EP1145378B1 - Dual-band transmission device and antenna therefor - Google Patents

Description

The present invention relates generally to radio transmission devices, in particular portable radiotelephones, and more particularly to antennas which are produced according to the microstrip technique to be included in such devices.

Such an antenna comprises a patch which is typically formed by etching a metal layer. It is called in English by specialists "microstrip patch antenna" for "microstrip pellet antenna".

The microstrip technique is a planar technique that applies both to the realization of lines transmitting 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.

This technique is distinguished from various other techniques also using conductive elements on a thin substrate, and in particular that of the coplanar lines in which the electric field is established on the upper surface of the substrate and symmetrically between d firstly a central conductive ribbon and secondly two conductive pads located on either side of this ribbon from which they are respectively separated by two slots. In the case of a loop slot antenna, a patch is surrounded by a continuous conductive pad from which it is separated by a 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 resonant structures may be made according to the microstrip technique and may be the seat of various resonance modes, 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 electromagnetic wave at both ends of this path. In the context of such a description, it is considered that the latter wave propagates in an electromagnetic line which would be constituted by the mass, the substrate and the pellet and which would define a linear path devoid of width. In fact such a wave has wavelengths that extend transversely over the entire section that is offered to them by the antenna so that this description simplifies the reality in a sometimes excessive manner. Since it can be considered linear this path 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 length of the resonance path is typically substantially equal to half a wavelength, that is to say half the wavelength of the progressive wave 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 prevailing in 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 spatially radiated waves is at an edge of the pellet in a region where the magnitude of the electric field across the substrate is sufficiently large.

Resonances of other more or less complex types can be established in antennas of this kind, each resonance being characterized by a distribution of electric and magnetic fields oscillating in a zone of space including the antenna and the immediate vicinity of this one. They depend in particular on the configuration of the pellets, the latter may in particular have slots, possibly radiative. They also depend on the possible presence and 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 assimilated, even approximately, to perfect short circuits whose impedances would be zero.

• La 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 certain following conditions are met. If the above antenna is called the "first antenna," these conditions are as follows:

• The 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 appear implicitly in the distinction that is sometimes made between a physical or geometrical length and a so-called "electrical" 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.

For a given antenna configuration, several resonances may appear. They then make it possible to use the antenna at each of the frequencies of these resonances.

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 a resonant structure of this antenna. The resonances of this antenna also depend on the nature and location of this system. 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 an antenna made according to the microstrip technique 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 used to obtain several resonant frequencies. Three such antennas will be examined:

A first such known antenna is described in the patent document US-A-4,766,440 (Gegan ). 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 device has the form of a line which is made according to the microstrip technique but which is also said to be coplanar, because the microstrip extends in the plane of the pellet and penetrates between two notches of the latter. This device is provided with impedance transformation means to adapt it to the different input impedances respectively presented by the line at the different resonance frequencies used as working frequencies.

• La nécessité de prévoir des moyens de transformation d'impédance complique la réalisation.
• L'ajustement précis des fréquences de résonance à des valeurs souhaitées est difficile à réaliser.

This first known antenna has the following drawbacks:

• The need to provide impedance transformation means complicates the implementation.
• Accurate adjustment of the resonance frequencies to desired values is difficult to achieve.

A second known antenna differs from the previous one 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 slots extending in line segments inside the pellet. These slots and short circuits make it possible to reduce the difference between two frequencies corresponding to two resonances having said path in common but two mutually different respective modes which are designated by the digits (0,1) and (0,3). that is 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.

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

A third 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.

• L'écart entre les deux fréquences de résonance est trop petit dans certains cas d'application.
• La nécessité d'utiliser un système d'adaptation complique la réalisation de l'antenne.
• Il peut en être de même de la réalisation du dispositif de couplage de l'antenne sous la forme d'une ligne coaxiale.

This third known antenna has the following drawbacks:

• The difference between the two resonance frequencies is too small in some application cases.
• The need to use an adaptation system complicates the realization of the antenna.
• It may be the same for the realization of the coupling device of the antenna in the form of a coaxial line.

The document WO-A-99/38227 discloses a dual-band antenna having a slot and a short-circuit, the origin of the slot and the short-circuit being on different sides of the patch.

The document JP-A-08250917 discloses an antenna structure similar to that of the invention, but being adapted to a single frequency band.

