Electronically tunable microwave reflector
First Claim
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1. An electronically tunable microwave reflector, comprising:
- a ground plane, the ground plane having a ground plane surface;
an array of generally flat, circular disk metal electrodes arranged in a single layer of rows and columns in a two-dimensional lattice spaced vertically from the ground plane surface by a distance less than a wavelength of microwave energy to be reflected by the reflector, the electrodes having a diameter less than said wavelength, each of the electrodes beingadjacent to up to two of the electrodes in a same one of the rows,adjacent to up to two of the electrodes in a same one of the columns, anddiagonal to up to four of the electrodes in adjacent ones of the rows and columns;
a corresponding array of vertical three-dimensional conductor-free regions above the ground plane and between diagonal electrodes, the regions having a lattice cross-sectional area of at least one-half that of the electrodes;
a plurality of variable capacitance structures arranged for controllably varying a capacitance between adjacent ones of said electrodes;
a first array of conductors connecting a first set of the metal electrodes to the ground plane surface; and
a second array of conductors connecting a second set of the metal electrodes to respective bias voltage sources.
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Abstract
Exemplary embodiments of a structured surface are described which can efficiently reflect, steer or focus incident electromagnetic radiation. The surface impedance may be adjustable and can impart a phase shift to the incident wave using tunable electrical components of the surface. An array of electrodes interconnected by variable capacitors may be used for beam steering and phase modulation. In an exemplary embodiment, the electrodes have a circular configuration.
47 Citations
15 Claims
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1. An electronically tunable microwave reflector, comprising:
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a ground plane, the ground plane having a ground plane surface; an array of generally flat, circular disk metal electrodes arranged in a single layer of rows and columns in a two-dimensional lattice spaced vertically from the ground plane surface by a distance less than a wavelength of microwave energy to be reflected by the reflector, the electrodes having a diameter less than said wavelength, each of the electrodes being adjacent to up to two of the electrodes in a same one of the rows, adjacent to up to two of the electrodes in a same one of the columns, and diagonal to up to four of the electrodes in adjacent ones of the rows and columns; a corresponding array of vertical three-dimensional conductor-free regions above the ground plane and between diagonal electrodes, the regions having a lattice cross-sectional area of at least one-half that of the electrodes; a plurality of variable capacitance structures arranged for controllably varying a capacitance between adjacent ones of said electrodes; a first array of conductors connecting a first set of the metal electrodes to the ground plane surface; and a second array of conductors connecting a second set of the metal electrodes to respective bias voltage sources. - View Dependent Claims (2, 3, 4, 5, 6)
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7. A tunable impedance surface structure for reflecting RF energy, comprising:
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a dielectric substrate; a ground plane having a ground plane surface arranged at a lower surface of the substrate; a plurality of flat circular disk conductive electrodes arranged in a single layer of rows and columns on an upper surface of the substrate and spaced vertically from said ground plane by a distance less than a wavelength at an operating RF frequency, each of the electrodes being adjacent to up to two of the electrodes in a same one of the rows, adjacent to up to two of the electrodes in a same one of the columns, and diagonal to up to four of the electrodes in adjacent ones of the rows and columns; a corresponding plurality of vertical three-dimensional conductor-free regions above the ground plane and between diagonal electrodes, the regions having a lattice cross-sectional area of at least one-half that of the electrodes; a plurality of variable capacitance structures electrically connected between adjacent ones of the plurality of electrodes, said variable capacitance structures respectively arranged for controllably varying the capacitance between said adjacent electrodes; a first array of conductors connecting a first set of the electrodes to the ground plane surface; and a second array of conductors connecting a second set of the electrodes to respective bias voltage sources, wherein the arrangement of the plurality of conductive electrodes, the plurality of vertical conductor-free regions, and the plurality of variable capacitance structures combine to provide low edge parasitic capacitance between adjacent electrodes and capacitance tuning over a frequency range of operation. - View Dependent Claims (8, 9, 10, 11, 12)
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13. A tunable impedance surface structure for reflecting, steering, or focusing electromagnetic energy, comprising:
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an electrically conductive ground plane; a plurality of flat circular disk electrically conductive electrodes arranged in a single layer of rows and columns in a two-dimensional lattice structure spaced vertically from said ground plane by a distance less than a wavelength at an operating frequency of the electromagnetic energy, each of the electrodes being adjacent to up to two of the electrodes in a same one of the rows, adjacent to up to two of the electrodes in a same one of the columns, and diagonal to up to four of the electrodes in adjacent ones of the rows and columns; a corresponding plurality of vertical three-dimensional conductor-free regions above the ground plane and between diagonal electrodes, the regions having a lattice cross-sectional area of at least one-half that of the electrodes; and a plurality of variable capacitance structures electrically connected between adjacent ones of the plurality of electrodes, said variable capacitance structures respectively arranged for controllably varying the capacitance between said adjacent electrodes, wherein the arrangement of the plurality of conductive electrodes, the plurality of vertical conductor-free regions, and the plurality of variable capacitance structures combine to provide low edge parasitic capacitance between adjacent electrodes and capacitance tuning over a frequency range of operation, the electrodes have a diameter which is a fraction of said wavelength, and the electrodes are spaced from adjacent electrodes by a spacing distance which is less than said wavelength. - View Dependent Claims (14, 15)
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Specification