阅读说明：本技术 复用器 (Multiplexer ) 是由 桑原英司 于 2019-07-15 设计创作，主要内容包括：本发明涉及复用器。该复用器包括：第一端子；第二端子；第三端子；第一滤波器,其连接在所述第一端子和所述第二端子之间,包括第一电容器、第一电感器以及一个或更多个第一声波谐振器,并且具有第一通带；第二滤波器,其连接在所述第一端子和所述第三端子之间,包括第二电容器、第二电感器以及一个或更多个第二声波谐振器,并且具有比所述第一通带高的第二通带；基板,其具有表面,所述一个或更多个第一声波谐振器中的至少一个第一声波谐振器以及所述一个或更多个第二声波谐振器中的至少一个第二声波谐振器位于该表面上；以及金属结构,其位于所述表面上并且位于所述至少一个第一声波谐振器和所述至少一个第二声波谐振器之间。(The present invention relates to multiplexers. The multiplexer includes: a first terminal; a second terminal; a third terminal; a first filter connected between the first terminal and the second terminal, including a first capacitor, a first inductor, and one or more first acoustic wave resonators, and having a first pass band; a second filter connected between the first terminal and the third terminal, including a second capacitor, a second inductor, and one or more second acoustic resonators, and having a second pass band higher than the first pass band; a substrate having a surface on which at least one of the one or more first acoustic resonators and at least one of the one or more second acoustic resonators are located; and a metallic structure located on the surface and between the at least one first acoustic resonator and the at least one second acoustic resonator.)

1. A multiplexer, the multiplexer comprising:

a first terminal;

a second terminal;

a third terminal;

a first filter connected between the first terminal and the second terminal, including a first capacitor, a first inductor, and one or more first acoustic wave resonators, and having a first pass band;

a second filter connected between the first terminal and the third terminal, including a second capacitor, a second inductor, and one or more second acoustic resonators, and having a second pass band higher than the first pass band;

a substrate having a surface on which at least one of the one or more first acoustic resonators and at least one of the one or more second acoustic resonators are located; and

a metal structure located on the surface and between the at least one first acoustic resonator and the at least one second acoustic resonator.

2. The multiplexer of claim 1, wherein the metal structure is a metal film on the surface.

3. The multiplexer according to claim 2, wherein a plurality of the metal films are provided, and the metal films are arranged in a direction intersecting a direction from the at least one first acoustic wave resonator to the at least one second acoustic wave resonator.

4. The multiplexer of claim 2, wherein the metal film is positioned to cover the at least one second acoustic resonator when the at least one second acoustic resonator is viewed from the at least one first acoustic resonator.

5. The multiplexer of any one of claims 1 to 4, wherein the metallic structure is not electrically connected to any of the first filter, the second filter, and other conductive patterns on the surface.

6. The multiplexer of any one of claims 1 to 4, wherein the metal structure is electrically connected to a ground of the first and second filters in the multiplexer.

7. The multiplexer of any one of claims 1 to 4, wherein the metal structure is not electrically connected to any of the first and second filters in the multiplexer and is electrically connected to a ground that is electrically independent from the first and second filters.

8. The multiplexer according to any one of claims 1 to 4, wherein between the first and second terminals the first capacitor is connected in series and/or in shunt, the first inductor is connected in series and/or in shunt, and the one or more first acoustic wave resonators are connected in series and/or in shunt, and

between the first terminal and the third terminal, the second capacitor is connected in series and/or in shunt, the second inductor is connected in series and/or in shunt, and the one or more second acoustic resonators are connected in series and/or in shunt.

9. The multiplexer of any one of claims 1 to 4,

the first pass band has a width of 300MHz or more, and

the second pass band has a width of 300MHz or greater.

10. The multiplexer of any one of claims 1 to 4,

the first filter has a first guard band,

the second filter has a second guard band,

at least a portion of the first pass band overlaps at least a portion of the second guard band, and

at least a portion of the second pass band overlaps at least a portion of the first guard band.

