EP1630898A1 - Antenne textile - Google Patents

Antenne textile Download PDF

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Publication number
EP1630898A1
EP1630898A1 EP04405541A EP04405541A EP1630898A1 EP 1630898 A1 EP1630898 A1 EP 1630898A1 EP 04405541 A EP04405541 A EP 04405541A EP 04405541 A EP04405541 A EP 04405541A EP 1630898 A1 EP1630898 A1 EP 1630898A1
Authority
EP
European Patent Office
Prior art keywords
antenna
textile
patch
rectangle
microstrip line
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Withdrawn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
EP04405541A
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German (de)
English (en)
Inventor
Ivo Locher
Maciej Klemm
Gerhard Tröster
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.)
Eidgenoessische Technische Hochschule Zurich ETHZ
Original Assignee
Eidgenoessische Technische Hochschule Zurich ETHZ
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 Eidgenoessische Technische Hochschule Zurich ETHZ filed Critical Eidgenoessische Technische Hochschule Zurich ETHZ
Priority to EP04405541A priority Critical patent/EP1630898A1/fr
Publication of EP1630898A1 publication Critical patent/EP1630898A1/fr
Withdrawn legal-status Critical Current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
    • H01Q1/27—Adaptation for use in or on movable bodies
    • H01Q1/273—Adaptation for carrying or wearing by persons or animals
    • 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 invention is in the field of textile antennas.
  • Textile antennas are antennas that comprise a textile substrate with a conductive patch and ground plane and may be affixed to or integrated in clothing, furniture or other textile material. They are for example used in connection with wearable computing.
  • Wearable computing is a new, fast growing field. Steadily progressing miniaturization in microelectronics along with other new technologies enables wearable computing to integrate functionality in clothing allowing entirely new applications. Medical prevention with continuously monitoring the patient's health condition is such an application necessitating sensing devices close to the patient's body. With wearable computing, it has become possible to integrate such sensing devices in the clothing, which offers unobtrusiveness and body proximity. As a next step, patients would benefit if a health condition can be directly communicated to a medical center. The implementation of antennas in textiles is therefore a logical next step.
  • textile antennas include applications in the automotive industry, namely antennas in seats of a car.
  • textile antennas have to fulfill the additional requirement of being drapable. 'Drapability' means that something can be bent in all directions at the same time.
  • a textile has this property in contrast to standard flexible substrates, which usually have a preferred bending direction.
  • a textile antenna must have a flat and planar structure such that it does not affect wearing comfort.
  • Textile antennas available so far were designed with rectangular patches with probe feed (C.f. P. Salonen and H. Hurme, IEEE Antennas and Propagation Society International Symposium vol. 2, June 2003, pp. 700-703; and M. Tanaka and J.H. Hang, IEEE Antennas and Propagation Society International Symposium vol. 2, June 2003, pp. 704-707).
  • Such antennas provide a linear polarization.
  • the orientation of the textile antenna may vary as a function of time, for example if the person wearing the textile antenna moves.
  • Linear polarization brings about a dependence of the antenna's efficiency on the relative orientation of transmitting (Tx) antenna and receiving (Rx) antenna.
  • the probe feed causes elements to stick up from an antenna plane, so that it is not practical for wearable computing.
  • the antenna according to the invention comprises a flexible, electrically conductive ground plane and a flexible, electrically conductive antenna patch. Textile, non-conductive material is arranged between the ground plane and the antenna patch as a dielectric textile substrate.
  • the antenna is essentially characterized in that it provides circular polarization or nearly circular polarization, and that it comprises a microstrip feed line.
  • a microstrip feed line in this context is a strip-shaped conductor structure for feeding the radiating part of the antenna with an AC voltage, being provided on the textile substrate, and meeting the radiating main part of the antenna patch.
  • the microstrip feed line is in the same plane as the antenna patch main part.
  • electromagnetic radiation emitted by an antenna is said to be circularly polarized if the axial ratio is smaller than 3 dB.
  • the axial ratio is the ratio between the major axis component of the electric field amplitude and the minor axis component of the electric field amplitude, major axis and minor axis referring to the polarization ellipse.
  • 'nearly circular polarization implicates that the ratio is not greater than 6 dB, preferably not greater than 4 dB.
  • a further insight of the invention is that it is even possible to provide a circularly polarized antenna comprising a microstrip line feed, although this makes antenna design again more complicated.
  • a microstrip line feed is excellently suited for wearable computing since it lies entirely in the antenna patch plane and does not affect wearing comfort.
