Radio-frequency circuit and communication device

Desired characteristics can be achieved. A radio-frequency circuit includes an inductor and a switch. The inductor has a first end and a second end. The switch has a first input-output terminal, a second input-output terminal, a first switching terminal coupled to the first end of the inductor, and a second switching terminal coupled to the second end of the inductor. The switch can switch between a first state and a second state. In the first state, the first input-output terminal is coupled to the first switching terminal, and the second input-output terminal is coupled to the second switching terminal. In the second state, the first input-output terminal is coupled to the second switching terminal, and the second input-output terminal is coupled to the first switching terminal.

BACKGROUND ART

Technical Field

The present disclosure generally relates to radio-frequency circuits and communication devices and more particularly relates to a radio-frequency circuit including an inductor and a communication device including the radio-frequency circuit.

Heretofore, radio-frequency circuits supporting a plurality of frequency bands have been known (refer to, for example, Patent Document 1). The radio-frequency circuit described in Patent Document 1 includes an input-side impedance matching circuit and an output-side impedance matching circuit. The input-side impedance matching circuit includes a first inductor mounted on a mounting board. The output-side impedance matching circuit includes a second inductor mounted on the mounting board.Patent Document 1: Japanese Unexamined Patent Application Publication No. 2019-68205

BRIEF SUMMARY

The possibility exists that the radio-frequency circuit described in Patent Document 1 cannot achieve desired characteristics when the first inductor and the second inductor are arranged in a particular manner on the mounting board and accordingly coupled to each other.

The present disclosure provides a radio-frequency circuit and a communication device that can achieve desired characteristics.

A radio-frequency circuit according to an aspect of the present disclosure includes an inductor and a switch. The inductor has a first end and a second end. The switch has a first input-output terminal, a second input-output terminal, a first switching terminal coupled to the first end of the inductor, and a second switching terminal coupled to the second end of the inductor. The switch can switch between a first state and a second state. In the first state, the first input-output terminal is coupled to the first switching terminal, and the second input-output terminal is coupled to the second switching terminal. In the second state, the first input-output terminal is coupled to the second switching terminal, and the second input-output terminal is coupled to the first switching terminal.

A communication device according to an aspect of the present disclosure includes the radio-frequency circuit and a signal processing circuit. The signal processing circuit processes at least one of a receive signal transferred from an antenna terminal and a transmit signal to be transferred to the antenna terminal.

The radio-frequency circuit according to the aspect of the present disclosure and the communication device according to the aspect of the present disclosure can achieve desired characteristics.

DETAILED DESCRIPTION

Hereinafter, radio-frequency circuits and communication devices according to first to third embodiments will be described with reference to the drawings.

First Embodiment

(1) CONFIGURATION OF RADIO-FREQUENCY CIRCUIT

Firstly, a configuration of a radio-frequency circuit1according to the first embodiment will be described with reference toFIG.1.

The radio-frequency circuit1according to the first embodiment is used in, for example, a communication device100. The communication device100is, for example, a mobile phone such as a smartphone. The communication device100is not limited to a mobile phone but may be, for example, a wearable terminal such as a smartwatch. The radio-frequency circuit1supports, for example, carrier aggregation and dual connectivity.

The radio-frequency circuit1is provided in the communication device100that, for example, supports multiple bands in compliance with a communication standard such as Long Term Evolution (LTE). The radio-frequency circuit1can provide, for example, bidirectional transfer of full duplex communication by allocating different frequencies to transmit signals (transmitting radio-frequency signals) and receive signals (received radio-frequency signals) in accordance with frequency division duplex (FDD).

The radio-frequency circuit1can be electrically coupled to an external substrate (not illustrated in the drawing). The external substrate is, for example, a mother substrate of a mobile phone or communication device. Here, the condition that the radio-frequency circuit1can be electrically coupled to the external substrate includes, in addition to the case in which the radio-frequency circuit1is directly mounted on the external substrate, the case in which the radio-frequency circuit1is indirectly mounted on the external substrate. The case in which the radio-frequency circuit1is indirectly mounted on the external substrate includes, for example, the case in which the radio-frequency circuit1is mounted on another radio-frequency circuit mounted on the external substrate.

The radio-frequency circuit1according to the present embodiment includes an inductor81and a switch18.

The inductor81has a first end811and a second end812. The switch18has a terminal181serving as a first input-output terminal, a terminal182as a second input-output terminal, a terminal183as a first switching terminal, and a terminal184as a second switching terminal. The terminal183is coupled to the first end811of the inductor81. The terminal184is coupled to the second end812of the inductor81. The terminal181serving as the first input-output terminal is, for example, an input terminal. The terminal182serving as the second input-output terminal is, for example, an output terminal.

The switch18can switch between a first state and a second state. In the first state, the terminal181is coupled to the terminal183, and the terminal182is coupled to the terminal184(refer toFIG.2A). In the second state, the terminal181is coupled to the terminal184, and the terminal182is coupled to the terminal183(refer toFIG.2B).

The radio-frequency circuit1according to the first embodiment further includes switches2,3, and4. The switch2has a common terminal20and a plurality (three inFIG.1) of selection terminals of selection terminals21,22, and23. The switch3has a common terminal30and a plurality (three inFIG.1) of selection terminals of selection terminals31,32, and33. The switch4has a common terminal40and a plurality (three inFIG.1) of selection terminals of selection terminals41,42, and43. In the radio-frequency circuit1according to the first embodiment, the switches3and18are formed by a single chip component200.

The radio-frequency circuit1according to the first embodiment further includes a power amplifier5, a low-noise amplifier6, and a low pass filter9. The power amplifier5amplifies a transmit signal to be transferred to an antenna terminal T1. The low-noise amplifier6amplifies a receive signal transferred from the antenna terminal T1. The low pass filter9is electrically coupled to the antenna terminal T1.

The radio-frequency circuit1according to the first embodiment further includes a plurality (three inFIG.1) of duplexers of duplexers10,11, and12. The duplexer10includes a transmit filter101and a receive filter102. The duplexer11includes a transmit filter111and a receive filter112. The duplexer12includes a transmit filter121and a receive filter122.

The radio-frequency circuit1according to the first embodiment further includes an output matching circuit7, an input matching circuit8, a plurality (three inFIG.1) of matching circuits of matching circuits13,14, and15. The matching circuits13,14, and15and the duplexers10,11, and12are provided in one-to-one correspondence. The output matching circuit7is disposed in a signal path between an output terminal52of the power amplifier5and the common terminal20of the switch2. The input matching circuit8is disposed in a signal path between the common terminal30of the switch3and an input terminal61of the low-noise amplifier6. The matching circuit13is disposed in a signal path between the duplexer10and the selection terminal41of the switch4. The matching circuit14is disposed in a signal path between the duplexer11and the selection terminal42of the switch4. The matching circuit15is disposed in a signal path between the duplexer12and the selection terminal43of the switch4.

The radio-frequency circuit1according to the first embodiment further includes the antenna terminal T1, a signal input terminal T2, and a signal output terminal T3. The signal input terminal T2is coupled to an input terminal51of the power amplifier5. The signal output terminal T3is coupled to an output terminal62of the low-noise amplifier6. The antenna terminal T1is coupled to the low pass filter9.

(2) CONSTITUENT ELEMENTS OF RADIO-FREQUENCY CIRCUIT

Next, constituent elements of the radio-frequency circuit1according to the first embodiment will be described with reference toFIG.1.

The duplexer10includes the transmit filter101and the receive filter102.

The transmit filter101is a transmit filter supporting a first communication band and configured to pass a first transmit signal. The transmit filter101has an input terminal and an output terminal. The input terminal of the transmit filter101is coupled to the selection terminal21of the switch2. The output terminal of the transmit filter101is coupled to the selection terminal41of the switch4.

The receive filter102is a receive filter supporting the first communication band and configured to pass a first receive signal. The receive filter102has an input terminal and an output terminal. The input terminal of the receive filter102is coupled to the selection terminal41of the switch4. The output terminal of the receive filter102is coupled to the terminal (first input-output terminal)31of the switch3.

In the radio-frequency circuit1, the output terminal of the transmit filter101and the input terminal of the receive filter102are both coupled to the selection terminal41of the switch4. This means that in the radio-frequency circuit1the output terminal of the transmit filter101and the input terminal of the receive filter102are bound together.

The duplexer11includes the transmit filter111and the receive filter112.

The transmit filter111is a transmit filter supporting a second communication band and configured to pass a second transmit signal. The transmit filter111has an input terminal and an output terminal. The input terminal of the transmit filter111is coupled to the selection terminal22of the switch2. The output terminal of the transmit filter111is coupled to the selection terminal42of the switch4.

