EP1073143B1 - Dual polarisation printed antenna and corresponding array - Google Patents

Abstract

The invention relates a printed bi-polarization acrial comprising first, second and third superimposed substrate lates (1, 2. 3); a first metal deposit (4), situated on the external face of said first substrate plate (1) which defines at least one first radiating element (5, 6) of the dipole type, in the form of a T, the horizontal bar of said T being constituted by two radiating lateral strands separated by a coupling slit; a first power supply line (7) pursuant to a first polarization, situated between said first and second substrate plates (1, 2) and supplying power to said at least one first radiating element (5, 6); a second metal deposit (8). situated on the external face of said third substrate plate (3) and defining at least one second radiating element of the dipole type (9, 10), in the form of a T, the horizontal bar of said T being constituted by two radiating lateral strands separated by a coupling slit; a second power supply line (11) pursuant to a second polarization, situated between said second and third substrate plates (2, 3) and supplying power to said at least one second radiating element (9, 10).

Description

The field of the invention is that of microwave antennas. More specifically, the invention relates to a printed antenna bi-polarization, and a corresponding antenna array.

The antenna according to the present invention has many applications. It can for example be used as a probe in antenna test devices by radio-frequency measurement. It should be recalled that such devices make it possible, in particular, to carry out radio coverage forecasts, measurements of devices (mobile or other) with a view to compliance with standards, verification of the securing of the useful signals transmitted, or else measures intended to to studies of the interactions of radio waves with people.

It can also be used in the field of telecommunications, for example in the base stations of a radio communication system (GSM or other), or in a multimedia satellite receiver.

In all these applications, it is conventionally desired that the antenna used has an omnidirectional radiation pattern (approaching an infinitesimal dipole), a wide bandwidth and excellent polarization purity.

In the context of the present invention, it is furthermore desirable for the antenna to be double polarized. Indeed, there is a generalization of the use of this type of polarized duplex antenna.

It is also because of this generalization that an antenna test device now requires the implementation of polarization duplex probes, that is to say able to measure two orthogonal components of the electric field. Indeed, the measurement performed by the test device must include providing, for the antenna under test, polarization decoupling characteristics. It is therefore understood that the probe itself must have excellent isolation between its access and have very low levels of cross polarization.

Conventionally, open-type or horn antennas are used as measurement probes. However, these have a significant "thickness" (5 to 10 wavelengths λ) which becomes unacceptable for use in frequency bands below 3 GHz.

In order to solve this congestion problem, some may have been tempted by the printed technology. Indeed, one of the major interests of this technology is to allow the realization of small size antennas (whose thickness remains generally of the order of λ / 4) and low weight. In addition, numerous structures of polarized duplex printed antennas are known throughout the literature.

But, in practice, there is currently no bi-polarized printed antenna having an omnidirectional radiation pattern, a wide bandwidth and excellent polarization purity. Indeed, they are all currently made of resonant metal pellets (or "resonant patches"), supplied by coupling (lines or slots cut in a ground plane) or by contact (coaxial probes). However, the use of "resonant patches" unfortunately leads to reduced bandwidths (rarely more than 20% at ROS (Stationary Wave Ratio) less than 2). The known printed antennas verify only two of the three criteria (namely omnidirectional radiation pattern and polarization purity), and are therefore not suitable for the aforementioned applications.

The invention particularly aims to overcome these disadvantages of the state of the art.

More precisely, one of the objectives of the present invention is to provide a bi-polarization printed antenna having not only an omnidirectional radiation pattern and excellent polarization purity, but also a wide bandwidth (for example greater than 50% at ROS <2).

The invention also aims to provide such an antenna that can operate in circular polarization.

Another object of the invention is to provide such an antenna having an increased directivity.

• des première, seconde et troisième plaques de substrat superposées ;
• un premier dépôt métallique, situé sur la face externe de ladite première plaque de substrat et définissant au moins un premier élément rayonnant du type dipôle, en forme de T, la barre horizontale dudit T étant constituée de deux brins latéraux rayonnants séparés par une fente de couplage ;
• une première ligne d'alimentation selon une première polarisation, située entre lesdites première et seconde plaques de substrat et alimentant ledit au moins un premier élément rayonnant ;
• un second dépôt métallique, situé sur la face externe de ladite troisième plaque de substrat et définissant au moins un second élément rayonnant du type dipôle, en forme de T, la barre horizontale dudit T étant constituée de deux brins latéraux rayonnants séparés par une fente de couplage ;
• une seconde ligne d'alimentation selon une seconde polarisation, située entre lesdites seconde et troisième plaques de substrat et alimentant ledit au moins un second élément rayonnant.

