ALL-DIGITAL GPS RECEIVER MECHANIZATION

Peter C. Ould and Robert J. Van Wechel

Peer Reviewed

Abstract: This paper describes all-digital baseband correlation processing of GPS signals. The features of this highly digital mechanization are its (1) potential for improved anti-jamming (AJ) performance, (2) fast acquisition by a digital matched filter, (3) reduction of adjustment, (4) increased system reliability, and (5) provision of a basis for realization of the high degree of very large-scale integration (VLSI) potential for development of small economical GPS sets. Described are an experimental GPS receiver/digital processing system that has been operating for two years, and an improved engineering development model that is now in test. The basic technical approach consists of a broadband, fix-tuned RF converter followed by a digitizer, digital-matched-filter acquisition section; phase-and delay-lock tracking via baseband digital correlation; software acquisition logic and loop filter implementation; and all-digital implementation of the feedback numerically controlled oscillators (NCOs) and code generator. Baseband in-phase (I) and quadrature (Q) tracking is performed by an arctangent angle detector followed by a phase-unwrapping algorithm that eliminates false locks induced by sampling and data bit transitions, and yields a wide pull-in frequency range approaching one-fourth of the loop iteration frequency. Test data from the experimental unit includes basic resolution and computation noise of the digital processing, pseudorange and range-rate errors, and acquisition times for the digital matched filter.
Published in: NAVIGATION, Journal of the Institute of Navigation, Volume 28, Number 3
Pages: 178 - 188
Cite this article: Ould, Peter C., Van Wechel, Robert J., "ALL-DIGITAL GPS RECEIVER MECHANIZATION", NAVIGATION, Journal of The Institute of Navigation, Vol. 28, No. 3, Fall 1981, pp. 178-188.
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