WO2003032438A1 - Structures possedant des proprietes magnetiques - Google Patents

Structures possedant des proprietes magnetiques Download PDF

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Publication number
WO2003032438A1
WO2003032438A1 PCT/GB2002/004376 GB0204376W WO03032438A1 WO 2003032438 A1 WO2003032438 A1 WO 2003032438A1 GB 0204376 W GB0204376 W GB 0204376W WO 03032438 A1 WO03032438 A1 WO 03032438A1
Authority
WO
WIPO (PCT)
Prior art keywords
sleeve
roll
elongate means
frequency
swiss
Prior art date
Application number
PCT/GB2002/004376
Other languages
English (en)
Inventor
Michael Charles Keogh Wiltshire
Timothy Charles Steele
Original Assignee
Marconi Uk Intellectual Property Ltd
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 Marconi Uk Intellectual Property Ltd filed Critical Marconi Uk Intellectual Property Ltd
Priority to GB0406558A priority Critical patent/GB2396969A/en
Publication of WO2003032438A1 publication Critical patent/WO2003032438A1/fr

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Classifications

    • 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
    • H01Q15/006—Selective devices having photonic band gap materials or materials of which the material properties are frequency dependent, e.g. perforated substrates, high-impedance surfaces
    • 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
    • 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

Definitions

  • This invention relates to structures with magnetic properties at radio frequencies.
  • the invention particularly relates to structures comprising an array of elements having capacitance and inductance, magnetic permeability being exhibited at wavelengths greater than the spacing of the elements (Magnetism From Conductors and Enhanced Non-Linear Phenomena, J B Pendry, A J Holden, D J Robbins and W J Stewart, IEEE Transactions on Microwave Theory and Techniques, 1999, 47, 2075-2084).
  • These microstructures can be designed to show quite large positive or negative permeability in the r.f. range, for example, at MHz or GHz.
  • the elements are spaced at less than a fifth of the wavelength of the radiation at which the microstructure is resonant, but they could be spaced by greater amounts (less than one half of the resonant wavelength for example), or lesser amounts (less than one tenth, or less than one hundredth), of the resonant wavelength, for example.
  • the magnetic permeability varies with the frequency of the incoming radiation, and the use to which the structure is put often requires a predetermined magnetic permeability.
  • the structures can be used as an r.f. flux guide (WO 01/67750, WO 01/67125) which requires a positive enhanced magnetic permeability.
  • the structures can also be used as an r.f. screen (WO 01/67553, WO 01/67126), for which the magnetic permeability should be zero or negative at the frequency of interest.
  • the structures have been proposed for focussing (British Patent Application No. 0015067.2) which requires a magnetic permeability of -1.
  • the structure must be tuned to a precise value, for example, 21.3 MHz.
  • One form which the elements of such a microstructure can take is a roll of conducting sheet, the turns of which are separated by insulating material (a so-called “Swiss roll” structure). Inductance is provided by currents circulating around the curved wall of the Swiss rolls, and capacitance is provided by the self-capacitance between the inner and outer ends of the roll.
  • the r.f. frequency to which the microstructure is tuned is the frequency to which each element is tuned.
  • Figure 1 shows a Swiss roll element 1, together with a typical arrangement of the rolls in an array 2.
  • the material is designed to produce a magnetic permeability ⁇ eff to incoming radiation K normal to the axes of the rolls, the magnetic vector H of which is parallel to the axes of the rolls, according to the following formula:
  • r is the core radius
  • a lattice spacing
  • N the number of turns of the spiral.
  • the sheet resistance of the conductive layer is p, while the permittivity of the dielectric
  • interlayer is between the conducting sheets of the roll ⁇ .
  • Co is the speed of light in vacuo and ⁇ o is the
  • the frequency of the incoming r.f. radiation is ⁇ .
  • each individual element of the array should have a narrow resonant peak in the permeability, and that all these should lie at the same frequency.
  • tightness of the winding even a small variation in the layer spacing, caused by differences in the winding, can have a significant effect on the resonant frequency.
  • substrate of 12 ⁇ m of Kapton (Trade Mark)) is used to construct Swiss rolls for use in the region of 30 MHz, a spread of resonant frequency of about 10% is observed.
  • resonant element which, when arranged in an array, are suitable for forming microstructures with magnetic properties at r.f. frequency are disclosed in WO 00/41270, for example, a stack of planar loops, and the stack operates in a similar manner to the Swiss rolls. Because the planar loops can be printed, there should be less variation between the resonant peaks corresponding to each individual stack of such planar loops.
  • the invention provides a structure with magnetic properties comprising an array of elongate means having capacitance and inductance, the structure exhibiting magnetic permeability at r.f. frequencies, at least one elongate means having a sleeve extending from an end of the elongate means for tuning the elongate means to a desired r.f. frequency.
  • the sleeve or sleeves enable the elongate means to be tuned all to the same r.f. frequency or to be adjusted from one r.f. frequency to another.
  • the sleeve advantageously comprises a roll of conducting sheet, the turns of which are separated by an insulating material. This adds to, the capacitance of the elongate means to facilitate tuning.
