JP2000124783A - Semiconductor high frequency changeover circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a semiconductor high frequency changeover circuit with a small number of input/output terminals. SOLUTION: This semiconductor high frequency changeover circuit is provided with an RF (high frequency) switch 1, capacitors C1-C3 and a low-pass filter 2 and the RF switch 1 is provided with an SPDT(single pole double throw) switch 11 and an inverter 12. Since the signal input terminal of the SPDT switch 11 and the power supply terminal of the inverter 12 are both connected to the power supply/signal input terminal Sin of the RF switch 1, the need of a dedicated power supply terminal is eliminated and the number of the input terminals of the RF switch 1 is reduced. One end of the low-pass filter 2 and the capacitor C1 is connected to the power supply/signal input terminal Sin, respectively, an external power supply input terminal VDD is connected to the other end of the low-pass filter 2 and an external signal input terminal is connected to the other end of the capacitor C1. The low-pass filter 2 is provided so as to prevent the leakage of high frequency signals inputted to the external signal input terminal to the external power supply input terminal.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor high-frequency switching circuit for branching a high-frequency signal input from the outside into two or more systems in accordance with the logic of a control signal. It is intended for RF switches and the like used in electronic devices that handle signals.

[0002]

2. Description of the Related Art FIG. 2 is a circuit diagram showing an internal configuration of a conventional semiconductor high-frequency switching circuit used to split a high-frequency signal. As shown in FIG. 2, a conventional semiconductor high-frequency switching circuit includes a high-frequency switch (hereinafter, referred to as an RF switch).
1 and capacitors C1 to C4. The RF switch 1 includes a single-input double-output (SPDT) type switch (hereinafter referred to as SPDT switch) 11 having one input and two outputs, and an inverter 12.
And

As shown in detail in FIG. 3, the SPDT switch 11 is composed of two MOS transistors Q1 and Q2.
The gate terminal of one transistor Q1 is connected to the inverter 12
And the gate terminal of the other transistor Q2 is connected to the output terminal of the inverter 12.

[0006] The inverter 12 shown in FIG. 2 operates by receiving a power supply voltage from the outside. Therefore, the RF switch 1 of FIG. 2 includes a power supply terminal Vin for supplying power and a ground terminal.
GND, a high-frequency signal input terminal Sin, and a plurality of signal output terminals Sout1, Sout2 for outputting branched high-frequency signals.
And a control signal input terminal Vc for switching control of the SPDT switch 11. As described above, the conventional RF switch 11 shown in FIG. 2 requires at least five input / output terminals.

On the other hand, single pole single throw (SPS) with one input and one output
When a T) -type switch is used, a signal input terminal is required for each signal output terminal, so that the number of terminals of the RF switch 11 increases as compared with the case where a single-pole, double-throw switch is used.

[0006]

The RF switch 11 is generally housed in a small plastic mold.
When the number of terminals is increased, the size of the plastic mold must be increased accordingly, and the size cannot be reduced.

The present invention has been made in view of the above points, and an object of the present invention is to provide a semiconductor high-frequency switching circuit having a small number of input / output terminals.

[0008]

In order to solve the above-mentioned problems, the present invention provides a semiconductor high-frequency switch for outputting an input high-frequency signal from one of a plurality of output terminals in accordance with the logic of a control signal. In the circuit, a switching circuit that switches from which output terminal the input high-frequency signal is output, a switching control circuit that controls the switching circuit, and a high-frequency signal input terminal that inputs a high-frequency signal to an input terminal of the switching circuit. A power supply terminal for supplying a power supply voltage, and a high impedance circuit connected between the high frequency signal input terminal and the power supply terminal, and a connection path between the high frequency signal input terminal and the high impedance circuit,
A power supply terminal of the switching control circuit and an input terminal of the switching circuit are connected to each other.

The invention of claim 1 will be described with reference to FIG. 1, for example. A "switching circuit" is an SPDT switch 11, a "switching control circuit" is an inverter 12, and a "high-frequency signal input terminal" is an external signal input terminal. RF_IN, the “power supply terminal” corresponds to the power supply input terminal VDD, and the “high impedance circuit” corresponds to the low-pass filter 2.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A semiconductor high-frequency switching circuit according to the present invention will be specifically described below with reference to the drawings.

FIG. 1 is a circuit diagram of an embodiment of a semiconductor high-frequency switching circuit according to the present invention. The semiconductor high-frequency switching circuit of FIG. 1 includes an RF switch 1 and a coupling capacitor C.
1 to C3 and a low-pass filter (LPF) 2.

As shown in FIG. 2, the RF switch 1 includes a single-input / double-output single-pole / double-throw switch (SPDT switch) 11;
And an inverter 12. The input terminal of the SPDT switch 11 is connected to the power / signal input terminal Sin of the RF switch 1, and the output terminal of the SPDT switch 11 is connected to the signal output terminals Sout1 and Sout2 of the RF switch 1, respectively. The input terminal of the inverter 12 is connected to the control signal input terminal Vc of the RF switch 1, and the power terminal of the inverter 12 is connected to the RF terminal.
Inverter 1 is connected to power / signal input terminal Sin of switch 1.
The ground terminals 2 are connected to the ground terminal GND of the RF switch 1, respectively.