11. The multiplexer of claim 10, wherein the first pass band and the second guard band are wider than frequency bands of 1700Mhz to 2200Mhz, and the second pass band and the first guard band are wider than frequency bands of 2300Mhz to 2690 Mhz.

Technical Field

Certain aspects of the present disclosure relate to multiplexers.

Background

Filters in which an LC circuit formed of a capacitor and an inductor is provided with an acoustic wave resonator are known as disclosed in, for example, japanese patent application laid-open nos. 2018-129680 and 2018-129683 (hereinafter, referred to as patent documents 1 and 2, respectively).

Disclosure of Invention

According to an aspect of the present invention, there is provided a multiplexer including: a first terminal; a second terminal; a third terminal; a first filter connected between the first terminal and the second terminal, including a first capacitor, a first inductor, and one or more first acoustic wave resonators, and having a first pass band; a second filter connected between the first terminal and the third terminal, including a second capacitor, a second inductor, and one or more second acoustic resonators, and having a second pass band higher than the first pass band; a substrate having a surface on which at least one of the one or more first acoustic resonators and at least one of the one or more second acoustic resonators are located; and a metal structure located on the surface and between the at least one first acoustic resonator and the at least one second acoustic resonator.

Drawings

Fig. 1A is a block diagram of a multiplexer according to a first embodiment, and fig. 1B is a plan view of a substrate in the first embodiment;

fig. 2A is a plan view of an acoustic wave resonator in the first embodiment, and fig. 2B is a sectional view of another acoustic wave resonator in the first embodiment;

fig. 3A is a sectional view of a multiplexer according to a first embodiment, and fig. 3B is a sectional view of a package in the first embodiment;

FIG. 4 is a circuit diagram of an exemplary circuit of the first embodiment;

FIG. 5 illustrates a transfer characteristic of the exemplary circuit illustrated in FIG. 4;

FIGS. 6A and 6B are plan views of samples A and B, respectively;

fig. 7A and 7B are plan views of samples C and D, respectively;

FIG. 8 is a plan view of a specimen E;

fig. 9A illustrates the isolation characteristics of samples a and B, and fig. 9B illustrates the isolation characteristics of samples a and C;

fig. 10A illustrates the isolation characteristics of samples a and D, and fig. 10B illustrates the isolation characteristics of samples a and E;

fig. 11 illustrates isolation characteristics of samples a to E;

fig. 12 is a circuit diagram of an exemplary circuit of a first variation of the first embodiment; and

fig. 13 is a circuit diagram of an exemplary circuit of a second modification of the first embodiment.

Detailed Description

When an acoustic wave resonator is provided to an LC circuit, the steepness of attenuation between the passband and the guard band is improved. However, when a filter having an acoustic wave resonator is used in a multiplexer, the isolation characteristic may deteriorate.

Hereinafter, a description will be given of an embodiment of the present invention with reference to the accompanying drawings.

First embodiment

Fig. 1A is a block diagram of a multiplexer according to a first embodiment. As illustrated in fig. 1A, the terminal Ta is coupled to the antenna 48. The filter 40 is connected between the terminal Ta and the terminal T1. The filter 42 is connected between the terminal Ta and the terminal T2. The filter 44 is connected between the terminal Ta and the terminal T3. The filter 42 includes the LC circuit 41 and the acoustic wave resonator 46. The filter 44 includes an LC circuit 43 and an acoustic wave resonator 47. Each of the LC circuits 41 and 43 is a circuit formed of a capacitor and an inductor, and does not include an acoustic wave resonator. The LC circuit 41 is electrically connected to the acoustic wave resonator 46, and the LC circuit 43 is electrically connected to the acoustic wave resonator 47. The acoustic wave resonators 46 and 47 are located on a single substrate 10.

