High-frequency circuit and communication device

Abstract

A high-frequency circuit (1) comprises: a filter (11) having a passband width including a transmission band of a communication band A; and a filter (22) having a passband width including a reception band of a communication band B. The communication band A and the communication band B are a band combination capable of simultaneous communication. The transmission band of the communication band A includes a sub-band X overlapping the reception band of the communication band B and a sub-band Y not overlapping the reception band of the communication band B. The reception band of the communication band B includes the sub-band X and a sub-band Z not overlapping the transmission band of the communication band A. The passband width of the filter (11) is variable to a first passband width including the sub-band X and the sub-band Y and to a second passband width that includes the sub-band Y and that is narrower than the first passband width.

Description

High-frequency circuits and communication devices

[0001] The present invention relates to a high-frequency circuit and a communication device.

[0002] Multi-band front-end circuits are required to transmit and receive multiple high-frequency signals with low loss and high isolation.

[0003] Patent Document 1 discloses a high-frequency module (high-frequency circuit) having a configuration in which a plurality of filters with different passbands are connected to an antenna via a multiplexer (switch).

[0004] US Patent Application Publication No. 2016 / 0127015

[0005] 3GPP (registered trademark) (3rd Generation Partnership Project) is considering simultaneous transmission of signals in two communication bands whose frequency bands partially overlap.

[0006] An object of the present invention is to provide a small-sized high-frequency circuit and communication device that can simultaneously transmit signals in two communication bands with partially overlapping frequency bands while suppressing degradation of isolation and receiving sensitivity.

[0007] In order to achieve the above object, a high-frequency circuit according to one aspect of the present invention comprises: a first filter having a passband that includes a first frequency band, which is one of the transmission band and reception band of a first communication band; and a second filter having a passband that includes a second frequency band, which is the other of the transmission band and reception band of a second communication band, wherein the first communication band and the second communication band are a band combination that allows simultaneous communication, the first frequency band includes a first sub-band that overlaps with the second frequency band and a second sub-band that does not overlap with the second frequency band, the second frequency band includes the first sub-band and a third sub-band that does not overlap with the first communication band, and the passband of the first filter is variable to a first passband that includes the first sub-band and the second sub-band, and a second passband that includes the second sub-band and is narrower than the first passband.

[0008] According to the present invention, it is possible to provide a small-sized high-frequency circuit and communication device that can simultaneously transmit signals in two communication bands whose frequency bands partially overlap, while suppressing degradation of isolation and receiving sensitivity.

[0009] FIG. 1 is a circuit configuration diagram of a high-frequency circuit and a communication device according to an embodiment. FIG. 2 is a diagram illustrating the frequency relationship of communication bands and the pass characteristics of a filter applied to the high-frequency circuit according to the embodiment. FIG. 3A is a circuit diagram illustrating a connection state of a first switch in the high-frequency circuit according to the embodiment when a signal in a first communication band is transmitted alone. FIG. 3B is a circuit diagram illustrating a connection state of a first switch in the high-frequency circuit according to the embodiment when a signal in a first communication band and a signal in a second communication band are simultaneously transmitted. FIG. 4A is a diagram illustrating the frequency relationship of communication bands and the pass characteristics of a filter applied to a high-frequency circuit according to Modification 1. FIG. 4B is a diagram illustrating the frequency relationship of communication bands and the pass characteristics of a filter applied to a high-frequency circuit according to Modification 2. FIG. 5A is a diagram illustrating a first example of the circuit configuration of a first filter according to the embodiment. FIG. 5B is a diagram illustrating a second example of the circuit configuration of a first filter according to the embodiment. FIG. 5C is a diagram illustrating a third example of the circuit configuration of a first filter according to the embodiment. FIG. 6 is a diagram illustrating the frequency relationship of communication bands and the pass characteristics of a filter applied to a high-frequency circuit according to Modification 3. Fig. 7A is a circuit configuration diagram showing a first connection state of a high-frequency circuit according to Modification 4. Fig. 7B is a diagram illustrating the frequency relationship of communication bands applied to the high-frequency circuit according to Modification 4 and the pass characteristics of a filter in the first connection state. Fig. 8A is a circuit configuration diagram showing a second connection state of a high-frequency circuit according to Modification 4. Fig. 8B is a diagram illustrating the frequency relationship of communication bands applied to the high-frequency circuit according to Modification 4 and the pass characteristics of a filter in the second connection state. Fig. 9A is a circuit configuration diagram of a high-frequency circuit and a diver circuit according to Modification 5. Fig. 9B is a circuit configuration diagram of a high-frequency circuit and a primary circuit according to Modification 6.

[0010] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Note that the embodiments described below are all comprehensive or specific examples. The numerical values, shapes, materials, components, arrangements and connection forms of the components shown in the following embodiments are merely examples and are not intended to limit the present invention.

[0011] It should be noted that the drawings are schematic diagrams in which emphasis, omission, or adjustment of proportions has been appropriately made to illustrate the present invention, and are not necessarily strictly illustrated, and may differ from the actual shapes, positional relationships, and proportions. In the drawings, the same reference numerals are used to denote substantially the same components, and redundant explanations may be omitted or simplified.

[0012] In this disclosure, "connected" refers not only to direct connection via a connection terminal and / or a wiring conductor, but also to electrical connection via other circuit elements. Also, "connected between A and B" refers to connection to A and B on a path connecting A and B.

[0013] In addition, in this disclosure, a "transmission path" refers to a transmission line configured with a wiring through which a high-frequency transmission signal propagates, an electrode directly connected to the wiring, and a terminal directly connected to the wiring or the electrode, etc. Also, a "reception path" refers to a transmission line configured with a wiring through which a high-frequency reception signal propagates, an electrode directly connected to the wiring, and a terminal directly connected to the wiring or the electrode, etc.

[0014] Also, in this disclosure, the passband of a filter is defined as the frequency band between two frequencies that are 3 dB greater than the minimum insertion loss within the passband.

[0015] (Embodiment) [1. Circuit Configuration of High-Frequency Circuit 1 and Communication Device 4] The circuit configuration of a high-frequency circuit 1 and a communication device 4 according to this embodiment will be described with reference to Fig. 1. Fig. 1 is a circuit configuration diagram of the high-frequency circuit 1 and the communication device 4 according to the embodiment.

[0016] [1.1 Circuit Configuration of Communication Device 4] First, a description will be given of the circuit configuration of the communication device 4. As shown in Fig. 1 , the communication device 4 according to this embodiment includes a high-frequency circuit 1, antennas 2a and 2b, and an RF signal processing circuit (RFIC) 3.

[0017] The high-frequency circuit 1 transmits high-frequency signals between the antennas 2a and 2b and the RFIC 3. The detailed circuit configuration of the high-frequency circuit 1 will be described later.

[0018] Antenna 2a is connected to antenna terminal 101 of high frequency circuit 1, and transmits high frequency signals output from high frequency circuit 1, and also receives high frequency signals from the outside and outputs them to high frequency circuit 1. Antenna 2b is connected to antenna terminal 102 of high frequency circuit 1, and transmits high frequency signals output from high frequency circuit 1, and also receives high frequency signals from the outside and outputs them to high frequency circuit 1.

[0019] The RFIC 3 is an example of a signal processing circuit that processes high-frequency signals. Specifically, the RFIC 3 performs signal processing, such as down-conversion, on a high-frequency reception signal input via the reception path of the high-frequency circuit 1, and outputs the reception signal generated by the signal processing to a baseband signal processing circuit (BBIC: not shown). The RFIC 3 also performs signal processing, such as up-conversion, on a transmission signal input from the BBIC, and outputs the high-frequency transmission signal generated by the signal processing to the transmission path of the high-frequency circuit 1. The RFIC 3 also has a control unit that controls switches, amplifiers, and the like included in the high-frequency circuit 1. Note that some or all of the functions of the RFIC 3 as a control unit may be implemented outside the RFIC 3, and may be implemented, for example, in the BBIC or the high-frequency circuit 1.

[0020] In the communication device 4 according to this embodiment, the antennas 2a and 2b are not essential components.

[0021] [1.2 Circuit Configuration of High-Frequency Circuit 1] Next, a description will be given of the circuit configuration of the high-frequency circuit 1. As shown in Fig. 1 , the high-frequency circuit 1 includes filters 11, 12, 21, and 22, a switch 50, power amplifiers 31 and 41, low-noise amplifiers 32 and 42, antenna terminals 101 and 102, high-frequency input terminals 110 and 130, and high-frequency output terminals 120 and 140.

[0022] The antenna terminal 101 is connected to the antenna 2a and the terminal 50a of the switch 50. The antenna terminal 102 is connected to the antenna 2b and the terminal 50b of the switch 50. The radio frequency input terminal 110 is connected to the RFIC 3 and the power amplifier 31 and is a terminal for receiving a radio frequency transmission signal from the RFIC 3. The radio frequency input terminal 130 is connected to the RFIC 3 and the power amplifier 41 and is a terminal for receiving a radio frequency transmission signal from the RFIC 3. The radio frequency output terminal 120 is connected to the RFIC 3 and the low noise amplifier 32 and is a terminal for outputting a radio frequency reception signal to the RFIC 3. The radio frequency output terminal 140 is connected to the RFIC 3 and the low noise amplifier 42 and is a terminal for outputting a radio frequency reception signal to the RFIC 3.

[0023] FIG. 2 is a diagram illustrating the frequency relationship between communication band A and communication band B applied to the high-frequency circuit 1 according to the embodiment, and the pass characteristics of the filters 11 and 22. In FIG.

[0024] In this embodiment, communication band A is an example of a first communication band, and communication band B is an example of a second communication band. Communication band A and communication band B are a band combination that allows simultaneous communication. As shown in Fig. 2, the transmission band (A-Tx) of communication band A and the reception band (B-Rx) of communication band B partially overlap in frequency.

[0025] In this embodiment, the transmission band of communication band A is an example of a first frequency band, and the reception band of communication band B is an example of a second frequency band. As shown in Fig. 2, the transmission band of communication band A includes a sub-band X (first sub-band) that overlaps with the reception band of communication band B, and a sub-band Y (second sub-band) that does not overlap with the reception band of communication band B. The reception band of communication band B includes a sub-band X (first sub-band) that overlaps with the transmission band of communication band A, and a sub-band Z (third sub-band) that does not overlap with the transmission band of communication band A.

