Noise in RF-CMOS mixers: a simple physical model

TLDR

Flicker noise in zero‑ or low‑IF wireless receiver mixers can degrade overall receiver sensitivity. The model explains frequency translation in mixers and provides simple equations to estimate flicker and white noise at the output of a switching active mixer. A qualitative physical model explains flicker noise mechanisms, predicts white noise, and its predictions are validated by measurements and simulations, showing mixer noise depends on LO amplitude and other parameters.

Abstract

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.