WO2004019448A1 - Low-volume antenna - Google Patents

Low-volume antenna Download PDF

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Publication number
WO2004019448A1
WO2004019448A1 PCT/FR2003/002553 FR0302553W WO2004019448A1 WO 2004019448 A1 WO2004019448 A1 WO 2004019448A1 FR 0302553 W FR0302553 W FR 0302553W WO 2004019448 A1 WO2004019448 A1 WO 2004019448A1
Authority
WO
WIPO (PCT)
Prior art keywords
coil
antenna
antenna according
conductive
slot
Prior art date
Application number
PCT/FR2003/002553
Other languages
French (fr)
Inventor
Ayoub Annabi
Roland Vincent
Daniel Leclerc
Original Assignee
Amphenol Socapex
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 Amphenol Socapex filed Critical Amphenol Socapex
Priority to JP2004530302A priority Critical patent/JP2005536164A/en
Priority to AU2003274267A priority patent/AU2003274267A1/en
Priority to EP03758253A priority patent/EP1530815A1/en
Publication of WO2004019448A1 publication Critical patent/WO2004019448A1/en

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Classifications

    • 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
    • H01Q1/12—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
    • 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
    • H01Q1/36—Structural form of radiating elements, e.g. cone, spiral, umbrella; Particular materials used therewith
    • H01Q1/362—Structural form of radiating elements, e.g. cone, spiral, umbrella; Particular materials used therewith for broadside radiating helical antennas

