JPH0345023A - High frequency changeover circuit - Google Patents

Abstract

PURPOSE:To prevent crosstalk of a transmission output to a receiver without use of a PIN diode switch with high dielectric strength by providing a circulator, a PIN diode switch and a detection circuit so as to utilize the isolation between terminals of the circulator. CONSTITUTION:The circuit is provided with a PIN diode switch 13, a circulator 14 and a detection circuit 16, an output of a transmitter 11 connects to a 1st terminal (a) of the circulator, an antenna 15 connects to a 2nd terminal (b) of the circulator and an input of the PIN diode switch 13 and the input of the detection circuit 16 connect to a 3rd terminal (c) of the circulator. The output of the PIN diode switch 13 connects to a receiver 12 and the output of the detection circuit 16 connects to the transmitter 11. The detection circuit 16 detects a level between the 3rd terminal (c) of the circulator 14 and the input of the PIN diode switch 13 and sends its output to the transmitter 11. Thus, crosstalk of an output of the transmitter to the input of the receiver is prevented without using the PIN diode switch with high dielectric strength.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a high frequency switching circuit in a radio device that switches between a transmitter and a receiver and uses an antenna in common.

[Conventional technology]

Conventionally, a high frequency switching circuit in a radio device that switches between a transmitter and a receiver and uses a common antenna is a high-voltage PIN diode connected to the output of a transmitter 21, as shown in FIG. switch 26 and receiver 22
It has a structure in which the output of a high-voltage pin diode switch 26 and the input of the pin diode switch 23 are connected to an antenna 25.

In such a conventional high frequency switching circuit, when transmitting, by turning on the high voltage pin diode switch 26 and turning off the pin diode switch 23, the output of the transmitter 21 is supplied to the antenna 25, and the transmission output is transmitted from the antenna. Sent out. At this time, the pin diode switch 23 is off, preventing the output of the transmitter 21 from being routed to the input of the receiver 22.

Also, during reception, by turning off the high-voltage pin diode switch 26 and turning on the pin diode switch 23, the output of the transmitter 21 is prevented from going around to the input of the receiver 22, and the output from the antenna 25 is A receive input was provided to receiver 22.

However, the conventional high frequency switching circuit described above requires a pin diode switch 26 that can directly pass the output of the transmitter 21. This pin diode switch 26 needs to have a high withstand voltage and take measures against heat generated by insertion loss, etc., which makes the pin diode switch 26 expensive and large.
This also had the disadvantage of increasing the size of the radio.

Therefore, the inventor of the present application proposed a high frequency switching circuit shown in FIG. 3 which eliminates the above-mentioned drawbacks.

The high frequency switching circuit shown in FIG. 3 has a pin diode switch 33 and a circulator 34, the output of the transmitter 31 is connected to the first terminal a of the circulator, and the antenna 35 is connected to the second terminal of the circulator. is connected, and the input of the pin diode switch 33 is connected to the third terminal C of the circulator. A receiver 32 is connected to the output of this pin diode switch 33.

In this high frequency switching circuit, during transmission, the output of the transmitter 31 is input to the first terminal a of the circulator 34,
According to the rotation direction of the circulator 34, the signal is output to the second terminal of the circulator 34, supplied to the antenna 35, and a transmission output is output. At this time, the pin diode switch 33 is turned off to prevent the output of the transmitter 331 from going around to the input of the receiver 32.

During reception, the reception input to the antenna 35 is input to the second terminal C of the circulator 34 and output from the third terminal C, and by turning on the pin diode switch 33, the reception input is received. It is supplied to the container 32.

This high-frequency switching circuit does not use a high-voltage pin diode switch that directly passes the transmission output, but isolates the first terminal a and third terminal C of the circulator 34 (approximately 20 to 30 dB) and The pin diode switch 33 connected to the input of the receiver 32 can prevent the transmitted output from going around to the receiver 32.

[Problems to be Solved by the Invention] However, in the high frequency switching circuit shown in FIG. and is output from the third terminal C, and an excessive input enters the pin diode switch 33.
There was a drawback that the pin diode switch 33 was destroyed.

An object of the present invention is to provide a high frequency switching circuit that eliminates such drawbacks.

