High frequency circuit and communication device

Abstract

A high frequency circuit (1) comprising: power amplifiers (11 and 12); a transformer (42) that is provided with a primary coil (421) which has, on each end, an input terminal (421a) connected to the output end of the power amplifier (11), and an input terminal (421b) connected to the output end of the power amplifier (12), respectively, and that is further provided with a secondary coil (422) which has, on both ends, output terminals (422a and 422b); a switch (51) connected between the output terminal (422b) and the ground; and a switch (52) connected between an intermediate node (422c) of the secondary coil (422) and the ground.

Description

High frequency circuits and communication devices

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

[0002] Patent Document 1 discloses a transformer that can selectively output a high-frequency signal from both ends of an output coil (secondary coil) by selectively connecting both ends of the output coil to ground depending on the frequency band of the high-frequency signal.

[0003] International Publication No. 2023 / 017760

[0004] However, with the above-described conventional technology, it is difficult to adjust the load impedance seen from the power amplifier when the output power of the high-frequency signal varies.

[0005] Therefore, the present invention provides a high-frequency circuit and a communication device that can adjust the load impedance seen from the power amplifier in accordance with the output power of a high-frequency signal.

[0006] A high-frequency circuit according to one aspect of the present invention includes a first power amplifier and a second power amplifier, a transformer including a primary coil having at both ends a first input terminal connected to an output end of the first power amplifier and a second input terminal connected to an output end of the second power amplifier, and a secondary coil having at both ends a first output terminal and a second output terminal, a first switch connected between the second output terminal and ground, and a second switch connected between an intermediate node of the secondary coil and ground.

[0007] 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.

[0008] According to the present invention, the load impedance seen from the power amplifier can be adjusted in accordance with the output power of the high frequency signal.

[0009] Fig. 1 is a circuit configuration diagram of a communication device and a high-frequency circuit according to a first embodiment. Fig. 2 is a diagram for explaining a first mode of the high-frequency circuit according to the first embodiment. Fig. 3 is a diagram for explaining a second mode of the high-frequency circuit according to the first embodiment. Fig. 4 is a circuit configuration diagram of a communication device and a high-frequency circuit according to a second embodiment. Fig. 5 is a diagram for explaining the first mode of the high-frequency circuit according to the second embodiment. Fig. 6 is a diagram for explaining the second mode of the high-frequency circuit according to the second embodiment.

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

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

[0012] In the following description, "connected" includes not only direct connection by a connection terminal and / or wiring conductor, 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. "Directly connected" means direct connection by a connection terminal and / or wiring conductor without going through other circuit elements.

[0013] "A is switchably connected to B" means that the connection and disconnection between A and B can be switched, and that A is connected to B via a switch. Note that "A is connected to B" includes "A is switchably connected to B."

[0014] "Terminal" means a point at which a conductor within a circuit element terminates, and is to be construed as any point on or the entire conductor between circuit elements, not just a single point, provided the impedance of the conductor between circuit elements is sufficiently low.

[0015] "Node" means a point between circuit elements, and is understood to mean any point on a conductor between circuit elements or the entire conductor, not just a single point, if the impedance of the conductor between the circuit elements is sufficiently low.

[0016] The term "transmission band" refers to a frequency band used for transmission in a communication device. The term "reception band" refers to a frequency band used for reception in a communication device. For example, in a frequency division duplex (FDD) band, different frequency bands (e.g., an uplink band and a downlink band) are used as the transmission band and the reception band. For example, in a time division duplex (TDD) band, the same frequency band is used as the transmission band and the reception band.

[0017] "Power class" refers to a classification of the output power of user equipment (UE) defined by the maximum output power, and the smaller the power class value, the higher the maximum output power allowed. For example, 3GPP (registered trademark) defines power classes 1, 1.5, 2, and 3. Specifically, power class 1 defines the maximum output power as 31 dBm. power class 1.5 defines the maximum output power as 29 dBm. power class 2 defines the maximum output power as 26 dBm. power class 3 defines the maximum output power as 23 dBm.

[0018] The maximum output power of a UE is defined as the maximum output power at the antenna terminal. The maximum output power of a UE is measured using a method defined by 3GPP or the like. For example, the maximum output power is measured by measuring the radiated power at the antenna. Instead of measuring the radiated power, the maximum output power of the antenna can also be measured by providing a terminal near the antenna and connecting a measuring instrument (e.g., a spectrum analyzer) to the terminal.

[0019] 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.

[0020] (First Embodiment) The circuit configuration of a communication device 5 and a high-frequency circuit 1 according to a first embodiment will be described with reference to Fig. 1. Fig. 1 is a circuit configuration diagram of a communication device 5 and a high-frequency circuit 1 according to the present embodiment.

[0021] 1 is an exemplary circuit diagram, and the communication device 5 and the radio frequency circuit 1 may be implemented using any of a wide variety of circuit implementations and circuit technologies. Therefore, the description of the communication device 5 and the radio frequency circuit 1 provided below should not be construed as limiting.

[0022] [1.1. 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.

[0023] 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.

[0024] 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. The circuit configuration of the high-frequency circuit 1 will be described in detail later.

[0025] 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 may 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.

[0026] 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 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 some 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 and / or the high-frequency circuit 1.

[0027] The BBIC 4 is a baseband signal processing circuit that processes signals using a frequency band lower than the high-frequency signals 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. Note that part or all of the BBIC 4 may not be included in the communication device 5.

[0028] [1.2. Circuit Configuration of High-Frequency Circuit 1] The high-frequency circuit 1 includes power amplifiers 11 and 12, filters 31, 32, 33, and 34, transformers 41 and 42, switch circuits 50 and 58, switches 51, 52, and 57, an antenna connection terminal 100, and a high-frequency input terminal 110.

[0029] 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 58 inside the high frequency circuit 1.

[0030] 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 transformer 41 inside the radio frequency circuit 1.

[0031] The power amplifiers 11 and 12 form a differential amplification circuit and are connected in parallel between the transformers 41 and 42. The power amplifiers 11 and 12 can amplify the differential signal supplied from the transformer 41 and can supply the amplified differential signal to the transformer 42.

[0032] The power amplifier 11 is an example of a first power amplifier, and is connected between the transformers 41 and 42. Specifically, the input end of the power amplifier 11 is connected to the output terminal 412a of the transformer 41, and the output end of the power amplifier 11 is connected to the input terminal 421a of the transformer 42.

