Ambiguity Resolution Using Dual Band Spread Spectrum

D. M. Wild and R. J. Palmer

Abstract:	A single frequency VHF positioning system developed by Accutrak Systems has continually demonstrated repeatable absolute two-dimensional positioning within 15cm (1ó) over areas as large as 400 square kms. This accuracy has enabled the land-based radio beacon system to achieve the capability of auto-steering agricultural vehicles during field operations such as harrowing. Since the system uses a single frequency it suffers from the ambiguity problem inherent to wave ranging systems and therefore requires an initialization procedure before it can be used. This requirement can be cumbersome if the system happens to fail during field operations where the closest initialization point may be several hundred meters or more away. It is possible to remove the requirement of this initialization procedure by using spread spectrum techniques. Since the carrier frequency is in the VHF band any attempt to resolving the ambiguity directly from a code chip would require a fast chip rate. This solution places heavy demands for bandwidth as a result. The required bandwidth can be reduced by using dual carriers to allow an intermediary widelane to help resolve the ambiguity.
Published in:	Proceedings of the 58th Annual Meeting of The Institute of Navigation and CIGTF 21st Guidance Test Symposium (2002) June 24 - 26, 2002 Hyatt Regency Hotel Albuquerque, NM
Pages:	148 - 153
Cite this article:	Wild, D. M., Palmer, R. J., "Ambiguity Resolution Using Dual Band Spread Spectrum," Proceedings of the 58th Annual Meeting of The Institute of Navigation and CIGTF 21st Guidance Test Symposium (2002), Albuquerque, NM, June 2002, pp. 148-153.
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