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Short baseline helicopter positioning radar for low visibility

  • US 8,354,951 B2
  • Filed: 04/28/2010
  • Issued: 01/15/2013
  • Est. Priority Date: 05/07/2009
  • Status: Active Grant
First Claim
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1. A method for determining position of an aircraft with respect to a ground station, comprising:

  • transmitting a signal from the aircraft, the signal comprising a plurality of electromagnetic signals, each signal having a different selected frequency, wherein transmission of each frequency is followed by a time interval of no transmission such that multiple path signals have decreased in amplitude by a predetermined amount;

    detecting the signals at an array of sensors disposed on the ground surface in a selected pattern, the array including at least one reference sensor and at least three spaced apart phase difference determination sensors;

    determining a difference in phase of the signals between the reference sensor and each of the phase difference determination sensors by determining a relationship between frequency and phase difference between signals detected by the reference sensor and each time difference determination sensor at each of a plurality of frequencies without using a time reference between sensors; and

    determining a spatial position of the aircraft from the time differences.

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