The filter 40 is a filter that allows a signal in a low frequency band to pass therethrough, the filter 42 is a filter that allows a signal in an intermediate frequency band to pass therethrough, and the filter 44 is a filter that allows a signal in a high frequency band to pass therethrough. Filters 40, 42 and 44 are band pass filters. The filter 40 may be a low pass filter. The filter 44 may be a high pass filter. The filter 40 allows signals at a low frequency band to pass therethrough and suppresses signals at a middle frequency band and a high frequency band. The filter 42 allows signals in the middle frequency band to pass therethrough and suppresses signals in the low frequency band and the high frequency band. The filter 44 allows signals at a high frequency band to pass therethrough and suppresses signals at a low frequency band and a middle frequency band.

The low frequency band is a frequency band of 700MHz to 960MHz, the middle frequency band is a frequency band of 1710MHz to 2200MHz, and the high frequency band is a frequency band of 2300MHz to 2690 MHz. Each of the low band, the middle band, and the high band includes a plurality of bands supporting a band standard (E-UTRA operating band) corresponding to Long Term Evolution (LTE).

The pass band of filter 42 is wider than the intermediate frequency band and the pass band of filter 44 is wider than the high frequency band. The pass band widths of the middle and high frequency bands are 300MHz or more. The filters 42 and 44 having this wide frequency band are formed of LC circuits. However, the gap between the passband of the mid-band and the passband of the high-band is 100 MHz. Therefore, the filters 42 and 44 are required to achieve attenuation steepness between the pass band and the guard band. However, when the filter is formed of an LC circuit, the steepness is insufficient. Accordingly, the acoustic wave resonators 46 and 47 are coupled to the LC circuits 41 and 43, respectively. This configuration improves steepness in the filters 42 and 44.

Fig. 1B is a plan view of the substrate in the first embodiment. As illustrated in fig. 1B, the acoustic wave resonators 46 and 47 are located on the upper surface of the substrate 10. The metal pattern 15 is located directly on the upper surface of the substrate 10 between the acoustic wave resonators 46 and 47, or on the upper surface of the substrate 10 between the acoustic wave resonators 46 and 47 with an insulating film interposed therebetween. The metal pattern 15 is a metal film such as, but not limited to, a copper film, a gold film, an aluminum film, or a nickel film. When the acoustic wave resonators 46 and 47 are located on a single substrate 10, the size of the multiplexer is reduced. However, the acoustic wave resonators 46 and 47 interfere with each other through the substrate 10, and thus, the isolation characteristic between the filters 42 and 44 deteriorates. In the first embodiment, the provision of the metal pattern 15 improves the isolation characteristic between the filters 42 and 44.

Fig. 2A is a plan view of an exemplary acoustic wave resonator in the first embodiment, and fig. 2B is a sectional view of another exemplary acoustic wave resonator in the first embodiment. Fig. 2A illustrates a case where the acoustic wave resonators 46 and 47 are surface acoustic wave resonators. An interdigital transducer (IDT)50 and a reflector 52 are located on the upper surface of the substrate 10. The IDT 50 has a pair of comb-shaped electrodes 50a facing each other. The comb-shaped electrode 50a includes a plurality of electrode fingers 50b and a bus bar 50c connecting the electrode fingers 50 b. Reflectors 52 are located on both sides of the IDT 50. The IDT 50 excites surface acoustic waves on the substrate 10. The substrate 10 is a piezoelectric substrate such as, but not limited to, a lithium tantalate substrate, a lithium niobate substrate, or a crystal substrate. The substrate 10 may be a composite substrate having the following structure: the piezoelectric substrate is bonded on a support substrate such as, but not limited to, a sapphire substrate, a spinel substrate, an alumina substrate, a crystalline substrate, or a silicon substrate. The IDT 50 and the reflectors 52 are formed of, for example, an aluminum film or a copper film. A protective film or a temperature compensation film may be positioned on the substrate 10 to cover the IDT 50 and the reflectors 52.