As described above, in the semiconductor high-frequency switching circuit of FIG. 1, both the signal input terminal of the SPDT switch 11 and the power supply terminal of the inverter 12 in the RF switch 1 are connected to the power supply / signal input terminal Sin of the RF switch 1. By the way, R
The number of input terminals of the F switch 1 is reduced.

Power supply / signal input terminal Sin of RF switch 1
Has a low-pass filter 2 and a coupling capacitor C
1 is connected to one end, and the other end of the low-pass filter 2 is connected to an external power supply input terminal VDD.
Is connected to an external signal input terminal RF_IN.

The low-pass filter 2 shown in FIG. 1 is provided to prevent a high-frequency signal input to the external signal input terminal RF_IN from leaking to the external power supply input terminal VDD, and is configured by combining a resistor, a capacitor, and the like. . The illustrated RF switch 1 is configured using, for example, a GaAs transistor.

Next, the operation of the semiconductor high-frequency switching circuit of FIG. 1 will be described. For example, 1G is connected to the external signal input terminal RF_IN.
A high frequency signal higher than Hz is input. This high-frequency signal is input to the power / signal input terminal Sin of the RF switch 1 via the coupling capacitor C1. The low-pass filter 2 is connected to this input terminal, and the other end of the low-pass filter 2 is connected to the external power supply input terminal VDD.
In, a high-frequency signal with the power supply voltage input to the external power supply input terminal VDD as a reference (DC level) is input to in.

If the external signal input terminal RF_IN is directly connected to the external power supply input terminal VDD, a high-frequency signal may leak to the external power supply input terminal VDD side. Input terminal VDD
And the low-pass filter 2 is provided between them to prevent leakage of high-frequency signals.

The inverter 12 in the RF switch 1
Is supplied with a power supply voltage from the power supply / signal input terminal Sin of the RF switch 1, it is not necessary to provide a dedicated power supply terminal for the RF switch 1, and the R
The number of input terminals of the F switch 1 can be reduced. Therefore, the semiconductor high-frequency switching circuit can be downsized.

In the above-described embodiment, an example is described in which a single-input, double-throw (SPDT) switch having one input and two outputs is used. However, the present invention can be similarly applied to a case in which a switch having three or more outputs is used. In this case, a switch switching control circuit (for example, a multiplexer) is provided instead of the inverter 12 in FIG.
The power supply terminal of FIG.
What is necessary is just to connect the signal input terminal Sin.

FIG. 1 shows an example in which the low-pass filter 2 is provided to prevent a high-frequency signal from leaking to the external power supply input terminal VDD. However, instead of the low-pass filter 2, various high-impedance circuits ( For example, a high-resistance element or the like may be used.

[0021]

As described above in detail, according to the present invention, a high impedance circuit is provided between a high-frequency signal input terminal and a power supply terminal, and a connection path between the high impedance circuit and the high-frequency signal input terminal is switched. Since the power supply terminal of the control circuit and the input terminal of the switching circuit are connected to each other, a dedicated power supply terminal for driving the switching control circuit is not required, and the high-frequency switch ( RF switch) can be reduced. Further, by reducing the number of input terminals, the entire circuit can be downsized.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of an embodiment of a semiconductor high-frequency switching circuit according to the present invention.

FIG. 2 is a circuit diagram showing an internal configuration of a conventional semiconductor high-frequency switching circuit.

FIG. 3 is a circuit diagram showing a detailed configuration of the RF switch of FIG. 2;

[Explanation of symbols]

 1 RF switch 11 SPDT switch 12 Inverter

Claims (4)

[Claims] In a semiconductor high-frequency switching circuit for outputting an input high-frequency signal from one of a plurality of output terminals in accordance with the logic of a control signal, it is determined from which output terminal the input high-frequency signal is output. A switching circuit that switches, a switching control circuit that controls the switching circuit, a high-frequency signal input terminal that inputs a high-frequency signal to an input terminal of the switching circuit, a power supply terminal that supplies a power supply voltage, the high-frequency signal input terminal, A high-impedance circuit connected between the power supply terminals, a connection path between the high-frequency signal input terminal and the high-impedance circuit, a power supply terminal of the switching control circuit, and an input terminal of the switching circuit. A semiconductor high-frequency switching circuit connected to each other. 2. The high frequency semiconductor switching circuit according to claim 1, wherein said high impedance circuit is a low-pass filter. 3. The semiconductor according to claim 1, wherein the switching control circuit is an inverter that inverts and outputs an input signal, and the control signal is an input signal and an output signal of the inverter. High frequency switching circuit. 4. The switching circuit is a single-input, double-output, single-pole, double-throw switch, and converts a high-frequency signal input to the high-frequency signal input terminal according to a logic of an input signal and an output signal of the inverter. 4. The semiconductor high-frequency switching circuit according to claim 3, wherein the signal is output from one of two output terminals of the switch.