Improved Blind Decision Feedback Equalizer with Self-Adapted Structure for High Order QAM signals

This paper brings some noticeable improvements to a blind decison feedback equalizer recently introduced and mainly characterized by its self-adapted structure. In its starting-up mode, this equalizer is linear and recursive and controlled by a whitening criterion for the recursive part and the Godard criterion for the transversal one. However, in the case of high order QAM signals, the whole performances can be largely improved when the Godard algorithm is gradually replaced by the radius directed algorithm. This novel switching procedure is investigated for a 64-QAM on a typical telephone line and on a severe non minimum phase channel. The results are really convincing since this strategy brings a more accurate equalization, which allows the new equalizer to safely reach its final state of decision feedback equalizer (tracking mode). Needless to say that such an improved blind equalizer turns out to be particularly well-suited for applications such as HDTV.