Improving Performance of Down Conversion Active Mixer using Negative Admittanc

Abstract

This paper presents a new down conversion active mixer with high conversion gain and the ability to achieve low flicker noise for direct conversion receivers in wireless local area networks (WLANs). The effect of negative admittance on the performance of the Gilbert cell mixer is analyzed in terms of conversion gain (CG) and flicker noise. The analytical results show that by setting the negative admittance parameters, the proposed mixer can achieve low flicker noise. The negative admittance is implemented using a negative capacitance and a negative resistance in parallel. The proposed mixer is designed and simulated using TSMC 0.18m CMOS technology in Cadence Spectre-RF at the input frequency (RF) of 2.4 GHz and intermediate frequency (IF) of 10 MHz. Simulation results show the flicker noise is reduced more than 14 dB at the frequency of 1 kHz. Moreover, the proposed mixer exhibits a conversion gain of 13.2 dB and a flicker noise corner frequency of 6 kHz. Dual Side Band noise figure (DSB-NF) at the frequency of 10 MHz is 4.4 dB, and the third-order intermodulation intercept point (IIP3) is -10 dBm and input return loss (S11) is less than -18 dB at the input frequency of 2.4 GHz. The power dissipation is 21.5 mW from the power supply of 1.8 V.