These various objectives, as well as others which will appear subsequently, are achieved according to the invention with the aid of a bi-polarization printed antenna comprising:

• first, second and third superimposed substrate plates;
• a first metal deposit, located on the outer face of said first substrate plate and defining at least one first T-shaped dipole type radiating element, the horizontal bar of said T being consisting of two radiating lateral strands separated by a coupling slot;
• a first supply line in a first polarization, located between said first and second substrate plates and feeding said at least one first radiating element;
• a second metal deposit, located on the outer face of said third substrate plate and defining at least one second T-shaped dipole radiating element, the horizontal bar of said T being constituted by two radiating lateral strands separated by a slot of coupling;
• a second power supply line according to a second polarization, located between said second and third substrate plates and supplying said at least one second radiating element.

The general principle of the invention therefore consists in superimposing at least one first printed T-dipole and at least one second T printed dipole, each having a distinct polarization. There is thus obtained a structure with three substrate layers and four metallization layers (two for the radiating elements and two for the supply lines). This topology avoids the physical intersections between the supply lines and thus limits the risks of parasitic couplings.

In this way, the bi-polarization antenna according to the invention benefits from all the advantages associated with the "monopolarization" T-printed dipole, namely a small space requirement, easy mechanical retention, an omnidirectional radiation pattern and a wide bandwidth. (greater than 50% at ROS <2). In addition, it is a simple technology to implement.

For a detailed description of the T printed dipole, reference may in particular be made to French Patent No. 93 14276.

It should be noted that the small size of the antenna according to the invention (in particular in thickness) makes it particularly suitable for the aforementioned test devices, and in particular those in the near field. It is recalled that the latter make it possible to measure the radio-electric field emitted at a short distance by electronic equipment (under test). Such measures are intended to provide a better understanding of phenomena of short-range propagation of electronic devices, and to allow the demonstration of the interactions between the waves radiated by the apparatus and the human body (which is often made difficult by the extreme proximity of the apparatus).

In a preferred embodiment of the invention, said first metal deposit defines two first dipole-type radiating elements, each T-shaped and contiguous to each other by the free end of the vertical bar of each T Said first supply line has two branches each supplying one of the first two radiating elements. Said second metal deposit defines two second dipole-type radiating elements, each T-shaped and contiguous to each other by the free end of the vertical bar of each T. Said second feed line has two branches feeding each one of the two second radiating elements.

By joining in pairs T-elements associated with the same polarization, we introduce a geometric symmetry that improves the polarization purity (very low cross-polarization levels) and isolation between access.

Preferably, the longitudinal axis of the T of said first radiating elements is shifted by about 90 ° relative to the longitudinal axis of the T of said second radiating elements.

In this way, an additional level of symmetry is introduced, which further improves the polarization purity and the isolation between access.

Advantageously, the vertical bar of the T of each radiating element constitutes a ground plane for at least a portion of said first and second supply lines. The vertical bars of the T of the first elements thus constitute a first ground plane, while the vertical bars of the T of the second elements therefore constitute a second ground plane. Thus, the supply lines function as triplic elements (striplines), and are therefore shielded (they are between the first and second ground planes). This eliminates the problems of parasitic leaks and diffractions, which would be likely to deteriorate the performance (in particular of polarization purity) of the overall structure.

The invention also relates to a dual-band, dual-polarized printed antenna in each band.

The invention also provides networking of the antenna described above, so as to obtain an increased directivity.

