GB2480435A - Directional antenna with a leaky wave structure and a high impedance surface arrangement - Google Patents

Directional antenna with a leaky wave structure and a high impedance surface arrangement Download PDF

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Publication number
GB2480435A
GB2480435A GB201008165A GB201008165A GB2480435A GB 2480435 A GB2480435 A GB 2480435A GB 201008165 A GB201008165 A GB 201008165A GB 201008165 A GB201008165 A GB 201008165A GB 2480435 A GB2480435 A GB 2480435A
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GB
United Kingdom
Prior art keywords
antenna
vehicle
high impedance
leaky wave
periodic structure
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.)
Withdrawn
Application number
GB201008165A
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GB201008165D0 (en
Inventor
Edward James Totten
Timothy John Murphy
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.)
Selex Elsag Ltd
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Selex Elsag Ltd
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Filing date
Publication date
Application filed by Selex Elsag Ltd filed Critical Selex Elsag Ltd
Priority to GB201008165A priority Critical patent/GB2480435A/en
Publication of GB201008165D0 publication Critical patent/GB201008165D0/en
Publication of GB2480435A publication Critical patent/GB2480435A/en
Withdrawn legal-status Critical Current

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Classifications

    • HELECTRICITY
    • H01BASIC ELECTRIC ELEMENTS
    • H01QANTENNAS, i.e. RADIO AERIALS
    • H01Q1/00Details of, or arrangements associated with, antennas
    • H01Q1/27Adaptation for use in or on movable bodies
    • H01Q1/28Adaptation for use in or on aircraft, missiles, satellites, or balloons
    • H01Q1/281Nose antennas
    • HELECTRICITY
    • H01BASIC ELECTRIC ELEMENTS
    • H01QANTENNAS, i.e. RADIO AERIALS
    • H01Q13/00Waveguide horns or mouths; Slot antennas; Leaky-waveguide antennas; Equivalent structures causing radiation along the transmission path of a guided wave
    • H01Q13/20Non-resonant leaky-waveguide or transmission-line antennas; Equivalent structures causing radiation along the transmission path of a guided wave
    • H01Q13/206Microstrip transmission line antennas
    • HELECTRICITY
    • H01BASIC ELECTRIC ELEMENTS
    • H01QANTENNAS, i.e. RADIO AERIALS
    • H01Q13/00Waveguide horns or mouths; Slot antennas; Leaky-waveguide antennas; Equivalent structures causing radiation along the transmission path of a guided wave
    • H01Q13/20Non-resonant leaky-waveguide or transmission-line antennas; Equivalent structures causing radiation along the transmission path of a guided wave
    • H01Q13/28Non-resonant leaky-waveguide or transmission-line antennas; Equivalent structures causing radiation along the transmission path of a guided wave comprising elements constituting electric discontinuities and spaced in direction of wave propagation, e.g. dielectric elements or conductive elements forming artificial dielectric
    • HELECTRICITY
    • H01BASIC ELECTRIC ELEMENTS
    • H01QANTENNAS, i.e. RADIO AERIALS
    • H01Q15/00Devices for reflection, refraction, diffraction or polarisation of waves radiated from an antenna, e.g. quasi-optical devices
    • H01Q15/0006Devices acting selectively as reflecting surface, as diffracting or as refracting device, e.g. frequency filtering or angular spatial filtering devices
    • HELECTRICITY
    • H01BASIC ELECTRIC ELEMENTS
    • H01QANTENNAS, i.e. RADIO AERIALS
    • H01Q19/00Combinations of primary active antenna elements and units with secondary devices, e.g. with quasi-optical devices, for giving the antenna a desired directional characteristic
    • HELECTRICITY
    • H01BASIC ELECTRIC ELEMENTS
    • H01QANTENNAS, i.e. RADIO AERIALS
    • H01Q21/00Antenna arrays or systems
    • H01Q21/06Arrays of individually energised antenna units similarly polarised and spaced apart
    • H01Q21/061Two dimensional planar arrays
    • H01Q21/065Patch antenna array

