EP1172885B1 - Short-circuit microstrip antenna and dual-band transmission device including that antenna - Google Patents

Abstract

The antenna of said transmitter is a microstrip antenna. A rear edge of its patch is provided with a short circuit by means of which a quarter-wave primary resonance can be excited by a coplanar line formed by two coupling slots in an area. Separator slots separate said area from another area in which a secondary resonance can be established at twice the frequency of the primary resonance from a slotted line extending one slot of the coplanar line. The invention applies in particular to the production of a dual-mode mobile telephone to the GSM and DCS standards.

Description

The present invention relates generally to radio transmission devices, in particular portable radio telephones, and more particularly to antennas which are made using at least one conductive layer to be included in such devices.

Such an antenna comprises a patch which is typically formed by etching a metal layer. It is often performed using the microstrip technique and is then called in English by the specialists "microstrip patch antenna" for "microstrip patch antenna".

The microstrip technique is a planar technique that applies both to the realization of transmission lines transmitting guided waves, possibly carrying signals, and to that of antennas coupling between such lines and radiated waves. It uses ribbons and / or conductive pads formed on the upper surface of a thin dielectric substrate. A conductive layer extends over the lower surface of this substrate and constitutes a ground of the line or antenna. Such a pellet is typically wider than such ribbon and its shapes and dimensions are important features of the antenna. The shape of the substrate is typically that of a rectangular flat sheet of constant thickness and the pellet is also typically rectangular. But this is not an obligation. In particular, it is known that a variation in the thickness of the substrate may widen the bandwidth of such an antenna and that the tablet may take various forms and for example be circular. The electric field lines extend between the ribbon or pellet and the ground layer as they pass through the substrate. A transmission line operating in this manner will be hereinafter microstrip line.

This technique differs from coplanar techniques which also use conductive elements on a thin substrate, and in particular that of transmission lines in which the electric field is established on the upper surface of the substrate and in a symmetrical manner between a part a central conductor ribbon and secondly 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 manner is hereinafter called coplanar line. In an antenna made according to this technique, a pellet is surrounded by a continuous conductive pad from which it is separated by a slot.

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

Antennas made according to these techniques typically, although not necessarily, resonant structures capable of being the seat of standing waves for coupling with radiated waves in space.

Various types of such resonant structures can be made, for 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 referred to hereinafter as "resonances". In schematic form, each such resonance can be described as being a standing wave formed by the superposition of two progressive 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, the latter wave being an electromagnetic wave propagating on this path in the line constituted for example by the mass, the substrate and the pellet. This path is imposed by the constituent elements of the antenna. It can be rectilinear or curved. It will be referred to hereinafter as the "resonance path". The frequency of the resonance is inversely proportional to the time taken by the traveling wave considered above to travel this path.

A first type of resonance can be called a "half wave". In this type, the resonance path length is typically substantially equal to half a wavelength, that is to say half the wavelength of the wave. progressive as considered above. The antenna is then called "half wave". This type of resonance can be defined in a general manner by the presence of an electrical current node at each of the two ends of such a path, the length of which 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 is at least one of the two ends of this path, these ends being located in the regions where the amplitude of the electric field which is applied for example through 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 half wave type on the one hand in that the resonance path typically has a length substantially equal to one quarter wave, that is to say one quarter of the wavelength defined above. For this the resonant structure must include a short circuit at one end of this path, the word short circuit designating a connection connecting the mass and the chip. In addition this short circuit must have an impedance sufficiently small to be able to impose such a resonance. This type of resonance can be defined in a general manner by the presence of an electric field node fixed by such a short circuit in the vicinity of an edge of the chip and by an electrical current node located at the other end of the resonance path. The length of the latter can also be equal to an integer number of half-wavelengths adding to said quarter wavelength. The coupling with the space radiated waves is on an edge of the patch in a region where the magnitude of the electric field is sufficiently large.

Resonances of other types may be established, each of these types being characterized by a distribution of electric and magnetic fields oscillating in a space zone including the antenna and the immediate vicinity thereof. They depend in particular on the configuration of the pellets, the latter may in particular have slots, possibly radiative. In the case of antennas made using the microstrip technique, these resonances also depend on the possible presence and the localization of short-circuits as well as electrical models representative of these short-circuits when they are imperfect short-circuits, that is to say when they are not comparable, even approximately, with perfect short-circuits of which the 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 bring about a resonance presenting what can be called a virtual node. Such a node appears when the following conditions are met, the antenna above 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 pellet of a second antenna.
• This second antenna is identical to this first antenna within the limits of this area except that this second antenna is devoid of the short circuit in question.
• The pellet of this second antenna extends not only to the area already mentioned, which then constitutes a main area of this second antenna, but also to 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 is also a node for the resonance of the first antenna. For an antenna such as this first antenna, such a node will be hereinafter referred to as "virtual" because it is located in an area which is situated outside the pellet of this antenna and in which no electric field or magnetic capable of directly recognizing the presence of this node.

