EP0954055A1 - Dual-frequency radiocommunication antenna realised according to microstrip technique - Google Patents

Abstract

The same patch antenna produces a quarter wave resonance across one dimension and a half wave resonance across the second dimension.

Description

The present invention relates, in general, to the devices for radiocommunication, in particular portable radiotelephones, and it relates more particularly to the antennas which are produced according to the microstrip technique to be included in such devices. Such a antenna includes a patch which is typically formed by etching of a metallic layer. It is called in English by specialists "microstrip patch antenna" for "microstrip type patch antenna".

The microstrip technique is a planar technique that applies both to the realization of lines transmitting signals and to that antennas coupling between such lines and waves radiated. It uses conductive tapes and / or pads formed on the upper surface of a thin dielectric substrate which separates them from conductive layer extending over the lower surface of this substrate and constituting a mass of the line or the antenna. Such a tablet is typically wider than such a ribbon and its shapes and dimensions constitute important features of the antenna. The shape of the substrate is typically that of a flat rectangular sheet of constant thickness and the the patch is also typically rectangular. But this is by no means a obligation. In particular, it is known that a variation in the thickness of the substrate, for example according to an exponential law, makes it possible to widen the band bandwidth of such an antenna and that the shape of the patch can in particular be circular. The electric field lines extend between the ribbon or the pellet and the mass layer crossing the substrate.

This technique differs from various other techniques using them also conductive elements on a thin substrate, and in particular of that coplanar lines in which the electric field is established on the surface top of the substrate and symmetrically between on the one hand a ribbon central conductor and on the other hand two conductive pads located on the one and on the other side of this ribbon from which they are respectively separated by two slots. In the case of an antenna a patch is surrounded by a conductive pad continuous from which it is separated by a slit.

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

In a schematic way, a distinction can be made between various types of resonant structures which can be produced according to the microstrip technique, these types corresponding respectively to various resonance modes of these structures. A first type is the most common and can be called "half wave". Being admitted that a dimension of the pellet constitutes a length and extends in a so-called longitudinal direction, this length is typically substantially equal to half a wave, i.e. half the wavelength of a propagating electromagnetic wave in this direction in the line formed by the mass, the substrate and the pastille. The antenna is then called "half wave". This type of resonance can be generally defined by the presence of a current node electric at each of the two ends of this length which can therefore also be equal to said half wave multiplied by an integer other that a. This number is typically odd. Coupling with waves radiated is done at the ends of this length, these ends being located in regions where the amplitude of the electric field prevailing in the substrate is maximum.

A second type of resonant structure which can be produced according to this same technique can be called "quarter wave". It differs from said type half wave on the one hand by the fact that the patch typically has a length substantially equal to a quarter wave, i.e. a quarter of a length wavelength, this length of the patch and this wavelength being defined as above, the antenna then being called "quarter wave". It differs from others apart from the fact that a significant short circuit is made at one end of this length between the mass and the patch so as to impose a mode of resonance of a type called "quarter wave". This type of resonance can be defined generally by the presence of a fixed electric field node by this short circuit at one end of the length of the patch and by a electric current node located at the other end of this length. This last can therefore also be equal to a whole number of half-waves in addition to said quarter wave. The coupling with the radiated waves is done at the other end of this length, this other end being located in the region where the amplitude of the electric field through the substrate is maximum.

• de la configuration des pastilles, ces dernières pouvant notamment présenter des fentes, éventuellement radiatives,
• de l'éventuelle présence et de la localisation de courts-circuits ainsi que des modèles électriques représentatifs de ces courts-circuits, ces derniers n'étant pas toujours assimilables, même approximativement, à des courts-circuits parfaits dont les impédances seraient nulles,
• et des dispositifs de couplage qui ont été inclus dans ces antennes pour permettre de coupler leurs structures résonantes à un organe de traitement de signal tel qu'un émetteur, ainsi que de la localisation de ces dispositifs.

Still other modes of resonance can be established in planar antennas. These modes depend in particular:

• the configuration of the pellets, the latter possibly having slots, possibly radiative,
• the possible presence and location of short circuits as well as the representative electrical models of these short circuits, the latter not always being assimilated, even approximately, to perfect short circuits whose impedances would be zero,
• and coupling devices which have been included in these antennas to allow their resonant structures to be coupled to a signal processing member such as a transmitter, as well as the location of these devices.

