CN107634782B

CN107634782B - High-frequency front-end circuit and communication device

Info

Publication number: CN107634782B
Application number: CN201710573081.8A
Authority: CN
Inventors: 竹内壮央; 宫崎大辅; 奥田哲朗
Original assignee: Murata Manufacturing Co Ltd
Current assignee: Murata Manufacturing Co Ltd
Priority date: 2016-07-15
Filing date: 2017-07-14
Publication date: 2020-01-03
Anticipated expiration: 2037-07-14
Also published as: CN107634782A; JP2018019392A; JP6822299B2

Abstract

The invention provides a small-sized high-frequency front-end circuit capable of maintaining low-loss signal propagation characteristics even when a CA operation is performed. A high-frequency front-end circuit (1) is provided with: a first filter (11) having a first pass band and connected to the antenna common terminal (101); a second filter (12) connected to the antenna common terminal (101) and having a second pass band; a switch (21) having a common terminal (21c) and selection terminals (21a, 21b), the common terminal (21c) being connected to the first filter (11); and a third filter (13) connected to the selection terminal (21a) and disposed between the switch (21) and the input/output terminal (102), wherein the reflection coefficient in the second pass band when the first filter (11) is viewed solely from the antenna common terminal (101) side is greater than the reflection coefficient in the second pass band when the third filter (13) is viewed solely from the antenna common terminal (101) side.

Description

High-frequency front-end circuit and communication device

Technical Field

The invention relates to a high-frequency front-end circuit and a communication device.

Background

In recent years, it is desired to support a plurality of frequencies and radio systems (multi-band and multi-mode) with one terminal. In order to support multi-band and multi-mode front-end modules, it is required to perform high-speed processing on a plurality of transmission/reception signals without deteriorating the quality. It is particularly desired to perform carrier aggregation for simultaneously transmitting and receiving high-frequency signals of a plurality of frequency bands.

Patent document 1 discloses an RF system including an LB (low band) diversity antenna, an MB (mid band)/HB (high band) diversity antenna, and a diversity module (see fig. 6 of patent document 1). The diversity module includes a single-pole multi-throw switch connected to an MB/HB diversity antenna, a plurality of filters connected to the single-pole multi-throw switch, and an amplifier circuit connected to the plurality of filters. The plurality of filters respectively take each frequency band as a pass band. With this configuration, a Carrier Aggregation (CA) operation can be realized in which communication is performed using high-frequency signals of a plurality of frequency bands simultaneously.

Patent document 1: japanese patent laid-open publication No. 2015-208007

In the RF system described in patent document 1, when two or more filters are CA-operated, it is necessary to open the pass band of one filter and the pass band of the other filter. Thus, even when the CA operation is performed, one filter can propagate a high-frequency signal with low loss without being affected by the impedance of the other filter.

However, if there are a large number of combinations of frequency bands for CA operation, and there are a plurality of such combinations, the impedance of each filter needs to be adjusted for each combination of frequency bands, so that each filter design becomes complicated, and it is difficult to optimize the filter characteristics of all the filters. Further, the larger the number of combinations of frequency bands for CA operation, the larger the number of selection terminals of the single-pole multi-throw type switch, and the larger the single-pole multi-throw type switch.

Disclosure of Invention

The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a small-sized high-frequency front-end circuit and a communication device capable of maintaining low-loss signal propagation characteristics even when CA operation is performed.

In order to achieve the above object, a high-frequency front-end circuit according to one aspect of the present invention includes: an antenna common terminal connected to the antenna element; a first input/output terminal and a second input/output terminal; a first filter having a first terminal and a second terminal, the first filter having a first passband, the first terminal being connected to the antenna common terminal; a second filter connected to the antenna common terminal, disposed between the antenna common terminal and the second input/output terminal, and having a second passband different from the first passband; a switch having a common terminal and a plurality of selection terminals, the common terminal being connected to the second terminal; and a third filter connected to a first selection terminal of the plurality of selection terminals and disposed between the switch and the first input/output terminal, wherein a reflection coefficient in the second pass band when the first filter is viewed from the antenna common terminal side alone is larger than a reflection coefficient in the second pass band when the third filter is viewed from the antenna common terminal side alone.

In the case where the first filter and the second filter constituting the demultiplexing/multiplexing circuit are commonly connected to each other via the antenna common terminal, the insertion loss in the second pass band of the second filter is affected by the reflection characteristic observed from the antenna common terminal side of the first filter in addition to the insertion loss of the second filter alone. More specifically, the insertion loss in the second pass band of the second filter decreases as the reflection coefficient in the second pass band viewed from the common terminal side of the first filter increases.

According to the above configuration, the reflection coefficient in the second pass band of the first filter is larger than the reflection coefficient in the second pass band of the third filter. Here, since the third filter disposed at the subsequent stage of the first filter is given more importance to the filter pass characteristic and the attenuation characteristic than to the reflection characteristic, it is possible to realize a good pass characteristic between the first filter and the third filter. In other words, the insertion loss due to the first filter, the third filter, or both of the first filter and the third filter among the insertion loss in the second pass band of the second filter can be effectively reduced without disposing a switch between the antenna element and the first filter and the second filter, and therefore, a small-sized high-frequency front-end circuit capable of maintaining the signal propagation characteristic with low loss even when the CA operation is performed can be provided.

The first filter and the third filter may each include two or more elastic wave resonators, and a reflection coefficient in the second pass band when one or more elastic wave resonators arranged on the antenna common terminal side among the two or more elastic wave resonators constituting the first filter are viewed from the antenna common terminal side as a single body may be larger than a reflection coefficient in the second pass band when one or more elastic wave resonators arranged on the antenna common terminal side among the two or more elastic wave resonators constituting the third filter are viewed from the antenna common terminal side as a single body.

In a filter including a plurality of elastic wave resonators, the reflection coefficient of one elastic wave resonator closest to a common terminal is dominant for the reflection coefficient viewed from the common terminal side. This can effectively reduce the insertion loss due to the first filter, the third filter, or both of the insertion losses in the second pass band of the second filter.

At least one of the first filter and the third filter may have a ladder-type filter structure, and the one or more elastic wave resonators disposed on the antenna common terminal side may include at least one of a series-arm resonator and a parallel-arm resonator.

This makes it possible to reduce the insertion loss caused by the first filter, the third filter, or both of the insertion losses in the second pass band of the second filter while ensuring low loss factors of the first filter and the third filter.

At least one of the first filter and the third filter may have a longitudinal coupling type filter structure.

This makes it possible to adapt the first filter and the third filter to filter characteristics requiring attenuation enhancement or the like.

The second input/output terminal may be connected to a second amplifier circuit, and a filter circuit may not be provided between the second filter and the second amplifier circuit.

In the latter stage of the second filter, a plurality of filters corresponding to a plurality of frequency bands included in the second passband and narrower than the second passband are also generally arranged. However, it is not necessary to further arrange a filter circuit on a signal path in a frequency band where a filter characteristic higher than that of the second filter is not required, in other words, between the second filter and the second amplifier circuit. This enables further miniaturization of the high-frequency front-end circuit.

Further, the present invention may further include: a third input/output terminal; and a fourth filter connected to the antenna common terminal, disposed between the antenna common terminal and the third input/output terminal, and having a third pass band, wherein the first filter, the second filter, and the fourth filter constitute a triplexer, and the first pass band, the second pass band, and the third pass band are applied to a low band (LB: 698) 960MHz), a middle band (MBa: 1710-.

Thus, the first filter and the second filter can be applied to the triplexers corresponding to LB, MBa, and HBa. Therefore, a small high-frequency front-end circuit can be realized which can maintain low-loss signal propagation characteristics even when CA operation is performed in a configuration including triplexers corresponding to LB, MBa, and HBa.

Further, the present invention may further include: a third input/output terminal and a fourth input/output terminal; a fourth filter connected to the antenna common terminal, disposed between the antenna common terminal and the third input/output terminal, and having a third pass band; and a fifth filter connected to the antenna common terminal, disposed between the antenna common terminal and the fourth input/output terminal, and having a fourth pass band, wherein the first filter, the second filter, the fourth filter, and the fifth filter constitute a quadruple multiplexer, the first pass band, the second pass band, the third pass band, and the fourth pass band are applied to a low band (LB: 698 + 960MHz), a medium band (MBa: 1710-.

Thus, the first filter and the second filter can be applied to the quadplexers corresponding to LB, MBa, MHBa, and HBa. Therefore, a small high-frequency front-end circuit can be realized which can maintain low-loss signal propagation characteristics even when CA operation is performed in a configuration including quadruplers corresponding to LB, MBa, MHBa, and HBa.

Further, the present invention may further include: a third input/output terminal and a fourth input/output terminal; a fourth filter connected to the antenna common terminal, disposed between the antenna common terminal and the third input/output terminal, and having a third pass band; and a fifth filter connected to the antenna common terminal, disposed between the antenna common terminal and the fourth input/output terminal, and having a fourth passband, wherein the first, second, fourth, and fifth filters constitute a quadruple multiplexer, and the first, second, third, and fourth passbands are applied to a middle-low band (MLB: 1475.9-2025 MHz), a middle-high band (MBb: 2110-2200 MHz), a middle-high band (MHBa: 2300-2400 MHz or MHBb: 2300-2370 MHz), and a high band (HBb: 2496-2690 MHz), and the first passband is any one of the middle-low band, the middle-high band, and the high band.

Thus, the first filter and the second filter can be applied to quadplexers corresponding to MLB, MBb, MHBa, and HBb. Therefore, a small high-frequency front-end circuit can be realized that can maintain low-loss signal propagation characteristics even when CA operation is performed in a configuration including quadruplers corresponding to MLB, MB, MHB, and HB.

Further, the present invention may further include: a third input/output terminal and a fourth input/output terminal; a fourth filter connected to the antenna common terminal, disposed between the antenna common terminal and the third input/output terminal, and having a third pass band; and a fifth filter connected to the antenna common terminal and disposed between the antenna common terminal and the fourth input/output terminal, and has a fourth passband, the first filter, the second filter, the fourth filter, and the fifth filter constituting a quadruple multiplexer, the first pass band, the second pass band, the third pass band and the fourth pass band are applied to a middle-low frequency band (MLB: 1475.9-2025 MHz), a middle-high frequency band (MBb: 2110-2200 MHz), a middle-high frequency band (MHBa: 2300-2400 MHz or MHBb: 2300-2370 MHz), a high frequency band (HBb: 2496-2690 MHz), the first passband is any one of the middle-low band, the middle-high band, and the high-high band, the second passband is the middle-high band, the second filter and the second amplifier circuit are connected to each other through a signal path without a filter circuit.

Thus, the first filter and the second filter can be applied to quadplexers corresponding to MLB, MBb, MHBa, and HBb. In addition, when the pass characteristic of the band included in the MHBa is satisfied by the pass characteristic of the second filter, the filter circuit may not be disposed on the signal path of the band. Therefore, a more compact high-frequency front-end circuit can be realized that can maintain low-loss signal propagation characteristics even during CA operation in a configuration including quadruplers corresponding to MLB, MBb, MHBa, and HBb.

The signal path connecting the second filter and the second amplifier circuit may be a path for transmitting and receiving Band40a (reception Band: 2300 minus 2370 MHz).

Thus, since the pass characteristic of Band40a included in MHBa is satisfied by the pass characteristic of the second filter, the filter circuit may not be arranged on the signal path of Band40 a. Therefore, a more compact high-frequency front-end circuit can be realized that can maintain low-loss signal propagation characteristics even during CA operation in a configuration including quadruplers corresponding to MLB, MBb, MHBa, and HBb.

The signal path connecting the second filter and the second amplifier circuit may be a path for transmitting and receiving a signal in Band40 (reception Band: 2300-2400 MHz).

Thus, since the pass characteristic of Band40 included in MHBa is satisfied by the pass characteristic of the second filter, the filter circuit need not be arranged on the signal path of Band 40. Therefore, a more compact high-frequency front-end circuit can be realized that can maintain low-loss signal propagation characteristics even during CA operation in a configuration including quadruplers corresponding to MLB, MBb, MHBa, and HBb.

Further, the present invention may further include: a third input/output terminal and a fourth input/output terminal; a fourth filter connected to the antenna common terminal, disposed between the antenna common terminal and the third input/output terminal, and having a third pass band; and a fifth filter connected to the antenna common terminal and disposed between the antenna common terminal and the fourth input/output terminal, and has a fourth passband, the first filter, the second filter, the fourth filter, and the fifth filter constituting a quadruple multiplexer, the first pass band, the second pass band, the third pass band and the fourth pass band are applied to a middle-low frequency band (MLB: 1475.9-2025 MHz), a middle-high frequency band (MBb: 2110-2200 MHz), a middle-high frequency band (MHBa: 2300-2400 MHz or MHBb: 2300-2370 MHz), a high frequency band (HBb: 2496-2690 MHz), the first passband is any one of the middle-low band, the middle-high band, and the middle-high band, the second passband is the high band, the second filter and the second amplifier circuit are connected to each other through a signal path without a filter circuit.

Thus, the first filter and the second filter can be applied to quadplexers corresponding to MLB, MBb, MHBa, and HBb. In addition, when the pass characteristic of the band included in HBb is satisfied by the pass characteristic of the second filter, the filter circuit may not be disposed on the signal path of the band. Therefore, a more compact high-frequency front-end circuit can be realized that can maintain low-loss signal propagation characteristics even during CA operation in a configuration including quadruplers corresponding to MLB, MBb, MHBa, and HBb.

The signal path connecting the second filter and the second amplifier circuit may be a path for transmitting and receiving Band41 (reception Band: 2496-2690 MHz).

Thus, since the pass characteristic of Band41 included in HBb is satisfied by the pass characteristic of the second filter, a filter circuit need not be provided in the signal path of Band 41. Therefore, a more compact high-frequency front-end circuit can be realized that can maintain low-loss signal propagation characteristics even during CA operation in a configuration including quadruplers corresponding to MLB, MBb, MHBa, and HBb.

In addition, the first passband may be located on a higher frequency side than the second passband, the first filter and the third filter may each include one or more elastic wave resonators, the one or more elastic wave resonators constituting the first filter may each be a surface acoustic wave resonator including a substrate having a piezoelectric layer and an IDT electrode formed on the substrate, and any one of the following may be used as a surface acoustic wave in the first filter: (1) in the presence of LiNbO₃A rayleigh wave propagating through the piezoelectric layer; (2) in the field of chemical synthesis of LiTaO₃A leakage wave propagating through the piezoelectric layer; and (3) a polymer prepared from LiNbO₃And a love wave propagating through the piezoelectric layer.

The reflection loss in a lower frequency range than the resonance point and anti-resonance point of the elastic wave resonator is used in the case of LiNbO₃Rayleigh waves propagating through the structured piezoelectric layer are guided by LiTaO₃Leakage wave propagating in the piezoelectric layer and leakage wave propagating in the LiNbO₃When any one of the love waves propagating through the piezoelectric layer is a surface acoustic wave, the surface acoustic wave is smaller than when another elastic wave is used.