Although such "virtual nodes" are not classically taken into account in these terms to describe resonances, they implicitly appear 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 the pellet of the first of these antennas, the physical or geometrical length would be that of this pellet, and the electric length of this pellet would be in fact the physical length or geometry of the pellet of the second antenna.

The coupling of an antenna to a signal processing element such as an emitter is typically done via a connection assembly comprising a connection line which is external to this antenna and which terminates with a signaling system. integrated coupling to this antenna to couple this line to one or more resonances that can be established 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 the connection assembly is often referred to as a supply line of this antenna.

The present invention relates to various types of devices such as mobile telephones, base stations for the latter, automobiles and airplanes or air missiles. In the case of a portable radiotelephone, the continuous nature of the lower ground layer of an antenna made using the microstrip technique makes it possible to easily limit the radiation power intercepted by the body of the user of the device. In the case of automobiles and especially in the case of airplanes or missiles whose outer surface is metallic and has a curved profile making it possible to obtain low aerodynamic drag, the antenna may be shaped to this profile so as not to reveal additional aerodynamic drag annoying.

• 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 a conductive layer antenna must have the following qualities:

• it must be bi-frequency, that is to say it must be able to emit and / or efficiently receive waves radiated on two frequencies separated by a large spectral difference,
• it must be capable of being connected to a signal processing unit by means of a single connecting line for all the working frequencies of a transmission device without giving rise in this line to a standing wave ratio troublesome parasites,
• and it must not be necessary for this purpose to use a frequency multiplexer or demultiplexer.

Many known antennas have been made or proposed as part of the microstrip technique so as to have these three qualities. They differ from each other by the means included therein to allow the establishment and coupling of several resonant frequencies having different frequencies. Several such antennas will be examined.

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 pellet of this antenna has the shape of a circular disk 10 allowing this antenna to present two half-wave resonances whose paths are established respectively according to a diameter AA of this disk and according to the length an arcuate slot 24 inscribed in this disc. The coupling system is in the form of a line 16 constituting a quarter-wave transformer and connected at an inner point to the area of the wafer so as to give the real part of the input impedance of the antenna of substantially equal values for these two resonances. Impedance matching slots 26 and 28 are concentrically inscribed in the disk 10 so that the imaginary part of this input impedance also has substantially equal values for these two resonances. Line 16 is made according to the microstrip technique. That is, it is not performed according to the technique of coplanar lines as defined above. This document however also states that this line is coplanar, but this only indicates that the ribbon of this microstrip line extends in the plane of the pellet 10. Two slots are formed in the conductive layer of this pellet on either side of this ribbon to allow an end segment of this line to penetrate the area of this pellet 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 the line 16 at its inner end to the pellet 10. Despite this continuity and this apparent asymmetry, the specialists understand that in practice no wave propagates along 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 generally rectangular shape allowing this antenna to present two half-wave resonances whose paths are established along a length and a width of this patch. Moreover, it has a U-shaped curved slot which is entirely internal to this pellet. This slot is radiative and shows an additional resonance mode established in another path. 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 circularly polarized wave through the combination of two modes with the same frequency and crossed linear polarizations. The coupling system has the form of a line which is made according to the technique of microstrips, but which is also said to be coplanar, this as in the previous document Gegan, 769. This system is provided with impedance transforming means to adapt it to the different input impedances respectively presented by the line at the different resonance frequencies 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 patent document US-A-4,771,291 (LO et al). Its pellet has punctual short-circuits and slits extending along straight lines the pellet. These slots and short circuits make it possible to reduce the difference between two frequencies corresponding to two resonances having said common path but two mutually different respective modes which are designated by the digits (0,1) and (0,3). to say that this common path is occupied by a half wave or three half waves depending on the mode considered. The ratio between these two frequencies can thus be lowered from 3 to 1.8. Punctual short circuits consist of conductors crossing the substrate. The coupling system is constituted by a coaxial line whose central conductor passes through the substrate of the antenna to connect to the patch of the latter and whose ground conductor connects to the ground of the antenna.