[0026] In the present disclosure, "partial overlap between one band and another band" does not only mean that a portion of the frequency range of one band overlaps with a portion of the frequency range of the other band, but also means that a point at the low frequency end or high frequency end of one band coincides with a point at the high frequency end or low frequency end of the other band, but does not coincide at other frequencies.

[0027] That is, in this embodiment, the subband X may be configured with only one predetermined frequency point.

[0028] In the present disclosure, each of communication band A, communication band B, and communication bands C and D described below refers to a frequency band predefined by a standardization organization (e.g., 3GPP (registered trademark), IEEE (Institute of Electrical and Electronics Engineers)), etc. for a communication system constructed using radio access technology (RAT). Examples of communication systems that can be used include, but are not limited to, a Long Term Evolution (LTE) system, a 5th Generation (5G)-New Radio (NR) system, and a Wireless Local Area Network (WLAN) system.

[0029] The filter 11 is an example of a first filter, and has a passband that includes the transmission band (first frequency band) of the communication band A. More specifically, the passband of the filter 11 is variable between a first passband that includes subband X and subband Y, and a second passband that includes subband Y and is narrower than the first passband. In other words, the filter 11 varies between a first characteristic having the first passband and a second characteristic having the second passband, for example, in response to a control signal output from the RFIC 3. One end of the filter 11 is connected to a terminal 50c (first terminal) of the switch 50 (first switch), and the other end of the filter 11 is connected to the output terminal of the power amplifier 31.

[0030] The filter 22 is an example of a second filter, and has a pass band that includes the reception band (second frequency band) of the communication band B. One end of the filter 22 is connected to the terminal 50d (second terminal) of the switch 50 (first switch), and the other end of the filter 22 is connected to the input terminal of the low-noise amplifier 42.

[0031] The filter 12 has a passband that includes the receive band of the communication band A. One end of the filter 12 is connected to a terminal 50 c of the switch 50 , and the other end of the filter 12 is connected to the input terminal of the low noise amplifier 32 .

[0032] The filter 21 has a pass band that includes the transmission band of the communication band B. One end of the filter 21 is connected to the terminal 50 d of the switch 50 , and the other end of the filter 21 is connected to the output terminal of the power amplifier 41 .

[0033] The switch 50 is an example of a first switch and has a terminal 50a (first antenna connection terminal), a terminal 50b (second antenna connection terminal), a terminal 50c (first terminal), and a terminal 50d (second terminal). The switch 50 is a double-pole double-throw (DPDT) switch that switches between connection and disconnection between the terminals 50a and 50c, between connection and disconnection between the terminals 50a and 50d, between connection and disconnection between the terminals 50b and 50c, and between connection and disconnection between the terminals 50b and 50d. The terminal 50a is connected to the antenna terminal 101, the terminal 50b is connected to the antenna terminal 102, the terminal 50c is connected to the filters 11 and 12, and the terminal 50d is connected to the filters 21 and 22. With the above connection configuration, switch 50 switches between connecting and disconnecting antenna 2a and filters 11 and 12, between connecting and disconnecting antenna 2a and filters 21 and 22, between connecting and disconnecting antenna 2b and filters 11 and 12, and between connecting and disconnecting antenna 2b and filters 21 and 22.

[0034] The power amplifier 31 has an output terminal connected to the filter 11 and an input terminal connected to a radio frequency input terminal 110. The power amplifier 31 amplifies a radio frequency transmission signal (hereinafter referred to as a transmission signal) of the communication band A input from the radio frequency input terminal 110.

[0035] The power amplifier 41 has an output terminal connected to the filter 21 and an input terminal connected to the high frequency input terminal 130. The power amplifier 41 amplifies the transmission signal of the communication band B input from the high frequency input terminal 130.

[0036] The low-noise amplifier 32 has an input terminal connected to the filter 12 and an output terminal connected to the high-frequency output terminal 120. The low-noise amplifier 32 amplifies a high-frequency received signal of communication band A (hereinafter referred to as the received signal) input from the antenna terminal 101 or 102.

[0037] The low noise amplifier 42 has an input terminal connected to the filter 22 and an output terminal connected to the high frequency output terminal 140. The low noise amplifier 42 amplifies the received signal of communication band B input from the antenna terminal 101 or 102.

[0038] In the above configuration, the high-frequency circuit 1 can execute (1) a first mode in which a transmission signal in sub-band Y of communication band A and a reception signal in sub-band Z of communication band B are simultaneously transmitted; (2) a second mode in which a transmission signal in communication band A is transmitted but a reception signal in communication band B is not transmitted; and (3) a third mode in which a reception signal in communication band B is transmitted but a transmission signal in communication band A is not transmitted.

[0039] 3A is a circuit diagram showing a connection state of the switch 50 in the high-frequency circuit 1 according to the embodiment when a signal of communication band A is transmitted alone, and FIG. 3B is a circuit diagram showing a connection state of the switch 50 in the high-frequency circuit 1 according to the embodiment when a transmission signal of communication band A and a reception signal of communication band B are transmitted simultaneously.

[0040] In the above configuration, when the second mode is executed, the filter 11 is set to the first passband, so that the transmission signal of communication band A can be transmitted using the entire transmission band of communication band A. When the second mode is executed, the terminals 50a and 50c of the switch 50 are connected, as shown in FIG. 3A. Furthermore, when the second mode is executed, it is desirable to disconnect the terminals 50b and 50d of the switch 50. This allows the transmission signal of communication band A that passes through the filter 11 to be transmitted with low loss.

[0041] Furthermore, when the third mode is executed, the received signal of communication band B can be transmitted using the filter 22. When the third mode is executed, the terminals 50b and 50d of the switch 50 are connected. Furthermore, when the third mode is executed, it is desirable to disconnect the terminals 50a and 50c of the switch 50. This allows the received signal of communication band B that passes through the filter 22 to be transmitted with low loss.

[0042] 3B, the filter 11 is set to the second passband, and the terminals 50a and 50c of the switch 50 are connected, and the terminals 50b and 50d are connected, thereby improving the isolation between the transmission signal of the communication band A that passes through the filter 11 and the reception signal of the communication band B that passes through the filter 22, and suppressing deterioration in the reception sensitivity of the communication band B.

[0043] A first example of a conventional configuration for implementing the first mode is to use a single coband filter having a passband that includes the partially overlapping transmission band of communication band A and the reception band of communication band B. However, in this case, it is not possible to prevent the transmission signal of communication band A from leaking into the reception path of communication band B via the coband filter, resulting in a deterioration in the reception sensitivity of communication band B.

[0044] A second example of a conventional configuration for implementing the first mode includes a first high-frequency circuit that transmits a transmission signal in communication band A and a second high-frequency circuit that transmits a reception signal in communication band B, with the first and second high-frequency circuits being completely separated. However, in this case, if the first and second high-frequency circuits are placed close to each other, mutual interference between the transmission signal in communication band A and the reception signal in communication band B will increase, resulting in a deterioration in isolation. Furthermore, ensuring a distance between the first and second high-frequency circuits in order to ensure isolation will result in an increase in the size of the circuit.

[0045] In contrast, in the high-frequency circuit 1 according to the present embodiment, the passband of the filter 11 is variable, so that even if the filter 11 and the filter 22 are disposed close to each other, mutual interference between the transmission signal of the communication band A and the reception signal of the communication band B during the first mode can be suppressed, thereby ensuring isolation. Therefore, it is possible to provide a compact high-frequency circuit 1 that can simultaneously transmit the transmission signal of the communication band A and the reception signal of the communication band B while suppressing degradation of isolation and reception sensitivity.

[0046] In the high-frequency circuit 1 according to this embodiment, the switch 50 (first switch) may be an SPDT (Single Pole Double Throw) switch instead of a DPDT switch. In this case, only one antenna is connected to the high-frequency circuit 1. That is, the first switch has one antenna connection terminal, a first terminal, and a second terminal, and switches between connection and disconnection between the antenna connection terminal and the first terminal, and between connection and disconnection between the antenna connection terminal and the second terminal. The antenna connection terminal is connected to one antenna, the first terminal is connected to filters 11 and 12, and the second terminal is connected to filters 21 and 22.

[0047] When the first switch is an SPDT switch, the filter 11 is set to the first passband when the second mode is executed, so that the transmission signal of the communication band A can be transmitted using the entire transmission band of the communication band A. When the second mode is executed, the antenna connection terminal of the first switch is connected to the first terminal. Furthermore, when the second mode is executed, it is desirable to disconnect the antenna connection terminal of the first switch from the second terminal. This allows the transmission signal of the communication band A that passes through the filter 11 to be transmitted with low loss.

[0048] Furthermore, when the first switch is an SPDT type switch, the filter 22 can be used to transmit the received signal of communication band B when the third mode is executed. When the third mode is executed, the antenna connection terminal and the second terminal of the first switch are connected. Furthermore, when the third mode is executed, it is desirable to disconnect the antenna connection terminal and the first terminal of the first switch. This allows the received signal of communication band B that passes through the filter 22 to be transmitted with low loss.

[0049] Furthermore, when the first switch is an SPDT switch and the first mode is executed, the filter 11 is set to the second passband, the antenna connection terminal of the first switch is connected to the first terminal, and the antenna connection terminal is connected to the second terminal, thereby improving isolation between a transmission signal of communication band A passing through the filter 11 and a reception signal of communication band B passing through the filter 22, and suppressing deterioration of the reception sensitivity of communication band B.

[0050] In the high-frequency circuit 1 according to this embodiment, the filters 11 and 22 are essential components, and other circuit elements are not necessary.

[0051] In the high-frequency circuit 1 according to this embodiment, the communication band A is, for example, either band 8 for 4G-LTE (transmission band: 880-915 MHz, reception band: 925-960 MHz) or band n8 for 5G-NR (transmission band: 880-915 MHz, reception band: 925-960 MHz), and the communication band B is, for example, either band 5 for 4G-LTE (transmission band: 824-849 MHz, reception band: 869-894 MHz) or band n5 for 5G-NR (transmission band: 824-849 MHz, reception band: 869-894 MHz).

