EP3611797A1 - Structure polyedrique tessellee partiellement transparente aux signaux radiofrequence - Google Patents

Structure polyedrique tessellee partiellement transparente aux signaux radiofrequence Download PDF

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Publication number
EP3611797A1
EP3611797A1 EP18275122.2A EP18275122A EP3611797A1 EP 3611797 A1 EP3611797 A1 EP 3611797A1 EP 18275122 A EP18275122 A EP 18275122A EP 3611797 A1 EP3611797 A1 EP 3611797A1
Authority
EP
European Patent Office
Prior art keywords
polyhedral
tessellated
cells
structure according
cell
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
EP18275122.2A
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German (de)
English (en)
Inventor
designation of the inventor has not yet been filed The
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
BAE Systems PLC
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BAE Systems PLC
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by BAE Systems PLC filed Critical BAE Systems PLC
Priority to EP18275122.2A priority Critical patent/EP3611797A1/fr
Priority to PCT/GB2019/052286 priority patent/WO2020035687A1/fr
Priority to AU2019323153A priority patent/AU2019323153A1/en
Priority to EP19755958.6A priority patent/EP3837738A1/fr
Priority to US17/267,264 priority patent/US20210313673A1/en
Publication of EP3611797A1 publication Critical patent/EP3611797A1/fr
Pending legal-status Critical Current

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01Q—ANTENNAS, i.e. RADIO AERIALS
    • H01Q1/00—Details of, or arrangements associated with, antennas
    • H01Q1/42—Housings not intimately mechanically associated with radiating elements, e.g. radome
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01Q—ANTENNAS, i.e. RADIO AERIALS
    • H01Q15/00—Devices for reflection, refraction, diffraction or polarisation of waves radiated from an antenna, e.g. quasi-optical devices
    • H01Q15/0006—Devices acting selectively as reflecting surface, as diffracting or as refracting device, e.g. frequency filtering or angular spatial filtering devices
    • H01Q15/0013—Devices acting selectively as reflecting surface, as diffracting or as refracting device, e.g. frequency filtering or angular spatial filtering devices said selective devices working as frequency-selective reflecting surfaces, e.g. FSS, dichroic plates, surfaces being partly transmissive and reflective
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01Q—ANTENNAS, i.e. RADIO AERIALS
    • H01Q17/00—Devices for absorbing waves radiated from an antenna; Combinations of such devices with active antenna elements or systems
    • H01Q17/001—Devices for absorbing waves radiated from an antenna; Combinations of such devices with active antenna elements or systems for modifying the directional characteristic of an aerial

