Timing Recovery By Symbol Spaced and Fractionally Spaced Equalizers

Abstract

This paper presents a study of the digital timing recovery for high speed QAM receivers based on the symbol spaced and fractionally spaced equalizers (FSE). The aim of the investigation is to fix the intersymbol interference (ISI) caused by the clock phase error and frequency error between the transmitter and the receiver by the complex adaptive equalizer, hereby eliminating the interpolator and the timing error detector (TED). By this approach it is intended to improve the performance and the cost-effectiveness of the VDSL receiver chip. Both the blind equalization and the adaptation with the use of the training sequences are discussed. The model of the introduced phase error is described. The influence of the phase error on the signal to be detected is studied in the time and the frequency domain. During the investigation of the equalizers' behaviour two basic operation conditions of the receiver are considered. First, the received signal is corrupted by the constant phase error. Thi..