Improving cable television transmission by means of an optimal coherent carrier system
Abstract
The use of phase-coupled vision carriers for transmission in a multichannel cable television system, with a view to reducing the intermodulation and crossmodulation interference resulting from the nonlinearity of the wide-band transmission system, is discussed. To be able to evaluate the improvement, as compared to conventional non-coherent signal transmission, the problem of the optimum phase relationship is examined theoretically. The results of trials with an experimental 27-channel installation show the reduction in interference that can be obtained by fixing the phases of the carriers according to a code found by a process of optimisation.