In addition, for a given antenna configuration, several modes of resonance may appear and allow use of the antenna several frequencies corresponding to these modes.

The present invention will in particular be characterized by the choice of certain "resonance paths" which will be specified below. This is why the meaning given below to the expression "resonance path" will be defined as follows:

Each resonance mode can be described as resulting from the superposition of two waves propagating in two opposite directions on a same path by reflecting alternately at the two ends of this path. This path is imposed by the constituent elements of the antenna. he constitutes said "resonance path" for this resonance mode. It is straight and longitudinal in the case of half-wave and quarter-wave antennas previously mentioned. But it can also conform to a slit curved radiative. In all cases the resonant frequency is inversely proportional to the time during which a progressive wave considered above travels this resonance path. The expression "mode of resonance "will sometimes be replaced below by the term" resonance ".

The coupling of an antenna to a signal processing device such that a transmitter is typically done through a set of connection comprising a coupling device included in this antenna, and an external connection line to this antenna and connecting the device for coupling to the signal processing device.

In the case of a transmitting antenna with a resonant structure, respective functions of the coupling device, the connection line and the antenna are as follows: the function of the connection line is to carry a radio frequency or microwave signal from the transmitter to the antenna terminals. Throughout such a line the signal is propagates in the form of a traveling wave without undergoing, at least in principle, significant modification of its characteristics. The function of coupling device is to transform the signal supplied by the line of connection so that this signal excites a resonance of the antenna, i.e. the energy of the traveling wave carrying this signal is transferred to a standing wave settling in the antenna with characteristics defined by the latter. This transfer is generally imperfect, i.e. that the coupling device reflects part of the energy towards the line of connection which gives rise in this latter to a wave parasitic stationary. The corresponding standing wave rate varies in frequency function and the diagram of this variation defines the antenna bandwidths. As for the antenna, it transfers energy from the standing wave useful to a wave radiated in space. The signal supplied by the transmitter thus undergoes a first transformation to pass from the form from a traveling wave to that of a standing wave, then a second transformation which gives it the shape of a radiated wave. In the case of a receiving antenna the signal takes the same forms in the same organs but he takes them in reverse order.

The coupling device and the connection line can be performed using a technique other than that of microstrips, for example in the form of coaxial or coplanar lines. Their natures and their dimensions are chosen so as to obtain a mutual adaptation of the impedances of the various organs traversed by the signals, this to limit the stray reflections.

With reference to the case of transmitting antennas, all of connection of an antenna is often referred to as constituting a line power supply to this antenna.

The present invention relates to antennas able to be included in various types of devices. These devices include radiotelephones laptops, base stations for them, automobiles and planes or aerial missiles. In the case of a portable radiotelephone the continuity of the lower mass layer of an antenna produced using microstrip technique makes it easy to limit the power of radiation intercepted by the body of the user of the device. In the the case of automobiles and especially in that of planes or missiles whose outer surface is metallic and has a curved profile allowing to obtain a low aerodynamic drag, the antenna can be conformed to this profile so as not to show aerodynamic drag additional annoying.

• elle doit être bifréquence 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 fonctionnement d'un dispositif de radiocommunication 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 of this kind must have the following qualities:

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

Many known dual-frequency antennas have been produced or proposed as part of the microstrip technique. They different each other by the means used to obtain several frequencies of resonance. Three such antennas will be examined:

A first such known antenna is described in patent document US-A-4,766,440 (Gan). The patch 10 of this antenna has a generally rectangular shape allowing this antenna to have two half-wave resonances whose paths are established along a length and a width of this patch. Furthermore, it has a curved U-shaped slot which is entirely internal to this patch. This slit is radiative and reveals an additional mode of resonance establishing itself along another path. It also makes it possible, by a suitable choice of its shape and its dimensions, to bring the frequencies of the resonance modes to desired values which gives the possibility of emitting a wave with circular polarization thanks to the association of two modes with the same frequency and crossed linear polarizations. The coupling device has the form of a line which is produced according to the microstrip technique but which it is also said to be coplanar, this because the microstrip extends in the plane of the patch and enters 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 resonant frequencies used as operating 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 disadvantages in particular:

• The need to provide means for impedance transformation complicates the implementation.
• It is difficult to precisely adjust the resonant frequencies to desired values.

