WO2022071186A1

WO2022071186A1 - Multiplexer

Info

Publication number: WO2022071186A1
Application number: PCT/JP2021/035267
Authority: WO
Inventors: 茂生小笹
Original assignee: 株式会社村田製作所
Priority date: 2020-09-30
Filing date: 2021-09-27
Publication date: 2022-04-07

Abstract

This multiplexer (1) comprises: a common terminal (tc); a first terminal (t1) and a second terminal (t2); a first filter circuit (10) provided on a first path (r1) connecting the common terminal (tc) and the first terminal (t1); and a second filter circuit (50) provided on a second path (r2) connecting the common terminal (tc) and the second terminal (t2). The first filter circuit (10) has a plurality of parallel arm resonators (P1-P4). In a pass band of the second filter circuit (50), the resistance (Zr) of a single parallel arm resonator (P1), closest to the common terminal (tc) among the plurality of parallel arm resonators (P1-P4), is the lowest.

Description

Multiplexer

The present invention relates to a multiplexer having a plurality of filters.

Conventionally, a multiplexer having a plurality of filters is known. As an example of this type of multiplexer, Patent Document 1 discloses a multiplexer including one filter and the other filter. One filter is composed of a ladder type filter having a series arm resonator and a parallel arm resonator.

International Publication No. 2016/031391

For example, when one filter has a parallel arm resonator, the insertion loss of the pass band of the other filter may decrease due to the influence of the parallel arm resonator.

An object of the present invention is to suppress a decrease in insertion loss in the pass band of the other filter in a multiplexer including one filter and the other filter.

In order to achieve the above object, the multiplexer according to one aspect of the present invention is provided on a first path connecting a common terminal, a first terminal and a second terminal, and the common terminal and the first terminal. A first filter circuit and a second filter circuit provided on a second path connecting the common terminal and the second terminal are provided, and the first filter circuit has a plurality of parallel arm resonators. However, in the pass band of the second filter circuit, the resistance of a single parallel arm resonator closest to the common terminal among the plurality of parallel arm resonators is the smallest.

According to the present invention, in a multiplexer including one filter and the other filter, it is possible to suppress a decrease in the insertion loss of the pass band of the other filter.

FIG. 1 is a circuit configuration diagram showing a multiplexer in a study example of the present invention. FIG. 2 is a graph showing the impedance characteristics of the parallel arm resonator included in the first filter circuit of the multiplexer shown in FIG. FIG. 3 is a Smith chart showing the impedance characteristics of the parallel arm resonator shown in FIG. FIG. 4 is a graph showing the resistance of a single parallel arm resonator shown in FIG. FIG. 5 is a Smith chart showing the impedance characteristics of the remaining circuit excluding the series arm resonator from the first filter circuit shown in FIG. FIG. 6 is a Smith chart showing the impedance characteristics of the first filter circuit shown in FIG. FIG. 7 is a graph showing the conductance of the first filter circuit shown in FIG. FIG. 8 is a graph showing the passage characteristics of the second filter circuit shown in FIG. FIG. 9 is a circuit configuration diagram showing a multiplexer according to the embodiment. FIG. 10 is a diagram showing the structure of the IDT electrode of the elastic wave resonator included in the first filter circuit of the multiplexer according to the embodiment. FIG. 11A is a diagram showing design parameters of the parallel arm resonator included in the first filter circuit of the embodiment. FIG. 11B is a diagram showing design parameters of the parallel arm resonator included in the first filter circuit of the comparative example. FIG. 12A is a graph showing the impedance characteristics of the parallel arm resonators in the embodiment. FIG. 12B is a graph showing the impedance characteristics of the parallel arm resonators in the comparative example. FIG. 13A is a Smith chart showing the impedance characteristics of the parallel arm resonators in the embodiment. FIG. 13B is a Smith chart showing the impedance characteristics of the parallel arm resonators in the comparative example. FIG. 14A is a graph showing the resistance of a single parallel arm resonator in the embodiment. FIG. 14B is a graph showing the resistance of a single parallel arm resonator in the comparative example. FIG. 15 is a Smith chart showing the impedance characteristics of the first filter circuit of the multiplexer in Examples and Comparative Examples. FIG. 16 is a graph showing the conductance of the first filter circuit of the multiplexer in Examples and Comparative Examples. FIG. 17 is a diagram showing the pass characteristics of the second filter circuit of the multiplexer in Examples and Comparative Examples. FIG. 18 is a diagram showing an equivalent circuit of parallel arm resonators. FIG. 19 is a diagram showing the design parameters of the parallel arm resonator and the resonance resistance of the parallel arm resonator. FIG. 20 is a diagram showing the relationship between the resonance resistance of the parallel arm resonator and the design parameter. FIG. 21 is a graph showing the impedance characteristics of a circuit in which an inductor is connected to a parallel arm resonator. FIG. 22 is a graph showing the resistance of a circuit in which an inductor is connected to a parallel arm resonator.

(Background to the present invention)
The background to the present invention will be described with reference to Examples 1 and 2 of the present invention as examples. It should be noted that Study Examples 1 and 2 of the present invention are examples for explaining the present invention, not the prior art.

FIG. 1 is a circuit configuration diagram showing a multiplexer 1 in Study Examples 1 and 2 of the present invention.

Each multiplexer 1 of the examples 1 and 2 includes a first filter circuit 10 which is one filter and a second filter circuit 50 which is the other filter. The first filter circuit 10 is arranged on the first path r1 connecting the common terminal tc and the first terminal t1. The second filter circuit 50 is arranged on the second path r2 connecting the common terminal tc and the second terminal t2. The first filter circuit 10 is composed of a ladder type filter including a series arm resonator S0 and a parallel arm resonator P0. The series arm resonator S0 is arranged on the first path r1 on the common terminal ct side of the parallel arm resonator P0.

For example, the pass band of the first filter circuit 10 is 1805 MHz to 1880 MHz, and the pass band of the second filter circuit 50 is 1710 MHz to 1785 MHz. Hereinafter, the pass band of the first filter circuit 10 may be referred to as an own band, and the pass band of the second filter circuit 50 may be referred to as a mating band.

