The Tracking Algorithm Research Of BD-â…¡ Receiver

With the improvement of information technology, Satellite navigation system hasbeen widely used in social life and military field. BD-II is taking up with Chineseindependent innovation. With the gradual improvement of BD-II system, the BD-IIreceiver has become one of the research hotspot. And the base-band signal processing isthe sticking point of the receiving performance.The base-band tracking of BD-II receiver is researched in this paper. Firstly, thedirect sequence spread spectrum (DSSS) technique and the tracking technology ofBD-II were introduced. Then, compared with GPS, the composition, trait, and signalstructure of BD-II system were analyzed in detail, especially the Gold code. Theprinciple of phase-locked loop and its digital realization were also introduced. Thestructures and the phase discriminators of tracking loop were researched in the design.Tracking loop consists of two parts：code tracking loop and carrier tracking loop. Incode tracking loop, a non-coherent early-late code delay locked loop was used. And incarrier tracking loop, a third order phase locked loop of Costas assisted by a secondorder frequency locked loop of CPAFC was used. Finally, the modules of the trackingloop above were described with Hardware Description Language. And the moduleswere simulated and analyzed by using ISE and Modelsim. The simulation resultsindicate that the tracking loop can lock the signal successfully, thus proving thecorrectness and feasibility of the design.