Metamaterials for surfaces and waveguides

• US 9,768,516 B2
• Filed: 12/04/2014
• Issued: 09/19/2017
• Est. Priority Date: 08/22/2008
• Status: Active Grant

• Current Assignee: Duke University
• Original Assignee: Duke University
• Inventors: Smith, David R., Liu, Ruopeng, Cui, Tie Jun, Cheng, Qiang, Gollub, Jonah N.
• Primary Examiner(s): Nguyen, Hoang
• Assistant Examiner(s): TRAN, HAI V
• Application Number:
  US14/560,939
• Publication Number:
  US 20150116187A1
• Time in Patent Office: 1,020 Days
• Field of Search: 343909, 343702, 343700 MS
• CPC Class Codes: H01P 1/2005 Electromagnetic photonic bandgaps [EPB], or photonic bandgaps [PBG]
• CPC Class Codes: H01P 3/081 Microstriplines
• CPC Class Codes: H01Q 15/00 Devices for reflection, refraction, diffraction or polarisation of waves radiated from an antenna, e.g. quasi-optical devices variable for purpose of altering directivity H01Q3/00; arrangements of such devices for guiding waves H01P3/20; variable for purpose of modulation H03C7/02
• CPC Class Codes: H01Q 15/0086 said selective devices having materials with a synthesized negative refractive index, e.g. metamaterials or left-handed materials
• CPC Class Codes: H01Q 15/04 comprising wave-guiding channel or channels bounded by effective conductive surfaces substantially perpendicular to the electric vector of the wave, e.g. parallel-plate waveguide lens
• CPC Class Codes: H01Q 3/44 varying the electric or magnetic characteristics of reflecting, refracting, or diffracting devices associated with the radiating element

Abstract

Complementary metamaterial elements provide an effective permittivity and/or permeability for surface structures and/or waveguide structures. The complementary metamaterial resonant elements may include Babinet complements of “split ring resonator” (SRR) and “electric LC” (ELC) metamaterial elements. In some approaches, the complementary metamaterial elements are embedded in the bounding surfaces of planar waveguides, e.g. to implement waveguide based gradient index lenses for beam steering/focusing devices, antenna array feed structures, etc.

Claims

1. An apparatus, comprising:

a waveguide;

a plurality of adjustable elements distributed along the waveguide, each having a dipolar response to a guided wave mode of the waveguide, the plurality of adjustable elements corresponding to a plurality of apertures in a bounding conducting surface of the waveguide, wherein the plurality of adjustable elements is distributed along the waveguide with a fixed subwavelength spacing sufficient to define an effective medium for the guided wave mode.

2. The apparatus of claim 1, wherein the dipolar response is a magnetic dipolar response or an electric dipole response.

3. The apparatus of claim 1, wherein the waveguide is a planar waveguide.

4. The apparatus of claim 1, wherein the waveguide is a transmission line structure.

5. The apparatus of claim 1, wherein the waveguide is a microstrip waveguide.

6. The apparatus of claim 1, wherein the adjustable elements include a nonlinear dielectric material.

7. The apparatus of claim 1, wherein the adjustable elements include lumped devices.

8. The apparatus of claim 7, wherein the lumped devices include varactors.

9. The apparatus of claim 7, wherein the lumped devices include active devices.

10. The apparatus of claim 1, wherein the adjustable elements have adjustable capacitances.

11. The apparatus of claim 10, wherein the adjustable elements include varactors and the adjustable capacitances are adjustable varactor capacitances.

12. The apparatus of claim 1, wherein the adjustable elements have narrow-band responses for frequencies in a vicinity of one or more resonance frequencies of the adjustable elements.

13. The apparatus of claim 1, wherein the plurality of adjustable elements is a plurality of adjustable metamaterial elements.

14. A method, comprising:

selecting an electromagnetic function; and

for a waveguide with a plurality of adjustable elements corresponding to a plurality of apertures in a bounding conducting surface of the waveguide, determining values of adjustable dipolar responses of the adjustable elements to provide the electromagnetic function, wherein the plurality of adjustable elements is distributed along the waveguide with a fixed subwavelength spacing sufficient to define an effective medium for a guided wave mode of the waveguide.

15. The method of claim 14, wherein the adjustable dipolar responses are functions of one or more control inputs, and the method include:

providing the one or more control inputs corresponding to the determined values of the adjustable dipolar responses.

16. The method of claim 15, wherein the adjustable elements include active devices.

17. The method of claim 16, wherein the providing of the one or more control inputs includes adjusting bias voltages for the active devices.

18. The method of claim 14, wherein the determining includes determining according to a regression analysis or with a lookup table.

19. The method of claim 14, wherein the electromagnetic function is a beam-steering or beam-focusing function.

20. The method of claim 14, wherein the plurality of adjustable elements is a plurality of adjustable metamaterial elements.

21. A system, comprising:

a control unit that includes circuitry configured to determine values of adjustable dipolar responses for a plurality of adjustable elements corresponding to a plurality of apertures in a bounding conducting surface of a waveguide, the determined values providing a selected electromagnetic function, wherein the plurality of adjustable elements is distributed along the waveguide with a fixed subwavelength spacing sufficient to define an effective medium for a guided wave mode of the waveguide.

22. The system of claim 21, wherein the selected electromagnetic function is a beam-steering or beam-focusing function.

23. The system of claim 21, wherein the adjustable dipolar responses are functions of one or more control inputs, and the circuitry is further configured to provide the one or more control inputs.

24. The system of claim 23, further comprising:

the waveguide and the plurality of adjustable elements.

25. The system of claim 24, wherein the adjustable elements include active devices.

26. The system of claim 25, wherein the one or more control inputs include bias voltage inputs for the active devices.

27. The system of claim 21, wherein the plurality of adjustable elements is a plurality of adjustable metamaterial elements.