Design And Implementation Of Tracking Algorithn For High Dynamic BOC Spread Spectrum Signal

Satellite navigation system tremendous boost to the national economy and in themilitary field, the countries in the world are actively establishing and promoting theirown independent satellite navigation system. The BOC modulation is proposed as a newmodulation scheme with the development of States navigation system, it has theadvantages of spectrum splitting and frequency band sharing. In the satellite navigationsystem, the high-speed movement between navigation receiver and navigation satellitegenerates a larger Doppler frequency shift when receiving signals, resulting in the signalreception failure. Therefore, the BOC modulation signal tracking technology in highdynamic conditions is deeply studied in this paper. A tracking algorithm is designed tomeet the dynamic conditions, and validated detailed by MATLAB.First, a carrier tracking loop is proposed to solve the problem of huge Doppler shiftin high dynamic conditions, its main idea is using the Four-Quadrant Frequencydiscriminator to lead Doppler shift to the working range of the frequency-locked loopfirst, And then tracking the frequency by the frequency-locked loop, or tacking thephase accurately by phase-locked loop when the frequency locked to a small range. Thisalgorithm lies in the determination of the loop noise bandwidth of each of the loop filter.Because of the deeply study of the noise performance and dynamic response of the loopfilter,the loop noise bandwidth is obtained to meet the scope of loop dynamicperformance, which the working range of the frequency-locked loop is3~8Hz, theworking range of the phase-locked loop is9~18Hz， and getting a conclusion that theloop noise bandwidth becomes greater in the work-range,the loop convergences faster.Finally, the simulations of different ways of working on the phase-locked loop andfrequency-locked loop show that, carrier tracking program has the best performance inhigh dynamic conditions.Secondly, there is a detailed analysis of the code tracking method. On the basis ofdelay lock loop, many methods are proposed to solve the multi-peak of the correlationfunction of the BOC signal, such as2N discriminators, bump jump and ASPECT. TheASPECT is selected as the code tracking algorithm for its best performance finally. Considering the impact of high dynamic, carrier tracking loop is always used to assistcode tracking loop because of its high-precision characteristics.Finally, the overall simulation verify the feasibility of the program trackingalgorithm after combined the carrier tracking loop and code tracking loop. The resultsshow that, when the carrier under the maximum dynamic that the initial Dopplerfrequency shift in the range of500Hz, the acceleration of carrier is10g, the jerk ofcarrier is4g/s, tracking loop can properly locked to correct frequency within100ms.