The Research Of GPS Signals System Applied In Near Infrared Spectrometer

The positioning technology represented by GPS has been one of the fastestgrowing information industry，and widely used in many fields. In order to savemanpower, reduce human error rate and achieve the map of mineral distribution, Theauthor makes GPS technology applied to portable near infrared spectrometer formineral analysis in the lab. The spectrometer is often used indoors, in forest or in wildplace where GPS signal is very weak. Under such circumstances ordinary GPSreceiver circumstances ordinary GPS receiver always could not search the GPS signal,so it is required to develop a GPS receiver which is for getting weak signals. Thepaper is based on the structure of GPS receiver, make some work for weak signalssuch as algorithm analysis, experimental testing and simulation. The main contentsare as follow:1First, the paper explains the meaning and purpose of the research fromthe domestic, international situation and GPS background. Then the paper introducesthe structure of GPS system and signal characteristics, focusing on the carrier, C/Aand the navigation message.2GPS receiver algorithm was studied. According to the progress of signalprocessing, the author analyzed the traditional algorithm of the serial signalacquisition linear search, unit search, parallel frequency search and parallel codephase search in order to improve the computing speed, also analyzed the carrier ringand ring code when signal tracking and the bit synchronization and framesynchronization when extracting of the navigation data.3For the problem of GPS indoor weak signal, the author proposed animproved algorithm, included coherent integration, non-coherent integrationand differential coherent integration in terms of signal acquisition.Finding that theability of improve the signal to noise ratio of the coherent integration is the best,differential coherent is followed and non-coherent integration is the worst. But thecomputation of coherent integration is the largest, which is nearly10times that of other algorithms. Finally, the simulation experiments show that the differentialcoherent is the best.4By the use of the chip REB–3571, the author designed hardware and softwareprograms to achieve GPS time and the latitude and longitude and displayedon PC. In serial transmission, the author realized a time sharing transmission of datato solve the problem that the problem of GPS data occupies the serial port privately,and made spectral data can share a serial transmission. Finally, a capture algorithm isadded in the program and tested by experiment.