JP2011229029A - High frequency switching circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a high frequency switching circuit capable of switching over a transmission system of high frequency signals at high speed by rapidly removing charges on PIN diodes with a simple circuit configuration.SOLUTION: A first minus power source (a minus power source) 4 applies a reverse bias voltage to a PIN diode (a diode) 6 via an NPN type transistor (a first semiconductor switch) 2, and a first plus power source (a plus power source) 5 supplies a forward current to the PIN diode 6 via a PNP type transistor (a second semiconductor switch) 3. A second minus power source (a minus power source) 13 applies a reverse bias voltage to a PIN diode (a diode) 15 via an NPN type transistor (a first semiconductor switch) 11, and a second plus power source (a plus power source) 14 supplies a forward current to the PIN diode 15 via a PNP type transistor (a second semiconductor switch) 12. In this way, the system of high frequency signals can be switched over at high speed.

Description

  The present invention relates to a high-frequency switching circuit that switches a transmission system of a high-frequency signal using a semiconductor switch.

  A high-frequency switching circuit that switches a transmission system of a high-frequency signal by using a PIN (Positive-Intrinsic-Negative) diode in which an intermediate layer (I layer) having a low impurity concentration is formed between the P layer and the N layer is widely known. ing. Since this PIN diode can change the high-frequency series resistance by controlling the current flowing in the forward direction, it is preferably used for a high-frequency switching circuit or a high-frequency variable attenuator for switching a high-frequency signal transmission system. ing.

  FIG. 4 is a circuit diagram of a commonly used high-frequency switching circuit. In FIG. 4, a first positive power source 24 and a second positive power source 33 are voltage supply sources having a higher voltage than the third positive power source 27. The first switching circuit 21 supplies / cuts off the base current to the transistor 22. When the base current from the first switching circuit 21 to the transistor 22 is cut off, a reverse bias voltage is applied from the first positive power source 24 to the PIN diode 26 via the resistor 23, and the PIN diode 26 is turned off. Therefore, no high frequency signal is transmitted between the first input terminal 25 and the output terminal 29.

  Further, when the base current is supplied from the first switching circuit 21 to the transistor 22, the transistor 22 is turned on, and the forward current is supplied from the third positive power source 27 to the PIN diode 26 via the resistor 28. The high frequency signal is transmitted between the first input terminal 25 and the output terminal 29. Note that the magnitude of the forward current of the PIN diode 26 at this time is determined by the value of the resistor 28 connected in series to the third positive power source 27.

  Similarly, the second switching circuit 30 supplies / cuts off the base current to the transistor 31. When the base current from the second switching circuit 30 to the transistor 31 is cut off, a reverse bias voltage is applied from the second positive power source 33 via the resistor 32 to the PIN diode 35, and the PIN diode 35 is turned off. Therefore, no high frequency signal is transmitted between the second input terminal 34 and the output terminal 29.

  Further, when the base current is supplied from the second switching circuit 30 to the transistor 31, the transistor 31 is turned on, and the forward current is supplied from the third plus power source 27 via the resistor 28 to the PIN diode 35. The high frequency signal is transmitted between the second input terminal 34 and the output terminal 29. Note that the magnitude of the forward current of the PIN diode 35 at this time is determined by the value of the resistor 28 connected in series to the third positive power source 27.

  In this way, the first switching circuit 21 and the second switching circuit 30 alternately turn on / off the transistor 22 and the transistor 31, thereby causing the PIN diode 26 and the PIN diode 35 to alternately reverse bias. A voltage is applied and a forward current is supplied. Accordingly, the high-frequency signal transmission path between the first input terminal 25 and the output terminal 29 and the high-frequency signal transmission path between the second input terminal 34 and the output terminal 29 can be switched alternately.

  In addition, as a related technology of a high-frequency switching circuit for switching a high-frequency signal transmission system at high speed, both ends of the PIN diode are forcibly short-circuited by a semiconductor switch to have the same potential, so that the PIN diode is turned on at high speed. A technique for switching to OFF is disclosed (for example, see Patent Document 1). According to this technology, by short-circuiting both ends of the PIN diode by the semiconductor switch, the charge accumulated in the PIN diode can be discharged rapidly by the semiconductor switch. Can be done.

