Adaptive antenna arrays for precision GNSS receivers

Antenna arrays with adaptive filters are currently used to provide interference suppression capabilities for Global Navigation Satellite System (GNSS) receivers. An adaptive array allows greater performance over a single element antenna by providing beamforming/null steering in the directions of satellites and interference sources. Unfortunately, there are some important limitations to the GNSS adaptive arrays in use today. For example, in the process of suppressing interference, adaptive antennas may inadvertently distort the GNSS signal and introduce bias errors into the receiver's position and time estimates. Furthermore, many systems produce suboptimal interference suppression performance, which degrades the accuracy of the navigation solution. To overcomes these limitations, this dissertation develops novel adaptive antenna algorithms and techniques suitable for precision GNSS receivers. Three primary contributions are made. First, it develops an approach for optimal suppression of interference. For a GNSS application, this corresponds to an adaptive filter that maximizes carrier-to-noise ratio (C/N0). The second contribution is the development of approaches for preventing the adaptive antenna array from introducing errors into the GNSS receiver measurements. These techniques take the form of a special adaptive filter algorithm and additional receiver logic that mathematically guarantee zero antenna-induced error even during interference suppression. Since mitigation of these errors requires accurate antenna manifold information, a calibration procedure is needed to obtain the antenna manifolds in an efficient and practical manner. Consequently, the third contribution is a novel self-calibration algorithm. This algorithm simultaneously estimates the antenna manifold and navigation information "on-the-fly". Collectively, these contributions advance the state-of-the-art in GNSS adaptive antennas in terms of performance, precision and practicality.