Automatic frequency control device for satellite communications ground

Abstract

The present invention relates to an automatic frequency control device and an automatic gain control device which have the advantage of improving the efficiency of a system with very low signal-to-noise ratio by compensating for frequency error generated at the local oscillator of a satellite or on the receive paths by demodulating the modulated signal continuously sent out from a transmit earth station for transmitting information without using the separate pilot frequency at a receive terminal of a receive earth station and locking at local oscillator of a frequency downconverter to a voltage controlled oscillator tracking an error after detecting a phase error of a carrier by using demodulated data, by compensating the frequency error due to Doppler frequency deviation by locking a local oscillator of a frequency upconverter to a voltage controlled oscillator tracking a phase change according to Doppler frequency deviation included in the clock after recovering the clock from the demodulated data, and by controlling the gain of the variable gain amplifier through the bias restricting the level of peak noise after mean square detecting of demodulated data.