Patent ID: 6724343
Filing Date: 2004-04-20
Classification: G01S

Abstract:
A system for increasing the signal recovery capability of a Global Positioning System (GPS) receiver having an antenna for receiving a plurality of GPS signals from a plurality of GPS satellites, a down converter for down-converting the plurality of received signals, and an analog-to-digital (A/D) converter for converting the plurality of down-converted signals to a plurality of digital signals, each signal being modulated by a carrier wave and coded by a unique code and having an I (in) and Q (quadrature) phase component, comprising:a correlator array for correlating each of the plurality of digital signals by multiplying the I and Q phases by the carrier wave and unique code to extract the GPS signal, adding a location offset, accumulating the results of the correlation, and latching the results until a predetermined time; a coherent combiner for coherent combining the accumulated results at the predetermined time; a non-coherent combiner for non-coherent combining the coherent combined results for a time period sufficient to raise a correlation peak to a predetermined level above a noise floor to produce a plurality of non-coherent bin observables; a correlation grid detector for 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, and determining an argument maximum of the bi-quadratic surface; a correlation grid estimator for estimating epoch pseudorange and Doppler variables based on the argument maximum; and a Kalman filter for estimating errors in at least one of position, velocity, user clock, frequency, and ionosphere states based on the estimated epoch pseudorange and Doppler variables.