High frequency circuit and communication device

Abstract

A high-frequency circuit (1) comprises: a transmission filter (31) having a passband including a transmission band of a band (A) that is an FDD band; a transmission filter (32) having a passband including a transmission band of the band (A); a reception filter (33) having a passband including a reception band of the band (A); and a synthesizer (41) including a terminal (411) connected to an antenna connection terminal (100), a terminal (412) connected to an output end of the transmission filter (31), and a terminal (413) connected to an output end of the transmission filter (32) and an input end of the reception filter (33).

Description

High frequency circuits and communication devices

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

[0002] The 3GPP (registered trademark) (3rd Generation Partnership Project) is considering applying a power class (e.g., power class 2) that allows a higher maximum output power than conventional ones to frequency division duplex (FDD) bands. Patent Document 1 discloses a high-frequency circuit that can support a power class that allows a higher maximum output power by combining two high-frequency signals that are respectively amplified by two power amplifiers.

[0003] International Publication No. 2022 / 138001

[0004] However, with the above-described conventional technology, the reception characteristics of the FDD band may be degraded.

[0005] Therefore, the present invention provides a high-frequency circuit and a communication device that can suppress deterioration of reception characteristics in the FDD band.

[0006] A high-frequency circuit according to one aspect of the present invention comprises a first transmit filter having a passband that includes the transmit band of the FDD band, a second transmit filter having a passband that includes the transmit band of the FDD band, a third receive filter having a passband that includes the receive band of the FDD band, and a combiner including a first terminal connected to an antenna connection terminal, a second terminal connected to an output terminal of the first transmit filter, and a third terminal connected to the output terminal of the second transmit filter and the input terminal of the third receive filter.

[0007] A communication device according to one aspect of the present invention includes a signal processing circuit that processes a high-frequency signal, and the high-frequency circuit that transmits the high-frequency signal between the signal processing circuit and an antenna.

[0008] According to the present invention, it is possible to suppress deterioration of reception characteristics in the FDD band.

[0009] FIG. 1 is a circuit configuration diagram of a communication device according to embodiment 1. FIG. 2 is a circuit configuration diagram of a first example of a combiner according to embodiment 1. FIG. 3 is a circuit configuration diagram of a second example of a combiner according to embodiment 1. FIG. 4 is a circuit configuration diagram of a communication device according to embodiment 2. FIG. 5 is a circuit configuration diagram of a communication device according to a modification of embodiment 2. FIG. 6 is a circuit configuration diagram of a communication device according to embodiment 3. FIG. 7 is a diagram showing transmission paths and reception paths in a first mode of a communication device according to embodiment 3. FIG. 8 is a diagram showing transmission paths and reception paths in a second mode of a communication device according to embodiment 3.

[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 of the circuit configuration, "connected" includes not only direct connection by connection terminals and / or wiring conductors, but also electrical connection via other circuit elements. "A is switchably connected to B" means that the connection and disconnection between A and B can be switched, and A is connected to B via a switch. "A is connected to B" includes "A is switchably connected to B." "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 in the path connecting A and B. "Path connecting A and B" means a path made up of a conductor electrically connecting A to B.

[0013] "Terminal" means a point where a conductor within an element terminates. Note that terminal is understood to mean 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.

[0014] The "passband of a filter" is defined as the portion of the frequency spectrum transmitted by the filter over which the output power is not attenuated by more than 3 dB below the maximum output power. The upper and lower ends of the passband of a bandpass filter are therefore identified as the higher and lower frequencies of the two points at which the output power is attenuated by 3 dB below the maximum output power.

[0015] 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 an 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.

[0016] "Power class" refers to a classification of the output power of a user equipment (UE) defined by its maximum output power, and the smaller the power class value, the higher the maximum output power allowed. For example, 3GPP 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.

[0017] 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.

[0018] The "band corresponding to a power class" refers to a frequency band in which the power class can be used, and is defined by standards, etc. For example, in 3GPP, n2, n5, n8, n13, n25, n26, n28, n66, n71, and n85 are being considered as FDD bands for 5G NR corresponding to power class 2.

[0019] Terms indicating the relationship between elements, such as "parallel" and "perpendicular," terms indicating the shape of elements, such as "rectangle," and numerical ranges do not only indicate the strict meaning, but also include a substantially equivalent range, for example, an error of a few percent.

[0020] (First Embodiment) A first embodiment will be described. A 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 (also referred to as a mobile 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 circuit configuration of a communication device 5 and a high-frequency circuit 1 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.

[0022] 1 is an exemplary circuit configuration, 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.

[0023] [1.1 Circuit Configuration of Communication Device 5] First, the circuit configuration of a communication device 5 according to this embodiment will be described with reference to Fig. 1. 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 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 later.

[0025] The antenna 2 is connected to the antenna connection terminal 100 of 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. The antenna 2 can also receive a high-frequency signal from the outside of the communication device 5 and output it to the high-frequency circuit 1. The antenna 2 does not have to be included in the communication device 5. The communication device 5 may also 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 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 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.

[0028] [1.2 Circuit Configuration of High-Frequency Circuit 1] Next, the circuit configuration of the high-frequency circuit 1 according to this embodiment will be described with reference to Fig. 1. The high-frequency circuit 1 includes a power amplifier 10, a low-noise amplifier 20, transmit filters 31 and 32, a receive filter 33, a combiner 41, a divider 42, an antenna connection terminal 100, a high-frequency input terminal 110, and a high-frequency output terminal 120.