Therefore, when the first filter is a high-frequency side filter and the second filter is a low-frequency side filter, the reflection coefficient in the second pass band of the first filter can be made larger than the reflection coefficient in the second pass band of the third filter. This can reduce the insertion loss due to the first filter, the third filter, or both of the insertion losses in the second pass band of the second filter.

In the third filter, the elastic wave Resonator may be formed of an SMR (solid Mounted Resonator) or an FBAR (Film Bulk Acoustic Resonator).

This increases the reflection coefficient of the first filter, and ensures the low loss factor and the pass band gradient of the third filter.

In addition, the first passband may be located on a higher frequency side than the second passband, each of the first filter and the third filter may include one or more elastic wave resonators, each of the one or more elastic wave resonators constituting the first filter may be a surface acoustic wave resonator including a substrate having a piezoelectric layer and an IDT electrode formed on the substrate, and the elastic wave resonator in the first filter may have a sonic velocity laminated film structure including the piezoelectric layer having the IDT electrode formed on one main surface, a high sonic velocity support substrate having a sonic velocity higher than that of an elastic wave propagating through the piezoelectric layer, and a low sonic velocity film disposed between the high sonic velocity support substrate and the piezoelectric layer and having a sonic velocity lower than that of an elastic wave propagating through the piezoelectric layer, in the third filter, the elastic wave resonator is formed of an SMR or an FBAR.

The reflection coefficient in the low frequency range from the resonance point and anti-resonance point of the acoustic wave resonator is larger in the case of the acoustic velocity film laminated structure than in the case of the acoustic wave resonator composed of the SMR or FBAR.

Therefore, when the first filter is a high-frequency side filter and the second filter is a low-frequency side filter, the reflection coefficient in the second pass band of the first filter can be made larger than the reflection coefficient in the second pass band of the third filter. This can reduce the insertion loss due to the first filter, the third filter, or both of the insertion losses in the second pass band of the second filter. In addition, it is possible to increase the reflection coefficient of the first filter and secure the low loss factor of the third filter and the steepness of the pass band.

Further, the first passband may be located on a lower frequency side than the second passband, the first filter and the third filter may each include one or more elastic wave resonators, and the first filter may be configured such that: (1) is used in LiNbO₃Rayleigh waves propagating in the constituted piezoelectric layer are regarded as elastic surface waves; (2) the elastic wave resonator is composed of SMRs; and (3) bulletsThe radio wave resonator is constituted by an FBAR.

In a higher frequency range than the resonance point and anti-resonance point of the acoustic wave resonator, an unnecessary wave due to bulk wave leakage is generated, and the intensity of the unnecessary wave can be minimized in any one of the following cases: is used in LiNbO₃Rayleigh waves propagating in the constituted piezoelectric layer are regarded as elastic surface waves; the elastic wave resonator is formed by the SMR and the elastic wave resonator is formed by the FBAR.

Therefore, when the first filter is a low-frequency side filter and the second filter is a high-frequency side filter, the reflection coefficient in the second pass band of the first filter can be made larger than the reflection coefficient in the second pass band of the third filter. This can reduce the insertion loss due to the first filter, the third filter, or both of the insertion losses in the second pass band of the second filter.

In addition, in the third filter, any one of the following may be used: (1) an acoustic wave resonator having a sound velocity film laminated structure including a piezoelectric layer having an IDT electrode formed on one principal surface, a high-sound-velocity support substrate that has a higher bulk wave sound velocity than an acoustic wave sound velocity propagating through the piezoelectric layer, and a low-sound-velocity film that is disposed between the high-sound-velocity support substrate and the piezoelectric layer and has a lower bulk wave sound velocity than the acoustic wave sound velocity propagating through the piezoelectric layer; (2) is used in LiTaO₃The leakage wave propagating in the structured piezoelectric layer is regarded as a surface acoustic wave; and (3) is used in LiNbO₃The love wave propagating through the piezoelectric layer is formed as a surface acoustic wave.

This makes it possible to increase the reflection coefficient of the first filter, ensure low loss factor and good temperature characteristics of the third filter when the third filter has a sound velocity film laminated structure, and utilize LiNbO for the third filter₃When the generated love wave is a surface acoustic wave, a wide bandwidth of the third filter can be secured.

In addition, the first passband may be located on a lower frequency side than the second passbandThe first filter and the third filter each include one or more elastic wave resonators, the elastic wave resonators constituting the first filter and the third filter are surface acoustic wave resonators each including a substrate having a piezoelectric layer and an IDT electrode formed on the substrate, in the first filter, the acoustic wave resonator has a sound velocity film laminated structure including the piezoelectric layer having the IDT electrode formed on one main surface, a high sound velocity support substrate that has a high bulk sound velocity higher than a bulk sound velocity propagated through the piezoelectric layer, and a low sound velocity film that is disposed between the high sound velocity support substrate and the piezoelectric layer and has a low bulk sound velocity lower than the bulk sound velocity propagated through the piezoelectric layer, and (1) the acoustic wave resonator is formed of LiTaO.₃The leakage wave propagating through the piezoelectric layer is used as a surface acoustic wave or (2) as a surface acoustic wave₃The love wave propagating through the piezoelectric layer is formed as a surface acoustic wave.

In the high frequency range from the resonance point and anti-resonance point of the elastic wave resonator, unnecessary waves due to bulk wave leakage are generated, and when the acoustic velocity film laminated structure is employed, the intensity of the unnecessary waves can be higher than that of the unnecessary waves generated by the LiTaO₃Using LiNbO as a surface acoustic wave or₃The love wave of (2) is small as a surface acoustic wave.

Therefore, when the first filter is a low-frequency side filter and the second filter is a high-frequency side filter, the reflection coefficient in the second pass band of the first filter can be made larger than the reflection coefficient in the second pass band of the third filter. This can reduce the insertion loss due to the first filter, the third filter, or both of the insertion losses in the second pass band of the second filter. LiNbO is used as the third filter₃When the generated love wave is a surface acoustic wave, a wide bandwidth of the third filter can be secured.

In addition, the first passband may be located on a lower frequency side than the second passband, and the first filter and the second filter may be located on a lower frequency side than the second passbandThe three filters each include one or more elastic wave resonators, the elastic wave resonators constituting the first filter and the third filter are surface acoustic wave resonators each including a substrate having a piezoelectric layer and an IDT electrode formed on the substrate, and the first filter is used by the LiTaO₃The leakage wave propagating through the piezoelectric layer is used as a surface acoustic wave in the third filter, and is made of LiNbO₃The love wave propagating through the piezoelectric layer is formed as a surface acoustic wave.

In a range higher than the resonance point and anti-resonance point of the elastic wave resonator, an unnecessary wave due to bulk wave leakage is generated, and LiTaO is used₃The intensity of the unnecessary wave can be higher than that of a leakage wave of (2) when LiNbO is used as the surface acoustic wave₃The love wave of (2) is small as a surface acoustic wave.

Therefore, when the first filter is a low-frequency side filter and the second filter is a high-frequency side filter, the reflection coefficient in the second pass band of the first filter can be made larger than the reflection coefficient in the second pass band of the third filter. This can reduce the insertion loss due to the first filter, the third filter, or both of the insertion losses in the second pass band of the second filter. The third filter uses LiNbO₃When the generated love wave is a surface acoustic wave, a wide bandwidth of the third filter can be secured.

In addition, the first passband may be located on a higher frequency side than the second passband, the first filter and the third filter may each include one or more elastic wave resonators, and the first filter may be configured such that: (1) is used in LiNbO₃Rayleigh waves propagating in the constituted piezoelectric layer are regarded as elastic surface waves; (2) is used in LiTaO₃The leakage wave propagating in the structured piezoelectric layer is regarded as a surface acoustic wave; (3) is used in LiNbO₃The love wave propagating in the piezoelectric layer is used as an elastic surface wave; (4) the elastic wave resonator is composed of SMRs; and (5) the elastic wave resonator is formed of an FBAR, and the third element isIn the filter, the elastic wave resonator has a sound velocity film laminated structure including a piezoelectric layer having an IDT electrode formed on one principal surface, a high sound velocity support substrate that is higher in the sound velocity of a bulk wave propagated through the piezoelectric layer than the sound velocity of the elastic wave propagated through the piezoelectric layer, and a low sound velocity film that is disposed between the high sound velocity support substrate and the piezoelectric layer and is lower in the sound velocity of the bulk wave propagated through the piezoelectric layer than the sound velocity of the elastic wave propagated through the piezoelectric layer.

When the acoustic wave resonator has a sound velocity film laminated structure, a rayleigh wave noise is generated in the vicinity of 0.76 times the resonance frequency of the acoustic wave resonator. Therefore, by making the third filter have the sonic film laminated structure and making the first filter have no sonic film laminated structure, the reflection coefficient in the second pass band of the first filter can be increased while ensuring low loss factor and good temperature characteristics of the third filter.

Therefore, when the first filter is a high-frequency side filter and the second filter is a low-frequency side filter, the insertion loss of the second filter in the second pass band can be reduced by the first filter, the third filter, or both.

In addition, the first passband may be located on a higher frequency side than the second passband, the first filter and the third filter may each include one or more elastic wave resonators, and the first filter may be configured such that: (1) is used in LiNbO₃Rayleigh waves propagating in the constituted piezoelectric layer are regarded as elastic surface waves; (2) is used in LiNbO₃The love wave propagating in the piezoelectric layer is used as an elastic surface wave; (3) an acoustic wave resonator having a sound velocity film laminated structure including a piezoelectric layer having an IDT electrode formed on one principal surface, a high-sound-velocity support substrate that has a higher bulk wave sound velocity than an acoustic wave sound velocity propagating through the piezoelectric layer, and a low-sound-velocity film that is disposed between the high-sound-velocity support substrate and the piezoelectric layer and has a lower bulk wave sound velocity than the acoustic wave sound velocity propagating through the piezoelectric layer; (4) the elastic wave resonator is composed of SMRs;and (5) the elastic wave resonator is formed of FBAR, and the third filter is formed of LiTaO₃The leakage wave propagating through the piezoelectric layer is formed as a surface acoustic wave.

In the utilization of LiTaO₃When the leakage wave of (2) is an elastic wave, a rayleigh clutter occurs in the vicinity of 0.76 times the resonance frequency of the elastic wave resonator. Thus, by using LiTaO in the third filter₃The leakage wave of (2) is an elastic wave, and LiTaO is not used in the first filter₃The leakage wave of (2) can effectively increase the reflection coefficient in the second pass band of the first filter as an elastic wave.

Further, the first passband may be located on a lower frequency side than the second passband, the first filter and the third filter may each include one or more elastic wave resonators, and the first filter may be configured such that: (1) an acoustic wave resonator having a sound velocity film laminated structure including a piezoelectric layer having an IDT electrode formed on one principal surface, a high-sound-velocity support substrate that has a higher bulk wave sound velocity than an acoustic wave sound velocity propagating through the piezoelectric layer, and a low-sound-velocity film that is disposed between the high-sound-velocity support substrate and the piezoelectric layer and has a lower bulk wave sound velocity than the acoustic wave sound velocity propagating through the piezoelectric layer; (2) is used in LiTaO₃The leakage wave propagating in the structured piezoelectric layer is regarded as a surface acoustic wave; (3) is used in LiNbO₃The love wave propagating in the piezoelectric layer is used as an elastic surface wave; (4) the elastic wave resonator is composed of SMRs; and (5) the elastic wave resonator is formed of an FBAR, and the LiNbO is used for the third filter₃The rayleigh wave propagating through the structured piezoelectric layer is referred to as a surface acoustic wave.

In the utilization of LiNbO₃As an elastic waveNext, a higher order mode is generated in the vicinity of 1.2 times the resonance frequency of the elastic wave resonator. Therefore, by using LiNbO in the third filter₃The first filter does not use LiNbO as an elastic wave₃The rayleigh wave of (a) can be used as an elastic wave, and the reflection coefficient in the second pass band of the first filter can be effectively increased.

Therefore, when the first filter is a low-frequency side filter and the second filter is a high-frequency side filter, the insertion loss of the second filter in the second pass band can be reduced by the first filter, the third filter, or both.

Further, the first passband is located on a lower frequency side than the second passband, the first filter and the third filter each include one or more elastic wave resonators, and the first filter may be any one of: (1) is used in LiNbO₃Rayleigh waves propagating in the constituted piezoelectric layer are regarded as elastic surface waves; (2) an elastic wave resonator having a sound velocity film laminated structure including a piezoelectric layer having an IDT electrode formed on one principal surface, a high sound velocity support substrate that has a higher bulk sound velocity than an elastic wave sound velocity propagating through the piezoelectric layer, and a low sound velocity film that is disposed between the high sound velocity support substrate and the piezoelectric layer and has a lower bulk sound velocity than the elastic wave sound velocity propagating through the piezoelectric layer; (3) is used in LiTaO₃The leakage wave propagating in the structured piezoelectric layer is regarded as a surface acoustic wave; (4) the elastic wave resonator is composed of SMRs; and (5) the elastic wave resonator is formed of an FBAR, and the LiNbO is used for the third filter₃The love wave propagating through the piezoelectric layer is formed as a surface acoustic wave.

In the utilization of LiNbO₃When the love wave of (2) is an elastic wave, a higher-order mode is generated in the vicinity of 1.2 times the resonance frequency of the elastic wave resonator. Therefore, by using LiNbO in the third filter₃The first filter does not use LiNbO as an elastic wave₃The second pass of the first filter can be effectively enlarged as an elastic waveThe reflection coefficient in the band.

The two or more elastic wave resonators constituting the first filter and the third filter may be surface acoustic wave resonators each including a substrate having a piezoelectric layer and an IDT electrode formed on the substrate, and the first filter and the third filter may be formed of LiTaO₃The leakage wave propagating through the piezoelectric layer is made to be a surface acoustic wave, and the IDT electrode constituting the first filter and the IDT electrode constituting the third filter are different in film thickness or duty ratio.

In the utilization of LiTaO₃When the leakage wave of (2) is an elastic wave, a rayleigh clutter occurs on the low frequency side of the resonance frequency of the elastic wave resonator. In contrast, by making the film thickness or duty ratio of the IDT electrode different between the first filter and the third filter, the frequency of generation of rayleigh wave noise in the first filter can be shifted outside the second passband. This makes it possible to effectively increase the reflection coefficient in the second pass band of the first filter and reduce the insertion loss due to the first filter, the third filter, or both of the insertion losses in the second pass band of the second filter.

The two or more elastic wave resonators constituting the first filter and the third filter may be surface acoustic wave resonators each including a substrate having a piezoelectric layer and an IDT electrode formed on the substrate, and the elastic wave resonators in the first filter and the third filter may have a sound velocity film laminated structure including the piezoelectric layer having the IDT electrode formed on one main surface, a high sound velocity support substrate having a high sound velocity higher than a sound velocity of a bulk wave propagating through the piezoelectric layer, and a low sound velocity film arranged between the high sound velocity support substrate and the piezoelectric layer and having a low sound velocity lower than the sound velocity of the bulk wave propagating through the piezoelectric layer, and in the first filter and the third filter, the thickness of the IDT electrode may be equal to or greater than the thickness of the IDT electrode, The IDT electrode has a different duty ratio and a different film thickness.

