A modified code tracking loop based on dual structure

Abstract

A modified code tracking loop for tracking the pseudo-random noise code in direct sequence spread spectrum signal is proposed. The modified loop differs from the typical through imposing a dual structure which incorporates a coarse loop with large loop parameters and an accurate loop with small loop parameters. The expression of the convergence time for the second-order delay-locked loop (DLL) is derived to measure the time of the convergence process. Two concepts, accuracy improvement and time improvement are defined to exhibit the performance enhancement of the modified loop. Simulation results show that the proposed method can realize a better trade-off between tracking accuracy and convergence time in the whole simulated carrier-to-noise ratio range. Also, the robustness of the modified loop is verified through eliminating the second convergence process which is regarded as the worst issue in the parameter-switching DLL.