[0052] [1.3 Circuit Configuration of High-Frequency Circuit According to Modification 1] Note that the filter 11 may not vary the pass band, and the filter 22 may vary the pass band.

[0053] The high-frequency circuit according to Modification 1 includes filters 11, 12, 21, and 22, a switch 50, power amplifiers 31 and 41, low-noise amplifiers 32 and 42, antenna terminals 101 and 102, high-frequency input terminals 110 and 130, and high-frequency output terminals 120 and 140. The high-frequency circuit according to this modification differs from the high-frequency circuit 1 according to the embodiment only in that filter 11 is a filter with a fixed pass band and filter 22 is a filter with a variable pass band. Hereinafter, a description of the high-frequency circuit according to this modification that is the same as that of the high-frequency circuit 1 according to the embodiment will be omitted, and the description will focus on the different configurations.

[0054] 4A is a diagram illustrating the frequency relationship between communication band A and communication band B applied to the high-frequency circuit according to the first modification of the embodiment, and the pass characteristics of filters 11 and 22. In this modification, communication band A is an example of the second communication band, and communication band B is an example of the first communication band. Communication band A and communication band B are a band combination that allows simultaneous communication. As shown in FIG. 4A, the transmission band (A-Tx) of communication band A and the reception band (B-Rx) of communication band B partially overlap in frequency.

[0055] In this modification, the reception band of communication band B is an example of a first frequency band, and the transmission band of communication band A is an example of a second frequency band. As shown in Fig. 4A , the reception band of communication band B includes a subband X (first subband) that overlaps with the transmission band of communication band A, and a subband Z (second subband) that does not overlap with the transmission band of communication band A. Furthermore, the transmission band of communication band A includes a subband X (first subband) that overlaps with the reception band of communication band B, and a subband Y (third subband) that does not overlap with the reception band of communication band B.

[0056] The filter 22 is an example of a first filter and has a passband that includes the reception band (first frequency band) of the communication band B. More specifically, the filter 22 varies a first passband that includes subband X and subband Z and a second passband that includes subband Z and is narrower than the first passband. In other words, the filter 22 varies a third characteristic that has the first passband and a fourth characteristic that has the second passband. One end of the filter 22 is connected to a terminal 50d (first terminal) of the switch 50 (first switch), and the other end of the filter 22 is connected to the input end of the low-noise amplifier 42.

[0057] The filter 11 is an example of a second filter, and has a pass band that includes the transmission band (second frequency band) of the communication band A. One end of the filter 11 is connected to the terminal 50c (second terminal) of the switch 50 (first switch), and the other end of the filter 11 is connected to the input terminal of the power amplifier 31.

[0058] The switch 50 is an example of a first switch, and has a terminal 50a (first antenna connection terminal), a terminal 50b (second antenna connection terminal), a terminal 50c (second terminal), and a terminal 50d (first terminal).

[0059] In the above configuration, the high-frequency circuit according to this modified example can execute (1) a first mode in which a transmission signal in sub-band Y of communication band A and a reception signal in sub-band Z of communication band B are simultaneously transmitted; (2) a second mode in which a transmission signal in communication band A is transmitted but a reception signal in communication band B is not transmitted; and (3) a third mode in which a reception signal in communication band B is transmitted but a transmission signal in communication band A is not transmitted.

[0060] According to the above configuration, when the third mode is executed, by setting the filter 22 to the first pass band, it is possible to transmit the reception signal of communication band B using the entire reception band of communication band B. Furthermore, when the second mode is executed, it is possible to transmit the transmission signal of communication band A using the filter 11. Furthermore, when the first mode is executed, by setting the filter 22 to the second pass band, it is possible to improve isolation between the reception signal of communication band B that passes through the filter 22 and the transmission signal of communication band A that passes through the filter 11, and it is possible to suppress deterioration of the reception sensitivity of communication band B.

[0061] In the high-frequency circuit according to this modification, the passband of the filter 22 is variable, so that even if the filters 11 and 22 are disposed close to each other, mutual interference between the transmission signal of communication band A and the reception signal of communication band B during execution of the first mode can be suppressed, thereby ensuring isolation. Therefore, it is possible to provide a compact high-frequency circuit that can simultaneously transmit the transmission signal of communication band A and the reception signal of communication band B while suppressing degradation of isolation and reception sensitivity.

[0062] In the high-frequency circuit of this modified example, communication band A is, for example, either band 8 for 4G-LTE or band n8 for 5G-NR, and communication band B is, for example, either band 5 for 4G-LTE or band n5 for 5G-NR.

[0063] [1.4 Circuit Configuration of High-Frequency Circuit According to Modification 2] It should be noted that both the filters 11 and 22 may have variable passbands.

[0064] The high-frequency circuit according to Modification 2 includes filters 11, 12, 21, and 22, a switch 50, power amplifiers 31 and 41, low-noise amplifiers 32 and 42, antenna terminals 101 and 102, high-frequency input terminals 110 and 130, and high-frequency output terminals 120 and 140. The high-frequency circuit according to this modification differs from the high-frequency circuit 1 according to the embodiment only in that both filters 11 and 22 are filters with variable passbands. Hereinafter, a description of the high-frequency circuit according to this modification that is the same as that of the high-frequency circuit 1 according to the embodiment will be omitted, and the description will focus on the different configurations.

[0065] 4B is a diagram illustrating the frequency relationship between communication band A and communication band B applied to the high-frequency circuit according to the second modification of the embodiment, and the pass characteristics of filters 11 and 22. In this modification, communication band A is an example of a first communication band, and communication band B is an example of a second communication band. Communication band A and communication band B are a band combination that allows simultaneous communication. As shown in FIG. 4B, the transmission band (A-Tx) of communication band A and the reception band (B-Rx) of communication band B partially overlap in frequency.

[0066] In this modification, the transmission band of communication band A is an example of a first frequency band, and the reception band of communication band B is an example of a second frequency band. As shown in Fig. 4B , the transmission band of communication band A includes a subband X (first subband) that overlaps with the reception band of communication band B, and a subband Y (second subband) that does not overlap with the reception band of communication band B. Furthermore, the reception band of communication band B includes a subband X (first subband) that overlaps with the transmission band of communication band A, and a subband Z (third subband) that does not overlap with the transmission band of communication band A.

[0067] The filter 11 is an example of a first filter and has a passband that includes the transmission band (first frequency band) of the communication band A. More specifically, the filter 11 varies a first passband that includes subband X and subband Y and a second passband that includes subband Y and is narrower than the first passband. In other words, the filter 11 varies a first characteristic having the first passband and a second characteristic having the second passband. One end of the filter 11 is connected to a terminal 50c (first terminal) of the switch 50 (first switch), and the other end of the filter 11 is connected to the output terminal of the power amplifier 31.

[0068] The filter 22 is an example of a second filter and has a passband that includes the reception band (second frequency band) of the communication band B. More specifically, the filter 22 varies a third passband that includes subband X and subband Z and a fourth passband that includes subband Z and is narrower than the third passband. In other words, the filter 22 varies a third characteristic that has the third passband and a fourth characteristic that has the fourth passband. One end of the filter 22 is connected to the terminal 50d (second terminal) of the switch 50 (first switch), and the other end of the filter 22 is connected to the input end of the low-noise amplifier 42.

[0069] In the above configuration, the high-frequency circuit according to this modified example can execute (1) a first mode in which a transmission signal in sub-band Y of communication band A and a reception signal in sub-band Z of communication band B are simultaneously transmitted; (2) a second mode in which a transmission signal in communication band A is transmitted but a reception signal in communication band B is not transmitted; and (3) a third mode in which a reception signal in communication band B is transmitted but a transmission signal in communication band A is not transmitted.

[0070] According to the above configuration, when the second mode is executed, by setting the filter 11 to the first pass band, it is possible to transmit a transmission signal of communication band A using the entire transmission band of communication band A. Furthermore, when the third mode is executed, it is possible to transmit a reception signal of communication band B using the filter 22. Furthermore, when the first mode is executed, by setting the filter 11 to the second pass band and the filter 22 to the fourth pass band, it is possible to further suppress mutual interference between a transmission signal of communication band A that passes through the filter 11 and a reception signal of communication band B that passes through the filter 22, thereby improving isolation and suppressing deterioration in the reception sensitivity of a reception signal of communication band B.

[0071] In the high-frequency circuit according to this modification, the passbands of the filters 11 and 22 are variable, so that even if the filters 11 and 22 are disposed close to each other, high isolation can be ensured between the transmission signal of the communication band A and the reception signal of the communication band B when the first mode is executed. Therefore, it is possible to provide a compact high-frequency circuit that can simultaneously transmit the transmission signal of the communication band A and the reception signal of the communication band B while suppressing degradation of isolation and reception sensitivity.

[0072] In the high-frequency circuit of this modified example, communication band A is, for example, either band 8 for 4G-LTE or band n8 for 5G-NR, and communication band B is, for example, either band 5 for 4G-LTE or band n5 for 5G-NR.

[0073] [1.5 Example of Circuit Configuration of Filter 11] Next, an example of the circuit configuration of the filter 11 that varies the passband will be illustrated.

[0074] Fig. 5A is a diagram illustrating a first example of a circuit configuration of the filter 11 according to the embodiment, Fig. 5B is a diagram illustrating a second example of a circuit configuration of the filter 11 according to the embodiment, and Fig. 5C is a diagram illustrating a third example of a circuit configuration of the filter 11 according to the embodiment.

[0075] The filter 11 shown in FIG. 5A includes circuit elements 71, 72, and 73, a switch 56, and an acoustic wave resonator 60. The circuit elements 71 and 72 are connected in series on a series arm path connecting terminals 111 and 112. The acoustic wave resonator 60 is connected between the connection point of the circuit elements 71 and 72 and ground. The switch 56 is connected in series with the acoustic wave resonator 60 on a parallel arm path connecting the connection point and ground. The circuit element 73 is connected in parallel to the switch 56. Each of the circuit elements 71, 72, and 73 is, for example, an inductor, a capacitor, or an acoustic wave resonator. The resonant bandwidth (the frequency difference between the antiresonant frequency and the resonant frequency) of the acoustic wave resonator 60 is variable depending on whether the switch 51 is conductive or non-conductive. As a result, the passband of the filter 11 of this example is variable depending on whether the switch 56 is conductive or non-conductive.