[0033] The power amplifier 12 is an example of a second power amplifier, and is connected between the transformers 41 and 42. Specifically, the input end of the power amplifier 12 is connected to the output terminal 412b of the transformer 41, and the output end of the power amplifier 12 is connected to the input terminal 421b of the transformer 42.

[0034] 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.

[0035] The transformer 41 is a so-called balun that can convert an unbalanced signal (single-ended signal) into a balanced signal (differential signal). The transformer 41 includes a primary coil 411, a secondary coil 412 that can be electromagnetically coupled to the primary coil 411, input terminals 411 a and 411 b, and output terminals 412 a and 412 b.

[0036] The primary coil 411 has input terminals 411a and 411b at both ends. That is, one end of the primary coil 411 is the input terminal 411a, and the other end of the primary coil 411 is the input terminal 411b. The input terminal 411a is connected to the high-frequency input terminal 110. The input terminal 411b is connected to ground.

[0037] The secondary coil 412 has output terminals 412a and 412b at both ends. That is, one end of the secondary coil 412 is the output terminal 412a, and the other end of the secondary coil 412 is the output terminal 412b. The output terminal 412a is connected to the input terminal of the power amplifier 11. The output terminal 412b is connected to the input terminal of the power amplifier 12.

[0038] The transformer 41 does not have to be included in the high-frequency circuit 1. For example, the transformer 41 may be connected between the RFIC 3 and the high-frequency circuit 1, or may be included in the RFIC 3. The transformer 41 may also be replaced with a phase adjuster and a divider. In this case, the divider may be, for example, a Wilkinson coupler or a quadrature hybrid coupler.

[0039] The transformer 42 is a so-called balun and can convert a balanced signal into an unbalanced signal. The transformer 42 includes a primary coil 421 and a secondary coil 422.

[0040] The primary coil 421 has input terminals 421a and 421b at both ends. That is, one end of the primary coil 421 is the input terminal 421a, and the other end of the primary coil 421 is the input terminal 421b. The input terminal 421a is an example of a first input terminal and is connected to the output terminal of the power amplifier 11. The input terminal 421b is an example of a second input terminal and is connected to the output terminal of the power amplifier 12.

[0041] The secondary coil 422 is a coil that can be electromagnetically coupled to the primary coil 421. The secondary coil 422 has output terminals 422a and 422b at both ends. That is, one end of the secondary coil 422 is the output terminal 422a, and the other end of the secondary coil 422 is the output terminal 422b. The output terminal 422a is an example of a first output terminal, and is connected to the common terminal 501 of the switch circuit 50, and is switchably connected to ground via the switch 57. The output terminal 422b is an example of a second output terminal, and is connected to the common terminal 502 of the switch circuit 50, and is switchably connected to ground via the switch 51.

[0042] The secondary coil 422 has an intermediate node 422c between the output terminals 422a and 422b. The intermediate node 422c is switchably connected to ground via the switch 52. The number of turns from the output terminal 422a to the intermediate node 422c is fewer than the number of turns from the output terminal 422b to the intermediate node 422c. In other words, the intermediate node 422c is closer to the output terminal 422a than to the output terminal 422b. Note that the position of the intermediate node 422c on the secondary coil 422 is not limited to this position. For example, the number of turns from the output terminal 422a to the intermediate node 422c may be the same as the number of turns from the output terminal 422b to the intermediate node 422c, or may be greater than the number of turns from the output terminal 422b to the intermediate node 422c.

[0043] The switch 51 is an example of a first switch and is connected between the output terminal 422b and ground. The switch 51 can switch between connecting and disconnecting the output terminal 422b to ground. The switch 51 is configured, for example, by a single-pole single-throw (SPST) type switch circuit.

[0044] The switch 52 is an example of a second switch and is connected between the intermediate node 422c and ground. The switch 52 can switch between connecting and disconnecting the intermediate node 422c to ground. The switch 52 is configured, for example, as an SPST type switch circuit. Note that the combination of the switches 51 and 52 may be configured as an SPDT (Single-Pole Double-Throw) type switch circuit.

[0045] The switch 57 is an example of a seventh switch, and is connected between the output terminal 422a of the transformer 42 and ground. The switch 57 can switch between connecting and disconnecting the output terminal 422a to ground. The switch 57 is configured, for example, with an SPST type switch circuit. Note that the switch 57 does not need to be included in the high-frequency circuit 1. In this case, the output terminal 422a does not need to be connectable to ground.

[0046] The filter 31 is an example of a first filter, and is a bandpass filter having a passband that includes the transmission band of Band A, and has power resistance corresponding to a first power class (e.g., power class 2). The filter 31 is connected between the switch circuits 50 and 58. Specifically, one end of the filter 31 is connected to the selection terminal 503 of the switch circuit 50, and the other end of the filter 31 is connected to the selection terminal 581 of the switch circuit 58.

[0047] The filter 32 is an example of a second filter, and is a bandpass filter having a passband that includes the transmission band of band B, and has power resistance corresponding to the first power class. The filter 32 is connected between the switch circuits 50 and 58. Specifically, one end of the filter 32 is connected to the selection terminal 504 of the switch circuit 50, and the other end of the filter 32 is connected to the selection terminal 582 of the switch circuit 58.

[0048] The filter 33 is an example of a third filter, and is a bandpass filter having a passband that includes the transmission band of Band A. The filter 33 has power durability corresponding to the second power class (e.g., power class 3) but does not have power durability corresponding to the first power class (e.g., power class 2). The filter 33 is connected between the switch circuits 50 and 58. Specifically, one end of the filter 33 is connected to the selection terminal 505 of the switch circuit 50, and the other end of the filter 33 is connected to the selection terminal 583 of the switch circuit 58.

[0049] The filter 34 is an example of a fourth filter, and is a bandpass filter having a passband that includes the transmission band of Band C, and has power resistance corresponding to the second power class. The filter 34 is connected between the switch circuits 50 and 58. Specifically, one end of the filter 34 is connected to the selection terminal 506 of the switch circuit 50, and the other end of the filter 34 is connected to the selection terminal 584 of the switch circuit 58.

[0050] The filters 31 to 34 may be, but are not limited to, a surface acoustic wave (SAW) filter, a bulk acoustic wave (BAW) filter, an LC filter, a dielectric filter, or any combination thereof.

[0051] The filters 31 to 34 are not limited to band-pass filters. Some or all of the filters 31 to 34 may be band elimination filters, high-pass filters, or low-pass filters. Furthermore, some or all of the filters 31 to 34 do not have to be included in the high-frequency circuit 1.

