Antenna Techniques to Optimize Pseudorange Measurements for Ground Based Ranging Sources

Jeff Dickman and Chris G. Bartone

Abstract:	This paper discusses methods to mitigate pseudorange biases resulting from exceeding the dynamic range of a GPS receiver for ground based ranging sources. Dynamic range is an important consideration when using an airport pseudolite (APL) because the received power levels vary over a wider range than if they were transmitted by the GPS constellation. Two situations can cause the dynamic range of a receiver to be exceeded. First, the received power level could get too large because of antenna proximity during an aircraft approach. Second, the gain pattern of the transmitting and receiving antennas can cause the received power to rapidly vary during an end becomes saturated because of either situation, it can cause the output to become nonlinear. This nonlinearity could lead to meter level errors in the position solution [1]. Previous field-testing has shown biases ranging from three to three and a half meters with typical hardware [1] when exceeding the dynamic range (40 dB). By using some basic antenna techniques, this problem can be substantially reduced and nearly eliminated. A model was developed to simulate an approach and determine the resulting power profile for several ground siting locations. A typical top-mounted GPS patch antenna was used for airborne GPS/pseudolite reception. Based on this study, a region of “ideal” transmitting antenna siting locations will be presented. Specifications for a new APL transmitting antenna will be defined. This paper will convey the results of the antenna siting study, pattern specification and antenna prototype analysis for ground based ranging sources. aircraft approach. If a component in the receiver front
Published in:	Proceedings of the 57th Annual Meeting of The Institute of Navigation (2001) June 11 - 13, 2001 Albuquerque, NM
Pages:	263 - 274
Cite this article:	Dickman, Jeff, Bartone, Chris G., "Antenna Techniques to Optimize Pseudorange Measurements for Ground Based Ranging Sources," Proceedings of the 57th Annual Meeting of The Institute of Navigation (2001), Albuquerque, NM, June 2001, pp. 263-274.
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