A Method of Reducing Disturbance in Existing Receivers Caused by Multiplexed Signals Compatible with the NTSC Standard

Abstract

In a television system in which detail information is multiplexed with a carrier and transmitted on a NTSC channel, the picture-quality on existing receivers is degraded by the disturbance caused by the multiplexed component.
A “shuffling” method by which the phase of the multiplexing carrier is shifted on a line and field basis is proposed to reduce the disturbance. The locations of the carriers with various shift patterns in three-dimensional frequency space and the characteristics of the human visual system are discussed.
Subjective assessment tests are carried out in order to select the best shift pattern. As a result, the method using the most suitably shuffled carrier reduces the disturbance to less than 50% for ordinary scenes and 38 % for some particular scenes.