Patent ID: 7873342

Claim:
A low IF (intermediate frequency) receiver of rejecting an image signal, comprising: a low noise amplifier amplifying a radio frequency (RF) signal: a quadrature I/Q mixer generating an I signal and a Q signal by down-converting the amplified RF signal into an IF signal; a phase and gain control block generating an I′ signal and a Q′ signal which are obtained by changing phases and amplitudes of the I signal and the Q signal by using a real signal; and a signal complex filter minimizing the image signal in the IF signal and passing the real signal by performing filtering on the I′ signal and the Q′ signal; wherein the phase and gain control block comprises: a phase and gain control circuit generating the I′ signal and the Q′ signal which are obtained by changing the phases and gains of the I signal and the Q signal in response to a phase control signal used for controlling a phase and a gain control signal used for controlling a gain; and a control signal generation circuit generating the phase control signal and the gain control signal by using the I′ signal, the Q′ signal, and the real signal output from signal complex filter; wherein the phase and gain control circuit comprises: an I signal control circuit outputting the I′ signal by controlling the phase and the gain of the I signal in response to the phase control signal and the gain control signal; and a Q signal control circuit outputting the Q′ signal by controlling the phase and the gain of the Q signal in response to the phase control signal and the gain control signal; wherein the I signal control circuit comprises: a first operation amplifier including a positive input terminal applied with the I signal and a negative input terminal applied with a reference voltage; a first variable resistor which is connected between the positive input terminal and an output terminal of the first operation amplifier and has a resistance that is changed in response to the gain control signal; and a first variable capacitor which is connected between the positive input terminal and the output terminal of the first operation amplifier and has a capacitance that is changed in response to the phase control signal, and wherein the Q signal control circuit comprises: a second operation amplifier including a positive input terminal applied with the Q signal and a negative input terminal applied with the reference voltage; a second variable resistor which is connected between the positive input terminal and an output terminal of the second operation amplifier and has a resistance that is changed in response to the gain control signal; and a second variable capacitor which is connected between the positive input terminal and the output terminal of the second operation amplifier and has a capacitance that is changed in response to the phase control signal.