| Traditional high frequency (HF) frequency hopping techniques don't meet the demands of the future frequency hopping communication used in the military and civil fields, for their disadvantages of low frequency hopping rate, narrow frequency hopping bandwidth, low number of frequency hopping slots, and low information transmission rate. In order to solve these problems, we discuss the multi-carrier frequency hopping technique, which is based on orthogonal frequency division multiplexing (OFDM) modulation and demodulation, using several frequency-hopping slots but not one to transmit data at each frequency hopping period. Compared to the traditional frequency hopping techniques, the multi-carrier frequency hopping mechanism proposed in this paper has some advantages, such as the abilities to improve the frequency hopping rate, to broaden the frequency hopping bandwidth, to increase the number of frequency hopping slots and the rate of information transmission, and to improve the efficiency of frequency spectrum with no difficulty. In this paper, several key problems are researched, including the multi-carriers frequency hopping sequences design based on the theories of single-carrier frequency hopping sequences design, the implementation of broadband system in HF channel based on multi-branch combination in the base band domain, the symbol detection in HF channel with very low signal to noise ratio (SNR) based on matched filtering between the received signals and local training sequence which is a constant amplitude zero auto correlation sequence (CAZAC), etc. Finally, a prototype design for the multi-carrier frequency hopping system is presented, on Xilinx Spartan serial XC2S100E filed programmable gate array (FPGA). Experimental results show that multi-carrier frequency hopping system can be implemented on FPGAs conveniently, so the complexity of frequency hopping radio design can be depressed using the technique proposed in this thesis. |
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