JP2005252345A - High-frequency switch - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem that an operation at a high frequency is impossible because an FET must be increased in size for high withstand power, and this causes an increase in parasitic capacity at the time of switch-off, resulting in reduction in cutoff frequency, while an FET switch composed of a 1/4 wavelength impedance transformer and a parallel FET (Field Effect Transistor) is given as one example of a conventional high-frequency switch. <P>SOLUTION: One of output terminals of a hybrid circuit is short-circuited or opened, and an FET connected to the other is controlled to be turned on/off, thereby performing reflecting type switching operation. Since input power is distributed by the hybrid circuit and the input power to the FET can be reduced by half, the FET size can be reduced and the operation at a high frequency is enabled. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a high frequency switch.

  Currently, high frequency switches have already been reported in many papers and academic societies, and it is well known that various proposals have been made regarding their circuit configurations.

  As an example of such a high-frequency switch, a FET switch composed of a quarter-wavelength impedance transformer and a parallel FET (Field Effect Transistor), which reduces the voltage applied to the FET, thereby providing high withstand power against passing signals. What has been realized is known (for example, see Non-Patent Document 1).

IEICE Microwave and Millimeterwave Monolithic Circuits Symposium Dijest, pp-42-46, June 1982 "An X-band 10W monolithic transmit-receive GaAs FET switch" (page 43, Fig. 4)

  However, in recent microwave communication and radar systems, it is desired to increase the frequency and power of transmission signals. In the microwave transceiver used in these systems, the output signal of the transmitter may be input to the receiver and high output power may be input to the low noise amplifier. For this reason, it is necessary to provide a high-power high-frequency switch on the input side to the receiver so that the output signal of the transmitter does not enter the receiver.

  For this purpose, it is required to increase the power resistance without degrading the high-frequency characteristics of the high-frequency switch, but it is practically difficult. In particular, in the conventional high-power-resistant switch, it is necessary to satisfy both conflicting demands for reducing the parasitic capacitance at the time of pinch-off of the FET being used and increasing the breakdown voltage. However, so far, a high-power switch having sufficient performance has not been realized.

  In order to increase the power resistance of the high-frequency switch, it is necessary to increase the FET size, and the parasitic capacitance at the time of pinch-off increases. As a result, the cutoff frequency is lowered, and there is a problem that the operation at a high frequency cannot be performed.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to obtain a high-frequency switch that has good high-frequency characteristics and realizes high power durability.

  The high-frequency switch according to the present invention has a pair of input terminals and a pair of output terminals, one of which is grounded with a 90 ° hybrid coupler and one terminal connected to the other output terminal of the 90 ° hybrid coupler. And a switching element that short-circuits or opens the other terminal, and the switching element is equivalently grounded when in the on state, and is equivalently open when in the off state.

  A first 90 ° hybrid coupler having a pair of input terminals and a pair of output terminals, one input terminal of which is connected to a ground resistor, a pair of input terminals and a pair of output terminals, A second 90 ° hybrid coupler having an input terminal connected to one output terminal of the first 90 ° hybrid coupler and one output terminal grounded, a pair of input terminals, and a pair of output terminals; A third 90 ° hybrid coupler having one input terminal connected to the other output terminal of the first 90 ° hybrid coupler and one output terminal grounded, a pair of input terminals, and a pair of output terminals. One input terminal is connected to the other output terminal of the second 90 ° hybrid coupler, and the other input terminal is connected to the other output terminal of the third 90 ° hybrid coupler. A fourth 90 ° hybrid coupler whose terminal is connected to a ground resistor, a first FET whose drain terminal is connected to the other output terminal of the second 90 ° hybrid coupler, and whose source terminal is grounded; And a second FET having a terminal connected to the other output terminal of the third 90 ° hybrid coupler and a source terminal grounded.

