Nonlinear Noise Modeling: Using Nonlinear Circuit Simulators to Simulate Noise in the Nonlinear Domain

Noise is a random signal, a perturbation of dc bias and RF signals. It is usually necessary that digital electronics provide a low bit error rate or error vector magnitude to guarantee the reliable digital transmission of data. Microwave electronics are commonly expected to amplify or mix these digital signals with high linearity and without adding significant noise, which translates to the requirement of a 10-dB signal-to-noise ratio (SNR) in a communication system. In the case of a nonlinear circuit, it might not always be clear how noise could be an issue at all. Firstly, the signal is several tens of decibels larger than in the smallsignal domain. Secondly, one might consider nonlinear distortions to be the first limiting factor.