EP0783189A1 - Microwave planar antenna array for communicating with geostationary television satellites - Google Patents

Abstract

The antenna (1) is formed from a stack of circuit boards. There are three sets of earth boards (10-12) and each has a number of RF radiating holes (120). Each board has two sets of circuit feed boards (17,14) sandwiched between it and the next earth board. Each board is formed from individual RF radiating patches which radiate into the upper holes. The feed lines are made from a coplanar waveguide, or microstrip, and the two boards provide two 90 degree separated polarisation returns.

Description

The invention relates to a receiving and / or transmitting microwave flat array antenna.

It relates more particularly to a dual polarization and double beam antenna.

It also relates to the application of such an antenna to the individual reception of two geostationary television satellites, or "DTH" according to the Anglo-Saxon expression ("Direct To Home"), for example in X band (12.1 GHz).

It is clear that the double beam antennas are very interesting for many applications such as the reception of two satellites placed on different orbital positions. We can cite the pairs of satellites such as ASTRA and TELECOM, ASTRA and EUTELSAT, etc.

In the current technique, use is made of parabolic antennas provided with two reception heads offset from the focal point, each being intended to receive one of the beams. Motorized satellite dishes can also be used which allow the reception of two or more satellites, but are of a high cost price.

This type of antenna is cumbersome by nature, even if the high radiated power of recent satellites has made it possible to significantly reduce its overall dimensions. The aesthetics of these antennas is not free from criticism either.

An interesting alternative to this type of antenna could be constituted by planar array antennas, produced essentially on the basis of multilayer printed circuit boards, more particularly antennas of the radiant-slot type.

However, despite numerous studies, there are currently no, for general public applications of the aforementioned type, double beam and double polarization planar antennas, which are both economical and capable of being mass produced. series.

In addition, this type of antenna must have a high efficiency and bandwidth so as to cover the bandwidth of the satellites to be received (typically 20% of the combined band).

Many planar antennas have been proposed. However, these are either projects that have not passed the laboratory stage (experimental antennas), or antennas for professional use, for example for radar applications.

Non-exhaustively, the following antennas can be cited:

An experimental planar antenna of the double beam type with radial line was proposed in the article by Jun-Ichi Takada et al. : "A Dual Beam-Polarized Radial Line Slot Antenna", published in "IEE Antennas and Propagation Society International Symposium", 1993, pages 1624-1627. However, this antenna allows only one polarization per beam. It should also be noted that a radial line antenna only allows a limited bandwidth (less than 5% of the combined bandwidth). In addition, tight manufacturing constraints are inherent in the structure adopted, even if we are content with a single beam version. Naturally, the problems are even greater for a double beam version.

Inclined beams for array type antennas can be generated by supplying the radiating elements, with which these antennas are provided, by progressive phase shift signals, so as to adapt to the phase differences of the inclined wave received by each element. radiant.

This phase shift can be obtained in the network supply circuit by numerous methods, for example by using phase shifters, delay lines, etc. These methods are well known in the case of radar applications or space transmissions.

For passive fixed-beam networks, this phase shift can be obtained by an appropriate modification of the length of the supply lines, as shown, for example, in the book by RP OWENS: "Handbook of Microstrip Antennas", JR James Hall, PS Hall, IEE, Vol II., 1989, Peter Peregrinus, London, pages 825-843 and 858-866, (see more particularly figure 14.9).

For multiple beams, several phase excitations of the radiating elements must be provided, by means of beam conformers. For this purpose, one can use Blass or Butler matrices, for example.

These methods can be implemented in a relatively simple manner for linear networks. This is no longer at all the case for two-dimensional plane networks. It becomes very difficult to install the required circuits: power lines, dividers, hybrid circuits, etc., especially when there are hundreds of radiating elements, which is the case with network antennas. large dimensions, suitable for reception of direct broadcast television satellites. Indeed, these components must be inserted between the radiating elements.

In addition, for this type of application, the serial power supplies described in the aforementioned book (Figure 14.33) are not, in any case, suitable, because the bandwidth is limited for large networks.

