High-frequency switch circuit and transceiver circuit

Abstract

The present invention provides a high-frequency switch circuit and a transceiver circuit that operate normally even in frequency bands higher than the quasi-millimeter wave band. [Solution] The high-frequency switch circuit 1 comprises a first transmission line 11, a second transmission line 12 provided between the first transmission line 11 and ground, and a switch 13 provided between the first transmission line 11 and the second transmission line 12, wherein the sum of the line length of the first transmission line 11 and the line length of the second transmission line 12 is an odd multiple of 1 / 4 the wavelength of the high-frequency signal flowing through the first transmission line.

Description

Technical Field

[0001] The present invention relates to a high-frequency switch circuit and a transmission / reception circuit.

Background Art

[0002] Many wireless communication devices that perform wireless communication using high-frequency signals include a high-frequency switch circuit for switching the signal path of the high-frequency signal. For example, a wireless communication device that transmits and receives high-frequency signals includes a high-frequency switch circuit that switches a circuit connected to an antenna between a transmission circuit and a reception circuit. By this high-frequency switch circuit, the transmission path and the reception path of the high-frequency signal are switched, so that transmission and reception of the high-frequency signal can be performed.

[0003] Patent Document 1 below discloses a high-frequency switch circuit used for switching the signal path of a high-frequency signal in the quasi-millimeter wave band. This high-frequency switch circuit is a circuit that switches a port connected to an antenna port between a transmission port and a reception port. This high-frequency switch circuit includes a high-frequency switch in which a switch is arranged between a matching circuit formed so that the line length becomes 1 / 4 wavelength and the ground. By switching this high-frequency switch to a short or open state, whether the port connected to the antenna port becomes a transmission port or a reception port can be switched.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] Incidentally, the high-frequency switch circuit disclosed in Patent Document 1 mentioned above operates normally if the switch provided in the high-frequency switch is ideal, because the matching circuit functions as a λ / 4 open stub or a λ / 4 short stub. However, in frequency bands higher than the quasi-millimeter wave band (for example, the millimeter wave band), the parasitic capacitance of the switch becomes significant when switching the switch, and there is a problem that the switching between the λ / 4 open stub and the λ / 4 short stub does not operate normally.

[0006] This invention has been made in view of the above circumstances, and aims to provide a high-frequency switch circuit and a transmitting / receiving circuit that operate normally even in frequency bands higher than the quasi-millimeter wave band. [Means for solving the problem]

[0007] To solve the above problems, a high-frequency switch circuit (1) according to a first aspect of the present invention comprises a first transmission line (11), a second transmission line (12) provided between the first transmission line and ground, and a switch (13) provided between the first transmission line and the second transmission line, wherein the sum of the line length of the first transmission line and the line length of the second transmission line is an odd multiple of 1 / 4 the wavelength of the high-frequency signal flowing through the first transmission line.

[0008] The high-frequency switch circuit of the present invention has a first transmission line on one side of the switch and a second transmission line on the other side of the switch, and the sum of the line lengths of the first and second transmission lines is an odd multiple of 1 / 4 the wavelength of the high-frequency signal. Therefore, it is possible to provide a high-frequency switch circuit that operates normally even in frequency bands higher than the quasi-millimeter wave band.

[0009] A second aspect of the present invention is a high-frequency switch circuit in the first aspect of the present invention, wherein the switch is a semiconductor transistor connected in series with the first transmission line and the second transmission line.

[0010] A third aspect of the present invention is a high-frequency switch circuit in which the line length of the first transmission line and the line length of the second transmission line are the same, in the first or second aspect of the present invention.

[0011] A high-frequency switch circuit according to a fourth aspect of the present invention is a high-frequency switch circuit according to a first or second aspect of the present invention in which the line length of the first transmission line and the line length of the second transmission line are different.

[0012] A fifth aspect of the present invention is a high-frequency switch circuit according to any one of the first to fourth aspects of the present invention, wherein the first transmission line and the second transmission line have different characteristic impedances.

[0013] A high-frequency switch circuit according to a sixth aspect of the present invention is a high-frequency switch circuit according to any one of the first to fifth aspects of the present invention, wherein the characteristic impedances of the first transmission line and the second transmission line are different from the impedance of the external circuit to which the first transmission line is connected.

