High-frequency circuit and communication device

Abstract

A high-frequency circuit (1) is provided with: a filter (31) having a passband including the transmission bands of FDD bands A and B and at least a part of the reception band of the FDD band A; a filter (32) having a passband including the reception band of the FDD band A; a filter (33) having a passband including the reception band of the FDD band B; and a switch circuit (51) including a common terminal (510) connected to an antenna connection terminal, a selection terminal (511) connected to the filter (31), a selection terminal (512) connected to the filter (32), and a selection terminal (513) connected to the filter (33). The transmission bands of the FDD bands A and B are included in the frequency gap between the reception band of the FDD band A and the reception band of the FDD band B.

Description

High frequency circuits and communication devices

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

[0002] In mobile communication devices such as mobile phones, the number of filters included in front-end circuits is increasing with the advancement of multi-band communication. Patent Document 1 discloses a multiplexer (high-frequency circuit) that can reduce the number of filters by using filters with passbands that include the transmission bands of multiple FDD bands.

[0003] In addition, 3GPP (registered trademark) (3rd Generation Partnership Project) is considering applying high power classes (e.g., power classes 1, 1.5, 2, etc.) that allow higher maximum output power than conventional classes to frequency division duplex (FDD) bands.

[0004] Japanese Patent Application Laid-Open No. 2021-125775

[0005] However, in the conventional technology, a filter having a passband that includes the transmission band of a plurality of FDD bands has a large signal loss, making it difficult to support high power classes.

[0006] Therefore, the present invention provides a high-frequency circuit and a communication device that can reduce the number of filters and the signal loss.

[0007] A high-frequency circuit according to one aspect of the present invention comprises: a first filter having a passband that includes the transmission band of a first FDD band and a second FDD band and at least a portion of the reception band of the first FDD band; a second filter having a passband that includes the reception band of the first FDD band; a third filter having a passband that includes the reception band of the second FDD band; and a first switch circuit including a first common terminal connected to an antenna connection terminal, a first selection terminal connected to the first filter, a second selection terminal connected to the second filter, and a third selection terminal connected to the third filter, wherein the transmission bands of the first FDD band and the second FDD band are included in a frequency gap between the reception band of the first FDD band and the reception band of the second FDD band.

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

[0009] According to the present invention, it is possible to reduce the number of filters and the signal loss.

[0010] FIG. 1 is a circuit configuration diagram of a communication device according to an embodiment. FIG. 2 is a graph showing the pass characteristics of first filters according to an embodiment and a comparative example. FIG. 3 is a diagram showing a first mode of a high-frequency circuit according to an embodiment. FIG. 4 is a diagram showing a second mode of a high-frequency circuit according to an embodiment. FIG. 5 is a diagram showing a third mode of a high-frequency circuit according to an embodiment. FIG. 6 is a graph showing the pass characteristics of first filters according to a modified example and a comparative example.

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

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

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

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

[0015] "Connecting a common terminal to multiple select terminals simultaneously" means that there is a time when the common terminal is connected to multiple select terminals. In other words, "connecting a common terminal to multiple select terminals simultaneously" means that the common terminal is connected to multiple select terminals at a certain point in time. Therefore, "connecting a common terminal to multiple select terminals simultaneously" does not only mean starting to connect the common terminal to all of the multiple select terminals at the same time, but also includes connecting the common terminal to some of the multiple select terminals and then connecting the common terminal to the rest of the multiple select terminals while those connections are continued.

[0016] The "filter passband" is the portion of the frequency spectrum transmitted by the filter, defined as the frequency band between two frequencies 3 dB above the minimum power insertion loss.

[0017] 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 (uplink band and 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.

[0018] "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 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.

[0019] 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.

[0020] A "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, 3GPP is considering making FDD bands such as 2, 5, 8, 13, 25, 26, 28, 66, 71, and 85 compatible with power class 2 in LTE (Long Term Evolution) or 5GNR (5th Generation New Radio).

[0021] 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.

[0022] (Embodiments) The following describes embodiments.

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

[0024] 1 is an exemplary configuration, and communication device 5 may be implemented using any of a wide variety of circuit implementations and circuit technologies, and therefore the description of communication device 5 provided below should not be construed as limiting.

[0025] The communication device 5 can be used to provide wireless connectivity. For example, the communication device 5 can be implemented in a UE in a cellular network (also called a mobile network), such as a mobile phone, a smartphone, a tablet computer, or a wearable device. 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) (also 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.

[0026] 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.

[0027] 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.

