Analysis of Phase-Locked Timing Extraction Circuits for Pulse Code Transmission

An analysis is presented of the performance of phaselocked timing extraction circuits for baseband pulse code transmission. The phase error of the extracted timing wave is influenced by the properties of three essential stages in signal processing: prefiltering, nonlinear treatment, and narrow-band filtering. The analysis enables us to calculate quantitatively the quasi-static and the dynamic part of the phase error for arbitrary but specified types of signal processing. This is more than can be done with existing theory in the case of resonant-type timing extraction circuits. Examples are given for practical cases, and conditions for optimum performance are derived. Furthermore, the behavior of such phase-locked circuits in a chain of repeaters is investigated, and in particular, the propagation law for jitter. Byrne´s model, as used for resonant-type timing extraction circuits, therefore is generalized. It is shown analytically and experimentally that by proper implementation of the timing extraction circuit, considerable improvement can be obtained as compared with resonant-type circuits.