Intermodulation distortion in frequency multiplexed satellite repeaters

Expressions have been derived that describe the output spectra (i.e., signal plus distortion) of a saturating amplifier when the input consists of a large number of independent carriers whose amplitudes, bandwidths, and center frequencies may be independently specified. The resulting equations have been programmed on the GE 635 computer using the fast Fourier transform algorithm, permitting rapid computation of the output spectra for very complex input signal formats. Program outputs have been checked against the results of previous authors, e.g., Cahn [1] and against a measured transfer characteristic of a Hughes model 24H traveling wave tube, with good agreement. The program has been found very useful in design optimization studies of channelized communications repeaters with up to 60 channels.