Definitions

  • the present invention relates to a low volume antenna intended to be used in particular but not exclusively in a portable radiotelephone.
  • plate antennas of the PiFa type or similar in radiotelephones.
  • These plate antennas which are essentially constituted by a ground plane and by a radiating plate, more generally a radiant element parallel to the ground plane, also include a short-circuit connection between the radiant element and the ground plane as well as '' A 50 ⁇ antenna supply most often carried out using a microstrip line or a printed circuit.
  • the minimum distance between the radiant element and the ground plane is of the order of 7 to 10 mm, at least when the dielectric disposed between the radiant element and the ground plane is Even.
  • This thickness of the order of 7 to 10 mm is considered to be too great for the production of radiotelephones.
  • Known plate antennas do not therefore meet the second condition stated above.
  • An object of the present invention is to provide an antenna which can be used in particular in a portable radiotelephone which has a very small volume and a reduced thickness.
  • the small volume antenna comprises a radiant element, said radiant element being constituted by means forming a coil having an axis, said coil being connected to an antenna conductor, and it comprises in addition a conductive element parallel to the axis of said coil which comprises means forming a slot arranged opposite said coil means.
  • the antenna is constituted by means forming a coil whose axis is parallel to a conductive element which is provided with a slot or an arrangement similar to a slot, opposite the means forming the coil.
  • the coil means consist of a conductive wire in the form of a helical coil.
  • this coil can have a reduced diameter, of the order, for example, of 3 mm, and the distance between the slit conductive element and the axis of this coil can also be very reduced, by l '' from 1.7 to 2 mm. An antenna is thus obtained whose overall thickness is less than 4 mm.
  • the coil element can be a coil in the usual sense of the term, that is to say a helix formed from a conductive wire.
  • the coil element may also be a coil
  • the conductive element can be a conductive surface.
  • this surface can be formed by the ground plane of the antenna and the slot is closed and has a substantially rectangular shape corresponding to the apparent outline of the coil.
  • This surface can also be a conductive plate.
  • the slot is open, that is to say, it opens into the periphery of the conductive surface.
  • the conductive element can also be a wired conductive element. In this case, it is folded back to present two substantially parallel elongated portions defining between them the equivalent of an open slot.
  • FIG. 1A is a vertical sectional view of a first embodiment of the antenna according to the invention.
  • FIG. 1B is a top view of the antenna shown in Figure 1A;
  • - Figure 2 is a view of a first alternative embodiment of the antenna of Figure 1A;
  • FIG. 3 is a partial view of the antenna showing an alternative embodiment of the helical coil
  • FIG. 4A is a vertical sectional view of a second embodiment of the antenna according to the invention.
  • FIG. 4B is a detail view showing the particular shape of "flat" coils used
  • FIG. 5A and 5B show a second alternative embodiment of the antenna in vertical section and in top view
  • - Figure 6 is a vertical sectional view of a third alternative embodiment of the invention.
  • FIG. 7A and 7B are views respectively in elevation and from above of an antenna comprising a second embodiment of the conductive element.
  • the antenna consists essentially of a ground plane 10 consisting of an electrically conductive material which is for example mounted or deposited on an insulating support 12. As shown better in FIG. 1B in the ground plane 10, one realizes a slot 14 whose shape will be described in more detail later.
  • the antenna also comprises a radiant element constituted by a helical coil 16 whose axis XX 'is parallel to the ground plane 10.
  • One of the ends 16a of the coil 16 is connected to the antenna supply 18 constituted for example by a coaxial cable 20 whose central conductor 20a is electrically connected to the end 16a of the coil and whose shield 20b is connected to the ground plane 10.
  • the coil 16 has a length L and a diameter d.
  • FIG. 1B shows in more detail the particular shape of the slot 14 produced in the ground plane 10.
  • This slot 14 has the shape of a rectangle substantially circumscribed around the external contour of the coil 16.
  • the slot rectangular 14 has a length I which is substantially equal to the length L of the coil and a width I 'substantially equal to the diameter d of the coil 16.
  • This slot is closed, that is to say, it does not open out not in the periphery of the ground plane.
  • the coil 16 has a diameter d equal to 3 mm and the distance h between the ground plane 10 and the axis XX ′ of the coil 16 is equal to 1.72 mm.
  • the distance h between the coil, the ground plane and the diameter d of this coil are linked by the following formula:
  • ⁇ r 1 for air and Z 0 is equal to 50 ⁇ .
  • the length L of the coil is equal to 20 mm.
  • the dimensions of the slot 14 are therefore 20 mm by 3 mm.
  • Such a bandwidth is not only widely acceptable for producing a portable radiotelephone, but it is approximately twice that obtained with antennas, for example antennas of the PiFa type.
  • the total thickness of the antenna is reduced since, in the example considered, this thickness is less than 3.5 mm and that the construction of the antenna is also relatively simple, in particular because of the shape rectangular of the slot 14 to be produced in the ground plane.
  • FIG 2 there is shown a first alternative embodiment of the first embodiment in which the supply of the coil 16 by the antenna cable 20 is different.
  • the axial conductor of the cable 20a is connected to a current point 22 of the coil 16 while the end 16a of this coil is connected to the ground plane 10. This gives a "shunt" attack on the antenna which allows the realization of an impedance corresponding to an inductive component.
  • FIG 3 there is shown an alternative embodiment of the coil 16 which then bears the reference 30.
  • This coil comprises a first portion 32 whose turns have a first pitch PI and a second portion 34 whose turns have a pitch P2 different from PI.
  • the helical antenna has a constant diameter d. Tests carried out with this type of helical coils have shown that the antenna actually works in two or three frequency bands defined by the judicious choice of the steps PI and P2 of the two portions of the helical coil.
  • FIG. 4B there is a ground plane 40 which is provided with a closed slot 42 and with a radiant element 44 constituted by a flat coil 44 shown in FIG. 4B.
  • the flat coil 44 is formed by a zigzag shape of a flat conductive element 46. It can also be a metallization produced on an insulating substrate.
  • the end 46a of the flat antenna 44 is connected to the antenna conductor 48 constituted by the coaxial cable 50. More precisely 46a is connected to the central conductor 50a of the cable 50.
  • conductive plate is meant either a conductive metal sheet in which the open slot is machined, or a conductive deposit made on an insulating substrate.
  • the coil 16 is shown, which can be identical to those which are shown in FIGS. 1A and 3.
  • the antenna also comprises a conductive plate 50 which is parallel to the axis XX 'of the coil 16. The distance h between the axis of the coil and the plate is the same as in FIG. 1A. This plate is not electrically connected to any other component of the antenna.
  • the plate 50 is provided with a slot 52 whose contour corresponds to the shape of the coil.
  • This outline 54 may have the general shape of a rectangle with two short sides in the form of semicircles 54a and 54b. It has been demonstrated that in this embodiment, for the antenna to present an acceptable gain, it is necessary for the slot 52 to open out by an extension 56 in the periphery 50a of the plate.
  • the plate can have a length L1 equal to 35 mm and a width equal to 9 mm, the coil having the dimensions already mentioned in connection with FIGS. 1A and 1B.
  • the antenna therefore has very small dimensions.
  • the end 16a of the coil is connected to the central conductor 60 of the coaxial supply cable 62.
  • the plate 50 is electrically isolated from the conductor 60.
  • This antenna can be mounted on a printed circuit 64 of a portable radio telephone or of any other device with internal antenna.
  • the shield 62a of the cable 62 is connected to a suitable ground of the printed circuit.
  • the antenna With this second embodiment, the same performance is obtained as with the first embodiment.
  • the antenna With a coil 16 with two separate steps, the antenna can operate in the GSM and DCS frequency band.
  • Figure 6 there is shown another embodiment of the antenna according to the invention. According to this embodiment, there is the coil 16 and the conductive plate 50 with its open slot 52. The end 16a of the coil 16 is connected to the conductive plate 50 while the axial conductor 60 of the antenna cable is connected at an intermediate point 16b of the coil 16.
  • FIGS. 7A and 7B show an embodiment of the antenna in which the conductive element is not constituted by a conductive surface but by a conductive wire element 70.
  • the wire element preferably has a diameter at least equal to 2.5 mm. It comprises two substantially rectilinear portions 72 and 74 substantially parallel to one another.
  • the first ends 72a, 74a of the straight portions are connected together by a curved portion 76.
  • the second end 72b of the portion 72 is electrically connected to the shield of the coaxial cable 62, while the second end 74b of the portion 74 is free.
  • This wire element 70 thus defines the equivalent of a slot 76 which is open.
  • the two portions 72 and 74 of the wire element 70 are substantially coplanar and arranged in a plane parallel to the axis XX ′ of the coil 16.

Abstract

The invention relates to a low-volume antenna comprising a radiating element. The aforementioned radiating element consists of coil-forming means (16) having a given axis, said coil-forming means being connected to an antenna conductor (18). The invention also comprises a conductive element (10) which is disposed parallel to the axis of the coil-forming means and which comprises a slit (14) which is disposed opposite said coil-forming means.