[0029] The antenna connection terminal 100 is an external connection terminal of the high-frequency circuit 1, and is connected to the antenna 2 outside the high-frequency circuit 1. The antenna connection terminal 100 is also connected to a combiner 41 inside the high-frequency circuit 1. This allows the high-frequency circuit 1 to supply a transmission signal to the antenna 2 and receive a reception signal from the antenna 2 via the antenna connection terminal 100.

[0030] The radio frequency input terminal 110 is an external connection terminal of the radio frequency circuit 1, and is connected to the RFIC 3 outside the radio frequency circuit 1. The radio frequency input terminal 110 is also connected to the input end of the power amplifier 10 inside the radio frequency circuit 1. This allows the radio frequency circuit 1 to supply the power amplifier 10 with a transmission signal received from the RFIC 3 via the radio frequency input terminal 110.

[0031] The radio frequency output terminal 120 is an external connection terminal of the radio frequency circuit 1, and is connected to the RFIC 3 outside the radio frequency circuit 1. The radio frequency output terminal 120 is also connected to the output end of the low noise amplifier 20 inside the radio frequency circuit 1. This allows the radio frequency circuit 1 to supply the received signal amplified by the low noise amplifier 20 to the RFIC 3 via the radio frequency output terminal 120.

[0032] The power amplifier 10 is connected between the radio frequency input terminal 110 and the transmit filters 31 and 32. Specifically, the input terminal of the power amplifier 10 is connected to the radio frequency input terminal 110. On the other hand, the output terminal of the power amplifier 10 is connected to the transmit filters 31 and 32 via a distributor 42. The power amplifier 10 can amplify a transmit signal supplied from the RFIC 3 via the radio frequency input terminal 110, using power supplied from a power supply (not shown).

[0033] The power amplifier 10 may be configured with a heterojunction bipolar transistor (HBT) and may be manufactured using a semiconductor material. Examples of the semiconductor material that may be used include silicon germanium (SiGe) and gallium arsenide (GaAs). The amplifying transistor of the power amplifier 10 is not limited to an HBT. For example, the power amplifier 10 may be configured with a high electron mobility transistor (HEMT) or a metal-semiconductor field effect transistor (MESFET). In this case, gallium nitride (GaN) or silicon carbide (SiC) may be used as the semiconductor material.

[0034] In this embodiment, power amplifier 10 corresponds to a first power class (e.g., power class 2, 1.5, or 1) that is defined by a higher maximum output power. In other words, power amplifier 10 can amplify a transmission signal up to an output power that can satisfy the maximum output power of the terminal defined by the first power class.

[0035] Note that a part or all of the power amplifier 10 does not have to be included in the high-frequency circuit 1. In this case, a part or all of the power amplifier 10 may be connected between the RFIC 3 and the high-frequency input terminal 110, or may be included in the RFIC 3.

[0036] The low-noise amplifier 20 is connected between the receive filter 33 and the high-frequency output terminal 120. Specifically, the input terminal of the low-noise amplifier 20 is connected to the receive filter 33. On the other hand, the output terminal of the low-noise amplifier 20 is connected to the high-frequency output terminal 120. The low-noise amplifier 20 can amplify the receive signal that has passed through the receive filter 33 using power supplied from a power supply (not shown).

[0037] The low-noise amplifier 20 may be configured with a field-effect transistor (FET) and may be manufactured using a semiconductor material. Examples of the semiconductor material that may be used include single crystal silicon, gallium nitride (GaN), and silicon carbide (SiC). The amplifying transistors of the low-noise amplifier 20 are not limited to FETs. For example, part or all of the low-noise amplifier 20 may be configured with bipolar transistors.

[0038] Note that a part or all of the low-noise amplifier 20 does not have to be included in the high-frequency circuit 1. In this case, a part or all of the low-noise amplifier 20 may be connected between the high-frequency output terminal 120 and the RFIC 3, or may be included in the RFIC 3.

[0039] The transmit filter 31 is an example of a first transmit filter, and has a passband that includes the transmit band of band A. The transmit filter 31 is connected between the antenna connection terminal 100 and the power amplifier 10. Specifically, the output end of the transmit filter 31 is connected to the antenna connection terminal 100 via a combiner 41. On the other hand, the input end of the transmit filter 31 is connected to the power amplifier 10 via a distributor 42. The transmit filter 31 only needs to have a power durability corresponding to a second power class (e.g., power class 3) that is defined by a lower maximum output power, and does not necessarily have a power durability corresponding to a first power class (e.g., power class 2, 1.5, or 1) that is defined by a higher maximum output power.

[0040] The first power class is a power class that allows a higher maximum output power than the second power class. Examples of the first power class include power class 2, power class 1.5, and power class 1. If a new power class is defined in the standard, the new power class may be used as the first power class.

[0041] The transmit filter 32 is an example of a second transmit filter, and has a passband that includes the transmit band of band A. The transmit filter 32 is connected between the antenna connection terminal 100 and the power amplifier 10. Specifically, the output end of the transmit filter 32 is connected to the antenna connection terminal 100 via a combiner 41. On the other hand, the input end of the transmit filter 32 is connected to the power amplifier 10 via a distributor 42. The transmit filter 32 only needs to have a power handling capability corresponding to the second power class defined by a lower maximum output power, and does not necessarily have a power handling capability corresponding to the first power class defined by a higher maximum output power.