[0076] 5B includes circuit elements 71, 72, and 73, a switch 56, and an acoustic wave resonator 60. The circuit elements 71 and 72 are connected in series on a series arm path connecting terminals 111 and 112. The acoustic wave resonator 60 is connected between the connection point of the circuit elements 71 and 72 and ground. The series connection circuit of the switch 56 and the circuit element 73 is connected in parallel to the acoustic wave resonator 60. Each of the circuit elements 71, 72, and 73 is, for example, an inductor, a capacitor, or an acoustic wave resonator. The resonance bandwidth of the acoustic wave resonator 60 is variable depending on whether the switch 56 is conductive or non-conductive. As a result, the passband of the filter 11 of this example is variable depending on whether the switch 56 is conductive or non-conductive.

[0077] The filter 11 shown in FIG. 5C includes circuit elements 71 and 72, a variable circuit element 74, and an acoustic wave resonator 60. The circuit elements 71 and 72 are connected in series on a series arm path connecting terminals 111 and 112. The acoustic wave resonator 60 is connected between the connection point of the circuit elements 71 and 72 and ground. The variable circuit element 74 is connected between the connection point of the circuit elements 71 and 72 and ground. Each of the circuit elements 71 and 72 is, for example, an inductor, a capacitor, or an acoustic wave resonator. The variable circuit element 74 is, for example, a variable inductor or a variable capacitor. Note that the variable circuit element 74 may be configured with an inductor, a capacitor, or an acoustic wave resonator and a switch. The resonance bandwidth of the acoustic wave resonator 60 is variable by varying the physical quantity (inductance value or capacitance value) of the variable circuit element 74. As a result, the passband of the filter 11 of this example is variable by varying the physical quantity of the variable circuit element 74.

[0078] [1.6 Circuit Configuration of High-Frequency Circuit According to Modification 3] The passband of the filter 11 may include one of the transmission band and the reception band of the communication band C (third communication band).

[0079] The high-frequency circuit according to Modification 3 includes filters 11, 12, 21, and 22, a switch 50, power amplifiers 31 and 41, low-noise amplifiers 32 and 42, antenna terminals 101 and 102, high-frequency input terminals 110 and 130, and high-frequency output terminals 120 and 140. The high-frequency circuit according to this modification differs from the high-frequency circuit 1 according to the embodiment only in that the pass band of filter 11 includes the transmission band of communication band C (third communication band). Hereinafter, a description of the high-frequency circuit according to this modification that is the same as that of the high-frequency circuit 1 according to the embodiment will be omitted, and the description will focus on the different configurations.

[0080] 6 is a diagram illustrating the frequency relationship between communication bands A, B, and C applied to a high-frequency circuit according to a third modification of the embodiment, as well as the passband characteristics of filters 11 and 22. In this modification, communication band A is an example of a first communication band, and communication band B is an example of a second communication band. Communication bands A and B are a band combination that allows simultaneous communication. As shown in FIG. 6, the transmission band (A-Tx) of communication band A and the reception band (B-Rx) of communication band B partially overlap in frequency. Furthermore, the transmission band (C-Tx) of communication band C overlaps with sub-band Y of the transmission band of communication band A, but does not overlap with sub-band X.

[0081] The filter 11 is an example of a first filter, and has a pass band that includes the transmission band of the communication band A (first frequency band) and the transmission band of the communication band C.

[0082] In the above configuration, the high-frequency circuit according to variant example 3 can execute (1) a first mode in which a transmission signal of sub-band Y of communication band A and a reception signal of sub-band Z of communication band B are simultaneously transmitted; (2) a second mode in which a transmission signal of communication band A is transmitted but a reception signal of communication band B is not transmitted; (3) a third mode in which a reception signal of communication band B is transmitted but a transmission signal of communication band A is not transmitted; and (4) a fourth mode in which a transmission signal of communication band C is transmitted.

[0083] When the fourth mode is executed, the filter 11 is set to the second passband, thereby improving the signal quality of the transmission signal of the communication band C that passes through the filter 11 .

[0084] In the high-frequency circuit according to this modification, the transmission band of the communication band C may overlap with the sub-band X. In this case, when the fourth mode is executed, the filter 11 is set to the first passband, so that the transmission signal of the communication band C can be transmitted using the entire transmission band of the communication band C.

[0085] Furthermore, in the high-frequency circuit according to this modification, the band that overlaps with the transmission band of communication band A may not be the transmission band of communication band C, but may be the reception band of communication band C. In this case, when transmitting a reception signal of communication band C, the filter 11 is set to the second pass band, thereby making it possible to suppress deterioration of the reception sensitivity of communication band C.

[0086] Furthermore, in the high-frequency circuit according to the first modification, the passband of the filter 22 may include one of the transmission band and reception band of the communication band C (third communication band). In this case, when transmitting a transmission signal or reception signal of the communication band C, setting the filter 22 to the third passband or the fourth passband can improve the quality of the transmission signal of the communication band C or suppress deterioration of the reception sensitivity of the communication band C.

[0087] Furthermore, in the high-frequency circuit according to Modification 2, the pass band of filter 11 or the pass band of filter 22 may include one of the transmission band and reception band of communication band C (third communication band). In this case, when transmitting a transmission signal or reception signal of communication band C, by setting filter 11 to the first pass band or the second pass band, or setting filter 22 to the third pass band or the fourth pass band, it is possible to improve the quality of the transmission signal of communication band C or to suppress deterioration of the reception sensitivity of communication band C.

[0088] In the high-frequency circuit of this modified example, communication band A is, for example, either band 8 for 4G-LTE or band n8 for 5G-NR, communication band B is, for example, either band 5 for 4G-LTE or band n5 for 5G-NR, and communication band C is, for example, band n106 for 5G-NR (transmit band: 896-901 MHz, receive band: 935-940 MHz).

[0089] [1.7 Circuit Configuration of High-Frequency Circuit 1A According to Modification 4] In this modification, a circuit that simultaneously transmits a signal of communication band D, which does not overlap with communication band A and communication band B, will be described.

[0090] Fig. 7A is a circuit configuration diagram illustrating a first connection state of the high-frequency circuit 1A according to Modification 4. Fig. 7B is a diagram illustrating an example of the frequency relationship of each communication band applied to the high-frequency circuit 1A according to Modification 4 and the pass characteristics of each filter in the first connection state.

[0091] Fig. 8A is a circuit configuration diagram illustrating a second connection state of the high-frequency circuit 1A according to Modification 4. Fig. 8B is a diagram illustrating an example of the frequency relationship of each communication band applied to the high-frequency circuit 1A according to Modification 4 and the pass characteristics of each filter in the second connection state.

[0092] 7A and 8A , the high-frequency circuit 1A according to the fourth modification includes filters 11, 12, 13, 21, and 22, a switch 51, a matching circuit 75, power amplifiers 31, 33, and 41, low-noise amplifiers 32 and 42, antenna terminals 101 and 102, high-frequency input terminals 110, 130, and 150, and high-frequency output terminals 120 and 140. The high-frequency circuit 1A according to this modification differs from the high-frequency circuit 1 according to the embodiment in that it includes an additional circuit element for transmitting signals of communication band D. Hereinafter, the high-frequency circuit 1A according to this modification will be described mainly with respect to the different configuration, and a description of the same configuration as that of the high-frequency circuit 1 according to the embodiment will be omitted.

[0093] Antenna terminal 101 is connected to antenna 2a and terminal 51a of switch 51. Antenna terminal 102 is connected to antenna 2b and terminal 51b of switch 51. High frequency input terminal 150 is connected to power amplifier 33 and is a terminal for receiving a transmission signal.

[0094] In this modification, communication band A is an example of a first communication band, communication band B is an example of a second communication band, and communication band D is an example of a fourth communication band. Communication band A, communication band B, and communication band D are a band combination that allows simultaneous communication. As shown in FIGS. 7B and 8B , the transmission band (A-Tx) of communication band A and the reception band (B-Rx) of communication band B partially overlap in frequency. Furthermore, the transmission band (D-Tx) of communication band D does not overlap in frequency with the transmission band (A-Tx) of communication band A and the reception band (B-Rx) of communication band B.

[0095] In this modification, the transmission band of communication band A is an example of a first frequency band, the reception band of communication band B is an example of a second frequency band, and the transmission band of communication band D is an example of a third frequency band. As shown in Figures 7B and 8B, the transmission band of communication band A includes sub-band X (first sub-band) that overlaps with the reception band of communication band B, and sub-band Y (second sub-band) that does not overlap with the reception band of communication band B. Furthermore, the reception band of communication band B includes sub-band X (first sub-band) that overlaps with the transmission band of communication band A, and sub-band Z (third sub-band) that does not overlap with the transmission band of communication band A.

[0096] The filter 11 is an example of a first filter, and varies a first passband that includes subband X and subband Y and a second passband that includes subband Y and is narrower than the first passband. In other words, the filter 11 varies a first characteristic having the first passband and a second characteristic having the second passband. One end of the filter 11 is connected to a terminal 51 c (first terminal) of the switch 51 (first switch), and the other end of the filter 11 is connected to the output terminal of the power amplifier 31.

[0097] The filter 22 is an example of a second filter, and has a pass band that includes the reception band (second frequency band) of the communication band B. One end of the filter 22 is connected to the terminal 51d (second terminal) of the switch 51 (first switch), and the other end of the filter 22 is connected to the input terminal of the low-noise amplifier 42.

[0098] The filter 12 has a pass band that includes the reception band of the communication band A. One end of the filter 12 is connected to the terminal 51 c of the switch 51 , and the other end of the filter 12 is connected to the input terminal of the low-noise amplifier 32 .

[0099] The filter 21 has a pass band that includes the transmission band of the communication band B. One end of the filter 21 is connected to the terminal 51 d of the switch 51 , and the other end of the filter 21 is connected to the output terminal of the power amplifier 41 .

[0100] The filter 13 is an example of a third filter, and has a pass band that includes the transmission band (third frequency band) of the communication band D. One end of the filter 13 is connected to the terminal 51c (first terminal) of the switch 51 (first switch), and the other end of the filter 13 is connected to the output terminal of the power amplifier 33.

