Method for designing a modulated metasurface antenna structure

Patent metadata

Field	Value
Publication number	US-9685709-B2
Application number	US-201315104866-A
Country	US
Kind code	B2
Filing date	Dec 16, 2013
Priority date	Dec 16, 2013
Publication date	Jun 20, 2017
Grant date	Jun 20, 2017

Abstract

A method for designing a surface pattern for an impedance surface which results in a position-dependent target impedance of said impedance surface, and the impedance surface having the position-dependent target impedance radiates a desired first-type electromagnetic field radiation in reaction to being irradiated by a second-type electromagnetic field radiation. The method includes obtaining a first modal representation on the basis of the first-type electromagnetic field radiation in terms of a set of base modes that are chosen in accordance with a model function of the position-dependent target impedance, and obtaining a second modal representation on the basis of the second-type electromagnetic field radiation and the model function in terms of the set of base modes. The method further includes obtaining a first position-dependent quantity indicative of the position-dependent target impedance on the basis of the first modal representation and the second modal representation by determining values for a plurality of parameters of the model function for maximizing an overlap between the first modal representation and the second modal representation, and obtaining, as the surface pattern, a second position-dependent quantity indicative of geometric characteristics of the impedance surface on the basis of the first position-dependent quantity and a relationship between geometric characteristics of the impedance surface and corresponding impedance values.

First claim

The invention claimed is:

1. A method for designing a surface pattern for an impedance surface which, if provided on said impedance surface, results in a position-dependent target impedance of said impedance surface, and the impedance surface having the position-dependent target impedance radiates a desired first-type electromagnetic field radiation in reaction to being irradiated by a second-type electromagnetic field radiation, the method comprising:
determining a first modal representation on the basis of the first-type electromagnetic field radiation in terms of a set of base modes that are chosen in accordance with a model function of the position-dependent target impedance;
determining a second modal representation on the basis of the second-type electromagnetic field radiation and the model function in terms of the set of base modes;
obtaining a first position-dependent quantity indicative of the position-dependent target impedance on the basis of the first modal representation and the second modal representation by determining values for a plurality of parameters of the model function for maximizing an overlap between the first modal representation and the second modal representation; and
determining, as the surface pattern, a second position-dependent quantity indicative of geometric characteristics of the impedance surface on the basis of the first position-dependent quantity and a relationship between geometric characteristics of the impedance surface and corresponding impedance values.

2. The method according to claim 1 , wherein obtaining the first position-dependent quantity comprises:
calculating a reaction integral of the first-type electromagnetic field radiation and a third-type electromagnetic field radiation, that would be radiated by an impedance surface having a position-dependent impedance in accordance with the model function and being irradiated by the second-type electromagnetic field radiation; and
maximizing the reaction integral.

3. The method according to claim 1 , further comprising a step of partitioning the impedance surface into a plurality of elements of area,
wherein the relationship between geometric characteristics of the impedance surface and corresponding impedance values is a relationship between geometric characteristics of the elements of area and corresponding impedance values; and
wherein obtaining the second position-dependent quantity comprises, for each of the plurality of elements of area, obtaining geometric characteristics of the element of area on the basis of the first position-dependent quantity and the relationship between geometric characteristics of the elements of area and the corresponding impedance values.

4. The method according to claim 1 , further comprising:
determining the set of base modes so that each of the base modes may propagate on the impedance surface if the impedance surface is provided with a position-dependent impedance in accordance with the model function.

5. The method according to claim 2 , wherein
obtaining the first modal representation includes decomposing the first-type electromagnetic field radiation into a plurality of first modes, wherein each of the plurality of first modes corresponds to a respective one of the set of base modes; and
obtaining the second modal representation includes decomposing the third-type electromagnetic field radiation into a plurality of second modes, wherein each of the plurality of second modes corresponds to a respective one of the set of base modes.

6. The method according to claim 5 , wherein obtaining the first position-dependent quantity comprises, for each of the set of base modes for which a corresponding first mode in the plurality of first modes and a corresponding second mode in the plurality of second modes exists, calculating an outer product between the corresponding first mode and the corresponding second mode.

7. The method according to claim 1 , wherein one of the plurality of parameters of the model function relates to a period of spatial modulation of the position-dependent target impedance on the impedance surface.

8. The method according to claim 1 , wherein the model function of the position-dependent target impedance relates to a decomposition of the position-dependent target impedance into a plurality of terms, each relating to a spline wavelet.

9. The method according to claim 1 , wherein the model function of the position-dependent target impedance relates to a decomposition of the position-dependent target impedance into a plurality of products of spline wavelets and phase factors.

10. The method according to claim 1 , wherein the position-dependent target impedance is of tensorial type.

11. The method according to claim 1 , wherein the first-type electromagnetic field radiation is circularly polarized.

12. The method according to claim 1 , wherein the second-type electromagnetic field radiation is anisotropic with respect to a center of the impedance surface.

13. The method according to claim 1 , wherein the geometric characteristics of at least a subgroup of the plurality of elements of area respectively relate to a configuration of a conducting structure of predetermined shape provided on a dielectric material.

14. The method according to claim 3 , wherein the geometric characteristics of at least a subgroup of the plurality of elements of area respectively relate to a thickness of a dielectric material.

15. The method according to claim 3 , wherein the geometric characteristics of at least a subgroup of the plurality of elements of area respectively relate to a configuration of one or more openings in a metal layer.

16. The method according to claim 1 , wherein the geometric characteristics of the impedance surface relate to a thickness of a dielectric material.

17. The method according to claim 1 , further comprising:
comparing the first-type electromagnetic field radiation to a fourth-type electromagnetic field radiation would be radiated by the impedance surface provided with the determined surface pattern in reaction to being irradiated by the second-type electromagnetic field radiation;
adjusting at least one of the model function of the position-dependent target impedance and the second-type electromagnetic field radiation; and
repeating the steps according to claim 1 to obtain an adjusted surface pattern.

Assignees

• ESA

Inventors

• Sabbadini Marco
• Minatti Gabriele
• Maci Stefano
• Patrizio De Vita Paolo

Classifications

• H01Q21/24

  Combinations of antenna units polarised in different directions for transmitting or receiving circularly and elliptically polarised waves or waves linearly polarised in any direction {(circularly polarised patch antennas H01Q9/0428; circularly polarised horns H01Q13/0241; cross-polarised horns H01Q13/0258; polarisation converters H01Q15/242; cross-polarised rear feeds H01Q19/136; crossed polarisation dual antenna H01Q25/001)} · CPC title

• H01Q15/00 Primary

  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 title

• H01Q15/0066 Primary

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