Fig. 2B illustrates a case where the acoustic wave resonators 46 and 47 are piezoelectric thin film resonators. The piezoelectric film 56 is located on the substrate 10. The lower electrode 54 and the upper electrode 58 are positioned so as to sandwich the piezoelectric film 56. An air gap 55 is formed between the lower electrode 54 and the substrate 10. A region where the lower electrode 54 and the upper electrode 58 face each other across at least a part of the piezoelectric film 56 is a resonance region 57. The lower electrode 54 and the upper electrode 58 in the resonance region 57 excite an acoustic wave in a thickness expansion mode in the piezoelectric film 56. The substrate 10 is, for example, a sapphire substrate, a spinel substrate, an alumina substrate, a glass substrate, a crystal substrate, or a silicon substrate. The lower electrode 54 and the upper electrode 58 are formed of a metal film such as, but not limited to, ruthenium film. The piezoelectric film 56 is, for example, an aluminum nitride film.

Fig. 3A is a sectional view of a multiplexer according to a first embodiment. As illustrated in fig. 3A, LC circuits 41 and 43 and a package 45 are mounted between the substrate 36 and the cover 38. The terminals 35 are located on the lower surface of the substrate 36. The LC circuits 41 and 43 are dielectric filters in which capacitors and inductors are formed of a multilayer body in which dielectric layers are laminated. The dielectric layer is, for example, a ceramic layer. The LC circuits 41 and 43 may be formed of chip capacitors and chip inductors. The package 45 is a package in which the substrate 10 is mounted. The base plate 36 is, for example, a printed board, and the cover 38 is, for example, an insulating board such as, but not limited to, a resin board. The terminal 35 is terminals Ta and T1 to T3, and is electrically connected to the LC circuits 41 and 43 and the package 45.

Fig. 3B is a sectional view of the package in the first embodiment. As illustrated in fig. 3B, the substrate 10 is mounted on the circuit board 20. The circuit board 20 includes a plurality of insulating layers 20a and 20b stacked. The insulating layers 20a and 20b are, for example, resin layers or ceramic layers. The wiring layer 24a and the ring-shaped metal layer 32 are located on the upper surface of the circuit board 20. The wiring layer 24b is located on the insulating layer 20 b. A penetration electrode 26a penetrating the insulating layer 20a and a penetration electrode 26b penetrating the insulating layer 20b are provided. The terminals 28 are located on the lower surface of the circuit board 20. The wiring layers 24a and 24b, the penetration electrodes 26a and 26b, and the terminals 28 are formed of a metal layer such as, but not limited to, a copper layer, a gold layer, an aluminum layer, or a nickel layer.

The acoustic wave resonator 12 and the wiring 14 are located on the lower surface of the substrate 10. The acoustic wave resonator 12 is the acoustic wave resonators 46 and 47 illustrated in fig. 2A and 2B. The wiring 14 is formed of a metal layer such as, but not limited to, a copper layer, a gold layer, and an aluminum layer. The wiring 14 and the wiring layer 24a are bonded by the bump 16. Bumps 16 are metal bumps such as, but not limited to, gold bumps, copper bumps, or solder bumps. The substrate 10 is flip-chip mounted on a circuit board 20 with bumps 16 so that the acoustic wave resonator 12 faces the circuit board 20 via an air gap 18. The terminal 28 is electrically connected to the acoustic wave resonator 12 through the penetration electrode 26a, the wiring layer 24b, the penetration electrode 26b, the wiring layer 24a, the bump 16, and the wiring 14.

The sealing part 30 is positioned to surround the substrate 10. The lower surface of the sealing part 30 is bonded to the annular metal layer 32. The sealing part 30 is made of metal such as solder or insulating material such as resin. The cap 34 is positioned on the upper surfaces of the substrate 10 and the sealing part 30. The cover 34 is a metal plate or an insulating plate.