• permettre de réaliser simplement une antenne bi-fréquence,
• permettre de choisir plus librement que précédemment le rapport des fréquences centrales de deux bandes de travail d'un dispositif de transmission, et plus particulièrement de réaliser pour ce dispositif une antenne telle que le rapport de deux fréquences de résonance utiles de cette antenne soit compris entre 1,25 et 5 environ et notamment voisin de 2,
• donner à cette antenne une bande passante suffisamment large autour de chacune de ces deux fréquences de résonance pour permettre de situer dans chacune de ces deux bandes une fréquence d'émission et une fréquence de réception de ce dispositif sans faire apparaître de diaphonie,
• permettre un ajustement facile et précis de ces deux fréquences de résonance,
• permettre d'utiliser un dispositif de couplage unique et facilement adaptable en impédance pour chacune de ces 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 dual-frequency antenna,
• allow to choose more freely than before the ratio of the center frequencies of two working bands of a transmission device, and more particularly to achieve for this device an antenna such that the ratio of two useful resonant frequencies of this antenna is between 1.25 and 5 approximately and in particular close to 2,
• give this antenna a bandwidth sufficiently wide around each of these two resonance frequencies to allow to locate in each of these two bands a transmission frequency and a reception frequency of this device without causing crosstalk,
• enable easy and precise adjustment of these two resonance frequencies,
• allow to use a single coupling device and easily adaptable impedance for each of these two resonant frequencies, and
• limit the dimensions of this antenna.

And for these purposes it relates in particular to an antenna according to claim 1 and a dual-band transmission device according to claim 23.

Preferably, the separating slot is located, all along its length except in the vicinity of its origin, or at least a major part of its length, and on both sides, at a distance from the periphery of the upper pellet to the distance of the bottom of this slot at this periphery.

Preferably the origin of the separating slot is close to said short circuit so as to give the two said resonances two respective resonance paths both extending from this short circuit, one of these two paths being extending only into said body and the other extending into that body and into said tail.

Other embodiments are defined in the dependent claims.

• La figure 1 représente la pastille d'une antenne réalisée selon un premier mode de mise en oeuvre de cette invention.
• La figure 2 représente la pastille d'une antenne réalisée selon un deuxième mode de mise en oeuvre de cette invention.
• La figure 3 représente une vue en perspective d'un dispositif de transmission incluant l'antenne dont la pastille est représentée par la figure 2.
• La figure 4 représente une vue partielle d'un côté arrière d'une antenne réalisée selon un troisième mode de mise en oeuvre de cette invention.
• La figure 5 représente la pastille d'une antenne réalisée selon un quatrième mode de mise en oeuvre de cette invention, ce mode étant généralement préféré.
• La figure 6 représente la fente séparatrice de la pastille de la figure 5.

Various aspects of the present invention will be better understood from the description below and the accompanying schematic figures. When two elements are designated in several of these figures by the same numbers and / or letters of reference, they have the same function in two modes of implementation of this invention or it is.d'une same element.

• The figure 1 represents the patch of an antenna made according to a first embodiment of this invention.
• The figure 2 represents the patch of an antenna made according to a second embodiment of this invention.
• The figure 3 represents a perspective view of a transmission device including the antenna whose pellet is represented by the figure 2 .
• The figure 4 is a partial view of a rear side of an antenna made according to a third embodiment of this invention.
• The figure 5 represents the pellet of an antenna made according to a fourth embodiment of this invention, this mode being generally preferred.
• The figure 6 represents the separating slot of the tablet of the figure 5 .

• Un substrat diélectrique 2 présentant deux surfaces principales mutuellement opposées s'étendant selon des directions définies dans cette antenne et constituant 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. Ses deux surfaces principales constituent respectivement une surface inférieure S1 et une surface supérieure S2.
• Une couche conductrice inférieure s'étendant par exemple sur la totalité de cette surface inférieure et constituant une masse 4 de cette antenne.
• Une couche conductrice supérieure s'étendant sur une aire de cette surface supérieure 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 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 raccordant électriquement la pastille 6 à la masse 4 à partir du segment 10 du bord arrière de cette pastille. Dans un premier et un deuxième mode de mise en oeuvre de cette invention, ce court-circuit est formé par une couche conductrice S s'étendant sur une surface de tranche du substrat 2, surface qui est typiquement plane et constitue alors un plan de court-circuit. Dans un troisième mode de mise en oeuvre il est constitué par trois composants discrets R, L et D 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. Cette 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 Figures 1 to 3 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 extending along defined directions in this antenna and constituting 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. Its two main surfaces respectively constitute a lower surface S1 and an upper surface S2.
• A lower conductive layer extending for example over the entire lower surface and constituting a mass 4 of this antenna.
• An upper conductive layer extending over an area of this upper surface above the mass 4 so as to form a pellet 6. In general this pellet has a length and a width extending in two horizontal directions constituting a direction longitudinal DL and a transverse direction DT, respectively, and its periphery can be considered as constituted by four edges extending two to two approximately 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 must be understood that the wafer 6 can deviate from the shape of such a rectangle without departing from the scope of this invention. One of these edges extends generally 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 electrically connecting the chip 6 to the ground 4 from the segment 10 of the rear edge of this chip. In a first and a second embodiment of this invention, this short circuit is formed by a conductive layer S extending on a wafer surface of the substrate 2, which surface is typically flat and then constitutes a short plane. -circuit. In a third mode of implementation it consists of three discrete components R, L and D 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 an electric field node at least virtual near the segment 10 and be of the quarter wave type. This resonance and its frequency will be called "primary resonance" and "primary frequency" hereafter. 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 comprises on the one hand a main conductor constituted by a coupling ribbon C1 extending on the upper surface S2 of the substrate. This ribbon is connected to the chip 6 at a connection point 18 which may for example be located on the leading edge 14. The distance from the rear edge 10 at this point constitutes a connection number. This system also comprises a ground conductor constituted by the layer 4. It is part of a connection assembly which connects the resonant structure of the antenna to a signal processing unit T, for example to excite one or several resonances of the antenna from this body 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.

