A 1.2V High Linearity Mixer Design

Abstract

This paper introduces double balance active mixer which is designed by Barrie Gilbert, it shows good characteristics in linearity, gain and isolation. In 1998, Barrie Gilbert present multi-tanh principle with bipolar transistors. So this paper uses the multi-tanh technique to design some new structure in order to improve linearity and gain. First we double the transconductor level with four NMOS transistors, then we tripled the transconductor level with six NMOS transistors, meanwhile we keep the circuit is symmetry. Using Cadence SpectreRF, the circuits show better linearity and gain, yet noise figure increase, so it exists a tradeoff among these parameters of active mixer. In this paper, the circuit simulated in 2.4 GHz down-conversion mixer with 0.18 mum process, IIP3 and ldB compression point achieved 8.5 dBm and 2 dBm, gain is 4 dB, power assumption is 6 mW. Although this new architecture being used in down conversion mixer, it can be applied in up conversion active mixers too.