  According to the present invention, the power of the high-frequency signal applied to the switching element can be reduced by distributing the input signal to the switching element using the 90 ° hybrid coupler. In addition, since an element with a low withstand voltage can be used, a microwave high power withstand switch having good high frequency characteristics can be obtained.

Embodiment 1 FIG.
Hereinafter, Embodiment 1 of the high frequency switch according to the present invention will be described with reference to the drawings.
FIG. 1 is a configuration diagram showing a circuit configuration of a microwave high power durability switch constituting the high frequency switch according to the first embodiment.
This circuit includes a hybrid circuit 5 and an FET 6 as a switching element. The hybrid circuit 5 includes one input terminal 1 (hereinafter referred to as terminal 1) for inputting a high-frequency signal, the other input terminal 2 (hereinafter referred to as terminal 2) serving as an isolation terminal, and one output terminal 3 (hereinafter referred to as terminal) that is grounded. 3) and the other output terminal 4 (hereinafter referred to as terminal 4), and operates as a 90 ° hybrid coupler. The 90 ° hybrid coupler is composed of a Lange coupler, a branch line coupler, or the like (see, for example, JP-A-2001-203502).

  The drain terminal of the FET 6 is connected to the output terminal 4 of the hybrid circuit 5. The source terminal of the FET 6 is grounded. The gate terminal of the FET 6 constitutes an FET control terminal 7 that controls the on / off operation of the FET 6. When a control voltage of about 0 V is applied to the FET control terminal 7, the FET 6 operates as a resistance element. FIG. 2 shows an equivalent circuit of the present circuit in this state, and shows the FET 6 as the FET on-resistance 8. Since the FET on-resistance 8 is small, the terminal 4 can be regarded as equivalently grounded. Further, when a voltage that becomes pinch-off (a negative voltage smaller than the pinch-off voltage) is applied to the FET control terminal 7, the FET 6 exhibits capacitance. FIG. 3 shows an equivalent circuit of this circuit in this state, and shows the FET 6 as the FET off capacitance 9. Since the FET off capacitor 9 has a small capacitance, the terminal 4 can be regarded as an equivalent open state.

Next, the operation of this circuit will be described.
First, the operation of the hybrid circuit 5 will be described with reference to FIG.
As shown in FIG. 4A, when a high frequency signal (hereinafter referred to as a signal) is input from the terminal 1, the signal is equally distributed to the terminal 3 and the terminal 4, and the signal hardly appears at the terminal 2. Further, the phase of the signal output to the terminal 4 is delayed by 90 ° with respect to the signal output to the terminal 3. The same applies when input is made from the terminal 2, the terminal 3, and the terminal 4, and the respective states are shown in FIG. 4 (b) to FIG. 4 (d).

Next, the operation when the microwave high power durability switch is turned on will be described.
When ON, a voltage of about 0 V is applied to the FET control terminal 7. A signal input from the input terminal 1 is equally distributed to the terminals 3 and 4. Since terminal 3 is grounded and terminal 4 is equivalently grounded (short circuit) as shown in FIG. 2, it is totally reflected back to hybrid circuit 5 and transmitted to terminal 1 and terminal 2, respectively.

Since the signals reflected by the terminals 3 and 4 are transmitted to the terminal 1 with a phase difference of 180 °, the signals cancel each other and no signal appears at the terminal 1. In addition, since the phases of the signals reflected by the terminals 3 and 4 are transmitted to the terminal 2 in the same phase, the signals are added to each other and appear.
Therefore, the signal input to the terminal 1 is transmitted to the terminal 2, and the microwave high power resistance switch is turned on.

  Next, the operation when the microwave high power resistance switch is off will be described. When off, a voltage (for example, −5 V) is applied to the FET control terminal 7 so as to pinch off. A signal input from the terminal 1 is equally distributed to the terminals 3 and 4. Since the terminal 3 is grounded and the terminal 4 is equivalently opened as shown in FIG. 3, it is totally reflected back to the hybrid circuit 5 and transmitted to the terminal 1 and the terminal 2, respectively. At this time, since the terminal 4 is open, the reflected signal is 180 degrees out of phase with respect to the case where the terminal 4 is grounded.