Description

Antenne de faible volume Low volume antenna
La présente invention a pour objet une antenne de faible volume destinée à être utilisée notamment mais non exclusivement dans un radiotéléphone portatif.The present invention relates to a low volume antenna intended to be used in particular but not exclusively in a portable radiotelephone.
Dans les radiotéléphones portatifs, on connaît l'utilisation d'antennes en forme d'hélice qui sont le plus souvent montées à l'extérieur du boîtier du radiotéléphone. Ces antennes peuvent avoir une dimension relativement réduite mais elles sont disposées à l'extérieur du boîtier pour être associées à un plan de masse qui est disposé lui à l'intérieur du boîtier du radiotéléphone.In portable radiotelephones, the use of helix-shaped antennas is known which are most often mounted outside the radiotelephone housing. These antennas may have a relatively small dimension but they are arranged outside the housing to be associated with a ground plane which is arranged inside the radiotelephone housing.
On sait que la tendance dans la réalisation des radiotéléphones est de supprimer toute antenne externe pour disposer celle-ci à l'intérieur du boîtier. La tendance est également à la réduction des dimensions du radiotéléphone ou du moins à l'intégration dans le radiotéléphone pour une dimension externe donnée d'un plus grand nombre de composants.We know that the trend in the production of radiotelephones is to remove any external antenna to have it inside the housing. The trend is also towards reducing the dimensions of the radiotelephone or at least integrating it into the radiotelephone for a given external dimension of a larger number of components.
Il en résulte qu'il est intéressant pour la conception d'un radiotéléphone de disposer d'une antenne interne et de dimensions relativement réduites. Pour satisfaire à la première condition, on a proposé d'utiliser dans les radiotéléphones des antennes à plaque du type PiFa ou similaire. Ces antennes à plaque qui sont constituées essentiellement par un plan de masse et par une plaque rayonnante, plus généralement un élément radiant parallèle au plan de masse, comportent également une connexion de court-circuit entre l'élément radiant et le plan de masse ainsi qu'une alimentation d'antenne à 50 Ω réalisée le plus souvent à l'aide d'une ligne microstrip ou d'un circuit imprimé.It follows that it is advantageous for the design of a radiotelephone to have an internal antenna and relatively small dimensions. To satisfy the first condition, it has been proposed to use plate antennas of the PiFa type or similar in radiotelephones. These plate antennas which are essentially constituted by a ground plane and by a radiating plate, more generally a radiant element parallel to the ground plane, also include a short-circuit connection between the radiant element and the ground plane as well as '' A 50 Ω antenna supply most often carried out using a microstrip line or a printed circuit.
Dans la gamme de fréquences utilisées pour les radiotéléphones et notamment pour la gamme de fréquences correspon- dant au GSM qui est de l'ordre de 920 MHz, la distance minimale entre l'élément radiant et le plan de masse est de l'ordre de 7 à 10 mm, du moins lorsque le diélectrique disposé entre l'élément radiant et le plan de masse est de Pair. Cette épaisseur de l'ordre de 7 à 10 mm est considérée comme trop importante pour la réalisation des radiotéléphones. Or, on constate que, si l'on cherche à réduire l'épaisseur de l'antenne PiFa pour porter celle-ci par exemple à moins de 5 mm, la bande passante de cette antenne est considérablement réduite, ce qui la rend pratiquement inutilisable. Les antennes à plaque connues ne répondent donc pas davantage à la deuxième condition énoncée ci-dessus.In the frequency range used for radiotelephones and in particular for the frequency range corresponding to GSM which is of the order of 920 MHz, the minimum distance between the radiant element and the ground plane is of the order of 7 to 10 mm, at least when the dielectric disposed between the radiant element and the ground plane is Even. This thickness of the order of 7 to 10 mm is considered to be too great for the production of radiotelephones. However, we note that, if we seek to reduce the thickness of the PiFa antenna to bring it for example to less than 5 mm, the bandwidth of this antenna is considerably reduced, making it practically unusable. Known plate antennas do not therefore meet the second condition stated above.
Un objet de la présente invention est de fournir une antenne notamment utilisable dans un radiotéléphone portatif qui présente un très faible volume et une épaisseur réduite.An object of the present invention is to provide an antenna which can be used in particular in a portable radiotelephone which has a very small volume and a reduced thickness.
Pour atteindre ce but selon l'invention, l'antenne de faible volume comprend un élément radiant, ledit élément radiant étant constitué par des moyens formant une bobine présentant un axe, ladite bobine étant raccordée à un conducteur d'antenne, et elle comprend en outre un élément conducteur parallèle à l'axe de ladite bobine qui comporte des moyens formant une fente disposée en regard desdits moyens formant bobine.To achieve this object according to the invention, the small volume antenna comprises a radiant element, said radiant element being constituted by means forming a coil having an axis, said coil being connected to an antenna conductor, and it comprises in addition a conductive element parallel to the axis of said coil which comprises means forming a slot arranged opposite said coil means.