[Means to solve the problem]

The present invention provides a high frequency switching circuit for a radio device that switches between a transmitter and a receiver and uses an antenna in common, comprising a circulator, a pin diode switch, and a detection circuit, wherein a first terminal of the circulator is connected to the transmitter. A second terminal of the circulator is connected to an antenna, a third terminal of the circulator is connected to an input of the pin diode switch and an input of the detection circuit, and the output of the pin diode switch is connected to the output of the pin diode switch. connected to an input of the receiver, an output of the detection circuit is connected to the transmitter, the detection circuit detects a level between a third terminal of the circulator and an input of the pin diode switch; It is characterized in that its output is supplied to the transmitter.

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings.

The high frequency switching circuit shown in FIG. 1 includes a pin diode switch 13. It has a circulator 14 and a detection circuit 16, the output of the transmitter 11 is connected to the first terminal a of the circulator, the antenna 15 is connected to the second terminal of the circulator, and the third terminal C of the circulator is connected to the output of the transmitter 11. is the input of the pin diode switch 13 and the detection circuit 16.
input is connected. The output of this pin diode switch 13 is connected to the receiver 12, and the output of the detection circuit 16 is connected to the transmitter 11.

The detection circuit 16 detects the level between the third terminal C of the circulator 14 and the input of the pin diode switch 13, and sends its output to the transmitter 11.

That is, the high frequency switching circuit of this embodiment has a configuration in which a detection circuit 16 is added to the high frequency switching circuit of FIG. 3 proposed by the inventor of the present application.

Next, the operation of this embodiment will be explained.

During transmission, the output of the transmitter 11 is input to the first terminal a of the circulator 14, and according to the rotation direction of the circulator 14, is output to the second terminal a of the circulator 14, and is supplied to the antenna 15, so that the transmission output is Output.

At this time, the pin diode switch 13 is turned off,
This prevents the output of the transmitter 11 from going around to the input of the receiver 12.

During reception, the reception input to the antenna 15 is input to the second terminal C of the circulator 14 and output from the third terminal C, and by turning on the pin diode switch 13, the reception input is received. It is supplied to the container 12.

The normal operation in this embodiment is similar to the normal operation in the high frequency switching circuit shown in FIG. 3, but when the antenna 15 has some abnormality, it operates as follows.

If the antenna 15 has some abnormality and the transmitted output is reflected, the reflected power is input to the second terminal C of the circulator 14 and output from the third terminal C, and if excessive force is applied to the pin diode switch 13. , the pin diode switch 13 will be destroyed, so the third terminal C of the circulator 14 and the pin diode switch 13 will be damaged.
A detection circuit 16 added between the pin diode switch detects the reflected power of the transmitted output and controls the transmitter 11 by, for example, stopping the transmitted output when the reflected power exceeds the specified value. 13 and receiver 12 can be protected.

〔Effect of the invention〕

As described above, by using isolation between the terminals of the circulator, the present invention can prevent the transmission output from going around to the receiver without using a high-voltage pin diode switch. Therefore, the price of radio equipment is reduced.

This has the effect of downsizing.

Furthermore, according to the present invention, the pin diode switch and the receiver can be protected by detecting reflected power caused by an abnormality in the antenna using a detection circuit and controlling the transmission output of the transmitter.

[Brief explanation of drawings]

FIG. 1 is a diagram showing one embodiment of the present invention, and FIG. 2 is a diagram showing an embodiment according to the present invention.
FIG. 3 is a diagram showing a conventional high frequency switching circuit, and FIG. 3 is a diagram showing a high frequency switching circuit according to an existing proposal. 11・ 12・ 13・ 14・ 5 16・ a ・ b ・ C◆ ・Transmitter・Receiver・Pin diode switch・Circulator・Antenna・Detection circuit・First terminal of circulator・Second terminal of circulator Third terminal of circulator

Claims (1)

[Claims] (1) A high frequency switching circuit for a radio device that switches between a transmitter and a receiver and uses an antenna in common, which includes a circulator, a pin diode switch, and a detection circuit, and the first terminal of the circulator is connected to the transmitter. a second terminal of the circulator is connected to an antenna, a third terminal of the circulator is connected to an input of the pin diode switch and an input of the detection circuit, and the output of the pin diode switch is connected to the an output of the detection circuit is connected to the transmitter; the detection circuit detects a level between the third terminal of the circulator and the input of the pin diode switch; A high frequency switching circuit, characterized in that it supplies an output to the transmitter.