[0042] The receive filter 33 is an example of a third receive filter, and has a passband that includes the receive band of band A. The receive filter 33 is connected between the antenna connection terminal 100 and the low-noise amplifier 20. Specifically, the input terminal of the receive filter 33 is connected to the antenna connection terminal 100 via a combiner 41. On the other hand, the output terminal of the receive filter 33 is connected to the low-noise amplifier 20.

[0043] The transmit filters 31 and 32 and the receive filter 33 are implemented as, but not limited to, a surface acoustic wave (SAW) filter, a bulk acoustic wave (BAW) filter, an LC resonator filter, a dielectric resonator filter, or any combination thereof.

[0044] Band A is a frequency band for communication systems built using radio access technology (RAT). Band A is predefined by standardization organizations (e.g., 3GPP and the Institute of Electrical and Electronics Engineers (IEEE)). Examples of communication systems include 5GNR (5th Generation New Radio) systems, LTE (Long Term Evolution) systems, and WLAN (Wireless Local Area Network) systems.

[0045] Band A is an FDD band corresponding to the first power class. For example, n2, n5, n8, n13, n25, n26, n28, n66, n71, or n85 for 5G NR is used as Band A. Note that Band A is not limited to these. For example, an LTE band may be used as Band A.

[0046] The combiner 41 includes terminals 411, 412, and 413. The terminal 411 is an example of a first terminal and is connected to the antenna connection terminal 100. The terminal 412 is an example of a second terminal and is connected to the output terminal of the transmit filter 31. The terminal 413 is an example of a third terminal and is connected to the output terminal of the transmit filter 32 and the input terminal of the receive filter 33.

[0047] In the combiner 41, the isolation between the terminals 412 and 413 is sufficiently large in the transmission band and reception band of band A. This makes it possible to prevent the transmission signal that has passed through the filter 31 from leaking into the transmission / reception path to which the filters 32 and 33 are connected. Furthermore, the impedance in the reception band of band A when viewing the transmission filter 31 from the terminal 411 is sufficiently large. This makes it possible to prevent the reception signal input from the antenna 2 from leaking into the transmission path to which the filter 31 is connected.

[0048] As a result, the band A transmission signal that has passed through the transmission filter 31 and input to the terminal 412 and the band A transmission signal that has passed through the transmission filter 32 and input to the terminal 413 are combined by the combiner 41 and output from the terminal 411 to the antenna 2 via the antenna connection terminal 100. Furthermore, the reception signal that has been input to the terminal 411 from the antenna 2 via the antenna connection terminal 100 is output from the terminal 413 to the reception filter 33.

[0049] Various combiners can be used depending on the phase difference between the two input signals as the combiner 41. The detailed circuit configuration of the combiner 41 will be described later with reference to FIGS.

[0050] The distributor 42 includes terminals 421, 422, and 423. The terminal 421 is an example of a fourth terminal and is connected to the output end of the power amplifier 10. The terminal 422 is an example of a fifth terminal and is connected to the input end of the transmit filter 31. The terminal 423 is an example of a sixth terminal and is connected to the input end of the transmit filter 32.

[0051] As a result, the divider 42 can divide the transmission signal of band A supplied from the RFIC 3 via the high-frequency input terminal 110 into two signals and output them to the transmission filters 31 and 32. The circuit configuration of the divider 42 may be the same as that of the combiner 41.

[0052] The divider 42 may be an equal divider or an unequal divider. That is, the distribution ratio between the terminals 422 and 423 of the divider 42 may be 1:1 or M:N (M and N are different natural numbers). For example, if M is greater than N, the average power of the transmission band of band A at the terminal 413 of the combiner 41 can be made lower than the average power of the transmission band of band A at the terminal 412 of the combiner 41.

[0053] The average power in the transmission band of Band A at terminals 412 and 413 can be determined by connecting a measuring instrument (such as a spectrum analyzer) to each of terminals 412 and 413 and measuring the power simultaneously for the same period.

[0054] [1.3 Circuit Configuration of Combiner 41] Next, the circuit configuration of the combiner 41 according to this embodiment will be described with reference to Fig. 2 and Fig. 3. Fig. 2 and Fig. 3 are circuit configuration diagrams of different examples of the combiner 41 according to this embodiment.

[0055] 2 and 3 are exemplary circuit configurations, and the combiner 41 may be implemented using any of a wide variety of circuit implementations and circuit techniques, and therefore the description of the combiner 41 provided below should not be construed as limiting.

[0056] 2 , the combiner 41 is a Wilkinson coupler and includes transmission lines TL1 and TL2 and a resistor R1. The transmission line TL1 is connected between terminals 411 and 412 and forms a quarter-wave transmission line for Band A. The transmission line TL2 is connected between terminals 411 and 413 and forms a quarter-wave transmission line for Band A. The resistor R1 is connected in parallel with the transmission lines TL1 and TL2 between the terminals 411 and 412. With this configuration, the combiner 41 can combine two in-phase Band A transmit signals that have passed through the transmit filters 31 and 32, respectively, into one signal. Note that each of the transmission lines TL1 and TL2 may include an inductor and / or a capacitor.

[0057] In the example of FIG. 3 , the combiner 41 is a 90-degree hybrid coupler and includes transmission lines TL3, TL4, TL5, and TL6. Each of the transmission lines TL3 to TL6 constitutes a quarter-wave transmission line for Band A. The transmission line TL3 is connected between terminals 411 and 412. The transmission line TL4 is connected between terminals 412 and 413. The transmission lines TL5 and TL6 are connected in series between terminals 411 and 413. With this configuration, the combiner 41 can combine two Band A transmission signals having a phase difference of 90 degrees that have passed through the transmit filters 31 and 32, respectively, into one signal. Note that each of the transmission lines TL3 to TL6 may include an inductor and / or a capacitor.