According to the present invention the separating slot 17 extends from the rear edge 10,11 of the pellet to a bottom 15 of this slot, at a distance from the lateral edges 14 and 16 and the front edge 12. The body 31 is thus connected to the tail 33 by a tail connection passage 32. This passage has a length W2 extending in the direction DT and a width L2 extending in the direction DL between the leading edge 14 and the bottom 15 This body has a width W1 extending along the direction DT. The slot 17 separates the rear edge on the one hand a body base 10 belonging to the body 31 and provided with the short circuit S and on the other hand, a tail base 11 belonging to the tail 33, this tail base having W4 width extending in the transverse direction DT. A vertex 13 of this tail is constituted by the junction zone of this tail with the passage 32. A length of this tail extends along the direction DL of the base 11 at this vertex. A width of this tail is defined at each point of this length and extends along the direction DT.

In the context of the first embodiment of this invention shown in figure 1 the widths of the body, the passage and the tail of the pellet are uniform and an antenna whose pellet is thus produced can meet the needs generally felt in the field of radiotelephones in that its primary and secondary frequencies can be in a report neighbor of two.

A second embodiment, however, appeared preferable to the first mode. In this second mode, the width W4 of the base 11 of the tail 33 is larger than the width W2 of its vertex 13. More preferably, the width of this tail increases from its vertex to its base, passing through several intermediate values between the widths of this summit and this base. More preferably this growth of the width of the tail is a continuous growth, and this tail has for example the shape of a trapezium whose large and the small base are constituted by the base and the top of this tail.

More preferably, the length L3 of the tail 33 is between 50% and 100% of the length L1 of the body 31, the ratio F2 / F1 of the secondary frequency F2 to the primary frequency F1 being between 1.9 and 2, 1.

More preferably the width W4 of the base 11 of the tail 33 is between 50% and 150% of the width W1 of the body 31. In addition, if it is considered that the passage 32 and the top 13 of this tail constitute a set of connection of this tail and that a smaller width of this set constitutes an effective tail connection width, this effective width W3 is preferably between 10% and 70% of the width W4 of this base.

Preferably, in the second and third embodiments of this invention, the substrate 2 includes in at least a part of its two mutually distinct and superimposed layers, these two layers respectively constituting a lower dielectric layer 21 carrying the mass 4 and an upper dielectric layer 22 carrying the wafer 6. This upper dielectric layer advantageously has a greater relative permittivity and possibly a smaller thickness That of this lower dielectric layer and these two layers extend over the entire area of the substrate. Such a difference between the two layers has the advantage of increasing the radiation efficiency over a long distance. In addition, it facilitates an adjustment of the resonant frequencies.

More preferably the antenna includes a conductive insert 23 extending in a fraction of the area of the pellet 6 between the two lower dielectric layers 21 and upper 22. This fraction advantageously extends under the passage 32 and in the vicinity of the front edge 12. This insert can have a width L5 = 5 mm, and a length W5 = 20 mm, a medium of this length coinciding with the middle of the front edge 12. It provides the advantage that the choice of its position and its dimensions allow to adjust the secondary frequency without modifying the primary frequency in a troublesome way.

According to a variant not shown, this same advantage could be obtained using a tongue constituted by a thin copper sheet extending in continuity with the body 31 and projecting from it and the substrate from the front edge 12. Such a tab can be bent at will on this edge to deviate from the plane of the pellet and closer to the vertical slice plane of the substrate. It is the choice of its inclination that then allows the desired frequency adjustment.

In the context of said first and second embodiments, various compositions and values will be given hereinafter by way of examples. The length and the width of the substrate are respectively indicated according to the longitudinal directions DL and transverse DT. The mass of the antenna covers the underside of the substrate. The short circuit S occupies the entire width of the base of the body 31.

