EP1172885A1 - Short-circuit microstrip antenna and dual-band transmission device including that antenna - Google Patents

Abstract

The antenna (1) of this device is produced using the microstrip technique. A rear edge (10) of its patch (6) is provided with a short circuit (S) by which a quarter wave primary resonance can be excited by a coplanar line formed by two coupling slots (F1, F2) in a zone (Z1). Slots separators (F4, F5) separate this zone from another zone (Z2) in which a secondary resonance can be established at a frequency twice that of the primary resonance from a slotted line (F3) extending one (F2) of the slits of the coplanar line.

The invention applies in particular to the production of a dual mode radiotelephony system using the two GSM and DCS standards.

Description

The present invention relates, in general, to the devices for radio transmission, in particular portable radiotelephones, and it concerns more particularly the antennas which are produced using at least one conductive layer to be included in such devices.

Such an antenna includes a patch which is typically constituted by etching of a metallic layer. It is often carried out according to the technique microstrips and it is then called in English by specialists "microstrip patch antenna" for "microstrip type patch antenna".

The microstrip technique is a planar technique that applies to both at the realization of transmission lines transmitting waves guided, possibly carrying signals, and to that of antennas carrying a coupling between such lines and radiated waves. She uses conductive tapes and / or pads formed on the upper surface of a thin dielectric substrate. A conductive layer extends over the surface bottom of this substrate and constitutes a mass of the line or the antenna. Such a patch is typically wider than such a ribbon and its shapes and dimensions are important features of the antenna. The substrate shape is typically that of a rectangular flat sheet of constant thickness and the patch is also typically rectangular. But this is by no means an obligation. In particular, it is known that a varying the thickness of the substrate can widen the bandwidth of such antenna and that the patch can take various forms and for example be circular. The electric field lines extend between the ribbon or the pellet and the mass layer crossing the substrate. A line of transmission operating in this way will be said below line microstrip.

This technique differs from coplanar techniques which use them also conductive elements on a thin substrate, and in particular of that transmission lines in which the electric field is established on the upper surface of the substrate and symmetrically between on the one hand a central conductive tape and on the other hand two conductive pads located on either side of this ribbon from which they are respectively separated by two slots, a transmission line operating in this way being hereinafter called the coplanar line. In an antenna produced according to this technique, a patch is surrounded by a continuous conductive pad whose it is separated by a slit.

According to a technique which is also coplanar, a transmission line is consisting of a slit formed in a conductive layer and the field electric of the transmitted wave is established in the plane of this layer between the two edges of this slot.

The antennas produced according to these techniques typically constitute, although not necessarily, resonant structures capable of being the standing wave seat for coupling with waves radiated into space.

Various types of such resonant structures can be produced, for example example, according to the microstrip technique and each such structure can be the seat of at least one resonance mode, such modes being more briefly called "resonances" below. Schematically each such resonance can be described as a standing wave formed by the superposition of two traveling waves propagating in two opposite directions on the same path, these two waves resulting from the alternative reflection of the same progressive wave at both ends of this path, this last wave being an electromagnetic wave propagating on this path in the line constituted for example by the mass, the substrate and the tablet. This path is imposed by the constituent elements of the antenna. he can be straight or curved. It will be designated hereafter by the expression “journey of resonance ". The frequency of the resonance is inversely proportional to the time taken by the traveling wave considered above to travel this route.

A first type of resonance can be called "half wave". In this type the length of the resonance path is typically substantially equal to one half wavelength i.e. half the wavelength of the wave progressive considered above. The antenna is then called "half wave". This type of resonance can be broadly defined by the presence an electric current node at each of the two ends of such a path whose length can therefore also be equal to said half-wavelength multiplied by an integer other than one. This number is typically odd. The coupling with the radiated waves takes place at at least one of the two ends of this path, these ends being located in regions where the amplitude of the electric field which is applied for example across the substrate is maximum.

A second type of resonance that can be obtained in the context of this same technique can be called "quarter wave". It differs from said type half wave on the one hand by the fact that the resonance path typically has a length substantially equal to a quarter wave, i.e. a quarter of the wavelength defined above. For this, the resonant structure must have a short circuit at one end of this path, the word short circuit designating a connection connecting the ground and the patch. In addition this short circuit must have an impedance small enough to be able to impose such resonance. This type of resonance can be generally defined by the presence of an electric field node fixed by such a short circuit to the near an edge of the patch and by an electric current node located the other end of the resonance path. The length of the latter can therefore also be equal to a whole number of half-wavelengths added to said quarter wavelength. The coupling with the radiated waves in the space is made on an edge of the patch in a region where the amplitude of the electric field is sufficiently large.

