Improvement of CATV Transmission Using an Optimum Coherent Carrier System

Aiming at the development of future multichannel CATV-transmission systems the utilization of phase-coherent picture carriers is discussed as a means of reducing intermodulation-and crossmodulation-distortion arising in the line repeater amplifiers. The paper presents experimental and theoretical data for comparison of transmission performance. As a basis the non-coherent operation is reviewed. In order to evaluate the improvement by a coherent system the problem of optimum carrier phase relation is investigated. Experimental results demonstrate the suppression of distortion, if the phases are adjusted according to a certain code which was found by optimization.