[0014] A transmitting / receiving circuit (2) according to one aspect of the present invention comprises a transmitting circuit (21) provided between an input port (P1) and an input / output port (P2), a receiving circuit (22) provided between the input / output port and an output port (P3), a capacitor (23) provided between the output terminal of the transmitting circuit and the input terminal of the receiving circuit, and a high-frequency switch circuit (1) according to any one of the first to sixth aspects, wherein the first transmission line is connected to the connection point (Q) between the receiving circuit and the capacitor. [Effects of the Invention]

[0015] The present invention has the advantage of providing high-frequency switching circuits and transmitting / receiving circuits that operate normally even in frequency bands higher than the quasi-millimeter wave band. [Brief explanation of the drawing]

[0016] [Figure 1]It is a diagram showing the main configuration of a high-frequency switch circuit according to an embodiment of the present invention. [Figure 2] It is a diagram showing an equivalent circuit of a high-frequency switch circuit according to an embodiment of the present invention when the switch is in the on state. [Figure 3] It is a diagram showing an equivalent circuit of a high-frequency switch circuit according to an embodiment of the present invention when the switch is in the off state. [Figure 4] It is a diagram showing the main configuration of a transmission / reception circuit according to an embodiment of the present invention. [Figure 5] It is a diagram showing an equivalent circuit of a transmission / reception circuit according to an embodiment of the present invention. [Figure 6] It is a diagram showing an example of a simulation result of a high-frequency switch circuit according to an embodiment of the present invention. [Figure 7] It is a diagram showing another example of a simulation result of a high-frequency switch circuit according to an embodiment of the present invention.

Embodiments for Carrying Out the Invention

[0017] Hereinafter, referring to the drawings, a high-frequency switch circuit and a transmission / reception circuit according to embodiments of the present invention will be described in detail. In the drawings referred to below, for ease of understanding, the dimensions of each member are appropriately changed and illustrated as necessary.

[0018] 〈High-Frequency Switch Circuit〉 FIG. 1 is a diagram showing the main configuration of a high-frequency switch circuit according to an embodiment of the present invention. As shown in FIG. 1, the high-frequency switch circuit 1 of the present embodiment includes a first transmission line 11, a second transmission line 12, and a switch 13. The high-frequency switch circuit 1 of the present embodiment is used in a circuit for transmitting a high-frequency signal in a frequency band higher than the quasi-millimeter wave band (for example, the millimeter wave band), for example.

[0019] The first transmission line 11 is a line through which a high-frequency signal is transmitted. The second transmission line 12 is, like the first transmission line 11, a line through which a high-frequency signal is transmitted. The second transmission line 12 is provided between the first transmission line 11 and the ground. The switch 13 is a switch that is turned on or off by a control signal input from the outside. The switch 13 is provided between the first transmission line 11 and the second transmission line 12.

[0020] That is, the first transmission line 11, the switch 13, and the second transmission line 12 are connected in series in this order between the external connection terminal T and the ground. Specifically, one end of the first transmission line 11 is connected to the external connection terminal T, and the other end is connected to one end of the switch 13. One end of the switch 13 is connected to the other end of the first transmission line 11, and the other end is connected to one end of the second transmission line 12. One end of the second transmission line 12 is connected to the other end of the switch 13, and the other end is connected to the ground.

[0021] The first transmission line 11 and the second transmission line 12 are designed such that the sum of their line lengths is 1 / 4 of the wavelength of the high-frequency signal. That is, if the wavelength of the high-frequency signal is λ, the sum of the line length of the first transmission line 11 and the line length of the second transmission line 12 is λ / 4. Note that the line length of the first transmission line 11 and the line length of the second transmission line 12 may be the same or different.

[0022] The first transmission line 11 and the second transmission line 12 may have the same characteristic impedance, or their characteristic impedances may be different from each other. The characteristic impedances of the first transmission line 11 and the second transmission line 12 may be the same as or different from the impedance of an external circuit (for example, a circuit including the transmission circuit 21, the reception circuit 22, and the capacitor 23 shown in FIG. 4) to which the first transmission line 11 is connected.