  The signals reflected at the terminals 3 and 4 are transmitted to the terminal 1 in the same phase, and the signals reflected at the terminals 3 and 4 are transmitted to the terminal 2 with a phase difference of 180 °, so that they cancel each other. Accordingly, no signal appears at the terminal 2.

  Therefore, the signal input to the terminal 1 is not transmitted to the terminal 2, and the microwave high power resistance switch is turned off.

  Further, the power of the high-frequency signal applied to the FET 6 is half that of the signal distributed by the hybrid circuit 5 and input to the terminal 1. Accordingly, an element with a low withstand voltage can be used, and therefore a microwave high power withstand switch having good high frequency characteristics can be obtained. Note that when a signal is input to the terminal 2, the signal output to the terminal 1 can be turned on and off in the same manner.

  Furthermore, since the power applied to the FET 6 is halved, when the FET 6 is on, the applied current is the reciprocal of the square root of 2, so the gate width of the FET 6 is reduced by the same ratio. It is possible to reduce the FET size. As a result, the parasitic capacitance at the time of switch-off can be reduced, so that the cutoff frequency can be further increased and the high-frequency characteristics are improved.

In addition, although the example which earth | grounded the terminal 3 was demonstrated in FIG. 1, the terminal 3 is good also as an open terminal. In this case, the signal input from the terminal 1 is output from the terminal 2 when the FET 6 is in a pinch-off state (a voltage for pinching off is applied to the FET control terminal 7). When the FET 6 is in an ON state (applying a control voltage of about 0 V to the FET control terminal 7), the signal is output from the terminal 1.
Of course, in the example of FIG. 1, it goes without saying that another switching element such as a PIN diode may be used instead of the FET 6.

Embodiment 2. FIG.
The second embodiment according to the present invention will be described below.
FIG. 5 is a circuit configuration diagram of the microwave high power resistance switch according to the second embodiment. In the microwave high power resistance switch according to the first embodiment, a quarter wavelength transmission line 10 is provided between the terminal 4 and the drain terminal of the FET 6. Are connected to form a circuit.

  In FIG. 5, when the FET 6 is in the ON state, the terminal 4 can be regarded as open due to the impedance reversal action of the quarter wavelength transmission line 10, and the microwave high power withstand switch is turned off. When the FET 6 is in the off state, the terminal 4 can be regarded as a short circuit, and the microwave high power withstand switch is turned on. Therefore, in contrast to the operation shown in the first embodiment, the on / off state of the FET and the on / off state of the microwave high withstand voltage switch are reversed.

  At this time, the ¼ wavelength transmission line 10 is adjusted so as to have a ¼ wavelength including the parasitic component due to the physical size of the FET 6, so that the parasitic component of the FET 6 is not affected, and the high frequency characteristic is obtained. Can be obtained.

Embodiment 3 FIG.
Embodiment 3 according to the present invention will be described below.
FIG. 6 shows a microwave high power resistance switch including two microwave high power resistance switches 23 and 24, a hybrid circuit 15, a hybrid circuit 20, and termination circuits 21 and 22. Since the microwave high power resistance switches 23 and 24 are the same microwave high power resistance switches as in the first embodiment, the hybrid circuit and the FET are indicated by the same reference numerals for convenience. The hybrid circuits 15 and 20 are each composed of a 90 ° hybrid coupler.
In the hybrid circuit 15, the terminal 11 constitutes a signal input terminal for high-frequency signals, and the terminal 12 constitutes an isolation terminal, forming a pair of input terminals. The terminals 13 and 14 of the hybrid circuit 15 constitute a pair of output terminals. The terminals 16 and 17 of the hybrid circuit 20 constitute a pair of input terminals. The terminals 18 and 19 of the hybrid circuit 20 constitute a pair of output terminals. Each of the termination circuits 21 and 22 constitutes a termination resistor whose one end is grounded. The other end of the termination circuit 21 is connected to the terminal 12 of the hybrid circuit 15. The other end of the termination circuit 22 is connected to the terminal 22 of the hybrid circuit 20.

