Global Navigation Satellite System Software Defined Radio
The GNSS world is quickly growing. The United States' GPS, the European Union's Galileo, China's Compass, and Russia's GLONASS systems are all developing or modernizing their signals, and there will soon be more navigation satellites in space than ever before. The goal of this research was to develop an initial capability for an AFIT GNSS software receiver. This software receiver is intended to be used for research purposes at the Advanced Navigation Technology (ANT) Center. First a GPS only software receiver was built. It successfully acquired, tracked, and provided reasonable position estimates. Next, the receiver was successfully modified to acquire and track a Compass satellite. This only required relatively small changes in the receiver software. During the tracking process, an interesting finding was discovered concerning the secondary code structure. There are in fact two secondary codes that the transmitter alternates. After AFIT's software receiver was configured properly, the signal was successfully tracked. Finally, the receiver was modified to track one of Galileo's satellites, GIOVE A. After correct parametric changes were made, successful acquisition and tracking of the GIOVE A signal was accomplished. AFIT's GNSS software receiver was shown to provide a high degree of flexibility and accuracy in acquiring and tracking GNSS signals.