NRZ timing recovery technique for band limited channels

Numerous clock and data recovery techniques have been reported in recent years, but data rate has been limited by bandwidth. NRZ data such as used in Ethernet or Sonet, when transmitted over band-limited channels, suffer from dc wandering, where the received waveform is represented as a sum of individual symbol responses. The long tails of data symbols interfere with subsequent symbols, causing inter-symbol interference (ISI). The nonlinear decision-feedback equalizer (DFE) is well known to remove post-cursor ISI without amplifying high-frequency noise. This paper reports an NRZ timing recovery technique working with a DFE that enables data transmission at a rate five times higher than the standard rate. Furthermore, a timing recovery technique using a data-triggered phase detector is reported to sustain phase locking to NRZ data even with more than 600 consecutive missing transitions.