Definitions

  • the present invention relates to a structure at least partially transparent to radio frequency signals and a method of manufacturing the same.
  • RF antennas Materials for use in housings and bases for radio frequency (RF) antennas, such as radars, are known. These materials include foams and traditional honeycombs. However, foams tend to be dense and hence heavy in order to be structurally supportive. Traditional honeycombs tend to be anisotropic to RF signals, which can have a negative impact on a sensor's signal processing capability.
  • a structure at least partially transparent to radio frequency signals the structure being formed of a tessellated polyhedral material comprising a plurality of polyhedral cells.
  • Each of the plurality of polyhedral cells may be a rhombic dodecahedral.
  • each of the polyhedral cells may be a triangular prism, hexagonal prism, cube, truncated octahedron, gyrobifastigium, elongated dodecahedron, or non-self-intersecting quadrilateral prism.
  • the tessellated polyhedral material may comprise a first polyhedral cell and a second polyhedral cell, wherein the first polyhedral cell has a different shape to the second polyhedral cell.
  • the first polyhedral cell is a tetrahedron and the second polyhedral cell is an octahedron.
  • the structure may further comprise three third polyhedral cells, wherein the first polyhedral cell is an octahedron, the second polyhedral cell is a truncated octahedron and each of the three third polyhedral cells is a cube.
  • Each of the plurality of polyhedral cells may be filled with a filler material.
  • the filler material may be conductive and/or magnetic.
  • the filler material may be an insulator.
  • the filler material may be a foam or other polymer.
  • the foam or polymer may be doped with nanoscale graphitic particles, carbon nanotubes, barium hexaferrite, barium titanate or titanium dioxide.
  • each of the plurality of polyhedral cells comprises a plurality of faces and wherein each face is between 0.1mm and 4mm thick, . More preferably, each face of the plurality of polyhedral cells is between 0.3mm and 2mm thick. Even more preferably, each face of the plurality of polyhedral cells is about 0.5mm thick.
  • each of the plurality of polyhedral cells may comprise a lattice structure.
  • the structure is between 50 and 600mm thick. More preferably, the structure is between 200 and 500mm thick. Even more preferably, the structure is 300mm thick.
  • the plurality of polyhedral cells may be formed from a filament material comprising a thermoplastic polymer, a ceramic or a composite.
  • the filament material may comprise one of polyactide (PLA), Acrylonitrile Butadiene Styrene (ABS), Nylon, or Polyethylene Terephthalate (PET).
  • the filament material may be doped with conductive and/or magnetic particles, such that electrical parameters of the tessellated polyhedral material can be selected.
  • the conductive/magnetic particles may include carbon, iron, carbon nanotubes, graphene, metal-coated carbon nanotubes.
  • the structure may comprise a conductive and/or magnetic ink disposed on at least part of a surface of the tessellated polyhedral material. The surface may be the inside surface and/or the outside surface of the tessellated polyhedral material.
  • individual cells are selected to be coated in a conductive and/or magnetic ink.
  • the ink may contain iron oxide.
  • a sensor fairing comprising the structure according to the first aspect.
  • the sensor fairing may be a radome.
  • a support structure for supporting an RF antenna comprising the structure according to the first aspect.
  • a radar absorbent material being formed of a tessellated polyhedral material comprising a plurality of polyhedral cells, wherein either:
  • the radar absorbent material may be opaque to radio frequency signals.
  • a structure having a first section at least partially transparent to radio frequency signals and a second section substantially opaque to radio frequency signals, wherein the first section and second section are formed of a tessellated polyhedral material comprising a plurality of polyhedral cells.
  • the first section may comprise the structure according to the first aspect.
  • a method of manufacturing a structure at least partially transparent to RF signals comprising using fused deposition modelling to form a tessellated polyhedral material comprising a plurality of polyhedral cells from a filament material.
  • the method further may further comprise mixing conductive and/or magnetic particles with the filament material such that the electrical parameters of the tessellated polyhedral material can be selected. Additionally or alternatively, the method may comprise applying a conductive and/or magnetic ink to at least part of a surface of the tessellated polyhedral material.
  • Embodiments herein relate generally to structures for RF (radio frequency) antennas. These structures include for example housings, fairings, radomes, and casings for protecting antennas while still allowing an RF signal to be received or transmitted therethrough.
  • the structures described herein may extend around a vehicle. Part of the structure may be transparent to RF signals, while another part may be semi-transparent or even opaque to RF signals. Some structures may require an element of selective signal attenuation to prevent a vehicle or building to which the antenna is mounted affecting a signal measurement.