Fig. 4 is a circuit diagram of an exemplary circuit of the first embodiment. As illustrated in fig. 4, the filter 40 includes capacitors C11 to C13 and inductors L11 and L12. Inductors L11 and L12 are connected in series between terminals Ta and T1. The capacitor C11 is connected in parallel with the inductor L12. Capacitors C12 and C13 are connected in shunt between terminals Ta and T1.

The filter 42 includes capacitors C21 to C23, inductors L21 and L22, and an acoustic wave resonator R21. Capacitors C21-C23 are connected in series between terminals Ta and T2. The inductor L21 is connected in parallel with the capacitors C22 and C23. The inductor L22 and the acoustic wave resonator R21 are connected in shunt between the terminals Ta and T2.

The filter 44 includes capacitors C31 to C33, inductors L31 to L33, and an acoustic wave resonator R31. Capacitors C31-C33 are connected in series between terminals Ta and T3. The inductor L31 is connected in parallel with the capacitors C31 and C32, and the inductor L32 is connected in parallel with the capacitor C33. The inductor L33 and the acoustic wave resonator R31 are connected in shunt between the terminals Ta and T3.

Filters 40, 42, and 44 are commonly coupled to node N1. The filters 42 and 44 have a capacitor C01 and an inductor L01 as a common circuit between the node N1 and the node N2. The capacitor C01 and the inductor L01 are connected in series between the node N1 and the node N2. Filter 40 acts as a low pass filter and filters 42 and 44 act as band pass filters.

Fig. 5 illustrates a transmission characteristic of the exemplary circuit illustrated in fig. 4. The solid line indicates the transmission characteristic of the filter 42 (transmission characteristic from T2 to Ta), and the broken line indicates the transmission characteristic of the filter 44 (transmission characteristic from T3 to Ta). As illustrated in fig. 5, the pass band of filter 42 includes a frequency band in the middle band MB, and the pass band of filter 44 includes a frequency band in the high band HB. In the frequency band between the middle band MB and the high band HB, the attenuation of the filters 42 and 44 changes abruptly.

When the acoustic wave resonators 46 and 47 are formed on the single substrate 10 as illustrated in fig. 1B, the size of the multiplexer is reduced. However, the signal in the pass band of the filter 44 input from the terminal T2 leaks to the terminal T3 through the acoustic wave resonators 46 and 47. In addition, the signal in the pass band of the filter 42 input from the terminal T3 leaks to the terminal T2 through the acoustic wave resonators 46 and 47. Therefore, the isolation characteristic of the multiplexer deteriorates. Thus, the isolation between the acoustic wave resonators 46 and 47 is simulated.

Simulation of

Fig. 6A to 8 are plan views of samples a to E, respectively. Sample a corresponds to a comparative example, and samples B to E correspond to the first embodiment. As illustrated in fig. 6A, in sample a, the acoustic wave resonators 46 and 47 and the wiring 14 are located on the substrate 10. An arrangement direction of electrode fingers (a propagation direction of acoustic wave propagation) in which the acoustic wave resonators 46 and 47 are arranged is defined as an X direction, an extending direction in which the electrode fingers extend is defined as a Y direction and a direction perpendicular to the substrate 10 is defined as a Z direction.

The acoustic wave resonators 46 and 47 are, for example, acoustic wave resonators R21 and R31 in fig. 4. The wiring 14 is coupled to the acoustic wave resonators 46 and 47. As illustrated in fig. 3B, the bump 16 is located on the wiring 14. Tab 16 includes a ground tab Bg coupled to ground, a tab B2 coupled to LC circuit 41, and a tab B3 coupled to LC circuit 43. The dimension of the substrate 10 in the Y direction is denoted by D1, and the dimension of the substrate 10 in the X direction is denoted by D2. The width of the wiring 14a between the ground and the acoustic wave resonator R21 is denoted by D4, and the width of the wiring 14b between the ground and the acoustic wave resonator R31 is denoted by D5, and the distance between the wirings 14a and 14b is denoted by D3.

