Design of a high linearity CMOS mixer using ADS

A new technique is presented to improve the linearity of Gilbert mixer firstly.The main idea is to replace the former mixer structure with a cross-connected differential one.When one specific design condition is fulfilled,the third-order harmonic of the output signal is canceled,improving the third-order intercept point of the mixer.The suppling voltage is 1.8V,and a RF signal is 5GHz.Based on 0.18μm CMOS process,the mixer is designed and simulated with Agilent ADS(Advanced Design System).The simulation results show that the IP3 is improved by 3.5dB,and the conversion gain is improved by 4.8dB after improving the structure.