[0052] Note that bands A to C are frequency bands for communication systems constructed using radio access technology (RAT), and are defined in advance by standardization organizations (e.g., 3GPP and IEEE (Institute of Electrical and Electronics Engineers)). Examples of communication systems include a 5GNR (5th Generation New Radio) system, a 4GLTE (4th Generation Long Term Evolution) system, and a WLAN (Wireless Local Area Network) system. In this embodiment, bands A and B support a first power class, and band C does not support the first power class. Note that a band supporting a power class means that signals of that band can be transmitted at that power class. The power classes supported by a band are defined in advance by standards, etc.

[0053] The first power class is a power class defined by a higher maximum output power than the second power class. The second power class is a power class defined by a lower maximum output power than the first power class. Examples of combinations of the first and second power classes include a combination of power classes 2 and 3, a combination of power classes 1.5 and 3, and a combination of power classes 1.5 and 2.

[0054] The switch circuit 50 includes common terminals 501 and 502 and selection terminals 503, 504, 505, and 506. The common terminal 501 is connected to the output terminal 422a of the transformer 42. The common terminal 502 is connected to the output terminal 422b of the transformer 42. The selection terminals 503 to 506 are connected to the filters 31 to 34, respectively.

[0055] In such a connection configuration, the switch circuit 50 can selectively connect the common terminals 501 and 502 to the selection terminals 503 to 506 based on a control signal from the RFIC 3, for example.

[0056] The switch circuit 50 is configured by, for example, a DPDT (Double-Pole Double-Throw) type switch circuit, and includes switches 53 , 54 , 55 and 56 .

[0057] The switch 53 is an example of a third switch, and is connected between the common terminal 501 and the selection terminal 503. Specifically, one end of the switch 53 is connected to the output terminal 422a of the transformer 42 via the common terminal 501, and the other end of the switch 53 is connected to the filter 31 via the selection terminal 503. The switch 53 can switch between connecting and disconnecting the transformer 42 to the filter 31.

[0058] The switch 54 is an example of a fourth switch, and is connected between the common terminal 501 and the selection terminal 504. Specifically, one end of the switch 54 is connected to the output terminal 422a of the transformer 42 via the common terminal 501, and the other end of the switch 54 is connected to the filter 32 via the selection terminal 504. The switch 54 can switch between connecting and disconnecting the transformer 42 to the filter 32.

[0059] The switch 55 is an example of a fifth switch, and is connected between the common terminal 502 and the selection terminal 505. Specifically, one end of the switch 55 is connected to the output terminal 422b of the transformer 42 via the common terminal 502, and the other end of the switch 55 is connected to the filter 33 via the selection terminal 505. The switch 55 can switch between connecting and disconnecting the transformer 42 to the filter 33.

[0060] The switch 56 is an example of a sixth switch, and is connected between the common terminal 502 and the selection terminal 506. Specifically, one end of the switch 56 is connected to the output terminal 422b of the transformer 42 via the common terminal 502, and the other end of the switch 56 is connected to the filter 34 via the selection terminal 506. The switch 56 can switch between connecting and disconnecting the transformer 42 to the filter 34.

[0061] Each of the switches 53 to 56 is an SPST-type switch circuit and is configured with one or more semiconductor elements connected in series. Each of the one or more semiconductor elements is, for example, a field effect transistor (FET). In each of the switches 53 to 56, the number of the one or more semiconductor elements connected in series is defined as the stack number. In this embodiment, the stack number of the switch 53 and the stack number of the switch 54 are each greater than the stack number of the switch 55 and are also greater than the stack number of the switch 56. Note that the gate length of the FET of the switch 53 and the gate length of the FET of the switch 54 may each be longer than the gate length of the switch 55 and may also be longer than the gate length of the switch 56.

[0062] The switch circuit 50 does not have to be included in the high-frequency circuit 1. For example, if the filters 32 and 34 are not included in the high-frequency circuit 1, the output terminals 422a and 422b may be connected to the filters 31 and 33, respectively, without going through the switch circuit 50.

[0063] The switch circuit 58 includes a common terminal 580 and selection terminals 581, 582, 583, and 584. The common terminal 580 is connected to the antenna connection terminal 100. The selection terminals 581 to 584 are connected to the filters 31 to 34, respectively.

[0064] In such a connection configuration, the switch circuit 58 can selectively connect the common terminal 580 to the selection terminals 581 to 584, for example, based on a control signal from the RFIC 3. The switch circuit 58 is configured, for example, by an SP4T (Single-Pole Quadruple-Throw) type switch circuit.

[0065] The switch circuit 58 does not have to be included in the high-frequency circuit 1. For example, if the communication device 5 has two antennas and the filters 32 and 34 are not included in the high-frequency circuit 1, the filters 31 and 33 may be connected to the two antennas, respectively, without going through the switch circuit 58.

[0066] [1.3. Multiple Communication Modes of High-Frequency Circuit 1] Next, multiple communication modes of the high-frequency circuit 1 configured as above will be described.

[0067] [1.3.1. First Mode] First, the first mode included in the multiple communication modes will be described with reference to Fig. 2. Fig. 2 is a diagram showing the first mode of the high-frequency circuit 1 according to this embodiment. In the following figures, dashed arrows indicate the path of the high-frequency signal.

[0068] The first mode is a communication mode for transmitting a signal in band A in power class 2 (PC2), which is an example of the first power class.

[0069] In the first mode, switch 51 is closed, and switches 52 and 57 are open. Furthermore, switch circuit 50 connects common terminal 501 to selection terminal 503 by closing switch 53. Furthermore, switch circuit 50 opens switches 54 to 56, so that common terminal 501 is not connected to selection terminal 504 and common terminal 502 is not connected to selection terminals 505 and 506. Furthermore, switch circuit 58 connects common terminal 580 to selection terminal 581 and is not connected to selection terminals 582 to 584.

[0070] As a result, the transmit signal of band A is transmitted from RFIC 3 to antenna 2 via high frequency input terminal 110, transformer 41, power amplifiers 11 and 12, transformer 42, switch circuit 50, filter 31, switch circuit 58, and antenna connection terminal 100.

[0071] [1.3.2. Second Mode] Next, the second mode included in the plurality of communication modes will be described with reference to Fig. 3. Fig. 3 is a diagram showing the second mode of the high-frequency circuit 1 according to this embodiment.

[0072] The second mode is a communication mode for transmitting a signal in band A in power class 3 (PC3), which is an example of the second power class.