Resonances of other types can be established, each of these types is characterized by a distribution of electric and magnetic fields which oscillate in an area of space including the antenna and the immediate vicinity of this one. They depend in particular on the configuration of the pellets, these the latter may in particular have slots, possibly radiative. In the case of antennas produced using the microstrips, these resonances also depend on the possible presence and localization of short circuits as well as electrical models representative of these short circuits when these are short circuits imperfect, that is to say when they cannot be assimilated, even approximately, to perfect short-circuits whose impedances would be zero.

• Cette distribution des champs dans la première antenne est sensiblement identique à une distribution pouvant être induite dans une aire identique appartenant à la pastille d'une deuxième antenne.
• Cette deuxième antenne est identique à cette première antenne dans les limites de cette aire sauf que cette deuxième antenne y est dépourvue du court-circuit en question.
• La pastille de cette deuxième antenne s'étend non seulement sur l'aire déjà mentionnée qui constitue alors une aire principale de cette deuxième antenne, mais aussi sur une aire complémentaire.
• Enfin, la distribution de champs en question apparaissant dans l'aire principale de cette deuxième antenne s'accompagne d'un noeud de champ électrique ou magnétique apparaissant dans cette aire complémentaire.

The presence of such an imperfect short-circuit in an antenna can cause a resonance to appear which presents what can be called a virtual node. Such a node appears when the following conditions are met, the above antenna being a first antenna:

• This distribution of the fields in the first antenna is substantially identical to a distribution that can be induced in an identical area belonging to the patch of a second antenna.
• This second antenna is identical to this first antenna within the limits of this area except that this second antenna has no short-circuit in question there.
• The patch of this second antenna extends not only over the area already mentioned which then constitutes a main area of this second antenna, but also over a complementary area.
• Finally, the distribution of fields in question appearing in the main area of this second antenna is accompanied by an electric or magnetic field node appearing in this complementary area.

To describe the resonance appearing in the first antenna, it can then be considered that the node appearing in the second antenna also constitutes a node for the resonance of the first antenna. For a antenna such as this first antenna such a node will be said below "Virtual" because it is located in an area that is located outside the patch of this antenna and in which therefore no field appears electric or magnetic likely to allow direct observation the presence of this node.

Although such "virtual nodes" are not conventionally taken into account account in these terms to describe resonances they appear implicitly in the distinction that is sometimes made between a length physical or geometric and a so-called "electric" length of the same pellet. In the case of the two antennas considered above, and about of the patch of the first of these antennas, the physical length or geometric would be that of this patch, and the electrical length of this same pad would actually be the physical or geometric length of the pad from the second antenna.

The coupling of an antenna to a signal processing device such as a transmitter is typically done through a set of connection comprising a connection line which is external to this antenna and which ends with a coupling system integrated into this antenna to couple this line to one or more resonances that can settle in one or more resonant structures of this antenna. The resonances also depend on the nature and location of this system. The latter makes it possible to use the antenna at each of the frequencies of these resonances. With reference to the case of transmitting antennas, all of connection is often referred to as a power line from this antenna.

The present invention relates to various types of devices such as portable radiotelephones, base stations for the latter, automobiles and airplanes or air missiles. In the case of a portable radio the continuous nature of the lower mass layer of an antenna produced using the microstrip technique makes it possible to limit easily the radiation power intercepted by the body of the user of the device. In the case of automobiles and especially in that of airplanes or missiles with a metallic exterior surface and curved profile to obtain a low aerodynamic drag, the antenna can be conformed to this profile so as not to show annoying additional aerodynamic drag.

• elle doit être bi-fréquence c'est à dire qu'elle doit pouvoir émettre et/ou recevoir efficacement des ondes rayonnées sur deux fréquences séparées par un écart spectral important,
• elle doit pouvoir être raccordée à un organe de traitement de signal à l'aide d'une seule ligne de raccordement pour l'ensemble des fréquences de travail d'un dispositif de transmission sans donner naissance dans cette ligne à un taux d'ondes stationnaires parasites gênant,
• et il ne doit pas être nécessaire pour cela d'utiliser un multiplexeur ou démultiplexeur en fréquence.

