Fractal-rectangular reactive impedance surface for antenna miniaturization
Various examples are provided that are related to fractal-based reactive impedance surfaces. These surfaces allow for miniaturization of antennas. In one example, a fractal rectangular reactive impedance surface (FR-RIS) includes a plurality of fractal rectangular (FR) patches having an outer edge defined by a fractal rectangular pattern that is repeated along each side of inner FR patches of the plurality of FR patches. The fractal rectangular pattern of a FR patch matches with the fractal rectangular pattern of an adjacent FR patch. An antenna can include a planar antenna disposed over the FR-RIS.
1. An antenna, comprising:
a ground plane;
a fractal rectangular reactive impedance surface (FR-RIS) disposed over and separate from the ground plane,
wherein the FR-RIS comprises a plurality of fractal rectangular (FR) patches including a plurality of inner FR patches surrounded by a plurality of outer FR patches, wherein the plurality of outer FR patches are distributed along an outer edge of the FR-RIS,
wherein each of the plurality of inner FR patches comprises an outer edge defined by a fractal rectangular pattern that is repeated along each side of the inner FR patch and each of the plurality of the outer FR patches comprises an outer edge defined by the fractal rectangular pattern repeated along at least two sides of the outer FR patch and not repeated along at least one side of the outer FR patch, the at least one side of the outer FR patch defining a portion of the outer edge of the FR-RIS,
wherein the fractal rectangular pattern along one side of one of the plurality of FR patches matches with the fractal rectangular pattern along an adjacent side of an adjacent FR patch of the plurality of FR patches with the fractal rectangular patterns of the adjacent sides interdigitated; and
a planar antenna disposed over and separate from the FR-RIS.
2. The antenna of claim 1 , wherein the fractal rectangular pattern comprises a rectangular tab extending outward from each side of each of the plurality of inner FR patches and a corresponding rectangular recess extending inward from each side of each of the plurality of inner FR patches.
3. The antenna of claim 1 , wherein the FR-RIS comprises a gap between the fractal rectangular patterns on the adjacent sides of the adjacent FR patches of the plurality of FR patches, wherein a gap distance between the adjacent FR patches is substantially constant.
4. The antenna of claim 3 , wherein a capacitance of the FR-RIS is based at least in part upon a length of the outer edge of each of the plurality of FR patches.
5. The antenna of claim 1 , wherein the FR-RIS comprises a substrate disposed between the planar antenna and the plurality of FR patches.
6. The antenna of claim 5 , wherein the planar antenna is coupled to a feeding line that passes through the plurality of FR patches and the substrate, wherein the feeding line is not coupled to the plurality of FR patches or the ground plane.
7. The antenna of claim 6 , wherein the feeding line is a coaxial feeding line.
8. The antenna of claim 1 , wherein the plurality of FR patches are disposed on a first side of a substrate, and the ground plane is disposed on a second side of the substrate opposite the plurality of FR patches.
9. The antenna of claim 8 , wherein an inductance of the FR-RIS is based at least in part upon a distance between the ground plane and the plurality of FR patches.
10. The antenna of claim 9 , wherein the inductance of the FR-RIS is further based upon a shape of the FR patches.
11. The antenna of claim 1 , wherein the planar antenna is a patch antenna.
12. The antenna of claim 11 , wherein the patch antenna comprises a slot.
13. The antenna of claim 12 , wherein the slot is rotated with respect to the patch antenna.
14. The antenna of claim 13 , wherein the slot is rotated at an angle of 45 degrees with respect to the outer edges of the plurality of FR patches.
15. The antenna of claim 1 , wherein the outer edge of the FR-RIS defines a rectangular shape.
16. The antenna of claim 15 , wherein the rectangular shape is a square.
17. The antenna of claim 15 , wherein each of the plurality of outer FR patches are trimmed along the at least one side defining the portion of the outer edge of the FR-RIS to provide the rectangular shape.
18. The antenna of claim 15 , wherein the patch antenna disposed over the FR-RIS has a rectangular shape, wherein an outer edge of the patch antenna is substantially parallel with the outer edge of the FR-RIS.
19. The antenna of claim 18 , wherein the patch antenna is smaller than the FR-RIS.