Other types of power supply have been proposed, for example in European patent application EP-A-0 252 779 (Emmanuel RAMMOS), more particularly with reference to FIG. 16. The structure described (length of the line of excitation and output connectors) provides a large bandwidth. However, the antenna described allows a double polarization or a double beam, but not both at the same time.

Finally, the combination of series power supplies and matrices or hybrid circuits is also possible. Such a combination is disclosed in the aforementioned book, more particularly with regard to FIG. 14.35, but it also does not allow sufficient bandwidth for the preferred application of the invention. In addition, its implementation is limited, in practical terms, to networks of relatively small dimensions.

One possible solution, responding both to the needs which are felt for the preferred application of the invention and to the problems raised, would consist in making transitions between the radiating elements to multilayer supply networks. This technique has been used in the case of the generation of double polarization for networks of vertical transitions. It is described in the aforementioned book, opposite figure 14.32.

However, it should be noted that radiating elements with transitions are practically excluded for the production of antennas for reception of direct broadcast television satellites. Indeed, they have a low bandwidth, require the use of high performance dielectrics and imply very high manufacturing tolerances. Even in the case of a double polarization, simply at two levels, networks with power transitions for a satellite reception antenna are not suitable. Such networks have not been marketed, a fortiori, at the manufacturing stage, this type of transition network is not compatible for multilayer power supplies, without having to use vertical transitions, welding steps. , etc., provisions which are very complex and costly to implement.

The lessons which can be drawn from the antennas of the known art and from the studies carried out by the Applicant show that, realistically, an antenna for "general public" needs must be derived, in a simple way, from an existing planar antenna model. It must, moreover, offer a reception capacity double beam and double polarization, for its application to the reception of television satellites with direct diffusion. More generally, it must be able to offer transmission and / or reception capacity, having this dual property, for less specific applications.

The invention therefore sets itself the goal of an antenna of the aforementioned type, compatible with all the requirements mentioned, in particular a low cost price, a simple manufacture and not requiring compliance with high tolerances, and finally offering a high efficiency and a wide bandaged. It also offers the above double property.

To do this, the antenna according to the invention retains most of the characteristics of the structure adopted for flat antennas according to the prior art, advantageously those of the antenna described in European patent application EP-A-0 252 779 cited above.

The latter antenna, in an alternative embodiment allowing double polarization, comprises slot radiating elements. To do this, a stack is provided consisting of three metal ground plates provided with recesses and a pair of suspended microstrips, in printed circuit. These microstrips are interposed between the ground plates, one for vertical polarization, the other for horizontal polarization.

As will be described below, in more detail, to achieve the goal set by the invention, it suffices to add to this basic structure a pair of supply circuits, one arranged on top of the sandwich made up of the three aforementioned plates, the other below.

In a preferred variant of the invention, each pair of microstrips, or more generally of transmission lines, has the capacity of double polarization.

By these provisions, the antenna according to the invention has a reception and / or transmission capacity in double polarization and in double beam, which enables it to receive and / or transmit, from and / or to two different directions, a signal electromagnetic having two different polarizations.

The subject of the invention is therefore a planar microwave antenna comprising a plurality of slotted radiating elements, arranged in space according to a determined configuration, the antenna consisting of a multilayer stack comprising first, second and third plates. mass, substantially parallel to each other, each provided with shaped recesses determined and aligned in pairs along an axis orthogonal to the planes formed by the three plates, and first and second independent excitation circuits, arranged in first and second planes, the first plane being located between the first and second ground plates and the second plane being located between the second and third ground plates, these excitation circuits being made up of suspended lines of signal transmission, cooperating with the recesses by electromagnetic coupling to form said radiating elements, the excitation circuits being arranged so that the antenna emits and / or receives first and second beams of electromagnetic waves, towards and / or from two directions inclined with respect to each other, characterized in that said stack comprises at least third and fourth independent excitation circuits, arranged in third and fourth planes, in c e that these excitation circuits consist of suspended lines for transmitting signals and in that they are arranged so as to co-operate with said recesses and the first and second excitation circuits, by electromagnetic coupling, so obtaining a double polarization for each of said first and second beams of electromagnetic waves.

