WO2023068206A1 - Multiplexer - Google Patents

Abstract

A multiplexer (1) comprises a filter (11) that has a first passband and a filter (21) that has a second passband that has a higher frequency than the first passband. One end of filter (11) is connected to one end of filter (21). Filter (21) has one or more elastic wave resonators that are arranged on a series arm path that connects the one end and another end of filter (21). The elastic wave resonators include a series arm resonator that is the elastic wave resonator connected closest to the one end, and the antiresonant frequency fa1 of the series arm resonator is at or below the frequency at the high-frequency end of the first passband.

Description

multiplexer

The present invention relates to a multiplexer with acoustic wave filters.

Patent Document 1 discloses an inductance element having one end connected to a first common terminal and the other end connected to a second common terminal, and a first acoustic wave filter connected to the first common terminal without an inductance element. , and a plurality of acoustic wave filters connected to a second common terminal. According to this, the insertion loss within the passband of each acoustic wave filter connected to the common terminal can be reduced.

JP 2019-220877 A

However, the multiplexer described in Patent Document 1 poses a problem of the loss of the acoustic wave filters (hereinafter referred to as bundling loss) due to the common connection of the plurality of acoustic wave filters to the second common terminal. For example, when one of the plurality of acoustic wave filters connected to the second common terminal is set to filter A (passband A) and the other one is set to filter B (passband B), the bundling loss of filter A is , increases as the conductance in the passband A of the filter B increases. Therefore, as the number of acoustic wave filters connected to the second common terminal increases, the conductance in the passband A of the acoustic wave filters connected in parallel increases, and the bundling loss of the filters A increases. The insertion loss of A increases.

Therefore, the present invention has been made to solve the above problems, and an object of the present invention is to provide a multiplexer in which the insertion loss within the passband of each commonly connected acoustic wave filter is reduced.

To achieve the above object, a multiplexer according to an aspect of the present invention includes a first elastic wave filter having a first passband and a second elastic wave filter having a second passband having a higher frequency than the first passband. a filter, wherein one end of the first elastic wave filter and one end of the second elastic wave filter are connected, the second elastic wave filter has one or more elastic wave resonators, and one or more elastic wave resonators the element is arranged on a series arm path connecting one end and the other end of the second elastic wave filter, and includes a series arm resonator connected closest to one end of the one or more elastic wave resonators; The antiresonant frequency of the resonator is equal to or lower than the frequency of the high frequency end of the first passband.

Further, a multiplexer according to an aspect of the present invention includes a first elastic wave filter having a first passband and a second elastic wave filter having a second passband having a higher frequency than the first passband, Each of the first elastic wave filter and the second elastic wave filter is composed of a surface acoustic wave resonator having an IDT (InterDigital Transducer) electrode, and one end of the first elastic wave filter and one end of the second elastic wave filter are connected. and the second acoustic wave filter has one or more surface acoustic wave resonators, and the one or more surface acoustic wave resonators are arranged on a series arm path connecting one end and the other end of the second acoustic wave filter. and includes a series arm resonator connected closest to one end among one or more surface acoustic wave resonators, and the electrode finger pitch of the IDT electrodes constituting the series arm resonator is included in the first acoustic wave filter It is larger than any of the electrode finger pitches of the IDT electrodes constituting all surface acoustic wave resonators.

Further, a multiplexer according to an aspect of the present invention includes a first elastic wave filter having a first passband and a second elastic wave filter having a second passband having a higher frequency than the first passband, Each of the first elastic wave filter and the second elastic wave filter is formed between the support substrate, the first electrode and the second electrode formed on one surface of the support substrate, and the first electrode and the second electrode. and one end of the first acoustic wave filter and one end of the second acoustic wave filter are connected, and the second acoustic wave filter includes one or more bulk acoustic wave filters. and one or more bulk acoustic wave resonators are arranged on a series arm path connecting one end and the other end of the second bulk acoustic wave filter, and among the one or more bulk acoustic wave resonators, A piezoelectric layer that includes a series arm resonator connected close to one end, and that constitutes the series arm resonator is higher than any of the piezoelectric layers that constitute all the bulk acoustic wave resonators included in the first acoustic wave filter. thick.

According to the present invention, it is possible to provide a multiplexer in which the insertion loss within the passband of each commonly connected acoustic wave filter is reduced.

FIG. 1 is a circuit configuration diagram of a multiplexer according to Embodiment 1. FIG. 2A is a diagram showing a first example of a circuit configuration of a second elastic wave filter that constitutes the multiplexer according to Embodiment 1. FIG. 2B is a diagram illustrating a second example of a circuit configuration of a second elastic wave filter that configures the multiplexer according to Embodiment 1. FIG. 3A is a plan view and a cross-sectional view schematically showing a first example of an elastic wave resonator that constitutes the elastic wave filter according to Embodiment 1. FIG. 3B is a cross-sectional view schematically showing a second example of the elastic wave resonator that constitutes the elastic wave filter according to Embodiment 1. FIG. 3C is a cross-sectional view schematically showing a third example of the elastic wave resonator that constitutes the elastic wave filter according to Embodiment 1. FIG. 4A is a graph comparing pass characteristics of second acoustic wave filters according to Example 1 and Comparative Example 1. FIG. 4B is a Smith chart comparing impedance characteristics viewed from the common terminal of the second acoustic wave filters according to Example 1 and Comparative Example 1. FIG. 5A is a graph showing pass characteristics of first elastic wave filters (for transmission) of multiplexers according to Example 1 and Comparative Example 1. FIG. 5B is a graph showing pass characteristics of the first elastic wave filter (for reception) of the multiplexers according to Example 1 and Comparative Example 1. FIG. FIG. 6 is a circuit configuration diagram of a multiplexer according to the second embodiment. FIG. 7A compares the impedance characteristics of the first passband (transmission) viewed from the first common terminal when the first elastic wave filter and the second elastic wave filter are commonly connected in Example 2 and Comparative Example 2. Smith chart. FIG. 7B compares the impedance characteristics of the first passband (reception) viewed from the first common terminal when the first elastic wave filter and the second elastic wave filter are commonly connected in Example 2 and Comparative Example 2. Smith chart. 7C is a Smith chart comparing the impedance characteristics of the second passband viewed from the first common terminal when the first elastic wave filter and the second elastic wave filter are commonly connected in Example 2 and Comparative Example 2. FIG. be. FIG. 7D compares the impedance characteristics of the third passband (transmission) viewed from the first common terminal when the first elastic wave filter and the second elastic wave filter are commonly connected in Example 2 and Comparative Example 2. Smith chart. FIG. 7E compares the impedance characteristics of the third passband (receiving) viewed from the first common terminal when the first elastic wave filter and the second elastic wave filter are commonly connected in Example 2 and Comparative Example 2. Smith chart. 8A shows the impedance characteristics of the first passband (transmission) viewed from the second common terminal when the inductor, the first elastic wave filter, and the second elastic wave filter are commonly connected in Example 2 and Comparative Example 2. FIG. It is a comparative graph. 8B shows the impedance characteristics of the first passband (reception) viewed from the second common terminal when the inductor, the first elastic wave filter, and the second elastic wave filter are commonly connected in Example 2 and Comparative Example 2. It is a comparative graph. 8C is a graph comparing the impedance characteristics of the second passband viewed from the second common terminal when the inductor, the first elastic wave filter, and the second elastic wave filter are commonly connected in Example 2 and Comparative Example 2; is. 8D shows the impedance characteristics of the third passband (transmission) viewed from the second common terminal when the inductor, the first elastic wave filter, and the second elastic wave filter are commonly connected in Example 2 and Comparative Example 2. FIG. It is a comparative graph. 8E shows the impedance characteristics of the third passband (receiving) viewed from the second common terminal when the inductor, the first elastic wave filter, and the second elastic wave filter are commonly connected in Example 2 and Comparative Example 2. FIG. It is a comparative graph. FIG. 9 is a graph comparing the conductance characteristics seen from the second common terminal when the inductor, the first elastic wave filter, and the second elastic wave filter are connected in common between Example 2 and Comparative Example 2. FIG. FIG. 10 is a graph comparing the impedance characteristics seen from the second common terminal of the multiplexers according to the second embodiment and the second comparative example between the second embodiment and the second comparative example. 11A is a graph showing pass characteristics of second elastic wave filters (for reception) of multiplexers according to Example 2 and Comparative Example 2. FIG. 11B is a graph showing pass characteristics of the third elastic wave filter (for transmission) of the multiplexers according to Example 2 and Comparative Example 2. FIG. 11C is a graph showing pass characteristics of the third acoustic wave filter (for reception) of the multiplexers according to Example 2 and Comparative Example 2. FIG.

