Dynamic Navigation Receiver P Code Acquisition And Carrier Tracking Technology Research

Spread spectrum communication technology is based on Claude E.Shannon's information theory. Comparing with other communication technologies it has the advantage of low probability of intercepting, a high immunity to interference, hiding the useful information and multiple-access communication ability. Now this technology has been applied in various communication fields.The Direct Sequence Spread Spectrum (DSSS) is the most ordinary one within the spread spectrum communication technologies. It has been applied in satellite navigation and position system widely. This paper focuses on the technology of P code acquisition and carrier tracking of DSSS signal in the high dynamic circumstance.In the high dynamic circumstance, the Doppler shifts between satellite and receiver arose the losing of correlation power, and bring the drop of correlation peak value, and reduce the acquitsition performance of spread spectrum code. Furthermore, P code whose cycle is very long(7 days) is research object in this paper. Using traditional ways it is very difficult to capture it. So a new method which is based on memory and carrier frequency search and FFT spectrum analysis is proposed in this paper. This P code acquisition method can search the code phase and carrier Doppler shifts at the same time.After capturing the P code, the phase locked by the acquisition model.Then the acquisition model send a phase error and Doppler shifts to carrier tracking model. The carrier tracking and P code tracking model begin to work. Although the Doppler shifts have been compressed when the P code was captured, it is very difficult to track the carrier if using ordinary phase lock loop(PLL). In this paper proposes a new carrier tracking method which unite the AFC and Costas algorithms together to track the carrier. In order to reduce the remanet phase error, the phase revolving model is added which can improve the precision of the output data.In this paper, the P code acquisition and carrier tracking algorithms had been transformed into Verilog HDL and realized in FPGA. The research result of this paper can be applied in the high dynamic satellite navigation receiver as well as ordinary satellite navigation receiver.