Abstract

An antenna comprises a leaky wave periodic structure 2 and a high impedance surface 3 arranged to suppress the propagation of surface waves in unwanted directions. The antenna thereby can be used to generate a directional radiation beam. The antenna may be located on or in the body of a vehicle. The leaky periodic structure 2 may have an array of conductive patches and a ground plane 4 connected electrically and physically to a conductive body 5 of a vehicle such as the nose region of an aircraft or part of a road or sea-going vehicle. The directional antenna may provide a very low profile arrangement which can be located at the front of a vehicle without interfering with the aerodynamics of the vehicle or the vision of the vehicle driver or with other equipment associated with the vehicle. The antenna may provide a radiation beam with a maximum gain in the direction of travel of the vehicle.

Description

AN ANTENNA

This invention relates to an antenna and arose when considering a design requirement for a directional antenna to be located at the front of an aircraft and having maximum gain in the forward direction. The antenna was required to have a very low profile so that it would not interfere with the pilot's vision or the aerodynamic properties of the aircraft surface.

It is known that it is possible to make a low profile antenna using a pattern of conductive patches spaced above, but not electrically connected to, a ground plane.

This arrangement encourages propagation of electromagnetic waves across that surface at a design frequency range so that energy tends to be radiated from the edges.

Such an arrangement is called a "leaky wave structure" and it can be used as a low profile antenna having characteristics similar to a vertical dipole in that energy tends to be radiated omnidirectionally in azimuth. An example is described in Patent specification US6285325 which envisages the use of a single row of rectangular patches with a co-axial line feed. Another example is described in the paper "A low Profile Surfizce Wave Antenna Equivalent to a vertical Monopole Antenna" by Fan Yang et a! published in 2004 by the Electrical Engineering Department of the University of Ga4fornia at Los Angeles and employs a two dimensional array of conductive patches having a horizontal dipole feed.

A leaky wave structure does not provide a solution to the abovementioned problem because its omnidirectional characteristics necessarily mean that gain is not maximized in the required forward direction. Furthermore, if the structure were mounted on a conductive body of the aircraft, surface wave energy would tend to be transmitted through that body, resulting in possible interference with the aircraft's control systems and possible dangerous sparking.

An unrelated type of structure, known as a "high impedance surface," or "electromagnetic bandgap material" is described for example in patent specification W099/50929. An electromagnetic bandgap material comprises a pattern of conductors or patches supported above a ground-plane and connected electrically to it. Each adjacent pair of conductors or patches forms, with the adjacent part of the ground plane, a resonant LC circuit, presenting a high impedance at its resonant frequency. These electromagnetic bandgap materials are known principally for their ability to reflect incident electromagnetic radiation without the 180° phase change that would be expected when a conductive ground plane is used as a reflector.

Instead, within a design bandwidth (the "bandgap"), the phase change is between +90° and 9O0. Bandgap materials also have the known benefit of suppressing the propagation of electromagnetic waves across the ground-plane thus avoiding loss of energy and, in the case of phased arrays, avoiding unwanted interaction with adjacent antenna elements.

The inventors have now realised that that it is possible to combine a leaky wave periodic structure with a high impedance bandgap surface so that the latter suppresses the propagation of surface waves in unwanted directions, resulting in a low profile antenna that is also directional.

Accordingly this invention provides an antenna comprising a leaky wave periodic structure, as herein defined, and a high impedance surface, also as herein defined, the high impedance surface being arranged to suppress the propagation of surface waves in unwanted directions from the leaky wave periodic structure thereby giving directivity to the antenna.

Thus, in the invention, the high impedance surface is used principally or wholly for its effect in suppressing surface waves generated elsewhere, a function for which it has not previously been used or considered useful.

