Simulation models of functional blocks in communication systems fall into three broad categories as follows:
Linear time-invariant causal systems such as filters and static communication channels
Linear time-varying systems such as fading channels and linear equalizers
Nonlinear time-invariant systems such as high-power amplifiers, limiters, and phase-locked loops (PLLs)
While most of the functional blocks in a communication system are either linear or can be approximated by linear behavior, there are many functional blocks that are nonlinear. Some of these components are inherently nonlinear and are intentionally included in the system to improve performance. A limiter, for example, is a nonlinear ...