Phase and time-difference precision direction finding system
AssigneeHughes Electronics Corporation
InventorsRick J. Lioio, Gary E. Clayton, Robert A. Deaton
Life of this patent
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Abstract
A precision direction finding system for making precision angle of arrival estimates for a signal received through two antenna elements separated in space. Phase interferometry is used to determine a precise angle of arrival, with multiple ambiguities due to the periodic nature of the phase difference related to geometric angle. The interferometric ambiguities are resolved using the time difference of arrival (TDOA) of the signal at the two antenna elements. TDOA is measured using leading edge envelope detection for simple pulsed signals, and predetection correlation for phase and frequency modulated signals.
Claims14
A precision direction finding system responsive to RF signals for determining a precise estimate of an angle of arrival (AOA) of the RF signal relative to a system antenna array, comprising:
- first and second antenna elements separated in space;
- receiver and processing apparatus responsive to first and second signals received at said first and second antenna elements, said apparatus for determining a frequency of said received signals, for determining a phase difference between corresponding phases of said first and second signals received at said first and second antenna elements, and for determining a time difference of arrival (TDOA) of said respective first and second signals at said first and second antenna elements;
- angle calculation apparatus responsive to said phase difference and said frequency for performing a phase interferometry determination of a set of multiple ambiguous estimates of said AOA, for performing a TDOA angle calculation to provide a coarse estimate of said AOA, and for selecting as a precision estimate of said AOA the ambiguous estimate which is closest to said coarse estimate.
A method for determining a precise estimate of an angle of arrival (AOA) of received RF signals relative to a antenna array of first and second antenna elements separated in space by a distance D, comprising the steps of:
- processing first and second signals at said first and second antenna elements in response to the received RF signals to determine a frequency of said received signals, to determine a phase difference between corresponding phases of said first and second signals received at said first and second antenna elements, and to determine a time difference of arrival (TDOA) of said respective first and second signals at said first and second antenna elements;
- calculating a set of multiple ambiguous estimates of said AOA using phase interferometry in response to said phase difference and said frequency;
- performing a TDOA angle calculation using said TDOA to provide a coarse estimate of said AOA;
- and
- selecting as a precision estimate of said AOA that ambiguous estimate comprising said set which is closest to said coarse estimate.
Dependencies are inferred from the claim text.