The circuit configurations of the multiplexers 1 of Study Examples 1 and 2 are the same as each other, but the characteristics of the parallel arm resonator P0 are different as shown below. First, with reference to FIGS. 2 to 4, the relationship between the characteristics of the parallel arm resonator P0 of the first filter circuit 10 and the loss generated in the mating band will be described.

FIG. 2 is a graph showing the impedance characteristics of the parallel arm resonator P0 included in the first filter circuit 10 of the multiplexer 1 shown in FIG. In this figure, the position corresponding to 1805 MHz in the own band is indicated by the marker M7, and the position corresponding to 1880 MHz is indicated by the marker M8. Further, the position corresponding to 1710 MHz in the other band is indicated by the marker M5, and the position corresponding to 1785 MHz is indicated by the marker M6.

The parallel arm resonator P0 of Study Example 1 and the parallel arm resonator P0 of Study Example 2 have impedance characteristics as shown in FIG.

FIG. 3 is a Smith chart showing the impedance characteristics of the parallel arm resonator P0 shown in FIG. The parallel arm resonator P0 of the study example 1 has an impedance characteristic located closer to the outer peripheral circle of the Smith chart than the parallel arm resonator P0 of the study example 2 in the mating band indicated by the markers M5 to M6. That is, the parallel arm resonator P0 of the study example 1 has a smaller loss generated in the mating band than the parallel arm resonator P0 of the study example 2.

FIG. 4 is a graph showing the resistance of the parallel arm resonator P0 shown in FIG. 2 alone. FIG. 4 shows the actual impedance portion of the impedance characteristics shown in FIG. As shown in this figure, in the mating band indicated by the markers M5 to M6, the resistance of the parallel arm resonator P0 alone is smaller in the study example 1 than in the study example 2.

As shown in FIGS. 3 and 4, the resistance of the parallel arm resonator P0 alone is related to the loss generated in the mating band. For example, in order to reduce the loss generated in the mating band, it is desirable to reduce the resistance of the parallel arm resonator P0 alone.

Next, with reference to FIGS. 5 to 8, the influence of the series arm resonator S0 and the parallel arm resonator P0 of the first filter circuit 10 on the mating band will be described.

FIG. 5 is a Smith chart showing the impedance characteristics of the remaining circuits excluding the series arm resonator S0 from the first filter circuit 10 shown in FIG. Specifically, FIG. 5 shows the characteristics when the remaining circuit including the parallel arm resonator P0 is viewed from the node n1 of the first path r1 to which the parallel arm resonator P0 is connected. ..

As shown in FIG. 5, in the mating band indicated by the markers M5 to M6, the impedance characteristic of the study example 2 is farther from the outer circle of the Smith chart than the study example 1. The reason why the impedance characteristic is separated from the outer peripheral circle is that the resistance component (resistance component) of the parallel arm resonator P0 described above is larger in the study example 2 than in the study example 1.

FIG. 6 is a Smith chart showing the impedance characteristics of the first filter circuit 10 shown in FIG. FIG. 7 is a graph showing the conductance of the first filter circuit 10 shown in FIG. FIG. 8 is a graph showing the passage characteristics of the second filter circuit 50 shown in FIG. 6 and 7 show a circuit in which the series arm resonator S0 is added to the parallel arm resonator P0 shown in FIG. 5, that is, the first filter circuit 10 including the series arm resonator S0 is viewed from the common terminal tk side. The characteristics of the case are shown.

By adding the series arm resonator S0 to the parallel arm resonator P0, the impedance characteristic rotates counterclockwise and the impedance characteristic in the mating band moves to the open side, as shown in FIG. However, even when the impedance characteristic moves to the open side, the resistance component of the parallel arm resonator P0 remains. Therefore, as shown in FIG. 7, the conductance in the mating band is larger in the study example 2 than in the study example 1. As a result, as shown in FIG. 8, when the pass characteristics (EL characteristics) of the second filter circuit 50 are compared, the insertion loss in the pass band of the second filter circuit 50 is lower in the study example 2 than in the study example 1. ing.

In this way, by adding the series arm resonator S0 to the parallel arm resonator P0, the impedance characteristic of the first filter circuit 10 can be moved to the open side on the Smith chart. However, if the resistance component of the original parallel arm resonator P0 is large, even if the Smith chart is moved to the open side, the Smith chart will not stick to the outer peripheral circle, and the real part component will become large. In order to reduce the loss generated in the mating band, it is necessary to reduce the resistance of the parallel arm resonator P0 before adding the series arm resonator S0.

In the present embodiment, the parallel arm resonator of the first filter circuit 10 has the following configuration in order to suppress the reduction of the insertion loss in the pass band of the second filter circuit 50.

Hereinafter, embodiments of the present invention will be described in detail with reference to embodiments and drawings. It should be noted that all of the embodiments described below show comprehensive or specific examples. The numerical values, shapes, materials, components, arrangement of components, connection modes, etc. shown in the following embodiments are examples, and are not intended to limit the present invention. Among the components in the following embodiments, the components not described in the independent claims are described as arbitrary components. Also, the sizes of the components shown in the drawings, or the ratio of sizes, are not always exact. Further, in each figure, the same reference numerals are given to substantially the same configurations, and duplicate explanations may be omitted or simplified. Further, in the following embodiments, "connected" includes not only the case of being directly connected but also the case of being electrically connected via another element or the like.

(Embodiment)
[1. Multiplexer configuration]
The configuration of the multiplexer according to the embodiment will be described with reference to FIG.

FIG. 9 is a circuit configuration diagram showing the multiplexer 1 according to the embodiment. Note that FIG. 9 also shows the antenna element 9.