Hereinafter, embodiments of the present invention will be described in detail using examples, modifications, and drawings. It should be noted that the embodiments and modifications described below are all comprehensive or specific examples. Numerical values, shapes, materials, constituent elements, arrangement of constituent elements, connection forms, and the like shown in the following examples and modifications are examples, and are not intended to limit the present invention. Among the components in the following examples and modifications, components not described in independent claims will be described as optional components. Also, the sizes or size ratios of components shown in the drawings are not necessarily exact.

Also, in the following embodiments, the passband of the filter is defined as the frequency band between two frequencies that are 3 dB larger than the minimum value of the insertion loss in the passband.

(Embodiment 1)
[1.1 Circuit Configuration of Multiplexer 1]
FIG. 1 is a circuit configuration diagram of a multiplexer 1 according to the first embodiment. As shown in the figure, the multiplexer 1 includes filters 11 , 12 and 21 , an antenna connection terminal 90 , a common terminal 91 , input terminals 110 and 210 and an output terminal 120 .

The antenna connection terminal 90 is connected to, for example, an antenna element. Common terminal 91 is an example of a first common terminal, and is connected to the output terminal of filter 11 , the input terminal of filter 12 , and the output terminal of filter 21 .

The filter 11 is an example of a first acoustic wave filter, and has a passband (first passband) including the band A transmission band. One end (output end) of the filter 11 is connected to the common terminal 91, and the other end (input end) is connected to the input terminal 110 (first input/output terminal). Filter 11 has one or more elastic wave resonators.

The filter 12 has a passband including the band A reception band. One end (input end) of the filter 12 is connected to the common terminal 91 and the other end (output end) is connected to the output terminal 120 . Filter 12 has one or more elastic wave resonators.

The filter 21 is an example of a second acoustic wave filter, and has a passband (second passband) including the transmission band of band B. One end (output end) of the filter 21 is connected to the common terminal 91, and the other end (input end) is connected to the input terminal 210 (second input/output terminal). Filter 21 has one or more elastic wave resonators. The filter 21 is arranged on a series arm path connecting the common terminal 91 and the input terminal 210 and includes a series arm resonator connected closest to the common terminal 91 among the one or more elastic wave resonators.

The transmission band of band B has a higher frequency than the transmission band and reception band of band A.

Here, the anti-resonance frequency fa1 of the series arm resonator is equal to or lower than the frequency of the high frequency end of the first passband.

As band A, for example, LTE (Long Term Evolution) Band 3 (transmission band: 1710-1785 MHz, reception band: 1805-1880 MHz) is applied, and as band B, for example, LTE Band 1 (transmission band: 1920-1980 MHz, reception band: 2110-2170 MHz).

Note that one of the filters 11 and 12 may be omitted in the multiplexer 1 according to the present embodiment. Filters other than filters 11 , 12 and 21 may be connected to common terminal 91 .

Also, the antenna connection terminal 90, the input terminals 110 and 210, the output terminal 120, and the common terminal 91 may not be included in the multiplexer 1.

[1.2 Structure of elastic wave filter]
Here, the circuit configuration of the filter 21 forming the multiplexer 1 and the structure of the elastic wave resonator forming each filter will be illustrated.

FIG. 2A is a diagram showing a first example of the circuit configuration of the filter 21 that constitutes the multiplexer 1 according to the first embodiment. FIG. 2B is a diagram showing a second example of the circuit configuration of the filter 21 forming the multiplexer 1 according to the first embodiment.

The filter 21 according to the present embodiment has, for example, the circuit configuration of the elastic wave filter 21A shown in FIG. 2A or the elastic wave filter 21B shown in FIG. 2B.

The elastic wave filter 21A shown in FIG. 2A includes series arm resonators 101 to 105, parallel arm resonators 151 to 154, and an inductor 161.

The series arm resonators 101 to 105 are arranged on a series arm path connecting the input terminal 210 and the common terminal 91 . Each of the parallel arm resonators 151-154 is connected between each connection point of the series arm resonators 101-105 and the input terminal 210 and the ground. With the above connection configuration, the acoustic wave filter 21A constitutes a ladder-type bandpass filter. Inductor 161 is connected between the connection point of parallel arm resonators 151, 152 and 153 and the ground, and adjusts the attenuation pole in the filter pass characteristics. In acoustic wave filter 21A shown as the first example of filter 21, the number of series arm resonators and parallel arm resonators is arbitrary, and inductor 161 may be omitted.

The elastic wave filter 21B shown in FIG. 2B includes a longitudinal coupling filter section 203, series arm resonators 201 and 202, and parallel arm resonators 251 and 253.

The longitudinal coupling filter unit 203 has, for example, nine IDTs, each of which is composed of a pair of IDT electrodes facing each other. Series arm resonators 201 and 202 and parallel arm resonator 251 constitute a ladder filter section. With the connection configuration described above, the elastic wave filter 21B constitutes a bandpass filter. In elastic wave filter 21B shown as the second example of filter 21, the number of series arm resonators and parallel arm resonators and the number of IDTs constituting longitudinally coupled filter section 203 are arbitrary.

In the first example, the series arm resonator 101 is arranged on the series arm path connecting the common terminal 91 and the input terminal 210, and is connected closest to the common terminal 91 among the one or more elastic wave resonators. It is a series arm resonator.

Further, in the second example, the series arm resonator 201 is arranged on the series arm path connecting the common terminal 91 and the input terminal 210, and is closest to the common terminal 91 among the one or more elastic wave resonators. connected series arm resonators.

