Frequency-feedback receiver as a low-threshold demodulator in f.m. f.d.m. satellite systems

With application to satellite communication, a concurrent investigation of the threshold extension to be expected in f.m. f.d.m. operation from the frequency feedback demodulator (f.m.f.b.) and the dynamic tracking filter (d.t.f.) has revealed a close similarity, both algebraically in the expressions governing a performance assessment and quantitatively in the predicted threshold extensions. This paper and a companion paper give an analysis of both types of low-threshold demodulator, show comparisons between theory and measurement for a system capacity of 240 channels and present theoretical curves showing the predicted threshold extension for a 600-channel system to be 4dB. The papers provide evidence that the COMSAT formula is unnecessarily pessimistic in its prediction of the threshold extension available for large-capacity f.m. f.d.m. satellite systems.