Image Number 3 for United States Patent #4494242.
In a high-speed digital data system, it is advantageous to sample incoming data pulses at the baud-rate rather than at the Nyquist-rate. In such a system of the type that includes a dispersive channel (e.g., an unloaded subscriber twisted pair with bridged taps), effective baud-rate sampling and reliable pulse recovery at a receiver depend on the availability of a suitable pulse synchronization or timing recovery technique. In accordance with this invention, timing recovery is based on the recognition that the precursor portion of the response of the channel is relatively invariant and predictable. By selecting a specified threshold point in a small-amplitude region of the precursor portion, a basis is provided for generating accurated bipolar error signals that insure consistent baud-rate sampling of received pulses.