• fréquence de résonance primaire : F1 = 980 MHz,
• fréquence de résonance secondaire : F2 = 1900 MHz,
• impédance d'entrée : 50 ohms,
• composition des couches conductrices : cuivre,
• épaisseur de ces couches : 17 microns,
• largeur du conducteur C1 : 5mm,

The following indications are valid for each of these two modes:

• primary resonant frequency: F1 = 980 MHz,
• secondary resonant frequency: F2 = 1900 MHz,
• input impedance: 50 ohms,
• composition of conductive layers: copper,
• thickness of these layers: 17 microns,
• conductor width C1: 5mm,

• longueur du substrat : 30mm,
• largeur du substrat : 20 mm,
• composition du substrat : stratifié à base de fluoro-polymère tel que PTFE ayant une permittivité relative εr égale à 5 et un facteur de dissipation tg δ égal à 0,002,
• épaisseur du substrat : 5 mm,
• longueur de la pastille : 20 mm,
• largeur du corps de la pastille : 13 mm,
• cote de raccordement : 2 mm,
• largeur de la fente séparatrice : 3 mm,
• longueur de cette fente : 26 mm
• largeur de la queue : 4 mm, et
• 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

The following indications are valid for the first mode of implementation:

• length of the substrate: 30mm,
• substrate width: 20 mm,
• composition of the substrate: fluoro-polymer-based laminate such as PTFE having a relative permittivity εr equal to 5 and a dissipation factor tg δ equal to 0.002,
• substrate thickness: 5 mm,
• length of the pellet: 20 mm,
• width of the body of the pellet: 13 mm,
• connection dimension: 2 mm,
• width of the separation slot: 3 mm,
• length of this slot: 26 mm
• width of the tail: 4 mm, and
• 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 rates of 3.5 or less;

• longueur du substrat : 32 mm,
• largeur du substrat : 26 mm,
• composition d'une couche inférieure 21 du substrat : mousse de faible permittivité,
• épaisseur de cette couche inférieure : 2 mm,
• composition d'une couche supérieure 22 du substrat : stratifié à base de fluoro-polymère tel que PTFE ayant une permittivité relative εr égale à 5 et un facteur de dissipation tg δ égal à 0,002,
• épaisseur de cette couche supérieure : 3 mm,
• longueur de la pastille : L1= 32 mm,
• largeur du corps de la pastille : W1 = 12 mm,
• cote de raccordement : L4 = 2 mm,
• longueur du passage : W2 = 4 mm,
• largeur du passage : L2 = 2 mm,
• queue 33 symétrique autour d'un axe parallèle au bord de tête 14,
• largeur du sommet 13 de la queue 33 : W3 = 2 mm,
• largeur de la base 11 de la queue 33 : W4 = 12 mm,
• longueur de la queue 33 : L3 = 30 mm,
• largeur des bandes passantes autour des fréquences primaire et secondaire : 3,5% et 4% de ces fréquences, respectivement, ces largeurs étant mesurées à taux d'ondes stationnaires inférieur ou égal à 3,5.

The following indications are valid for the second mode of implementation of the invention:

• length of the substrate: 32 mm,
• substrate width: 26 mm,
• composition of a lower layer 21 of the substrate: foam of low permittivity,
• thickness of this lower layer: 2 mm,
• composition of an upper layer 22 of the substrate: laminate based on fluoro-polymer such as PTFE having a relative permittivity εr equal to 5 and a dissipation factor tg δ equal to 0.002,
• thickness of this upper layer: 3 mm,
• length of the pellet: L1 = 32 mm,
• width of the body of the pellet: W1 = 12 mm,
• connection dimension: L4 = 2 mm,
• length of the passage: W2 = 4 mm,
• width of the passage: L2 = 2 mm,
• symmetrical tail 33 around an axis parallel to the leading edge 14,
• width of the top 13 of the tail 33: W3 = 2 mm,
• width of the base 11 of the tail 33: W4 = 12 mm,
• length of the tail 33: L3 = 30 mm,
• width of the bandwidths around the primary and secondary frequencies: 3.5% and 4% of these frequencies, respectively, these widths being measured at standing wave ratio less than or equal to 3.5.

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 of the edges of the patch 6. This will be expressed by saying that this edge is the primary or secondary radiative edge according to the resonance considered.

In the first embodiment of the invention, the primary radiative edge is the front edge 12, which corresponds to a quarter-wave type primary resonance having an electric field node on segment 10. The observed value of the primary frequency nevertheless suggests that the path of this resonance has been somewhat lengthened by the presence of the passage 32 and the tail 33. If the length of the chip was imposed such an elongation would give the primary frequency a value more weak in the presence of the slit 17 than in his absence. In the typical case where it is the value of this primary frequency which is imposed, the presence of this slot makes it possible to reduce the length of the pellet, which is a generally sought advantage. This advantage would remain if this antenna were included in a single-band transmission device that would only use the primary resonance of that antenna.

