Effects of I/Q mismatch on measurement of periodic movement using a Doppler radar sensor

In this paper, the effect of I/Q mismatch in a 5.8 GHz direct-conversion quadrature Doppler radar sensor detecting periodic movement is studied. The measured movement amplitude under specific I/Q amplitude or phase mismatch is affected by the residual phase, which is determined by the nominal distance from the target to the antenna. It was found that there exist optimal residual phases minimizing the degradation of detection accuracy caused by amplitude and phase mismatches. Experiments were conducted to verify the theory.