Spaceborne Dual-frequency Software Gps Receiver For Study

After ShenZhou â…£unmaned spacecraft launched successfully on Dec 30 2002, the orbit of the spacecraft had been observed four times with single-frequency GPS receiver,SLR and USB. The radial accuracy was better than 2 m, met the requirement of the task. The mission of integrated precise orbit determination in next stage of Chinese maned spacecraft mission requires better accuracy. Because the single-frequecy GPS receiver can't observe the ionospheric delay directly and the ionosphere corrections can't meet the demand of the accuracy, the research of spacecraft held dual-frequency GPS receiver must be deployed. In this paper, spacecraft held dual-frequency GPS receiver has been designed. The receiver is compatible with other navigation systems such as GLONASS navigation system etc., and can work in high dynamic and weak signals enviroment. Its outputs include the C/A pseudrange, L1 carrier phase, L2 carrier phase and the L2 ionospheric delays. Based on the software radio theory, this paper studies the structure of general navigation receiver first. The general receiver consists of broad-band antennas and other general hardware platforms. It is compatible with other navigation systems such as GLONASS, Galileo and BeiDou by loading various softwares. Compared to traditional receivers, software radio based receier can implement more complex algorithms and obtains great advantages in tracking accuracy, anti-interference and weak signals processing. The spacecraft held GPS receiver must work in high dynamic enviroment, so it will encounter high Doppler frequency, weak signals, great ionospheric delay range,etc.. This kind of GPS receivers and relevant technologies which involve such sensitive fields such as military are blocked from the foreign to our country. In this paper, these signals acquisition and tracking algorithms for high dynamic circumstances have been developed independently. Finally, the tracking algorithms of GPS L2 signals are dicussed in this paper. Because of the influence of AS technology, the common way to access the L2 signals of GPS is forbidden. In this paper, we obtain the...