Noise in RF-CMOS mixers: a simple physical model

Flicker noise in the mixer of a zero- or low-intermediate frequency (IF) wireless receiver can compromise overall receiver sensitivity. A qualitative physical model has been developed to explain the mechanisms responsible for flicker noise in mixers. The model simply explains how frequency translations take place within a mixer. Although developed to explain flicker noise, the model predicts white noise as well. Simple equations are derived to estimate the flicker and white noise at the output of a switching active mixer. Measurements and simulations validate the accuracy of the predictions, and the dependence of mixer noise on local oscillator (LO) amplitude and other circuit parameters.