On the baseband representation of a bandpass nonlinearity

Modeling, analysis, and compensation of nonlinearities in the transmitter (the power amplifier, in particular) has attracted a lot of attention recently. Given the same bandpass polynomial or Volterra representation of the nonlinear system, two different baseband formulations have appeared in the literature. The purpose of this correspondence is to examine the discrepancy between the two and to affirm that proper conjugation must be applied in the baseband representation of bandpass nonlinearities. A predistortion linearization test-bed experiment is conducted to illustrate the concepts.