EP0924797A1 - Multifrequency microstrip antenna and apparatus using the same - Google Patents

Abstract

Each slot represents a quarter wavelength at a different frequency and each slot is mutually decoupled so that different resonant frequencies can be established for the antenna. The resonance frequency is easily adjustable.

Description

The present invention relates to antennas produced according to the microstrip technique. Such an antenna includes a patch which is typically formed by etching a metal layer. She is called in English by specialists "microstrip patch antenna" for "antenna to microstrip type pellet ".

• celle des lignes triplaques qui est généralement connue sous l'appellation anglaise "stripline" et dans laquelle un ruban est compris entre la couche de masse inférieure et une couche de masse supérieure, cette dernière devant dans le cas d'une antenne présenter une fente pour permettre un couplage avec des ondes rayonnées ,
• celle des lignes à fente dans laquelle le champ électrique s'établit entre deux parties d'une couche conductrice formée sur la surface supérieure du substrat et séparées l'une de l'autre par une fente, cette dernière devant, dans le cas d'une antenne, déboucher typiquement sur un évidement plus large facilitant un couplage avec des ondes rayonnées, par exemple en formant une structure résonante, et
• celle des lignes coplanaires dans laquelle le champ électrique s'établit sur la surface supérieure du substrat et d'une manière symétrique entre d'une part un ruban conducteur central et d'autre part deux plages conductrices situées de part et d'autre de ce ruban dont elles sont respectivement séparées par deux fentes. Dans le cas d'une antenne, ce ruban se raccorde typiquement à une pastille plus large pour former une structure résonante permettant un couplage avec les ondes rayonnées.

The microstrip technique is a planar technique which is applicable both to the production of lines transmitting signals and to that of antennas realizing a coupling between such lines and radiated waves. It uses conductive tapes and / or pads formed on the upper surface of a thin dielectric substrate which separates them from a layer of conductive mass extending over the lower surface of this substrate. Such a patch is typically wider than such a ribbon and its shapes and dimensions constitute important characteristics of the antenna. The shape of the substrate is typically that of a rectangular flat sheet of constant thickness. But this is by no means an obligation. In particular, it is known that a variation in the thickness of the substrate according to an exponential law makes it possible to widen the passband of such an antenna and that the shape of the sheet can deviate from a rectangle. The electric field lines extend between the ribbon or the patch and the ground layer crossing the substrate. This technique differs from various other techniques which also use conductive elements on a thin substrate, namely:

• that of the triplate lines which is generally known under the English name "stripline" and in which a ribbon is included between the layer of lower mass and a layer of higher mass, the latter in the case of an antenna having a slot for allow coupling with radiated waves,
• that of slit lines in which the electric field is established between two parts of a conductive layer formed on the upper surface of the substrate and separated from each other by a slit, the latter in front of, in the case of an antenna, typically leading to a wider recess facilitating coupling with radiated waves, for example by forming a resonant structure, and
• that of the coplanar lines in which the electric field is established on the upper surface of the substrate and in a symmetrical manner between on the one hand a central conductive strip and on the other hand two conductive pads located on either side of this ribbon from which they are respectively separated by two slits. In the case of an antenna, this strip typically connects to a larger patch to form a resonant structure allowing coupling with the radiated waves.

Regarding the creation of antennas, the presentation will be sometimes limited below for the purpose of simplification to the sole case of an antenna transmitter connected to a transmitter. But it must be understood that the provisions described could also apply in the case of receiving antennas connected to a receiver. For the same purpose it will be accepted that the substrate has the form of a horizontal sheet.

In a schematic way, a distinction can be made between two fundamental types of resonant structures that can be produced using the microstrip technique. A first type can be called "half-wave". The antenna is then called "half-wave" or "electric". Being admitted that a dimension of its patch constitutes a length and extends according to a so-called longitudinal direction, this length is substantially equal to half of the wavelength of an electromagnetic wave propagating in this direction in the line formed by the mass, the substrate and the pellet. The coupling with the radiated waves is done at the ends of this length, these extremities being located in regions where the amplitude of the electric field prevailing in the substrate is maximum.

A second type of resonant structure that can be produced according to this same technique can be called "quarter wave". The antenna is then called "quarter wave" or "magnetic". It differs from a half-wave antenna by part by the fact that its pellet has a length substantially equal to a quarter of the wavelength, this length of the patch and this wavelength being defined as above, on the other hand by the fact that a significant short circuit is made at one end of this length between the mass and the patch of so as to impose a quarter wave type resonance including a node of electric field is fixed by this short circuit. Coupling with waves radiated is done at the other end of this length, this other end being located in the region where the amplitude of the electric field across 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.

