Johns Hopkins University

Robert L Henderson

Dennis J Duven

Mark S Asher

Lloyd A Linstrom

Mark A Asher

Disclosed is a system and method for reducing a bit-depth requirement for an A/D converter in a GPS receiver having an antenna for receiving an analog input signal and a low noise amplifier for amplifying the input signal, comprising a filter for filtering about a bandwidth B the amplified signal; a down-conversion module centering the frequency of the filtered signal about a center frequency f; an automatic gain controller (AGC) for setting a set point of the input signal; an adder for adding noise to the gain controlled signal, said noise based upon the bandwidth B and center frequency f; and an analog to digital (A/D) converter for converting the added noise signal to a digital signal, wherein the noise added to the gain controlled signal reduces the bit depth requirement of the A/D converter.

Bit depth reduction for analog to digital conversion in global positioning system

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.

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Ellicott City, MD, United States of America

Robert L Henderson