WAAS Reference Receiver Measurement Performance and Tolerance in the Presence of RF Interference

Bryan R. Townsend, Karl W. Shallberg and Donald T. Cox

Abstract:	This paper characterizes the effects of RF interference on the Wide Area Augmentation System (WAAS) reference receiver. Interference has the potential to significantly degrade GPS receiver measurement accuracy, and if severe enough, can cause the receiver to not track GPS signals altogether. Careful performance evaluation such as receiver tolerance to different types of interference is critical for identifying future system upgrades. The WAAS reference receiver is actually comprised of three integrated receivers, each utilizing distinct measurement and data processing techniques (multipath estimating delay lock loop, narrow correlator, and wide correlator). These three receivers also employ an adaptive multi-bit A-D conversion process, which provides significant immunity to the effects of CW interference. Interference tests were conducted in a laboratory environment to baseline each receiver’s tolerance and measurement performance for various interference signals. Types of interference signals tested were CW, random noise waveforms (12 Hz to 12 MHz bandwidth), and pulsed. Based on these test results and analysis of WAAS Functional Verification System data, this paper also considers the utility of certain receiver measurements (AGC, C/No and A-D accumulator bins) for detecting interference events. Incorporating such a continuous RF interference monitoring capability into WAAS increases system robustness as well as aids in the investigative work associated with identifying and mitigating interference sources.
Published in:	Proceedings of the 1998 National Technical Meeting of The Institute of Navigation January 21 - 23, 1998 Westin Long Beach Hotel Long Beach, CA
Pages:	739 - 748
Cite this article:	Townsend, Bryan R., Shallberg, Karl W., Cox, Donald T., "WAAS Reference Receiver Measurement Performance and Tolerance in the Presence of RF Interference," Proceedings of the 1998 National Technical Meeting of The Institute of Navigation, Long Beach, CA, January 1998, pp. 739-748.
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