Power amplification circuit, high frequency circuit, and communication device

Abstract

A power amplification circuit (10) comprises: power amplifiers (11, 12); an orthogonal hybrid circuit (15) that includes an input terminal (151) which is connected to a high-frequency input terminal (13), an output terminal (152) which is connected to an input end of the power amplifier (11), and an output terminal (153) which is connected to an input end of the power amplifier (12); a synthesis circuit (16) that includes an input terminal (161) which is connected to an output end of the power amplifier (11), an input terminal (162) which is connected to an output end of the power amplifier (12), and an output terminal (163) which is connected to a high-frequency output terminal (14); a capacitor (171) that is connected between the output end of the power amplifier (11) and the input terminal (161); a series LC circuit (172) that is connected between the ground and a path which connects the output end of the power amplifier (11) and the input terminal (161); and a parallel LC circuit (181) that is connected between the output end of the power amplifier (12) and the input terminal (162).

Description

Power amplifier circuit, high frequency circuit and communication device

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

[0002] Patent Document 1 discloses a power amplifier circuit (balanced amplifier) ​​that includes two amplification paths that respectively amplify two transmission signals having a phase difference of 90 degrees from each other in order to suppress fluctuations in transmission power due to load fluctuations.

[0003] JP 2012-147352 A

[0004] However, since the second harmonic distortion is not canceled in a balanced amplifier, a circuit for attenuating the second harmonic is required, which may result in an increase in the size of the communication device.

[0005] Therefore, the present invention provides a power amplifier circuit, a high-frequency circuit, and a communication device that can suppress second harmonic distortion and reduce the size of the communication device.

[0006] A power amplifier circuit according to one aspect of the present invention includes a first power amplifier, a second power amplifier, a radio-frequency input terminal, a radio-frequency output terminal, a quadrature hybrid circuit including a first input terminal connected to the radio-frequency input terminal, a first output terminal connected to an input terminal of the first power amplifier, and a second output terminal connected to an input terminal of the second power amplifier, a combining circuit including a second input terminal connected to an output terminal of the first power amplifier, a third input terminal connected to the output terminal of the second power amplifier, and a third output terminal connected to the radio-frequency output terminal, a first capacitor connected between the output terminal of the first power amplifier and the second input terminal, an LC series circuit connected between a path connecting the output terminal of the first power amplifier and the second input terminal and ground, and an LC parallel circuit connected between the output terminal of the second power amplifier and the third input terminal.

[0007] A radio-frequency circuit according to one aspect of the present invention includes the power amplifier circuit described above, a first filter having a pass band that includes a first transmission band, a second filter having a pass band that includes a second transmission band, and a first switch circuit including a first common terminal connected to a radio-frequency output terminal of the power amplifier circuit, a first selection terminal connected to the first filter, and a second selection terminal connected to the second filter.

[0008] A communication device according to one aspect of the present invention comprises a signal processing circuit configured to process a high-frequency signal, and the high-frequency circuit configured to transmit the high-frequency signal between the signal processing circuit and an antenna.

[0009] According to the present invention, it is possible to suppress second harmonic distortion and reduce the size of a communication device.

[0010] FIG. 1 is a circuit configuration diagram of a communication device according to an embodiment. FIG. 2 is a circuit configuration diagram of a power amplifier circuit according to Comparative Example 1. FIG. 3 is a circuit configuration diagram of a power amplifier circuit according to Comparative Example 2. FIG. 4 is a Smith chart showing the impedance of the power amplifier circuit according to the embodiment. FIG. 5 is a graph showing the insertion loss of the power amplifier circuit according to the embodiment. FIG. 6 is a Smith chart showing the impedance of the power amplifier circuit according to Comparative Example 1. FIG. 7 is a graph showing the insertion loss of the power amplifier circuit according to Comparative Example 1. FIG. 8 is a Smith chart showing the impedance of the power amplifier circuit according to Comparative Example 2. FIG. 9 is a graph showing the insertion loss of the power amplifier circuit according to Comparative Example 2. FIG. 10 is a circuit configuration diagram of a low-pass filter according to Modification 1. FIG. 11 is a graph showing the insertion loss of the power amplifier circuits according to the embodiment and Modification 1. FIG. 12 is a circuit configuration diagram of a high-pass filter according to Modification 2. FIG. 13 is a circuit configuration diagram of a high-pass filter according to Modification 3.

[0011] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Note that the embodiments described below are all comprehensive or specific examples. The numerical values, shapes, materials, components, arrangements and connection forms of the components shown in the following embodiments are merely examples and are not intended to limit the present invention.

[0012] It should be noted that the drawings are schematic diagrams in which emphasis, omission, or adjustment of proportions has been appropriately made to illustrate the present invention, and are not necessarily strictly illustrated, and may differ from the actual shapes, positional relationships, and proportions. In the drawings, the same reference numerals are used to denote substantially the same components, and redundant explanations may be omitted or simplified.

[0013] In the following description, "connected" includes not only direct connection by connection terminals and / or wiring conductors, but also electrical connection via other circuit elements. "C is connected between A and B" means that one end of C is connected to A and the other end of C is connected to B, and C is arranged in series on the path connecting A and B. "Path connecting A and B" means a path made up of a conductor electrically connecting A to B.

[0014] "Terminal" means a point where a conductor within an element terminates. Note that terminal is interpreted as any point on the conductor between elements or the entire conductor, not just a single point, provided the impedance of the conductor between elements is sufficiently low.

[0015] The "filter passband" is the portion of the frequency spectrum transmitted by the filter, defined as the frequency band between two frequencies 3 dB above the minimum power insertion loss.

[0016] The term "transmission band" refers to a frequency band used for transmission in a communication device, and the term "reception band" refers to a frequency band used for reception in a communication device. For example, in user equipment (UE) of a cellular network (also called a mobile network), the transmission band and reception band of the FDD band are the uplink band and the downlink band, respectively. On the other hand, in a base station (BS) of the cellular network, the transmission band and reception band of the FDD band are the downlink band and the uplink band, respectively. Also, for example, the transmission band and reception band of the TDD band are the same frequency band.

[0017] Terms indicating the relationship between elements, such as "parallel" and "perpendicular," terms indicating the shape of elements, such as "straight line," and numerical ranges do not only express strict meanings, but also include substantially equivalent ranges, for example, including an error of about several percent.

[0018] (Embodiment) The circuit configurations of a communication device 5, a high frequency circuit 1, and a power amplifier circuit 10 according to this embodiment will be described with reference to Fig. 1. Fig. 1 is a circuit configuration diagram of a communication device 5 according to this embodiment.

