A high IIP2 direct-conversion mixer using an even-harmonic reduction technique for cellular CDMA/PCS/GPS applications

An even-harmonic reduction technique to enhance IIP2 (second order input intercept point) performance in a direct-conversion mixer is proposed based on a simplified analysis of second-order intermodulation. Using the proposed technique, IIP2 performance can be improved while reducing sensitivity to operating condition and output load mismatch. Direct-conversion mixers for cellular CDMA, PCS, and GPS applications are designed and fabricated in a 0.35 /spl mu/m SiGe BiCMOS process. Measurement results show 40 dB improvement and reduced sensitivity of IIP2, which are consistent with simulation results.