terminal T4 is an example of a 2 nd ground terminal.

IN a line U1 connecting the input terminal IN and the output terminal OUT, five series-arm resonators S1 to S5 are connected IN series IN order from the input terminal IN side. The six parallel-arm resonators P1 to P6 are connected in parallel so as to branch from a plurality of wirings on the line U1 separated by the series-arm resonators S1 to S5.

The parallel arm resonator P4 is an example of the 4 th parallel arm resonator, and has one end connected to the wiring between the input terminal IN and the series arm resonator S1 and the other end connected to one end of the inductor L1 via the terminal T1. The other end of the inductor L1 is connected to ground (ground). One end of the parallel-arm resonator P6 is connected to a wiring between the series-arm resonator S1 and the series-arm resonator S2, and the other end is connected to one end of the inductor L2 via the terminal T2. The other end of inductor L2 is connected to ground. The parallel arm resonator P1 is an example of the 1 st parallel arm resonator, and has one end connected to a wiring between the series arm resonator S2 and the series arm resonator S3 and the other end connected to one end of the inductor L3 via the terminal T3. The other end of inductor L3 is connected to ground.

The parallel arm resonator P2 is an example of a 2 nd parallel arm resonator, and has one end connected to a wiring between the series arm resonator S2 and the series arm resonator S3 and the other end connected to ground via a terminal T4. The parallel arm resonator P3 is an example of the 3 rd parallel arm resonator, and has one end connected to the wiring between the series arm resonator S3 and the series arm resonator S4 and the other end connected to the ground via the terminal T4. The parallel arm resonator P5 is an example of the 5 th parallel arm resonator, and has one end connected to the wiring between the series arm resonator S4 and the series arm resonator S5 and the other end connected to the ground via the terminal T4. As described above, the terminal T4 is shared by the parallel-arm resonators P2, P3, and P5.

The anti-resonance frequency of the parallel-arm resonator P1 is the largest among the anti-resonance frequencies of the parallel-arm resonators P1 to P6 included in the filter device 10. The inductance of the inductor L3 is the largest among the inductances of the inductors L1 to L3 connected in series to the parallel arm resonators included in the filter device 10. The anti-resonance frequency of the parallel-arm resonator P2 is the largest among the anti-resonance frequencies of the parallel-arm resonators P2, P3, and P5 that are not connected in series with the inductor, and are included in the filter device 10.

Further, for example, it is preferable that the anti-resonance frequency of each of the parallel-arm resonators P3 and P5, which are not connected in series with the inductor, included in the filter device is higher than a predetermined ratio (about 99.5%, about 99.0%, about 98.5%, about 98.0%, about 95.0%, about 90.0%, about 85.0%, about 80.0%, or the like) with respect to the anti-resonance frequency of the parallel-arm resonator P2. In other words, the pitch of the comb-shaped electrodes of parallel-arm resonator P2 is preferably greater than the predetermined ratio with respect to the pitch of the comb-shaped electrodes of each of parallel-arm resonators P3 and P5.

Next, the layout of the filter chip 100 will be described with reference to fig. 2. Fig. 2 is a diagram showing an example of a plan view of the filter chip 100 included in the filter device 10 according to embodiment 1. IN fig. 2, for convenience of explanation, the terminals IN, OUT, T1 to T4, the wiring pattern, the series-arm resonators S1 to S5, and the parallel-arm resonators P1 to P6 are each shown IN a perspective manner as appropriate so that their arrangement becomes clear.

As shown IN fig. 2, the filter chip 100 is provided with the input terminal IN and the output terminal OUT, and ground terminals T1 to T4, and a wiring pattern is provided so as to connect these terminals. The filter chip 100 may comprise, for example, LiTaO₃Thereby forming the structure. Series-arm resonators S1 to S5 and parallel-arm resonators P1 to P6 are disposed at predetermined positions of the wiring pattern, respectively.

The series-arm resonators S1 to S5 and the parallel-arm resonators P1 to P6 may be configured as, for example, Surface Acoustic Wave (SAW) elements, piezoelectric thin-film resonators, Bulk Acoustic Wave (BAW) elements, and the like. For example, assuming that the pitch of comb-shaped electrodes (IDT) is λ and the sound velocity in the piezoelectric substrate constituting the SAW filter is v, the resonance frequency fr of the SAW filter can be represented by fr ═ v/λ [ Hz ]. Therefore, for example, the pitch of the comb-shaped electrodes can be adjusted to obtain a desired resonance frequency fr.

