TIMING RECOVERY IN A DIGITALLY IMPLEMENTED DATA RECEIVER

摘要

Pulse amplitude modulated (PAM) receiver in which timing errors are corrected without requiring that the signal sampling operations of the receiver be synchronized with those of the transmitter. The invention is applicable particularly to multichannel PAM systems in which a common analog-digital converter receives inputs from a plurality of channels serving independently timed transmitters. The inputs to the converter are supplied by a commutator which samples the incoming channels rapidly enough to obtain several samples per signal pulse. From these samples is determined the extent to which the pulse peak lags or leads a particular one of the sampling times. By passing the digitized samples through an interpolating filter whose coefficients are selected according to the estimated timing error, the system enables digital codes representing the peak values of the sampled pulses to be emitted in synchronism with the successive closures of an output sampling gate for the respective channel.