JPH08288703A - Microwave switch - Google Patents

Abstract

PURPOSE: To easily adjust operation frequency in a wide band by a microwave switch. CONSTITUTION: A transmission line 16 opening at its one end and having prescribed length and characteristic impedance is connected to the drain terminal of an FET 1 and a transmission line 17 opening at its one end and having prescribed length and characteristic impedance is connected to the drain terminal of an FET 2. Respective source terminals of the FETs 1, 2 are grounded respectively through transmission lines 18, 19 shorter than 1/4 wavelength. In each FET, its drain and source are not mutually connected and its propagation characteristic in a low frequency area is not deteriorated. Since the transmission lines 16, 17 of which one-ends are opened are connected to the drain terminals of respective FETs 1, 2, resonance frequency can be adjusted by the trimming of the transmission lines 16, 17 even when the capacity between the source and drain of each FET is different from a designed value by the influence of a process or the like, so that it is unnecessary to redesign and retry the microwave switch.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a microwave switch using a field effect transistor (FET).

[0002]

2. Description of the Related Art Conventionally, as this type of microwave switch, for example, one described in Japanese Patent Laid-Open No. 4-113702 is known.

Referring to FIG. 7, the illustrated microwave switch includes FETs 1 and 2, and the gate terminals of the FETs 1 and 2 are connected to each other. This connection point is connected to the bias terminal 11 via the transmission line 5. It is connected. FET
The source terminals of 1 and 2 are grounded, and FET1
The drain terminal of is connected to the drain terminal of the FET 2 via the transmission line 7. Further, the drain terminal of the FET 1 is connected to the first signal input / output terminal 9 via the transmission line 6, and the drain terminal of the FET 2 is connected to the second signal input / output terminal via the transmission line 8. Furthermore, FE
The drain and source of T1 are connected by an inductor 3, and similarly, the drain and source of FET2 are connected by an inductor 4.

In this microwave switch, when a negative bias voltage smaller than the pinch-off voltage of the FETs 1 and 2 is applied to the bias terminal 11, a capacitive component appears between the drain and source of the FETs 1 and 2, and the inductors 3 and 4 will be connected in parallel. As a result, a parallel resonant circuit having a design frequency designed in advance is formed, and a high impedance state is established. Therefore, the microwave input from the first input / output terminal 9 is output from the second input / output terminal 10.

On the other hand, when a bias voltage of zero is applied to the bias terminal 11, the drain and source of the FETs 1 and 2 are in a low impedance state, and grounded via the FETs 1 and 2 input from the first input / output terminal 9. Flow to.
As a result, the microwave is not output from the second input / output terminal 10.

[0006]

By the way, in the above microwave switch, when the voltage applied to the bias terminal 11 is zero, the propagation characteristics are deteriorated due to the capacitance formed between the source and drain of the FETs 1 and 2. To prevent
An inductor that resonates with the capacitance at the desired frequency is connected between the drain and source of ET to cancel the influence of the capacitance.

As described above, in the above microwave switch, since the inductor is connected between the drain and the source of the FET, that is, the drain and the source of the FET are connected in a direct current manner, the low frequency region is used. The propagation characteristics of are deteriorated.

In addition, due to the influence of the process, etc.
If the source-drain capacitance of T is different from the design value, the inductor must be adjusted to adjust the resonance frequency, but considering that it is generally impossible to trim the inductor, the microwave switch There is a problem in that redesign and trial production are required.

An object of the present invention is to provide a microwave switch which has a wide band and whose operating frequency can be easily adjusted.

[0010]

According to the present invention, a first FET having a first gate terminal, a first source terminal, and a first drain terminal and a second gate terminal, a second source. A second FE having a terminal and a second drain terminal
T, the first gate terminal is connected to the second gate terminal at a connection point, and the connection point is connected to the bias terminal via a first transmission line having a predetermined length and characteristic impedance. , The first and second source terminals are respectively grounded, and the first drain terminal is connected to the second drain terminal via a second transmission line having a predetermined length and characteristic impedance, The first
Has a drain terminal connected to the first signal input / output terminal via a third transmission line having a predetermined length and characteristic impedance, and the second drain terminal has a predetermined length and characteristic impedance. A microwave switch connected to a second signal input / output terminal via a fourth transmission line, the fifth transmission line having one end open to the first drain terminal and having a predetermined length and characteristic impedance. And a sixth transmission line having one end opened to the second drain terminal and having a predetermined length and a characteristic impedance is connected to the second drain terminal. And the first and second
The source terminals may be grounded via the seventh and eighth transmission lines having a predetermined length and characteristic impedance, respectively.

