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Improving cable television transmission by means of an optimal coherent carrier system

: Krick, W.

Rundfunktechnische Mitteilungen 23 (1979), Nr.5, S.209, 211-16
ISSN: 0035-9890
Fraunhofer HHI ()
cable television; interference suppression; optimal coherent carrier system; crossmodulation interference; phase coupled vision carriers; intermodulation interference

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.