Influence of data modulation and Doppler effects on the performance of a delay locked loop

The influence of Doppler effects on the tracking performance of a noncoherent second-order delay-locked loop (DLL) operating on a data modulated signal is investigated. For the performance analysis the author considers the tracking accuracy (steady state error and jitter) of the linear DLL and the reliability of the nonlinear loop. The nonlinear analysis concerning the loop reliability makes use of an asymptotic expansion for the mean exit time (mean time to lose lock, MTLL) which has been derived by applying the singular perturbation method. In particular, the author gives optimal loop parameters and the optimal bandwidth of the bandpass filter in the loop arms to achieve a maximum MTLL. Due to Doppler effects the optimal loop parameters are rather different using either linear or nonlinear analyses