Gain/phase imbalance and DC offset compensation in quadrature modulators

This paper describes a technique to estimate gain and phase imbalances and DC offsets in a quadrature modulator and to pre-compensate the in-phase and quadrature signals, so that image suppression is maximized and LO leakage is minimized at the modulator output. To validate the technique, an experiment with two 2.5 GHz direct modulators was conducted, and the results show that both the image suppression and LO leakage can be improved by at least 20 dB.