  • the antenna patch and preferably also the ground plane are made of an electrically conductive textile, such as a conductive fabric.
  • Conductive fabrics are textiles the threads of which are conductive.
  • the threads of which the conductive fabric is made are plated by a metal or are drenched in conductive ink or the like. Plating or drenching may take place before or after weaving.
  • conductive fabrics may be manufactured by imprinting a conductor material on a (non-conductive) already woven or knitted textile. In conductive fabrics, conduction mainly occurs along the threads, so that the electrical resistance is locally highly anisotropic. This is not problematic for linear polarization, where one oscillation mode is sufficient.
  • the conductive fabrics may be approximated to be plane conductors, especially if the patch has an essentially rectangular shape and if the edges of said rectangle are parallel to threads of the fabric. Otherwise, a higher sheet resistance ( ⁇ /square) would have to be considered in the computation.
  • the patch essentially has the shape of an almost quadratic rectangle. 'Almost quadratic' means that the dimensions of the sides differ by not more than 5-20%.
  • the microstrip line contacts the rectangle at one of its corners.
  • the rectangle has two truncated corners opposing each other, the microstrip line contacting the rectangle in the middle of one of its edges.
  • the rectangle has a centrally located strip-shaped slot, the strip-shaped slot running diagonally with respect to the rectangle (in an angle of about 45° with respect to the rectangle edges or with respect to a coordinate system of the antenna patch plane in which one axis is parallel to the microstrip feed line and the other axis is perpendicular thereto), the microstrip line contacting the rectangle in the middle of one of its edges.
  • the patch comprises at least one strip-shaped indentation in the rectangle. At least one strip-shaped indentation may run perpendicularly to the feed line in order to tune circular radiation. Also, strip-shaped indentations may be provided that run parallel to the microstrip line and effectively extend the microstrip line into the rectangle in order to match antenna input impedance and microstrip feed line impedance.
  • the antenna comprises an antenna patch 1 on a textile substrate 2, namely on a polyamid spacer fabric with a thickness of 6 mm.
  • This fabric comprises a number of advantages. It is light, has a good drapability and is dimensionally stable in height. Due to its being very light and because it comprises a high fraction of air, its permittivity ⁇ r is close to 1. A measurement reveals a permittivity of around 1.15 at a frequency of 2.4 GHz.
  • the textile antenna comprises a ground plane (not visible), which is substantially larger than the patch and spans more than the entire surface of the section of the fabric shown in the photo.
  • the ground plane's size is such that it may be considered to be infinite in all four directions of the plane defined by the fabric.
  • the ground plane's size is at least the size of the patch, preferably at least four times or at least eight times its size.
  • the conductive material of the antenna patch 1 of Fig. 1 as well as of the ground plane is a conductive fabric, namely a nickel-plated woven textile. Nickel shows high resistance against oxidation and corrosion.
  • the antenna patch and the ground plane are attached to the spacer fabric by ammonia-based textile glue.
  • An electrical connection between the microstrip line 1.2 and the ground plane, respectively, and a transceiver electronics is established by conductive two-component glue.
  • the conductive layer is usually around 200 nm to 400 nm, which is smaller than the skin depth in the concerned materials at the above specified frequencies. Thus, by varying the thickness, damping properties may be controlled in a certain range.
  • plated textiles instead of plated textiles, also other thin conductive materials may be used, for example metal foils or, especially preferred, conductive paste which may be directly imprinted on the textile.
  • the conductivity of the conductive patch and ground plane material if the material is a plated woven or knitted material or an imprint on a textile, is governed by the property of the conductive fabric.
  • the resistance mainly arises from the contact resistance of transitions between crossed threads: The more transitions the current has to make in order to flow between two points, the higher the resistance between these two points.
  • the path between two points is divided into squares to be crossed (the square sides being parallel to the threads). The resistance is measured in ⁇ /square. For the material used for the embodiment of Fig. 1, the resistance is about 5 ⁇ /square.
  • the patch 1 comprises a main part 1.1 and a microstrip line 1.2.
  • the main part has an essentially rectangular, almost quadratical shape, with truncated corners 1.3 opposing each other.
  • the microstrip line 1.2 has an arbitrary length and contacts the rectangle 1.1 in the middle of one of its edges.
  • the patch rectangle comprises three strip-shaped indentations 1.4, 1.5, 1.6:
  • the first indentation 1.4 runs from a side of the rectangle towards the interior.
  • the other two indentations 1.5, 1.6 are essentially parallel to the microstrip and effectively extend it into the rectangle.
  • the dimensions of the patch correspond for example to the dimension of the patch indicated further below in Fig. 3.
