Susceptibility of GPS Receiver Technology to Ultra Wideband Impulse Radio Transmissions

Miguel A. Cardoza, Douglas A. Cummings, Mark Wolf and Aaron Kerkhoff

Abstract:	GPS receivers are susceptible to RF interference from both intentional radiators and unintentional radiators. Currently the FCC Part 15 rules govern the amount of RF energy digital devices may radiate into GPS bands. These rules have provisions governing both intentional RF radiators and unintentional RF radiators. Recently (11 May 2000) the FCC has issued an NPRM, or Notice of Proposed Rulemaking to alter the current FCC Part 15 rules to allow the legal operation of ultra wideband RF devices. The term “ultra wideband” currently defines any radiated waveform whose fractional bandwidth is greater than 25%. This definition spans a number of current technologies. One subset of technologies within this broad definition is a group of technologies know as “impulse radio”. These technologies utilize short pulses of RF energy with pulse durations typically on the order of .5 to 1.5 nanoseconds with other pulse durations possible. Current Ultra Wideband Impulse Radio (UWIR) devices and systems have fractional bandwidths that can approach 100%. These systems have the potential to radiate energy into the GPS bands, thereby causing interference to GPS receivers. The nature of UWIR devices give rise to a number of commercial applications spanning high speed, secure, local area network communications capabilities, positioning capabilities for avalanche rescues, and through-wall imaging devices for law enforcement [Maney, 1999]. For DOD applications, UWIR technology has the potential to revolutionize many military applications, including communications, through-wall surveillance, obstacle avoidance, and wide area sensing, as well as its more traditional roles in mine detection [Hewish and Gourley, 1999]. This paper outlines the preliminary results of testing done by the Applied Research Laboratories, the University of Texas at Austin (ARL:UT) on the susceptibility of GPS receiver technology to UWIR transmissions. Two classes of GPS receiver technology were tested in this study: aviation and survey grade receivers. Impact on GPS performance was assessed at four stages in the GPS process: satellite acquisition, satellite retention, measurement performance, and positioning performance. A variety of tests were completed in both a scientifically controlled laboratory environment in which a GPS simulator signal combined with UWIR signals where transmitted through coaxial cable to the GPS receivers and a “real-world” radiated tests in which the GPS receivers were tracking the GPS constellation while being subjected to UWIR radiated signals. This testing has been sponsored by the Ultra Wideband Testing Consortium and the data obtained in this effort is intended to be made available to the public in order for the community to form its own responses to the NPRM.
Published in:	Proceedings of the 13th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 2000) September 19 - 22, 2000 Salt Palace Convention Center Salt Lake City, UT
Pages:	993 - 1001
Cite this article:	Cardoza, Miguel A., Cummings, Douglas A., Wolf, Mark, Kerkhoff, Aaron, "Susceptibility of GPS Receiver Technology to Ultra Wideband Impulse Radio Transmissions," Proceedings of the 13th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 2000), Salt Lake City, UT, September 2000, pp. 993-1001.
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