High-frequency circuit and communication device

Abstract

A high-frequency circuit (1) is provided with: an antenna connection terminal (101), an input terminal (111), and an output terminal (121); a filter (31) having a passband including at least a portion of a transmission band of a frequency band (A) for FDD; a filter (32) having a passband including at least a part of a reception band of frequency band A; and a switch (41) having terminals (411-413), in which the antenna connection terminal (101) is connected to the terminal (411), the filter (31) is connected between the terminal (412) and the input terminal (111), the filter (32) is connected between the terminal (413) and the output terminal (121), the switch (41) being configured to switch between a first connection in which the terminal (411) is connected to the terminal (412) and the terminal (411) is not connected to the terminal (413), a second connection in which the terminal (411) is not connected to the terminal (413), and a third connection in which the terminal (413) is not connected to the terminal (412) and the filter (32) is connected to the terminal (413). In the second connection, the terminal (411) is connected to the terminal (413) and the terminal (411) is not connected to the terminal (412), and in the third connection, the terminal (411) is simultaneously connected to the terminals (412, 413).

Description

Technical Field

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

[0002] 3GPP (registered trademark) (3rd Generation Partnership Project) has been studying power classes (eg, power classes 1, 1.5, 2, etc.) that allow higher maximum output power than before in mobile communication systems. Patent document 1 discloses a high-frequency circuit that can be used in a mobile communication system.

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Publication No. 2021-016049 Summary of the invention

[0006] Problem that the invention aims to solve

[0007] When such a high power level is applied to a frequency band for frequency division duplex (FDD), a high isolation is required between the transmission filter and the reception filter, and there is a possibility that the loss in the transmission filter and / or the reception filter increases.

[0008] Therefore, the present invention provides a high-frequency circuit and a communication device capable of suppressing an increase in loss of a transmission filter and a reception filter used in a frequency band for FDD.

[0009] Solutions for solving problems

[0010] A high-frequency circuit according to one embodiment of the present invention comprises: an antenna connection terminal, an input terminal, and an output terminal; a first filter having a passband including at least a portion of a transmission band of a first frequency band for frequency division duplexing; a second filter having a passband including at least a portion of a reception band of the first frequency band; and a first switch having a first terminal, a second terminal, and a third terminal, wherein the antenna connection terminal is connected to the first terminal, the first filter is connected between the second terminal and the input terminal, the second filter is connected between the third terminal and the output terminal, and the first switch is configured to switch between a first connection, a second connection, and a third connection, wherein in the first connection, the first terminal is connected to the second terminal and is not connected to the third terminal, in the second connection, the first terminal is connected to the third terminal and is not connected to the second terminal, and in the third connection, the first terminal is connected to both the second terminal and the third terminal.

[0011] A high-frequency circuit according to one embodiment of the present invention includes: a first antenna connection terminal, a second antenna connection terminal, an input terminal, and an output terminal; a first filter having a passband including at least a portion of a transmission band of a first frequency band for frequency division duplexing; a second filter having a passband including at least a portion of a reception band of the first frequency band; and a first switch having a first terminal, a second terminal, a third terminal, and a fourth terminal, wherein the first antenna connection terminal is connected to the first terminal, the second antenna connection terminal is connected to the second terminal, the first filter is connected between the third terminal and the input terminal, and the second filter is connected between the fourth terminal and the output terminal, and the first switch is configured to switch between a first connection, a second connection, and a third connection, wherein in the first connection, one of the first terminal and the second terminal is connected to the third terminal, and neither of the first terminal and the second terminal is connected to the fourth terminal, wherein in the second connection, one of the first terminal and the second terminal is connected to the fourth terminal, and neither of the first terminal and the second terminal is connected to the third terminal, and wherein in the third connection, one of the first terminal and the second terminal is connected to the third terminal, and the other of the first terminal and the second terminal is connected to the fourth terminal.

[0012] Effects of the Invention

[0013] According to the high-frequency circuit according to one embodiment of the present invention, it is possible to suppress an increase in loss of a transmission filter and a reception filter used in a frequency band for FDD. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 This is a circuit configuration diagram of a communication device according to Embodiment 1.

[0015] Figure 2 This is a diagram showing transmission of a signal in frequency band A at a high power level by the communication device according to Embodiment 1.

[0016] Figure 3 This is a diagram showing reception of a signal in frequency band A at a high power level by the communication device according to Embodiment 1.

[0017] Figure 4 This is a diagram showing transmission and reception of a signal in frequency band A at a low power level by the communication device according to Embodiment 1.

[0018] Figure 5 This is a circuit configuration diagram of a communication device according to Embodiment 2.

[0019] Figure 6 This is a diagram showing transmission of a signal in frequency band A at a high power level by the communication device according to the second embodiment.

[0020] Figure 7This is a diagram showing reception of a signal in frequency band A at a high power level by the communication device according to the second embodiment.

[0021] Figure 8 This is a diagram showing transmission and reception of a signal in frequency band A at a low power level by the communication device according to the second embodiment.

[0022] Fig. 9 This is a circuit configuration diagram of a communication device according to Embodiment 3.

[0023] Fig.10 This is a diagram showing transmission of a signal in frequency band A at a high power level by the communication device according to the third embodiment.

[0024] Fig.11 This is a diagram showing reception of a signal in frequency band A at a high power level by the communication device according to the third embodiment.

[0025] Fig.12 This is a diagram showing transmission and reception of a signal in frequency band A at a low power level by the communication device according to Embodiment 3.

[0026] Fig.13 This is a circuit configuration diagram of a communication device according to a fourth embodiment.

[0027] Fig.14 This is a diagram showing transmission of a signal in frequency band A at a high power level by a communication device according to Embodiment 4.

[0028] Fig.15 This is a diagram showing reception of a signal in frequency band A at a high power level by the communication device according to the fourth embodiment.

[0029] Fig.16 This is a diagram showing transmission and reception of a signal in frequency band A at a low power level by the communication device according to the fourth embodiment. DETAILED DESCRIPTION

[0030] The following are embodiments of the present invention described in detail using the accompanying drawings. In addition, the embodiments described below all represent general or specific examples. The numerical values, shapes, materials, components, configurations of components, and connection methods shown in the following embodiments are examples, and their purpose is not to limit the present invention.

[0031] In addition, each figure is a schematic diagram that appropriately emphasizes, omits, or adjusts the ratio in order to illustrate the present invention, and is not necessarily strictly illustrated, and sometimes differs from the actual shape, positional relationship, and ratio. In each figure, the same reference numerals are marked for substantially the same structure, and repeated descriptions are sometimes omitted or simplified.

[0032] In the circuit structure of the present invention, "connection" includes not only direct connection through connecting terminals and / or wiring conductors, but also electrical connection via other circuit elements. "Connected between A and B" means connected between A and B and both A and B, and means connected in series to the path connecting A and B. "A is connected to B and C at the same time" means that at least a part of the first period in which A and B are connected overlaps in time with at least a part of the second period in which A and C are connected, and is not limited to complete overlap of the first period and the second period (i.e., the start and end of the first period coincide with the start and end of the second period).

[0033] In the present invention, "transmission band" refers to a frequency band used for transmission in a communication device. In addition, "reception band" refers to a frequency band used for reception in a communication device. For example, in an FDD band, different frequency bands are used as a transmission band and a reception band, and in a time division duplex (TDD) band, the same frequency band is used for a transmission band and a reception band. In particular, in a case where the communication device functions as a user terminal (UE: User Equipment) of a cellular communication system, in the FDD band, an uplink operation band (uplink operation band) can be used as a transmission band, and a downlink operation band (downlink operation band) can be used as a reception band. On the contrary, in a case where the communication device functions as a base station (BS: Base Station) of a cellular communication system, in the FDD band, a downlink operation band can be used as a transmission band, and an uplink operation band can be used as a reception band.

[0034] In the present invention, the passband of a filter refers to a portion of the spectrum transmitted by the filter, and is defined as a frequency band where the output power is not attenuated by more than 3dB compared to the maximum output power. Thus, the upper and lower limit frequencies of the passband of a bandpass filter are the frequencies of the point where the output power is attenuated by 3dB compared to the maximum output power.

[0035] In the present invention, a "terminal" refers to a point where a conductor in an element ends. In addition, when the impedance of a path between elements is sufficiently low, a terminal is interpreted not only as a single point but also as an arbitrary point on the path between elements or the entire path.

[0036] (Implementation Method 1)

[0037] [1.1 Circuit Structure of Communication Device 5]

[0038] First, refer to Figure 1 The circuit configuration of the communication device 5 according to the present embodiment will be described. Figure 1It is a circuit configuration diagram of the communication device 5 according to the present embodiment.

[0039] The communication device 5 is equivalent to the UE in the cellular communication system, and is typically a mobile phone, a smart phone, a tablet computer, a wearable device, etc. In addition, the communication device 5 may also be an IoT (Internet of Things) sensor device, a medical / health care device, a vehicle, an unmanned aerial vehicle (UAV) (so-called drone), or an unmanned guided vehicle (AGV). In addition, the communication device 5 may also be used as a BS in the cellular communication system.

[0040] like Figure 1 As shown, the communication device 5 includes a high frequency circuit 1 , an antenna 2 , a RFIC (Radio Frequency Integrated Circuit) 3 , and a BBIC (Baseband Integrated Circuit) 4 .

[0041] The high-frequency circuit 1 transmits a high-frequency signal between the antenna 2 and the RFIC 3. The internal structure of the high-frequency circuit 1 will be described later.

[0042] The antenna 2 is connected to the antenna connection terminal 101 of the high frequency circuit 1. The antenna 2 can transmit a high frequency signal output from the high frequency circuit 1, and can also receive a high frequency signal from the outside and output it to the high frequency circuit 1.