The receive filter112is a receive filter supporting the second communication band and configured to pass a second receive signal. The receive filter112has an input terminal and an output terminal. The input terminal of the receive filter112is coupled to the selection terminal42of the switch4. The output terminal of the receive filter112is coupled to the terminal (first input-output terminal)32of the switch3.

In the radio-frequency circuit1, the output terminal of the transmit filter111and the input terminal of the receive filter112are both coupled to the selection terminal42of the switch4. This means that in the radio-frequency circuit1the output terminal of the transmit filter111and the input terminal of the receive filter112are bound together.

The duplexer12includes the transmit filter121and the receive filter122.

The transmit filter121is a transmit filter supporting a third communication band and configured to pass a third transmit signal. The transmit filter121has an input terminal and an output terminal. The input terminal of the transmit filter121is coupled to the selection terminal23of the switch2. The output terminal of the transmit filter121is coupled to the selection terminal43of the switch4.

The receive filter122is a receive filter supporting the third communication band and configured to pass a third receive signal. The receive filter122has an input terminal and an output terminal. The input terminal of the receive filter122is coupled to the selection terminal43of the switch4. The output terminal of the receive filter122is coupled to the terminal (first input-output terminal)33of the switch3.

In the radio-frequency circuit1, the output terminal of the transmit filter121and the input terminal of the receive filter122are both coupled to the selection terminal43of the switch4. This means that in the radio-frequency circuit1the output terminal of the transmit filter121and the input terminal of the receive filter122are bound together.

The first communication band, which is the pass band of the transmit filter101and the receive filter102, is, for example, Band8. The second communication band, which is the pass band of the transmit filter111and the receive filter112, is, for example, Band20. The third communication band, which is the pass band of the transmit filter121and the receive filter122, is, for example, Band13.

(2.2) Power Amplifier

The power amplifier5is an amplifier configured to amplify the first, second, and third transmit signals. The power amplifier5is disposed in a transmit path coupling the antenna terminal T1and the signal input terminal T2. More specifically, the power amplifier5is provided between the output matching circuit7and the signal input terminal T2. The power amplifier5has the input terminal51and the output terminal52. The input terminal51is coupled to an external circuit (for example, a signal processing circuit16) via the signal input terminal T2. The signal input terminal T2is a terminal for inputting radio-frequency signals (first, second, and third transmit signals) from the external circuit to the radio-frequency circuit1. The output terminal52is coupled to an input end of the output matching circuit7(a first end of an inductor71).

The power amplifier5is controlled by, for example, a radio-frequency (RF) signal processing circuit161of the signal processing circuit16described later, but the power amplifier5may be controlled by a power amplifier controller (not illustrated in the drawing).

The low-noise amplifier6is an amplifier configured to amplify with low noise the first, second, and third receive signals. The low-noise amplifier6is disposed in a receive path coupling the antenna terminal T1and the signal output terminal T3. More specifically, the low-noise amplifier6is disposed between the switch3and the signal output terminal T3. The low-noise amplifier6has the input terminal61and the output terminal62. The input terminal61is coupled to the terminal (second input-output terminal)36of the switch3. The output terminal62is coupled to an external circuit (for example, the signal processing circuit16) via the signal output terminal T3. The signal output terminal T3is a terminal for outputting radio-frequency signals from the radio-frequency circuit1to the external circuit.

The low-noise amplifier6is controlled by, for example, the RF signal processing circuit161of the signal processing circuit16.

The switch2has the common terminal20and a plurality (three inFIG.1) of selection terminals of the selection terminals21,22, and23. The switch2switches connections between the common terminal20and the selection terminals21,22, and23. More specifically, the switch2switches among the state in which the common terminal20is coupled to the selection terminal21, the state in which the common terminal20is coupled to the selection terminal22, and the state in which the common terminal20is coupled to the selection terminal23. The switch2may be implemented by, for example, a single pole triple throw (SP3T) switch.

The switch3has the common terminal30and a plurality (three inFIG.1) of selection terminals of the selection terminals31,32, and33. The switch3switches connections between the common terminal30and the selection terminals31,32, and33. More specifically, the switch3switches among the state in which the common terminal30is coupled to the selection terminal31, the state in which the common terminal30is coupled to the selection terminal32, and the state in which the common terminal30is coupled to the selection terminal32. The switch3may be implemented by, for example, an SP3T switch.

The switch18has the terminal181serving as the first input-output terminal, the terminal182as the second input-output terminal, the terminal183as the first switching terminal, and the terminal184as the second switching terminal. The terminal181serving as the first input-output terminal is, for example, an input terminal. The terminal182serving as the second input-output terminal is, for example, an output terminal. The switch18switches connections between the terminals181and182and the terminals183and184. The switch18may be implemented by, for example, a dual pole dual throw (DPDT) switch.

The switch18can switch between the first state and the second state to reverse the direction of current flow in the inductor81. In the first state, the terminal181as the first input-output terminal is coupled to the terminal183as the first switching terminal, and the terminal182as the second input-output terminal is coupled to the terminal184as the second switching terminal (refer toFIGS.2A and3A). In the second state, the terminal181as the first input-output terminal is coupled to the terminal184as the second switching terminal, and the terminal182as the second input-output terminal is coupled to the terminal183as the first switching terminal (refer toFIGS.2B and3B).

In the radio-frequency circuit1according to the first embodiment, the single chip component200implements both the switch3for switching signal paths for receive signals in different communication bands and the switch18for changing the direction of current flow in the inductor81; in other words, the switch18for changing the direction of current flow in the inductor81is integrated with the switch3for switching signal paths for receive signals in different communication bands. The term “integrated” means that the two switches3and18are physically integrated with each other.

The switch4has the common terminal40and a plurality (three inFIG.1) of selection terminals of the selection terminals41,42, and43. The switch4switches connections between the common terminal40and the selection terminals41,42, and43. More specifically, the switch4switches among the state in which the common terminal40is coupled to the selection terminal41, the state in which the common terminal40is coupled to the selection terminal42, and the state in which the common terminal40is coupled to the selection terminal43. The switch4may be implemented by, for example, an SP3T switch.

The switches2,3,4, and18are controlled by, for example, the RF signal processing circuit161of the signal processing circuit16, but the switches2,3,4, and18may be controlled by a power amplifier controller (not illustrated in the drawing).

(2.5) Output Matching Circuit

The output matching circuit7is disposed in the signal path between the output terminal52of the power amplifier5and the common terminal20of the switch2. The output matching circuit7is a circuit for providing impedance matching between the power amplifier5and the transmit filters101,111, and121coupled respectively to the selection terminals21,22, and23of the switch2. The output matching circuit7includes a plurality (two inFIG.1) of inductors of the inductor71and an inductor72and a plurality (three inFIG.1) of capacitors of capacitors73,74, and75.

The first end of the inductor71is coupled to the output terminal52of the power amplifier5, and a second end of the inductor71is coupled to a first end of the inductor72. A second end of the inductor72is coupled to a first end of the capacitor75, and a second end of the capacitor75is coupled to the common terminal20of the switch2. This means that in the radio-frequency circuit1according to the first embodiment the inductors71and72and the capacitor75are coupled in series with each other between the output terminal52of the power amplifier5and the common terminal20of the switch2.

The capacitor73is coupled between a node of the inductors71and72and the ground. The capacitor74is coupled to a node of the inductor72and the capacitor75and the ground.

(2.6) Input Matching Circuit

The input matching circuit8is disposed in the signal path between the common terminal30of the switch3and the input terminal61of the low-noise amplifier6. The input matching circuit8is a circuit for providing impedance matching between the low-noise amplifier6and the receive filters102,112, and122coupled respectively to the terminals31,32, and33of the switch3. The input matching circuit8includes a plurality (two inFIG.1) of inductors of the inductor81and an inductor82.

The inductor81has the first end811and the second end812. The first end811of the inductor81is coupled to the terminal183(first switching terminal) of the switch18. The second end812of the inductor81is coupled to the terminal184(second switching terminal) of the switch18. The inductor82is coupled between the ground and a signal path between the common terminal30of the switch3and the terminal181of the switch18.

(2.7) Matching Circuit

The matching circuit13is disposed in a signal path between the duplexer10and the switch4. The matching circuit13is a circuit for providing impedance matching between an antenna17coupled to the antenna terminal T1and the duplexer10. The matching circuit13includes an inductor131. The inductor131is coupled between the ground and the signal path between the duplexer10and the switch4.