[0058] [1.4 Summary] As described above, the high-frequency circuit 1 according to this embodiment includes a transmit filter 31 having a pass band that includes the transmit band of band A, which is the FDD band, a transmit filter 32 having a pass band that includes the transmit band of band A, a receive filter 33 having a pass band that includes the receive band of band A, and a combiner 41 that includes a terminal 411 connected to the antenna connection terminal 100, a terminal 412 connected to the output end of the transmit filter 31, and a terminal 413 connected to the output end of the transmit filter 32 and the input end of the receive filter 33.

[0059] This allows the combiner 41 to combine two transmission signals that have passed through the two transmission filters 31 and 32, respectively. Therefore, each of the transmission filters 31 and 32 does not need to be able to handle the power of the combined transmission signal, thereby reducing the power durability requirement for each of the transmission filters 31 and 32. This is particularly effective when a higher maximum output power is required. Furthermore, the reception filter 33 is connected to the terminal 423 of the combiner 41, not the terminal 421. That is, the reception filter 33 is connected to a transmission path through which a lower-power transmission signal is transmitted. This reduces the leakage of transmission signals into the reception path, thereby suppressing degradation of reception characteristics. Furthermore, this also reduces the power durability requirement for the reception filter 33. This is particularly effective when a higher maximum output power is required, similar to the transmission filters 31 and 32.

[0060] Furthermore, for example, in the high-frequency circuit 1 according to this embodiment, the combiner 41 may be a Wilkinson coupler.

[0061] According to this, since a Wilkinson coupler is used for the combiner 41, it is possible to ensure isolation between the terminals 412 and 413. Therefore, it is possible to prevent the transmission signal that has passed through the transmission filter 31 from leaking to the reception filter 33 via the combiner 41, and it is possible to prevent deterioration of the reception characteristics.

[0062] Furthermore, for example, in the high-frequency circuit 1 according to this embodiment, the combiner 41 may be a 90-degree hybrid coupler.

[0063] According to this, a 90-degree hybrid coupler is used for the combiner 41, thereby ensuring isolation between the terminals 412 and 413. Therefore, it is possible to prevent the transmission signal that has passed through the transmission filter 31 from leaking to the reception filter 33 via the combiner 41, thereby suppressing deterioration of the reception characteristics.

[0064] For example, the high-frequency circuit 1 according to this embodiment may further include a power amplifier 10, and a distributor 42 including a terminal 421 connected to the output end of the power amplifier 10, a terminal 422 connected to the input end of the transmit filter 31, and a terminal 423 connected to the input end of the transmit filter 32.

[0065] This allows the transmission signal to be amplified by one power amplifier 10, thereby suppressing an increase in the number of power amplifiers and contributing to a reduction in the size of the communication device 5.

[0066] Furthermore, for example, in the high-frequency circuit 1 according to this embodiment, the average power in the transmission band of band A at the terminal 413 may be lower than the average power in the transmission band of band A at the terminal 412 .

[0067] In this way, the receive filter 33 is connected to the terminal 423 to which a lower power transmit signal is input, rather than to the terminal 422 to which a higher power transmit signal is input, thereby further suppressing leakage of the transmit signal into the receive path and further suppressing deterioration of the receive characteristics.

[0068] Furthermore, for example, in the high-frequency circuit 1 according to this embodiment, band A corresponds to the first power class, which is defined by a maximum output power higher than that of power class 3.

[0069] This requires a maximum output power higher than the conventional maximum output power of 23 dBm for power class 3, which has a significant effect in reducing the power durability requirements for the transmit filters 31 and 32 and the receive filter 33.

[0070] 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.

[0071] This allows the communication device 5 to achieve the same effect as the high-frequency circuit 1.

[0072] (Embodiment 2) Next, embodiment 2 will be described. In this embodiment, the main difference is that not only the filter but also the power amplifier is divided into two. The following describes this embodiment with reference to the drawings, focusing on the differences from embodiment 1.

[0073] [2.1 Circuit Configuration of High-Frequency Circuit 1A] The circuit configuration of the high-frequency circuit 1A according to this embodiment will be described with reference to Fig. 4. Note that the communication device 5A according to this embodiment is the same as the communication device 5 according to the first embodiment except that the high-frequency circuit 1 is replaced with the high-frequency circuit 1A, and therefore description thereof will be omitted.

[0074] 4 is a circuit diagram of a communication device 5A according to this embodiment. Note that FIG. 4 is an exemplary circuit configuration, and the communication device 5A and the high-frequency circuit 1A can be implemented using any of a wide variety of circuit implementations and circuit technologies. Therefore, the description of the high-frequency circuit 1A provided below should not be interpreted as limiting.

[0075] The high-frequency circuit 1A includes power amplifiers 11 and 12, a low-noise amplifier 20, transmit filters 31 and 32, a receive filter 33, a combiner 41, a distributor 42, an antenna connection terminal 100, a high-frequency input terminal 110, and a high-frequency output terminal 120.

[0076] The power amplifier 11 is an example of a first power amplifier, and is connected between the radio frequency input terminal 110 and the transmit filter 31. Specifically, the input end of the power amplifier 11 is connected to the radio frequency input terminal 110 via the divider 42. On the other hand, the output end of the power amplifier 11 is connected to the transmit filter 31. The power amplifier 11 can amplify a transmit signal supplied from the RFIC 3 via the radio frequency input terminal 110 and the divider 42, using power supplied from a power supply (not shown).