A second known antenna differs from the previous one by the use of a single resonance path. It is described in patent document US-A-4,771,291 (LO et al). Its patch has punctual short-circuits and slits extending along respective straight segments inside the patch. 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 respective mutually different modes which are designated by the numbers (0,1) and (0,3), c ' that is to say that this common path is occupied by a half wave or by three half waves depending on the mode considered. The ratio between these two frequencies can thus be lowered from 3 to 1.8. The point short-circuits are formed by conductors crossing the substrate.

• L'encombrement correspond à trois demi-ondes.
• L'incorporation des courts-circuits ponctuels complique la réalisation de l'antenne.
• Le dispositif de couplage de l'antenne sous la forme d'une ligne coaxiale nécessite un ajustage précis de la position de la structure coaxiale traversant le substrat, pour obtenir une bonne adaptation à une ligne d'alimentation ayant une impédance de 50 ohms, pour les deux fréquences de fonctionnement.

This second known antenna has the following disadvantages in particular:

• The size corresponds to three half-waves.
• The incorporation of specific short circuits complicates the creation of the antenna.
• The antenna coupling device in the form of a coaxial line requires a precise adjustment of the position of the coaxial structure passing through the substrate, to obtain a good adaptation to a supply line having an impedance of 50 ohms, for the two operating frequencies.

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

• 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 disadvantages in particular:

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

• permettre de réaliser simplement une antenne bifréquence en choisissant plus librement que précédemment le rapport de deux fréquences de résonance utiles de cette antenne, et plus particulièrement de réaliser une telle antenne pour que ce rapport soit compris entre 0,2 et 0,8 environ et notamment voisin de 0,5,
• donner à cette antenne une bande passante suffisamment large autour de chacune de ces deux fréquences de résonance pour permettre de situer dans cette bande une fréquence d'émission et une fréquence de réception sans faire apparaítre 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 in particular the following aims:

• make it possible to simply produce a dual-frequency antenna by choosing more freely than previously the ratio of two useful resonant frequencies of this antenna, and more particularly to produce such an antenna so that this ratio is between 0.2 and 0.8 approximately and in particular close to 0.5,
• give this antenna a sufficiently wide bandwidth around each of these two resonant frequencies to make it possible to locate in this band a transmission frequency and a reception frequency without causing crosstalk to appear,
• allow easy and precise adjustment of these two resonance frequencies,
• allow the use of a single coupling device which is easily adaptable in impedance for each of these two resonant frequencies, and
• limit the dimensions of this antenna.

And for these purposes it has in particular for object a dual-frequency antenna produced using the microstrip technique. This antenna has a patch having a rear edge, a front edge opposite this rear edge, and two lateral edges joining this rear edge to this front edge. This rear edge is provided with a short circuit allowing a quarter wave type resonance to establish themselves in this antenna with an electric field node fixed by this short circuit and a resonance path extending between said trailing edge and said front edge. This antenna further includes a coupling device antenna allowing it to be coupled to a signal processing device such than a transmitter or receiver. Compared to the third known antenna previously mentioned, this antenna according to the invention is characterized by the fact that its coupling device has a differentiating asymmetry one of the lateral edges of the patch relative to the other so as to allow this device to couple this antenna to said processing member signal not only for said quarter wave resonance, but also for a half-wave type resonance establishing in this antenna with a resonance path extending between the two lateral edges of the pastille.

