Gps Ionospheric Scintillation Measurements Using a Beam Steering Antenna

The ionosphere can affect GPS receivers by degrading the signal strength, in some cases causing loss of carrier lock, and by degrading the accuracy of differential corrections. As we enter the solar maximum years, these effects will become more severe, causing frequent GPS outages in the polar and equatorial regions and over the entire North American landmass when magnetic storms occur. These ionospheric anomalies can potentially have a massive effect as more systems, such as nationwide air transportation, are coming to rely on GPS measurements. A ground monitoring system is being built to detect and characterize these events. To allow ionospheric data to be collected reliably even during large GPS signal fades, a high gain antenna array has been developed and integrated with a digital GPS receiver. An innovative beam steering approach has been implemented using a low cost, PC-based architecture. The array significantly improves the signal/noise ratio for each satellite allowing the receiver to continue tracking even during extreme signal fades caused by scintillation. This paper describes the beam steering array and digital receiver achitecture used to track the low signal-to-noise GPS signals and presents the results of initial measurements of the array high gain performance.