Recovery of data clock signals

Abstract

A single link digital telemetry system transmits data in serial form from a sending station. The data clock signal is recovered at a receiving station for data synchronization purposes. To achieve recovery of the data clock signal the incoming data is synchronized with a high frequency clock of n times the original data clock frequency; the fast clock is utilized to drive a data latch so that on each positive incoming data edge the latch produces a synchronized data pulse for feeding to a recirculating shift register n bits long, which is also driven by the fast clock. The original data pulse can be recovered merely by tapping off from a chosen location on the register. Continuity of recovery of the data clock signal is assured because even when synchronized data pulses are not being produced by the latch due to gaps or sequences of identical bits in the incoming data stream, the last digital word inserted into the register merely recirculates until the shift register is re-synchronized by the next synchronized data pulse occurring on the next incoming rising data edge.