JPH05252016A - High frequency switch - Google Patents

Abstract

PURPOSE:To obtain a high frequency switch obtaining a low current consumption and a high isolation in the high frequency switch used for various high frequency radio equipments. CONSTITUTION:The switch consists of a resonator section composed of a resonance line 10 having an attenuation characteristic (trap) at a required frequency and a device section composed of a transistor(TR) having either of an ON resistance and a GaAs FET11. The resonator section is connected in parallel between the terminals of various devices having an ON resistance and the ON resistance is controlled by turning on/off the power supply supplied to the device to cause/loose the trap of the resonator section, thereby controlling the transmission/interruption of a transmission signal. Thus, the very economical high frequency switch ensuring low power consumption and high isolation is obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-frequency switch used in various high-frequency radio devices, communication devices, measuring instruments and the like.

[0002]

2. Description of the Related Art A high-frequency switch is generally used in a high-frequency radio device, a communication device, a high-frequency measuring instrument, etc., especially for branching or blocking a high-frequency transmission signal.

For example, in a wireless device, a typical one is often used for transmitting and receiving signals from an antenna section.

An example of the structure is shown in FIGS. FIG. 10 shows a diode type high frequency switch, and 1 is a PIN diode. As the bias circuit, DC
It is composed of a cutoff capacitor 2, a bypass capacitor 3, a high frequency choke coil 4, and a resistance element 5.

This high frequency switch is a PIN diode 1
This utilizes the fact that the internal resistance changes linearly by the forward current of (1), and supplies and biases a signal by supplying a bias to the control terminal 7.

FIG. 11 shows a high frequency switch composed of an FET, which is composed of a field effect transistor (FET) 8 having a control terminal 9 at the gate and input / output terminals at the source and drain. The switch is controlled by supplying a bias to the gate.
7 is a resistance.

This high-frequency switch utilizes the fact that the channel resistance of the FET 8 changes remarkably depending on the gate bias. In order to switch between the source and drain, 0V is applied to the control terminal in the ON state, while the OFF state is applied. Then the threshold voltage of FET8 (negative voltage)
The operation is performed by applying the following voltages.

[0008]

However, in the above configuration, the diode method is used when the transmission signal is cut off (switch O
In order to obtain the required attenuation characteristics of FF), the consumption current flowing through the diode is about 10 mA, and although the current consumption is small in the dual gate FET, the negative power supply is required for the gate control, which causes practical difficulties. There is. Further, the attenuation amount (isolation) when the signal is cut off is limited to 20 to 30 dB.

The present invention solves the above-mentioned conventional problems, and an object of the present invention is to realize a circuit with low current consumption and a single power source, and to obtain high attenuation characteristics when a transmission signal is cut off. ..

[0010]

A first means of the present invention for attaining this object comprises a line or a resonator part composed of a capacitance and a line, and a device part composed of a GaAs FET, The resonator is connected in parallel between two terminals (drain and source) having the ON resistance of the FET.

The second means of the present invention is to use a GaAs FET as a switching element, connect the switching element and the capacitor in series, and further connect a resonator section formed of a line, the switching element and the capacitor in series circuit. Is connected in parallel, and a high-frequency switch for controlling passage of a signal in a transmission line by controlling the switching element is provided.

[0012]

With the above-described structure of the present invention, the resonator constituted by the line designed to resonate at a desired frequency has an attenuation characteristic (trap) corresponding to the Q value (resistance) of the line, that is, the line. , The signal level at the trap frequency is reduced by the amount of attenuation.

The first means of the present invention utilizes the fact that the amount of attenuation of the resonator changes depending on the Q value (resistance), and the resonant line is connected in parallel to the channel resistance (between drain and source) of the FET. By supplying a predetermined bias to the device, the on-resistance is controlled, that is, the trap of the resonator is generated and erased to block or pass the transmission signal.

On the other hand, the second means of the present invention is to use a GaAs FET as a switch element because the channel resistance of the FET remarkably changes depending on the gate bias. As a switching element connected in series with the capacitor,
Utilizing the channel resistance of GaAs FET, the capacitor is connected in series with either the drain or the source having the channel resistance of FET, and a control terminal is provided on the drain to use a single power supply, and a predetermined bias is applied. To control the on-resistance. That is, due to the switching operation of the FET, a trap of the resonator is generated at a predetermined frequency in the OFF state, and the signal is blocked. Also,
When the switching element is in the ON state, a capacitance is formed in parallel with the line, a parallel resonant circuit of the line and the capacitance is formed, the resonance trap moves to a low range, and the signal of the transmission line passes.

