Performance analysis of digital second order delay locked loops for direct sequence spread spectrum systems with Doppler shift and A/D quantization

The non-coherent second-order digital delay locked loop with Doppler shift present is analyzed. The analysis is unique on two counts. First, the effects of the loop A/D quantization on the loop performance, which have been neglected previously, are examined. Second, MTLL (mean time to lose lock) and MSE (mean square error) are evaluated more accurately than by previous methods. Numerical results show that: (1) the number of quantization levels significantly alters the loop behavior, including the lock-in range, transient responses, MTLL and MSE; and (2) the traditional analysis based on Gaussian approximation may result in a large error in performance evaluation when the A/D quantization is taken into account.