The multiplexer 1 is a demultiplexer or combiner including a plurality of filters having different frequency pass bands. As shown in FIG. 9, the multiplexer 1 includes a first filter circuit 10 which is one filter and a second filter circuit 50 which is the other filter. Further, the multiplexer 1 includes a common terminal tc, a first terminal t1 and a second terminal t2. The pass bands of the first filter circuit 10 and the second filter circuit 50 are the same as those of Study Examples 1 and 2 described above.

The common terminal ct is an antenna terminal of the multiplexer 1, and is connected to an antenna element 9 arranged outside the multiplexer 1. Further, the common terminal tc is connected to each of the first filter circuit 10 and the second filter circuit 50. Specifically, the common terminal tc is connected to the first filter circuit 10 via the node n0 between the first filter circuit 10 and the first terminal t1, and the second filter circuit 50 via the node n0. Connected to. The node n0 is a bundling point where the first path r1 and the second path r2, which will be described later, are bundled.

The first terminal t1 is connected to the first filter circuit 10. Further, the first terminal t1 is connected to an RF signal processing circuit (not shown) via an amplifier circuit or the like (not shown) arranged outside the multiplexer 1.

The second terminal t2 is connected to the second filter circuit 50. Further, the second terminal t2 is connected to an RF signal processing circuit (not shown) via an amplifier circuit or the like (not shown) arranged outside the multiplexer 1.

The first filter circuit 10 is arranged on the first path r1 connecting the common terminal tc and the first terminal t1. The first filter circuit 10 is, for example, a reception filter having a downlink frequency band (reception band) as a pass band, and is set so that the pass band is higher than that of the second filter circuit 50.

The first filter circuit 10 includes series arm resonators S1, S2, S3, S4, S5 and parallel arm resonators P1, P2, P3, P4, which are elastic wave resonators. The surface acoustic wave resonator is, for example, a SAW (Surface Acoustic Wave) resonator using an elastic surface wave.

The series arm resonators S1 to S5 are arranged on the first path (series arm) r1 connecting the common terminal tc and the first terminal t1. The series arm resonators S1 to S5 are connected in series in this order from the common terminal tc toward the first terminal t1. The series arm resonator S1 is provided on the common terminal ct side of the plurality of parallel arm resonators P1 to P4.

The parallel arm resonators P1 to P4 are paths (parallel) connecting the nodes n1, n2, n3, n4 between the adjacent series arm resonators S1 to S5 on the first path r1 and the reference terminal (ground). Arms) are connected in parallel to each other. Specifically, among the parallel arm resonators P1 to P4, one end of the parallel arm resonator P1 closest to the common terminal tc is connected to the node n1 between the series arm resonators S1 and S2, and the other end is connected to the node n1. It is connected to the reference terminal. One end of the parallel arm resonator P2 is connected to the node n2 between the series arm resonators S2 and S3, and the other end is connected to the reference terminal. One end of the parallel arm resonator P3 is connected to the node n3 between the series arm resonators S3 and S4, and the other end is connected to the reference terminal. One end of the parallel arm resonator P4 is connected to the node n4 between the series arm resonators S4 and S5, and the other end is connected to the reference terminal.

As described above, the first filter circuit 10 is arranged on the five series arm resonators S1 to S5 arranged on the first path r1 and on the path connecting the first path r1 and the reference terminal. It has a T-shaped ladder filter structure composed of four parallel arm resonators P1 to P4. The number of series arm resonators and parallel arm resonators constituting the first filter circuit 10 is not limited to five or four, and the number of series arm resonators is two or more and the number of parallel arm resonators is two or more. It should be.

The second filter circuit 50 is arranged on the second path r2 connecting the common terminal tc and the second terminal t2. The second filter circuit 50 is, for example, a transmission filter having an uplink frequency band (transmission band) as a pass band, and is set so that the pass band is lower than that of the first filter circuit 10.

The second filter circuit 50 includes series arm resonators S51, S52, S53, S54, S55 and parallel arm resonators P51, P52, P53, P54 which are elastic wave resonators.

The series arm resonators S51 to S55 are arranged on the second path (series arm) r2 connecting the common terminal tc and the second terminal t2. The series arm resonators S51 to S55 are connected in series in this order from the common terminal tc toward the second terminal t2.

The parallel arm resonators P51 to P54 are parallel to each other on the path (parallel arm) connecting each node between the adjacent series arm resonators S51 to S55 on the second path r2 and the reference terminal (ground). It is connected. As described above, the second filter circuit 50 is arranged on the five series arm resonators S51 to S55 arranged on the second path r2 and the path connecting the second path r2 and the reference terminal 4. It has a T-shaped ladder filter structure composed of two parallel arm resonators P51 to P54.

The second filter circuit 50 is not limited to the above configuration, and may be appropriately designed according to the required filter characteristics and the like. The second filter circuit 50 may have a vertically coupled elastic wave resonator or may have a π-type ladder filter structure. Further, each resonator constituting the second filter circuit 50 is not limited to the SAW resonator, and may be, for example, a BAW (Bulk Acoustic Wave) resonator. Further, the second filter circuit 50 may be configured without using a resonator, and may be, for example, an LC resonance filter or a dielectric filter.

The first filter circuit 10 is required to have characteristics that do not reduce the insertion loss in the pass band of the second filter circuit 50. Therefore, in the present embodiment, the resistance of the single parallel arm resonator P1 is set to be smaller than the resistance of the other parallel arm resonators P2 to P4 alone. This will be explained in detail later.

[2. Structure of IDT electrode of elastic wave resonator]
FIG. 10 is a diagram showing a structure of an IDT (InterDigital Transducer) electrode 30 of an elastic wave resonator included in the first filter circuit 10 of the multiplexer 1. Since the parallel arm resonator is an example of an elastic wave resonator, here, the structure of the IDT electrodes 30 of the parallel arm resonators P1 to P4 will be described by taking the elastic wave resonator as an example. Note that this figure is a simplified description of the structure of the IDT electrode, and the number and length of the electrode fingers included in the IDT electrode are different from the actual ones.

The elastic wave resonator includes a substrate 320 having piezoelectricity, an electrode layer 325 constituting the IDT electrode 30 formed on the substrate 320, and a dielectric layer 326 provided on the substrate 320 so as to cover the IDT electrode 30. And formed by. The elastic wave resonator may include a reflector in addition to the IDT electrode 30.

