System and method for tracking targets in a multipath environment
First Claim
1. A method for determining the presence of multipath conditions when tracking a target with a radar comprising the steps of:
- transmitting a first signal with an antenna having a first predetermined beamwidth and directed in a first direction towards said target;
receiving target reflected first signals with said antenna directed in said first direction;
generating a first elevation signal from said target reflected first signals;
transmitting a second signal with an antenna having a second predetermined beamwidth and directed in a second direction towards said target, said second direction being angularly offset in elevation from said first direction by a predetermined angle;
receiving target reflected second signals with said antenna directed in said second direction;
generating a second elevation signal from said target reflected second signals;
subtracting said first and second elevation signals to provide an elevation difference signal; and
generating a first signal indicative of multipath conditions at times said elevation difference signal exceeds a first predetermined value.
1 Assignment
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Accused Products
Abstract
A method and apparatus is described for determining the presence of multipath conditions when tracking a target with a radar wherein the radar includes apparatus for transmitting signals and receiving target reflected signals along two boresight reference lines angularly displaced less than one beamwidth and means for processing the target reflected signals along both boresight reference lines to provide an elevation estimate of the target by target reflected signals along both boresight reference lines and to derive the quadrature component, if any, along both boresight reference line axes. A difference in target elevation derived from target reflected signals along both boresight reference lines or the presence of a quadrature component along one or both boresight reference lines is used to determine the presence of multipath conditions and to provide signals to select one of the elevation signals for tracking or to provide an estimate of target position. The selected elevation signal may be filtered and may have a correction factor added to it.
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Citations
54 Claims
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1. A method for determining the presence of multipath conditions when tracking a target with a radar comprising the steps of:
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transmitting a first signal with an antenna having a first predetermined beamwidth and directed in a first direction towards said target; receiving target reflected first signals with said antenna directed in said first direction; generating a first elevation signal from said target reflected first signals; transmitting a second signal with an antenna having a second predetermined beamwidth and directed in a second direction towards said target, said second direction being angularly offset in elevation from said first direction by a predetermined angle; receiving target reflected second signals with said antenna directed in said second direction; generating a second elevation signal from said target reflected second signals; subtracting said first and second elevation signals to provide an elevation difference signal; and generating a first signal indicative of multipath conditions at times said elevation difference signal exceeds a first predetermined value. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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12. Apparatus for determining the presence of multipath conditions when tracking a target with a radar comprising:
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means for transmitting a first signal including an antenna having a first predetermined beamwidth and directed in a first direction towards said target; means for receiving target reflected first signals with said antenna directed in said first direction; means for generating a first elevation signal from said target reflected first signals; means for transmitting a second signal including an antenna having a second predetermined beamwidth and directed in a second direction towards said target, said second direction being angularly offset in elevation from said first direction by a predetermined angle; means for receiving target reflected second signals with said antenna directed in said second direction; means for generating a second elevation signal from said target reflected second signals; means for subtracting said first and second elevation signals to provide an elevation difference signal; and means for generating a first signal indicative of multipath conditions at times said elevation difference signal exceeds a first predetermined value. - View Dependent Claims (13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24)
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25. A method for determining the presence of multipath conditions when tracking a target with a radar, comprising the steps of:
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collecting radar echoes at two antenna positions spaced apart by a predetermined angle in elevation relative to one another; processing said radar echoes at said two antenna positions to generate at least an in-phase angle error signal at said antenna positions; converting said in-phase signals to target elevation measurements; detecting the difference between said target elevation measurements; and generating a first signal when said difference exceeds a first predetermined value to indicate a multipath condition. - View Dependent Claims (26)
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27. A system for target information processing in a multipath environment comprising:
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antenna means positioned to detect radar echoes in two beams angularly spaced a predetermined distance; a radar receiving channel for each of said antenna means; means for processing the radar echoes to generate at least in-phase signals for each channel; means for converting said in-phase signals to elevation measurements; means for detecting the difference between said elevation measurements to provide a difference signal; and means for selecting one of said radar receiving channels in accordance with said difference signal.
