JPH05206818A - Semiconductor switch - Google Patents

Abstract

PURPOSE:To provide the semiconductor switch of low loss and, in addition, of high power resistance. CONSTITUTION:A first hybrid circuit 8, a first and a second circuits whose input terminals are connected respectively to a pair of the input/output terminals 10, 15 of one side of the first hybrid circuit 8, and which are provided with biasing means consisting of field effect transistors 13, 18 grounded at one electrodes other than gate electrodes and inductors 11, 16 and to impress bias voltage to the gate electrodes of the field effect transistors 13, 18, and are constituted so as to form filters to make a pair of the input/output terminals 10, 15 respectively into a grounded state in a biased state that low impedance is realized between the drain and the source electrodes of the field effect transistors 13, 18, and pass working frequency in the biased state that high impedance is realized between the drain and the source electrodes of the field effect transistors 14, 19, and a second hybrid circuit 9 whose pair of the input/ output terminals of one side are connected to the output terminal of the first circuit and the output terminal of the second circuit are provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor switch for switching electric signal paths.

[0002]

2. Description of the Related Art FIG. V. MLEVI
GE et. al, “Resonated GaAs”
FET Devices for Microwave
Switching "IEEE ED, vol.ED
-28, NO. 2, Feb. 1981 PP. 198-
It is an equivalent circuit diagram which shows an example of a structure of the conventional semiconductor switch shown by 204 used for a microwave band. In the figure, the drain of the first field effect transistor 2 and the drain of the second field effect transistor 3 are connected to the first input / output terminal 1. The second input / output terminal 4 is connected to the source of the first field effect transistor 2, and the second field effect transistor 3
The third input / output terminal 5 is connected to the source of the. Furthermore, the drain and source of the first field effect transistor 2 are connected by the first inductor 6, and the drain and source of the second field effect transistor 3 are connected by the second inductor 7. The gate of the first field effect transistor 2 and the second field effect transistor 3
A bias is applied to the gate of the gate from the outside, but the bias circuit and the like for that purpose are omitted here.

Next, the operation will be described. In this operation description, first, a case where a low power microwave is incident from the first input / output terminal 1 is described, and then a case where a microwave having a relatively high power level of about several W is incident is described. The problems that arise in this case will be mentioned.
Here, for simplicity, the first field effect transistor 2
The second field effect transistor 3 is the same, and the first inductor 6 and the second inductor 7 are also the same. 8 and 9 are equivalent circuit diagrams for explaining the operation. First, in the case where a low-power microwave enters from the first input / output terminal 1 and propagates to the second input / output terminal 4. think of. An equivalent circuit diagram in this case is shown in FIG. At this time, the gate of the first field effect transistor 2 is set to the ground potential of 0V. At the same time, a negative bias voltage Vbias lower than the pinch-off voltage Vp is applied to the gate of the second field effect transistor 3.
In this biased state, the impedance between the drain and the source of the first field effect transistor 2 becomes low, and the resistance is equivalently represented by R1. On the other hand, the impedance between the drain and the source of the second field effect transistor 3 is relatively high and is equivalently represented by the capacitor indicated by C1. When the respective elements are selected so that the capacitor C1 and the second inductor 7 resonate in parallel at the required frequency, this parallel resonance circuit exhibits a higher impedance than that of C1 alone and blocks radio waves. Therefore, the microwave incident from the first input / output terminal 1 passes through the first field effect transistor 2 and appears at the second input / output terminal 4.

Then, when the bias voltages applied to the gates of the first field effect transistor 2 and the second field effect transistor 3 are reversed, an equivalent circuit is shown in FIG.
Since each field effect transistor has an impedance opposite to that shown in FIG. 8 above, the microwave incident from the first input / output terminal 1 receives
Appears to. That is, by setting the gate bias voltages of the first field effect transistor 2 and the second field effect transistor 3 to 0 V and Vbias and switching them alternately,
It operates as a switch that switches the microwave path.

Next, consider a case where a microwave of a high power level is incident on the first input / output terminal 1. At this time, one of the field effect transistors exhibits low impedance, and the other field effect transistor exhibits high impedance.
A large voltage is applied between the drain and source electrodes of the field effect transistor that has high impedance. As a result, when the applied voltage exceeds the breakdown voltage of the gate, the field effect transistor is damaged. For example, set the characteristic impedance of each input / output terminal to 50
When Ω and Vbias are -5V and the input power is 3W, the maximum voltage applied between the gate and source electrodes is 13.5V. This voltage is not a value that can be easily realized in a field effect transistor in which the resistance R1 between the drain and source electrodes in the state of 0V gate bias voltage is reduced to obtain a low loss switch.