The substrate 320 is, for example, a LiNbO ₃ substrate (lithium niobate substrate) having a cut angle of 127.5 °. When a Rayleigh wave is used as an elastic wave propagating in the substrate 320, the cut angle of the substrate 320 is preferably 120 ° ± 20 ° or 300 ° ± 20 °.

The electrode layer 325 has a structure in which a plurality of metal layers are laminated. The electrode layer 325 is formed by, for example, laminating a Ti layer, an Al layer, a Ti layer, a Pt layer, and a NiCr layer in this order from the top.

The dielectric layer 326 is, for example, a film containing silicon dioxide (SiO ₂ ) as a main component. The dielectric layer 326 is provided for the purpose of adjusting the frequency temperature characteristic of the IDT electrode 30, protecting the electrode layer 325 from the external environment, or enhancing the moisture resistance.

Each of the IDT electrodes 30 is composed of a pair of first comb-shaped electrodes ca and second comb-shaped electrodes cb facing each other. The first comb-shaped electrode ca has a comb-shaped shape and is composed of a plurality of electrode finger fas parallel to each other and a bus bar electrode connecting one end of each of the plurality of electrode finger fas. .. The second comb-shaped electrode cb has the shape of a comb tooth and is composed of a plurality of electrode fingers fb parallel to each other and a bus bar electrode connecting one ends of the plurality of electrode fingers fb to each other. Each bus bar electrode is formed so as to extend along the elastic wave propagation direction d1. The electrode finger fa and the electrode finger fb are formed so as to extend in the orthogonal direction d2 of the elastic wave propagation direction d1, intersperse with each other in the orthogonal direction d2, and face the elastic wave propagation direction d1.

Here, the design parameters of the elastic wave resonator, such as wavelength λ, logarithm P of IDT electrode 30, cross width L, duty D, and electrode film thickness T, will be described.

The wavelength of the elastic wave resonator is defined by the wavelength λ which is the repetition period of the plurality of electrode fingers fa or fb constituting the IDT electrode 30. The electrode pitch is 1/2 of the wavelength λ, the line width of each electrode finger fa and fb constituting each comb tooth-shaped electrode ca and cb is W, and the adjacent electrode finger fa and the electrode finger fb are used. When the space width between them is S, it is defined by the electrode pitch = (W + S). The crossing width L is a distance between the pair of comb-shaped electrodes ca and cb, and is a length at which the electrode fingers fa and fb overlap each other when viewed from the elastic wave propagation direction d1. The duty D of the IDT electrode 30 is the line width occupancy of the plurality of electrode fingers fa and fb, and is defined by D = W / (W + S). The logarithm P of the IDT electrode 30 is the number of pairs when the electrode fingers fa and fb are set as one set, and is defined by P = (total number of electrode fingers-1) / 2. The electrode film thickness T is the thickness of the electrode layer 325. When the electrode layer 325 is composed of a plurality of metal layers, for example, the total film thickness when each metal layer is converted into a density and replaced with an Al layer is adopted. Specifically, when the electrode layer 325 has a laminated structure consisting of a first metal layer, a second metal layer, and a third metal layer, the Al equivalent film thickness of the first metal layer is the first metal. It is a value obtained by dividing the product of the layer density and the film thickness of the first metal layer by the density of Al, and the Al equivalent film thickness of the electrode layer 325 is the first metal layer, the second metal layer, and the third. It is the total of the Al equivalent film thickness of each of the metal layers of.

The resistance of each parallel arm resonator P1 to P4 alone can be adjusted by changing these design parameters.

[3. Comparison of Examples and Comparative Examples]
The characteristics of the multiplexer 1 of the embodiment having the above configuration will be described in comparison with the characteristics of the multiplexer of the comparative example. In the following, an embodiment, which is an example of the embodiment, will be described as an example. Further, since the multiplexer of the comparative example has the same circuit configuration as that of FIGS. 9 and 10, it will be described here using the same reference numerals as those of the embodiment.

FIG. 11A is a diagram showing design parameters of the parallel arm resonators P1 to P4 included in the first filter circuit 10 of the embodiment. FIG. 11B is a diagram showing design parameters of the parallel arm resonators P1 to P4 included in the first filter circuit 10 of the comparative example. These figures show wavelength λ, logarithm P, cross width L and duty D, which are examples of design parameters. These figures also show the design parameters of the series arm resonators S1 to S5.

As shown in FIG. 11A, in the embodiment, among the plurality of parallel arm resonators P1 to P4, the logarithm P of the IDT electrode 30 of the parallel arm resonator P1 is the largest, and the cross width L of the parallel arm resonator P1 is the largest. Is set to be the shortest. On the other hand, as shown in FIG. 11B, in the comparative example, among the plurality of parallel arm resonators P1 to P4, the logarithm P of the IDT electrode 30 of the parallel arm resonator P1 is the smallest, and the parallel arm resonator P1 intersects. The width L is set to be the longest. In the examples and the comparative examples, the wavelength λ of the parallel arm resonator P1 is the same, and the duty D of the parallel arm resonator P1 is also the same. The same applies to the other parallel arm resonators P2 to P4.

The characteristics of the parallel arm resonators P1 to P4 of the examples and comparative examples having the above design parameters will be described.

FIG. 12A is a graph showing the impedance characteristics of the parallel arm resonators P1 to P4 in the embodiment. FIG. 12B is a graph showing the impedance characteristics of the parallel arm resonators P1 to P4 in the comparative example. As shown in FIGS. 12A and 12B, each of the parallel arm resonators P1 to P4 has a resonance frequency (resonance point) within the mating band (1710 MHz to 1785 MHz) or in the vicinity of the mating band. The resonance frequency of the parallel arm resonator P1 may be in a band between the pass band (own band) of the first filter circuit 10 and the pass band (counterband) of the second filter circuit.