The invention also relates to the application of such an antenna to the direct reception of geostationary television satellites placed on different orbital positions.

• La figure 1 illustre schématiquement, en coupe, une antenne selon l'art connu, conforme à celle décrite à la figure 6 la demande de brevet européen EP-A-0 252 779 ;
• La figure 2 représente en vue éclatée en coupe d'un des éléments rayonnants d'une telle antenne ;
• La figure 3 illustre un exemple de lignes d'alimentation en circuit imprimé pour une telle antenne ;
• La figure 4 illustre schématiquement, en coupe, un premier mode de réalisation d'une antenne selon l'invention ;
• La figure 5 est une figure de détail illustrant dans l'espace, en écorché partiel, un exemple de réalisation d'une ligne microruban utilisable pour l'antenne selon la figure 4 ;
• La figure 6 illustre schématiquement, en coupe, un deuxième mode de réalisation d'une antenne selon l'invention ;
• La figure 7 illustre schématiquement, en coupe, un troisième mode de réalisation d'une antenne selon l'invention ;
• Les figures 8 à 10 illustrent, en coupe, trois modes de réalisation d'organes d'espacement entre plaques ;
• Les figures 11 à 15 illustrent, dans l'espace, en écorché partiel, cinq exemples de réalisation de lignes de transmission et d'éléments rayonnants utilisables pour l'antenne selon l'invention ;
• La figure 16 illustre schématiquement, en vue éclatée, un exemple de réalisation complet d'antenne selon l'invention ;

The invention will be better understood and other characteristics and advantages will appear on reading the description which follows with reference to the appended figures, and among which:

• Figure 1 schematically illustrates, in section, an antenna according to the prior art, in accordance with that described in Figure 6, European patent application EP-A-0 252 779;
• Figure 2 shows an exploded sectional view of one of the radiating elements of such an antenna;
• FIG. 3 illustrates an example of supply lines in printed circuit for such an antenna;
• FIG. 4 schematically illustrates, in section, a first embodiment of an antenna according to the invention;
• Figure 5 is a detail figure illustrating in space, partially cut away, an embodiment of a microstrip line usable for the antenna according to Figure 4;
• FIG. 6 schematically illustrates, in section, a second embodiment of an antenna according to the invention;
• FIG. 7 schematically illustrates, in section, a third embodiment of an antenna according to the invention;
• Figures 8 to 10 illustrate, in section, three embodiments of spacers between plates;
• FIGS. 11 to 15 illustrate, in space, partially cut away, five exemplary embodiments of transmission lines and radiating elements usable for the antenna according to the invention;
• FIG. 16 schematically illustrates, in exploded view, a complete embodiment of the antenna according to the invention;

As indicated, numerous planar antenna structures have been proposed, in particular that described in the above-mentioned European patent application EP-A-0 252 779. To fix the ideas, although variants may be made to this latter structure, an example of antenna in accordance with the invention will now be described with reference to the latter. It should however be clearly understood that this cannot in any way limit the scope of the invention.

We will also place ourselves in the context of the preferred application of the invention, that is to say the reception of two direct broadcast television satellites placed on different orbital positions. It follows that the antenna receives the two beams emitted under equally different reception angles.

We will first briefly recall the main characteristics of the basic structure of such an antenna, with reference to Figures 1 and 2. Figure 1 schematically shows the planar antenna At in section. Figure 2 illustrates, in cutaway, a detail of this antenna relating to one of the radiating elements Er _i ; i being any index between 1 and the total number of radiating elements. It should indeed be understood that this type of antenna has many radiating elements Er _i , distributed, for example, along the rows and columns of a matrix configuration, so as to form an array.

