Holographic mode conversion for electromagnetic radiation

Patent metadata

Field	Value
Publication number	US-9570812-B2
Application number	US-201514638961-A
Country	US
Kind code	B2
Filing date	Mar 4, 2015
Priority date	Mar 4, 2015
Publication date	Feb 14, 2017
Grant date	Feb 14, 2017

Abstract

The present disclosure provides systems and methods associated with mode conversion for electromagnetic field modification. A mode converting structure (holographic metamaterial) is formed with a distribution of dielectric constants chosen to convert an input electromagnetic field pattern from a first mode to a second mode to attain a target electromagnetic field pattern (near or far) that is different from the input electromagnetic field pattern. A solution to a holographic equation provides a sufficiently accurate approximation of a distribution of dielectric constants that can be used in conjunction with an electromagnetic radiation device with a known output field pattern to attain a target field pattern. A voxel-based discretization of the distribution of dielectric constants can be used to generate the mode converting structure and/or to facilitate the optimization algorithms. One or more optimization algorithms can be used to improve the efficiency of the mode conversion.

First claim

What is claimed is:

1. An apparatus, comprising:
a mode converting structure with a volumetric distribution of dielectric constants configured to be positioned relative to an electromagnetic radiation (EMR) device, to modify a field pattern of the EMR device for a finite frequency range from a first mode to a second mode,
wherein the mode converting structure is divided into a plurality of sub-wavelength voxels,
wherein each voxel has a length, width, and height, with a maximum dimension that is less than half of a wavelength of a frequency within the finite frequency range, and
wherein each voxel is assigned one of a plurality of dielectric constants to approximate the distribution of dielectric constants of the mode converting structure.

2. The apparatus of claim 1 , wherein the EMR device comprises a radio frequency (RF) antenna.

3. The apparatus of claim 1 , wherein the first mode comprises a near-field distribution corresponding to one of: a short electric dipole, a magnetic dipole, a crossed dipole, a half-wave dipole antenna, a Yagi-Uda antenna, a rectangular patch antenna, a patch over ground plane, an un-shorted rectangular waveguide opening, an open termination of a coaxial cable, an un-shorted terminus of a transmission line, a rectangular horn, a circular horn, a horn with a parabolic dish, an aperture antenna, an MSAT antenna, an aperture antenna array, an endfire antenna array, a passive phased array, an active phased array, a directional antenna, a floodlight, a spotlight, a light emitting diode (LED), an LED array, and a directional LED array.

4. The apparatus of claim 1 , wherein the second mode comprises a near-field distribution corresponding to one of: a short electric dipole, a magnetic dipole, a crossed dipole, a half-wave dipole antenna, a Yagi-Uda antenna, a rectangular patch antenna, a patch over ground plane, an un-shorted rectangular waveguide opening, an open termination of a coaxial cable, an un-shorted terminus of a transmission line, a rectangular horn, a circular horn, a horn with a parabolic dish, an aperture antenna, an MSAT antenna, an aperture antenna array, an endfire antenna array, a passive phased array, an active phased array, a directional antenna, a floodlight, a spotlight, a light emitting diode (LED), an LED array, and a directional LED array.

5. The apparatus of claim 1 , wherein the volumetric distribution is approximately homogeneous in one spatial dimension in a coordinate system, such that the volumetric distribution of the mode converting structure is effectively two-dimensional.

6. The apparatus of claim 5 , wherein the coordinate system is Cartesian, such that the volumetric distribution corresponds to a uniform extrusion of a planar two-dimensional distribution perpendicular to its plane.

7. The apparatus of claim 5 , wherein the coordinate system is cylindrical, such that the volumetric distribution corresponds to a uniform rotation of a two-dimensional planar cross section around a selected axis of revolution.

8. The apparatus of claim 1 , wherein the volumetric distribution of dielectric constants is selected based on an equation for a holographic solution.