This invention relates more particularly to the case where an antenna with a conductive layer must have the following qualities:

• it must be dual-frequency, that is to say that it must be able to efficiently transmit and / or receive radiated waves on two frequencies separated by a significant spectral difference,
• it must be possible to be connected to a signal processor using a single connection line for all the working frequencies of a transmission device without giving rise in this line to a standing wave rate annoying parasites,
• and it should not be necessary for this to use a frequency multiplexer or demultiplexer.

Many known antennas have been produced or proposed in the framework of the microstrip technique so as to present these three qualities. They differ from each other by the means included therein to allow the establishment and coupling of multiple frequencies resonances with different frequencies. Several such antennas are going be reviewed.

A first such known antenna is described in the patent document US-A- 4,692,769 (Gegan, 769). In a first mode of implementation the patch of this antenna has the shape of a circular disc 10 allowing this antenna to present two half wave resonances whose paths are established respectively according to a diameter AA of this disc and according to the length of a slot in an arc 24 inscribed in this disc. The system coupling has the form of a line 16 constituting a transformer quarter wave and connecting at an interior point to the area of the patch of so as to give the real part of the input impedance of the antenna values substantially equal for these two resonances. Slots impedance matching 26 and 28 are concentrically entered in the disc 10 so that the imaginary part of this input impedance has, it also, substantially equal values for these two resonances. Line 16 is produced using the microstrip technique. That is to say that it is not not performed using the coplanar line technique as defined above before. This document also states, however, that this line is coplanar, but this only indicates that the ribbon of this microstrip line extends in the plane of the patch 10. Two slits are formed in the layer conductive of this patch on either side of this ribbon to allow a terminal segment of this line to enter the area of this patch without creating in this segment a parasitic contact of this ribbon with this pellet. One of these two slots is continued by an extension which constitutes the impedance matching slot 28 so that an asymmetry appears to be presented by line 16 at its inner end to the patch 10. Despite this apparent continuity and asymmetry, specialists understand that in practice no wave propagates over the length of the impedance matching slot 28.

A second known antenna is described in the patent document US-A- 4,766,440 (Gegan, 440). The patch 10 of this antenna has a shape general rectangular allowing this antenna to present two half wave resonances whose paths are established along a length and a width of this patch. Furthermore it has a curved slit in the shape of U which is entirely internal to this patch. This slit is radiative and brings up an additional mode of resonance established according to a other route. It also allows, by a suitable choice of its shape and its dimensions, to bring the frequencies of the resonance modes to desired values which gives the possibility of emitting a wave at circular polarization thanks to the association of two modes having the same frequency and crossed linear polarizations. The coupling system has the form of a line which is produced according to the technique of microstrips, but which is also said to be coplanar, as in the previous document Gegan, 769. This system is provided with means of impedance transformations to adapt it to different impedances input respectively presented by the line at the different frequencies of resonance used as working frequencies.

A third known antenna differs from the previous ones by the use of a single resonance path. It is described in the document of US-A patent 4,771,291 (LO et al). Its patch has short circuits punctuals and slits extending along straight segments inside the tablet. These slots and short-circuits reduce the gap between two frequencies corresponding to two resonances having said common path but two respective mutually different modes which are designated by digits (0,1) and (0,3), i.e. this common path is occupied by a half wave or by three half waves depending on the mode considered. The relationship between these two frequencies can be lowered as well from 3 to 1.8. Short circuits punctuals are formed by conductors crossing the substrate. The coupling system consists of a coaxial line whose conductor central crosses the antenna substrate to connect to the patch of the latter and whose ground conductor is connected to the ground of the antenna.

This antenna has the particular disadvantage that its manufacture is complicated by the incorporation of punctual short circuits.

A fourth known dual-frequency antenna differs from the previous ones by the use of a quarter wave resonance. It is described in an article: IEEE ANTENNAS AND PROPAGATION SOCIETY INTERNATONAL SYMPOSIUM DIGEST, NEWPORT BEACH, JUNE 18-23, 1995, pages 2124-2127 Boag et al "Dual Band Cavity-Backed Quarter-wave Patch Antenna". A first resonant frequency is defined by the dimensions and the characteristics of the substrate and the patch of this antenna. A resonance substantially the same type is obtained at a second frequency on the same resonance path thanks to the use of an adaptation system.

