Ultra Wideband/GPS Interference Testing

Mr. Douglas A. Cummings
Research Scientist IV
Applied Research Laboratories
University of Texas at Austin

Friday, November 3rd, 3:00 PM, ENS 302

cummings@arlut.utexas.edu

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 large 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.

This presentation outlines the preliminary results of testing done at the Applied Research Laboratories, the University of Texas at Austin (ARL:UT) on the susceptibility of GPS receiver technology to UWIR transmissions. Three classes of GPS receiver technology were tested in this study: aviation, OEM, 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 test in which the GPS simulator and the UWIR signals where transmitted through coaxial cable to the GPS receivers and in "real-world" radiated tests in which the GPS receivers were tracking the GPS constellation while being subjected to UWIR radiated signals.

Biography

Douglas A. Cummings holds a BS in Electrical Engineering from Arizona State University. His professional career includes more than 8 years of telecommunications experience to include the design, installation, and evaluation of CDMA based cellular systems, as well as systems integration and test experience on the Iridium satellite communications system. He is currently the Coordinator of the Center for Ultra Wideband Research and Engineering (CURE) and a member of the Advanced Systems Division of the Applied Research Laboratories.

A list of Telecommunications and Signal Processing Seminars is available at from the ECE department Web pages under "Seminars". The Web address for the Telecommunications and Signal Processing Seminars is http://signal.ece.utexas.edu/seminars