Research On The Synchronization Acquisition Technique For Shortwave Frequency-Hopping Communication Using Frequency Estimation

The core problem of shortwave lies in how to keep normal communication under various interference environments. The strong ability of anti-interference and the function of random address selection make frequency-hopping (FH) communication have a wide application perspective in shortwave radio area. Synchronization is a key technique in shortwave FH communication system, which has direct influences on the performance of the whole FH system. Therefore, it has a practical significance to develop a technique for fast synchronization. Synchronization includes acquisition and trackingAccording to the analysis and comparison of different synchronization scheme based on the principle of shortwave FH system, a scheme of "short code piloting long code" is employed in this paper. The acquisition method of the short code in synchronization is especially studied. A FH acquisition technique based on the frequency estimation is introduced. And the frequency estimation is implemented by an autoregressive and adaptive algorithm of spectrum estimation. In this paper, the analysis in theory of this technique is made, the flow of acquisition is presented, and the performance simulation under various channel conditions is completed. Finally, the hardware circuit of several key units of the synchronization system is designed. The generator of M sequence, the circuit of DDS and the unit of frequency estimation are implemented with FPGA, which is convenient for real-time processing of data and makes the circuits more flexible and more extensible. Moreover, a brief introduction of the concepts of bit synchronization and frame synchronization is provided in this paper.Simulation and experimental results show that the acquisition method and its design consideration and implementation presented in this paper can meet the aim of fast acquisition. It is applicable for shortwave FH communication.