  Furthermore, as another related technique, a pair of diodes are reversely connected to each other via a capacitor, and the forward current is controlled to be conductive / non-conductive, whereby the diode is made conductive and a high-frequency signal is applied. A technique for making a high-frequency signal cut off is disclosed (see Patent Document 2). According to this technique, since the diodes are connected in series with reverse polarity, it is possible to prevent a high-power high-frequency signal that causes the diodes to conduct without passing a forward current.

JP 59-210702 A JP 2008-194180 A

  However, the general high-frequency switching circuit as shown in FIG. 4 has the following problems. That is, the first problem is that the reverse bias applied to the PIN diode 26 (or PIN diode 35) from the first positive power source 24 (or second positive power source 33) when the transistor 22 (or transistor 31) is OFF. Since the voltage is limited by the resistor 23 (or resistor 32) connected in series with the first positive power supply 24 (or second positive power supply 33), the charge of the PIN diode 26 (or PIN diode 35) is removed. It takes time to do so, and high frequency signals cannot be switched on / off at high speed.

  The second problem is that when the transistor 22 (or the transistor 31) is turned on, the first positive power source 24 (or the second positive power source 33) for reverse biasing the PIN diode 26 (or the PIN diode 35) is used. Since current flows to the transistor 22 (or the transistor 31), useless consumption current is generated. As a result, the resistance value of the resistor 23 (or resistor 32) must be increased, and it takes time to remove the charge, and the high-frequency signal cannot be switched ON / OFF at high speed.

  Further, the third problem is that a high reverse bias voltage is required particularly in a high-power high-frequency circuit, but the first positive power supply 24 for reverse bias is supplied to the PIN diode 26 via the resistor 23. Therefore (or because the second positive power supply 33 for reverse bias is supplied to the PIN diode 35 via the resistor 32), a voltage drop corresponding to the resistance occurs in the reverse bias voltage, and the PIN diode 26 (or PIN diode 35) cannot be applied with a sufficient reverse bias voltage. That is, in order to apply a sufficient reverse bias voltage, a higher voltage must be set in consideration of the voltage drop of the resistor.

  Further, since the technology disclosed in Patent Document 1 removes the charge of the PIN diode by short-circuiting both ends of the PIN diode with a semiconductor switch, the potentials at both ends of the PIN diode are the same. Since it takes time until the charges are removed, it takes time to switch the transmission system of the high-frequency signal. Furthermore, the technique disclosed in Patent Document 2 is different in that a high-frequency current is blocked by connecting a PIN diode with a reverse polarity, but the potential at both ends of the PIN diode is the same as in Patent Document 1. Therefore, it cannot be applied to a high-frequency switching circuit that switches a high-frequency signal transmission system at high speed.

  The present invention has been made in view of the above circumstances, and provides a high-frequency switching circuit capable of switching a high-frequency signal transmission system at high speed by rapidly removing the charge of a PIN diode with a simple circuit configuration. The purpose is that.

  In order to achieve the above object, the first configuration of the present invention has a plurality of transmission paths for transmitting a high-frequency signal, and alternately connects / disconnects diodes connected in series to the respective transmission paths. A high-frequency switching circuit that performs system switching of the high-frequency signal, and applies a reverse bias voltage directly to the diodes connected to the transmission paths of the plurality of systems via the first semiconductor switch. A negative power source and a positive power source for supplying a forward current to the diodes connected to the transmission paths of the plurality of systems via a second semiconductor switch, and the negative power source for each of the diodes. By alternately applying a reverse bias voltage from the positive power supply and a forward current from the positive power source, the high-frequency signal system It is characterized by carrying out the exchange.

  According to the configuration of the present invention, a reverse bias voltage is directly applied to a diode (PIN diode) connected in series to a high-frequency signal transmission path without passing through a resistor. Therefore, the electric charge accumulated when the diode (PIN diode) is turned on is rapidly removed when the diode is turned off. Thereby, the transmission path of the high frequency signal transmitted through the diode can be switched at high speed.

1 is a circuit diagram of a high frequency switching circuit according to a first embodiment of the present invention. It is a circuit diagram of the high frequency switching circuit which is the 2nd Embodiment of this invention. It is a circuit diagram of the high frequency switching circuit which is the 3rd Embodiment of this invention. It is a circuit diagram of a related high frequency switching circuit.

