Automatic gain control adaptive for plural modulation schemes

An automatic gain control circuit applicable to a receiver including:

• an adjustment circuit including a low-noise amplifier and a variable-gain amplifier for adjusting amplification of a received signal in response to a low-noise amplification control signal and a variable-gain amplification control signal which are respectively input to said low-noise amplifier and variable-gain amplifier as adjustment control signals;
• and
• a plurality of demodulators for demodulating an adjustment result of said adjustment circuit respectively for a plurality of modulation schemes,
• said control circuit comprising:
• a scaling circuit for comparing the adjustment result with a predetermined target value and using a comparison result and a scaling coefficient to perform a scaling;
• an adder for adding a scaling result of said scaling circuit to a delayed immediately preceding control voltage to generate a control voltage;
• and
• a control signal generator, comprising a timing generator for generating an update-timing signal, for generating the low-noise amplification control signal and the variable-gain amplification control signal from the control voltage in response to the update-timing signal,
• said scaling circuit determining a first scaling coefficient for a positive value and a second scaling coefficient for a negative value as the scaling coefficient according to each of the plurality of modulation schemes, determining a sign of the comparison result, using the first scaling coefficient for operation when the sign is positive and the second scaling coefficient for operation when the sign is negative.