Patent ID: 7057426

Claim:
A receiver comprising: an orthogonal demodulator using an input signal, a first local oscillation signal, a second local oscillation signal, a first reference signal, and a second reference signal, the orthogonal demodulator comprising a first frequency converter, a second frequency converter, and a phase shifter; the first frequency converter including: a first variable gain amplifier which amplifies the first local oscillation signal according to a first gain control signal, and outputs an amplified first local oscillation signal; a first even harmonic mixer which is supplied with the input signal and the amplified first local oscillation signal and outputs an output signal whose frequency corresponds to a difference between a frequency of the input signal and a frequency of two or more even numbered times a frequency of the amplified first local oscillation signal; a first amplitude detector which is supplied with the amplified first local oscillation signal and outputs a first direct current signal having an amplitude corresponding to an amplitude of the amplified first local oscillation signal; and a first comparator which compares the first reference signal with the first direct current signal to generate an output signal as the first gain control signal; the second frequency converter including: a second variable gain amplifier which amplifies the second local oscillation signal according to a second gain control signal, and outputs an amplified second local oscillation signal; a second even harmonic mixer which is supplied with the input signal and the amplified second local oscillation signal and outputs an output signal whose frequency corresponds to a difference between a frequency of the input signal and a frequency of two or more even numbered times a frequency of the amplified second local oscillation signal; a second amplitude detector which is supplied with the amplified second local oscillation signal and outputs a second direct current signal having an amplitude corresponding to an amplitude of the amplified second local oscillation signal; and a second comparator which compares the second reference signal with the second direct current signal to generate an output signal as the second gain control signal; and the phase shifter outputting the first local oscillation signal and the second local oscillation signal with a given phase difference therebetween to the first frequency converter and the second frequency converter; a received signal state detector configured to detect a received signal state and output a detection signal; and a controller supplied with the detection signal and configured to output a control signal used for setting a conversion gain and an operation state to the first frequency converter and the second frequency converter.