On economical timing-error detectors for QAM receivers

Abstract

This paper deals with timing jitter reduction in the timing recovery loop of a digital QAM receiver. The main contribution, which is derived analytically, is an economical prefilter to reduce the timing jitter in timing recovery loops containing either the early–late or the Gardner timing-error detector (TED). The proposed prefilter has the advantage of being an infinite impulse response filter that is placed inside the TED and runs at the symbol rate. For small roll off factors, it is shown with a computer simulation that a single-pole filter placed inside either the early–late or the Gardner detector is quite effective in reducing the timing jitter.