Theory and Methods for Design of Pulse Shapes for Broadcast Teletext

摘要

This report describes the theoretical and practical engineering constraints, considerations and methods for pulse shape design for North American broadcast teletext transmissions, and describes the design and performance of new overall (i.e., end-to-end) and transmitted pulse shapes. The principles and ideas described are for broadcast over-the-air transmission but they are also applicable to satellite and cable transmission of broadcast teletext signals. The broadcast teletext model is described. Basic constraints and considerations from the Nyquist theory and its extensions are given. The practical and engineering constraints on teletext pulse shapes are discussed in detail. A review is provided of the theory and design methods for teletext pulse shaping, including analytical approaches which do not appear to have been applied to this problem previously, and numerical approaches. Modelling and simulation approaches are described, including a new, comprehensive simulation program. The design of improved overall and transmitted pulse shapes is described, and their performance evaluated and compared to that obtained with the other common pulse shapes.