• la figure 1 présente une vue de dessus, faisant néanmoins apparaître les différentes couches constitutives superposées, d'un mode de réalisation préférentiel de l'antenne selon l'invention ;
• la figure 2 présente une vue de côté de l'antenne de la figure 1 ;
• la figure 3 présente une courbe de variation, en fonction de la fréquence, du rapport d'onde stationnaire pour l'antenne de la figure 1 ;
• la figure 4 présente une courbe de variation, en fonction de la fréquence, de l'isolation aux accès pour l'antenne de la figure 1 ;
• la figure 5 présente une courbe de variation, dans un abaque de Smith, de l'impédance d'entrée pour l'antenne de la figure 1 ;
• les figures 6 et 7 présentent des diagrammes de rayonnement pour les accès H et V respectivement de l'antenne de la figure 1 ;
• les figures 8, 9 et 10 présentent trois variantes de moyens de déphasage permettant à l'antenne selon l'invention de générer une polarisation circulaire ;
• la figure 11 présente une vue de côté de l'antenne de la figure 1 incluant en outre des moyens de déphasage ;
• les figures 12 et 13 présentent deux variantes de moyens de réflexion permettant de supprimer une partie du rayonnement arrière de l'antenne de la figure 1 ;
• les figures 14 et 15 présentent deux variantes de mise en réseau de l'antenne de la figure 1 ; et
• la figure 16 présente une vue de côté d'une variante bi-bande de l'antenne selon l'invention.

Other features and advantages of the invention will appear on reading the following description of a preferred embodiment of the invention, given by way of indicative and nonlimiting example, and the appended drawings, in which:

• FIG. 1 shows a view from above, nevertheless showing the different superimposed constituent layers, of a preferred embodiment of the antenna according to the invention;
• Figure 2 shows a side view of the antenna of Figure 1;
• FIG. 3 shows a variation curve, as a function of frequency, of the standing wave ratio for the antenna of FIG. 1;
• FIG. 4 shows a variation curve, as a function of frequency, of the access isolation for the antenna of FIG. 1;
• FIG. 5 shows a variation curve, in a Smith chart, of the input impedance for the antenna of FIG. 1;
• Figures 6 and 7 show radiation patterns for access H and V respectively of the antenna of Figure 1;
• FIGS. 8, 9 and 10 show three variants of phase shift means enabling the antenna according to the invention to generate a circular polarization;
• Figure 11 shows a side view of the antenna of Figure 1 further including phase shift means;
• Figures 12 and 13 show two variants of reflection means for removing a portion of the rear radiation of the antenna of Figure 1;
• Figures 14 and 15 show two variants of networking of the antenna of Figure 1; and
• Figure 16 shows a side view of a two-band variant of the antenna according to the invention.

The invention therefore relates to a bi-polarization printed antenna. In the remainder of the description, the case of horizontal and vertical polarizations is considered. It's clear however, the invention applies to other types of double polarization (polarizations at ± 45 ° for example).

• des première, seconde et troisième plaques de substrat, 1 à 3, superposées (représentées sur la figure 2 uniquement) ;
• un premier dépôt métallique 4, situé sur la face externe la de la première plaque de substrat 1 et définissant deux premiers éléments rayonnants 5, 6 du type dipôle, chacun en forme de T et accolés l'un à l'autre par l'extrémité libre de la barre verticale 5a, 6a de chaque T, la barre horizontale 5b, 6b de chaque T étant constituée de deux brins latéraux rayonnants 5c, 5d et 6c, 6d séparés par une fente de couplage 5e, 6e ;
• une première ligne d'alimentation 7 selon une première polarisation, située entre les première et seconde plaques de substrat 1, 2 et possédant deux branches 7a, 7b (grâce à un diviseur par deux non représenté) alimentant chacune l'un des deux premiers éléments rayonnants 5, 6 ;
• un second dépôt métallique 8, situé sur la face externe 3a de la troisième plaque de substrat 3 et définissant deux seconds éléments rayonnants 9, 10 du type dipôle, chacun en forme de T et accolés l'un à l'autre par l'extrémité libre de la barre verticale 9a, 10a de chaque T, la barre horizontale 9b, 10b de chaque T étant constituée de deux brins latéraux rayonnants 9c, 9d et 10c, 10d séparés par une fente de couplage 9e, 10e ;
• une seconde ligne d'alimentation 11 selon une seconde polarisation, située entre les seconde et troisième plaques de substrat 2, 3 et possédant deux branches 11a, 11b (grâce à un diviseur par deux non représenté) alimentant chacune l'un des deux seconds éléments rayonnants 9, 10.