[0028] The antenna 2 is connected to the high-frequency circuit 1. The antenna 2 can receive a high-frequency signal from the high-frequency circuit 1 and transmit it to the outside of the communication device 5. Furthermore, the antenna 2 can receive a high-frequency signal from the outside of the communication device 5 and supply it to the high-frequency circuit 1. The antenna 2 does not have to be included in the communication device 5. Furthermore, the communication device 5 may include one or more antennas in addition to the antenna 2.

[0029] The RFIC 3 is an example of a signal processing circuit that processes high-frequency signals. Specifically, the RFIC 3 can perform signal processing on a transmission signal input from the BBIC 4 by up-conversion or the like, and output the high-frequency transmission signal generated by the signal processing to the high-frequency circuit 1. Furthermore, the RFIC 3 can also perform signal processing on a high-frequency reception signal input via the 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, 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.

[0030] 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.

[0031] [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. Note that Fig. 1 is an exemplary circuit configuration, and the high-frequency circuit 1 can be implemented using any of a wide variety of circuit implementations and circuit technologies. Therefore, the description of the high-frequency circuit 1 provided below should not be interpreted as limiting.

[0032] The high frequency circuit 1 includes a power amplifier 10 , a low noise amplifier 20 , filters 31 , 32 , 33 and 34 , switch circuits 51 , 52 and 53 , an antenna connection terminal 100 , a high frequency input terminal 110 , and a high frequency output terminal 120 .

[0033] 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 51 inside the high frequency circuit 1.

[0034] The radio frequency input terminal 110 is an external connection terminal of the radio frequency circuit 1, and is a terminal for receiving a radio frequency signal from the RFIC 3. The radio frequency input terminal 110 is connected to the RFIC 3 outside the radio frequency circuit 1, and is connected to the power amplifier 10 inside the radio frequency circuit 1.

[0035] The radio frequency output terminal 120 is an external connection terminal of the radio frequency circuit 1, and is a terminal for supplying a radio frequency signal to the RFIC 3. The radio frequency output terminal 120 is connected to the RFIC 3 outside the radio frequency circuit 1, and is connected to the low noise amplifier 20 inside the radio frequency circuit 1.

[0036] The power amplifier 10 is connected between the radio frequency input terminal 110 and the switch circuit 52. Specifically, the input terminal of the power amplifier 10 is connected to the radio frequency input terminal 110, and the output terminal of the power amplifier 10 is connected to a common terminal 520 of the switch circuit 52. The power amplifier 10 can amplify transmission signals of FDD bands A and B using power supplied from a power supply (not shown).

[0037] 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 include silicon germanium (SiGe) and gallium arsenide (GaAs). The amplifying transistors of the power amplifier 10 are not limited to HBTs. 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. Furthermore, some or all of the amplifying transistors of the power amplifier 10 may be complementary metal oxide semiconductors (CMOS) or may be manufactured using a silicon-on-insulator (SOI) process. In this case, silicon (Si) may be used as the semiconductor material.

[0038] The low-noise amplifier 20 is connected between the switch circuit 53 and the high-frequency output terminal 120. Specifically, the input terminal of the low-noise amplifier 20 is connected to a common terminal 530 of the switch circuit 53, and 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 received signals of FDD bands A and B using power supplied from a power supply (not shown).

[0039] The low-noise amplifier 20 can be configured with field-effect transistors (FETs) and can be manufactured using semiconductor materials. Examples of semiconductor materials that can be used include silicon monocrystal (Si), gallium nitride (GaN), and silicon carbide (SiC). Note that the amplifying transistors of the low-noise amplifier 20 are not limited to FETs. For example, some or all of the amplifying transistors of the low-noise amplifier 20 may be bipolar transistors.

[0040] The filter 31 is an example of a first filter, and is a bandpass filter having a passband that includes the transmission bands of FDD bands A and B and at least a portion of the reception band of FDD band A. The filter 31 is capable of passing a transmission signal of FDD band A (A-Tx(PC2)) transmitted in power class 2 and a transmission signal of FDD band B (B-Tx(PC3)) transmitted in power class 3. The filter 31 can attenuate a reception signal of FDD band B, but does not necessarily have to attenuate a reception signal of FDD band A. One end of the filter 31 is connected to a selection terminal 511 of the switch circuit 51, and the other end of the filter 31 is connected to a selection terminal 521 of the switch circuit 52.

[0041] The filter 32 is an example of a second filter, and is a bandpass filter having a passband that includes the receive band of FDD band A. The filter 32 is capable of passing a receive signal (A-Rx) of FDD band A and attenuating a transmit signal of FDD band A. One end of the filter 32 is connected to a selection terminal 512 of the switch circuit 51, and the other end of the filter 32 is connected to a selection terminal 531 of the switch circuit 53.