In the related technology, a reverse bias voltage is applied to the PIN diode using a relatively high value resistor. Thereby, the charge of the PIN diode can be removed at a higher speed than when both ends of the PIN diode are short-circuited, and the high-frequency signal transmission system can be switched at a relatively high speed. However, since the current is limited by the resistance, the charge removal is also limited, and as a result, the high-speed signal switching is also limited. Furthermore, since a wasteful current flows through the transistor when the PIN diode is turned on, the resistance value must be increased. Therefore, there is a limit to high-speed switching of the transmission system of the high-frequency signal. Therefore, according to the embodiment of the present invention, the reverse bias voltage is directly applied to the PIN diode without using a resistor, thereby removing charges accumulated in the PIN diode more rapidly, thereby switching the transmission system of the high-frequency signal. Realizing further speedup of time.
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

First embodiment

  FIG. 1 is a circuit diagram of a high-frequency switching circuit according to the first embodiment of the present invention. This high-frequency switching circuit is characterized in that a high-frequency signal transmission system is switched at high speed by directly applying a reverse bias voltage to the PIN diode.

  First, the configuration of the high-frequency switching circuit according to the first embodiment shown in FIG. 1 will be described. In FIG. 1, the first switching circuit 1 supplies a current to either the base of the NPN transistor 2 or the base of the PNP transistor 3. When the NPN transistor 2 is turned on, it applies a reverse bias voltage from the first negative power source 4 to the PIN diode 6. When the PNP transistor 3 is turned on, the forward current from the first positive power source 5 is supplied to the PIN diode 6.

  The PIN diode 6 performs ON / OFF switching of the high-frequency signal transmitted from the first input terminal 7a. The resistor 9 determines the magnitude of the forward current flowing through the PIN diode 6 and the PIN diode 15. The output terminal 8a outputs the high frequency signal transmitted from the first input terminal 7a or the second input terminal 16a to the outside.

  Similarly, the second switching circuit 10 supplies a current to either the base of the NPN transistor 11 or the base of the PNP transistor 12. When turned on, the NPN transistor 11 applies a reverse bias voltage from the second negative power source 13 to the PIN diode 15. The PNP transistor 12 supplies a forward current from the second positive power source 14 to the PIN diode 15 when turned on. The PIN diode 15 performs ON / OFF switching of the high-frequency signal transmitted from the second input terminal 16a.

  The first switching circuit 1 and the second switching circuit 2 can be easily realized by, for example, a discrete flip-flop circuit using transistors, or a D-flip flop or a JK-flip flop. Accordingly, these switching circuits are well known to those skilled in the art, and are not directly related to the present invention, so that detailed description thereof is omitted.

  Next, the operation of the high frequency switching circuit according to the first embodiment shown in FIG. 1 will be described. In FIG. 1, the first switching circuit 1 supplies a current to either the base of the NPN transistor 2 or the base of the PNP transistor 3. When a current is supplied from the first switching circuit 1 to the base of the NPN transistor 2, a reverse bias voltage is applied from the first negative power source 4 to the PIN diode 6, so that the PIN diode 6 is turned OFF, and the first The high frequency signal from the input terminal 7a is not output to the output terminal 8a.

  When a current is supplied from the first switching circuit 1 to the base of the PNP transistor 3, the forward current is supplied from the first positive power source 5 to the PIN diode 6, so that the PIN diode 6 is turned on. The high frequency signal from the first input terminal 7a is output to the output terminal 8a. Note that the forward current of the PIN diode 6 at this time is determined by the value of the resistor 9.

  Similarly, the second switching circuit 10 supplies a current to either the base of the NPN transistor 11 or the base of the PNP transistor 12. When a current is supplied from the second switching circuit 10 to the base of the NPN transistor 11, a reverse bias is applied from the second negative power supply 13 to the PIN diode 15, so that the PIN diode 15 is turned OFF and the second input The high frequency signal from the terminal 16a is not output to the output terminal 8a.

  When a current is supplied from the second switching circuit 10 to the base of the PNP transistor 12, forward current is supplied from the second positive power source 14 to the PIN diode 15, so that the PIN diode 6 is turned on. The high frequency signal from the second input terminal 16a is output to the output terminal 8a. Note that the forward current of the PIN diode 15 at this time is determined by the value of the resistor 9.