  • the elongate means may comprise a roll of conducting sheet, the turns of which are separated by an insulating material, and such a sleeve may extend inside the roll or may surround the roll, with or without a spacer between the exterior of the roll and the interior of the sleeve, or the exterior of the sleeve and the interior of the roll.
  • the sleeve is preferably, but does not have to be, of the same material as the roll, which is usually selected for inherently desirable properties for the application in question, and the width of sleeve in the winding direction may be chosen to produce a desired adjustment in the resonant frequency.
  • the resonant frequency of an unadjusted roll can be measured by inserting it into a coil which is driven at a suitable r.f. frequency and measuring the variation of inductance and resistance with frequency. The frequency at which the resistance peaks corresponds to the resonant frequency of the roll. A particular width of sleeve may then be chosen using previous measurements to obtain the desired offset in the resonant frequency. Alternatively, the length of overlap of a given sleeve could be adjusted.
  • the invention is equally applicable to a sleeve extending down the hollow axis of a column of planar loops forming an elongate means having capacitance and inductance.
  • Figure 1 shows a known Swiss roll resonant elongate means together with an array of such Swiss rolls
  • Figure 2 shows part of a Swiss roll resonant element in axial cross-section together with a tuning sleeve which is also shown projected into an unwound position;
  • Figure 3 is a graph of relative frequency shift against sleeve width for a particular length of Swiss roll resonant element for three different overhangs of the sleeve relative to the roll; and
  • Figure 4 is a plot of the frequency distribution of one batch of Swiss rolls before and after tuning.
  • a structure with magnetic properties comprises an array of Swiss roll resonant elements such as is shown in Figure 1.
  • Each Swiss roll 1 of the array 2 comprises a roll of conducting sheet, the turns of which are separated by means of an insulating material (not shown) such that adjacent turns are separated by a radial distance d.
  • Such a microstructured material exhibits non-unity magnetic permeability at wavelengths much greater than the spacing of the element to incoming radiation K incident normal to the axes of the rolls, the magnetic vector H of which is parallel to the axes of the rolls.
  • the microstructured material can take any of the forms described in WO 00/41270 or WO 01/67549.
  • a sleeve is applied if required to an end of each Swiss roll, in order to bring its resonant frequency to a target resonant frequency, in this example, 32.3 MHz.
  • a Swiss roll is shown comprising Espanex (Trade Mark) 3 rolled onto a mandrel 4, and to one end of the roll is applied a sleeve 5 of the same material.
  • the sleeve 5 is also in the form of a roll of Espanex (Trade Mark), the sheet of Espanex (Trade Mark) having length 1, width w and overhang over the end of the Swiss roll 1-x.
  • the sleeve 5 is co-extensive with the roll 3 over a length x.
  • the width of the sleeve is selected to bring the resonant frequency to the target frequency.
  • the width necessary is established by experiments carried out using a variety of sleeves of different length, width and overhang to establish their impact on the resonant frequency.
  • the experiments were carried out using 3 different overhangs of the sleeve relative to the end of the Swiss roll i.e. the overhang 1-x being successively 15mm, 10mm and 5mm for the plots on the graph shown in Figure 3 from top to bottom, respectively.
  • each roll is fitted with a sleeve of appropriate width, if necessary, in order to tune them to the desired target frequency.
  • Figure 4 shows the frequency distribution of the 50mm rolls before and after tuning to the target frequency of 32.3 MHz. It will be noted that the spread of frequencies has been greatly reduced.
  • Adhesive is used to secure the sleeve in position.
  • the reason that the sleeve tunes the Swiss roll to which it is attached is that the capacitance of the combined structure is altered. It follows that it is not necessary for the material of the sleeve to be the same as that of the Swiss roll. Other thicknesses and types of rolls of conductor could be applied to the end, successive turns being spaced by an electrical insulator, although it will usually be found desirable to use the same material as that of the Swiss roll, because that has usually been selected for advantageous properties for the use to which the structure is to be put. There is no need for the sleeve to surround the outside of the Swiss roll, and it could in fact be inserted into the end of the Swiss roll, provided the mandrel was suitably cut away to allow this.
  • the sleeve there is no necessity for the sleeve to be in contact with the end of the Swiss roll. Insulating packing material could be wrapped around the end of the Swiss roll and the sleeve could be wound around this. Equally, if the sleeve was inserted into the end of the Swiss roll, it could be spaced from the inside thereof by a suitable spacer.
  • the length of the overhang could be adjusted instead for sleeves of a given width to produce a desired tuning adjustment.
  • the sense of winding of the sleeve has no significant effect on the tuning.
  • a second sleeve may be added to the opposite end of the roll if desired. This has an additive effect.
  • two 30mm sleeves, arranged on the two ends of the roll have the same effect as a single 60mm sleeve, arranged to have the same total overhang distance.
  • sleeves could be used with split cylinders or with columns of printed loops, both as described in WO 00/41270, although in the latter case it would probably be simpler for the sleeves to extend into the ends of the spirals, the substrate being suitably bored through.
  • the resonant elements described have been for use in the MHz region, the invention is applicable to any radio frequency including microwave, for example in the GHz region as well.