FIG. 3A is a plan view and a cross-sectional view schematically showing a first example of elastic wave resonators of filters 11, 12 and 21 according to Embodiment 1. FIG. The figure illustrates the basic structure of elastic wave resonators that constitute the filters 11, 12 and 21. As shown in FIG. Note that the elastic wave resonator 60 shown in FIG. 3A is for explaining a typical structure of an elastic wave resonator, and the number and length of the electrode fingers constituting the electrodes are Not limited.

The acoustic wave resonator 60 is composed of a piezoelectric substrate 50 and comb electrodes 60a and 60b.

As shown in (a) of FIG. 3A, a pair of interdigitated electrodes 60a and 60b are formed on the substrate 50 so as to face each other. The comb-shaped electrode 60a is composed of a plurality of parallel electrode fingers 61a and busbar electrodes 62a connecting the plurality of electrode fingers 61a. The comb-shaped electrode 60b is composed of a plurality of parallel electrode fingers 61b and a busbar electrode 62b connecting the plurality of electrode fingers 61b. The plurality of electrode fingers 61a and 61b are formed along a direction orthogonal to the elastic wave propagation direction (X-axis direction).

The IDT electrode 54, which is composed of a plurality of electrode fingers 61a and 61b and busbar electrodes 62a and 62b, has a laminated structure of an adhesion layer 540 and a main electrode layer 542, as shown in (b) of FIG. 3A. It's becoming

The adhesion layer 540 is a layer for improving adhesion between the substrate 50 and the main electrode layer 542, and is made of Ti, for example. The material of the main electrode layer 542 is, for example, Al containing 1% Cu. Protective layer 55 is formed to cover comb electrodes 60a and 60b. The protective layer 55 is a layer for the purpose of protecting the main electrode layer 542 from the external environment, adjusting frequency temperature characteristics, and increasing moisture resistance. is.

It should be noted that the materials forming the adhesion layer 540, the main electrode layer 542 and the protective layer 55 are not limited to the materials described above. Furthermore, the IDT electrode 54 may not have the laminated structure described above. The IDT electrode 54 may be composed of, for example, metals or alloys such as Ti, Al, Cu, Pt, Au, Ag, and Pd, and may be composed of a plurality of laminates composed of the above metals or alloys. may Also, the protective layer 55 may not be formed.

Next, the laminated structure of the substrate 50 will be described.

As shown in (c) of FIG. 3A, the substrate 50 includes a high acoustic velocity support substrate 51, a low acoustic velocity film 52, and a piezoelectric film 53. The high acoustic velocity support substrate 51, the low acoustic velocity film 52, and the piezoelectric film 53 are It has a structure laminated in this order.

The piezoelectric film 53 is, for example, a θ° Y-cut X-propagation LiTaO ₃ piezoelectric single crystal or piezoelectric ceramics (lithium tantalate single crystal cut along a plane normal to an axis rotated θ° from the Y axis with the X axis as the central axis, (or ceramics, single crystal or ceramics in which surface acoustic waves propagate in the X-axis direction). Note that the material of the piezoelectric single crystal used as the piezoelectric film 53 and the cut angle θ are appropriately selected according to the required specifications of each filter.

The high acoustic velocity support substrate 51 is a substrate that supports the low acoustic velocity film 52 , the piezoelectric film 53 and the IDT electrodes 54 . The high acoustic velocity support substrate 51 is a substrate in which the acoustic velocity of bulk waves in the high acoustic velocity support substrate 51 is faster than acoustic waves such as surface waves and boundary waves propagating through the piezoelectric film 53, and surface acoustic waves are generated. It functions so that it is confined in the portion where the piezoelectric film 53 and the low sound velocity film 52 are laminated and does not leak below the high sound velocity support substrate 51 . The high acoustic velocity support substrate 51 is, for example, a silicon substrate.

The low sound velocity film 52 is a film in which the sound velocity of the bulk wave in the low sound velocity film 52 is lower than that of the bulk wave propagating through the piezoelectric film 53 , and is arranged between the piezoelectric film 53 and the high sound velocity support substrate 51 . be. This structure and the nature of the elastic wave to concentrate its energy in a low-temperature medium suppresses leakage of the surface acoustic wave energy to the outside of the IDT electrode. The low-temperature velocity film 52 is, for example, a film whose main component is silicon dioxide.

In addition, according to the laminated structure of the substrate 50, it is possible to significantly increase the Q value at the resonance frequency and the antiresonance frequency compared to the conventional structure using a single layer of piezoelectric substrate. That is, since an acoustic wave resonator with a high Q value can be configured, it is possible to configure a filter with a small insertion loss using the acoustic wave resonator.

The high acoustic velocity support substrate 51 has a structure in which a support substrate and a high acoustic velocity film having a higher acoustic velocity than elastic waves such as surface waves and boundary waves propagating through the piezoelectric film 53 are laminated. may have In this case, the support substrate includes piezoelectric materials such as sapphire, lithium tantalate, lithium niobate, and quartz, alumina, magnesia, silicon nitride, aluminum nitride, silicon carbide, zirconia, cordierite, mullite, steatite, and fort. Various ceramics such as stellite, dielectrics such as glass, semiconductors such as silicon and gallium nitride, and resin substrates can be used. The high acoustic velocity film includes aluminum nitride, aluminum oxide, silicon carbide, silicon nitride, silicon oxynitride, DLC film, diamond, media containing these materials as main components, and media containing mixtures of these materials as main components. etc., various high acoustic velocity materials can be used.

FIG. 3B is a cross-sectional view schematically showing a second example of elastic wave resonators of filters 11, 12 and 21 according to the first embodiment. The elastic wave resonator 60 shown in FIG. 3A shows an example in which the IDT electrodes 54 are formed on the substrate 50 having the piezoelectric film 53. The substrate on which the IDT electrodes 54 are formed is shown in FIG. 3B. Thus, the piezoelectric single crystal substrate 57 may be a single piezoelectric layer. The piezoelectric single crystal substrate 57 is composed of, for example, a piezoelectric single crystal of LiNbO ₃ . The acoustic wave resonator according to this example is composed of a piezoelectric single crystal substrate 57 of LiNbO ₃ , an IDT electrode 54 , and a protective layer 58 formed on the piezoelectric single crystal substrate 57 and the IDT electrode 54 . .

The piezoelectric film 53 and the piezoelectric single crystal substrate 57 described above may be appropriately changed in laminated structure, material, cut angle, and thickness according to the required transmission characteristics of the elastic wave filter device. Even an acoustic wave resonator using a LiTaO ₃ piezoelectric substrate having a cut angle other than the cut angle described above can produce the same effects as the acoustic wave resonator 60 using the piezoelectric film 53 described above.

Also, the substrate on which the IDT electrodes 54 are formed may have a structure in which a supporting substrate, an energy trapping layer, and a piezoelectric film are laminated in this order. An IDT electrode 54 is formed on the piezoelectric film. The piezoelectric film is, for example, LiTaO ₃ piezoelectric single crystal or piezoelectric ceramics. The support substrate is the substrate that supports the piezoelectric film, the energy confinement layer, and the IDT electrodes 54 .