On comprend que, selon l'invention, l'antenne est constituée par des moyens formant une bobine dont l'axe est parallèle à un élément conducteur qui est munie d'une fente ou d'une disposition analogue à une fente, en regard des moyens formant la bobine.It is understood that, according to the invention, the antenna is constituted by means forming a coil whose axis is parallel to a conductive element which is provided with a slot or an arrangement similar to a slot, opposite the means forming the coil.
Comme on l'expliquera ultérieurement plus en détail, cette disposition d'antenne, dont le volume est très faible et dont l'épaisseur est inférieure à 5 mm permet néanmoins, notamment dans la gamme de fréquences correspondant au système GSM, d'obtenir une bande passante non seulement suffisante, mais bien supérieure à celle que l'on obtient avec des antennes classiques, cette bande passante pour cette gamme de fréquences pouvant atteindre 100 à 120 MHz, et un gain suffisant. Selon un mode préféré de mise en oeuvre, les moyens formant bobine sont constitués par un fil conducteur en forme de bobine hélicoïdale.As will be explained later in more detail, this antenna arrangement, the volume of which is very small and the thickness of which is less than 5 mm nevertheless makes it possible, in particular in the frequency range corresponding to the GSM system, to obtain a bandwidth not only sufficient, but much higher than that obtained with conventional antennas, this bandwidth for this frequency range up to 100 to 120 MHz, and sufficient gain. According to a preferred embodiment, the coil means consist of a conductive wire in the form of a helical coil.
Les essais réalisés montrent que cette bobine peut avoir un diamètre réduit, de l'ordre, par exemple, de 3 mm, et la distance entre l'élément conducteur à fente et l'axe de cette bobine peut également être très réduite, de l'ordre de 1,7 à 2 mm. On obtient ainsi une antenne dont l'épaisseur globale est inférieure à 4 mm.The tests carried out show that this coil can have a reduced diameter, of the order, for example, of 3 mm, and the distance between the slit conductive element and the axis of this coil can also be very reduced, by l '' from 1.7 to 2 mm. An antenna is thus obtained whose overall thickness is less than 4 mm.
L'élément formant bobine peut être une bobine au sens habituel du terme, c'est-à-dire une hélice constituée à partir d'un fil conducteur. L'élément formant bobine peut être également une bobineThe coil element can be a coil in the usual sense of the term, that is to say a helix formed from a conductive wire. The coil element may also be a coil
"plate" constituée par des métallisations sur un support isolant. L'élément conducteur peut être une surface conductrice. Dans ce cas, cette surface peut être constituée par le plan de masse de l'antenne et la fente est fermée et a sensiblement une forme rectangulaire correspondant au contour apparent de la bobine. Cette surface peut également être une plaque conductrice. Dans ce dernier cas, la fente est ouverte, c'est-à-dire qu'elle débouche dans la périphérie de la surface conductrice."flat" formed by metallizations on an insulating support. The conductive element can be a conductive surface. In this case, this surface can be formed by the ground plane of the antenna and the slot is closed and has a substantially rectangular shape corresponding to the apparent outline of the coil. This surface can also be a conductive plate. In the latter case, the slot is open, that is to say, it opens into the periphery of the conductive surface.
L'élément conducteur peut également être un élément conducteur filaire. Dans ce cas, il est replié pour présenter deux portions allongées sensiblement parallèles définissant entre elles l'équivalent d'une fente ouverte.The conductive element can also be a wired conductive element. In this case, it is folded back to present two substantially parallel elongated portions defining between them the equivalent of an open slot.
D'autres caractéristiques et avantages de l'invention apparaîtront mieux à la lecture de la description qui suit de plusieurs modes de réalisation de l'invention donnés à titre d'exemples non limitatifs. La description se réfère aux figures annexées, sur lesquelles :Other characteristics and advantages of the invention will appear better on reading the following description of several embodiments of the invention given by way of nonlimiting examples. The description refers to the appended figures, in which:
- la figure 1A est une vue en coupe verticale d'un premier mode de réalisation de l'antenne conforme à l'invention ;- Figure 1A is a vertical sectional view of a first embodiment of the antenna according to the invention;
- la figure 1B est une vue de dessus de l'antenne montrée sur la figure 1A ; - la figure 2 est une vue d'une première variante de réalisation de l'antenne de la figure 1A ;- Figure 1B is a top view of the antenna shown in Figure 1A; - Figure 2 is a view of a first alternative embodiment of the antenna of Figure 1A;
- la figure 3 est une vue partielle de l'antenne montrant une variante de réalisation de la bobine hélicoïdale ;- Figure 3 is a partial view of the antenna showing an alternative embodiment of the helical coil;
- la figure 4A est une vue en coupe verticale d'un deuxième mode de réalisation de l'antenne selon l'invention ;- Figure 4A is a vertical sectional view of a second embodiment of the antenna according to the invention;
