The Effects of Quadratic AM-PM Conversion in Frequency-Division Multiplexed Multiple-Access Communication Satellite Systems

A traveling-wave tube amplifier such as those employed in frequency-division multiplexed multiple-access communication-satellite repeaters is considered. The amplifier nonlinearity is assumed to follow an error-function characteristic, and the AM-PM conversion is taken to be a quadratic function of the envelope of the input signal. An exact expression allowing for both arbitrary amounts of amplifier saturation and AM-PM conversion is derived for the autocorrelation function of the amplifier output when the input is a Gaussian bandpass process. Distortion spectra are calculated for the parameters of a typical travelingwave tube transmitter.