  • embodiments relate to materials for use in structures through which RF signals need to pass.
  • RF signals include signals with all frequencies between about 30Hz and 500GHz.
  • RF signals include microwave signals, which are signals having a frequency of between about 300MHz and 300GHz.
  • Figure 1 shows a structure 20 in the form of a radome for an aircraft, for example a fighter jet or a civilian airliner.
  • Radomes are an example of housings for protecting signal emitters/receivers (also referred to herein as antennas) 10, specifically radar emitters/receivers, from atmospheric conditions. Radomes are typically transparent to radio waves.
  • a radome is disposed on the nose of an aircraft, however, aircraft such as Airborne Early Warning and Control aircraft have radomes disposed on the tail, wing, ventral or dorsal sections of the aircraft.
  • sensors such as Magnetic Anomaly Detectors, Global Navigation Satellite System (GNSS), Wi-Fi, satellite communication or ADS-B, also require housings such as fairings to protect their signal receivers and/or transmitters (i.e. antennas) 10. It is advantageous to make housings for antennas 10 lightweight yet structurally resilient and isotropic to the frequency of the electromagnetic spectrum measured by the sensor. Anisotropic barriers result in sensor anomalies such as lensing caused by varying electrical path lengths in different directions.
  • Figure 2 shows a typical prior art material construction used in structures for housing RF antennas.
  • the material takes the form of a traditional honeycomb.
  • the traditional honeycomb is an array of hollow cells formed between thin vertical walls. The cells are often columnar and hexagonal in shape.
  • a honeycomb-shaped structure provides a material with minimal density and relative high out-of-plane compression properties and out-of-plane shear properties.
  • traditional honeycombs tend to be anisotropic to RF signal propagation.
  • a foam such as a Rohacell WF.
  • Foams tend to be isotropic to radiation, however high density foams (of the order of 150kg/m 3 ) are required to make a structure supportive or resistant to compression. This tends to make the housing relatively heavy, which is not desirable when the housing is disposed on a vehicle where weight needs to be minimised, such as an aircraft or high performance car.
  • Figure 3 shows a tessellated polyhedral structure 100 for use in forming a structure 20 according to an embodiment.
  • the tessellated polyhedral structure 100 (or polyhedral honeycomb) comprises a plurality of rhombic dodecahedra 22 (each rhombic dodecahedron being a cell).
  • the rhombic dodecahedron 22 is a convex polyhedron with twelve congruent rhombic faces.
  • the diagonals of the rhombi are in the ratio 1: ⁇ 2.
  • the rhombic dodecahedron 22 is a space-filling polyhedron.
  • the tessellated polyhedral structure 100 In the tessellated polyhedral structure 100, three cells 22 meet at each edge.
  • the tessellated polyhedral structure 100 is thus cell-transitive, face-transitive and edge-transitive; but it is not vertex-transitive, as it has two kinds of vertex.
  • the vertices with the obtuse rhombic face angles have four cells 22.
  • the vertices with the acute rhombic face angles have six cells 22.
  • a tessellated rhombic dodecahedron tends to exhibit mechanical compressive strength closer to isotropy than a traditional honeycomb. Additionally, the tessellated rhombic dodecahedron is substantially electrically isotropic. However, while tessellation of a rhombic dodecahedron is advantageous, in other embodiments different types of polyhedrons are tessellated to form the structure 20. Particularly, the structure 20 is formed of tessellated space-filling polyhedrons. For example, in one embodiment, the structure 20 is formed of a combination of tetrahedrons and octahedrons.
  • the structure 20 is formed of a combination of octahedrons, truncated octahedrons and cubes. The octahedrons, truncated octahedrons and cubes are combined in the ratio 1:1:3.
  • the structure 20 is formed of a space-filling compound of tetrahedrons and truncated tetrahedrons.
  • the structure 20 is formed of tessellated triangular prisms, tessellated hexagonal prisms, tessellated cubes, tessellated truncated octahedrons, tessellated gyrobifastigiums, tessellated elongated dodecahedrons, tessellated squashed dodecahedrons or a tessellation of any non-self-intersecting quadrilateral prism.
  • Figure 3 shows cells 22 having a plurality of faces
  • the cells 22 comprise a framework, or lattice, structure.
  • the tessellated polyhedral structure 100 is an open cell structure.
  • the outside surface of the tessellated polyhedral structure 100 is coated in a thin layer of material such as fabric, paint, quart glass or other low-loss thin material.
  • each cell 22 or selected cells 22 are filled with a filler material.
  • the filler material may be conductive and/or magnetic.
  • the filler material may be an insulator.
  • the filler material may be a foam or polymer.
  • the foam or polymer may be doped with nanoscale graphitic particles, carbon nanotubes, barium hexaferrite, barium titanate or titanium dioxide.
  • each cell 22 or selected cells 22 are formed as solid blocks.