The terminal 1 of the hybrid circuit 5 that constitutes the microwave high power durability switch 23 is connected to the terminal 13 of the hybrid circuit 15. The terminal 2 of the hybrid circuit 5 constituting the microwave high power durability switch 23 is connected to the terminal 16 of the hybrid circuit 20. One of the terminals 3 and 4 of the hybrid circuit 5 constituting the microwave high power resistance switch 23 is grounded as in the first embodiment, and the other is connected to the drain terminal of the FET 6. The source terminal of the FET 6 is grounded.
Terminal 1 of hybrid circuit 5 constituting microwave high power resistance switch 24 is connected to terminal 14 of hybrid circuit 15. The terminal 2 of the hybrid circuit 5 that constitutes the microwave high power durability switch 24 is connected to the terminal 17 of the hybrid circuit 20. One of the terminals 3 and 4 of the hybrid circuit 5 constituting the microwave high power resistance switch 23 is grounded as in the first embodiment, and the other is connected to the drain terminal of the FET 6. The source terminal of the FET 6 is grounded.
A high frequency signal (hereinafter referred to as a signal) input from the terminal 11 is distributed to the terminal 13 and the terminal 14 by the hybrid circuit 15 and output to the microwave high power resistance switches 23 and 24, respectively.

  When the microwave high power resistance switches 23 and 24 are in the OFF state, the signal returns to the terminal 1 as described in the first embodiment, so that the signal returns to the terminal 13 and the terminal 14 of the hybrid circuit 15 and is distributed to the terminal 11. And transmitted to the terminal 12. At this time, the phase of the signal transmitted to the terminal 11 is shifted by 180 °, and therefore no signal appears at the terminal 11. Further, since the signals transmitted to the isolation terminal 12 have the same phase, the added signal appears at the terminal 12. The signal output to the terminal 12 is absorbed by the termination circuit 21.

  When the microwave high power resistance switches 23 and 24 are in the ON state, the signals that have passed through the microwave high power resistance switches are transmitted to the terminals 16 and 17 and are transmitted to the terminals 18 and 19 through the hybrid circuit 20. At this time, the signals transmitted to the terminal 19 are added because they have the same phase. Even when a signal is input to the terminal 19, the signal to the terminal 11 can be turned on and off in the same manner as described above.

  As described above, since the signal does not return to the terminal 11 regardless of whether the microwave high power withstand switch is on or off, a microwave high power withstand switch having better reflection characteristics than the first embodiment can be obtained. .

  Of course, in the example of FIG. 6, it goes without saying that another switching element such as a PIN diode may be used instead of each FET.

It is a figure for demonstrating the microwave high electric power tolerance switch of Embodiment 1 of this invention. It is a figure for demonstrating the equivalent circuit at the time of ON of the microwave high electric power tolerance switch of Embodiment 1 of this invention. It is a figure for demonstrating the equivalent circuit at the time of OFF of the microwave high electric power tolerance switch of Embodiment 1 of this invention. It is a figure for demonstrating operation | movement of the hybrid circuit 5 of the microwave high electric power tolerance switch of Embodiment 1 of this invention. It is a figure for demonstrating the microwave high electric power tolerance switch of Embodiment 2 of this invention. It is a figure for demonstrating the microwave high electric power tolerance switch of Embodiment 3 of this invention.

Explanation of symbols

  1 to 4 terminals, 5 hybrid circuit, 6 FET, 7 FET control terminal, 8 FET on resistance, 9 FET off capacity, 10 1/4 wavelength transmission line, 11 to 14 terminal, 15 hybrid circuit, 16 to 19 terminal, 20 Power synthesis circuit, 21, 22 Termination circuit, 23, 24 Microwave high power durability switch.