[0011]

In the present invention, one end is opened to the drain terminal of each FET and the FET has a predetermined length (for example, longer than 1/4 wavelength).
Since the transmission line is connected, the resonance frequency can be adjusted over a wide band. As a result, when the bias voltage is lower than the pinch-off voltage of the FET, it is possible to prevent the deterioration of the propagation characteristics due to the source-drain capacitance.

Further, one end is opened to the drain terminal of each FET and has a predetermined length (for example, shorter than 1/4 wavelength).
By connecting the transmission line, it is possible to prevent the deterioration of the propagation characteristics due to the inductive component between the drain and the ground when the bias voltage is zero.

[0013]

EXAMPLES The present invention will be described below with reference to examples.

First, a first embodiment of a microwave switch according to the present invention will be described with reference to FIG. The illustrated microwave includes FETs 1 and 2, and FET1
And 2 gate terminals are connected to each other. The connection point is connected to the bias terminal 11 via the transmission line 5 having a length of ¼ wavelength and a characteristic impedance of 50Ω. The source terminals of the FETs 1 and 2 are connected to the ground terminal, and the drain terminal of the FET 1 is F through a transmission line 7 having a length of ¼ wavelength and a characteristic impedance of 50Ω.
It is connected to the drain terminal of ET2. The drain terminal of FET1 has a characteristic impedance of 50Ω at any length.
Is connected to the first signal input / output terminal 9 via the transmission line 6. Furthermore, the drain terminal of FET2 has a length of 1
It is connected to the second signal input / output terminal 10 via the transmission line 8 having a characteristic impedance of 50Ω at / 4 wavelength. Further, the drain terminal of the FET 1 has a transmission line 16 having a predetermined length and characteristic impedance with one end open.
Similarly, the drain terminal of the FET 2 is connected to the transmission line 17 having a predetermined length and a characteristic impedance, one end of which is open.

In the microwave switch shown in FIG. 1, when the voltage of the bias terminal 11 is lower than the pinch-off voltage of the FETs 1 and 2, the equivalent circuit becomes the circuit shown in FIG.
As shown in FIG. 2, the impedance between the connection point of the transmission lines 6 and 16 and the ground becomes a capacitive component 113, and
The transmission line 16 longer than / 4 wavelength has an inductance 116
Therefore, the capacitance component 113 and the inductor 116 form a parallel resonance circuit. Similarly, the impedance between the connection point of the transmission lines 8 and 17 and the ground is the capacitive component 114.
And the transmission line 17 longer than 1/4 wavelength becomes the inductance 117, and the capacitance component 114 and the inductor 1
Reference numeral 17 constitutes a parallel resonance circuit.

As can be easily understood from the above,
The impedance between the connection point with the transmission lines 6 and 16 and the ground becomes infinite, and similarly, the transmission lines 8 and 17
The impedance between the connection point with and the ground is infinite. As a result, the microwave input from the first input / output terminal 9 is output from the second input / output terminal 10.

On the other hand, when the voltage at the bias terminal 11 is zero,
The equivalent circuit is the circuit shown in FIG. As shown in FIG. 3, the impedance between the connection point of the transmission lines 6 and 16 and the ground is almost zero (short circuit). Similarly, the impedance between the connection point of the transmission lines 8 and 17 and the ground is also short-circuited. As a result, the microwave input from the first input / output terminal 9 does not appear in the second input / output terminal 10 because it goes to the ground.

In the above-mentioned embodiment, when the voltage of the bias terminal 11 is smaller than the pinch-off voltage of the FET, the operation center frequency of the switch can be easily made by adjusting the transmission lines 16 and 17.

Next, a second embodiment of the microwave switch according to the present invention will be described with reference to FIG. FIG.
In the microwave switch shown in FIG. 2, the same components as those of the microwave switch shown in FIG. In this embodiment, FET1
1 has the same components as the switch, except that the source terminals of 2 and 2 are connected to the ground terminal via transmission lines 18 and 19, respectively, which are shorter than 1/4 wavelength.

