System Identification of a GNSS Receiver's RF Filter Impulse Response Function

Mark L. Psiaki and Brady W. O'Hanlon

Abstract:	Techniques are developed to identify the net complex envelop impulse response function of a GNSS receiver's RF filters by comparing received and theoretical PRN code auto-correlation functions. This impulse response function can be used to accurately characterize PRN code distortion in a GNSS receiver for purposes of designing advanced signal processing algorithms. Such algorithms might be used in a narrow-band spoofing detector based on P(Y) code signals or in a narrow-band delay-lock loop discriminator that mitigates multi-path effects. The RF filter system identification calculations begin by computing the distorted cross-correlation between an exact replica PRN code and the received signal, as is done in a typical delay-lock loop (DLL). Many more code offsets are used than for a typical DLL, on the order of hundreds, and this off-line calibration procedure may average minutes worth of accumulation data in order to deduce highly accurate measures of the distorted cross-correlation. The distorted cross-correlation is equated to a convolution of the unknown impulse response function with the known undistorted PRN code autocorrelation function. The use of this relationship at many code offsets provides sufficient observability to estimate the nodal coefficients in a spline model of the desired impulse response function. Experimental tests of this technique have been conducted on two receiver types. The test results exhibit good self-consistency of the modeled distortions of multiple signals received by the same RF front-end. They also agree reasonably well with manufacturer data sheets for the RF front-end filters.
Published in:	Proceedings of the 24th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2011) September 20 - 23, 2011 Oregon Convention Center, Portland, Oregon Portland, OR
Pages:	3690 - 3708
Cite this article:	Psiaki, Mark L., O'Hanlon, Brady W., "System Identification of a GNSS Receiver's RF Filter Impulse Response Function," Proceedings of the 24th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2011), Portland, OR, September 2011, pp. 3690-3708.
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