Automatic gain control circuit of radio receiver

Details Automatic gain control circuit of radio receiver Automatic gain control circuit of radio receiver

1997-04-21

1999-12-07

Chin, Stephen

Pulse or digital communications

Receivers

Automatic gain control

4552501, 4552471, 4552341, H04L 2708, H04B 106

Patent

active

059995785

ABSTRACT:
An automatic gain control circuit which is digitally embodied to prevent deterioration of bit error rate generated by saturation of a low noise amplifier located at the front stage of a receiver through an input of high power to an antenna, thereby simplifying construction thereof and improving commercialization. The automatic gain control circuit of a radio data communication system using a spread spectrum method utilizes a low noise amplifier for low noise amplifying a bandpass filtered signal received through an antenna; a limiter for generating a received signal strength indicator voltage in order to constantly maintain the signal received as a local oscillation frequency through the antenna before downward frequency conversion; a unit for separating the a signal transmitted through the limiter to I and Q channels; a comparator for comparing the received signal strength indicator voltage with a given reference voltage; a D flip-flop for inputting an output of the comparator applied to a data input terminal in synchronization to a given first control signal; an AND gate for ANDing the output of the D flip-flop and the first control signal; a field effect transistor having a gate for receiving the output of the AND gate therein, a drain provided with a given voltage, and source connected to power supply terminal of the low noise amplifier through a resistor; and, a modem for sensing carrier, generating the sensed signal as the first control signal, and outputting digital demodulation data from a signal separated to the I and Q channels.

REFERENCES:
patent: 5507023 (1996-04-01), Suganuma et al.
patent: 5722062 (1998-02-01), Nakanishi et al.

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