As illustrated in FIGS. 1 and 2, in a preferred embodiment, the antenna according to the present invention comprises:

• first, second and third substrate plates, 1 to 3, superimposed (shown in Figure 2 only);
• a first metal deposit 4, located on the outer face 1a of the first substrate plate 1 and defining two first dipole-type radiating elements 5, 6, each T-shaped and contiguous to each other by the end free of the vertical bar 5a, 6a of each T, the horizontal bar 5b, 6b of each T being constituted by two radiating lateral strands 5c, 5d and 6c, 6d separated by a coupling slot 5e, 6e;
• a first power supply line 7 according to a first polarization, located between the first and second substrate plates 1, 2 and having two branches 7a, 7b (thanks to a divider by two not shown) each supplying one of the first two elements radiating 5, 6;
• a second metal deposit 8, located on the outer face 3a of the third substrate plate 3 and defining two second radiating elements 9, 10 of the dipole type, each T-shaped and contiguous to each other by the end free of the vertical bar 9a, 10a of each T, the horizontal bar 9b, 10b of each T consisting of two radiating lateral strands 9c, 9d and 10c, 10d separated by a coupling slot 9e, 10e;
• a second power supply line 11 according to a second polarization, located between the second and third substrate plates 2, 3 and having two branches 11a, 11b (by means of a divider by two not shown) each supplying one of the two second elements radiating 9, 10.

The first power supply line 7 has a first access (denoted "access V", for vertical access, in FIG. 1). Likewise, the second feed line 11 has a second access (denoted "access H", for horizontal access, in FIG. 1).

Each of the ports H, V of the supply lines 7, 11 is for example connected to a connector (not shown) of the SMA type (or other) itself connected to a coaxial cable.

The longitudinal axis of the T of the first radiating elements 5,6 is shifted by about 90 ° with respect to the longitudinal axis of the T of the second radiating elements 9, 10. Thus, we have a perfectly symmetrical topology, in the form of a cross . In other words, the first and second metal deposits 4, 8 have in this example the same shape (including the square-shaped conductive central surface discussed below), and are simply shifted by a quarter of a turn. one compared to the other.

The vertical bars of the T of the first radiating elements 5, 6 constitute a first ground plane for the first and second supply lines 7, 11 (and in particular for the divider by 2 included in each of these). Similarly, the vertical bars of the T of the second radiating elements 9, 10 constitute a second ground plane for the first and second supply lines 7, 11 (in particular for the divider by 2 included in each of these). The first and second feed lines therefore function as stripline elements. The free end of each of these vertical bars of T is widened, so as to increase the surface of the ground planes. In the illustrated example, the enlargement results in obtaining, in the center of each of the first and second metal deposits 4, 8, a conductive surface of square shape.

Each of the supply line branches 7a, 7b, 11a, 11b has a first end portion extending along an axis intercepting the axis of the slot of one of the radiating elements and protruding from the axis of the slot of one of the radiating elements of a first variable length of adaptation (or series stub) 11. Furthermore, the slot of each of the radiating elements has a second end portion protruding from the axis of the first portion end of a second variable adaptation length (or parallel stub) 12. For the sake of clarity, the first and second adaptation lengths 11, 12 are referenced, in FIG. 1, only for one branches of power (that referenced 7b). A suitable choice of these series and parallel stubs 11, 12 makes it possible to adapt the radiating element concerned to a wide band.

The antenna may further comprise variable capacitance means (not shown) for electrically acting on the first and second variable adaptation lengths (serial and parallel stubs) of each of the radiating elements. It is recalled that this electric action has the same effect as a lengthening or a decrease physical (that is to say real) stub on which one acts. Examples of such variable capacity means are described in detail in French Patent No. 93 14276, to which reference may be made.

• encombrement (cf. fig. 1 et 2) : L = 160 mm, l = 160 mm et h = 45 mm ;
• substrat : Duroïd type verre téflon, de permittivité relative ε_r = 2,2 et d'épaisseur 1,52 mm (pour chacune des trois plaques de substrat 1, 2, 3).