As illustrated in fig. 6B, in sample B, a plurality of metal patterns 15 are located on the substrate 10 between the wirings 14a and 14B. The dummy bump Bg0 not electrically connected to any of the acoustic wave resonators 46 and 47 is located on one metal pattern 15. The distance in the Y direction between the adjacent metal patterns 15 is denoted by D11, the distance in the X direction between the adjacent metal patterns 15 is denoted by D12, the distance between the wiring 14a and the metal pattern 15 adjacent to the wiring 14a is denoted by D13, and the distance between the wiring 14b and the metal pattern 15 adjacent to the wiring 14b is denoted by D14. The width of the metal pattern 15 in the X direction is denoted by D15. The other structures and dimensions are the same as those of sample a.

As illustrated in fig. 7A, in sample C, one metal pattern 15 is located between the acoustic wave resonators 46 and 47. The metal pattern 15 is not electrically connected to any of the acoustic wave resonators R21 and R31 in the package 45 illustrated in fig. 3B. The distance between the wiring 14a and the metal pattern 15 is denoted by D21, and the distance between the wiring 14b and the metal pattern 15 is denoted by D22. The width of the metal pattern 15 in the Y direction is denoted by D23. Other structures and dimensions are the same as those of sample B, and thus a description thereof is omitted.

As illustrated in fig. 7B, in sample D, the ground bump Bga is located on the metal pattern 15. The ground bumps Bga are electrically connected to the ground bumps Bg in the package 45. The other structures are the same as those of sample C, and thus description thereof is omitted.

As illustrated in fig. 8, in sample E, the ground bump Bgb is located on the metal pattern 15. The ground bump Bgb is electrically independent from the package 45 and the ground bump Bg in the multiplexer (i.e., the ground of the filters 40, 42, and 44). The ground bump Bg is coupled to the ground of a circuit board (e.g., the substrate 36 in fig. 3A) on which the package 45 is mounted through the terminal 28. The other structures are the same as those of sample C, and thus description thereof is omitted.

The simulation was performed by combining the results of electromagnetic field simulation of the packages other than the acoustic wave resonators R21 and R31 and the S parameters of the acoustic wave resonators R21 and R31. The calculated isolation from terminal T2 to terminal T3 was modeled as the isolation from terminal 28 to which bump B2 is coupled to terminal 28 to which bump B3 is coupled.

The simulation conditions were as follows:

acoustic wave resonator 46: a surface acoustic wave resonator having a resonant frequency of 2.26 GHz;

acoustic wave resonator 47: a surface acoustic wave resonator having a resonance frequency of 2.27 GHz;

substrate 10: a lithium tantalate substrate with thickness of 150 μm, rotated at 42 ° Y-cut X-propagation;

circuit board 20: a ceramic substrate having a thickness of 140 μm;

size: d1 ═ 870 μm, D2 ═ 630 μm, D3 ═ 210 μm, D4 ═ D5 ═ 50 μm, D11 ═ 30 μm, D12 ═ 36 μm, D13 ═ 51 μm, D14 ═ 34 μm, D15 ═ 36 μm, D21 ═ 51 μm, D22 ═ 34 μm, and D23 ═ 125 μm.

Fig. 9A to 10B illustrate isolation characteristics of each of the sample a and the samples B to E, respectively. As illustrated in fig. 9A, the isolation of sample B is superior to that of sample a in the range a1 of 1GHz to about 2.2GHz and the range a2 of about 2.5GHz to about 5.7 GHz. In the range A3 of about 2.2GHz to about 2.5GHz, the isolation of samples A and B is approximately the same.

As illustrated in fig. 9B, the isolation of sample C is superior to that of sample a in the range a1 of 1GHz to about 2.1GHz and the range a2 of about 2.3GHz to about 4.8 GHz. However, in the range A3 of about 2.1GHz to about 2.3GHz, the isolation of sample A is better than that of sample C.

