Binary decision feedback with envelope detection

The performance of discarding and of cumulative decision-feedback systems employing null-zone reception is evaluated for two common types of envelope detection. Compared with a synchronous phase-detection system, of course, the envelope-detection systems necessarily suffer somewhat, both because of the loss of phase information and because of the threshold effect which occurs below roughly 0 db. Nevertheless, feedback is again shown to permit an unlimited trade-off between error probability and transmission time.