[0043] RFIC 3 is an example of a signal processing circuit that processes a high-frequency signal. Specifically, RFIC 3 can perform signal processing on a transmission signal input from BBIC 4 by up-conversion, etc., and output the high-frequency transmission signal generated by the signal processing to the transmission path of the high-frequency circuit 1. Furthermore, RFIC 3 can perform signal processing on a high-frequency reception signal input via the reception path of the high-frequency circuit 1 by down-conversion, etc., and output the reception signal generated by the signal processing to BBIC 4. In addition, RFIC 3 may also have a control unit that controls switches and amplifiers, etc., that are included in the high-frequency circuit 1. In addition, part or all of the functions of RFIC 3 as a control unit may also be installed outside RFIC 3, for example, may also be installed on BBIC 4 and / or the high-frequency circuit 1.

[0044] BBIC 4 is a baseband signal processing circuit that performs signal processing using an intermediate frequency band lower than the frequency of the high frequency signal transmitted by high frequency circuit 1. As the signal processed by BBIC 4, for example, an image signal for displaying an image and / or a voice signal for making a call via a speaker are used.

[0045] In addition, in the communication device 5 according to the present embodiment, the antenna 2 and the BBIC 4 are not essential components.

[0046] [1.2 Circuit structure of high frequency circuit 1]

[0047] Next, refer to Figure 1 The circuit structure of the high frequency circuit 1 is described below. The high frequency circuit 1 includes a power amplifier 11, a low noise amplifier 21, filters 31 to 34, switches 41 to 43, a terminator 51, an antenna connection terminal 101, an input terminal 111, and an output terminal 121. The components of the high frequency circuit 1 are described below in order.

[0048] The antenna connection terminal 101 is connected to the antenna 2 outside the high-frequency circuit 1 , and is connected to the switch 41 inside the high-frequency circuit 1 .

[0049] The input terminal 111 is a terminal for receiving a high-frequency signal from outside the high-frequency circuit 1. Figure 1 In the embodiment, the input terminal 111 is connected to the RFIC 3 outside the high frequency circuit 1 , and is connected to the power amplifier 11 inside the high frequency circuit 1 .

[0050] The power amplifier 11 is an active circuit that obtains an output signal having energy greater than that of an input signal (transmission signal) based on power supplied from a power supply. The power amplifier 11 includes an amplifying transistor and may also include an inductor and / or a capacitor. The internal structure of the power amplifier 11 is not particularly limited. For example, the power amplifier 11 may also be a multi-stage amplifier, a differential amplifier, or a Doherty amplifier.

[0051] In this embodiment, the power amplifier 11 is connected between the input terminal 111 and the filters 31 and 33 to amplify the transmission signals of the frequency bands A and B. Specifically, the input end of the power amplifier 11 is connected to the input terminal 111. The output end of the power amplifier 11 is connected to the filters 31 and 33 via the switch 42.

[0052] The low noise amplifier 21 is an active circuit that obtains an output signal having energy greater than that of an input signal (received signal) based on power supplied from a power supply. The low noise amplifier 21 includes an amplifying transistor and may also include an inductor and / or a capacitor. The internal structure of the low noise amplifier 21 is not particularly limited.

[0053] In this embodiment, the low noise amplifier 21 is connected between the output terminal 121 and the filters 32 and 34, and can amplify the reception signals of the frequency bands A and C. Specifically, the input end of the low noise amplifier 21 is connected to the filters 32 and 34 via the switch 43. The output end of the low noise amplifier 21 is connected to the output terminal 121.

[0054] The filter 31 (A-Tx) is an example of a first filter, and is a bandpass filter having a passband including at least a portion of the transmission band of the frequency band A for FDD. That is, the passband of the filter 31 may include only a portion of the transmission band of the frequency band A, or may include the entire transmission band of the frequency band A. One end of the filter 31 is connected to the output end of the power amplifier 11 via the switch 42. The other end of the filter 31 is connected to the antenna connection terminal 101 via the switch 41.

[0055] The filter 32 (A-Rx) is an example of a second filter, and is a bandpass filter having a passband including at least a portion of the reception band of the frequency band A for FDD. That is, the passband of the filter 32 may include only a portion of the reception band of the frequency band A, or may include the entire reception band of the frequency band A. One end of the filter 32 is connected to the input end of the low noise amplifier 21 via the switch 43. The other end of the filter 32 is connected to the antenna connection terminal 101 via the switch 41.

[0056] The filter 33 (B-Tx) is an example of a third filter, and is a bandpass filter having a passband including at least a portion of the transmission band of the frequency band B. That is, the passband of the filter 33 may include only a portion of the transmission band of the frequency band B, or may include the entire transmission band of the frequency band B. One end of the filter 33 is connected to the output end of the power amplifier 11 via the switch 42. The other end of the filter 33 is connected to the antenna connection terminal 101 via the switch 41.

[0057] The filter 34 (C-Rx) is an example of a fourth filter, and is a bandpass filter having a passband including at least a portion of the reception band of the frequency band C. That is, the passband of the filter 34 may include only a portion of the reception band of the frequency band C, or may include the entire reception band of the frequency band C. One end of the filter 34 is connected to the input end of the low noise amplifier 21 via the switch 43. The other end of the filter 34 is connected to the antenna connection terminal 101 via the switch 41.

[0058] The filters 31 to 34 may be configured using any of a surface acoustic wave (SAW) filter, a bulk acoustic wave (BAW) filter, an LC resonance filter, and a dielectric filter, but are not limited to these filters.

[0059] Frequency bands A to C are frequency bands used for communication systems built using radio access technology (RAT). Frequency bands A to C are predefined by standardization organizations such as 3GPP and IEEE (Institute of Electrical and Electronics Engineers). Examples of communication systems include 5GNR (5th Generation New Radio) systems, LTE (Long Term Evolution) systems, and WLAN (Wireless Local Area Network) systems.

[0060] Band A is an example of the first band and is a band for FDD. Band A may be, for example, Band 66 for LTE or n66 for 5GNR, but is not limited thereto.

[0061] Band B is an example of a second band, and may be any of a band for FDD, a band for time division duplex (TDD), and a band for SUL (Supplementary Uplink). Band B may be, for example, Band 25 for LTE or n25 for 5GNR, but is not limited thereto.

[0062] Band C is an example of a third band, and may be any of a band for FDD, a band for TDD, and a band for SDL (Supplementary Downlink). Band C may be, for example, Band 30 for LTE or n30 for 5GNR, but is not limited thereto.

[0063] The switch 41 is an example of a first switch, and is connected between the antenna connection terminal 101 and the filters 31 to 34. Specifically, the switch 41 has terminals 411 to 416. The terminal 411 is an example of a first terminal, and is connected to the antenna connection terminal 101. The terminal 412 is an example of a second terminal, and is connected to the filter 31. The terminal 413 is an example of a third terminal, and is connected to the filter 32. The terminal 414 is an example of a fourth terminal, and is connected to the terminator 51. The terminal 415 is an example of a fifth terminal, and is connected to the filter 33. The terminal 416 is an example of a sixth terminal, and is connected to the filter 34.

[0064] In this connection structure, the switch 41 can connect the terminals 411 and 414 to the terminals 412, 413, 415, and 416 based on a control signal from the RFIC 3, for example. The switch 41 is composed of a multi-connection type switch circuit.

[0065] Specifically, switch 41 can at least switch between a first connection, a second connection and a third connection. Here, in the first connection, terminal 411 is connected to terminal 412, and terminal 411 is not connected to terminal 413. At this time, terminal 414 can be connected to terminal 413 at will. In the second connection, terminal 411 is not connected to terminal 412, and terminal 411 is connected to terminal 413. At this time, terminal 414 can be connected to terminal 412 at will. In the third connection, terminal 411 is connected to terminals 412 and 413 at the same time.

[0066] In this embodiment, the switch 41 can switch the first connection and the second connection in time when the first power level is applied to the frequency band A. On the other hand, when the second power level is applied to the frequency band A, the switch 41 can maintain the third connection.

[0067] In addition, power class refers to the classification of the output power of the terminal specified by the maximum output power, etc. The smaller the power class value, the higher the maximum output power allowed. For example, in 3GPP, the maximum output power of power class 1 is 31dBm, the maximum output power of power class 1.5 is 29dBm, the maximum output power of power class 2 is 26dBm, and the maximum output power of power class 3 is 23dBm.

[0068] The maximum output power of the terminal is defined by the output power at the antenna end of the terminal. The maximum output power of the terminal is determined, for example, by a method defined by 3GPP or the like. Figure 1 In the embodiment, the maximum output power is measured by measuring the radiation power at the antenna 2. In addition, instead of measuring the radiation power, the output power of the antenna 2 can be measured by providing a terminal near the antenna 2 and connecting a measuring instrument (such as a spectrum analyzer) to the terminal.

[0069] The first power level is a power level specified at a maximum output power above a specified power, referred to herein as a high power level. The second power level is a power level specified at a maximum output power less than a specified power, referred to herein as a low power level. The specified power may be predetermined based on experience and / or by experiment, and is not particularly limited. For example, when 26 dBm is used as the specified power, the high power level includes power levels 1, 1.5, and 2, and the low power level includes power level 3. In addition, the power levels are not limited to these, and if a new power level is defined, the new power level may also be classified as either a high power level or a low power level.

[0070] The switch 42 is an example of a second switch, and is connected between the power amplifier 11 and the filters 31 and 33. Specifically, the switch 42 has terminals 421 to 423. The terminal 421 is connected to the output end of the power amplifier 11. The terminal 422 is connected to the filter 31. The terminal 423 is connected to the filter 33.

