Research And Realization Of Key Technology Of GPS Software Receiver

GPS software receiver which is based on the idea of “software radio” is a very importanttopic in the current satellite navigation research. The GPS software receiver has the features oflow cost, high flexibility, ease of development and so on, and it is suit for deeply research ofbaseband algorithm. With the rapid development of national satellite navigation systems,receiver with multiple system, signal and frequency will become a trend, which makes satellitenavigation research focusing on the receiver signal processing algorithm. In a word, the study ofGPS software receiver, especially the study of the baseband signal processing algorithm, is ofgreat importance.GPS software receiver baseband acquisition algorithm and tracking algorithm are deeplyresearched in this paper. Based on the study of traditional acquisition algorithm and threshold, adifferential coherent accumulated acquisition algorithm based on FFT is proposed. Blockaccumulation of coherent integration, doppler circular frequency search and differential coherentaccumulation of the coherent result are used to balance the relationship of acquisition sensitivityand operation efficiency. In tracking algorithm, based on the deep research of second-orderPLL’s model and effect of parameters on performance, an improved tracking loop combinedCostas loop with DLL based on carrier aided has been proposed, and the noise performance isgood. Software implementation of the baseband algorithm based on C++language is provided inthe paper at last. The system core modules have been compiled into dynamic links library, whichimproves encapsulation and flexibility of software.Based on the simulated intermediate frequency signal and real intermediate frequency data,experiments and analysises are performed in this paper to prove high sensitivity of the proposedacquisition algorithm, which is able to receive-39dB weak signal in theory. Up to four GPSsatellites have been successfully acquired and signal has been tracked steadily. Navigaton datahas been demodulated in real time. The result shows that the GPS software receiver designed inthis paper has basic function of baseband signal processing, and the positioning result reaches theprecision of hardware receiver, so the practicability of baseband algorithm is proved.