  In this way, the first switching circuit 1 and the second switching circuit 10 alternately turn on / off the NPN transistor 2 and the PNP transistor 3, and the NPN transistor 11 and the PNP transistor 12 alternately. By doing so, the PIN diode 6 and the PIN diode 15 can be turned ON / OFF alternately. Thus, the high-frequency signal transmission system between the first input terminal 7a and the output terminal 8a and the high-frequency signal transmission system between the second input terminal 16a and the output terminal 8a can be switched alternately. it can.

  In this embodiment, a reverse bias voltage is directly applied to the PIN diode 6 (or PIN diode 15) without passing through a resistor. Therefore, the charge accumulated when the PIN diode 6 (or PIN diode 15) is turned on is rapidly removed when the PIN diode 6 (or PIN diode 15) is turned off. Thereby, the transmission system of the high frequency signal transmitted through the PIN diode 6 and the high frequency signal transmitted through the PIN diode 15 can be switched at high speed.

Second embodiment

  FIG. 2 is a circuit diagram of a high frequency switching circuit according to a second embodiment of the present invention. In the second embodiment, a filter bank circuit configured based on the high frequency switching circuit of the first embodiment shown in FIG. 1 is shown. Therefore, the first input terminal 7a shown in FIG. 1 is replaced with the first filter 7b in FIG. 2, the second input terminal 16a shown in FIG. 1 is replaced with the second filter 16b in FIG. The output terminal 8a shown in FIG. 1 is replaced with an antenna 8b in FIG. There is no change in the other configurations.

  The filter bank circuit is an array of band pass filters. Therefore, the high frequency switching circuit shown in FIG. 2 is shown as a filter bank circuit that divides a high frequency input signal into a plurality of components by a filter and outputs the divided components.

  First, the configuration of the high-frequency switching circuit according to the second embodiment shown in FIG. 2 will be described. In FIG. 2, the first switching circuit 1 supplies a current to either the base of the NPN transistor 2 or the base of the PNP transistor 3. When the NPN transistor 2 is turned on, it applies a reverse bias voltage from the first negative power source 4 to the PIN diode 6. When the PNP transistor 3 is turned on, the forward current from the first positive power source 5 is supplied to the PIN diode 6. The first filter 7b is composed of a band-pass filter, and selects and outputs a high-frequency signal having a desired frequency from the input high-frequency signal.

  Further, the PIN diode 6 performs ON / OFF switching of the high-frequency signal selected and output from the first filter 7b. The resistor 9 determines the magnitude of the forward current flowing through the PIN diode 6 and the PIN diode 15. The antenna 8b transmits the high-frequency signal selected and output by the first filter 7b or the second filter 16b to the air.

  Similarly, the second switching circuit 10 supplies a current to either the base of the NPN transistor 11 or the base of the PNP transistor 12. When turned on, the NPN transistor 11 applies a reverse bias voltage from the second negative power source 13 to the PIN diode 15. The PNP transistor 12 supplies a forward current from the second positive power source 14 to the PIN diode 15 when turned on. The second filter 16b is composed of a bandpass filter, and selects and outputs a high frequency signal having a desired frequency from the input high frequency signal. The PIN diode 15 performs ON / OFF switching of the high-frequency signal selected and output by the second filter 16b.

  Next, the operation of the high frequency switching circuit shown in FIG. 2 will be described. The first switching circuit 1 supplies a current to either the base of the NPN transistor 2 or the base of the PNP transistor 3. When a current is supplied from the first switching circuit 1 to the base of the NPN transistor 2, a reverse bias voltage is applied from the first negative power supply 4 to the PIN diode 6 and the PIN diode 6 is turned off. The high-frequency signal that has passed through the first filter 7b is not output to the antenna 8b.

  Further, when a current is supplied from the first switching circuit 1 to the base of the PNP transistor 3, a forward current is supplied from the first positive power source 5 to the PIN diode 6, so that the first filter 7b The selected high-frequency signal is output to the air via the antenna 8b. At this time, the magnitude of the forward current of the PIN diode 6 is determined by the value of the resistor 9.

  Similarly, the second switching circuit 10 supplies a current to either the base of the NPN transistor 11 or the base of the PNP transistor 12. When a current is supplied from the second switching circuit 10 to the base of the NPN transistor 11, a reverse bias voltage is applied from the second negative power source 13 to the PIN diode 15, and the PIN diode 15 is turned off. The high-frequency signal selected by the second filter 16 is not output to the antenna 8b.

