Patent ID: 8422610

Claim:
An IQ phase mismatch correction circuit arranged to correct an IQ mismatch between I-phase and Q-phase digital baseband signals, the IQ phase mismatch correction circuit comprising: a first digital filter arranged to perform a first or higher order digital filtering process to an I-phase input signal in a time domain; a second digital filter arranged to perform a first or higher order digital filtering process to a Q-phase input signal in the time domain; two or more control circuits arranged to independently generate two or more control variables to derive two or more coefficients of the transfer functions of the first and second digital filters in the time domain, and supply the control variables to the first and second digital filters; and one or more pairs of analyzing filters arranged to change frequency characteristics of an I-phase output signal and a Q-phase output signal so that the frequency characteristics are different from those of original signals, respectively, the I-phase output signal being a differential signal or a composite signal between a delayed signal of the I-phase input signal and an output signal from the second digital filter, the Q-phase output signal being a differential signal or a composite signal between a delayed signal of the Q-phase input signal and an output signal from the first digital filter, wherein a first control circuit of the two or more control circuits is configured to measure a temporally averaged IQ phase mismatch state between the I-phase output signal and the Q-phase output signal, and to feed back the IQ phase mismatch state to the first and second digital filters as a first variable, which is one of the two or more control variables, and a second control circuit other than the first control circuit of the two or more control circuits is configured to measure a temporally averaged IQ phase mismatch state between output signals on an I-phase side and a Q-phase side of one corresponding pair of analyzing filters of the one or more pairs of analyzing filters, and to feed back the IQ phase mismatch state to the first and second digital filters as a second variable, which is another one of the two or more control variables.