Signal separation circuit, transmission / reception circuit, and wireless device

Abstract

Provided is a signal separation circuit capable of reducing sneak interference from a transmission circuit to a reception circuit and achieving reductions in insertion loss of a circuit element and weight. The signal separation circuit is provided with: a transmission path circuit on a transmitter side, a transmission path circuit on an antenna side, and a transmission path circuit on a receiver side, each having a first port, a second port connected to the first port via a transmission path with a 90° phase delay, and a third port connected to the first port via a transmission path with a 180° phase delay; a first circulator in which the second port of the transmission path circuit on the transmitter side, the third port of the transmission path circuit on the antenna side, and the second port of the transmission path circuit on the receiver side are connected in order; and a second circulator in which the third port of the transmission path circuit on the transmitter side, the second port of the transmission path circuit on the antenna side, and the third port of the transmission path circuit on the receiver side are connected in order.

Description

Signal separation circuit, transmitting / receiving circuit, and radio device

[0001] The present invention relates to a signal separation circuit that separates and processes a transmission signal and a reception signal transmitted and received via an antenna, and to a transmission / reception circuit and a radio device that have the signal separation circuit.

[0002] Conventionally, circuits configured using circuit elements such as duplexers, isolators, circulators, and bandpass filters have been known as signal separation circuits that separate and process transmission signals and reception signals in wireless communications such as full-duplex and FDD (frequency division multiplexing) systems.

[0003] For example, Patent Document 1 discloses a circuit of a transceiver device that includes a duplexer connected to an antenna, a low-noise amplifier circuit that amplifies the output signal of the duplexer, a power amplifier that amplifies the transmission signal, and an isolator inserted between the duplexer and the power amplifier.

[0004] Furthermore, Patent Document 2 discloses a communication circuit including a first filter that filters a transmission signal supplied from a transmitting unit, a second filter that is a variable filter that filters a reception signal and supplies the filtered reception signal to a receiving unit, a circulator that supplies the transmission signal supplied from the first filter to an antenna and also supplies a reception signal received from outside via the antenna to the second filter, and control means that controls the frequency band filtered by the second filter.

[0005] JP 2006-166277 A JP 2015-146527 A

[0006] In the above-mentioned signal separation circuit, there is a need to reduce the loop interference caused by the transmission signal transmitted from the transmitter looping back to the receiver and interfering with it, as well as to reduce the insertion loss and weight of the circuit elements.

[0007] A signal separation circuit according to one aspect of the present invention is a signal separation circuit that separates and processes a transmission signal and a reception signal transmitted and received via an antenna. This signal separation circuit includes a transmitter-side transmission path circuit, an antenna-side transmission path circuit, a receiver-side transmission path circuit, a first circulator, and a second circulator. The transmitter-side transmission path circuit has a first port to which a transmission signal from the transmitter is input, a second port connected to the first port by a transmission path with a 90° phase delay, and a third port connected to the first port by a transmission path with a 180° phase delay. The antenna-side transmission path circuit has a first port connected to the antenna, a second port connected to the first port by a transmission path with a 90° phase delay, and a third port connected to the first port by a transmission path with a 180° phase delay. The receiver-side transmission line circuit has a first port that outputs a received signal to the receiver, a second port connected to the first port by a transmission line with a 90° phase delay, and a third port connected to the first port by a transmission line with a 180° phase delay. The first circulator has three ports arranged in a circular manner to enable unidirectional transmission between adjacent ports, and the second port of the transmitter-side transmission line circuit, the third port of the antenna-side transmission line circuit, and the second port of the receiver-side transmission line circuit are connected to the three ports in the circular arrangement, in that order. The second circulator has three ports arranged in a circular manner to enable unidirectional transmission between adjacent ports, and the third port of the transmitter-side transmission line circuit, the second port of the antenna-side transmission line circuit, and the third port of the receiver-side transmission line circuit are connected to the three ports in the circular arrangement, in that order.

[0008] In the signal separation circuit, the transmitter-side transmission line circuit, the antenna-side transmission line circuit, and the receiver-side transmission line circuit may each be a 90° hybrid circuit having a fourth port connected to the first port by a transmission line with a 90° phase delay, and a termination impedance element may be connected to the fourth port of the 90° hybrid circuit.

[0009] A signal separation circuit according to another aspect of the present invention is a signal separation circuit that separates and processes a transmission signal and a reception signal transmitted and received via an antenna. This signal separation circuit includes a transmitter-side transmission line circuit, an antenna-side transmission line circuit, a receiver-side transmission line circuit, a first circulator, and a second circulator. The transmitter-side transmission line circuit has a first port to which a transmission signal from the transmitter is input, a second port connected to the first port via a transmission line with no phase delay, and a third port connected to the first port via a transmission line with a 90° phase delay. The antenna-side transmission line circuit has a first port connected to the antenna, a second port connected to the first port via a transmission line with no phase delay, and a third port connected to the first port via a transmission line with a 90° phase delay. The receiver-side transmission line circuit has a first port to output a reception signal to the receiver, a second port connected to the first port via a transmission line with a 90° phase delay, and a third port connected to the first port via a transmission line with a 180° phase delay. The first circulator has three ports arranged in a circular manner to enable unidirectional transmission between adjacent ports, and the second port of the transmitter-side transmission line circuit, the third port of the antenna-side transmission line circuit, and the second port of the receiver-side transmission line circuit are connected to the three ports in that order. The second circulator has three ports arranged in a circular manner to enable unidirectional transmission between adjacent ports, and the third port of the transmitter-side transmission line circuit, the second port of the antenna-side transmission line circuit, and the third port of the receiver-side transmission line circuit are connected to the three ports in that order.

[0010] In the signal separation circuit, the transmitter-side transmission line circuit may include a branching circuit that branches a transmission signal input to the first port and outputs the branched signal to the second port and a relay port, and a phase shifter with a 90° phase delay connected between the relay port and the third port, the antenna-side transmission line circuit may include a branching circuit that branches a reception signal input to the first port and outputs the branched signal to the second port and a relay port, and a phase shifter with a 90° phase delay provided between the relay port and the third port, and the receiver-side transmission line circuit may be a 90° hybrid circuit having a fourth port connected to the first port by a transmission line with a 90° phase delay, and a terminating impedance element may be connected to the fourth port of the 90° hybrid circuit.

[0011] According to yet another aspect of the present invention, there is provided a transceiver circuit for transmitting and receiving signals in an FDD (Frequency Division Duplex) system via a plurality of different frequency bands, the transceiver circuit including any one of the signal separation circuits described above. Here, the transceiver circuit may include a power amplifier for amplifying the transmission signal, a transmission band filter provided between a first port of a transmission line circuit on the transmitter side and an output port of the power amplifier, a low-noise amplifier for amplifying a reception signal, and a reception band filter provided between the first port of the transmission line circuit on the receiver side and an input port of the low-noise amplifier.