• un organe de traitement de signal adapté à être accordé au voisinage d'au moins deux fréquences prédéterminées pour émettre et/ou recevoir un signal électrique à chacune de ces deux fréquences, et
• une antenne raccordée à cet organe de traitement pour coupler ledit signal électrique à des ondes rayonnées. Cette antenne est réalisée selon la technique des microrubans. Sa pastille a un bord muni d'un court-circuit et constituant un bord arrière. Elle a aussi un bord avant opposé à ce bord arrière, et deux bords latéraux joignant ce bord arrière à ce bord avant. Le court-circuit permet à une résonance du type quart d'onde de s'établir dans l'antenne avec un noeud de champ électrique fixé par ce court-circuit et un trajet de résonance s'étendant entre ledit bord arrière et ledit bord avant. Cette résonance a une fréquence qui est l'une des dites fréquences prédéterminées et qui constitue une fréquence de résonance quart d'onde. Ce dispositif est caractérisé par le fait que l'autre dite fréquence prédéterminée est une fréquence de résonance demi onde constituée par la fréquence d'une résonance du type demi onde s'établissant dans cette antenne avec un trajet de résonance s'étendant entre les deux dits bords latéraux. Les types de résonances considérés dans le cadre de cette invention ont été définis d'une manière générale ci-avant.

The present invention also relates to a dual-frequency radiocommunication device, this device comprising:

• a signal processing device adapted to be tuned in the vicinity of at least two predetermined frequencies for transmitting and / or receiving an electrical signal at each of these two frequencies, and
• an antenna connected to this processing member for coupling said electrical signal to radiated waves. This antenna is produced using the microstrip technique. Its patch has an edge provided with a short circuit and constituting a rear edge. It also has a front edge opposite this rear edge, and two lateral edges joining this rear edge to this front edge. The short circuit allows a quarter wave type resonance to be established in the antenna with an electric field node fixed by this short circuit and a resonance path extending between said rear edge and said front edge . This resonance has a frequency which is one of said predetermined frequencies and which constitutes a quarter wave resonance frequency. This device is characterized by the fact that the other so-called predetermined frequency is a half-wave resonance frequency constituted by the frequency of a half-wave type resonance establishing in this antenna with a resonance path extending between the two said lateral edges. The types of resonances considered in the context of this invention have been defined in general above.

Whatever the nature of the antenna coupling device which will be used to allow this radiocommunication device to operate in the two spectral bands centered on the two frequencies of quarter wave and half wave resonance, this invention has an advantage in the case where the ratio between two operating frequencies desired values, and more particularly in the case where this ratio is between 0.2 and 0.8 approximately and in particular close to 0.5. This advantage is to allow to achieve this desired relationship in a way relatively simple and effective. It is obtained through the combined use of two resonance modes which are, one of a so-called quarter wave type, the other of a said half wave type, and which are established from traveling waves traversing the same area in two respective directions mutually crossed.

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

FIG. 1 represents a perspective view of a device for radiocommunication produced according to this invention.

Figure 2 shows a top view of the antenna of the Figure 1.

FIG. 3 represents a diagram of the variation of a coefficient of reflection measured at the input of this same antenna and plotted on the ordinate, in function of the frequency of a signal feeding this antenna, this frequency being plotted on the abscissa.

• 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 du type désigné mondialement par le mot anglais patch. De manière générale cette pastille a une longueur et une largeur s'étendant selon deux dites directions horizontales qui seront définies ci-après et qui constituent 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 sensiblement 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 pourrait s'écarter de la forme d'un rectangle sans sortir du cadre de cette invention. Plus particulièrement les directions DL et DT peuvent former un angle différent de 90 degrés, lesdits bords de cette pastille peuvent ne pas être rectilignes et ne pas être séparés par des sommets anguleux et la dite longueur de la pastille peut être plus courte que sa dite largeur. L'un de ces bords s'étend selon la direction transversale DT et constitue un bord arrière 10. 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 C2 raccordant électriquement la pastille 6 à la masse 4 à partir du bord arrière de cette pastille. Ce court-circuit est formé par une couche conductrice s'étendant sur une surface de tranche du substrat, surface qui est typiquement plane et constitue alors un plan de court-circuit. Il impose à une résonance de l'antenne de présenter un noeud de champ électrique sur le bord arrière 10 et d'être au moins approximativement du type quart d'onde. La fréquence de cette résonance sera appelée ci-après "fréquence de résonance quart d'onde". 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 est suffisamment étendu et a une impédance suffisamment basse pour imposer à l'antenne l'existence d'une résonance dudit type quart d'onde.