In this first embodiment, the secondary radiative edge is constituted by the base 11 of the shank 33. The observed value of the secondary frequency suggests that the path of the secondary resonance borrows, from the short circuit S, no only the length of the body 31, but also those of the passage 32 and the tail 33 and that this resonance is essentially a resonance of the half-wave type, the length of its path being however close to three quarters of the wavelength with two nodes of electric field one of which would be imposed by the short circuit S and the other would be close to the top 13 of the tail 33.

In the second embodiment of the invention the primary radiative edge is the base 11 of the tail 33 and the value of the primary frequency indicates that the primary resonance path of the quarter-wave type borrows from short circuit S, not only the length of the body 31, but also those of the passage 32 and the tail 33. In the typical case where it is the value of this primary frequency which is imposed, the presence of the slot 17 therefore allows to reduce the length of the pellet more strongly than in the first embodiment.

In this second embodiment, the secondary radiative edge is constituted by the front edge 12. The observed value of the secondary frequency suggests that the path of the secondary resonance extends over the length of the body 3 and that this resonance is essentially a resonance of the quarter wave type.

Preferably and as shown in figure 2 for this second mode, the body 31 is provided with a protrusion 34 extending in the plane of the pellet 6, projecting on the leading edge 14, in the vicinity of the front edge 12. In the context of this invention it has indeed, it was found that such an excrescence had the advantage of widening the bandwidths of the resonances of the antenna. This protrusion may be rectangular and then have a length L6 = 10 mm and a width W6 = 6 mm. Such an outgrowth 34 is also represented at figure 5 for the fourth mode of implementation of the invention, mode in which it is formed projecting on the rear edge 10 in the vicinity of the leading edge 14

According to a provision shown in figure 4 and used in the third embodiment of this invention, which is preferred for some applications of this invention, the short circuit has a fairly large impedance at the primary frequency so that the primary resonance is substantially different from a resonance which could be induced in the antenna in the vicinity of this frequency if this short circuit had no impedance. This impedance is at the same time quite small at this frequency to fix an electric field node of this resonance in the vicinity of the base 10 of the body 31, this node being at least virtual. This arrangement has the disadvantage of complicating the realization of the short circuit. But it has the sometimes major advantage that a suitable choice made according to this invention for the components of such an impedance allows that the resonances of an antenna or its physical characteristics are better adapted to the use of this antenna if the short circuit had no impedance.

More particularly, preferably, the impedance of this short circuit has an inductive component L. Such an inductive component makes it possible to reveal a quarter-wave type resonance having a virtual electric field node located behind the base 10 , that is to say outside the pellet 6. It thus provides an advantage which is to allow to further reduce the length of this pellet when the frequency F1 of the primary resonance is imposed.

The impedance of the short-circuit may also have a resistive component R, such a component providing the advantage of making it possible to increase the widths of the bandwidths of the antenna. It can also have a controlled component produced by a diode D provided with a decoupling capacitor connected in parallel and not shown. Such a component provides the advantage of controlling the frequency or bandwidth of a resonance of the antenna. Such components are easily made using at least one discrete component connected between the chip 6 and the mass 4.

The advantages indicated above as being related to the choice of the components of the impedance of a short-circuit requiring a resonance of the quarter-wave type would also appear in an antenna of which only this resonance would be used, and / or in an antenna whose pellet would be devoid of the slot 17 previously described.

Preferably, in the second and third embodiments of this invention, the substrate 2 includes in at least a part of its area two mutually distinct and superposed layers, these two layers respectively constituting a lower dielectric layer 21 carrying the mass 4. and an upper dielectric layer 22 carrying the wafer 6. This upper dielectric layer advantageously has a greater relative permittivity and possibly a smaller thickness than those of this lower dielectric layer and these two layers extend over the entire surface of the substrate. such difference between the two layers has the advantage of increasing the efficiency of radiation at great distances. In addition, it facilitates an adjustment of the resonant frequencies.

More preferably the antenna includes a conductive insert 23 extending in a fraction of the area of the pellet 6 between the two lower dielectric layers 21 and upper 22. This fraction advantageously extends under the passage 32 and in the vicinity of the front edge 12. This insert can have a width L5 = 5 mm, and a length W5 = 20 mm, a medium of this length coinciding with the middle of the front edge 12. It provides the advantage that the choice of its position and its dimensions allow to adjust the secondary frequency without modifying the primary frequency in a troublesome way.

According to a variant not shown, this same advantage could be obtained using a tongue constituted by a thin copper sheet extending in continuity with the body 31 and overflowing with the latter and the substrate from the front edge 12. Such a tab can be bent at will on this edge to deviate from the plane of the pellet and more or less close to the vertical slice plane of the substrate. It is the choice of its inclination that then allows the desired frequency adjustment.