[0073] In the second mode, switches 52 and 57 are closed, and switch 51 is open. Furthermore, switch circuit 50 connects common terminal 502 to selection terminal 505 by closing switch 55. Furthermore, switch circuit 50 opens switches 53, 54, and 56, thereby not connecting common terminal 501 to selection terminals 503 and 504, and not connecting common terminal 502 to selection terminal 506. Furthermore, switch circuit 58 connects common terminal 580 to selection terminal 583, and not connecting it to selection terminals 581, 582, and 584.

[0074] As a result, the transmit signal of band A is transmitted from RFIC 3 to antenna 2 via high frequency input terminal 110, transformer 41, power amplifiers 11 and 12, transformer 42, switch circuit 50, filter 33, switch circuit 58, and antenna connection terminal 100.

[0075] The multiple communication modes of the high-frequency circuit 1 may include other communication modes in addition to the first and second modes. For example, the multiple communication modes may include a third mode in which a signal in Band B is transmitted at Power Class 2 and / or a fourth mode in which a signal in Band C is transmitted at Power Class 3.

[0076] [1.4. Summary] As described above, the high-frequency circuit 1 according to this embodiment includes the power amplifiers 11 and 12, the transformer 42 including the primary coil 421 having, at both ends, an input terminal 421 a connected to the output end of the power amplifier 11 and an input terminal 421 b connected to the output end of the power amplifier 12, and the secondary coil 422 having, at both ends, output terminals 422 a and 422 b, the switch 51 connected between the output terminal 422 b and ground, and the switch 52 connected between the intermediate node 422 c of the secondary coil 422 and ground.

[0077] This allows the output terminal 422b and intermediate node 422c of the secondary coil 422 of the transformer 42 to be switchably connected to ground. Therefore, the transformation ratio of the transformer 42 can be switched, thereby changing the load impedance seen from the output terminals of the power amplifiers 11 and 12. For example, when higher output power is required, a smaller load impedance can be set by connecting the output terminal 422b to ground. Also, when lower output power is required, a larger load impedance can be set by connecting the intermediate node 422c to ground. Furthermore, switching the load impedance according to the output power also allows the output terminal and signal path to be switched. Therefore, the characteristics (e.g., withstand voltage, power resistance, etc.) of circuit components on the signal path can be optimized for each signal path according to the output power, contributing to the miniaturization of circuit components. Furthermore, because shunt switches (switches 51 and 52) are used to switch the transformation ratio of the transformer 42, signal loss can be reduced more than when a series switch is used.

[0078] Furthermore, for example, in the high-frequency circuit 1 according to this embodiment, the number of turns in the secondary coil 422 from the output terminal 422a to the intermediate node 422c may be smaller than the number of turns from the output terminal 422b to the intermediate node 422c.

[0079] This makes it possible to prevent the voltage applied to the output terminal 422a from becoming too high when the intermediate node 422c is connected to ground, and to prevent an increase in the withstand voltage required of the circuit elements on the signal path connected to the output terminal 422a.

[0080] For example, the high-frequency circuit 1 according to this embodiment may further include filters 31, 32, 33 and 34, a switch 53 connected between the output terminal 422a and the filter 31, a switch 54 connected between the output terminal 422a and the filter 32, a switch 55 connected between the output terminal 422b and the filter 33, and a switch 56 connected between the output terminal 422b and the filter 34.

[0081] According to this, the two filters 31 and 32 are switchably connected to the output terminal 422a by the switches 53 and 54, and the two filters 33 and 34 are switchably connected to the output terminal 422b by the switches 55 and 56. Therefore, it is possible to optimize the withstand voltage of the switches on the signal paths connected to the output terminals 422a and 422b, respectively. In particular, since it is not necessary for all of the switches 53 to 56 to have a high withstand voltage, it is possible to reduce the size of the switch circuit 50.

[0082] For example, in the high-frequency circuit 1 according to this embodiment, the number of stacks of the switch 53 and the number of stacks of the switch 54 may each be greater than the number of stacks of the switch 55, and may also be greater than the number of stacks of the switch 56.

[0083] This allows the withstand voltage of the switches 53 and 54 connected to the output terminal 422a, through which the signals amplified by the power amplifiers 11 and 12 are output, to be increased in a connection state that can further reduce the load impedance. Therefore, the signal path connected to the output terminal 422a can be used as a signal path for a transmission signal that requires higher output power. Furthermore, the number of stacks of the switches 55 and 56 connected to the output terminal 422b can be reduced, allowing the size of the switch circuit 50 to be reduced.

[0084] Furthermore, for example, in the high-frequency circuit 1 according to this embodiment, the gate length of the FET of switch 53 and the gate length of the FET of switch 54 may each be longer than the gate length of the FET of switch 55 and may also be longer than the gate length of the FET of switch 56.

[0085] This makes it possible to further increase the withstand voltage of the switches 53 and 54 connected to the output terminal 422a through which the signals amplified by the power amplifiers 11 and 12 are output in a connection state that can further reduce the load impedance. This therefore increases the withstand voltage of the signal path that enables the power amplifiers 11 and 12 to achieve higher output power. Furthermore, since the number of stacks of the switches 55 and 56 connected to the output terminal 422b can be reduced, the size of the switch circuit 50 can be reduced.

[0086] Furthermore, for example, in the high-frequency circuit 1 according to this embodiment, in a first mode for transmitting a high-frequency signal in a first power class, the switches 51 and 53 may be closed and the switches 52, 54, 55 and 56 may be open, and in a second mode for transmitting a high-frequency signal in a second power class defined by a maximum output power lower than that of the first power class, the switches 52 and 55 may be closed and the switches 51, 53, 54 and 56 may be open.

[0087] According to this, in the first power class, which allows a higher maximum output power, the load impedance can be reduced by connecting the output terminal 422b to ground, thereby enabling the power amplifiers 11 and 12 to achieve higher output power. On the other hand, in the second power class, which is limited to a lower maximum output power, the load impedance can be increased by connecting the intermediate node 422c to ground, thereby enabling the power amplifiers 11 and 12 to achieve higher power efficiency. Furthermore, the output terminal and signal path of the transformer 42 can be switched between the first power class and the second power class, thereby optimizing the withstand voltage of the switches 53 to 56 on each signal path. In particular, the withstand voltage of the switches 55 and 56 can be made lower than the withstand voltage of the switches 53 and 54, enabling the switch circuit 50 to be made more compact.

[0088] Furthermore, for example, the high-frequency circuit 1 according to this embodiment may further include a switch 57 connected between the output terminal 422a and the ground.

