Artificial magnetic conductor, and antenna

1. An artificial magnetic conductor having a surface impedance greater than 100Ω, said artificial magnetic conductor comprising a ground plane, and a first frequency-selective surface that is transparent for certain wavelengths and reflective for a range of wavelengths, said first frequency-selective surface comprising an array of conductive resonant elements arranged alongside one another in at least two different directions parallel to said ground plane, wherein each conductive resonant element comprises a sub-layer of ferromagnetic material having a relative permeability greater than 10 at a frequency of 2 GHz and having a thickness less than the skin depth of said ferromagnetic material.

2. The artificial magnetic conductor of claim 1 , wherein each conductive resonant element of said first frequency-selective surface comprises a stack of sub-layers, each of said sub-layers in said stack having a thickness that is less than 10 μm in a direction at right angles to said ground plane.

3. The artificial magnetic conductor of claim 2 , wherein at least one sub-layer of each conductive resonant element comprises an antiferromagnetic sub-layer directly deposited at a location selected from the group consisting of on said ferromagnetic sub-layer and under said ferromagnetic sub-layer.

4. The artificial magnetic conductor of claim 2 , wherein at least one sub-layer of each conductive resonant element comprises a dielectric material having a relative permittivity greater than 10 at a frequency of 2 GHz.

5. The artificial magnetic conductor of claim 2 , wherein at least one sub-layer of each conductive resonant element comprises a metal sub-layer.

6. The artificial magnetic conductor of claim 5 , wherein at least one sub-layer of each conductive resonant element comprises an antiferromagnetic sub-layer directly deposited at a location selected from the group consisting of on said ferromagnetic sub-layer and under said ferromagnetic sub-layer.

7. The artificial magnetic conductor of claim 1 , further comprising at least one additional frequency-selective surface, wherein said frequency-selective surfaces of said artificial magnetic conductor are stacked one on top of the other in a direction at right angles to said ground plane, each of said frequency-selective surfaces comprising an array of conductive resonant elements arranged alongside one another in at least two different directions parallel to said ground plane and separated from one another by a layer of dielectric material having a thickness greater than 10 μm.

8. The artificial magnetic conductor of claim 7 , wherein each conductive resonant element of each of said frequency-selective surfaces is formed by at least one sub-layer of a ferromagnetic material having a relative permeability greater than 10 at a frequency of 2 GHz and having a thickness less than the skin depth of said ferromagnetic material.

9. The artificial magnetic conductor of claim 1 , wherein each conductive resonant element is electrically insulated from said ground plane by a layer of dielectric material.

10. The artificial magnetic conductor of claim 1 , wherein each conductive resonant element extends along a plane that forms an angle with said ground plane, said angle being between five degrees and forty-five degrees.

11. An antenna comprising the artificial magnetic conductor as recited in claim 1 , said artificial magnetic conductor having a resonance frequency, and a conductor suitable for radiating or for receiving electromagnetic waves at a working frequency that is between half of said resonance frequency and twice said resonance frequency, said conductor extending in a plane parallel to said artificial magnetic conductor and being separated from a closest frequency-selective surface of said artificial magnetic conductor by a distance less than one-tenth of a wavelength of an electromagnetic wave at said resonance frequency.