The energy confinement layer consists of one or more layers, and the velocity of the bulk acoustic wave propagating through at least one layer is greater than the velocity of the elastic wave propagating near the piezoelectric film. For example, the energy trapping layer may have a laminated structure of a low acoustic velocity layer and a high acoustic velocity layer. The sound velocity layer is a film in which the sound velocity of bulk waves in the sound velocity layer is lower than the sound velocity of elastic waves propagating through the piezoelectric film. The high acoustic velocity layer is a film in which the acoustic velocity of bulk waves in the high acoustic velocity layer is higher than the acoustic velocity of elastic waves propagating through the piezoelectric film. Note that the support substrate may be a high acoustic velocity layer.

Also, the energy trapping layer may be an acoustic impedance layer having a configuration in which a low acoustic impedance layer with a relatively low acoustic impedance and a high acoustic impedance layer with a relatively high acoustic impedance are alternately laminated. .

Here, an example (working example) of the electrode parameters of the IDT electrodes forming the acoustic wave resonator 60 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 61a or 61b forming the IDT electrode 54 shown in (b) of FIG. 3A. The electrode finger pitch is 1/2 of the wavelength λ, the line width of the electrode fingers 61a and 61b constituting the comb-shaped electrodes 60a and 60b is W, and the distance between the adjacent electrode fingers 61a and 61b is When the space width is S, it is defined as (W+S). Moreover, as shown in (a) of FIG. 3A, the intersecting width L of the pair of comb-shaped electrodes 60a and 60b is the overlap of the electrode fingers 61a and 61b when viewed from the elastic wave propagation direction (X-axis direction). is the length of the electrode finger that The electrode duty of each acoustic wave resonator is the line width occupation ratio of the plurality of electrode fingers 61a and 61b, and is the ratio of the line width to the sum of the line width and space width of the plurality of electrode fingers 61a and 61b. and is defined as W/(W+S). Also, the height of the comb electrodes 60a and 60b is h. Hereinafter, parameters related to the shape of the IDT electrodes of the acoustic wave resonator, such as the wavelength λ, the electrode finger pitch, the crossing width L, the electrode duty, and the height h of the IDT electrodes 54, are defined as electrode parameters.

In the IDT electrodes 54 , if the intervals between adjacent electrode fingers are not constant, the electrode finger pitch of the IDT electrodes 54 is defined by the average electrode finger pitch of the IDT electrodes 54 . The average electrode finger pitch of the IDT electrode 54 is defined by the total number of the electrode fingers 61a and 61b included in the IDT electrode 54 being Ni, and the electrode finger positioned at one end of the IDT electrode 54 in the elastic wave propagation direction and It is defined as Di/(Ni-1), where Di is the center-to-center distance from the positioned electrode finger.

For example, when the film thickness of the IDT electrode, the film thickness of the protective layer, and the electrode duty are constant, the resonance frequency and the antiresonance frequency of the surface acoustic wave resonator shift to the lower frequency side as the electrode finger pitch of the IDT electrode increases. shift.

FIG. 3C is a cross-sectional view schematically showing a third example of elastic wave resonators of filters 11, 12 and 21 according to the first embodiment. Bulk acoustic wave resonators are shown as acoustic wave resonators of filters 11, 12 and 21 in FIG. 3C. As shown in the figure, the bulk acoustic wave resonator has, for example, a support substrate 65, a lower electrode 66, a piezoelectric layer 67, and an upper electrode 68. , a piezoelectric layer 67, and an upper electrode 68 are laminated in this order.

The support substrate 65 is a substrate for supporting the lower electrode 66, the piezoelectric layer 67, and the upper electrode 68, and is, for example, a silicon substrate. The support substrate 65 is provided with a cavity in a region in contact with the lower electrode 66 . This allows the piezoelectric layer 67 to vibrate freely.

The lower electrode 66 is an example of a first electrode and is formed on one surface of the support substrate 65 . The upper electrode 68 is an example of a second electrode and is formed on one surface of the support substrate 65 . The lower electrode 66 and the upper electrode 68 are made of Al containing 1% Cu, for example.

The piezoelectric layer 67 is formed between the lower electrode 66 and the upper electrode 68 . The piezoelectric layer 67 is made of, for example, ZnO (zinc oxide), AlN (aluminum nitride), PZT (lead zirconate titanate), KN (potassium niobate), LN (lithium niobate), LT (lithium tantalate), The main component is at least one of quartz and LiBO (lithium borate).

The bulk acoustic wave resonator having the above laminated structure induces a bulk acoustic wave in the piezoelectric layer 67 by applying electrical energy between the lower electrode 66 and the upper electrode 68 to generate resonance. It is. A bulk acoustic wave generated by this bulk acoustic wave resonator propagates between the lower electrode 66 and the upper electrode 68 in a direction perpendicular to the film surface of the piezoelectric layer 67 . That is, the bulk acoustic wave resonator is a resonator that utilizes bulk acoustic waves.

For example, as the film thickness of the piezoelectric layer 67 increases, the resonance frequency and anti-resonance frequency of the bulk acoustic wave resonator shift to the low frequency side.

[1.3 Characteristics of Multiplexer 1]
The impedance characteristics (admittance characteristics) and pass characteristics of the multiplexer 1 according to the present embodiment will be described below while comparing the multiplexers of the first embodiment and the first comparative example.

The multiplexer according to Example 1 is an example of the multiplexer 1 according to the present embodiment. The multiplexer according to Comparative Example 1 is not included in the multiplexers according to this embodiment.

1, the multiplexer according to the first embodiment includes filters 11 and 12, an acoustic wave filter 21A (filter 21), an antenna connection terminal 90, a common terminal 91, input terminals 110 and 210, and an output 4A, the antiresonance frequency fa1 of the series arm resonator 101 connected closest to the common terminal 91 among the elastic wave resonators of the elastic wave filter 21A is the same as the filter 11 (FIG. 4A). 4A is located within the passband of A-Tx). Among the filters 11 and 12 and the acoustic wave filter 21A, the passband of the filter 11 is located on the lowest frequency side, and the passband of the acoustic wave filter 21A is located on the highest frequency side.

On the other hand, the multiplexer according to Comparative Example 1 has a circuit configuration similar to that of the multiplexer according to Example 1. , and is located on the high frequency side of the low end of the passband (B-Tx in FIG. 4A) of the elastic wave filter 21A.

FIG. 4B is a Smith chart comparing the impedance characteristics of the acoustic wave filters 21A according to Example 1 and Comparative Example 1 viewed from the common terminal 91. FIG. The figure shows the impedance characteristics of the elastic wave filter 21A alone as viewed from the common terminal 91 side in Example 1 and Comparative Example 1. FIG.

In the elastic wave filter 21A according to Comparative Example 1, the impedance of the passband (A-Tx) of the filter 11 is located away from the open point (around 5 o'clock on the Smith chart).

On the other hand, in the elastic wave filter 21A according to the first embodiment, since the antiresonance frequency fa1 of the series arm resonator 101 is located within the passband (A-Tx) of the filter 11, the passband (A-Tx ) is located near the open point (near 3:30 on the Smith chart) compared to Comparative Example 1.

