Automatic gain control circuit using gain shift

An automatic gain control (AGC) circuit, comprising:

• a low noise RF amplifying module with an adjustable gain, configured for amplifying a received high frequency signal to be an amplified high frequency signal with the same frequency;
• a frequency converter configured for converting the amplified high frequency signal into an IF/Baseband signal;
• an IF/Baseband amplifying module with an adjustable gain, configured for amplifying the IF/Baseband signal to be an amplified IF/Baseband signal;
• an A/D converter configured for converting the amplified IF/Baseband signal into a digital IF/Baseband signal;
• an AGC module configured for detecting a level of the digital IF/Baseband signal, comparing the detected level with a reference level and generating a digital AGC signal and a digital gain distribution control signal based upon the comparison result;
• and
• a gain distribution module subject to the control of the digital AGC signal and the digital gain distribution control signal and configured for generating digital gain control signals to selectively adjust at least one of the gains of the low noise RF amplifying module and the IF/Baseband amplifying module in a digital manner to keep the IF/Baseband signal outputted from the IF/Baseband amplifying module at a desired level.