A Study on Linearity of Mixers for Homodyne Receivers

Abstract: In this thesis the linearity characteristics of passive mixers for wide band homodyne receivers are studied. The circuits are simulated using Cadence Spectre with models from a 65nm RF/Analogue CMOS process. Linearity dependence of common mode voltage, load impedance, switch network arrangement and local oscillator drive circuitry is studied and analysed. The thesis also covers methods for the linearisation of baseband ampliers. Three linearised ampliers for frequencies down to DC are demonstrated. The linearised ampliers are then used in passive mixer circuits to analyse the eects of baseband linearity improvement on complete mixer linearity. The results from this test show that improving the open loop linearity of the baseband amplier has an appreciable impact on mixer linearity. The work presented in this thesis was performed at Ericsson AB in Kista, Stockholm, Sweden during the period January to June 2013.