In the case of using the sound velocity film laminated structure, a rayleigh wave clutter is generated on the low frequency side of the resonance frequency of the elastic wave resonator. In contrast, by making the film thickness or the duty ratio of the IDT electrode different between the first filter and the third filter, the frequency of generation of rayleigh wave noise in the first filter can be shifted outside the second passband. This makes it possible to effectively increase the reflection coefficient in the second pass band of the first filter and reduce the insertion loss due to the first filter, the third filter, or both of the insertion losses in the second pass band of the second filter.

The two or more acoustic wave resonators constituting the first filter and the third filter may be surface acoustic wave resonators each including a substrate having a piezoelectric layer, an IDT electrode formed on the substrate, and a protective film formed on the IDT electrode, and (1) LiNbO is used for the first filter and the third filter₃Rayleigh waves propagating through the piezoelectric layer, or (2) Rayleigh waves propagating through LiNbO₃The love wave propagating through the piezoelectric layer is a surface acoustic wave, and any one of the thickness of the IDT electrode, the duty ratio of the IDT electrode, and the thickness of the protective film is different between the first filter and the third filter.

In the utilization of LiNbO₃Rayleigh wave or LiNbO of₃When the love wave of (2) is a surface acoustic wave, a higher-order mode is generated on the high-frequency side of the resonance frequency of the elastic wave resonator. In contrast, in the first filter and the third filter, the frequency of the higher-order mode in the first filter can be shifted outside the second passband by making the thickness of the IDT electrode, the duty ratio of the IDT electrode, or the thickness of the low-speed film different. Thereby, the size of the device can be effectively increasedThe reflection coefficient in the second pass band of the first filter can reduce the insertion loss caused by the first filter, the third filter, or both of the insertion losses in the second pass band of the second filter.

In the first filter and the third filter, the elastic wave resonator may have a sound velocity film laminated structure including the piezoelectric layer having the IDT electrode formed on one main surface, a high sound velocity support substrate having a higher sound velocity than the sound velocity of the bulk wave propagating through the piezoelectric layer, and a low sound velocity film disposed between the high sound velocity support substrate and the piezoelectric layer and having a lower sound velocity than the sound velocity of the elastic wave propagating through the piezoelectric layer, the high sound velocity support substrate may be formed of a silicon crystal, and the first filter and the third filter may be formed of an elastic surface wave resonator including a substrate having a piezoelectric layer and an IDT electrode formed on the substrate, the piezoelectric layer has a film thickness, the low-sound-velocity film has a film thickness, and the high-sound-velocity support substrate has a silicon crystal orientation different from each other.

In the case of using the sonic film laminated structure, a higher-order mode is generated on the high-frequency side of the resonance frequency of the elastic wave resonator. In contrast, in the first filter and the third filter, the film thickness of the piezoelectric layer, the film thickness of the low-sound-velocity film, or the silicon crystal orientation of the high-sound-velocity support substrate are made different from each other, whereby the frequency of generation of the higher-order mode in the first filter can be shifted outside the second passband. This makes it possible to effectively increase the reflection coefficient in the second pass band of the first filter and reduce the insertion loss due to the first filter, the third filter, or both of the insertion losses in the second pass band of the second filter.

The two or more elastic wave resonators constituting the first filter and the third filter may be surface acoustic wave resonators each including a substrate having a piezoelectric layer and an IDT electrode formed on the substrate, and may be arranged above the substrateThe first filter and the third filter are based on the use of (1) LiTaO₃Leakage wave propagating through the piezoelectric layer, or (2) leakage wave propagating through LiNbO₃The love wave propagating through the piezoelectric layer is formed as a surface acoustic wave, and the IDT electrodes are different in film thickness between the first filter and the third filter.

In the utilization of LiTaO₃Leakage wave of (2) or LiNbO₃When the love wave of (2) is a surface acoustic wave, a bulk wave (unnecessary wave) is generated on the high frequency side of the resonance frequency of the acoustic wave resonator. In contrast, by making the thickness of the IDT electrode different between the first filter and the third filter, the frequency of generation of the bulk wave in the first filter can be shifted outside the second passband. This makes it possible to effectively increase or decrease the reflection coefficient in the second pass band of the first filter, and to decrease the insertion loss due to the first filter, the third filter, or both of the insertion losses in the second pass band of the second filter.

Further, the present invention may further include: a first amplifier circuit connected to the first input/output terminal; and a second amplifier circuit connected to the second input/output terminal.

In this way, in the high-frequency front-end circuit including the amplifier circuit, the insertion loss due to the first filter, the third filter, or both of the first filter and the third filter can be reduced in the insertion loss in the second pass band of the second filter.

A communication device according to an aspect of the present invention includes: an RF signal processing circuit that processes a high-frequency signal transmitted and received by the antenna element; and the high-frequency front-end circuit described above, which transmits the high-frequency signal between the antenna element and the RF signal processing circuit.

Thus, a small communication device can be provided which can reduce the insertion loss caused by the first filter, the third filter, or both of the insertion losses in the second pass band of the second filter.

According to the present invention, a small high-frequency front-end circuit or communication device that can reduce propagation loss of a high-frequency signal even when CA operation is performed can be provided.

Drawings

Fig. 1A is a circuit configuration diagram of a high-frequency front-end circuit according to embodiment 1.

Fig. 1B is a diagram illustrating reflection characteristics of the high-frequency front-end circuit according to embodiment 1.

Fig. 2 is a diagram illustrating a problem in the case where two filters are commonly connected via a common terminal.

Fig. 3A is a circuit configuration diagram of a demultiplexer circuit according to modification 1 of embodiment 1.

Fig. 3B is a circuit configuration diagram of a demultiplexer circuit according to modification 2 of embodiment 1.

Fig. 3C is a circuit configuration diagram of a demultiplexer circuit according to modification 3 of embodiment 1.

Fig. 4 is a circuit configuration diagram of a communication device according to modification 4 of embodiment 1.

Fig. 5A is a circuit configuration diagram of a high-frequency front-end circuit according to modification 5 of embodiment 1.

Fig. 5B is a circuit configuration diagram of the high-frequency front-end circuit according to modification 6 of embodiment 1.

Fig. 5C is a circuit configuration diagram of the high-frequency front-end circuit according to modification 7 of embodiment 1.

Fig. 5D is a circuit configuration diagram of the high-frequency front-end circuit according to modification 8 of embodiment 1.

Fig. 6 is an example schematically showing a plan view and a cross-sectional view of a filter resonator according to embodiment 2.

Fig. 7A is a diagram illustrating reflection characteristics in the low frequency region 1 of the high frequency front end circuit according to embodiment 2.

Fig. 7B is a diagram showing a combination of the configurations of the first filter and the third filter in embodiment 2.

Fig. 8A is a diagram illustrating bulk wave leakage in the high-frequency region 1 of the high-frequency front-end circuit according to variation 1 of embodiment 2.

Fig. 8B is a diagram showing a combination of the configurations of the first filter and the third filter in modification 1 of embodiment 2.

Fig. 9A is a diagram illustrating generation of a spurious in the low frequency region 2 of the high frequency front end circuit in modification 2 of embodiment 2.

Fig. 9B is a diagram showing a combination of the configurations of the first filter and the third filter in modification 2 of embodiment 2.

Fig. 10A is a diagram illustrating generation of a high-order mode in the high-frequency region 2 of the high-frequency front-end circuit according to variation 3 of embodiment 2.

Fig. 10B is a diagram showing a combination of the configurations of the first filter and the third filter in modification 3 of embodiment 2.

Fig. 11A is a diagram showing degradation of the reflection loss due to the higher-order mode of the first filter in embodiment 2.

Fig. 11B is a diagram showing parameters for differentiating the configurations of the first filter and the third filter in modification 4 of embodiment 2.

Fig. 11C is a diagram showing parameters for differentiating the configurations of the first filter and the third filter in modification 5 of embodiment 2.

Fig. 12 is a diagram showing parameters for differentiating the configurations of the first filter and the third filter in modification 6 of embodiment 2.

Fig. 13A is a circuit configuration diagram of the high-frequency front-end circuit according to embodiment 3.

Fig. 13B is a circuit configuration diagram of the high-frequency front-end circuit of the comparative example.

Detailed Description

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The embodiments described below are all general or specific examples. The numerical values, shapes, materials, constituent elements, arrangement and connection of constituent elements, and the like shown in the following embodiments are examples, and are not intended to limit the present invention. Among the components in the following embodiments, components not described in the independent claims are described as arbitrary components. The sizes of the components shown in the drawings and the ratio of the sizes are not necessarily strict.

(embodiment mode 1)

[1.1 Structure of high-frequency front-end Circuit ]

Fig. 1A is a circuit configuration diagram of the high-frequency front-end circuit 1 according to embodiment 1. As shown in the figure, the high-frequency front-end circuit 1 includes a first filter 11, a second filter 12, a third filter 13, a switch 21, an antenna common terminal 101, and input/

output terminals

102 and 103. The high-frequency front-end circuit 1 is a complex elastic wave filter device including a first filter 11 and a second filter 12 commonly connected to each other via an antenna common terminal 101.

The common terminal 101 can be connected to an antenna element, for example, and the input/

output terminals

102 and 103 can be connected to a high-frequency signal processing circuit via an amplifier circuit.

The first filter 11 is a filter having a first terminal connected to the antenna common terminal 101 and having a first pass band, and a second terminal.

The second filter 12 is connected to the antenna common terminal 101, is disposed between the antenna common terminal 101 and the input/output terminal 103, and has a second passband different from the first passband.

The first filter 11 and the second filter 12 constitute a demultiplexing/multiplexing circuit.

The switch 21 is a switch circuit having a common terminal 21c and selection terminals 21a (first selection terminals) and 21b, and the common terminal 21c is connected to the second terminal of the first filter 11.

The third filter 13 is connected to the selection terminal 21a (first selection terminal), and is disposed between the switch 21 and the input/output terminal 102.

Further, a filter having a different passband from the third filter may be connected to the selection terminal 21b (second selection terminal) of the switch 21, or an amplifier circuit may be directly connected thereto. The number of the selection terminals of the switch 21 may be 3 or more. The passband of the filter connected to the selection terminal 21b (second selection terminal) may overlap with the passband of the third filter. Even in this case, the high-frequency signal passing through the first filter 11 can be propagated by concentrating it to 1 path via the

selection terminal

21a or 21b by the switch 21.

The circuit configuration of the stage subsequent to the second filter 12 (on the opposite side of the antenna common terminal 101) may be the same as the circuit configuration of the stage subsequent to the first filter 11, or the second filter 12 and the amplifier circuit may be directly connected without disposing a switch.

Fig. 1B is a diagram illustrating reflection characteristics of the high-frequency front-end circuit 1 according to embodiment 1. In the figure, the transmission characteristics of the first filter 11 and the second filter 12 and the reflection characteristics of the first filter 11 and the third filter 13, which are commonly connected through the antenna common terminal 101, are shown. Here, in the high-frequency front-end circuit 1 of the present embodiment, the reflection coefficient in the pass band 12H (second pass band) when the first filter 11 is viewed from the antenna common terminal 101 side alone is larger than the reflection coefficient in the pass band 12H (second pass band) when the third filter 13 is viewed from the common terminal 101 side alone.

The frequency relationship between the first filter and the third filter is not limited to the case where the first filter 11 is on the low frequency side and the second filter is on the high frequency side as shown in fig. 1B, and the first filter 11 may be on the high frequency side and the second filter on the low frequency side.

[1.2 insertion loss reduction effect of the second filter by the first filter, the third filter, or both of the high-frequency front-end circuit ]

Fig. 2 is a diagram illustrating a problem in the case where two filters (filter a and filter B) are commonly connected via an antenna common terminal. As shown in fig. 2, it is assumed that a filter a (pass band a) and a filter B (pass band B) are branching circuits commonly connected through an antenna common terminal. The insertion loss of the demultiplexer in this case is considered.

The insertion loss of the pass band a in the filter a is deteriorated by the influence of the filter B in addition to the insertion loss of the filter a itself. Here, the insertion loss caused by the filter B among the insertion losses of the filter a is affected by the reflection characteristic in the pass band a of the filter B. More specifically, as for the insertion loss due to the filter B among the insertion losses of the filter a, the larger the reflection coefficient when the filter B is viewed from the antenna common terminal side in the preceding filter B commonly connected through the antenna common terminal is, the more the insertion loss due to the filter B among the insertion losses of the filter a decreases.

When the above-described configuration for reducing the insertion loss caused by the filter on the object side to be commonly connected is applied to the high-frequency front-end circuit 1 of the present embodiment, it is necessary to increase the reflection coefficient of the high-frequency signal of the second passband to be propagated from the antenna common terminal 101 to the input/output terminal 102 in order to allow the high-frequency signal of the second passband propagating from the antenna common terminal 101 to the input/output terminal 103 to pass through while suppressing the insertion loss caused by the filter on the object side to be commonly connected. In other words, in order to reduce the insertion loss caused by the first filter 11, the third filter 13, or both of the insertion losses in the second pass band of the second filter 12, it is necessary to increase the reflection coefficient in the second pass band when the first filter 11 and the third filter 13 connected in series are viewed from the antenna common terminal 101.

In addition, when a plurality of filters are connected in series, the filters close to the antenna common terminal among the filters connected in series have a high degree of contribution to the reflection coefficient when the filters connected in series are viewed from the antenna common terminal side. In other words, in order to reduce the insertion loss due to the filter on the common connection target side out of the insertion losses of the second filter 12, it is effective to increase the reflection coefficient in the second pass band of the first filter 11 close to the antenna common terminal 101 out of the first filter 11 and the third filter 13 connected in series.

On the other hand, it is necessary to improve the reflection characteristics of the first filter 11 and the third filter 13 connected in series as described above, and to ensure filter characteristics such as the pass characteristic, the attenuation characteristic, the temperature characteristic, and the bandwidth of the first filter 11 and the third filter 13 connected in series in accordance with required specifications or the like. Depending on the filter configuration, there are cases where both the reflection characteristic and the filter characteristic are not compatible.

From the above-described viewpoint, the inventors have found that, in the first filter 11 and the third filter 13 connected in series, the reflection coefficient is preferentially increased in the first filter 11 having a large influence on the reflection characteristic, and the filter characteristics such as the pass characteristic, the attenuation characteristic, the temperature characteristic, and the bandwidth are secured in the third filter 13 having a small influence on the reflection characteristic.

According to the configuration of the high-frequency front-end circuit 1 of the present embodiment, the reflection coefficient in the second pass band of the first filter 11 is larger than the reflection coefficient in the second pass band of the third filter 13. Here, since the third filter 13 disposed at the subsequent stage places more importance on the filter pass characteristic and the attenuation characteristic than on the reflection characteristic, the reflection coefficient in the second pass band when the first filter 11, the switch 21, and the third filter 13 are viewed from the antenna common terminal 101 side can be increased more effectively without deteriorating the filter characteristic of the third filter 13. Thus, the insertion loss due to the first filter 11, the third filter 13, or both of the first filter 11 and the third filter 13 in the insertion loss in the second pass band of the second filter 12 can be effectively reduced without arranging a switch between the antenna element and the splitting/combining circuit including the first filter 11 and the second filter 12, and therefore, a small-sized high-frequency front-end circuit 1 capable of maintaining low-loss signal propagation characteristics even during CA operation can be provided.