  • the thickness of the faces of each cell 22 is about 0.5mm. That said, the thickness of each face could be between 0.1mm and 4mm.
  • the thickness of the structure 20 is between 50mm and 600mm.
  • the depth of the structure 20 from the outer most point, where it contacts the air, to the inner most point where it faces the radar antenna 10, is between 50mm and 600mm.
  • Figure 4 shows a tessellated polyhedral structure 200 according to another embodiment.
  • the cells 44 forming the tessellated polyhedral structure 200 are bitruncated cubes, or truncated octahedrons.
  • the tessellated polyhedral structure 200 is a bitruncated cubic honeycomb also known as a truncated octahedrille.
  • the transmission loss of a tessellated polyhedral structure 100 comprising a plurality of rhombic dodecahedrons tends to increase at around 12GHz. This is a result of the cell 22 size becoming approximately half a wavelength, at which point the cells 22 become resonant. Therefore, it can be advantageous to mix space-filling polyhedrons of different sizes or shapes in the same tessellated material, as this tends to increase the bandwidth of the tessellated polyhedral structure 100 and damp resonant frequencies. Smaller polyhedrons resonate at a higher frequency.
  • additive layer manufacturing is used to manufacture the tessellated polyhedral structure 100. More specifically, in one embodiment fused deposition modelling (FDM) is used to create the tessellated polyhedral structure 100.
  • FDM fused deposition modelling
  • This 3D printing technique allows the complex shapes to be printed directly. The technique also provides control over the electrical parameters of the material.
  • the tessellated polyhedral structure 100 is preferably manufactured from a filament material.
  • the filament material is a thermoplastic polymer, such as Polyactide (PLA), Acrylonitrile Butadiene Styrene (ABS), or Nylon.
  • PLA Polyactide
  • ABS Acrylonitrile Butadiene Styrene
  • Nylon Nylon
  • other materials such as ceramic and composites may be used.
  • Figure 3 shows the tessellated polyhedral structure 100 as being built of a number of distinct cells 22, this is only for ease of understanding the structure. In preferred embodiments, the tessellated polyhedral structure 100 is built up in layers, and therefore the cells 22 are integrally formed.
  • the filament material is mixed with carbon or metallic particles such as iron, before the filament material is formed into a tessellated polyhedral structure 100.
  • the structure 20 in some embodiments is a frequency selective surface.
  • an area of the structure 20 in the intended field of regard of the antenna 10 may be an RF-transparent window, while the rest of the structure 20 may be opaque to RF signals.
  • the structure in both the transparent, or partially transparent, and opaque sections of the structure 20, the structure has the same tessellated polyhedral structure 100.
  • the tessellated polyhedral structure 100 is either coated in a conductive and/or magnetic ink or made from a filament material having conductive and/or magnetic particles mixed therein.
  • the electrical properties of individual cells 22 within the tessellated polyhedral structure 100 can be adjusted by mixing (or not mixing) conductive and/or magnetic particles with the filament material. Therefore, a partially RF-transparent section of structure 20 can be constructed.
  • the filament material may also be mixed with non-conductive fibres such that the formed tessellated polyhedral structure 100 tends to have improved mechanical properties.
  • the tessellated polyhedral structure 100 is coated with a conductive and/or magnetic ink in order to introduce the electrical transmission loss. Coating may be performed after the tessellated polyhedral structure 100 is formed, or the ink may be co-disposed with each layer of the tessellated polyhedral structure 100.
  • the ink may be disposed on the inside surface of the tessellated polyhedral structure, or the outside surface.
  • the ink may contain iron oxide, for example.
  • a surface of a vehicle can be manufactured in which some areas, such as those adjacent antennas 10, are transparent to RF signals, and other areas are opaque or not transparent to RF signals.
  • Figure 5 is a comparison of the electric properties of a structure 20 made from an undoped tessellated polyhedral structure 100 according to an embodiment of the present invention, and a structure made from a traditional honeycomb.
  • the tessellated polyhedral structure 100 exhibits a roughly 4dB improvement (i.e. minimisation) of transmission loss across the frequency 6GHz to 18GHz, compared with the traditional honeycomb.
  • the improvement in transmission loss exhibited by the tessellated polyhedral structure 100 reduces at frequencies above about 12GHz.
  • the tessellated polyhedral structure 100 exhibits an about 1.5dB reduction in transmission loss.
  • the material 100 is also beneficial for making other structures related to RF antennas.
  • the material 100 may be used in a support structure onto which an RF antenna is attached.
  • the structure 20 may also be the skin of a vehicle, for example an aircraft, ship or submarine. The skin may be divided into sections, some of which may be opaque to RF signals while others are transparent or partially transparent to RF signals.

