JPH09284072A - Transmission circuit and its automatic transmission power adjustment method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To simplify the circuit configuration of the transmission circuit employing a varactor diode multiplier and to reduce the cost. SOLUTION: A varactor diode 83 has a characteristic such that the auto-bias voltage V generated across both terminals of the varactor diode 8 is reduced as a high frequency output increases. Then the voltage V is amplified by a DC amplifier 9 to be used for a signal to control a gain of a variable gain amplifier amplifying an intermediate frequency signal. Through the constitution above, a directional coupler to distribute a high frequency output and a detector to detect a level of an output of the directional coupler or the like are not required, the circuit is made small and the cost is reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transmission circuit and a transmission power automatic adjusting method thereof, and more particularly to a transmission circuit using a varactor diode multiplier and a transmission power automatic adjusting method thereof.

[0002]

2. Description of the Related Art FIG. 2 shows a conventional circuit of a transmission circuit in which an intermediate frequency signal is amplified and then converted into a transmission frequency by a multiplier using a varactor diode for transmission. In the figure, an input intermediate frequency signal is amplified by a variable gain amplifier 1 and converted into a transmission frequency by a varactor diode multiplier 2. The multiplied high frequency signal is input to the band pass filter 4 via the isolator 3, where unnecessary waves are removed and transmitted.

A part of the transmission high frequency output is branched by the directional coupler 5, converted into a DC signal corresponding to the high frequency output level by the detector 6, amplified by the DC amplifier 7, and sent to the control terminal of the variable gain amplifier 1. Applied to form a feedback loop. This feedback loop operates as an automatic power adjustment circuit for keeping the output level of the transmitted high frequency signal constant.

[0004]

SUMMARY OF THE INVENTION In the above-mentioned conventional transmission circuit, a directional coupler, a detector,
Also, a DC amplifier is required, and the circuit becomes larger by this amount.
It became complicated and was a cause of high cost.

It is an object of the present invention to provide a transmitter circuit using a varactor diode multiplier, which is capable of downsizing the circuit structure and cost thereof, and a transmission power automatic adjusting method thereof. is there.

[0006]

In order to achieve the above object, in the present invention, a variable gain amplifier for amplifying an intermediate frequency signal and an output signal of the variable gain amplifier are multiplied by using a varactor diode. A multiplier for generating a high frequency signal, a band pass filter for generating a transmission high frequency signal by removing unnecessary waves contained in the high frequency signal of the multiplier output, and between both terminals of the varactor diode of the multiplier. And a DC amplifier for amplifying a self-bias voltage generated in the variable gain amplifier to generate a control voltage for controlling the gain of the variable gain amplifier.

Further, according to the present invention, there is provided a transmission power automatic adjusting method for a transmission circuit, wherein the intermediate frequency signal is amplified by a variable gain amplifier and then multiplied by a multiplier using a varactor diode and output. The automatic transmission power of the transmission circuit is characterized in that the self-bias voltage generated between both terminals of the varactor diode is amplified by a DC amplifier to control the gain of the variable gain amplifier to control the transmission power. An adjustment method is disclosed.

[0008]

Embodiments of the present invention will be described below. FIG. 1 is a block diagram showing a configuration example of a transmission circuit according to the present invention, in which a variable gain amplifier 1, an isolator 3, and a bandpass filter 4 are the same as those in the conventional circuit of FIG. The structure of the varactor diode multiplier 8 is the same as the conventional one, but the self-bias voltage V generated between both terminals of the varactor diode 83 inside thereof is taken out to the outside, which is amplified by the DC amplifier 9 and changed. It is a feature of this embodiment that it is used as a feedback control voltage to the gain amplifier 1.

FIG. 3 shows an example of characteristics of the varactor diode multiplier 8. As the level of the intermediate frequency signal (IF) input via the matching circuit (MN) 81 increases, the level of the high frequency output output via the matching circuit (MN) 82 also increases. The terminal voltage V of the self-biasing resistor 84 of the varactor diode 83, which is generated as a result, decreases as the intermediate frequency signal level increases, as shown in the lower part of FIG. Therefore, the voltage V can be used as a quantity representing the output level, although the increase / decrease relation of the output level of the radio frequency signal (RF) is opposite.

The present invention utilizes the characteristics of this varactor diode multiplier and inversely amplifies the terminal voltage V of the varactor diode 83, that is, the self-biasing resistor 84 by the DC amplifier 9 and feedback-controls it to the variable gain amplifier 1. As a result, automatic power adjustment is performed. Therefore, the conventional directional coupler and detector are not required, and the circuit configuration can be downsized and the cost can be reduced.

[0011]

According to the present invention, there is an effect that the transmission circuit using the varactor diode multiplier can be downsized, the number of parts can be reduced, and the cost can be reduced.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration example of a transmission circuit according to the present invention.

FIG. 2 is a block diagram showing a configuration example of a conventional transmission circuit.

FIG. 3 is a diagram showing a characteristic example of a varactor diode multiplier.

[Description of Reference Signs] 1 variable gain amplifier 3 isolator 4 bandpass filter 5 directional coupler 6 detector 7 DC amplifier 8 varactor diode multiplier 9 DC amplifier 81 matching circuit 82 matching circuit 83 varactor diode 84 self-biasing resistor

Claims (2)

[Claims] 1. A variable gain amplifier for amplifying an intermediate frequency signal, a multiplier for multiplying an output signal of the variable gain amplifier by using a varactor diode, and a high frequency signal, and a multiplier output of the multiplier. A bandpass filter that removes unnecessary waves included in a high frequency signal to generate a transmission high frequency signal, and a gain of the variable gain amplifier is controlled by amplifying a self-bias voltage generated between both terminals of a varactor diode of the multiplier. And a direct current amplifier for generating a control voltage for operating the transmitter circuit. 2. A transmission power automatic adjusting method for a transmission circuit, wherein the intermediate frequency signal is amplified by a variable gain amplifier and then multiplied by a multiplier using a varactor diode and output. A transmission power automatic adjusting method for a transmission circuit, wherein a self-bias voltage generated between both terminals is amplified by a DC amplifier to control the gain of the variable gain amplifier to control the transmission power.