[0006]

Since the conventional semiconductor switch is constructed as described above, it has a low loss and a few watts.
A field effect transistor with low resistance and high power resistance is required to obtain high power withstanding capability, but such a field effect transistor cannot be easily obtained. It was difficult to realize the switch.

The present invention has been made to solve the above problems, and an object thereof is to obtain a semiconductor switch having low loss and high power resistance.

[0008]

In order to achieve the above object, a semiconductor switch according to the present invention has a first hybrid circuit and a pair of input / output terminals of one of the first hybrid circuit. A field effect transistor having an end connected to one electrode other than the gate electrode is grounded, and an inductor, comprising bias means for applying a bias voltage to the gate electrode of the field effect transistor, and between the drain and source electrodes of the field effect transistor. The pair of input / output terminals are grounded in a bias state in which the impedance is low, and a filter is formed to pass the used frequency in a bias state in which the drain-source electrode of the field effect transistor has a high impedance. First circuit and second circuit, and one pair of input / output terminals Each is obtained and a second hybrid circuit connected to the output terminals of the second circuit of the first circuit.

[0009]

In the semiconductor switch configured as described above, when an electric signal of a low power level is input from the first hybrid circuit, the first switch is provided between the first hybrid circuit and the second hybrid circuit. When the drain and source electrodes of the field-effect transistors of the first circuit and the second circuit are placed in a biased state with a high impedance, a capacitor and an inductor that are equivalently expressed by the field-effect transistor form a filter that passes the used frequency. The electric signal passes through the second hybrid circuit side and is output, and does not appear on the first hybrid circuit side. Next, when a high power electric signal of several W is similarly input from the first hybrid circuit,
When one of the pair of input / output terminals of the first hybrid circuit is grounded in the bias state where the drain-source electrode of the field effect transistor has a low impedance, the RF voltage applied to the field effect transistor is low. Even if the breakdown voltage of the field effect transistor is small, it is possible to handle electric power of several W. In this case, the input electric signal is reflected by the first hybrid circuit side and output, and does not appear on the second hybrid circuit side.

[0010]

Embodiment 1 FIG. 1 is a circuit configuration diagram showing an embodiment of the present invention. A first hybrid circuit 8 such as a coupled line type 90 degree hybrid and a second hybrid circuit 9 are used, and a first input / output terminal 10 of the first hybrid circuit 8 is connected via a third inductor 11 to It is connected to the first input / output terminal 12 of the second hybrid circuit 9. Third inductor 1
The drains of the third field effect transistor 13 and the fourth field effect transistor 14 whose sources are grounded are connected to both ends of 1. On the other hand, similarly, the second input / output terminal 15 of the first hybrid circuit 8 is connected to the second input / output terminal 17 of the second hybrid circuit 9 via the fourth inductor 16. Fourth inductor 16
The drains of the fifth field effect transistor 18 and the sixth field effect transistor 19 whose sources are grounded are connected to both ends of the. A terminating resistor 21 whose one end is grounded is connected to the third input / output terminal 20 of the second hybrid circuit 9. Further, a bias is applied to the gates of the four field effect transistors through a bias circuit (not shown).

Next, the operation will be described. 2 and 3 are equivalent circuit diagrams for explaining the operation. Here, for simplification, the four field effect transistors 13, 14, 18, and 19 of the third, fourth, fifth, and sixth are all the same,
The third and fourth inductors 11 and 16 are also the same. Similar to the description of the operation of the field effect transistor in the conventional example, by switching the bias voltage applied to the gate of the field effect transistor between 0 V and the pinch-off voltage, the drain and source of the field effect transistor are switched between a resistor and a capacitor. be able to. Here, these resistors and capacitors are represented as Ra and Ca, respectively. In the operation description given below, first, the case where a low-power microwave is input is described, and then,
A case where a microwave having a relatively high power level of about several W is input will be described.

FIG. 2 is an equivalent circuit diagram for explaining the operation when a low power microwave is input. Apply a pinch-off voltage to the gate of the field effect transistor,
A capacitor Ca is equivalently provided between the drain and the source. This capacitor Ca and the third inductor 11,
The fourth inductor 16 constitutes a π-type low-pass filter having a pass band at a required frequency. The third input / output terminal 22 of the first hybrid circuit 8
The more incident microwave is the first hybrid circuit 8
Appears at the first input / output terminal 10 and the second input / output terminal 15. The microwave appearing at the first input / output terminal 10 of the first hybrid circuit 8 causes the third field effect transistor 13, the fourth field effect transistor 14, and the third inductor 11 which are equivalent to the capacitor Ca to appear. It passes through and is input to the first input / output terminal 12 of the second hybrid circuit 9. On the other hand, in the same manner, the microwaves appearing at the second input / output terminal 15 of the first hybrid circuit 8 become the fifth field effect transistor 18 and the sixth field effect transistor 19 that exhibit the equivalent capacitor Ca. It passes through the fourth inductor 16 and is input to the second input / output terminal 17 of the second hybrid circuit 9. In this way, the two microwaves that have entered the second hybrid circuit 9 are combined and appear as an output at the fourth input / output terminal 23 of the second hybrid circuit 9. In this case, each field effect transistor is in a state of exhibiting a relatively high impedance, but since the power level is low, the voltage above the breakdown voltage is not applied to the gate, and the field effect transistor is damaged. There is no. Moreover, since the equivalent capacitor Ca is used as a part of the low-pass filter, radio waves can be transmitted in a wide band.
The unbalanced components of the two microwaves incident on the second hybrid circuit 9 appear at the third input / output terminal 20 of the second hybrid circuit 9 and are absorbed by the terminating resistor 21.

