JP2743884B2 - Microwave switch - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a microwave switch using an FET (field effect transistor).

[0002]

2. Description of the Related Art FIG. 5 shows an example of the configuration of a conventional FET microwave switch. As a conventional microwave semiconductor switch, for example, in Japanese Patent Application Laid-Open No. 4-113702, two FETs are connected to a connection point of an input / output line, and a line of an inductor line connected in parallel to the two FETs. There has been proposed a configuration in which high isolation performance over a wide band can be obtained by shifting the length.

In FIG. 5, 31 and 32 are FETs, 4
And 5 indicate inductors, and 90, 2, 3, and 8 indicate transmission lines. Reference numeral 11 denotes a bias terminal, and reference numerals 23 and 24 denote first and second signal input / output terminals.

Referring to FIG. 5, in this conventional microwave switch, the gate terminal of FET 31 and the gate terminal of FET 32 are commonly connected, and the connection point and bias terminal 11 are connected.
And the transmission line 8 is connected between the FET 31 and the FET 32
Is connected to the ground line, the transmission line 2 is connected between the drain terminal of the FET 31 and the drain terminal of the FET 32, and the transmission line 90 is connected between the drain terminal of the FET 31 and the first signal input / output terminal 23. And FET3
The transmission line 3 is connected between the drain terminal 2 and the second signal input / output terminal 24.
And inductors 4 and 5 are respectively connected between the drain and the source.

In this conventional microwave switch,
Microwave is incident from the first signal input / output terminal 23 and appears on the second signal input / output terminal 24 (propagated and output).
For this purpose, a negative bias voltage smaller than the pinch-off voltage of the FET is applied to the bias terminal 11. At that time, FE
The capacitance between the drain and the source of the T31 and the FET 32 becomes a high-impedance state by resonating at a design frequency with the inductor 4 and the inductor 5 connected in parallel with each other, and becomes a high-impedance state. The wave propagates to the second signal input / output terminal 24 and appears.

On the other hand, in order to prevent the microwave incident from the first signal input / output terminal 23 from appearing on the second signal input / output terminal 24, a bias voltage of zero (0) V is applied to the bias terminal 11. The drain of FET31 and FET32
The source is in a low impedance state, and the microwave incident from the first signal input / output terminal 23 flows to the ground through the FET, and does not appear at the second signal input / output terminal 24.

[0007]

In the above-mentioned conventional microwave switch, the voltage of the bias terminal 11 is set to the pinch-off V.
In order to prevent the deterioration of the propagation characteristics due to the source-drain capacitance of the FETs 31 and 32 at the time, an inductor that resonates with the capacitance at a desired frequency is connected in parallel between the drain and the source of the FET, thereby reducing the The effects of the components were eliminated.

However, in the conventional microwave switch, since the inductors 4 and 5 are respectively connected between the drains and the sources of the FETs 31 and 32, the drains and the sources of the FETs 31 and 32 are connected in a DC manner. If the propagation characteristics in the low frequency region deteriorate and the capacitance between the source and drain of the FET is different from the design value due to the influence of the process (for example, variation), the deviation of the resonance frequency is adjusted. Therefore, there is a problem that the switch circuit needs to be redesigned and reproduced because the inductor cannot be trimmed.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to solve the above-mentioned problems and to realize a microwave switch capable of adjusting the operating frequency in a wide band.

[0010]

In order to achieve the above-mentioned object, the present invention provides a semiconductor device comprising a gate terminal of a first FET and the first FET.
Connect the gate terminal of the second FET with the same characteristics as the FET.
And a predetermined voltage is applied between the connection point and the first bias terminal.
Connect the first transmission line of length and characteristic impedance
And a source terminal and a ground terminal of the first and second FETs.
The second and third of the same length and characteristic impedance between
Are connected, and the drain of the first FET is connected.
Between the IN terminal and the drain terminal of the second FET.
Connect a fourth transmission line with a fixed length and characteristic impedance.
Then, the drain terminals of the first and second FETs are connected to the first and second FETs.
A predetermined length and characteristic impedance between the second signal input / output terminal
Connect the fifth and sixth transmission lines of the impedance, respectively,
The source terminal is grounded to the drain terminal of the first FET.
, And having a characteristic equal to that of the first FET,
The drain terminal of the second FET is connected to the drain terminal of the second FET.
A source terminal connected to ground at the rain terminal;
Drain terminal of the fourth FET having the same characteristics as the FET of the fourth embodiment.
And the gate terminal of the third FET is connected to the fourth
Connected to the gate terminal of the FET, the third and fourth F
Between the connection point of the gate terminal of ET and the second bias terminal
Switch connected to a seventh transmission line
And has the following features .

[0011] The voltage of the first bias terminal is
A second bias terminal set near the pinch-off voltage;
Voltage around 0V or near the pinch-off voltage of the FET.
The drain-source capacitance that appears,
The second transmission line and the third transmission line.
Series resonance circuit or parallel resonance circuit
The first and second signal input / output terminals are disconnected or connected.
You .

