Airborne Hopping Data Link Key Technology Research

From the development history of airborne hopping data link technology, this paper discusses the frequency hopping synchronization technology. In the case of high-precision synchronization, it is necessary to apply a kind of new modulation scheme BOC modulation. BOC(Binary Offset Carrier) modulation, which makes the spectrum split and move to both sides of the carrier frequency, so tha the frequency band can be multiplexed and avoiding spectrum aliasing of different signal. In ASPeCT of autocorrelation function(ACF) of the modulation signal, BOC modulation signals’ s ACF’s peaks are shaper compared with BPSK modulation signals. Therefore, BOC modulation signal having a high code loop tracking accuracy, strong anti-interference ability and better resistance to multipath capability. On the other hand, since the multi-peaks ACF of BOC modulation signals, we have to solve ambiguous acquisition problem for this kind of modulation signals. Therefore, it is necessary to study some unambiguous acquisition schemes.This paper described the purpose and significance of the subject, introduced the research status and development trends in this filed. Then, I analyzed the BOC signal model, power spectral density(PSD) and ACF of BOC modulation signals. From study, we know that multi-peaks of BOC ACF lead to ambiguous acquisition, so I introduced many unambiguous acquisition algorithms for BOC modulation signals. Then, I introduced two classical unambiguous acquisition algorithms, which named ASPeCT algorithm and Filtered algorithm, respectively. In addition, I also introduced an algorithm which can eliminate side-peaks of BOC ACF deeply. In contrast to the above algorithms’ s characteristic and drawbacks, I poposed a novel unambiguous acquisition for BOC(n,n) signals. By MATLAB simulation, I found that the algorithm poposed can completely elimate side-peaks, but the width of BOC correlation function’s main peak is wider than that of BOC ACF’s main peak, and the ratio of main peak’s height to main peak’s width is fixed, too. Therefore, based on ASPeCT algorithm, an improved unambiguous acquisition algorithm had been proposed. By setting the appropriate parameters of algorithm, this scheme elimates sub-peaks completely, and formates a sharper peak, which leads to a much accurater acquisition. From MATLAB simulation, I compared the acquisition performance of above algorithms, which are ASPeCT algorithm, Filtered algorithm, similar algorithm and proposed algorithm. From simulation, I found that the proposed algorithm performs better compared with other three algorithms in peak-to-average ratio, signal detection probability, miss acquisition probability ASPeCTs. Finally, based on the above theoretical analysis, I completed the FPGA module design of BOC(n,n) signal acquisition algorithm, and I designed the module interface.