Effects of Multipath Fading on Non-coherent Delay Locked Loops for DS-SS Communication System

In this paper we theoretically analyzed the influences of multipath fading on code sequence synchronous tracking non-coherent delay-locked loops (DLLs) for direct sequence spread spectrum communication system. Focusing on the non-coherent DLLs research in the presence of multipath propagation, this paper proposes that when the output tracking error signal of delay locked discriminators is zero, the relative tracking error would not equal zero. Moreover, this paper shows that there are additional tracking error introduced by multipath propagation, and only when the relative tracking error equals the multipath propagation pertinent tracking error, could we have the error signal as zero. The relationship between multipath propagation pertinent tracking error and multipath relative delay is obtained by theoretical derivation and the simulation curves verify the derivational analysis results. Therefore, due to the randomness of multipath propagation pertinent tracking error, the traditional fixed tracking error elimination algorithm in multipath propagation environment is unavailable.