[0071] In this connection structure, the switch 42 can connect the terminal 421 exclusively to the terminals 422 and 423 based on the control signal from the RFIC 3, for example. That is, the switch 42 can switch between the connection between the power amplifier 11 and the filter 31 and the connection between the power amplifier 11 and the filter 33. The switch 42 is composed of, for example, a SPDT (Single-Pole Double-Throw) type switch circuit.

[0072] The switch 43 is an example of a third switch, and is connected between the low noise amplifier 21 and the filters 32 and 34. Specifically, the switch 43 has terminals 431 to 433. The terminal 431 is connected to the input end of the low noise amplifier 21. The terminal 432 is connected to the filter 32. The terminal 433 is connected to the filter 34.

[0073] In this connection structure, the switch 43 can connect the terminal 431 exclusively to the terminals 432 and 433 based on the control signal from the RFIC 3, for example. That is, the switch 43 can switch between the connection between the low noise amplifier 21 and the filter 32 and the connection between the low noise amplifier 21 and the filter 34. The switch 43 is composed of, for example, an SPDT type switch circuit.

[0074] Such switches 41 to 43 can be implemented in one semiconductor integrated circuit. Alternatively, switches 41 to 43 may be implemented in a plurality of semiconductor integrated circuits.

[0075] The terminator 51 is connected to the terminal 414 of the switch 41, and is configured to absorb and consume high-frequency signals. As the terminator 51, for example, a 50Ω resistor can be used.

[0076] also, Figure 1 The circuit structure of the high-frequency circuit 1 is an example and is not limited to this. The high-frequency circuit 1 only needs to have at least filters 31 and 32, a switch 41, an antenna connection terminal 101, an input terminal 111 and an output terminal 121, and may not have other circuit elements. For example, the high-frequency circuit 1 may not have the terminator 51. In this case, the switch 41 may not have the terminal 414. In addition, for example, the high-frequency circuit 1 may not have the filter 33 and / or 34. In this case, the switch 41 may not have the terminal 415 and / or 416. In addition, the high-frequency circuit 1 may also have two power amplifiers connected to the filters 31 and 33, respectively, instead of the power amplifier 11 and the switch 42. Similarly, the high-frequency circuit 1 may also have two low-noise amplifiers connected to the filters 32 and 34, respectively, instead of the low-noise amplifier 21 and the switch 43.

[0077] [1.3 Transmission and reception of frequency band A at each power level]

[0078] Next, transmission and reception in the frequency band A at each power level of the communication device 5 according to the present embodiment will be described.

[0079] [1.3.1 Transmission and reception of frequency band A at high power level]

[0080] First, refer to Figure 2 and Figure 3 To illustrate the transmission and reception of frequency band A at high power level. Figure 2 1 is a diagram showing transmission of a signal in the frequency band A at a high power level by the communication device 5 according to the present embodiment. Figure 3 1 is a diagram showing reception of a signal in the frequency band A at a high power level by the communication device 5 according to the present embodiment.

[0081] In addition, the transmission and reception of signals at a high power level refers to the transmission and reception of signals under the condition that the maximum output power specified by the high power level is allowed. That is, in the transmission of signals at a high power level, not only a high-frequency signal having an output power equal to the maximum output power of the high power level can be transmitted, but also a high-frequency signal having an output power less than the maximum output power of the high power level can be transmitted.

[0082] At high power levels, RFIC 3 switches transmission and reception exclusively by controlling the switches of high frequency circuit 1. Specifically, switch 41 switches between a first connection and a second connection. In the first connection, terminal 411 is connected to terminal 412, and terminal 414 is connected to terminal 413 (see Figure 2 ), in the second connection, the terminal 411 is connected to the terminal 413, and the terminal 414 is connected to the terminal 412 (refer to Figure 3 ). In addition, the connection between the terminal 414 and the terminal 413 in the first connection and the connection between the terminal 414 and the terminal 412 in the second connection are not essential but are arbitrary connections.

[0083] As a result, in the transmission of the signal in the frequency band A at a high power level, Figure 2 As shown, the transmission signal of the frequency band A input from the RFIC 3 to the input terminal 111 is amplified by the power amplifier 11 and then transmitted to the antenna 2 via the switch 42 , the filter 31 , the switch 41 and the antenna connection terminal 101 .

[0084] On the other hand, in the reception of the signal of band A at a high power level, as Figure 3 As shown, the reception signal of frequency band A input from antenna 2 to antenna connection terminal 101 is transmitted to low noise amplifier 21 via switch 41 , filter 32 and switch 43 , amplified by low noise amplifier 21 , and then transmitted to RFIC 3 via output terminal 121 .

[0085] In this way, in the transmission and reception of the signal in the frequency band A for FDD at a high power level, the transmission signal and the reception signal are separated not only in frequency but also in time.

[0086] [1.3.2 Transmission and reception of frequency band A at low power level]

[0087] Next, refer to Figure 4 To illustrate the transmission and reception of frequency band A at low power levels. Figure 4 1 is a diagram showing transmission and reception of a signal in the frequency band A at a low power level by the communication device 5 according to the present embodiment.

[0088] At a low power level, the RFIC 3 performs transmission and reception simultaneously by controlling the switches of the high frequency circuit 1. Specifically, the switch 41 maintains the third connection in which the terminal 411 is connected to the terminal 412 and the terminal 411 is connected to the terminal 413 (see Figure 4 ).

[0089] As a result, in the transmission of the signal in the frequency band A at a low power level, Figure 4 As shown, the transmission signal of the frequency band A input from the RFIC 3 to the input terminal 111 is amplified by the power amplifier 11 and then transmitted to the antenna 2 via the switch 42 , the filter 31 , the switch 41 and the antenna connection terminal 101 .

[0090] On the other hand, in the reception of the signal of frequency band A at a low power level, as Figure 4As shown, the reception signal of frequency band A input from antenna 2 to antenna connection terminal 101 is transmitted to low noise amplifier 21 via switch 41 , filter 32 and switch 43 , amplified by low noise amplifier 21 , and then transmitted to RFIC 3 via output terminal 121 .

[0091] In this way, in the transmission and reception of signals in the frequency band A for FDD at a low power level, the transmission signal and the reception signal are separated in frequency.

[0092] [1.4 Effects, etc.]

[0093] As described above, the high-frequency circuit 1 according to the present embodiment includes: the antenna connection terminal 101, the input terminal 111, and the output terminal 121; the filter 31 having a passband including at least a part of the transmission band of the frequency band A for FDD; the filter 32 having a passband including at least a part of the reception band of the frequency band A; and the switch 41 having terminals 411 to 413, wherein the antenna connection terminal 101 is connected to the terminal 411, the filter 31 is connected between the terminal 412 and the input terminal 111, and the filter 32 is connected between the terminal 413 and the output terminal 121, and the switch 41 is configured to switch between a first connection, a second connection, and a third connection, in which the terminal 411 is connected to the terminal 412 and the terminal 411 is not connected to the terminal 413 in the first connection, the terminal 411 is connected to the terminal 413 and the terminal 411 is not connected to the terminal 412 in the second connection, the terminal 411 is connected to the terminal 413 and the terminal 411 is not connected to the terminal 412 in the second connection, and the terminal 411 is connected to both the terminal 412 and the terminal 413 in the third connection.

[0094] According to this, the first connection and the second connection of the switch 41 are switched in time. Therefore, the transmission signal and the reception signal of the frequency band A for FDD can be divided not only in frequency but also in time to perform duplex communication, thereby reducing the requirements for the isolation characteristics between the transmission filter and the reception filter of the frequency band A. In other words, the design of the filters 31 and 32 becomes easy, and the increase in the loss of the filters 31 and 32 can be suppressed. As a result, the output power of the power amplifier 11 can be reduced, and the noise can be reduced and the life of the power supply can be extended. In addition, if the third connection of the switch 41 is maintained, the communication speed can be increased compared with the case of switching the first connection and the second connection in time.

[0095] In addition, for example, in the high-frequency circuit 1 involved in the present embodiment, when a high power level specified by a maximum output power greater than a specified power is applied to frequency band A, the switch 41 may switch the first connection and the second connection according to time, and when a low power level specified by a maximum output power less than a specified power is applied to frequency band A, the switch 41 may maintain the third connection.

[0096] According to this, at a high power level, the first connection and the second connection of the switch 41 are switched in time. Therefore, at a high output power, the isolation characteristic between the filter 31 and the filter 32 is required to be higher, and the isolation characteristic requirement can be lowered. As a result, the output power of the power amplifier 11 can be reduced at a high output power, and the effect of reducing noise and extending the life of the power supply is large. On the contrary, at a low power level, the third connection of the switch 41 is maintained, so that at a low output power, the isolation characteristic requirement is lowered, and the decrease in communication speed can be suppressed.

[0097] In addition, for example, in the high-frequency circuit 1 involved in this embodiment, the switch 41 may also have a terminal 414, which is connected to the terminator 51. In the first connection, the terminal 414 may also be connected to the terminal 413, and in the second connection, the terminal 414 may also be connected to the terminal 412.

[0098] Accordingly, in the first connection and the second connection, when the terminals 412 and 413 of the switch 41 are not used for transmission of high-frequency signals, the terminals 412 and 413 of the switch 41 can be terminated, thereby further improving the isolation characteristics.

[0099] In addition, for example, the high-frequency circuit 1 according to the present embodiment may further include a power amplifier 11 connected between the filter 31 and the input terminal 111 .