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28. A method for determining multiscattering conditions while tracking with a monopulse radar comprising the steps of:
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directing the boresight of an antenna at the target; radiating pulses toward the target; receiving target reflected pulses; generating a first elevation error signal with respect to the position of said antenna boresight; directing the boresight of said antenna at a predetermined angle above the target, said predetermined angle being small enough to enable illumination of the target by the main beam; radiating pulses toward the target; receiving target reflected pulses; generating a second elevation error signal with respect to the position of said antenna boresight; and comparing the difference between said first and second elevation signals to a predetermined value to generate a signal indicative of a multipath condition when said difference exceeds said predetermined value.
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29. A method of determining the position of a target comprising the steps of:
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transmitting first and second radar signals that are offset angularly in elevation from each other by a predetermined angle; generating a first elevation signal and a second elevation signal in response to target reflected signals of said first and second transmitted signals, respectively; subtracting one of said first and second elevation signals from the other to provide an elevation difference signal; comparing said difference signal to a first predetermined value to generate a first signal at times said elevation difference signal exceeds said first predetermined value; generating a first quadrature signal and a second quadrature signal in response to target reflected signals of said first and second transmitted signals, respectively; comparing said first quadrature signal with a second predetermined value and said second quadrature signal with a third predetermined value to generate a second signal at times said first quadrature signal exceeds said second predetermined value and a third signal at times said second quadrature signal exceeds said third predetermined value; and selecting one of said first and second elevation signals as the position of said target in response to said first, second and third signals. - View Dependent Claims (30, 31, 32, 33, 35, 36, 37, 38)
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34. A method of determining the position of a target comprising the steps of:
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transmitting first and second radar signals that are offset angularly in elevation from each other by a predetermined angle; generating a first elevation signal and a second elevation signal in response to target reflected signals of said first and second transmitted signals, respectively; subtracting one of said first and second elevation signals from the other to provide an elevation difference signal; comparing said difference signal to a first predetermined value to generate a first signal at times said elevation difference signal exceeds said first predetermined value; generating a first quadrature signal and a second quadrature signal in response to target reflected signals of said first and second transmitted signals, respectively; comparing said first quadrature signal with a second predetermined value and said second quadrature signal with a third predetermined value to generate a second signal at times said first quadrature signal exceeds said second predetermined value and a third signal at times said second quadrature signal exceeds said third predetermined value; generating at first times a table of elevation correction values in response to the values of said elevation difference signal, first quadrature signal and said second quadrature signal and selecting at second times an elevation correction value from said table in response to the value of said elevation difference signal, first quadrature signal and said second quadrature signal; adding said selected elevation correction value to said second elevation signal to form a third elevation signal; and selecting one of said first, second or third elevation signals as the position of said target in response to said first, second and third signals.
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39. Apparatus for determining the position of a target comprising:
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means for transmitting first and second radar signals that are offset angularly in elevation from each other by a predetermined angle; means for generating a first elevation signal and a second elevation signal in response to target reflected signals of said first and second transmitted signals, respectively; means for subtracting one of said first and second elevation signals from the other to provide an elevation difference signal; means for generating a first signal at times said elevation difference signal exceeds a first predetermined value; means for generating a first quadrature signal and a second quadrature signal in response to target reflected signals of said first and second transmitted signals, respectively; means for generating a second signal at times said first quadrature signal exceeds a second predetermined value and a third signal at times said second quadrature signal exceeds a third predetermined value; and means for selecting one of said first and second elevation signals as the position of said target in response to said first, second and third signals. - View Dependent Claims (40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 52, 53, 54)
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51. Apparatus for determining the position of a target comprising:
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means for transmitting first and second radar signals that are offset angularly in elevation from each other by a predetermined angle; means for generating a first elevation signal and a second elevation signal in response to target reflected signals of said first and second transmitted signals, respectively; means for subtracting one of said first and second elevation signals from the other to provide an elevation difference signal; means for generating a first signal at times said elevation difference signal exceeds a first predetermined value; means for generating a first quadrature signal and a second quadrature signal in response to target reflected signals of said first and second transmitted signals, respectively; means for generating a second signal at times said first quadrature signal exceeds a second predetermined value and a third signal at times said second quadrature signal exceeds a third predetermined value; means for generating at first times a table of elevation correction values in response to the values of said elevation difference signal, first quadrature signal and said second quadrature signal and for selecting at second times an elevation correction value from said table in response to the value of said elevation difference signal, first quadrature signal and said second quadrature signal; means for adding said selected elevation correction value to said second elevation signal to form a third elevation signal; and means for selecting one of said first, second or third elevation signals as the position of said target in response to said first, second and third signals.
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Specification