Apparatus and methods to provide a surface having a tunable emissivity

Patent metadata

Field	Value
Publication number	US-9487311-B2
Application number	US-201213342723-A
Country	US
Kind code	B2
Filing date	Jan 3, 2012
Priority date	Jan 3, 2012
Publication date	Nov 8, 2016
Grant date	Nov 8, 2016

Abstract

Apparatus and methods to provide a surface having a tunable emissivity are disclosed. An example apparatus includes an impedance layer comprising a layer of dielectric material to be attached to an electrically reflective ground plane, and a plurality of resonators arranged within the impedance layer, wherein an emissivity of the apparatus is based on a characteristic of the resonators.

First claim

What is claimed is:

1. An apparatus, comprising:
an impedance layer comprising a layer of dielectric material to be attached to an electrically reflective ground plane; and
a plurality of resonators arranged within the impedance layer, the plurality of resonators positioned a quarter-wavelength of a resonant frequency of the resonators from the electrically reflective ground plane, a first one of the plurality of resonators comprising a plurality of conductive elements;
an amorphous oxide semiconductor material in contact with the plurality of conductive elements to electrically couple the plurality of conductive elements; and
a conductive material to, when a voltage is applied to the conductive material based on an incident angle of radiation on the apparatus, adjust a resistivity of the amorphous oxide semiconductor material such that an emissivity of the apparatus changes based on the incident angle of the radiation.

2. An apparatus as defined in claim 1 , wherein the plurality of conductive elements are electrically connected via a resistive material.

3. An apparatus as defined in claim 1 , wherein the resonators are arranged to be substantially parallel to the electrically reflective ground plane.

4. An apparatus as defined in claim 1 , wherein the plurality of conductive elements are structured as an antenna, and the amorphous oxide semiconductor material is in contact with the antenna such that the amorphous oxide semiconductor material is a load on the antenna.

5. An apparatus as defined in claim 4 , wherein the conductive material is to change the load on the antenna when the voltage is applied to the conductive material.

6. An apparatus as defined in claim 1 , wherein the amorphous oxide semiconductor material comprises at least one of indium gallium zinc oxide, zinc indium oxide, or zinc tin oxide.

7. An apparatus as defined in claim 1 , wherein the amorphous oxide semiconductor material is to retain an adjusted resistivity after removal of the voltage from the conductive material.

8. An apparatus as defined in claim 1 , wherein the conductive material has a sheet resistivity of at least 40 kilo-ohms per square.

9. An apparatus as defined in claim 1 , wherein the plurality of resonators are positioned a distance from the electrically reflective ground plane, the distance being based on long wavelength infrared energy.

10. An apparatus as defined in claim 1 , further comprising an anti-reflection coating attached to the impedance layer to be opposite the electrically reflective ground plane.

11. An apparatus as defined in claim 10 , wherein the anti-reflection coating has a thickness substantially equal to one-quarter of a wavelength of interest.

12. An apparatus as defined in claim 10 , wherein the anti-reflection coating has a thickness substantially equal to a distance from the resonators to the electrically reflective ground plane.

13. A spacecraft coating, comprising:
an impedance layer comprising a layer of dielectric material to be attached to an electrically reflective surface on the spacecraft; and
a plurality of resonators arranged within the impedance layer, the plurality of resonators positioned a quarter-wavelength of a resonant frequency of the resonators from the electrically reflective surface on the spacecraft, a first one of the plurality of resonators comprising a plurality of conductive elements and having a first impedance;
a resistive material in contact with the plurality of conductive elements to electrically couple the plurality of conductive elements, the resistive material having a second impedance; and
a conductor layer to:
when a first voltage is applied to the conductor layer, adjust a resistivity of the resistive material to increase a difference between the first impedance and the second impedance to decrease an emissivity of the coating; and
when a second voltage is applied to the conductor layer, adjust the resistivity of the resistive material to reduce the difference between the first impedance and the second impedance to increase the emissivity of the coating.

14. A spacecraft coating as defined in claim 13 , wherein at least one of the first voltage or the second voltage is based on an incident angle of the spacecraft to radiation source.

15. A metamaterial having a tunable emissivity, comprising:
a plurality of resonators positioned a quarter-wavelength of a resonant frequency of the resonators from a ground plane such that energy reflected from the resonators at the resonant frequency and energy reflected from the ground plane at the resonant frequency result in destructive interference, a first one of the resonators comprising multiple physically separate conductive components;
a dielectric layer positioned between the plurality of resonators and the ground plane;
a resistive material in contact with the first one of the resonators, the resistive material to exhibit electron migration in response to an electric field to thereby change a resistivity of an electrically conductive channel connecting the multiple physically separate conductive components of the first one of the resonators; and
a conductive layer to apply the electric field to change an absorption by the first one of the resonators to thereby change an amount of destructive interference occurring within the dielectric layer.

16. A metamaterial as defined in claim 15 , wherein the first one of the resonators has a width substantially equal to one-half of a wavelength corresponding to the resonant frequency.

17. A metamaterial as defined in claim 15 , wherein the first one of the resonators comprises a crossed dipole antenna having a plurality of antenna arms.

18. A metamaterial as defined in claim 15 , wherein the electric field is to decrease a difference between a first impedance of the resistive material and an impedance value associated with the first one of the resonators to increase an emissivity of the metamaterial.

19. A metamaterial as defined in claim 15 , wherein the electric field is to increase a difference between a first impedance of the resistive material and an impedance value associated with the first one of the resonators to decrease an emissivity of the metamaterial.

20. An apparatus, comprising:
an impedance layer comprising a layer of dielectric material to be attached to an electrically reflective ground plane; and
a plurality of resonators arranged within the impedance layer, a first one of the plurality of resonators comprising a plurality of conductive elements;
an amorphous oxide semiconductor material in contact with the plurality of conductive elements to electrically couple the plurality of conductive elements; and
a conductive material to, when a voltage is applied to the conductive material based on an incident angle of radiation on the apparatus, adjust a resistivity of the amorphous oxide semiconductor material such that an emissivity of the apparatus changes based on the incident angle of the radiation, the voltage being based on the cosine of an angle between the radiation and a normal angle of an exterior surface of the apparatus, and wherein the voltage is to change the emissivity of the apparatus such that an absorption of the radiation matches an emitted radiation of the apparatus.

Assignees

• Davis Keith J
• Boeing Co

Inventors

• Davis Keith J

Classifications

• G02B1/002

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

• G02F2202/30

  Metamaterials · CPC title

• H01Q15/002

  said selective devices being reconfigurable or tunable, e.g. using switches or diodes · CPC title

• B64G1/50 Primary

  for temperature control · CPC title

• G02B5/204

  in which spectral selection is performed by means of a conductive grid or array, e.g. frequency selective surfaces (for use with wavelengths longer than the infrared light H01Q15/0006) · CPC title