[0089] This makes it possible to connect the output terminal 422a to ground when the intermediate node 422c is connected to ground and a high-frequency signal is output from the output terminal 422b, thereby improving the isolation between the output terminals 422a and 422b of the transformer 42.

[0090] Furthermore, for example, in the high-frequency circuit 1 according to the present embodiment, in a first mode for transmitting a high-frequency signal in a first power class, the switches 51 and 53 may be closed and the switches 52, 54, 55, 56 and 57 may be open, and in a second mode for transmitting a high-frequency signal in a second power class defined by a maximum output power lower than that of the first power class, the switches 52, 55 and 57 may be closed and the switches 51, 53, 54 and 56 may be open.

[0091] This makes it possible to connect the output terminal 422a to ground when the intermediate node 422c is connected to ground and a high-frequency signal is output from the output terminal 422b in order to transmit a high-frequency signal in the second power class, thereby improving the isolation between the output terminals 422a and 422b of the transformer 42.

[0092] Furthermore, the communication device 5 according to this embodiment includes an RFIC 3 configured to process high-frequency signals, and a high-frequency circuit 1 configured to transmit high-frequency signals between the RFIC 3 and the antenna 2.

[0093] This allows the effects of the high frequency circuit 1 to be realized in the communication device 5.

[0094] (Embodiment 2) Next, embodiment 2 will be described. A communication device 5A and a high-frequency circuit 1A according to this embodiment mainly differ from the communication device 5 and the high-frequency circuit 1 according to embodiment 1 in that they support the transmission of signals for two communication systems. The communication device 5A and the high-frequency circuit 1A according to this embodiment will be described below with reference to the drawings, focusing on the differences from the communication device 5 and the high-frequency circuit 1 according to embodiment 1.

[0095] 4 is a circuit diagram of a communication device 5A and a high-frequency circuit 1A according to this embodiment. Note that FIG. 4 is an exemplary circuit diagram, and the communication device 5A and the high-frequency circuit 1A may be implemented using any of a wide variety of circuit implementations and circuit technologies. Therefore, the following description of the communication device 5A and the high-frequency circuit 1A should not be construed as limiting.

[0096] [2.1. Circuit Configuration of Communication Device 5A] The communication device 5A according to this embodiment can be used to provide wireless connection, similar to the communication device 5 according to embodiment 1. The communication device 5A includes a high-frequency circuit 1A, antennas 2a and 2b, an RFIC 3, and a BBIC 4. That is, the communication device 5A differs from the communication device 5 according to embodiment 1 in that it includes a high-frequency circuit 1A instead of the high-frequency circuit 1 and antennas 2a and 2b instead of the antenna 2.

[0097] The antenna 2a is an antenna for 2G GSM (2nd Generation Global System for Mobile Communications). The antenna 2b is an antenna for 5G NR and / or 4G LTE. The antennas 2a and 2b are both connected to the high-frequency circuit 1A. The antennas 2a and 2b can receive high-frequency signals from the high-frequency circuit 1A and transmit them to the outside of the communication device 5A. Furthermore, the antennas 2a and 2b may receive high-frequency signals from the outside of the communication device 5A and supply them to the high-frequency circuit 1A. The antennas 2a and 2b do not have to be included in the communication device 5A. Furthermore, the communication device 5A may have one or more antennas in addition to the antennas 2a and 2b.

[0098] [2.2. Circuit Configuration of High-Frequency Circuit 1A] The high-frequency circuit 1A according to this embodiment includes power amplifiers 11 and 12, filters 31A and 32A, transformers 41 and 42, switch circuits 50A and 58A, switches 51, 52, and 57, antenna connection terminals 101 and 102, and a high-frequency input terminal 110. That is, the high-frequency circuit 1A differs from the high-frequency circuit 1 according to embodiment 1 in that it includes filters 31A and 32A instead of filters 31 to 34, switch circuits 50A and 58A instead of switch circuits 50 and 58, and antenna connection terminals 101 and 102 instead of antenna connection terminal 100. In this embodiment, switch 57 is an example of a fifth switch.

[0099] The antenna connection terminal 101 is an external connection terminal of the high frequency circuit 1A. The antenna connection terminal 101 is connected to the antenna 2a outside the high frequency circuit 1A, and is connected to the output terminal 422a of the transformer 42 inside the high frequency circuit 1A.

[0100] The antenna connection terminal 102 is an external connection terminal of the high frequency circuit 1 A. The antenna connection terminal 102 is connected to the antenna 2 b outside the high frequency circuit 1 A, and is connected to the switch circuit 58 A inside the high frequency circuit 1 A.

[0101] The filter 31A is an example of a first filter and is a bandpass filter having a passband that includes the transmission band of band A. The power class supported by the filter 31A is not particularly limited. The filter 31A is connected between the switch circuits 50A and 58A. Specifically, one end of the filter 31A is connected to the selection terminal 501A of the switch circuit 50A, and the other end of the filter 31A is connected to the selection terminal 581A of the switch circuit 58A.

[0102] The filter 32A is an example of a second filter, and is a bandpass filter having a passband that includes the transmission band of band B. The power class supported by the filter 32A is not particularly limited. The filter 32A is connected between the switch circuits 50A and 58A. Specifically, one end of the filter 32A is connected to the selection terminal 502A of the switch circuit 50A, and the other end of the filter 32A is connected to the selection terminal 582A of the switch circuit 58A.

[0103] The filters 31A and 32A may be, but are not limited to, a SAW filter, a BAW filter, an LC filter, a dielectric filter, or any combination thereof.

[0104] The filters 31A and 32A are not limited to band-pass filters. Some or all of the filters 31A and 32A may be band elimination filters, high-pass filters, or low-pass filters. Furthermore, some or all of the filters 31A and 32A do not have to be included in the high-frequency circuit 1A.

[0105] The switch circuit 50A includes a common terminal 500A and selection terminals 501A and 502A. The common terminal 500A is connected to the output terminal 422b of the transformer 42. The selection terminals 501A and 502A are connected to the filters 31A and 32A, respectively.

[0106] In such a connection configuration, the switch circuit 50A can selectively connect the common terminal 500A to the selection terminals 501A and 502A based on a control signal from the RFIC 3, for example.

[0107] The switch circuit 50A is configured as, for example, an SPDT type switch circuit, and includes switches 53A and 54A.

[0108] The switch 53A is an example of a third switch, and is connected between the common terminal 500A and the selection terminal 501A. Specifically, one end of the switch 53A is connected to the output terminal 422b via the common terminal 500A, and the other end of the switch 53A is connected to the filter 31A via the selection terminal 501A. The switch 53A can switch between connecting and disconnecting the transformer 42 to the filter 31A.