In practice, various types of resonance can be established in such antennas. These types 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 resonance modes may appear and allow use of the antenna at several frequencies corresponding to these modes.

The coupling of such an antenna to a signal processing device as a transmitter is typically done not only through a coupling device included in this antenna, but also a line of external connection to this antenna and connecting the coupling device to the signal processor. If we consider a functional chain including the signal processor, the connection line, the coupling device and the resonant structure, the coupling and the connection line are made so that this chain has a uniform impedance over its entire length, which avoids parasitic reflections opposing good coupling.

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, this is to say that the energy of the traveling wave carrying this signal is transferred to a standing wave established in the antenna with defined characteristics by the latter. As for the antenna, it transfers the energy of this wave stationary at a wave radiated in space. The signal provided by the transmitter thus undergoes a first transformation to pass from the shape of a wave progressive to that of a standing wave, then a second transformation which gives it the shape of a radiated wave. In the case of an antenna receiving the signal takes the same forms in the same organs but the transformations are done in reverse order and direction.

The connection lines can be made according to a technique other than planar, for example in the form of coaxial lines.

Antennas produced using planar techniques are included in various types of devices. These devices include portable radiotelephones, base stations for the latter, automobiles and airplanes or air missiles. In the case of a portable radio the continuous nature of the lower mass layer of this antenna 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 that of planes or missiles whose surface exterior is metallic and has a curved profile to obtain a low aerodynamic drag, the antenna can be shaped to this profile so as not to show additional aerodynamic drag annoying.

• un substrat diélectrique plan ;
• un conducteur constituant un plan de masse, sur la surface inférieure de ce substrat ;
• trois zones conductrices s'étendant sur la surface supérieure du substrat et ayant chacune une forme allongées donnant à l'antenne une forme de double C ou chandelier à trois branches.
• un dispositif de couplage d'antenne commun à toutes les zones conductrices.

European patent application EP 0 749 176 describes an antenna produced using the microstrip technique, this antenna comprising:

• a planar dielectric substrate;
• a conductor constituting a ground plane, on the lower surface of this substrate;
• three conductive zones extending over the upper surface of the substrate and each having an elongated shape giving the antenna a shape of double C or candlestick with three branches.
• an antenna coupling device common to all conductive areas.

The area in the middle of the candlestick has a field node electric fixed by a series of short circuits to the ground plane, this series short circuits being arranged along the axis of symmetry of this zone.

The conductive areas are separated from each other by slots of relatively large width (0.7 cm for a wavelength of 3.3 cm), this which makes it possible to make an antenna of smaller size than that of the antennas known, for a given wavelength. However, this antenna cannot not operate properly on multiple frequencies, for example in a multiband radiotelephone.

• elle doit être multifréquence c'est à dire qu'elle doit pouvoir émettre et/ou recevoir efficacement sur plusieurs fréquences de fonctionnement,
• 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,
• et il ne doit pas être nécessaire pour cela d'utiliser un multiplexeur ou démultiplexeur en fréquence.

The present invention relates more particularly to the case where an antenna of this kind must have the following qualities:

• it must be multi-frequency, that is to say it must be able to transmit and / or receive efficiently on several operating frequencies,
• it must be possible to be connected to a signal processor using a single connection line for all operating frequencies,
• and it should not be necessary for this to use a frequency multiplexer or demultiplexer.

Several known antennas are produced according to the technique of microstrips and have the above qualities. They will be examined:

A first known antenna is described in the document of US-A-4,766,440 (Gegan). The patch 10 of this antenna has a U-shaped curved slot which is continuous and entirely internal to this pastille. This slit is radiative and shows a mode of resonance additional antenna. It also allows, by a suitable choice of its shape and its dimensions, to bring the frequencies of the modes of resonance with desired values which gives the possibility of associating two cross linear polarization modes for emitting a polarization wave circular. The supply line ends with a coupling device which is a line produced using the microstrip technique as specified above but which 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 transformation means impedance to adapt it to the different input impedances respectively presented by the line at the different resonance frequencies used as operating frequencies.

• L'antenne étant du type demi-onde, sa dimension longitudinale peut être gênante dans le cas où une miniaturisation est souhaitable.
• 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 antenna being of the half-wave type, its longitudinal dimension can be troublesome in the case where miniaturization is desirable.
• The need to provide means for impedance transformation complicates the implementation.
• It is difficult to precisely adjust the resonant frequencies to desired values.

• L'inconvénient ci-dessus lié au type demi-onde.
• Les polarisations des ondes émises aux deux fréquences de résonance de l'antenne sont nécessairement croisées, ce qui peut compliquer la réalisation de certains systèmes de télécommunication utilisant cette antenne.