Further, the reflection coefficient in the second pass band of the first filter 11 is preferably 0.9 or more.

In the high-frequency front-end circuit 1 according to the present embodiment, the filters commonly connected to the antenna common terminal 101 are not limited to two filters, i.e., the first filter 11 and the second filter 12, and three or more filters may be commonly connected to the antenna common terminal 101.

[ Structure of wave splitting/combining circuit of 1.3 modification ]

Fig. 3A is a circuit configuration diagram of a demultiplexer circuit according to modification 1 of embodiment 1. In the figure, a circuit configuration of a triplexer applied to a wavelength division/multiplexing circuit of the high-frequency front-end circuit according to the present embodiment is illustrated.

The high-frequency front-end circuit of this modification includes, as a splitter/combiner circuit, LB (698-960 MHz) filters 11L, MBa (1710-2200 MHz) filters 11M1 and HBa (2300-2690 MHz) filters 11H1 connected to the antenna common terminal 101.

In other words, the high-frequency front-end circuit according to modification 1 includes a fourth filter having a third passband, which is connected to the antenna common terminal 101, in addition to the first filter 11 and the second filter 12. Here, the first filter 11 of embodiment 1 corresponds to any one of the LB filter 11L, MBa filter 11M1 and HBa filter 11H1 in the present modification.

Fig. 3B is a circuit configuration diagram of a demultiplexer circuit according to modification 2 of embodiment 1. In the figure, a circuit configuration of a quadruplex device applied to a wavelength division/multiplexing circuit of the high-frequency front-end circuit according to the present embodiment is illustrated.

The high-frequency front-end circuit of this modification is provided, as a splitter/combiner circuit, with an LB (low band: 698-.

In other words, the high-frequency front-end circuit according to modification 2 includes, in addition to the first filter 11 and the second filter 12, a fourth filter having a third passband and a fifth filter having a fourth passband, which are connected to the antenna common terminal 101. Here, the first filter 11 of embodiment 1 corresponds to any one of the LB filter 11L, MBa filter 11M1, the MHBa filter 11MH1, and the HBb filter 11H2 in the present modification.

Fig. 3C is a circuit configuration diagram of a demultiplexer circuit according to modification 3 of embodiment 1. In the figure, a circuit configuration of a quadruplex device applied to a wavelength division/multiplexing circuit of the high-frequency front-end circuit according to the present embodiment is illustrated.

The high-frequency front-end circuit of this modification is provided, as a branching/combining circuit, with an MLB (middle-low band: 1475.9-2025 MHz) filter 11L1, MBb (middle-low band: 2110-.

In other words, the high-frequency front-end circuit according to modification 3 includes, in addition to the first filter 11 and the second filter 12, a fourth filter having a third passband and a fifth filter having a fourth passband, which are connected to the antenna common terminal 101. Here, the first filter 11 of embodiment 1 corresponds to any one of the MLB filter 11L1, the MBb filter 11M2, the MHBa filter 11MH1, and the HBb filter 11H2 in the present modification.

[1.4 Structure of high-frequency front-end Circuit in modification 4 ]

Fig. 4 is a circuit configuration diagram of a communication device 3 according to modification 4 of embodiment 1. In the figure, a communication device 3 of the present embodiment is shown. The communication device 3 is constituted by the high-frequency front-end circuit 2 and the high-frequency signal processing circuit (RFIC)40 of modification 4.

The high-frequency front-end circuit 2 includes an antenna common terminal 101,

demultiplexer circuits

10 and 14, switches 21 and 22, a filter circuit 15, and an amplifier circuit 30.

The branching circuit 10 is connected to the antenna common terminal 101, and is composed of a low-pass filter 10A (pass band: 699-960 MHz) and a high-pass filter 10B (pass band: 1475.9-2690 MHz).

The branching circuit 14 is connected to the high-pass filter 10B and is composed of an MLB filter 11A (1475.9-2025 MHz), an MBb filter 11B (2110 + 2200MHz), an MHBa filter 11C (2300 + 2400MHz or 2300 + 2370MHz), and a HBb filter 11D (2496 + 2690 MHz).

The switch 21 is composed of

switches

21A, 21C, and 21D. The switch 22 is constituted by

switches

22A, 22B, 22C, and 22D.

The filter circuit 15 is constituted by

filters

13a, 13b, 13c, 13d, 13e, 13f, 13g, 13h, 13j, and 13 k.

The amplifier circuit is constituted by

LNAs

31, 32, 33, 34, 35, and 36.

The demultiplexing circuit 14 divides the frequency band of the high-frequency signal into 4 band groups. More specifically, the MLB filter 11A passes signals of Ba (band a), Bb (band B), Bc (band C), Bd (band D), and Be (band e), the MBb filter 11B passes signals of Bp (band p), the MHBa filter 11C passes signals of Bf (band f) and Bg (band g), and the HBb filter 11D passes signals of Bh (band h), Bj (band j), and Bk (band k).

The switch 21A has a common terminal connected to the MLB filter 11A, and select terminals connected to the filters 13a (ba), 13b (bb), 13c (bc), and 13d/13e (Bd/Be).

The switch 21C has a common terminal connected to the MHBa filter 11C, and select terminals connected to the filters 13f (bf) and 13g (bg).

The common terminal of the switch 21D is connected to HBb the filter 11D, and the selection terminals are connected to the filters 13h (bh), 13j (bj), and 13k (bk).

The common terminal of the switch 22B is connected to the LNA31, and each selection terminal is connected to the MBb filter 11B and the filter 13 d.

The common terminal of the switch 22A is connected to the LNA32, and the selection terminals are connected to the

filters

13c, 13b, and 13 e.

The common terminal of the switch 22D is connected to the LNA33, and the selection terminals are connected to the

filters

13k, 13h, and 13 j.

The common terminal of the switch 22C is connected to the LNA34, and the selection terminals are connected to the

filters

13f and 13 g.

The pass band (1475.9-2025 MHz) of the MLB filter 11A is wider than and includes the pass bands of the filters 13a (ba), 13b (bb), 13c (bc), 13d/13e (Bd/Be). The MBb filter 11B (2110-2200 MHz) contains passbands of Bp. The MHBa filter 11C (2300 minus 2400MHz or 2300 minus 2370MHz) is wider than the pass bands of the filters 13f (Bf) and 13g (Bg), and includes the pass bands. HBb the pass bandwidths of filter 11D (2496-2690 MHz) and filters 13h (Bh), 13j (Bj) and 13k (Bk) include the pass bands.

The high frequency signal processing circuit (RFIC)40 is connected to the output terminals of the LNAs 31 to 36, performs signal processing on the high frequency reception signals input from the antenna elements via the reception signal paths of the respective frequency bands by down-conversion or the like, and outputs the reception signals generated by the signal processing to the baseband signal processing circuit of the subsequent stage. The RF signal processing circuit 40 is, for example, an RFIC. In addition, the high frequency signal processing circuit (RFIC)40 outputs control signals S1A, S1C, S1D, S2A, S2B, S2C, and S2D to the

switches

21A, 21C, 21D, 22A, 22B, 22C, and 22D, respectively, according to the frequency band used. Thereby, each switch switches the connection of the signal path.

In the communication device 3 having the above-described configuration, for example, by switching the

switches

21A, 21C and 21D, 1 band is selected from each of MLB (1475.9-2025 MHz), MBb (2110-.

Here, the configuration of the high-frequency front-end circuit 1 of embodiment 1 can be applied to the high-frequency front-end circuit 2 of the present modification. In other words, the combination of the first filter 11 and the third filter 13 in the high-frequency front-end circuit 1 includes (1) an MLB filter 11A and a filter 13a (ba); (2) MLB filter 11A and filter 13b (bb); (3) MLB filter 11A and filter 13c (bc); (4) MLB filter 11A and filter 13d/13e (Bd/Be); (5) MHBa filter 11C and filter 13f (bf); (6) MHBa filter 11C and filter 13g (bg); (7) HBb filter 11D and filter 13h (Bh); (8) HBb Filter 11D and filters 13j (Bj), HBb Filter 11D and filters 13k (Bk). The second filter 12 includes at least one of the MLB filter 11A, MBb filter 11B, MHBa filter 11C and HBb filter 11D.

For example, when (1) the MLB filter 11A and the filter 13a (Ba) are selected as the combination of the first filter 11 and the third filter 13, and the MBb filter 11B is selected as the second filter 12, the reflection coefficient in 2110-2200 MHz of the MLB filter 11A (the pass band of the MBb filter 11B) is set to be much smaller than the reflection coefficient in 2110-2200 MHz of the filter 13a (the pass band of the MBb filter 11B).

For example, when (1) the MLB filter 11A and the filter 13a (ba) are selected as the combination of the first filter 11 and the third filter 13, and three filters, i.e., the MBb filter 11B, MHBa filter 11C and the HBb filter 11D, are selected as the second filter 12, the reflection coefficients in 2110-.

According to the above configuration, even if the number of frequency bands in which CA operation is performed increases, the relationship between the reflection characteristics of the demultiplexer circuit 14 and the filter circuit 15 is set to be the relationship between the reflection characteristics of the first filter 11 and the third filter 13 in embodiment 1, and thus, for example, the relationship can be applied to all CA combinations specified in the 3GPP standard. Further, by setting the relationship of the reflection characteristics of the demultiplexer circuit 14 and the filter circuit 15, the frequency band corresponding to the filter circuit 15 in the subsequent stage can be easily changed. Therefore, a module having an optimum band structure can be provided for each destination with a simplified circuit design.

In the present modification, a high-frequency front-end circuit for reception that receives a high-frequency signal from an antenna element and transmits the signal to the high-frequency signal processing circuit 40 is illustrated, but the high-frequency front-end circuit may be a high-frequency front-end circuit for transmission or reception. In the case of a high-frequency front-end circuit for transmission, the amplifier circuit 30 is composed of a power amplifier. In the case of a high-frequency front-end circuit for transmission and reception, the filter circuit 15 is configured by a duplexer assigned to each frequency band.

[1.5 Structure of high-frequency front-end Circuit in variation 5 ]

Fig. 5A is a circuit configuration diagram of the high-frequency front-end circuit 2A according to modification 5 of embodiment 1. The high-frequency front-end circuit 2A of the present modification differs from the high-frequency front-end circuit 2 of modification 4 in that the

filters

13g and 13k are not arranged. Hereinafter, the high-frequency front-end circuit 2A of the present modification will be described mainly with respect to the differences from the high-frequency front-end circuit 2 of modification 4, with the description omitted for the same points.

In the high-frequency front-end circuit 2A, when the pass band of the MHBa filter 11C is 2300-2370 MHz, for example, the pass band coincides with the pass band of B40a (equivalent to Bg: pass band 2300-2370 MHz) disposed at the rear stage of the MHBa filter 11C. On the other hand, the filter 13f disposed at the subsequent stage of the MHBa filter 11C corresponds to B30 (pass band 2350-. Here, since the pass characteristic of the signal of B40a is satisfied by the pass characteristic of the MHBa filter 11C, the filter 13g need not be arranged on the signal path of B40 a. Therefore, a more compact high-frequency front-end circuit having a low-loss signal propagation characteristic can be realized even in the CA operation in a configuration including the demultiplexer circuit 14 (quadplexer) corresponding to MLB, MBb, MHBa, and HBb.

In the high-frequency front-end circuit 2A, when the passband of the MHBa filter 11C is 2300 minus 2400MHz, for example, the passband coincides with the passband of B40 (corresponding to Bg: the passband 2300 minus 2400MHz) disposed at the subsequent stage of the MHBa filter 11C. On the other hand, the filter 13f disposed at the subsequent stage of the MHBa filter 11C corresponds to B30 (pass band 2350-. Here, since the pass characteristic of the signal of B40 is satisfied by the pass characteristic of the MHBa filter 11C, the filter 13g need not be arranged on the signal path of B40. Therefore, a more compact high-frequency front-end circuit having a low-loss signal propagation characteristic can be realized even in the CA operation in a configuration including the demultiplexer circuit 14 (quadplexer) corresponding to MLB, MBb, MHBa, and HBb.

In the high-frequency front-end circuit 2A, the pass band of the HBb filter 11D is 2496-2690 MHz, and coincides with the pass band of B41 disposed at the rear stage of the HBb filter 11D. On the other hand, the filter 13h disposed at the subsequent stage of the HBb filter 11D corresponds to, for example, B38 (pass band 2570 + 2620MHz), and is included in the pass band 2496 + 2690MHz of the filter 11D HBb. The filter 13j disposed at the rear stage of the HBb filter 11D corresponds to B7 (pass band 2620-2690 MHz), for example, and is included in the pass band 2496-2690 MHz of the HBb filter 11D. Here, since the pass characteristic of the signal of B41 is satisfied by the pass characteristic of the HBb filter 11D, the filter 13k does not need to be arranged on the signal path of B41. Therefore, a more compact high-frequency front-end circuit having a low-loss signal propagation characteristic can be realized even in the CA operation in a configuration including the demultiplexer circuit 14 (quadplexer) corresponding to MLB, MBb, MHBa, and HBb.

[1.6 Structure of high-frequency front-end Circuit in modification 6 ]

Fig. 5B is a circuit configuration diagram of the high-frequency front-end circuit 2B according to modification 6 of embodiment 1. The high-frequency front-end circuit 2B of the present modification differs from the high-frequency front-end circuit 2 of modification 4 in the point where a transmission (Tx) bypass path is added. Hereinafter, the high-frequency front-end circuit 2B of the present modification will be described mainly with respect to the differences from the high-frequency front-end circuit 2 of modification 4, with the description omitted.

The high-frequency front-end circuit 2B includes an antenna common terminal 101, demultiplexer circuits 10 (low-pass filter 10A, high-pass filter 10B) and 14(MLB filter 11A, MBb filter 11B, MHBa filter 11C, HBb filter 11D), switches 21 (switch 21E, switch 21C, switch 21D) and 22 (not shown), a filter circuit 15 (filters 13a to 13k), and an amplifier circuit 30 (not shown).

The switch 21 is composed of

switches

21E, 21C, and 21D.

The switch 21E has a common terminal connected to the MLB filter 11A, and select terminals connected to the transmission (Tx) bypass path and the filters 13a (ba), 13b (bb), 13c (bc), and 13d/13E (Bd/Be).

The transmission (Tx) bypass path is a path for propagating a transmission signal belonging to a frequency band of the MLB/LMB, and is a path for propagating a signal of at least one transmission range of a frequency band a, a frequency band b, a frequency band c, a frequency band d, and a frequency band e, for example.

The pass band (1475.9-2025 MHz) of the MLB filter 11A is wider than the transmission pass band propagating through the transmission (Tx) bypass path and the pass bands of the filters 13a (ba), 13b (bb), 13c (bc), and 13d/13e (Bd/Be), and includes the pass bands. The MBb filter 11B (2110-2200 MHz) contains passbands of Bp. The MHBa filter 11C (2300 minus 2400MHz or 2300 minus 2370MHz) is wider than the pass bands of the filters 13f (Bf) and 13g (Bg), and includes the pass bands. HBb Filter 11D (2496-2690 MHz) is wider than each pass band of filters 13h (Bh), 13j (Bj), and 13k (Bk), and includes the pass bands.

