Linearity improvement in a CMOS down-conversion active mixer for WLAN applications

This paper presents an active down-conversion mixer for wireless local area network applications. The proposed down-conversion mixer is designed for 2-3 GHz radio frequency (RF) band and an intermediate frequency of 100 MHz using RF-TSMC CMOS 0.18 mu m technology. A new fully differential Darlington cell is introduced in the RF transconductance stage to effectively suppress third-order nonlinearity. In addition, the conversion gain and noise performance of the proposed mixer are improved by using an active load and current bleeding technique. The proposed mixer has been simulated by Cadence Spectre-RF. Post-layout simulation results show the third-order input intercept point can be improved up to 12.5 dBm by optimum biasing of the Darlington cell. The proposed mixer achieves the high conversion gain of 14.5 dB and the low double side-band noise figure of 4.55 dB at the input frequency of 2.4 GHz. The mixer operates at the supply voltage of 1.8 V with power consumption of 17.4 mW.