Experimental Tests of Unaided Weak Signal Acquisition Methods Using a Software Receiver

G.W. Heckler, J.L. Garrison

Abstract:	A flexible software receiver, and a GPS signal recorder are used to test new methods for weak signal tracking using actual broadcast signals and a set of local oscillators each having different stabilities. A single antenna feed is split across two identical RF front ends. One front end receives a full power signal while the other is attenuated by a variable amount. The two front ends feed into two identical PCI A/D cards, which synchronously digitize and quantize their respective input signals. The front end and sample clocks are phased locked to a reference oscillator. The full strength signal is tracked using a conventional delay-lock loop (DLL) and phase lock loop (PLL) to produce a reference solution. The attenuated signal is saved for processing by a snapshot" acquisition method which can apply a very long coherent integration, across multiple, unknown, data bits. This laboratory system is used to test a recently published modification to the Double Block Zero Padding (DBZP) [1] algorithm. This Modified DBZP (MDBZP) [2] performs an organized test of possible bit edge locations and data bit combinations, while searching for a satellite in delay and Doppler. The computational efficiency of the algorithm, as implemented into a software receiver, will be studied. Trade studies, balancing acquisition threshold against the number of calculations will be used to determine the optimal coherent and incoherent integration times, and make an assessment on the feasibility of implementing this method in low cost and low power devices. Final validation of the method is obtained by comparing a 15 dB-Hz recorded signal with a synchronously recorded 45 dB-Hz signal."
Published in:	Proceedings of the 19th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2006) September 26 - 29, 2006 Fort Worth Convention Center Fort Worth, TX
Pages:	1309 - 1320
Cite this article:	Heckler, G.W., Garrison, J.L., "Experimental Tests of Unaided Weak Signal Acquisition Methods Using a Software Receiver," Proceedings of the 19th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2006), Fort Worth, TX, September 2006, pp. 1309-1320.
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