[0023] Switch 13 is, for example, a semiconductor transistor. Switch 13 may be an FET (Field Effect Transistor) or a BJT (Bipolar Junction Transistor). If switch 13 is an FET, for example, the drain terminal is connected to the other end of the first transmission line 11, the source terminal is connected to one end of the second transmission line 12, and a control signal is input to the gate terminal. If switch 13 is a BJT, for example, the collector terminal is connected to the other end of the first transmission line 11, the emitter terminal is connected to one end of the second transmission line 12, and a control signal is input to the base terminal. Note that switch 13 may be a semiconductor transistor other than an FET or BJT.

[0024] Multiple switches 13 may be provided between the first transmission line 11 and the second transmission line 12. For example, multiple switches 13 may be connected in series, or multiple switches 13 may be connected in parallel, between the first transmission line 11 and the second transmission line 12. For example, if multiple switches 13 are connected in series, the voltage applied to one switch 13 can be reduced. This allows, for example, a transistor with a low voltage rating to be used as a switch 13.

[0025] Figure 2 shows the equivalent circuit of a high-frequency switch circuit according to one embodiment of the present invention when the switch is in the ON state. When switch 13 of the high-frequency switch circuit 1 is in the ON state, switch 13 can be represented by its resistive component in the ON state (on-resistance). Therefore, as shown in Figure 2, the high-frequency switch circuit 1 is equivalent to a circuit in which the first transmission line 11, the on-resistance of switch 13, and the second transmission line 12 are connected in this order between the external connection terminal T and ground. Since this circuit operates as a λ / 4 short stub, the impedance seen from the external connection terminal T is a high impedance close to an open circuit.

[0026] Figure 3 shows the equivalent circuit of a high-frequency switch circuit according to one embodiment of the present invention when the switch is in the off state. When switch 13 of the high-frequency switch circuit 1 is in the off state, switch 13 can be represented by a capacitor based on parasitic capacitance. Therefore, as shown in Figure 3, the high-frequency switch circuit 1 is equivalent to a circuit in which a first transmission line 11, a capacitor (parasitic capacitance of switch 13), and a second transmission line 12 are connected in this order between the external connection terminal T and ground.

[0027] This circuit operates as an LC resonant circuit (LCL resonant circuit) that includes the inductance (L) component of the first transmission line 11, the capacitance (C) component based on the parasitic capacitance of the switch 13, and the inductance (L) component of the second transmission line 12. Therefore, the impedance seen from the external connection terminal T is a low impedance close to a short circuit.

[0028] In the case of high-frequency signals below the quasi-millimeter wave band, the circuit will function as an LC resonant circuit even if the line length of either the first transmission line 11 or the second transmission line 12 shown in Figure 3 is set to λ / 4 and the other line is omitted. However, in the case of high-frequency signals in a frequency band higher than the quasi-millimeter wave band (for example, the millimeter wave band), such a circuit will no longer function as an LC resonant circuit because the parasitic capacitance of switch 13 becomes too large.

[0029] In this embodiment, a transmission line with a line length of λ / 4 is, so to speak, divided into a first transmission line 11 and a second transmission line 12, which are arranged on either side of the switch 13. When the switch 13 is in the off state, an LCL resonant circuit is formed. As a result, even high-frequency signals in a frequency band higher than the quasi-millimeter wave band (for example, the millimeter wave band) will resonate, and the impedance seen from the external connection terminal T can be made low impedance, close to a short circuit.

[0030] As mentioned above, as long as the sum of the lengths of the first transmission line 11 and the second transmission line 12 is λ / 4, the lengths of the first transmission line 11 and the second transmission line 12 may be the same or different. The resonance conditions of the LCL resonant circuit described above change depending on the length of the first transmission line 11, the length of the second transmission line 12, and the magnitude of the parasitic capacitance of the switch 13. For this reason, it is desirable to adjust the lengths of the first transmission line 11 and the second transmission line 12 in accordance with the magnitude of the parasitic capacitance of the switch 13.

[0031] <Transmit / receive circuit> Figure 4 shows the main components of a transmitting / receiving circuit according to one embodiment of the present invention. As shown in Figure 4, the transmitting / receiving circuit 2 of this embodiment comprises a transmitting circuit 21, a receiving circuit 22, a capacitor 23, and a high-frequency switch circuit 1. The transmitting / receiving circuit of this embodiment transmits and receives high-frequency signals in a frequency band higher than the quasi-millimeter wave band (for example, the millimeter wave band).