The matching circuit14is disposed in a signal path between the duplexer11and the switch4. The matching circuit14is a circuit for providing impedance matching between the antenna17coupled to the antenna terminal T1and the duplexer11. The matching circuit14includes an inductor141. The inductor141is coupled between the ground and the signal path between the duplexer11and the switch4.

The matching circuit15is disposed in a signal path between the duplexer12and the switch4. The matching circuit15is a circuit for providing impedance matching between the antenna17coupled to the antenna terminal T1and the duplexer12. The matching circuit15includes an inductor151. The inductor151is coupled between the ground and the signal path between the duplexer12and the switch4.

(2.8) Low Pass Filter

The low pass filter9is disposed in a signal path between the switch4and the antenna terminal T1. The low pass filter9includes an inductor91and a capacitor92.

The inductor91is coupled between the common terminal40of the switch4and the antenna terminal T1; in other words, a first end of the inductor91is coupled to the common terminal40of the switch4, and a second end of the inductor91is coupled to the antenna terminal T1.

The capacitor92is coupled between the common terminal40of the switch4and the antenna terminal T1; in other words, a first end of the capacitor92is coupled to the common terminal40of the switch4, and a second end of the capacitor92is coupled to the antenna terminal T1.

This means that in the radio-frequency circuit1according to the first embodiment the inductor91and the capacitor92are coupled in parallel with each other between the common terminal40of the switch4and the antenna terminal T1.

(3) CONFIGURATION OF COMMUNICATION DEVICE

Next, a configuration of the communication device100according to the first embodiment will be described with reference toFIG.1.

As illustrated inFIG.1, the communication device100includes the radio-frequency circuit1, the signal processing circuit16, and the antenna17.

The antenna17is coupled to the antenna terminal T1of the radio-frequency circuit1. The antenna17has a functionality of transmitting by emission as a radio wave at least one of the first, second, and third transmit signals outputted by the radio-frequency circuit1. The antenna17also has a functionality of receiving as a radio wave at least one of the first, second, and third receive signals and outputting the signal to the radio-frequency circuit1.

The signal processing circuit16includes the RF signal processing circuit161and a baseband signal processing circuit162. The signal processing circuit16processes the first, second, and third transmit signals and the first, second, and third receive signals.

The RF signal processing circuit161is, for example, a radio frequency integrated circuit (RFIC) and processes radio-frequency signals. The RF signal processing circuit161processes by, for example, upconversion a radio-frequency signal outputted by the baseband signal processing circuit162and outputs the processed radio-frequency signal to the radio-frequency circuit1.

Specifically, the RF signal processing circuit161processes by, for example, upconversion the first transmit signal outputted by the baseband signal processing circuit162and outputs the processed first transmit signal to a first transmit path in the radio-frequency circuit1. The first transmit path is a path routed through the transmit filter101of the duplexer10out of the transmit paths coupling the antenna terminal T1and the signal input terminal T2.

The RF signal processing circuit161also processes by, for example, upconversion the second transmit signal outputted by the baseband signal processing circuit162and outputs the processed second transmit signal to a second transmit path in the radio-frequency circuit1. The second transmit path is a path routed through the transmit filter111of the duplexer11out of the transmit paths coupling the antenna terminal T1and the signal input terminal T2.

The RF signal processing circuit161also processes by, for example, upconversion the third transmit signal outputted by the baseband signal processing circuit162and outputs the processed third transmit signal to a third transmit path in the radio-frequency circuit1. The third transmit path is a path routed through the transmit filter121of the duplexer12out of the transmit paths coupling the antenna terminal T1and the signal input terminal T2.

The RF signal processing circuit161also processes by, for example, downconversion a radio-frequency signal outputted by the radio-frequency circuit1and outputs the processed radio-frequency signal to the baseband signal processing circuit162.

Specifically, the RF signal processing circuit161processes the first receive signal outputted from a first receive path in the radio-frequency circuit1and outputs the processed first receive signal to the baseband signal processing circuit162. The first receive path is a path routed through the receive filter102of the duplexer10out of the receive paths coupling the antenna terminal T1and the signal output terminal T3.

The RF signal processing circuit161also processes the second receive signal outputted from a second receive path in the radio-frequency circuit1and outputs the processed second receive signal to the baseband signal processing circuit162. The second receive path is a path routed through the receive filter112of the duplexer11out of the receive paths coupling the antenna terminal T1and the signal output terminal T3.

The RF signal processing circuit161also processes the third receive signal outputted from a third receive path in the radio-frequency circuit1and outputs the processed third receive signal to the baseband signal processing circuit162. The third receive path is a path routed through the receive filter122of the duplexer12out of the receive paths coupling the antenna terminal T1and the signal output terminal T3.

The baseband signal processing circuit162is, for example, a baseband integrated circuit (BBIC). The baseband signal processing circuit162processes in a predetermined manner transmit signals from outside of the signal processing circuit16. The receive signal processed by the baseband signal processing circuit162is used as, for example, an image signal for displaying an image or a sound signal for phone calls.

The RF signal processing circuit161also functions as a controller for controlling the switches2,3, and4, the power amplifier5, and the low-noise amplifier6included in the radio-frequency circuit1in accordance with the communication band (frequency band) in use. Specifically, the RF signal processing circuit161uses a control signal to control the switches2,3, and4, the power amplifier5, and the low-noise amplifier6. The controller may be provided outside the RF signal processing circuit161; for example, the controller may be provided in the radio-frequency circuit1or the baseband signal processing circuit162.

(4) OPERATION OF RADIO-FREQUENCY CIRCUIT

(4.1) First Operation

Next, a first operation of the radio-frequency circuit1according to the first embodiment will be described with reference toFIGS.2A and2B.

In the radio-frequency circuit1according to the first embodiment, for example, the input matching circuit8includes the inductor81mounted at a mounting board (not illustrated in the drawing). In the radio-frequency circuit1, for example, the matching circuit13includes the inductor131mounted at the mounting board. Depending on at least either the position or orientation of the inductor81of the input matching circuit8relative to the inductor131of the matching circuit13, the inductors81and131may cause magnetic coupling. This may worsen the isolation between the transmit and receive paths particularly in the transmit frequency band, and as a result, transmit signals may leak into the receive path, resulting in deterioration of receive sensitivity.

To address the problem described above, the radio-frequency circuit1according to the first embodiment is configured in the following manner. The following description uses an example of the magnetic coupling between the inductor81of the input matching circuit8and the inductor131of the matching circuit13, but the same description holds for the magnetic coupling between the inductor81of the input matching circuit8and the inductor141of the matching circuit14and the magnetic coupling between the inductor81of the input matching circuit8and the inductor151of the matching circuit15. Also, the following description uses as an example the case in which the common terminal30of the switch3is coupled to the selection terminal31, but the same description holds for the case in which the common terminal30is coupled to the selection terminal32or the selection terminal33.

In the radio-frequency circuit1according to the first embodiment, the inductor in which the direction of current flow is changed in accordance with the connection state of the switch is the inductor81coupled to the input side of the low-noise amplifier6. In the radio-frequency circuit1according to the first embodiment, the inductors that may cause magnetic coupling with the inductor described above are the inductor131of the matching circuit13, the inductor141of the matching circuit14, and the inductor151of the matching circuit15.

InFIG.2A, the switch18is in the first state. When the switch18is in the first state, the terminal181as the first input-output terminal is coupled to the terminal183as the first switching terminal, and the terminal182as the second input-output terminal is coupled to the terminal184as the second switching terminal. In this case, a current flows through the inductor81of the input matching circuit8in the direction indicated by an arrow A1. Accordingly, a magnetic field is generated around the inductor81in the direction corresponding to the current. At this time, a current also flows through the inductor131of the matching circuit13, and a magnetic field is generated around the inductor131in the direction corresponding to the current.

When the direction of the magnetic field generated around the inductor81is identical to the direction of the magnetic field generated around the inductor131, the magnetic field generated around the inductor81and the magnetic field generated around the inductor131strengthen each other, and consequently, the inductors81and131cause magnetic coupling. This worsens the isolation between the transmit and receive paths particularly in the transmit frequency band, and as a result, transmit signals leak into the receive path, resulting in degradation of receive sensitivity

In this case, the direction of current flow in the inductor81can be reversed by switching the switch18to the second state as illustrated inFIG.2B. Specifically, in the switch18, the terminal181as the first input-output terminal is coupled to the terminal184as the second switching terminal, and the terminal182as the second input-output terminal is coupled to the terminal183as the first switching terminal. In this state, a current flows through the inductor81of the input matching circuit8in the direction indicated by an arrow A2opposite to the arrow A1. Accordingly, a magnetic field is generated around the inductor81in the direction corresponding to the current.