[0100] According to this, the high frequency circuit 1 includes the power amplifier 11 , and thus the transmission signal can be amplified in the high frequency circuit 1 .

[0101] In addition, for example, the high-frequency circuit 1 according to the present embodiment may further include: a filter 33 having a passband including at least a part of the transmission band of the frequency band B; and a switch 42 connected between the power amplifier 11 and the filters 31 and 33, and the switch 41 may further include a terminal 415 connected to the filter 33. Here, the switch 42 may be configured to switch between the connection between the power amplifier 11 and the filter 31 and the connection between the power amplifier 11 and the filter 33.

[0102] According to this, the power amplifier 11 is connected to the two filters 31 and 33 via the switch 42. Therefore, the power amplifier 11 can be shared by the two frequency bands A and B, which can contribute to the miniaturization of the communication device 5.

[0103] In addition, for example, the high-frequency circuit 1 according to the present embodiment may further include a low-noise amplifier 21 connected between the filter 32 and the output terminal 121 .

[0104] According to this, since the high-frequency circuit 1 includes the low-noise amplifier 21 , it is possible to amplify the received signal in the high-frequency circuit 1 .

[0105] In addition, for example, the high-frequency circuit 1 according to the present embodiment may further include: a filter 34 having a passband including at least a portion of the reception frequency band of the frequency band C; and a switch 43 connected between the low-noise amplifier 21 and the filters 32 and 34, and the switch 41 may further include a terminal 416 connected to the filter 34. Here, the switch 43 may also be configured to switch between the connection between the low-noise amplifier 21 and the filter 32 and the connection between the low-noise amplifier 21 and the filter 34.

[0106] According to this, the low noise amplifier 21 is connected to the two filters 32 and 34 via the switch 43. Therefore, the low noise amplifier 21 can be shared by the two frequency bands A and C, which can contribute to the miniaturization of the communication device 5.

[0107] Furthermore, the communication device 5 according to the present embodiment includes an RFIC 3 that processes a high-frequency signal and a high-frequency circuit 1 that transmits the high-frequency signal between the RFIC 3 and the antenna 2 .

[0108] According to this, the effect of the high-frequency circuit 1 described above can also be achieved by the communication device 5 .

[0109] (Implementation Method 2)

[0110] Next, Embodiment 2 is described. This embodiment is different from Embodiment 1 mainly in that the communication device includes two antennas. This embodiment is described below with reference to the drawings, focusing on the differences from Embodiment 1.

[0111] [2.1 Circuit Configuration of Communication Device 5A]

[0112] Figure 5 2 is a circuit diagram of a communication device 5A according to the present embodiment. The communication device 5A according to the present embodiment includes antennas 2 a and 2 b instead of the antenna 2 , and includes a high-frequency circuit 1A instead of the high-frequency circuit 1 .

[0113] The high-frequency circuit 1A transmits a high-frequency signal between the antennas 2a and 2b and the RFIC 3. The internal structure of the high-frequency circuit 1A will be described later.

[0114] Antenna 2a is connected to antenna connection terminal 101A of high frequency circuit 1A. Antenna 2b is connected to antenna connection terminal 102A of high frequency circuit 1A. Antennas 2a and 2b can each transmit a high frequency signal output from high frequency circuit 1A, and can also receive a high frequency signal from the outside and output it to high frequency circuit 1A.

[0115] In addition, in the communication device 5A according to the present embodiment, the antennas 2a and 2b and the BBIC 4 are not essential components.

[0116] [2.2 Circuit structure of high frequency circuit 1A]

[0117] Next, refer to Figure 5 The circuit structure of the high frequency circuit 1A is described below. The high frequency circuit 1A includes a power amplifier 11, a low noise amplifier 21, filters 31 to 34, switches 41A, 42 and 43, a terminator 51, antenna connection terminals 101A and 102A, an input terminal 111 and an output terminal 121. Figure 1 The components of the high-frequency circuit 1A will be described focusing on the differences between the high-frequency circuit 1 and the high-frequency circuit 1A.

[0118] The antenna connection terminal 101A is an example of a first antenna connection terminal, and is connected to the antenna 2a outside the high-frequency circuit 1A, and is connected to the switch 41A inside the high-frequency circuit 1A.

[0119] The antenna connection terminal 102A is an example of a second antenna connection terminal, and is connected to the antenna 2b outside the high-frequency circuit 1A, and is connected to the switch 41A inside the high-frequency circuit 1A.

[0120] The switch 41A is an example of a first switch, and is connected between the antenna connection terminals 101A and 102A and the filters 31 to 34. Specifically, the switch 41A has terminals 411A to 417A. The terminal 411A is an example of a first terminal, and is connected to the antenna connection terminal 101A. The terminal 412A is an example of a second terminal, and is connected to the antenna connection terminal 102A. The terminal 413A is an example of a third terminal, and is connected to the filter 31. The terminal 414A is an example of a fourth terminal, and is connected to the filter 32. The terminal 415A is an example of a fifth terminal, and is connected to the terminator 51. The terminal 416A is an example of a sixth terminal, and is connected to the filter 33. The terminal 417A is an example of a seventh terminal, and is connected to the filter 34.

[0121] In this connection structure, the switch 41A can connect the terminals 411A, 412A, and 415A to the terminals 413A, 414A, 416A, and 417A based on a control signal from the RFIC 3. The switch 41A is configured by a multi-connection type switch circuit.

[0122] Specifically, switch 41A can at least switch between the first connection, the second connection and the third connection. Here, in the first connection, only one of terminals 411A and 412A is connected to terminal 413A, and terminals 411A and 412A are not connected to terminal 414A. At this time, terminal 415A can be connected to terminal 414A at will. In the second connection, terminals 411A and 412A are not connected to terminal 413A, and only one of terminals 411A and 412A is connected to terminal 414A. At this time, terminal 415A can be connected to terminal 413A at will. In the third connection, one of terminals 411A and 412A is connected to terminal 413A, and the other of terminals 411A and 412A is connected to terminal 414A.

[0123] In this embodiment, the switch 41A can switch between the first connection and the second connection in a time-dependent manner when a high power level is applied to the frequency band A. On the other hand, when a low power level is applied to the frequency band A, the switch 41A can maintain the third connection.

[0124] also, Figure 5 The circuit structure of the high-frequency circuit 1A is an example and is not limited to this. The high-frequency circuit 1A only needs to include at least filters 31 and 32, a switch 41A, antenna connection terminals 101A and 102A, an input terminal 111, and an output terminal 121, and may not include other circuit elements. For example, the high-frequency circuit 1A may not include the terminator 51. In this case, the switch 41A may not include the terminal 415A. In addition, for example, the high-frequency circuit 1A may not include filters 33 and / or 34. In this case, the switch 41A may not include terminals 416A and / or 417A. In addition, the high-frequency circuit 1A may also include two power amplifiers connected to the filters 31 and 33, respectively, instead of the power amplifier 11 and the switch 42. Similarly, the high-frequency circuit 1A may also include two low-noise amplifiers connected to the filters 32 and 34, respectively, instead of the low-noise amplifier 21 and the switch 43.

[0125] [2.3 Transmission and reception of frequency band A at each power level]

[0126] Next, transmission and reception in the frequency band A at each power level of the communication device 5A according to the present embodiment will be described.

[0127] [2.3.1 Transmission and reception of band A at high power level]

[0128] First, refer to Figure 6 and Figure 7 To illustrate the transmission and reception of frequency band A at high power level. Figure 61 is a diagram showing transmission of a signal in the frequency band A at a high power level by the communication device 5A according to the present embodiment. Figure 7 1 is a diagram showing reception of a signal in the frequency band A at a high power level by the communication device 5A according to the present embodiment.

[0129] At high power levels, RFIC 3 switches exclusively between transmission and reception by controlling the switches of high frequency circuit 1A. Specifically, switch 41A switches between a first connection and a second connection. In the first connection, terminal 411A is connected to terminal 413A, and terminal 415A is connected to terminal 414A (see Figure 6 ), in the second connection, the terminal 412A is connected to the terminal 414A, and the terminal 415A is connected to the terminal 413A (refer to Figure 7 ). In addition, the connection between the terminal 415A and the terminal 414A in the first connection and the connection between the terminal 415A and the terminal 413A in the second connection are not essential but are arbitrary connections.

[0130] As a result, in the transmission of the signal in the frequency band A at a high power level, Figure 6 As shown, the transmission signal of frequency band A input to the input terminal 111 from the RFIC 3 is amplified by the power amplifier 11 and then transmitted to the antenna 2a via the switch 42, the filter 31, the switch 41A and the antenna connection terminal 101A.

[0131] On the other hand, in the reception of the signal of band A at a high power level, as Figure 7 As shown, the reception signal of frequency band A input from antenna 2b to antenna connection terminal 102A is transmitted to low noise amplifier 21 via switch 41A, filter 32 and switch 43, amplified by low noise amplifier 21, and transmitted to RFIC 3 via output terminal 121.

[0132] In this way, in the transmission and reception of the signal in the frequency band A for FDD at a high power level, the transmission signal and the reception signal are separated not only in frequency but also in time.

[0133] [2.3.2 Transmission and reception of frequency band A at low power level]

[0134] Next, refer to Figure 8 To illustrate the transmission and reception of frequency band A at low power levels. Figure 8 1 and 2 are diagrams showing transmission and reception of signals in the frequency band A at a low power level by the communication device 5A according to the present embodiment.

[0135] At low power levels, RFIC 3 performs transmission and reception simultaneously by controlling the switches of high frequency circuit 1A. Specifically, switch 41A maintains a third connection in which terminal 411A is connected to terminal 413A and terminal 412A is connected to terminal 414A (see Figure 8 ).

