Training signal and receiver design for multipath channel characterization for TV broadcasting

The problem of multipath propagation in television terrestrial broadcasting can be solved by channel equalization. Such equalization is needed for an enhanced NTSC system and is particularly critical in most HDTV (high-definition television) proposals. Techniques for precisely characterizing a multipath channel are proposed. These characterizations can be used to reduce hardware complexity and to speed up equalizer convergence. In particular, an approach that provides an opportunity to track changing ghosts at a weak signal level (low signal-to-noise ratio) is proposed. A modified pseudorandom noise (PN) sequence and a properly designed correlator are used. The correlator, matched to a modified PN sequence, provides noise rejection that is 24 dB better than that obtained from the use of a single pulse. No long-term averaging is needed to improve the signal-to-noise ratio. Therefore, it has better system convergence speed and makes it possible to track changing ghosts, or it can tradeoff the speed of convergence against the use of vertical blanking interval by sending the ghost cancellation reference signal less frequently