# US 10,320,085 B1 · High efficiency short backfire antenna using anisotropic impedance walls > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 10,320,085 B1 - Document ID: US10320085B1 - Status: Granted - Kind: B1 - Application number: 14/715,500 - Filed: 2015-05-18 - Granted: 2019-06-11 - Earliest claimed: 2014-06-06 - Assignees: Lockheed Martin Corporation - Applicants: Lockheed Martin Corporation - Inventors: Erik Lier; Matthew George Bray; Thomas Henry Hand; Bonnie Gean Martin - Web page: https://patentgrep.com/patent/US10320085B1 ## CPC - H01Q 19/10: using reflecting surfaces - H01Q 15/0086: {said selective devices having materials with a synthesized negative refractive index, e.g. metamaterials or left-handed materials} - H01Q 15/244: {converting a linear polarised wave into a circular polarised wave (guided wave H01P1/17)} - H01Q 19/022: {for reducing the edge scattering of reflectors} - H01Q 19/108: {Combination of a dipole with a plane reflecting surface (H01Q19/106 takes precedence; strip line H01Q9/065)} - H01Q 19/185: wherein the surfaces are plane - H01Q 21/06: Arrays of individually energised antenna units similarly polarised and spaced apart - H01Q 21/062: {using dipole aerials; (H01Q21/067, H01Q21/068 take precedence)} - H01Q: ANTENNAS, i.e. RADIO AERIALS (radiators or antennas for microwave heating H05B6/72) ## Abstract A high efficiency short backfire antenna (SBFA) includes a cylindrical reflector and a feed structure. The conductive cylindrical reflector is configured to collect or to radiate electromagnetic waves. The cylindrical reflector has a reflector base and a reflector wall. The feed structure is electromagnetically coupled to the cylindrical reflector. The reflector wall includes a dielectric liner formed on an inside surface of the cylindrical reflector, and the dielectric liner is covered with a structured anisotropic impedance surface. ## Claims ### Claim 1 A high efficiency short backfire antenna (SBFA), the antenna comprising: a conductive cylindrical reflector configured to collect or to radiate electromagnetic waves, the cylindrical reflector having a reflector base and a reflector wall; and a feed structure electromagnetically coupled to the cylindrical reflector, wherein: the cylindrical reflector is a hollow cylinder, the feed structure comprises a hexagonal patch element assembly and a perforated hexagonal sub-reflector, the reflector base is formed in a hexagonal shape, the reflector wall includes a dielectric liner formed on an inside surface of the cylindrical reflector, and the dielectric liner is covered with a structured anisotropic impedance surface. ### Claim 2 (depends on 1) The antenna of claim 1, wherein the anisotropic impedance surface comprises an electromagnetically (EM) hard surface, wherein the dielectric liner comprises an artificial dielectric, and wherein the artificial dielectric comprises a honeycomb structure. ### Claim 3 (depends on 1) The antenna of claim 1, wherein a value for a diameter of the reflector base is within the range of approximately 1.8 to 2.2 wavelength (λ) of the electromagnetic waves. ### Claim 4 (depends on 3) The antenna of claim 3, wherein a value for a height of the reflector wall is within the range of 0.25 to 1.5λ of the electromagnetic waves. ### Claim 5 (depends on 1) The antenna of claim 1, wherein the structured anisotropic impedance surface comprises one of a corrugated, a strip-loaded, or a metamaterial surface, wherein the strip-loaded surface comprises longitudinal strips of an electrically conductive material, wherein the electrically conductive material comprises a metal, wherein the longitudinal strips are tapered. ### Claim 6 (depends on 5) The antenna of claim 5, wherein the longitudinal strips comprise rotationally symmetric longitudinal strips, wherein the longitudinal strips have a uniform width value and a uniform spacing value, wherein the uniform spacing value is larger or equal to the uniform width value. ### Claim 7 (depends on 1) The antenna of claim 1, wherein the antenna further comprises a 90° hybrid configured to convert the field between linear and circular polarization. ### Claim 8 (depends on 1) The antenna of claim 1, wherein the patch feed comprises a dual patch feed with a balun, and wherein the dual patch feed is optimized for high power handling. ### Claim 9 A method for providing a high efficiency short backfire antenna (SBFA), the method comprising: providing a conductive cylindrical reflector that is configured to collect or to radiate electromagnetic waves, the cylindrical reflector having a reflector base and a reflector wall; and providing a feed structure that is electromagnetically coupled to the cylindrical reflector, wherein: the cylindrical