[0101] The matching circuit 75 is an example of an impedance matching circuit and is connected between the terminal 51e and the ground. The matching circuit 75 is configured with, for example, at least one of an inductor, a capacitor, and an acoustic wave resonator.

[0102] The switch 51 is an example of a first switch and a second switch, and has a terminal 51a (first antenna connection terminal), a terminal 51b (second antenna connection terminal), a terminal 51c (first terminal), a terminal 51d (second terminal), and a terminal 51e. The terminals 51a, 51b, 51c, and 51d of the switch 51 constitute a first switch, and the terminals 51a and 51e of the switch 51 constitute a second switch. The switch 51 switches between connection and disconnection between the terminals 51a and 51c, between connection and disconnection between the terminals 51a and 51d, between connection and disconnection between the terminals 51b and 51c, and between connection and disconnection between the terminals 51b and 51d. The switch 51 also switches between connection and disconnection between the terminals 51a and 51e. The switch 51 may be a switch circuit configured with a first switch having terminals 51a, 51b, 51c, and 51d, and a second switch having terminals 51a and 51e.

[0103] Terminal 51a is connected to antenna terminal 101, terminal 51b is connected to antenna terminal 102, terminal 51c is connected to filters 11, 12, and 13, terminal 51d is connected to filters 21 and 22, and terminal 51e is connected to matching circuit 75. With the above connection configuration, switch 51 switches between connecting and disconnecting antenna 2a and filters 11 to 13, between connecting and disconnecting antenna 2a and filters 21 and 22, between connecting and disconnecting antenna 2b and filters 11 to 13, between connecting and disconnecting antenna 2b and filters 21 and 22, and between connecting and disconnecting antenna 2a and matching circuit 75. Note that switch 51 may switch between connecting and disconnecting terminal 51c and terminal 51e instead of switching between connecting and disconnecting terminal 51a and terminal 51e. In this case, the switch 51 switches between connection and disconnection between the filters 11 to 13 and the matching circuit 75, instead of switching between connection and disconnection between the antenna 2a and the matching circuit 75.

[0104] The power amplifier 33 has an output terminal connected to the filter 13 and an input terminal connected to the high frequency input terminal 150. The power amplifier 33 amplifies the transmission signal of the communication band D input from the high frequency input terminal 150.

[0105] In the above configuration, the high-frequency circuit 1A can execute (1) a fifth mode in which a transmission signal of sub-band Y of communication band A, a reception signal of sub-band Z of communication band B, and a transmission signal of communication band D are simultaneously transmitted; (2) a sixth mode in which a transmission signal of communication band A and a transmission signal of communication band D are simultaneously transmitted, but a reception signal of communication band B is not transmitted; and (3) a third mode in which a reception signal of communication band B is transmitted, but a transmission signal of communication band A is not transmitted.

[0106] 7A and 7B, when the sixth mode is executed, the filter 11 is set to the first passband, so that the transmission signal of the communication band A can be transmitted using the entire transmission band of the communication band A. In this case, the terminal 51a is connected to the terminal 51c, and the terminal 51d is not connected to the terminals 51a and 51b. Furthermore, the terminal 51a is not connected to the terminal 51e.

[0107] 8A and 8B , when the fifth mode is executed, the filter 11 is set to the second passband. At this time, the terminals 51a and 51c are connected, and the terminals 51b and 51d are connected. This improves the isolation between the transmission signal of communication band A that passes through the filter 11 and the reception signal of communication band B that passes through the filter 22, thereby suppressing deterioration in the reception sensitivity of the communication band B.

[0108] However, when switching from the sixth mode to the fifth mode, as shown in Figures 7B and 8B, by changing the pass band of filter 11 from the first pass band to the second pass band, the attenuation characteristics of filter 11 in the transmission band of communication band D change (resulting in the attenuation characteristics indicated by the dashed line in Figure 8B (matching circuit 75 not connected)). In contrast, when switching to the fifth mode, terminal 51a and terminal 51e are further connected, thereby connecting matching circuit 75 to filters 11, 12, and 13. This makes it possible to adjust the attenuation characteristics of filter 11 when the pass band changes, and improve the attenuation characteristics of filter 11 in the transmission band of communication band D (resulting in the attenuation characteristics indicated by the solid line in Figure 8B (matching circuit 75 connected)).

[0109] Therefore, in simultaneous transmission of signals of two communication bands A and B, whose frequency bands partially overlap, it is possible to suppress deterioration of isolation and receiving sensitivity, and it is possible to transmit communication band D, which transmits simultaneously with communication band A and communication band B, with low loss.

[0110] In the high-frequency circuit according to this modification, the communication band A is, for example, either band 8 for 4G-LTE or band n8 for 5G-NR, and the communication band B is, for example, either band 5 for 4G-LTE or band n5 for 5G-NR. The communication band D is, for example, either band 28 (transmit band: 703-748 MHz, receive band: 758-803 MHz) or band 12 (transmit band: 699-716 MHz, receive band: 729-746 MHz) for 4G-LTE, or either band n28 (transmit band: 703-748 MHz, receive band: 758-803 MHz) or band n12 (transmit band: 699-716 MHz, receive band: 729-746 MHz) for 5G-NR.

[0111] 9A is a circuit configuration diagram of a high-frequency circuit 1B and a diver circuit 5B according to Modification 5. The high-frequency circuit 1B is an example of a high-frequency circuit according to the present invention, and is connected to the diver circuit 5B. As shown in FIG. 9A, the high-frequency circuit 1B according to this modification includes filters 11, 12, 13, 21, 22, and 23, a switch 52, and a matching circuit 75.

[0112] The filter 11 is an example of a first filter and has a passband that includes the transmission band of band n8 (communication band A) for 5G-NR. Band n8 for 5G-NR is an example of a first communication band.

[0113] The filter 12 has a passband that includes the receive band of band n8 for 5G-NR.

[0114] The filter 21 has a passband including the transmission band of band n5 (communication band B) for 5G-NR and the transmission band of band n26 (transmission band: 814-849 MHz, reception band: 859-894 MHz). Band n5 for 5G-NR is an example of a second communication band.

[0115] Filter 22 is an example of a second filter and has a passband that includes the reception band of band n5 and the reception band of band n26 for 5G-NR.

[0116] The filter 13 has a passband that includes the transmission band of band n28 (communication band D) for 5G-NR or the transmission band of band n12 (communication band D) for 5G-NR.

[0117] The filter 23 has a passband that includes the receiving band of band n28 for 5G-NR or the receiving band of band n12 for 5G-NR.

[0118] In this modification, band n8 and band n5 are a band combination that allows simultaneous communication. The transmission band of band n8 and the reception band of band n5 partially overlap in frequency. The transmission band of band n8 is an example of a first frequency band, and the reception band of band n5 is an example of a second frequency band. The transmission band of band n8 includes subband X (first subband) that overlaps with the reception band of band n5, and subband Y (second subband) that does not overlap with the reception band of band n5. Furthermore, the reception band of band n5 includes subband X (first subband) that overlaps with the transmission band of band n8, and subband Z (third subband) that does not overlap with the transmission band of band n8.

[0119] The filter 11 is variable between a first passband that includes subbands X and Y and a second passband that includes subband Y and is narrower than the first passband. One end of the filter 11 is connected to a first selection terminal of the switch 52.

[0120] The filter 22 has a passband that includes the subband X and the subband Z. One end of the filter 22 is connected to the second selection terminal of the switch 52 .

[0121] The matching circuit 75 is an example of an impedance matching circuit, and is connected between the third selection terminal of the switch 52 and ground.

[0122] Switch 52 is an example of a first switch, and switches between connection and disconnection between the first antenna and filters 11 and 12, between connection and disconnection between the first antenna and filters 21 and 22, between connection and disconnection between the first antenna and filters 13 and 23, between connection and disconnection between the first antenna and diver circuit 5B, between connection and disconnection between the second antenna and filters 11 and 12, between connection and disconnection between the second antenna and filters 21 and 22, between connection and disconnection between the second antenna and filters 13 and 23, between connection and disconnection between the second antenna and diver circuit 5B, and between connection and disconnection between the second antenna and matching circuit 75.

[0123] As shown in FIG. 9A, the diver circuit 5B includes filters 82 and 92 and a switch 53.

[0124] Filter 92 has a passband that includes the receive band of band n5 and the receive band of band n26 for 5G-NR.

[0125] Filter 82 has a passband that includes the receive band of band n8 for 5G-NR.

[0126] The switch 53 switches between connecting and disconnecting the third antenna and filter 92, between connecting and disconnecting the third antenna and filter 82, between connecting and disconnecting the third antenna and high-frequency circuit 1B, between connecting and disconnecting the fourth antenna and filter 92, between connecting and disconnecting the fourth antenna and filter 82, and between connecting and disconnecting the fourth antenna and high-frequency circuit 1B.

[0127] In the above configuration, the high-frequency circuit 1B and the diver circuit 5B can execute (1) a first mode in which a transmission signal of sub-band Y of communication band A and a reception signal of sub-band Z of communication band B are simultaneously transmitted, (2) a second mode in which a transmission signal of communication band A is transmitted but a reception signal of communication band B is not transmitted, and (3) a third mode in which a reception signal of communication band B is transmitted but a transmission signal of communication band A is not transmitted.

[0128] In the above configuration, when the second mode is executed, the filter 11 is set to the first passband, so that the transmission signal of the communication band A can be transmitted using the entire transmission band of the communication band A. Furthermore, when the second mode is executed, the filter 11 is connected to the first antenna or the second antenna.

[0129] When the third mode is executed, the filter 22 can be used to transmit the received signal of the communication band B. When the third mode is executed, the filter 22 is connected to the first antenna or the second antenna.

[0130] 9A , the filter 11 is set to the second passband, and the filter 11 is connected to the second antenna, and the filter 22 is connected to the first antenna. Alternatively, the first antenna or the second antenna may be connected to a matching circuit 75. This improves the isolation between the transmission signal of communication band A that passes through the filter 11 and the reception signal of communication band B that passes through the filter 22, and suppresses deterioration of the reception sensitivity of communication band B.

[0131] 9A, when the first mode is executed, the filter 82 may be connected to the fourth antenna, and the filter 92 may be connected to the third antenna, so that the received signal of the communication band A and the received signal of the communication band B can be received by the diver circuit 5B.