The coupling system appears to be typing with a coaxial line, the system adapter being placed at the end of such a line, the conductor of which axial is extended through the antenna substrate to connect to the pastille of the latter.

Other known antennas include three conductive layers namely two pellets superimposed on the same mass. They present so in particular the disadvantage that the addition of the thicknesses of substrates dielectric interposed between these layers gives the antenna a thickness total excessive.

In general, the antennas known above have the disadvantage that it is difficult and therefore expensive to obtain both the values desired for the frequencies of their resonances and a good coupling of each of these resonances to a signal processor.

• permettre de réaliser simplement une antenne bi-fréquence, pourvue d'un système facilement adaptable en impédance pour chacune de deux fréquences de résonance, et
• limiter les dimensions de cette antenne.

The present invention has in particular the following aims:

• allow a dual frequency antenna to be produced simply, provided with a system easily adaptable in impedance for each of two resonant frequencies, and
• limit the dimensions of this antenna.

And, for these purposes, it has in particular for object a layer antenna conductive, a coupling system of this antenna including a line coplanar formed by two slits extending in a conductive layer of this antenna and respectively constituting two coupling slots primary. According to this invention, said coupling system further includes a slotted line formed by a slit connecting to one of the two said slits primary coupling and constituting a secondary coupling slot.

Preferably this antenna includes a patch and a cooperating mass with this patch using the microstrip technique and the so-called coupling are formed in this pellet. But, according to another provision possible, a coupling system consisting of such slots would be formed in the mass of such an antenna.

• une zone de résonance primaire, cette zone incluant la dite ligne coplanaire, et
• une zone de résonance secondaire, cette zone incluant la dite ligne à fente.

More preferably, the said pellet includes a separator assembly including at least one separator slot and making two zones appear in this pellet constituting respectively:

• a primary resonance zone, this zone including the said coplanar line, and
• a secondary resonance zone, this zone including the said slotted line.

Various aspects of the present invention will be better understood using the description below and attached schematic figures. When the same element is represented in several of these figures it is designated there by same reference numbers and / or letters.

FIG. 1 represents a copper sheet cut to constitute after folding the short circuit and the patch of an antenna produced according to a first embodiment of this invention.

FIG. 2 represents a simplified perspective view of a device for transmission including the antenna whose patch is shown in Figure 1.

FIG. 3 represents a top view of an antenna produced according to a second embodiment of this invention.

• Un substrat diélectrique 2 présentant deux surfaces principales mutuellement opposées constituant respectivement une surface inférieure et une surface supérieure et s'étendant selon des directions horizontales DL et DT, ces directions pouvant dépendre de la zone considérée de l'antenne. Ce substrat peut présenter des formes diverses comme précédemment exposé.
• Une couche conductrice inférieure s'étendant par exemple au moins sur la totalité de la surface inférieure du substrat et constituant une masse 4 de cette antenne. La figure 2 montre seulement une partie de cette couche débordant de cette surface inférieure.
• Une couche conductrice supérieure représentée aux figures 1 à 3 et s'étendant sur une aire de la surface supérieure du substrat au-dessus de la masse 4 de manière à constituer une pastille 6. De manière générale cette pastille a une longueur et une largeur s'étendant selon deux directions horizontales constituant une direction longitudinale DL et une direction transversale DT, respectivement, et sa périphérie peut être considérée comme constituée par quatre bords s'étendant deux à deux à peu près selon ces deux directions. Quoique les mots longueur et largeur s'appliquent usuellement aux deux dimensions mutuellement perpendiculaires d'un objet rectangulaire, la longueur étant plus grande que la largeur, il doit être compris que la pastille 6 peut s'écarter largement de la forme d'un tel rectangle sans sortir du cadre de cette invention. L'un de ces bords s'étend de manière générale selon la direction transversale DT et constitue un bord arrière incluant deux segments 10 et 11. Un bord avant 12 est opposé à ce bord arrière. Deux bords latéraux 14 et 16 joignent ce bord arrière à ce bord avant.
• Enfin un court circuit S raccordant électriquement la pastille 6 à la masse 4 à partir du segment 10 du bord arrière de cette pastille. Ce court-circuit est formé par une couche conductrice s'étendant sur une surface de tranche du substrat 2, surface qui est typiquement plane et constitue alors un plan de court-circuit. Mais il pourrait aussi être constitué par un ou plusieurs composants discrets connectés en parallèle entre la masse 4 et la pastille 6. Dans chacun de ces modes il impose à au moins une résonance de l'antenne de présenter un noeud de champ électrique au moins virtuel au voisinage du segment 10 et d'être du type quart d'onde. Une telle résonance et sa fréquence seront appelées ci-après «résonance primaire» et «fréquence primaire». Les dits bords arrière, avant et latéraux et les directions longitudinale et transversale sont définis par la position d'un tel court-circuit dans la mesure où ce court-circuit est suffisamment important, c'est à dire notamment où son impédance est suffisamment basse pour imposer à l'antenne l'existence d'une résonance présentant un tel noeud de champ électrique.