In this case, the direction of the magnetic field generated around the inductor81is opposite to the direction of the magnetic field generated around the inductor131, and the magnetic field generated around the inductor81and the magnetic field generated around the inductor131cancel each other out. As such, it is possible to hinder the magnetic coupling between the inductors81and131. This can suppress degradation of the isolation between the transmit and receive paths particularly in the transmit frequency band, and as a result, it is possible to suppress degradation of receive sensitivity during the transmit operation.

Similarly, by switching the switch18between the first state and the second state, it is possible to hinder the magnetic coupling between the inductor81of the input matching circuit8and the inductor72of the output matching circuit7and the magnetic coupling between the inductor81of the input matching circuit8and the inductor91of the low pass filter9. In this case, the inductor in which the direction of current flow is changed by the switch is the inductor81of the input matching circuit8, and the inductors that may cause magnetic coupling with this inductor are the inductor72of the output matching circuit7and the inductor91of the low pass filter9.

(4.2) Second Operation

Next, a second operation of the radio-frequency circuit1according to the first embodiment will be described with reference toFIGS.3A and3B.

In the radio-frequency circuit1according to the first embodiment, the single input matching circuit8is provided for the three receive paths (first, second, and third receive paths) as described above. Thus, for example, depending on at least either the position or orientation of the inductor81of the input matching circuit8relative to the inductor131of the matching circuit13and the inductor141of the matching circuit14, the inductor81may cause magnetic coupling with the inductor131or141.

The following description uses as an example the case in which the direction of current flow in the inductor81is changed between the first receive path and the second receive path, but the same description holds for the case in which the direction of current flow in the inductor81is changed between the first receive path and the third receive path and in the case in which the direction of current flow in the inductor81is changed between the second receive path and the third receive path.

InFIG.3A, the switch18is in the first state. When the switch18is in the first state, the terminal181as the first input-output terminal is coupled to the terminal183as the first switching terminal, and the terminal182as the second input-output terminal is coupled to the terminal184as the second switching terminal. In this case, a current flows through the inductor81of the input matching circuit8in the direction indicated by the arrow A1. Accordingly, a magnetic field is generated around the inductor81in the direction corresponding to the current. At this time, a current also flows through the inductor131of the matching circuit13, and a magnetic field is generated around the inductor131in the direction corresponding to the current.

In this case, when the direction of the magnetic field generated around the inductor81of the input matching circuit8is opposite to the direction of the magnetic field generated around the inductor131of the matching circuit13, the magnetic field generated around the inductor81and the magnetic field generated around the inductor131cancel each other out, and consequently, the magnetic coupling between the inductors81and131is hindered. This can suppress degradation of the isolation between the transmit and receive paths particularly in the transmit frequency band, and as a result, it is possible to reduce the likelihood of leaking transmit signals into the receive path and achieve favorable receive sensitivity during the transmit operation.

Next, when the terminal181as the first input-output terminal is coupled to the terminal183as the first switching terminal in the case of receiving the second receive signal through the second receive path, a current flows in the inductor81of the input matching circuit8in the direction indicated by the arrow A1, and a magnetic field is generated around the inductor81in the direction corresponding to the current. At this time, a current also flows through the inductor141of the matching circuit14, and a magnetic field is generated around the inductor141in the direction corresponding to the current.

In this case, when the direction of the magnetic field generated around the inductor81is identical to the direction of the magnetic field around the inductor141so that the inductors81and141cause magnetic coupling, switching the switch18to the second state can hinder the magnetic coupling between the inductors81and141. Specifically, in the switch18, the terminal181as the first input-output terminal is coupled to the terminal184as the second switching terminal, and the terminal182as the second input-output terminal is coupled to the terminal183as the first switching terminal as illustrated inFIG.3B. In this state, a current flows through the inductor81of the input matching circuit8in the direction indicated by the arrow A2opposite to the arrow A1. Accordingly, a magnetic field is generated around the inductor81in the direction corresponding to the current.

As a result, the direction of the magnetic field generated around the inductor81is opposite to the direction of the magnetic field generated around the inductor141, and the magnetic field generated around the inductor81and the magnetic field generated around the inductor141cancel each other out. As such, it is possible to hinder the magnetic coupling between the inductors81and141. This can suppress degradation of the isolation between the transmit and receive paths particularly in the transmit frequency band, and as a result, it is possible to reduce the likelihood of leaking transmit signals into the receive path and achieve favorable receive sensitivity during the transmit operation. As described above, the radio-frequency circuit1according to the first embodiment can select (change), for each of the different communication bands, the direction of current flow in the inductor81of the input matching circuit8, in other words, the direction of the magnetic field generated around the inductor81. Furthermore, the input matching circuit8does not need to include inductors for different communication bands, and thus, the radio-frequency circuit1can be downsized.

In this case, the inductor in which the direction of current flow is changed by the switch is the inductor81of the input matching circuit8, and the inductors that may cause magnetic coupling with this inductor are the inductor131of the matching circuit13and the inductor141of the matching circuit14.

The following provides descriptions of modifications of the first embodiment.

(5.1) First Modification

The radio-frequency circuit1according to the first embodiment is configured as illustrated inFIG.1such that, of the inductors81and82included in the input matching circuit8, the direction of current flow in the inductor81is changeable. By contrast, as illustrated inFIGS.4A and4B, of the inductors81and82included in the input matching circuit8, the direction of current flow in the inductor82may be changeable. The radio-frequency circuit1according to a first modification will be described below with reference toFIGS.4A and4B. Concerning the radio-frequency circuit1according to the first modification, substantially the same constituent elements as the radio-frequency circuit1according to the first embodiment are assigned the same reference characters, and descriptions thereof are not repeated.

The radio-frequency circuit1according to the first modification includes, as illustrated inFIGS.4A and4B, the switches3and18. In the radio-frequency circuit1according to the first modification, the switches3and18are formed by a single chip component200A; in other words, the switch18is integrated with the switch3.

The switch3has the common terminal30and a plurality (three inFIG.4A) of selection terminals of the selection terminals31,32, and33as illustrated inFIGS.4A and4B. The switch3switches connections between the common terminal30and the selection terminals31,32, and33. More specifically, the switch3switches among the state in which the common terminal30is coupled to the selection terminal31, the state in which the common terminal30is coupled to the selection terminal32, and the state in which the common terminal30is coupled to the selection terminal33. The switch3may be implemented by, for example, an SP3T switch.

The switch18has a plurality (four inFIG.4A) of the terminals181,182,183, and184. The switch18can switch between the first state and the second state to reverse the direction of current flow in the inductor82. In the first state, the terminal181is coupled to the terminal183, and the terminal182is coupled to the terminal184(refer toFIG.4A). In the second state, the terminal181is coupled to the terminal184, and the terminal182is coupled to the terminal183. The switch18may be implemented by, for example, a DPDT switch.

The common terminal30of the switch3is coupled to the terminal181of the switch18. The common terminal30is also coupled to the input terminal61of the low-noise amplifier6via the inductor81. The selection terminal31is coupled to the output terminal of the receive filter102of the duplexer10. The selection terminal32is coupled to the output terminal of the receive filter112of the duplexer11. The selection terminal33is coupled to the output terminal of the receive filter122of the duplexer12.

The terminal182of the switch18is grounded. The terminal183of the switch18is coupled to a first end821of the inductor82of the input matching circuit8, and the terminal184of the switch18is coupled to a second end822of the inductor82. This means that the terminals183and184of the switch18are coupled to the both ends of the inductor82.

In the radio-frequency circuit1according to the first modification, the terminal181is the first input-output terminal and, for example, an input terminal. In the radio-frequency circuit1, the terminal182is the second input-output terminal and, for example, an output terminal. In the radio-frequency circuit1, the terminal183is the first switching terminal, and the terminal184is the second switching terminal.

Next, an operation of the radio-frequency circuit1will be described with reference toFIGS.4A and4B. When the switch18is in the first state, as illustrated inFIG.4A, the terminal181is coupled to the terminal183, and the terminal182is coupled to the terminal184. A current thus flows through the inductor82of the input matching circuit8in the direction indicated by the arrow A1. When the switch18is in the second state, as illustrated inFIG.4B, the terminal181is coupled to the terminal184, and the terminal182is coupled to the terminal183. A current thus flows through the inductor82of the input matching circuit8in the direction indicated by the arrow A2. As described above, in the radio-frequency circuit1according to the first modification, the direction of current flow in the inductor82can be reversed by switching the switch18to the first state or the second state. Accordingly, it is possible to reverse the direction of the magnetic field generated around the inductor82.