Claims (7)

A 90 ° hybrid coupler having a pair of input terminals and a pair of output terminals, with one output terminal grounded;
Switching in which one terminal is connected to the other output terminal of the 90 ° hybrid coupler, and the other terminal is grounded, which is equivalently grounded when in the on state and equivalently open when in the off state Elements,
High frequency switch with A 90 ° hybrid coupler having a pair of input terminals and a pair of output terminals, with one output terminal connected to the open end;
Switching in which one terminal is connected to the other output terminal of the 90 ° hybrid coupler, and the other terminal is grounded, which is equivalently grounded when in the on state and equivalently open when in the off state Elements,
High frequency switch with The switching element according to claim 1, wherein a transmission line having a quarter wavelength is connected between the other output terminal of the 90 ° hybrid coupler and the switching element. A first 90 ° hybrid coupler having a pair of input terminals and a pair of output terminals, with one input terminal connected to a ground resistor;
A second 90 ° hybrid coupler having a pair of input terminals and a pair of output terminals, one input terminal connected to one output terminal of the first 90 ° hybrid coupler, and one output terminal grounded When,
A third 90 ° hybrid coupler having a pair of input terminals and a pair of output terminals, one input terminal connected to the other output terminal of the first 90 ° hybrid coupler, and one output terminal grounded When,
A pair of input terminals and a pair of output terminals, one input terminal being connected to the other input terminal of the second 90 ° hybrid coupler and the other input terminal being the other of the third 90 ° hybrid coupler; A fourth 90 ° hybrid coupler having one output terminal connected to a ground resistor,
One terminal is connected to the other output terminal of the second 90 ° hybrid coupler, the other terminal is grounded, and is equivalently grounded in the on state, and is equivalently opened in the off state. A first switching element
One terminal is connected to the other output terminal of the third 90 ° hybrid coupler, the other terminal is grounded, and is equivalently grounded when in the on state, and is equivalently open when in the off state A second switching element
High frequency switch with A 90 ° hybrid coupler having a pair of input terminals and a pair of output terminals, with one output terminal grounded;
FET whose drain terminal is connected to the other output terminal of the 90 ° hybrid coupler, the source terminal is grounded, and the voltage applied to the gate terminal is switched and controlled between a pinch-off voltage and a voltage higher than the pinch-off voltage, and
High frequency switch with A 90 ° hybrid coupler having a pair of input terminals and a pair of output terminals, with one output terminal connected to the open end;
FET whose drain terminal is connected to the other output terminal of the 90 ° hybrid coupler, the source terminal is grounded, and the voltage applied to the gate terminal is switched and controlled between a pinch-off voltage and a voltage higher than the pinch-off voltage, and
High frequency switch with A first 90 ° hybrid coupler having a pair of input terminals and a pair of output terminals, with one input terminal connected to a ground resistor;
A second 90 ° hybrid coupler having a pair of input terminals and a pair of output terminals, one input terminal connected to one output terminal of the first 90 ° hybrid coupler, and one output terminal grounded When,
A third 90 ° hybrid coupler having a pair of input terminals and a pair of output terminals, one input terminal connected to the other output terminal of the first 90 ° hybrid coupler, and one output terminal grounded When,
A pair of input terminals and a pair of output terminals, one input terminal being connected to the other input terminal of the second 90 ° hybrid coupler and the other input terminal being the other of the third 90 ° hybrid coupler; A fourth 90 ° hybrid coupler having one output terminal connected to a ground resistor,
A first FET having a drain terminal connected to the other output terminal of the second 90 ° hybrid coupler and a source terminal grounded;
A second FET having a drain terminal connected to the other output terminal of the third 90 ° hybrid coupler and a source terminal grounded;
High frequency switch with

Images