[0019] 1 is an exemplary circuit configuration diagram, and the communication device 5, the high-frequency circuit 1, and the power amplifier circuit 10 can be implemented using any of a wide variety of circuit implementations and circuit technologies. Therefore, the following descriptions of the communication device 5, the high-frequency circuit 1, and the power amplifier circuit 10 should not be interpreted as limiting.

[0020] [1. Circuit Configuration of Communication Device 5] The communication device 5 according to this embodiment can be used to provide wireless connectivity. For example, the communication device 5 can be implemented in UEs in a cellular network, such as mobile phones, smartphones, tablet computers, and wearable devices. In another example, the communication device 5 can be implemented to provide wireless connectivity to Internet of Things (IoT) sensor devices, medical / healthcare devices, cars, unmanned aerial vehicles (UAVs) (so-called drones), and automated guided vehicles (AGVs). In yet another example, the communication device 5 can be implemented to provide wireless connectivity in a wireless access point or a wireless hotspot.

[0021] The communication device 5 includes a high-frequency circuit 1, an antenna 2, an RFIC (Radio Frequency Integrated Circuit) 3, and a BBIC (Baseband Integrated Circuit) 4.

[0022] The high-frequency circuit 1 is connected between the antenna 2 and the RFIC 3. The high-frequency circuit 1 can transmit high-frequency signals between the antenna 2 and the RFIC 3.

[0023] The antenna 2 is connected to the high-frequency circuit 1. The antenna 2 can receive a high-frequency signal from the high-frequency circuit 1 and transmit it to the outside of the communication device 5. Furthermore, the antenna 2 can receive a high-frequency signal from the outside of the communication device 5 and supply it to the high-frequency circuit 1. The antenna 2 does not have to be included in the communication device 5. Furthermore, the communication device 5 may include one or more antennas in addition to the antenna 2.

[0024] The RFIC 3 is an example of a signal processing circuit that processes high-frequency signals. Specifically, the RFIC 3 can perform signal processing on a transmission signal input from the BBIC 4 by up-conversion or the like, and output the high-frequency transmission signal generated by the signal processing to the high-frequency circuit 1. Furthermore, the RFIC 3 can also perform signal processing on a high-frequency reception signal input via the reception path of the high-frequency circuit 1 by down-conversion or the like, and output the reception signal generated by the signal processing to the BBIC 4. The RFIC 3 may also have a control unit that controls switches, power amplifiers, and the like included in the high-frequency circuit 1. Note that part or all of the functions of the RFIC 3 as a control unit may be included outside the RFIC 3, and may be included in, for example, the BBIC 4 or the high-frequency circuit 1.

[0025] The BBIC 4 is a baseband signal processing circuit that processes signals using a frequency band lower than the high-frequency signal transmitted by the high-frequency circuit 1. The signals processed by the BBIC 4 include, for example, image signals for image display and / or audio signals for calls via a speaker. The BBIC 4 does not necessarily have to be included in the communication device 5.

[0026] 2. Circuit Configuration of High-Frequency Circuit 1 The high-frequency circuit 1 includes a power amplifier circuit 10, low-noise amplifiers 21, 22, and 23, filters 31, 32, 33, 34, 35, and 36, switch circuits 41 and 42, an antenna connection terminal 100, a high-frequency input terminal 110, and high-frequency output terminals 121, 122, and 123.

[0027] The antenna connection terminal 100 is an external connection terminal of the high frequency circuit 1. The antenna connection terminal 100 is connected to the antenna 2 outside the high frequency circuit 1, and is connected to the switch circuit 42 inside the high frequency circuit 1.

[0028] The radio frequency input terminal 110 is an external connection terminal of the radio frequency circuit 1. The radio frequency input terminal 110 is connected to the RFIC 3 outside the radio frequency circuit 1, and is connected to the power amplifier circuit 10 inside the radio frequency circuit 1.

[0029] The radio frequency output terminals 121, 122, and 123 are external connection terminals of the radio frequency circuit 1. The radio frequency output terminals 121, 122, and 123 are connected to the RFIC 3 outside the radio frequency circuit 1, and are connected to the low noise amplifiers 21, 22, and 23 inside the radio frequency circuit 1, respectively.

[0030] The power amplifier circuit 10 is connected between the radio frequency input terminal 110 and the switch circuit 41. Specifically, the radio frequency input terminal 13 of the power amplifier circuit 10 is connected to the radio frequency input terminal 110 of the radio frequency circuit 1, and the radio frequency output terminal 14 of the power amplifier circuit 10 is connected to the switch circuit 41. The power amplifier circuit 10 can amplify the transmission signals of bands A, B, and C using the power supply voltage Vcc.

[0031] The low-noise amplifier 21 is connected between the filter 34 and the high-frequency output terminal 121. Specifically, the input terminal of the low-noise amplifier 21 is connected to the filter 34, and the output terminal of the low-noise amplifier 21 is connected to the high-frequency output terminal 121. The low-noise amplifier 21 can amplify the received signal of Band A using power supplied from a power supply (not shown).

[0032] The low-noise amplifier 22 is connected between the filter 35 and the high-frequency output terminal 122. Specifically, the input terminal of the low-noise amplifier 22 is connected to the filter 35, and the output terminal of the low-noise amplifier 22 is connected to the high-frequency output terminal 122. The low-noise amplifier 22 can amplify the received signal of Band B using power supplied from a power supply (not shown).

[0033] The low-noise amplifier 23 is connected between the filter 36 and the high-frequency output terminal 123. Specifically, the input terminal of the low-noise amplifier 23 is connected to the filter 36, and the output terminal of the low-noise amplifier 23 is connected to the high-frequency output terminal 123. The low-noise amplifier 23 can amplify the received signal of Band C using power supplied from a power supply (not shown).

[0034] The low-noise amplifiers 21 to 23 may be configured with field-effect transistors (FETs) and may be manufactured using semiconductor materials. Examples of the semiconductor materials that may be used include silicon monocrystal (Si), gallium nitride (GaN), and silicon carbide (SiC). The amplifying transistors of the low-noise amplifiers 21 to 23 are not limited to FETs. For example, some or all of the low-noise amplifiers 21 to 23 may be configured with bipolar transistors.

[0035] The filter 31 is an example of a first filter, and is a bandpass filter having a passband that includes the transmission band (A-Tx) of band A. The filter 31 passes transmission signals of band A and attenuates reception signals of band A and signals of other bands. The filter 31 is connected between the switch circuits 41 and 42. Specifically, one end of the filter 31 is connected to a selection terminal 421 of the switch circuit 42, and the other end of the filter 31 is connected to a selection terminal 411 of the switch circuit 41.