Basically, the antenna shown in these FIGS. 1 and 2 is of the line type with suspended microstrips, constituted by central conductors 140 carried by a dielectric support sheet 14. This is suspended between two metal plates, upper and lower, 12 and 11, respectively. The plates are each provided with recesses (circular in the example described), 120 and 110, respectively, aligned in pairs at the projecting terminations of the central conductors 140 forming microstrips.

In reality, the variant of planar array antenna At, illustrated in FIGS. 1 and 2, is more complex, because it allows a double polarization or a double beam.

To do this, two additional plates, 10 and 13, are provided.

The plate 13 is a sheet of dielectric material and supports elongated conductors 130 forming microstrips and similar to the conductors 140. They are however arranged in two directions orthogonal to each other.

The plate 10 is a metal plate and supports recesses 100, aligned with the recesses 110 and 120.

More precisely, for each radiating element Er _i of the network of the antenna At, two independent power supply lines (not shown) are arranged on two separate planes, for example the planes of the dielectric sheets 13 and 14. The microstrips 130 and 140 constitute the active terminations of these supply lines.

The basic multi-plate structure of the planar array antenna At therefore consists of five plates or sheets. This basic multi-plate structure is completed by a reflective metallic bottom plate 15.

The excitation in "vertical" polarization is provided, for example, by the microstrip circuit 140, and the "horizontal" polarization is provided, in this case by the microstrip circuit 130. The functions can naturally be reversed.

It should be noted that in the example described, the median mass plate 11 is used by the two microstrip circuits 130 and 140.

The relative positioning of planes 10, 13, 11, 14 and 12 and 15, the dimensioning of the recesses 120 and 110 and the length of the projecting terminations of the central conductors 130 and 140 are determined so that the recesses 120 and 110 play the role of radiant slots electromagnetically coupled to the power line, for a relatively wide operating frequency band.

The recesses, 120 and 110, of the same pair, have their centers aligned on a vertical axis (that is to say orthogonal to the plates of the structure) and can have equal diameters. However, the diameters of the recesses of the same pair may be slightly different, which has the effect of increasing the bandwidth.

Indeed, the operating frequency of each recess depends essentially on its dimensions, and if two recesses of the same pair have slightly different central operating frequencies, the total bandwidth is increased. The diameter of the recesses, 120 and 110, is of the order of 0.3 to 0.7 wavelength.

Advantageously, the spacing between two consecutive elements, on a line or a column of the above-mentioned matrix configuration, is typically within a range 0.7 to 0.9 wavelength.

The bottom reflecting plate 15 makes it possible to impose a determined direction on the radiated energy. It is located at a distance from the multi-plate structure of the antenna At on the order of a quarter of the wavelength. This distance is very important, because it gives the possibility of optimizing the operation jointly with the dimensions of the power supply line, 130 and 140, and of the various printed networks of microstrips.

The adaptation of each excitation line can be obtained by adjusting the length of the advancing terminations opposite the aforementioned recesses, 100, 110 and 120, and the distance separating the multi-plate structure from the bottom reflecting plate 15. In conferring a phase shift of + 90 ° and -90 ° to the signals conveyed by the excitation lines, one can obtain a circular polarization, right or left, respectively. If a -3 dB hybrid circuit is used to combine the signals from the two linear polarization outputs, double circular polarization can be obtained.

To obtain two inclined beams with such an array antenna, it suffices to excite the radiating elements Er _i by appropriately phase-shifted signals. This can be obtained simply by modifying the supply lines in printed circuit illustrated in FIG. 3, which conform to those represented in FIG. 16 of the aforementioned European patent application.

To fix the ideas, FIG. 3 shows the configuration of the excitation circuits carried by the dielectric support 14, referenced with respect to two orthonormal axes YX. The primary supply circuit Ca starts from a single line entering the plate 14, parallel to the axis Y (in the example described) and which is regularly subdivided into a tree structure consisting of a series of lines parallel to the axes Y and X. The ultimate endings of this tree structure feed the microstrips 140. In FIG. 3, a great symmetry of the topology of the circuits is observed with respect to the center C of the plate 14 (first subdivision). In addition, all the lines constituting the supply circuits pass between the slots of the radiating elements Er _i and draw nested "H" s, connected to each other, oriented alternately along the two axes X and Y, and the dimensions of which decrease regularly.

