EP2267838A2 - Raumfüllende Miniaturantennen - Google Patents

Raumfüllende Miniaturantennen Download PDF

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Publication number
EP2267838A2
EP2267838A2 EP10180798A EP10180798A EP2267838A2 EP 2267838 A2 EP2267838 A2 EP 2267838A2 EP 10180798 A EP10180798 A EP 10180798A EP 10180798 A EP10180798 A EP 10180798A EP 2267838 A2 EP2267838 A2 EP 2267838A2
Authority
EP
European Patent Office
Prior art keywords
network
antenna
sfc
curve
slot
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Withdrawn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
EP10180798A
Other languages
English (en)
French (fr)
Other versions
EP2267838A3 (de
Inventor
Carles Puente Baliarda
Edouard Jean Louis Rozan
Jaime Anguera Pros
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.)
Fractus SA
Original Assignee
Fractus SA
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 Fractus SA filed Critical Fractus SA
Priority claimed from EP05012854A external-priority patent/EP1592083B1/de
Publication of EP2267838A2 publication Critical patent/EP2267838A2/de
Publication of EP2267838A3 publication Critical patent/EP2267838A3/de
Withdrawn legal-status Critical Current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
    • H01Q1/12—Supports; Mounting means
    • H01Q1/22—Supports; Mounting means by structural association with other equipment or articles
    • H01Q1/24—Supports; Mounting means by structural association with other equipment or articles with receiving set
    • H01Q1/241—Supports; Mounting means by structural association with other equipment or articles with receiving set used in mobile communications, e.g. GSM
    • H01Q1/242—Supports; Mounting means by structural association with other equipment or articles with receiving set used in mobile communications, e.g. GSM specially adapted for hand-held use
    • H01Q1/243—Supports; Mounting means by structural association with other equipment or articles with receiving set used in mobile communications, e.g. GSM specially adapted for hand-held use with built-in antennas
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01Q—ANTENNAS, i.e. RADIO AERIALS
    • H01Q1/00—Details of, or arrangements associated with, antennas
    • H01Q1/12—Supports; Mounting means
    • H01Q1/22—Supports; Mounting means by structural association with other equipment or articles
    • H01Q1/24—Supports; Mounting means by structural association with other equipment or articles with receiving set
    • H01Q1/241—Supports; Mounting means by structural association with other equipment or articles with receiving set used in mobile communications, e.g. GSM
    • H01Q1/246—Supports; Mounting means by structural association with other equipment or articles with receiving set used in mobile communications, e.g. GSM specially adapted for base stations
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01Q—ANTENNAS, i.e. RADIO AERIALS
    • H01Q1/00—Details of, or arrangements associated with, antennas
    • H01Q1/36—Structural form of radiating elements, e.g. cone, spiral, umbrella; Particular materials used therewith
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01Q—ANTENNAS, i.e. RADIO AERIALS
    • H01Q1/00—Details of, or arrangements associated with, antennas
    • H01Q1/36—Structural form of radiating elements, e.g. cone, spiral, umbrella; Particular materials used therewith
    • H01Q1/38—Structural form of radiating elements, e.g. cone, spiral, umbrella; Particular materials used therewith formed by a conductive layer on an insulating support
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01Q—ANTENNAS, i.e. RADIO AERIALS
    • H01Q9/00—Electrically-short antennas having dimensions not more than twice the operating wavelength and consisting of conductive active radiating elements
    • H01Q9/04—Resonant antennas
    • H01Q9/0407—Substantially flat resonant element parallel to ground plane, e.g. patch antenna