  • a left-hand circularly polarized radio signal is generated.
  • Other antenna sizes and designs would be useable for other frequency ranges, i.e. the MHz frequency range.
  • the radiating edges of the patch are the edge in the main part 1.1 that is contacted by the microstrip line 1.2 and the opposing edge for a first radiation component and the other edges for a second radiation component.
  • the truncated corners set off excitement of the mode causing the second component.
  • the radiation components emitted by these edges superpose in a manner that left-hand circularly polarized radiation is created.
  • Fig. 2 shows three basic shapes of patches of circularly polarized textile antennas of the invention.
  • the invention is not restricted to these three basic shapes; rather these are mere examples of shapes on which an antenna design may be based on.
  • the first basic shape 11 corresponds to the shape of the antenna described with reference to Fig. 1.
  • the main part 11.1 of the patch has the shape of a rectangle with two truncated corners opposing each other.
  • the microstrip line 11.2 contacts the rectangle in the middle of one of its edges.
  • the patch essentially has the shape of a rectangle, the microstrip line 12.2 contacting the rectangle at one of its corners.
  • the third basic shape 13 comprises a main part 13.1 being a rectangle with a centrally located strip-shaped slot 13.3, the strip-shaped slot 13.3 running diagonally with respect to the rectangle (i.e. in an angle of about 45° with respect to the Cartesian coordinate system shown in the figure), the microstrip line 13.2 contacting the rectangle in the middle of one of its edges and having an angle of about 45° with respect to the slot 13.3.
  • indentations may be used to amplify radiation components along a particular edge in order to tune the antenna.
  • indentations parallel to the microstrip line - for example of the manner shown in Fig. 1 - may be used to engineer the microstrip line's terminating impedance so that it matches the line impedance (or characteristic impedance) of the microstrip line in order to avoid undesired reflections which reduce the total efficiency of the antenna.
  • Fig. 3 The exact shape of the patch of the textile antenna of Fig. 1 is shown in Fig. 3 .
  • the figure includes indications of dimensions.
  • a microstrip line with a standard characteristic impedance of 50 ⁇ (ignoring ohmic losses) would be rather wide (28 mm) compared to the patch dimensions. Since such a wide line would restrict the length of the radiating edges, it would then be difficult to achieve circularly polarized radiation. Therefore, the shown embodiment is a 75 ⁇ system resulting in a feed line width of 14 mm.
  • a patch 21 of a second embodiment of a textile antenna is shown in Fig. 4 , which also comprises dimension values. Also this embodiment comprises an indentation 21.4 serving as perturbation slit.
  • Fig. 5a presents the measured axial ratio at an angle of 0° for the textile antenna of Figs. 1 and 3 as a function of the frequency.
  • An axial ratio below 3 dB is obtained from 2.29 to 2.36 GHz.
  • the bandwidth of circular polarization according to a first definition (axial ratio below 3 dB) is thus attained with a bandwidth of 3% with respect to a center frequency at 2.32 GHz.
  • Nearly circular polarization according to the definition given above is achieved in the entire considered range between 2.2 GHz and 2.4 GHz.
  • Fig. 5b shows the measured input matching s 11 (solid curve) as a function of the frequency.
  • the smaller the input matching i.e. the lower the dB value
  • the accepted power is at a steep maximum around frequencies of 2.2-2.3 GHz.
  • the radiation efficiency i.e. the ratio between emitted radiation power and the accepted power is usually in the range of 60% to 90%, depending on resistance losses and properties of the dielectric textile substrate.
  • Fig. 6a and Fig. 6b show the measured radiation intensity for left hand circular polarization as a function of the radiation direction.
  • Figs. 6a and 6b depict the angular dependency in the y-z-plane and the x-z-plane, respectively, if the antenna is in the x-y-plane.
  • Both figures show a somewhat reduced radiation intensity into a backward (or downward) direction but a relatively broad region with a high intensity in the forward direction.
  • the figures also show the radiation proportion with right hand circular polarization (dashed lines). In the forward direction, the right-hand circular polarization is much weaker (by about 15 dB) than the left-hand circularly polarized radiation. It follows that a high proportion of the power going into the microstrip line is transformed into left-hand circularly polarized radiation in a forward direction.
  • the antenna can be tuned to fulfill the Bluetooth specification, i.e. a frequency range and antenna coverage of around 10 m for 1 mW power and around 100 m for about 20 mW power.
  • the above described embodiments are by no means the only ways to carry out the invention but may be altered in many ways.
  • the patch and ground plane materials and the textile materials may be varied.
  • any electrically conductive and drapable material may be used for the ground plane and for the patch.
  • Ground plane and patch may be provided on any textile material.
  • the antenna design i.e. the patch shape and microstrip width