Next, the pattern layer will be described with reference to fig. 3A to 3F. The filter device 10 includes a pattern layer in which the filter chips 100 are stacked. The pattern layer may be formed by forming a conductive circuit pattern, a via hole, or the like on a substrate made of an insulator such as ceramic. In the pattern layer, for example, inductors L1 to L3 are formed as wiring patterns.

The pattern layer is formed by sequentially stacking a 1 st layer 200A shown in fig. 3A, a 2 nd layer 200B shown in fig. 3B, a 3 rd layer 200C shown in fig. 3C, a 4 th layer 200D shown in fig. 3D, a 5 th layer 200E shown in fig. 3E, and a 6 th layer 200F shown in fig. 3F.

An input terminal IN provided on the filter chip 100 and a wiring pattern U provided from the 1 st layer 200A to the 6 th layer 200F_INAnd (4) connecting. Further, an output terminal OUT provided at the filter chip 100 and a wiring pattern U provided from the 1 st layer 200A to the 6 th layer 200F_OUTAnd (4) connecting.

The terminal T1 provided on the filter chip 100 is connected to the wiring pattern U2 provided from the 1 st layer 200A to the 4 th layer 200D. The wiring pattern U2 is spirally wound around the 1 st to 4 th layers 200A to 200D, thereby constituting an inductor L1.

The terminal T2 provided on the filter chip 100 is connected to the wiring pattern U3 provided from the 1 st layer 200A to the 4 th layer 200D. The wiring pattern U3 is spirally wound around the 1 st to 4 th layers 200A to 200D, thereby constituting an inductor L2.

The terminal T3 provided on the filter chip 100 is connected to the wiring pattern U4 provided from the 1 st layer 200A to the 4 th layer 200D. The wiring pattern U4 is spirally wound around the 1 st to 4 th layers 200A to 200D, thereby constituting an inductor L3.

The wiring patterns U2, U3, and U4 are combined in the 5 th layer 200E as a wiring pattern U6. The wiring pattern U6 in the 5 th layer 200E is connected to three terminals in the 6 th layer 200F, respectively.

As described above, the terminal T4 provided on the filter chip 100 is connected to each of the parallel-arm resonators P2, P3, and P5 provided on the filter chip 100. The terminal T4 is connected to a wiring pattern U5 provided from the 1 st layer 200A to the 4 th layer 200D. The wiring patterns U5 in the 4 th layer 200D are connected to the wiring patterns U6 in the 5 th layer 200E.

As shown in fig. 3B, in the filter device 10 according to embodiment 1, the distance D23 between the inductor L2 and the inductor L3 is smaller than the distance D13 between the inductor L1 and the inductor L3. Thereby, the degree of magnetic coupling of the inductor L1 and the inductor L3 becomes smaller than the degree of magnetic coupling of the inductor L2 and the inductor L3. Therefore, regarding the inductors (inductors L1 and L2) other than the inductor L3 included IN the filter device 10, the degree of magnetic coupling with the inductor L3 of the inductor decreases as the distance between the wiring connecting the inductor L3 and the wiring connecting the inductor U1 connecting the input terminal IN and the output terminal OUT increases. Therefore, in the filter device 10, the order of the distance between the inductors on the circuit corresponds to the order of the magnitude of the degree of magnetic coupling between the inductors. This improves the frequency characteristics of the filter device 10 described later.

Next, the frequency characteristics of the filter device 10 according to embodiment 1 will be described with reference to fig. 4A and 4B. Fig. 4A and 4B are graphs showing simulation results of frequency characteristics (attenuation characteristics) in the filter devices 10 according to embodiment 1 and comparative example. Here, the filter device according to the comparative example is a filter device in which the parallel arm resonator P1 having the highest anti-resonance frequency among the parallel arm resonators P1 to P6 and the inductor L3 having the highest inductance among the inductors L1 to L3 are not connected in series, and the parallel arm resonator P1 and the parallel arm resonator P2 are not connected to the same wiring on the line U1.

In the present example, a Band41 Band in the 3GPP standard is shown. In the graphs shown in fig. 4A and 4B, the horizontal axis represents the frequency (MHz) of the signal, and the vertical axis represents the insertion loss (S21) (dB) of the signal.

In fig. 4A, the frequency characteristics 300 and 310 are graphs showing the results of embodiment 1 and comparative example in 10dB units (scale on the left vertical axis), and the frequency characteristics 320 and 330 are graphs showing the results of embodiment 1 and comparative example in 1dB units (scale on the right vertical axis). In fig. 4B, frequency characteristics 340 and 350 are graphs showing the results of embodiment 1 and the comparative example, respectively.

