System and method of orbital angular momentum (OAM) diverse signal processing using classical beams
First Claim
1. An apparatus, comprising:
- an orbital angular momentum (OAM) source comprising an electromagnetic (EM) source that generates an electromagnetic beam in an initial state having zero orbital angular momentum (OAM) and a first diffractive element that converts the beam into a source beam having a prescribed source state with one or more non-zero OAM components;
a tag comprising a second diffractive element on a friendly hard target, said tag matched to said OAM source to reflect the source beam to transform the non-zero OAM components of the prescribed source state to a different prescribed return state in a return beam; and
a receiver that measures the OAM components of the return beam and with knowledge of the prescribed source state of the source beam and the transformation implemented by the OAM tag compares the measured OAM components to the nonzero OAM components of the prescribed source state to identify the tag.
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Abstract
The present invention describes a system and method of OAM diverse signal processing using classical beams for applications in which OAM signal character is controlled such as optical tagging and applications in which OAM signal character is not controlled such as clutter mitigation and interference cancellation for target detection, identification etc. This is accomplished by transmitting a source beam having a prescribed state with one or more non-zero OAM components, reflecting the beam off a ‘tagged’ or ‘untagged’ target and receiving the return beam in the direct return path to measure the one or more OAM components to identify the target. OAM processing provides additional degrees of processing freedom to greatly enhance the processing capabilities to detect and identify both ‘tagged’ and ‘untagged’ targets.
22 Citations
29 Claims
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1. An apparatus, comprising:
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an orbital angular momentum (OAM) source comprising an electromagnetic (EM) source that generates an electromagnetic beam in an initial state having zero orbital angular momentum (OAM) and a first diffractive element that converts the beam into a source beam having a prescribed source state with one or more non-zero OAM components; a tag comprising a second diffractive element on a friendly hard target, said tag matched to said OAM source to reflect the source beam to transform the non-zero OAM components of the prescribed source state to a different prescribed return state in a return beam; and a receiver that measures the OAM components of the return beam and with knowledge of the prescribed source state of the source beam and the transformation implemented by the OAM tag compares the measured OAM components to the nonzero OAM components of the prescribed source state to identify the tag. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22)
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23. An apparatus comprising:
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a source that generates an electromagnetic beam in an initial state having zero orbital angular momentum (OAM); a first diffractive element that converts the beam into a source beam having a prescribed source state with one or more non-zero OAM components; a tag that reflects the source beam to control the non-zero OAM components in a return beam, wherein said tag comprises a second diffractive element that alters the one or more non-zero OAM components of the prescribed source state in a known manner; and a receiver that measures the OAM components of the return beam and compares the measured OAM components to the nonzero OAM components of the prescribed source state to identify the tag, wherein the tag is matched to the prescribed source state of the source beam such that for any deviations from the prescribed source state the OAM components in the return beam are unintelligible to the receiver.
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24. An apparatus, comprising:
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a source that generates an electromagnetic source beam having a prescribed source state with one or more non-zero OAM components; a tag that reflects the source beam to transform the non-zero OAM components to a different prescribed return state in a return beam; and a receiver in a direct return path that approximately retraces the source path, said receiver measures the OAM components of the return beam and with knowledge of the prescribed source state of the source beam and the transformation implemented by the OAM tag compares the measured OAM to the non-zero OAM components of the prescribed source state to identify the tag, wherein the tag is matched to the prescribed source state of the source beam such that for any deviations from the prescribed source state the OAM components in the return beam are unintelligible to the receiver. - View Dependent Claims (25)
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26. An apparatus, comprising:
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a plurality of sources that generate RF beams in an initial state having zero orbital angular momentum (OAM); a plurality of diffractive elements that convert respective beams passing there through into source beams each having a different prescribed source state with one or more non-zero OAM components; a multiplexer that multiplexes the source beams into a time sequence; an antenna that transmits the multiplexed source beam, said multiplexed source beam reflected off a target in a background to produce a return beam in which the OAM components are altered differently by the target and background; and a receiver in the directed reflected path of the return beam that measures the one or more OAM components of the return beam and processes the alterations of the OAM components from the different prescribed source states to discriminate the target from the background. - View Dependent Claims (27, 28)
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29. An apparatus, comprising:
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a source that generates a radio frequency (RF) beam in an initial state having zero orbital angular momentum (OAM); a plurality of different diffractive elements selected in sequence that convert the RF beam into a temporally-agile source beam having a temporally-agile prescribed source state with one or more non-zero OAM components that change with the selection of each said diffractive element, said temporally-agile source beam reflected off a target in a background to produce a temporally-agile return beam in which the OAM components are altered differently by the target and background; and a receiver in the directed reflected path of the return beam that measures the one or more OAM components of the temporally-agile return beam and processes the alterations of the OAM components from the prescribed source state to discriminate the target from the background.
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Specification