Also in the radio-frequency circuit1according to the first modification, the direction of the magnetic field generated around the inductor82of the input matching circuit8can be reversed by switching the switch18to the first state or the second state. Consequently, it is possible to hinder the magnetic coupling between the inductor82and another inductor (for example, the inductor131of the matching circuit13).

In the radio-frequency circuit1according to the first modification, the direction of the magnetic field generated around the inductor82of the input matching circuit8can be changed for each of the different communication bands by switching the switch18to the first state or the second state. With this configuration, the radio-frequency circuit1can be smaller than if inductors are provided for different communication bands.

(5.2) Second Modification

In the radio-frequency circuit1according to the first embodiment, the switch18is switched to the first state or the second state between, for example, the case of receiving the first receive signal through the first receive path and the case of transmitting the second receive signal through the second receive path. By contrast, the switch18may be switched to the first state or the second state between, for example, the case of receiving the first receive signal through the first receive path and the case of transmitting the second transmit signal through the second transmit path.

In this case, the first receive signal received through the first receive path and the second transmit signal transmitted by the second transmit path are simultaneously transmitted and received by, for example, carrier aggregation. In this case, the first receive signal and the second transmit signal may be simultaneously transmitted and received by, for example, dual connectivity.

In this case, the inductor in which the direction of current flow is changed by the switch is the inductor81(first inductor) of the input matching circuit8, and the inductor that may cause magnetic coupling with this inductor is the inductor72(second inductor) coupled to the output side of the power amplifier5.

Also in this case, by switching the switch18to the first state or the second state, it is possible to hinder the magnetic coupling between the inductors72and81.

(5.3) Third Modification

In the radio-frequency circuit1according to the first modification the switch3for switching signal paths for receive signals in different communication bands is integrated with the switch18for changing the direction of current flow in the inductor81, but the switches3and18may be separately formed.

Second Embodiment

A radio-frequency circuit1A and a communication device100A according to a second embodiment will be described with reference toFIGS.5,6A, and6B.

The radio-frequency circuit1A according to the second embodiment differs from the radio-frequency circuit1according to the first embodiment in that the direction of current flow in the inductor72of the output matching circuit7coupled to the output side of the power amplifier5is changeable.

Substantially the same constituent elements as the radio-frequency circuit1according to the first embodiment are assigned the same reference characters, and descriptions thereof are not repeated. The communication device100A is the same as the communication device100according to the first embodiment except the radio-frequency circuit1A, and the description thereof is not repeated.

(1) CONFIGURATION OF RADIO-FREQUENCY CIRCUIT

Firstly, a configuration of the radio-frequency circuit1A according to the second embodiment will be described with reference toFIG.5.

The radio-frequency circuit1A according to the second embodiment includes the switches2,3, and4and a switch19as illustrated inFIG.5. The radio-frequency circuit1A further includes the power amplifier5, the low-noise amplifier6, and the low pass filter9. The radio-frequency circuit1A further includes a plurality (three inFIG.5) of duplexers of the duplexers10,11, and12. The radio-frequency circuit1A further includes the output matching circuit7, the input matching circuit8, a plurality (three inFIG.5) of matching circuits of the matching circuits13,14, and15. In the radio-frequency circuit1A according to the second embodiment, the switches2and19are implemented by a single chip component300; in other words, the switch19for changing the direction of current flow in the inductor72is integrated with the switch2for switching signal paths for transmit signals in different communication bands. The term “integrated” means that the two switches2and19are physically integrated with each other.

The switch2has the common terminal20and a plurality (three inFIG.5) of selection terminals of the selection terminals21,22, and23as illustrated inFIG.5. The switch2switches connections between the common terminal20and the selection terminals21,22, and23. More specifically, the switch2switches among the state in which the common terminal20is coupled to the selection terminal21, the state in which the common terminal20is coupled to the selection terminal22, and the state in which the common terminal20is coupled to the selection terminal23. The switch2may be implemented by, for example, an SP3T switch.

The switch19has a plurality (four inFIG.5) of terminals191,192,193, and194. The switch19can switch between a first state and a second state to reverse the direction of current flow in the inductor72. In the first state, the terminal191is coupled to the terminal193, and the terminal192is coupled to the terminal194(refer toFIG.6A). In the second state, the terminal191is coupled to the terminal194, and the terminal192is coupled to the terminal193(refer toFIG.6B). The switch19may be implemented by, for example, a DPDT switch.

The common terminal20of the switch2is coupled to the terminal191of the switch19via the capacitor75of the output matching circuit7. The selection terminal21is coupled to the input terminal of the transmit filter101of the duplexer10. The selection terminal22is coupled to the input terminal of the transmit filter111of the duplexer11. The selection terminal23is coupled to the input terminal of the transmit filter121of the duplexer12.

The terminal192of the switch19is coupled to the output terminal52of the power amplifier5via the inductor71of the output matching circuit7. The terminal193of the switch19is coupled to a first end721of the inductor72of the output matching circuit7, and the terminal194of the switch19is coupled to a second end722of the inductor72. This means that the terminals193and194of the switch19are coupled to the both ends of the inductor72. The capacitor74of the output matching circuit7is coupled between the ground and a signal path between the capacitor75of the output matching circuit7and the terminal191of the switch19. The capacitor73of the output matching circuit7is coupled between the ground and a signal path between the inductor71of the output matching circuit7and the terminal192of the switch19.

The switch3has the common terminal30and a plurality (three inFIG.5) of selection terminals of the selection terminals31,32, and33. The switch3switches connections between the common terminal30and the selection terminals31,32, and33. More specifically, the switch3switches among the state in which the common terminal30is coupled to the selection terminal31, the state in which the common terminal30is coupled to the selection terminal32, and the state in which the common terminal30is coupled to the selection terminal33. The switch3may be implemented by, for example, an SP3T switch.

The common terminal30is coupled to the input terminal61of the low-noise amplifier6via the inductor81of the input matching circuit8. The selection terminal31is coupled to the receive filter102of the duplexer10. The selection terminal32is coupled to the receive filter112of the duplexer11. The selection terminal33is coupled to the receive filter122of the duplexer12.

In the radio-frequency circuit1A according to the second embodiment, the terminal191is the first input-output terminal and, for example, an output terminal. In the radio-frequency circuit1A, the terminal192is the second input-output terminal and, for example, an input terminal. In the radio-frequency circuit1A, the terminal193is the first switching terminal, and the terminal194is the second switching terminal.

(2) OPERATION OF RADIO-FREQUENCY CIRCUIT

(2.1) First Operation

Next, an operation of the radio-frequency circuit1A according to the second embodiment will be described with reference toFIGS.6A and6B.

In the radio-frequency circuit1A according to the second embodiment, for example, the output matching circuit7includes the inductor72mounted at a mounting board (not illustrated in the drawing). In the radio-frequency circuit1A, for example, the matching circuit13includes the inductor131mounted at the mounting board. Depending on at least either the position or orientation of the inductor72of the output matching circuit7relative to the inductor131of the matching circuit13, the inductors72and131may cause magnetic coupling. This may worsen the isolation between the transmit and receive paths particularly in the receive frequency band, and as a result, noises in the receive band may increase at the time of transmission, resulting in degradation of receive sensitivity during the transmit operation.

To address the problem described above, the radio-frequency circuit1A according to the second embodiment is configured in the following manner. The following description uses an example of the magnetic coupling between the inductor72of the output matching circuit7and the inductor131of the matching circuit13, but the same description holds for the magnetic coupling between the inductor72of the output matching circuit7and the inductor141of the matching circuit14and the magnetic coupling between the inductor72of the output matching circuit7and the inductor151of the matching circuit15. Also, the following description uses as an example the case in which the common terminal20of the switch2is coupled to the selection terminal21, but the same description holds for the case in which the common terminal20is coupled to the selection terminal22or the selection terminal23.

In the radio-frequency circuit1A according to the second embodiment, the inductor in which the direction of current flow is changed by the switch is the inductor72coupled to the output side of the power amplifier5. In the radio-frequency circuit1A according to the second embodiment, the inductors that may cause magnetic coupling with the inductor described above are the inductor131of the matching circuit13, the inductor141of the matching circuit14, and the inductor151of the matching circuit15.

InFIG.6A, the switch19is in the first state. When the switch19is in the first state, the terminal191as the first input-output terminal is coupled to the terminal193as the first switching terminal, and the terminal192as the second input-output terminal is coupled to the terminal194as the second switching terminal. In this case, a current flows through the inductor72of the output matching circuit7in the direction indicated by an arrow B1. Accordingly, a magnetic field is generated around the inductor72in the direction corresponding to the current. At this time, a current also flows through the inductor131of the matching circuit13, and a magnetic field is generated around the inductor131in the direction corresponding to the current.

