Optimum Adaptive Filtering for GNSS Antenna Arrays

Andrew J. O’Brien, Inder J. Gupta

Abstract:	Antenna arrays with space-time adaptive processing (STAP) are commonly used to provide adaptive interference suppression capabilities for receivers. Recently, there has been increasing use of these adaptive antennas in conjunction with global navigation satellite system (GNSS) applications. In this case, the receiver must estimate the time-of-arrival (TOA) of a known, spread-spectrum ranging signal by measuring its carrier phase and/or code delay. However, in the process of suppressing interference, STAP-based adaptive antennas may inadvertently introduce bias errors into these measurements. Since, in this case, the pattern of the antenna is adaptive, traditional antenna calibration procedures are not applicable. In order to prevent these antenna-induced bias errors, this paper derives a STAP filtering algorithm which constrains the adaptive antenna system to produce zero antenna-induced biases while simultaneously maximizing the effective carrierto- noise ratio ( C/N0 ). Simulations demonstrate that, in most cases, achieving a zero-bias system requires only a negligible trade-off in C/N0 performance and that the C/N0 of our algorithm approaches the theoretical upper performance bound. This fact holds true in scenarios both with and without interference, with any length STAP filter, and irregardless of the antenna used. Practical implementation considerations are also explored.
Published in:	Proceedings of the 21st International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2008) September 16 - 19, 2008 Savannah International Convention Center Savannah, GA
Pages:	2796 - 2805
Cite this article:	Updated citation: Published in NAVIGATION: Journal of the Institute of Navigation
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