So, to transform a dual polarization antenna into a dual beam antenna, for the reception or transmission of two beams inclined with respect to each other, it suffices to determine the configuration of the supply lines to transmit to the radiating elements Er _i suitably phase-shifted signals. This can be obtained by adjusting the length of the lines to the radiating elements Er _i or by shifting the thresholds of the power dividers supplying these lines, or both as described in the aforementioned book, with more specific reference to Figure 14.9.

The overall structure of the antenna At remains unchanged, since the modifications are made only to the printed circuit supply network and do not affect the rest of the components.

However, as indicated, this type of antenna allows only a double polarization or a double beam. It does not allow double property, that is to say double polarization and the double beam (two distinct directions of emission and / or reception).

On the contrary, according to one of the important characteristics, the antenna according to the invention has both the capacity of double beam and of double polarization.

To do this, according to a first embodiment illustrated schematically in FIG. 4, it suffices to add, to the basic multi-plate structure which has just been described with reference to FIGS. 1 and 2, two additional circuits, 160 and 170 These circuits are each made up of microstrips suspended in printed circuits, for the double polarization of one of the two beams (the beam arbitrarily referenced No. 1). They are placed, the first, 170, on a dielectric sheet 17, placed at the "top" of the sandwich (in this case above the upper plate 12); the second, 160, on a dielectric sheet 16, placed below the bottom plate 10.

• microrubans 170: polarisation horizontale du faisceau N° 1 ;
• microrubans 140: polarisation horizontale du faisceau N° 2 ;
• microrubans 130: polarisation verticale du faisceau N° 2 ;
• microrubans 160: polarisation verticale du faisceau N° 1.

The functionality of the circuits of the different layers of the sandwich forming the basic structure of the antenna 1 is, for example, as follows:

• microstrips 170: horizontal polarization of beam No. 1;
• microstrips 140: horizontal polarization of beam No. 2;
• microstrips 130: vertical polarization of beam No. 2;
• microstrips 160: vertical polarization of beam No. 1.

Other combinations are naturally possible.

Naturally, the above microstrips cooperate with the recesses, 100, 101 and 120, of the metal plates 10, 11 and 12 so as to form radiating elements with slot Er _i .

For each radiating element Er _i , as illustrated in more detail in FIG. 5, the microstrips, 160 and 170, are arranged (in the example described) on their respective supports, 16 and 17, in two directions orthogonal to each other, D ₁₆₀ and D ₁₇₀ , to obtain crossed polarizations, that is to say horizontal and vertical.

It is easy to see that most of the structure of the antenna according to the prior art is preserved. Only the addition of the two circuits, upper 160 and lower 170, is necessary. The additional cost of this addition, whether in terms of equipment or additional manufacturing operations, is very low (a few percent).

The middle metal plate can be omitted by appropriately spacing the circuits surrounding it.

Other variants of sandwich structures can be implemented, as shown in FIGS. 6 and 7.

FIG. 6 schematically illustrates, in section, a first variant. The flat antenna, referenced here 1 ′, consists, as before, of three metal plates 10, 11 and 12, provided with recesses, 100, 110 and 120, respectively, to form the radiating elements with slot Er _i . The distribution in the sandwich layers is also different. The circuits 160 are placed above the plate 10 (supposed to be the bottom plate of the sandwich). The circuits 130 and 140 are located on either side (below and above, respectively) of the intermediate plate 11. The circuits 170 are located below the plate 12.

The microstrips, in this embodiment, can be replaced by coplanar waveguides.

• microrubans ou guides d'onde coplanaires 170 : polarisation N°1, faisceau N° 1 ;
• microrubans ou guides d'onde coplanaires 140 : polarisation N° 2, faisceau N° 1 ;
• microrubans ou guides d'onde coplanaires 130 : polarisation N° 1, faisceau N° 2 ;
• microrubans ou guides d'onde coplanaires 160 : polarisation N° 1, faisceau N° 1.

