Analysis of LO leakage due to LO mismatch in CMOS Gilbert mixer for direct conversion application

The DC offset caused by the LO-RF feedthrough in the mixer of a direct conversion receiver is a serious problem. The LO leakage caused by the LO mismatch in double-balanced CMOS Gilbert mixers is examine and analyzed in four cases, no LO mismatch, LO phase mismatch only, LO amplitude mismatch only and the combination of the two mismatches. The relation between the mismatch and the LO leakage is derived. Simulation results shown are consistent with the analysis