[0012] According to yet another aspect of the present invention, there is provided a transmission / reception circuit for transmitting and receiving full-duplex signals via the same frequency band, the transmission / reception circuit including any one of the signal separation circuits described above. This transmission / reception circuit may include: a power amplifier for amplifying the transmission signal; an isolator provided between a first port of the transmission path circuit on the transmitter side and an output port of the power amplifier; a low-noise amplifier for amplifying the reception signal; a signal generation unit for generating an interference suppression signal by multiplying the transmission signal branched from the output port of the power amplifier by a weight calculated in advance based on information about a transmission path response between the output port of the power amplifier and the output port of the low-noise amplifier; and an interference suppression unit connected to the output port of the low-noise amplifier and for adding or subtracting the interference suppression signal to or from the reception signal amplified by the low-noise amplifier.

[0013] A wireless device according to yet another aspect of the present invention includes any one of the above-described transmission / reception circuits, an antenna, a transmitter, and a receiver.

[0014] According to the present invention, in a signal separation circuit that separates and processes a transmission signal and a reception signal transmitted and received via an antenna, it is possible to reduce loop interference, in which a transmission signal transmitted from a transmitter returns to a receiver and causes interference, and to reduce the insertion loss and weight of circuit elements.

[0015] FIG. 1 is an explanatory diagram showing an example of a schematic configuration of a wireless device according to an embodiment. FIG. 2A is an explanatory diagram of wireless communication using an FDD (Frequency Division Duplex) system. FIG. 2B is an explanatory diagram of wireless communication using a TDD (Time Division Duplex) system. FIG. 2C is an explanatory diagram of wireless communication using a full-duplex system. FIG. 3 is an explanatory diagram showing an example of a signal separation circuit using a duplexer in an FDD wireless device according to a reference example. FIG. 4 is an explanatory diagram showing an example of a signal separation circuit using a circulator and a bandpass filter in an FDD wireless device according to another reference example. FIG. 5 is an explanatory diagram showing an example of a signal separation circuit according to an embodiment. FIG. 6 is an explanatory diagram showing an example of the flow of a transmission signal in the signal separation circuit of FIG. 5 and the signal strength and phase at each port. FIG. 7 is an explanatory diagram showing an example of the flow of a reception signal in the signal separation circuit of FIG. 5 and the signal strength and phase at each port. FIG. 8 is an explanatory diagram showing another example of a signal separation circuit according to an embodiment. FIG. 9 is an explanatory diagram showing an example of the flow of a transmission signal in the signal separation circuit of FIG. 8 and the signal strength and phase at each port. Fig. 10 is an explanatory diagram showing an example of the flow of a received signal in the signal separation circuit of Fig. 8 and the signal strength and phase at each port. Fig. 11 is an explanatory diagram showing an example of a transceiver circuit for FDD communication having the signal separation circuit of Fig. 5. Fig. 12 is an explanatory diagram showing another example of a transceiver circuit for full duplex communication having the signal separation circuit of Fig. 5. Fig. 13 is an explanatory diagram showing an example of a transceiver circuit for FDD communication having the signal separation circuit of Fig. 8. Fig. 14 is an explanatory diagram showing another example of a transceiver circuit for full duplex communication having the signal separation circuit of Fig. 8.

[0016] Hereinafter, embodiments of the present invention will be described with reference to the drawings. The circuit according to the embodiment described herein is a signal separation circuit that separates and processes a transmission signal and a reception signal transmitted and received via an antenna of a wireless device. One example of this signal separation circuit uses a transmission line circuit that combines a 90° hybrid circuit and a circulator, thereby reducing loop interference, which occurs when a transmission signal transmitted from a transmitter sneaks back to a receiver and interferes with the receiver, and also achieving reduced insertion loss and weight of the circuit elements. Another example of the signal separation circuit uses a transmission line circuit that combines a branch circuit, a 90° phase shifter, and a circulator, thereby reducing loop interference, which occurs when a transmission signal transmitted from a transmitter sneaks back to a receiver and interferes with the receiver, and also achieving reduced insertion loss and weight of the circuit elements.

[0017] Fig. 1 is an explanatory diagram showing an example of a schematic configuration of a wireless device 10 according to this embodiment. In Fig. 1, the wireless device 10 includes an antenna 20, a transmission / reception circuit 30, a transmitter 40, and a receiver 50. The transmission / reception circuit 30 includes a signal separation circuit 300 that separates and processes a transmission signal and a reception signal transmitted and received via the antenna 20, a power amplifier 360 that amplifies the transmission signal output from the transmitter 40, and a low-noise amplifier 370 that amplifies the reception signal received by the antenna 20 and before being input to the receiver.

[0018] The wireless device 10 is a device that transmits and receives high-frequency wireless signals used in mobile communications and the like via an antenna 20. The frequency band of the wireless signals may be, for example, a microwave frequency band below 20 GHz (e.g., low band, mid band, or Sub6 band), or a millimeter wave frequency band from 20 GHz to 300 GHz (e.g., 28 GHz band, 31 GHz band, 38 GHz band, or 39 GHz band). Here, the low band is a frequency band of 3.5 GHz or less (e.g., 900 MHz band), and the mid band is a frequency band above 3.5 GHz and below 6 GHz (e.g., 3.7 GHz band, 4.5 GHz band). The low band and mid band are collectively referred to as the Sub6 band.

[0019] The wireless device 10 may be, for example, a wireless device mounted on a high altitude platform station (HAPS) (also referred to as a "high altitude pseudosatellite" or "stratospheric platform") having an airborne repeater-type wireless repeater that constitutes an airborne platform, and performing wireless communication of at least one of a service link and a feeder link. The wireless device 10 may also be a wireless device mounted on a gateway device (also referred to as a "feeder station"; hereinafter referred to as a "GW station") for the HAPS that is provided on the ground (or on the sea, etc.) and performing wireless communication of the feeder link with the HAPS wireless repeater. The wireless device 10 may also be a wireless device mounted on a terminal device (user device) that performs wireless communication of the service link with an airborne repeater-type wireless repeater or a terrestrial base station.

[0020] A HAPS is an airborne or levitating communications platform that is positioned in an airspace at a predetermined altitude and forms a three-dimensional cell (three-dimensional area) in a cell formation target airspace at a predetermined altitude toward a target service area.

[0021] The HAPS is a wireless relay device (hereinafter also referred to as a "relay communication station") equipped with the wireless device of this embodiment on the fuselage of an aircraft or floating body that is controlled by autonomous control or external control to float or fly in a high-altitude airspace (floating airspace) 100 km or less above ground or sea level. The airspace in which the HAPS is located may be, for example, stratospheric airspace at an altitude of 18 km or more and 50 km or less. This airspace may also be an airspace with relatively stable weather conditions at an altitude of 15 km or more and 25 km or less, and particularly may be an airspace at an altitude of approximately 20 km.