In accordance with the figure 5 , the antenna made according to the fourth embodiment of this invention differs from previous antennas in particular by the fact that the origin O of the separating slot 17 and the short circuit S are close to the point common to both rear sides 10 and tail 16, the edges of this separating slot being concave on the side of the body 31 and convex on the side of the tail 33, so as to give the two said resonances two respective resonance paths extending from this short -circuit, one of these two paths extending only in this body and the other extending in this body and in this tail. In addition, the antenna coupling tape C1 and the protrusion 34 are connected to the rear edge 10. This antenna has the particular advantage of having a large bandwidth.

• fréquence de résonance primaire : F1 = 910 MHz,
• fréquence de résonance secondaire : F2 = 1800 MHz,
• largeur des bandes passantes autour des fréquences primaire et secondaire : 9 % et 8 % de ces fréquences, respectivement, ces largeurs étant mesurées à taux d'ondes stationnaires inférieur ou égal à 3,
• impédance d'entrée : 50 ohms,
• composition des couches conductrices : cuivre,
• épaisseur de ces couches : 200 microns,
• composition du substrat : mousse ayant une permittivité relative εr égale à 1 et un facteur de dissipation tg δ égal à 0,0001 ,
• épaisseur du substrat : 7 mm,
• longueur de la pastille 6 : W1= 24 mm,
• largeur de la pastille : L1= 35 mm,
• largeur du ruban C1 : 1,5 mm,
• largeur du court-circuit S : L4= 3,5 mm,
• cote de raccordement : L5= 5 mm,
• largeur de la fente séparatrice 17 : 1,5 mm,
• longueur de cette fente : 50 mm,
• abscisse maximale « xm » atteinte sur le trajet de cette fente : 21 mm,
• abscisse « xe » de l'extrémité de cette fente : 8 mm,
• ordonnée « ye» de l'extrémité de cette fente : 32 mm,
• largeur de l'excroissance 34 : L6 = 5 mm ; au plus,
• longueur de cette excroissance : W6 = 10 mm ; au plus.

In the context of this fourth embodiment, various compositions and values will be given below by way of example. As shown on the figure 6 , The lengths and widths are respectively set according to the longitudinal directions DL and DT cross. "X" abscissa and "y" ordinate are respectively measured along these same directions from the origin of the separating slot located on the periphery of the pellet. The mass of the antenna covers the underside of the substrate.

• primary resonant frequency: F1 = 910 MHz,
• secondary resonant frequency: F2 = 1800 MHz,
• width of the bandwidths around the primary and secondary frequencies: 9% and 8% of these frequencies, respectively, these widths being measured at standing wave ratio of less than or equal to 3,
• input impedance: 50 ohms,
• composition of conductive layers: copper,
• thickness of these layers: 200 microns,
• composition of the substrate: foam having a relative permittivity εr equal to 1 and a dissipation factor tg δ equal to 0.0001,
• substrate thickness: 7 mm,
• length of the pellet 6: W1 = 24 mm,
• width of the pellet: L1 = 35 mm,
• ribbon width C1: 1.5 mm,
• short-circuit width S: L4 = 3.5 mm,
• connection dimension: L5 = 5 mm,
• width of the separating slot 17: 1.5 mm,
• length of this slot: 50 mm,
• maximum abscissa "xm" reached on the path of this slot: 21 mm,
• abscissa "xe" of the end of this slot: 8 mm,
• ordinate "ye" of the end of this slot: 32 mm,
• width of the protrusion 34: L6 = 5 mm; at most,
• length of this growth: W6 = 10 mm; at most.

An adjustment of the dimensions of this protrusion allows a fine adjustment of the spectral positions of the bandwidths of the antenna.

In this fourth embodiment, the front edge 12 and the trailing edge 16 each constitute a primary radiative edge, and the value of the primary frequency indicates that the primary resonance path of the quarter-wave type borrows from short circuit S, not only of the body 31 to the passage 32, but also a length of the tail 33. In this mode the leading edge 14, the rear edge of the slot 17 and the rear edge 10 of the pellet each constitutes a secondary radiative edge and the observed value of the secondary frequency suggests that the path of the secondary resonance is contained in the body 31 and that this resonance is of a relatively complex type.

This invention also relates to an antenna as previously described.

• une fréquence d'émission haute située dans ladite bande fréquentielle haute,
• une fréquence de réception haute située dans cette bande fréquentielle haute,
• une fréquence d'émission basse située dans ladite bande fréquentielle basse, et
• une fréquence de réception basse située dans cette bande fréquentielle basse.

It is particularly applicable to the realization of a radiotelephone system. Such a system includes base stations and portable terminals and it can be realized within the framework of a GSM standard using frequencies close to 900 MHz and / or in the context of a DCS standard using frequencies close to 1800 MHz. In such a system, base stations or portable terminals may each include a transmission device according to this invention. In such a device adapted for this purpose the antenna is able to operate in a high frequency band in the vicinity of said secondary frequency and in a low frequency band in the vicinity of said primary frequency. The processing unit T is then tunable to four mutually distinct working frequencies which constitute:

• a high transmission frequency located in said high frequency band,
• a high reception frequency located in this high frequency band,
• a low transmission frequency located in said low frequency band, and
• a low reception frequency located in this low frequency band.