[0012]

In the microwave switch of the present invention, the first
When the voltage of the control signal bias terminal is 0 V and the voltage of the second control signal bias terminal is smaller than the pinch-off voltage of the FET, a parallel resonance circuit is formed, and in the resonance frequency band of this parallel resonance circuit, The signal input to the first input / output terminal is propagated and output to the second input / output terminal.

Further, when the first control voltage signal for the bias terminal is rather smaller than the pinch-off voltage of the FET, and the voltage of the second control signal for bias terminal is 0V, the series resonant circuit, i.e. a short circuit is formed The signal input to the first input / output terminal does not appear at the second input / output terminal.

[0014]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a diagram showing a configuration of an embodiment of the present invention.

Referring to FIG. 1, a microwave switch according to the present embodiment includes a gate terminal of an FET 21 and an FET 22.
Are connected in common, and the length is 1/4 at a predetermined frequency between the connection point and the first bias terminal 11.
A transmission line 8 having a wavelength (= λ / 4) and a characteristic impedance of 50Ω is connected, and transmission lines 15 and 16 having a characteristic impedance of 50Ω are connected between source terminals of the FETs 21 and 22 and a ground line, respectively. A transmission line 2 having a characteristic impedance of 50Ω is connected between the drain terminal and the drain terminal of the FET 22, and a characteristic impedance of 50Ω is connected between the drain terminals of the FETs 21 and 22 and the first and second signal input / output terminals 23 and 24. The transmission lines 90 and 3 are connected respectively.

In the microwave switch according to this embodiment, the drain terminal of the FET 21 is connected to the drain terminal of the FET 32 whose source terminal is connected to ground, and the drain terminal of the FET 22 is connected to the source terminal to ground. Connected to the drain terminal of the FET 33
The gate terminal of the FET 32 and the gate terminal of the FET 33 are connected in common, and the connection point and the second bias terminal 12
長 wavelength (= λ) at a predetermined frequency between
/ 4), a transmission line 18 having a characteristic impedance of 50Ω is provided.

In order to explain the operation of the microwave switch according to the present embodiment, the following matters are assumed.

(1) The FETs 21, 22, 32, and 33 are all of the depletion type and have the same characteristics.

(2) First and second bias terminals 11,
12 is 0 V, the drains of all the FETs
The sources have equal low resistance components (resistance values R to 0).

(3) First and second bias terminals 11,
When the voltage of No. 12 is smaller than the pinch-off voltage of the FET, the capacitance component (Cp) becomes equal between the drain and the source of all the FETs.

(4) In the desired frequency band, the transmission line 1
5 and 16 are equal inductive components (L).

From the above preconditions, in the microwave switch shown in FIG. 1, the voltage of the first bias terminal 11 is 0 V and the voltage of the second bias terminal 12 is the FET.
, The equivalent circuit becomes the circuit shown in FIG.

Referring to FIG. 2, the impedance between the connection point between transmission line 90 and transmission line 2 and the ground is an FET.
32, a capacitor (C
p) Inductance (L) representing 132 and transmission line 15
115 and a parallel resonance circuit.

Similarly, the impedance between the connection point between the transmission line 2 and the transmission line 3 and the ground is a capacitor (Cp) 133 representing the capacitance between the drain and source of the FET 33 and an inductance (L) representing the transmission line 16. 116 and a parallel resonance circuit.

As can be easily understood from the above,
The impedance between the connection point between the transmission line 90 and the transmission line 2 and the ground becomes infinite at the frequency f = 1 / (L × Cp), and similarly, the impedance between the connection point between the transmission line 2 and the transmission line 3 and the ground. The impedance between the frequency f = 1 / (L ×
Cp) becomes infinite.

As a result, the microwave input from the first input / output terminal 23 is output from the second input / output terminal 24.

On the other hand, when the voltage at the first bias terminal 11 and the voltage at the second bias terminal 12 are smaller than the pinch-off voltage of the FET, the equivalent circuit is the circuit shown in FIG.

Referring to FIG. 3, the impedance between the connection point between transmission line 90 and transmission line 2 and the ground is an FET.
32, a capacitor (C
p) 132 and a parallel circuit of a series resonance circuit composed of an inductance (L) 115 and a capacitor (Cp) 101.

Similarly, the impedance between the connection point between the transmission line 2 and the transmission line 3 and the ground is a capacitor (Cp) 133 representing the capacitance between the drain and the source of the FET 33.
And inductance (L) 116 and capacitor (Cp)
102 and a parallel circuit with the series resonance circuit composed of

From the above, the impedance between the connection point between the transmission line 90 and the transmission line 2 and the ground is short-circuited (short-circuited) at the frequency (angular frequency ω) f = 1 / (L × Cp). Similarly, the impedance between the connection point between the transmission line 2 and the transmission line 3 and the ground is equal to the frequency f = 1 /
A short circuit occurs at (L × Cp). As a result, the microwave input from the first input / output terminal 23 is not output from the second input / output terminal 24.