The performance of an exemplary antenna according to the preferred embodiment described above is now presented with reference to FIGS. 3 to 7. In this example, the antenna has the following characteristics:

• overall dimensions (see Figs 1 and 2): L = 160 mm, l = 160 mm and h = 45 mm;
• substrate: Teflon glass-type duroid with a relative permittivity ε _r = 2.2 and a thickness of 1.52 mm (for each of the three substrate plates 1, 2, 3).

This antenna is extremely broadband since it works from 0.6 GHz to 1.1 GHz for a ROS less than 2 (see fig.3). This corresponds to more than 75% of bandwidth. It is recalled that this percentage is obtained by division of the bandwidth by the central frequency of this band.

Its isolation remains below -30 dB from 0.75 GHz to 1.1 GHz (see fig.4).

Its impedance curve (see fig.5) shows a coupling loop characteristic of the dipole element, the latter being associated on the one hand with its series stub (feed line which goes beyond the slot of coupling) and on the other hand to its parallel stub (slot that extends beyond the power line). It is the presence of this loop that guarantees a low frequency dispersion and reflects the efficiency of the power supply device.

His radiation patterns (see Fig.6 and 7) were measured at 980 MHz. They highlight, for both accesses of the antenna, the excellent properties of symmetry of the structure. Note also the low level of cross polarization it generates (less than - 30 dB in the axis of the element).

The antenna according to the invention also makes it possible to simply and efficiently generate the circular polarization, by feeding the pairs of first 5, 6 and second 9, 10 radiating elements in quadrature. In other words, there is introduced between these two couples a phase shift of π / 2 in time. For this purpose, the antenna further comprises phase shift means.

Several variants of these phase shift means are now described with reference to FIGS. 8 to 11. It is clear that these examples are given only indicative, other solutions that can be envisaged without departing from the scope of the present invention.

A first solution (see Fig. 8) is to use a hybrid element 80. This hybrid element, well known, comprises two input terminals 81, 82 and two output terminals 83, 84. In the present application, one injects on one of the input terminals (if the antenna is transmitting), or receives (if the antenna is operating in reception), or a signal in right circular polarization (for example on the terminal of input 81), ie a signal in left circular polarization (for example on the input terminal 82). The output terminals 83, 84 are respectively connected to the H and V ports of the first and second supply lines 7, 11.

A second solution (see Fig. 9) is to use a rat-race ring 90. This rat-race ring, also well known, also includes two input terminals 91, 92 and two output terminals 93, 94. Its implementation, in the context of the present application, is identical to that described above for the hybrid element 80.

A third solution (see fig.10), more compact, consists of using localized elements (inductors and capacities). The corresponding assembly (well known in itself) 100 also comprises two input terminals 101, 102 and two output terminals 103, 104. Its implementation, in the context of the present application, is identical to that described. above for the hybrid element 80.

Whatever the solution adopted, these phase shift means may be integrated on a printed circuit to be placed in the middle of the superimposed structure. In this case, as illustrated in FIG. 11, the second substrate plate 2 (or central plate) is divided into two sub-layers 2A and 2B, between which is positioned the printed circuit (or metal deposit) 12 supporting the means of phase shift. This printed circuit 12 is connected on the one hand to the access V of the first supply line 7, via a first metallized hole (or through contact) 13, and on the other hand to the access H of the second feed line 11, via a second metallized hole 14.

Furthermore, optionally, the antenna may include reflection means, to increase its directivity by removing some of its radiation. This involves, for example, removing a back radiation from the antenna, to direct the radiated energy forward and increase the directivity of the antenna a few dB, while maintaining broadband performance.

Two variants of these reflection means are now presented with reference to FIGS. 12 and 13. It is clear that these examples are only indicative, other solutions that can be envisaged without departing from the scope of the present invention.

A first solution (see Fig. 12) is to introduce the antenna 120 (as previously described) in a waveguide section 121. This makes it possible to easily constitute a duplex feed system in a guide. waves.

A second solution (see Fig. 13) is to use a ground plane 131 at about λ / 3 of the antenna 130 (as previously described). It will be noted that the radiation patterns shown in FIGS. 6 and 7 were obtained in the presence of a ground plane.

It is also possible, in order to increase the obtain an increased directivity, to network the antenna as described above. In other words, the antenna is then the basic element of the network.