[0136] As a result, in the transmission of the signal in the frequency band A at a low power level, Figure 8 As shown, the transmission signal of frequency band A input to the input terminal 111 from the RFIC 3 is amplified by the power amplifier 11 and then transmitted to the antenna 2a via the switch 42, the filter 31, the switch 41A and the antenna connection terminal 101A.

[0137] On the other hand, in the reception of the signal of frequency band A at a low power level, as Figure 8 As shown, the reception signal of frequency band A input from antenna 2b to antenna connection terminal 102A is transmitted to low noise amplifier 21 via switch 41A, filter 32 and switch 43, amplified by low noise amplifier 21, and transmitted to RFIC 3 via output terminal 121.

[0138] In this way, in the transmission and reception of signals in the frequency band A for FDD at a low power level, the transmission signal and the reception signal are separated in frequency.

[0139] In addition, Figure 6 to Figure 8 In the embodiment, antenna 2a is used for transmission and antenna 2b is used for reception, but the present invention is not limited thereto. Antenna 2a may also be used for reception, or for both transmission and reception. In addition, antenna 2b may also be used for transmission, or for both transmission and reception.

[0140] [2.4 Effects, etc.]

[0141] As described above, the high-frequency circuit 1A according to the present embodiment includes: antenna connection terminals 101A and 102A, an input terminal 111, and an output terminal 121; a filter 31 having a passband including at least a portion of a transmission frequency band of frequency band A for FDD; a filter 32 having a passband including at least a portion of a reception frequency band of frequency band A; and a switch 41A having terminals 411A to 414A, wherein the antenna connection terminal 101A is connected to the terminal 411A, the antenna connection terminal 102A is connected to the terminal 412A, the filter 31 is connected between the terminal 413A and the input terminal 111, and the filter 32 is connected to the terminal 414A. Between the terminal 414A and the output terminal 121, the switch 41A is configured to switch between a first connection, a second connection, and a third connection. In the first connection, one of the terminals 411A and 412A is connected to the terminal 413A, and neither the terminal 411A nor the terminal 412A is connected to the terminal 414A. In the second connection, one of the terminals 411A and 412A is connected to the terminal 414A, and neither the terminal 411A nor the terminal 412A is connected to the terminal 413A. In the third connection, one of the terminals 411A and 412A is connected to the terminal 413A, and the other of the terminals 411A and 412A is connected to the terminal 414A.

[0142] According to this, the first connection and the second connection of the switch 41A are switched in time. Therefore, the transmission signal and the reception signal of the frequency band A for FDD can be divided not only in frequency but also in time to perform duplex communication, thereby reducing the requirements for the isolation characteristics between the transmission filter and the reception filter of the frequency band A. In other words, the design of the filters 31 and 32 becomes easy, and the increase in the loss of the filters 31 and 32 can be suppressed. As a result, the output power of the power amplifier 11 can be reduced, and the noise can be reduced and the life of the power supply can be extended. In addition, if the third connection of the switch 41A is maintained, the communication speed can be increased compared with the case of switching the first connection and the second connection in time.

[0143] In addition, for example, in the high-frequency circuit 1A involved in the present embodiment, when a high power level specified by a maximum output power greater than a specified power is applied to frequency band A, the switch 41A may switch the first connection and the second connection according to time, and when a low power level specified by a maximum output power less than a specified power is applied to frequency band A, the switch 41A may maintain the third connection.

[0144] Accordingly, at a high power level, the first connection and the second connection of the switch 41A are switched in time. Therefore, at a high output power level, the isolation characteristic between the filter 31 and the filter 32 is required to be higher, and the isolation characteristic requirement can be lowered. As a result, the output power of the power amplifier 11 can be reduced at a high output power level, which has a great effect on reducing noise and extending the life of the power supply. On the contrary, at a low power level, the third connection of the switch 41A is maintained, so that at a low output power level, the isolation characteristic requirement is lowered, and the decrease in communication speed can be suppressed.

[0145] In addition, for example, in the high-frequency circuit 1A involved in this embodiment, the switch 41A may also have a terminal 415A, which is connected to the terminator 51. In the first connection, the terminal 415A may also be connected to the terminal 414A, and in the second connection, the terminal 415A may also be connected to the terminal 413A.

[0146] According to this, in the first connection and the second connection, when the terminals 413A and 414A of the switch 41A are not used for transmission of high-frequency signals, the terminals 413A and 414A of the switch 41A can be terminated, thereby further improving the isolation characteristics.

[0147] In addition, for example, the high-frequency circuit 1A according to the present embodiment may further include a power amplifier 11 connected between the filter 31 and the input terminal 111 .

[0148] According to this, since the high-frequency circuit 1A includes the power amplifier 11 , it is possible to amplify the transmission signal in the high-frequency circuit 1A.

[0149] In addition, for example, the high-frequency circuit 1A according to the present embodiment may further include: a filter 33 having a passband including at least a part of the transmission frequency band of the frequency band B; and a switch 42 connected between the power amplifier 11 and the filters 31 and 33, and the switch 41A may further include a terminal 416A connected to the filter 33. Here, the switch 42 may be configured to switch between the connection between the power amplifier 11 and the filter 31 and the connection between the power amplifier 11 and the filter 32.

[0150] According to this, the power amplifier 11 is connected to the two filters 31 and 33 via the switch 42. Therefore, the power amplifier 11 can be shared by the two frequency bands A and B, which can contribute to the miniaturization of the communication device 5A.

[0151] In addition, for example, the high-frequency circuit 1A according to the present embodiment may further include a low-noise amplifier 21 connected between the filter 32 and the output terminal 121 .

[0152] According to this, since the high-frequency circuit 1A includes the low-noise amplifier 21 , it is possible to amplify the received signal in the high-frequency circuit 1A.

[0153] In addition, for example, the high-frequency circuit 1A according to the present embodiment may further include: a filter 34 having a passband including at least a part of the reception frequency band of the frequency band C; and a switch 43 connected between the low-noise amplifier 21 and the filters 32 and 34, and the switch 41A may further include a terminal 417A connected to the filter 34. Here, the switch 43 may be configured to switch between the connection between the low-noise amplifier 21 and the filter 32 and the connection between the low-noise amplifier 21 and the filter 34.

[0154] According to this, the low noise amplifier 21 is connected to the two filters 32 and 34 via the switch 43. Therefore, the low noise amplifier 21 can be shared by the two frequency bands A and C, which can contribute to the miniaturization of the communication device 5A.

[0155] Furthermore, the communication device 5A according to the present embodiment includes an RFIC 3 that processes a high-frequency signal and a high-frequency circuit 1A that transmits the high-frequency signal between the RFIC 3 and the antennas 2a and 2b.

[0156] According to this, the effect of the high-frequency circuit 1A described above can also be achieved by the communication device 5A.

[0157] (Implementation 3)

[0158] Next, Embodiment 3 is described. This embodiment is a modified example of Embodiment 1, and is different from Embodiment 1 mainly in that a capacitor is connected to switch 41 (switch 41B in this embodiment) in Embodiment 1. Hereinafter, this embodiment will be described with reference to the drawings, centering on the differences from Embodiment 1.

[0159] [3.1 Circuit Configuration of Communication Device 5B]

[0160] Fig. 9 2 is a circuit diagram of a communication device 5B according to the present embodiment. The communication device 5B according to the present embodiment is the same as the communication device 5 according to the first embodiment except that it includes a high-frequency circuit 1B instead of the high-frequency circuit 1, and therefore the description thereof is omitted.

[0161] [3.2 Circuit structure of high frequency circuit 1B]

[0162] Next, refer to Fig. 9The circuit structure of the high frequency circuit 1B is described below. The high frequency circuit 1B includes a power amplifier 11, a low noise amplifier 21, filters 31 to 34, switches 41B, 42 and 43, a terminator 51, a capacitor 52, an antenna connection terminal 101, an input terminal 111 and an output terminal 121. Figure 1 The components of the high-frequency circuit 1B will be described focusing on the differences between the high-frequency circuit 1 and the high-frequency circuit 1B.

[0163] The switch 41B is an example of a first switch, and is connected between the antenna connection terminal 101 and the filters 31 to 34. Specifically, the switch 41B has terminals 411 to 417. The terminal 417 is an example of a seventh terminal, and is connected to the capacitor 52.

[0164] In this connection structure, the switch 41B can connect the terminals 411 and 414 to the terminals 412, 413, 415, 416, and 417 based on a control signal from the RFIC 3, for example. The switch 41B is configured by a multi-connection type switch circuit.

[0165] Specifically, switch 41B can at least switch between the first connection, the second connection and the third connection. Here, in the first connection, terminal 411 is connected to terminals 412 and 417, and terminal 411 is not connected to terminal 413. At this time, terminal 414 can be connected to terminal 413 at will. In the second connection, terminal 411 is not connected to terminal 412, and terminal 411 is connected to terminals 413 and 417. At this time, terminal 414 can be connected to terminal 412 at will. In the third connection, terminal 411 is connected to terminals 412 and 413 at the same time.

[0166] In this embodiment, similar to Embodiment 1, when the first power level is applied to frequency band A, switch 41B can switch between the first connection and the second connection in a time-dependent manner. Also, when the second power level is applied to frequency band A, switch 41B can maintain the third connection.

[0167] The capacitor 52 is a variable capacitor connected between the terminal 417 of the switch 41B and the ground, and when the filter that can be connected to the terminal 411 is not connected to the terminal 411, the capacitor 52 can compensate for the parasitic capacitance of the filter. For example, in the first connection, the capacitor 52 can compensate for the parasitic capacitance of at least one of the filters 32 to 34 that are not connected to the terminal 411. In addition, for example, in the second connection, the capacitor 52 can compensate for the parasitic capacitance of at least one of the filters 31, 33, and 34 that are not connected to the terminal 411.

