The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Apr. 20, 2004
Filed:
Apr. 24, 2003
Mark S. Asher, Ellicott City, MD (US);
Lloyd A. Linstrom, Columbia, MD (US);
Robert L. Henderson, Ellicott City, MD (US);
Dennis J. Duven, Silver Spring, MD (US);
The Johns Hopkins University, Baltimore, MD (US);
Abstract
Disclosed is a system and method for increasing the weak signal recovery capability of a Global Positioning System (GPS) receiver correlating each of the plurality of digital signals by multiplying the I and Q phases by the carrier and code, adding a location offset, accumulating the results of the correlation, and latching the results until a predetermined time; coherent combining the accumulated results at the predetermined time; non-coherent combining the coherent combined results for a time period sufficient to raise a correlation peak to a predetermined point above a noise floor to produce a plurality of non-coherent bin observables; determining a maximum value of the plurality of bin observables and comparing the maximum value to predetermined threshold; determining grid locations of bin observables having maximum values greater than the predetermined threshold; determining a bi-quadratic surface using the grid locations; determining an argument maximum of the bi-quadratic surface; estimating epoch pseudorange and Doppler variables based on the argument maximum; estimating errors in at least one of position, velocity, orientation, user clock, frequency, and ionosphere states on the estimated epoch pseudorange and Doppler variables; and determining at least one of position, velocity and orientation by correcting for the estimated errors.