[0022] HAPS, which functions as an airborne platform, can provide ultra-wide area mobile communication services directly to UE (terminal equipment) on the ground from the stratosphere at altitudes of 18 km or more and 50 km or less (especially around 20 km). Airborne platforms consisting of HAPS are attracting attention as a new form of communication for use in large-scale disasters and other situations.

[0023] The HAPS may be equipped with at least one of a battery and a solar power generation system and fly using electric power. The HAPS may be a solar plane-type HAPS or an airship-type HAPS. The HAPS may also be an artificial satellite (e.g., a communications satellite), a balloon, or an unmanned aerial vehicle (UAV) such as a drone or an unmanned aircraft system (UAS). The HAPS may also fly using at least one of a battery and an engine as a power source. The UAV may be, for example, an unmanned aircraft that flies using fuel or a drone that flies using a battery or the like.

[0024] The wireless device 10 configured as described above has challenges, including reducing the device's weight, reducing loop interference of the transmission signal, and reducing the insertion loss of the circuit elements that make up the device. Reducing the device's weight is particularly important for wireless devices 10 intended for aerial platforms such as UAVs and HAPSs. Therefore, there is a need to use a dual-purpose antenna as the antenna 20 of the wireless device 10. Furthermore, in wireless devices that perform FDD (Frequency Division Duplex) wireless communication (see FIG. 2A), which divides the transmission signal and reception signal on the frequency axis, as used in mobile communications, unlike TDD wireless communication (see FIG. 2B), which uses different time slots for transmission and reception, if the frequency separation between the transmission band and the reception band is narrow, there is a risk of loop interference from the transmitter's transmission circuit to the receiver's reception circuit, and there is a need to reduce the loop interference. To reduce the loop interference, a multi-stage filter with a steep frequency characteristic is required in the transmission and reception circuit of the wireless device, but such a multi-stage filter poses challenges in terms of weight and insertion loss. Furthermore, multi-stage filters are large, resulting in challenges in size, weight, and power consumption. Furthermore, in wireless devices that perform full-duplex wireless communication (see FIG. 2C), which achieves double the frequency utilization efficiency by simultaneously transmitting and receiving using the same frequency, filters that separate the transmitted signal from the received signal on the frequency axis and switches that switch between transmission and reception over time cannot be used, so it is necessary to use separate antennas for transmission and reception and to provide analog and digital interference cancellers, making it difficult to reduce the weight.

[0025] 3 is an explanatory diagram showing an example of a signal separation circuit using a duplexer 380 in an FDD-based wireless device according to a reference example. In FIG. 3, the frequency bands Tx and Rx indicated by dashed lines are the transmission band and reception band, respectively. The filter characteristics BPF(T) and BPF(R) indicated by dotted lines in the figure are the filter characteristics of a multi-stage transmission band-pass filter (hereinafter also referred to as a "transmission band filter") 380T and a multi-stage reception passband filter (hereinafter also referred to as a "reception band filter") 380R, respectively, which constitute the duplexer 380.

[0026] 3, a transmission signal X output from a transmitter is amplified by a power amplifier 360, and the amplified transmission signal X' is input to a duplexer 380 via an isolator 382. The transmission signal X'' passes through a transmission band filter 380T of the duplexer 380 and is transmitted from the antenna 20. Meanwhile, when a reception signal Y'' received by the antenna 20 is input to the duplexer 380, a reception signal Y' passes through a reception band filter 380R and is input to a low-noise amplifier 370. The reception signal Y amplified by the low-noise amplifier 370 is input to a receiver.

[0027] 3, when the transmit band filter 380T and receive band filter 380R of the duplexer 380 are cavity-type multistage filters, a transmit / receive isolation characteristic of about 85 dB is obtained and an insertion loss of about 1 dB occurs, but the weight is large, about 500 g to 1 kg. Also, when the transmit band filter 380T and receive band filter 380R are dielectric-type multistage filters, the weight is lighter, about 50 g, compared to cavity-type multistage filters, but the transmit / receive isolation characteristic is about 60 dB and the insertion loss is about 2.5 dB, which are inferior characteristics.

[0028] 4 is an explanatory diagram showing an example of a signal separation circuit using a circulator 388 and bandpass filters 384 and 386 in an FDD radio device according to another embodiment of the present invention. In FIG. 4, a transmit signal X output from a transmitter is amplified by a power amplifier 360, and the amplified transmit signal X' is input to a transmit bandpass filter 384 via an isolator 382. The transmit signal that has passed through the transmit bandpass filter 384 passes through a circulator 388 and is transmitted from the antenna 20. Meanwhile, a receive signal received by the antenna 20 passes through the circulator 388 and is input to a receive bandpass filter 386, and the receive signal that has passed through the receive bandpass filter 386 is input to a low-noise amplifier 370. A receive signal Y amplified by the low-noise amplifier 370 is input to a receiver.

[0029] In the signal separation circuit using circulator 388 and bandpass filters 384, 386 of Figure 4, if each of bandpass filters 384, 386 is a dielectric type multi-stage filter that can achieve frequency isolation of about 10 MHz, when combined with circulator 388, a transmission / reception isolation characteristic of about 80 dB can be obtained, and the weight will be about 50 g, but the insertion loss will be large at about 2.4 dB.

[0030] The signal separation circuit in the wireless device of this embodiment does not use a multi-stage filter which is heavy and has a large insertion loss, but instead uses a transmission line circuit such as a 90° hybrid circuit, thereby reducing loop interference, which occurs when a transmission signal sent from a transmitter sneaks back to a receiver and causes interference, and also reducing the insertion loss and weight of circuit elements.

[0031] 5 is an explanatory diagram showing an example of a signal separation circuit 300 according to an embodiment. In FIG. 5, the signal separation circuit 300 includes a transmitter-side transmission path circuit (hereinafter referred to as a "transmission transmission path circuit") 310, an antenna-side transmission path circuit (hereinafter referred to as an "antenna transmission path circuit") 320, a receiver-side transmission path circuit (hereinafter referred to as a "reception transmission path circuit") 330, a first circulator 340, and a second circulator 350.

[0032] The transmission transmission line circuit 310 has a first port P1 to which a transmission signal from a transmission circuit (transmitter) is input, a second port P2 connected to the first port P1 by a transmission line with a 90° phase delay, and a third port P3 connected to the first port P1 by a transmission line with a 180° phase delay.

[0033] The antenna transmission path circuit 320 has a first port P1 connected to the antenna 20, a second port P2 connected to the first port P1 by a transmission path with a 90° phase delay, and a third port P3 connected to the first port P1 by a transmission path with a 180° phase delay.

[0034] The receiving transmission line circuit 330 has a first port P1 that outputs a received signal to a receiving circuit (receiver), a second port P2 connected to the first port P1 by a transmission line with a 90° phase delay, and a third port P3 connected to the first port P1 by a transmission line with a 180° phase delay.

