Analysis of the simultaneous transmission system for a picture and narrowband signals

Abstract

Systematic investigation is made on the noise generated in an FM transmission system for the simultaneous transmission of wideband picture signals and narrowband voice and data facsimile signals. In thermal noise analysis, tradeoffs are carried out between the noise characteristics resulting due to the methods of modulation and multiplexing of narrowband signals. Methods of handling the cross noise and distortion noise, caused by narrowband signals are described. As far as the methods of modulation of the subcarrier wave which corresponds to the narrowband signal are concerned, AM, FM and PSK are considered. The FM and PSK are taken as the focus of present discussion. As far as the distorition noise is concerned, besides the noise of narrowband signal, it is necessary to account for the noise that drops into the picture signal band. The reason for the former is considered mainly to be the differential gain (DG), and the reason for the latter varies depending on the dropping frequency of the noise. The computed values agree very well with the experimental characteristics. For the medium of transmission of multiple signals that include wideband picture signals, the frequency modulation formula has an advantage and the probability of its future development is large.