FIG. 13A is a Smith chart showing the impedance characteristics of the parallel arm resonators P1 to P4 in the embodiment. FIG. 13B is a Smith chart showing the impedance characteristics of the parallel arm resonators P1 to P4 in the comparative example. As shown in FIG. 13A, the parallel arm resonator P1 of the embodiment has an impedance characteristic located closer to the outer peripheral circle of the Smith chart than the other parallel arm resonators P2 to P4. On the other hand, as shown in FIG. 13B, the impedance characteristic of the parallel arm resonator P1 of the comparative example is separated from the outer circumference circle of the Smith chart.

FIG. 14A is a graph showing the resistance of the parallel arm resonators P1 to P4 in the embodiment. FIG. 14B is a graph showing the resistance of the parallel arm resonators P1 to P4 in the comparative example.

As shown in FIG. 14A, in the embodiment, the resistance of the parallel arm resonator P1 alone is smaller than the resistance of the other parallel arm resonators P2 to P4 alone in the entire range of the mating band. For example, the magnitude relationship of the resistance in the embodiment is P1 <P4 <P3 <P2, and the resistance of the parallel arm resonator P1 alone is the smallest. On the other hand, as shown in FIG. 14B, in the comparative example, the resistance of the parallel arm resonator P1 alone is larger than the resistance of the other parallel arm resonators P2 to P4 alone in the mating band. For example, the magnitude relationship of the resistance in the comparative example is P4 <P3 <P2 <P1, and the resistance of the parallel arm resonator P1 alone is the largest. The resistance is the average value of the resistance of a single parallel arm resonator in the mating band.

Next, the frequency characteristics of the first filter circuit 10 having the parallel arm resonators P1 to P4 and the second filter circuit 50 will be described.

FIG. 15 is a Smith chart showing the impedance characteristics of the first filter circuit 10 in Examples and Comparative Examples. FIG. 15 shows the impedance characteristics and the admittance characteristics of the first filter circuit 10 when viewed from the common terminal ct side. As shown in FIG. 15, in the mating band, the first filter circuit 10 of the embodiment has an impedance characteristic closer to the outer circumference circle of the Smith chart than the first filter circuit 10 of the comparative example. Therefore, in the embodiment, the loss generated in the mating band is smaller than that in the comparative example.

FIG. 16 is a graph showing the conductance of the first filter circuit 10 in Examples and Comparative Examples. FIG. 16 shows the admittance real part, that is, the conductance of the first filter circuit 10 when viewed from the common terminal ct side. As shown in FIG. 16, the example has a smaller conductance in the mating band than the comparative example.

FIG. 17 is a diagram showing the passage characteristics of the second filter circuit 50 of the multiplexer 1. FIG. 17A shows a passing characteristic including a matching loss, and FIG. 17B shows an EL characteristic which is a passing characteristic after removing the matching loss. As shown in FIGS. 17 (a) and 17 (b), the examples can suppress the reduction of the insertion loss in the mating band as compared with the comparative example.

In this way, by reducing the resistance of the parallel arm resonator P1 located closest to the common terminal tc, the conductance of the first filter circuit 10 can be reduced in the mating band. As a result, it is possible to suppress the signal of the pass band of the second filter circuit 50 from flowing into the first filter circuit 10, and it is possible to suppress the reduction of the insertion loss of the pass band of the second filter circuit 50.

[4. How to set the resistance of parallel arm resonators]
Next, a method of setting the resistance of the parallel arm resonators P1 to P4 will be described. In the above embodiment, the logarithm P and the intersection width L have been described as examples as design parameters for changing the resistance, but other design parameters will also be described here.

FIG. 18 is a diagram showing an equivalent circuit of parallel arm resonators. As shown in FIG. 18, the equivalent circuit of the parallel arm resonator is represented by three resistance components R1, R2, R3, two capacitance components C1 and C2, and one inductance component L1.

Here, the capacitance components C1 and C2 and the inductance component L1 correspond to the impedance imaginary part and are not related to the resistance setting which is the impedance real part. Further, the resistance component R3 is a value that is negligibly large for setting the resistance. Therefore, as shown in the following (Equation 1), the resistance Zr of the parallel arm resonator is represented by the total value of the resistance component R1 and the resistance component R2.

Zr = R1 + R2 ... (Equation 1)

In the vicinity of the resonance frequency, the resistance component R1 is a resistance component expressing the resistance loss of the electrode fingers fa and fb of the IDT electrode 30, and the resistance component R2 is a resistance component expressing the signal propagation loss in the elastic wave propagation direction d1. Is. The resistance loss of the electrode fingers fa and fb and the signal propagation loss are values that vary depending on design parameters such as the logarithm P of the IDT electrode 30, the intersection width L, the duty D, and the electrode film thickness T. Therefore, multivariate analysis was performed by shaking the values of the logarithm P, the cross width L, the duty D, and the electrode film thickness T, which are the design parameters, and the relationship between the resistance components R1 and R2 and each design parameter was obtained.

In the following, the relationship between the resistance component R1 and the design parameter is shown in (Equation 2), and the relationship between the resistance component R2 and the design parameter is shown in (Equation 3).

R1 = c1 + (c2 ・ T) ＋ (c3 ・ D) ^＋ (c4 ・ P) ＋ (c5 ・ L) ＋ (c6 ・ T2) ^＋ (c7 ・ D2) ＋ (c8 ・ P2) ^＋ (c9)・ P ³ ) ＋ (c10 ・ T ・ D) ＋ (c11 ・ TP) ＋ (c12 ・ TL) ＋ (c13 ・ D ・ P) ＋ (c14 ・ D ・ L) ＋ (c15 ・ P ・L) ・・・ (Equation 2)

R2 = c21 + (c22 ・ T) ＋ (c23 ・ D) ＋ (c24 ・ P) ＋ (c25 ・ L) ＋ (c26 ・ D ² ) ＋ (c27 ・ P ² ) ＋ (c28 ・ P ³ ) ＋ (c29・ L ² ) ＋ (c30 ・ T ・ P) ＋ (c31 ・ D ・ P) ＋ (c32 ・ D ・ L) ＋ (c33 ・ P ・ L) ・・・ (Equation 3)

Note that each of c1 to c15 in (Equation 2) and c21 to c33 in (Equation 3) are coefficients.