When the direction of the magnetic field generated around the inductor72is identical to the direction of the magnetic field generated around the inductor131, the magnetic field generated around the inductor72and the magnetic field generated around the inductor131strengthen each other, and consequently, the inductors72and131cause magnetic coupling. This worsens the isolation between the transmit and receive paths particularly in the receive frequency band, and as a result, noises in the receive band increase at the time of transmission, resulting in degradation of receive sensitivity during the transmit operation.

In this case, the direction of current flow in the inductor72can be reversed by switching the switch19to the second state as illustrated inFIG.6B. Specifically, in the switch19, the terminal191as the first input-output terminal is coupled to the terminal194as the second switching terminal, and the terminal192as the second input-output terminal is coupled to the terminal193as the first switching terminal. In this state, a current flows through the inductor72of the output matching circuit7in the direction indicated by an arrow B2opposite to the arrow B1. Accordingly, a magnetic field is generated around the inductor72in the direction corresponding to the current.

In this case, the direction of the magnetic field generated around the inductor72is opposite to the direction of the magnetic field generated around the inductor131, and the magnetic field generated around the inductor72and the magnetic field generated around the inductor131cancel each other out. As such, it is possible to hinder the magnetic coupling between the inductors72and131. This can suppress degradation of the isolation between the transmit and receive paths particularly in the receive frequency band, and as a result, it is possible to reduce noises in the receive band at the time of transmission and suppress degradation of receive sensitivity during the transmit operation.

Similarly, by switching the switch19between the first state and the second state, it is possible to hinder the magnetic coupling between the inductor72of the output matching circuit7and the inductor81of the input matching circuit8and the magnetic coupling between the inductor72of the output matching circuit7and the inductor91of the low pass filter9. In this case, the inductor in which the direction of current flow is changed by the switch is the inductor72of the output matching circuit7, and the inductors that may cause magnetic coupling with this inductor are the inductor81of the input matching circuit8and the inductor91of the low pass filter9.

(2.2) Second Operation

Next, a second operation of the radio-frequency circuit1A according to the second embodiment will be described.

In the radio-frequency circuit1A according to the second embodiment, the single output matching circuit7is provided for the three transmit paths (first, second, and third transmit paths) as described above. Thus, for example, depending on at least either the position or orientation of the inductor72of the output matching circuit7relative to the inductor131of the matching circuit13and the inductor141of the matching circuit14, the inductor72may cause magnetic coupling with the inductor131or141.

The following description uses as an example the case in which the direction of current flow in the inductor72is changed between the first transmit path and the second transmit path, but the same description holds for the case in which the direction of current flow in the inductor72is changed between the first transmit path and the third transmit path and in the case in which the direction of current flow in the inductor72is changed between the second transmit path and the third transmit path.

When the switch19is in the first state, the terminal191as the first input-output terminal is coupled to the terminal193as the first switching terminal, and the terminal192as the second input-output terminal is coupled to the terminal194as the second switching terminal. In the switch2, the common terminal20is coupled to the selection terminal21. In this case, a current flows through the inductor72of the output matching circuit7in the direction indicated by the arrow B1. Accordingly, a magnetic field is generated around the inductor72in the direction corresponding to the current. At this time, a current also flows through the inductor131of the matching circuit13, and a magnetic field is generated around the inductor131in the direction corresponding to the current.

In this case, when the direction of the magnetic field generated around the inductor72of the output matching circuit7is opposite to the direction of the magnetic field generated around the inductor131of the matching circuit13, the magnetic field generated around the inductor72and the magnetic field generated around the inductor131cancel each other out, and consequently, the magnetic coupling between the inductors72and131is hindered. This can suppress degradation of the isolation between the transmit and receive paths particularly in the receive frequency band, and as a result, it is possible to reduce noises in the receive band at the time of transmission and suppress degradation of receive sensitivity during the transmit operation.

Next, when the terminal191as the first input-output terminal is coupled to the terminal193as the first switching terminal in the case of transmitting the second transmit signal through the second transmit path, a current flows in the inductor72of the output matching circuit7in the direction indicated by the arrow B1, and a magnetic field is generated around the inductor72in the direction corresponding to the current. At this time, because the common terminal20is coupled to the selection terminal22in the switch2, a current also flows through the inductor141of the matching circuit14, and a magnetic field is generated around the inductor141in the direction corresponding to the current.

In this case, when the direction of the magnetic field generated around the inductor72is identical to the direction of the magnetic field around the inductor141so that the inductors72and141cause magnetic coupling, switching the switch19to the second state can hinder the magnetic coupling between the inductors72and141. Specifically, in the switch19, the terminal191as the first input-output terminal is coupled to the terminal194as the second switching terminal, and the terminal192as the second input-output terminal is coupled to the terminal193as the first switching terminal. In this state, a current flows through the inductor72of the output matching circuit7in the direction indicated by the arrow B2opposite to the arrow B1. Accordingly, a magnetic field is generated around the inductor72in the direction corresponding to the current.

As a result, the direction of the magnetic field generated around the inductor72is opposite to the direction of the magnetic field generated around the inductor141, and the magnetic field generated around the inductor72and the magnetic field generated around the inductor141cancel each other out. As such, it is possible to hinder the magnetic coupling between the inductors72and141. This can suppress degradation of the isolation between the transmit and receive paths particularly in the receive frequency band, and as a result, it is possible to reduce noises in the receive band at the time of transmission and suppress degradation of receive sensitivity during the transmit operation. As described above, the radio-frequency circuit1A according to the second embodiment can select (change), for each of the different communication bands, the direction of current flow in the inductor72of the output matching circuit7, in other words, the direction of the magnetic field generated around the inductor72. Moreover, the radio-frequency circuit1A can be smaller than if inductors are provided for different communication bands.

In this case, the inductor in which the direction of current flow is changed by the switch is the inductor72of the output matching circuit7, and the inductors that may cause magnetic coupling with this inductor are the inductors131,141, and151of the matching circuits13,14, and15.

The following provides descriptions of modifications of the second embodiment.

(3.1) First Modification

In the radio-frequency circuit1A according to the second embodiment, the switch19is switched to the first state or the second state between, for example, the case of transmitting the first transmit signal through the first transmit path and the case of transmitting the second transmit signal through the second transmit path. By contrast, the switch19may be switched to the first state or the second state between, for example, the case of transmitting the first transmit signal through the first transmit path and the case of receiving the second receive signal through the second receive path.

In this case, the first transmit signal transmitted through the first transmit path and the second receive signal received by the second receive path are simultaneously transmitted and received by, for example, carrier aggregation. In this case, the first transmit signal and the second receive signal may be simultaneously transmitted and received by, for example, dual connectivity.

In this case, the inductor in which the direction of current flow is changed by the switch is the inductor72(first inductor) coupled to the output side of the power amplifier5, and the inductor that may cause magnetic coupling with this inductor is the inductor81(second inductor) coupled to the input side of the low-noise amplifier6.

Also in this case, by switching the switch19to the first state or the second state, it is possible to hinder the magnetic coupling between the inductors72and81.

(3.2) Second Modification

In the radio-frequency circuit1A according to the second embodiment the switch2for switching signal paths for receive signals in different communication bands is integrated with the switch19for changing the direction of current flow in the inductor72, but the switches2and19may be separately formed.

Third Embodiment

A radio-frequency circuit1B and a communication device100B according to a third embodiment will be described with reference toFIGS.7,8A, and8B.

The radio-frequency circuit1B according to the third embodiment differs from the radio-frequency circuit1according to the first embodiment and the radio-frequency circuit1A according to the second embodiment in that the direction of current flow in the inductor91included in the low pass filter9is changeable. Substantially the same constituent elements as the radio-frequency circuit1according to the first embodiment or the radio-frequency circuit1A according to the second embodiment are assigned the same reference characters, and descriptions thereof are not repeated. The communication device100B is the same as the communication device100according to the first embodiment except the radio-frequency circuit1B, and the description thereof is not repeated.

(1) CONFIGURATION OF RADIO-FREQUENCY CIRCUIT

Firstly, the radio-frequency circuit1B according to the third embodiment will be described with reference toFIG.7.

The radio-frequency circuit1B according to the third embodiment includes the switches2and3and a switch4A as illustrated inFIG.7. The radio-frequency circuit1B further includes the power amplifier5, the low-noise amplifier6, and the low pass filter9. The radio-frequency circuit1B further includes a plurality (three inFIG.7) of duplexers of the duplexers10,11, and12. The radio-frequency circuit1B further includes the output matching circuit7, the input matching circuit8, a plurality (three inFIG.5) of matching circuits of the matching circuits13,14, and15.