The series arm resonator 101 (elastic wave resonator) has a small capacitance (near the high frequency side of fa1) or a large inductance (near the low frequency side of fa1) near the anti-resonance frequency fa1. In the elastic wave filter 21A according to the first embodiment, the anti-resonance frequency fa1 is positioned within the passband (A-Tx) of the filter 11, so that the passband ( A-Tx) is compared with the impedance of the passband (A-Tx) seen from the common terminal 91 side of the acoustic wave filter 21A alone according to Comparative Example 1, in the counterclockwise direction of the equal resistance circle or closer to the open point (lower capacitance), or in the clockwise direction of the equal resistance circle and closer to the open point (higher inductance).

The fact that the impedance of the passband (A-Tx) in the acoustic wave filter 21A alone is located on the more open side on the equal resistance circle means that the conductance of the passband (A-Tx) in the acoustic wave filter 21A alone is Equivalent to making it smaller.

5A is a graph showing pass characteristics of the filter 11 of the multiplexer according to Example 1 and Comparative Example 1. FIG. FIG. 5B is a graph showing pass characteristics of the filters 12 of the multiplexers according to Example 1 and Comparative Example 1. In FIG. As shown in FIG. 5A, in the multiplexer according to the first embodiment, the conductance of the passband (A-Tx) in the elastic wave filter 21A alone can be made smaller, so that the filters 11 and 12 and the elastic wave filter 21A are connected to the common terminal. The so-called bundling loss when connected to 91 can be reduced.

Note that, as shown in FIG. 5B, the multiplexer according to the first embodiment can also reduce the insertion loss of the filter 12 . This is because the anti-resonance frequency fa1 of the series arm resonator 101 is located on the lower frequency side than the passband (A-Rx) of the filter 12, so that the impedance of the passband (A-Rx) is different from that of Comparative Example 1. This is because it is located near the open point by comparison.

According to this, in the multiplexer according to the first embodiment, it is possible to reduce the insertion loss within the passband of the filters 11 and 12 connected to the common terminal 91.

In the multiplexer 1 according to the present embodiment, the anti-resonance frequency fa1 of the series arm resonator 101 may be located on the lower frequency side than the passband (A-Tx) of the filter 11. Even in this case, the series arm resonator 101 has a small capacitance in the passband (A-Tx). It is possible to reduce the insertion loss within the passband of the filter 11 connected to the common terminal 91 .

In the multiplexer according to the first embodiment, the anti-resonance frequency fa1 of the series arm resonator 101 connected closest to the common terminal 91 among the elastic wave resonators of the elastic wave filter 21A is the same as that of the filter 11 (A-Tx). It is characterized by being located within the passband. Instead of this feature, the multiplexer according to Modification 1 includes filters 11 and 12, elastic wave filter 21A (filter 21), antenna connection terminal 90, common terminal 91, input terminals 110 and 210, and output terminal 120, and the acoustic wave filter 21A has one or more surface acoustic wave resonators, and the one or more surface acoustic wave resonators are series arm paths connecting one end and the other end of the acoustic wave filter 21A. The electrode finger pitch of the IDT electrodes 54 that constitute the series arm resonator includes a series arm resonator connected closest to the one end of the one or more surface acoustic wave resonators arranged above the filter. 11 may be larger than any of the electrode finger pitches of the IDT electrodes 54 constituting all the surface acoustic wave resonators.

According to this, the anti-resonance frequency fa1 of the series arm resonator of the elastic wave filter 21A is located within the passband of the filter 11 or on the lower frequency side than the passband. Therefore, it is possible to obtain the same effect as the multiplexer according to the first embodiment.

In the multiplexer according to Modification 1, when the thickness of the IDT electrode 54, the thickness of the protective layer 55, and the electrode duty of the surface acoustic wave resonators constituting the acoustic wave filter 21A and the filter 11 are the same, The above effect is exhibited remarkably.

Further, the multiplexer according to Modification 2 includes filters 11 and 12, an acoustic wave filter 21A (filter 21), an antenna connection terminal 90, a common terminal 91, input terminals 110 and 210, and an output terminal 120. Each of the acoustic wave filter 21A and the filter 11 includes, as shown in FIG. 3C, a supporting substrate 65, a lower electrode 66 and an upper electrode 68 formed on one surface of the supporting substrate 65, and a lower electrode 66 and an upper electrode. and a piezoelectric layer 67 formed between the electrode 68 and a bulk acoustic wave resonator. The elastic wave filter 21A has one or more bulk acoustic wave resonators, and the one or more bulk acoustic wave resonators are arranged on a series arm path connecting one end and the other end of the elastic wave filter 21A. The piezoelectric layer 67 includes the series arm resonator connected closest to the one end of the one or more acoustic wave resonators, and the piezoelectric layer 67 that constitutes the series arm resonator has all the bulk acoustic wave resonators included in the filter 11. It may be characterized by being thicker than any of the piezoelectric layers 67 that make up the child.

According to this, the anti-resonance frequency fa1 of the series arm resonator of the elastic wave filter 21A is located within the passband of the filter 11 or on the lower frequency side than the passband. Therefore, it is possible to obtain the same effect as the multiplexer according to the first embodiment.

(Embodiment 2)
[2.1 Circuit Configuration of Multiplexer 2]
FIG. 6 is a circuit diagram of the multiplexer 2 according to the second embodiment. As shown in the figure, the multiplexer 2 includes filters 11, 12, 21, 31 and 32, an inductor 41, an antenna connection terminal 90, common terminals 91, 92 and 93, and input terminals 110, 210 and 310. , and output terminals 120 and 320 . Multiplexer 2 according to the present embodiment has filters 31 and 32, inductor 41, common terminals 92 and 93, input terminal 310, and output terminal 320 added, compared to multiplexer 1 according to the first embodiment. Points are different. Hereinafter, regarding the multiplexer 2 according to the present embodiment, the description of the same configuration as that of the multiplexer 1 according to the first embodiment will be omitted, and the different configuration will be mainly described.

The common terminal 91 is an example of a first common terminal, and is connected to the output end of the filter 11, the input end of the filter 12, the output end of the filter 21, and one end of the inductor 41.

The common terminal 93 is an example of a second common terminal and is connected to the other end of the inductor 41 and the common terminal 92 .

The filter 31 is an example of a third acoustic wave filter, and has a passband (third passband) including the band C transmission band. One end (output end) of the filter 31 is connected to the common terminal 92, and the other end (input end) is connected to the input terminal 310 (third input/output terminal).

The filter 32 has a passband including the band C reception band. One end (input end) of the filter 32 is connected to the common terminal 92 and the other end (output end) is connected to the output terminal 320 .

The inductor 41 is an example of an inductance element, and has one end connected to a common terminal 91 and the other end connected to a common terminal 93 .

The one or more elastic wave resonators of the filter 21 are arranged on a series arm path connecting the common terminal 91 and the input terminal 210, and are connected closest to the common terminal 91 among the one or more elastic wave resonators. including a series arm resonator. The anti-resonance frequency fa1 of the series arm resonator is equal to or lower than the frequency of the high frequency end of the first passband.

The transmission band of band B is higher in frequency than the transmission band and reception band of band A and lower in frequency than the transmission band and reception band of band C.

