Timing Recovery in Synchronous Equalized Data Communication

The best estimation of sampler timing in adaptively equalized systems is examined. First, two previous approaches to the estimation problem are reviewed and are found to have fundamental shortcomings. The first technique sets the timing instants coincident with the peak of the unequalized system impulse response. Under certain circumstances this technique can produce nulls in the spectrum of the sampled system, thus preventing efficient operation of the equalizer. The second technique sets the timing instants so as to minimize the residual distortion of the equalized system. This does assure proper operation but requires a second equalizer structure and also requires an accurate initial estimate of sampler phase which it cannot provide itself. A timing recovery technique based on band-edge component maximization which circumvents these problems is presented. Although the scheme is not optimal, it efficiently and effectively recovers timing in synchronous equalized data communication systems.