The switch4A has terminals44,45, and46serving as the first input-output terminal, a terminal49as the second input-output terminal, a terminal47as the first switching terminal, and a terminal48as the second switching terminal. The terminals44,45, and46serving as the first input-output terminal are, for example, input terminals. The terminal49serving as the second input-output terminal is, for example, an output terminal. The switch4A switches connections between the terminals47and48and the terminals44,45,46, and49. The switch4A may be implemented by, for example, a dual pole quadruple throw (DP4T) switch.

The terminal44of the switch4A is coupled to the duplexer10. The terminal45of the switch4A is coupled to the duplexer11. The terminal46of the switch4A is coupled to the duplexer12. The terminal47of the switch4A is coupled to a first end911of the inductor91of the low pass filter9. The terminal48of the switch4A is coupled to a second end912of the inductor91. The terminal49of the switch4A is coupled to the antenna terminal T1.

The switch4A can switch between a first state and a second state to reverse the direction of current flow in the inductor91. In the first state, the terminal44,45, or46as the first input-output terminal is coupled to the terminal47as the first switching terminal, and the terminal49as the second input-output terminal is coupled to the terminal48as the second switching terminal (refer toFIG.8A). In the second state, the terminal44,45, or46as the first input-output terminal is coupled to the terminal48as the second switching terminal, and the terminal49as the second input-output terminal is coupled to the terminal47as the first switching terminal (refer toFIG.8B).

This means that in the radio-frequency circuit1B according to the third embodiment the single switch4A implements both a switch electrically coupled to the antenna terminal T1and a switch for changing the direction of current flow in the inductor91; in other words, a switch for changing the direction of current flow in the inductor91is integrated with a switch electrically coupled to the antenna terminal T1. The term “integrated” means that the two switches are functionally and physically integrated with each other.

(2) OPERATION OF RADIO-FREQUENCY CIRCUIT

(2.1) First Operation

Next, a first operation of the radio-frequency circuit1B according to the third embodiment will be described with reference toFIGS.8A and8B.

In the radio-frequency circuit1B according to the third embodiment, for example, the low pass filter9includes the inductor91mounted at a mounting board (not illustrated in the drawing). In the radio-frequency circuit1B, for example, the output matching circuit7includes the inductor72mounted at the mounting board. Depending on at least either the position or orientation of the inductor91of the low pass filter9relative to the inductor72of the output matching circuit7, the inductors72and91may cause magnetic coupling. This may degrade the attenuation (degree of reduction) of harmonic waves of transmit signals transmitted by the antenna17to the outside.

To address the problem described above, the radio-frequency circuit1B according to the third embodiment is configured in the following manner. The following description uses an example of the magnetic coupling between the inductor91of the low pass filter9and the inductor72of the output matching circuit7, but the same description holds for the magnetic coupling between the inductor91of the low pass filter9and the inductor81of the input matching circuit8. Also, the following description uses as an example the case in which the first input-output terminal is the terminal44, but the same description holds for the case in which the first input-output terminal is the terminal45or46.

In the radio-frequency circuit1B according to the third embodiment, the inductor in which the direction of current flow is changed by the switch is the inductor91included in the low pass filter9, and the inductor that may cause magnetic coupling with this inductor is the inductor72of the output matching circuit7or the inductor81of the input matching circuit8.

InFIG.8A, the switch4A is in the first state. When the switch4A is in the first state, the terminal44as the first input-output terminal is coupled to the terminal47as the first switching terminal, and the terminal49as the second input-output terminal is coupled to the terminal48as the second switching terminal. In this case, a current flows through the inductor91of the low pass filter9in the direction indicated by an arrow C1. Accordingly, a magnetic field is generated around the inductor91in the direction corresponding to the current. At this time, a current also flows through the inductor72of the output matching circuit7, and a magnetic field is generated around the inductor72in the direction corresponding to the current.

When the direction of the magnetic field generated around the inductor91is identical to the direction of the magnetic field generated around the inductor72, the magnetic field generated around the inductor91and the magnetic field generated around the inductor72strengthen each other, and consequently, the inductors91and72cause magnetic coupling. This degrades the attenuation of harmonic waves of transmit signals transmitted by the antenna17to the outside.

In this case, the direction of current flow in the inductor91can be reversed by switching the switch4A to the second state as illustrated inFIG.8B. Specifically, in the switch4A, the terminal44as the first input-output terminal is coupled to the terminal48as the second switching terminal, and the terminal49as the second input-output terminal is coupled to the terminal47as the first switching terminal. In this state, a current flows through the inductor91of the low pass filter9in the direction indicated by an arrow C2opposite to the arrow C1. Accordingly, a magnetic field is generated around the inductor91in the direction corresponding to the current.

In this case, the direction of the magnetic field generated around the inductor91is opposite to the direction of the magnetic field generated around the inductor72, and the magnetic field generated around the inductor91and the magnetic field generated around the inductor72cancel each other out. As such, it is possible to hinder the magnetic coupling between the inductors91and72. As a result, it is possible to suppress degradation of the attenuation of harmonic waves of transmit signals transmitted by the antenna17to the outside.

(2.2) Second Operation

Next, a second operation of the radio-frequency circuit1B according to the third embodiment will be described.

In the radio-frequency circuit1B according to the third embodiment, the single low pass filter9is provided for the three transmit paths (first, second, and third transmit paths) as described above. Thus, for example, depending on at least either the position or orientation of the inductor91of the low pass filter9relative to the inductor131of the matching circuit13and the inductor141of the matching circuit14, the inductor91may cause magnetic coupling with the inductor131or141.

The following description uses as an example the case in which the direction of current flow in the inductor91is changed between the first transmit path and the second transmit path, but the same description holds for the case in which the direction of current flow in the inductor91is changed between the first transmit path and the third transmit path and in the case in which the direction of current flow in the inductor91is changed between the second transmit path and the third transmit path.

When the switch4A is in the first state, the terminal44as the first input-output terminal is coupled to the terminal47as the first switching terminal, and the terminal49as the second input-output terminal is coupled to the terminal48as the second switching terminal. In this case, a current flows through the inductor91of the low pass filter9in the direction indicated by the arrow C1. Accordingly, a magnetic field is generated around the inductor91in the direction corresponding to the current. At this time, a current also flows through the inductor131of the matching circuit13, and a magnetic field is generated around the inductor131in the direction corresponding to the current.

In this case, when the direction of the magnetic field generated around the inductor91of the low pass filter9is opposite to the direction of the magnetic field generated around the inductor131of the matching circuit13, the magnetic field generated around the inductor91and the magnetic field generated around the inductor131cancel each other out, and consequently, the magnetic coupling between the inductors91and131is hindered. As a result, it is possible to suppress degradation of the attenuation of harmonic waves of transmit signals transmitted by the antenna17to the outside.

Next, when the terminal45as the first input-output terminal is coupled to the terminal47as the first switching terminal in the case of transmitting the second transmit signal through the second transmit path, a current flows in the inductor91of the low pass filter9in the direction indicated by the arrow C1, and a magnetic field is generated around the inductor91in the direction corresponding to the current. At this time, a current also flows through the inductor141of the matching circuit14, and a magnetic field is generated around the inductor141in the direction corresponding to the current.

In this case, when the direction of the magnetic field generated around the inductor91is identical to the direction of the magnetic field around the inductor141so that the inductors91and141cause magnetic coupling, switching the switch4A to the second state can hinder the magnetic coupling between the inductors91and141. Specifically, in the switch4A, the terminal45as the first input-output terminal is coupled to the terminal48as the second switching terminal, and the terminal49as the second input-output terminal is coupled to the terminal47as the first switching terminal. In this state, a current flows through the inductor91of the low pass filter9in the direction indicated by the arrow C2opposite to the arrow C1. Accordingly, a magnetic field is generated around the inductor91in the direction corresponding to the current.

As a result, the direction of the magnetic field generated around the inductor91is opposite to the direction of the magnetic field generated around the inductor141, and the magnetic field generated around the inductor91and the magnetic field generated around the inductor141cancel each other out. As such, it is possible to hinder the magnetic coupling between the inductors91and141. As a result, it is possible to suppress degradation of the attenuation of harmonic waves of transmit signals transmitted by the antenna17to the outside. As described above, the radio-frequency circuit1B according to the third embodiment can select (change), for each of the different communication bands, the direction of current flow in the inductor91of the low pass filter9, in other words, the direction of the magnetic field generated around the inductor91. Moreover, the radio-frequency circuit1B can be smaller than if inductors are provided for different communication bands.