According to the above configuration, a signal path connecting the transmission (Tx) bypass path, the switch 21E, MLB, the filter 11A, the high-pass filter 10B, and the antenna common terminal 101 can be used as the transmission signal path.

According to the above configuration, the transmission signal belonging to MLB/LMB and the reception signal belonging to MB, MHB, HB can be CA-operated by the antenna connected to the antenna common terminal 101. In other words, the antenna connected to the antenna common terminal 101 can be used not only for reception but also for transmission and reception.

In the present modification, the transmission (Tx) bypass path is connected to the switch 21E for switching the band in the MLB/LMB, but the transmission (Tx) bypass path may be connected to the switch 21C for switching the band in the MHB or the switch 21D for switching the band in the HB.

[1.7 Structure of high-frequency front-end Circuit in modification 7 ]

Fig. 5C is a circuit configuration diagram of the high-frequency front-end circuit 2C according to modification 7 of embodiment 1. The high-frequency front-end circuit 2C of the present modification differs from the high-frequency front-end circuit 2 of modification 4 in the point of addition of a transmission (Tx) path including a transmission filter. Hereinafter, the high-frequency front-end circuit 2C of the present modification will be described mainly with respect to the differences from the high-frequency front-end circuit 2 of modification 4, with the description omitted for the same points.

The high-frequency front-end circuit 2C includes an antenna common terminal 101, demultiplexer circuits 10 (low-pass filter 10A, high-pass filter 10B) and 14(MLB filter 11A, MBb filter 11B, MHBa filter 11C, HBb filter 11D), switches 21 (switch 21F, switch 21C, switch 21D) and 22 (not shown), a filter circuit 15 (filters 13a to 13k and transmission filter 13t), and an amplifier circuit 30 (not shown).

The switch 21 is composed of

switches

21F, 21C, and 21D.

The switch 21F has a common terminal connected to the MLB filter 11A, and select terminals connected to the transmission (Tx) path and the filters 13a (ba), 13b (bb), 13c (bc), and 13d/13e (Bd/Be). The switch 21F is a switch capable of being simultaneously connected to the common terminal and two or more selection terminals.

A transmission filter 13t is disposed in the transmission (Tx) path.

The pass band (1475.9-2025 MHz) of the MLB filter 11A is wider than and includes the pass bands of the transmission filter 13t, the filters 13a (ba), 13b (bb), 13c (bc), and 13d/13e (Bd/Be). The MBb filter 11B (2110-2200 MHz) contains passbands of Bp. The MHBa filter 11C (2300 minus 2400MHz or 2300 minus 2370MHz) is wider than the pass bands of the filters 13f (Bf) and 13g (Bg), and includes the pass bands. HBb Filter 11D (2496-2690 MHz) is wider than each pass band of filters 13h (Bh), 13j (Bj), and 13k (Bk), and includes the pass bands.

According to the above configuration, it is possible to simultaneously use a transmission signal path connecting the transmission (Tx) path, the switch 21F, MLB, the filter 11A, the high-pass filter 10B, and the antenna common terminal 101, and a reception signal path connecting any one of the antenna common terminal 101, the high-pass filter 10B, MLB, the filter 11A, the switch 21F, and the filters 13a to 13 e. This enables simultaneous transmission and reception in the same frequency band. The antenna connected to the antenna common terminal 101 can be used not only for reception but also for transmission and reception.

Further, assuming a configuration in which the transmission (Tx) path is also connected to a high-frequency front-end circuit different from the high-frequency front-end circuit 2C, in this case, two systems of the high-frequency front-end circuit 2C and the different high-frequency front-end circuit enable a so-called two-uplink transmission operation by two antennas.

In the present modification, the transmission (Tx) path is connected to the switch 21F for switching the band in the MLB/LMB, but the transmission (Tx) path may be connected to the switch 21C for switching the band in the MHB or the switch 21D for switching the band in the HB.

[1.8 Structure of high-frequency front-end Circuit according to modification 8 ]

Fig. 5D is a circuit configuration diagram of the high-frequency front-end circuit 2D according to modification 8 of embodiment 1. The high-frequency front-end circuit 2D of the present modification differs from the high-frequency front-end circuit 2 of modification 4 in the point where the transmission/reception (Tx/Rx) path including the duplexer is added. Hereinafter, the high-frequency front-end circuit 2D of the present modification will be described mainly with respect to the differences from the high-frequency front-end circuit 2 of modification 4, with the same points omitted for explanation.

The high-frequency front-end circuit 2D includes an antenna common terminal 101, demultiplexer circuits 10 (low-pass filter 10A, high-pass filter 10B) and 14(MLB filter 11A, MBb filter 11B, MHBa filter 11C, HBb filter 11D), switches 21 (

switches

21G, 21C, 21D) and 22 (not shown), a filter circuit 15 (filters 13a to 13k), and an amplifier circuit 30 (not shown).

The switch 21 is constituted by

switches

21G, 21C, and 21D.

The switch 21G has a common terminal connected to the MLB filter 11A, and select terminals connected to a transmission/reception (Tx/Rx) path and filters 13a (ba), 13b (bb), 13c (bc), and 13d/13e (Bd/Be).

A duplexer including a transmission filter 13t1 and a reception filter 13r1 is disposed in a transmission/reception (Tx/Rx) path.

The pass band (1475.9-2025 MHz) of the MLB filter 11A is larger than the pass bands of the duplexer disposed in the transmission/reception (Tx/Rx) path, the filters 13a (ba), 13b (bb), 13c (bc), and 13d/13e (Bd/Be), and includes the pass bands. The MBb filter 11B (2110-2200 MHz) contains passbands of Bp. The MHBa filter 11C (2300 minus 2400MHz or 2300 minus 2370MHz) is wider than the pass bands of the filters 13f (Bf) and 13g (Bg), and includes the pass bands. HBb Filter 11D (2496-2690 MHz) is wider than each pass band of filters 13h (Bh), 13j (Bj), and 13k (Bk), and includes the pass bands.

According to the above configuration, the transmission/reception (Tx/Rx) path can use a signal path connecting the switch 21G, MLB, the filter 11A, the high-pass filter 10B, and the antenna common terminal 101. This makes it possible to simultaneously transmit and receive the transmission signal and the reception signal of the same frequency band propagating through the transmission/reception (Tx/Rx) path. The antenna connected to the antenna common terminal 101 can be used not only for reception but also for transmission and reception.

Further, assuming that the transmission/reception (Tx/Rx) path is also connected to a high-frequency front-end circuit different from the high-frequency front-end circuit 2D, in this case, it is possible to perform a so-called two-uplink transmission operation by two antennas by two systems of the high-frequency front-end circuit 2D and the different high-frequency front-end circuit.

In the present modification, the transmission/reception (Tx/Rx) path is connected to the switch 21G for switching the band in the MLB/LMB, but the transmission/reception (Tx/Rx) path may be connected to the switch 21C for switching the band in the MHB or the switch 21D for switching the band in the HB.

(embodiment mode 2)

In embodiment 1, a case has been described in which, in a configuration in which the first filter 11 and the second filter 12 are connected in common via the antenna common terminal and the first filter 11 and the third filter 13 are connected in series via the switch, it is preferable to increase the reflection coefficient in the first filter 11 having a large influence on the reflection characteristic and secure filter characteristics such as the pass characteristic, the attenuation characteristic, the temperature characteristic, and the bandwidth in the third filter 13 having a small influence on the reflection characteristic. In the present embodiment, from the above-described viewpoint, a combination of the configurations of the first filter 11 and the third filter 13 is exemplified.

In the present embodiment, first filter 11 and third filter 13 are formed of elastic wave resonators, and may have a ladder-type filter structure. In this case, the one or more elastic wave resonators disposed on the antenna common terminal 101 side include at least one of a series arm resonator and a parallel arm resonator. This can reduce the insertion loss of the first filter 11, the third filter 13, or both of the insertion losses in the second pass band of the second filter 12 while ensuring the low loss factors of the first filter 11 and the third filter 13.

The first filter 11 and the third filter 13 may have a vertical coupling type filter structure. This makes it possible to adapt the first filter 11 and the third filter 13 to filter characteristics that require attenuation enhancement or the like.

Examples of the structure of the elastic Wave resonator include a Surface Acoustic Wave (SAW) resonator, an smr (solid Mounted resonator), and an fbar (film Bulk Acoustic resonator) using baw (Bulk Acoustic Wave).

Here, the first filter 11 and the third filter 13 each include two or more elastic wave resonators, and the reflection coefficient in the second pass band in the case where one or more elastic wave resonators arranged on the antenna common terminal 101 side among the two or more elastic wave resonators constituting the first filter 11 are viewed from the antenna common terminal 101 side as a single body may be larger than the reflection coefficient in the second pass band in the case where one or more elastic wave resonators arranged on the antenna common terminal 101 side among the two or more elastic wave resonators constituting the third filter 13 are viewed from the antenna common terminal 101 side as a single body.

In the filter including a plurality of elastic wave resonators, the reflection coefficient of one elastic wave resonator closest to the antenna common terminal 101 is dominant for the reflection coefficient viewed from the antenna common terminal 101 side. This can effectively reduce the insertion loss of the second filter 12 in the second pass band due to the first filter 11, the third filter 13, or both of them.

Hereinafter, a specific combination of configurations in which the reflection coefficient is increased by the first filter 11 at the front stage and the filter characteristics such as the pass characteristic, the attenuation characteristic, the temperature characteristic, and the bandwidth are improved by the third filter at the rear stage will be described.

First, an example of the structure of an elastic wave resonator will be described.

[2.1 elastic wave resonator Structure ]

Fig. 6 is an example schematically showing a plan view and a cross-sectional view of a filter resonator according to embodiment 2. Fig. 6 shows a case where the elastic Wave resonators (series arm resonators and parallel arm resonators) according to the present embodiment are, for example, Surface Acoustic Wave (SAW) resonators. In the figure, a schematic plan view and a schematic cross-sectional view showing the configuration of one elastic wave resonator out of a plurality of resonators constituting the first filter 11 and the third filter 13 are illustrated. The elastic wave resonator shown in fig. 6 is an example for explaining a typical configuration of the plurality of resonators, and the number, length, and the like of electrode fingers constituting the electrodes are not limited thereto.

Each of the resonators of the first filter 11 and the third filter 13 is composed of a substrate 80 having a piezoelectric layer 83, and IDT (inter digital Transducer)

electrodes

71a and 71b having a comb-like shape.

As shown in the plan view of fig. 6, a pair of

IDT electrodes

71a and 71b facing each other are formed on the piezoelectric layer 83. The IDT electrode 71a is composed of a plurality of electrode fingers 172a parallel to each other and a bus bar electrode 171a connecting the plurality of electrode fingers 172 a. The IDT electrode 71b is composed of a plurality of electrode fingers 172b parallel to each other and a bus bar electrode 171b connecting the plurality of electrode fingers 172 b. The plurality of

electrode fingers

172a and 172b are formed along a direction orthogonal to the X-axis direction.

As shown in the cross-sectional view of fig. 7, the IDT electrode 71 composed of the plurality of

electrode fingers

172a and 172b and the

bus bar electrodes

171a and 171b has a laminated structure of the adhesion layer 72 and the main electrode layer 73.

The adhesion layer 72 is a layer for improving adhesion between the piezoelectric layer 83 and the main electrode layer 73, and Ti, for example, is used as a material. The thickness of the adhesion layer 72 is, for example, about 10 nm.

As a material for the main electrode layer 73, for example, Al containing 1% Cu can be used. The film thickness of the main electrode layer 73 is, for example, about 130 nm.

The protective film 84 is formed to cover the

IDT electrodes

71a and 71 b. The protective film 84 is a layer for protecting the main electrode layer 73 from the external environment, for the purpose of adjusting the frequency-temperature characteristics, improving the moisture resistance, and the like, and is, for example, a film containing silicon dioxide as a main component. The thickness of the protective film 84 is, for example, about 30 nm.

The materials constituting the adhesion layer 72, the main electrode layer 73, and the protective film 84 are not limited to the above materials. The IDT electrode 71 may not have the above-described laminated structure. The IDT electrode 71 may be made of a metal such as Ti, Al, Cu, Pt, Au, Ag, Pd, or an alloy, or may be made of a plurality of stacked bodies made of the above-described metal or alloy. Further, the protective film 84 may not be formed.

Next, a laminated structure of the substrate 80 will be described.

As shown in the lower stage of fig. 6, the substrate 80 includes a high-sound-velocity support substrate 81, a low-sound-velocity film 82, and a piezoelectric layer 83, and has a structure (sound-velocity-film laminated structure) in which the high-sound-velocity support substrate 81, the low-sound-velocity film 82, and the piezoelectric layer 83 are laminated in this order.

Piezoelectric layer 83X propagating LiTaO cut, for example, from 42 ° Y₃A piezoelectric single crystal or a piezoelectric ceramic (lithium tantalate single crystal or ceramic obtained by cutting a surface having an axis rotated by 42 ° from the Y axis as the center axis and the normal line, or a single crystal or ceramic in which a surface acoustic wave propagates in the X axis direction). In this case, the elastic wave resonator uses the leakage wave as the elastic wave.

In addition, the piezoelectric layer 83 is made of 128 ° Y cut X propagating LiNbO, for example₃Piezoelectric single crystal or piezoelectric ceramic. In this case, the elastic wave resonator uses rayleigh waves as elastic waves.

The piezoelectric layer 83 is formed by Y-cutting X-propagating LiNbO, for example₃Piezoelectric single crystal or piezoelectric ceramic. In this case, the elastic wave resonator uses a love wave as an elastic wave.

The single crystal material, cut angle, and laminated structure of the piezoelectric layer 83 can be appropriately selected in accordance with the required pattern of the filter (filter characteristics such as pass characteristic, attenuation characteristic, temperature characteristic, and bandwidth).

The high-sound-velocity support substrate 81 is a substrate that supports the low-sound-velocity film 82, the piezoelectric layer 83, and the IDT electrode 71. The high-sound-velocity support substrate 81 is also a substrate in which the sound velocity of the bulk wave in the high-sound-velocity support substrate 81 is higher than the surface wave or boundary wave elastic wave propagating through the piezoelectric layer 83, and functions to seal the surface acoustic wave to the portion where the piezoelectric layer 83 and the low-sound-velocity film 82 are laminated, thereby preventing the surface acoustic wave from leaking to the lower side of the high-sound-velocity support substrate 81. The high-speed support substrate 81 is, for example, a silicon substrate and has a thickness of, for example, 200 μm. The high-sound-velocity support substrate 81 may be made of any one of the following materials: (1) a piezoelectric body such as aluminum nitride, aluminum oxide, silicon carbide, silicon nitride, silicon, sapphire, lithium tantalate, lithium niobate, or crystal, (2) various ceramics such as alumina, zirconia, cordierite, mullite, talc, or forsterite, (3) magnesium diamond, (4) a material containing each of the above materials as a main component, and (5) a material containing a mixture of the above materials as a main component.

