Using interaction between two nonlinear systems to improve IIP3 in active mixers

Abstract

A new linearisation technique for active mixers is introduced to enhance the third-order input intercept point (IIP3). This technique is based on the cancellation of the third-order Volterra kernel in the output current of the transconductance stage by using the interaction between two nonlinear systems. In this scheme, a nonlinear circuit is employed prior to the conventional mixer to improve the total IIP3 by adjusting its second-order Volterra kernel magnitude and phase. Moreover, the added circuit increases the conversion gain of the mixer. The simulation results show that both the IIP3 and the conversion gain simultaneously improve by 13 and 11.4 dB, respectively, compared with the conventional active mixer.