A Delay-Lock Loop for Tracking Pulsed-Envelope Signals

A sampled-data delay-lock loop (SDDLL) which tracks the arrival time of a biphase modulated, pulsed-envelope RF signal is described. A pseudo-noise (PN) code generator is used as the modulation source as in conventional delay-lock loop tracking devices. Time base shifting of the loop's local clock is performed by digital means. The technique permits the use of a stable-frequency clock to maintain accurate timing between timing correction instants. An expression is derived for the standard deviation of the timing error due to additive Gaussian noise at the SDDLL input. Experimental results are then given which include the effects of control-system quantization error on timing jitter. Assuming that the errors due to input noise and quantized timing corrections are independent and additive, the theoretical and experimental results agree to within approximately one decibel.