[0077] The power amplifier 12 is an example of a second power amplifier, and is connected between the radio frequency input terminal 110 and the transmit filter 32. Specifically, the input end of the power amplifier 12 is connected to the radio frequency input terminal 110 via the divider 42. On the other hand, the output end of the power amplifier 12 is connected to the transmit filter 32. The power amplifier 12 can amplify a transmit signal supplied from the RFIC 3 via the radio frequency input terminal 110 and the divider 42, using power supplied from a power supply (not shown).

[0078] In this embodiment, each of the power amplifiers 11 and 12 corresponds to a second power class (e.g., power class 3) defined by a lower maximum output power. In other words, each of the power amplifiers 11 and 12 does not necessarily correspond to a first power class (e.g., power class 2, 1.5, or 1) defined by a higher maximum output power. Even in such a case, the high-frequency circuit 1A can comply with the first power class by combining two transmission signals amplified by the two power amplifiers 11 and 12.

[0079] [2.2 Summary] As described above, the high-frequency circuit 1A according to this embodiment may further include the power amplifier 11 connected to the input terminal of the transmit filter 31, and the power amplifier 12 connected to the input terminal of the transmit filter 32.

[0080] In this way, two transmission signals amplified by the two power amplifiers 11 and 12 can be combined by the combiner 41, so that each of the power amplifiers 11 and 12 does not need to be able to handle the power of the combined transmission signal, and the output power requirement for each of the power amplifiers 11 and 12 can be reduced.

[0081] Furthermore, for example, the high-frequency circuit 1A according to this embodiment may include a distributor 42 including a terminal 421 connected to the high-frequency input terminal 110, a terminal 422 connected to the input terminal of the power amplifier 11, and a terminal 423 connected to the input terminal of the power amplifier 12.

[0082] This allows the high-frequency circuit 1A to split one transmission signal into two transmission signals, thereby suppressing an increase in the number of high-frequency input terminals 110 connected to the RFIC 3.

[0083] (Variation of Second Embodiment) In the second embodiment, the distributor 42 does not have to be included in the high-frequency circuit 1A, and may be included in, for example, the RFIC 3. Such a high-frequency circuit 1B according to a variation of the second embodiment will be described with reference to the drawings.

[0084] The circuit configuration of a high-frequency circuit 1B according to this modification will be described with reference to Fig. 5. Note that a communication device 5B according to this modification is similar to the communication device 5 according to the first embodiment except that the high-frequency circuit 1 is replaced with a high-frequency circuit 1B, and therefore description thereof will be omitted.

[0085] The high-frequency circuit 1B includes power amplifiers 11 and 12, a low-noise amplifier 20, transmit filters 31 and 32, a receive filter 33, a combiner 41, an antenna connection terminal 100, high-frequency input terminals 111 and 112, and a high-frequency output terminal 120.

[0086] Each of the radio frequency input terminals 111 and 112 is an external connection terminal of the radio frequency circuit 1B and is connected to the RFIC 3 outside the radio frequency circuit 1B. The radio frequency input terminals 111 and 112 are also connected to the power amplifiers 11 and 12 inside the radio frequency circuit 1B, respectively. This allows the radio frequency circuit 1B to supply a transmission signal received from the RFIC 3 via the radio frequency input terminal 111 to the power amplifier 11, and to supply a transmission signal received from the RFIC 3 via the radio frequency input terminal 112 to the power amplifier 12.

[0087] (Embodiment 3) Next, embodiment 3 will be described. This embodiment differs from embodiments 1 and 2 mainly in that it is possible to switch between using and not using the combiner 41. Hereinafter, this embodiment will be described with reference to the drawings, focusing on the differences from embodiments 1 and 2.

[0088] [3.1 Circuit Configuration of High-Frequency Circuit 1C] The circuit configuration of the high-frequency circuit 1C according to this embodiment will be described with reference to Fig. 6. Note that the communication device 5C according to this embodiment is the same as the communication device 5 according to the first embodiment except that the high-frequency circuit 1 is replaced with the high-frequency circuit 1C, and therefore description thereof will be omitted.

[0089] 6 is a circuit configuration diagram of a communication device 5C according to this embodiment. Note that FIG. 6 is an exemplary circuit configuration, and the communication device 5C and the high-frequency circuit 1C can be implemented using any of a wide variety of circuit implementations and circuit technologies. Therefore, the description of the high-frequency circuit 1C provided below should not be interpreted as limiting.

[0090] The high-frequency circuit 1C includes power amplifiers 11 and 12, a low-noise amplifier 20, transmit filters 31 and 32, a receive filter 33, a combiner 41, switch circuits 51 and 52, an antenna connection terminal 100, high-frequency input terminals 111 and 112, and a high-frequency output terminal 120.

[0091] The switch circuit 51 is an example of a first switch circuit and includes terminals 511, 512, 513, 514, and 515. The terminal 511 is an example of a seventh terminal and is connected to the output end of the transmit filter 31. The terminal 512 is an example of an eighth terminal and is connected to the output end of the transmit filter 32 and the input end of the receive filter 33. The terminal 513 is an example of a ninth terminal and is connected to the terminal 412 of the combiner 41. The terminal 514 is an example of a tenth terminal and is connected to the terminal 413 of the combiner 41. The terminal 515 is an example of an eleventh terminal and is switchably connected to the antenna connection terminal 100 via the switch circuit 52.