[0015]

(Embodiment 1) A first embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows an overall circuit diagram of this embodiment, and FIG. 2A and FIG.
Fig. 3 shows a high frequency equivalent circuit and its transmission characteristics during FF.
(A) and (b) show a high frequency equivalent circuit and its transmission characteristics when the control voltage is ON.

In FIG. 1, a resonance line 10 having a required resonance frequency, a resonator portion composed of a DC blocking capacitor 15, and a GaAs having three terminals of a drain, a source and a gate.
And the resonance line 10 is connected in parallel between the drain and the source. Also, capacity 1
Reference numerals 7, 18, and 19 serve as a bypass capacitor, and resistors 12, 13, and 14 create a DC bias condition.

The on-resistance between the drain and the source of the GaAs FET 11 is controlled by turning on the terminal 16 (5
V) / OFF (0V) operation.

Next, the equivalent circuits of FIGS. 2 and 3 and their transmission characteristics will be described. FIG. 2A shows an equivalent circuit when a voltage of 0 V is applied to the control terminal 16 with nothing applied.

That is, when the control voltage is OFF, FET1
No. 1 does not operate, and the resistance between the drain and the source shows an extremely high value (high impedance in high frequency), and there is no influence on the line 10 which is a resonator, and Cd shown in FIG.
s, Cgs, Cgd, the total capacitance between the terminals and the line 1
A resonant trap formed with 0 is formed as a transmission characteristic.

On the other hand, FIGS. 3A and 3B show the control terminal 16
An equivalent circuit and its transmission characteristics when a voltage of 5 V is applied to the circuit are shown.

When the control voltage is ON, the FET 11 is turned ON, and the resistance value between the drain and the source shows a finite value (several tens of Ω to several hundred Ω). Therefore, the line 10 that is a resonator
, A resistor is connected in parallel with it, the unloaded Q value of the resonator is reduced, traps do not occur, and the signal passes through the input and output with a constant transmission loss as shown in FIG. 3B. ..

By adopting the above-mentioned configuration, the resonator has a larger signal attenuation (transmission signal OFF) effect by the amount of attenuation of the resonator than that of a high-frequency switch composed of a single FET, and a wide band characteristic of a GaAs FET. It provides an economical method that can be realized with a single power source and further reduced power consumption (1 mA or less).

(Second Embodiment) A second embodiment of the present invention will be described below with reference to the drawings.

FIG. 4 is a circuit diagram of the high frequency switch according to the present embodiment. The same parts as those in FIG. 1 are designated by the same reference numerals.

That is, the resonator and the device section are the same as those in the first embodiment.
Taking the same configuration as the above, as the device unit in this embodiment,
A silicon bipolar type transistor 20 is used.

That is, the base of the transistor 20 is used as a ground terminal, the collector and the emitter are used as input / output terminals, and the collector is provided with a control terminal for switching operation of the transistor.

(Embodiment 3) A third embodiment of the present invention will be described below with reference to the drawings.

FIG. 5 shows a circuit diagram of the high frequency switch in this embodiment. That is, the resonator section and the device section are shown in FIG.
In the present embodiment, a variable capacitance element of a trimmer 21 is inserted and connected between the drain and gate of the device section, and a trap generated when the control voltage is turned off in the resonator section and the device section is used as the trimmer. The frequency is controlled by.

By inserting and connecting this variable capacitance element, it is possible to absorb variations in the resonance line portion or the device.

(Embodiment 4) A fourth embodiment of the present invention will be described below with reference to the drawings.

FIG. 6 shows an overall circuit diagram of this embodiment, and FIG.
8A and 8B show a high frequency equivalent circuit and its transmission characteristics when the control voltage is OFF, and FIGS. 8A and 8B show a high frequency equivalent circuit and its transmission characteristic when the control voltage is ON. Shows.

In FIG. 6, a first transmission line composed of a line 22 having a required frequency, a FET 23 using GaAs having three terminals of a drain, a source and a gate, and the FET 2 are provided.
3 and a second transmission line composed of a series circuit of a capacitor 24, and the first and second transmission lines are connected in parallel. Here, 25 is an RFC coil,
Further, the resistors 26 and 27 create a DC bias condition. Further, the terminal 28 controls the on-resistance between the drain and the source of the GaAs FET 23 and is turned on (H
The switching operation of the FET 23 is performed by (IGH) / OFF (LOW).

Next, the operation will be described with reference to the equivalent circuits shown in FIGS. FIG. 7A shows an equivalent circuit when the voltage applied to the control terminal 16 is 0V.

That is, when the control voltage is OFF, FET2
3 does not work, the on-resistance between the drain and source shows an extremely high value (high impedance in high frequency),
There is no influence on the line 22 that is a resonator, and a single resonance trap of the line 22 is formed as a transmission characteristic.

Therefore, this transmission signal is attenuated by the attenuation amount of the resonance trap, and the signal is blocked.