[0109] The switch 54A is an example of a fourth switch, and is connected between the common terminal 500A and the selection terminal 502A. Specifically, one end of the switch 54A is connected to the output terminal 422b via the common terminal 500A, and the other end of the switch 54A is connected to the filter 32A via the selection terminal 502A. The switch 54A can switch between connecting and disconnecting the transformer 42 to the filter 32A.

[0110] The switch circuit 50A does not have to be included in the high-frequency circuit 1A. For example, if the filter 32A is not included in the high-frequency circuit 1A, the output terminal 422b may be connected to the filter 31A without going through the switch circuit 50A.

[0111] The switch circuit 58A includes a common terminal 580A and selection terminals 581A and 582A. The common terminal 580A is connected to the antenna connection terminal 102. The selection terminals 581A and 582A are connected to the filters 31A and 32A, respectively.

[0112] In such a connection configuration, the switch circuit 58A can selectively connect the common terminal 580A to the selection terminals 581A and 582A, for example, based on a control signal from the RFIC 3. The switch circuit 58A is configured as, for example, an SPDT type switch circuit.

[0113] The switch circuit 58A does not have to be included in the high-frequency circuit 1A. For example, if the filter 32A is not included in the high-frequency circuit 1A, the filter 31A may be connected to the antenna connection terminal 102 without going through the switch circuit 58A.

[0114] [2.3. Multiple Communication Modes of High-Frequency Circuit 1A] Next, multiple communication modes of the high-frequency circuit 1A configured as above will be described.

[0115] [2.3.1. First Mode] First, the first mode included in the plurality of communication modes will be described with reference to Fig. 5. Fig. 5 is a diagram showing the first mode of the high-frequency circuit 1A according to this embodiment.

[0116] The first mode is a communication mode for transmitting 2G GSM signals.

[0117] In the first mode, the switch 51 is closed, and the switches 52 and 57 are open. The switch circuit 50A also opens the switches 53A and 54A, thereby not connecting the common terminal 500A to the selection terminals 501A and 502A.

[0118] As a result, the 2G GSM signal is transmitted from the RFIC 3 via the high frequency input terminal 110, the transformer 41, the power amplifiers 11 and 12, the transformer 42, and the antenna connection terminal 101 to the antenna 2a.

[0119] [2.3.2. Second Mode] Next, the second mode included in the plurality of communication modes will be described with reference to Fig. 6. Fig. 6 is a diagram showing the second mode of the high-frequency circuit 1A according to this embodiment.

[0120] The second mode is a communication mode for transmitting 5G NR signals or 4G LTE signals. Specifically, the second mode is a communication mode for transmitting signals in band A of 5G NR or 4G LTE.

[0121] In the second mode, switches 52 and 57 are closed, and switch 51 is open. Switch circuit 50A also connects common terminal 500A to selection terminal 501A by closing switch 53A. Conversely, switch circuit 50A does not connect common terminal 500A to selection terminal 502A by opening switch 54A. Switch circuit 58A also connects common terminal 580A to selection terminal 581A, but does not connect it to selection terminal 582A.

[0122] As a result, the 5G NR signal or 4G LTE signal is transmitted from RFIC 3 to antenna 2b via high frequency input terminal 110, transformer 41, power amplifiers 11 and 12, transformer 42, switch circuit 50A, filter 31A, switch circuit 58A, and antenna connection terminal 102.

[0123] The multiple communication modes of the high-frequency circuit 1A may include other communication modes in addition to the first and second modes. For example, the multiple communication modes may include a third mode in which a signal in 5G NR or 4G LTE band B is transmitted.

[0124] [2.4. Summary] As described above, the high-frequency circuit 1A according to this embodiment includes the power amplifiers 11 and 12, the transformer 42 including the primary coil 421 having, at both ends, an input terminal 421a connected to the output end of the power amplifier 11 and an input terminal 421b connected to the output end of the power amplifier 12, and the secondary coil 422 having, at both ends, output terminals 422a and 422b, the switch 51 connected between the output terminal 422b and ground, and the switch 52 connected between the intermediate node 422c of the secondary coil 422 and ground.

[0125] This allows the output terminal 422b and intermediate node 422c of the secondary coil 422 of the transformer 42 to be switchably connected to ground. Therefore, the transformation ratio of the transformer 42 can be switched, thereby changing the load impedance seen from the output terminals of the power amplifiers 11 and 12. For example, when higher output power is required, a smaller load impedance can be set by connecting the output terminal 422b to ground. Also, when lower output power is required, a larger load impedance can be set by connecting the intermediate node 422c to ground. Furthermore, switching the load impedance according to the output power also allows the output terminal and signal path to be switched. Therefore, the characteristics (e.g., withstand voltage, power resistance, etc.) of circuit components on the signal path can be optimized for each signal path according to the output power, contributing to the miniaturization of circuit components. Furthermore, because shunt switches (switches 51 and 52) are used to switch the transformation ratio of the transformer 42, signal loss can be reduced more than when a series switch is used.

[0126] Furthermore, for example, in the high-frequency circuit 1A according to this embodiment, the number of turns in the secondary coil 422 from the output terminal 422a to the intermediate node 422c may be smaller than the number of turns from the output terminal 422b to the intermediate node 422c.

[0127] This makes it possible to prevent the voltage applied to the output terminal 422a from becoming too high when the intermediate node 422c is connected to ground, and to prevent an increase in the withstand voltage required of the circuit elements on the signal path connected to the output terminal 422a.

[0128] For example, the high-frequency circuit 1A according to this embodiment may further include filters 31A and 32A, a switch 53A connected between the output terminal 422b and the filter 31A, and a switch 54A connected between the output terminal 422b and the filter 32A.

[0129] In this configuration, the two filters 31A and 32A are switchably connected to the output terminal 422b by the switches 53A and 54A. Therefore, the switches 53A and 54A are not connected to the output terminal 422a, and therefore are not required to have a withstand voltage corresponding to the high-frequency signal output from the output terminal 422a. As a result, it is possible to suppress an increase in the withstand voltage required of the switches 53A and 54A, and it is possible to reduce the size of the switch circuit 50A.

[0130] For example, in the high-frequency circuit 1A according to this embodiment, in a first mode for transmitting a 2G GSM signal, switch 51 may be closed and switches 52, 53A, and 54A may be open, and in a second mode for transmitting a 5G NR signal or a 4G LTE signal, switches 52 and 53A may be closed and switches 51 and 54A may be open.