A second known antenna is described in patent document US-A-4,692,769 (Gegan). Its patch has a slot extending in an arc or a line segment inside the patch. This slot shows an additional mode of resonance. The ends of the slit in an arc have enlargements which make it possible to give the input impedance of the antenna the same value for the different operating frequencies. This second known antenna has the following disadvantages in particular:

• The above drawback related to the half-wave type.
• The polarizations of the waves emitted at the two resonant frequencies of the antenna are necessarily crossed, which can complicate the production of certain telecommunications systems using this antenna.

A third known antenna is described in the document of US-A-4,771,291 (LO et al). Its patch has slots extending along respective line segments inside the patch. These slots reduce the difference between the two operating frequencies. Occasional short circuits also reduce this difference. They are formed by conductors passing through the substrate.

• L'inconvénient ci-dessus lié au type demi-onde.
• L'incorporation des courts-circuits ponctuels complique la réalisation de l'antenne.
• Il en est de même de l'alimentation de l'antenne par une ligne coaxiale.

This third known antenna has the following disadvantages in particular:

• The above drawback related to the half-wave type.
• The incorporation of specific short circuits complicates the creation of the antenna.
• It is the same for the supply of the antenna by a coaxial line.

• limiter les dimensions d'une antenne multifréquence,
• permettre un ajustement facile et précis des fréquences de fonctionnement de cette antenne, et
• permettre d'utiliser un dispositif de couplage unique et facilement adaptable en impédance pour plusieurs fréquences de travail.

The present invention has in particular the following aims:

• limit the dimensions of a multifrequency antenna,
• allow easy and precise adjustment of the operating frequencies of this antenna, and
• allow the use of a single coupling device that is easily adaptable in impedance for several working frequencies.

• un substrat diélectrique plan ;
• un conducteur constituant un plan de masse, sur la surface inférieure (S1) de ce substrat ;
• plusieurs zones conductrices s'étendant sur la surface supérieure du substrat et ayant chacune une forme allongées donnant à l'antenne une forme en chandelier ;
• un dispositif de couplage d'antenne commun à toutes les zones conductrices ;
• et étant caractérisée en ce que ces zones conductrices sont séparées l'une de l'autre par des fentes de largeurs très inférieures aux longueurs d'onde d'utilisation de l'antenne ;
• en ce que ces zones conductrices sont suffisamment découplées mutuellement pour permettre à diverses résonances de s'établir, respectivement, dans diverses aires formées par ces zones, ces résonances étant au moins approximativement du type quart d'onde ;
• et en ce que chacune de ces zones a un noeud de champ électrique fixé par au moins un court-circuit vers le plan de masse, et que ce court-circuit est situé au voisinage de la base du chandelier.

And for these purposes, it has in particular for object a multifrequency antenna produced according to the microstrip technique, this antenna comprising:

• a planar dielectric substrate;
• a conductor constituting a ground plane, on the lower surface (S1) of this substrate;
• a plurality of conductive zones extending over the upper surface of the substrate and each having an elongated shape giving the antenna a candlestick shape;
• an antenna coupling device common to all conductive areas;
• and being characterized in that these conductive zones are separated from each other by slots of widths much less than the wavelengths of use of the antenna;
• in that these conductive zones are mutually sufficiently decoupled to allow various resonances to be established, respectively, in various areas formed by these zones, these resonances being at least approximately of the quarter wave type;
• and in that each of these zones has an electric field node fixed by at least one short circuit to the ground plane, and that this short circuit is located in the vicinity of the base of the candlestick.

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

FIG. 1 represents a perspective view of a device for communication including a first antenna produced according to this invention.

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

FIG. 3 represents a front view of this same antenna.

Figure 4 shows a diagram of the variation of a reflection coefficient in decibels at the input of this same antenna in function of the frequency expressed in MHz.

Figure 5 shows a top view of a second antenna made according to this invention.