[0036] The filter 32 is an example of a second filter, and is a bandpass filter having a passband that includes the transmission band (B-Tx) of band B. The filter 32 passes transmission signals of band B and attenuates reception signals of band B and signals of other bands. The filter 32 is connected between the switch circuits 41 and 42. Specifically, one end of the filter 32 is connected to a selection terminal 422 of the switch circuit 42, and the other end of the filter 32 is connected to a selection terminal 412 of the switch circuit 41.

[0037] The filter 33 is an example of a third filter, and is a band-pass filter having a passband that includes the transmission band (C-Tx) of band C. The filter 33 passes transmission signals of band C and attenuates reception signals of band C and signals of other bands. The filter 33 is connected between the switch circuits 41 and 42. Specifically, one end of the filter 33 is connected to the selection terminal 423 of the switch circuit 42, and the other end of the filter 33 is connected to the selection terminal 413 of the switch circuit 41.

[0038] The filter 34 is an example of a fourth filter, and is a band-pass filter having a passband that includes the receive band (A-Rx) of band A. The filter 34 passes receive signals of band A and attenuates transmit signals of band A and signals of other bands. The filter 34 is connected between the switch circuit 42 and the low-noise amplifier 21. Specifically, one end of the filter 34 is connected to a selection terminal 421 of the switch circuit 42, and the other end of the filter 34 is connected to the input end of the low-noise amplifier 21.

[0039] The filter 35 is an example of a fifth filter, and is a band-pass filter having a passband that includes the receive band (B-Rx) of band B. The filter 35 passes receive signals of band B and attenuates transmit signals of band B and signals of other bands. The filter 35 is connected between the switch circuit 42 and the low-noise amplifier 22. Specifically, one end of the filter 35 is connected to the selection terminal 422 of the switch circuit 42, and the other end of the filter 35 is connected to the input end of the low-noise amplifier 22.

[0040] The filter 36 is an example of a sixth filter, and is a band-pass filter having a passband that includes the receive band (C-Rx) of band C. The filter 36 passes receive signals of band C and attenuates transmit signals of band C and signals of other bands. The filter 36 is connected between the switch circuit 42 and the low-noise amplifier 23. Specifically, one end of the filter 36 is connected to a selection terminal 423 of the switch circuit 42, and the other end of the filter 36 is connected to the input end of the low-noise amplifier 23.

[0041] The filters 31 to 36 may be, but are not limited to, SAW filters, BAW filters, LC filters, or dielectric filters, or any combination thereof.

[0042] Bands A to C are frequency bands for communication systems built using radio access technology (RAT), and are defined in advance by standardization organizations (e.g., 3GPP (registered trademark) (3rd Generation Partnership Project) 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.

[0043] Band A is an example of a first band. The transmission band of band A is lower than the transmission bands of bands B and C. Band B is an example of a second band. The transmission band of band B is higher than the transmission bands of bands A and C. Band C is an example of a third band. The transmission band of band C is higher than the transmission band of band A and lower than the transmission band of band B. In other words, the lower end of the transmission band of band A is lower than the lower ends of the transmission bands of bands B and C, and the upper end of the transmission band of band B is higher than the upper ends of the transmission bands of bands A and C.

[0044] For example, bands A to C can be any combination that satisfies the above transmission band conditions, including bands 5, 8, 26, and 28 for LTE, and n5, n8, n26, and n28 for 5G NR. Note that bands A to C are not limited to the frequency bands exemplified here.

[0045] The switch circuit 41 is an example of a first switch circuit and is connected between the power amplifier circuit 10 and the filters 31 to 33. The switch circuit 41 includes a common terminal 410 and selection terminals 411, 412, and 413. The common terminal 410 is an example of a first common terminal and is connected to the high-frequency output terminal 14 of the power amplifier circuit 10. The selection terminal 411 is an example of a first selection terminal and is connected to the filter 31. The selection terminal 412 is an example of a second selection terminal and is connected to the filter 32. The selection terminal 413 is an example of a third selection terminal and is connected to the filter 33.

[0046] In such a connection configuration, the switch circuit 41 can selectively connect the common terminal 410 to the selection terminals 411 to 413, for example, based on a control signal from the RFIC 3. The switch circuit 41 is configured, for example, as an SP3T (Single-Pole Triple-Throw) type switch circuit.

[0047] The switch circuit 42 is an example of a second switch circuit, and is connected between the antenna connection terminal 100 and the filters 31 to 36. The switch circuit 42 includes a common terminal 420 and selection terminals 421, 422, and 423. The common terminal 420 is an example of a second common terminal, and is connected to the antenna connection terminal 100. The selection terminal 421 is an example of a fourth selection terminal, and is connected to the filters 31 and 34. The selection terminal 422 is an example of a fifth selection terminal, and is connected to the filters 32 and 35. The selection terminal 423 is an example of a sixth selection terminal, and is connected to the filters 33 and 36.

[0048] In such a connection configuration, the switch circuit 42 can selectively connect the common terminal 420 to the selection terminals 421 to 423 based on, for example, a control signal from the RFIC 3. The switch circuit 42 is configured as, for example, an SP3T type switch circuit.

[0049] 3. Circuit Configuration of Power Amplifier Circuit 10 The power amplifier circuit 10 includes power amplifiers 11 and 12, a high-frequency input terminal 13, a high-frequency output terminal 14, a quadrature hybrid circuit 15, a combiner circuit 16, a high-pass filter (HPF) 17, a low-pass filter (LPF) 18, inductors 191, 192, 193, and 194, and a capacitor 195.

[0050] The radio frequency input terminal 13 is an external connection terminal of the power amplifier circuit 10 and is a terminal for receiving a radio frequency signal from the RFIC 3. The radio frequency input terminal 13 is connected to a radio frequency input terminal 110 of the radio frequency circuit 1 outside the power amplifier circuit 10, and is connected to an input terminal 151 of the quadrature hybrid circuit 15 inside the power amplifier circuit 10.

[0051] The quadrature hybrid circuit 15 is also called a 90-degree hybrid coupler, and can divide a high-frequency signal supplied from the RFIC 3 via the high-frequency input terminal 13 into two high-frequency signals having a phase difference of 90 degrees and supply them to the power amplifiers 11 and 12, respectively. Specifically, the quadrature hybrid circuit 15 includes an input terminal 151 and output terminals 152 and 153. The input terminal 151 is an example of a first input terminal and is connected to the high-frequency input terminal 13. The output terminal 152 is an example of a first output terminal and is connected to the input terminal of the power amplifier 11. The output terminal 153 is an example of a second output terminal and is connected to the input terminal of the power amplifier 12.