[0131] According to this, when transmitting a 2GGSM signal, which requires a higher maximum output power, the output terminal 422b can be connected to ground to reduce the load impedance, thereby achieving higher output power in the power amplifiers 11 and 12. On the other hand, when transmitting a 5G NR signal or a 4G LTE signal, which requires only a lower maximum output power, the intermediate node 422c can be connected to ground to increase the load impedance, thereby achieving higher power efficiency in the power amplifiers 11 and 12. Furthermore, the output terminal and signal path of the transformer 42 can be switched between the 2GGSM signal and the 5G NR signal or the 4G LTE signal, thereby optimizing the withstand voltage of the switches 53A and 54A on the path of the 5G NR signal or the 4G LTE signal. In particular, there is no need to adjust the withstand voltage of the switches 53A and 54A to correspond to the 2GGSM signal, thereby enabling the switch circuit 50A to be miniaturized.

[0132] Furthermore, for example, the high-frequency circuit 1A according to the present embodiment may further include a switch 57 connected between the output terminal 422a and the ground.

[0133] This makes it possible to connect the output terminal 422a to ground when the intermediate node 422c is connected to ground and a high-frequency signal is output from the output terminal 422b, thereby improving the isolation between the output terminals 422a and 422b of the transformer 42.

[0134] Also, for example, in the high-frequency circuit 1A according to this embodiment, in a first mode for transmitting a 2G GSM signal, switch 51 may be closed and switches 52, 53A, 54A and 57 may be open, and in a second mode for transmitting a 5G NR signal or a 4G LTE signal, switches 52, 53A and 57 may be closed and switches 51 and 54A may be open.

[0135] This makes it possible to connect the output terminal 422a to ground when the intermediate node 422c is connected to ground and a 5G NR signal or a 4G LTE signal is output from the output terminal 422b, thereby improving the isolation between the output terminals 422a and 422b of the transformer 42.

[0136] In addition, the communication device 5A of this embodiment includes an RFIC 3 configured to process high-frequency signals, and a high-frequency circuit 1A configured to transmit high-frequency signals between the RFIC 3 and the antennas 2a and 2b.

[0137] This allows the effects of the high-frequency circuit 1A to be realized in the communication device 5A.

[0138] (Other Embodiments) While the high-frequency circuit and communication device according to the present invention have been described above based on the embodiments, the high-frequency circuit and communication device according to the present invention are not limited to the above embodiments. The present invention also includes other embodiments realized by combining any of the components in the above embodiments, modifications obtained by applying various modifications to the above embodiments that would occur to those skilled in the art without departing from the spirit of the present invention, and various devices incorporating the above-mentioned high-frequency circuit.

[0139] For example, in the circuit configurations of the high-frequency circuits according to the above embodiments, other circuit elements, wiring, etc. may be inserted between the paths connecting the circuit elements and signal paths disclosed in the drawings. For example, in the first embodiment, a capacitor may be connected between the output terminal 422a of the transformer 42 and the common terminal 501 of the switch circuit 50, and / or between the output terminal 422b of the transformer 42 and the common terminal 502 of the switch circuit 50. For example, in the first embodiment, an impedance matching circuit may be connected between the filters 31 to 34 and the switch circuit 58. For example, in the first embodiment, a coupler may be connected between the common terminal 580 of the switch circuit 58 and the antenna connection terminal 100. For example, in the second embodiment, a capacitor may be connected between the output terminal 422b of the transformer 42 and the common terminal 500A of the switch circuit 50A. For example, in the second embodiment, a filter (e.g., a low-pass filter) may be connected between the output terminal 422a of the transformer 42 and the antenna connection terminal 101.

[0140] In the above embodiments, the high-frequency circuits 1 and 1A may include a receiving path, in which case the high-frequency circuits 1 and 1A may include a receiving filter, a low-noise amplifier, and the like.

[0141] In the first embodiment, the filter 34 may be a filter having a passband that includes the transmission band of band B instead of band C. Furthermore, the filter 33 may be a filter having a passband that includes the transmission band of another band instead of band A.

[0142] In the above-described embodiments, the power amplifiers 11 and 12 constitute a differential amplifier circuit that amplifies a differential signal, but this is not limiting. For example, the power amplifiers 11 and 12 may constitute a balanced amplifier circuit that amplifies signals having a phase difference of 90 degrees. Furthermore, the power amplifiers 11 and 12 may be a carrier amplifier and a peak amplifier, or may constitute a Doherty amplifier circuit.

[0143] The following describes the features of the high-frequency circuit and communication device described based on the above embodiments.

[0144] <1> A high-frequency circuit comprising: a first power amplifier and a second power amplifier; a transformer including a primary coil having at both ends a first input terminal connected to an output end of the first power amplifier and a second input terminal connected to an output end of the second power amplifier; and a secondary coil having at both ends a first output terminal and a second output terminal; a first switch connected between the second output terminal and ground; and a second switch connected between an intermediate node of the secondary coil and ground.

[0145] <2> The high-frequency circuit according to <1>, wherein the number of turns of the secondary coil from the first output terminal to the intermediate node is smaller than the number of turns from the second output terminal to the intermediate node.

[0146] <3> The high-frequency circuit according to <1> or <2>, further comprising: a first filter, a second filter, a third filter, and a fourth filter; a third switch connected between the first output terminal and the first filter; a fourth switch connected between the first output terminal and the second filter; a fifth switch connected between the second output terminal and the third filter; and a sixth switch connected between the second output terminal and the fourth filter.

[0147] <4> The high-frequency circuit according to <3>, wherein the number of stacks of the third switch and the number of stacks of the fourth switch are each greater than the number of stacks of the fifth switch and greater than the number of stacks of the sixth switch.

[0148] <5> The high-frequency circuit according to <3>, wherein a gate length of a field effect transistor (FET) of the third switch and a gate length of a field effect transistor (FET) of the fourth switch are each longer than a gate length of a field effect transistor (FET) of the fifth switch and longer than a gate length of a field effect transistor (FET) of the sixth switch.

[0149] <6> The high-frequency circuit according to any one of <3> to <5>, wherein in a first mode for transmitting a high-frequency signal in a first power class, the first switch and the third switch are closed, and the second switch, the fourth switch, the fifth switch, and the sixth switch are opened; and in a second mode for transmitting a high-frequency signal in a second power class defined by a maximum output power lower than that of the first power class, the second switch and the fifth switch are closed, and the first switch, the third switch, the fourth switch, and the sixth switch are opened.

