Research On Key Techniques Of Frequency Hopping Based On Software Radio

The system of frequency hopping is a measure of the spread spectrum communication. With anti-jamming, anti-intercept, near-far resistance and code division multiple access properties, it became popular in modern military communication and mobile communication. This paper researches the fast frequency hopping system and accomplishes the design of the system and the baseband realization.Firstly, with the analysis and comparison of the performance of various commonly used digital modulation methods, the system choose GMSK modulation. And this paper presents an algorithm for GMSK modulation based on DDS and DSP in order to fullfill the system requirements. Secondly, it also researches the key techniques of frequency-hopper, frequency hopping sequence, frequency hopping network, frequency hopping synchronization and so on in baseband design. This paper adopts DDS as frequency hopper, Walsh code as spreading sequence. It realizes the baseband signal transmitter of a high speed frequency hopping system with 1000hps and 203hps based on the SDR(Software Definition Radio)in the PCB composed of DSP, CPLD, DDS and so on. Finally, according to the analysis of the chaotic sequence, this paper proposes a design of network and synchronization for frequency hopping. Moreover, the simulations whose results show that the new design gives better performance in both network and synchronization compared with traditional ones are also given in this paper.