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EP04405541A 2004-08-31 2004-08-31 Antenne textile Withdrawn EP1630898A1 (fr)

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EP04405541A EP1630898A1 (fr) 2004-08-31 2004-08-31 Antenne textile

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Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2008012300A1 (fr) * 2006-07-26 2008-01-31 Universität Bremen Antenne en matériau composite renforcé en fibres et procédé de fabrication d'une antenne en matériau composite renforcé en fibres
JP2010507457A (ja) * 2006-10-23 2010-03-11 アボット ダイアベティス ケア インコーポレイテッド 流体送達および人体検体監視のための可撓パッチ
US9478852B2 (en) 2013-08-22 2016-10-25 The Penn State Research Foundation Antenna apparatus and communication system
US10070810B2 (en) 2006-10-23 2018-09-11 Abbott Diabetes Care Inc. Sensor insertion devices and methods of use
CN109524768A (zh) * 2018-11-16 2019-03-26 天津工业大学 一种可洗的柔性可穿戴介质埋藏圆极化微带天线
US10362972B2 (en) 2006-09-10 2019-07-30 Abbott Diabetes Care Inc. Method and system for providing an integrated analyte sensor insertion device and data processing unit

Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2003075405A1 (fr) * 2002-03-06 2003-09-12 Communications Research Laboratory, Independent Administrative Institution Antenne microruban

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2003075405A1 (fr) * 2002-03-06 2003-09-12 Communications Research Laboratory, Independent Administrative Institution Antenne microruban
EP1492198A1 (fr) * 2002-03-06 2004-12-29 National Institute of Information and Communications Technology, Independent Administrative Institution Antenne microruban

Non-Patent Citations (2)

* Cited by examiner, † Cited by third party
Title
JAMES P S & HALL J R: "HANDBOOK OF MICROSTRIP ANTENNAS, Vol. 1 and 2", 1989, PETER PEREGRINUS LTD., LONDON, UK, ISBN: 0-86341-150-9, XP002315556 *
TANAKA M ET AL: "Wearable microstrip antenna", IEEE ANTENNAS AND PROPAGATION SOCIETY INTERNATIONAL SYMPOSIUM. 2003 DIGEST. APS. COLUMBUS, OH, JUNE 22 - 27, 2003, NEW YORK, NY : IEEE, US, vol. VOL. 4 OF 4, 22 June 2003 (2003-06-22), pages 704 - 707, XP010649878, ISBN: 0-7803-7846-6 *

Cited By (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2008012300A1 (fr) * 2006-07-26 2008-01-31 Universität Bremen Antenne en matériau composite renforcé en fibres et procédé de fabrication d'une antenne en matériau composite renforcé en fibres
US10362972B2 (en) 2006-09-10 2019-07-30 Abbott Diabetes Care Inc. Method and system for providing an integrated analyte sensor insertion device and data processing unit
JP2010507457A (ja) * 2006-10-23 2010-03-11 アボット ダイアベティス ケア インコーポレイテッド 流体送達および人体検体監視のための可撓パッチ
US9259175B2 (en) 2006-10-23 2016-02-16 Abbott Diabetes Care, Inc. Flexible patch for fluid delivery and monitoring body analytes
US10070810B2 (en) 2006-10-23 2018-09-11 Abbott Diabetes Care Inc. Sensor insertion devices and methods of use
US10363363B2 (en) 2006-10-23 2019-07-30 Abbott Diabetes Care Inc. Flexible patch for fluid delivery and monitoring body analytes
US11234621B2 (en) 2006-10-23 2022-02-01 Abbott Diabetes Care Inc. Sensor insertion devices and methods of use
US11724029B2 (en) 2006-10-23 2023-08-15 Abbott Diabetes Care Inc. Flexible patch for fluid delivery and monitoring body analytes
US9478852B2 (en) 2013-08-22 2016-10-25 The Penn State Research Foundation Antenna apparatus and communication system
US9912045B2 (en) 2013-08-22 2018-03-06 The Penn State Research Foundation Antenna apparatus and communication system
CN109524768A (zh) * 2018-11-16 2019-03-26 天津工业大学 一种可洗的柔性可穿戴介质埋藏圆极化微带天线

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