[0092] In this connection configuration, the switch circuit 51 can connect the terminal 511 to the terminal 513 and can exclusively connect the terminal 512 to the terminals 514 and 515, for example, based on a control signal from the RFIC 3. The switch circuit 51 is configured by combining, for example, an SPST (Single-Pole Single-Throw) type switch circuit and an SPDT (Single-Pole Double-Throw) type switch circuit.

[0093] The switch circuit 52 is an example of a second switch circuit and includes terminals 521, 522, and 523. The terminal 521 is an example of a twelfth terminal and is connected to the antenna connection terminal 100. The terminal 522 is an example of a thirteenth terminal and is connected to the terminal 411 of the combiner 41. The terminal 523 is an example of a fourteenth terminal and is connected to the terminal 515 of the switch circuit 51.

[0094] In this connection configuration, the switch circuit 52 can exclusively connect the terminal 521 to the terminals 522 and 523 based on, for example, a control signal from the RFIC 3. The switch circuit 52 is configured as, for example, an SPDT type switch circuit.

[0095] The switch circuit 52 does not have to be included in the high-frequency circuit 1 C. In this case, the terminal 515 of the switch circuit 51 and the terminal 411 of the combiner 41 may be directly connected to the antenna connection terminal 100 .

[0096] [3.2 Communication Modes of Communication Device 5C and High-Frequency Circuit 1C] Next, two communication modes of the communication device 5C and the high-frequency circuit 1C will be described with reference to Fig. 7 and Fig. 8. In Fig. 7 and Fig. 8, dashed arrows indicate transmission paths and reception paths.

[0097] [3.2.1 First Mode] First, the first mode will be described with reference to Fig. 7. Fig. 7 is a diagram showing the transmission path and reception path in the first mode of the high-frequency circuit 1C according to this embodiment.

[0098] The first mode is a control mode used when the first power class is applied to band A. In the first mode, as shown in Fig. 7, the two transmit filters 31 and 32 for band A are connected to the antenna connection terminal 100 via a combiner 41. Specifically, the switch circuit 51 connects the terminal 511 to the terminal 513, and the terminal 512 to the terminal 514, but does not connect to the terminal 515. Furthermore, the switch circuit 52 connects the terminal 521 to the terminal 522, but does not connect to the terminal 523.

[0099] As a result, the band A transmission signal supplied from the RFIC 3 via the radio frequency input terminal 111 is transmitted to the terminal 412 of the combiner 41 via the power amplifier 11, the transmission filter 31, and the switch circuit 51. Furthermore, the band A transmission signal supplied from the RFIC 3 via the radio frequency input terminal 112 is transmitted to the terminal 413 of the combiner 41 via the power amplifier 12, the transmission filter 32, and the switch circuit 51. Then, the two band A transmission signals input to the terminals 412 and 413 of the combiner 41, respectively, are combined into one signal and transmitted to the antenna connection terminal 100 via the switch circuit 52.

[0100] On the other hand, the band A reception signal supplied from the antenna 2 via the antenna connection terminal 100 is transmitted to the high frequency output terminal 120 via the switch circuit 52, the combiner 41, the switch circuit 51, the reception filter 33 and the low noise amplifier 20.

[0101] [3.2.2 Second Mode] Next, the second mode will be described with reference to Fig. 8. Fig. 8 is a diagram showing the transmission path and reception path in the second mode of the high-frequency circuit 1C according to this embodiment.

[0102] The second mode is a control mode used when the second power class is applied to band A. In the second mode, as shown in Fig. 8 , only one of the two transmit filters 31 and 32 for band A (transmit filter 32 in Fig. 8 ) is connected to the antenna connection terminal 100 without passing through the combiner 41. Specifically, the switch circuit 51 does not connect the terminal 511 to the terminal 513, and connects the terminal 512 to the terminal 515, but is not connected to the terminal 514. Furthermore, the switch circuit 52 connects the terminal 521 to the terminal 523, but is not connected to the terminal 522.

[0103] As a result, the band A transmission signal supplied from the RFIC 3 via the high frequency input terminal 112 is transmitted to the antenna connection terminal 100 via the power amplifier 12 , the transmission filter 32 and the switch circuits 51 and 52 .

[0104] On the other hand, the band A reception signal supplied from the antenna 2 via the antenna connection terminal 100 is transmitted to the high frequency output terminal 120 via the switch circuits 52 and 51 , the reception filter 33 and the low noise amplifier 20 .

[0105] Although the mode applied to the high-frequency circuit 1C is selected based on the power class here, this is not limiting. For example, the mode applied to the high-frequency circuit 1C may be selected based on the signal quality and / or power efficiency required for transmission. Specifically, the first mode may be used when signal quality is prioritized in transmission in band A, and the second mode may be used when power efficiency is prioritized in transmission in band A. Furthermore, the mode applied to the high-frequency circuit 1C may be selected based on a combination of the power class and the signal quality and / or power efficiency. Specifically, the first mode is used when the first power class is applied to band A, and the second mode is used when power efficiency is prioritized in transmission in band A. Here, even when the second power class is applied to band A, the first mode may be used when signal quality is prioritized.

[0106] [3.3 Summary] As described above, the high-frequency circuit 1C according to this embodiment may further include a switch circuit 51, and the switch circuit 51 may include a terminal 511 connected to the output terminal of the transmit filter 31, a terminal 512 connected to the output terminal of the transmit filter 32 and the input terminal of the receive filter 33, a terminal 513 connected to the terminal 412 of the combiner 41, a terminal 514 connected to the terminal 413 of the combiner 41, and a terminal 515 connected to the antenna connection terminal 100.