[0132] 9B is a circuit configuration diagram of a high-frequency circuit 1C and a primary circuit 5C according to Modification 6. The high-frequency circuit 1C is an example of a high-frequency circuit according to the present invention, and is connected to the primary circuit 5C. As shown in FIG. 9B , the high-frequency circuit 1C according to this modification includes filters 11, 12, 22, and 23, a switch 55, and a matching circuit 75.

[0133] The filter 11 is an example of a first filter and has a passband that includes the transmission band of band n8 (communication band A) for 5G-NR. Band n8 for 5G-NR is an example of a first communication band.

[0134] The filter 12 has a passband that includes the receive band of band n8 for 5G-NR.

[0135] Filter 22 is an example of a second filter and has a passband that includes the reception band of band n5 (communication band B) for 5G-NR and the reception band of band n26.

[0136] The filter 23 has a passband that includes the receiving band of band n28 (communication band D) for 5G-NR or the receiving band of band n12 for 5G-NR.

[0137] In this modification, band n8 and band n5 are a band combination that allows simultaneous communication. The transmission band of band n8 and the reception band of band n5 partially overlap in frequency. The transmission band of band n8 is an example of a first frequency band, and the reception band of band n5 is an example of a second frequency band. The transmission band of band n8 includes subband X (first subband) that overlaps with the reception band of band n5, and subband Y (second subband) that does not overlap with the reception band of band n5. Furthermore, the reception band of band n5 includes subband X (first subband) that overlaps with the transmission band of band n8, and subband Z (third subband) that does not overlap with the transmission band of band n8.

[0138] The filter 11 is variable between a first passband that includes subbands X and Y and a second passband that includes subband Y and is narrower than the first passband. One end of the filter 11 is connected to a first selection terminal of the switch 55.

[0139] The filter 22 has a passband that includes the subband X and the subband Z. One end of the filter 22 is connected to the second selection terminal of the switch 55 .

[0140] The matching circuit 75 is an example of an impedance matching circuit, and is connected between the third selection terminal of the switch 55 and ground.

[0141] Switch 55 is an example of a first switch, and switches between connection and disconnection of the first antenna and filters 11 and 12, between connection and disconnection of the first antenna and filter 22, between connection and disconnection of the first antenna and filter 23, between connection and disconnection of the first antenna and primary circuit 5C, between connection and disconnection of the second antenna and filters 11 and 12, between connection and disconnection of the second antenna and filter 22, between connection and disconnection of the second antenna and filter 23, between connection and disconnection of the second antenna and primary circuit 5C, and between connection and disconnection of the second antenna and matching circuit 75.

[0142] As shown in FIG. 9B, the primary circuit 5C includes filters 82, 83, 84, 91, and 92, and a switch 54.

[0143] Filter 82 has a passband that includes the receive band of band n8 for 5G-NR.

[0144] The filter 83 has a passband that includes the transmission band of band n28 for 5G-NR or the transmission band of band n12 for 5G-NR.

[0145] The filter 84 has a passband that includes the receive band of band n28 for 5G-NR or the receive band of band n12 for 5G-NR.

[0146] Filter 91 has a passband that includes the transmission band of band n5 and the transmission band of band n26 for 5G-NR.

[0147] Filter 92 has a passband that includes the receive band of band n5 and the receive band of band n26 for 5G-NR.

[0148] The switch 54 switches between connecting and disconnecting the third antenna and filter 82, between connecting and disconnecting the third antenna and filters 83 and 84, between connecting and disconnecting the third antenna and filters 91 and 92, between connecting and disconnecting the third antenna and high-frequency circuit 1C, between connecting and disconnecting the fourth antenna and filter 82, between connecting and disconnecting the fourth antenna and filters 83 and 84, between connecting and disconnecting the fourth antenna and filters 91 and 92, and between connecting and disconnecting the fourth antenna and high-frequency circuit 1C.

[0149] In the above configuration, the high-frequency circuit 1C and the primary circuit 5C can execute (1) a first mode in which a transmission signal of sub-band Y of communication band A and a reception signal of sub-band Z of communication band B are simultaneously transmitted, (2) a second mode in which a transmission signal of communication band A is transmitted but a reception signal of communication band B is not transmitted, and (3) a third mode in which a reception signal of communication band B is transmitted but a transmission signal of communication band A is not transmitted.

[0150] In the above configuration, when the second mode is executed, the filter 11 is set to the first passband, so that the transmission signal of the communication band A can be transmitted using the entire transmission band of the communication band A. Furthermore, when the second mode is executed, the filter 11 is connected to the first antenna or the second antenna.

[0151] When the third mode is executed, the filter 22 can be used to transmit the received signal of the communication band B. When the third mode is executed, the filter 22 is connected to the first antenna or the second antenna.

[0152] 9B , the filter 11 is connected to the second antenna, and the filter 22 is connected to the first antenna. Alternatively, the first antenna or the second antenna may be connected to a matching circuit 75. This improves the isolation between the transmission signal of communication band A that passes through the filter 11 and the reception signal of communication band B that passes through the filter 22, thereby suppressing deterioration in the reception sensitivity of the communication band B.

[0153] 9B, when the first mode is executed, filter 82 may be connected to the fourth antenna, and filters 91 and 92 may be connected to the third antenna, thereby allowing the received signal of communication band A and the received signal of communication band B to be simultaneously transmitted by primary circuit 5C.

[0154] [2. Effects, etc.] As described above, the high-frequency circuit 1 according to this embodiment includes the filter 11 having a passband that includes a first frequency band, which is one of the transmission band and reception band of the communication band A, and the filter 22 having a passband that includes the second frequency band, which is the other of the transmission band and reception band of the communication band B, wherein the communication band A and the communication band B are a band combination that allows simultaneous communication, the first frequency band includes a sub-band X that overlaps with the second frequency band and a sub-band Y that does not overlap with the second frequency band, the second frequency band includes sub-band X and a sub-band Z that does not overlap with the first frequency band, and the passband of the filter 11 is variable between a first passband that includes sub-band X and sub-band Y, and a second passband that includes sub-band Y and is narrower than the first passband.

[0155] According to this, when a signal of the first frequency band is transmitted alone, the signal can be transmitted using the entire bandwidth of the first frequency band by setting filter 11 to the first passband. On the other hand, when a signal of subband Y is passed through filter 11 and a signal of subband Z is passed through filter 22 for simultaneous transmission, even if filter 11 and filter 22 are disposed close to each other, setting filter 11 to the second passband can improve isolation between the two signals, thereby suppressing deterioration in receiving sensitivity when the signals of subband Y and subband Z are simultaneously transmitted. Therefore, it is possible to provide a small-sized high-frequency circuit 1 that can simultaneously transmit signals of communication band A and communication band B while suppressing deterioration in isolation and receiving sensitivity.

[0156] For example, in the high-frequency circuit 1, when only the first frequency band signal out of the first frequency band signal and the second frequency band signal is transmitted, the pass band of the filter 11 becomes the first pass band, and when the first frequency band signal and the second frequency band signal are transmitted simultaneously, the pass band of the filter 11 becomes the second pass band.

[0157] This improves the isolation between signals in the first frequency band and signals in the second frequency band, and suppresses deterioration in reception sensitivity.

[0158] For example, in the high-frequency circuit 1, the first frequency band is a transmission band of the communication band A, and the second frequency band is a reception band of the communication band B.

[0159] According to this, when a transmission signal of communication band A is transmitted alone, by setting filter 11 to the first pass band, the transmission signal can be transmitted using the entire transmission band of communication band A. On the other hand, when a transmission signal of communication band A is passed through filter 11 and a reception signal of communication band B is passed through filter 22 for simultaneous transmission, even if filter 11 and filter 22 are disposed close to each other, setting filter 11 to the second pass band can improve isolation between the two signals, thereby suppressing deterioration in reception sensitivity when a transmission signal of communication band A and a reception signal of communication band B are simultaneously transmitted. Therefore, it is possible to provide a small-sized high-frequency circuit 1 that can simultaneously transmit a transmission signal of communication band A and a reception signal of communication band B while suppressing deterioration in isolation and reception sensitivity.

[0160] Furthermore, for example, in the high-frequency circuit according to the first modification, the first frequency band is a reception band of the communication band B, the second frequency band is a transmission band of the communication band A, and the filter 22 is variable between a first pass band including the subbands X and Z and a second pass band including the subband Z and narrower than the first pass band.

[0161] According to this, when a received signal of communication band B is transmitted alone, by setting the filter 22 to the first pass band, the received signal can be transmitted using the entire receive band of communication band B. On the other hand, when a received signal of communication band B is passed through the filter 22 and a transmit signal of communication band A is passed through the filter 11 for simultaneous transmission, by setting the filter 22 to the second pass band, isolation between the two signals can be improved, and deterioration of the receive sensitivity of communication band B when they are transmitted simultaneously can be suppressed.

[0162] Furthermore, for example, in the high-frequency circuit according to the third modification, when subband Y overlaps with at least one of the transmission band and reception band of communication band C, and subband X does not overlap with at least one of the transmission band and reception band of communication band C, and a signal of at least one of the transmission band and reception band of communication band C is transmitted, the passband of filter 11 becomes the second passband.

[0163] According to this, when transmitting a signal of communication band C, the filter 11 is set to the second passband, thereby making it possible to improve the quality of the signal of communication band C passing through the filter 11 .

[0164] Also, for example, in the high-frequency circuit according to variant example 3, communication band C is band n106 for 5G-NR.

[0165] Furthermore, for example, in the high-frequency circuit according to the second modification, the filter 11 varies a first passband that includes subbands X and Y and a second passband that includes subband Y and is narrower than the first passband, and the filter 22 varies a third passband that includes subbands X and Z and a fourth passband that includes subband Z and is narrower than the third passband.

[0166] This allows the passbands of filters 11 and 22 to be variable, so that even if filters 11 and 22 are placed close to each other, isolation between signals in communication band A and signals in communication band B can be ensured. This makes it possible to suppress deterioration in receiving sensitivity when signals in subband Y and subband Z are transmitted simultaneously.

