Quantitative Spectrum Analysis on High Latitude and Equatorial Ionosphere Scintillation

J. Wang, Y. Morton, Q. Zhou, W. Pelgrum

Abstract:	Ionosphere scintillations, often happen in both high latitude and low latitude regions, can cause significant amplitude and/or phase fluctuations of GNSS signals, which degrades GNSS signal tracking in terms of accuracy and reliability. Improvements in receiver tracking algorithms can potentially mitigate these degradations. However, a thorough understanding of the scintillations and their impact on GNSS signal propagation are prerequisite to a successful design of the required algorithms. The spectral distribution of scintillation signals provides critical information in GNSS signal receiver carrier tracking loop design. During severer ionosphere scintillation, GNSS signals experience simultaneous amplitude fading and phase fluctuation. The phase fluctuation introduces signal dynamics. Conventional GNSS signal carrier tracking loop is not designed to handle concurrent high signal dynamics and deep amplitude fading. In order to design robust tracking algorithms that can maintain lock of signals during strong ionosphere scintillation, it is necessary to gain first hand understanding of the signal dynamic range typically associated with high latitude and equatorial scintillations. Previous spectral analysis of scintillation signals are limited to simple Fourier transform of scintillation signals over the entire disturbed period. Since scintillation is a complex non-stationary phenomenon, such treatment does not capture the spectral evolution of the scintillation signal. Our recent study has demonstrated that an adaptive periodogram technique (APT) can generate high resolution time-frequency information for the scintillation signal carrier phase and signal intensity [1] [2]. By applying APT, we were able to analyze and compare the spectral characteristics of selected ionosphere scintillation data collected by our monitoring sites locating at Alaska (62.4°N), Hong Kong (22.3°N) and Singapore (1.4°N) [3][4]. Cross comparisons were conducted based on the frequency profiles at particular APT spectrum thresholds and statistical distributions of signal duration. Our case studies suggested that during large scale phase scintillation events, the high frequency components tend to have larger magnitude and last longer at high latitude regions than at low latitude and equatorial regions. The objective of this paper is to provide more evidence to support the above observation, by presenting a quantitative analysis on the spectral characteristics of both high latitude and low latitude scintillations based on the previously mentioned three data collection sites and a new site at Ascension Island (7.9°S). Ultimately, the results will be used to improve receiver tracking algorithms at each location independently.
Published in:	Proceedings of the 26th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS+ 2013) September 16 - 20, 2013 Nashville Convention Center, Nashville, Tennessee Nashville, TN
Pages:	1833 - 1839
Cite this article:	Wang, J., Morton, Y., Zhou, Q., Pelgrum, W., "Quantitative Spectrum Analysis on High Latitude and Equatorial Ionosphere Scintillation," Proceedings of the 26th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS+ 2013), Nashville, TN, September 2013, pp. 1833-1839.
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