Perturbation size and harmonic limitations in affine approximation for time invariant periodicity preservation systems

Affine approximation is a technique used to model time-invariant periodicity preservation (TIPP) systems, which represent a broad class of wireless system nonlinear components. This approach approximates the harmonic transfer characteristics of a nonlinear system and, as a consequence, is expected to be very useful in both waveform design and circuit optimization. While this approach is useful, there are limitations of this approximation based on the strength of the nonlinearity, the size of the perturbation imposed on the large-signal operating condition, and the number of harmonics used to approximate the signal. This paper examines some sample TIPP nonlinearities and show that the affine approximation accuracy often degrades for increasing perturbation size and when a reduced number of harmonics is used to approximate system results for waveforms containing significant harmonic content.