Noise and intermodulation mechanisms in CMOS downconverters

A noise and intermodulation distortion (IMD) analysis of CMOS downconverters, such as the widely used CMOS Gilbert cell, is presented. A qualitative physical model has been developed to explain the mechanisms responsible for noise and IMD in mixers. The contribution of all internal noise source and IMD to the output current is calculated through simple equations. The accuracy of the predictions about theory results are validated via comparing with simulation results, and the dependence of mixer noise and IMD on local oscillator (LO) amplitude and other circuit parameters are.