[0035] The first circulator 340 has three ports P1, P2, and P3 that are circularly arranged to allow one-way transmission between adjacent ports. In the first circulator 340, the second port P2 of the transmitting transmission line circuit 310, the third port P3 of the antenna transmission line circuit 320, and the second port P2 of the receiving transmission line circuit 330 are connected to the three circularly arranged ports P1, P2, and P3, in that order.

[0036] The second circulator 350 has three ports P1, P2, and P3 that are circularly arranged to allow one-way transmission between adjacent ports. In the second circulator 350, the third port P3 of the transmitting transmission line circuit 310, the second port P2 of the antenna transmission line circuit 320, and the third port P3 of the receiving transmission line circuit 330 are connected to the three circularly arranged ports P1, P2, and P3, in that order.

[0037] 5, the transmitting transmission line circuit 310, the antenna transmission line circuit 320, and the receiving transmission line circuit 330 each use 90° hybrid circuits 312, 322, and 332, which are four-port type transmission line circuits, each having a first port P1, a second port P2, a third port P3, and a fourth port P4 connected to the first port P1 by a transmission line with a 90° phase delay. The fourth port P4 of each of the 90° hybrid circuits 312, 322, and 332 is terminated with 50Ω and has a characteristic impedance Z ０ A 50Ω termination impedance element is connected.

[0038] Here, the 90° hybrid circuit is a directional coupler that has an output phase difference of 90 degrees. The 90° hybrid circuit may be, for example, a transmission line circuit using a coupled transmission line, or a branch-line type transmission line circuit that combines four transmission lines. For example, a branch-line type 90° hybrid circuit has a characteristic impedance Z ０ Two quarter-wave transmission lines with a characteristic impedance Z ０ This is a transmission line circuit configured by connecting two quarter-wave transmission lines of √√2 (for example, 35Ω) in a ring shape. The input and output impedances of the four ports (P1 to P4) of the 90° hybrid circuit are Z ０ is.

[0039] 6 is an explanatory diagram showing an example of the flow of a transmission signal in the signal separation circuit 300 of FIG. 5 and the signal strength and phase at each port. In the 90° hybrid circuit 312 of the transmission transmission line circuit 310, a transmission signal e is input to the first port P1. ｊ０ When the signal is input, the signal is split into two signals, and a signal with a phase delay of 90° and a signal strength of 1 / 2 is generated. ｊ（π／２） is output from the second port P2, and a signal 0.5e with a signal strength of 1 / 2 and a phase delay of 180° is output. ｊπ is output from the third port P3.

[0040] A 90° phase-delayed signal 0.5e is output from the second port P2 of the 90° hybrid circuit 312. ｊ（π／２）is input to the first port P1 of the first circulator 340, is output from the second port P2 of the first circulator 340 without any change in signal strength or phase, and is input to the third port P3 of the 90° hybrid circuit 322 of the antenna transmission line circuit 320. On the other hand, the 180° phase-delayed signal 0.5e output from the third port P3 of the 90° hybrid circuit 312 ｊπ is input to the first port P1 of the second circulator 350, is output from the second port P2 of the second circulator 350 without any change in signal strength or phase, and is input to the second port P2 of the 90° hybrid circuit 322 of the antenna transmission line circuit 320.

[0041] In the 90° hybrid circuit 322 of the antenna transmission line circuit 320, the 90° phase-delayed signal 0.5e input to the third port P3 ｊ（π／２） and the signal 0.5e with a phase delay of 180° input to the second port P2. ｊπ and a low-loss transmission signal e with a phase delay of 270° is output from the first port P1. ｊ（３π／２） is output and transmitted from the antenna 20. In this way, the transmission signal from the transmitter can be transmitted to the antenna 20 with almost no loss.

[0042] 90° phase delay signal 0.5e ｊ（π／２） In the first circulator 340, the signal strength is reduced by about 20 dB to 0.05e ｊ（π／２） is output from the third port P3 and input to the second port P2 of the 90° hybrid circuit 332 of the receiving transmission line circuit 330. On the other hand, a signal 0.5e with a phase delay of 180° ｊπ In the second circulator 350, the signal strength is reduced by 20 dB to 0.05e ｊπ is output from the third port P3 and input to the third port P3 of the 90° hybrid circuit 332.

[0043] In the 90° hybrid circuit 332 of the receiving transmission line circuit 330, the 90° phase-delayed signal 0.05e input to the second port P2 is ｊ（π／２） and the 180° phase-delayed signal 0.05e input to the third port P3. ｊπand are combined in opposite phase, and no signal is output from the first port P1. In this way, high isolation is achieved by both the first circulator 340, the second circulator 350, and the receiving transmission line circuit 330, making it possible to suppress leakage of the transmission signal into the receiving circuit (receiver).

[0044] In the 90° hybrid circuit 332 of the receiving transmission line circuit 330, the 90° phase-delayed signal 0.05e input to the second port P2 ｊ（π／２） and the 180° phase-delayed signal 0.05e input to the third port P3. ｊπ are combined, and a 270° phase-delayed transmission signal 0.1e is output from the fourth port P4. ｊ（３π／２） However, since this can be absorbed by the 50 ohm termination, it does not cause interference (leakage) to the receiving circuit (receiver).

[0045] 7 is an explanatory diagram showing an example of the flow of a received signal in the signal separation circuit 300 of FIG. 5 and the signal strength and phase at each port. In the 90° hybrid circuit 322 of the antenna transmission path circuit 320, the received signal e is transmitted from the antenna 20 to the first port P1. ｊ０ When the signal is input, the signal is split into two signals, and a signal with a phase delay of 90° and a signal strength of 1 / 2 is generated. ｊ（π／２） is output from the second port P2, and a signal 0.5e with a signal strength of 1 / 2 and a phase delay of 180° is output. ｊπ is output from the third port P3.

[0046] A 90° phase-delayed signal 0.5e is output from the second port P2 of the 90° hybrid circuit 322. ｊ（π／２） is input to the second port P2 of the second circulator 350, is output from the third port P3 of the second circulator 350 without any change in signal strength or phase, and is input to the third port P3 of the 90° hybrid circuit 332 of the receiving transmission line circuit 330. On the other hand, the 180° phase-delayed signal 0.5e output from the third port P3 of the 90° hybrid circuit 322 ｊπis input to the second port P2 of the first circulator 340, is output from the third port P3 of the first circulator 340 without any change in signal strength or phase, and is input to the second port P2 of the 90° hybrid circuit 332 of the receiving transmission line circuit 330.