One way in which the invention may be performed will now be described by way of example with reference to the accompanying drawings in which: Fig. 1. is a perspective view of an antenna constructed in accordance with the invention; Fig. 2 is a detail of part of the antenna of Fig. 1 shown partly in cross-section through the line II -II of Fig. 1; and Fig. 3 is a schematic illustration of an aircraft carrying the antenna of Figs 1 and 2.

Referring first to Fig 1, there is shown an antenna formed from a flexible sheet 1 of dielectric material carrying, on its top surface, an array of regularly spaced square conductive patches 2. This array of patches 2 is surrounded, on three sides, by a further array of similar conductive patches 3 shown cross-hatched on the drawing.

Referring to Fig. 2 it can be seen that the underside of the dielectric sheet 1 carries a conductive ground plane layer 4 lying directly beneath the patches 2 and 3 but not connected electrically to them. The ground plane 4 is physically and electrically bonded to the body 5 of an aircraft nose. A co-axial feed line 6 is connected between the ground plane 4 and one of the patches 2 The ground plane 4, in co-operation with the patches 2 forms a "leaky wave structure" effective, at a design frequency range, to transmit or receive electromagnetic energy in the plane of the structure. Without the features now to be described, radiation would be substantially uniform in all directions in this horizontal plane.

Referring now to the patches 3, each of these is connected by a conductive post 7 to the ground plane 4 so as to produce a U-shaped electromagnetic bandgap structure surrounding the leaky wave structure on three sides. The posts 7 can be made using any conventional process for forming connections between opposite sides of circuit boards. The effect of the bandgap structure is to suppress surface waves in all directions except that in which the antenna is required to radiate or receive energy.

The inventors have found that at least three rows of patches 3 are required to achieve the optimum effect. In the illustrated embodiment, four rows are employed at each side and seven rows at the back, it being particularly important that energy should not be transmitted towards the cockpit of the aircraft..

The result is that the arrangement as shown in the drawings is effective to suppress the surface waves around three sides of the leaky wave structure so that the latter, in combination with the high impedance surface, acts as a highly directional antenna, the gain of which is greatest in just one, forward direction, as indicated schematically bythe lobe 8onFig3.

It will be appreciated that many variations to the illustrated example are possible within the scope of the accompanying claims. For example, the shape of the patches 2 and 3 need not be square but could for example be hexagonal, Maltese crosses or flat spirals. The also the illustrated arrangement of the patches 2 to form a rectangular array could be varied to form an array of different shape. In some circumstances it may be desired to design an antenna having principal lobes in more than one direction for example forward and back or side to side, in which case the patches 3 forming the high impedance surface could be arranged differently, for example just on opposite sides of the patch array 2. Finally, although the invention arose in consideration of the particular needs of an aircraft, the invention may also be useful in other environments where a low profile antenna directional is needed, for example on a road or sea-going vehicle where wind resistance needs to be minimised in electronic radio handsets where some degree of directionality is required to protect the user from radiated energy.

DEFINITIONS

In this specification the following terms shall be construed as having the following meanings.

"High impedance surface" means an electromagnetic bandgap material comprising a group of electrically conductive patches arranged above a ground plane and electrically connected to the ground plane so as to suppress propagation of electromagnetic waves across the ground plane at a design frequency range.

"Leaky wave structure" means a group of electrically conductive patches arranged above a ground plane but not electrically connected to the ground plane so as to encourage or enhance propagation of electromagnetic waves across that surface at a design frequency range.

Claims (5)

  1. CLATMS1. An antenna comprising a leaky wave periodic structure, as herein defined, and a high impedance surface, also as herein defined, the high impedance surface being arranged to suppress the propagation of surface waves in unwanted directions from the leaky wave periodic structure thereby giving directivity to the antenna.
  2. 2. An antenna according to Claim 1 located on or in the body of a vehicle.
  3. 3. An antenna according to Claim 2 characterised in that the leaky periodic structure has a ground plane connected electrically and physically to a conductive body of the vehicle.
  4. 4. An antenna according to Claim 2 characterised in that the vehicle is an aircraft and the antenna is on or in a nose of the aircraft.
  5. 5. An antenna according to any preceding Claim characterised in that the The leaky periodic structure have a shared ground plane.
GB201008165A 2010-05-17 2010-05-17 Directional antenna with a leaky wave structure and a high impedance surface arrangement Withdrawn GB2480435A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
GB201008165A GB2480435A (en) 2010-05-17 2010-05-17 Directional antenna with a leaky wave structure and a high impedance surface arrangement