In addition, for example, Band 3 of LTE is applied as band A, Band 1 of LTE is applied as band B, and Band 7 of LTE is applied as band C (transmission band: 2500-2570 MHz, reception band : 2620-2690 MHz) applies.

In addition, in the multiplexer 2 according to the present embodiment, one of the filters 11 and 12 may be omitted, and one of the filters 31 and 32 may be omitted. Filters other than filters 11 , 12 , 21 , 31 and 32 may be connected to common terminal 91 or 92 .

Also, the antenna connection terminal 90, the input terminals 110, 210 and 310, the output terminals 120 and 320, and the common terminals 91, 92 and 93 may not be included in the multiplexer 2.

[2.2 Characteristics of Multiplexer 2]
Hereinafter, the impedance characteristics and pass characteristics of the multiplexer 2 according to the present embodiment will be described while comparing the multiplexers of Example 2 and Comparative Example 2. FIG.

The multiplexer according to Example 2 is an example of the multiplexer 2 according to this embodiment. The multiplexer according to Comparative Example 2 is not included in the multiplexers according to this embodiment.

As shown in FIG. 6, the multiplexer according to the second embodiment includes an acoustic wave filter 21A (filter 21), filters 11, 12, 31 and 32, an inductor 41, an antenna connection terminal 90, common terminals 91 and 92 and 93, input terminals 110, 210 and 310, and output terminals 120 and 320, and is the opposite of the series arm resonator 101 connected closest to the common terminal 91 among the elastic wave resonators of the elastic wave filter 21A. The resonance frequency fa1 is located within the passband (A-Tx) of the filter 11. FIG. Among the filters 11, 12, 31, 32 and the acoustic wave filter 21A, the passband of the filter 11 is located on the lowest frequency side, and the passband of the filter 32 is located on the highest frequency side.

On the other hand, the multiplexer according to Comparative Example 2 has a circuit configuration similar to that of the multiplexer according to Example 2. is located on the high frequency side of the low end of the passband (B-Tx) of the elastic wave filter 21A.

FIG. 7A shows the impedance characteristics (admittance characteristics) of the passband (A-Tx) viewed from the common terminal 91 when the filters 11 and 12 and the acoustic wave filter 21A (filter 21) are commonly connected, in Example 2 and for comparison. 2 is a Smith chart compared in Example 2; FIG. 7B shows the impedance characteristics (admittance characteristics) of the passband (A−Rx) viewed from the common terminal 91 when the filters 11 and 12 and the elastic wave filter 21A (filter 21) are commonly connected. and a Smith chart compared in Comparative Example 2. FIG. 7C shows the impedance characteristics (admittance characteristics) of the passband (B-Tx) viewed from the common terminal 91 when the filters 11 and 12 and the elastic wave filter 21A (filter 21) are commonly connected. and a Smith chart compared in Comparative Example 2. FIG. 7D shows the impedance characteristics (admittance characteristics) of the passband (C-Tx) viewed from the common terminal 91 when the filters 11 and 12 and the elastic wave filter 21A (filter 21) are commonly connected. and a Smith chart compared in Comparative Example 2. FIG. 7E shows the impedance characteristics (admittance characteristics) of the passband (C-Rx) viewed from the common terminal 91 when the filters 11 and 12 and the acoustic wave filter 21A (filter 21) are connected in common. and a Smith chart compared in Comparative Example 2.

In the first embodiment, since the anti-resonance frequency fa1 of the series arm resonator of the elastic wave filter 21A is positioned within the passband (A-Tx), the impedance ( admittance) shifted in the open direction with respect to Comparative Example 1. In other words, the susceptance of the elastic wave filter 21A shifted to a smaller direction. The lower the susceptance, the lower the capacitiveness.

From this, as shown in FIG. 7A, even when the filters 11 and 12 and the elastic wave filter 21A are connected to the common terminal 91, the impedance (admittance) of the passband (A-Tx) is , the capacitiveness shifts to a direction smaller than that of . Further, as shown in FIG. 7B, even when the filters 11 and 12 and the elastic wave filter 21A are connected to the common terminal 91, the impedance (admittance) of the passband (A-Rx) is It shifts in the direction of smaller capacitiveness.

As shown in FIG. 7C, when the filters 11 and 12 and the elastic wave filter 21A are connected to the common terminal 91, the capacitive series arm resonators are arranged in series in the elastic wave filter 21A. , the impedance (admittance) of the passband (B-Tx) shifts in the direction in which the capacitiveness is slightly larger than that of the second comparative example.

7D and 7E, when the filters 11 and 12 and the elastic wave filter 21A are connected to the common terminal 91, the impedance (C-Tx) and the passband (C-Rx) of the passband (C-Rx) The admittance) is not affected by the frequency arrangement of the series arm resonators of the elastic wave filter 21A, so it is not substantially shifted as compared with the second comparative example.

FIG. 8A shows the impedance characteristics (admittance characteristics) of the passband (A-Tx) viewed from the common terminal 93 when the inductor 41, the filters 11 and 12, and the acoustic wave filter 21A are commonly connected, in Example 2 and Comparative Example. 2 is a Smith chart for comparison. Further, FIG. 8B shows the impedance characteristics (admittance characteristics) of the passband (A-Rx) viewed from the common terminal 93 when the inductor 41, the filters 11 and 12, and the acoustic wave filter 21A are commonly connected, in the second embodiment and the 6 is a Smith chart compared in Comparative Example 2. FIG. Further, FIG. 8C shows the impedance characteristics (admittance characteristics) of the passband (B-Tx) viewed from the common terminal 93 when the inductor 41, the filters 11 and 12, and the elastic wave filter 21A are commonly connected. 6 is a Smith chart compared in Comparative Example 2. FIG. FIG. 8D shows the impedance characteristics (admittance characteristics) of the passband (C-Tx) viewed from the common terminal 93 when the inductor 41, the filters 11 and 12, and the acoustic wave filter 21A are connected in common. 6 is a Smith chart compared in Comparative Example 2. FIG. FIG. 8E shows the impedance characteristics (admittance characteristics) of the passband (C-Rx) viewed from the common terminal 93 when the inductor 41, the filters 11 and 12, and the acoustic wave filter 21A are connected in common. 6 is a Smith chart compared in Comparative Example 2. FIG.

As shown in FIGS. 8A to 8C, when the filters 11 and 12 and the acoustic wave filter 21A are connected at the common terminal 91, the admittance of the band (A-Tx, A-Rx, B-Tx) is equal conductance of 50 Ω An inductor 41 is connected so as to ride on (the inductive side of) the circle. At this time, in Example 2, compared to Comparative Example 2, the filters 11 and 12 and the elastic wave filter 21A, which are commonly connected to each other, are positioned at a position where the admittance when viewed from the common terminal 91 is small in capacitiveness (Fig. 7A and 7B). Therefore, as shown in FIGS. 8A and 8B, in order to shift the admittance to (the inductive side of) the equal conductance circle of 50Ω, the inductance value of the inductor 41 in Example 2 is higher than that in Comparative Example 2. growing.

