Nonlinearity Analysis of Analog/RF Circuits Using Combined Multisine and Volterra Analysis

Modern integrated radio systems require highly linear analog/RF circuits. Two-tone simulations are commonly used to study a circuit´s nonlinear behavior. Very often, however, this approach suffers limited insight. To gain insight into nonlinear behavior, we use a multisine analysis methodology to locate the main nonlinear components (e.g. transistors) both for weakly and strongly nonlinear behavior. Under weakly nonlinear conditions, selective Volterra analysis is used to further determine the most important nonlinearities of the main nonlinear components. As shown with an example of a 90 nm CMOS wideband low-noise amplifier, the insights obtained with this approach can be used to reduce nonlinear circuit behavior, in this case with 10 dB. The approach is valid for wideband and thus practical excitation signals, and is easily applicable both to simple and complex circuits