[0042] The filter 33 is an example of a third filter, and is a bandpass filter having a passband that includes the receive band of FDD band B. The filter 33 is capable of passing receive signals (B-Rx) of FDD band B and attenuating transmit signals of FDD band B. One end of the filter 33 is connected to a selection terminal 513 of the switch circuit 51, and the other end of the filter 33 is connected to a selection terminal 532 of the switch circuit 53.

[0043] The filter 34 is an example of a fourth filter, and is a bandpass filter having a passband that includes the transmission band of FDD band A. The filter 34 is capable of passing a transmission signal (A-Tx(PC3)) of FDD band A that is transmitted in power class 3, and is capable of attenuating a reception signal of FDD band A. One end of the filter 34 is connected to a selection terminal 514 of the switch circuit 51, and the other end of the filter 34 is connected to a selection terminal 522 of the switch circuit 52. The filter 34 does not necessarily have to be included in the high-frequency circuit 1.

[0044] The filters 31 to 34 may be, but are not limited to, surface acoustic wave (SAW) filters, bulk acoustic wave (BAW) filters, LC resonant filters, dielectric resonant filters, or any combination thereof.

[0045] The switch circuit 51 is an example of a first switch circuit and includes a common terminal 510 and selection terminals 511, 512, 513, and 514. The common terminal 510 is an example of a first common terminal and is connected to the antenna connection terminal 100. The selection terminal 511 is an example of a first selection terminal and is connected to the filter 31. The selection terminal 512 is an example of a second selection terminal and is connected to the filter 32. The selection terminal 513 is an example of a third selection terminal and is connected to the filter 33. The selection terminal 514 is an example of a fourth selection terminal and is connected to the filter 34.

[0046] In such a connection configuration, the switch circuit 51 can switch between connection and disconnection between the common terminal 510 and each of the selection terminals 511 to 514, for example, based on a control signal from the RFIC 3. In other words, the switch circuit 51 can switch between connection and disconnection between the antenna connection terminal 100 and each of the filters 31 to 34. The switch circuit 51 is configured, for example, as a multi-connection type switch circuit.

[0047] The switch circuit 52 is an example of a second switch circuit and is connected between the power amplifier 10 and the filters 31 and 34. Specifically, the switch circuit 52 includes a common terminal 520 and selection terminals 521 and 522. The common terminal 520 is an example of a second common terminal and is connected to the output end of the power amplifier 10. The selection terminal 521 is an example of a fifth selection terminal and is connected to the filter 31. The selection terminal 522 is an example of a sixth selection terminal and is connected to the filter 34.

[0048] In such a connection configuration, the switch circuit 52 can selectively connect the common terminal 520 to the selection terminals 521 and 522, for example, based on a control signal from the RFIC 3. That is, the switch circuit 52 can switch the connection of the power amplifier 10 between the filters 31 and 34. The switch circuit 52 is configured, for example, as an SPDT (Single-Pole Double-Throw) type switch circuit.

[0049] The switch circuit 53 is an example of a third switch circuit, and is connected between the low-noise amplifier 20 and the filters 32 and 33. Specifically, the switch circuit 53 includes a common terminal 530 and selection terminals 531 and 532. The common terminal 530 is an example of a third common terminal, and is connected to the input end of the low-noise amplifier 20. The selection terminal 531 is an example of a seventh selection terminal, and is connected to the filter 32. The selection terminal 532 is an example of an eighth selection terminal, and is connected to the filter 33.

[0050] In such a connection configuration, the switch circuit 53 can selectively connect the common terminal 530 to the selection terminals 531 and 532, for example, based on a control signal from the RFIC 3. That is, the switch circuit 53 can switch the connection of the low-noise amplifier 20 between the filters 32 and 33. The switch circuit 53 is configured, for example, as an SPDT type switch circuit.

[0051] The switch circuits 51 to 53 can be configured with a plurality of MOSFETs (Metal-Oxide-Semiconductor Field-Effect Transistors) and are implemented, for example, in one semiconductor integrated circuit. The switch circuits 51 to 53 may be implemented individually in three semiconductor integrated circuits, or may be implemented in any combination in two semiconductor integrated circuits.

[0052] 1 is an example, and the circuit configuration of the high-frequency circuit 1 is not limited to the configuration in FIG. 1. For example, the high-frequency circuit 1 may include one or more additional filters for other frequency bands. The one or more additional filters may be connected to any of the selection terminals 511 to 514 of the switch circuit 51, or may be connected to an additional selection terminal of the switch circuit 51.