It is able to transmit or receive a signal when it is tuned to a said transmission frequency or to a said reception frequency, respectively.

This invention makes it possible to give each of these two frequency bands a sufficient width, not only to avoid a crosstalk between the spectral transmit and receive channels located in this band, but also to make it possible to choose between several possible positions of these channels. in this band. The low frequency band corresponds to the GSM standard and the high frequency band to the DCS standard. Thus, base stations and / or dual-mode terminals are produced economically, that is to say capable of operating in the context of any of these standards.

For example, the high transmit and receive frequencies can be respectively 1750 and 1840 MHz and the frequencies Low transmit and receive can be 890 and 940 MHz, respectively.

Claims (24)

1. An antenna produced according to the microstrip technique for a dual-band transmission device, which device comprises:

   - a signal processing unit (T) adapted to be frequency-tunable in two operating bands respectively extending around two predetermined central frequencies for transmitting and/or receiving an electrical signal in either of those two bands,

   - an antenna connection assembly including electrical conductors (C1, C2, C3, C4) connecting that processing unit to that antenna in order to couple said electrical signal to radiated waves,

   which antenna comprises:

   - a conductive mass (4)

   - a conductive patch (6) having a periphery (10, 12, 14, 16), said patch having a general rectangular shape and said periphery including a rear edge;

   - a short circuit (S) formed on said rear edge (10) of that periphery, and

   - a separating slot (17) having an origin (O) constituted by an opening formed on said rear edge (10) of that periphery, which slot penetrates into said patch beginning at that origin (O),

   said short-circuit and that separating slot allowing two resonances to be in effect in that antenna, one of those two resonances being of the quarter-wave type with an electric field node that is at least virtual fixed by that short-circuit, this resonance constituting a primary resonance and having a primary frequency (F1) roughly equal to one of said two central frequencies, another of those two resonances constituting a secondary resonance having a secondary frequency (F2) roughly equal to the other one of the two central frequencies,
   said electrical conductors of the connection assembly including said mass and a main antenna coupling conductor (C1) belonging to said patch so as to make it possible to couple said antenna to said signal processing unit (T) around each of the said two central frequencies,
   said separating slot (17) extending into said patch all the way to the bottom (15) of that slot located a sufficiently short distance away from said periphery so that the slot partially separates that patch into, first, a body (31) including set of main antenna coupling conductor and equipped with said short-circuit and, second, a tail (33) that does not have that circuit and is electrically connected to said connection assembly only by means of that body and a passageway (32) constituted by an area of that patch between that bottom and that periphery.
2. An antenna according to claim 1, characterized in that the majority of the length of said separating slot (17) and its two sides are further away from said periphery than they are from its said bottom (15) on that periphery.
3. An antenna according to claim 1, characterized in that the entire length of said separating slot (17) and its two sides, except in the vicinity of its said origin (O), are located further away from said periphery than they are from its said bottom (15) on that periphery.
4. An antenna according to claim 1, characterized in that said origin (O) of the separating slot (17) is in the vicinity of said short-circuit (S) so as to give both of said resonances two respective resonance paths both extending from that short-circuit, one of those two paths extending only into said body (31) and the other extending into that body and into said tail (33).
5. An antenna according to claim 4, characterized in that the edges of said separating slot (17) are concave on the side of said body (31) and convex on the side of said tail (33).
6. An antenna according to claim 1, including:

   - a dielectric substrate (2) exhibiting two main surfaces opposite one another extending in horizontal directions (DL, DT) from that antenna, those two surfaces respectively constituting a lower surface (S1) and an upper surface (S2),

   - a lower conductive layer extending along said lower surface and constituting said mass of that antenna,

   - an upper conductive layer extending along an area of said upper surface above said mass so as to constitute said patch (6),

   - said short-circuit (S), that short-circuit electrically connecting said patch (6) to said mass (4) from a segment of said periphery of that patch.
7. An antenna according to claim 6, characterized in that said patch (6) has a general rectangular shape, its said periphery including:

   - an edge equipped with said short-circuit (S) and constituting a rear edge (10,11),

