Research On Acquisition Algorithm Of BOC And Its Derived Signals

With the rapid development of global navigation satellite systems,the number of navigation systems is increasing.For example,the most widely used GPS navigation system and the increasingly popular Chinese BeiDou navigation system.So navigation frequency band become more and more crowded,and they are interferce with each other.In this case,a BOC(Binary Offset Carrier)modulated signal was successfully proposed to solve the problem.With the in-depth study of the BOC signal,some BOC derived signals were also proposed to be applied to each navigation systems.In addition,there are many interference factors in the actual environment,which brings difficulties to the acquisition of BOC and its derivative signals.Therefore,it has become a hot discussed and difficult point for scholars at home and abroad.On the basis of detailed studying the structure and properties of BOC and its derived signals,the acquisition problem of BOC signals at lower signal noise ratio and BOC and high-order DBOC(Double Binary Offset Carrier)modulated signals for high dynamic environment are studied,and uses an improved method to achieve the unambiguous general acquisition of BOC and its derived signals.The main work of the thesis is as follows:(1)Aiming at the problem of BOC signal acquisition under low signal noise ratio conditions,the combined acquisition algorithm based on batch processing and TK(Teager Kaiser)operator is studied.Firstly,the technologies of batch processing and averaging processing are applied for the received signals and combined spreading codes.The technology of frequency domain circular moving is applied for the received signals to achieve the Doppler frequency offset compensation.Then,multiple frequency offset compensation sequence and the combined spreading code take circular correlation operation and the maximum correlation value sequence is processed by the TK operator.The research shows that,under the same conditions,the detection performance is effectively improve,and the BOC signal can be captured under the condition of low SNR.(2)Aiming at the problem that the Doppler rate caused by acceleration in high dynamic environment to reduce the acquisition performance of BOC signal,an improved windowing method based on PMF-FRFT(Partial Matched Filtering and Fractional Fourier Fast Transform)is studied,which can directly achieve the effective accquisition of BOC signals under Doppler rate.For the problem that the Doppler rate caused by jerk in high dynamic environment can not accurately acquisition DBOC signals,the algorithm for PMF-FFT(Partial Matched Filtering and Fast Fourier Transform)is studied.According to the problem of low detection performance caused by the related loss and scallop loss,the discrete spectrum correction method is used.Firstly,the DPT(Discrete Polynomial phase Transform)is used to reduce the high order dynamic term of the received signal,and then the PMF-FFT algorithm is redesigned for the DBOC signal.Finally,the spectrum correction method is used to correct the maximum power spectrum after FFT.The research shows that,under the same conditions,the use of the spectrum correction method effectively improves the acquisition performance.(3)Aiming at the problem of general unambiguous acquisition are difficult for BOC and its derivative signals,an improved unambiguous acquisition method based on pseudo-correlation functions is studied.Firstly,the concept of step-shape bits vector was proposed to obtain a unified expression of cross-correlation function and designed two new step-shape vectors.Then,a single peak was obtained by the synthesis between the received signal and shape code vector corresponding to the reference signal.Finally,a generalized unambiguous acquisition was synthesized by combined the single peak and autocorrelation functions.The research shows that,under the same conditions,the proposed method can be applied to BOC and its derivative signals,which can eliminate the ambiguity of autocorrelation function.