• 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 autre direction est également définie dans cette antenne. Elle forme un angle avec chacune de ces directions horizontales et constitue une direction verticale DV. L'angle formé est typiquement un angle droit. Mais cette direction verticale peut aussi faire des angles différents avec ces directions horizontales et elle peut elle aussi dépendre de la zone considérée. Le substrat présente plusieurs surfaces de tranches, telles que la surface S3, qui relient chacune un bord de la surface inférieure à un bord correspondant de la surface supérieure et qui contiennent cette direction verticale.
• Une couche conductrice inférieure s'étendant sur 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. Cette pastille a une configuration spécifique à cette antenne. Elle a aussi une longueur et une largeur s'étendant selon deux dites directions horizontales constituant une direction longitudinale DL et une direction transversale DT, respectivement, cette dernière direction étant parallèle à la surface de tranche S3. 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 d'une telle forme sans sortir du cadre de cette invention. Plus particulièrement les directions DL et DT peuvent former un angle différent de 90 degrés, les bords de cette pastille peuvent ne pas être rectilignes et sa dite longueur peut être plus courte que sa dite largeur. L'un de ces bords se situe à l'intersection de la surface supérieure S2 et de la surface de tranche S3. Il s'étend donc selon la direction transversale DT. Il constitue un bord arrière 10 et définit selon la direction longitudinale DL un sens vers l'arrière DB dirigé vers ce bord arrière et un sens vers l'avant DF opposé à ce sens vers l'arrière. Par ailleurs la configuration de la pastille 6 forme au moins une fente F1 à l'intérieur de cette pastille. La présence de cette fente fait apparaítre au moins une résonance supplémentaire dans un groupe de résonances de cette antenne. Ce groupe inclut plusieurs résonances correspondant respectivement à plusieurs modes de fonctionnement et à plusieurs fréquences de fonctionnement de cette antenne. Il peut aussi inclure des résonances non exploitées pour l'utilisation de l'antenne.
• Enfin un court circuit C2 raccordant électriquement la pastille 6 à la masse 4. Ce court-circuit est formé dans la surface de tranche S3 qui est typiquement plane et constitue alors un plan de court-circuit. Il impose à des résonances de l'antenne d'être au moins approximativement du type quart d'onde.

The first 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. Another direction is also defined in this antenna. It forms an angle with each of these horizontal directions and constitutes a vertical direction DV. The angle formed is typically a right angle. But this vertical direction can also make different angles with these horizontal directions and it can also depend on the zone considered. The substrate has several wafer surfaces, such as the surface S3, which each connect an edge of the lower surface to a corresponding edge of the upper surface and which contain this vertical direction.
• A lower conductive layer extending over 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. This patch has a configuration specific to this antenna. It also has a length and a width extending in two said horizontal directions constituting a longitudinal direction DL and a transverse direction DT, respectively, this latter direction being parallel to the wafer surface S3. 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 such a shape without leaving the part of this invention. More particularly, the directions DL and DT can form an angle different from 90 degrees, the edges of this patch may not be straight and its said length may be shorter than its said width. One of these edges is located at the intersection of the upper surface S2 and the edge surface S3. It therefore extends in the transverse direction DT. It constitutes a rear edge 10 and defines in the longitudinal direction DL a rearward direction DB directed towards this rear edge and a forward direction DF opposite to this rearward direction. Furthermore, the configuration of the patch 6 forms at least one slot F1 inside this patch. The presence of this slot causes at least one additional resonance to appear in a group of resonances of this antenna. This group includes several resonances corresponding respectively to several operating modes and to several operating frequencies of this antenna. It can also include unused resonances for the use of the antenna.
• Finally a short circuit C2 electrically connecting the pad 6 to ground 4. This short circuit is formed in the wafer surface S3 which is typically planar and then constitutes a short circuit plane. It requires resonances of the antenna to be at least approximately of the quarter wave type.

The antenna further includes a coupling device having more particularly the shape of a coupling line. This device includes on the one hand, a main conductor made up of two sections C1 and C3 and connected to the patch 6 at an internal connection point 18. It comprises on the other hand an equally composite ground conductor which cooperates with this main conductor and which will be described later. It constitutes all or part of a connection assembly which connects the resonant structure of the antenna to a signal processor 8, for example to drive one or more resonances of the antenna from this organ in case it is a transmitting antenna. In addition to this device the connection set typically includes a connecting line such as C4, C5, which is external to the antenna and which comprises two conductors. At one end of this line on the antenna side, these two conductors are connected respectively with two connecting conductors which belong to the device coupling and which can be considered as constituting two terminals of the antenna. At the other end of this line, the two conductors of this last are connected respectively to two terminals of the processing unit signal. This line can in particular be of the coaxial type, of the type to microstrip or coplanar type. In case the antenna considered constitutes a receiving antenna, this same assembly transmits the received signals through this antenna to the signal processor. The various elements of this together have the respective functions previously defined.

The signal processor is able to operate at those resonant frequencies which constitute said frequencies of antenna operation. It can be composite and then include a element permanently tuned into each of these frequencies of operation. It can also include a tunable element.

The present invention also relates to a device for communication including an antenna according to this invention and a said communication device signal processing connected to this antenna by a so-called set of connection.

The antenna given in example is a dual-frequency antenna, it is to say that it must be able to give rise to at least two resonances so to operate in two modes corresponding to two frequencies of operation. For this purpose a slot is formed in the patch 6 and leads forward outside the latter. It constitutes a slit longitudinal divider F1. The longitudinal extent occupied by this slot defines in this patch a region before Z2, Z1, Z12, the slot itself separating in this region a primary zone Z1 from a secondary zone Z2. A rear region ZA extends between this front region and the rear edge 10. De preferably this rear region is shorter and preferably still much shorter in the longitudinal direction DL than this region before.