Now, with reference to FIGS. 14 and 15, two particular embodiments of such a network are presented. It is clear that these are only indicative, various variants that can be envisaged without departing from the scope of the present invention.

In the first embodiment (see Fig. 14), the network is one-dimensional. It presents a directional radiation pattern in elevation (as shown schematically by the arc of circle referenced 140) and wide (even omnidirectional) in azimuth (as shown schematically by the arc of circle referenced 141). A network having such qualities is particularly suitable for antennas of the base stations of radio communication systems (for example GSM or DCS).

In the second embodiment (see Fig. 15), the array is two-dimensional plane. It allows significant pointing up to low elevations, thanks to its elementary diagram less directive than that of traditional resonant printed elements (patches). A network having such qualities is suitable for ground antennas, intended for reception in the context of satellite multimedia applications.

As illustrated in FIG. 15, the networking can be combined with the use of reflection means (for example a ground plane).

We now present, in connection with Figure 16, a two-band variant of the antenna according to the invention.

In the center of the superposition, the various constituent layers (three substrate plates 1, 2, 3, two supply lines 7, 11, and two pairs of radiating elements T connected 4, 8) of the antenna are found. of Figure 1. It is assumed that they operate in a first frequency band.

• des quatrième et cinquième plaques de substrat 20, 21, superposées contre la face externe de la première plaque de substrat 1, et des sixième et septième plaques de substrat 22, 23, superposées contre la face externe de la troisième plaque de substrat 3 ;
• un troisième dépôt métallique 24, situé sur la face externe de la cinquième 21 plaque de substrat et définissant un couple de troisièmes éléments rayonnants en T ;
• une troisième ligne d'alimentation 25 selon l'une deux polarisations, située entre les quatrième et cinquième plaques de substrat 20, 21 et alimentant les troisièmes éléments rayonnants ;
• un quatrième dépôt métallique 26, situé sur la face externe de la septième plaque de substrat 23 et définissant un couple de quatrièmes éléments rayonnants en T ;
• une quatrième ligne d'alimentation 27 selon l'autre des polarisations, située entre les sixième et septième plaques de substrat 22, 23 et alimentant les quatrièmes éléments rayonnants.

Moreover, in order to allow its operation in another frequency band, the antenna comprises the following other layers:

• fourth and fifth substrate plates 20, 21, superimposed against the outer face of the first substrate plate 1, and sixth and seventh substrate plates 22, 23 superimposed against the outer face of the third substrate plate 3;
• a third metal deposit 24, located on the outer face of the fifth substrate plate 21 and defining a pair of third T-shaped radiating elements;
• a third feed line 25 in one of two polarizations, located between the fourth and fifth substrate plates 20, 21 and feeding the third radiating elements;
• a fourth metal deposit 26, located on the outer face of the seventh substrate plate 23 and defining a pair of fourth T-shaped radiating elements;
• a fourth feed line 27 according to the other of the polarizations, located between the sixth and seventh substrate plates 22, 23 and feeding the fourth radiating elements.

The dimensions of the third and fourth metal deposits 24, 26, which are at the ends of the superposition, must be smaller than those of the first and second metal deposits 4, 8. In other words, the second frequency band must be larger than high in frequency than the first.

It is clear that it is easy, while remaining within the scope of the present invention, to go from this dual-band printed antenna to a multi-band printed antenna, with at least three frequency bands and one bi-polarization in each band. . Indeed, it is sufficient for each new band to add four layers of substrate (two on either side of the superposition) and four metallization layers (two for the radiating elements and two for the supply lines).

Claims (14)

1. Dual-polarization printed antenna, characterized in that it comprises:

   - first, second and third superimposed substrate plates (1,2,3);

   - a first metallic deposition (4), situated on the external face of said first substrate plate (1) and defining at least one first radiating element (5,6) of the dipole type, in the form of a T-shape, the horizontal bar of said T consisting of two radiating lateral strands separated by a coupling slot;

   - a first feed line (7) for supplying according to a first polarization, situated between said first and second substrate plates (1,2) and supplying said at least one first radiating element (5,6);

   - a second metallic deposition (8), situated on the external face of said third substrate plate (3) and defining at least one second radiating element of the dipole type (9,10), in the form of a T-shape, the horizontal bar of said T consisting of two radiating lateral strands separated by a coupling slot;