The values of each coefficient in (Equation 2) are c1 = 3.2056, c2 = −0.012122, c3 = −3.0427, c4 = −0.0192227, c5 = 0.017022, c6 = 0.000019000, c7 = 1.4970, c8 = 0.000071764, c9 = -0.000000010704, c10 = 0.0042089, c11 = 0.000015041, c12 = -0.000030710, c13 = 0.0032706, c14 = -0.0070267 , C15 = -0.000020600.

The values of each coefficient in (Equation 3) are c21 = 1.0914, c22 = -0.00013798, c23 = -0.69470, c24 = -0.0072613, c25 = -0.0055282, c26 = 0.28288. , C27 = 0.000028894, c28 = -0.0000000044315, c29 = 0.000013794, c30 = 0.000000054938, c31 = 0.00071880, c32 = 0.0016717, c33 = 0.0000066557.

FIG. 19 is a diagram showing the design parameters of the parallel arm resonators P1 to P4 and the resonance resistance of the parallel arm resonators P1 to P4. FIG. 19 (a) shows the design parameters and the resonance resistance of the embodiment, and FIG. 19 (b) shows the design parameters and the resonance resistance of the comparative example. The resonance resistance is the resistance at the resonance frequency of the parallel arm resonator, and is calculated based on (Equation 1) to (Equation 3). Since the electrode layer is composed of an Al layer, a Ti layer, and a SiO ₂ layer, the value obtained by converting the density of the Ti layer and the SiO ₂ layer and then totaling the Al layer is defined as the electrode film thickness T.

In FIG. 19A, the resonance resistance of the parallel arm resonator P1 alone is smaller than that of the other parallel arm resonators P2 to P4. That is, the design parameters are determined so that the resonance resistance of the parallel arm resonator P1 is the smallest among the plurality of parallel arm resonators P1 to P4. In this way, by using (Equation 1) to (Equation 3), the logarithm P, the cross width L, the duty D, and the electrode film thickness T of the IDT electrode 30 are determined, and the resonance resistance of the parallel arm resonator P1 is small. Can be set to be. By reducing the resonance resistance, the resistance near the resonance frequency can be reduced, and the decrease in insertion loss in the mating band can be suppressed.

Next, the relationship between the resonance resistance obtained by shaking each design parameter and each design parameter is shown.

FIG. 20 is a diagram showing the relationship between the resonance resistance of the parallel arm resonators P1 to P4 and the design parameters. 20 (a) shows the relationship between the resonance resistance and the duty D, FIG. 20 (b) shows the relationship between the resonance resistance and the cross width L, and FIG. 20 (c) shows the resonance resistance and the logarithmic P. The relationship, FIG. 20 (d) shows the relationship between the resonance resistance and (intersection width / logarithm), and FIG. 20 (e) shows the relationship between the resonance resistance and the electrode film thickness T.

As shown in FIG. 20 (a), the resonance resistance can be reduced by increasing the duty D. As shown in FIG. 20B, the resonance resistance can be reduced by shortening the crossing width L. As shown in FIG. 20 (c), the resonance resistance can be reduced by increasing the logarithm P. As shown in FIG. 20 (d), the resonance resistance can be reduced by reducing (intersection width / logarithm). As shown in FIG. 20 (e), the resonance resistance can be reduced by increasing the electrode film thickness T.

By determining the design parameters based on the trends shown in FIGS. 20 (a) to 20 (e), it is possible to efficiently set the resonance resistance and resistance of the parallel arm resonators.

(Other Study Examples of the Present Invention)
Next, another study example of the present invention will be described. In this study example, an example in which an inductor is inserted in series between the parallel arm resonator P1 and the ground will be described.

FIG. 21 is a graph showing the impedance characteristics of a circuit in which an inductor is connected to the parallel arm resonator P1. FIG. 22 is a graph showing the resistance of a circuit in which an inductor is connected to the parallel arm resonator P1. The inductor connected to the parallel arm resonator P1 is, for example, an SMD (surface mount component), and the Q value is 30. Note that FIGS. 21 and 22 also show an example in which the inductor is 0, that is, an example in which the inductor is not connected to the parallel arm resonator P1.

As shown in FIG. 21, the larger the inductance value of the inductor connected to the parallel arm resonator P1, the higher the resonance frequency exists on the lower frequency side. Further, as shown in FIG. 22, the larger the inductance value of the inductor connected to the parallel arm resonator P1, the larger the resistance Zr. The resistance Zr increases because the inductance value and the Q value are related. In order to reduce the resistance Zr, it is necessary to make the inductor component of the parallel arm resonator P1 closest to the common terminal tc as small as possible.

Therefore, it is desirable that the parallel arm resonator P1 is directly connected to the ground without using an inductor. Further, for example, when a plurality of parallel arm resonators P1 to P4 are directly connected to the ground without using an inductor or the like, the length of the wiring connecting the parallel arm resonator P1 closest to the common terminal ct and the ground. It is desirable that the length is shorter than the length of the wiring connecting the other parallel arm resonators P2 to P4 and the ground.

(summary)
As described above, the multiplexer 1 according to the present embodiment is provided on the first path r1 connecting the common terminal tc, the first terminal t1 and the second terminal t2, and the common terminal tc and the first terminal t1. The first filter circuit 10 is provided, and the second filter circuit 50 provided on the second path r2 connecting the common terminal tc and the second terminal t2 is provided. The first filter circuit 10 has a plurality of parallel arm resonators P1 to P4. In the pass band of the second filter circuit 50, among the plurality of parallel arm resonators P1 to P4, the resistance Zr of the single parallel arm resonator P1 closest to the common terminal ct is the smallest.