[0052] The power amplifier 11 is an example of a first power amplifier, and is connected between the quadrature hybrid circuit 15 and the high-pass filter 17. Specifically, the input terminal of the power amplifier 11 is connected to the output terminal 152 of the quadrature hybrid circuit 15, and the output terminal of the power amplifier 11 is connected to the high-pass filter 17. The power amplifier 11 can amplify a high-frequency signal with a phase delay of 45 degrees relative to the input signal.

[0053] The power amplifier 12 is an example of a second power amplifier, and is connected between the quadrature hybrid circuit 15 and the low-pass filter 18. Specifically, the input end of the power amplifier 12 is connected to the output terminal 153 of the quadrature hybrid circuit 15, and the output end of the power amplifier 12 is connected to the low-pass filter 18. The power amplifier 12 can amplify a high-frequency signal with a phase lead of 45 degrees relative to the signal.

[0054] The power amplifiers 11 and 12 may be configured with heterojunction bipolar transistors (HBTs) and may be manufactured using semiconductor materials. Examples of the semiconductor materials that may be used include silicon germanium (SiGe) and gallium arsenide (GaAs). The amplifying transistors of the power amplifiers 11 and 12 are not limited to HBTs. For example, the power amplifiers 11 and 12 may be configured with high electron mobility transistors (HEMTs) or metal-semiconductor field effect transistors (MESFETs). In this case, gallium nitride (GaN) or silicon carbide (SiC) may be used as the semiconductor material. Some or all of the amplifying transistors of the power amplifiers 11 and 12 may be configured with complementary metal oxide semiconductors (CMOS) or may be manufactured using a silicon-on-insulator (SOI) process. In this case, single crystal silicon (Si) may be used as the semiconductor material.

[0055] The high-pass filter 17 includes a capacitor 171 and an LC series circuit 172, and is connected between the power amplifier 11 and the combining circuit 16. The high-pass filter 17 can advance the phase of the high-frequency signal amplified by the power amplifier 11 by 45 degrees.

[0056] The capacitor 171 is an example of a first capacitor, and is connected between the output terminal of the power amplifier 11 and the input terminal 161 of the combining circuit 16. Specifically, one of the two electrodes of the capacitor 171 is connected to the output terminal of the power amplifier 11 via the inductor 191, and the other of the two electrodes of the capacitor 171 is connected to the input terminal 161 of the combining circuit 16.

[0057] The LC series circuit 172 includes a capacitor 173 and an inductor 174, and is connected between a path connecting the output end of the power amplifier 11 and the input terminal 161 of the combiner circuit 16 and ground. One of the two electrodes of the capacitor 173 is connected to the path connecting the inductor 191 and the capacitor 171. The other of the two electrodes of the capacitor 173 is connected to the inductor 174. One end of the inductor 174 is connected to the capacitor 173, and the other end of the inductor 174 is connected to ground. Note that in the LC series circuit 172, the capacitor 173 may be connected between the inductor 174 and ground.

[0058] The LC series circuit 172 is a circuit for attenuating the second harmonic. Therefore, the resonant frequency of the LC series circuit 172 falls within a frequency range from 1.8 to 2.5 times the frequency of the transmission bands of bands A to C. In this embodiment, of bands A to C, band A has the lowest transmission band and band B has the highest transmission band. Therefore, the resonant frequency of the LC series circuit 172 falls within a frequency range from 1.8 times the frequency at the low end of the transmission band of band A to 2.5 times the frequency at the high end of the transmission band of band B.

[0059] The low-pass filter 18 includes an LC parallel circuit 181 and a capacitor 184, and is connected between the power amplifier 12 and the combining circuit 16. The low-pass filter 18 can delay the phase of the high-frequency signal amplified by the power amplifier 12 by 45 degrees.

[0060] The LC parallel circuit 181 includes an inductor 182 and a capacitor 183, and is connected between the output end of the power amplifier 12 and the input terminal 162 of the combining circuit 16. One end of the inductor 182 is connected to the output end of the power amplifier 12 via an inductor 192, and the other end of the inductor 182 is connected to the input terminal 162 of the combining circuit 16. One of the two electrodes of the capacitor 183 is connected to the output end of the power amplifier 12 via the inductor 192, and the other of the two electrodes of the capacitor 183 is connected to the input terminal 162 of the combining circuit 16.

[0061] The LC parallel circuit 181 is a circuit for attenuating the second harmonic. Therefore, the resonant frequency of the LC parallel circuit 181 falls within a frequency range from 1.8 to 2.5 times the frequency of the transmission bands of bands A to C. In this embodiment, of bands A to C, band A has the lowest transmission band and band B has the highest transmission band. Therefore, the resonant frequency of the LC parallel circuit 181 falls within a frequency range from 1.8 times the frequency at the low end of the transmission band of band A to 2.5 times the frequency at the high end of the transmission band of band B.

[0062] The capacitor 184 is an example of a second capacitor, and is connected between the ground and a path connecting the output end of the power amplifier 12 and the input terminal 162 of the combining circuit 16. Specifically, one of the two electrodes of the capacitor 184 is connected to the path connecting the inductor 192 and the LC parallel circuit 181, and the other of the two electrodes of the capacitor 184 is connected to the ground.

[0063] It should be noted that the LC series circuit 172 does not have to be included in the high-pass filter 17, and the LC parallel circuit 181 does not have to be included in the low-pass filter 18. For example, the LC series circuit 172 may be connected between the ground and a path connecting the high-pass filter 17 and the combiner circuit 16 or the inductor 191. Furthermore, for example, the LC parallel circuit 181 may be connected between the low-pass filter 18 and the combiner circuit 16 or the inductor 192.

[0064] The capacitors 171, 173, 183, and 184 and the inductors 174 and 182 may be implemented using chip capacitors and chip inductors. The chip capacitors and chip inductors refer to surface mount devices (SMDs) that constitute the capacitors and inductors, respectively. Note that the implementation of the capacitors 171, 173, 183, and 184 and the inductors 174 and 182 is not limited to chip capacitors and chip inductors. For example, the capacitors 171, 173, 183, and 184 and the inductors 174 and 182 may be implemented using wiring on a module substrate, or may be implemented on an integrated passive device (IPD).