In accordance with FIG. 2 and in a manner known per se, the resonant structure of an antenna according to this invention comprises the following elements:

• A dielectric substrate 2 having two mutually opposite main surfaces constituting respectively a lower surface and an upper surface and extending in horizontal directions DL and DT, these directions being able to depend on the considered zone of the antenna. This substrate can have various shapes as previously exposed.
• A lower conductive layer extending for example at least over the whole of the lower surface of the substrate and constituting a mass 4 of this antenna. Figure 2 shows only part of this layer projecting from this lower surface.
• An upper conductive layer represented in FIGS. 1 to 3 and extending over an area of the upper surface of the substrate above the mass 4 so as to constitute a patch 6. In general, this patch has a length and a width s extending in two horizontal directions constituting a longitudinal direction DL and a transverse direction DT, respectively, and its periphery can be considered as constituted by four edges extending two by two roughly in these two directions. Although the words length and width usually apply to the two mutually perpendicular dimensions of a rectangular object, the length being greater than the width, it should be understood that the patch 6 can deviate widely from the shape of such a rectangle without departing from the scope of this invention. One of these edges generally extends in the transverse direction DT and constitutes a rear edge including two segments 10 and 11. A front edge 12 is opposite this rear edge. Two lateral edges 14 and 16 join this rear edge to this front edge.
• Finally a short circuit S electrically connecting the patch 6 to ground 4 from segment 10 of the rear edge of this patch. This short circuit is formed by a conductive layer extending over a wafer surface of the substrate 2, a surface which is typically planar and then constitutes a short circuit plane. But it could also be constituted by one or more discrete components connected in parallel between the ground 4 and the patch 6. In each of these modes it requires at least one resonance of the antenna to present an electric field node at least virtual in the vicinity of segment 10 and to be of the quarter wave type. Such resonance and its frequency will hereinafter be called "primary resonance" and "primary frequency". Said rear, front and side edges and the longitudinal and transverse directions are defined by the position of such a short circuit insofar as this short circuit is sufficiently large, that is to say in particular where its impedance is sufficiently low. to impose on the antenna the existence of a resonance having such an electric field node.

The antenna further includes a coupling system. This system does part of a connection set which connects the resonant structure of the antenna to a signal processing unit T, for example to excite a or more resonances of the antenna from this organ in the event that it it is a transmitting antenna. In addition to this system, all of connection typically has a connection line which is external to the antenna. This line can in particular be of the coaxial type, of the type microstrip or coplanar type. In Figure 1 it has been symbolically represented in the form of two conducting wires C2 and C3 connecting respectively the mass 4 and the ribbon C1 at the two terminals of the signal processing T. But it should be understood that this line would be practice preferably carried out in the form of a microstrip line or of a coaxial line.

The signal processor T is adapted to operate at predetermined working frequencies which are at least close to useful resonant frequencies of the antenna, i.e. which are included in bandwidths centered on these resonance frequencies. he can be composite and then include an element tuned so permanent on each of these working frequencies. It can also include a tunable element on the various working frequencies. said primary resonant frequency constitutes such a resonant frequency useful.

In the context of the present invention, the coupling system of the antenna is composite: it first includes a primary coupling line formed by two slots extending in the patch 6 and constituting respectively two primary coupling slots F1 and F2; it then includes a secondary coupling line formed by another slot F3 which is connects to one of these two primary coupling slots, for example the slot F2, and which constitutes a secondary coupling slot. Without that is necessary in the context of this invention, the widths of these slots of coupling are for example uniform, their paths are for example straight, and the secondary coupling slot extends for example in the alignment of the primary coupling slot to which it connects. These widths and thickness and permittivity of the substrate are such that the lines primary and secondary coupling respectively constitute a line coplanar and a slotted line of the types previously described.