[0107] This allows the switch circuit 51 to switch between a transmission path that connects the two transmission filters 31 and 32 to the antenna connection terminal 100 via the combiner 41, and a transmission path that connects the transmission filter 32 to the antenna connection terminal 100 without passing through the combiner 41. Therefore, by selecting the transmission path that connects the two transmission filters 31 and 32 to the antenna connection terminal 100 via the combiner 41, it is possible to reduce the power of the transmission signals that pass through each of the transmission filters 31 and 32. Furthermore, by selecting the transmission path that connects the transmission filter 32 to the antenna connection terminal 100 without passing through the combiner 41, it is possible to suppress loss of the transmission signal that has passed through the transmission filter 32.

[0108] For example, the high-frequency circuit 1C according to this embodiment may further include a switch circuit 52, and the switch circuit 52 may include a terminal 521 connected to the antenna connection terminal 100, a terminal 522 connected to the terminal 411 of the combiner 41, and a terminal 523 connected to the terminal 515 of the switch circuit 51.

[0109] This allows the switch circuit 52 to also switch between a transmission path that connects the two transmission filters 31 and 32 to the antenna connection terminal 100 via the combiner 41 and a transmission path that connects the transmission filter 32 to the antenna connection terminal 100 without going through the combiner 41. This makes it possible to improve isolation between the two transmission paths.

[0110] Furthermore, for example, the high-frequency circuit 1C according to the present embodiment may have a first mode and a second mode, and in the first mode, (i) the switch circuit 51 may connect the terminal 511 to the terminal 513 and may connect the terminal 512 to the terminal 514, and (ii) the switch circuit 52 may connect the terminal 521 to the terminal 522, and in the second mode, (i) the switch circuit 51 may connect the terminal 512 to the terminal 515, and (ii) the switch circuit 52 may connect the terminal 521 to the terminal 523.

[0111] According to this, by using the first mode, the two transmit filters 31 and 32 are connected to the antenna connection terminal 100 via the combiner 41, and by using the second mode, the transmit filter 32 is connected to the antenna connection terminal 100 without going through the combiner 41.

[0112] Furthermore, for example, in the high-frequency circuit 1C according to the present embodiment, the first mode may be used when the first power class is applied to band A, and the second mode may be used when the second power class defined by a maximum output power lower than that of the first power class is applied to band A.

[0113] According to this, by using the first mode in a higher power class (i.e., the first power class), it is possible to reduce the maximum power of the transmission signal in Band A that passes through each of the transmission filters 31 and 32, and to reduce the power durability required of each of the two transmission filters 31 and 32. Furthermore, in a lower power class (i.e., the second power class), it is possible to avoid signal loss due to the combiner 41, and to improve power efficiency.

[0114] (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.

[0115] For example, in the circuit configurations of the various circuits according to the above embodiments, other circuit elements and wiring may be inserted between the paths connecting the circuit elements and signal paths disclosed in the drawings. For example, an impedance matching circuit may be inserted between the amplifier and the filter and / or between the filter and the combiner. The impedance matching circuit may be configured, for example, with an inductor and / or a capacitor, but is not limited thereto.

[0116] In each of the above embodiments, the high-frequency circuit may include a filter and / or an amplifier for a band different from band A. For example, a receiving filter having a passband that includes the receiving band of band B, which is different from band A, may be connected to terminal 413 of combiner 41.

[0117] The following describes the features of the high-frequency circuit and communication device described based on the above embodiments.

[0118] <1> A high-frequency circuit comprising: a first transmit filter having a passband that includes a transmit band of an FDD band; a second transmit filter having a passband that includes the transmit band of the FDD band; a third receive filter having a passband that includes the receive band of the FDD band; and a combiner including a first terminal connected to an antenna connection terminal, a second terminal connected to an output terminal of the first transmit filter, and a third terminal connected to an output terminal of the second transmit filter and an input terminal of the third receive filter.

[0119] <2> The high-frequency circuit according to <1>, wherein the combiner is a Wilkinson coupler.

[0120] <3> The high-frequency circuit according to <1>, wherein the combiner is a 90-degree hybrid coupler.

[0121] <4> The radio frequency circuit according to any one of <1> to <3>, further comprising: a power amplifier; and a distributor including a fourth terminal connected to an output terminal of the power amplifier, a fifth terminal connected to an input terminal of the first transmit filter, and a sixth terminal connected to an input terminal of the second transmit filter.

[0122] <5> The radio frequency circuit according to any one of <1> to <3>, further comprising: a first power amplifier connected to an input terminal of the first transmit filter; and a second power amplifier connected to an input terminal of the second transmit filter.

[0123] <6> The high-frequency circuit according to <5>, further comprising a divider including a fourth terminal connected to a high-frequency input terminal, a fifth terminal connected to an input end of the first power amplifier, and a sixth terminal connected to an input end of the second power amplifier.

[0124] <7> The high-frequency circuit according to any one of <1> to <6>, wherein an average power of the transmission band of the FDD band at the third terminal is lower than an average power of the transmission band of the FDD band at the second terminal.

[0125] <8> The high-frequency circuit according to any one of <1> to <7>, further comprising a first switch circuit, the first switch circuit including: a seventh terminal connected to an output terminal of the first transmit filter; an eighth terminal connected to an output terminal of the second transmit filter and an input terminal of the third receive filter; a ninth terminal connected to a second terminal of the combiner; a tenth terminal connected to a third terminal of the combiner; and an eleventh terminal connected to the antenna connection terminal.

