Characterization of Spectral Regrowth in Microwave Amplifiers Based on the Nonlinear Transformation of a Complex Gaussian Process

A statistical technique is presented for the characterization of spectral regrowth at the output of a nonlinear amplifier driven by a digitally modulated carrier in a digital radio system. The technique yields an analytical expression for the autocorrelation function of the output signal as a function of the statistics of the quadrature input signal transformed by a behavioral model of the amplifier. The amplifier model, a baseband equivalent representation, is derived from a complex radio-frequency envelope model, which itself is developed from readily available measured or simulated amplitude modulation–amplitude modulation and amplitude modulation–phase modulation data. The technique is used in evaluating the spectral regrowth for a CDMA signal.