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EP18275122.2A 2018-08-16 2018-08-16 Structure polyedrique tessellee partiellement transparente aux signaux radiofrequence Pending EP3611797A1 (fr)

Priority Applications (5)

Application Number Priority Date Filing Date Title
EP18275122.2A EP3611797A1 (fr) 2018-08-16 2018-08-16 Structure polyedrique tessellee partiellement transparente aux signaux radiofrequence
PCT/GB2019/052286 WO2020035687A1 (fr) 2018-08-16 2019-08-14 Structure
AU2019323153A AU2019323153A1 (en) 2018-08-16 2019-08-14 A structure
EP19755958.6A EP3837738A1 (fr) 2018-08-16 2019-08-14 Structure
US17/267,264 US20210313673A1 (en) 2018-08-16 2019-08-14 Structure at least partially transparent to radio frequency signals

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
EP18275122.2A EP3611797A1 (fr) 2018-08-16 2018-08-16 Structure polyedrique tessellee partiellement transparente aux signaux radiofrequence

Publications (1)

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EP3611797A1 true EP3611797A1 (fr) 2020-02-19

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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN111987450A (zh) * 2020-07-31 2020-11-24 中国航空工业集团公司济南特种结构研究所 一种防护功能天线结构
FR3142121A1 (fr) * 2022-11-22 2024-05-24 Commissariat A L'energie Atomique Et Aux Energies Alternatives Pièce comportant une structure monolithique architecturée en treillis

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2005002841A1 (fr) * 2003-07-02 2005-01-13 Commonwealth Scientific And Industrial Research Organisation Materiaux dielectriques composites
GB2433842A (en) * 1995-08-02 2007-07-04 Marconi Gec Ltd An artificially structured dielectric material
US20090096687A1 (en) * 2007-03-13 2009-04-16 Richard Gentilman Methods and apparatus for high performance structures
US20170176977A1 (en) * 2015-12-22 2017-06-22 Industrial Technology Research Institute Additive manufacturing method for three-dimensional object

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2433842A (en) * 1995-08-02 2007-07-04 Marconi Gec Ltd An artificially structured dielectric material
WO2005002841A1 (fr) * 2003-07-02 2005-01-13 Commonwealth Scientific And Industrial Research Organisation Materiaux dielectriques composites
US20090096687A1 (en) * 2007-03-13 2009-04-16 Richard Gentilman Methods and apparatus for high performance structures
US20170176977A1 (en) * 2015-12-22 2017-06-22 Industrial Technology Research Institute Additive manufacturing method for three-dimensional object

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN111987450A (zh) * 2020-07-31 2020-11-24 中国航空工业集团公司济南特种结构研究所 一种防护功能天线结构
FR3142121A1 (fr) * 2022-11-22 2024-05-24 Commissariat A L'energie Atomique Et Aux Energies Alternatives Pièce comportant une structure monolithique architecturée en treillis
WO2024110498A1 (fr) * 2022-11-22 2024-05-30 Commissariat A L'energie Atomique Et Aux Energies Alternatives Pièce comportant une structure monolithique architecturée en treillis

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