The development of a high definition television (HDTV) terrestrial, broadcasting emission mask

Abstract

This paper analyzes the case of HDTV channels, upper and lower, first adjacent to an existing NTSC station assignment and considers the interference from an HDTV adjacent channel, spillover spectra as undesirable co-channel interference into the NTSC channel. A subjective weighting function is developed for random noise interference to NTSC images at the video baseband level. A filter function representing the human visual system at specified viewing distances as a function of image height is developed, first for monochrome, and then extended to color images. The baseband subjective weighting function is modified to include the process of television canier modulation and demodulation. This carrier modified weighting function is then used to evaluate typical spillover spectra created by high power amplifiers when driven by a modulated digital HDTV signal. BTSC stereo audio (with SAP) is also included in the interference evaluation. Spectral out-of-band spillover limits are established based on the threshold of visibility of the interference as a function of the mileage separation between adjacent channel NTSC and HDTV stations. A high power bandpass filter and band elimination notches are included in the analysis. The results are then applied to two methods of determining spectral emission compliance: measurement of the out-of-band interference spectra with a weighting function, or alternatively, the use of an emission mask.