Novel techniques for multipath mitigation for airborne Global Positioning System (GPS) receivers

US Department of Defense is heavily dependent on the Global Positioning System (GPS) for geolocation, navigation, timekeeping and other military operations. Multipath due to the structure (platform on which the GPS receiver is mounted) scattering can degrade the accuracy of GPS measurements (code and carrier phase) by tens of centimeters. For an airborne platform, reflection or diffraction of the satellite signal from wings, tail, stabilizers or any other large appendage of the aircraft fuselage leads to signal multipath, and these multipath cause biases in code and carrier phase measurements. During this project, we propose to study the performance of two novel adaptive weighting algorithms in the presence of platform generated multipaths. The adaptive weighting algorithms are designed for GPS anti-jam antennas (CRPAs) to null the interfering signals without distorting the satellite signals. We will investigate the performance of the two weighting algorithms in simultaneous nulling of the interfering signals and mitigation of the platform generated multipath. The two weighting algorithms use the knowledge of the in situ antenna manifolds to minimize the distortion of the satellite signals. The sensitivity of the two algorithms to errors in antenna manifold will also be investigated. Our investigation will also include reduced size CRPAs whose foot print is limited to 5" in diameter.