  Further, when a current is supplied from the second switching circuit 10 to the base of the PNP transistor 12, a forward current is supplied from the second positive power source 14 to the PIN diode 15, so that the second filter 16b The selected high-frequency signal is output to the air via the antenna 8b.

  In this way, the first switching circuit 1 and the second switching circuit 10 alternately turn on / off the NPN transistor 2 and the PNP transistor 3, and the NPN transistor 11 and the PNP transistor 12 alternately. By doing so, the PIN diode 6 and the PIN diode 15 can be turned ON / OFF alternately. As a result, the high frequency signal selected by the first filter 7b and the high frequency signal selected by the second filter 16b are alternately switched and output to the air via the antenna 8b.

  At this time, since the reverse bias voltage is directly applied to the PIN diode 6 or the PIN diode 15 from the first negative power source 4 or the second negative power source 13 without passing through a resistor, The charge of the PIN diode 15 can be removed rapidly. Therefore, the transmission system of the high-frequency signal selected by the first filter 7b or the second filter 16b can be switched at high speed and output to the antenna 8b.

Third embodiment

  FIG. 3 is a circuit diagram of a high frequency switching circuit according to a third embodiment of the present invention. The basic configuration of the high-frequency switching circuit of the third embodiment shown in FIG. 3 is almost the same as that of FIG. 2, but in FIG. 2, the filter bank circuit is switched on the output side, whereas in FIG. The difference is that the filter bank circuit is switched on the input side. Accordingly, the circuit configuration of the high-frequency switching circuit of FIG. 3 is slightly different from that of FIG. 2, so that the configuration contents of FIG.

  In FIG. 3, the first switching circuit 1 supplies a current to either the base of the NPN transistor 2 or the base of the PNP transistor 3. The NPN transistor 2 applies a reverse bias voltage from the first negative power source 4 to the PIN diode 6 when ON. The PNP transistor 3 supplies a forward current from the first positive power source 5 to the PIN diode 6 when ON. The PIN diode 6 supplies the high frequency signal selected by the first filter 7 c to the input terminal 7. The first filter 7c selects a high-frequency signal having a desired frequency from a high-frequency signal input from the outside. The resistor 17 determines the magnitude of the forward current of the PIN diode 6 and the PIN diode 15.

  Similarly, the second switching circuit 10 supplies a current to either the base of the NPN transistor 11 or the base of the PNP transistor 12. The NPN transistor 11 applies a reverse bias voltage from the second negative power source 13 to the PIN diode 15 when ON. The PNP transistor 12 supplies a forward current from the second positive power source 14 to the PIN diode 15 when ON. The PIN diode 15 supplies the high frequency signal selected by the second filter 10 c to the input terminal 7. The second filter 10c selects a high-frequency signal having a desired frequency from high-frequency signals input from the outside.

  Next, the operation of the filter bank circuit of FIG. 3 will be described. The first switching circuit 1 supplies a current to either the base of the NPN transistor 2 or the base of the PNP transistor 3. When a current is supplied to the base of the NPN transistor 2, a reverse bias voltage is applied from the first negative power supply 4 to the PIN diode 6, so that a high frequency signal from the first filter 7 c is supplied to the input terminal 7. Not.

  When a current is supplied to the base of the PNP transistor 3, a forward current is supplied from the first positive power source 5 to the PIN diode 6, so that the PIN diode 6 is turned on and the first filter 7c is turned on. Is supplied to the input terminal 7. The magnitude of the forward current of the PIN diode 6 at this time is determined by the value of the resistor 17.

  Similarly, the second switching circuit 10 supplies a current to either the base of the NPN transistor 11 or the base of the PNP transistor 12. When a current is supplied to the base of the NPN transistor 11, a reverse bias voltage is applied from the second negative power source 13 to the PIN diode 15, so that a high frequency signal from the second filter 16 c is supplied to the input terminal 7. Not.

  When a current is supplied to the base of the PNP transistor 12, forward current is supplied from the second positive power source 14 to the PIN diode 15, so that the PIN diode 15 is turned on and the second filter 16c is turned on. Is supplied to the input terminal 7. The magnitude of the forward current of the PIN diode 15 at this time is determined by the value of the resistor 17.