Due to the magnitude of this inductance value, as shown in FIGS. 8D and 8E, the impedance of the passband (C-Tx and C-Rx) when looking at the filters 11, 12 and the acoustic wave filter 21A from the common terminal 93 is , the second embodiment is closer to the open point than the second comparative example.

FIG. 9 is a graph comparing the conductance characteristics seen from the common terminal 93 when the inductor 41, the filters 11 and 12, and the acoustic wave filter 21A are commonly connected between Example 2 and Comparative Example 2. FIG. As shown in the figure, when the filters 11 and 12 and the elastic wave filter 21A are commonly connected, the conductance of the passband (C-Tx and C-Rx) seen from the common terminal 93 is compared in the second embodiment. It is smaller than Example 2. As a result, when inductor 41, filters 11 and 12, acoustic wave filter 21A, and filters 31 and 32 are connected at common terminal 93, the insertion loss in the passband of each filter can be reduced.

FIG. 10 is a Smith chart comparing the impedance characteristics seen from the common terminal 93 of the multiplexers according to Example 2 and Comparative Example 2 in Example 2 and Comparative Example 2. FIG. Specifically, FIG. 10(a) shows the impedance characteristics of the passband (A-Tx), and FIG. 10(b) shows the impedance characteristics of the passband (A-Rx). (c) of FIG. 10 shows the impedance characteristics of the passband (B-Tx), (d) of FIG. 10 shows the impedance characteristics of the passband (C-Tx), and (e) of FIG. shows the impedance characteristics of the passband (C-Rx). It can be seen that by commonly connecting the five filters at the common terminal 93, the impedance of any passband is matched to approximately 50Ω.

FIG. 11A is a graph showing pass characteristics of the filter 12 (A-Rx) of the multiplexer according to Example 2 and Comparative Example 2. FIG. 11B is a graph showing pass characteristics of the filter 31 (C-Tx) of the multiplexer according to Example 2 and Comparative Example 2. FIG. 11C is a graph showing pass characteristics of the filter 32 (C-Rx) of the multiplexer according to Example 2 and Comparative Example 2. FIG. In the filters 12, 31 and 32, the insertion loss in the passband is reduced in the second embodiment compared to the second comparative example.

[3 Effects, etc.]
As described above, the multiplexer 1 according to the first embodiment and the multiplexer 2 according to the second embodiment include the filter 11 having the first passband and the filter having the second passband higher in frequency than the first passband. 21, one end of the filter 11 and one end of the filter 21 are connected, the filter 21 has one or more elastic wave resonators, and the one or more elastic wave resonators are connected to the one end of the filter 21 A series arm resonator arranged on a series arm path connecting with the other end and connected closest to the one end among the one or more elastic wave resonators, and the antiresonance frequency fa1 of the series arm resonator is , below the frequency of the high frequency end of the first passband.

According to this, the series arm resonator has a small capacitance or a large inductance near the anti-resonance frequency fa1. In the filter 21, the anti-resonance frequency fa1 is positioned within the passband (A-Tx) of the filter 11 or on the low frequency side, so that the passband (A-Tx) seen from the common terminal 91 side of the filter 21 alone is The impedance will be in the counterclockwise direction of the circle of equal resistance and located closer to the open point (smaller capacitance) or in the clockwise direction of the circle of equal resistance and located closer to the open point (larger inductance). . Positioning the impedance of the passband (A-Tx) in the single filter 21 on the open side of the equal resistance circle makes the conductance of the passband (A-Tx) in the single filter 21 smaller. are equivalent. Therefore, it is possible to reduce the so-called bundling loss when the filters 11 and 21 are connected to the common terminal 91, and to provide a multiplexer in which the insertion loss within the passband of each filter is reduced.

Also, for example, in multiplexers 1 and 2, the anti-resonance frequency fa1 of the series arm resonator may be located within the first passband.

According to this, in the filter 21, the anti-resonance frequency fa1 is positioned within the first passband of the filter 11, so the impedance of the first passband viewed from the common terminal 91 side of the filter 21 alone is closer to the open point. will come closer. Therefore, the so-called bundling loss when the filters 11 and 21 are connected to the common terminal 91 can be further reduced.

Further, for example, the multiplexers 1 and 2 further include one or more acoustic wave filters connected to one end of the filter 11 and one end of the filter 21, and the passbands of the filters 11 and 21 and the one or more acoustic wave filters Among them, the first passband of the filter 11 may be located on the lowest frequency side.

Also, for example, in the multiplexers 1 and 2, the second passband of the filter 21 may be located on the highest frequency side among the passbands of the filters 11 and 21 and the one or more elastic wave filters.

Further, for example, the multiplexers 1 and 2 further include a common terminal 91 connected to one end of the filter 11 and one end of the filter 21, an input terminal 110 connected to the other end of the filter 11, and the other end of the filter 21. and an input terminal 210 .

For example, the multiplexer 2 further includes a filter 31 having a third passband higher in frequency than the second passband, and an inductor 41. One end of the inductor 41 is connected to one end of the filter 11 and one end of the filter 21. , and the other end of the inductor 41 may be connected to one end of the filter 31 .

According to this, when the filters 11 and 21 are connected to the common terminal 91 by the inductor 41, the admittances of the first passband and the second passband are arranged on (the inductive side of) the 50Ω isoconductance circle. , but since the admittance seen from the common terminal 91 of the common-connected filters 11 and 21 is located at a small capacitive position, the admittance is shifted to (the inductive side of) the 50Ω isoconductance circle. The inductance value of the inductor 41 for is larger. As this inductance value increases, the impedance (admittance) of the third passband viewed from common terminal 93 to filters 11 and 21 approaches the open point (has small conductance). Therefore, when the inductor 41 and the filters 11, 21 and 31 are connected at the common terminal 93, the insertion loss in the passband of each filter can be reduced.

Also, for example, the multiplexer 2 may further include a common terminal 93 connected to the other end of the inductor 41 and one end of the filter 31 , and an input terminal 310 connected to the other end of the filter 31 .

Further, the multiplexer according to Modification 1 includes a filter 11 having a first passband and a filter 21 having a second passband higher in frequency than the first passband, and each of the filters 11 and 21 One end of the filter 11 and one end of the filter 21 are connected, the filter 21 has one or more surface acoustic wave resonators, and the one or more surface acoustic wave The resonator is arranged on a series arm path connecting the one end and the other end of the filter 21, and includes a series arm resonator connected closest to the one end among the one or more surface acoustic wave resonators, The electrode finger pitch of the IDT electrodes forming the series arm resonator is greater than the electrode finger pitches of the IDT electrodes forming all the surface acoustic wave resonators included in the filter 11 .

According to this, in the filter 21, the antiresonance frequency fa1 is positioned within the passband (A-Tx) of the filter 11 or on the low frequency side, and the passband ( A-Tx) is either in the counterclockwise direction of the equal resistance circle and located closer to the open point (low capacitance) or in the clockwise direction of the equal resistance circle and located closer to the open point (inductance large). Therefore, it is possible to reduce the so-called bundling loss when the filters 11 and 21 are connected to the common terminal 91, and to provide a multiplexer in which the insertion loss within the passband of each filter is reduced.