[0168] As the capacitor 52 , a DTC (Digital Tunable Capacitor) can be used, but the present invention is not limited thereto. In addition, the capacitance of the capacitor 52 does not necessarily have to be variable.

[0169] [3.3 Transmission and reception of frequency band A at each power level]

[0170] Next, transmission and reception in the frequency band A at each power level of the communication device 5B according to the present embodiment will be described.

[0171] [3.3.1 Transmission and reception of frequency band A at high power level]

[0172] First, refer to Fig.10 and Fig.11 To illustrate the transmission and reception of frequency band A at high power level. Fig.10 1 is a diagram showing transmission of a signal in the frequency band A at a high power level by the communication device 5B according to the present embodiment. Fig.11 1 is a diagram showing reception of a signal in the frequency band A at a high power level by the communication device 5B according to the present embodiment.

[0173] At high power levels, RFIC 3 switches transmission and reception exclusively by controlling the switches of high frequency circuit 1B. Specifically, switch 41B switches between a first connection and a second connection. In the first connection, terminal 411 is connected to terminals 412 and 417, and terminal 414 is connected to terminal 413 (see Fig.10 ), in the second connection, the terminal 411 is connected to the terminals 413 and 417, and the terminal 414 is connected to the terminal 412 (refer to Fig.11 ). In addition, the connection between the terminal 414 and the terminal 413 in the first connection and the connection between the terminal 414 and the terminal 412 in the second connection are not essential but are arbitrary connections.

[0174] As a result, in the transmission of the signal in the frequency band A at a high power level, Fig.10 As shown, the transmission signal of the frequency band A input to the input terminal 111 from the RFIC 3 is amplified by the power amplifier 11 and then transmitted to the antenna 2 via the switch 42 , the filter 31 , the switch 41B and the antenna connection terminal 101 .

[0175] On the other hand, in the reception of the signal of band A at a high power level, as Fig.11 As shown, the reception signal of frequency band A input from antenna 2 to antenna connection terminal 101 is transmitted to low noise amplifier 21 via switch 41B, filter 32 and switch 43 , amplified by low noise amplifier 21 , and then transmitted to RFIC 3 via output terminal 121 .

[0176] In this way, in the transmission and reception of the signal in the frequency band A for FDD at a high power level, the transmission signal and the reception signal are separated not only in frequency but also in time.

[0177] [3.3.2 Transmission and reception of frequency band A at low power level]

[0178] Next, refer to Fig.12 To illustrate the transmission and reception of frequency band A at low power levels. Fig.12 1 and 2 are diagrams showing transmission and reception of signals in the frequency band A at a low power level by the communication device 5B according to the present embodiment.

[0179] At low power level, RFIC 3 performs transmission and reception simultaneously by controlling the switches of high frequency circuit 1B. Specifically, switch 41B maintains the third connection in which terminal 411 is connected to terminal 412 and terminal 413 is connected (see Fig.12 ).

[0180] As a result, in the transmission of the signal in the frequency band A at a low power level, Fig.12 As shown, the transmission signal of frequency band A input from RFIC3 to input terminal 111 is amplified by power amplifier 11 and then transmitted to antenna 2 via switch 42 , filter 31 , switch 41B and antenna connection terminal 101 .

[0181] On the other hand, in the reception of the signal of frequency band A at a low power level, as Fig.12 As shown, the reception signal of frequency band A input from antenna 2 to antenna connection terminal 101 is transmitted to low noise amplifier 21 via switch 41B, filter 32 and switch 43 , amplified by low noise amplifier 21 , and then transmitted to RFIC 3 via output terminal 121 .

[0182] In this way, in the transmission and reception of signals in the frequency band A for FDD at a low power level, the transmission signal and the reception signal are separated in frequency.

[0183] [3.4 Effects, etc.]

[0184] As described above, in the high-frequency circuit 1B according to the present embodiment, the switch 41B may further include the terminal 417 , and the high-frequency circuit 1B may further include the capacitor 52 connected between the terminal 417 and the ground. In the first connection, the terminal 411 may further be connected to the terminal 417 .

[0185] According to this, in the first connection where the filter 41 is connected to the terminal 411 and the filter 42 is not connected to the terminal 411, the parasitic capacitance of the filter 42 can be compensated by connecting the capacitor 52 to the terminal 411. Therefore, the change of the load impedance of the filter 41 can be suppressed, and the change of the characteristics of the filter 41 can be suppressed.

[0186] Furthermore, for example, in the high-frequency circuit 1B according to the present embodiment, the capacitor 52 may be a variable capacitor, and in the second connection, the terminal 411 may be further connected to the terminal 417 .

[0187] According to this, in the second connection in which the filter 42 is connected to the terminal 411 and the filter 41 is not connected to the terminal 411, the parasitic capacitance of the filter 41 can be compensated by connecting the capacitor 52 to the terminal 411. Therefore, the change of the load impedance of the filter 42 can be suppressed, and the change of the characteristics of the filter 42 can be suppressed.

[0188] (Implementation 4)

[0189] Next, Embodiment 4 is described. This embodiment is a modified example of Embodiment 2, and is different from Embodiment 2 mainly in that a capacitor is connected to switch 41A (switch 41C in this embodiment) in Embodiment 2. Hereinafter, this embodiment will be described with reference to the drawings, centering on the differences from Embodiment 2.

[0190] [4.1 Circuit Structure of Communication Device 5C]

[0191] Fig.13 The communication device 5C according to the present embodiment is the same as the communication device 5A according to the second embodiment except that it includes a high-frequency circuit 1C instead of the high-frequency circuit 1A, so the description thereof is omitted.

[0192] [4.2 Circuit structure of high-frequency circuit 1C]

[0193] Next, refer to Fig.13 The circuit structure of the high frequency circuit 1C is described below. The high frequency circuit 1C includes a power amplifier 11, a low noise amplifier 21, filters 31 to 34, switches 41C, 42 and 43, a terminator 51, capacitors 52 and 53, antenna connection terminals 101A and 102A, an input terminal 111 and an output terminal 121. Figure 5 The components of the high-frequency circuit 1C will be described mainly with respect to the differences from the high-frequency circuit 1A.

[0194] The switch 41C is an example of a first switch and is connected between the antenna connection terminals 101A and 102A and the filters 31 to 34. Specifically, the switch 41C has terminals 411A to 419A. The terminal 418A is an example of an eighth terminal and is connected to the capacitor 52. The terminal 419A is an example of a ninth terminal and is connected to the capacitor 53.

[0195] In this connection structure, the switch 41C can connect the terminals 411A, 412A, and 415A to the terminals 413A, 414A, and 416A to 419A based on, for example, a control signal from the RFIC 3. The switch 41C is configured by a multi-connection type switch circuit.

[0196] Specifically, switch 41C is at least capable of switching between a first connection, a second connection, and a third connection. Here, in the first connection, only one of terminals 411A and 412A is connected to terminals 413A and 418A, and terminals 411A and 412A are not connected to terminal 414A. At this time, terminal 415A can be connected to terminal 414A at will. In the second connection, terminals 411A and 412A are not connected to terminal 413A, and only one of terminals 411A and 412A is connected to terminals 414A and 419A. At this time, terminal 415A can be connected to terminal 413A at will. In the third connection, one of terminals 411A and 412A is connected to terminals 413A and 418A, and the other of terminals 411A and 412A is connected to terminals 414A and 419A.

[0197] In this embodiment, similarly to Embodiment 2, when the first power level is applied to frequency band A, switch 41C can switch between the first connection and the second connection in a time-dependent manner. Also, when the second power level is applied to frequency band A, switch 41C can maintain the third connection.

[0198] Capacitor 52 is an example of a first capacitor and is a variable capacitor. Capacitor 52 is connected between terminal 418A of switch 41C and ground, and when a filter that can be connected to terminal 411A is not connected to terminal 411A, capacitor 52 can compensate for the parasitic capacitance of the filter. For example, in the first connection, capacitor 52 can compensate for the parasitic capacitance of at least one of filters 32 to 34 that is not connected to terminal 411A.

[0199] Capacitor 53 is an example of a second capacitor and is a variable capacitor. Capacitor 53 is connected between terminal 419A of switch 41C and ground, and when a filter that can be connected to terminal 412A is not connected to terminal 412A, capacitor 53 can compensate for the parasitic capacitance of the filter. For example, in the second connection, capacitor 53 can compensate for the parasitic capacitance of at least one of filters 31, 33, and 34 that are not connected to terminal 412A.

[0200] DTC can be used as the capacitors 52 and 53, but the present invention is not limited thereto. In addition, the capacitance of the capacitors 52 and / or 53 may not be variable.

[0201] [4.3 Transmission and reception of frequency band A at each power level]

[0202] Next, transmission and reception in the frequency band A at each power level of the communication device 5C according to the present embodiment will be described.

[0203] [4.3.1 Transmission and reception of frequency band A at high power level]

[0204] First, refer to Fig.14 and Fig.15 To illustrate the transmission and reception of frequency band A at high power level. Fig.14 1 is a diagram showing transmission of a signal in the frequency band A at a high power level by the communication device 5C according to the present embodiment. Fig.15 1 is a diagram showing reception of a signal in the frequency band A at a high power level by the communication device 5C according to the present embodiment.