Landscapes

  • Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • Coils Or Transformers For Communication (AREA)

Abstract

L'invention se rapporte à une matière microstructurée composée d'un réseau d'éléments résonants constituant une structure de roulé, présentant une capacité et une inductance telles que la structure possède une perméabilité magnétique prédéterminée à des fréquences RF. Au moins un des moyens allongés formant un roulé, constitué d'une matière conductrice (3) enroulée de manière intercalée avec une matière isolante sur un mandrin (4), est réglé à une fréquence souhaitée par l'application d'un manchon enroulé dans la structure, à une de ses extrémités et formant un dépassement donné (x), et possède une largeur appropriée, qui peut être déterminée, par exemple, à partir des mesures de référence indiquant la largeur nécessaire pour réaliser un réglage souhaité. Il est également possible d'effectuer le réglage en sélectionnant un dépassement approprié pour une largeur de manchon donnée.
PCT/GB2002/004376 2001-10-08 2002-09-27 Structures possedant des proprietes magnetiques WO2003032438A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
GB0406558A GB2396969A (en) 2001-10-08 2002-09-27 Structures with magnetic properties

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB0124088A GB2380860A (en) 2001-10-08 2001-10-08 Structures with magnetic properties
GB0124088.6 2001-10-08

Publications (1)

Publication Number Publication Date
WO2003032438A1 true WO2003032438A1 (fr) 2003-04-17

Family

ID=9923393

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/GB2002/004376 WO2003032438A1 (fr) 2001-10-08 2002-09-27 Structures possedant des proprietes magnetiques

Country Status (2)

Country Link
GB (2) GB2380860A (fr)
WO (1) WO2003032438A1 (fr)

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0439337A2 (fr) * 1990-01-25 1991-07-31 Yoshiyuki Naito Absorbeur d'ondes à large bande
US5812080A (en) * 1995-12-27 1998-09-22 Takahashi; Michiharu Broad-band radio wave absorber
WO2000041270A1 (fr) * 1999-01-04 2000-07-13 Marconi Caswell Limited Structure dotee de proprietes magnetiques

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2360138A (en) * 2000-03-06 2001-09-12 Marconi Caswell Ltd Screens for RF magnetic flux

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0439337A2 (fr) * 1990-01-25 1991-07-31 Yoshiyuki Naito Absorbeur d'ondes à large bande
US5812080A (en) * 1995-12-27 1998-09-22 Takahashi; Michiharu Broad-band radio wave absorber
WO2000041270A1 (fr) * 1999-01-04 2000-07-13 Marconi Caswell Limited Structure dotee de proprietes magnetiques

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
SASAKI T ET AL: "Generation of homogeneous high magnetic fields within superconducting @?Swiss roll@?", CRYOGENICS, IPC SCIENCE AND TECHNOLOGY PRESS LTD. GUILDFORD, GB, vol. 35, no. 5, 1 May 1995 (1995-05-01), pages 339 - 343, XP004038164, ISSN: 0011-2275 *

Also Published As

Publication number Publication date
GB2380860A (en) 2003-04-16
GB0406558D0 (en) 2004-04-28
GB2396969A (en) 2004-07-07
GB0124088D0 (en) 2001-11-28

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