9. The apparatus of claim 8 , wherein the volumetric distribution of dielectric constants is selected using the equation:
∈ hol ( x,y,z )−1=β E goal ·E in */|E in | 2 ,

wherein ∈ hol (x,y,z) is the volumetric distribution of dielectric constants in an x, y, z coordinate system,
wherein β is a selectable normalization constant,
wherein E in is the input field distribution of electromagnetic radiation from the EMR device on the surface of the mode converting structure relative to the x, y, z coordinate system, and
wherein E goal is the output field distribution of electromagnetic radiation from the mode converting structure relative to the x, y, z coordinate system.

10. The apparatus of claim 8 , wherein the volumetric distribution of dielectric constants is selected using the equation:
∈ hol ( x,y,z )−1=β| E goal +E in | 2 /|E in | 2 ,

wherein ∈ hol (x,y,z) is the volumetric distribution of dielectric constants in an x, y, z coordinate system,
wherein β is a selectable normalization constant,
wherein E in is the input field distribution of electromagnetic radiation from the EMR device on the surface of the mode converting structure relative to the x, y, z coordinate system, and
wherein E goal is the output field distribution of electromagnetic radiation from the mode converting structure relative to the x, y, z coordinate system.

11. The apparatus of claim 8 , wherein the volumetric distribution of dielectric constants is selected using the equation:
∈ hol ( x,y,z )−α+β E goal ·E in */|E in | 2 ,

wherein ∈ hol (x,y,z) is the volumetric distribution of dielectric constants in an x, y, z coordinate system,
wherein α and β are selectable constants,
wherein E in is the input field distribution of electromagnetic radiation from the EMR device on the surface of the mode converting structure relative to the x, y, z coordinate system,
wherein E goal is the output field distribution of electromagnetic radiation from the mode converting structure relative to the x, y, z coordinate system.

12. The apparatus of claim 11 , wherein for values of ∈ hol below a minimum threshold, the volumetric distribution of dielectric constants is set to a predetermined minimum value, ∈ min .

13. The apparatus of claim 11 , wherein for values of ∈ hol above a maximum threshold, the volumetric distribution of dielectric constants is set to a predetermined maximum value, ∈ max .

14. The apparatus of claim 1 , wherein the volumetric distribution of dielectric constants is selected using an optimization algorithm in which the dielectric constants are treated as optimizable variables.

15. The apparatus of claim 1 , wherein the mode converting structure includes a metamaterial.

16. The apparatus of claim 1 , wherein the mode converting structure comprises at least two metamaterials, wherein each of the metamaterials has a different dielectric constant.

17. The apparatus of claim 16 , wherein at least one of the metamaterials has an effective dielectric constant less than 1 for the finite frequency range.

18. The apparatus of claim 16 , wherein at least one of the metamaterials has a complex permittivity value.

19. The apparatus of claim 18 , wherein the at least one metamaterial with the complex permittivity value functions as an effective gain medium for the finite frequency range.

20. The apparatus of claim 18 , wherein the effective dielectric constant of the at least one metamaterial with the complex permittivity value has a negative imaginary part for the finite frequency range.

21. The apparatus of claim 1 , wherein at least some of the voxels are rectangular parallelepipeds.

22. The apparatus of claim 1 , wherein at least some of the voxels have more than six planar faces.

Assignees

• Elwha Llc

Inventors

• Driscoll Tom
• Hunt John Desmond
• Landy Nathan Ingle
• Smith David R
• Urzhumov Yaroslav A

Classifications

• G03H1/0808

  Methods of numerical synthesis, e.g. coherent ray tracing [CRT], diffraction specific · CPC title

• B33Y50/00

  Data acquisition or data processing for additive manufacturing · CPC title

• B33Y80/00

  Products made by additive manufacturing · CPC title

• G02B1/002 Primary

  made of materials engineered to provide properties not available in nature, e.g. metamaterials · CPC title

• G03H5/00

  Holographic processes or apparatus using particles or using waves other than those covered by groups G03H1/00 or G03H3/00 for obtaining holograms; Processes or apparatus for obtaining an optical image from them (G03H1/22 takes precedence; construction of electron microscopes H01J37/26; {investigating or analysing materials by the use of microwaves G01N22/00, by the use of particles wave or X-rays G01N23/00, G21K7/00}) · CPC title