GNSS Signal Waveform Estimation with 2.4 m Dish Antenna and a Synthetic Aperture Antenna

Ronny Blum, Dominik Dötterböck, Thomas Pany

Abstract:	Ensuring high quality GNSS requires monitoring of the transmitted satellite signals. Distortions within the transmitted waveform may decrease the accuracy of the provided navigation service and indicate a satellite payload failure. Precise knowledge of the transmitted waveform also allows to use code tracking algorithms with variable early-late spacing. In general, the receiver hardware delay (or code bias) does depend on the spacing, but by precisely knowing the waveform this dependence can be computed and eliminated. The most straight forward way to monitor and estimate the transmitted GNSS waveform is the use of a high gain dish antenna which amplifies the signal above the noise level. Proper experiments have been conducted several times and have been reported in literature. The required effort is high as dish antennas require mechanical steering towards the satellite of interest and only one satellite can be monitored at a time. By using signal processing techniques, standard GNSS antennas can be used for signal waveform estimation. Exemplary techniques are known under the name Vision correlator or W-correlator and use correlation and averaging techniques. These techniques provide a similar or better gain as a dish antenna depending on the averaging time but require a known spreading code. A major drawback of using standard GNSS antennas is the effect of reflected GNSS signals onto the estimation process. Even minor multipath reflections will show up as deformations of the estimated waveform. A possible and efficient approach to remove the multipath effect on waveform estimation is the use of controlled reception pattern antennas (CRPAs). A CRPA requires multiple antenna elements whose signals are processed in pre- or post-correlation way. CRPAs can also be realized with a synthetic aperture by artificially moving the antenna along a circle. The advantage of a synthetic aperture is that only a single antenna element is involved, no electrical cross-coupling exists and that larger apertures can be realized. A disadvantage is the required clock stability during the estimation process. Instead of mechanical movement of the antenna, several antenna elements at different locations can be used in a timely sequentially way. In this work, we investigate the use of a synthetic aperture antenna (realized with mechanical motion) for GNSS waveform estimation. The synthetic aperture antenna has a rotation radius of 50 cm and a rotation speed of 1 Hz.
Published in:	Proceedings of the 30th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS+ 2017) September 25 - 29, 2017 Oregon Convention Center Portland, Oregon
Pages:	3731 - 3744
Cite this article:	Blum, Ronny, Dötterböck, Dominik, Pany, Thomas, "GNSS Signal Waveform Estimation with 2.4 m Dish Antenna and a Synthetic Aperture Antenna," Proceedings of the 30th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS+ 2017), Portland, Oregon, September 2017, pp. 3731-3744. https://doi.org/10.33012/2017.15228
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