[0065] The combiner circuit 16 combines two in-phase high-frequency signals that have passed through the high-pass filter 17 and the low-pass filter 18, respectively, and supplies the combined signal to the high-frequency output terminal 14. Specifically, the combiner circuit 16 includes input terminals 161 and 162 and an output terminal 163. The input terminal 161 is an example of a second input terminal and is connected to the output terminal of the power amplifier 11 via the high-pass filter 17. The input terminal 162 is an example of a third input terminal and is connected to the output terminal of the power amplifier 12 via the low-pass filter 18. The output terminal 163 is an example of a third output terminal and is connected to the high-frequency output terminal 14.

[0066] The inductor 191 is connected between the power amplifier 11 and the high-pass filter 17. Specifically, one end of the inductor 191 is connected to the power amplifier 11, and the other end of the inductor 191 is connected to the high-pass filter 17. Note that the inductor 191 is optional and does not have to be included in the power amplifier circuit 10.

[0067] The inductor 192 is connected between the power amplifier 12 and the low-pass filter 18. Specifically, one end of the inductor 192 is connected to the power amplifier 12, and the other end of the inductor 192 is connected to the low-pass filter 18. Note that the inductor 192 is optional and does not have to be included in the power amplifier circuit 10.

[0068] The inductor 193 is a so-called choke inductor, and is connected between a power supply that supplies the power supply voltage Vcc and an output terminal (e.g., collector terminal) of the power amplifier 11. Specifically, one terminal of the inductor 193 is connected to the power supply, and the other terminal of the inductor 193 is connected to a path that connects the output terminal of the power amplifier 11 and the inductor 191. Note that the inductor 193 is optional and does not need to be included in the power amplifier circuit 10.

[0069] The inductor 194 is a so-called choke inductor, and is connected between a power supply that supplies the power supply voltage Vcc and an output terminal (e.g., collector terminal) of the power amplifier 12. Specifically, one terminal of the inductor 194 is connected to the power supply, and the other terminal of the inductor 192 is connected to a path connecting the output terminal of the power amplifier 12 and the inductor 192. Note that the inductor 194 is optional and does not need to be included in the power amplifier circuit 10.

[0070] Capacitor 195 is a so-called bypass capacitor, and is connected between the ground and a path connecting the power supply and power amplifier 11, and between the ground and a path connecting the power supply and power amplifier 12. Specifically, one of the two electrodes of capacitor 195 is connected to the path connecting the power supply and inductors 193 and 194, and the other of the two electrodes of capacitor 195 is connected to ground. Note that capacitor 195 is optional and does not need to be included in power amplifier circuit 10.

[0071] 4. Characteristics of the Power Amplifier Circuit 10 Next, the characteristics of the power amplifier circuit 10 configured as above will be described while comparing it with the characteristics of the power amplifier circuits 10X and 10Y according to the first and second comparative examples.

[0072] First, the circuit configurations of power amplifier circuits 10X and 10Y according to comparative examples 1 and 2 will be described with reference to Fig. 2 and Fig. 3. Fig. 2 is a circuit configuration diagram of the power amplifier circuit 10X according to comparative example 1. Fig. 3 is a circuit configuration diagram of the power amplifier circuit 10Y according to comparative example 2.

[0073] 2, the power amplifier circuit 10X according to the first comparative example includes a low-pass filter 18X instead of the low-pass filter 18. The low-pass filter 18X includes an inductor 182 and a capacitor 184, but does not include the capacitor (capacitor 183 in FIG. 1) connected in parallel with the inductor 182 between the output end of the power amplifier 12 and the input terminal 162 of the combiner circuit 16.

[0074] 3 , the power amplifier circuit 10Y according to the second comparative example includes a low-pass filter 18Y instead of the low-pass filter 18. Like the low-pass filter 18X, the low-pass filter 18Y does not include a capacitor (capacitor 183 in FIG. 1 ) connected in parallel with the inductor 182 between the output terminal of the power amplifier 12 and the input terminal 162 of the combiner circuit 16. Furthermore, the low-pass filter 18Y includes an LC series circuit 186 connected between ground and a path connecting the output terminal of the power amplifier 12 and the input terminal 162 of the combiner circuit 16. The LC series circuit 186 includes a capacitor 184 and an inductor 185 connected between the capacitor 184 and ground.

[0075] The characteristics of the power amplifier circuit 10 according to this embodiment will be described with reference to FIGS. 4 to 9, while comparing it with the characteristics of the power amplifier circuits 10X and 10Y according to the first and second comparative examples.

[0076] Fig. 4 is a Smith chart showing the impedance of the power amplifier circuit 10 according to the present embodiment. Fig. 5 is a graph showing the insertion loss of the power amplifier circuit 10 according to the present embodiment. Fig. 6 is a Smith chart showing the impedance of the power amplifier circuit 10X according to Comparative Example 1. Fig. 7 is a graph showing the insertion loss of the power amplifier circuit 10X according to Comparative Example 1. Fig. 8 is a Smith chart showing the impedance of the power amplifier circuit 10Y according to Comparative Example 2. Fig. 9 is a graph showing the insertion loss of the power amplifier circuit 10Y according to Comparative Example 2.

[0077] 4, 6, and 8, impedance Zin1 is the impedance from the fundamental frequency f0 to the second harmonic frequency 2f0 when the power amplifier 11 is viewed from the input terminal 161 of the combining circuit 16, and impedance Zin2 is the impedance from the frequency f0 to the frequency 2f0 when the power amplifier 12 is viewed from the input terminal 162 of the combining circuit 16.

[0078] In the power amplifier circuit 10 according to this embodiment, as shown in FIG. 4, the impedances Zin1 and Zin2 are conjugate with each other at the frequency f0. Therefore, at the frequency f0, the attenuation can be suppressed, and the transmission loss can be reduced. On the other hand, the impedances Zin1 and Zin2 are not conjugate with each other at frequencies between f0 and 2f0, and are short-circuited and open-circuited at the frequency 2f0. Therefore, the attenuation increases as the frequency increases from f0 to 2f0, and an attenuation pole is formed at the frequency 2f0. In particular, at the frequency 2f0, the mismatch is large, and the attenuation can be effectively increased. As a result, the power amplifier circuit 10 can achieve low loss in the f0 band and high attenuation in the 2f0 band, as shown in FIG. 5.