In accordance with FIGS. 1 and 2 and in a manner known per se, an antenna according to the present invention firstly comprises a resonant structure which itself comprises the following elements:

• A dielectric substrate 2 having two mutually opposite main surfaces extending in directions defined in this antenna and constituting horizontal directions DL and DT, these directions being able to depend on the considered zone of the antenna. This substrate can have various shapes as previously exposed. Its two main surfaces respectively constitute a lower surface S1 and an upper surface S2.
• A lower conductive layer extending for example over the whole of this 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 constitute a patch 6 of the type designated worldwide by the English word patch. In general, this patch has a length and a width extending in two said horizontal directions which will be defined below and which constitute a longitudinal direction DL and a transverse direction DT, respectively, and its periphery can be considered to be constituted by four edges extending two by two substantially in these two directions. Although the words length and width usually apply to the two mutually perpendicular dimensions of a rectangular object, the length being greater than the width, it should be understood that the patch 6 could deviate from the shape of a rectangle without go beyond the scope of this invention. More particularly the directions DL and DT can form an angle different from 90 degrees, said edges of this patch may not be straight and not be separated by angular vertices and said length of the patch may be shorter than its said width . One of these edges extends in the transverse direction DT and constitutes a rear edge 10. 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 C2 electrically connecting the patch 6 to ground 4 from the rear edge of this patch. This short circuit is formed by a conductive layer extending over a wafer surface of the substrate, a surface which is typically planar and then constitutes a short circuit plane. It requires resonance of the antenna to present an electric field node on the rear edge 10 and to be at least approximately of the quarter wave type. The frequency of this resonance will be called hereinafter "quarter wave resonance frequency". Said rear, front and side edges and the longitudinal and transverse directions are defined by the position of such a short circuit insofar as this short circuit is sufficiently large, that is to say in particular is sufficiently large and has a sufficiently low impedance to impose on the antenna the existence of a resonance of said quarter wave type.

The antenna further includes a coupling device. These measures comprises on the one hand a main conductor constituted by a ribbon of coupling C1 extending over the upper surface S2 of the substrate and connected to the patch 6 at an internal connection point 18. It also comprises a ground conductor formed by layer 4. It constitutes all or part a connection assembly which connects the resonant structure of the antenna to a signal processor 22, for example to excite one or more resonances of the antenna from this member in the case where it is a transmitting antenna. In addition to this device, all of connection typically has a connection line which is external to the antenna. This line can in particular be of the coaxial type, of the type microstrip or coplanar type.

• un conducteur principal présentant la forme d'un ruban de raccordement C3 s'étendant sur la surface supérieure S2 du substrat 2 en continuité avec le ruban de couplage C1, et
• un conducteur de masse s'étendant sur la surface inférieure du substrat en continuité avec la masse de l'antenne. Ce conducteur est par exemple constitué comme cette masse par la couche conductrice inférieure 4.

In the context of the present invention at least a fraction of a length of this connection line is advantageously of the microstrip type and more particularly comprises:

• a main conductor having the form of a connection strip C3 extending over the upper surface S2 of the substrate 2 in continuity with the coupling strip C1, and
• a ground conductor extending over the lower surface of the substrate in continuity with the ground of the antenna. This conductor is for example constituted like this mass by the lower conductive layer 4.

In Figure 1 the remaining fraction of the connection line a has been symbolically represented in the form of two conducting wires C4 and C5 connecting ground 4 and ribbon C3 respectively to the two terminals of the signal processor 22. But it should be understood that this fraction remaining would in practice be preferably carried out in the form of a line to microstrip or coaxial line.

The signal processor 22 is adapted to operate at predetermined operating frequencies which are at least close to useful resonant frequencies of the antenna, i.e. which are included in bandwidths centered on these resonance frequencies. he can be composite and then have an element tuned so permanent on each of these operating frequencies. He can too include a tunable element on the various frequencies of operation. Said quarter wave resonance frequency constitutes a such useful resonant frequency.

In accordance with the present invention another so-called frequency of useful resonance is a half wave resonance frequency formed by the frequency of a resonance of said half-wave type being established in this antenna with a resonance path extending between the two lateral edges 14 and 16.