[0205] At high power levels, RFIC 3 switches exclusively between transmission and reception by controlling the switches of high frequency circuit 1C. Specifically, switch 41C switches between a first connection and a second connection. In the first connection, terminal 411A is connected to terminals 413A and 418A, and terminal 415A is connected to terminal 414A (see Fig.14 ), in the second connection, the terminal 412A is connected to the terminals 414A and 419A, and the terminal 415A is connected to the terminal 413A (refer to Fig.15 ). In addition, the connection between the terminal 415A and the terminal 414A in the first connection and the connection between the terminal 415A and the terminal 413A in the second connection are not essential but are arbitrary connections.

[0206] As a result, in the transmission of the signal in the frequency band A at a high power level, Fig.14 As shown, the transmission signal of the frequency band A input to the input terminal 111 from the RFIC 3 is amplified by the power amplifier 11 and then transmitted to the antenna 2a via the switch 42, the filter 31, the switch 41C and the antenna connection terminal 101A.

[0207] On the other hand, in the reception of the signal of band A at a high power level, as Fig.15 As shown, the reception signal of frequency band A input from antenna 2b to antenna connection terminal 102A is transmitted to low noise amplifier 21 via switch 41C, filter 32 and switch 43, and is amplified by low noise amplifier 21 and then transmitted to RFIC 3 via output terminal 121.

[0208] In this way, in the transmission and reception of the signal in the frequency band A for FDD at a high power level, the transmission signal and the reception signal are separated not only in frequency but also in time.

[0209] [4.3.2 Transmission and reception of frequency band A at low power level]

[0210] Next, refer to Fig.16 To illustrate the transmission and reception of frequency band A at low power levels. Fig.16 1 and 2 are diagrams showing transmission and reception of signals in the frequency band A at a low power level by the communication device 5C according to the present embodiment.

[0211] At low power levels, RFIC 3 performs transmission and reception simultaneously by controlling the switches of high frequency circuit 1C. Specifically, switch 41C maintains a third connection in which terminal 411A is connected to terminals 413A and 418A, and terminal 412A is connected to terminals 414A and 419A (see Fig.16 ).

[0212] As a result, in the transmission of the signal in the frequency band A at a low power level, Fig.16 As shown, the transmission signal of the frequency band A input to the input terminal 111 from the RFIC 3 is amplified by the power amplifier 11 and then transmitted to the antenna 2a via the switch 42, the filter 31, the switch 41C and the antenna connection terminal 101A.

[0213] On the other hand, in the reception of the signal of frequency band A at a low power level, as Fig.16 As shown, the reception signal of frequency band A input from antenna 2b to antenna connection terminal 102A is transmitted to low noise amplifier 21 via switch 41C, filter 32 and switch 43, and is amplified by low noise amplifier 21 and then transmitted to RFIC 3 via output terminal 121.

[0214] In this way, in the transmission and reception of signals in the frequency band A for FDD at a low power level, the transmission signal and the reception signal are separated in frequency.

[0215] [4.4 Effects, etc.]

[0216] As described above, in the high-frequency circuit 1C involved in this embodiment, the switch 41C may also have a terminal 418A, and the high-frequency circuit 1C may also have a capacitor 52 connected between the terminal 418A and the ground. In the first connection and the third connection, the terminal 411A may also be connected to the terminal 418A.

[0217] According to this, in the first connection and the third connection in which the filter 41 is connected to the terminal 411A and the filter 42 is not connected to the terminal 411A, the capacitor 52 is connected to the terminal 411A, thereby compensating for the parasitic capacitance of the filter 42. Therefore, the change in the load impedance of the filter 41 can be suppressed, and the change in the characteristics of the filter 41 can be suppressed.

[0218] In addition, for example, in the high-frequency circuit 1C involved in this embodiment, the switch 41C may also have a terminal 419A, and the high-frequency circuit 1C may also have a capacitor 53, which is connected between the terminal 419A and the ground. In the second connection and the third connection, the terminal 411A may also be connected to the terminal 419A.

[0219] According to this, in the second connection and the third connection in which the filter 42 is connected to the terminal 412A and the filter 41 is not connected to the terminal 412A, the capacitor 53 is connected to the terminal 412A to compensate for the parasitic capacitance of the filter 41. Therefore, the change of the load impedance of the filter 42 can be suppressed, and the change of the characteristics of the filter 42 can be suppressed.

[0220] (Other embodiments)

[0221] The high-frequency circuit and communication device involved in the present invention are described above based on the embodiments, but the high-frequency circuit and communication device involved in the present invention are not limited to the above embodiments. The present invention also includes other embodiments implemented by combining any constituent elements in the above embodiments, variations obtained by implementing various variations that can be thought of by a person skilled in the art to the above embodiments within the scope of the main purpose of the present invention, and various devices having the above high-frequency circuit built therein.

[0222] For example, in the circuit structure of the high-frequency circuit involved in each of the above-mentioned embodiments, other circuit elements and wiring etc. may be inserted between the paths connecting the circuit elements and signal paths disclosed in the drawings. For example, an impedance matching circuit may be inserted between a power amplifier and a filter and / or between a low-noise amplifier and a filter.

[0223] In addition, in each of the above embodiments, the power level is used as a condition for switching whether the transmission signal and the reception signal of the FDD frequency band are separated or not separated in time, but the present invention is not limited thereto. For example, the transmission signal and the reception signal of the FDD frequency band may be switched whether they are separated or not separated in time according to the S / N ratio of the reception signal.

[0224] Next, features of the high-frequency circuit and the communication device described in the above-mentioned embodiments are shown.

[0225] <1> A high frequency circuit having:

[0226] Antenna connection terminal, input terminal and output terminal;

[0227] a first filter having a passband including at least a portion of a transmission frequency band of a first frequency band for frequency division duplexing;

[0228] a second filter having a passband including at least a portion of a receive frequency band of the first frequency band; and

[0229] a first switch having a first terminal, a second terminal and a third terminal,

[0230] Wherein, the antenna connection terminal is connected to the first terminal,

[0231] The first filter is connected between the second terminal and the input terminal,

[0232] The second filter is connected between the third terminal and the output terminal,

[0233] The first switch is configured to switch between a first connection, a second connection, and a third connection.

[0234] In the first connection, the first terminal is connected to the second terminal, and the first terminal is not connected to the third terminal,

[0235] In the second connection, the first terminal is connected to the third terminal, and the first terminal is not connected to the second terminal,

[0236] In the third connection, the first terminal is connected to the second terminal and the third terminal at the same time.

[0237] <2> according to <1> The high frequency circuit described, wherein

[0238] When a first power level specified by a maximum output power greater than a specified power is applied to the first frequency band, the first switch switches the first connection and the second connection according to time.

[0239] The first switch maintains the third connection in a situation where a second power level specified by a maximum output power smaller than the specified power is applied to the first frequency band.

[0240] <3> according to <1> or <2> The high frequency circuit described, wherein

[0241] The first switch further has a fourth terminal, and the fourth terminal is connected to the terminator.

[0242] In the first connection, the fourth terminal is also connected to the third terminal,

[0243] In the second connection, the fourth terminal is also connected to the second terminal.

[0244] <4> according to <1> ~ <3> A high-frequency circuit as described in any one of the items , wherein:

[0245] The high-frequency circuit further includes a power amplifier connected between the first filter and the input terminal.

[0246] <5> according to <4> The high frequency circuit described, wherein

[0247] The high frequency circuit further comprises:

[0248] a third filter having a passband including at least a portion of a transmission frequency band of the second frequency band; and

[0249] a second switch connected between the power amplifier and the first filter and the third filter,

[0250] The first switch further has a fifth terminal connected to the third filter.

[0251] <6> according to <5> The high frequency circuit described, wherein

[0252] The second switch is configured to switch between connection between the power amplifier and the first filter and connection between the power amplifier and the third filter.

[0253] <7> according to <1> ~ <6> A high-frequency circuit as described in any one of the items , wherein:

[0254] The high-frequency circuit further includes a low-noise amplifier connected between the second filter and the output terminal.

[0255] <8> according to <7> The high frequency circuit described, wherein

[0256] The high frequency circuit further comprises:

[0257] a fourth filter having a passband including at least a portion of a reception frequency band of a third frequency band; and

[0258] a third switch connected between the low noise amplifier and the second filter and the fourth filter,

[0259] The first switch further has a sixth terminal connected to the fourth filter.

[0260] <9> according to <8> The high frequency circuit described, wherein

[0261] The third switch is configured to switch between connection between the low noise amplifier and the second filter and connection between the low noise amplifier and the fourth filter.

[0262] <10> A communication device, comprising:

[0263] A signal processing circuit that processes the high frequency signal; and

[0264] according to <1> ~ <9> The high-frequency circuit described in any one of the items transmits the high-frequency signal between the signal processing circuit and the antenna.

[0265] <11> A high frequency circuit having:

[0266] A first antenna connection terminal, a second antenna connection terminal, an input terminal, and an output terminal;

[0267] a first filter having a passband including at least a portion of a transmission frequency band of a first frequency band for frequency division duplexing;

[0268] a second filter having a passband including at least a portion of a receive frequency band of the first frequency band; and

[0269] a first switch having a first terminal, a second terminal, a third terminal and a fourth terminal,

[0270] Wherein, the first antenna connection terminal is connected to the first terminal,

[0271] The second antenna connection terminal is connected to the second terminal,

[0272] The first filter is connected between the third terminal and the input terminal,

[0273] The second filter is connected between the fourth terminal and the output terminal,

[0274] The first switch is configured to switch between a first connection, a second connection, and a third connection.

[0275] In the first connection, one of the first terminal and the second terminal is connected to the third terminal, and neither the first terminal nor the second terminal is connected to the fourth terminal.