- la figure 4B est une vue de détail montrant la forme particulière de bobines "plates" utilisées ;- Figure 4B is a detail view showing the particular shape of "flat" coils used;
- les figures 5A et 5B montrent une deuxième variante de réalisation de l'antenne en coupe verticale et en vue de dessus ; - la figure 6 est une vue en coupe verticale d'une troisième variante de réalisation de l'invention ; et- Figures 5A and 5B show a second alternative embodiment of the antenna in vertical section and in top view; - Figure 6 is a vertical sectional view of a third alternative embodiment of the invention; and
- les figures 7A et 7B sont des vues respectivement en élévation et de dessus d'une antenne comprenant un deuxième mode de réalisation de l'élément conducteur. En se référant tout d'abord aux figures 1A et 1B, on va décrire un premier mode de réalisation préféré de l'antenne selon l'invention. L'antenne est constituée essentiellement par un plan de masse 10 constitué par un matériau conducteur de l'électricité qui est par exemple monté ou déposé sur un support isolant 12. Comme le montre mieux la figure 1B dans le plan de masse 10, on réalise une fente 14 dont la forme sera décrite plus en détail ultérieurement. L'antenne comporte également un élément radiant constitué par une bobine hélicoïdale 16 dont l'axe X-X' est parallèle au plan de masse 10. Une des extrémités 16a de la bobine 16 est reliée à l'alimentation d'antenne 18 constituée par exemple par un câble coaxial 20 dont le conducteur central 20a est raccordé électriquement à l'extrémité 16a de la bobine et dont le blindage 20b est relié au plan de masse 10. La bobine 16 a une longueur L et un diamètre d.- Figures 7A and 7B are views respectively in elevation and from above of an antenna comprising a second embodiment of the conductive element. Referring first to Figures 1A and 1B, we will describe a first preferred embodiment of the antenna according to the invention. The antenna consists essentially of a ground plane 10 consisting of an electrically conductive material which is for example mounted or deposited on an insulating support 12. As shown better in FIG. 1B in the ground plane 10, one realizes a slot 14 whose shape will be described in more detail later. The antenna also comprises a radiant element constituted by a helical coil 16 whose axis XX 'is parallel to the ground plane 10. One of the ends 16a of the coil 16 is connected to the antenna supply 18 constituted for example by a coaxial cable 20 whose central conductor 20a is electrically connected to the end 16a of the coil and whose shield 20b is connected to the ground plane 10. The coil 16 has a length L and a diameter d.
La figure 1B montre plus en détail la forme particulière de la fente 14 réalisée dans le plan de masse 10. Cette fente 14 a la forme d'un rectangle sensiblement circonscrit au contour externe de la bobine 16. En d'autres termes, la fente rectangulaire 14 a une longueur I qui est sensiblement égale à la longueur L de la bobine et une largeur I' sensiblement égale au diamètre d de la bobine 16. Cette fente est fermée, c'est-à-dire, qu'elle ne débouche pas dans la périphérie du plan de masse. Dans un exemple particulier de réalisation, la bobine 16 a un diamètre d égal à 3 mm et la distance h entre le plan de masse 10 et l'axe X-X' de la bobine 16 est égale à 1,72 mm.FIG. 1B shows in more detail the particular shape of the slot 14 produced in the ground plane 10. This slot 14 has the shape of a rectangle substantially circumscribed around the external contour of the coil 16. In other words, the slot rectangular 14 has a length I which is substantially equal to the length L of the coil and a width I 'substantially equal to the diameter d of the coil 16. This slot is closed, that is to say, it does not open out not in the periphery of the ground plane. In a particular embodiment, the coil 16 has a diameter d equal to 3 mm and the distance h between the ground plane 10 and the axis XX ′ of the coil 16 is equal to 1.72 mm.
En effet, pour obtenir une impédance donnée pour l'antenne, typiquement 50 Ω, la distance h entre la bobine, le plan de masse et le diamètre d de cette bobine sont reliés par la formule suivante :Indeed, to obtain a given impedance for the antenna, typically 50 Ω, the distance h between the coil, the ground plane and the diameter d of this coil are linked by the following formula:
Figure imgf000006_0001
Figure imgf000006_0001
Dans cette formule, εr = 1 pour l'air et Z0 est égal à 50 Ω.In this formula, ε r = 1 for air and Z 0 is equal to 50 Ω.
En outre, dans ce mode de réalisation, la longueur L de la bobine est égale à 20 mm. Les dimensions de la fente 14 sont donc de 20 mm par 3 mm.In addition, in this embodiment, the length L of the coil is equal to 20 mm. The dimensions of the slot 14 are therefore 20 mm by 3 mm.
Les essais réalisés avec l'antenne telle qu'elle vient d'être définie précédemment ont montré qu'on obtenait pour la gamme de fréquences correspondant au système GSM, c'est-à-dire pour une fréquence centrale de l'ordre de 920 MHz, une bande passante qui va de 100 à 120 MHz.The tests carried out with the antenna as it has just been defined above have shown that one obtained for the frequency range corresponding to the GSM system, that is to say for a central frequency of the order of 920 MHz, a bandwidth ranging from 100 to 120 MHz.
