Active 2nd-order intermodulation calibration for direct-conversion receivers

Abstract

A temperature-compensated active IM2 calibration circuit for direct-conversion receivers is fabricated with a mixer in 0.25mum CMOS. A squaring circuit senses the RF signal and generates a calibration current to cancel mixer IM2 distortion. The loading effect and noise contribution are minimized by gain boosting. IIP2 is boosted >20dB to >80dBm in the IMT band. The calibration circuit draws 1.5mA