Microwave antennas
First Claim
1. A dual-reflector microwave antenna comprisinga main reflector having a shape that is a portion of a paraboloid generated by revolution of a parabola around having a single, common axis of rotation and symmetry, a primary feed extending along said axis on the concave side of the main reflector and having an aperture spaced away from said main reflector, and a subreflector located beyond the end of said primary feed for reflecting radiation from the main reflector into the primary feed and for reflecting radiation from the primary feed onto the main reflector, said subreflector having an image-inverting surface configuration that has a ring focus located between the main reflector and the subreflector and extending around said axis of revolution of said paraboloid, said ring focus having a diameter at least as large as the diameter of the aperture of said primary feed.
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Abstract
A dual-reflector microwave antenna includes a main reflector having a shape that is a portion of a paraboloid generated by revolution of a parabola around having a single, common axis of rotation and symmetry. A primary feed extends along the axis of the main reflector on the concave side of the main reflector, and a subreflector located beyond the end of said primary feed has an image-inverting surface configuration that has a ring focus located between the main reflector and the subreflector and extending around the axis of the main reflector. In either a single or dual-reflector antenna, the main reflector has a shield with a band of dielectric or conductive material extending around at least a portion of the inner surface of the shield for reducing the return loss of the antenna. Patterns may be improved by providing a shield of absorber material extending around the outer periphery of at least an end portion of the primary feed. In the case of a dual-reflector antenna, return loss may be reduced by providing a dielectric or electrically conductive element between the primary feed and the subreflector, and/or by providing an annulus of absorber material on the surface of the subreflector.
320 Citations
63 Claims
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1. A dual-reflector microwave antenna comprising
a main reflector having a shape that is a portion of a paraboloid generated by revolution of a parabola around having a single, common axis of rotation and symmetry, a primary feed extending along said axis on the concave side of the main reflector and having an aperture spaced away from said main reflector, and a subreflector located beyond the end of said primary feed for reflecting radiation from the main reflector into the primary feed and for reflecting radiation from the primary feed onto the main reflector, said subreflector having an image-inverting surface configuration that has a ring focus located between the main reflector and the subreflector and extending around said axis of revolution of said paraboloid, said ring focus having a diameter at least as large as the diameter of the aperture of said primary feed.
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22. A dual reflector microwave antenna comprising
a main reflector having a shape that is a portion of at least one paraboloid and having an axis of symmetry, a primary feed extending along said axis and having an aperture spaced away from said main reflector, a subreflector located beyond the end of said primary feed for reflecting energy from said primary feed onto said main reflector, and for reflecting energy from said main reflector into said primary feed, and a dielectric or electrically conductive non-supporting disc between said primary feed and said subreflector for reducing the return loss of the antenna.
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40. A dual reflector microwave antenna comprising
a main reflector having a shape that is a portion of at least one paraboloid and having an axis of symmetry, a primary feed extending along said axis and having an aperture spaced away from said main reflector, a subreflector located beyond the end of said primary feed for reflecting energy from said primary feed onto said main reflector, and for reflecting energy from said main reflector into said primary feed, and an annulus of absorber material on the surface of said subreflector for reducing the return loss of the antenna.
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59. A reflector-type microwave antenna comprising
a reflector having a shape that is a portion of at least one paraboloid and having an axis of symmetry, a primary feed for transmitting microwave energy to and from said main reflector and having an aperture spaced away from said main reflector, and a shield of absorber material extending around the outer periphery of at least the end portion of said primary feed.
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61. A reflector-type microwave antenna comprising
a main reflector having a shape that is a portion of at least one paraboloid and having an axis of symmetry, a primary feed for transmitting microwave energy to and from said main reflector and having an aperture spaced away from said main reflector, and a shield extending around the outer periphery of said reflector and projecting from said reflector in the same direction as the energy being transmitted by said reflector from said primary feed, and a band of dielectric or electrically conductive material extending around at least a portion of the inner surface of said shield for reducing the return loss of the antenna.
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62. A dual reflector microwave antenna comprising
a main reflector having a shape that is a portion of at least one paraboloid and having an axis of symmetry, a primary feed for transmitting microwave energy to and from said main reflector and having an aperture spaced away from said main reflector, a subreflector located beyond the end of said primary feed for reflecting energy from said primary feed onto said main reflector, and for reflecting energy from said main reflector into said primary feed, said subreflector having an image-inverting surface configuration that has a ring focus located between the main reflector and the subreflector and extending around said axis of revolution of said paraboloid, said ring focus having a diameter at least as large as the diameter of the aperture of said primary feed, and a shield extending around the outer periphery of said main reflector and projecting from said main reflector in the same direction as the energy being transmitted by said main reflector from said subreflector, and pads of absorber material on the inner surface of said shield for improving the horizontal pattern of the antenna.
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63. A method of transmitting microwave signals, said method comprising
providing a main reflector having a shape that is a portion of a paraboloid generated by revolution of a parabola around having a single, common axis of rotation and symmetry, transmitting microwave signals through a primary feed extending along said axis on the concave side of the main reflector and having an aperture spaced away from said main reflector, said microwave signals being launched through said aperture, and reflecting said microwave signals launched through said aperture from a subreflector located beyond the end of said primary feed onto said main reflector, said subreflector having an image-inverting surface configuration that has a ring focus located between the main reflector and the subreflector and extending around said axis of revolution of said paraboloid, said ring focus having a diameter at least as large as the diameter of the aperture of said primary feed.
Specification