Research And Implementation Of The Tracking Algorithm Of BOC-Modulated Signal

With the development and construction of Compass Navigation System, GPS System of USA, GLONASS System of Russia and Galileo of European Union, the signal system of satellite navigation system is in the stage of transition.In order to meet the development needs of the system, BOC modulation become the main modulation in these satellite navigation system. Compared with traditional PSK modulated signal,the BOC brings the some advantages,such as higher precise measurement capability and reduce the noise interference. But the ambiguity in acquisition and tracking of the BOC-modulated signal which is caused by the multi-peaks of the auto-correlation function. The paper is mainly research the tracking problem of the BOC-modulated signal in receiver, meanwhile, the high performance and good versatility tracking method is the significant foundation for favorable performance BOC receiver’s development.Firstly,the paper analyzes the characteristics of the BOC-modulated signals from the model of BOC-modulated signals,autocorrelation function and power spectral density function. And explains the advantage and disadvantage by comparing with the PSK-modulated signals.Illustrating ambiguity in tracking of the BOC-modulated signals, which is caused by the multi-peaks of the auto-correlation function.What’s more,the paper describe three traditional tracking algorithm which are eliminating the ambiguity of the BOC-modulated signal,such as BPSK-like, ASPe CT and Bump-Jump.Meanwhile,analyzes the tracking algorithms and suitable situation of three traditional tracking method, and illustrates the tracking performance with MATLAB.Aiming at the disadvantage of the traditional tracking algorithm for BOC-modulated signals,the paper makes good use of the characteristic of BOC-modulated signal, improves and realizes the tri-loop tracking algorithm which is working well for the BOCmodulated signal. The improved tracking method adds an extra subcarrier tracking loop under the code tracking and carrier tracking loop conditions,three tracking loops working independently. The paper considers the subcarrier as a special PN code in subcarrier tracking loop and using delay lock loop to tracking, or considers the subcarrier as sine carrier signal for tracking by PLL. In this condition, two kinds of tri-loop tracking method like SDLL and SPLL, can be derived from the paper. In addition,the paper compares and analyzes the SDLL tracking and SPLL tracking’s performance from output SNR and tracking jitter. Then, the paper derives the process of two kinds of tri-loop tracking principle and provides the MATLAB simulation results. The results of simulation shows, the SPLL and SDLL tracking loop are not only suitable for low-order BOC modulation, but also work well for high-order BOC modulation.Finally, in order to test and verify the engineering feasibility of the tri-loop tracking algorithms on FPGA + DSP hardware platform, using SPLL tracking method realizes the BOC(1,1) modulated signal tracking.The advantages of tri-loop tracking algorithm such as good tracking performance and versatility and well feasibility was proved through MATLAB simulation and hardware implementing.