Research And Realization On The Key Technology Of GPS Software Receiver Baseband Signal Processing

GPS global satellite positioning system has become the top global navigation satellitesystem because of its global, all-weather, real-time to provide navigation and positioningservices in the sea, continent, aviation three areas. At the same time, it is the hottest researchobject for the global research institutions. Growing market demand of GPS products and itsstable and powerful features make all countries constantly commit to GPS navigation andpositioning algorithm and application platform development and research, of which, for thestudy at the method of GPS signal acquisition is especially necessary. The traditional GPSsignal acquisition method can’t make the best of both worlds in the acquisition time andresources consumption and circuit complexity. The GPS signal acquisition has a directimpact on GPS navigation and positioning work, so design a simple and fast GPS signalacquisition method is particularly important.This study mainly completed work on putting forward a new simple and quickacquisition method of the baseband signal processing unit in GPS software receiver, at thesame time studied some other parts like GPS signal tracking, data analysis, positioncalculating, and realized these parts in the hardware platform based on FPGA+DSP. Themethod of GPS signal acquisition in the baseband signal processing unit can reduce bothtime consumption and resource consumption, at the same time will be a method of quicklyacquisition. In1ms integral time and a Doppler frequency, this method can get1023correlation value in1023code phase. This study used a carrier tracking loop whichcombined four phase frequency locking loop and costas phase locking loop, it can realizecarrier tracking and acquisition when the GPS receiver is in a high dynamic movementpatterns as well as in a low signal-to-noise ratio. This receiver can track GPS signal anddemodulat GPS data, then according the data to determine the position of receiver.The GPS signal received by antenna should be performed a series of operations aboutfiltering, mixing, AD conversion into8bit digital signal for signal processing. Among them,through the Verilog HDL language programming, realize multiple phase rotation digitaldown-convertion of GPS signal and acquisition of C/A code. Through the C programming, realize work of GPS signal tracking and data demodulation and position calculating design.At this time, the whole work of baseband signal processing unit has completed, this designcan work in the hardware platform based on FPGA+DSP, and display capture trackingstatus of every satellite in order to real-time monitor every satellite condition.