Research On The Acquisition For BOC And TDDM-BOC Signals

With the rapid development of technology and economy,the importance of positioning and navigation is self-evident in military and people's lives,so the global navigation satellite system has been developing rapidly.With the increase of the number of satellites launched by navigation systems in the world,the interaction between navigation systems is becoming more and more serious.The appearance of BOC(Binary Offset Carrier)modulation signal is a good solution to the problem of the incompatibility of different signals in the same frequency band.Moreover,the actual capture environment may be more complex,so the study of the capture of BOC and its derived signals in complex environment becomes more meaningful.Among them,the TDDM-BOC modulation signal is worth in-depth study because of its unique confidentiality and anti-interference ability,the signal has been applied to the Bei-dou navigation system,so the capture of the BOC signal and the TDDM-BOC signal has become a hot issue in the field of satellite navigation.In this paper,the acquisition methods of BOC signal and TDDM-BOC signal are studied.The main research content of this paper can summarize in the following 3 aspects:(1)In order to solve the problem that the fuzziness of capture that the multi-peak of the auto-correlation function of BOC signal in the residual frequency bias environment,a window PMF-FFT acquisition algorithm is studied.Firstly,keep relative sliding state between receiving signal and the local PN code,and then the signal is segmented and accumulated,in order to prevent the leakage of the spectrum,the data is added to the window,then go on the fast fourier transform of accumulated data,the spectral peak exceeds the threshold that captures successfully.The simulation results show that the proposed algorithm can achieve the purpose of capturing the signal.(2)In view of the problem that BOC signals is difficult to capture in multipath environment and the problem of side peak cancellation algorithm is difficult to be unified,proposes a Rake model using maximum ratio combining method to eliminate the multipath spread spectrum,then the edge peak elimination algorithm is unified that using the generalized spread spectrum symbol waveform.Finally,the acquisition function is synthesized by the correlation function.Through simulation analysis,we can get that the new algorithm has more precise capture accuracy than the SCPC(Sub Carrier Phase Cancellation)method.For the modulation order 2 of sin-BOC(1,1)signal and cos-BOC(1,1)signal,the detection performance has improved 4dB and 2dB than SCPC algorithm respectively.(3)Aiming at the problem of TDDM-BOC signal is difficult to capture,put forward two kinds of the acquisition algorithm of sine and cosine TDDM-BOC signal and use three cubic spline interpolation method to accurate phase,the sinusoidal TDDM-BOC signal acquisition algorithm is that obtain the cross-correlation function of the modulated local pseudo code and TDDM-BOC signal,then the auto-correlation function of the signal is obtained,finally,the capture function is obtained by linear synthesis of sub-correlation function.TDDM-BOC signal acquisition algorithm of cosine type is different from linear combination rule capture function in a similar manner.The simulation results show that the two algorithms have better suppression effect on the sub peaks,peak energy is stronger,and the capture effect is more obvious than the correlation reconstruction algorithm and the SCPC algorithm.