[0126] <9> The high-frequency circuit according to <8>, further comprising a second switch circuit, the second switch circuit including: a twelfth terminal connected to the antenna connection terminal; a thirteenth terminal connected to the first terminal of the combiner; and a fourteenth terminal connected to the eleventh terminal of the first switch circuit.

[0127] <10> The high-frequency circuit according to <9>, having a first mode and a second mode, wherein in the first mode, (i) the first switch circuit connects the seventh terminal to the ninth terminal and connects the eighth terminal to the tenth terminal, and (ii) the second switch circuit connects the twelfth terminal to the thirteenth terminal, and in the second mode, (i) the first switch circuit connects the eighth terminal to the eleventh terminal, and (ii) the second switch circuit connects the twelfth terminal to the fourteenth terminal.

[0128] <11> The high-frequency circuit according to <10>, wherein the first mode is used when a first power class is applied to the FDD band, and the second mode is used when a second power class defined by a maximum output power lower than that of the first power class is applied to the FDD band.

[0129] <12> The high-frequency circuit according to any one of <1> to <11>, wherein the FDD band corresponds to a first power class defined by a maximum output power higher than that of power class 3.

[0130] <13> A communication device comprising: a signal processing circuit that processes a high-frequency signal; and the high-frequency circuit according to any one of <1> to <11> that transmits the high-frequency signal between the signal processing circuit and an antenna.

[0131] The present invention can be widely used as a high-frequency circuit disposed in the front end of communication devices such as mobile phones.

[0132] REFERENCE SIGNS LIST 1, 1A, 1B, 1C High frequency circuit 2 Antenna 3 RFIC 4 BBIC 5, 5A, 5B, 5C Communication device 10, 11, 12 Power amplifier 20 Low noise amplifier 31, 32 Transmitting filter 33 Receiving filter 41 Combiner 42 Distributor 51, 52 Switch circuit 100 Antenna connection terminal 110, 111, 112 High frequency input terminal 120 High frequency output terminal 411, 412, 413, 421, 422, 423, 511, 512, 513, 514, 515, 521, 522, 523 Terminal R1 Resistor TL1, TL2, TL3, TL4, TL5, TL6 Transmission line

Claims

1. A high-frequency circuit comprising: a first transmission filter having a passband including a transmission band of an FDD band; a second transmission filter having a passband including a transmission band of the FDD band; a third reception filter having a passband including a reception band of the FDD band; and a synthesizer including a first terminal connected to an antenna connection terminal, a second terminal connected to an output end of the first transmission filter, and a third terminal connected to an output end of the second transmission filter and an input end of the third reception filter.

2. The high-frequency circuit according to claim 1, wherein the synthesizer is a Wilkinson coupler.

3. The high-frequency circuit according to claim 1, wherein the synthesizer is a 90-degree hybrid coupler.

4. The high-frequency circuit according to any one of claims 1 to 3, further comprising: a power amplifier; and a distributor including a fourth terminal connected to an output end of the power amplifier, a fifth terminal connected to an input end of the first transmission filter, and a sixth terminal connected to an input end of the second transmission filter.

5. The high-frequency circuit according to any one of claims 1 to 3, further comprising: a first power amplifier connected to an input end of the first transmission filter; and a second power amplifier connected to an input end of the second transmission filter.

6. The high-frequency circuit according to claim 5, further comprising a distributor including a fourth terminal connected to a high-frequency input terminal, a fifth terminal connected to an input end of the first power amplifier, and a sixth terminal connected to an input end of the second power amplifier.

7. The high-frequency circuit according to any one of claims 1 to 6, wherein an average power of the transmission band of the FDD band at the third terminal is lower than an average power of the transmission band of the FDD band at the second terminal.

8. The high-frequency circuit according to any one of claims 1 to 7, further comprising a first switch circuit, the first switch circuit including: a seventh terminal connected to an output end of the first transmission filter; an eighth terminal connected to an output end of the second transmission filter and an input end of the third reception filter; a ninth terminal connected to a second terminal of the synthesizer; a tenth terminal connected to a third terminal of the synthesizer; and an eleventh terminal connected to the antenna connection terminal.

9. The high-frequency circuit further includes a second switch circuit. The second switch circuit includes a twelfth terminal connected to the antenna connection terminal, a thirteenth terminal connected to the first terminal of the synthesizer, and a fourteenth terminal connected to the eleventh terminal of the first switch circuit. The high-frequency circuit according to claim 8.

10. The high-frequency circuit has a first mode and a second mode. In the first mode, (i) the first switch circuit connects the seventh terminal to the ninth terminal and connects the eighth terminal to the tenth terminal, and (ii) the second switch circuit connects the twelfth terminal to the thirteenth terminal. In the second mode, (i) the first switch circuit connects the eighth terminal to the eleventh terminal, and (ii) the second switch circuit connects the twelfth terminal to the fourteenth terminal. The high-frequency circuit according to claim 9.

11. When the first power class is applied to the FDD band, the first mode is used. When a second power class defined by a maximum output power lower than the first power class is applied to the FDD band, the second mode is used. The high-frequency circuit according to claim 10.

12. The FDD band corresponds to a first power class defined by a maximum output power higher than power class 3. The high-frequency circuit according to any one of claims 1 to 11.

13. A communication device comprising: a signal processing circuit that processes a high-frequency signal; and the high-frequency circuit according to any one of claims 1 to 12 that transmits the high-frequency signal between the signal processing circuit and the antenna.

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