[0150] <7> The high-frequency circuit according to any one of <3> to <5>, further comprising a seventh switch connected between the first output terminal and ground.

[0151] <8> The high-frequency circuit according to <7>, wherein in a first mode for transmitting a high-frequency signal in a first power class, the first switch and the third switch are closed, and the second switch, the fourth switch, the fifth switch, the sixth switch, and the seventh switch are open; and in a second mode for transmitting a high-frequency signal in a second power class defined by a maximum output power lower than that of the first power class, the second switch, the fifth switch, and the seventh switch are closed, and the first switch, the third switch, the fourth switch, and the sixth switch are open.

[0152] <9> The high-frequency circuit according to <1> or <2>, further comprising: a first filter and a second filter; a third switch connected between the second output terminal and the first filter; and a fourth switch connected between the second output terminal and the second filter.

[0153] <10> The radio frequency circuit according to <9>, wherein in a first mode for transmitting a 2G GSM (2nd Generation Global System for Mobile Communications) signal, the first switch is closed, and the second switch, the third switch, and the fourth switch are open; and in a second mode for transmitting a 5GNR (5th Generation New Radio) signal or a 4G LTE (4th Generation Long Term Evolution) signal, the second switch and the third switch are closed, and the first switch and the fourth switch are open.

[0154] <11> The high-frequency circuit according to <9> or <10>, further comprising a fifth switch connected between the first output terminal and ground.

[0155] <12> The radio frequency circuit according to <11>, wherein in a first mode for transmitting a 2G GSM signal, the first switch is closed, and the second switch, the third switch, the fourth switch, and the fifth switch are open; and in a second mode for transmitting a 5G NR signal or a 4G LTE signal, the second switch, the third switch, and the fifth switch are closed, and the first switch and the fourth switch are open.

[0156] <13> 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 <1> to <12> configured to transmit the high-frequency signal between the signal processing circuit and an antenna.

[0157] The present invention can be widely used as a high-frequency circuit disposed in the front end of communication devices such as mobile phones.

[0158] REFERENCE SIGNS LIST 1, 1A High frequency circuit 2, 2a, 2b Antenna 3 RFIC 4 BBIC 5, 5A Communication device 11, 12 Power amplifier 31, 31A, 32, 32A, 33, 34 Filter 41, 42 Transformer 50, 50A, 58, 58A Switch circuit 51, 52, 53, 53A, 54, 54A, 55, 56, 57 Switch 100, 101, 102 Antenna connection terminal 110 High frequency input terminal 411, 421 Primary coil 411a, 411b, 421a, 421b Input terminal 412, 422 Secondary coil 412a, 412b, 422a, 422b Output terminal 422c Intermediate node 500A, 501, 502, 580, 580A Common terminals 501A, 502A, 503, 504, 505, 506, 581, 581A, 582, 582A, 583, 584 Selection terminals

Claims

1. A high-frequency circuit comprising: a first power amplifier and a second power amplifier; a transformer including a primary coil having at both ends a first input terminal connected to the output end of the first power amplifier and a second input terminal connected to the output end of the second power amplifier, and a secondary coil having at both ends a first output terminal and a second output terminal; a first switch connected between the second output terminal and ground; and a second switch connected between an intermediate node of the secondary coil and ground.

2. The high frequency circuit according to claim 1, wherein the number of turns in the secondary coil from the first output terminal to the intermediate node is smaller than the number of turns from the second output terminal to the intermediate node.

3. The high-frequency circuit according to claim 1 or 2, further comprising: a first filter, a second filter, a third filter, and a fourth filter; a third switch connected between the first output terminal and the first filter; a fourth switch connected between the first output terminal and the second filter; a fifth switch connected between the second output terminal and the third filter; and a sixth switch connected between the second output terminal and the fourth filter.

4. The high frequency circuit according to claim 3, wherein the number of stacks of the third switch and the number of stacks of the fourth switch are each greater than the number of stacks of the fifth switch and greater than the number of stacks of the sixth switch.

5. The high-frequency circuit according to claim 3, wherein the gate length of the FET (Field Effect Transistor) of the third switch and the gate length of the FET of the fourth switch are each longer than the gate length of the FET of the fifth switch and longer than the gate length of the FET of the sixth switch.

6. The high-frequency circuit according to any one of claims 3 to 5, wherein in a first mode for transmitting a high-frequency signal in a first power class, the first switch and the third switch are closed, and the second switch, the fourth switch, the fifth switch, and the sixth switch are open, and in a second mode for transmitting a high-frequency signal in a second power class defined by a maximum output power lower than that of the first power class, the second switch and the fifth switch are closed, and the first switch, the third switch, the fourth switch, and the sixth switch are open.

7. The high-frequency circuit according to any one of claims 3 to 5, further comprising a seventh switch connected between the first output terminal and ground.

8. The high-frequency circuit according to claim 7, wherein in a first mode for transmitting a high-frequency signal in a first power class, the first switch and the third switch are closed, and the second switch, the fourth switch, the fifth switch, the sixth switch, and the seventh switch are open, and in a second mode for transmitting a high-frequency signal in a second power class defined by a maximum output power lower than that of the first power class, the second switch, the fifth switch, and the seventh switch are closed, and the first switch, the third switch, the fourth switch, and the sixth switch are open.

9. The high-frequency circuit according to claim 1 or 2, further comprising: a first filter and a second filter; a third switch connected between the second output terminal and the first filter; and a fourth switch connected between the second output terminal and the second filter.

10. The radio frequency circuit according to claim 9, wherein in a first mode for transmitting a 2G GSM (2nd Generation Global System for Mobile Communications) signal, the first switch is closed and the second switch, the third switch, and the fourth switch are open; and in a second mode for transmitting a 5GNR (5th Generation New Radio) signal or a 4G LTE (4th Generation Long Term Evolution) signal, the second switch and the third switch are closed and the first switch and the fourth switch are open.

11. The high-frequency circuit according to claim 9 or 10, further comprising a fifth switch connected between the first output terminal and ground.

12. The high frequency circuit according to claim 11, wherein in a first mode for transmitting a 2G GSM signal, the first switch is closed and the second switch, the third switch, the fourth switch and the fifth switch are open; and in a second mode for transmitting a 5G NR signal or a 4G LTE signal, the second switch, the third switch and the fifth switch are closed and the first switch and the fourth switch are open.

13. A communication device comprising: a signal processing circuit configured to process a high-frequency signal; and a high-frequency circuit according to any one of claims 1 to 12 configured to transmit the high-frequency signal between the signal processing circuit and an antenna.

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