   - a second feed line (11) for supplying according to a second polarization, situated between said second and third substrate plates (2,3) and supplying said at least one second radiating element (9,10).
2. Antenna according to Claim 1, characterized in that said first metallic deposition (4) defines two first radiating elements (5,6) of the dipole type, each in the form of a T-shape and adjoining one another via the free end of the vertical bar of each T,
   in that said first feed line (7) possesses two branches (7a,7b) each supplying one of the two first radiating elements,
   in that said second metallic deposition (8) defines two second radiating elements (9,10) of the dipole type, each in the form of a T-shape and adjoining one another via the free end of the vertical bar of each T,
   and in that said second feed line (11) possesses two branches (11a, 11b) each supplying one of the two second radiating elements.
3. Antenna according to Claim 2, characterized in that the longitudinal axis of the T of said first radiating elements (5,6) is shifted by about 90° with respect to the longitudinal axis of the T of said second radiating elements (9,10).
4. Antenna according to any one of Claims 1 to 3, characterized in that the vertical bar of the T of each radiating element constitutes an earth plane for at least one part of said first and second feed lines (7, 11) .
5. Antenna according to Claim 4, characterized in that the free end of the vertical bar of at least one of the Ts is widened, so as to increase the surface area of said earth plane.
6. Antenna according to any one of Claims 1 to 5, characterized in that each of said feed lines or of said feed line branches has a first end portion extending along an axis intercepting the axis of the slot of one of said radiating elements and overshooting said axis of the slot of one of said radiating elements by a first variable adaptation length (11),
   and in that the slot of each of said radiating elements has a second end portion overshooting the axis of said first end portion by a second variable adaptation length (12).
7. Antenna according to Claim 6, characterized in that it furthermore comprises variable-capacitance means, making it possible to act electrically on at least one of said first and second variable adaptation lengths of at least one of said radiating elements.
8. Antenna according to any one of Claims 1 to 7, characterized in that said first and second polarizations form a pair belonging to the group comprising:

   - the pair (horizontal polarization, vertical polarization);

   - the pair (+45° polarization, -45° polarization).
9. Antenna according to any one of Claims 1 to 9, characterized in that it furthermore comprises means (80;90;100) for phase shifting said first and second feed lines with respect to one another, by about π/2 over time, in such a way that said antenna generates a circular polarization.
10. Antenna according to Claim 9, characterized in that said phase shifting means belong to the group comprising:

    - hybrid elements (80);

    - "rat-race" rings (90);

    - solutions based on localized elements (100).
11. Antenna according to any one of Claims 1 to 10, characterized in that it furthermore comprises reflection means (121;131) making it possible to remove part of the radiation of said antenna.
12. Antenna according to Claim 11, characterized in that said reflection means belong to the group comprising:

    - ground planes (131);

    - waveguide portions (121).
13. Dual-band printed antenna, with dual-polarization in each band, characterized in that it comprises the constituent elements of an antenna according to any one of Claims 1 to 12, for dual-polarization operation in a first frequency band,
    and in that it furthermore comprises, for dual-polarization operation in a second frequency band:

    - fourth and fifth substrate plates (20,21), superimposed against the external face of said first substrate plate (1), and sixth and seventh substrate plates (22,23), superimposed against the external face of said third substrate plate (3);

    - a third metallic deposition (24), situated on the external face of said fifth substrate plate and defining at least one third radiating element of the dipole type, in the form of a T-shape, the horizontal bar of said T consisting of two radiating lateral strands separated by a coupling slot;

    - a third feed line (25) for supplying according to one of said first and second polarizations, situated between said fourth and fifth substrate plates and supplying said at least one third radiating element;

    - a fourth metallic deposition (26), situated on the external face of said seventh substrate plate and defining at least one fourth radiating element of the dipole type, in the form of a T-shape, the horizontal bar of said T consisting of two radiating lateral strands separated by a coupling slot;

    - a fourth feed line (27) for supplying according to the other of said first and second polarizations, situated between said sixth and seventh substrate plates and supplying said at least one fourth radiating element.
14. Antenna array, characterized in that it comprises at least two antennas according to any one of Claims 1 to 13.

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