Video transmission by adaptive frequency modulation

SNR (signal-to-noise ratio) in a demodulated video signal is a function of the modulation index, which is proportional to the ratio of frequency excursion to input signal amplitude. The index is made as high as possible to obtain the best noise performance in blank areas without undue distortion due to RF spectrum truncation in busy areas. It is shown that this tradeoff can be markedly improved by adjusting the modulation index adaptively. This greatly improves the noise performance in just those areas where the noise would otherwise be most visible. Essential system concepts are presented, and the derivation of the adaptation factors is discussed. The principles are applied to a monochrome system and then the processing of color images is considered. Results of a computer simulation of two of the many possible implementations of this adaptive scheme are presented.<>