[0053] 3. Frequency Bands and Pass Characteristics of Filter 31 Now, the FDD bands A and B and the pass characteristics of filter 31 will be described with reference to Fig. 2. Fig. 2 is a graph showing the pass characteristics of filter 31 according to the present embodiment and a comparative example. In Fig. 2, the horizontal axis represents frequency, and the vertical axis represents gain.

[0054] First, FDD bands A and B used in this embodiment will be described. FDD bands A and B are examples of a first FDD band and a second FDD band, respectively. FDD bands A and B are frequency bands for a communication system constructed using a radio access technology (RAT), and are defined in advance by a standardization organization (e.g., 3GPP and the Institute of Electrical and Electronics Engineers (IEEE)). Examples of communication systems include a 5G NR system, an LTE system, and a WLAN (Wireless Local Area Network) system.

[0055] 2, the transmission band (A-Tx) of FDD band A and the transmission band (B-Tx) of FDD band B are included in the frequency gap between the reception band (A-Rx) of FDD band A and the reception band (B-Rx) of FDD band B. Note that FDD band A supports power class 2, while FDD band B does not support power class 2.

[0056] In this embodiment, the transmission band of FDD band A and the transmission band of FDD band B are higher than the reception band of FDD band B and lower than the reception band of FDD band A. As FDD band A that satisfies these conditions, Band 8 for LTE or n8 for 5G NR can be used, and as FDD band B, Band 20 for LTE or n20 for 5G NR can be used. Note that FDD bands A and B are not limited to these.

[0057] Next, the pass characteristics of the filter 31 according to this embodiment will be described in comparison with the pass characteristics of a filter according to a comparative example. The filter 31 according to this embodiment is a filter that passes transmission signals of bands A and B and attenuates reception signals of band B. In other words, the filter 31 according to this embodiment is a filter that requires sufficient attenuation in the reception band of band B but does not require sufficient attenuation in the reception band of band A. On the other hand, the filter according to the comparative example is a filter that passes transmission signals of bands A and B and attenuates reception signals of bands A and B. In other words, the filter according to the comparative example is a filter that requires sufficient attenuation in the reception bands of bands A and B.

[0058] The pass band of the filter 31 includes the transmit band (A-Tx) of band A, the transmit band (B-Tx) of band B, and part of the receive band (A-Rx) of band A, but does not include the receive band (B-Rx) of band B or the remainder of the receive band (A-Rx) of band A. Specifically, the lower end of the pass band of the filter 31 is lower than the lower end of the transmit band (B-Tx) of band B and higher than the upper end of the receive band (B-Rx) of band B. The upper end of the pass band of the filter 31 is higher than the lower end of the receive band (A-Rx) of band A and lower than the upper end of the receive band (A-Rx) of band A.

[0059] As described above, in this embodiment, the passband of filter 31 includes a portion of the reception band (A-Rx) of band A, so that a steep attenuation between the transmission band (A-Tx) and reception band (A-Rx) of band A is not necessary, and the gain of the passband in the transmission band of FDD band A can be improved compared to the comparative example, thereby reducing the passband loss.

[0060] On the other hand, the pass band of the filter according to the comparative example includes the transmission band (A-Tx) of band A and the transmission band (B-Tx) of band B, but does not include the reception band (A-Rx) of band A. Specifically, the low end of the pass band of the filter according to the comparative example is lower than the low end of the transmission band (B-Tx) of band B and higher than the high end of the reception band (B-Rx) of band B. The high end of the pass band of the filter according to the comparative example is higher than the high end of the transmission band (A-Tx) of band A and lower than the low end of the reception band (A-Rx) of band A.

[0061] As described above, in the comparative example, the passband of the filter cannot include the receive band (A-Rx) of band A, so a steep attenuation is required between the transmit band (A-Tx) and receive band (A-Rx) of band A, which reduces the gain of the passband in the transmit band of FDD band A more than in this embodiment and increases the passband loss.

[0062] [4. Multiple Communication Modes] Next, multiple communication modes of the high-frequency circuit 1 will be described.

[0063] [4.1. First Mode] First, the first mode included in the multiple communication modes will be described with reference to Fig. 3. Fig. 3 is a diagram showing the first mode of the high-frequency circuit 1 according to this embodiment. In the following figures, dashed arrows represent the transmission path and reception path of the high-frequency signal.

