Research On The Algorithm For Navigation Weak Signal Acquisition Of BD-2

In recent years, with the widely application of Global Navigation SatelliteSystem(GNSS), it has got the rapid development. The Beidou System(BDS),independently developed and built by China, which has received widespread attentionand research in our country and abroad, as its important significance to the nationaldefense of our country. In2013, China satellite navigation system management officeannounced the two civil signal specification files, which is marked the BD-2will enterthe civilian areas. The acquisition performance determines the positioning precision ofBD-2system directly. As the navigation signal between the satellites and the users isaffected by multipath effect, shadow fading, noise and some other factors in thetransmission process, resulting in the users who are in doors, groups of buildings,forests and other complex environment are hard to capture signals. In order to meet theneeds of a wider range of users, researching the BD-2acquisition algorithm which havegreater sensitivity is imperative.In this dissertation, we mostly focus on the navigation weak signal acquisitionalgorithm of BD-2and the main content of this dissertation is as follows:Firstly, the B1I/B2I signals of BD-2are studied. Given the transmitter structure ofthe B1I/B2I signal of BD-2，introduced the characteristics of the B1I/B2I signal ofBD-2and the related characteristics and the spectral characteristics of its ranging code,given two kinds structures and modulation mode of BD-2navigation message, and builtthe digital signal model of BD-2B1I/B2I.Secondly, the general principle of BD-2signal acquisition is studied. Given thereceiver structure of BD-2, introduced some common methods of PN acquisition,analyzed the key element and process of BD-2signal acquisition, accomplished thesimulation experiment and performance analysis of parallel acquisition algorithm whichis based on FFT, and introduced the performance indicators of BD-2acquisitionalgorithm.Then, presented the parallel searching acquisition algorithm for weak BD-2signals.Introduced the key element influencing the quality of navigation signals, and thenpresented coherent accumulation acquisition algorithm, coherent-noncoherentaccumulation acquisition algorithm, coherent-differential accumulation acquisitionalgorithm, and optimal half-bit coherent-noncoherent accumulation acquisition algorithm that could eliminate the effects of navigation data bit transition, which arebased on parallel searching. Introduced the principle and implementation steps of thesealgorithms in detail, got the performance analysises by simulation experiments to thesealgorithms, and then compared the acquisition performance of these algorithms.Finally, presented a long-bit coherent acquisition algorithm based on differentialdecision for BD-2weak signals. Introduced the principle, implementation steps and theprocess of differential decision and coherent accumulation. By simulation experimentsand performance analyzing, comparing this algorithm with general acquisitionalgorithm based on parallel searching for BD-2weak signals, got the superiority of thisalgorithm, ultimately, summarized the advantages of this algorithm in BD-2weaksignals capturing.