[0276] In the second connection, one of the first terminal and the second terminal is connected to the fourth terminal, and neither the first terminal nor the second terminal is connected to the third terminal.

[0277] In the third connection, one of the first terminal and the second terminal is connected to the third terminal, and the other of the first terminal and the second terminal is connected to the fourth terminal.

[0278] <12> according to <11> The high frequency circuit described, wherein

[0279] In a condition where a first power level specified by a maximum power greater than a specified maximum power is applied to the first frequency band, the first switch switches the first connection and the second connection according to time.

[0280] The first switch maintains the third connection in a condition where a second power level specified at a maximum power smaller than the specified maximum power is applied to the first frequency band.

[0281] <13> according to <11> or <12> The high frequency circuit described, wherein

[0282] The first switch further has a fifth terminal, and the fifth terminal is connected to the terminator.

[0283] In the first connection, the fifth terminal is also connected to the fourth terminal,

[0284] In the second connection, the fifth terminal is also connected to the third terminal.

[0285] <14> according to <11> ~ <13> A high-frequency circuit as described in any one of the items , wherein:

[0286] The high-frequency circuit further includes a power amplifier connected between the first filter and the input terminal.

[0287] <15> according to <14> The high frequency circuit described, wherein

[0288] The high frequency circuit further comprises:

[0289] a third filter having a passband including at least a portion of a transmission frequency band of the second frequency band; and

[0290] a second switch connected between the power amplifier and the first filter and the third filter,

[0291] The first switch further has a sixth terminal connected to the third filter.

[0292] <16> according to <15> The high frequency circuit described, wherein

[0293] The second switch is configured to switch between connection between the power amplifier and the first filter and connection between the power amplifier and the third filter.

[0294] <17> according to <11> ~ <16> A high-frequency circuit as described in any one of the items , wherein:

[0295] The high-frequency circuit further includes a low-noise amplifier connected between the second filter and the output terminal.

[0296] <18> according to <17> The high frequency circuit described, wherein

[0297] The high frequency circuit further comprises:

[0298] a fourth filter having a passband including at least a portion of a reception frequency band of a third frequency band; and

[0299] a third switch connected between the low noise amplifier and the second filter and the fourth filter,

[0300] The first switch further has a seventh terminal, and the seventh terminal is connected to the fourth filter.

[0301] <19> according to <18> The high frequency circuit described, wherein

[0302] The third switch is configured to switch between connection between the low noise amplifier and the second filter and connection between the low noise amplifier and the fourth filter.

[0303] <20> A communication device, comprising:

[0304] A signal processing circuit that processes the high frequency signal; and

[0305] according to <11> ~ <19> The high-frequency circuit described in any one of the items transmits the high-frequency signal between the signal processing circuit and the antenna.

[0306] Industrial Applicability

[0307] The present invention can be widely used in communication devices such as mobile phones as a high-frequency circuit disposed in a front end portion.

[0308] Description of Reference Numerals

[0309] 1, 1A, 1B, 1C: high frequency circuit; 2, 2a, 2b: antenna; 3: RFIC; 4: BBIC; 5, 5A, 5B, 5C: communication device; 11: power amplifier; 21: low noise amplifier; 31, 32, 33, 34: filter; 41, 41A, 41B, 41C, 42, 43: switch; 51: terminator; 52, 53: capacitor; 101, 101A, 102A: antenna connection terminal; 111: input terminal; 121: output terminal; 411, 411A, 412, 412A, 413, 413A, 414, 414A, 415, 415A, 416, 416A, 417, 417A, 418A, 419A, 421, 422, 423, 431, 432, 433: terminals.

Claims

1. A high frequency circuit having: Antenna connection terminal, input terminal and output terminal; a first filter having a passband including at least a portion of a transmission frequency band of a first frequency band for frequency division duplexing; a second filter having a passband including at least a portion of a receive frequency band of the first frequency band; as well as a first switch having a first terminal, a second terminal and a third terminal, Wherein, the antenna connection terminal is connected to the first terminal, The first filter is connected between the second terminal and the input terminal, The second filter is connected between the third terminal and the output terminal, The first switch is configured to switch between a first connection, a second connection, and a third connection. In the first connection, the first terminal is connected to the second terminal, and the first terminal is not connected to the third terminal, In the second connection, the first terminal is connected to the third terminal, and the first terminal is not connected to the second terminal, In the third connection, the first terminal is connected to the second terminal and the third terminal at the same time.

2. The high frequency circuit according to claim 1, wherein: When a first power level specified by a maximum output power greater than a specified power is applied to the first frequency band, the first switch switches the first connection and the second connection according to time. The first switch maintains the third connection in a situation where a second power level specified by a maximum output power smaller than the specified power is applied to the first frequency band.

3. The high frequency circuit according to claim 1 or 2, wherein: The first switch further has a fourth terminal, and the fourth terminal is connected to the terminator. In the first connection, the fourth terminal is also connected to the third terminal, In the second connection, the fourth terminal is also connected to the second terminal.

4. The high frequency circuit according to any one of claims 1 to 3, wherein: The high-frequency circuit further includes a power amplifier connected between the first filter and the input terminal.

5. The high frequency circuit according to claim 4, wherein: The high frequency circuit further comprises: a third filter having a passband including at least a portion of a transmission frequency band of the second frequency band; and a second switch connected between the power amplifier and the first filter and the third filter, The first switch further has a fifth terminal connected to the third filter.

6. The high frequency circuit according to any one of claims 1 to 5, wherein: The high-frequency circuit further includes a low-noise amplifier connected between the second filter and the output terminal.

7. The high frequency circuit according to claim 6, wherein: The high frequency circuit further comprises: a fourth filter having a passband including at least a portion of a reception frequency band of a third frequency band; and a third switch connected between the low noise amplifier and the second filter and the fourth filter, The first switch further has a sixth terminal connected to the fourth filter.

8. The high frequency circuit according to any one of claims 1 to 7, wherein: The first switch further has a seventh terminal, The high-frequency circuit further includes a capacitor connected between the seventh terminal and ground, and in the first connection, the first terminal is also connected to the seventh terminal.

9. The high frequency circuit according to claim 8, wherein: The capacitor is a variable capacitor, In the second connection, the first terminal is also connected to the seventh terminal.

10. A communication device comprising: A signal processing circuit that processes the high frequency signal; and The high-frequency circuit according to any one of claims 1 to 9, wherein the high-frequency signal is transmitted between the signal processing circuit and an antenna.

11. A high frequency circuit comprising: A first antenna connection terminal, a second antenna connection terminal, an input terminal, and an output terminal; a first filter having a passband including at least a portion of a transmission frequency band of a first frequency band for frequency division duplexing; a second filter having a passband including at least a portion of a receive frequency band of the first frequency band; as well as a first switch having a first terminal, a second terminal, a third terminal and a fourth terminal, Wherein, the first antenna connection terminal is connected to the first terminal, The second antenna connection terminal is connected to the second terminal, The first filter is connected between the third terminal and the input terminal, The second filter is connected between the fourth terminal and the output terminal, The first switch is configured to switch between a first connection, a second connection, and a third connection. In the first connection, one of the first terminal and the second terminal is connected to the third terminal, and neither the first terminal nor the second terminal is connected to the fourth terminal. In the second connection, one of the first terminal and the second terminal is connected to the fourth terminal, and neither the first terminal nor the second terminal is connected to the third terminal. In the third connection, one of the first terminal and the second terminal is connected to the third terminal, and the other of the first terminal and the second terminal is connected to the fourth terminal.

12. The high frequency circuit according to claim 11, wherein: In a condition where a first power level specified by a maximum power greater than a specified maximum power is applied to the first frequency band, the first switch switches the first connection and the second connection according to time. The first switch maintains the third connection in a condition where a second power level specified at a maximum power smaller than the specified maximum power is applied to the first frequency band.

13. The high frequency circuit according to claim 11 or 12, wherein: The first switch further has a fifth terminal, and the fifth terminal is connected to the terminator. In the first connection, the fifth terminal is also connected to the fourth terminal, In the second connection, the fifth terminal is also connected to the third terminal.

14. The high frequency circuit according to any one of claims 11 to 13, wherein: The high-frequency circuit further includes a power amplifier connected between the first filter and the input terminal.

15. The high frequency circuit according to claim 14, wherein: The high frequency circuit further comprises: a third filter having a passband including at least a portion of a transmission frequency band of the second frequency band; and a second switch connected between the power amplifier and the first filter and the third filter, The first switch further has a sixth terminal connected to the third filter.

16. The high frequency circuit according to any one of claims 11 to 15, wherein: The high-frequency circuit further includes a low-noise amplifier connected between the second filter and the output terminal.

17. The high frequency circuit according to claim 16, wherein: The high frequency circuit further comprises: a fourth filter having a passband including at least a portion of a reception frequency band of a third frequency band; and a third switch connected between the low noise amplifier and the second filter and the fourth filter, The first switch further has a seventh terminal, and the seventh terminal is connected to the fourth filter.

18. The high frequency circuit according to any one of claims 11 to 17, wherein: The first switch further has an eighth terminal, The high frequency circuit further includes a first capacitor connected between the eighth terminal and ground. In the first connection and the third connection, the first terminal is also connected to the eighth terminal.

19. The high frequency circuit according to claim 18, wherein: The first switch further has a ninth terminal, The high frequency circuit further includes a second capacitor connected between the ninth terminal and the ground. In the second connection and the third connection, the first terminal is also connected to the ninth terminal.

20. A communication device comprising: A signal processing circuit that processes the high frequency signal; and The high-frequency circuit according to any one of claims 11 to 19, wherein the high-frequency signal is transmitted between the signal processing circuit and an antenna.

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