Definitions

  • the present invention generally refers to a new family of antennas of reduced size based on an innovative geometry, the geometry of the curves named as Space-Filling Curves (SFC).
  • An antenna is said to be a small antenna (a miniature antenna) when it can be fitted in a small space compared to the operating wavelength. More precisely, the radiansphere is taken as the reference for classifying an antenna as being small.
  • the radiansphere is an imaginary sphere of radius equal to the operating wavelength divided by two times ⁇ ; an antenna is said to be small in terms of the wavelength when it can be fitted inside said radiansphere.
  • a novel geometry the geometry of Space-Filling Curves (SFC) is defined in the present invention and it is used to shape a part of an antenna.
  • SFC Space-Filling Curves
  • the invention is applicable to the field of the telecommunications and more concretely to the design of antennas with reduced size.
  • a small antenna features a large input reactance (either capacitive or inductive) that usually has to be compensated with an external matching/loading circuit or structure. It also means that is difficult to pack a resonant antenna into a space which is small in terms of the wavelength at resonance. Other characteristics of a small antenna are its small radiating resistance and its low efficiency.
  • SFC Space-Filling Curves
  • the dimension (D) is often used to characterize highly complex geometrical curves and structures such those described in the present invention.
  • the box-counting dimension (which is well-known to those skilled in mathematics theory) is used to characterize a family of designs.
  • an Iterated Function System (IFS) a Multireduction Copy Machine (MRCM) or a Networked Multireduction Copy Machine (MRCM) algorithm can be used to construct some space-filling curves as those described in the present invention.
  • the key point of the present invention is shaping part of the antenna (for example at least a part of the arms of a dipole, at least a part of the arm of a monopole, the perimeter of the patch of a patch antenna, the slot in a slot antenna, the loop perimeter in a loop antenna, the horn cross-section in a horn antenna, or the reflector perimeter in a reflector antenna) as a space-filling curve, that is, a curve that is large in terms of physical length but small in terms of the area in which the curve can be included.
  • a space-filling curve a curve composed by at least ten segments which are connected in such a way that each segment forms an angle with their neighbours, that is, no pair of adjacent segments define a larger straight segment, and wherein the curve can be optionally periodic along a fixed straight direction of space if and only if the period is defined by a non-periodic curve composed by at least ten connected segments and no pair of said adjacent and connected segments define a straight longer segment.
  • the design of such SFC it can never intersect with itself at any point except the initial and final point (that is, the whole curve can be arranged as a closed curve or loop, but none of the parts of the curve can become a closed loop).
  • a space-filling curve can be fitted over a flat or curved surface, and due to the angles between segments, the physical length of the curve is always larger than that of any straight line that can be fitted in the same area (surface) as said space-filling curve. Additionally, to properly shape the structure of a miniature antenna according to the present invention, the segments of the SFC curves must be shorter than a tenth of the free-space operating wavelength.
  • Figure 1 and Figure 2 show some examples of SFC curves.
  • Drawings (1 ), ( 3 ) and (4) in Figure 1 show three examples of SFC curves named SZ curves.
  • a curve that is not an SFC since it is only composed of 6 segments is shown in drawing (2) for comparison.
  • the drawings (7) and (8) in Figure 2 show another two particular examples of SFC curves, formed from the periodic repetition of a motive including the SFC curve (1). It is important noticing the substantial difference between these examples of SFC curves and some examples of periodic, meandering and not SFC curves such as those in drawings (5) and (6) in Figure 2 .
  • curves (5) and (6) are composed by more than 10 segments, they can be substantially considered periodic along a straight direction (horizontal direction) and the motive that defines a period or repetition cell is constructed with less than 10 segments (the period in drawing (5) includes only four segments, while the period of the curve (6) comprises nine segments) which contradicts the definition of SFC curve introduced in the present invention.
  • SFC curves are substantially more complex and pack a longer length in a smaller space; this fact in conjunction with the fact that each segment composing and SFC curve is electrically short (shorter than a tenth of the free-space operating wavelength as claimed in this invention) play a key role in reducing the antenna size.
  • the class of folding mechanisms used to obtain the particular SFC curves described in the present invention are important in the design of miniature antennas.
  • FIG. 3 describes a preferred embodiment of an SFC antenna.
  • the three drawings display different configurations of the same basic dipole.
  • a two-arm antenna dipole is constructed comprising two conducting or superconducting parts, each part shaped as an SFC curve.
  • SFC curve the SZ curve (1) of Figure 1
  • other SFC curves as for instance, those described in Figs. 1 , 2 , 6 , 8 , 14 , 19 , 20 , 21 , 22 , 23 , 24 or 25 could be used instead.
  • the two closest tips of the two arms form the input terminals (9) of the dipole.
