Patent ID: 7761071

Claim:
An AM-modulated signal reception circuit which receives an AM-modulated signal Vi in two states of a large amplitude state and a small amplitude state, and which identifies the two states; comprising: a gain control amplifier block (GCA-B) whose gain is controlled by a peak value voltage Vp from a peak value input terminal, and which amplifies the input AM-modulated signal Vi so as to deliver an output Vo; an envelope detection circuit (SDet) which detects an envelope of the amplification output Vo of said gain control amplifier block (GCA-B); a comparator circuit (Comp) which compares an output of said envelope detection circuit (SDet) and a reference voltage VR 2 so as to output a logic signal TCO; and a peak detection circuit (PDet) which receives the output signal TCO of said comparator circuit (Comp) as a control input, which, when the control input is an “H” status (or “L” status), detects a peak value of the output Vo of said gain control amplifier block (GCA-B) so as to deliver the detection peak value Vp to the peak value input terminal of said control amplifier block (GCA-B), and which, when the output signal of said comparator circuit (Comp) has changed into the “L” status (or “H” status), holds the detection peak value Vp detected immediately before the change, so as to output the held detection peak value to said peak value input terminal.