The internal connection point 18 is outside the area secondary and it is preferably located in the primary zone Z1. A said mode of operation then constitutes a primary mode in which a wave stationary is established thanks to a propagation of progressive waves in the two directions of this longitudinal direction or of a direction close to this last, these waves propagating in an area including this primary zone and this rear region, substantially excluding the secondary zone Z2. Another operating mode constitutes a secondary mode in which a wave stationary is established thanks to a propagation of progressive waves in the two same directions, these waves propagating in another area including the primary and secondary areas and the rear region.

Within the framework of this arrangement, the rear region ZA has a first function which is to couple the secondary zone to the primary zone to allow the establishment of the secondary mode. She has a second function which is to allow the short circuit present on the rear edge of play its role in each of these two areas. The antenna is then, at least approximately, for each operating frequency, of the quarter type wave.

The configurations of the pad and the coupling device and more particularly the longitudinal position of the internal connection point 18 are chosen so as to show a desired value predetermined impedance presented by the antenna for the signal processing or more typically for a connection line connecting this body to this device. This impedance will be called below antenna impedance. In the case of a transmitting antenna it is usually called input impedance. Its desired value is advantageously equal to the impedance of the connection line. It is why, preferably, the position of the connection point gives the antenna impedance substantially the same value for the various operating frequencies.

It is generally helpful if the operating frequencies have predetermined desired values. These values can be advantageously obtained by a suitable choice of dimensions respective longitudinal zones primary Z1 and secondary Z2. It is why, in the context of the present invention, these two dimensions are typically different. As a result, the front edge of the patch deviates then necessarily of a transverse straight line.

In the case more particularly described the configuration of the pad 6 preferably further forms a slot extending in the direction transverse DT. This slot constitutes a transverse separating slot F2 partially separating this primary zone from the rear region ZA. Of preferably it connects to the rear end of the separating slot longitudinal F1.

The configuration of the patch 6 advantageously still forms at least one slot F3 extending in the primary zone Z1 in the direction longitudinal DL. Preferably this slot extends forward from the transverse separating slot F2. It can be called a lowering slot. frequency because its role is to lower the operating frequencies in an increasing measure with its length. It not only allows limit the length of the pad necessary to obtain desired values operating frequencies, but also to adjust these frequencies thanks to a suitable adjustment of the length of this slot.

Preferably the antenna has a plane of symmetry extending in the longitudinal DL and vertical DV directions, the trace of this plane in the upper surface of the substrate constituting an axis of symmetry A for the pellet 6. When two elements are symmetrical to each other with respect to the axis or in the plane of symmetry the number included in the reference signs of the one who is right in the figures is equal to the corresponding number of that of left increased by 10. The coupling device and the primary zone Z1 extend in the vicinity of axis A and the configuration of the patch forms two said longitudinal separating slots F1, F11 on either side of this zone primary. The secondary zone then comprises two parts Z2, Z12 located respectively beyond these two slots.

Under these conditions, all of the separating slots F1, F2, F11, F12 has the shape of a U. The branches and the base of this U are longitudinal and transverse respectively. This base has an interval axial 20 extending on either side of the axis to connect the primary zone Z1 to short circuit C2, C12 via an axial part of the region rear ZA.

According to an advantageous arrangement, the coupling line which constitutes the antenna coupling device comprises a conductor belonging to the upper conductive layer. More precisely a section C1 of said main conductor enters in the longitudinal direction DL into the area of the patch 6. It extends between a rear end close to the edge rear 10 and a front end constituting the internal connection point 18. This section of main conductor is in the form of a ribbon and can be called horizontal coupling tape. As known per se this ribbon is laterally limited by two notches. But, in the antenna of this invention, these two notches are sufficiently narrow in the direction DT and long enough in DL direction to be able to be respectively considered as two longitudinal slots F4 and F14. These two slots separate this ribbon from the patch 6 and will be called hereinafter slots coupling. The choice of their width is due to the fact that the line parameters of which this coupling tape constitutes the main conductor can advantageously be determined by conceiving this line as a line coplanar able to excite the antenna in a distributed way along the length of this line rather than as a microstrip type line intended for excite the antenna only at the end of this line, the ground conductor of this coplanar line then being mainly constituted in the manner of a coplanar line by the parts of the patch located laterally on the side and other of this ribbon beyond the two slots F4 and F14 and not by the mass of the antenna as in a microstrip line. This line will be called below horizontal coplanar line.