FIG. 3 is an equivalent circuit diagram for explaining the operation when a high-power microwave is input. The voltage applied to the gate of the field effect transistor is 0 V, and the drain and the source are equivalently resistors Ra. The resistance value of the resistor Ra can be set to several Ω or less, and is usually selected as the power source impedance and load impedance of the switch.
Can be made smaller than Ω. The microwave input from the third input / output terminal 22 of the first hybrid circuit 8 is the same as when the low power microwave is input. It appears at the second input / output terminal 15. Here, the first input / output terminal 10 and the second input / output terminal 15 of the first hybrid circuit 8 are almost respectively formed by the third field effect transistor 13 and the fifth field effect transistor 18 having the resistance Ra. It is a short circuit. Therefore, the two microwaves appearing at the first input / output terminal 10 and the second input / output terminal 15 of the first hybrid circuit 8 are reflected,
It is combined and appears as an output at the fourth input / output terminal 24 of the first hybrid circuit 8. At this time, since the first hybrid circuit 8 and the second hybrid circuit 9 are doubly cut off by the two low-resistance resistors Ra, respectively, the third input circuit of the second hybrid circuit 9 is connected. No microwave appears at the output terminal 20 and the fourth input / output terminal 23.

Embodiment 2 FIG. 4 shows an example in which the semiconductor switch according to the present invention is used as a transmission / reception changeover switch. Field effect transistor 1
With the bias applied to 3, 14, 18, and 19 being 0 V, the output from the transmitter 25 is the high output amplifier 26.
The signal is amplified by and is transmitted from the antenna 27. On the other hand, in the state where the bias applied to the field effect transistors 13, 14, 18 and 19 is the pinch-off voltage, the antenna 2
The received wave from No. 7 is amplified by the low noise amplifier 28 and received by the receiver 29. As a result of such configuration and operation,
The combined output of the electric waves leaked to the first input / output terminal 12 and the second input / output terminal 17 of the second hybrid circuit 9 at the time of transmission is sent to the fourth input / output terminal 23 of the second hybrid circuit 9. It does not appear, but appears at the third input / output terminal 20 of the second hybrid circuit 9 and is absorbed by the terminating resistor 21.
Therefore, according to this configuration using the switch according to the present invention, problems such as damage of the low noise amplifier 28, generation of unnecessary waves, saturation of the receiver 29, etc., due to the transmission wave of high power entering the low noise amplifier 28. Can be resolved. At the same time, the limiter circuit or the like conventionally used for such an application becomes unnecessary.

Embodiment 3 In the above embodiment, the case where a π-type low-pass filter is constructed has been described. However, the present invention is not limited to this, and as shown in FIG. The eight field effect transistors 30 and 31 and the fifth, sixth, seventh, and eighth inductors 32, 33, 34, and 35 may be used to form a T-type low-pass filter. With this configuration, there is an advantage that the switch can be configured with a small number of field effect transistors. Furthermore, a hybrid configuration may be used, such as using a π-type low-pass filter as the first circuit and a T-type low-pass filter as the second circuit. Further, in the above embodiment, the case where the low-pass filter is configured has been described, but the present invention is not limited to this, and may be configured by a high-pass filter or a band-pass filter that passes a used frequency. good.

Embodiment 4 In the above embodiment, the case where the filter for passing the used frequency is composed of three elements including the inductor and the field effect transistor has been described. However, the present invention is not limited to this, and as shown in FIG. 6, the ninth, tenth, eleventh, twelfth, thirteenth, fourteenth, fifteenth,
Sixteenth field effect transistor 36, 37, 38, 3
9, 40, 41, 42, 43, and ninth, tenth, eleventh, twelfth, thirteenth, fourteenth inductors 44, 45,
46, 47, 48, 49 may be used to form a multistage low pass filter. With this configuration, a wider band can be achieved. Further, as the ninth and thirteenth field effect transistors 36 and 40, those having a very small resistance value at an applied bias of 0 V are used, and the characteristic impedance of the low-pass filter is the first hybrid circuit 8 side. From the first hybrid circuit 9 side to the second hybrid circuit 9 side, the field effect transistors and the inductors are selected so as to increase in a stepwise manner. The loss at the time of wave incidence can be made extremely small.