[0064] The first mode is a communication mode for transmitting FDD band A signals in power class 2 and for transmitting and receiving FDD band A signals in half duplex. That is, in the first mode, the maximum output power of FDD band A signals is allowed to be 26 dBm, which is the maximum output power of power class 2, and transmission and reception of FDD band A signals are switched over time.

[0065] In this first mode, switch circuit 51 switches the connection of common terminal 510 over time between selection terminals 511 and 512. Switch circuit 52 connects common terminal 520 to selection terminal 521. Switch circuit 53 connects common terminal 530 to selection terminal 531.

[0066] As a result, the transmit signal of band A is transmitted from the RFIC 3 to the antenna 2 via the radio frequency input terminal 110, the power amplifier 10, the switch circuit 52, the filter 31, the switch circuit 51, and the antenna connection terminal 100. The receive signal of band A is transmitted from the antenna 2 to the RFIC 3 via the antenna connection terminal 100, the switch circuit 51, the filter 32, the switch circuit 53, the low noise amplifier 20, and the radio frequency output terminal 120.

[0067] [4.2. Second Mode] Next, the second mode will be described with reference to Fig. 4. Fig. 4 is a diagram showing the second mode of the high-frequency circuit 1 according to this embodiment.

[0068] The second mode is a communication mode for transmitting FDD band A signals at power class 3 and for transmitting and receiving FDD band A signals in full duplex. That is, in the second mode, the maximum output power of FDD band A signals is allowed to be 23 dBm, which is the maximum output power of power class 3, and transmission and reception of FDD band A signals are performed simultaneously.

[0069] In this second mode, the switch circuit 51 simultaneously connects the common terminal 510 to the selection terminals 512 and 514. The switch circuit 52 connects the common terminal 520 to the selection terminal 522. The switch circuit 53 connects the common terminal 530 to the selection terminal 531.

[0070] As a result, the transmit signal of band A is transmitted from the RFIC 3 to the antenna 2 via the radio frequency input terminal 110, the power amplifier 10, the switch circuit 52, the filter 34, the switch circuit 51, and the antenna connection terminal 100. The receive signal of band A is transmitted from the antenna 2 to the RFIC 3 via the antenna connection terminal 100, the switch circuit 51, the filter 32, the switch circuit 53, the low noise amplifier 20, and the radio frequency output terminal 120.

[0071] [4.3. Third Mode] Next, the third mode will be described with reference to Fig. 5. Fig. 5 is a diagram showing the second mode of the high-frequency circuit 1 according to this embodiment.

[0072] The third mode is a communication mode for transmitting FDD band B signals in power class 3 and for transmitting and receiving FDD band B signals in full duplex. That is, in the third mode, the maximum output power of FDD band B signals is allowed to be 23 dBm, which is the maximum output power of power class 3, and transmission and reception of FDD band B signals are performed simultaneously.

[0073] In this third mode, the switch circuit 51 simultaneously connects the common terminal 510 to the selection terminals 511 and 513. The switch circuit 52 connects the common terminal 520 to the selection terminal 521. The switch circuit 53 connects the common terminal 530 to the selection terminal 532.

[0074] As a result, the transmit signal of band B is transmitted from the RFIC 3 to the antenna 2 via the radio frequency input terminal 110, the power amplifier 10, the switch circuit 52, the filter 31, the switch circuit 51, and the antenna connection terminal 100. The receive signal of band B is transmitted from the antenna 2 to the RFIC 3 via the antenna connection terminal 100, the switch circuit 51, the filter 33, the switch circuit 53, the low noise amplifier 20, and the radio frequency output terminal 120.

[0075] [5. Summary] As described above, the high-frequency circuit 1 according to this embodiment includes: filter 31 having a passband that includes the transmission band of FDD bands A and B and at least a part of the reception band of FDD band A; filter 32 having a passband that includes the reception band of FDD band A; filter 33 having a passband that includes the reception band of FDD band B; and switch circuit 51 that includes common terminal 510 connected to the antenna connection terminal, selection terminal 511 connected to filter 31, selection terminal 512 connected to filter 32, and selection terminal 513 connected to filter 33; and the transmission band of FDD bands A and B is included in the frequency gap between the reception band of FDD band A and the reception band of FDD band B.

[0076] In this configuration, the passband of filter 31 includes the transmission bands of FDD bands A and B, allowing for a reduction in the number of filters compared to a configuration in which two filters are included that correspond one-to-one to the transmission bands of FDD bands A and B. Furthermore, the passband of filter 31 includes at least a portion of the reception band of FDD band A. Therefore, half-duplex communication can be performed in FDD band A by using filters 31 and 32, and full-duplex communication can be performed in FDD band B by using filters 31 and 33. Such filter 31 eliminates the need for a steep attenuation between the transmission band and reception band of FDD band A, allowing for a reduction in pass loss in the transmission band of FDD band A. In other words, the high-frequency circuit 1 allows for a reduction in the number of filters and a reduction in signal loss.