To enable the radiocommunication device according to the invention to work, the antenna coupling device must be able to perform its coupling function for each of the two frequencies of quarter wave and half wave resonance. According to an embodiment of this invention this ability is obtained by the fact that this device has, relative to a longitudinal axis not shown of the antenna, an asymmetry which differentiates one of the two lateral edges of the patch from the other. This asymmetry of the coupling device can be obtained from various known ways. It can in particular affect the position, the orientation and / or dimensions of all or part of this device. However, it appeared that making the latter in the form of a coaxial line would inappropriate, at least if this line was vertical. This device can advantageously be formed according to a planar technique at the level of the patch and / or that of the antenna mass.

More particularly the patch 6 has the usual shape of a rectangle and the asymmetry of the antenna coupling device can advantageously be made by the following arrangement: the patch 6 has a slot coupling input 20 opening to the outside of this pellet through a first lateral edge 14 of this patch and extending from this first lateral edge, for example in the transverse direction DT, up to a end of this slot. A C1 coupling tape then extends over the surface top of the substrate inside this coupling input slot from of this first lateral edge. It is connected to this patch at the end of this slot, this end constituting an internal connection point 18. The distances from this point to a first lateral edge 14 and to the rear edge 10 respectively constitute a connection depth L3 and a dimension of connection L4. The ground conductor of the antenna coupling device consists of the ground 4 of the antenna.

Preferably the ratio L1 / L2 of the length of the pellet to its width is between 2.5 and 0.625 approximately.

Preferably, said connection depth L3 is included between approximately 8% and 25% of the width L2 of the patch 6.

Preferably, said connection dimension L4 is between 25% and approximately 75% of the length L1 of the patch 6.

Preferably, the short circuit C2 extends over only one segment of said rear edge 10 and this segment has a length of between 10% and 90% of the width L2 of the patch 6.

• fréquence de résonance quart d'onde : F1 = 980 MHz,
• fréquence de résonance demi onde : F2 = 1900 MHz,
• impédance d'entrée : 50 Ohms,
• composition et épaisseur du substrat : résine époxy ayant une permittivité relative ε_r égale à 3 et un facteur de dissipation tgδ égal à 0,003,
• épaisseur du substrat : 2 mm,
• composition des couches conductrices : cuivre,
• épaisseur de ces couches : 17 microns
• longueur du substrat : 65 mm,
• largeur du substrat : 70 mm,
• longueur de la pastille : L1 = 60 mm,
• largeur de la pastille: L2= 60 mm,
• profondeur de raccordement L3 = 10 mm,
• cote de raccordement : L4 = 30 mm,
• largeur du conducteur C1 et du conducteur C3 : 5 mm,
• largeur de la fente 20 : 0,7 mm,
• largeur du conducteur de court-circuit C2 : 36 mm.

In the context of an embodiment of an antenna according to this invention, various compositions and values will be indicated below by way of numerical example. The length and the width of the substrate are respectively indicated in the longitudinal directions DL and transverse directions DT.

• quarter wave resonance frequency: F1 = 980 MHz,
• half wave resonance frequency: F2 = 1900 MHz,
• input impedance: 50 Ohms,
• composition and thickness of the substrate: epoxy resin having a relative permittivity ε _r equal to 3 and a dissipation factor tgδ equal to 0.003,
• substrate thickness: 2 mm,
• composition of conductive layers: copper,
• thickness of these layers: 17 microns
• substrate length: 65 mm,
• substrate width: 70 mm,
• length of the patch: L1 = 60 mm,
• width of the patch: L2 = 60 mm,
• connection depth L3 = 10 mm,
• connection dimension: L4 = 30 mm,
• width of conductor C1 and conductor C3: 5 mm,
• width of the slot 20: 0.7 mm,
• width of the short-circuit conductor C2: 36 mm.

The diagram in Figure 3 was drawn from measurements made on the antenna whose encrypted characteristics have been indicated above. Sure this figure the 0 dB level corresponds to the horizontal reference line superior. The difference between two horizontal tracking lines is 3 dB. The extreme frequencies of the scale represented are 200 and 2000 MHz. The difference between two vertical tracking lines represents 180 MHz. The pics of resonance presented by the diagram correspond to the frequencies of quarter wave resonance F1 and half wave F2 previously indicated.

