IIP2 and DC Offsets in the Presence of Leakage at LO Frequency

Abstract

Device mismatch in a mixer is generally believed to be the major contributor of second-order distortion that limits the performance of a direct conversion receiver. In this brief, we show that even with perfect matching, leakage at local oscillator frequency prior to mixing creates large second-order distortion when the third-order input intercept point of the receiver is not sufficiently large. Measurement data from a quad-band global system for mobile communications/global packet radio service transceiver implemented in 90-nm digital CMOS process is also presented to support our claim