JPH06152285A - Agc circuit - Google Patents

Abstract

PURPOSE:To make the device compact without requiring complicated control circuits by inputting amplitudes I, Q from a waveform shaping circuit and a digital signal from A/D converter and generating an AGC signals on the calculation by a signal processing circuit. CONSTITUTION:The detection voltage detected by a detection circuit 6 is A/D converted 8 at every specific timing by a timing signal 12 from a waveform shaping circuit 2 and outputted to a signal processing circuit 1. The circuit 1 is provided with a memory function, storing the detection characteristic of the circuit 6 and discriminating the detection level based on the output of a converter 8. The signal processing circuit 1 generates and outputs an AGC signal 11 by calculation to let the detection level judged by the output of the converter 8 approach the output level calculated from amplitudes (i) and (q) of an orthogonal basement signal. The signal 11 is D/A converted by a D/A converter 7 the specific timing by the timing signal 12. By generating the AGC voltage to control the gain of the RF amplifier circuit 5, the output of it is kept constant.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an AGC circuit, and more particularly to an AGC circuit used as an amplifier circuit for a digitally modulated RF signal.

[0002]

2. Description of the Related Art A conventional AGC circuit, as shown in FIG.
A signal processing circuit 1 for converting an input signal into a predetermined format to generate a modulated signal, a waveform shaping circuit 2 for converting the modulated signal into quadrature baseband signals I and Q, and a D / r quadrature baseband signal I / Q. A D / A converter 3 for A conversion, a quadrature modulation circuit 4 for quadrature modulation of its output, an RF amplification circuit 5 for amplifying its output, and a first detection circuit 9 for detecting the input of the RF amplification circuit 5. An amplifier 10 that amplifies the detection voltage of the detection circuit 9, a first sample hold circuit 11 that samples and holds the output of the amplifier 10 at a specific timing, and a second detection circuit 6 that detects the output of the RF amplification circuit 5. And a second sample-hold circuit 13 that samples and holds the detection voltage of the detection circuit 6 at a specific timing.
And a comparator 12 that compares the output voltage of the sample hold circuit 11 with the output voltage of the sample hold circuit 13 and applies an AGC voltage to the RF amplifier circuit 5. This conventional AGC circuit operates so that the amplified voltage of the input signal detection voltage of the RF amplification circuit 5 to be sampled by the amplifier 10 and the output signal detection voltage of the RF amplification circuit 5 become equal at a specific timing. It was

[0003]

In this conventional AGC circuit, in order to properly control the RF amplifier circuit 5, the total detection of the first detection circuit 9 and the amplifier 10 is performed in the amplitude variation range at the symbol timing. The characteristic and the detection characteristic of the second detection circuit 6 must be equal,
Actually, since the detection characteristics of the first detection circuit 9 and the second detection circuit 6 are different, a complicated circuit is required for controlling the gain of the amplifier 10. Further, there is a drawback that the AGC cannot be applied correctly because the total detection characteristics of the amplifier 10, the first detection circuit 9 and the amplifier 10 and the detection characteristics of the second detection circuit 6 differ due to changes in environment such as temperature.

An object of the present invention is to provide an AGC circuit which can control an amplifier circuit for a signal whose amplitude at a specific symbol timing does not become a constant value with a simple circuit configuration.

[0005]

The AGC circuit of the present invention is a signal processing circuit for converting an input signal into a predetermined format by a signal processing circuit to generate a modulated signal, and a quadrature baseband circuit from the modulated signal by a waveform shaping circuit. A waveform shaping circuit for outputting the amplitude values of the signals I, Q; a first D / A converter for D / A converting the baseband signals I, Q; and an output of the first D / A converter. A quadrature modulation circuit for quadrature modulation, an RF amplification circuit for amplifying the output of the quadrature modulation circuit, a detection circuit for detecting the output signal level of the RF amplification circuit, and an output voltage of the detection circuit with a specific timing signal A A / D converter for A / D conversion, the signal processing circuit includes amplitude values of the quadrature baseband signals I and Q, and the A / D converter.
The output of the converter is input and the AG obtained by arithmetic processing
The C signal is fed back to the RF amplifier circuit via the second D / A converter.

[0006]

The present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing an embodiment of the present invention.
In the embodiment of FIG. 1, the signal processing circuit 1, the waveform shaping circuit 2, the first D / A converter 3, the quadrature modulation circuit 4, the RF amplification circuit 5, the detection circuit 6, and the second D / A converter 7 are provided. , A / D converter 8. Here, the D / A converter 3, the quadrature modulation circuit 4, the RF amplification circuit 5, and the detection circuit 6 have the same configurations as those of the conventional example. The waveform shaping circuit 2 supplies the amplitude values i and q of the orthogonal baseband signals I and Q at a specific timing to the signal processing circuit 1. The signal processing circuit 1 has an arithmetic function and can calculate the output level from i and q. Further, the detection voltage detected by the detection circuit 6 is A / D converted by the A / D converter 8 at a specific timing by the timing signal 12 from the waveform shaping circuit 2 and output to the signal processing circuit 1. The signal processing circuit 1 has a memory function and stores the detection characteristics of the detection circuit 6,
The detection level is discriminated from the output of the converter 8. The signal processing circuit 1 calculates and generates an AGC signal 11 for performing control so that the detection level determined from the output of the A / D converter 8 approaches the output level calculated from i and q, and outputs it. The AGC signal 11 is D / A-converted by the second D / A converter 7 at a specific timing by the timing signal 12, and the AGC voltage 12 that controls the gain of the RF amplifier circuit 5.
Is generated to control the output of the RF amplification circuit 5 to be constant.

[0007]

As described above, in the AGC circuit of the present invention, the signal processing circuit operates from the waveform shaping circuit to the amplitudes of I, Q and A.
Since the digital signal from the / D converter 8 is input to generate the AGC signal by calculation, a complicated control circuit for adjusting the outputs of two different detection circuits as in the conventional example is not required, Moreover, there is an effect that the size can be reduced by reducing the number of elements.

[Brief description of drawings]

FIG. 1 is a block diagram of an embodiment of the present invention.

FIG. 2 is a block diagram of a conventional AGC circuit.

[Explanation of symbols]

 1 signal processing circuit 2 waveform shaping circuit 3, 7 D / A converter 4 quadrature modulation circuit 5 RF amplification circuit 6, 9 detection circuit 8 A / D converter 10 amplifier 11, 13 sample hold circuit 12 comparator

Claims (2)

[Claims] 1. A signal processing circuit for converting an input signal into a predetermined format by a signal processing circuit to generate a modulated signal, and a waveform shaping circuit for outputting amplitude values of quadrature baseband signals I and Q from the modulated signal. A waveform shaping circuit and a first D / A converter for D / A converting the baseband signals I and Q.
An A converter, a quadrature modulation circuit that quadrature modulates the output of the first D / A converter, an RF amplification circuit that amplifies the output of the quadrature modulation circuit, and an output signal level of the RF amplification circuit is detected. A detection circuit, an A / D converter for A / D converting an output voltage of the detection circuit with a specific timing signal, and an amplitude value of the quadrature baseband signals I and Q by the signal processing circuit and the A / D converter. The AGC circuit which inputs the output of the above, and feeds back the AGC signal obtained by the arithmetic processing to the RF amplifier circuit via the second D / A converter. 2. The AGC circuit according to claim 1, wherein the signal processing circuit has a function of storing a detection characteristic of the detection circuit.