• une zone de résonance primaire Z1, cette zone incluant la dite ligne coplanaire F1,F2, et
• une zone de résonance secondaire Z2, cette zone incluant la dite ligne à fente F3.

Le court circuit S permet alors au moins à la résonance primaire de s'établir dans sa zone selon le type quart d'onde avec un noeud de champ électrique au moins virtuel fixé par ce court-circuit et un trajet de résonance s'étendant à partir du bord arrière 10 vers le bord avant 12, des bords de cette zone incluant les bords latéraux 14 et 16. La zone de résonance secondaire Z2 s'étend, selon la direction longitudinale, à distance du bord arrière 10 et, selon la direction transversale, sur une partie médiane de la largeur W1 de la pastille en restant à distance de chacun de ces deux bords latéraux 14 et 16. Les fentes de couplage F1 et F2 formant la ligne coplanaire s'étendent selon cette direction longitudinale à partir de ce bord arrière.Preferably and as shown, the patch 6 includes a separator assembly including at least one separator slot such as F4 or F5 and making two zones appear in this patch constituting respectively:

• a primary resonance zone Z1, this zone including the said coplanar line F1, F2, and
• a secondary resonance zone Z2, this zone including the said slotted line F3.

The short circuit S then allows at least the primary resonance to be established in its zone according to the quarter wave type with an electric field node at least virtual fixed by this short circuit and a resonance path extending to from the rear edge 10 towards the front edge 12, from the edges of this zone including the lateral edges 14 and 16. The secondary resonance zone Z2 extends, in the longitudinal direction, at a distance from the rear edge 10 and, according to the direction transverse, over a median part of the width W1 of the patch, remaining at a distance from each of these two lateral edges 14 and 16. The coupling slots F1 and F2 forming the coplanar line extend in this longitudinal direction from this rear edge.

In the device given as an example, the slotted line F3 extends along the longitudinal direction so that the secondary resonance is of the half type wave with a resonance path extending in the transverse direction But it could be bent at right angles and the secondary resonance could be of the quarter wave type with a longitudinal resonance path like the primary resonance. The difference between the primary and secondary would then result from a difference between the dimensions longitudinal of the two zones, that is to say, the short-circuit being common, of a gap between the longitudinal positions of respective front edges of these two areas.

According to the first embodiment of the invention, the assembly separator includes two separating slots F4 and F5 extending into the patch 6 in the longitudinal direction DL from the front edge 12 of this patch, so that two side edges of the secondary resonance zone Z2 are respectively constituted by edges of these two slots and that an edge front of this area consists of a segment 13 of this front edge between these two slots.

In accordance with FIG. 1, a copper sheet constituting the pellet 6 has an extension extending forward beyond a line in front constitute the rear edge 10 of this patch. When manufacturing the antenna it is folded along this line around the rear edge of the substrate so that this extension is applied on the vertical edge of the substrate. Part of this extension is connected to the substrate to constitute the short circuit S. The latter extends in a median segment of this edge and it is made in two parts which are located on either side of the coupling C1, F1, F2. The other parts of this extension are not shown in Figure 2. They facilitate positioning of the patch on the substrate and that of them which extends the ribbon C1 makes it possible to connect this ribbon to the processing member T without intervening on the upper surface of the antenna.

• fréquence de résonance primaire : F1 = 940 MHz,
• fréquence de résonance secondaire : F2 = 1880 MHz,
• impédance d'entrée : 50 ohms,
• largeur des bandes passantes autour des fréquences primaire et secondaire : 2,5% et 2% de ces fréquences, respectivement, ces largeurs étant mesurées à taux d'ondes stationnaires inférieur ou égal à 3,5.
• composition du substrat : stratifié à base de fluoro-polymère tel que PTFE ayant une permittivité relative εr = 5 et un facteur de dissipation tg δ = 0,002,
• longueur et largeur du substrat égales à celles de la pastille dans la zone de résonance primaire Z1,
• épaisseur du substrat : L6 = 3 mm,
• épaisseur des feuilles de cuivre formant les couches conductrices : 17 µm,
• longueur de la pastille dans la zone de résonance primaire Z1 : L1 = 28,75.mm,
• longueur de la pastille dans la zone de résonance secondaire Z2 : L2= 27, 25 mm,
• largeur de la pastille : W1= 25 mm,
• largeur de la zone de résonance secondaire Z2 : W2 = 12,5 mm,
• longueur de la fente de couplage F1 : L4 = 13mm
• longueur totale des fentes de couplage F2 et F3 : L3 = 23 mm,
• largeur des fentes de couplage F1, F2 et F3 : W6 = 0,4 mm,
• largeur du conducteur C1 : W4 = 4,75 mm,
• longueur des fentes séparatrices F4 et F5 dans la zone Z2 : L5= 18 mm,
• largeur des fentes séparatrices F4, F5 et F6 : W5 = 1 mm
• largeur de chacune des deux parties du court circuit : W3 = 1 mm.

