Research On Key Techniques Of Synchronization Of Navigation Signals Based On BOC Modulation

The using of BOC modulated signals in the navigation systems has solved the problem of frequency crowing in navigation systems. Now, users have higher requirement on real-time ability and position precision, so more researches are focused on the development of a double-system or multi-system compatible and reconfigurable navigation receiver. At present, as the key technology in this kind of receiver, the synchronization process is mainly focusing on the PSK modulated signals. Even for the BOC modulated signals, most results are only focusing on certain form of BOC modulated signals. Therefore, the effective synchronization technique fitting for diversity BOC modulated signal will be researched as the key technique in this paper. This kind of arithmetic or proposal have two obvious design difficulty, BOC modulated signal that having different modulation order have multiple correlation peak values which will lead a false lock in receiver, it is difficult to improve the PN code phase measurement precision by increasing sampling points at the same time. Aim at this two questions, Following contributions are made to the in this thesis:(1) For the question that the sample on zero values of BOC modulated signal multiple correlation function having a bad influence, in this paper, according to the BOC ACF and BOC/PRN CCF character, a new BOC synchronization algorithm is proposed all alone which is based on the theory of fractal and reconfiguration, we naming it RZCC (Removing Zeros of Cross-Correlation) algorithm. The new algorithm eliminated the bad influence brought by the sample on zero values of BOC modulated signal multiple correlation function. Analysis and simulation have given many conclusions:In the same condition, First, RZCC algorithm has a much small calculation complexity, much wider application domain that it can apply to the higher modulation order, comparing with the three parallel tags algorithm. Second, RZCC algorithm has a more narrow correlation main peak comparing with the BPSK-like algorithm which can provide a better PN code tracking precision. Last, RZCC algorithm enhances the main correlation peak value which can lead a higher main lobe detection probability which can improve the anti-jamming ability. By choosing a proper early-late space, RZCC algorithm can eliminate the negative impact caused by multiple cross-zeros of discrimination phase curve, consequently reducing the false tracking probability.(2) For there are no an arithmetic which can fit for odd and even modulation orders at one time to the synchronization of BOC modulation signal, in this paper, according to the BOC ACF and BOC/QBOC CCF character, a new algorithm for synchronous main lobe detection on BOC modulated navigation signals was proposed by adding a local quadratic BOC branch in receiver synchronization loop, we naming it OQCC (Offset Quadratic Cross-Correlation) algorithm. Analysis and simulation have given many conclusions:In the same condition, First, OQCC algorithm has a better separation performance of main lobe and secondary peaks comparing with the unambiguous synthesized correlation algorithm and the 'Filtered'correlation algorithm. Second, OQCC algorithm has a much wider application range that it can be used in even and odd and higher modulation order BOC modulated signals synchronization process. Moreover, the new algorithm has a lower complexity which is better for the hardware implementation. Last, OQCC algorithm has reduced the secondary peaks detection probability largely by eliminating the secondary peak values. In a word, for having improved the synchronization efficiency and saved the hardware resource, OQCC algorithm can provide a technique guarantee for the practical application on the unambiguous acquisition of BOC modulated signals.(3) We present a proposal on how to improve the PN code phase measurement precision of BOC modulated signals by combining the sample game and Cubic-Spline interpolation algorithm, for resolving the problem bring by over-sampling and polynomial interpolation algorithm. Simulation results show that this proposal which has lower complexity is effective.(4) A new three steps reconfiguration idea is proposed, by the analysis and research on the existing and proposed algorithms of BOC modulated signals acquisition and tracking and improvement PN code phase measurement precision. The new idea has three steps which are reconfiguration requirement resolving, reconfiguration construction and reconfiguration implement. The new idea can be used to support the reconfiguration receiving plan of double-system or multi-system compatible and reconfigurable navigation receiver.