The functionality of the different layers of the sandwich 1 'is as follows:

• microstrips or coplanar waveguides 170: polarization No. 1, beam No. 1;
• microstrips or coplanar waveguides 140: polarization No. 2, beam No. 1;
• microstrips or coplanar waveguides 130: polarization No. 1, beam No. 2;
• microstrips or coplanar waveguides 160: polarization No. 1, beam No. 1.

In this embodiment, the term "polarization No. 1" represents either the horizontal polarization or the vertical polarization, the "polarization No. 2" representing the dual polarization. Indeed, this depends on the relative directions of the microstrips 160, 130, 140 and 170.

As before, other combinations are naturally possible.

FIG. 7 illustrates another example of a multi-plate structure of a planar array antenna, referenced here 1 ".

The sandwich forming the 1 "antenna consists of five metal plates, 10a, 10, 11, 12 and 12a (10a being the bottom plate of the 1" sandwich in FIG. 7), comprising recesses, 100a, 100, 110, 120 and 120a, respectively, and four sheets of dielectric material, 16, 13, 14 and 17, support for microstrips or coplanar waveguides: 160, 130, 140 and 170, respectively.

• microrubans ou guides d'onde coplanaires 170: polarisation N°1, faisceau N° 1 ;
• microrubans ou guides d'onde coplanaires 140: polarisation N° 2, faisceau N° 1 ;
• microrubans ou guides d'onde coplanaires 130: polarisation N° 1, faisceau N° 2 ;
• microrubans ou guides d'onde coplanaires 160: polarisation N° 1, faisceau N° 1.

The functionality of the different layers of the 1 "multi-ply structure is as follows:

• microstrips or coplanar waveguides 170: polarization No. 1, beam No. 1;
• microstrips or coplanar waveguides 140: polarization No. 2, beam No. 1;
• microstrips or coplanar waveguides 130: polarization No. 1, beam No. 2;
• microstrips or coplanar waveguides 160: polarization No. 1, beam No. 1.

The meanings "polarization N ° 1" and "polarization N ° 2" are identical to those adopted for the variant illustrated in FIG. 6.

We will now describe practical methods of producing planar antennas according to the various modes of the invention which have just been recalled. To fix the ideas, we will consider in what follows the example of the embodiment according to FIGS. 4 and 5 (microstrips), it being understood that the arrangements described below can be applied to the other embodiments. Likewise, in order not to overload the drawings, only the plane 16, support for the microstrips 160, the ground plane 10 comprising the recesses 100, and the plane 13, support for the microstrips 130 have been shown. The same arrangements are repeated between each pair of support plane - ground plane.

FIGS. 8 to 10 are detail figures, in section, illustrating three alternative embodiments allowing the spacing of the planes, 16 or 13, supports of the microstrips 130 and 160, relative to the ground plane 10.

According to a first variant, illustrated in FIG. 8, the spacing between two circuit support planes, for example planes 160 and 130, is obtained by bosses, 101 and 102, produced in the intermediate metallic ground plane 10. More precisely, these bosses have "positive" alternations (upwards, in the figure), 101, in contact with the support 13, and "negative" alternations (down, in the figure) in contact with the support 16. These supports, 16 and 13, are advantageously made up of dielectric films (for example Mylar® or Kapton®) on which are engraved, in printed circuits, microstrips 160 and 130, respectively. The thickness of these films is typically of the order of 25 to 75 μm.

For the preferred application of the invention, that is to say the reception of two geostationary television satellites, the wavelength being in the X band (12.1 GHz), the spacing between two support planes is typically in the range 0.5 to 2 mm. In the variant described with reference to FIG. 8, the bosses therefore have an "amplitude" of approximately 0.25 to 1 mm.

The spacing can also be provided by layers of dielectric expanded foam, of appropriate thickness.