[0079] On the other hand, in the power amplifier circuit 10X according to Comparative Example 1, as shown in FIG. 6, the impedances Zin1 and Zin2 maintain a conjugate relationship at frequency f0. However, because the low-pass filter 18X does not include an LC parallel circuit, the impedance Zin2 cannot approach an open state at frequency 2f0. As a result, as shown in FIG. 7, the power amplifier circuit 10X can achieve low loss in the f0 band, but cannot achieve sufficient attenuation in the 2f0 band.

[0080] In the power amplifier circuit 10Y according to Comparative Example 2, as shown in FIG. 8, the impedances Zin1 and Zin2 maintain a conjugate relationship at the frequency f0. However, the impedances Zin1 and Zin2 also maintain a conjugate relationship at frequencies between f0 and 2f0, resulting in unwanted responses. As a result, as shown in FIG. 9, the power amplifier circuit 10Y can achieve low loss in the f0 band, but cannot achieve sufficient attenuation across the entire 2f0 band.

[0081] As described above, in the power amplifier circuit 10 according to this embodiment, the inclusion of the LC parallel circuit 181 in the low-pass filter 18 makes it possible to bring the impedance Zin2 closer to an open state at the frequency 2f0, thereby effectively increasing attenuation in the 2f0 band. Furthermore, the inclusion of the LC parallel circuit 181 rather than an LC series circuit in the low-pass filter 18 makes it possible to prevent the LC impedances Zin1 and Zin2 from forming a conjugate relationship at frequencies between the frequencies f0 and 2f0, thereby making it possible to prevent attenuation from narrowing due to unnecessary responses. As a result, the amount of attenuation can be increased across the entire 2f0 band.

[0082] [5. Summary] As described above, the power amplifier circuit 10 according to this embodiment includes the power amplifier 11, the power amplifier 12, the radio-frequency input terminal 13, the radio-frequency output terminal 14, the quadrature hybrid circuit 15 including the input terminal 151 connected to the radio-frequency input terminal 13, the output terminal 152 connected to the input terminal of the power amplifier 11, and the output terminal 153 connected to the input terminal of the power amplifier 12, the combiner circuit 16 including the input terminal 161 connected to the output terminal of the power amplifier 11, the input terminal 162 connected to the output terminal of the power amplifier 12, and the output terminal 163 connected to the radio-frequency output terminal 14, the capacitor 171 connected between the output terminal of the power amplifier 11 and the input terminal 161, the LC series circuit 172 connected between the path connecting the output terminal of the power amplifier 11 and the input terminal 161 and ground, and the LC parallel circuit 181 connected between the output terminal of the power amplifier 12 and the input terminal 162.

[0083] As a result, the LC series circuit 172 can form a second harmonic attenuation pole in the path connecting the output terminal of the power amplifier 11 and the input terminal 161 of the combiner circuit 16, and the LC parallel circuit 181 can form a second harmonic attenuation pole in the path connecting the output terminal of the power amplifier 12 and the input terminal 162 of the combiner circuit 16. In this case, the second harmonic attenuation pole formed by the LC series circuit 172 is close to a short circuit, and the second harmonic attenuation pole formed by the LC parallel circuit 181 is close to an open circuit, thereby increasing the mismatch and effectively attenuating the second harmonic. Furthermore, the inductor 182 included in the LC parallel circuit 181 connected between the output terminal of the power amplifier 12 and the input terminal 162 of the combiner circuit 16 can delay the phase of the high-frequency signal by 45 degrees. Therefore, there is no need to separately add an inductor for attenuating the second harmonic and an inductor for phase adjustment, reducing the number of inductors and enabling the power amplifier circuit 10 to be more compact. As a result, the power amplifier circuit 10 can suppress second harmonic distortion and reduce the size of the communication device.

[0084] Furthermore, for example, the power amplifier circuit 10 according to the present embodiment may further include a capacitor 184 connected between the path connecting the output end of the power amplifier 12 and the input terminal 162 and the ground.

[0085] Even if the capacitor 184 is included in the power amplifier circuit 10 in this way, the LC series circuit 172 and the LC parallel circuit 181 can suppress second harmonic distortion and reduce the size of the communication device.

[0086] The high-frequency circuit 1 according to this embodiment also includes the power amplifier circuit 10, a filter 31 having a pass band that includes the transmission band of band A, a filter 32 having a pass band that includes the transmission band of band B, and a switch circuit 41 that includes a common terminal 410 connected to the high-frequency output terminal 14 of the power amplifier circuit 10, a selection terminal 411 connected to the filter 31, and a selection terminal 412 connected to the filter 32.

[0087] According to this, the power amplifier circuit 10 is used to amplify transmission signals not only in a single band but also in multiple bands, which results in the need to attenuate second harmonics over a wider band, and the LC series circuit 172 and the LC parallel circuit 181 can attenuate second harmonics more effectively.

[0088] Furthermore, for example, in the high-frequency circuit 1 according to this embodiment, the transmission band of band B may be higher than the transmission band of band A, and the resonant frequencies of the LC series circuit 172 and the LC parallel circuit 181 may be included in a frequency range from 1.8 times the frequency at the lower end of the transmission band of band A to 2.5 times the frequency at the upper end of the transmission band of band B.

[0089] This makes it possible to form an attenuation pole within or near the frequency range of the second harmonic of the transmission signals of bands A and B, thereby effectively attenuating the second harmonic.

[0090] For example, the high-frequency circuit 1 according to this embodiment may further include a filter 33 having a passband that includes the transmission band of band C, and the switch circuit 41 may further include a selection terminal 413 that is connected to the filter 33, and the transmission band of band C may be higher than the transmission band of band A and lower than the transmission band of band B.

[0091] According to this, the resonant frequencies of the LC series circuit 172 and the LC parallel circuit 181 fall within a frequency range from 1.8 times the frequency at the low end of the transmission band of the lowest of the three bands A to C to 2.5 times the frequency at the high end of the transmission band of the highest band B. Therefore, the second harmonics of the transmission signals of bands A to C can be effectively attenuated.

[0092] Furthermore, for example, the high-frequency circuit 1 according to this embodiment may further include a filter 34 having a pass band that includes the reception band of band A, a filter 35 having a pass band that includes the reception band of band B, a filter 36 having a pass band that includes the reception band of band C, and a switch circuit 42 that includes a common terminal 420 connected to the antenna connection terminal 100, a selection terminal 421 connected to the filters 31 and 34, a selection terminal 422 connected to the filters 32 and 35, and a selection terminal 423 connected to the filters 33 and 36.

[0093] This allows the high frequency circuit 1 to also receive signals in bands A to C.

[0094] In addition, the communication device 5 according to this embodiment includes an RFIC 3 configured to process high-frequency signals, and the high-frequency circuit 1 configured to transmit high-frequency signals between the RFIC 3 and the antenna 2.

