ANALYSIS OF A COHERENT FREQUENCY-HOPPED SPREAD-SPECTRUM RECEIVER IN THE PRESENCE OF JAMMING

A digital phase/timing tracking loop for a coherent frequency-hopped spread-spectrum receiver is analyzed. A training period is introduced to aid the system in entering the tracking mode; once in this latter mode, decision-directed measurements are used. The 5-curve, the conditional variance of the phase estimator, and the linear model of the loop are derived. Then, under minor assumptions, the phase error is modeled as a homogeneous finite Markov chain. Based on this model, we obtain the length of the training period and the approximate probability of entering the tracking range; in the tracking mode, we obtain the steady-state average probability of error and the mean-time to loss-of-lock. By limiting the maximum output magnitude of the phase estimator, we show that the tracking performance is close to that of coherent BPSK in the absence of jamming, or that assuming perfect synchronization, in the presence of partial-band jamming. The mean-time to loss-of-lock is shown to be several orders of magnitude larger than the expected length of training period. Finally, both the effects of a cubic channel phase response and a constant RF phase error are presented. © 1990 IEEE