reflector is a hollow cylinder, the feed structure comprises a hexagonal patch element assembly and a perforated hexagonal sub-reflector, the reflector base is formed in a hexagonal shape, the reflector wall includes an inside liner, and the inside liner comprises a dielectric material and includes an anisotropic impedance surface comprising longitudinal strips. ### Claim 10 (depends on 9) The method of claim 9, wherein providing the anisotropic impedance surface comprises providing an electromagnetically (EM) hard surface, wherein the dielectric liner comprises an artificial dielectric, and wherein the artificial dielectric comprises a honeycomb structure. ### Claim 11 (depends on 9) The method of claim 9, wherein the method further comprises allowing a diameter of the reflector base vary within the range of approximately 1.8 to 2.2 wavelength (λ) of the electromagnetic waves. ### Claim 12 (depends on 11) The method of claim 11, further comprising allowing a height of the reflector wall vary within the range of 0.25 to 1.5λ of the electromagnetic waves. ### Claim 13 (depends on 9) The method of claim 9, wherein the anisotropic impedance surface comprises an electromagnetically (EM) hard surface including longitudinal strips of an electrically conductive material that are formed on the inside liner, wherein the electrically conductive material comprises a metal, wherein the longitudinal strips are tapered. ### Claim 14 (depends on 9) The method of claim 9, wherein the longitudinal strips comprise rotationally symmetric longitudinal strips, and wherein the method further comprises allowing a width of each longitudinal strip vary and a distance between two adjacent longitudinal strips vary while keeping approximately uniform widths and distances across all longitudinal strips, wherein metrics of the performance of the SBFA include an aperture efficiency of the SBFA. ### Claim 15 (depends on 9) The method of claim 9, further comprising providing a 90 hybrid configured to convert the field between linear and circular polarization. ### Claim 16 (depends on 9) The antenna of claim 9, wherein the patch feed comprises a dual patch feed with a balun, and wherein the dual patch feed is optimized for high power handling. ### Claim 17 An antenna array comprising: a plurality of high efficiency short backfire antenna (SBFA) elements, each SBFA element comprising: a conductive cylindrical reflector comprising a reflector base and a reflector wall and configured to collect or to radiate electromagnetic waves; and a feed structure electromagnetically coupled to the cylindrical reflector and configured to convert collected electromagnetic waves to an induced electrical current or to convert a feed electrical current to electromagnetic waves for transmission by the SBFA, wherein: the feed structure comprises a hexagonal patch element assembly and a perforated hexagonal sub-reflector, the cylindrical reflector is a hollow cylinder, the reflector base is formed in a hexagonal shape, the reflector wall includes a dielectric liner formed on an inside surface of the cylindrical reflector, and the dielectric liner is covered with an anisotropic impedance surface. ### Claim 18 (depends on 17) The antenna array of claim 17, wherein: the reflector base is formed in one of a circular, a hexagonal, a square, or a multi-section shape, the dielectric material comprises foam material, the anisotropic impedance surface comprises an electromagnetically (EM) hard surface including longitudinal strips of an electrically conductive material, the anisotropic impedance surface comprises a metamaterial, the electrically conductive material comprises a metal, the longitudinal strips are tapered, the longitudinal strips comprise rotationally symmetric longitudinal strips, and the SBFA elements further comprises one of a dipole, a spiral, or a patch feed structure. ### Claim 19 (depends on 17) The antenna array of claim 17, wherein: each SBFA element comprises a hexagonal element, the plurality of SBFA elements are assembled on a honeycomb structural panel configured to serve as a common ground for the antenna array, the plurality of SBFA elements comprise SBFA walls that are configured to be joined by corner posts including card guides, each SBFA wall comprises at least one of a single sided or double-sided wall, the single sided wall comprises a perforated metal wall, a dielectric foam on one side of the perforated metal wall, and a polyamide flex circuit forming the anisotropic impedance surface, the double-sided wall comprises the perforated metal wall, the dielectric foam on both sides of the perforated metal wall, and the polyamide flex circuit covering the dielectric foam from an inside of the hexagonal element.