[0017]

As described above, according to the present invention, it is possible to obtain a semiconductor switch having low loss and high power resistance.

[Brief description of drawings]

FIG. 1 is a circuit configuration diagram of a first embodiment of the present invention.

FIG. 2 is an equivalent circuit diagram for explaining the operation of the first embodiment of the present invention.

FIG. 3 is an equivalent circuit diagram for explaining the operation of the first embodiment of the present invention.

FIG. 4 is a circuit configuration diagram of a transmission / reception change-over switch according to a second embodiment of the present invention.

FIG. 5 is a circuit configuration diagram of a third embodiment of the present invention.

FIG. 6 is a circuit configuration diagram of a fourth embodiment of the present invention.

FIG. 7 is a circuit configuration diagram of a conventional semiconductor switch.

FIG. 8 is an equivalent circuit diagram for explaining the operation of a conventional semiconductor switch.

FIG. 9 is an equivalent circuit diagram for explaining the operation of a conventional semiconductor switch.

[Explanation of symbols]

 1 1st input / output terminal 1 2 1st field effect transistor 3 2nd field effect transistor 4 2nd input / output terminal 5 3rd input / output terminal 6 1st inductor 7 2nd inductor 8 1st Hybrid circuit 9 Second hybrid circuit 10 First input / output terminal 11 of first hybrid circuit 11 Third inductor 12 First input / output terminal 13 of second hybrid circuit 13 Third field effect transistor 14 Fourth Field-effect transistor 15 Second input / output terminal of first hybrid circuit 16 Fourth inductor 17 Second input / output terminal of second hybrid circuit 18 Fifth field-effect transistor 19 Sixth field-effect transistor 20th Second input / output terminal 21 of hybrid circuit 21 Terminator 22 Third input / output terminal 23 of first hybrid circuit 23 Second input / output terminal of hybrid circuit 24 Second input / output terminal of first hybrid circuit 25 Transmitter 26 High power amplifier 27 Antenna 28 Low noise amplifier 29 Receiver 30 Seventh field effect transistor 31 Eighth Field effect transistor 32 fifth inductor 33 sixth inductor 34 seventh inductor 35 eighth inductor 36 ninth field effect transistor 37 tenth field effect transistor 38 eleventh field effect transistor 39 twelveth Field effect transistor 40 thirteenth field effect transistor 41 fourteenth field effect transistor 42 fifteenth field effect transistor 43 sixteenth field effect transistor 44 ninth inductor 45 tenth inductor 46 eleventh Inductor 47 12th Inductor 48 13th Inductor 49th fourteenth inductor

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[Procedure amendment]

[Submission date] February 15, 1993

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0005

[Correction method] Change

[Correction content]

Next, consider a case where a microwave of a high power level is incident on the first input / output terminal 1. At this time, one of the field effect transistors exhibits low impedance, and the other field effect transistor exhibits high impedance.
A large voltage is applied between the drain and source electrodes of the field effect transistor that has high impedance. As a result, when the applied voltage exceeds the breakdown voltage of the gate, the field effect transistor is damaged. For example, set the characteristic impedance of each input / output terminal to 50
When Ω and Vbias are -5V and the input power is 3W, the maximum voltage applied between the gate and source electrodes is 13.5V. A breakdown voltage equal to or higher than this voltage is not a value that can be easily realized in a field effect transistor in which the resistance R1 between the drain and source electrodes in the state of the gate bias voltage of 0 V is reduced to obtain a low loss switch.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yasuyuki Ito 5-1-1 Ofuna, Kamakura City Mitsubishi Electric Corporation Electronic Systems Research Institute (72) Inventor Fumio Takeda 5-1-1 Ofuna, Kamakura City Mitsubishi Electric Corporation Company Electronic Systems Laboratory

Claims (1)

[Claims] 1. A field effect transistor having an input terminal connected to each of a pair of input / output terminals of the first hybrid circuit and one of the pair of input / output terminals of the first hybrid circuit, and an electrode other than a gate electrode grounded, and an inductor. And a bias means for applying a bias voltage to the gate electrode of the field effect transistor, wherein the pair of input / output terminals are grounded in a bias state in which the drain and source electrodes of the field effect transistor have a low impedance, A first circuit and a second circuit configured to form a filter that passes a used frequency in a biased state in which a drain-source electrode of the field effect transistor has a high impedance, and one pair of input / output terminals are respectively provided. A second high connected to the output of the first circuit and the output of the second circuit. A semiconductor switch comprising a brid circuit.