As illustrated in fig. 10A, the isolation of sample D is superior to that of sample a in the range a1 of 1GHz to about 2.1GHz and the range a2 of about 2.3GHz to 4.8 GHz. However, in the range A3 of about 2.1GHz to about 2.3GHz, the isolation of sample A is better than the isolation of sample D.

As illustrated in fig. 10B, the isolation of sample E is superior to that of sample a in the range a1 of 1GHz to about 2.1GHz and the range a2 of about 2.3GHz to about 5.8 GHz. However, in the range A3 of about 2.1GHz to about 2.3GHz, the isolation of sample A is better than that of sample E.

Fig. 11 illustrates isolation characteristics of samples a to E. As illustrated in fig. 11, in the range a2 of about 2.3GHz to about 5GHz, the isolation of samples C to E is superior to that of sample B. However, in the range a3 of about 2.1Ghz to about 2.3Ghz, the isolation of samples C to E deteriorated more than that of sample a, while the isolation of sample B did not deteriorate. As seen above, in sample B, the isolation in range A3 did not deteriorate, and in ranges a1 and a2, the isolation of sample B was improved. In samples C to E, in the range A3, the isolation deteriorated, but in the range a2, the isolation was improved compared to that of sample B. As seen above, the arrangement of the metal pattern 15 is appropriately selected to improve isolation.

First modification of the first embodiment

Fig. 12 is a circuit diagram of an exemplary circuit of the first modification of the first embodiment. As illustrated in fig. 12, the filter 40 includes capacitors C11 to C13 and inductors L11 and L12. The filter 42 includes capacitors C21 to C24, inductors L21 to L24, and acoustic wave resonators R21 and R22. The filter 44 includes capacitors C31 to C33, inductors L31 to L35, and acoustic wave resonators R31 and R32. Filters 42 and 44 share capacitor C01. As in the first embodiment, the acoustic wave resonators R21, R22, R31, and R32 are located on a single substrate 10 illustrated in fig. 3B.

Second modification of the first embodiment

Fig. 13 is a circuit diagram of an exemplary circuit of a second modification of the first embodiment. As illustrated in fig. 13, capacitors C01 and C02 and inductors L01 to L03 are connected between the terminal Ta and the node N1. The filter 40 includes capacitors C11 and C12 and inductors L11 to L13. The filter 42 includes a capacitor C21, inductors L21 to L23, and acoustic wave resonators R21 to R25. The filter 44 includes capacitors C31 to C34, inductors L31 to L34, and acoustic wave resonators R31 to R33. The filters 42 and 44 share capacitors C03 to C07 and inductors L04 to L06.

As in the first and second modifications of the first embodiment, the filter 42 may include a plurality of acoustic wave resonators 46. The filter 44 may include a plurality of acoustic wave resonators 47. In addition, the acoustic wave resonator 46 may be connected in series between the terminals Ta and T2. The acoustic wave resonator 47 may be connected in series between the terminals Ta and T3. It is sufficient if at least one of the plurality of acoustic wave resonators 46 and at least one of the plurality of acoustic wave resonators 47 are located on a single substrate 10 illustrated in fig. 3B.

In the first embodiment and its modifications, the filter 42 (first filter) is connected between the terminal Ta (first terminal) and the terminal T2 (second terminal), and includes a first capacitor, a first inductor, and one or more first acoustic wave resonators. The filter 44 (second filter) is connected between the terminal Ta and the terminal T3 (third terminal), and includes a second capacitor, a second inductor, and one or more second acoustic resonators. The pass band (second pass band) of filter 44 is higher than the pass band (first pass band) of filter 42.

