Modulation of conventional TV signals in all-digital CATV network head ends

In this paper, a new digital intermediate frequency modulator for conventional TV signals using digital signal processing is presented. A composite colour video signal and two associated audio signals are converted into a digital composite TV signal with spectrum at intermediate frequency. The modulator is designed for the high quality requirements that exist in professional equipment for CATV head ends. The architecture of the digital modulator shown is optimized for an implementation with ASICs. The signal processing with reduced complexity is described in detail, the structures and the design of the filters are illustrated and the simulated results are presented.