Recent Improvements in Band-Shared Simultaneous Color-Television Systems: Part II-Color-Television Systems with Oscillating Color Sequence

An additional improvement in band-shared simultaneous color systems is described which reduces the visibility of phase errors in the subcarrier channel of the system. This improvement is obtained by periodically reversing the phase sequence (timing order) of the color subcarrier information, for example, after each scanning field so that phase errors may produce opposite types of color errors on adjacent lines in space. At normal viewing distances the human eye averages the color of adjacent elemental areas, thus giving a first-order correction for chromaticity errors due to phase errors in the color subcarrier channel. While this permits a greater tolerance on the phase of the reinserted subcarrier at the receiver, the major advantage results because vestigial sideband transmission of the color subcarrier information is made practical. The manner in which this latter feature can be used to improve both compatibility and the reproduced color pictures is described. The extent to which the improvements of Part I can be used with a system having an oscillating color sequence is also discussed.