Tuner and demodulator performance for cable distributed D2-MAC TV-signals

Results are presented of a system study on cable distribution of D2-MAC (time-multiplexed analog component) TV signals. With bit error rate as a D2-data performance parameter and visibility of disturbing signals as a performance reference for MAC-video components, system requirements are derived and related to existing concepts. The D2-MAC TV-signal is a time multiplex consisting of a duobinary D2-data part at a 10.125 Mb/s bitrate and a MAC-video part. The -time compression factor for luminance is 3/2; for both of the chrominance components the factor is 3. AM-vestigal sideband transmission on the cable is assumed with a vestigal sideband of VSB=0.75 MHz, and Nyquist filtering in the receiver, while 10% residual carrier is applied during black signal levels and 100% carrier is applied during white. The logical '1' -levels of the duobinary D2-data are specified at 19% and 91% with respect to the carrier level during white signal levels. It was found that the out-of-channel selectivity requirements are more severe than for conventional TV standards if no video-scrambling is applied. This conclusion can be extended to all time-multiplexed video systems. The performance of existing quasisynchronous demodulator concepts is insufficient for proper data recovery. Tilt is a critical parameter if no correction techniques are applied. The measuring methods as used for D2-data to investigate its sensitivity for tolerances on transmission parameters are found to be also suitable for other practical investigations on digital transmissions.<
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