JPH0964673A - Automatic gain control circuit and automatic gain control device using the circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To hold the gain and phase of an automatic gain control circuit between its input and output at fixed values. SOLUTION: The automatic gain control device is provided with a level adjusting circuit 3 for adjusting the level of an input signal and a phase adjusting circuit 8 for adjusting the phase of the input signal. The signal adjusted by respective adjusting circuits 3, 4 is amplified by an amplifier 4 at a prescribed amplification factor. The amplified output signal is attenuated by an attenuator 10 at the same attenuation rate as the amplification factor and the circuits 3, 8 are controlled so that a level difference between the attenuated output signal and the input signal becomes zero.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an automatic gain control circuit (hereinafter abbreviated as "AGC circuit" as appropriate) and an automatic gain control device using the same, and more particularly to gain adjustment and phase adjustment between its input and output.

[0002]

2. Description of the Related Art FIG. 4 is a block diagram showing a configuration of a conventional AGC circuit. In the figure, the conventional AGC circuit includes a directional coupler 2a for extracting a part of the input signal 100 input from the input terminal 1, a level adjuster 3 for adjusting the level of the input signal 100, and a signal after the adjustment. And an directional coupler 2b for extracting a part of the output signal of the amplifier 4.

The conventional AGC circuit has a directional coupler 2.
a detector 5a that detects the signal level from a and outputs a level signal, a detector 5b that detects the level of the signal from the directional coupler 2b and outputs a level signal, and the two detectors 5a, The control circuit 6 outputs the control signal 60 to the level adjuster 3 so that the difference between the level signals from 5b is always constant.

The operation of the conventional AGC circuit having such a configuration will be described below.

Input signal 100 input from the input terminal 1
Is distributed to the input to the level adjuster 3 and the input to the detector 5a by the directional coupler 2a. First, the signal input to the level adjuster 3 is amplified by the amplifier 4 to a desired level. This amplified signal is output by the directional coupler 2b to the output signal 700 to the output terminal 7 and the detector 5b.
Input to and distributed to.

On the other hand, a part of the input signal 100 extracted by the directional coupler 2a is converted into a level signal by the detector 5a and input to the control circuit 6. Similarly, the level signal from the detector 5b is also input to the control circuit 6. Then, the control circuit 6 compares the level signal from the input-side detector 5a with the level signal from the output-side detector 5b, and outputs the control signal 60 such that the level difference becomes constant. Output to. Therefore, the gain between the input and the output of the amplifier 4 can be kept constant.

Note that an automatic gain control device may be constructed by connecting a plurality of such AGC circuits in parallel, using the same signal as an input signal, and finally combining the amplified output signals of the respective circuits.

[0008]

[Problems to be Solved by the Invention] The above-mentioned conventional AGC
In the circuit, the gain between the input and output of the power amplifier can always be kept constant, but the phase cannot be kept constant. The automatic gain control circuit disclosed in Japanese Patent Laid-Open No. 61-276406 cannot maintain a constant phase.

If the phase cannot be kept constant as described above, there is a drawback that good characteristics cannot be obtained even if an automatic gain control device is constructed by connecting a plurality of AGC circuits in parallel as described above.

In the automatic gain control circuit disclosed in Japanese Unexamined Patent Publication No. 5-183359, an A / D converter and a ROM are provided for the purpose of compensating for phase fluctuations caused by variable gain control.
However, it is not possible to compensate for the phase shift due to the characteristics of the variable gain amplifier itself. Furthermore, there is also a drawback that the phase shifts due to a quantization error due to A / D conversion.

Further, in the AGC circuit of FIG. 4, control is performed to keep the level difference between the detection output on the input side and the detection output on the output side constant, so that the detection output characteristics and temperature characteristics of the two detectors 5a and 5b are controlled. There is also a drawback that the gain cannot be kept constant when there is a difference in.

The present invention has been made to solve the above-mentioned drawbacks of the prior art, and its object is to provide an automatic gain control circuit capable of keeping the gain and phase between input and output constant and an automatic gain control circuit using the automatic gain control circuit. It is to provide a gain control device.

