Recent Improvements in Band-Shared Simultaneous Color-Television Systems: Part I-The Constant-Luminance System and Related Improvements

A number of improvements in band-shared simultaneous color systems (the previously proposed "dot-sequential" system being one of this class) are described. These improvements reduce susceptibility to interference and permit color pictures to be obtained through a total bandwidth of only 4 mc. These color pictures are comparable to those obtained with a nonband-shared simultaneous color system using 4-mc bandwidth for each color. In order to explain these system improvements the simultaneous nature of the so-called "dot-sequential" system must first be developed. Then the constant-luminance system, in which the color subearrier information does not affect the brightness of the picture, may be described. Additional improvements consist of an improved subcarrier pattern to reduce crawling effects in the picture and sampling of the brightness signal at the transmitter to reduce "shimmer" resulting from cross talk of high vbideo-frequency components into the chromaticity channel. The manner in which this group of system modifications can be used to improve substantially both compatibility and the color picture is explained.