Nonlinearity

The nonlinearity of the functions implemented in a transceiver is traditionally seen as an additional source of distortion for the signal present in the line‐up. In practical electronic implementations, such linearity is always achieved at some cost. This chapter reviews and quantifies the impact on the wanted signal of the different kinds of nonlinear behavior that may occur in a practical implementation. It focuses mainly on the characterization of RF nonlinearity and its impact on transceiver performance. It also discusses the smooth AM‐AM conversion as it allows us to introduce most of the concepts classically used for the characterization of nonlinear RF devices. The chapter then reviews some of the results related to the hard limiter theory. Physical origins of AM‐PM conversion are also discussed. Baseband devices are devices which process lowpass analog signals. The devices are often implemented as feedback systems based on the extensive use of operational amplifiers.