On the other hand, FIG. 8A shows an equivalent circuit when a voltage of 5 V is applied to the control terminal. FE when the control voltage is ON
T22 is turned on, and the resistance value between the drain and the source shows a finite value (several 10Ω to several 100Ω). Therefore, the capacitor 24 is connected in parallel to the line 22 which is a resonator, the transmission line forms a parallel circuit of the line 22 and the capacitor 24, and the trap generated when the control voltage is OFF shifts to the low range. Therefore, the attenuation value is small in the frequency band of the transmission signal, and the signal is input as it is and passes through the output with a constant transmission loss.

By adopting the above-mentioned structure, the effect of blocking a signal larger by the amount of attenuation of the resonator than that of a high-frequency switch composed of a single FET or diode is provided, and the low power consumption characteristic of the GaAs FET is realized. (1 mA or less), and an economical method that can be realized with a single power source can be provided.

(Fifth Embodiment) A fifth embodiment of the present invention will be described below with reference to the drawings.

FIG. 9 shows a circuit diagram of the high frequency switch in this embodiment, and the same portions as those in FIG. 6 are designated by the same reference numerals.

The resonator and the device portion have the same basic structure as that of the fourth embodiment, and in this embodiment, the silicon bipolar type transistor 29 is used as the device portion.

That is, the base is connected to the ground terminal, the collector,
The emitter serves as an input / output terminal and the collector has a control terminal for switching operation of the transistor.

[0042]

As described above, according to the present invention, a high-frequency switch can be easily constructed by connecting a resonator formed of a line in parallel between the drain and source of a GaAs FET that is a device section. Moreover, since the control can be realized by a single power source, low power consumption and high isolation can be obtained.

The present invention also provides a quarter wavelength or 1 / wavelength.
A high-frequency switch can be easily configured by connecting in parallel a resonator composed of a line of two wavelengths and a series circuit of a switching element and a capacitor, and its control can be realized by a single power source, so that Power consumption and high isolation between input and output can be obtained.

[Brief description of drawings]

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

2A is an equivalent circuit diagram when the control voltage is OFF in the embodiment, and FIG. 2B is a transmission characteristic diagram when the control voltage is OFF in the embodiment.

3A is an equivalent circuit diagram when the control voltage is ON in the embodiment, and FIG. 3B is a transmission characteristic diagram when the control voltage is ON in the embodiment.

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

FIG. 5 is a circuit diagram of a high frequency switch according to a third embodiment of the present invention.

FIG. 6 is a circuit diagram of a high frequency switch according to a fourth embodiment of the present invention.

7A is an equivalent circuit diagram when the control voltage is OFF in the embodiment, and FIG. 7B is a transmission characteristic diagram when the control voltage is OFF in the embodiment.

8A is an equivalent circuit diagram when the control voltage is ON in the embodiment, and FIG. 8B is a transmission characteristic diagram when the control voltage is ON in the embodiment.

FIG. 9 is a circuit diagram of a high frequency switch according to a fifth embodiment of the present invention.

FIG. 10 is a circuit diagram of a conventional high frequency attenuator using a diode.

FIG. 11 is a circuit diagram of a high frequency attenuator using a conventional FET.

[Explanation of symbols]

 10 Resonance Line 11 FET 15 Capacitance 16 Control Terminal 20 Transistor 21 Trimmer 22 Line 23 FET 24 Capacitance 29 Transistor

Claims (5)

[Claims] 1. A resonator section composed of a two-terminal line, and a device section composed of a field effect transistor having a gate terminal connected to a ground terminal and having a drain terminal and a source terminal as input and output terminals, respectively. A high-frequency switch configured such that both ends of the resonator section are connected in parallel between a drain and a source of the device section, and an ON resistance between the drain and the source is controlled by a bias supply path provided at a drain terminal. 2. The device section according to claim 1, wherein the field effect transistor is replaced by a bipolar type transistor, the base terminal is connected to the ground terminal, and the collector and emitter terminals are connected as input and output terminals, respectively. High frequency switch. 3. A high frequency switch according to claim 1, wherein a variable capacitance element is inserted and connected between the drain and the gate of the field effect transistor. 4. A first transmission line composed of a two-terminal line, a field-effect transistor as a switching element having a gate terminal connected to a ground terminal and having a drain terminal and a source terminal as input and output terminals, respectively, and a series thereof. A high-frequency switch, comprising: a second transmission line having a capacity connected to the first transmission line, wherein the first transmission line and the second transmission line are connected in parallel. 5. The high frequency wave according to claim 1, wherein a bipolar type transistor is used as the switching element instead of the field effect transistor, and the base terminal is connected to the ground terminal and the collector and emitter terminals are connected as input and output terminals, respectively. switch.