This antenna has the particular disadvantage that its manufacture is complicated by the incorporation of 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 INTERNATIONAL DIGEST SYMPOSIUM, NEWPORT BEACH, JUNE 18-23, 1995, pp. 2124-2127 Boag et al "Dual Band Cavity-Backed Quarter-wave Patch Antenna A first resonance frequency is defined by the dimensions and characteristics of the substrate and the pellet of this antenna.A resonance of 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 of coaxial line type, the adaptation system being placed at the end of such a line, whose axial conductor is extended through the antenna substrate to connect to the latter's pad. .

A fifth known antenna is described in the document EP 0 923 156 . This antenna uses a coupling system including a coplanar line.

Other known antennas include three conductive layers, namely two pellets superposed above the same mass. They then have the particular disadvantage that the addition of the thicknesses of dielectric substrates interposed between these layers gives the antenna an excessive total thickness.

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

• 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 the following aims in particular:

• allow to realize simply a two-frequency antenna, provided with a system easily adaptable in impedance for each of two frequencies of resonance, and
• limit the dimensions of this antenna.

And, for these purposes, it particularly relates to a conductive layer antenna, a coupling system of this antenna including a coplanar line formed by two slots extending from an edge in a conductive layer of this antenna according to a longitudinal direction and respectively constituting two primary coupling slots. According to this invention, said coupling system further includes a slotted line formed by a slot connecting in the longitudinal direction to one of said two primary coupling slots in alignment thereof and constituting a coupling slot secondary.

Preferably this antenna includes a chip and a mass cooperating with this chip according to the microstrip technique and said coupling slots are formed in this chip. But, according to another possible arrangement, a coupling system constituted by 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 said pellet includes a separator assembly including at least one separating slot and making appear in this pellet two zones constituting respectively:

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

Various aspects of the present invention will be better understood from the description below and the accompanying schematic figures. When the same element is represented in more than one of these figures, it is designated by the same numbers and / or letters of reference.

The figure 1 represents a cut copper foil to constitute after folding the short circuit and the patch of an antenna made according to a first embodiment of this invention.

The figure 2 represents a simplified perspective view of a transmission device including the antenna whose pellet is represented by the figure 1 .

The figure 3 represents a top view of an antenna made 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 the figure 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 respectively constituting a lower surface and an upper surface and extending in horizontal directions DL and DT, these directions being able to depend on the considered area of the antenna. This substrate may have various shapes as previously stated.
• A lower conductive layer extending for example at least over the entire lower surface of the substrate and constituting a mass 4 of this antenna. The figure 2 shows only a part of this layer overflowing from this lower surface.
• An upper conductive layer shown in Figures 1 to 3 and extending over an area of the upper surface of the substrate above the mass 4 so as to constitute a pellet 6. In general this pellet has a length and a width extending in two horizontal directions constituting a longitudinal direction DL and a transverse direction DT, respectively, and its periphery may be considered as consisting of four edges extending two by two in approximately 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 must be understood that the wafer 6 may deviate widely from the shape of such rectangle without departing from the scope of this invention. One of these edges extends generally in the transverse direction DT and constitutes a trailing edge including two segments 10 and 11. A leading edge 12 is opposite to this trailing edge. Two lateral edges 14 and 16 join this rear edge to this front edge.
• Finally a short circuit S electrically connecting the chip 6 to the ground 4 from the segment 10 of the rear edge of this chip. This short circuit is formed by a conductive layer extending on a wafer surface of the substrate 2, which surface is typically flat and then constitutes a short-circuit plane. But it could also consist of one or more discrete components connected in parallel between the mass 4 and the chip 6. In each of these modes it imposes at least one resonance of the antenna to present a node of at least a virtual electric field near the segment 10 and be of the quarter wave type. Such resonance and its frequency will hereinafter be referred to as "primary resonance" and "primary frequency". Said said rear, front and lateral edges and the longitudinal and transverse directions are defined by the position of such a short circuit insofar as this short circuit is sufficiently important, 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 comprises a coupling system. This system is part of a connection assembly which connects the resonant structure of the antenna to a signal processing member T, for example to excite one or more resonances of the antenna from this organ in the case where it is a transmitting antenna. In addition to this system the connection assembly typically includes a connecting line which is external to the antenna. This line may in particular be of the coaxial type, of the microstrip type or of the coplanar type. On the figure 1 it has been symbolically represented in the form of two conducting wires C2 and C3 respectively connecting the mass 4 and the ribbon C1 to the two terminals of the signal processing unit T. But it must be understood that this line would in practice be made of preferably in the form of a microstrip line or a coaxial line.