The low-sound-velocity film 82 is a film in which the sound velocity of the bulk wave in the low-sound-velocity film 82 is lower than the sound velocity of the elastic wave propagating through the piezoelectric layer 83, and is disposed between the piezoelectric layer 83 and the high-sound-velocity support substrate 81. With this structure and the property that the elastic wave concentrates energy in a medium having a substantially low acoustic velocity, leakage of the surface acoustic wave energy to the outside of the IDT electrode can be suppressed. The low-speed diaphragm 82 is a diaphragm mainly composed of silicon dioxide, for example. The thickness of the low-speed diaphragm 82 is, for example, about 500 nm.

According to the above-described sonic film laminated structure of the substrate 80, the Q value at the resonance frequency and the antiresonance frequency can be significantly increased as compared with the conventional structure using a single-layer piezoelectric substrate. That is, since a surface acoustic wave resonator having a high Q value can be configured, a filter having a small insertion loss can be configured using the surface acoustic wave resonator.

The high-sound-speed support substrate 81 may have a structure in which a support substrate and a high-sound-speed film that has a higher sound speed of a bulk wave propagating than a surface wave propagating through the piezoelectric layer 83 or an elastic wave of a boundary wave are laminated. In this case, a support substrate may use a piezoelectric body such as sapphire, lithium tantalate, lithium niobate, or crystal; various ceramics such as alumina, magnesia, silicon nitride, aluminum nitride, silicon carbide, zirconia, cordierite, mullite, talc, forsterite, and the like; a dielectric such as glass; or semiconductors such as silicon and gallium nitride, resin substrates, and the like. As the high sound velocity film, various high sound velocity materials such as aluminum nitride, aluminum oxide, silicon carbide, silicon nitride, silicon oxynitride, DLC film, diamond, a medium containing the above materials as a main component, and a medium containing a mixture of the above materials as a main component can be used.

In the above description, the IDT electrode 71 constituting the acoustic wave resonator is formed on the substrate 80 having the piezoelectric layer 83, but the substrate on which the IDT electrode 71 is formed may be a piezoelectric substrate constituted by a single layer of the piezoelectric layer 83. The piezoelectric substrate in this case is made of, for example, LiTaO₃Piezoelectric single crystal or LiNbO₃And the like.

Note that, as long as the substrate on which the IDT electrode 71 is formed has the piezoelectric layer 83, a structure in which a piezoelectric layer is laminated on a support substrate may be used instead of the structure in which the entire substrate is composed of the piezoelectric layer.

Here, the design parameters of the IDT electrode 71 are explained. The wavelength of the surface acoustic wave resonator is defined by a wavelength λ that is a repetition period of the plurality of

electrode fingers

172a or 172b constituting the IDT electrode 71 shown in the middle of fig. 6. Note that 1/2 having an electrode pitch of wavelength λ is defined by (W + S) when the line width of

electrode fingers

172a and 172b constituting

IDT electrodes

71a and 71b is W and the space width between

adjacent electrode fingers

172a and 172b is S. As shown in the upper stage of fig. 6, the width L of the IDT electrode is the length of the electrode fingers 172a of the IDT electrode 71a and the electrode fingers 172b of the IDT electrode 71b overlapping each other when viewed from the X-axis direction. The electrode duty of each resonator is a line width occupancy rate of the plurality of

electrode fingers

172a and 172b, is a ratio of the line width to an added value of the line width and the space width of the plurality of

electrode fingers

172a and 172b, and is defined by W/(W + S).

[2.2 elastic wave resonator Structure-reflection coefficient in Low frequency region 1 ]

Hereinafter, a specific configuration combination in which the reflection coefficient is increased by the first filter 11 and the filter characteristics such as the pass characteristic, the attenuation characteristic, the temperature characteristic, and the bandwidth are improved by the third filter 13 will be described.

Fig. 7A is a diagram illustrating reflection characteristics in the low frequency region 1 of the high frequency front end circuit according to modification 2 of embodiment 2. As shown in the lower part of the figure, in the impedance characteristics of the elastic wave resonator, a resonance point at which the impedance is a minimum value and an anti-resonance point at which the impedance is a maximum value were confirmed. Here, in a region on the lower frequency side of the resonance point (low frequency region 1 in fig. 7A), the impedance differs depending on the structure of the elastic wave resonator, and the reflection characteristic is inferior depending on the magnitude of the impedance. More specifically, the compound represented by (1) LiNbO₃Rayleigh waves propagating through the structured piezoelectric layer, and (2) Rayleigh waves propagating through the LiTaO layer₃Leakage wave propagating in the piezoelectric layer, and (3) leakage wave propagating in the piezoelectric layer made of LiNbO₃A structure in which any one of love waves propagating in the piezoelectric layer is used as a surface acoustic wave, and (4) the soundThe membrane laminate structure has a larger reflection coefficient loss in the low frequency region 1 than in the SMR or FBAR.

Fig. 7B is a diagram showing a combination of the configurations of the first filter 11 and the third filter 13 according to embodiment 2.

In accordance with the relationship between the reflection coefficients, when the first passband of the first filter 11 is located on the higher frequency side than the second passband of the second filter 12, as shown in fig. 7B, the high-frequency front-end circuit according to the present embodiment may be configured such that any one of the following is used as the surface acoustic wave in the first filter 11: (1) in the presence of LiNbO₃Rayleigh waves propagating in the structured piezoelectric layer; (2) in the field of chemical synthesis of LiTaO₃Leakage waves propagating in the structured piezoelectric layer; and (3) a polymer prepared from LiNbO₃And a love wave propagating through the piezoelectric layer.

Thus, in the high-frequency front-end circuit, the reflection coefficient in the second pass band of the first filter 11 (pass band of the second filter 12) can be made larger than the reflection coefficient in the second pass band of the third filter 13 (pass band of the second filter 12). This can reduce the insertion loss of the second filter 12 in the second pass band due to the first filter 11, the third filter 13, or both of them.

On the other hand, in the third filter 13, the elastic wave resonator may be formed of SMR or FBAR.

Accordingly, the reflection coefficient of the second filter 12 can be increased by the configuration of the first filter 11, and the low loss factor of the second filter 12 and the steepness of the pass band can be secured by the configuration of the third filter 13.

As shown in fig. 7B, the elastic wave resonators constituting the first filter 11 may have the sonic film laminated structure described above, and the elastic wave resonators in the third filter 13 may be formed of SMRs or FBARs.

Thus, in the high-frequency front-end circuit, the reflection coefficient in the second pass band of the first filter 11 (pass band of the second filter 12) can be made larger than the reflection coefficient in the second pass band of the third filter 13 (pass band of the second filter 12). Therefore, the insertion loss of the insertion loss in the second pass band of second filter 12 caused by first filter 11, third filter 13, or both of them can be reduced. The reflection coefficient of the second filter 12 can be increased by the structure of the first filter 11, and the low loss factor of the second filter 12 and the steepness of the pass band can be secured by the above-described structure of the third filter 13.

[2.3 elastic wave resonator Structure-bulk wave leakage in high frequency region 1 ]

Fig. 8A is a diagram illustrating bulk wave leakage in the high-frequency region 1 of the high-frequency front-end circuit according to variation 1 of embodiment 2. As shown in the lower part of the figure, in a region on the high frequency side of the antiresonance point of the elastic wave resonator (high frequency region 1 in fig. 8A), impedance change due to bulk wave leakage (unnecessary wave) occurs, and reflection characteristics are inferior due to the impedance change. More specifically, the reflection loss caused by bulk wave leakage in the high-frequency region 1 is, in order from small to large: (1) is used in LiNbO₃Structures of elastic waves, SMRs and FBARs, which are rayleigh waves propagating in the structured piezoelectric body layer; (2) a sound velocity film laminated structure; (3) is used in LiTaO₃A structure in which a leakage wave propagating through the piezoelectric layer is an elastic wave; (4) is used in LiNbO₃The love wave propagating through the piezoelectric layer is an elastic wave.

Fig. 8B shows a combination of the configurations of the first filter 11 and the third filter 13 in modification 1 of embodiment 2.

According to the above-described order of superiority and inferiority of the reflection loss, when the first passband of the first filter 11 is located on the lower frequency side than the second passband of the second filter 12, as shown in fig. 8B, the first filter 11 on the lower frequency side of the high-frequency front-end circuit may be any of: (1) is used in LiNbO₃A structure in which a rayleigh wave propagating in the structured piezoelectric layer is an elastic surface wave; (2) the elastic wave resonator is composed of SMRs; and (3) the elastic wave resonator is formed of an FBAR.

Thus, in the high-frequency front-end circuit, the reflection coefficient in the second pass band of the first filter 11 on the low-frequency side (the pass band of the second filter 12 on the high-frequency side) can be made larger than the reflection coefficient in the second pass band of the third filter 13 (the pass band of the second filter 12 on the high-frequency side). Therefore, the insertion loss of the insertion loss in the second pass band of second filter 12 caused by first filter 11, third filter 13, or both of them can be reduced.

On the other hand, the third filter 13 may have any one of the following structures: (1) the sound velocity film laminated structure; (2) is used in LiTaO₃A structure in which a leakage wave propagating through the piezoelectric layer is an elastic surface wave; and (3) is used in LiNbO₃The love wave propagating through the piezoelectric layer is an elastic surface wave.

Thus, the reflection coefficient of the first filter 11 can be increased by the structure of the first filter 11, and the low loss factor and the good temperature characteristic of the third filter 13 can be ensured when the third filter 13 is formed as a sonic film laminated structure. In addition, LiNbO is used as the third filter 13₃When the love wave of (2) is a surface acoustic wave, a wide bandwidth of the third filter 13 can be secured.

In addition, the elastic wave resonator may have the sonic film laminated structure in the first filter 11, and the third filter 13 may have a structure (1) used in LiTaO₃The leakage wave propagating through the piezoelectric layer is used as an elastic surface wave or (2) as a structure of an elastic surface wave₃The love wave propagating through the piezoelectric layer is an elastic surface wave.

Thus, in the high-frequency front-end circuit, the reflection coefficient in the second pass band of the first filter 11 on the low-frequency side (the pass band of the second filter 12 on the high-frequency side) can be made larger than the reflection coefficient in the second pass band of the third filter 13 (the pass band of the second filter 12 on the high-frequency side). Therefore, the insertion loss of the insertion loss in the second pass band of second filter 12 caused by first filter 11, third filter 13, or both of them can be reduced. Further, LiNbO is used for the third filter 13₃When the love wave of (2) is a surface acoustic wave, a wide bandwidth of the third filter 13 can be secured.

In addition, LiTaO may be used as the first filter 11₃The leakage wave propagating through the piezoelectric layer is used as an elastic surface wave in the third filter 13, and is made of LiNbO₃The love wave propagating through the piezoelectric layer is an elastic surface wave.

Therefore, in the high-frequency front-end circuit, the reflection coefficient in the second pass band of the first filter 11 on the low-frequency side (the pass band of the second filter 12 on the high-frequency side) can be made larger than the reflection coefficient in the second pass band of the third filter 13 (the pass band of the second filter 12 on the high-frequency side). This can reduce the insertion loss of the second filter 12 in the second pass band due to the first filter 11, the third filter 13, or both of them. Further, LiNbO is used in the third filter 13₃When the love wave of (2) is a surface acoustic wave, a wide bandwidth of the third filter 13 can be secured.

[2.4 elastic wave resonator Structure-clutter in the Low frequency region 2 ]

Fig. 9A is a diagram illustrating generation of a spurious in the low frequency region 2 of the high frequency front end circuit in modification 2 of embodiment 2. As shown in the lower part of the figure, in a region on the lower frequency side of the resonance point of the elastic wave resonator (low frequency region 2 in fig. 9A), particularly, the sonic film laminated structure or the acoustic wave resonator is used by LiTaO₃In the structure of the leakage wave propagating through the piezoelectric body layer as an elastic wave, a rayleigh clutter occurs in the vicinity of 0.76 times the resonance frequency. Due to the noise generation, the impedance changes, and the reflection coefficient becomes smaller as the impedance changes.

When the first passband of the first filter 11 is located on the higher frequency side than the second passband of the second filter 12, as shown in fig. 9B, the first filter 11 may be any one of the following: (1) is used in LiNbO₃A structure in which a rayleigh wave propagating in the structured piezoelectric layer is an elastic surface wave; (2) is used in LiTaO₃Is composed ofA structure in which a leakage wave propagating in the piezoelectric layer is an elastic surface wave; (3) is used in LiNbO₃A structure in which a love wave propagating through the piezoelectric layer is an elastic surface wave; (4) the elastic wave resonator is composed of SMRs; and (5) the elastic wave resonator is formed of FBAR, and the elastic wave resonator of the third filter 13 has the above-described sonic film laminated structure.

In other words, by making the third filter 13 have the sonic film laminated structure and not making the first filter 11 have the sonic film laminated structure, the reflection coefficient in the second pass band of the first filter 11 (the pass band of the second filter 12 on the low frequency side) can be increased. Therefore, in the high-frequency front-end circuit, the insertion loss due to the first filter 11, the third filter 13, or both of the insertion losses in the second pass band of the second filter 12 can be reduced.

As shown in fig. 9B, the first filter 11 may be any one of the following: (1) is used in LiNbO₃A structure in which a rayleigh wave propagating in the structured piezoelectric layer is an elastic surface wave; (2) is used in LiNbO₃A structure in which a love wave propagating through the piezoelectric layer is an elastic surface wave; (3) the sound velocity film laminated structure; (4) the elastic wave resonator is composed of SMRs; and (5) the elastic wave resonator is formed of FBAR, and the third filter 13 is advantageously formed of LiTaO₃The leakage wave propagating through the piezoelectric layer is a surface acoustic wave.

In other words, by using LiTaO in the third filter 13₃The first filter 11 does not use LiTaO as an elastic wave₃The leakage wave of (2) can increase the reflection coefficient in the second pass band (pass band of the second filter 12 on the low frequency side) of the first filter 11 as an elastic wave. Therefore, in the high-frequency front-end circuit, the insertion loss due to the first filter 11, the third filter 13, or both of the insertion losses in the second pass band of the second filter 12 can be reduced.

[2.5 elastic wave resonator Structure-higher order modes in high frequency region 2 ]

Fig. 10A shows a high-frequency range of the high-frequency front-end circuit according to modification 3 of embodiment 2The generation of the high-order mode in the domain 2 will be described. As shown in the lower part of the figure, the region on the higher frequency side than the resonance point of the elastic wave resonator (high frequency region 2 in fig. 10A), particularly, the region used in the present invention is LiNbO₃Rayleigh waves propagating through the structured piezoelectric layer are used as elastic surface waves or LiNbO₃In the structure of the love wave propagating through the piezoelectric layer as an elastic surface wave, a higher-order mode is generated in the vicinity of 1.2 times the resonance frequency. The generation of the higher mode changes the impedance, and the reflection coefficient decreases with the change in the impedance.

Fig. 10B is a diagram showing a combination of the configurations of the first filter 11 and the third filter 13 in modification 3 of embodiment 2.