Une telle bande passante est non seulement largement acceptable pour la réalisation d'un radiotéléphone portatif, mais elle est approximativement deux fois supérieure à celle qu'on obtient avec les antennes par exemple les antennes du type PiFa.Such a bandwidth is not only widely acceptable for producing a portable radiotelephone, but it is approximately twice that obtained with antennas, for example antennas of the PiFa type.
Il faut souligner que l'épaisseur totale de l'antenne est réduite puisque, dans l'exemple considéré, cette épaisseur est inférieure à 3,5 mm et que la réalisation de l'antenne est également relativement simple, notamment en raison de la forme rectangulaire de la fente 14 à réaliser dans le plan de masse.It should be emphasized that the total thickness of the antenna is reduced since, in the example considered, this thickness is less than 3.5 mm and that the construction of the antenna is also relatively simple, in particular because of the shape rectangular of the slot 14 to be produced in the ground plane.
Sur la figure 2, on a représenté une première variante de réalisation du premier mode de réalisation dans lequel l'alimentation de la bobine 16 par le câble d'antenne 20 est différente. En effet, le conducteur axial du câble 20a est relié à un point courant 22 de la bobine 16 alors que l'extrémité 16a de cette bobine est reliée au plan de masse 10. On obtient ainsi une attaque "shunt" de l'antenne qui permet la réalisation d'une impédance correspondant à un composant selfique.In Figure 2, there is shown a first alternative embodiment of the first embodiment in which the supply of the coil 16 by the antenna cable 20 is different. Indeed, the axial conductor of the cable 20a is connected to a current point 22 of the coil 16 while the end 16a of this coil is connected to the ground plane 10. This gives a "shunt" attack on the antenna which allows the realization of an impedance corresponding to an inductive component.
Sur la figure 3, on a représenté une variante de réalisation de la bobine 16 qui porte alors la référence 30. Cette bobine comporte une première portion 32 dont les spires présentent un premier pas PI et une deuxième portion 34 dont les spires présentent un pas P2 différent de PI. Par ailleurs, l'antenne hélicoïdale présente un diamètre constant d. Les essais réalisés avec ce type de bobines hélicoïdales ont montré que l'antenne fonctionnait effectivement dans deux ou trois bandes de fréquences définies par le choix judicieux des pas PI et P2 des deux portions de la bobine hélicoïdale.In Figure 3, there is shown an alternative embodiment of the coil 16 which then bears the reference 30. This coil comprises a first portion 32 whose turns have a first pitch PI and a second portion 34 whose turns have a pitch P2 different from PI. Furthermore, the helical antenna has a constant diameter d. Tests carried out with this type of helical coils have shown that the antenna actually works in two or three frequency bands defined by the judicious choice of the steps PI and P2 of the two portions of the helical coil.
En se référant maintenant aux figures 4A et 4B, on va décrire une deuxième variante de réalisation de l'antenne. Dans cette variante de réalisation, on retrouve un plan de masse 40 qui est muni d'une fente fermée 42 et d'un élément radiant 44 constitué par une bobine plate 44 représentée sur la figure 4B. La bobine plate 44 est constituée par une forme en zigzag d'un élément conducteur plat 46. Il peut également s'agir d'une métallisation réalisée sur un substrat isolant. L'extrémité 46a de l'antenne plate 44 est raccordée au conducteur d'antenne 48 constitué par le câble coaxial 50. Plus précisément 46a est raccordée au conducteur central 50a du câble 50.Referring now to Figures 4A and 4B, we will describe a second alternative embodiment of the antenna. In this alternative embodiment, there is a ground plane 40 which is provided with a closed slot 42 and with a radiant element 44 constituted by a flat coil 44 shown in FIG. 4B. The flat coil 44 is formed by a zigzag shape of a flat conductive element 46. It can also be a metallization produced on an insulating substrate. The end 46a of the flat antenna 44 is connected to the antenna conductor 48 constituted by the coaxial cable 50. More precisely 46a is connected to the central conductor 50a of the cable 50.
Les essais réalisés avec ce deuxième mode de réalisation de l'antenne donnent également des résultats satisfaisants tout en étant inférieurs à ceux obtenus avec le premier mode de réalisation de cette antenne.The tests carried out with this second embodiment of the antenna also give satisfactory results while being less than those obtained with the first embodiment of this antenna.
En se référant aux figures 5A et 5B, on va décrire un deuxième mode de réalisation de l'antenne. Ce deuxième mode se distingue essentiellement du premier par le fait que la surface conductrice dans laquelle est ménagée la fente n'est pas le plan de masse de l'antenne mais une plaque conductrice. Par plaque conductrice, il faut entendre soit une tôle métallique conductrice dans laquelle la fente ouverte est usinée, soit un dépôt conducteur réalisé sur un substrat isolant.Referring to Figures 5A and 5B, we will describe a second embodiment of the antenna. This second mode is essentially distinguished from the first by the fact that the conductive surface in which the slot is formed is not the ground plane of the antenna but a conductive plate. By conductive plate is meant either a conductive metal sheet in which the open slot is machined, or a conductive deposit made on an insulating substrate.
