GPS/GLONASS Time Difference Measurements and Test Bed Development

摘要

A joint U.S. Coast Guard Academy/University of Leeds Global Positioning System(GPS)/GLONASS effort is described. The objectives of the effort are: To obtain independent measurements of GLONASS vs. GPS time at the Coast Guard Academy to complement the ongoing work at Leeds and thus establish a dual baseline on GPS/GLONASS time references, and to develop a general purpose signal and interference analysis test bed for educational purposes and for studying the effects of interference and jamming on user receivers. The test bed is based on the Hewlett Packard 89440A Vector Signal Analyzer system. For signal analysis and time measurements, the RF signal from an active antenna is bandlimited to 7 MHz bandwidth, down-coverted to 6 MHz and digitized at 25.6 MHz. For making Time of Arrival (TOA) measurements, time domain templates of the GPS/GLONASS C/A pseudorandom code sequences are calculated off-line and stored in the analyzer. The system is Cesium referenced and calculates the cross correlation and Doppler shift of the satellite signals. Establishing a dual baseline on the GPS/GLONASS time reference will greatly enhance any possible integration of the two systems in the future. Additionally the system is an ideal platform for teaching GPS/GLONASS and for allowing students to perform their own signal analysis due to the ease in applying any common DSP algorithm to the down-converted/sampled RF.