As shown by reference numeral E1 in fig. 4A, in the frequency characteristic of the filter device 10 according to embodiment 1, the input loss in the pass band is reduced as compared with the frequency characteristic of the filter device according to the comparative example. Further, as shown by reference numeral E2 in fig. 4A, in the frequency characteristic of the filter device 10 according to embodiment 1, the steepness of the attenuation characteristic of the attenuation band in the vicinity of the lower frequency side than the pass band is improved as compared with the frequency characteristic of the filter device according to the comparative example.

It can be said that this is mainly due to the following reason. That is, in the filter device 10 according to embodiment 1, the inductor L1 is connected in series to the parallel arm resonator P4, the inductor L2 is connected in series to the parallel arm resonator P6, and the inductor L3 is connected in series to the parallel arm resonator P1. Therefore, the anti-resonance frequency of each of the parallel-arm resonators P4, P6, and P1 is kept substantially as it is, and the resonance frequency shifts to the low frequency side. Further, if the anti-resonance frequency is kept substantially unchanged and the resonance frequency is shifted to the low frequency side, the inductance of the inductor used in the frequency characteristics of parallel-arm resonators P4, P6, and P1 can be used to reduce the capacitance of the resonator, and the mismatch loss can be improved. As a result, as shown by reference numeral E1, the input loss of the pass band is reduced in the frequency characteristic of the filter device 10. As described above, the anti-resonance frequency of the parallel-arm resonator P1 is the highest among the parallel-arm resonators P1 to P6 included in the filter device 10, and the inductance of the inductor L3 is the highest among the inductors L1 to L3 connected in series to these parallel-arm resonators. Therefore, it can be said that the effect of reducing the input loss of the passband by connecting the inductor in series with the parallel arm resonator is the greatest in the contribution by the series connection of the parallel arm resonator P1 and the inductor L3.

The filter device 10 according to embodiment 1 and the filter device according to the comparative example each include parallel arm resonators P2, P3, and P5 to which no inductor is connected in series. These parallel-arm resonators P2, P3, and P5 contribute to steepness of attenuation characteristics of the attenuation band near the low frequency side of the pass band. Here, in the filter device 10 according to embodiment 1, as described above, the parallel arm resonator P2 and the parallel arm resonator P1 (1 st parallel arm resonator) are connected to the same wiring on the line U1, and thus steepness of the attenuation characteristic of the attenuation band is more easily maintained. Therefore, as shown by reference numeral E2 in fig. 4A, in the filter device 10 according to embodiment 1, the steepness of the attenuation characteristic of the attenuation band in the vicinity of the lower frequency side than the pass band is improved as compared with the filter device according to the comparative example.

Further, in the filter device 10 according to embodiment 1, the other end of the parallel-arm resonator P1 is connected to the terminal T3 (1 st ground terminal), and the other end of the parallel-arm resonator P2 is connected to the terminal T4 (2 nd ground terminal) different from the terminal T3. Therefore, the other end of the parallel-arm resonator P1 and the other end of the parallel-arm resonator P2 are connected to the ground (in this example, the 5 th layer 200E in the pattern layer) at a position relatively far from the circuit outside the filter chip 100, and therefore the influence of the ground connection on the characteristics of the parallel-arm resonators P1 and P2 can be reduced.

As shown by reference numeral E3 in fig. 4B, in the frequency characteristic of the filter device 10 according to embodiment 1, the attenuation pole at the lower frequency side than the pass band moves to the lower frequency side (around 1900 to 2000 MHz) as compared with the frequency characteristic of the filter device according to the comparative example. This is the attenuation pole due to the inductor L3 included in the filter device 10 according to embodiment 1.

The filter device according to the embodiment is explained above. A filter device according to an embodiment includes: a plurality of series arm resonators provided on the filter chip; a plurality of parallel arm resonators provided on the filter chip; and a plurality of inductors respectively connected in series with a part of the parallel arm resonators included in the plurality of parallel arm resonators, in the filter device, a 1 st inductor having the largest inductance among the plurality of inductors is connected in series to a 1 st parallel arm resonator having the largest anti-resonance frequency among the plurality of parallel arm resonators, one end of the 1 st parallel arm resonator and one end of a 2 nd parallel arm resonator are connected to the same one of the plurality of wires separated by the plurality of series arm resonators on a line connecting the input terminal and the output terminal of the filter chip, the 2 nd parallel arm resonator is included in another part of the plurality of parallel arm resonators than the part of the parallel arm resonators, the other end of the 1 st parallel arm resonator is connected to a 1 st ground terminal of the filter chip, and the other end of the 2 nd parallel arm resonator is connected to a 2 nd ground terminal of the filter chip different from the 1 st ground terminal.