[0047] In the 90° hybrid circuit 332 of the receiving transmission line circuit 330, the 90° phase-delayed signal 0.5e input to the third port P3 is ｊ（π／２） and the signal 0.5e with a phase delay of 180° input to the second port P2. ｊπ and a low-loss transmission signal e with a phase delay of 270° is output from the first port P1. ｊ（３π／２） In this way, the received signal from the antenna 20 can be transmitted to the receiving circuit (receiver) with almost no loss.

[0048] 90° phase delay signal 0.5e ｊ（π／２） In the second circulator 350, the signal strength is reduced by 20 dB to 0.05e ｊ（π／２） is output from the first port P1 and input to the third port P3 of the 90° hybrid circuit 312 of the transmission line circuit 310. On the other hand, a signal 0.5e with a phase delay of 180° ｊπ In the first circulator 340, the signal strength is reduced by 20 dB to 0.05e ｊπ is output from the first port P1 and input to the second port P2 of the 90° hybrid circuit 312.

[0049] In the 90° hybrid circuit 312 of the transmission line circuit 310, the 90° phase-delayed signal 0.05e input to the third port P3 ｊ（π／２） and the signal 0.05e with a phase delay of 180° input to the second port P2. ｊπ are combined, and a received signal 0.1e with a phase delay of 270° is output from the first port P1. ｊ（３π／２） However, the received signal output from the first port P1 is sufficiently lower than the transmitted signal, and as will be described later, the isolation of the circulator can suppress reflections and leakage of the received signal into the transmission circuit (transmitter).

[0050] In the 90° hybrid circuit 312 of the transmission line circuit 310, the 90° phase-delayed signal 0.05e input to the third port P3 ｊ（π／２） and the signal 0.05e with a phase delay of 180° input to the second port P2. ｊπ and are combined in opposite phases, and no signal is output from the fourth port P4.

[0051] 8 is an explanatory diagram showing another example of a signal separation circuit 300 according to an embodiment. In FIG. 8, the signal separation circuit 300 includes a transmission transmission path circuit 310, an antenna transmission path circuit 320, a reception transmission path circuit 330, a first circulator 340, and a second circulator 350.

[0052] The transmission transmission line circuit 310 has a first port P1 to which a transmission signal from a transmission circuit (transmitter) is input, a second port P2 that outputs the transmission signal input to the first port P1 as is, and a third port P3 connected to the first port P1 by a transmission line 316 with a 90° phase delay.

[0053] The antenna transmission path circuit 320 has a first port P1 connected to the antenna 20, a second port P2 that outputs the received signal input to the first port P1 as is, and a third port P3 that is connected to the first port P1 by a transmission path 326 with a 90° phase delay.

[0054] The receiving transmission line circuit 330 has a first port P1 that outputs a received signal to a receiving circuit (receiver), a second port P2 connected to the first port P1 by a transmission line with a 90° phase delay, and a third port P3 connected to the first port P1 by a transmission line with a 180° phase delay.

[0055] The first circulator 340 has three ports P1, P2, and P3 that are circularly arranged to allow one-way transmission between adjacent ports. In the first circulator 340, the second port P2 of the transmitting transmission line circuit 310, the third port P3 of the antenna transmission line circuit 320, and the second port P2 of the receiving transmission line circuit 330 are connected to the three circularly arranged ports P1, P2, and P3, in that order.

[0056] The second circulator 350 has three ports P1, P2, and P3 that are circularly arranged to allow one-way transmission between adjacent ports. In the second circulator 350, the third port P3 of the transmitting transmission line circuit 310, the second port P2 of the antenna transmission line circuit 320, and the third port P3 of the receiving transmission line circuit 330 are connected to the three circularly arranged ports P1, P2, and P3, in that order.

[0057] In the configuration example of Fig. 8, the transmission transmission line circuit 310 has a branching circuit 314 that branches a transmission signal input to a first port P1 and outputs the branched signal to a second port P2 and a relay port P5, and a 90° phase-delay phase shifter 316 connected between the relay port P5 and a third port P3. The antenna transmission line circuit 320 has a branching circuit 324 that branches a reception signal input to the first port P1 and outputs the branched signal to the second port P2 and the relay port P5, and a 90° phase-delay phase shifter 326 provided between the relay port P5 and the third port P3. The reception transmission line circuit 330 has a 90° hybrid circuit 332 having a fourth port P4 connected to the first port P1 by a 90° phase-delay transmission line. The fourth port P4 of the 90° hybrid circuit is terminated with 50Ω and has a characteristic impedance Z ０ A 50Ω termination impedance element is connected.

[0058] 9 is an explanatory diagram showing an example of the flow of a transmission signal in the signal separation circuit 300 of FIG. 8 and the signal strength and phase at each port. In the branch circuit 314 of the transmission transmission line circuit 310, a transmission signal e is input to the first port P1. ｊ０ When the signal is input, the signal is split into two signals, and a signal with half the signal strength and no phase delay, 0.5e ｊ０ is output as is from the second port P2 and the relay port P5.

[0059] The signal 0.5e output from the second port P2 of the branch circuit 314 ｊ０ is input to the first port P1 of the first circulator 340, is output from the second port P2 of the first circulator 340 without any change in signal strength or phase, and is input to the third port P3 of the antenna transmission line circuit 320. On the other hand, the signal 0.5e output from the relay port P5 of the branch circuit 314ｊ０ is a 90° phase-delay signal 0.5e ｊ（π／２） After this, the signal is input to the first port P1 of the second circulator 350, output from the second port P2 of the second circulator 350 without any change in signal strength or phase, and input to the second port P2 of the branch circuit 324 of the antenna transmission path circuit 320.

[0060] The signal 0.5e input to the third port P3 of the antenna transmission line circuit 320 ｊ０ is a 90° phase-delay signal 0.5e ｊ（π／２） After this, the 90° phase-delayed signal 0.5e ｊ（π／２） and the 90° phase-delayed signal 0.5e input to the second port P2 of the branch circuit 324. ｊ（π／２） and a low-loss transmission signal e with a phase delay of 90° is output from the first port P1 of the branch circuit 324. ｊ（π／２） is output and transmitted from the antenna 20. In this way, the transmission signal from the transmitter can be transmitted to the antenna 20 with almost no loss.

[0061] The signal with no phase delay is 0.5e ｊ０ In the first circulator 340, the signal strength is reduced by about 20 dB to 0.05e ｊ０ is output from the third port P3 and input to the second port P2 of the 90° hybrid circuit 332 of the receiving transmission line circuit 330. On the other hand, the 90° phase-delayed signal 0.5e ｊ（π／２） In the second circulator 350, the signal strength is reduced by 20 dB to 0.05e ｊ（π／２） is output from the third port P3 and input to the third port P3 of the 90° hybrid circuit 332.

[0062] In the 90° hybrid circuit 332 of the receiving transmission line circuit 330, the signal 0.05e without phase delay input to the second port P2 ｊ０ and the 90° phase-delayed signal 0.05e input to the third port P3. ｊ（π／２）and are combined in opposite phase, and no signal is output from the first port P1. In this way, high isolation is achieved by both the first circulator 340, the second circulator 350, and the receiving transmission line circuit 330, making it possible to suppress leakage of the transmission signal into the receiving circuit (receiver).