The signal processing unit T is adapted to operate at predetermined working frequencies which are at least close to useful resonance frequencies of the antenna, that is to say which are included in passbands centered on these frequencies of frequencies. resonance. It can be composite and then include an element permanently assigned to each of these working frequencies. It can also include a tunable element on the various working frequencies. Said primary resonant frequency constitutes such a useful resonant frequency.

In the context of the present invention the coupling system of the antenna is composite: it firstly includes a primary coupling line formed by two slots extending in the chip 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 connected to one of these two primary coupling slots, for example the slot F2, and which constitutes a secondary coupling slot. Without this being necessary in the context of this invention, the widths of these coupling slots are for example uniform, their paths are for example rectilinear, and the secondary coupling slot extends for example in the alignment of the slot of primary coupling to which it is connected. These widths and the thickness and permittivity of the substrate are such that the primary and secondary coupling lines constitute respectively a coplanar line and a slit 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 1 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 tablet 6 includes a separator assembly including at least one separating slot such as F4 or F5 and showing in this tablet two areas 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 said slot 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 from the rear edge 10 to the front edge 12, edges of this zone including the side edges 14 and 16. The secondary resonance zone Z2 is extends, in the longitudinal direction, away from the rear edge 10 and, in the transverse direction, on a median portion of the width 1 of the chip 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 by way of example, the slot line F3 extends in the longitudinal direction so that the secondary resonance is of the half-wave type 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 as the primary resonance. The difference between the primary and secondary frequencies would then result from a difference between the longitudinal dimensions of the two zones, ie, the short circuit being common, of a difference between the longitudinal positions of respective front edges of these two areas.

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

In accordance with the figure 1 a copper foil constituting the patch 6 has an extension extending forwards beyond a line to form the rear edge 10 of this chip. During manufacture of the antenna it is folded along this line around the rear edge of the substrate so that this extension comes to apply 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 system C1, F1, F2. The other parts of this extension are not represented at the figure 2 . They facilitate the positioning of the pellet 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 er = 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 given below by way of example. The lengths and widths of the substrate and the wafer are respectively indicated according to the longitudinal DL and transverse directions DT.

• primary resonant frequency: F1 = 940 MHz,
• secondary resonant frequency: F2 = 1880 MHz,
• input impedance: 50 ohms,
• width of the bandwidths around the primary and secondary frequencies: 2.5% and 2% of these frequencies, respectively, these widths being measured at standing wave ratio less than or equal to 3.5.
• composition of the substrate: fluoro-polymer-based laminate such as PTFE having a relative permittivity er = 5 and a dissipation factor tg δ = 0.002,
• length and width of the substrate equal to those of the pellet 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 pellet in the primary resonance zone Z1:
  L1 = 28.75.mm,
• length of the pellet in the secondary resonance zone Z2:
  L2 = 27.25 mm,
• width of the pellet: 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 separating slots F4 and F5 in zone Z2: L5 = 18 mm,
• width of separating slots 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 in accordance with the figure 3 , the separator assembly includes a U-shaped separating slot spaced apart from the edges of the pellet 6. This slot has two branches F4 and F5 connected to each other by a base F6. These two branches extend in the longitudinal direction opposite and at a distance respectively from the lateral edges 14 and 16 and this base extends in the transverse direction opposite and at a distance from the front edge 12.

A supposed operation of the antennas made 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, on the other hand, the waves radiated in space, is mainly done on one or more of the edges of the patch 6 or separating slots. F4, F5 and F6 or through these slots. This will be expressed by saying that such an edge or slot is a primary or secondary radiative edge or a primary or secondary radiative slot depending on the resonance considered.

In both embodiments of the invention only one primary radiative edge is present. It is the front edge 12, which corresponds to a quarter-wave type primary resonance having an electric field node on the segment 10. In the first mode, two secondary radiative edges are constituted by the edges of the separating slots F4 and F5 at the edge of the zone Z2 near the front edge 13. In the second embodiment, the two secondary radiative slots consist of the slots F4 and F5, mainly at a distance from their rear ends, and the slot F6 constitutes an additional secondary radiative slot near its extremities.