[0013]

SUMMARY OF THE INVENTION An automatic gain control circuit according to the present invention comprises a level adjusting means for adjusting the level of an input signal, a phase adjusting means for adjusting the phase of the input signal, and a phase adjusting means after adjusting by these adjusting means. Amplifying means for amplifying a signal at a predetermined amplification rate, attenuating means for attenuating an amplified output signal of the amplifying means at the same attenuation rate as the amplification rate, and levels of the attenuated output signal of the attenuating means and the input signal. It is characterized in that it includes an adjusting means for controlling the level adjusting means and the phase adjusting means so that the difference becomes zero.

An automatic gain control device according to the present invention has a plurality of the above automatic gain control circuits each having the same signal as an input signal, and includes an adding means for adding all amplified output signals of these automatic gain control circuits. It is characterized by

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION The operation of the present invention is as follows.

Adjustment means for adjusting the level and phase of the input signal is provided. The signal adjusted by these adjusting means is amplified by a predetermined amplification factor. The amplified output signal is attenuated at the same attenuation rate as the amplification rate, and the adjusting means is controlled so that the level difference between the attenuated output signal and the input signal becomes zero.

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

FIG. 1 is a block diagram showing the configuration of an embodiment of an automatic gain control circuit according to the present invention, and the same portions as those in FIG. 4 are designated by the same reference numerals. In the figure, an automatic gain control circuit according to an embodiment of the present invention includes a directional coupler 2a for extracting a part of an input signal 100 from an input terminal 1 and distributing it to a level adjuster 3 side and a delay line 9 side. , A level adjuster 3 and a phase adjuster 8 which respectively perform level adjustment and phase adjustment of the signal input to the amplifier 4 according to the control signal 60 from the control circuit 6, and amplify the input signal to a desired level. And an directional coupler 2b for extracting a part of the signal amplified by the amplifier 4 and distributing it to the output signal 700 to the output terminal 7 side and the signal to the attenuator 10 side. It is composed of.

Further, in the figure, the automatic gain control circuit according to the present embodiment has a delay line 9 for delaying the signal distributed by the directional coupler 2a for a predetermined time, and an amplifier 4 for the signal distributed by the directional coupler 2b. Attenuator 10 for attenuating at the same attenuation factor as that of A., a combiner 11 for combining the attenuated output of this attenuator 10 and the delayed output of the delay line 9 and outputting a signal of the difference between them, and this combiner The detector 5 includes a detector 5 for detecting the detected signal, and a control circuit 6 for outputting a control signal 60 according to the detected output to control the level adjuster 3 and the phase adjuster 8.

Since the attenuator 10 is attenuated at the same attenuation factor as that of the amplifier 4, the combiner 11 outputs the signal between the input and output in the same state as when the amplifier 4 and the attenuator 10 are not present. A signal having a difference in gain and phase will be output.

Here, the delay time of the delay line 9 described above passes from the input terminal 1 through the directional coupler 2a, the level adjuster 3, the phase adjuster 8, the amplifier 4, the directional coupler 2b and the attenuator 10. And the delay time to the input of the combiner 11 is set to be equal to the delay time from the input terminal 1 to the input of the combiner 11 via the directional coupler 2a and the delay line 9. And

The attenuation amount and the coupling amount of the attenuator 10 and the directional coupler 2b determine the gain between the input and output terminals and are set so that a desired gain can be obtained. .

As shown in FIG. 2, the detector 5 is composed of a general detector circuit, and rectifies an input signal by a diode 50 and converts it into a DC voltage for output. The detection characteristic is a monotonically increasing characteristic.

Returning to FIG. 1, the control circuit 6 controls the level adjuster 3 and the phase adjuster 8 so that the level signal from the detector 5 is minimized.

Next, the operation of the AGC circuit having the above configuration will be described. The signal input to the input terminal 1 is distributed to the input to the level adjuster 3 and the delay line 9 side by the directional coupler 2a. First, the signal input to the level adjuster 3 is level-adjusted by the level adjuster 3 and then input to the phase adjuster 8 to be phase-adjusted. Then, these adjusted signals are amplified by the amplifier 4. The signal amplified by the amplifier 4 is directional coupler 2b.
Is distributed to the output signal 700 to the output terminal 7 and the input signal of the attenuator 10.

On the other hand, a part of the signal extracted by the directional coupler 2a is delayed by a predetermined delay time by the delay line 9 and then input to the combiner 11. A part of the output signal extracted by the directional coupler 2b is attenuated to a predetermined level by the attenuator 10, and then the combiner 11 is used.
Is input to.