It would allow the antenna to be coupled via a signal electromagnetic applied or collected by the external connection line to the rear end of this horizontal coplanar line between two terminals common to this horizontal coplanar line and to the antenna, these two terminals being respectively constituted by this ground conductor of this line and the back end of this ribbon. But, at least in the case of devices such as some radiotelephones, making the connection between the coupling and this external line through such conductors located in the pellet plan would complicate the manufacture of these devices.

More particularly the horizontal coplanar line in question extends along the axis A. It passes in the axial interval 20 of the base of the U, this interval being delimited by the two coupling slots F4 and F14. As previously indicated the position of the front end 18 of its conductor principal is determined to give a desired value to the impedance of the antenna. But this impedance also depends on other parameters such as widths of C1 coupling tape and coupling slots, as well as nature of the substrate.

According to another advantageous arrangement, said short circuit is a composite short-circuit comprising two short-circuit conductors C2 and C12. These two conductors extend in the vertical direction DV leaving between them a free interval. Each of them connects the ground 4 of the antenna to tablet 6.

• Un conducteur principal C3 s'étendant selon la direction verticale DV entre une extrémité inférieure et une extrémité supérieure dans l'intervalle laissé entre les deux conducteurs de court-circuit. Cette extrémité supérieure se raccorde à l'extrémité arrière du conducteur principal C1 de la ligne coplanaire horizontale. Ce conducteur principal de la ligne coplanaire verticale constitue en même temps ledit premier conducteur de raccordement, une première borne de l'antenne et un tronçon vertical du conducteur principal de la ligne de couplage.
• Et deux dits conducteurs de masse de cette ligne coopérant avec le conducteur C3 et constitués par les deux conducteurs de court-circuit C2 et C12. Ces deux conducteurs de court-circuit constituent en même temps conjointement une deuxième borne de l'antenne.

The antenna coupling line further comprises connection conductors which are formed on the wafer surface S3 and which can form a vertical coplanar line. Such a line is more particularly constituted by the following conductors:

• A main conductor C3 extending in the vertical direction DV between a lower end and an upper end in the space left between the two short-circuit conductors. This upper end is connected to the rear end of the main conductor C1 of the horizontal coplanar line. This main conductor of the vertical coplanar line constitutes at the same time said first connection conductor, a first antenna terminal and a vertical section of the main conductor of the coupling line.
• And two said ground conductors of this line cooperating with the conductor C3 and constituted by the two short-circuit conductors C2 and C12. These two short-circuit conductors simultaneously constitute a second terminal of the antenna.

In the case of a device of limited dimensions, the fact that these connection conductors are formed on the wafer surface S3 facilitates substantially the creation of a connection between on the one hand the coupling belonging to the antenna formed on the surface of the device and other hand, a connection line connecting this device to a processing unit signal. If this organ is located inside this device, this line can take the form of a coaxial line which, in the vicinity of the antenna, is perpendicular to the plane thereof. In other cases this provision of connection conductors facilitate the connection of the antenna to conductors carried by a motherboard on one side of which the substrate of the antenna has been previously fixed, the connection line then being typically, at least in the vicinity of the antenna, parallel to the direction longitudinal of it. Furthermore, the realization of such conductors of connection capable of forming antenna terminals on the wafer surface of the substrate only complicates the fabrication of the antenna negligible. On the one hand, the realization of short-circuit conductors is necessary for the manufactured antenna to be of the quarter wave type. Else apart the first connection conductor can be realized by a process at least analogous to that of making the short-circuit conductors and, in most cases, during the same manufacturing step.

• Formation d'une couche conductrice verticale sur la surface de tranche S3, et
• gravure de cette couche pour réaliser à la fois les deux conducteurs de court-circuit C2 et C12 et le premier conducteur de raccordement C3. Ces conducteurs constituent alors respectivement deux bandes de court-circuit et un ruban de couplage vertical.

More particularly, according to an advantageous arrangement specific to the first antenna given as an example, all of the connection conductors of the coupling device are produced collectively by the following steps:

• Formation of a vertical conductive layer on the wafer surface S3, and
• etching of this layer to produce both the two short-circuit conductors C2 and C12 and the first connection conductor C3. These conductors then respectively constitute two short-circuit strips and a vertical coupling strip.

Preferably the connection conductors occupy only a fraction of the rear edge 10. In the antenna given as an example it is essentially the same fraction as that of the primary zone Z1.

Preferably the widths of the coupling tapes and slots such that the coupling slots located on either side of these ribbons are chosen so as to give a uniform and suitable impedance, which is typically 50 ohms, to the coupling line formed by the lines vertical and horizontal coplanar. The impedance of the antenna is also adjusted by the choice of the position of the internal connection point 18.