[0077] For example, the high-frequency circuit 1 according to this embodiment may further include a filter 34 having a passband that includes the transmission band of FDD band A, and the switch circuit 51 may further include a selection terminal 514 connected to the filter 34.

[0078] According to this, full-duplex communication can be performed even in FDD band A by using filters 32 and 34.

[0079] Furthermore, for example, in the high-frequency circuit 1 according to the present embodiment, in a first mode in which a signal of FDD band A is transmitted in a first power class (e.g., power class 2) defined by a maximum output power higher than that of a second power class (e.g., power class 3), the switch circuit 51 may switch the connection of the common terminal 510 between the selection terminals 511 and 512 over time.

[0080] According to this, in the first power class, which allows a higher maximum output power, the filters 31 and 32 can be switched over time to perform half-duplex communication in FDD band A. In particular, in the first power class, the output power is higher, so the effect of reducing the transmission loss in the filter 31 is significant.

[0081] Furthermore, for example, in the high-frequency circuit 1 according to this embodiment, in the second mode in which a signal of FDD band A is transmitted in the second power class, the switch circuit 51 may connect the common terminal 510 to the selection terminals 512 and 514 simultaneously.

[0082] According to this, in the second power class, which is limited to a lower maximum output power, the filters 32 and 34 can be used simultaneously, enabling full-duplex communication in FDD band A. In the second power class, since the output power is lower, improving the communication speed is more effective than reducing the insertion loss.

[0083] Furthermore, for example, in the high-frequency circuit 1 according to this embodiment, in the third mode in which a signal of FDD band B is transmitted in the second power class, the switch circuit 51 may connect the common terminal 510 to the selection terminals 511 and 513 simultaneously.

[0084] This allows full-duplex communication in FDD band B to be performed using filters 31 and 33 simultaneously.

[0085] For example, the high-frequency circuit 1 according to this embodiment may further include a power amplifier 10, and a switch circuit 52 including a common terminal 520 connected to the power amplifier 10, a selection terminal 521 connected to the filter 31, and a selection terminal 522 selected by the filter 34.

[0086] This allows the power amplifier 10 to be used to amplify the transmission signal of FDD band A in the first power class and to amplify the transmission signals of FDD bands A and B in the second power class, thereby reducing the number of power amplifiers included in the high-frequency circuit 1.

[0087] For example, the high-frequency circuit 1 according to this embodiment may further include a low-noise amplifier 20, and a switch circuit 53 including a common terminal 530 connected to the low-noise amplifier 20, a selection terminal 531 connected to the filter 32, and a selection terminal 532 connected to the filter 33.

[0088] This allows the low noise amplifier 20 to be used to amplify the received signals of the FDD bands A and B, and the number of low noise amplifiers included in the high frequency circuit 1 can be reduced.

[0089] Also, for example, in the high-frequency circuit 1 according to this embodiment, the FDD band A may be Band 8 for LTE or n8 for 5G NR, and the FDD band B may be Band 20 for LTE or n20 for 5G NR.

[0090] As a result, the high-frequency circuit 1 can achieve the above-mentioned effects in an LTE system and / or a 5G NR system.

[0091] The communication device 5 according to this embodiment also includes an RFIC 3 that processes high-frequency signals, and a high-frequency circuit 1 that is configured to transmit high-frequency signals between the RFIC 3 and the antenna 2 .

[0092] This allows the effects of the high frequency circuit 1 to be realized in the communication device 5.

[0093] (Modification) Next, a modification of the above embodiment will be described. In this modification, the main difference from the above embodiment is the frequency band used. Below, this modification will be described with reference to FIG. 6, focusing on the differences from the above embodiment.

[0094] 6 is a graph showing the pass characteristics of the filter 31 according to this modification and the comparative example, in which the horizontal axis represents frequency and the vertical axis represents gain.

[0095] The FDD bands A and B used in this modified example will now be described. FDD bands A and B are examples of the first FDD band and the second FDD band, respectively. As in the embodiment, the transmission band (A-Tx) of FDD band A and the transmission band (B-Tx) of FDD band B are included in the frequency gap between the reception band (A-Rx) of FDD band A and the reception band (B-Rx) of FDD band B. Note that FDD band A supports power class 2, while FDD band B does not support power class 2.