With this configuration, in the filter device, it becomes possible to reduce the input loss of the passband while maintaining the steepness of the attenuation characteristic of the attenuation band.

In the above-described filter device, one end of a 3 rd parallel arm resonator included in the other part of the parallel arm resonators may be connected to a wiring different from a wiring to which one end of the 1 st parallel arm resonator and one end of the 2 nd parallel arm resonator are connected, among the plurality of wirings, and the other end of the 3 rd parallel arm resonator may be connected to the 2 nd ground terminal of the filter chip.

With this configuration, steepness of attenuation characteristics of the attenuation band in the vicinity of the lower frequency side than the pass band is improved.

In the above filter device, the plurality of parallel arm resonators may include: a 4 th parallel arm resonator connected to a wiring closest to the input terminal among the plurality of wirings; and a 5 th parallel arm resonator connected to a wiring closest to the output terminal among the plurality of wirings.

With this configuration, the series connection of the 1 st parallel arm resonator and the 1 st inductor is connected to a relatively central wiring on a line connecting the input terminal and the output terminal. This improves the above-described effect of reducing the input loss in the passband while maintaining the sharpness of the attenuation characteristics in the attenuation band.

In the above-described filter device, the anti-resonance frequency of the 2 nd parallel arm resonator may be higher than each of the anti-resonance frequencies of the parallel arm resonators other than the 2 nd parallel arm resonator in the other part of the parallel arm resonators.

With this configuration, steepness of attenuation characteristics of the attenuation band in the vicinity of the lower frequency side than the pass band is improved.

In the above-described filter device, each of the anti-resonance frequencies of the parallel arm resonators other than the 2 nd parallel arm resonator among the other part of the parallel arm resonators may be higher than about 99.5% of the anti-resonance frequency of the 2 nd parallel arm resonator.

With this configuration, steepness of attenuation characteristics of the attenuation band in the vicinity of the lower frequency side than the pass band is improved.

In the above-described filter device, the pitch of the 2 nd parallel arm resonator may be greater than about 99.5% of the pitch of each of the parallel arm resonators other than the 2 nd parallel arm resonator in the other part of the parallel arm resonators.

With this configuration, steepness of attenuation characteristics of the attenuation band in the vicinity of the lower frequency side than the pass band is improved.

In the above filter device, the filter chip may include LiTaO₃。

With this configuration, the frequency characteristics of the filter device are improved.

In the above filter device, the plurality of inductors may be provided on a pattern layer on which the filter chips are laminated.

With this configuration, the frequency characteristics of the filter device are improved, and the filter device can be easily manufactured.

In the above-described filter device, one end of a 2 nd inductor of the plurality of inductors may be connected to the other end of the parallel arm resonator having one end connected to one of the plurality of wirings other than the wiring to which the 1 st parallel arm resonator is connected, one end of a 3 rd inductor of the plurality of inductors may be connected to the other end of the parallel arm resonator having one end connected to a wiring of the plurality of wirings that is farther than the one wiring from the wiring to which the 1 st parallel arm resonator is connected, and a distance between the 1 st inductor and the 2 nd inductor may be smaller than a distance between the 1 st inductor and the 3 rd inductor.

With this configuration, in the filter device, the order of the distance between the inductors on the circuit corresponds to the order of the magnitude of the degree of magnetic coupling between the inductors. This improves the frequency characteristics of the filter device.

The filter device described above may also form part of a duplexer or part of a multiplexer.

With this configuration, a branching filter having improved frequency characteristics can be provided.

The above-described embodiments are intended to facilitate understanding of the present invention and are not intended to limit the present invention. The present invention can be modified or improved without departing from the gist thereof, and the present invention also includes equivalents thereof. That is, the embodiments to which design changes are appropriately applied to each embodiment by those skilled in the art are included in the scope of the present invention as long as the features of the present invention are provided. For example, the elements and their arrangement, materials, conditions, shapes, dimensions, and the like included in the embodiments are not limited to the illustrated elements and their arrangement, materials, conditions, shapes, dimensions, and the like, and can be appropriately modified. Further, the elements included in the respective embodiments can be combined as long as the combination is technically feasible, and embodiments combining them are included in the scope of the present invention as long as the features of the present invention are included.