Double-star Positioning Despreading Receiver

Satellite positioning navigation means using the position, velocity and time information supplied by the satellite positioning navigation system to localize, navigate and manage the target. The satellite positioning navigation system is very important to the survival and development of a country. Now, we have developed Two-satellite Positioning System based on the earth quiescency track. In this system, the PN codes acquisition and tracking , carrier wave's frequency and phase tracking are critical.This paper investigated several key problems of the implementation of two-satellite positioning digital de-spreading receiver with field-programmable gate array (FPGA). Based on analyzing several ways of PN codes' acquisition, multi-supposition matched filtering algorithm is proposed to fulfill the real time requirement of PN codes' acquisition and with less source requirement. Contrasting this method and traditional methods, faster acquisition , higher sensitivity and working in lower S/N condition is predominance. According to correlative characteristic of PN codes, early-late gate base-band loop is used for PN codes tracking. Agonic estimation is used for carrier frequency and phase tracking. Besides, theory analysis and simulation of receiver's sub-modules are presented and classified in this paper. Several schemes are simulated by using modelsim software after the sub-modules are implemented with VHDL language.