In the embodiment given as an example, the line of external connection to the antenna is a coaxial line. It includes a axial conductor C4. At a first end of the line this axial conductor is connected to conductor C3. At the other end of the line it is connected to a first terminal of the signal processing member 8. Over the length of the line is surrounded by a conductive sheath C5. At the first end of the line this sheath is connected to both the two short-circuit conductors C2 and C12. At the other end of the line it is connected to the other terminal of the signal processing member 8 which is constituted for example by a transmitter 8.

• fréquence de fonctionnement secondaire 870 MHz,
• impédance d'entrée : 50 Ohms,
• composition et épaisseur du substrat : résine époxy ayant une permittivité relative e_r = 4,3 et un facteur de dissipation tg d =0,02, épaisseur 1,6 mm,
• composition et épaisseur des couches conductrices :cuivre, 17 microns,
• longueur de la zone primaire Z1 : 26 mm,
• largeur de la zone Z1 : 29 mm,
• longueur des zones secondaires Z2 et Z12 : 30 mm,
• largeur de chacune de ces zones : 5,5 mm,
• longueur de la région arrière Z3 : 2,5 mm,
• longueur du conducteur C1 de la ligne coplanaire horizontale : 25 mm,
• largeur du conducteur C1 et du conducteur principal C3 de la ligne coplanaire verticale : 2,1 mm,
• hauteur du conducteur C3 : O,8 mm,
• largeur commune à toutes les fentes, cette largeur étant indiquée selon la direction horizontale pour les fentes transversales F2 et F12 :0,5 mm,
• longueur des fentes d'abaissement de fréquence F3 et F13 : 5 mm,
• largeur de l'intervalle axial 20 : 7 mm,
• largeur de chacun des conducteurs de court-circuit C2 et C12 : 5mm.

In the context of an embodiment of a transmitting antenna according to this invention, various compositions and values will be indicated below by way of numerical example. The lengths and widths are indicated respectively in the longitudinal directions DL and transverse directions DT.
primary operating frequency 940 MHz,

• secondary operating frequency 870 MHz,
• input impedance: 50 Ohms,
• composition and thickness of the substrate: epoxy resin having a relative permittivity e _r = 4.3 and a dissipation factor tg d = 0.02, thickness 1.6 mm,
• composition and thickness of the conductive layers: copper, 17 microns,
• length of primary zone Z1: 26 mm,
• width of zone Z1: 29 mm,
• length of secondary zones Z2 and Z12: 30 mm,
• width of each of these zones: 5.5 mm,
• length of the rear region Z3: 2.5 mm,
• length of the conductor C1 of the horizontal coplanar line: 25 mm,
• width of the conductor C1 and the main conductor C3 of the vertical coplanar line: 2.1 mm,
• conductor height C3: O, 8 mm,
• width common to all the slots, this width being indicated in the horizontal direction for the transverse slots F2 and F12: 0.5 mm,
• length of the frequency lowering slots F3 and F13: 5 mm,
• width of the axial gap 20: 7 mm,
• width of each of the short-circuit conductors C2 and C12: 5mm.

The second antenna given as an example of implementation of the present invention is shown in Figure 5 and is generally analogous to the first antenna previously described. When an element of this second antenna has the same functions as an element of this first antenna, it is designated by the same letters and / or reference numbers, except that the numbers formed by these numbers are increased by one hundred, the area primary Z101 of this second antenna being for example analogous to the primary zone Z1 of the first antenna. This second antenna differs from the first antenna on the following points:

First of all it is carried out in the case where three frequencies of are required. The patch 106 then further comprises two mutually symmetrical tertiary areas. A first shaped F101 slot of U partially separates the primary zone Z101 from the two secondary zones Z102 and Z112. It is included in a second F105 slot similarly shape similarly separating the secondary zones from the tertiary zones Z103 and Z113.

Then the short circuit is constituted by a single conductor C102 extending over the entire width of the patch 106 and the coupling between the primary, secondary and tertiary areas is carried out in the rear region ZA thanks to the axial interval 120. Finally, the antenna is coupled from of a vertical coaxial line. A terminal section of the C104 axial conductor of this line crosses the substrate 102 and is welded to the pad 106 in the primary zone Z101. It thus constitutes the antenna coupling device. The conductive sheath C105 of this line is soldered to ground not shown of the antenna, this mass consisting of a continuous conductive layer not shown covering the lower surface of the substrate 102. The part of this coaxial line extending below the antenna constitutes the line of connection thereof.

It should be understood that the number of frequencies of operation of an antenna produced according to the present invention can be greater than three, the patch of such an antenna then comprising, for example, in the case of four frequencies, a primary zone, two secondary zones, two tertiary zones and two quaternary zones.

Furthermore, the configurations of the pad and the short circuit do not are not necessarily symmetrical.