[0167] Furthermore, for example, in the high-frequency circuit according to the second modification, when only the first frequency band signal of the first frequency band signals and the second frequency band signals is transmitted, the pass band of the filter 11 is the first pass band, when only the second frequency band signal of the first frequency band signals and the second frequency band signals is transmitted, the pass band of the filter 22 is the third pass band, and when the first frequency band signals and the second frequency band signals are transmitted simultaneously, the pass band of the filter 11 is the second pass band and the pass band of the filter 22 is the fourth pass band.

[0168] This improves the isolation between signals in the first frequency band and signals in the second frequency band, and suppresses deterioration in reception sensitivity.

[0169] For example, the high-frequency circuit 1 further includes a switch 50 having a terminal 50a connected to an antenna, a terminal 50b connected to an antenna, a terminal 50c connected to the filter 11, and a terminal 50d connected to the filter 22.

[0170] This makes it possible to achieve independent transmission of a signal in the first frequency band passing through filter 11, independent transmission of a signal in the second frequency band passing through filter 22, and simultaneous transmission of a signal in the first frequency band passing through filter 11 and a signal in the second frequency band passing through filter 22.

[0171] Furthermore, for example, in the high-frequency circuit 1, when transmitting only the first frequency band signal out of the first frequency band signal and the second frequency band signal, the terminal 50c is connected to the terminal 50a, and the terminal 50d is connected to neither the terminal 50a nor the terminal 50b, and when transmitting the first frequency band signal and the second frequency band signal simultaneously, the terminal 50c is connected to the terminal 50a, and the terminal 50d is connected to the terminal 50b.

[0172] This makes it possible to achieve independent transmission of a signal in the first frequency band passing through filter 11, independent transmission of a signal in the second frequency band passing through filter 22, and simultaneous transmission of a signal in the first frequency band passing through filter 11 and a signal in the second frequency band passing through filter 22, while ensuring isolation.

[0173] For example, the high-frequency circuit 1A according to the fourth modification further includes a filter 13 connected to the terminal 51c and having a passband including a third frequency band that is one of the transmission band and reception band of the communication band D, a matching circuit 75, and a switch 51 that switches between connection and disconnection between the terminal 51c and the matching circuit 75, and the third frequency band does not overlap with the first frequency band or the second frequency band.

[0174] With the above configuration, the high-frequency circuit 1A can execute (1) a fifth mode in which signals of communication band A, communication band B, and communication band D are simultaneously transmitted, (2) a sixth mode in which signals of communication band A and communication band D are simultaneously transmitted, but signals of communication band B are not transmitted, and (3) a third mode in which signals of communication band B are transmitted, but signals of communication band A are not transmitted.

[0175] In contrast to this, with the above configuration, the matching circuit 75 can be switched between connected and disconnected when switching between modes, so that the attenuation characteristics of the filter 11 in the communication band D can be improved.

[0176] Furthermore, for example, in the high-frequency circuit 1A, when transmitting only the first frequency band signal out of the first frequency band signal and the second frequency band signal, the terminal 51c is connected to the terminal 51a, the terminal 51d is connected to neither the terminal 51a nor the terminal 51b, and the matching circuit 75 is connected to the terminals 51c and 51e, whereas when transmitting the first frequency band signal and the second frequency band signal simultaneously, the terminal 51c is connected to the terminal 51a, the terminal 51d is connected to the terminal 51b, and the matching circuit 75 is connected to the terminal 51c.

[0177] When switching from the sixth mode to the fifth mode, changing the pass band of the filter 11 from the first pass band to the second pass band changes the attenuation characteristics of the filter 11 in the communication band D. On the other hand, when switching to the fifth mode, further connecting a matching circuit 75 to the filter 11 makes it possible to adjust the attenuation characteristics of the filter 11 when the pass band changes, and improve the attenuation characteristics of the filter 11 in the communication band D. Therefore, in simultaneous transmission of signals of two communication bands A and B, which have partially overlapping frequency bands, it is possible to suppress deterioration in isolation and receiving sensitivity, and to transmit the communication band D, which is transmitted simultaneously with the communication bands A and B, with low loss.

[0178] Also, for example, in the high-frequency circuit 1A, the communication band D is either band 28 or band 12 for 4G-LTE, or band n28 or band n12 for 5G-NR.

[0179] Further, for example, in the high-frequency circuits 1, 1A and 1B, instead of the switches 50 and 51, a first switch of an SPDT type having an antenna connection terminal, a first terminal connected to the filter 11, and a second terminal connected to the filter 22 is provided.

[0180] This makes it possible to achieve independent transmission of a signal in the first frequency band passing through filter 11, independent transmission of a signal in the second frequency band passing through filter 22, and simultaneous transmission of a signal in the first frequency band passing through filter 11 and a signal in the second frequency band passing through filter 22.

[0181] Furthermore, for example, in the high-frequency circuits 1, 1A, and 1B, when transmitting only the first frequency band signal out of the first frequency band signal and the second frequency band signal, the first terminal is connected to the antenna connection terminal and the second terminal is not connected to the antenna connection terminal, and when transmitting the first frequency band signal and the second frequency band signal simultaneously, the first terminal is connected to the antenna connection terminal and the second terminal is connected to the antenna connection terminal.

[0182] This makes it possible to achieve independent transmission of a signal in the first frequency band passing through filter 11, independent transmission of a signal in the second frequency band passing through filter 22, and simultaneous transmission of a signal in the first frequency band passing through filter 11 and a signal in the second frequency band passing through filter 22, while ensuring isolation.

[0183] For example, in the high-frequency circuits 1, 1A, and 1B, the communication band A is either band 8 for 4G-LTE or band n8 for 5G-NR, and the communication band B is either band 5 for 4G-LTE or band n5 for 5G-NR.

[0184] Furthermore, for example, the communication device 4 includes an RFIC 3 that processes high-frequency signals, and a high-frequency circuit 1 that transmits high-frequency signals between the RFIC 3 and the antennas 2a and 2b.

[0185] This allows the effects of the high frequency circuit 1 to be realized in the communication device 4.

[0186] (Other Embodiments) While the high-frequency circuit and communication device according to the present invention have been described above based on the embodiments and modifications, the high-frequency circuit and communication device according to the present invention are not limited to the above-described embodiments and modifications. The present invention also includes other embodiments realized by combining any of the components in the above-described embodiments and modifications, modifications obtained by applying various modifications to the above-described embodiments and modifications that would occur to those skilled in the art without departing from the spirit of the present invention, and various devices incorporating the above-described high-frequency circuit and communication device.

[0187] For example, in the circuit configurations of the high-frequency circuits and communication devices according to the above-described embodiments and modifications, other circuit elements, wiring, etc. may be inserted between the paths connecting the circuit elements and signal paths shown in the drawings.

[0188] In addition, although the above-described embodiments use cellular bands for 5G-NR or LTE, communication bands for other radio access technologies may be used in addition to or instead of 5G-NR or LTE. For example, communication bands for wireless local area networks may be used.

[0189] The following describes the features of the high-frequency circuit and communication device described based on the above embodiment and modifications.

[0190] <1> A high-frequency circuit comprising: a first filter having a passband that includes a first frequency band that is one of a transmission band and a reception band of a first communication band; and a second filter having a passband that includes a second frequency band that is the other of the transmission band and the reception band of a second communication band, wherein the first communication band and the second communication band are a band combination that allows simultaneous communication, the first frequency band includes a first sub-band that overlaps with the second frequency band and a second sub-band that does not overlap with the second frequency band, and the second frequency band includes the first sub-band and a third sub-band that does not overlap with the first communication band, and the passband of the first filter is variable to a first passband that includes the first sub-band and the second sub-band, and a second passband that includes the second sub-band and is narrower than the first passband.

[0191] <2> The high-frequency circuit according to <1>, wherein when transmitting only the first frequency band signal out of the first frequency band signal and the second frequency band signal, the pass band of the first filter is the first pass band, and when transmitting the first frequency band signal and the second frequency band signal simultaneously, the pass band of the first filter is the second pass band.

[0192] <3> The high-frequency circuit according to <1> or <2>, wherein the first frequency band is a transmission band of the first communication band, and the second frequency band is a reception band of the second communication band.

[0193] <4> The high-frequency circuit according to <1> or <2>, wherein the first frequency band is a reception band of the first communication band, and the second frequency band is a transmission band of the second communication band.

[0194] <5> The high-frequency circuit according to any one of <1> to <4>, wherein the second subband overlaps with at least one of a transmission band and a reception band of a third communication band, the first subband does not overlap with the at least one of the transmission band and the reception band of the third communication band, and when transmitting a signal of the at least one of the transmission band and the reception band of the third communication band, the pass band of the first filter becomes the second pass band.

[0195] <6> The high-frequency circuit according to <5>, wherein the third communication band is band n106 for 5G-NR.

[0196] <7> The high-frequency circuit according to any one of <1> to <6>, wherein the second filter varies a third passband that includes the first subband and the third subband, and a fourth passband that includes the third subband and is narrower than the third passband.

[0197] <8> The high-frequency circuit according to <7>, wherein when transmitting only the first frequency band signal of the first frequency band signals and the second frequency band signals, the pass band of the first filter is the first pass band; when transmitting only the second frequency band signal of the first frequency band signals and the second frequency band signals, the pass band of the second filter is the third pass band; and when simultaneously transmitting the first frequency band signals and the second frequency band signals, the pass band of the first filter is the second pass band and the pass band of the second filter is the fourth pass band.

[0198] <9> The high-frequency circuit according to any one of <1> to <8>, further comprising: a first switch having a first antenna connection terminal, a second antenna connection terminal, a first terminal connected to the first filter, and a second terminal connected to the second filter.

[0199] <10> The high-frequency circuit according to <9>, wherein, when transmitting only the first frequency band signal out of the first frequency band signal and the second frequency band signal, the first terminal is connected to one of the first antenna connection terminal and the second antenna connection terminal, and the second terminal is connected to neither the first antenna connection terminal nor the second antenna connection terminal; and when simultaneously transmitting the first frequency band signal and the second frequency band signal, the first terminal is connected to the first antenna connection terminal or the second antenna connection terminal, and the second terminal is connected to the first antenna connection terminal or the second antenna connection terminal.

[0200] <11> The high-frequency circuit according to <9> or <10>, further comprising: a third filter connected to the first terminal and having a passband including a third frequency band that is one of a transmission band and a reception band of a fourth communication band; an impedance matching circuit; and a second switch that switches between connection and disconnection between the first terminal and the impedance matching circuit, wherein the third frequency band does not overlap with the first frequency band and the second frequency band.