   - an edge opposite that rear edge and constituting a front edge (12), and

   - two side edges joining that rear edge to a front edge and respectively constituting a head edge (14) and a tail edge (16), one length (L4) of that patch extending between that rear edge and said front edge (12) in a longitudinal direction (DL) constituted by a said horizontal direction, a width of that patch extending between its two said side edges along a said horizontal direction constituting a transverse direction (DT),
8. An antenna according to claim 6, characterized in that said short-circuit (R, L, D) has a fairly high impedance at said primary frequency so that said primary frequency is substantially different from a resonance that could be induced within said antenna in the vicinity of that frequency if that short-circuit had no impedance, that impedance simultaneously being low enough to set an electric field node of that resonance in the vicinity of that short-circuit, that node being at least virtual.
9. An antenna according to claim 8, characterized in that said impedance of the short-circuit (R, L, D) has an inductive component (L).
10. An antenna according to claim 8, characterized in that said impedance of the short-circuit has a resistive component (L).
11. An antenna according to claim 8, characterized in that said impedance of the short-circuit has a controlled component (L).
12. An antenna according to claim 8, characterized in that said short-circuit (R, L, D) comprises at least one discrete component connected between said patch (6) and said mass (4) of the antenna.
13. An antenna according to claim 6, characterized in that said dielectric substrate (2) includes in at least some of its area two mutually distinct, superimposed layers, those two layers respectively constituting a lower dielectric layer (21) bearing said mass (4) and an upper dielectric layer (22) bearing said patch (6).
14. An antenna according to claim 13, characterized in that said upper dielectric layer (22) has a relatively greater permittivity than said lower layer (21), those two layers extending into the entire area of said substrate (2).
15. An antenna according to claim 13, characterized in that it includes a conductive insert (23) extending into a fraction of the area of said patch (6) between said two lower (21) and upper (22) dielectric layers, that fraction extending at least under said passageway (32).
16. An antenna according to claim 7, characterized in that said body (31) is equipped with a protrusion (34) extending into the plane of said patch (6) in the vicinity of said passageway (32).
17. An antenna according to claim 7, characterized in that said separating slot (17) extends from said rear edge (10, 11) of said patch to said front edge (12) all the way to a bottom (1) of that slot at distances away from said two side edges and from that front edge, whereby said body (31) is connected to said tail (33) by a passageway (32) having a length and a width, that length (W2) extending in said transverse direction (DT), that width (L2) extending in said longitudinal direction (DL) between said front edge (14) and said bottom (15) of that slot (17), that slot separating said rear edge into a body base (10) belonging to said body and equipped with said short-circuit (S), and a tail base belonging to said tail, that tail base having a width (W4) extending in said transverse direction (DT), a peak (13) of that tail being constituted by the area where that tail joins with said passageway and having a width (W3) extending in that transverse direction, that tail having a length (L3) extending in said longitudinal direction (DL) of said tail base at that peak, a width of that tail being defined at each point of that length and extending in said transverse direction (DT).
18. An antenna according to claim 17, characterized in that said width (W4) of the base (11) of the tail (33) is larger than said width (W2) of the peak (13) of that tail.
19. An antenna according to claim 18, characterized in that said width of the tail (33) increases from said peak (13) at said base (11) of that tail while assuming intermediary value between said widths (W3, W4) from that peak and that base.
20. An antenna according to claim 19, characterized in that said length (L3) of the tail (33) is between 50% and 100% of said length (L1) of the body (31), the ratio F2/F1 of said secondary frequency (F2) to said primary frequency (F1) being between 1.9 and 2.1.
21. An antenna according to claim 19, characterized in that said width (W4) of the base (11) of the tail (33) is between 50% and 150% of said width (W1) of the body (31), said passageway (32) and said peak (13) of that tail constituting a connection assembly of that tail, a shorter width of that assembly constituting an actual tail connection width (W3), that actual width being between 10% and 70% of said width (W4) of that base.
22. An antenna according to claim 7, characterized in that said origin of the separating slot (17) and said short-circuit (S) are close to the point common to said rear side (10) and tail side (16), the edges of said separating slot (17) being concave on the side of said body (31) and convex on the side of said tail (33), so as to give the two said resonances two respective resonance paths both extending from that short-circuit, one of those two paths extending only in said body (31) and the other one extending into that body and into said tail (33).
23. A dual-band transmission device, which device comprises:

    - a signal processing unit (T) adapted to be frequency-tunable in two operating bands respectively extending around two predetermined central frequencies for transmitting and/or receiving an electrical signal in either of those two bands,

    - an antenna (1) according to one of the claims 1 to 22, and

    - an antenna connection assembly including electrical conductors (C1, C2, C3, C4) connecting that processing unit to that antenna in order to couple said electrical signal to radiated waves, those electrical conductors of the connection assembly including said mass and a main antenna coupling conductor (C1) belonging to said patch so as to make it possible to couple said antenna to said signal processing unit (T) around each of the said two central frequencies,
24. A transmission device according to claim 23, characterized in that said antenna coupling system (C1, 4) is a microstrip line comprising:

    - a strip constituting said main antenna coupling conductor (C1)
    and

    - said mass (4).

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