In the context of this first mode, various compositions and values will be indicated below by way of example. The lengths and widths of the substrate and the patch are indicated respectively in the longitudinal directions DL and transverse directions DT.

• primary resonant frequency: F1 = 940 MHz,
• secondary resonant frequency: F2 = 1880 MHz,
• input impedance: 50 ohms,
• width of the passbands around the primary and secondary frequencies: 2.5% and 2% of these frequencies, respectively, these widths being measured at standing wave rate less than or equal to 3.5.
• composition of the substrate: laminate based on fluoro-polymer such as PTFE having a relative permittivity εr = 5 and a dissipation factor tg δ = 0.002,
• length and width of the substrate equal to those of the patch in the primary resonance zone Z1,
• substrate thickness: L6 = 3 mm,
• thickness of the copper sheets forming the conductive layers: 17 μm,
• length of the patch in the primary resonance zone Z1: L1 = 28.75.mm,
• length of the patch in the secondary resonance zone Z2: L2 = 27, 25 mm,
• width of the patch: W1 = 25 mm,
• width of the secondary resonance zone Z2: W2 = 12.5 mm,
• length of the coupling slot F1: L4 = 13mm
• total length of the coupling slots F2 and F3: L3 = 23 mm,
• width of the coupling slots F1, F2 and F3: W6 = 0.4 mm,
• conductor width C1: W4 = 4.75 mm,
• length of the separating slits F4 and F5 in the zone Z2: L5 = 18 mm,
• width of the separating slits F4, F5 and F6: W5 = 1 mm
• width of each of the two parts of the short circuit: W3 = 1 mm.

According to the second embodiment of the invention and as shown in Figure 3, the separator assembly includes a separator slot U-shaped remaining at a distance from the edges of the patch 6. This slot has two branches F4 and F5 connected to each other by a base F6. These two branches extend in longitudinal direction opposite and at a distance lateral edges 14 and 16 respectively and this base extends along the transverse direction opposite and at a distance from the front edge 12.

A supposed operation of the antennas produced according to these two modes will be described.

The coupling between on the one hand the standing wave of each of the two primary and secondary resonances and secondly the waves radiated in the space, is mainly done on one or more of the edges of the patch 6 or separating slits F4, F5 and F6 or through these slits. This will be expressed by saying that such an edge or such a slit is a primary radiative edge or secondary or a primary or secondary radiative cleft depending on the resonance considered.

In the two embodiments of the invention, a single edge primary radiative is present. This is the front edge 12, which corresponds to a primary resonance of the quarter wave type having an electric field node in segment 10. In the first mode two secondary radiative edges consist of the edges of the separating slots F4 and F5 at the limit of the zone Z2 in the vicinity of the front edge 13. In the second mode the two secondary radiative slots are formed by the slots F4 and F5, mainly away from their rear ends, and the F6 slot constitutes an additional secondary radiative slit in the vicinity of its ends.

Claims (10)

