Research And Realization Of Double Estimation Tracking Loop Based On AltBOC Modulation Signals

With the rapid development of the global satellite navigation and positioning system,the narrower satellite navigation band has been increasingly crowded.There are overlapping bands between different systems,signal interference and other issues,which restricted the development of satellite navigation and positioning system.Therefore,the BOC signal modulation technology was proposed at the historic moment,it can realize the signal spectrum moving function,better solves the coexistence problem of different system signals,and is favored by people.However,the autocorrelation function of this kind of modulation signal has many peak characteristics,which leads to the ambiguity problem which is common in signal tracking.The ambiguity problem is one of the main problems of BOC signal synchronization technology.In this paper,the tracking structure is arised to realize the unambiguous tracking of AltBOC(15,10)signals.Firstly,we briefly summarize the GPS signal composition based on BPSK technology,and then introduce the principle of BOC signal modulation and the composition principle of several BOC modulation signals.At the same time,we analyze the autocorrelation characteristic and power spectrum of AltBOC signal,TMBOC signal and CBOC signal characteristic.The principle of classic trapping loop of BPSK signals is deduced in detail.Then,a more mature unambiguous capture and tracking algorithm is introduced.At the same time,it is concluded that any tracking algorithm has no universal applicability for BOC signal.The BOC modulation signals need to be synchronized with the unused tracking algorithm.The tracking structure for various modulation signals is listed.AltBOC(15,10)baseband signal is selected and an new structure of double estimation tracking loop is proposed.Based on classical tracking loop,this algorithm adds the idea of single subcarrier processing.The tracking loop of the AltBOC(15,10)baseband signal is realized by the code tracking loop and the sub-carrier tracking loop independently,and the coupling output of the control signal is realized.The ambiguity problem can be solved and the high precision of tracking can be obtained.Finally,the new tracking architecture is designed and implemented on the hardware verification platform,which is based on the FPGA core,and the unambiguous tracking of the baseband signal base of AltBOC(15,10)baseband is achieved by designing pseudo code tracking loop and subcarrier tracking loop.