[0032] The transmitting circuit 21 performs the necessary signal processing on the high-frequency signal to transmit the high-frequency signal. This signal processing includes, for example, amplification of the high-frequency signal. The transmitting circuit 21 is located between the input port P1 and the input / output port P2. The receiving circuit 22 performs the necessary signal processing to receive the transmitted high-frequency signal. This signal processing includes, for example, amplification using a low-noise amplifier. The receiving circuit 22 is located between the input / output port P2 and the output port P3.

[0033] Capacitor 23 is used to connect the receiving circuit 22 to the input / output port P2. Capacitor 23 is located between the output terminal of the transmitting circuit 21 and the input terminal of the receiving circuit 22. The high-frequency switch circuit 1 is connected such that the external connection terminal T shown in Figures 1-3 is connected to the connection point Q between the receiving circuit 22 and capacitor 23. In other words, the high-frequency switch circuit 1 is connected such that one end of the first transmission line 11 is connected to the connection point Q between the receiving circuit 22 and capacitor 23.

[0034] Figure 5 shows the equivalent circuit of a transmit / receive circuit according to one embodiment of the present invention. Figure 5(a) shows the equivalent circuit of the transmit / receive circuit 2 in transmit mode when transmitting a high-frequency signal, and Figure 5(b) shows the equivalent circuit of the transmit / receive circuit 2 in receive mode when receiving a high-frequency signal. In transmit mode, switch 13 of the high-frequency switch circuit 1 is in the off state, and in receive mode, switch 13 of the high-frequency switch circuit 1 is in the on state.

[0035] In transmit mode, the switch 13 of the high-frequency switch circuit 1 is turned off, making the high-frequency switch circuit 1 equivalent to the circuit shown in Figure 3. In other words, the impedance seen from the external connection terminal T becomes a low impedance close to a short circuit. As a result, the transmit / receive circuit 2 becomes a circuit that is almost equivalent to a circuit in which the connection point Q between the receive circuit 22 and capacitor 23 is grounded, as shown in Figure 5(a). In the circuit shown in Figure 5(a), the high-frequency signal input from input port P1 is output from input / output port P2 after signal processing necessary for transmitting the high-frequency signal is performed in the transmit circuit 21.

[0036] In receive mode, the switch 13 of the high-frequency switch circuit 1 is turned ON, making the high-frequency switch circuit 1 equivalent to the circuit shown in Figure 2. In other words, the impedance seen from the external connection terminal T becomes a high impedance close to an open circuit. As a result, the transmit / receive circuit 2 becomes a circuit that is almost equivalent to the circuit in which the connection point Q between the receive circuit 22 and the capacitor 23 is disconnected from the high-frequency switch circuit 1, as shown in Figure 5(b). In the circuit shown in Figure 5(b), the high-frequency signal input from the input / output port P2 is input to the receive circuit 22 via the capacitor 23, and after the necessary signal processing for receiving the high-frequency signal is performed in the receive circuit 22, it is output from the output port P3.

[0037] <Simulation results of high-frequency switch circuit> Figure 6 shows an example of simulation results for a high-frequency switch circuit according to one embodiment of the present invention. The simulation results in Figure 6 show the characteristics (impedance) of the high-frequency switch circuit 1 as a Smith chart when the ratio of the lengths of the first transmission line 11 and the second transmission line 12 is changed.

[0038] In this simulation, the frequency of the high-frequency signal is 28 GHz, and λ / 4 is 1320 μm. That is, the sum of the line length of the first transmission line 11 and the line length of the second transmission line 12 is 1320 μm.

[0039] The impedances Z11 and Z21 shown in Figure 6 are the impedances when the length of the first transmission line 11 is 1000 μm and the length of the second transmission line 12 is 320 μm. Impedance Z11 is the impedance when switch 13 of the high-frequency switch circuit 1 is in the ON state, and impedance Z21 is the impedance when switch 13 of the high-frequency switch circuit 1 is in the OFF state.