  • the terminals (9) have been drawn as conducting or superconducting circles, but as it is clear to those skilled in the art, such terminals could be shaped following any other pattern as long as they are kept small in terms of the operating wavelength.
  • the arms of the dipoles can be rotated and folded in different ways to finely modify the input impedance or the radiation properties of the antenna such as, for instance, polarization.
  • Another preferred embodiment of an SFC dipole is also shown in Figure 3 , where the conducting or superconducting SFC arms are printed over a dielectric substrate (10); this method is particularly convenient in terms of cost and mechanical robustness when the SFC curve is long. Any of the well-known printed circuit fabrication techniques can be applied to pattern the SFC curve over the dielectric substrate.
  • Said dielectric substrate can be for instance a glass-fibre board, a teflon based substrate (such as Cuclad®) or other standard radiofrequency and microwave substrates (as for instance Rogers 4003® or Kapton®).
  • the dielectric substrate can even be a portion of a window glass if the antenna is to be mounted in a motor vehicle such as a car, a train or an air-plane, to transmit or receive radio, TV, cellular telephone (GSM 900, GSM 1800, UMTS) or other communication services electromagnetic waves.
  • GSM 900, GSM 1800, UMTS cellular telephone
  • a balun network can be connected or integrated at the input terminals of the dipole to balance the current distribution among the two dipole arms.
  • an SFC antenna is a monopole configuration as shown in Figure 4 .
  • one of the dipole arms is substituted by a conducting or superconducting counterpoise or ground plane (12).
  • the ground and the monopole arm (here the arm is represented with SFC curve (1), but any other SFC curve could be taken instead) are excited as usual in prior art monopoles by means of, for instance, a transmission line (11).
  • Said transmission line is formed by two conductors, one of the conductors is connected to the ground counterpoise while the other is connected to a point of the SFC conducting or superconducting structure.
  • a coaxial cable (11) has been taken as a particular case of transmission line, but it is clear to any skilled in the art that other transmission lines (such as for instance a microstrip arm) could be used to excite the monopole.
  • the SFC curve can be printed over a dielectric substrate (10).
  • an SFC antenna is a slot antenna as shown, for instance in Figures 5 , 7 and 10 .
  • two connected SFC curves (following the pattern (1) of Figure 1 ) form an slot or gap impressed over a conducting or superconducting sheet (13).
  • a conducting or superconducting sheet 13
  • Such sheet can be, for instance, a sheet over a dielectric substrate in a printed circuit board configuration, a transparent conductive film such as those deposited over a glass window to protect the interior of a car from heating infrared radiation, or can even be part of the metallic structure of a handheld telephone, a car, train, boat or airplane.
  • the exciting scheme can be any of the well known in conventional slot antennas and it does not become an essential part of the present invention.
  • a coaxial cable (11) has been used to excite the antenna, with one of the conductors connected to one side of the conducting sheet and the other one connected at the other side of the sheet across the slot.
  • a microstrip transmission line could be used, for instance, instead of the coaxial cable.
  • Figure 10 describes another possible embodiment of an slot SFC antenna. It is also an slot antenna in a closed loop configuration.
  • the loop is constructed for instance by connecting four SFC gaps following the pattern of SFC (25) in Figure 8 (it is clear that other SFC curves could be used instead according to the spirit and scope of the present invention).
  • the resulting closed loop determines the boundary of a conducting or superconducting island surrounded by a conducting or superconducting sheet.
  • the slot can be excited by means of any of the well-known conventional techniques; for instance a coaxial cable (11) can be used, connecting one of the outside conductor to the conducting outer sheet and the inner conductor to the inside conducting island surrounded by the SFC gap.
  • such sheet can be, for example, a sheet over a dielectric substrate in a printed circuit board configuration, a transparent conductive film such as those deposited over a glass window to protect the interior of a car from heating infrared radiation, or can even be part of the metallic structure of a handheld telephone, a car, train, boat or air-plane.
  • the slot can be even formed by the gap between two close but not co-planar conducting island and conducting sheet; this can be physically implemented for instance by mounting the inner conducting island over a surface of the optional dielectric substrate, and the surrounding conductor over the opposite surface of said substrate.
  • the slot configuration is not, of course, the only way of implementing an SFC loop antenna.
  • a closed SFC curve made of a superconducting or conducting material can be used to implement a wire SFC loop antenna as shown in another preferred embodiment as that of Figure 9 .
  • a portion of the curve is broken such as the two resulting ends of the curve form the input terminals (9) of the loop.
  • the loop can be printed also over a dielectric substrate (10).
  • a dielectric antenna can be also constructed by etching a dielectric SFC pattern over said substrate, being the dielectric permitivity of said dielectric pattern higher than that of said substrate.
