Method for designing artificial surface impedance structures characterized by an impedance tensor with complex components
First Claim
1. A method for creating an artificial impedance surface characterized by an impedance tensor, comprising:
- selecting a desired far-field pattern for a surface;
determining design impedance values as a function of location on the surface that would produce the desired far-field pattern;
selecting a patterning shape for the surface, the patterning shape having at least one geometric characteristic; and
measuring sample tensor impedance component values for a plurality of test surfaces that have test patterning shapes that have varied measurements for the at least one geometric characteristic;
for each location on the surface,(i) determining what values of the at least one geometric characteristic would give impedance values that most closely approximate the design impedance values for that location and(ii) patterning the surface to include a unit cell with the patterning shape modified to have said at least one geometric characteristic would give impedance values that most closely approximate the design impedance values for that location.
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Abstract
A method for designing artificial impedance surfaces is disclosed. The method involves matching impedance component values required for a given far-field radiation pattern (determined, for example, by holographic means) with measured or simulated impedance component values for the units of a lattice of conductive structures used to create an artificial impedance surface, where the units of the lattice have varied geometry. For example, a unit could be a square conductive structure with a slice (removed or missing material) through it. The measured or simulated impedance components are determined by measuring wavevector values for test surfaces in three or more directions over any number of test surfaces, where each unit of a given test surface has the same geometric shape and proportions as all of the other units of that test surface, but each test surface has some form of variation in the unit geometry from the other test surfaces. These test measurements create a table of geometry vs. impedance components that are used to design the artificial impedance structure. Since polarization can be controlled, the structure can be an artificial impedance surface characterized by a tensor impedance having complex components.
76 Citations
15 Claims
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1. A method for creating an artificial impedance surface characterized by an impedance tensor, comprising:
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selecting a desired far-field pattern for a surface; determining design impedance values as a function of location on the surface that would produce the desired far-field pattern; selecting a patterning shape for the surface, the patterning shape having at least one geometric characteristic; and measuring sample tensor impedance component values for a plurality of test surfaces that have test patterning shapes that have varied measurements for the at least one geometric characteristic; for each location on the surface, (i) determining what values of the at least one geometric characteristic would give impedance values that most closely approximate the design impedance values for that location and (ii) patterning the surface to include a unit cell with the patterning shape modified to have said at least one geometric characteristic would give impedance values that most closely approximate the design impedance values for that location.
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2. A method for creating an artificial impedance surface characterized by an impedance tensor, comprising:
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selecting a lattice design for the artificial impedance surface having a plurality of unit frames; selecting, for the plurality unit frames, a surface patterning shape having at least one geometric characteristic that can be varied among the unit frames;
selecting a desired far-field pattern for the artificial impedance surface;
determining design impedance component values at each unit frame of the artificial impedance surface that would give the artificial impedance surface the desired far-field pattern;determining each of the at least one geometric characteristic as a function of sample impedance component values; for a given unit frame on the artificial impedance surface, use the at least one geometric characteristic as a function of the sample impedance component values and the design impedance component values to determine the values of the at least one geometric characteristic for said given unit frame that approximates the design impedance component values for said given unit frame; and patterning the artificial impedance surface with the surface patterning shape, varying the at least one geometric characteristic for each unit frame of the artificial impedance surface to substantially provide the desired far-field pattern. - View Dependent Claims (3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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13. An artificial impedance surface comprising:
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a dielectric base and a plurality of conductive structures on the dielectric base; wherein the plurality of conductive structures are geometrically and holographically patterned such that the artificial impedance surface is characterized by an impedance tensor with complex components. - View Dependent Claims (14, 15)
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Specification