According to the second variant, illustrated in FIG. 9, the spacing is obtained by means of spacers, 18, arranged between the planes 16 and 10, on the one hand, and the planes 10 and 13, on the other hand . Various materials can be used: plastic, foam, metal, etc. Likewise, the fixing can be obtained in a conventional manner: screwing, gluing, etc.

The spacers 18 can also be used as mode suppressors.

According to a third variant, illustrated in FIG. 10, the supports 16 and 13 are plates of dielectric material of greater thickness and are used both as a support and as a spacer. In this variant, on one or the other of the plates, 16 or 13, or also on the two plates, the metal ground circuit 10 comprising the recesses 100 is etched. In other words, at least one plates, 16 or 13, is a double-sided printed circuit.

Likewise, the type of transmission lines used can be, as already indicated, a microstrip. However, it can be made up of other conventional types: slotted line, co-planar line, two-wire line, radiating elements with a loop, dipole, slit, or any combination of these types of lines.

Figures 11 to 15 illustrate some of these different types of lines.

FIG. 11 illustrates an example of co-planar waveguides, 16c and 13c, produced on the supports 160 and 130, respectively, and separated by the ground plane 10 provided with the recesses 100.

Each line, in the example described, comprises an elongated central conductor, 131c or 161c, opening into a recessed area, 163c or 133c, of a metal area, 162c or 132c, for example of square or circular shape. The central conductor, 161c or 131c, is surrounded by a solid metal zone: the external conductors 162c or 132c, also surrounding the hollowed-out zone, 163c or 133c.

The ground plane 10 consists of a metal plate comprising recesses 100 aligned with the recesses 163c and 133c.

The printed circuit supports, 16 and 13, may consist, as previously, of dielectric films, if spacers or other spacers are used (FIGS. 8 or 9), or thicker dielectric plates (figure 10).

FIG. 12 illustrates an example of slotted lines, 16s and 13s, produced on the supports 16 and 13, respectively, and separated by the ground plane 10 provided with recesses 100.

Each slotted line, in the example described, comprises a central groove, 131s or 161s, opening into a recessed area, 162s or 132s, of a metal pad, 163s or 133s, for example of square shape. This central groove, 161s or 131s, is surrounded by a solid metal zone, 162s or 132s, also surrounding the recess, 163s or 133s.

The ground plane 10 and the supports, 16 and 13, retain the same structure as above.

FIG. 13 illustrates an example of two-wire lines with a dipole element, 16d and 13d, produced on the supports 16 and 13, respectively, and separated by the ground plane 10 provided with recesses 100.

Each line, in the example described, firstly comprises two parallel ribbons, 161d1 - 161d2 and 131d1 - 131d2, respectively. These two parallel ribbons extend, in a zone situated below (for line 16d) or above (for line 13d) of the recess 100, by two branches, 162d1 - 162d2 and 132d1 - 132d2, respectively, forming an angle of 90 ° with the aforementioned microstrips.

The ground plane 10 and the supports, 16 and 13, retain the same structure as above.

FIG. 14 illustrates an example of two-wire lines with a loop element, 16b and 13b, produced on the supports 16 and 13, respectively, and separated by the ground plane 10 provided with recesses 100.

Each line, in the example described, firstly comprises two parallel ribbons, 161b1 - 161b2 and 131b1 - 131b2, respectively. These two parallel ribbons extend, in an area located below (for line 16d) or above (for line 13d) of the recess 100, by a loop, 163b and 133b, respectively. More specifically, this loop, 163b and 133b, respectively, has the same shape as the recess 100, so as to be aligned with it.

Figure 15 illustrates another example of a suspended microstrip line configuration. The general structure is similar to that illustrated in Figure 5.

The only notable exception is that the microstrips, 16m and 13m, respectively, have two parts: a microstrip part proper, 161m and 131m, respectively, which ends in a solid central metal area, 162m and 132m, respectively. More precisely, this solid central metal area, 162m and 132m, has substantially the same shape as the recess 100, so as to be aligned with it.