In this case, the inductor in which the direction of current flow is changed by the switch is the inductor91included in the low pass filter9, and the inductors that may cause magnetic coupling with this inductor are the inductors131,141, and151of the matching circuits13,14, and15.

The following provides descriptions of modifications of the third embodiment.

(3.1) First Modification

In the radio-frequency circuit1B according to the third embodiment, the single switch4A implements both the switch for switching signal paths for receive signals (or transmit signals) in different communication bands and the switch for changing the direction of current flow in the inductor91as illustrated inFIG.7.

However, a single chip component400may implement both the switch4for switching signal paths for receive signals (or transmit signals) in different communication bands and a switch50for changing the direction of current flow in the inductor91as illustrated inFIG.9; in other words, the switch50for changing the direction of current flow in the inductor91may be integrated with the switch4for switching signal paths for receive signals (or transmit signals) in different communication bands. The term “integrated” means that the two switches (the switches4and50) are physically integrated with each other. Hereinafter, the radio-frequency circuit1B according to a first modification will be described with reference toFIG.9. Concerning the radio-frequency circuit1B according to the first modification, substantially the same constituent elements as the radio-frequency circuit1B according to the third embodiment are assigned the same reference characters, and descriptions thereof are not repeated.

The radio-frequency circuit1B according to the first modification includes the switches4and50instead of the switch4A, as illustrated inFIG.9. In the radio-frequency circuit1B according to the first modification, the switches4and50are formed by the single chip component400; in other words, the switch50is integrated with the switch4.

The switch4has, as illustrated inFIG.9, the common terminal40and a plurality (three inFIG.9) of selection terminals of the selection terminals41,42, and43. The switch4switches connections between the common terminal40and the selection terminals41,42, and43. More specifically, the switch4switches among the state in which the common terminal40is coupled to the selection terminal41, the state in which the common terminal40is coupled to the selection terminal42, and the state in which the common terminal40is coupled to the selection terminal43. The switch4may be implemented by, for example, an SP3T switch.

The switch50has a plurality (four inFIG.9) of terminals of terminals501,502,503, and504. The switch50can switch between a first state and a second state to reverse the direction of current flow in the inductor91. In the first state, the terminal501is coupled to the terminal503, and the terminal502is coupled to the terminal504(refer toFIG.9). In the second state, the terminal501is coupled to the terminal504, and the terminal502is coupled to the terminal503. The switch50may be implemented by, for example, a DPDT switch.

The common terminal40of the switch4is coupled to the terminal501of the switch50. The selection terminal41is coupled to the output terminal of the transmit filter101of the duplexer10and the input terminal of the receive filter102. The selection terminal42is coupled to the output terminal of the transmit filter111of the duplexer11and the input terminal of the receive filter112. The selection terminal43is coupled to the output terminal of the transmit filter121of the duplexer12and the input terminal of the receive filter122.

The terminal502of the switch50is coupled to the antenna terminal T1. The terminal503of the switch50is coupled to the first end911of the inductor91of the low pass filter9, and the terminal504of the switch50is coupled to the second end912of the inductor91. The terminal503of the switch50is also coupled to the first end of the capacitor92of the low pass filter9, and the terminal504of the switch50is coupled to the second end of the capacitor92. This means that the inductor91and the capacitor92are coupled in parallel with each other between the terminals503and504of the switch50.

In the radio-frequency circuit1B according to the first modification, the terminal501is the first input-output terminal and, for example, an input terminal. In the radio-frequency circuit1B, the terminal502is the second input-output terminal and, for example, an output terminal. In the radio-frequency circuit1B, the terminal503is the first switching terminal, and the terminal504is the second switching terminal.

Also in the radio-frequency circuit1B according to the first modification, the direction of the magnetic field generated around the inductor91of the low pass filter9can be reversed by switching the switch50between the first state and the second state. Consequently, it is possible to hinder the magnetic coupling between the inductor91and another inductor (for example, the inductor72of the output matching circuit7).

In the radio-frequency circuit1B according to the first modification, the direction of the magnetic field generated around the inductor91of the low pass filter9can be changed for each of the different communication bands by switching the switch50to the first state or the second state. With this configuration, the radio-frequency circuit1B can be smaller than if inductors are provided for different communication bands.

(3.2) Second Modification

In the radio-frequency circuit1B according to the first modification the switch4for switching signal paths for receive signals in different communication bands is integrated with the switch50for changing the direction of current flow in the inductor91, but the switches4and50may be separately formed.

According to the above description including the embodiments, the following aspects are disclosed.

A radio-frequency circuit (1;1A;1B) according to a first aspect includes an inductor (81;82;72;91) and a switch (18;19;4A,50). The inductor (81;82;72;92) has a first end (811;821;721;911) and a second end (812;822;722;912). The switch (18;19;4A,50) includes a first input-output terminal (181;191;44,45,46,501), a second input-output terminal (182;192;49,502), a first switching terminal (183;193;47,503) coupled to the first end (811;821;721;911) of the inductor (81;82;72;91), and a second switching terminal (184;194;48,504) coupled to the second end (812;722;912) of the inductor (81;82;72;91). The switch (18;19;4A,50) can switch between a first state and a second state. In the first state, the first input-output terminal (181;191;44,45,46,501) is coupled to the first switching terminal (183;193;47,503), and the second input-output terminal (182;192;49,502) is coupled to the second switching terminal (184;194;48,504). In the second state, the first input-output terminal (181;191;44,45,46,501) is coupled to the second switching terminal (184;194;48,504), and the second input-output terminal (182;192;49,502) is coupled to the first switching terminal (183;193;47,503).

With this aspect, desired characteristics can be achieved.

A radio-frequency circuit (1A) according to a second aspect further includes a power amplifier (5) with respect to the first aspect. The power amplifier (5) amplifies a transmit signal to be transferred to an antenna terminal (T1). The inductor is an inductor (72) coupled to the output side of the power amplifier (5).

The radio-frequency circuit (1) according to a third aspect further includes a low-noise amplifier (6) with respect to the first aspect. The low-noise amplifier (6) amplifies a receive signal transferred from the antenna terminal (T1). The inductor is the inductor (81;82) coupled to the input side of the low-noise amplifier (6).

The radio-frequency circuit (1B) according to a fourth aspect further includes a low pass filter (9) with respect to the first aspect. The low pass filter (9) is electrically coupled to the antenna terminal (T1). The inductor is the inductor (91) included in the low pass filter (9).

The radio-frequency circuit (1;1A;1B) according to a fifth aspect further includes another inductor (131,141,151,72,91;131,141,151,81,91;72,81) other than the inductor (81;82;72;91) in any one of the first to fourth aspects.

With this aspect, it is possible to hinder the magnetic coupling between the inductor (81;82;72;91) and the other inductor (131,141,151,72,91;131,141,151,81,91;72,81), and as a result, desired characteristics can be achieved.

In the radio-frequency circuit (1;1A;1B) according to a sixth aspect, with respect to any one of the first to fifth aspects, the switch (18;19;50) is integrated with a switch (2) for switching signal paths for transmit signals in different communication bands, a switch (3) for switching signal paths for receive signals in different communication bands, or a switch (4) electrically coupled to the antenna terminal (T1).

With this aspect, the radio-frequency circuit (1;1A;1B) can be smaller than if the switch (2), the switch (3), or the switch (4) is provided separately from the switch (18;19;50).

The radio-frequency circuit (1;1A) according to a seventh aspect further includes the power amplifier (5), the low-noise amplifier (6), and the other inductor (72;81) with respect to any one of the first to sixth aspects. The power amplifier (5) amplifies a transmit signal to be transferred to an antenna terminal (T1). The low-noise amplifier (6) amplifies a receive signal transferred from the antenna terminal (T1). The other inductor (72;81) is different from the inductor (81;72). The inductor (81;72) is one of the first inductor (72) coupled to the output side of the power amplifier (5) and the second inductor (81) coupled to the input side of the low-noise amplifier (6). The other inductor (72;81) is the other of the first inductor (72) and the second inductor (81). With the radio-frequency circuit (1), a transmit signal and a receive signal are simultaneously transmitted and received by carrier aggregation or dual connectivity.

With this aspect, desired characteristics can be achieved also in communications by carrier aggregation or dual connectivity.

A communication device (100;100A;100B) according to an eighth aspect includes the radio-frequency circuit (1;1A;1B) according to any one of the first to seventh aspects and a signal processing circuit (16). The signal processing circuit (16) processes at least one of a receive signal transferred from the antenna terminal (T1) and a transmit signal to be transferred to the antenna terminal (T1).

With this aspect, desired characteristics can be achieved.

REFERENCE SIGNS LIST