A Study Of Pilot/Data Combined Acquisition Technology

Global navigation satellite system(GNSS)plays an increasingly important role in high-tech warfare and daily life.The B1 C signal in the new generation Compass satellite navigation system adopts the signal structure including data channel pilot channel.The pilot channel is modulated by quadrature multiplexed binary offset carrier(QMBOC).In Compass B1 C signal,the performance of traditional acquisition methods can't meet the needs.In order to achieve high-precision acquisition of B1 C signal,this paper researches the B1 C signal as follows:(1)The signal structure of B1 C signal is deeply researched in this work.We mainly research the signal structure of the B1 C data and pilot channels,and focus on the QMBOC modulation signal on the pilot channel.The properties of QMBOC modulation signal include the implement and auto correlation function in the time domain and the power spectral density in the frequency domain.(2)The single channel acquisition algorithm and pilot/data combined acquisition algorithm of B1 C signal are researched in this paper.Because the pilot channel acquisition algorithm fails to utilize the signal power of the data channel,the sensitivity of the single channel acquisition algorithm is lower than pilot/data combined acquisition algorithm.In weak signal environment,the loss of signal energy can't be neglected.Pilot/data combined acquisition includes coherent combined,incoherent combined and differential combined.In order to further improve the acquisition performance,differential coherence combined acquisition is improved to reduce the noise introduced by the correlator.(3)The acquisition algorithm of B1 C signal with the constant false alarm rate(CFAR)detector is studied in this paper.The CFAR detector in radar detection is introduced into the B1 C signal acquisition algorithm to realize dynamic adjustment of acquisition threshold,so as to further improve the acquisition performance.In order to make full use of the advantages of CFAR detector,CFAR detector is also used in pilot/data incoherent combined acquisition algorithm.