  • FIG. 11 Another preferred embodiment is described in Figure 11 . It consists on a patch antenna, with the conducting or superconducting patch (30) featuring an SFC perimeter (the particular case of SFC (25) has been used here but it is clear that other SFC curves could be used instead).
  • the perimeter of the patch is the essential part of the invention here, being the rest of the antenna conformed, for example, as other conventional patch antennas: the patch antenna comprises a conducting or superconducting ground-plane (31) or ground counterpoise, an the conducting or superconducting patch which is parallel to said ground-plane or ground-counterpoise.
  • the spacing between the patch and the ground is typically below (but not restricted to) a quarter wavelength.
  • a low-loss dielectric substrate (10) (such as glass-fibre, a teflon substrate such as Cuclad® or other commercial materials such as Rogers® 4003) can be place between said patch and ground counterpoise.
  • the antenna feeding scheme can be taken to be any of the well-known schemes used in prior art patch antennas, for instance: a coaxial cable with the outer conductor connected to the ground-plane and the inner conductor connected to the patch at the desired input resistance point (of course the typical modifications including a capacitive gap on the patch around the coaxial connecting point or a capacitive plate connected to the inner conductor of the coaxial placed at a distance parallel to the patch, and so on can be used as well); a microstrip transmission line sharing the same ground-plane as the antenna with the strip capacitively coupled to the patch and located at a distance below the patch, or in another embodiment with the strip placed below the ground-plane and coupled to the patch through an slot, and even a microstrip transmission line with the strip co-plan
  • SFC antennas based also on the patch configuration are disclosed in Figure 13 and Figure 15 . They consist on a conventional patch antenna with a polygonal patch (30) (squared, triangular, pentagonal, hexagonal, rectangular, or even circular, to name just a few examples), with an SFC curve shaping a gap on the patch. Such an SFC line can form an slot or spurline (44) over the patch (as seen in Figure 15 ) contributing this way in reducing the antenna size and introducing new resonant frequencies for a multiband operation, or in another preferred embodiment the SFC curve (such as (25) defines the perimeter of an aperture (33) on the patch (30) ( Figure 13 ).
  • SFC curve such as (25) defines the perimeter of an aperture (33) on the patch (30) ( Figure 13 ).
  • Such an aperture contributes significantly to reduce the first resonant frequency of the patch with respect to the solid patch case, which significantly contributes to reducing the antenna size.
  • Said two configurations, the SFC slot and the SFC aperture cases can of course be use also with SFC perimeter patch antennas as for instance the one (30) described in Figure 11 .
  • Figure 12 describes another preferred embodiment of an SFC antenna. It consists on an aperture antenna, said aperture being characterized by its SFC perimeter, said aperture being impressed over a conducting ground-plane or ground-counterpoise (34), said ground-plane of ground-counterpoise consisting, for example, on a wall of a waveguide or cavity resonator or a part of the structure of a motor vehicle (such as a car, a lorry, an airplane or a tank).
  • the aperture can be fed by any of the conventional techniques such as a coaxial cable (11), or a planar microstrip or strip-line transmission line, to name a few.
  • Figure 16 shows another preferred embodiment where the SFC curves (41) are slotted over a wall of a waveguide (47) of arbitrary cross-section. This way and slotted waveguide array can be formed, with the advantage of the size compressing properties of the SFC curves.
  • Figure 17 depicts another preferred embodiment, in this case a horn antenna (48) where the cross-section of the antenna is an SFC curve (25).
  • the benefit comes not only from the size reduction property of SFC geometries, but also from the broadband behavior that can be achieved by shaping the horn cross-section. Primitive versions of these techniques have been already developed in the form of Ridge horn antennas.
  • a single squared tooth introduced in at least two opposite walls of the horn is used to increase the bandwidth of the antenna.
  • the richer scale structure of an SFC curve further contributes to a bandwidth enhancement with respect to prior art.
  • Figure 18 describes another typical configuration of antenna, a reflector antenna (49), with the newly disclosed approach of shaping the reflector perimeter with an SFC curve.
  • the reflector can be either flat or curve, depending on the application or feeding scheme (in for instance a reflectarray configuration the SFC reflectors will preferably be flat, while in focus fed dish reflectors the surface bounded by the SFC curve will preferably be curved approaching a parabolic surface).
  • Frequency Selective Surfaces can be also constructed by means of SFC curves; in this case the SFC are used to shape the repetitive pattern over the FSS.
  • the SFC elements are used in an advantageous way with respect to prior art because the reduced size of the SFC patterns allows a closer spacing between said elements. A similar advantage is obtained when the SFC elements are used in an antenna array in an antenna reflectarray.
EP10180798A 2000-01-19 2000-01-19 raumfüllende miniaturantennen Withdrawn EP2267838A3 (de)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
EP05012854A EP1592083B1 (de) 2000-01-19 2000-01-19 raumfüllende miniaturantennen
EP00909089A EP1258054B1 (de) 2000-01-19 2000-01-19 Raumfüllende miniaturantenne