Claims (10)

1. Patch antenna, a coupling system of this antenna including a coplanar line (F1, F2) formed by two slots extending from an edge (10) into a patch of this antenna in a longitudinal direction and respectively constituting two primary coupling slots (F1, F2), this antenna being characterised in that its coupling system further includes a slotted line formed by a slot (F3) connected in the longitudinal direction to one (F2) of said two primary coupling slots in alignment therewith and constituting a secondary coupling slot.
2. Antenna according to claim 1, this antenna including a patch (6) and a ground (4) cooperating with that patch in accordance with the microstrip technique, this antenna being characterised in that said coupling slots (F1, F2, F3) extend into said patch.
3. Antenna according to claim 3, this antenna being characterised in that said patch (6) includes a separator assembly including at least one separator slot (F4, F5) producing in this patch two areas respectively constituting:

   - a primary resonance area (Z1), this area including said coplanar line (F1, F2), and

   - a secondary resonance area (Z2), this area including said slotted line (F3).
4. Dual-band transmission device, this device including:

   - a signal processing unit (T) adapted to be tuned to a frequency in two operating bands respectively extending around two predetermined central frequencies to send and/or receive an electrical signal in each of those two bands, and

   - an antenna (1) including a plurality of mutually superposed patches to constitute at least one resonant structure, this antenna including a coupling system and being connected to said processing unit (T) via that coupling system to couple said electrical signal to radiated waves, this coupling system including a coplanar line formed by two slots extending from an edge (10) facing each other in one of said patches in a longitudinal direction and respectively constituting two coupling slots (F1, F2), this coplanar line coupling a resonance of this antenna to said electrical signal, this resonance constituting a primary resonance and having a primary frequency (F1) substantially equal to one of said two central frequencies, another resonance of this antenna constituting a secondary resonance having a secondary frequency (F2) substantially equal to the other of these two central frequencies,

   - this device being characterised in that said coupling system further includes a slotted line formed by a slot (F3) connected in the longitudinal direction to one (F2) of said two primary coupling slots in line therewith and constituting a secondary coupling slot, this slotted line coupling said secondary resonance to said electrical signal.
5. Transmission system according to claim 4, said antenna including:

   - a dielectric substrate (2) having two mutually opposed main surfaces extending in horizontal directions (DL, DT) of this antenna, these two surfaces constituting a lower surface (S1) and an upper surface (S2), respectively,

   - a lower conductive surface extending over said lower surface and constituting a ground (4) of this antenna, and

   - an upper conductive layer extending over an area of said upper surface above said ground in such a manner as to constitute a patch (6) cooperating with said ground (4) in accordance with the microstrip technique,

   - this device being characterised in that said coupling slots extend into said patch.
6. Transmission device according to claim 5, this device being characterised in that said patch includes a separator assembly including at least one separator slot (F4, F5) producing in the patch two areas respectively constituting:

   - a primary resonance area (Z1), this area including said coplanar line (F1, F2), and

   - a secondary resonance area (Z2), this area including said slotted line (F3).
7. Device according to claim 6, this device being characterised in that said patch (6) has an edge provided with a short-circuit (S) electrically connecting this patch (6) to said ground (4), this edge extending in one of said horizontal directions 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 two respective 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) consisting of another of said horizontal directions, a width of this patch extending between its said two lateral edges, said short-circuit enabling said primary resonance to be established in said primary resonance area in accordance with the quarter-wave type with an at least virtual electrical field node fixed by this short-circuit and a resonance path extending from this rear edge toward this front edge, edges of this area including said two lateral edges (14, 16), said secondary resonance area (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 portion of said width (W1) of the patch (6) remaining at a distance from each of these two lateral edges (14, 16), said two coupling slots (F1, F2) extending in this longitudinal direction from this rear edge forming said coplanar line.
8. Device according to claim 7, this device being characterised in that said slotted line (F3) extends in said longitudinal direction (DL) so that said secondary resonance is a half-wave type resonance having a resonance path extending in said transverse direction (DT).
9. Device according to claim 8, this device being characterised in that said separator assembly includes two separator slots (F4, F5) extending into said patch (6) in said longitudinal direction (DL) from said front edge (12) of this patch, so that two lateral edges of said secondary resonance area (Z2) respectively consist of edges of these two slots and a front edge of this area consists of a segment (13) of this front edge of the patch between these two slots.
10. Device according to claim 8, this device being characterised in that said separator assembly includes a U-shaped separator slot remaining at a distance from said edges of the patch (6), this slot having two branches (F4, F5) connected to each other by a base (F6), these two branches extending in said longitudinal direction (DL) facing and at a distance from said two lateral edges (14, 16), respectively, this base extending in said transverse direction (DT) facing and at a distance from said front edge (12).

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