[0095] This allows the communication device 5 to achieve the same effects as those of the power amplifier circuit 10 and the high-frequency circuit 1.

[0096] (Modification 1) Next, Modification 1 of the above embodiment will be described with reference to the drawings. The power amplifier circuit 10 according to this modification differs from the power amplifier circuit 10 according to the above embodiment in that it includes a low-pass filter 18A instead of the low-pass filter 18.

[0097] 10 is a circuit diagram of a low-pass filter 18A according to this modification. Note that FIG. 10 is an exemplary circuit diagram, and the low-pass filter 18A can be implemented using any of a wide variety of circuit implementations and circuit technologies. Therefore, the description of the low-pass filter 18A provided below should not be construed as limiting.

[0098] Like the low-pass filter 18, the low-pass filter 18A is connected between the power amplifier 12 and the combining circuit 16, and is capable of delaying the phase of the high-frequency signal amplified by the power amplifier 12 by 45 degrees. However, the low-pass filter 18A includes an LC parallel circuit 181 made up of an inductor 182 and a capacitor 183, but does not include a capacitor (capacitor 184 in FIG. 1 ) connected between the path connecting the output end of the power amplifier 12 and the LC parallel circuit 181 and ground.

[0099] The characteristics of the power amplifier circuit 10 according to this modification configured as above will be described with reference to Fig. 11. Fig. 11 is a graph showing the insertion loss of the power amplifier circuit 10 according to the above embodiment and this modification.

[0100] As shown in FIG. 11, the power amplifier circuit 10 according to this modification can also achieve low loss in the f0 band and high attenuation in the 2f0 band, similar to the power amplifier circuit 10 according to the embodiment.

[0101] Modification 2 Next, Modification 2 of the above embodiment will be described with reference to the drawings. The power amplifier circuit 10 according to this modification differs from the power amplifier circuit 10 according to the above embodiment in that it includes a high-pass filter 17A instead of the high-pass filter 17.

[0102] 12 is a circuit diagram of a high-pass filter 17A according to this modification. Note that FIG. 12 is an exemplary circuit diagram, and the high-pass filter 17A can be implemented using any of a wide variety of circuit implementations and circuit technologies. Therefore, the description of the high-pass filter 17A provided below should not be construed as limiting.

[0103] Similar to the high-pass filter 17, the high-pass filter 17A is connected between the output terminal of the power amplifier 11 and the input terminal 161 of the combiner circuit 16, and can advance the phase of the high-frequency signal amplified by the power amplifier 11 by 45 degrees. However, the high-pass filter 17A includes a capacitor 175 in addition to the capacitor 171 and the LC series circuit 172.

[0104] Capacitor 175 is connected between the output terminal of power amplifier 11 and capacitor 171. Specifically, one of the two electrodes of capacitor 175 is connected to the output terminal of power amplifier 11 via inductor 191, and the other of the two electrodes of capacitor 175 is connected to one of the two electrodes of capacitor 171.

[0105] The LC series circuit 172 is connected between the ground and a path connecting the other of the two electrodes of the capacitor 175 and one of the two electrodes of the capacitor 171 .

[0106] Like the power amplifier circuit 10 according to the above embodiment, the power amplifier circuit 10 according to this modification also includes the LC series circuit 172 and the LC parallel circuit 181, and therefore can achieve low loss in the f0 band and high attenuation in the 2f0 band.

[0107] Next, a third modification of the above embodiment will be described with reference to the drawings. The power amplifier circuit 10 according to this modification differs from the power amplifier circuit 10 according to the above embodiment in that it includes a high-pass filter 17B instead of the high-pass filter 17.

[0108] 13 is a circuit diagram of a high-pass filter 17B according to this modification. Note that FIG. 13 is an exemplary circuit diagram, and the high-pass filter 17B can be implemented using any of a wide variety of circuit implementations and circuit technologies. Therefore, the description of the high-pass filter 17B provided below should not be construed as limiting.

[0109] Similar to the high-pass filter 17, the high-pass filter 17B is connected between the output terminal of the power amplifier 11 and the input terminal 161 of the combiner circuit 16, and is capable of advancing the phase of the high-frequency signal amplified by the power amplifier 11 by 45 degrees. However, the high-pass filter 17B includes a capacitor 175 instead of the capacitor 171.

[0110] The capacitor 175 is connected between the output terminal of the power amplifier 11 and the input terminal 161 of the combining circuit 16. Specifically, one of the two electrodes of the capacitor 175 is connected to the output terminal of the power amplifier 11 via the inductor 191, and the other of the two electrodes of the capacitor 175 is connected to the input terminal 161 of the combining circuit 16.

[0111] The LC series circuit 172 is connected between the ground and a path connecting the other of the two electrodes of the capacitor 175 and the input terminal 161 of the combining circuit 16 .

[0112] Like the power amplifier circuit 10 according to the above embodiment, the power amplifier circuit 10 according to this modification also includes the LC series circuit 172 and the LC parallel circuit 181, and therefore can achieve low loss in the f0 band and high attenuation in the 2f0 band.

[0113] (Other Embodiments) The power amplifier circuit, high-frequency circuit, and communication device according to the present invention have been described above based on the embodiments and their modifications, but the power amplifier circuit, high-frequency circuit, and communication device according to the present invention are not limited to the above embodiments and their modifications. The present invention also includes other embodiments realized by combining any of the components in the above embodiments and their modifications, modifications obtained by applying various modifications to the above embodiments and their modifications that would occur to those skilled in the art without departing from the spirit of the present invention, and various devices incorporating the above power amplifier circuit or high-frequency circuit.

[0114] For example, in the circuit configurations of the power amplifier circuits or high-frequency circuits according to the above-described embodiments and their modifications, other circuit elements and wiring may be inserted between the paths connecting the circuit elements and signal paths shown in the drawings. For example, an impedance matching circuit may be connected between the output terminal 163 of the combiner circuit 16 and the common terminal 410 of the switch circuit 41 and / or between the common terminal 420 of the switch circuit 42 and the antenna connection terminal 100. Furthermore, for example, a coupler may be connected between the common terminal 420 of the switch circuit 42 and the antenna connection terminal 100. Furthermore, for example, an LC series circuit may be connected between the path connecting the output terminal of the power amplifier 11 and the inductor 191 and ground and / or between the path connecting the output terminal of the power amplifier 12 and the inductor 192 and ground. Furthermore, an LC series circuit may be connected between the path connecting the output terminal 163 of the combiner circuit 16 and the common terminal 410 of the switch circuit 41 and ground.