[0096] In this modification, the transmission band of FDD band A and the transmission band of FDD band B are higher than the reception band of FDD band A and lower than the reception band of FDD band B. As FDD band A that satisfies these conditions, Band 71 for LTE or n71 for 5G NR can be used, and as FDD band B, Band 12 for LTE or n12 for 5G NR can be used. Note that FDD bands A and B are not limited to these.

[0097] Next, the pass characteristics of the filter 31 according to this modification will be described in comparison with the pass characteristics of a filter according to a comparative example. Like the filter 31 according to the above embodiment, the filter 31 according to this modification is a filter that passes transmission signals of bands A and B and attenuates reception signals of band B. In other words, the filter 31 according to this modification is a filter that requires sufficient attenuation in the reception band of band B but does not require sufficient attenuation in the reception band of band A. On the other hand, the filter according to the comparative example is a filter that passes transmission signals of bands A and B and attenuates reception signals of bands A and B. In other words, the filter according to the comparative example is a filter that requires sufficient attenuation in the reception bands of bands A and B.

[0098] The pass band of the filter 31 includes the transmit band (A-Tx) of band A, the transmit band (B-Tx) of band B, and part of the receive band (A-Rx) of band A, but does not include the receive band (B-Rx) of band B or the remainder of the receive band (A-Rx) of band A. Specifically, the lower end of the pass band of the filter 31 is lower than the upper end of the receive band (A-Rx) of band A, and higher than the lower end of the receive band (A-Rx) of band A. The upper end of the pass band of the filter 31 is higher than the upper end of the transmit band (B-Tx) of band B, and lower than the lower end of the receive band (B-Rx) of band B.

[0099] On the other hand, the pass band of the filter according to the comparative example includes the transmission band (A-Tx) of band A and the transmission band (B-Tx) of band B, but does not include the reception band (A-Rx) of band A and the reception band (B-Rx) of band B. Specifically, the low end of the pass band of the filter according to the comparative example is lower than the low end of the transmission band (A-Tx) of band A and higher than the high end of the reception band (A-Rx) of band A. The high end of the pass band of the filter according to the comparative example is higher than the high end of the transmission band (B-Tx) of band B and lower than the low end of the reception band (B-Rx) of band B.

[0100] As described above, in the high-frequency circuit 1 according to this modified example, the FDD band A may be Band 71 for LTE or n71 for 5G NR, and the FDD band B may be Band 12 for LTE or n12 for 5G NR.

[0101] As a result, the high-frequency circuit 1 can achieve the above-mentioned effects in an LTE system and / or a 5G NR system.

[0102] (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 and communication device.

[0103] For example, in the circuit configurations of the high-frequency circuits and communication devices 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, an impedance matching circuit may be connected between the power amplifier 10 and the switch circuit 52, between the low-noise amplifier 20 and the switch circuit 53, between each of the filters 31 to 34 and the switch circuit 51, or between the switch circuit 51 and the antenna connection terminal 100. Furthermore, for example, a coupler may be connected between the switch circuit 51 and the antenna connection terminal 100.

[0104] In addition, for example, in the above embodiment, the first power class and the second power class are power class 2 and power class 3, respectively, but the combination of the first power class and the second power class is not limited to this. For example, the first power class may be power class 1 or 1.5, and the second power class may be power class 5.

[0105] The following describes the features of the high frequency circuit and communication device described based on the above embodiments.

[0106] <1> A high-frequency circuit comprising: a first filter having a passband that includes a transmission band of a first FDD band and a second FDD band and at least a part of a reception band of the first FDD band; a second filter having a passband that includes the reception band of the first FDD band; a third filter having a passband that includes the reception band of the second FDD band; and a first switch circuit including a first common terminal connected to an antenna connection terminal, a first selection terminal connected to the first filter, a second selection terminal connected to the second filter, and a third selection terminal connected to the third filter, wherein the transmission bands of the first FDD band and the second FDD band are included in a frequency gap between the reception band of the first FDD band and the reception band of the second FDD band.

[0107] <2> The high-frequency circuit according to <1>, wherein the high-frequency circuit further includes a fourth filter having a passband including a transmission band of the first FDD band, and the first switch circuit further includes a fourth selection terminal connected to the fourth filter.

[0108] <3> The high-frequency circuit according to <2>, wherein in a first mode in which a signal of the first FDD band is transmitted in a first power class defined by a maximum output power higher than that of a second power class, the first switch circuit switches the connection of the first common terminal between the first selection terminal and the second selection terminal over time.

[0109] <4> The high-frequency circuit according to <3>, wherein in a second mode in which a signal in the first FDD band is transmitted at the second power class, the first switch circuit simultaneously connects the first common terminal to the second selection terminal and the fourth selection terminal.

