James W Garrison

US Patent:

7358895, Apr 15, 2008

Filed:

Aug 25, 2005

Appl. No.:

11/212125

Inventors:

Nesreen I. Ziedan - Oxford OH, US
James L. Garrison - Lafayette IN, US

Assignee:

Purdue Research Foundation - West Lafayette IN

International Classification:

G01S 1/00
H04B 7/185

US Classification:

34235712

Abstract:

A method of acquiring a weak signal includes selecting a first predetection integration time (PIT) interval for processing a digital intermediate frequency (IF) signal, selecting a number of data bit edges within the PIT, computing a plurality of coherent integrations for each data bit edge, selecting a coherent integration, which corresponds to a most likely data combination for each data bit edge, from the plurality of coherent integrations, updating an incoherent integration total for each data bit edge with the coherent integration corresponding to the selected most likely data bit combination for each data bit edge, comparing the incoherent integration total for each data bit edge with a threshold after a predetermined number of steps of the coherent integration computations and incoherent integration total updates, and identifying a code delay from the incoherent integration. The method may also include determining a code delay from an estimated Doppler shift corresponding to the identified code delay. In this method, the coherent integrations are computed using a circular correlation technique that is performed in a manner so the coherent integrations are not independent from one another in successive steps.

US Patent:

7545894, Jun 9, 2009

Filed:

Mar 21, 2005

Appl. No.:

11/087065

Inventors:

Nesreen I. Ziedan - Oxford OH, US
James L. Garrison - Lafayette IN, US

Assignee:

Purdue Research Foundation - West Lafayette IN

International Classification:

H04B 7/10

US Classification:

375347, 34042619, 34053913, 34235705, 34235706, 34235712, 701213

Abstract:

A method acquires a location system signal that includes second data signals superimposed on the first data signals. The method includes iterating Doppler frequency offset values and time offsets to generate error signals, each representing a difference between summed consecutive correlation values and a corresponding estimated ideal value. Each error signal corresponds to a different time offset and an associated time period. The second data signal has a bit edge that occurs during the time period of each of the sums of consecutive correlation values. The presence of a bit edge during an associated time period increases the error signal. A measure of the minimum error is used to identify a time offset value that is used to develop a first determined Doppler frequency offset. A Kalman filter refines the first determined Doppler frequency offset.

US Patent:

20060115022, Jun 1, 2006

Filed:

Nov 30, 2005

Appl. No.:

11/290982

Inventors:

Nesreen Ziedan - Oxford OH, US
James Garrison - Lafayette IN, US

International Classification:

H04L 27/06
G01S 5/14

US Classification:

375340000, 342357150

Abstract:

A method of acquiring a signal in a high dynamic environment includes generating a first set of acquired signal power values, the first set comprising an acquired signal power value for each Doppler bin in a plurality of Doppler bins over a first predetection integration time (PIT) interval for processing a digital signal, and generating a second set of acquired signal power values, the second set comprising an acquired signal power value for each Doppler bin in the plurality of Doppler bins over a second subsequent predetection integration time (PIT) interval for processing the digital signal. The first and the second sets are used to generate at least three additional sets of acquired signal power values. A new set of acquired power values is generated by selecting the maximum of the summations for each Doppler bin from the three additional sets, and a Doppler shift is identified from the Doppler bin having the maximum summation value that is greater than a threshold value. The output of this method may be used to initialize a first and a second extended Kalman filters for tracking a carrier signal and a code signal, respectively.