Conductive layer antenna, a coupling system of this antenna including a coplanar line (F1, F2) formed by two slots extending in a conductive layer of this antenna and constituting respectively two primary coupling slots (F1, F2), antenna characterized in that its said coupling system further includes a slotted line formed by a slot (F3) connecting to one (F2) of the two said primary coupling slots and constituting a secondary coupling slot. Antenna according to claim 1, this antenna including a patch (6) and a mass (4) cooperating with this patch according to the microstrip technique, this antenna being characterized in that the said coupling slots (F1, F2, F3) extend into said patch. Antenna according to claim 3, this antenna being characterized in that its said patch (6) includes a separator assembly including at least one separating slot (F4, F5) and making two zones appear in this patch respectively constituting: a primary resonance zone (Z1), this zone including the said coplanar line (F1, F2) and a secondary resonance zone (Z2), this zone including the said slotted line (F3). Dual-band transmission device, this device comprising: a signal processing device (T) adapted to be tuned in frequency in two working bands extending respectively around two predetermined center frequencies to transmit and / or receive an electrical signal in each of these two bands, and an antenna (1) including a plurality of mutually superimposed conductive layers to constitute at least one resonant structure, this antenna including a coupling system and being connected to said processing member (T) via this coupling system for coupling said electrical signal to radiated waves, this coupling system including a coplanar line formed by two slits extending opposite each other in a said conductive layer and constituting respectively two coupling slots (F1, F2), this coplanar line coupling a resonance of this antenna to said electric signal, this resonance constituting a primary resonance and having a primary frequency (F1) substantially equal to one of the two said central frequencies, another resonance of this antenna constituting a secondary resonance having a secondary frequency (F2) substantially equal to l other of these two center frequencies,
this device being characterized by the fact that said coupling system further includes a slotted line formed by a slit (F3) connecting to one (F2) of the two said primary coupling slits and constituting a secondary coupling slit, this slotted line coupling said secondary resonance to said electrical signal. Transmission device according to claim 4, said antenna including: a dielectric substrate (2) having two mutually opposite main surfaces extending in horizontal directions (DL, DT) of this antenna, these two surfaces respectively constituting a lower surface (S1) and an upper surface (S2), a lower conductive layer extending over said lower surface and constituting a mass (4) of this antenna, and an upper conductive layer extending over an area of said upper surface above said mass so as to constitute a patch (6) cooperating with said mass (4) according to the microstrip technique, this device being characterized in that the said coupling slots extend into the said pad. Transmission device according to claim 5, this device being characterized in that the said patch includes a separator assembly including at least one separating slot (F4, F5) and causing two zones to appear in this patch respectively constituting: a primary resonance zone (Z1), this zone including the said coplanar line (F1, F2), and a secondary resonance zone (Z2), this zone including the said slotted line (F3). Device according to claim 6, this device being characterized by the fact that said patch (6) has an edge provided with a short circuit (S) electrically connecting this patch (6) to said mass (4), this edge s' extending in a said horizontal direction constituting a transverse direction (DT) and constituting a rear edge (10,11), this patch also having a front edge (12) opposite this rear edge, and two lateral edges joining this rear edge to this front edge and constituting respectively two lateral edges (14,16), a length (L1) of this patch extending between this rear edge and said front edge (12) in a longitudinal direction (DL) constituted by another said horizontal direction , a width of this patch extending between its two said lateral edges, said short circuit allowing said primary resonance to be established in said primary resonance zone according to the quarter-wave type with an electric field node that at least virtual fixed by this short circuit and a resonance path extending from this rear edge towards this front edge, edges of this area including the said two lateral edges (14,16), the said area of secondary resonance (Z2) extending in said longitudinal direction (DL) at a distance from the rear edge (10) and extending in said transverse direction (DT) over a median part of said width (W1) of the patch (6) remaining at a distance from each of these two lateral edges (14, 16), the two said coupling slots (F1, F2) forming said coplanar line extending in this longitudinal direction from this rear edge. Device according to Claim 7, this device being characterized in that the said slotted line (F3) extends in the said longitudinal direction (DL) so that the said secondary resonance is a half-wave type resonance having a resonance path s 'extending in said transverse direction (DT). Device according to Claim 8, this device being characterized in that the said separator assembly includes two separating slots (F4, F5) extending in the said pad (6) in the said longitudinal direction (DL) from the said front edge (12 ) of this patch, so that two lateral edges of said secondary resonance zone (Z2) are respectively constituted by edges of these two slots and that a front edge of this zone is constituted by a segment (13) of this edge front of the pad between these two slots. Device according to Claim 8, this device being characterized in that the said separator assembly includes a U-shaped separating slot remaining at a distance from the said edges of the patch (6), this slot having two branches (F4, F5) connected l 'to one another by a base (F6), these two branches extending in said longitudinal direction (DL) opposite and at a distance respectively from said two lateral edges (14,16), this base extending according to said transverse direction (DT) opposite and at a distance from said front edge (12).

Images