In this way, by making the resistance Zr of the single body of the parallel arm resonator P1 closest to the common terminal ct the smallest, the conductance of the first filter circuit 10 can be made smaller in the pass band of the second filter circuit 50. As a result, it is possible to suppress a decrease in the insertion loss of the pass band of the second filter circuit 50.

Further, the second filter circuit 50 may have a pass band on the lower frequency side than the pass band of the first filter circuit 10.

According to this, the conductance of the first filter circuit 10 can be reduced in the band on the lower frequency side than the pass band of the first filter circuit 10. As a result, it is possible to suppress a decrease in the insertion loss of the pass band of the second filter circuit 50 located on the lower frequency side of the pass band of the first filter circuit 10.

Further, each of the plurality of parallel arm resonators P1 to P4 has an IDT electrode 30, a resistance component R1 expressing the resistance loss of the electrode fingers fa and fb of the IDT electrode 30, and a signal in the elastic wave propagation direction d1. It may have a resistance Zr, which is a value obtained by summing up the resistance components R2 expressing the propagation loss of.

According to this, the resistance Zr of the parallel arm resonators P1 to P4 can be appropriately set so as to be small. As a result, the conductance of the first filter circuit 10 can be reduced, and the reduction of the insertion loss in the pass band of the second filter circuit 50 can be suppressed.

Further, the resistance component R1 expressing the resistance loss of the electrode finger and the resistance component R2 expressing the signal propagation loss are relational expressions in which the logarithm P of the IDT electrode 30, the cross width L, the duty D and the electrode film thickness T are variables. It may be a value derived by.

Further, in the above relational expression, Zr is a resistance, R1 is a resistance component expressing the resistance loss of the electrode finger of the IDT electrode, R2 is a resistance component expressing the signal propagation loss in the elastic wave propagation direction, and P is a logarithm. When L is the cross width, D is the duty, T is the electrode film thickness, and c1 to c15 and c21 to c33 are the coefficients, the above-mentioned (Equation 1), (Equation 2) and (Equation 3) are used. It may be represented by.

Further, among the plurality of parallel arm resonators P1 to P4, the resonance resistance of the parallel arm resonator P1 closest to the common terminal ct may be the smallest.

According to this, the conductance of the first filter circuit 10 can be reduced in at least a part of the pass band of the second filter circuit 50. As a result, it is possible to suppress a decrease in the insertion loss of the pass band of the second filter circuit 50.

Further, the first filter circuit 10 further has a series arm resonator S1, and the series arm resonator S1 may be provided on the common terminal ct side of the plurality of parallel arm resonators P1 to P4.

According to this, the series C component can be inserted between the parallel arm resonator P1 and the second filter circuit 50, and the conductance of the first filter circuit 10 can be reduced. As a result, it is possible to suppress a decrease in the insertion loss of the pass band of the second filter circuit 50.

Further, the resonance frequency of the parallel arm resonator P1 closest to the common terminal ct may be in the band between the pass band of the first filter circuit 10 and the pass band of the second filter circuit 50.

According to this, since the L component of the parallel arm resonator P1 does not enter the pass band of the second filter circuit 50, for example, when the series arm resonator S1 is added to the common terminal ct side, the impedance on the Smith chart. The characteristics can be sufficiently moved to the open side. As a result, it is possible to suppress a decrease in the insertion loss of the pass band of the second filter circuit 50.

Further, the parallel arm resonator P1 closest to the common terminal ct may be directly connected to the ground without using an inductor.

According to this, the resistance Zr of a single parallel arm resonator P1 can be reduced. As a result, the conductance of the first filter circuit 10 can be reduced, and the reduction of the insertion loss in the pass band of the second filter circuit 50 can be suppressed.

Further, the other parallel arm resonators P2 to P4 except for the parallel arm resonator P1 closest to the common terminal ct are directly connected to the ground without passing through the inductor, and the parallel arm resonator P1 closest to the common terminal ct and the ground are connected to the ground. The length of the wiring connecting the and may be shorter than the length of the wiring connecting the other parallel arm resonators P2 to P4 and the ground.

According to this, the resistance of the parallel arm resonator P1 alone can be made smaller than that of the other parallel arm resonators P2 to P4. As a result, the conductance of the first filter circuit 10 can be reduced, and the reduction of the insertion loss in the pass band of the second filter circuit 50 can be suppressed.

(Other embodiments)
Although the multiplexer according to the embodiment of the present invention has been described above with reference to the embodiments, the present invention includes another embodiment realized by combining arbitrary components in the above-described embodiment and the above-mentioned embodiments. The present invention also includes modification examples obtained by subjecting various modifications to the embodiments that can be conceived by those skilled in the art without departing from the gist of the present invention, and high frequency front-end circuits and communication devices including a multiplexer according to the present invention. ..

The above shows an example in which the parallel arm resonator P1 constitutes a part of the T-type ladder filter, but the present invention is not limited to this. For example, the first filter circuit 10 may have a π-type ladder filter structure, and the parallel arm resonator P1 may be arranged on the common terminal ct side of the series arm resonator S1. Further, the first filter circuit 10 includes a parallel arm resonator P1 which is a trap filter (a filter that attenuates only a certain frequency component), and the parallel arm resonator P1 is on the common terminal ct side of the series arm resonator S1. It may be provided in.

In the above, an example is shown in which the pass band of the first filter circuit 10 is set to be lower than the pass band of the second filter circuit 50, but the pass band of the first filter circuit 10 is not limited to this. , It may be set to be higher than the pass band of the second filter circuit 50.

In the above, an example in which the first filter circuit 10 is a transmission filter is shown, but the present invention is not limited to this, and the first filter circuit 10 may be a reception filter. Further, the multiplexer 1 is not limited to the configuration including both the transmission filter and the reception filter, and may be configured to include only the transmission filter or only the reception filter.

In the above, a multiplexer including two filters has been described as an example, but the present invention also relates to, for example, a triplexer in which the antenna terminals of three filters are shared and a hexaplexer in which the antenna terminals of six filters are shared. Can be applied. That is, the multiplexer need only have two or more filters.

