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

Abstract

The non-coherent second-order digital delay locked loop with the presence of Doppler shift is analyzed. The analysis is unique in two folds. First, the effects of the loop A/D quantization on the loop performance are examined that were neglected previously. Second, MTLL(mean time to lose lock) and MSE (mean square error) are evaluated more accurately than previous methods. Numerical results show that: (1) the number of quantization levels signiflcantly alters the loop behaviors, including the lock-in range, transient responses, M T L L 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.