[0063] In the 90° hybrid circuit 332 of the receiving transmission line circuit 330, the signal 0.05e without phase delay input to the second port P2 ｊ０ and the 90° phase-delayed signal 0.05e input to the third port P3. ｊ（π／２） are combined, and a 180° phase-delayed transmission signal 0.1e is output from the fourth port P4. ｊπ However, since this can be absorbed by the 50 ohm termination, it does not cause interference (leakage) to the receiving circuit (receiver).

[0064] 10 is an explanatory diagram showing an example of the flow of a received signal in the signal separation circuit 300 of FIG. 8 and the signal strength and phase at each port. In the branch circuit 324 of the antenna transmission path circuit 320, the received signal e is output from the antenna 20 to the first port P1. ｊ０ When the signal is input, the signal is split into two signals, and a signal with half the signal strength and no phase delay, 0.5e ｊ０ is output as is from the second port P2 and the relay port P5.

[0065] The signal 0.5e output from the second port P2 of the branch circuit 324 ｊ０ is input to the second port P2 of the second circulator 350, is output from the third port P3 of the second circulator 350 without any change in signal strength or phase, and is input to the third port P3 of the 90° hybrid circuit 332 of the receiving transmission line circuit 330. On the other hand, the signal 0.5e output from the relay port P5 of the branch circuit 324 ｊ０ is a 90° phase-delay signal 0.5e ｊ（π／２） After this, the signal is input to the second port P2 of the first circulator 340, output from the third port P3 of the first circulator 340 without any change in signal strength or phase, and input to the second port P2 of the 90° hybrid circuit 332 of the receiving transmission line circuit 330.

[0066] In the 90° hybrid circuit 332 of the receiving transmission line circuit 330, the signal 0.5e without phase delay input to the third port P3 is ｊ０ and the 90° phase-delayed signal 0.5e input to the second port P2. ｊ（π／２） and a low-loss transmission signal e with a phase delay of 180° is output from the first port P1. ｊπ In this way, the received signal from the antenna 20 can be transmitted to the receiving circuit (receiver) with almost no loss.

[0067] Signal with no phase delay 0.5e ｊ０ In the second circulator 350, the signal strength is reduced by 20 dB and the signal is 0.05e without phase delay. ｊ０ is output from the first port P1 and input to the third port P3 of the transmission line circuit 310. On the other hand, a signal 0.5e with a phase delay of 90° ｊ（π／２） In the first circulator 340, the signal strength is reduced by 20 dB to 0.05e ｊ（π／２） is output from the first port P1 and input to the second port P2 of the branch circuit 314 of the transmission line circuit 310.

[0068] A signal with no phase delay input to the third port P3 of the transmission line circuit 310 is 0.05e ｊ０ is a 90° phase-delay signal 0.05e ｊ（π／２） After that, the signal 0.05e with a phase delay of 90° input to the second port P2 is input to the relay port P5 of the branch circuit 314. In the branch circuit 314, the signal 0.05e with a phase delay of 90° input to the second port P2 is ｊ（π／２） and the 90° phase-delayed signal 0.05e input to the relay port P5. ｊ（π／２） and are combined, and a 90° phase-delayed received signal 0.1e is output from the first port P1 of the branch circuit 314. ｊ（π／２） However, the received signal output from the first port P1 is sufficiently lower than the transmitted signal, and as will be described later, the isolation of the circulator can suppress reflections and leakage of the received signal into the transmission circuit (transmitter).

[0069] 11 is an explanatory diagram showing an example of a transceiver circuit 30 for FDD communication having a signal separation circuit 300 according to an embodiment. In FIG. 11 , the transceiver circuit 30 is a transceiver circuit suitable for FDD communication, which transmits and receives FDD (frequency division duplex) signals via a plurality of different frequency bands. The transceiver circuit 30 includes any one of the signal separation circuits 300 described above. For example, the transceiver circuit 30 illustrated in FIG. 11 is a signal separation circuit 300 having 90° hybrid circuits 312, 322, and 332, a first circulator 340, and a second circulator 350. The transmitter / receiver circuit 30 also includes a power amplifier (PA) 360 that amplifies the transmission signal, a transmission band filter 361 provided between a first port P1 of the 90° hybrid circuit 312 of the transmission transmission line circuit 310 and an output port of the power amplifier 360, a low noise amplifier (LNA) 370 that amplifies the reception signal, and a reception band filter 371 provided between the first port P1 of the 90° hybrid circuit 332 of the reception transmission line circuit 330 and an input port of the low noise amplifier 370. Termination impedance elements (e.g., 50Ω termination elements) 318, 328, and 338 are connected to the fourth ports P4 of the transmission transmission line circuit (90° hybrid circuit) 310, the antenna transmission line circuit (90° hybrid circuit) 320, and the reception transmission line circuit (90° hybrid circuit) 330, respectively.

[0070] 11, the transmission band filter 361 and the reception band filter 371 do not need to be multi-stage filters because they do not require steep frequency characteristics (band-pass characteristics). Furthermore, if the leakage of the transmission signal into the reception circuit (receiver) is small, the reception band filter 371 may not be provided. Furthermore, if the leakage of the reflected wave signal in the circuit or the reception signal into the transmission circuit (transmitter) is small, the transmission band filter 361 may not be provided.

[0071] FIG. 12 is an explanatory diagram showing another example of a full-duplex communication transceiver circuit 30 including a signal separation circuit 300 according to an embodiment. In FIG. 12 , the transceiver circuit 30 is suitable for full-duplex communication, transmitting and receiving full-duplex signals via the same frequency band. The transceiver circuit 30 includes any one of the signal separation circuits 300 described above. For example, the transceiver circuit 30 illustrated in FIG. 12 is a signal separation circuit 300 including 90° hybrid circuits 312, 322, and 332, a first circulator 340, and a second circulator 350. The transceiver circuit 30 also includes a power amplifier (PA) 360 that amplifies a transmission signal, a circulator 362 that functions as an isolator and is provided between a first port P1 of the transmission line circuit (90° hybrid circuit) 312 and the output port of the power amplifier 360, and a low-noise amplifier (LNA) 370 that amplifies a reception signal. The isolation function of the circulator 362 makes it possible to suppress leakage (leakage) of reflected wave signals in the circuit and received signals into the transmission circuit (transmitter). Termination impedance elements (e.g., 50Ω termination elements) 318, 328, and 338 are connected to the fourth ports P4 of the transmission transmission line circuit (90° hybrid circuit) 310, the antenna transmission line circuit (90° hybrid circuit) 320, and the reception transmission line circuit (90° hybrid circuit) 330, respectively.