Further, the multiplexer according to Modification 2 includes a filter 11 having a first passband and a filter 21 having a second passband having a higher frequency than the first passband, and each of the filters 11 and 21 A bulk acoustic wave having a support substrate 65, a lower electrode 66 and an upper electrode 68 formed on one surface of the support substrate 65, and a piezoelectric layer 67 formed between the lower electrode 66 and the upper electrode 68. One end of the filter 11 and one end of the filter 21 are connected, the filter 21 has one or more bulk acoustic wave resonators, and the one or more bulk acoustic wave resonators of the filter 21 A series arm resonator arranged on a series arm path connecting the one end and the other end and connected closest to the one end among the one or more bulk acoustic wave resonators, constituting the series arm resonator. The piezoelectric layer 67 is thicker than any of the piezoelectric layers 67 forming all the bulk acoustic wave resonators included in the filter 11 .

According to this, in the filter 21, the antiresonance frequency fa1 is positioned within the passband (A-Tx) of the filter 11 or on the low frequency side, and the passband ( A-Tx) is either in the counterclockwise direction of the equal resistance circle and located closer to the open point (low capacitance) or in the clockwise direction of the equal resistance circle and located closer to the open point (inductance large). Therefore, it is possible to reduce the so-called bundling loss when the filters 11 and 21 are connected to the common terminal 91, and to provide a multiplexer in which the insertion loss within the passband of each filter is reduced.

(Other embodiments)
Although the multiplexer according to the present invention has been described above with reference to the embodiments, examples, and modifications, the present invention is not limited to the above-described embodiments, examples, and modifications. Modifications that can be made by those skilled in the art without departing from the scope of the present invention with respect to the above-described embodiments, examples, and modifications, and various devices incorporating the multiplexer according to the present invention. include.

Also, for example, in the multiplexers according to the above-described embodiments, examples, and modifications, matching elements such as inductors and capacitors, and switch circuits may be connected between the constituent elements. Note that the inductor may include a wiring inductor that is a wiring that connects each component.

Note that the resonance frequency fr1 and the antiresonance frequency fa1 shown in the above embodiments, examples, and modifications are obtained, for example, by contacting an RF probe to the two input/output electrodes of the elastic wave resonator to measure the reflection characteristics. It is derived by

The present invention can be widely used in communication equipment such as mobile phones as a low-loss multiplexer applicable to multi-band and multi-mode frequency standards.

Reference Signs List 1, 2 Multiplexer 11, 12, 21, 31, 32 Filter 21A, 21B Acoustic wave filter 41, 161 Inductor 50 Substrate 51 High acoustic velocity support substrate 52 Low acoustic velocity film 53 Piezoelectric film 54 IDT electrode 55, 58 Protective layer 57 Piezoelectric single crystal Substrate 60 Acoustic wave resonators 60a, 60b Comb electrodes 61a, 61b Electrode fingers 62a, 62b Busbar electrodes 65 Supporting substrate 66 Lower electrode 67 Piezoelectric layer 68 Upper electrode 90 Antenna connection terminal 91, 92, 93 Common terminal 101, 102, 103 , 104, 105, 201, 202 series arm resonators 110, 210, 310 input terminals 120, 320 output terminals 151, 152, 153, 154, 251, 253 parallel arm resonators 203 longitudinal coupling filter section 540 adhesion layer 542 main electrode layer

Claims (9)

1. a first acoustic wave filter having a first passband;
   a second acoustic wave filter having a second passband having a higher frequency than the first passband,
   one end of the first elastic wave filter and one end of the second elastic wave filter are connected,
   The second elastic wave filter has one or more elastic wave resonators,
   The one or more elastic wave resonators are arranged on a series arm path connecting the one end and the other end of the second elastic wave filter, and are connected closest to the one end among the one or more elastic wave resonators. including a series arm resonator with
   The anti-resonance frequency of the series arm resonator is equal to or lower than the frequency of the high frequency end of the first passband.
   multiplexer.
2. an anti-resonance frequency of the series arm resonator is located within the first passband;
   A multiplexer according to claim 1.
3. moreover,
   One or more elastic wave filters connected to the one end of the first elastic wave filter and the one end of the second elastic wave filter,
   Among the passbands of the first elastic wave filter, the second elastic wave filter, and the one or more elastic wave filters, the first passband of the first elastic wave filter is located on the lowest frequency side,
   3. Multiplexer according to claim 1 or 2.
4. Among the passbands of the first elastic wave filter, the second elastic wave filter, and the one or more elastic wave filters, the second passband of the second elastic wave filter is located on the highest frequency side,
   4. A multiplexer as claimed in claim 3.
5. moreover,
   a first common terminal connected to the one end of the first elastic wave filter and the one end of the second elastic wave filter;
   a first input/output terminal connected to the other end of the first acoustic wave filter;
   a second input/output terminal connected to the other end of the second elastic wave filter;
   A multiplexer according to any one of claims 1-4.
6. moreover,
   a third elastic wave filter having a third passband having a higher frequency than the second passband;
   and an inductance element,
   one end of the inductance element is connected to the one end of the first elastic wave filter and the one end of the second elastic wave filter;
   The other end of the inductance element is connected to one end of the third acoustic wave filter,
   A multiplexer according to any one of claims 1-5.
7. moreover,
   a second common terminal connected to the other end of the inductance element and the one end of the third elastic wave filter;
   a third input/output terminal connected to the other end of the third acoustic wave filter;
   7. Multiplexer according to claim 6.
8. a first acoustic wave filter having a first passband;
   a second acoustic wave filter having a second passband having a higher frequency than the first passband,
   Each of the first elastic wave filter and the second elastic wave filter is composed of a surface acoustic wave resonator having an IDT (InterDigital Transducer) electrode,
   one end of the first elastic wave filter and one end of the second elastic wave filter are connected,
   The second acoustic wave filter has one or more surface acoustic wave resonators,
   The one or more surface acoustic wave resonators are arranged on a series arm path connecting the one end and the other end of the second acoustic wave filter, and the one or more surface acoustic wave resonators are closest to the one end. including closely connected series arm resonators,
   The electrode finger pitch of the IDT electrodes forming the series arm resonator is greater than any of the electrode finger pitches of the IDT electrodes forming all the surface acoustic wave resonators included in the first acoustic wave filter.
   multiplexer.
9. a first acoustic wave filter having a first passband;
   a second acoustic wave filter having a second passband having a higher frequency than the first passband,
   Each of the first elastic wave filter and the second elastic wave filter,
   A bulk acoustic wave including a support substrate, a first electrode and a second electrode formed on one surface of the support substrate, and a piezoelectric layer formed between the first electrode and the second electrode. Consists of a resonator,
   one end of the first elastic wave filter and one end of the second elastic wave filter are connected,
   The second elastic wave filter has one or more bulk acoustic wave resonators,
   The one or more bulk acoustic wave resonators are arranged on a series arm path connecting the one end and the other end of the second second filter, and the one or more bulk acoustic wave resonators are closest to the one end. including closely connected series arm resonators,
   The piezoelectric layer forming the series arm resonator is thicker than any of the piezoelectric layers forming all the bulk acoustic wave resonators included in the first acoustic wave filter,
   multiplexer.

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