Claims (10)

Multifrequency antenna produced using the microstrip technique, this antenna comprising: a planar dielectric substrate (S3); a conductor (4) constituting a ground plane, on the lower surface (S1) of this substrate; several conductive zones (Z2, Z1, Z12; Z103, Z102, Z101, Z112, Z113) extending over the upper surface (S2) of the substrate and each having an elongated shape giving the antenna a candlestick shape; an antenna coupling device (C1, C3; C104, C105) common to all the conductive zones; and being characterized in that these conductive zones (Z2, Z1, Z12; Z103, Z102, Z101, Z112, Z113) are separated from each other by slots (F4, F14) of widths much less than the lengths d 'antenna usage wave; in that these conductive zones are mutually sufficiently decoupled to allow various resonances to be established, respectively, in various areas formed by these zones, these resonances being at least approximately of the quarter wave type; and in that each of these zones has an electric field node fixed by at least one short circuit (C2, C12; C102) to the ground plane (4), and that this short circuit is located in the vicinity of the base (C2, C12; C102) of the candlestick. Antenna according to claim 1, 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 ), another direction being further defined in this antenna and forming an angle with each of these horizontal directions, this other direction constituting a vertical direction (DV), 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 a patch (6), this patch having a configuration, a length and a width, this length and this width extending according to two said horizontal directions constituting a longitudinal direction (DL) and a transverse direction (DT), respectively, this configuration forming at least one slot (F1) inside this patch, this slot contributing to define for this antenna a group of resonances including several resonances corresponding respectively to several operating modes and to several operating frequencies of this antenna, and an antenna coupling device itself comprising: a main conductor (C1) connected to said pad at a connection point (18), and a ground conductor (6), so as to allow said antenna to be coupled to a signal processing device (8) by means of this device for each of said operating frequencies,
said antenna being characterized in that said short circuit (C2) electrically connects said patch (6) to said mass (4) on an edge of this patch, this edge extending in said transverse direction (DT) and constituting an edge rear (10) defining in this patch in said longitudinal direction (DL) a rearward direction (DB) directed towards this rear edge and a forwardward direction (DF) opposite to this rearward direction, two regions of this patch respectively constituting a rear region (Z3) contiguous to this rear edge and a front region (Z1, Z2, Z12) at the front of this rear region, a said slot opening out towards the front outside this patch so as to constitute a longitudinal separating slot (F1) dividing this front region into two said zones constituting respectively a primary zone (Z1) and a secondary zone (Z2), said connection point (18) being outside this secon zone daire. Antenna according to claim 2, this antenna being characterized by the fact that said rear region (Z3) is shorter in said direction longitudinal (DL) than said front region (Z1, Z2, Z12). Antenna according to claim 3, this antenna being characterized by the fact that said connection point (18) is located in said area primary (Z1), a said operating mode constituting a primary mode in which a standing wave is established by propagation of waves progressive in both directions from a direction at least close to this longitudinal direction, these waves propagating in a said area including this primary zone and said rear region by substantially excluding said zone secondary (Z2, Z12), another so-called operating mode constituting a secondary mode in which a standing wave is established thanks to a propagation of traveling waves in the same two directions, these waves propagating in another said area including these primary and secondary zones and this back region. Antenna according to claim 2, this antenna being characterized by the fact that the position of said connection point (18) gives a impedance of this antenna substantially the same value for the various say operating frequencies. Antenna according to claim 2, this antenna being characterized by the fact that said primary (Z1) and secondary (Z2) zones have respective mutually different dimensions according to said direction longitudinal (DL). Antenna according to claim 4, this antenna being characterized by the fact that said short circuit is formed only on a segment of said edge rear (10), the position of this segment in the width of said patch (6) being closer to that of said primary zone (Z1) than to that of said secondary zone (Z2), this segment constituting a short circuit segment (C2, C12), said configuration of this patch further forming a said slot extending in said transverse direction and constituting a separating slot transverse (F2) partially separating this primary zone from said region rear (Z3). Antenna according to claim 2, this antenna being characterized in that said configuration of the patch (6) also forms at least a slot (F3) extending in said primary zone (Z1) in said direction longitudinal (DL). An antenna according to any one of claims 2 to 8, this antenna being characterized in that it has a plane of symmetry extending in said longitudinal (DL) and vertical (DV) directions, the trace of this plane in said upper surface of the substrate constituting an axis of symmetry (A) for said pad (6), said coupling device and said zone primary (Z1) extending in the vicinity of this axis, said configuration of the patch forming two so-called longitudinal separating slots (F1, F11) and other of this primary zone, said secondary zone comprising two parts (Z2, Z12) located respectively beyond these two slots. Radio communication device including an antenna according to one any one of claims 2 to 9 and a said signal processor (8) connected to this antenna and adapted to operate at said frequencies of operation.

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