A Novel Software Defined GNSS Receiver for Performing Detailed Signal Analysis

J. York, J. Little, S. Nelsen, O. Caldwell, D. Munton

Abstract:	We will describe the design, implementation, and capa bilities of a novel software defined GNSS receiver that builds on our previous work. Most GNSS receivers are designed to meet the needs of the PNT community and are often ill suited for supporting detailed signal analysis. Standard RF test equipment such as vector and spectrum analyzers can be used with high gain dishes to perform some analysis on the signals but are expensive and not very portable. The instrument discussed here is a GNSS receiver that is capable of supporting detailed signal analysis that bridges the gap between traditional receivers and generic test equipment. This instrument is deployed to several globally distributed sites and is being used to monitor GPS and other GNSS. The instrument is comprised of four major subsystems: a direct-sampling digital front end (DFE) [1], a correlation and tracking engine, a high-rate output engine, and a command and control system. The DFE provides direct sampling of the L-band at approximately 2 gigasamples per second, followed by real-time direct digital down conversion inside of a Field Programmable Gate Array (FPGA). The correlation and tracking engine tracks the incident civil GNSS signals using a fast number theoretic technique we have previously described [2]. We will describe each of these subsystems with an emphasis on the characteristics that make this instrument unique. The outputs of this instrument are both traditional pseudorange/phase/Doppler/CN0 observations along with a more unique set of raw complex correlation values. The correlation values are output for a large number of delays around a tracked peak value and are output at a 1 kHz rate. This unique output stream is described along with the others that this instrument produces. We finish by discussing several applications this device is currently supporting. See [3] for results from one of these applications.
Published in:	Proceedings of the 2012 International Technical Meeting of The Institute of Navigation January 30 - 1, 2012 Marriott Newport Beach Hotel & Spa Newport Beach, CA
Pages:	1910 - 1921
Cite this article:	York, J., Little, J., Nelsen, S., Caldwell, O., Munton, D., "A Novel Software Defined GNSS Receiver for Performing Detailed Signal Analysis," Proceedings of the 2012 International Technical Meeting of The Institute of Navigation, Newport Beach, CA, January 2012, pp. 1910-1921.
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