Research On The Precise Tracking And Multipath Mitigation Technology Of BOC Signal

Today, science and technology develop rapidly, the global navigation satellite system which is shortly named as GNSS has been widely used in many fields, and people's daily lives have been inseparable from navigation technology. And the extensive use of navigation technology makes signal band very crowded. So there are many modern GNSS which began to use a new type of modulation signal - binary offset carrier modulation signal, namely BOC modulation signal, such as GPS, Galileo navigation and a second-generation system of Beidou navigation system using BOC modulation should decide. Compared to the traditional BPSK modulation signal, the BOC modulation signal have a better resistance to multipath interference performance, and it can make the signal power be shifted to the side lobes of the center frequency. And the side lobes are mainly responsible for the signal power. And this technology can avoid the congestion of the signal band. So the use of BOC signals have broad prospects, and this paper is also based on this signal. The main contents of this paper are summarized as follows:At first, this paper introduced the forming principle of BOC signals, and then it discussed the characteristics of BOC signals, and analyzed the power spectral density, the autocorrelation function. It introduced that the multimodal characteristics of the self-correlation function of the BOC signal is due to the possbility of the mistakenly lock.Subsequently, the focus of this article are to study the tracking method for BOC signals,and exemplified some tracking methods which are commonly used, and analyzed this tracking method, such as Bump-jump, ASPeCT, PCF. This paper also simulated and analyzed these methods for the multimodal characteristics of BOC signal. It was found that these methods all had disadvantages. Then we designed a tracking method with high precision named as three-ring double estimator algorithm which was for MBOC signal which was higher accuracy than BOC signal. This algorithm make made the estimated delay of subcarrier locked loop and code locked loop independent. And the use of ambiguous sub-carrier locked loop's simulated delay made unambiguous code locked loop's simulated delay more accurate.Multipath mitigation technique must be paid attention to and studied, and it had a great influence on the tracking loop. This paper studied on the multipath mitigation techniques of MBOC signal, including narrow-related technologie, PCF technology, HRC technology, and it simulated and analyzed them, and found out that these multipath mitigation techniques had advantages in controlling loss of lock or multipath suppression. This paper designed a technology named as the gate function which was similar to the HRC technology was used on MBOC signal. This technology generated a local auxiliary signal in the reciever, then it was correlated with the received signal. The correlation function with the correlation function of received signal and spreading code performed nonlinear calculations. Then This paper obtained a new mutipath suppression algorithm, which had a better multipath rejection performance and a better correlation function characteristic which was better than HRC technology.