A Fine Synchronization Method for Coherent Fast Frequency Hopping

Coherent fast frequency hopping (CFFH) is attracting growing attention owing to its good anti-jamming performance and the coherent combining ability. However, compared with the conventional non-coherent fast frequency hopping, CFFH requires a more precise system synchronization. In this pa-per, we propose a new fine synchronization algorithm for CFFH. This algorithm consists two stages, namely, open-loop stage and closed-loop stage. In the open-loop stage, a grid-based search parameter estimation method is proposed. In the closed-loop stage, we con-struct a fully coherent phase-locked loop (PLL) and a delay-locked loop (DLL) with decoding feedback structure to perform further fine estimation of the sys-tem clock skew and time delay, respectively. More-over, we analyze the effect of the search parameter set-tings on the estimation error and derive the root mean squared error (RMSE) of estimates in the steady state of the closed-loop stage. Finally, through simulation, the RMSE performance are compared with the corre-sponding Cramer-Rao low bound (CRLB) and conven-tional code loop estimation to show the effectiveness of proposed algorithm.