Sur ces figures, on a représenté la bobine 16 qui peut être identique à celles qui sont représentées sur les figures 1A et 3. L'antenne comprend également une plaque conductrice 50 qui est parallèle à l'axe X-X' de la bobine 16. La distance h entre l'axe de la bobine et la plaque est la même que sur la figure 1A. Cette plaque n'est électriquement reliée à aucun autre composant de l'antenne. La plaque 50 est munie d'une fente 52 dont le contour correspond à la forme de la bobine. Ce contour 54 peut avoir la forme générale d'un rectangle avec deux petits côtés en forme de demi-cercles 54a et 54b. On a mis en évidence que dans ce mode de réalisation, pour que l'antenne présente un gain acceptable, il est nécessaire que la fente 52 débouche par un prolongement 56 dans la périphérie 50a de la plaqueIn these figures, the coil 16 is shown, which can be identical to those which are shown in FIGS. 1A and 3. The antenna also comprises a conductive plate 50 which is parallel to the axis XX 'of the coil 16. The distance h between the axis of the coil and the plate is the same as in FIG. 1A. This plate is not electrically connected to any other component of the antenna. The plate 50 is provided with a slot 52 whose contour corresponds to the shape of the coil. This outline 54 may have the general shape of a rectangle with two short sides in the form of semicircles 54a and 54b. It has been demonstrated that in this embodiment, for the antenna to present an acceptable gain, it is necessary for the slot 52 to open out by an extension 56 in the periphery 50a of the plate.
50. La plaque peut avoir une longueur Ll égale à 35 mm et une largeur égale à 9 mm, la bobine ayant les dimensions déjà mentionnées en liaison avec les figures 1A et 1B. L'antenne a donc des dimensions très réduites.50. The plate can have a length L1 equal to 35 mm and a width equal to 9 mm, the coil having the dimensions already mentioned in connection with FIGS. 1A and 1B. The antenna therefore has very small dimensions.
L'extrémité 16a de la bobine est reliée au conducteur central 60 du câble coaxial d'alimentation 62. La plaque 50 est isolée électriquement du conducteur 60.The end 16a of the coil is connected to the central conductor 60 of the coaxial supply cable 62. The plate 50 is electrically isolated from the conductor 60.
Cette antenne peut être montée sur un circuit imprimé 64 d'un radio-téléphone portatif ou de tout autre appareil à antenne interne. Le blindage 62a du câble 62 est relié à une masse convenable du circuit imprimé. Avec ce deuxième mode de réalisation, on obtient les mêmes performances qu'avec le premier mode de réalisation. Avec une bobine 16 à deux pas distincts l'antenne peut fonctionner dans la bande de fréquence GSM et DCS. Sur la figure 6, on a représenté un autre mode de réalisation de l'antenne selon l'invention. Selon ce mode de réalisation, on retrouve la bobine 16 et la plaque conductrice 50 avec sa fente ouverte 52. L'extrémité 16a de la bobine 16 est reliée à la plaque conductrice 50 alors que le conducteur axial 60 du câble d'antenne est relié à un point intermédiaire 16b de la bobine 16.This antenna can be mounted on a printed circuit 64 of a portable radio telephone or of any other device with internal antenna. The shield 62a of the cable 62 is connected to a suitable ground of the printed circuit. With this second embodiment, the same performance is obtained as with the first embodiment. With a coil 16 with two separate steps, the antenna can operate in the GSM and DCS frequency band. In Figure 6, there is shown another embodiment of the antenna according to the invention. According to this embodiment, there is the coil 16 and the conductive plate 50 with its open slot 52. The end 16a of the coil 16 is connected to the conductive plate 50 while the axial conductor 60 of the antenna cable is connected at an intermediate point 16b of the coil 16.
Les figures 7A et 7B montrent un mode de réalisation de l'antenne dans lequel l'élément conducteur n'est pas constitué par une surface conductrice mais par un élément filaire conducteur 70. L'élément filaire a, de préférence, un diamètre au moins égal à 2,5 mm. Il comprend deux portions sensiblement rectilignes 72 et 74 sensiblement parallèles entre elles.FIGS. 7A and 7B show an embodiment of the antenna in which the conductive element is not constituted by a conductive surface but by a conductive wire element 70. The wire element preferably has a diameter at least equal to 2.5 mm. It comprises two substantially rectilinear portions 72 and 74 substantially parallel to one another.
Les premières extrémités 72a, 74a des portions rectilignes sont raccordées entre elles par une portion courbe 76. La deuxième extrémité 72b de la portion 72 est électriquement raccordée au blindage du câble coaxial 62, alors que la deuxième extrémité 74b de la portion 74 est libre. Cet élément filaire 70 définit ainsi l'équivalent d'une fente 76 qui est ouverte. Les deux portions 72 et 74 de l'élément filaire 70 sont sensiblement coplanaires et disposées dans un plan parallèle à l'axe X-X' de la bobine 16. The first ends 72a, 74a of the straight portions are connected together by a curved portion 76. The second end 72b of the portion 72 is electrically connected to the shield of the coaxial cable 62, while the second end 74b of the portion 74 is free. This wire element 70 thus defines the equivalent of a slot 76 which is open. The two portions 72 and 74 of the wire element 70 are substantially coplanar and arranged in a plane parallel to the axis XX ′ of the coil 16.

