Generalized autocorrelation analysis of spectral regrowth from bandpass nonlinear circuits

Estimation of spectral regrowth generated by a digitally modulated carrier passed through a nonlinear RF circuit is analyzed using a formulation of the output autocorrelation function. The estimation is based on developing an analytical expression for the output power spectrum when the nonlinearity is modeled as a complex power series model extracted from measured amplitude-to-amplitude (AM-AM) and amplitude-to-phase (AM-PM) characteristics. An analytical expression of the output power spectrum is developed from statistical moments for a complex Gaussian input signal. Comparisons are presented of measured versus predicted ACPR values for a CDMA amplifier.