When the first passband of the first filter 11 is located on the lower frequency side than the second passband of the second filter 12, as shown in fig. 10B, the first filter 11 may have any one of the following configurations: (1) the sound velocity film laminated structure; (2) is used in LiTaO₃A structure in which a leakage wave propagating through the piezoelectric layer is an elastic surface wave; (3) is used in LiNbO₃A structure in which a love wave propagating through the piezoelectric layer is an elastic surface wave; (4) SMR; and (5) FBAR, the third filter 13 is advantageously used in the filter made of LiNbO₃The rayleigh wave propagating through the structured piezoelectric layer is an elastic surface wave.

In other words, by using LiNbO in the third filter 13₃The first filter 11 does not use LiNbO as the elastic wave₃The rayleigh wave of (2) can be used as an elastic wave to increase the reflection coefficient in the second pass band of the first filter 11 (the pass band of the second filter 12 on the high frequency side). Therefore, in the high-frequency front-end circuit, the insertion loss due to the first filter 11, the third filter 13, or both of the insertion losses in the second pass band of the second filter 12 can be reduced.

As shown in fig. 10B, the first filter 11 may have any one of the following configurations: (1) is used in LiNbO₃A structure in which a rayleigh wave propagating in the structured piezoelectric layer is an elastic surface wave; (2) the speed of soundA film lamination structure; (3) is used in LiTaO₃A structure in which a leakage wave propagating through the piezoelectric layer is an elastic surface wave; (4) SMR; and (5) an FBAR provided in the third filter 13 and used in the LiNbO filter₃The love wave propagating through the piezoelectric layer is an elastic surface wave.

In other words, by using LiNbO in the third filter 13₃The first filter 11 does not use LiNbO as an elastic wave₃The love wave of (2) can increase the reflection coefficient in the second pass band (pass band of the second filter 12 on the high frequency side) of the first filter 11 as an elastic wave. Therefore, in the high-frequency front-end circuit, the insertion loss due to the first filter 11, the third filter 13, or both of the insertion losses in the second pass band of the second filter 12 can be reduced.

[2.6 adjustment of structural parameters of elastic wave resonator ]

Fig. 11A is a diagram showing degradation of the reflection loss due to the higher-order mode in the first filter 11 of embodiment 2. As shown in the figure, the reflection loss of the first filter 11 viewed from the antenna common terminal 101(Port1) increases on the high-frequency side of the resonance point due to the higher order mode (the broken line region in fig. 11A). Here, by changing the structural parameters of the elastic wave resonator, the frequency at which the reflection loss increases in the higher-order mode can be shifted to the high frequency side or the low frequency side. Alternatively, by changing the structural parameters of the elastic wave resonator, an increase in reflection loss due to higher order modes can be suppressed.

From this viewpoint, the inventors have found that the first filter 11 having a large influence on the reflection characteristic is configured to shift the frequency of generation of higher-order modes, noise, and the like to the outside of the pass band of the second filter 12 by changing the configuration parameters, and the third filter 13 having a small influence on the reflection characteristic is configured to optimize the configuration parameters so as to secure filter characteristics such as the pass characteristic, the attenuation characteristic, the temperature characteristic, and the bandwidth.

Fig. 11B is a diagram showing parameters for differentiating the configurations of the first filter 11 and the third filter 13 in modification 4 of embodiment 2.

Form the firstThe acoustic wave resonators of the filter 11 are surface acoustic wave resonators each including a substrate 80 having a piezoelectric layer 83 and an IDT electrode 71 formed on the substrate. The first filter 11 and the third filter are used in the LiTaO filter as shown in fig. 11B₃The leakage wave propagating through the piezoelectric layer is a surface acoustic wave, and the IDT electrode 71 of the first filter 11 and the IDT electrode 71 of the third filter 13 have different electrode thicknesses or different duty ratios.

In the utilization of LiTaO₃When the leakage wave of (2) is an elastic wave, a rayleigh clutter occurs on the low frequency side of the resonance frequency of the elastic wave resonator. In contrast, in the first filter 11 and the third filter 13, the frequency of generation of rayleigh wave noise in the first filter 11 can be shifted outside the second pass band (pass band of the second filter 12 on the low frequency side) by making the electrode film thickness or the duty ratio of the IDT electrode 71 different. This makes it possible to increase the reflection coefficient in the second pass band of first filter 11 (pass band of second filter 12 on the low frequency side), and to reduce the insertion loss due to first filter 11, third filter 13, or both of the insertion losses in the second pass band of second filter 12.

In the first filter 11 and the third filter 13, the acoustic wave resonator has the above-described sonic film laminated structure as shown in fig. 11B, and in the first filter 11 and the third filter 13, any one of the electrode thickness of the IDT electrode 71, the duty ratio of the IDT electrode 71, and the film thickness of the low-sonic film 82 may be different.

In the case of using the sound velocity film laminated structure, a rayleigh wave clutter is generated on the low frequency side of the resonance frequency of the elastic wave resonator. In contrast, in the first filter 11 and the third filter 13, the frequency of generation of rayleigh wave noise in the first filter 11 can be shifted outside the second pass band (pass band of the second filter 12 on the low frequency side) by making the electrode film thickness or the duty ratio of the IDT electrode 71 different. This makes it possible to increase the reflection coefficient in the second pass band of first filter 11 (pass band of second filter 12 on the low frequency side), and to reduce the insertion loss due to first filter 11, third filter 13, or both of the insertion losses in the second pass band of second filter 12.

Fig. 11C is a diagram showing parameters for differentiating the configurations of the first filter 11 and the third filter 13 in modification 5 of embodiment 2.

The acoustic wave resonators constituting the first filter 11 and the third filter 13 are surface acoustic wave resonators each including a substrate 80 having a piezoelectric layer 83, an IDT electrode 71 formed on the substrate, and a protective film 84 formed on the IDT electrode 71. The first filter 11 and the third filter 13 on the low frequency side are made of LiNbO as shown in fig. 11C₃Rayleigh waves propagating in the structured piezoelectric layer or LiNbO₃The love wave propagating through the piezoelectric layer thus constituted is a surface acoustic wave, and the first filter 11 and the third filter 13 differ in any one of the electrode thickness of the IDT electrode 71, the duty ratio of the IDT electrode 71, and the film thickness of the protective film 84.

In the utilization of LiNbO₃Rayleigh wave or LiNbO of₃When the love wave of (2) is a surface acoustic wave, a higher-order mode is generated on the high-frequency side of the resonance frequency of the elastic wave resonator. In contrast, in the first filter 11 and the third filter 13, the frequency of generation of the high-order mode in the first filter 11 can be shifted outside the second passband (the passband of the second filter 12 on the high frequency side) by making the electrode film thickness of the IDT electrode 71, the duty ratio of the IDT electrode 71, or the film thickness of the low-speed film 82 different. This makes it possible to increase the reflection coefficient in the second pass band of the first filter 11 (the pass band of the second filter 12 on the high-frequency side), and to reduce the insertion loss due to the first filter 11, the third filter 13, or both of the insertion losses in the second pass band of the second filter 12.

In the first filter 11 and the third filter 13, as shown in fig. 11C, the elastic wave resonator has the above-described sound velocity film laminated structure, the high sound velocity supporting substrate 81 is formed of a silicon crystal, and any one of the film thickness of the piezoelectric layer 83, the film thickness of the low sound velocity film 82, and the silicon crystal orientation of the high sound velocity supporting substrate 81 may be different in the first filter 11 and the third filter 13.

In the case of using the sonic film laminated structure, a higher-order mode is generated on the high-frequency side of the resonance frequency of the elastic wave resonator. In contrast, in the first filter 11 and the third filter 13, the film thickness of the piezoelectric layer 83, the film thickness of the low-sound-velocity film 82, or the silicon crystal orientation of the high-sound-velocity support substrate 81 are made different from each other, so that the frequency of generation of the high-order mode in the first filter 11 can be shifted outside the second passband (the passband of the second filter 12 on the high-frequency side). This makes it possible to increase the reflection coefficient in the second pass band of the first filter 11 (the pass band of the second filter 12 on the high-frequency side), and to reduce the insertion loss due to the first filter 11, the third filter 13, or both of the insertion losses in the second pass band of the second filter 12.

Fig. 12 is a diagram showing parameters for differentiating the configurations of the first filter 11 and the third filter 13 in modification 6 of embodiment 2.

The acoustic wave resonators constituting the first filter 11 and the third filter 13 are surface acoustic wave resonators each including a substrate 80 having a piezoelectric layer 83 and an IDT electrode 71 formed on the substrate. The first filter 11 and the third filter 13 are used in LiTaO₃Leakage wave propagating through the piezoelectric layer or LiNbO₃The love wave propagating through the piezoelectric layer thus constituted is a surface acoustic wave, and the electrode film thickness of the IDT electrode 71 differs between the first filter 11 and the third filter 13.

In the utilization of LiTaO₃Leakage wave of (2) or LiNbO₃When the love wave of (2) is a surface acoustic wave, a bulk wave (unnecessary wave) is generated on the high frequency side of the resonance frequency of the acoustic wave resonator. In contrast, in the first filter 11 and the third filter 13, the frequency of generation of the bulk wave in the first filter 11 can be shifted outside the second passband (the passband of the second filter 12 on the high frequency side) by making the electrode thicknesses of the IDT electrodes 71 different. This makes it possible to increase the reflection coefficient in the second pass band of the first filter 11 (pass band of the second filter 12 on the high-frequency side), and to reduce the insertion loss in the second pass band of the second filter 12 due to the first filter 11, the third filter 13, or both of themInsertion loss of (2).

(embodiment mode 3)

In the present embodiment, a configuration for realizing low loss and miniaturization of a high-frequency front-end circuit including a branching circuit connected to an antenna common terminal and filters corresponding to respective frequency bands arranged at a subsequent stage of the branching circuit will be described.

Fig. 13A is a circuit configuration diagram of the high-frequency front-end circuit 6 according to embodiment 3. The high-frequency front-end circuit 6 shown in the figure includes a common antenna terminal 101, an LB filter 11L, MB, a filter 11M, HB, a filter 13B for the filter 11H, B3, a filter 13f for the B30, and

LNAs

31, 32, and 34.

The LB filter 11L, MB, the filter 11M, and the HB filter 11H are branching circuits connected to the antenna elements.

The LB filter 11L is a low-band pass filter having a pass band in a low-band range (for example, 2GHz or less).

The HB filter 11H is a high-band pass filter having a passband in a high-band range (for example, 2.3GHz or more).

The MB filter 11M is a Band-pass filter having a pass Band of Band66 (2110-2200 MHz).

The filter 13b is a Band-pass filter having a pass Band of Band3 (1805-1880 MHz).

The filter 13f is a Band-pass filter having a passband of Band30 (2350-2360 MHz).

Here, the pass Band (2110-.

This allows the signal propagation paths of Band1 and Band4 to share the signal propagation path of Band 66. In other words, the high-frequency signals of Band1 and Band4 propagate on the signal path from MB filter 11M to LNA 31.

In the above circuit configuration, the CA operations of Band1 and Band3 and the CA operations of Band4 and Band30 are combinations of CA operations. In other words, Band1 and Band4, which are Band-overlapped, do not perform the CA action.

Fig. 13B is a circuit configuration diagram of the high-frequency front-end circuit 600 of the comparative example. As a circuit configuration for realizing the CA operation of Band1 and Band3 and the CA operation of Band4 and Band30, a high-frequency front-end circuit 600 of a comparative example has been proposed. The high-frequency front-end circuit 600 includes the antenna common terminal 101, the switch 21, the filter 13p for B1, the filter 13B for B3, the filter 13p for B4, the filter 13f for B30, and the

LNAs

31, 32, 31, and 34. In this configuration, the CA operation of Band1 and Band3 or the CA operation of Band4 and Band30 is selected by switching the switch 21.

In the case of performing such CA operation, as shown in the comparative example, the filter 13p for B1 and the filter 13p for B4 are generally separately prepared and switched by the switch 21. However, since most of the pass bands of Band1 and Band4 overlap, the filters can be shared by using a wide-Band MB filter 11M as in the high-frequency front-end circuit 6 of the present embodiment. In contrast, in the comparative example, the occupied area is wasted.

In other words, according to the high-frequency front-end circuit 6 of the present embodiment, the MB filter 11M having Band66 as the pass Band can be shared by the high-frequency signals of Band1 and Band 4. Thus, the passband of a plurality of bands is realized by one bandpass filter, and space saving can be realized. Further, since the number of filters through which the high-frequency signals of Band1 and Band4 pass can be reduced, the propagation loss of the high-frequency signals can be improved.

(other modifications, etc.)

While the multiplexer, the high-frequency front-end circuit, and the communication device according to the embodiments of the present invention have been described above by taking the embodiments and the modifications thereof, the present invention also includes other embodiments that are realized by combining any of the constituent elements of the above embodiments and modifications, modifications that are obtained by implementing various modifications that will occur to those skilled in the art to the above embodiments within a range that does not depart from the gist of the present invention, and various devices that incorporate the high-frequency front-end circuit and the communication device of the present invention.

For example, although the above description has been given by taking as an example a 2-division/multiplexing circuit in which two reception signal paths are commonly connected via a common terminal as a multiplexer, the present invention can also be applied to a division/multiplexing circuit in which, for example, a circuit including both a transmission path and a reception path and three or more signal paths are commonly connected via a common terminal.

In each filter included in the multiplexer, an inductor or a capacitor may be connected between the input/output terminal and each terminal such as the ground terminal, or a circuit element other than the inductor such as a resistance element or the capacitor may be added.

The present invention is applicable to a low-loss, small-sized, and low-cost multiplexer, high-frequency front-end circuit, and communication device of frequency specifications for multi-band and multi-mode applications, and is widely applicable to communication devices such as mobile phones.

Description of the reference numerals

1.2, 2A, 2B, 2C, 2D, 6, 600 … high frequency front end circuitry; 3 … a communication device; 10. 14 … wave splitting circuit; 10a … low pass filter; a 10B … high pass filter; 11 … a first filter; 11A, 11L1 … MLB filters; 11B, 11M2 … MBb filter; 11C, 11MH1 … MHBa filters; 11D, 11H2 … HBb filters; an 11H … HB filter; an 11H1 … HBa filter; an 11L … LB filter; an 11M … MB filter; an 11M1 … MBa filter; 11X, 12H … pass bands; 12 … a second filter; 13 … a third filter; 13a, 13b, 13c, 13d, 13e, 13f, 13g, 13h, 13j, 13k, 13p … filters; 13r1 … receiving a filter; 13t, 13t1 … transmit filters; 15 … filter circuit; 21. 22, 21A, 21C, 21D, 21E, 21F, 21G, 22A, 22B, 22C, 22D … switches; 21a, 12b … select terminals; 21c … common terminal; 30 … an amplifying circuit; 31. 32, 33, 34, 35, 36 … LNA; 71. 71a, 71b … IDT electrodes; 72 … clinging to the layer; 73 … main electrode layer; 80 … a substrate; 81 … high sound speed supporting substrate; 82 … low speed membranes; 83 … piezoelectric layer; 84 … protective film; 101 … antenna common terminal; 102. 103 … input/output terminals; 171a, 171b … bus bar electrodes; 172a, 172b … electrode fingers.