• 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.

The present invention is particularly applicable with advantage to the production of a radiotelephony system. It is known that such a system includes base stations and portable terminals and that it can be implemented within the framework of a GSM standard using frequencies close to 900 MHz and / or within the framework of a DCS standard. using frequencies close to 1800 MHz. In such a system, base stations or portable terminals may each include a radiocommunication device according to this invention. In such a device suitable for this use, the antenna is capable of operating in a high frequency band in the vicinity of said half-wave resonance frequency and in a low frequency band in the vicinity of said quarter-wave resonance frequency. Said signal processing member 22 can then be tuned to four said mutually distinct operating frequencies which constitute:

• a high transmission frequency located in said high frequency band,
• a high reception frequency situated 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 capable of transmitting or receiving a signal when it is tuned to a said transmission frequency or a said reception frequency, respectively.

This invention makes it possible to give each of these two bands sufficient width not only to avoid crosstalk between the emission and reception spectral channels located in this band, but also to allow to choose between several possible positions of these channels in this band. The low frequency band corresponds to the standard GSM and high frequency band to DCS standard. We thus realize economically base stations and / or dual mode terminals, say capable of operating under any of these standards.

For example, in the case of the antenna whose numerical characteristics have been given above, the frequencies transmit and receive high can be 1,750 and 1840 MHz and low transmit and receive frequencies can be 890 and 940 MHz respectively.

Claims (10)