Related Parent Applications (2)

Application Number Title Priority Date Filing Date
EP00909089.5 Division 2000-01-19
EP05012854.5 Division 2005-06-15

Publications (2)

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EP2267838A2 true EP2267838A2 (de) 2010-12-29
EP2267838A3 EP2267838A3 (de) 2011-05-04

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EP06120498A Withdrawn EP1724874A3 (de) 2000-01-19 2000-01-19 raumfüllende miniaturantennen
EP10180798A Withdrawn EP2267838A3 (de) 2000-01-19 2000-01-19 raumfüllende miniaturantennen
EP06007350A Withdrawn EP1699110A3 (de) 2000-01-19 2000-01-19 raumfüllende miniaturantennen

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Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE102011007058A1 (de) 2011-04-08 2012-10-11 Fraunhofer-Gesellschaft zur Förderung der angewandten Forschung e.V. Elektrische Leiterbahn
US9225388B2 (en) * 2012-07-03 2015-12-29 Intel Corporation Transmitting magnetic field through metal chassis using fractal surfaces

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GB8617076D0 (en) * 1986-07-14 1986-08-20 British Broadcasting Corp Video scanning systems
ES2112163B1 (es) * 1995-05-19 1998-11-16 Univ Catalunya Politecnica Antenas fractales o multifractales.
US6127977A (en) * 1996-11-08 2000-10-03 Cohen; Nathan Microstrip patch antenna with fractal structure
ES2236745T3 (es) * 1995-08-09 2005-07-16 Fractal Antenna Systems Inc. Antenas resonadores y elementos de carga fractales.
US6445352B1 (en) * 1997-11-22 2002-09-03 Fractal Antenna Systems, Inc. Cylindrical conformable antenna on a planar substrate
US6211889B1 (en) * 1998-06-30 2001-04-03 Sun Microsystems, Inc. Method and apparatus for visualizing locality within an address space

Non-Patent Citations (1)

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Title
R.C.HANSEN: "Fundamental Limitations on Antennas", PROC.IEEE, vol. 69, no. 2, February 1981 (1981-02-01)

Also Published As

Publication number Publication date
EP1724874A3 (de) 2007-07-25
EP1699110A3 (de) 2006-11-15
EP1724874A2 (de) 2006-11-22
EP1699110A2 (de) 2006-09-06
EP2267838A3 (de) 2011-05-04

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