Zero-IF Second Harmonic SiGe Mixer with DC Offset Cancellation

Abstract

A new second harmonically pumped SiGe mixer circuit topology is proposed. The proposed circuit is developed to be employed in integrated circuit receivers which use Zero-IF mixers. The proposed circuit topology is analyzed to determine the appropriate operating conditions. It has a unique mechanism to prevent the local oscillator (LO) leakage to radio frequency (RF) signal which results in DC offset voltage at the output. Detailed analysis results are given regarding the biasing dependence of the conversion voltage gain and the linearity of the produced pumping current. The results are also verified by simulation results. Simulation results show that the DC offset voltage at the output stays more than 80 dB below the intermediate frequency (IF) signal.