[0072] 12 further includes an interference suppression signal generator 372 and an interference suppression unit 373. The interference suppression signal generator 372 generates an interference suppression signal by multiplying a transmission signal branched from the output port of the power amplifier 360 by a weight W calculated in advance based on information about the transmission path response between the output port of the power amplifier 360 and the output port of the low-noise amplifier 370. The interference suppression unit 373 is connected to the output port of the low-noise amplifier 370, and applies (subtracts or adds) the interference suppression signal generated by the interference suppression signal generator 372 to the reception signal amplified by the low-noise amplifier 370. This makes it possible to further suppress leakage (leakage) of the transmission signal into the reception circuit (receiver).

[0073] 13 is an explanatory diagram showing another example of a transceiver circuit 30 for FDD communication having a signal separation circuit 300 according to an embodiment. In FIG. 13, the transceiver circuit 30 is a transceiver circuit suitable for FDD communication, which transmits and receives FDD (frequency division duplex) signals via multiple different frequency bands. The transceiver circuit 30 shown in FIG. 13 is the signal separation circuit 300 having the aforementioned branch circuits 314 and 326, 90° phase-delay phase shifters 316 and 326, a 90° hybrid circuit 332, a first circulator 340, and a second circulator 350. The transmitter / receiver circuit 30 also includes a power amplifier (PA) 360 that amplifies the transmission signal, a transmission band filter 361 provided between a first port P1 of the branch circuit 314 of the transmission transmission line circuit 310 and an output port of the power amplifier 360, a low noise amplifier (LNA) 370 that amplifies the reception signal, and a reception band filter 371 provided between a first port P1 of the 90° hybrid circuit 332 of the reception transmission line circuit 330 and an input port of the low noise amplifier 370. A termination impedance element (e.g., a 50 Ω termination element) 338 is connected to a fourth port P4 of the reception transmission line circuit (90° hybrid circuit) 330.

[0074] 13, the transmission band filter 361 and the reception band filter 371 do not need to be multi-stage filters because they do not require steep frequency characteristics (band-pass characteristics). Furthermore, if the leakage of the transmission signal into the reception circuit (receiver) is small, the reception band filter 371 may not be provided. Furthermore, if the leakage of the reflected wave signal in the circuit or the reception signal into the transmission circuit (transmitter) is small, the transmission band filter 361 may not be provided.

[0075] FIG. 14 is an explanatory diagram showing another example of a full-duplex communication transceiver circuit 30 including a signal separation circuit 300 according to an embodiment. In FIG. 14 , the transceiver circuit 30 is suitable for full-duplex communication, transmitting and receiving full-duplex signals via the same frequency band. The transceiver circuit 30 illustrated in FIG. 14 is the signal separation circuit 300 including the branch circuits 314 and 326, 90° phase-delay phase shifters 316 and 326, a 90° hybrid circuit 332, a first circulator 340, and a second circulator 350. The transceiver circuit 30 also includes a power amplifier (PA) 360 that amplifies a transmission signal, a circulator 362 that functions as an isolator and is provided between the first port P1 of the branch circuit 314 of the transmission transmission line circuit 310 and the output port of the power amplifier 360, and a low-noise amplifier (LNA) 370 that amplifies a reception signal. The isolation function of the circulator 362 makes it possible to suppress the leakage of reflected wave signals in the circuit and received signals into the transmission circuit (transmitter). A termination impedance element (e.g., a 50Ω termination element) 338 is connected to the fourth port P4 of the reception transmission line circuit (90° hybrid circuit) 330.

[0076] 4 further includes an interference suppression signal generator 372 and an interference suppression unit 373. The interference suppression signal generator 372 generates an interference suppression signal by multiplying a transmission signal branched from the output port of the power amplifier 360 by a weight W calculated in advance based on information about the transmission path response between the output port of the power amplifier 360 and the output port of the low-noise amplifier 370. The interference suppression unit 373 is connected to the output port of the low-noise amplifier 370, and applies (subtracts or adds) the interference suppression signal generated by the interference suppression signal generator 372 to the reception signal amplified by the low-noise amplifier 370. This makes it possible to further suppress leakage (leakage) of the transmission signal into the reception circuit (receiver).

[0077] A machine-learned model may be used to determine at least one of the channel response and the weight used to generate the interference suppression signal.

[0078] As described above, according to this embodiment, it is possible to reduce loop interference, which occurs when a transmission signal transmitted from a transmission circuit (e.g., a circuit including a transmitter and a power amplifier) ​​sneaks into a reception circuit (e.g., a circuit including a low-noise amplifier and a receiver) and interferes with the reception circuit, in the signal separation circuit 300 connected to the antenna 20, and in the transmission / reception circuit 30 and wireless device 10 that include the circuit 300. Moreover, because there is no need to use a multistage filter in the signal separation circuit 300, it is possible to reduce the insertion loss and weight of the circuit elements of the signal separation circuit 300.

[0079] In particular, this embodiment is suitable for a wireless device that performs full-duplex wireless communication or FDD wireless communication.

[0080] Furthermore, according to this embodiment, a common antenna for transmission and reception can be used as the antenna 20 of the wireless device 10, and the weight of the wireless device 10 can be further reduced.

[0081] Furthermore, the present invention can provide a transmitter / receiver circuit and a wireless device having a signal separation device that can reduce loop interference from the transmitter circuit to the receiver circuit, as well as reduce the insertion loss of circuit elements and reduce their weight, thereby contributing to the achievement of Goal 9 of the Sustainable Development Goals (SDGs), which is to "build resilient infrastructure, promote inclusive and sustainable industrialization, and promote industrial and technological innovation."

[0082] It should be noted that the processing steps and components of the signal separation circuit, transceiver circuit, transmitter circuit, receiver circuit, wireless device, and communication system described herein can be implemented by various means. For example, these steps and components may be implemented in hardware, firmware, software, or a combination thereof.

[0083] For hardware implementations, the processing units and other means used to implement the above steps and components in an entity (e.g., various circuit elements, transmitters, receivers, transceivers, amplifiers, filters, controllers, antennas, hard disk drives, or optical disk drives) may be implemented in one or more application specific integrated circuits (ASICs), digital signal processors (DSPs), digital signal processors (DSPDs), programmable logic devices (PLDs), field programmable gate arrays (FPGAs), processors, controllers, microcontrollers, microprocessors, electronic devices, other electronic units designed to perform the functions described herein, computers, or combinations thereof.

