Reception of Teletext Under Multipath Conditions

Information for data broadcasting services such as Teletext is transmitted as digital signals inserted in the vertical interval of the television video waveform. The specifications for these signals are drawn very carefully to ensure compatibility with the existing television system. This paper examines some of these specifications such as data rate and waveform shape, which must be selected to maintain the spectral energy within the television bandwidth. Using computer simulation, the transmitted signal and encoded teletext data (as defined in Broadcast Teletext Specifications´) will be examined for different multipath conditions. For all these experiments, echoes have been generated and evaluated at the baseband, ignoring system amplitude and group delay characteristics. These, in general, will have additional influence on decoding reliability.