Three-dimensional H-fractal bandgap materials and antennas

• US 20070236406A1
• Filed: 04/05/2006
• Published: 10/11/2007
• Est. Priority Date: 04/05/2006
• Status: Active Grant

• Current Assignee: Hong Kong University of Science and Technology
• Original Assignee: Hong Kong University of Science and Technology
• Inventors: Sheng, Ping, Wen, Weijia, Hou, Bo
• Granted Patent: US 7,482,994 B2
• Time in Patent Office: Days
• US Class Current: 343/909
• CPC Class Codes: H01Q 1/36 Structural form of radiating elements, e.g. cone, spiral, umbrella; Particular materials used therewithH01Q1/08, H01Q1/14 take precedence
• CPC Class Codes: H01Q 1/40 Radiating elements coated with or embedded in protective material
• CPC Class Codes: H01Q 15/006 Selective devices having photonic band gap materials or materials of which the material properties are frequency dependent, e.g. perforated substrates, high-impedance surfaces
• CPC Class Codes: H01Q 15/0093 having a fractal shape

Abstract

A three dimensional (3D) fractal structure with H as the mother element is hereby disclosed. Such a 3D structure can act as selective total microwave reflectors or selective microwave filters in transmission. When excited through current injection, such a 3D fractal structure can act as highly efficient antenna for radiating or detecting pre-determined microwaves, with the relevant wavelength much larger than the size of the radiation or detection structure.

Claims

1. A three-dimensional (3D) bandgap material comprising a three-dimensional fractal structure, tuned to define at least one predetermined transmission bandgap.

2. A bandgap material as claimed in claim 1 wherein said fractal structure is formed of a conductive material.

3. A bandgap material as claimed in claim 2 wherein said conductive fractal structure is embedded in a dielectric material.

4. A bandgap material as claimed in claim 1 wherein said fractal structure is formed by a dielectric material embedded in a conductive material.

5. A bandgap material as claimed in claim 1 wherein the fractal structure is formed with between 2 to 15 levels.

6. A bandgap material as claimed in claim 1 wherein the fractal structure is formed by subjecting a mother element to a repeated affine transformation through the whole three dimensions, with the rule that each line segment be perpendicular to the plane formed by the two lower-level lines.

7. A bandgap material as claimed in claim 6 wherein said mother element is an H-shape and said transformation comprises scaling.

8. A bandgap material as claimed in claim 1 wherein the low-frequency limit of the bandgap(s) possessed by the material is determined by the number of levels of said fractal pattern or the length of lowest-level line.

9. A bandgap material as claimed in claim 1 comprising a conducting three-dimensional H-fractal pattern formed with at least one bandgap at a wavelength that is larger than all the dimensions of the said material.

10. A bandgap material as claimed in claim 1 wherein said fractal structure is defined by dielectric materials forming a 3D H-fractal pattern embedded in a conducting material which has at least one bandgap at a wavelength that is larger than all the dimensions of the said material.

11. A bandgap material as claimed in claim 1 wherein said fractal structure is conductive and further comprising means for injecting current into said fractal structure.

12. A bandgap material as claimed in claim 1 further comprising at least one capacitive or inductive element in said fractal structure.

13. A method of forming a bandgap composite material comprising the step of forming a 3D H-fractal structure with a mother element whose dimensions and number of levels are selected to define at least one predetermined bandgap for said composite material.

14. A method of forming a bandgap composite material as claimed in claim 13 wherein said fractal structure is formed of conductive material and further comprising providing the means for injecting a current into said fractal structure to thereby alter the electromagnetic properties of said composite material.

15. A three-dimensional fractal antenna comprising a three-dimensional conductive fractal structure.

16. An antenna as claimed in claim 15 wherein said fractal structure is formed of a metal.

17. An antenna as claimed in claim 16 wherein said fractal structure is embedded in a dielectric material.

18. An antenna as claimed in claim 15 wherein the fractal structure is formed with between 2 to 15 levels.

19. An antenna as claimed in claim 15 wherein the fractal structure is formed by subjecting a mother element to a repeated affine transformation through the whole three dimensions, with the rule that each line segment be perpendicular to the plane formed by the two lower-level lines.

20. An antenna as claimed in claim 19 wherein said mother element is an H-shape and said transformation comprises scaling.

21. An antenna as claimed in claim 15 further comprising means for injecting a current to form a 3D radiating antenna with a radiated wavelength larger than all the linear dimensions of the antenna.

22. An antenna as claimed in claim 15 further comprising a capacitive or inductive element in said fractal structure.