Digital calibration of gain and linearity in a CMOS RF mixer

Abstract

This paper presents a new digital calibration technique that allows CMOS Gilbert cell down-conversion mixers to meet their block specifications under large process, temperature and power supply variations. The gain and IIP3 are calibrated by regulating the current of the input differential pair and by switching the loads. IIP2 calibration is achieved by using a novel technique that consists of offset voltages cancellation in the switching pairs. The technique is tested by calibrating a 0.18um CMOS mixer in several corner conditions. It is found that by using this calibration technique, the Gilbert cell mixer can achieve yields comparable to digital circuits, hence making it amenable to AMS SoC integration.