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB201008165A GB2480435A (en) 2010-05-17 2010-05-17 Directional antenna with a leaky wave structure and a high impedance surface arrangement

Publications (2)

Publication Number Publication Date
GB201008165D0 GB201008165D0 (en) 2010-06-30
GB2480435A true GB2480435A (en) 2011-11-23

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Family Applications (1)

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GB201008165A Withdrawn GB2480435A (en) 2010-05-17 2010-05-17 Directional antenna with a leaky wave structure and a high impedance surface arrangement

Country Status (1)

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GB (1) GB2480435A (en)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2494435A (en) * 2011-09-08 2013-03-13 Roke Manor Research Radio communication over a transmission medium using surface waves
CN106680923A (en) * 2016-10-28 2017-05-17 西北工业大学 Multispectral infrared filter array based on micro nano grating

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6285325B1 (en) * 2000-02-16 2001-09-04 The United States Of America As Represented By The Secretary Of The Army Compact wideband microstrip antenna with leaky-wave excitation
EP1505691A2 (en) * 2003-05-12 2005-02-09 Hrl Laboratories, Llc Steerable leaky wave antenna capable of both forward and backward radiation
US20090015499A1 (en) * 2007-07-09 2009-01-15 Shinichi Kuroda Antenna Apparatus
US20090128430A1 (en) * 2001-01-25 2009-05-21 Lee Jar J Conformal end-fire arrays on high impedance ground plane

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6285325B1 (en) * 2000-02-16 2001-09-04 The United States Of America As Represented By The Secretary Of The Army Compact wideband microstrip antenna with leaky-wave excitation
US20090128430A1 (en) * 2001-01-25 2009-05-21 Lee Jar J Conformal end-fire arrays on high impedance ground plane
EP1505691A2 (en) * 2003-05-12 2005-02-09 Hrl Laboratories, Llc Steerable leaky wave antenna capable of both forward and backward radiation
US20090015499A1 (en) * 2007-07-09 2009-01-15 Shinichi Kuroda Antenna Apparatus

Non-Patent Citations (2)

* Cited by examiner, † Cited by third party
Title
H Y D Yang et al, "IEEE MTT-S Digest", 2000, pages 1521 - 1524, "Surface wave band gaps and leaky modes on integrated circuit structures with planar periodic metallic elements". *
IEEE Transactions on Antennas and Propagation, Vol.53, No.1,January 2005, A P Feresidis et al, "Artificial magnetic conductor surfaces and their application to low profile high gain planar antennas". *

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2494435A (en) * 2011-09-08 2013-03-13 Roke Manor Research Radio communication over a transmission medium using surface waves
US9337895B2 (en) 2011-09-08 2016-05-10 Roke Manor Research Limited Electromagnetic surface wave guiding medium having a first surface with coupling nodes repositionable at arbitrary locations
GB2494435B (en) * 2011-09-08 2018-10-03 Roke Manor Res Limited Apparatus for the transmission of electromagnetic waves
CN106680923A (en) * 2016-10-28 2017-05-17 西北工业大学 Multispectral infrared filter array based on micro nano grating
CN106680923B (en) * 2016-10-28 2018-11-16 西北工业大学 A kind of multispectral infrared filtering chip arrays based on micro-nano grating

Also Published As

Publication number Publication date
GB201008165D0 (en) 2010-06-30

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Free format text: REGISTERED BETWEEN 20140619 AND 20140625

WAP Application withdrawn, taken to be withdrawn or refused ** after publication under section 16(1)