At least one of the one or more acoustic wave resonators 46 (one or more first acoustic wave resonators) and at least one of the one or more acoustic wave resonators 47 (one or more second acoustic wave resonators) are located on the upper surface (surface) of the substrate 10. The metal pattern 15 (metal structure) is located on the upper surface of the substrate 10 and between the at least one acoustic wave resonator 46 and the at least one acoustic wave resonator 47.

As with the simulated samples B to E, this structure improves isolation compared with the sample a without the metal pattern 15.

The metal structure is a metal film such as a metal pattern 15 on the surface of the substrate 10. This structure improves isolation.

As in sample B, a plurality of metal patterns 15 (metal films) are provided, and the metal patterns 15 are arranged in a direction intersecting with a direction from the at least one acoustic wave resonator 46 to the at least one acoustic wave resonator 47. This structure improves isolation.

As in samples C to E, the metal pattern 15 (metal film) is positioned so as to completely cover the at least one acoustic wave resonator 47 when the at least one acoustic wave resonator 47 is viewed from the at least one acoustic wave resonator 46. This structure improves isolation.

As in samples B and C, the metal pattern 15 may float over the filter 42 and the filter 44. That is, the metal pattern 15 is not electrically connected to any of the filters 42 and 44 and other conductive patterns on the surface of the substrate 10. As in sample D, the metal pattern 15 may be electrically connected to the grounds of the filter 42 and the filter 44 in the multiplexer. As in sample E, the metal pattern 15 may not be electrically connected to any of the filter 42 and the filter 44 in the multiplexer, and may be electrically connected to a ground independent from the filter 42 and the filter 44.

As illustrated in fig. 4, 12, and 13, in the filter 42, between the terminals Ta and T2, capacitors are connected in series and/or in shunt, inductors are connected in series and/or in shunt, and one or more acoustic wave resonators 46 are connected in series and/or in shunt. In the filter 44, between the terminals Ta and T3, capacitors are connected in series and/or in shunt, inductors are connected in series and/or in shunt, and one or more acoustic wave resonators 47 are connected in series and/or in shunt. This configuration allows filters 42 and 44 to form a band pass filter, a low pass filter, or a high pass filter.

The pass band width of the filters 42 and 44 is 300MHz or greater. It is difficult to form a filter having such a wide pass band using only acoustic wave resonators. Therefore, the filters 42 and 44 are constituted by capacitors, inductors, and acoustic wave resonators. Thus, the pass band is widened.

At least a portion of the pass band of filter 42 overlaps at least a portion of the guard band (second guard band) of filter 44. At least a portion of the pass band of filter 44 overlaps at least a portion of the guard band (first guard band) of filter 42. In such filters 42 and 44, it is necessary to improve the steepness of the attenuation between the pass band and the guard band. Therefore, the acoustic wave resonators 46 and 47 are used. However, the deterioration of the isolation between the acoustic wave resonators 46 and 47 deteriorates the isolation between the filters 42 and 44. Therefore, the metal pattern 15 is preferably provided.

The pass band of the filter 42 and the guard band of the filter 44 are wider than the frequency band of 1700MHz to 2200MHz, and the pass band of the filter 44 and the guard band of the filter 42 are wider than the frequency band of 2300MHz to 2690 MHz. In this case, in particular, it is necessary to improve the steepness of attenuation between the passband and the guard band. Therefore, the acoustic wave resonators 46 and 47 are used. However, the deterioration of the isolation between the acoustic wave resonators 46 and 47 deteriorates the isolation between the filters 42 and 44. Therefore, the metal pattern 15 is preferably provided.

The case where the filter 42 is a band-pass filter has been described, but the filter 42 may be a low-pass filter. The case where the filter 44 is a band-pass filter has been described, but the filter 44 may be a high-pass filter. The case where the multiplexer includes three filters 40, 42, and 44 has been described, but the multiplexer may include only two filters, or may include four or more filters.

Although the embodiments of the present invention have been described in detail, it should be understood that various changes, substitutions, and alterations can be made hereto without departing from the spirit and scope of the invention.