Further, when the voltage of the first bias terminal 11 is F
When the voltage is smaller than the pinch-off voltage of ET and the voltage of the second bias terminal 12 is 0 V, the equivalent circuit is the circuit shown in FIG.

Referring to FIG. 4, the impedance between the connection point between transmission circuit 90 and transmission line 2 and the ground is an FET.
A short circuit (short-circuit line) 232 representing a connection between the drain and the source 32; a series resonance circuit composed of an inductance (L) 115 and a capacitor (Cp) 101;
Is a parallel circuit.

Similarly, the impedance between the connection point between the transmission line 2 and the transmission line 3 and the ground is a short (short line) 133 representing the connection between the drain and source of the FET 33.
And inductance (L) 116 and capacitor (Cp)
102 and a parallel circuit with the series resonance circuit composed of

As described above, the impedance between the connection point between the transmission line 90 and the transmission line 2 and the ground is short-circuited in the entire frequency range, and similarly, the connection point between the transmission line 2 and the transmission line 3 and the ground. Is short-circuited in the entire frequency range.

As a result, the microwave input from the first input / output terminal 23 is not output from the second input / output terminal 24. At this time, even if the voltage of the first bias terminal 11 is 0 V, the microwave input from the first input / output terminal 23 is not output from the input / output terminal 24.

[0037]

As described above, the microwave switch of the present invention has the following remarkable effects.

(1) In the present invention, since there is no direct current connection between the drain and the source, there is no deterioration in propagation characteristics in a low frequency region.

(2) The pass frequency band and the cutoff frequency band of the switch can be set separately by adjusting the voltage of each bias terminal and changing the capacitance of each corresponding FET. A wide-band microwave switch can be realized without the need for design and re-production.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of an embodiment of a microwave switch according to the present invention.

FIG. 2 is a diagram showing an equivalent circuit of the embodiment of the present invention shown in FIG. 1 when the voltage at the bias terminal 11 is 0 V and the voltage at the bias terminal 12 is smaller than the pinch-off voltage of the FET. FIG.

FIG. 3 is a diagram showing an equivalent circuit of the embodiment of the present invention shown in FIG. 1, and includes a bias terminal 11 and a bias terminal 12;
FIG. 3 is a diagram showing an equivalent circuit when the voltage of the reference voltage is smaller than the pinch-off voltage of the FET.

FIG. 4 is a diagram showing an equivalent circuit of the embodiment of the present invention shown in FIG. 1, in which the voltage at the bias terminal 11 is smaller than the pinch-off voltage of the FET and the voltage at the bias terminal 12 is 0V. FIG.

FIG. 5 is a diagram showing a configuration of a conventional microwave switch.

[Explanation of symbols]

 21, 22, 31, 32, 33, 34 FET 4, 5, 115, 116 Inductor 101, 102, 132, 133 Capacitor 2, 3, 8, 15, 16, 18, 90 Transmission line 11, 12 Bias terminal 23, 24 input / output terminals

Claims (1)

(57) [Claims] A first terminal connected to a gate terminal of a first FET;
Connect to the gate terminal of the second FET with the same characteristics as ET
A predetermined length between the connection point and the first bias terminal.
And a first transmission line having a characteristic impedance and connecting between the source terminal of the first and second FETs and the ground terminal.
Second and third transmissions of length and characteristic impedance equal to
The transmission lines are connected to each other , and the drain terminal of the first FET and the drain terminal of the second FET are connected.
Predetermined length and characteristic impedance between drain terminal
4th transmission line, and the first and second FETs have drain terminals connected to the first and second FETs.
Predetermined length and characteristic impedance between signal input / output terminals
The fifth transmission line and the sixth transmission line are connected to each other , and the source terminal is connected to the drain terminal of the first FET.
, And having a characteristic equal to that of the first FET,
The drain terminal of the FET is connected , and the source terminal is grounded to the drain terminal of the second FET.
To the fourth FET having the same characteristics as the first FET.
The drain terminal of the FET is connected, and the gate terminal of the third FET is connected to the gate terminal of the fourth FET.
Is connected to over preparative terminal, connection point and a second gate terminal of said third and fourth FET
The seventh transmission line is not connected between the
A microwave switch , wherein the voltage of the first bias terminal is applied to a pinch-off current of an FET.
Voltage, and set the voltage of the second bias terminal to 0.
V or set near the pinch-off voltage of the FET
, The drain-source capacitance that appears, and the second,
A series composed of the inductance of the third transmission line
The first and second resonance circuits,
2. A microwave switch, wherein two signal input / output terminals are disconnected or connected .