Claims

REVENDICATIONS
1. Antenne de faible volume comprenant un élément radiant, caractérisée en ce que ledit élément radiant est constitué par des moyens formant une bobine présentant un axe, lesdits moyens formant bobine étant raccordés à un conducteur d'antenne, et en ce qu'elle comprend en outre un élément conducteur parallèle à l'axe des moyens formant bobine qui comporte des moyens formant fente disposés en regard desdits moyens formant bobine. 1. A small volume antenna comprising a radiant element, characterized in that said radiant element consists of means forming a coil having an axis, said coil means being connected to an antenna conductor, and in that it comprises further a conductive element parallel to the axis of the coil means which comprises slot means arranged opposite said coil means.
2. Antenne selon la revendication 1, caractérisée en ce que lesdits moyens formant bobine sont constitués par un fil conducteur en forme de bobine hélicoïdale.2. Antenna according to claim 1, characterized in that said coil means consist of a conductive wire in the form of a helical coil.
3. Antenne selon la revendication 2, caractérisée en ce que ledit élément conducteur est une surface conductrice et en ce que lesdits moyens formant fente sont constitués par une fente réalisée dans ladite surface conductrice.3. An antenna according to claim 2, characterized in that said conductive element is a conductive surface and in that said slot means are constituted by a slot made in said conductive surface.
4. Antenne selon la revendication 3, caractérisée en ce que ladite surface conductrice est le plan de masse de l'antenne.4. Antenna according to claim 3, characterized in that said conductive surface is the ground plane of the antenna.
5. Antenne selon la revendication 3, caractérisée en ce que ladite surface conductrice est une plaque conductrice distincte du plan de masse et en ce que ladite fente débouche dans la périphérie de ladite plaque.5. Antenna according to claim 3, characterized in that said conductive surface is a conductive plate distinct from the ground plane and in that said slot opens into the periphery of said plate.
6. Antenne selon l'une quelconque des revendications 4 et 5, caractérisée en ce que ladite fente a une forme rectangulaire dont un côté a une longueur sensiblement égale au diamètre de la bobine et dont l'autre côté a une longueur sensiblement égale à celle de la bobine.6. Antenna according to any one of claims 4 and 5, characterized in that said slot has a rectangular shape one side of which has a length substantially equal to the diameter of the coil and the other side of which has a length substantially equal to that of the coil.
7. Antenne selon l'une quelconque des revendications 4 à 6, caractérisée en ce que ledit conducteur d'antenne est connecté à une extrémité de la bobine. 7. Antenna according to any one of claims 4 to 6, characterized in that said antenna conductor is connected to one end of the coil.
8. Antenne selon la revendication 4, caractérisée en ce qu'une des extrémités de la bobine est raccordée électriquement au plan de masse et en ce que le conducteur d'antenne est raccordé à un point courant de la bobine.8. Antenna according to claim 4, characterized in that one of the ends of the coil is electrically connected to the ground plane and in that the antenna conductor is connected to a current point of the coil.
9. Antenne selon la revendication 2, caractérisée en ce que ledit élément conducteur est un élément filaire replié pour former deux parties principales sensiblement parallèles entre elles, chaque partie principale comportant une première extrémité raccordée à la première extrémité de l'autre partie principale, les moyens formant fente étant constitués par l'espace limité par les deux parties principales.9. An antenna according to claim 2, characterized in that said conductive element is a wire element folded back to form two main parts substantially parallel to each other, each main part having a first end connected to the first end of the other main part, the slit means being constituted by the space limited by the two main parts.
10. Antenne selon la revendication 9, caractérisée en ce que lesdites deux parties principales de l'élément filaire sont disposées sensiblement dans un même plan parallèle à l'axe de la bobine.10. Antenna according to claim 9, characterized in that said two main parts of the wire element are arranged substantially in the same plane parallel to the axis of the coil.
11. Antenne selon l'une quelconque des revendications 2 à 10, caractérisée en ce que ladite bobine en forme d'hélice comprend une première portion présentant un premier pas et une deuxième portion présentant un deuxième pas distinct du premier. 11. An antenna according to any one of claims 2 to 10, characterized in that said helical coil comprises a first portion having a first pitch and a second portion having a second pitch distinct from the first.
PCT/FR2003/002553 2002-08-21 2003-08-20 Low-volume antenna WO2004019448A1 (en)

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JP2004530302A JP2005536164A (en) 2002-08-21 2003-08-20 Small volume antenna
AU2003274267A AU2003274267A1 (en) 2002-08-21 2003-08-20 Low-volume antenna
EP03758253A EP1530815A1 (en) 2002-08-21 2003-08-20 Low-volume antenna

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FR0210434A FR2843835B1 (en) 2002-08-21 2002-08-21 LOW VOLUME ANTENNA
FR0210434 2002-08-21

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KR (1) KR20050058399A (en)
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JP5772868B2 (en) 2012-05-21 2015-09-02 株式会社村田製作所 ANTENNA DEVICE AND WIRELESS COMMUNICATION DEVICE

Citations (2)

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US5006861A (en) * 1989-04-20 1991-04-09 Motorola, Inc. Antenna
EP1231669A1 (en) * 2001-02-07 2002-08-14 The Furukawa Electric Co., Ltd. Antenna apparatus

Patent Citations (2)

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Publication number Priority date Publication date Assignee Title
US5006861A (en) * 1989-04-20 1991-04-09 Motorola, Inc. Antenna
EP1231669A1 (en) * 2001-02-07 2002-08-14 The Furukawa Electric Co., Ltd. Antenna apparatus

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Title
MORISHITA H ET AL: "SMALL BALANCE-FED HELICAL DIPOLE ANTENNA SYSTEM FOR HANDSET", VTC 2000-SPRING. 2000 IEEE 51ST. VEHICULAR TECHNOLOGY CONFERENCE PROCEEDINGS. TOKYO, JAPAN, MAY 15-18, 2000, IEEE VEHICULAR TECHNOLGY CONFERENCE, NEW YORK, NY: IEEE, US, vol. 2 OF 3. CONF. 51, 15 May 2000 (2000-05-15), pages 1377 - 1380, XP000968095, ISBN: 0-7803-5719-1 *

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KR20050058399A (en) 2005-06-16
EP1530815A1 (en) 2005-05-18
JP2005536164A (en) 2005-11-24

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