Theory and methods for design of pulse shapes for broadcast teletext

The main objective of this paper is to describe the theoretical and practical engineering constraints, considerations and methods for pulse shape design for North American broadcast teletext transmissions, and to describe the design and performance of new overall 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. A summary of overall objectives of pulse shape design is given. Basic constraints and considerations from the Nyquist theory are described. The practical and engineering constraints on teletext pulse shapes are discussed in detail. Pulse shape apportioning and specification are treated. A critical review is provided of the theory and design methods for teletext pulse shaping. A review of analytical and numerical approaches is given, including analytical approaches which do not appear to have been applied to this problem previously. Modelling and simulation approaches are described, including a new, comprehensive model. The design of improved overall and transmitted pulse shapes is described, and the performance evaluated and compared to that obtained with other common pulse shapes. Some perspectives about gains achievable by pulse shaping are provided.