[0201] <12> The high-frequency circuit according to <11>, wherein, when transmitting only the first frequency band signal of the first frequency band signals and the second frequency band signals, the first terminal is connected to one of the first antenna connection terminal and the second antenna connection terminal, the second terminal is connected to neither the first antenna connection terminal nor the second antenna connection terminal, and the impedance matching circuit is not connected to the first terminal; and when simultaneously transmitting the first frequency band signal and the second frequency band signal, the first terminal is connected to the first antenna connection terminal or the second antenna connection terminal, the second terminal is connected to the first antenna connection terminal or the second antenna connection terminal, and the impedance matching circuit is connected to the first terminal.

[0202] <13> The radio frequency circuit according to <11> or <12>, wherein the fourth communication band is any one of band 28 and band 12 for 4G-LTE and band n28 and band n12 for 5G-NR.

[0203] <14> The high-frequency circuit according to any one of <1> to <8>, further comprising: a first switch having an antenna connection terminal, a first terminal connected to the first filter, and a second terminal connected to the second filter.

[0204] <15> The high-frequency circuit according to <14>, wherein, when transmitting only the first frequency band signal out of the first frequency band signal and the second frequency band signal, the first terminal is connected to the antenna connection terminal and the second terminal is not connected to the antenna connection terminal; and when transmitting the first frequency band signal and the second frequency band signal simultaneously, the first terminal is connected to the antenna connection terminal and the second terminal is connected to the antenna connection terminal.

[0205] <16> The high-frequency circuit according to <14> or <15>, further comprising: a third filter connected to the first terminal and having a passband including a third frequency band that is one of a transmission band and a reception band of a fourth communication band; an impedance matching circuit; and a second switch that switches between connection and disconnection between the first terminal and the impedance matching circuit, wherein the third frequency band does not overlap with the first frequency band and the second frequency band.

[0206] <17> The high-frequency circuit according to <16>, wherein, when transmitting only the first frequency band signal of the first frequency band signals and the second frequency band signals, the first terminal is connected to the antenna connection terminal, the second terminal is not connected to the antenna connection terminal, and the impedance matching circuit is not connected to the first terminal; and when transmitting the first frequency band signal and the second frequency band signal simultaneously, the first terminal is connected to the antenna connection terminal, the second terminal is connected to the antenna connection terminal, and the impedance matching circuit is connected to the first terminal.

[0207] <18> The radio frequency circuit according to <16> or <17>, wherein the fourth communication band is any one of band 28 and band 12 for 4G-LTE and band n28 and band n12 for 5G-NR.

[0208] <19> The first communication band is either band 8 for 4G-LTE or band n8 for 5G-NR, and the second communication band is either band 5 for 4G-LTE or band n5 for 5G-NR. The radio frequency circuit according to any one of <1> to <18>.

[0209] <20> A communication device comprising: a signal processing circuit that processes a high-frequency signal; and the high-frequency circuit according to any one of <1> to <19> that transmits the high-frequency signal between the signal processing circuit and an antenna.

[0210] The present invention can be widely used as a high-frequency circuit disposed in the front end of communication devices such as mobile phones.

[0211] 1, 1A, 1B, 1C High frequency circuit 2a, 2b Antenna 3 RFIC 4 Communication device 5B Diver circuit 5C Primary circuit 11, 12, 13, 21, 22, 23, 82, 83, 84, 91, 92 Filter 31, 33, 41 Power amplifier 32, 42 Low noise amplifier 50, 51, 52, 53, 54, 55, 56 Switch 50a, 50b, 50c, 50d, 51a, 51b, 51c, 51d, 51e, 111, 112 Terminal 60 Acoustic wave resonator 71, 72, 73 Circuit element 74 Variable circuit element 75 Matching circuit 101, 102 Antenna terminal 110, 130, 150 High frequency input terminal 120, 140 High frequency output terminal

Claims

1. A high-frequency circuit comprising: a first filter having a passband including a first frequency band, which is one of a transmission band and a reception band of a first communication band; and a second filter having a passband including a second frequency band, which is the other of the transmission band and the reception band of a second communication band, wherein the first communication band and the second communication band are a band combination enabling simultaneous communication, the first frequency band includes a first sub-band that overlaps with the second frequency band and a second sub-band that does not overlap with the second frequency band, and the second frequency band includes the first sub-band and a third sub-band that does not overlap with the first communication band, and the passband of the first filter is variable to a first passband that includes the first sub-band and the second sub-band, and a second passband that includes the second sub-band and is narrower than the first passband.

2. The high-frequency circuit according to claim 1, wherein when only the first frequency band signal of the first frequency band signal and the second frequency band signal is transmitted, the pass band of the first filter is the first pass band, and when the first frequency band signal and the second frequency band signal are transmitted simultaneously, the pass band of the first filter is the second pass band.

3. The high-frequency circuit according to claim 1 or 2, wherein the first frequency band is a transmission band of the first communication band, and the second frequency band is a reception band of the second communication band.

4. The high-frequency circuit according to claim 1 or 2, wherein the first frequency band is a reception band of the first communication band, and the second frequency band is a transmission band of the second communication band.

5. A high-frequency circuit as described in any one of claims 1 to 4, wherein the second subband overlaps with at least one of a transmission band and a reception band of a third communication band, the first subband does not overlap with the at least one of the transmission band and the reception band of the third communication band, and when transmitting a signal of the at least one of the transmission band and the reception band of the third communication band, the pass band of the first filter becomes the second pass band.

6. The high-frequency circuit according to claim 5, wherein the third communication band is band n106 for 5G-NR.

7. The high-frequency circuit according to any one of claims 1 to 6, wherein the second filter varies a third passband that includes the first subband and the third subband, and a fourth passband that includes the third subband and is narrower than the third passband.

8. The high-frequency circuit according to claim 7, wherein when only the first frequency band signals of the first frequency band signals and the second frequency band signals are transmitted, the pass band of the first filter is the first pass band; when only the second frequency band signals of the first frequency band signals and the second frequency band signals are transmitted, the pass band of the second filter is the third pass band; when the first frequency band signals and the second frequency band signals are simultaneously transmitted, the pass band of the first filter is the second pass band and the pass band of the second filter is the fourth pass band.

9. A high-frequency circuit according to any one of claims 1 to 8, further comprising a first switch having a first antenna connecting terminal, a second antenna connecting terminal, a first terminal connected to said first filter, and a second terminal connected to said second filter.

10. The high-frequency circuit according to claim 9, wherein, when transmitting only the first frequency band signals of the first and second frequency band signals, the first terminal is connected to one of the first antenna connection terminal and the second antenna connection terminal and the second terminal is connected to neither the first antenna connection terminal nor the second antenna connection terminal, and when transmitting simultaneously the first frequency band signals and the second frequency band signals, the first terminal is connected to the first antenna connection terminal or the second antenna connection terminal and the second terminal is connected to the first antenna connection terminal or the second antenna connection terminal.

11. The high-frequency circuit according to claim 9 or 10, further comprising: a third filter connected to the first terminal and having a passband including a third frequency band which is one of a transmission band and a reception band of a fourth communication band; an impedance matching circuit; and a second switch which switches between connection and disconnection between the first terminal and the impedance matching circuit, wherein the third frequency band does not overlap with the first frequency band and the second frequency band.

12. The high-frequency circuit according to claim 11, wherein, when transmitting only the first frequency band signals of the first and second frequency band signals, the first terminal is connected to one of the first antenna connection terminal and the second antenna connection terminal, the second terminal is connected to neither the first antenna connection terminal nor the second antenna connection terminal, and the impedance matching circuit is not connected to the first terminal; and, when transmitting simultaneously the first frequency band signals and the second frequency band signals, the first terminal is connected to the first antenna connection terminal or the second antenna connection terminal, the second terminal is connected to the first antenna connection terminal or the second antenna connection terminal, and the impedance matching circuit is connected to the first terminal.

13. The high-frequency circuit according to claim 11 or 12, wherein the fourth communication band is either band 28 or band 12 for 4G-LTE, or band n28 or band n12 for 5G-NR.

14. The high-frequency circuit according to any one of claims 1 to 8, further comprising: a first switch having an antenna connection terminal, a first terminal connected to said first filter, and a second terminal connected to said second filter.

15. The high-frequency circuit according to claim 14, wherein, when transmitting only the first frequency band signals of the first frequency band signals and the second frequency band signals, the first terminal is connected to the antenna connection terminal and the second terminal is not connected to the antenna connection terminal, and when transmitting the first frequency band signals and the second frequency band signals simultaneously, the first terminal is connected to the antenna connection terminal and the second terminal is connected to the antenna connection terminal.

16. The high-frequency circuit according to claim 14 or 15, further comprising: a third filter connected to the first terminal and having a passband including a third frequency band which is one of a transmission band and a reception band of a fourth communication band; an impedance matching circuit; and a second switch which switches between connection and disconnection between the first terminal and the impedance matching circuit, wherein the third frequency band does not overlap with the first frequency band and the second frequency band.

17. The high-frequency circuit according to claim 16, wherein, when transmitting only the first frequency band signals of the first frequency band signals and the second frequency band signals, the first terminal is connected to the antenna connection terminal, the second terminal is not connected to the antenna connection terminal, and the impedance matching circuit is not connected to the first terminal; and, when transmitting the first frequency band signals and the second frequency band signals simultaneously, the first terminal is connected to the antenna connection terminal, the second terminal is connected to the antenna connection terminal, and the impedance matching circuit is connected to the first terminal.

18. The high-frequency circuit according to claim 16 or 17, wherein the fourth communication band is either band 28 or band 12 for 4G-LTE, or band n28 or band n12 for 5G-NR.

19. The radio frequency circuit according to any one of claims 1 to 18, wherein the first communication band is either band 8 for 4G-LTE or band n8 for 5G-NR, and the second communication band is either band 5 for 4G-LTE or band n5 for 5G-NR.

20. A communication device comprising: a signal processing circuit that processes a high-frequency signal; and a high-frequency circuit according to any one of claims 1 to 19 that transmits the high-frequency signal between the signal processing circuit and an antenna.

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