[0084] Furthermore, with regard to firmware and / or software implementations, the means, such as a processing unit, used to realize the above components may be implemented with a program (e.g., code, such as procedures, functions, modules, instructions, etc.) that performs the functions described herein. In general, any computer / processor-readable medium tangibly embodying firmware and / or software code may be used to implement the means, such as a processing unit, used to realize the above steps and components described herein. For example, the firmware and / or software code may be stored in a memory and executed by a computer or processor, such as in a control device. The memory may be implemented within the computer or processor, or external to the processor. The firmware and / or software code may also be stored on a computer or processor readable medium such as, for example, random access memory (RAM), read-only memory (ROM), non-volatile random access memory (NVRAM), programmable read-only memory (PROM), electrically erasable programmable read-only memory (EEPROM), flash memory, floppy disk, compact disk (CD), digital versatile disk (DVD), magnetic or optical data storage device, etc. The code may be executed by one or more computers or processors and may cause the computers or processors to perform certain aspects of the functionality described herein.

[0085] The medium may be a non-transitory recording medium. The program code may be in any format as long as it can be read and executed by a computer, processor, or other device or machine. For example, the program code may be in any of source code, object code, and binary code, or may be a mixture of two or more of these codes.

[0086] Moreover, the description of the embodiments disclosed herein is provided to enable any person skilled in the art to make or use the present disclosure. Various modifications to the present disclosure will be readily apparent to those skilled in the art, and the general principles defined herein may be applied to other variations without departing from the spirit or scope of the present disclosure. Thus, the present disclosure is not intended to be limited to the examples and designs described herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

[0087] 10: Radio device 20: Antenna 30: Transmitting / receiving circuit 40: Transmitter 50: Receiver 300: Signal separation circuit 310: Transmission transmission path circuit 312: 90° hybrid circuit 320: Antenna transmission path circuit 322: 90° hybrid circuit 324: Branch circuit 326: Phase shifter 330: Receiving transmission path circuit 332: 90° hybrid circuit 340: First circulator 350: Second circulator 360: Power amplifier 361: Transmission band filter 362: Circulator 370: Low noise amplifier 371: Receiving band filter 372: Interference suppression signal generation unit 373: Interference suppression unit

Claims

1. A signal separation circuit that separates and processes a transmission signal and a reception signal transmitted and received via an antenna, comprising: a transmitter-side transmission line circuit having a first port to which a transmission signal from a transmitter is input, a second port connected to said first port by a transmission line with a 90° phase delay, and a third port connected to said first port by a transmission line with a 180° phase delay; an antenna-side transmission line circuit having a first port connected to said antenna, a second port connected to said first port by a transmission line with a 90° phase delay, and a third port connected to said first port by a transmission line with a 180° phase delay; and a receiver-side transmission line circuit having a first port to output a reception signal to a receiver, a second port connected to said first port by a transmission line with a 90° phase delay, and a third port connected to said first port by a transmission line with a 180° phase delay; a first circulator having three ports arranged in a circular manner to enable unidirectional transmission between adjacent ports, the second port of the transmitter-side transmission line circuit, the third port of the antenna-side transmission line circuit, and the second port of the receiver-side transmission line circuit being connected to the three ports in that order; and a second circulator having three ports arranged in a circular manner to enable unidirectional transmission between adjacent ports, the third port of the transmitter-side transmission line circuit, the second port of the antenna-side transmission line circuit, and the third port of the receiver-side transmission line circuit being connected to the three ports in that order.

2. A signal separation circuit according to claim 1, wherein the transmitter-side transmission line circuit, the antenna-side transmission line circuit and the receiver-side transmission line circuit are each a 90° hybrid circuit having a fourth port connected to the first port by a transmission line with a 90° phase delay, and a termination impedance element is connected to the fourth port of the 90° hybrid circuit.

3. A signal separation circuit that separates and processes a transmission signal and a reception signal transmitted and received via an antenna, comprising: a transmitter-side transmission line circuit having a first port to which a transmission signal from a transmitter is input, a second port connected to the first port by a transmission line with no phase delay, and a third port connected to the first port by a transmission line with a 90° phase delay; an antenna-side transmission line circuit having a first port connected to the antenna, a second port connected to the first port by a transmission line with no phase delay, and a third port connected to the first port by a transmission line with a 90° phase delay; and a receiver-side transmission line circuit having a first port to output a reception signal to a receiver, a second port connected to the first port by a transmission line with a 90° phase delay, and a third port connected to the first port by a transmission line with a 180° phase delay; a first circulator having three ports arranged in a circular manner to enable unidirectional transmission between adjacent ports, the second port of the transmitter-side transmission line circuit, the third port of the antenna-side transmission line circuit, and the second port of the receiver-side transmission line circuit being connected to the three ports in that order; and a second circulator having three ports arranged in a circular manner to enable unidirectional transmission between adjacent ports, the third port of the transmitter-side transmission line circuit, the second port of the antenna-side transmission line circuit, and the third port of the receiver-side transmission line circuit being connected to the three ports in that order.

4. A signal separation circuit according to claim 3, wherein the transmitter-side transmission line circuit comprises: a branch circuit that branches a transmission signal input to the first port and outputs the branched signal to the second port and the relay port; and a phase shifter with a 90° phase delay connected between the relay port and the third port; the antenna-side transmission line circuit comprises: a branch circuit that branches a reception signal input to the first port and outputs the branched signal to the second port and the relay port; and a phase shifter with a 90° phase delay provided between the relay port and the third port; and the receiver-side transmission line circuit is a 90° hybrid circuit having a fourth port connected to the first port by a transmission line with a 90° phase delay, and a terminating impedance element is connected to the fourth port of the 90° hybrid circuit.

5. A transmission / reception circuit for transmitting and receiving signals in an FDD (Frequency Division Duplex) system via a plurality of different frequency bands, the transmission / reception circuit comprising a signal separation circuit according to any one of claims 1 to 4.

6. A transmission / reception circuit according to claim 5, comprising: a power amplifier for amplifying the transmission signal; a transmission band filter provided between a first port of the transmission line circuit on the transmitter side and an output port of the power amplifier; a low-noise amplifier for amplifying the reception signal; and a reception band filter provided between the first port of the transmission line circuit on the receiver side and an input port of the low-noise amplifier.

7. A transmitter / receiver circuit for transmitting and receiving full-duplex signals via the same frequency band, comprising a signal separation circuit according to any one of claims 1 to 4.

8. A transmission / reception circuit according to claim 7, comprising: a power amplifier that amplifies the transmission signal; an isolator provided between a first port of the transmission path circuit on the transmitter side and the output port of the power amplifier; a low-noise amplifier that amplifies the reception signal; a signal generation unit that generates an interference suppression signal by multiplying the transmission signal branched from the output port of the power amplifier by a weight calculated in advance based on information about the transmission path response between the output port of the power amplifier and the output port of the low-noise amplifier; and an interference suppression unit that is connected to the output port of the low-noise amplifier and adds or subtracts the interference suppression signal to the reception signal amplified by the low-noise amplifier.

9. A radio device comprising the transmitting and receiving circuit of claim 6, an antenna, a transmitter, and a receiver.

10. A radio device comprising the transmitting and receiving circuit of claim 8, an antenna, a transmitter, and a receiver.

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