[0040] The impedances Z12 and Z22 shown in Figure 6 are the impedances when the length of the first transmission line 11 is 920 μm and the length of the second transmission line 12 is 400 μm. Impedance Z12 is the impedance when switch 13 of the high-frequency switch circuit 1 is in the ON state, and impedance Z22 is the impedance when switch 13 of the high-frequency switch circuit 1 is in the OFF state.

[0041] The impedances Z13 and Z23 shown in Figure 6 are the impedances when the length of the first transmission line 11 is 840 μm and the length of the second transmission line 12 is 480 μm. Impedance Z13 is the impedance when switch 13 of the high-frequency switch circuit 1 is in the ON state, and impedance Z23 is the impedance when switch 13 of the high-frequency switch circuit 1 is in the OFF state.

[0042] The impedances Z14 and Z24 shown in Figure 6 are the impedances when the length of the first transmission line 11 is 760 μm and the length of the second transmission line 12 is 560 μm. Impedance Z14 is the impedance when switch 13 of the high-frequency switch circuit 1 is in the ON state, and impedance Z24 is the impedance when switch 13 of the high-frequency switch circuit 1 is in the OFF state.

[0043] Referring to the impedances Z11 to Z14 in Figure 6, it can be seen that when switch 13 of the high-frequency switch circuit 1 is in the ON state, the impedance does not change much even if the ratio of the lengths of the first transmission line 11 and the second transmission line 12 changes. Also, referring to the impedances Z21 to Z24 in Figure 6, it can be seen that when switch 13 of the high-frequency switch circuit 1 is in the OFF state, although the reactance changes slightly when the ratio of the lengths of the first transmission line 11 and the second transmission line 12 changes, the impedance does not change significantly.

[0044] Figure 7 shows another example of simulation results for a high-frequency switch circuit according to one embodiment of the present invention. The simulation results in Figure 7 show the characteristics of the high-frequency switch circuit 1 as a Smith chart when the semiconductor transistor used as switch 13 is changed and the ratio of the lengths of the first transmission line 11 and the second transmission line 12 is changed.

[0045] Furthermore, in this simulation, as in the simulation explained using Figure 6, the frequency of the high-frequency signal is 28 GHz and λ / 4 is 1320 μm. That is, the sum of the line length of the first transmission line 11 and the line length of the second transmission line 12 is 1320 μm. In addition, in this simulation, the gate width ratio of the semiconductor transistor (FET) used as switch 13 is changed. The gate width ratio of a semiconductor transistor is the ratio of the distance between the drain and source (channel length) to the length in the depth direction of the drain and source (channel width).

[0046] The impedances Z31 and Z41 shown in Figure 7 are those when the gate width ratio of the semiconductor transistor is "5", the length of the first transmission line 11 is 720 μm, and the length of the second transmission line 12 is 600 μm. Impedance Z31 is the impedance when switch 13 of the high-frequency switch circuit 1 is in the ON state, and impedance Z41 is the impedance when switch 13 of the high-frequency switch circuit 1 is in the OFF state.

[0047] The impedances Z32 and Z42 shown in Figure 7 are those when the gate width ratio of the semiconductor transistor is "4", the length of the first transmission line 11 is 880 μm, and the length of the second transmission line 12 is 440 μm. Impedance Z32 is the impedance when switch 13 of the high-frequency switch circuit 1 is in the ON state, and impedance Z42 is the impedance when switch 13 of the high-frequency switch circuit 1 is in the OFF state.

[0048] The impedances Z33 and Z43 shown in Figure 7 are those when the gate width ratio of the semiconductor transistor is "3", the length of the first transmission line 11 is 1040 μm, and the length of the second transmission line 12 is 280 μm. Impedance Z33 is the impedance when switch 13 of the high-frequency switch circuit 1 is in the ON state, and impedance Z43 is the impedance when switch 13 of the high-frequency switch circuit 1 is in the OFF state.

[0049] The impedances Z34 and Z44 shown in Figure 7 are those when the gate width ratio of the semiconductor transistor is "2", the length of the first transmission line 11 is 1120 μm, and the length of the second transmission line 12 is 200 μm. Impedance Z34 is the impedance when switch 13 of the high-frequency switch circuit 1 is in the ON state, and impedance Z44 is the impedance when switch 13 of the high-frequency switch circuit 1 is in the OFF state.