Dual frequency radiocommunication device, this device comprising: a signal processing device (22) adapted to be tuned in the vicinity of at least two predetermined frequencies for transmitting and / or receiving an electrical signal at each of these two frequencies, and an antenna (1) connected to this processing member for coupling said electrical signal to radiated waves, this antenna being produced according to the microstrip technique, a patch (6) of this antenna having an edge provided with a short circuit and constituting a rear edge (10), this patch also having a front edge (12) opposite this rear edge, and two lateral edges (14, 16) joining this rear edge to this front edge, said short circuit (C2) allowing a quarter wave type resonance to be established in said antenna with an electric field node fixed by this short circuit and a resonance path extending between said rear edge (10) and said front edge (12) , this quarter wave type resonance having a frequency constituted by a said predetermined frequency and constituting a quarter wave resonance frequency, this device being characterized by the fact that the other so-called predetermined frequency is a half-wave resonance frequency constituted by the frequency of a half-wave type resonance being established in this antenna with a resonance path extending between the two said lateral edges (14,16). Radiocommunication device according to claim 1, said antenna comprising: a dielectric substrate (2) having two mutually opposite main surfaces extending in directions defined in this antenna and constituting horizontal directions (DL and DT), these two surfaces respectively constituting a lower surface (S1) and an upper surface (S2 ), a lower conductive layer extending over said lower surface and constituting a mass (4) of this antenna, an upper conductive layer extending over an area of said upper surface above said mass so as to constitute said patch (6), said short circuit (C2), this short circuit electrically connecting said pad (6) to said ground (4) from said rear edge (10) of this pad, this edge extending in a said horizontal direction constituting a transverse direction (DT), a length of this patch extending between this rear edge and said front edge (12) in a longitudinal direction (DL) constituted by a said horizontal direction, the two said lateral edges of this patch respectively constituting a first lateral edge (14) and a second lateral edge (16), a width of this patch extending between these two lateral edges, and an antenna coupling device, this device itself comprising: a main conductor (C1), and a ground conductor (4), so as to allow coupling of said antenna to said signal processing member (22) by means of this antenna coupling device for each of said predetermined frequencies, said radiocommunication device being characterized in that said pad (6) has a coupling entry slot opening out of this pad through said first lateral edge (14) of this pad and extending from this first lateral edge in substantially said transverse direction to one end of this slot, said main conductor (C1) of the antenna coupling device having the form of a coupling ribbon extending over said upper surface of the substrate in said coupling entry slot from said first lateral edge of the patch, this strip connecting to this patch at said end of this slot, this end constituting an internal connection point (18), the distances from this point to this first side edge (14) and said rear edge (10) constituting respectively a connection depth (13) and a connection dimension (14), the said conductor of mass of the antenna coupling device consisting of said mass of the antenna. Radiocommunication device according to claim 2, the ratio (L1 / L2) from said length of the patch to said width of the patch being between 2.5 and 0.625 approximately. Radiocommunication device according to claim 3, said connection depth (L3) being between approximately 8% and 25% of said width (L2) of the patch (6). Radiocommunication device according to claim 3, said dimension of connection (L4) being between approximately 25% and 75% of said length (L1) of the patch (6). A radiocommunication device according to claim 3, said short circuit (C2) extending over a segment of said rear edge (10) of the patch, this segment having a length between 10% and 90% of said width (L2) of the tablet (6). Radiocommunication device according to claim 2, this device further comprising a connection line (C3, 4) extending outside said antenna to connect said antenna coupling device to said signal processing device, a at least part of a length of this connection line comprising: a main conductor in the form of a connecting strip (C3) extending over said upper surface of the substrate (2) in continuity with said coupling strip (C1), and a ground conductor (4) extending over said lower surface of the substrate in continuity with said ground of the antenna. Radiocommunication device according to any one of Claims 1 to 7, said antenna being able to operate in a high frequency band in the vicinity of said half-wave resonant frequency and in a low frequency band in the vicinity of said quarter-resonant frequency wave, said signal processing member (22) being tunable on four said mutually distinct predetermined frequencies and constituting: a high transmission frequency located in said high frequency band, a high reception frequency situated in this high frequency band, a low transmission frequency located in said low frequency band, and a low reception frequency situated in this low frequency band, this processing unit being capable of transmitting a signal or of receiving a signal when it is tuned to a said transmission frequency or to a said reception frequency, respectively. Dual frequency antenna produced using the microstrip technique, this antenna comprising: a patch (6) having an edge provided with a short circuit and constituting a rear edge (10), this patch also having a front edge (12) opposite this rear edge, and two lateral edges (14, 16) joining this rear edge to this front edge, said short circuit (C2) allowing a quarter wave type resonance to be established in said antenna with an electric field node fixed by this short circuit and a resonance path s 'extending between said rear edge and said front edge, and an antenna coupling device making it possible to couple this antenna to a signal processing member (22), this antenna being characterized by the fact that said antenna coupling device (20, C1,4) has an asymmetry differentiating a said lateral edge (14) of the patch from the other edge called lateral edge (16) of the patch so as to allow this device to couple this antenna to said signal processing member (22) not only for said resonance of the quarter wave type, but also for a resonance of the half wave type being established in this antenna with a resonance path extending between the two said lateral edges of the patch. Antenna according to claim 9, this antenna comprising: a dielectric substrate (2) having two mutually opposite main surfaces extending in directions defined in this antenna and constituting horizontal directions (DL and DT), these two surfaces respectively constituting a lower surface (S1) and an upper surface (S2 ), a lower conductive layer extending over said lower surface and constituting a mass (4) of this antenna, an upper conductive layer extending over an area of said upper surface above said mass so as to constitute said patch (6), said short circuit (C2), this short circuit electrically connecting this patch (6) to said mass (4) from said rear edge (10) of this patch, this edge extending in a said horizontal direction constituting a transverse direction (DT), a length (L1) of this patch extending between this rear edge and said front edge (12) in a longitudinal direction (DL) constituted by a said horizontal direction, the two said lateral edges of this patch constituting respectively a first lateral edge (14) and a second lateral edge (16), a width (L2) of this patch extending between these two lateral edges, and said antenna coupling device, this device itself comprising: a main conductor (C1), and a ground conductor (4) so as to allow said antenna to be coupled to a signal processing device (22) by means of this device, this antenna being characterized in that said patch (6) has a coupling input slot (20) opening to the outside of this patch through said first lateral edge (14) of this patch (6) and s' extending from this first lateral edge in substantially said transverse direction to one end (18) of this slot, said main conductor (C1) of the antenna coupling device having the shape of a coupling ribbon extending on said upper surface of the substrate in said coupling input slot from said first lateral edge of the patch, this strip connecting to said patch at said end of this slot, said ground conductor of the antenna coupling device being constituted by said mass (4) of the antenna.

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