The two signals input to the combiner 11 are combined by the combiner 11 and the difference signal between the two signals is output to the detector 5. The control circuit 6 controls the level adjuster 3 and the phase adjuster 8 so that the level signal from the detector 5 is always minimized, that is, the output signal of the combiner 11 is minimized.

Next, the conditions for minimizing the output signal from the combiner 11 will be described below. As shown in FIG. 3, in order to minimize the output signal of the combiner 11,
Vector A of signal from input terminal 1 via amplifier 4
And the vector B of the signal from the input terminal 1 via the delay line 9 have the same amplitude and the phases are inverted, that is, the phase difference is 180 °.

Therefore, in the control circuit 6, as shown in FIG.
, Both vectors have the same magnitude,
Moreover, the level adjuster 3 and the phase adjuster 8 are controlled so that the directions thereof are opposite to each other. That is, when the magnitudes of the two vectors are not the same or the directions are not exactly opposite, some voltage value is output from the detector 5. The control circuit 6 which receives the output of the detector 5 first adjusts the level adjuster 3 so that the output of the detector 5 is minimized. Next, the control circuit 6 controls the phase adjuster 8 so that the output of the detector 5 is minimized. In this case, if the output of the detector 5 does not decrease by advancing the phase, on the contrary, the phase is delayed. Adjust the level again if necessary.

By alternately controlling the level adjuster 3 and the phase adjuster 8 as described above, the output of the detector 5 is minimized, that is, the output signal of the combiner 11 becomes zero. .

The AGC circuit configured as described above automatically adjusts the signal passed through the amplifier to the signal passed through only the passive elements having stable amplitude and phase characteristics such as the directional coupler and the delay line. Since it is controlled, the gain and phase can be kept constant between the input and output of the amplifier.

Therefore, if a plurality of AGC circuits are connected in parallel, the same signal is used as an input signal, and the amplified output signals of the respective circuits are finally combined to constitute an automatic gain control device, the phase is kept constant. Since it can be maintained, good characteristics can be obtained.

Further, in the present AGC circuit, one detector is used for operation, and it is sufficient that the detection characteristic is satisfied only by a monotonic increase.

[0034]

As described above, according to the present invention, the amplified output of the amplifier is attenuated at the same attenuation rate as the amplification rate, and the input signal is adjusted so that the level difference between the attenuated output and the input signal becomes zero. By adjusting the level and the phase, there is an effect that the gain and the phase between the input and the output can be kept constant. Further, if a plurality of AGC circuits whose input and output gains and phases are kept constant are connected in parallel and their outputs are combined, an automatic gain control device having good characteristics can be obtained. is there.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of an automatic gain control circuit according to an embodiment of the present invention.

FIG. 2 is a circuit diagram showing a configuration example of a detector in FIG.

FIG. 3 is a vector diagram of an input signal of the combiner in FIG.

FIG. 4 is a block diagram showing a configuration of a conventional automatic gain control circuit.

[Explanation of symbols]

 1 Input Terminals 2a, 2b Directional Coupler 3 Level Adjuster 4 Amplifier 5 Detector 6 Control Circuit 7 Output Terminal 8 Phase Adjuster 9 Delay Line 10 Attenuator 11 Combiner

Claims (4)

[Claims] 1. A level adjusting means for adjusting the level of an input signal, a phase adjusting means for adjusting the phase of the input signal, and an amplifying means for amplifying the signal adjusted by these adjusting means at a predetermined amplification factor. Attenuating means for attenuating the amplified output signal of the amplifying means at the same attenuation rate as the amplifying rate, the level adjusting means and the level adjusting means so that the level difference between the attenuated output signal of the attenuating means and the input signal becomes zero. An automatic gain control circuit comprising: an adjusting unit that controls a phase adjusting unit. 2. The adjusting means alternates the signal synthesizing means for obtaining a level difference between the amplified output signal and the input signal, and the level adjusting means and the phase adjusting means alternately so as to minimize the synthesized output. The automatic gain control circuit according to claim 1, further comprising control means for controlling. 3. The automatic gain control circuit according to claim 2, further comprising a delay line for adjusting input timings of the amplified output signal and the input signal input to the signal synthesizing means. 4. The same signal is used as an input signal.
3. An automatic gain control device having a plurality of automatic gain control circuits according to any one of 3 and including an adding means for adding all amplified output signals of these automatic gain control circuits.