  In this manner, in the high frequency switching circuit of the third embodiment, since the transmission system of the high frequency signal is switched on the input side of the input terminal 7, the isolation on the input side can be enhanced. In such a configuration of the high-frequency switching circuit, the filter bank circuits of FIGS. 2 and 3 may be configured on the same circuit.

  Although the embodiments of the present invention have been described in detail with reference to the drawings, the specific configuration of the present invention is not limited to these embodiments, and the design does not depart from the spirit of the present invention. These changes are included in the present invention. For example, in each of the embodiments, a transistor is used as a suitable means for switching the power supply voltage. However, the present invention is not limited to this, and an FET (field effect transistor) may be used as necessary.

  Further, although cases have been described with the above embodiments where the high-frequency signal transmission path is switched between two systems, the high-frequency signal transmission path may be switched between three or more systems. For example, when switching a high-frequency signal with three transmission paths, in the high-frequency switching circuit of FIG. 1, a third switching circuit, a third negative power source, a third positive power source, and a third negative power source are further provided. A reverse bias voltage is applied and a forward current is supplied by a pair of NPN and PNP transistors for switching between a power source and a third positive power source, and a third negative power source and a third positive power source. A PIN diode may be provided.

  Since the high-frequency switching circuit of the present invention can switch the transmission path of a high-frequency signal at high speed with a simple circuit configuration, it can be effectively used for signal switching means of a communication system.

1,21 First switching circuit 2,11 NPN transistor (first semiconductor switch)
3,12 PNP type transistor (second semiconductor switch)
4 First negative power supply (negative power supply)
5 First positive power supply (positive power supply)
6,15 PIN diode (diode)
7 Input terminal 7a, 25 1st input terminal 7b, 7c 1st filter (filter)
8a, 29 Output terminal 10, 30 Second switching circuit 13 Second negative power source (negative power source)
14 Second positive power supply (positive power supply)
16a, 34 Second input terminal 16b, 16c Second filter (filter)
22, 31 NPN-type transistor 24 First positive power source 26, 35 PIN diode 27 Third positive power source 33 Second positive power source

Claims (7)

The high-frequency signal system has a plurality of transmission paths for transmitting a high-frequency signal, and alternately connects / disconnects diodes connected in series to the transmission paths constituting the multiple-system transmission paths. A high-frequency switching circuit for switching,
A negative power source for directly applying a reverse bias voltage to the diodes connected to the transmission paths via a first semiconductor switch;
A positive power source for supplying a forward current to the diodes connected to the transmission paths via a second semiconductor switch;
The high-frequency signal system is switched by alternately applying a reverse bias voltage from the negative power source and supplying a forward current from the positive power source to each diode. Switching circuit. The high-frequency signal system has a plurality of transmission paths for transmitting a high-frequency signal, and alternately connects / disconnects diodes connected in series to the transmission paths constituting the multiple-system transmission paths. A high-frequency switching circuit for switching,
A negative power source for directly applying a reverse bias voltage to the diodes connected to the transmission paths via a first semiconductor switch without using a resistor;
A positive power source for supplying a forward current to the diodes connected to the transmission paths via a second semiconductor switch;
The high-frequency signal system is switched by alternately applying a reverse bias voltage from the negative power source and supplying a forward current from the positive power source to each diode. Switching circuit.   3. The high frequency switching circuit according to claim 1, wherein the diode is a PIN diode in which an intermediate layer having a low impurity concentration is formed between the P layer and the N layer.   4. The high-frequency switching circuit according to claim 1, wherein the first semiconductor switch is composed of an NPN transistor, and the second semiconductor switch is composed of a PNP transistor. The transmission path includes a filter that selects a high-frequency signal having a desired frequency from the input high-frequency signal.
The high-frequency signal selected by the filter is applied to the PIN diode by alternately applying a reverse bias voltage from the minus power source and supplying a forward current from the plus power source. 5. The high frequency switching circuit according to claim 3, wherein system switching is performed.   6. The high frequency switching circuit according to claim 5, wherein the filter selects a high frequency signal having a desired frequency on an output side or an input side of the transmission path.   The high-frequency switching circuit according to claim 1 or 2, wherein the plurality of transmission paths include two transmission paths.

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