Further, the materials constituting the electrode layer 325 and the dielectric layer 326 of the IDT electrode 30 are not limited to the above-mentioned materials. Further, the IDT electrode 30 does not have to have the above-mentioned laminated structure. The IDT electrode 30 may be made of, for example, a metal or alloy such as Ti, Al, Cu, Pt, Au, Ag, Pd, or may be made of a plurality of laminates made of the above metal or alloy. You may.

Further, in the embodiment, a substrate having piezoelectricity is shown as the substrate 320, but the substrate may be a piezoelectric substrate composed of a single layer of a piezoelectric layer. The piezoelectric substrate in this case is composed of, for example, a piezoelectric single crystal of LiTaO ₃ or another piezoelectric single crystal such as LiNbO ₃ . Further, the substrate 320 on which the IDT electrode 30 is formed may be entirely made of a piezoelectric layer or may have a structure in which the piezoelectric layer is laminated on the support substrate, as long as it has piezoelectricity. Further, the cut angle of the substrate 320 according to the above embodiment is not limited. That is, the laminated structure, material, and thickness may be appropriately changed according to the required passing characteristics of the surface acoustic wave filter, and the LiTaO ₃ piezoelectric substrate or LiNbO having a cut angle other than the cut angle shown in the above embodiment may be changed. ₃ It is possible to obtain the same effect even with an elastic surface wave filter using a piezoelectric substrate or the like.

The present invention can be widely used in communication devices such as mobile phones as multiplexers, front-end circuits and communication devices.

1 multiplexer 9 antenna element 10 1st filter circuit 30 IDT electrode 50 2nd filter circuit 320 substrate 325 electrode layer 326 dielectric layer ca, cb comb tooth electrode C1, C2 capacitance component d1 elastic wave propagation direction d2 orthogonal direction D duty fa , Fb Electrode finger L Cross width L1 Inductance component n0, n1, n2, n3, n4 Node P log P0, P1, P2, P3, P4, P51, P52, P53, P54 Parallel arm resonator R1, R2, R3 Resistance component r1 1st path r2 2nd path S0, S1, S2, S3, S4, S5, S51, S52, S53, S54, S55 Series arm resonator ct Common terminal t1 1st terminal t2 2nd terminal T Electrode film thickness Zr resistance

Claims

Common terminal, 1st terminal and 2nd terminal,
A first filter circuit provided on a first path connecting the common terminal and the first terminal,
A second filter circuit provided on the second path connecting the common terminal and the second terminal, and
Equipped with
The first filter circuit has a plurality of parallel arm resonators and has a plurality of parallel arm resonators.
A multiplexer having the smallest resistance of a single parallel arm resonator closest to the common terminal among the plurality of parallel arm resonators in the pass band of the second filter circuit.
The multiplexer according to claim 1, wherein the second filter circuit has a pass band on the lower frequency side than the pass band of the first filter circuit.
Each of the plurality of parallel arm resonators has an IDT electrode, and the resistance component expressing the resistance loss of the electrode finger of the IDT electrode and the resistance component expressing the resistance loss of the signal in the elastic wave propagation direction are summed up. The multiplexer according to claim 1 or 2, which has the resistance.
The resistance component expressing the resistance loss of the electrode finger and the resistance component expressing the propagation loss of the signal are values derived by a relational expression with the logarithm, the cross width, the duty and the electrode film thickness of the IDT electrode as variables. The multiplexer according to claim 3.
The relational expression is
Zr is the resistance
R1 is used as a resistance component expressing the resistance loss of the electrode finger of the IDT electrode.
R2 is a resistance component that expresses signal propagation loss in the elastic wave propagation direction.
Let P be the logarithm
Let L be the crossing width
Let D be the duty
Let T be the electrode film thickness
c1, c2, c3, c4, c5, c6, c7, c8, c9, c10, c11, c12, c13, c14, c15, c21, c22, c23, c24, c25, c26, c27, c28, c29, c30, When c31, c32, and c33 are used as coefficients,
Zr = R1 + R2,
however,
R1 = c1 + (c2 ・ T) ＋ (c3 ・ D) ＋ (c4 ・ P) ＋ (c5 ・ L) ＋ (c6 ・ T2) ＋ (c7 ・ D2) ＋ (c8 ・ P2) ＋ (c9)・ P 3 ) ＋ (c10 ・ T ・ D) ＋ (c11 ・ TP) ＋ (c12 ・ TL) ＋ (c13 ・ D ・ P) ＋ (c14 ・ D ・ L) ＋ (c15 ・ P ・L),
R2 = c21 + (c22 ・ T) ＋ (c23 ・ D) ＋ (c24 ・ P) ＋ (c25 ・ L) ＋ (c26 ・ D 2 ) ＋ (c27 ・ P 2 ) ＋ (c28 ・ P 3 ) ＋ (c29・ L 2 ) + (c30 ・ T ・ P) ＋ (c31 ・ D ・ P) ＋ (c32 ・ D ・ L) ＋ (c33 ・ P ・ L),
The multiplexer according to claim 4.
The multiplexer according to any one of claims 1 to 5, wherein the parallel arm resonator closest to the common terminal has the smallest resonance resistance among the plurality of parallel arm resonators.
The first filter circuit further has a series arm resonator.
The multiplexer according to any one of claims 1 to 6, wherein the series arm resonator is provided on the common terminal side of the plurality of parallel arm resonators.
The multiplexer according to claim 7, wherein the resonance frequency of the parallel arm resonator closest to the common terminal is in the band between the pass band of the first filter circuit and the pass band of the second filter circuit.
The multiplexer according to any one of claims 1 to 8, wherein the parallel arm resonator closest to the common terminal is directly connected to the ground without an inductor.
The other parallel arm resonators except the parallel arm resonator closest to the common terminal are directly connected to the ground without an inductor.
The multiplexer according to claim 9, wherein the length of the wiring connecting the parallel arm resonator closest to the common terminal and the ground is shorter than the length of the wiring connecting the other parallel arm resonator and the ground.