[0115] The features of the power amplifier circuit, the high-frequency circuit, and the communication device explained based on the above-mentioned embodiments will be described below.

[0116] <1> A power amplifier circuit comprising: a first power amplifier; a second power amplifier; a radio frequency input terminal; a radio frequency output terminal; a quadrature hybrid circuit including a first input terminal connected to the radio frequency input terminal, a first output terminal connected to an input terminal of the first power amplifier, and a second output terminal connected to an input terminal of the second power amplifier; a combiner circuit including a second input terminal connected to an output terminal of the first power amplifier, a third input terminal connected to an output terminal of the second power amplifier, and a third output terminal connected to the radio frequency output terminal; a first capacitor connected between the output terminal of the first power amplifier and the second input terminal; an LC series circuit connected between a path connecting the output terminal of the first power amplifier and the second input terminal and ground; and an LC parallel circuit connected between the output terminal of the second power amplifier and the third input terminal.

[0117] <2> The power amplifier circuit according to <1>, further comprising a second capacitor connected between a path connecting the output end of the second power amplifier and the third input terminal and ground.

[0118] <3> A radio frequency circuit comprising: the power amplifier circuit according to <1> or <2>; a first filter having a pass band including a transmission band of a first band; a second filter having a pass band including a transmission band of a second band; and a first switch circuit including a first common terminal connected to the radio frequency output terminal of the power amplifier circuit, a first selection terminal connected to the first filter, and a second selection terminal connected to the second filter.

[0119] <4> The high-frequency circuit according to <3>, wherein a transmission band of the second band is higher than a transmission band of the first band, and a resonant frequency of each of the LC series circuit and the LC parallel circuit is included in a frequency range from 1.8 times a frequency at a low end of the transmission band of the first band to 2.5 times a frequency at a high end of the transmission band of the second band.

[0120] <5> The high-frequency circuit according to <3> or <4>, wherein the high-frequency circuit further includes a third filter having a pass band including a transmission band of a third band, the first switch circuit further includes a third selection terminal connected to the third filter, and the transmission band of the third band is higher than the transmission band of the first band and lower than the transmission band of the second band.

[0121] <6> The high-frequency circuit according to <5>, further comprising: a fourth filter having a passband including the reception band of the first band; a fifth filter having a passband including the reception band of the second band; a sixth filter having a passband including the reception band of the third band; and a second switch circuit including a second common terminal connected to an antenna connection terminal, a fourth selection terminal connected to the first filter and the fourth filter, a fifth selection terminal connected to the second filter and the fifth filter, and a sixth selection terminal connected to the third filter and the sixth filter.

[0122] <7> A communication device comprising: a signal processing circuit configured to process a high-frequency signal; and the high-frequency circuit according to any one of <3> to <6> configured to transmit the high-frequency signal between the signal processing circuit and an antenna.

[0123] The present invention can be widely used as a power amplifier circuit and a high-frequency circuit disposed in the front end of communication devices such as mobile phones.

[0124] 1 High frequency circuit 2 Antenna 3 RFIC 4 BBIC 5 Communication device 10, 10X, 10Y Power amplifier circuit 11, 12 Power amplifier 13, 110 High frequency input terminal 14, 121, 122, 123 High frequency output terminal 15 Quadrature hybrid circuit 16 Combiner circuit 17, 17A, 17B High pass filter 18, 18A, 18X, 18Y Low pass filter 21, 22, 23 Low noise amplifier 31, 32, 33, 34, 35, 36 Filter 41, 42 Switch circuit 100 Antenna connection terminal 151, 161, 162 Input terminal 152, 153, 163 Output terminal 171, 173, 175, 183, 184, 195 Capacitor 172, 186 LC series circuit 174, 182, 185, 191, 192, 193, 194 Inductor 181 LC parallel circuit 410, 420 Common terminal 411, 412, 413, 421, 422, 423 Selection terminal

Claims

1. A power amplifier circuit comprising: a first power amplifier; a second power amplifier; a radio frequency input terminal; a radio frequency output terminal; a quadrature hybrid circuit including a first input terminal connected to the radio frequency input terminal, a first output terminal connected to the input terminal of the first power amplifier, and a second output terminal connected to the input terminal of the second power amplifier; a combiner circuit including a second input terminal connected to the output terminal of the first power amplifier, a third input terminal connected to the output terminal of the second power amplifier, and a third output terminal connected to the radio frequency output terminal; a first capacitor connected between the output terminal of the first power amplifier and the second input terminal; an LC series circuit connected between a path connecting the output terminal of the first power amplifier and the second input terminal and ground; and an LC parallel circuit connected between the output terminal of the second power amplifier and the third input terminal.

2. The power amplifier circuit according to claim 1, further comprising a second capacitor connected between a path connecting the output end of the second power amplifier and the third input terminal and ground.

3. A radio frequency circuit comprising: a power amplifier circuit according to claim 1 or 2; a first filter having a pass band including a first band of transmission band; a second filter having a pass band including a second band of transmission band; and a first switch circuit including a first common terminal connected to the radio frequency output terminal of the power amplifier circuit, a first selection terminal connected to the first filter, and a second selection terminal connected to the second filter.

4. The high-frequency circuit according to claim 3, wherein the transmission band of the second band is higher than the transmission band of the first band, and the resonant frequency of each of the LC series circuit and the LC parallel circuit is included in a frequency range from 1.8 times the frequency at the lower end of the transmission band of the first band to 2.5 times the frequency at the upper end of the transmission band of the second band.

5. The high-frequency circuit according to claim 3 or 4, wherein the high-frequency circuit further comprises a third filter having a passband that includes a third band of transmission, the first switch circuit further includes a third selection terminal connected to the third filter, and the third band of transmission is higher than the first band of transmission and lower than the second band of transmission.

6. The high frequency circuit according to claim 5, further comprising: a fourth filter having a pass band including the receive band of the first band; a fifth filter having a pass band including the receive band of the second band; a sixth filter having a pass band including the receive band of the third band; and a second switch circuit including a second common terminal connected to an antenna connection terminal, a fourth selection terminal connected to the first filter and the fourth filter, a fifth selection terminal connected to the second filter and the fifth filter, and a sixth selection terminal connected to the third filter and the sixth filter.

7. A communication device comprising: a signal processing circuit configured to process a high-frequency signal; and the high-frequency circuit according to any one of claims 3 to 6 configured to transmit the high-frequency signal between the signal processing circuit and an antenna.

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