[0050] Referring to impedances Z31-Z34 in Figure 7, it can be seen that when switch 13 of the high-frequency switch circuit 1 is in the ON state, the resistance component of the impedance changes significantly when the semiconductor transistor is changed. However, it can be seen that the reactance does not increase significantly by changing the ratio of the lengths of the first transmission line 11 and the second transmission line 12 according to the semiconductor transistor. Similarly, referring to impedances Z41-Z44 in Figure 7, when switch 13 of the high-frequency switch circuit 1 is in the OFF state, it can be seen that the resistance component of the impedance changes significantly when the semiconductor transistor is changed, just as with impedances Z31-Z34. However, it can be seen that the reactance does not increase significantly by changing the ratio of the lengths of the first transmission line 11 and the second transmission line 12 according to the semiconductor transistor.

[0051] As described above, the high-frequency switch circuit 1 of this embodiment comprises a first transmission line 11, a second transmission line 12 provided between the first transmission line 11 and ground, and a switch 13 provided between the first transmission line 11 and the second transmission line 12. The sum of the line lengths of the first transmission line 11 and the second transmission line 12 is set to 1 / 4 the wavelength of the high-frequency signal. Therefore, it can operate normally even in frequency bands higher than the quasi-millimeter wave band.

[0052] Although a high-frequency switch circuit and a transmitting / receiving circuit according to one embodiment of the present invention have been described above, the present invention is not limited to the above embodiment and can be freely modified within the scope of the present invention. For example, in the above embodiment, the case in which the sum of the line length of the first transmission line 11 and the line length of the second transmission line 12 is 1 / 4 the length of the wavelength of the high-frequency signal was described as an example. However, the sum of the line length of the first transmission line 11 and the line length of the second transmission line 12 is not limited to 1 / 4 the length of the wavelength of the high-frequency signal, but may be an odd multiple of 1 / 4 the length of the wavelength of the high-frequency signal. That is, if n is a natural number, the sum of the line length of the first transmission line 11 and the line length of the second transmission line 12 may be a length expressed as (2n-1)λ / 4.

[0053] Furthermore, the application of the high-frequency switch circuit 1 of this embodiment is not limited to its use in the transmitting and receiving circuit described with reference to Figures 4 and 5. The high-frequency switch circuit 1 of this embodiment can be used, for example, in circuits, equipment, devices, etc., that transmit high-frequency signals in a frequency band higher than the quasi-millimeter wave band (for example, the millimeter wave band). [Explanation of Symbols]

[0054] 1…High-frequency switch circuit, 2…Transmit / receive circuit, 11…First transmission line, 12…Second transmission line, 13…Switch, 21…Transmitting circuit, 22…Receiving circuit, 23…Capacitor, P1…Input port, P2…Input / output port, P3…Output port, Q…Connection point

Claims

1. The first transmission line and A second transmission line is provided between the first transmission line and the ground, A switch provided between the first transmission line and the second transmission line, Equipped with, The sum of the line length of the first transmission line and the line length of the second transmission line is an odd multiple of 1 / 4 the wavelength of the high-frequency signal flowing through the first transmission line. High-frequency switch circuit.

2. The high-frequency switch circuit according to claim 1, wherein the switch is a semiconductor transistor connected in series with the first transmission line and the second transmission line.

3. The high-frequency switch circuit according to claim 1, wherein the line length of the first transmission line and the line length of the second transmission line are the same.

4. The high-frequency switch circuit according to claim 1, wherein the line length of the first transmission line and the line length of the second transmission line are different.

5. The high-frequency switch circuit according to claim 1, wherein the first transmission line and the second transmission line have different characteristic impedances.

6. The high-frequency switch circuit according to claim 1, wherein the characteristic impedances of the first transmission line and the second transmission line are different from the impedance of the external circuit to which the first transmission line is connected.

7. A transmission circuit is provided between the input port and the input / output port, A receiving circuit is provided between the input / output port and the output port, A capacitor is provided between the output terminal of the transmitting circuit and the input terminal of the receiving circuit, A high-frequency switch circuit according to any one of claims 1 to 6, wherein the first transmission line is connected to the connection point between the receiving circuit and the capacitor, A transmitting and receiving circuit equipped with this.

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