Claims

1. A high-frequency front-end circuit is provided with:

an antenna common terminal connected to the antenna element;

a first input/output terminal and a second input/output terminal;

a first filter having a first terminal and a second terminal, the first filter having a first passband, the first terminal being connected to the antenna common terminal;

a second filter connected to the antenna common terminal, disposed between the antenna common terminal and the second input/output terminal, and having a second passband different from the first passband;

a switch having a common terminal and a plurality of selection terminals, the common terminal being connected to the second terminal; and

a third filter connected to a first selection terminal among the plurality of selection terminals and arranged between the switch and the first input/output terminal,

the reflection coefficient in the second pass band is larger when the first filter is viewed solely from the antenna common terminal side than when the third filter is viewed solely from the antenna common terminal side.

2. The high-frequency front-end circuit according to claim 1,

the first filter and the third filter each include two or more elastic wave resonators,

the reflection coefficient in the second pass band when one or more of the two or more elastic wave resonators constituting the first filter are viewed from the antenna common terminal side as a single body is larger than the reflection coefficient in the second pass band when one or more of the two or more elastic wave resonators constituting the third filter are viewed from the antenna common terminal side as a single body.

3. The high-frequency front-end circuit according to claim 1 or 2,

at least one of the first filter and the third filter has a ladder-type filter structure,

the one or more elastic wave resonators disposed on the antenna common terminal side include at least one of a series arm resonator and a parallel arm resonator.

4. The high-frequency front-end circuit according to claim 1 or 2,

at least one of the first filter and the third filter has a longitudinally coupled filter structure.

5. The high-frequency front-end circuit according to claim 1 or 2,

the second input/output terminal is connected to a second amplifier circuit,

a filter circuit is not provided between the second filter and the second amplifier circuit.

6. The high-frequency front-end circuit according to claim 1 or 2, further comprising:

a third input/output terminal; and

a fourth filter connected to the antenna common terminal, arranged between the antenna common terminal and the third input/output terminal, and having a third pass band,

the first filter, the second filter and the fourth filter constitute a triplexer,

the first passband, the second passband, and the third passband are applied to a low frequency band, LB: 698 960MHz, mid band MBa: 1710-: 2300-2690 MHz of the total frequency of the microwave band,

the first passband is any one of the low band, the intermediate band, and the high band.

7. The high-frequency front-end circuit according to claim 1 or 2, further comprising:

a third input/output terminal and a fourth input/output terminal;

a fourth filter connected to the antenna common terminal, disposed between the antenna common terminal and the third input/output terminal, and having a third pass band; and

a fifth filter connected to the antenna common terminal, arranged between the antenna common terminal and the fourth input/output terminal, and having a fourth pass band,

the first filter, the second filter, the fourth filter, and the fifth filter constitute a quadruple multiplexer,

the first pass band, the second pass band, the third pass band, and the fourth pass band are applied to a low frequency band, LB: 698 960MHz, mid band MBa: 1710-: 2300-2400 MHz, high frequency band HBb: 2496 at a frequency of 2690MHz,

the first passband is any one of the low band, the middle band, and the high band.

8. The high-frequency front-end circuit according to claim 1 or 2, further comprising:

a third input/output terminal and a fourth input/output terminal;

the first passband, the second passband, the third passband, and the fourth passband are applied to a middle-low frequency band (MLB): 1475.9-2025 MHz, mid-band, i.e. MBb: 2110-2200 MHz, medium and high frequency band (MHBa: 2300-2400 MHz or MHBb: 2300-: 2496 at a frequency of 2690MHz,

the first passband is any one of the middle-low frequency band, the middle-high frequency band, and the high frequency band.

9. The high-frequency front-end circuit according to claim 5, further comprising:

a third input/output terminal and a fourth input/output terminal;

the first pass band is any one of the middle-low frequency band, the middle-high frequency band and the high frequency band,

the second passband is the mid to high frequency band,

the second filter and the second amplifier circuit are connected to each other through a signal path without a filter circuit.

10. The high-frequency front-end circuit according to claim 9,

the signal path connecting the second filter and the second amplifier circuit is a path for transmitting and receiving Band40a, and the reception Band of Band40a is 2300-2370 MHz.

11. The high-frequency front-end circuit according to claim 9,

the signal path connecting the second filter and the second amplifier circuit is a path for transmitting and receiving a Band40, and the reception Band of the Band40 is 2300-2400 MHz.

12. The high-frequency front-end circuit according to claim 5, further comprising:

a third input/output terminal and a fourth input/output terminal;

the first passband is any one of the middle-low frequency band, the middle-high frequency band, and the middle-high frequency band,

the second passband is the high frequency band,

13. The high-frequency front-end circuit according to claim 10,

the signal path connecting the second filter and the second amplifier circuit is a path for transmitting and receiving a Band41, and the reception Band of the Band41 is 2496-2690 MHz.

14. The high-frequency front-end circuit according to claim 1 or 2,

the first passband is located on a higher frequency side than the second passband,

the first filter and the third filter each include one or more elastic wave resonators,

the one or more acoustic wave resonators constituting the first filter are surface acoustic wave resonators each including a substrate having a piezoelectric layer and an IDT electrode formed on the substrate,

in the first filter, any one of the following is used as the surface acoustic wave: (1) in the presence of LiNbO₃A rayleigh wave propagating through the piezoelectric layer; (2) in the field of chemical synthesis of LiTaO₃A leakage wave propagating through the piezoelectric layer; and (3) a polymer prepared from LiNbO₃And a love wave propagating through the piezoelectric layer.

15. The high-frequency front-end circuit according to claim 14,

in the third filter, the elastic wave resonator is formed of smr (solid mount resonator) or fbar (film Bulk Acoustic resonator).

16. The high-frequency front-end circuit according to claim 1 or 2,

in the first filter, the acoustic wave resonator has a sound velocity film laminated structure including the piezoelectric layer having the IDT electrode formed on one main surface, a high sound velocity support substrate that has a high bulk wave sound velocity higher than a bulk wave sound velocity propagated through the piezoelectric layer, and a low sound velocity film that is disposed between the high sound velocity support substrate and the piezoelectric layer and has a low bulk wave sound velocity lower than the bulk wave sound velocity propagated through the piezoelectric layer,

in the third filter, the elastic wave resonator is formed of an SMR or an FBAR.

17. The high-frequency front-end circuit according to claim 1 or 2,

the first passband is located on a lower frequency side than the second passband,

in the first filter, any one of the following cases is used: (1) is used in LiNbO₃Rayleigh waves propagating in the constituted piezoelectric layer are regarded as elastic surface waves; (2) the elastic wave resonator is composed of SMRs; and (3) the elastic wave resonator is formed of an FBAR.

18. The high frequency front end circuit according to claim 17,

in the third filter, any one of the following cases is used: (1) an acoustic wave resonator having a sound velocity film laminated structure including a piezoelectric layer having an IDT electrode formed on one principal surface, a high-sound-velocity support substrate that has a higher bulk wave sound velocity than an acoustic wave sound velocity propagating through the piezoelectric layer, and a low-sound-velocity film that is disposed between the high-sound-velocity support substrate and the piezoelectric layer and has a lower bulk wave sound velocity than the acoustic wave sound velocity propagating through the piezoelectric layer; (2) is used in LiTaO₃The leakage wave propagating in the structured piezoelectric layer is regarded as a surface acoustic wave; and (3) is used in LiNbO₃The love wave propagating through the piezoelectric layer is formed as a surface acoustic wave.

19. The high-frequency front-end circuit according to claim 1 or 2,

the elastic wave resonators constituting the first filter and the third filter are surface acoustic wave resonators each including a substrate having a piezoelectric layer and an IDT electrode formed on the substrate,

in the third filter, (1) the filter is used in the LiTaO filter₃The leakage wave propagating through the piezoelectric layer is used as a surface acoustic wave, or (2) the leakage wave is used in a piezoelectric element made of LiNbO₃The love wave propagating through the piezoelectric layer is formed as a surface acoustic wave.

20. The high-frequency front-end circuit according to claim 1 or 2,

the first filter is made of LiTaO₃The leakage wave propagating through the piezoelectric layer is formed as a surface acoustic wave,

the third filter is made of LiNbO₃The love wave propagating through the piezoelectric layer is formed as a surface acoustic wave.

21. The high-frequency front-end circuit according to claim 1 or 2,

in the first filter, any one of the following cases is used: (1) is used in LiNbO₃Rayleigh waves propagating in the constituted piezoelectric layer are regarded as elastic surface waves; (2) is used in LiTaO₃The leakage wave propagating in the structured piezoelectric layer is regarded as a surface acoustic wave; (3) is used in LiNbO₃The love wave propagating in the piezoelectric layer is used as an elastic surface wave; (4) the elastic wave resonator is composed of SMRs; and (5) the elastic wave resonator is constituted by an FBAR,

in the third filter, the acoustic wave resonator has a sound velocity film laminated structure including a piezoelectric layer having IDT electrodes formed on one main surface, a high sound velocity support substrate that has a higher sound velocity than the acoustic velocity of the acoustic wave propagating through the piezoelectric layer, and a low sound velocity film that is disposed between the high sound velocity support substrate and the piezoelectric layer and has a lower sound velocity than the acoustic velocity of the acoustic wave propagating through the piezoelectric layer.

22. The high-frequency front-end circuit according to claim 1 or 2,

in the first filter, any one of the following cases is used: (1) is used in LiNbO₃Rayleigh waves propagating in the constituted piezoelectric layer are regarded as elastic surface waves; (2) is used in LiNbO₃The love wave propagating in the piezoelectric layer is used as an elastic surface wave; (3) the elastic wave resonator comprises a piezoelectric layer having IDT electrodes formed on one principal surface, a high-sound-speed support substrate having a higher sound speed than that of an elastic wave propagating through the piezoelectric layer, and a piezoelectric layer disposed between the high-sound-speed support substrate and the piezoelectric layer and connected to the piezoelectric layerA sound velocity film laminated structure including a low sound velocity film in which the sound velocity of an elastic wave propagating through the piezoelectric layer is lower than the sound velocity of a bulk wave propagating through the piezoelectric layer; (4) the elastic wave resonator is composed of SMRs; and (5) the elastic wave resonator is constituted by an FBAR,

the third filter is made of LiTaO₃The leakage wave propagating through the piezoelectric layer is formed as a surface acoustic wave.

23. The high-frequency front-end circuit according to claim 1 or 2,

in the first filter, any one of the following cases is used: (1) an acoustic wave resonator having a sound velocity film laminated structure including a piezoelectric layer having an IDT electrode formed on one principal surface, a high-sound-velocity support substrate that has a higher bulk wave sound velocity than an acoustic wave sound velocity propagating through the piezoelectric layer, and a low-sound-velocity film that is disposed between the high-sound-velocity support substrate and the piezoelectric layer and has a lower bulk wave sound velocity than the acoustic wave sound velocity propagating through the piezoelectric layer; (2) is used in LiTaO₃The leakage wave propagating in the structured piezoelectric layer is regarded as a surface acoustic wave; (3) is used in LiNbO₃The love wave propagating in the piezoelectric layer is used as an elastic surface wave; (4) the elastic wave resonator is composed of SMRs; and (5) the elastic wave resonator is constituted by an FBAR,

the third filter is made of LiNbO₃The rayleigh wave propagating through the structured piezoelectric layer is referred to as a surface acoustic wave.

24. The high-frequency front-end circuit according to claim 1 or 2,

in the first filter, any one of the following cases is used: (1) is used in LiNbO₃Rayleigh waves propagating in the constituted piezoelectric layer are regarded as elastic surface waves; (2) an acoustic wave resonator having a sound velocity film laminated structure including a piezoelectric layer having an IDT electrode formed on one principal surface, a high-sound-velocity support substrate that has a higher bulk wave sound velocity than an acoustic wave sound velocity propagating through the piezoelectric layer, and a low-sound-velocity film that is disposed between the high-sound-velocity support substrate and the piezoelectric layer and has a lower bulk wave sound velocity than the acoustic wave sound velocity propagating through the piezoelectric layer; (3) is used in LiTaO₃The leakage wave propagating in the structured piezoelectric layer is regarded as a surface acoustic wave; (4) the elastic wave resonator is composed of SMRs; and (5) the elastic wave resonator is constituted by an FBAR,

25. The high-frequency front-end circuit according to claim 2,

the two or more elastic wave resonators constituting the first filter and the third filter are surface acoustic wave resonators each including a substrate having a piezoelectric layer and an IDT electrode formed on the substrate,

in the first filter and the third filter, a leakage wave propagating through the piezoelectric layer made of LiTaO3 is used as a surface acoustic wave,

the IDT electrode constituting the first filter and the IDT electrode constituting the third filter are different in film thickness or duty ratio.

26. The high-frequency front-end circuit according to claim 2,

in the first filter and the third filter, the acoustic wave resonator has a sound velocity film laminated structure including the piezoelectric layer having the IDT electrode formed on one main surface, a high-sound-velocity support substrate on which a bulk sound velocity higher than an acoustic wave velocity propagating through the piezoelectric layer is propagated, and a low-sound-velocity film arranged between the high-sound-velocity support substrate and the piezoelectric layer and on which a bulk sound velocity lower than the acoustic wave velocity propagating through the piezoelectric layer is propagated,

in the first filter and the third filter, any one of a film thickness of the IDT electrode, a duty ratio of the IDT electrode, and a film thickness of the low-speed film is different.

27. The high-frequency front-end circuit according to claim 2,

the two or more elastic wave resonators constituting the first filter and the third filter are surface acoustic wave resonators each including a substrate having a piezoelectric layer, an IDT electrode formed on the substrate, and a protective film formed on the IDT electrode,

the first filter and the third filter are made of LiNbO (1)₃Rayleigh waves propagating through the piezoelectric layer or (2) LiNbO₃A love wave propagating through the piezoelectric layer as a surface acoustic wave;

in the first filter and the third filter, any one of a film thickness of the IDT electrode, a duty ratio of the IDT electrode, and a film thickness of the protective film is different.

28. The high-frequency front-end circuit according to claim 2,

the high-speed support substrate is made of silicon crystal,

in the first filter and the third filter, any one of a film thickness of the piezoelectric layer, a film thickness of the low-speed film, and a silicon crystal orientation of the high-speed support substrate is different.

29. The high-frequency front-end circuit according to claim 2,

in the first filter and the third filter, the use of (1) LiTaO₃Leakage wave propagating through the piezoelectric layer or (2) leakage wave propagating through the LiNbO₃The love wave propagating through the piezoelectric layer is formed as a surface acoustic wave,

in the first filter and the third filter, the IDT electrodes are different in film thickness.

30. The high-frequency front-end circuit according to claim 1 or 2, further comprising:

a first amplifier circuit connected to the first input/output terminal; and

and a second amplifier circuit connected to the second input/output terminal.

31. A communication device is provided with:

an RF signal processing circuit that processes a high-frequency signal transmitted and received by the antenna element; and

the high-frequency front-end circuit according to any one of claims 1 to 30, which transmits the high-frequency signal between the antenna element and the RF signal processing circuit.