In the microwave switch shown in FIG. 4, when the voltage at the bias terminal 11 is lower than the pinch-off voltage of the FET, the equivalent circuit becomes the circuit shown in FIG. As shown in FIG. 5, the drain-source impedance of the FET 1 becomes a capacitance component 120, and the transmission line 18 shorter than a quarter wavelength becomes an inductance 118 to form a series resonance circuit. Similarly, the impedance between the drain and the source of the FET 2 becomes a capacitance component 121, and the transmission line 19 shorter than ¼ becomes an inductance 119 to form a series resonance circuit.

As can be easily understood from the above,
At the resonance frequency, the impedance between the connection point of the transmission lines 6 and 16 and the ground becomes extremely low. Similarly, at the resonance frequency, the impedance between the connection point of the transmission lines 8 and 17 and the ground is extremely low. As a result, the microwave input from the first input / output terminal 9 does not appear in the second input / output terminal 10.

On the other hand, when the voltage at the bias terminal 11 is zero,
The equivalent circuit is the circuit shown in FIG. As shown in FIG. 6, the impedance between the connection point of the transmission lines 6 and 16 and the ground becomes an inductive component 118, which is 1/4.
The transmission line 16 shorter than the wavelength serves as a capacitor 126 to form a parallel resonance circuit. Similarly, transmission lines 8 and 17
The impedance between the connection point and the ground becomes an inductive component 119, and the transmission line 1 shorter than the quarter wavelength
7 serves as a capacitor 127 to form a parallel resonance circuit.

As can be easily understood from the above,
The impedance between the connection points of the transmission lines 6 and 16 and the ground is infinite, and similarly, the impedance between the connection point of the transmission lines 8 and 17 and the ground is infinite. As a result, the microwave input from the first input / output terminal 9 appears at the second input / output terminal 10.

In the above-described embodiment, when the voltage of the bias terminal 11 is zero, the operation center frequency of the switch can be easily changed by adjusting the transmission lines 16 and 17.

[0025]

As described above, in the present invention, the FE
Since it is not necessary to connect the drain and source of T in a direct current manner, there is no deterioration in the propagation characteristics in the low frequency region. further,
Since the transmission line whose one end is open is connected to the drain terminal of each FET, even if the source-drain capacitance of the FET is different from the design value due to the influence of the process etc., the transmission for adjusting the resonance frequency is performed. Lines can be trimmed without the need for microwave switch redesign and prototype.

[Brief description of drawings]

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

FIG. 2 is a diagram showing an equivalent circuit when the bias voltage is smaller than the pinch-off voltage in the microwave switch shown in FIG.

FIG. 3 is a diagram showing an equivalent circuit when the bias voltage is zero in the microwave switch shown in FIG.

FIG. 4 is a circuit diagram showing a second embodiment of the microwave switch according to the present invention.

5 is a diagram showing an equivalent circuit when the bias voltage is smaller than the pinch-off voltage in the microwave switch shown in FIG.

FIG. 6 is a diagram showing an equivalent circuit when the bias voltage is zero in the microwave switch shown in FIG.

FIG. 7 is a circuit diagram showing a conventional microwave switch.

[Explanation of symbols]

1, 2 FETs (field effect transistors) 3, 4, 116, 117, 118, 119 Inductors 113, 114, 120, 121, 126, 127 Capacitors 5, 6, 7, 8, 8, 16, 17, 18, 19 Transmission lines 9 First input / output terminal 10 Second input / output terminal 11 Bias terminal

Claims (2)

[Claims] 1. A first gate terminal, a first source terminal,
And a first FET having a first drain terminal and a second gate terminal, a second source terminal, and a second FET having a second drain terminal, the first gate terminal being a connection point The connection point is connected to the second gate terminal, the connection point is connected to a bias terminal through a first transmission line having a predetermined length and characteristic impedance, and the first and second source terminals are respectively grounded. And the first
Is connected to the second drain terminal via a second transmission line having a predetermined length and a characteristic impedance, and the first drain terminal has a third length and a characteristic impedance. Is connected to a first signal input / output terminal via a transmission line, and the second drain terminal is further connected to a second signal input / output terminal via a fourth transmission line having a predetermined length and characteristic impedance. In the connected microwave switch, one end is opened to the first drain terminal and a fifth transmission line having a predetermined length and characteristic impedance is connected, and one end is opened to the second drain terminal. A microwave switch, to which a sixth transmission line having a predetermined length and a characteristic impedance is connected. 2. The microwave switch according to claim 1, wherein the first and second source terminals are respectively grounded via seventh and eighth transmission lines having predetermined lengths and characteristic impedances. The microwave switch is characterized in that