[0110] <5> The high-frequency circuit according to <4>, wherein in a third mode in which a signal in the second FDD band is transmitted at the second power class, the first switch circuit simultaneously connects the first common terminal to the first selection terminal and the third selection terminal.

[0111] <6> The radio frequency circuit according to any one of <2> to <5>, further comprising: a power amplifier; and a second switch circuit including a second common terminal connected to the power amplifier, a fifth selection terminal connected to the first filter, and a sixth selection terminal selected by the fourth filter.

[0112] <7> The radio frequency circuit according to any one of <1> to <6>, further comprising: a low noise amplifier; and a third switch circuit including a third common terminal connected to the low noise amplifier, a seventh selection terminal connected to the second filter, and an eighth selection terminal connected to the third filter.

[0113] <8> The radio frequency circuit according to any one of <1> to <7>, wherein the first FDD band is Band 8 for LTE or n8 for 5G NR, and the second FDD band is Band 20 for LTE or n20 for 5G NR.

[0114] <9> The radio frequency circuit according to any one of <1> to <7>, wherein the first FDD band is Band 71 for LTE or n71 for 5G NR, and the second FDD band is Band 12 for LTE or n12 for 5G NR.

[0115] <10> 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 <9> configured to transmit the high-frequency signal between the signal processing circuit and an antenna.

[0116] The present invention can be widely used as a high-frequency circuit disposed in the front end of communication devices such as mobile phones.

[0117] REFERENCE SIGNS LIST 1 High frequency circuit 2 Antenna 3 RFIC 4 BBIC 5 Communication device 10 Power amplifier 20 Low noise amplifier 31, 32, 33, 34 Filter 51, 52, 53 Switch circuit 100 Antenna connection terminal 110 High frequency input terminal 120 High frequency output terminal 510, 520, 530 Common terminal 511, 512, 513, 514, 521, 522, 531, 532 Selection terminal

Claims

1. A high-frequency circuit comprising: a first filter having a passband that includes a transmission band of a first FDD band and a second FDD band and at least a portion of the reception band of the first FDD band; a second filter having a passband that includes the reception band of the first FDD band; a third filter having a passband that includes the reception band of the second FDD band; and a first switch circuit including a first common terminal connected to an antenna connection terminal, a first selection terminal connected to the first filter, a second selection terminal connected to the second filter, and a third selection terminal connected to the third filter, wherein the transmission bands of the first FDD band and the second FDD band are included in a frequency gap between the reception band of the first FDD band and the reception band of the second FDD band.

2. The high-frequency circuit according to claim 1, wherein the high-frequency circuit further comprises a fourth filter having a passband that includes a transmission band of the first FDD band, and the first switch circuit further includes a fourth selection terminal connected to the fourth filter.

3. The high-frequency circuit according to claim 2, wherein in a first mode in which a signal in the first FDD band is transmitted in a first power class defined by a maximum output power higher than that of a second power class, the first switch circuit switches the connection of the first common terminal between the first selection terminal and the second selection terminal over time.

4. The high-frequency circuit according to claim 3, wherein in a second mode in which a signal in the first FDD band is transmitted at the second power class, the first switch circuit simultaneously connects the first common terminal to the second selection terminal and the fourth selection terminal.

5. The high-frequency circuit according to claim 4, wherein in a third mode in which a signal in the second FDD band is transmitted at the second power class, the first switch circuit simultaneously connects the first common terminal to the first selection terminal and the third selection terminal.

6. The radio frequency circuit according to any one of claims 2 to 5, further comprising: a power amplifier; and a second switch circuit including a second common terminal connected to the power amplifier, a fifth selection terminal connected to the first filter, and a sixth selection terminal selected by the fourth filter.

7. The radio frequency circuit according to any one of claims 1 to 6, further comprising: a low noise amplifier; and a third switch circuit including a third common terminal connected to the low noise amplifier, a seventh selection terminal connected to the second filter, and an eighth selection terminal connected to the third filter.

8. The radio frequency circuit according to any one of claims 1 to 7, wherein the first FDD band is Band 8 for LTE or n8 for 5G NR, and the second FDD band is Band 20 for LTE or n20 for 5G NR.

9. The radio frequency circuit according to any one of claims 1 to 7, wherein the first FDD band is Band 71 for LTE or n71 for 5G NR, and the second FDD band is Band 12 for LTE or n12 for 5G NR.

10. 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 9 configured to transmit the high-frequency signal between the signal processing circuit and an antenna.

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