The solid central metal areas (for example the 162 m or 132 m areas in FIG. 15), as well as the recesses 100 may have various shapes: square, circular, elliptical, cruciform, annular, etc.

In addition, as indicated, in more complex embodiments, not illustrated, these different line structures can be combined.

Various known measures in the field of reception and / or of the wave emission of the aforementioned frequency range can be implemented within the framework of the invention: use of "baluns", elimination of parasitic modes by continuities of masses ("pins") made between mass planes, etc.

In practice, the structure of the complete antenna can be in accordance with that taught by the above-mentioned European patent application EP-A-0 252 779. Indeed, the complete antenna comprises two main parts: a multilayer stack and an external ground plane 15 forming a reflector.

FIG. 16 schematically illustrates an exemplary embodiment of a complete planar array antenna. To fix the ideas, we considered the antenna structure 1 ′ in the variant illustrated in FIG. 6.

The multi-plate stack constitutes a first part of the antenna, referenced A in FIG. 16.

According to this alternative embodiment, the upper plate of the stack is a ground plane 12 provided with recesses 120. The lower planes successively comprise, starting from the top, two planes, 17 and 14, of excitation circuits (FIG. 6: 170 and 140), a median ground plane 11 with recesses (FIG. 6: 110), again, two planes, 13 and 16, of excitation circuits (FIG. 6: 130 and 160), and one plane mass less than 10 with recesses (Figure 6: 100).

The excitation circuits constitute the active terminations of circuits for supplying Ca energy (for a transmitting antenna) or for transmitting signals (for a receiving antenna), shown in dotted lines in FIG. 16.

The recesses (for example 120, for the plate 12) are arranged regularly at the intersections of the rows and columns of a rectangular matrix.

It has been assumed that, in the example illustrated, the different plates were spaced apart using spacers 18.

The second part of the antenna 1 ′, referenced B in FIG. 16, consists of a metal housing 19, the bottom of which serves as an external mass and plays the role of the reflective plate 15. The space between the first circuit support or the first ground plane with recess, according to the embodiments (for example the ground plate 10 in the example described), can advantageously be filled with foam. Likewise, the plates can be spaced apart by layers of foam.

The assembly can naturally, and in a known manner, be completed by a protective envelope (not shown) permeable to waves, for example of plastic material.

The structure 19 forms a box, with its bottom and its folded side edges, 150 and 151. It is also possible (in a variant embodiment not shown) to use cavities behind each radiating element or group of radiating elements (for example columns ). This variant embodiment, in itself, is described in the aforementioned European patent application. This cavity structure generally allows a greater inclination of the two waves transmitted and / or received, one with respect to the other.

Finally, the invention allows multiple combinations of beam polarization: for example a double linear beam polarization, plus two crossed beam polarizations.

On reading the above, it is easy to see that the invention achieves the goals it has set for itself. One obtains in particular, without significantly increasing the complexity of the circuits, an antenna capable of transmitting and / or receive in two directions and in two polarizations, with good efficiency and sufficient combined bandwidth. The additional cost is also very limited. It follows that the antenna according to the teaching of the invention is perfectly usable for general public applications, in particular in the preferred application, that is to say the reception of two geostationary satellites for broadcasting programs of television.

It should be noted in particular that the ground planes, as well as the housing, can be produced simply by stamping metal sheet, which constitutes an operation, both not very complex and inexpensive.

It should however be clear that the invention is not limited to only the examples of embodiments precisely described, in particular in relation to FIGS. 4 to 16.

In particular, the different materials or the dimensions have been given only by way of example. The antenna essentially uses known technologies, per se, and commonly used in the field of transmission and / or reception, in particular in the frequency range of the order of 12 GHz in the preferred reception application. geostationary satellites. It follows that the aforementioned parameters (dimensions, choice of materials) constitute only a simple technological choice within the reach of those skilled in the art and which essentially depend on the precise application envisaged.

It should also be clear that, although particularly suitable for the aforementioned application, the invention cannot be confined to this single type of application. It applies equally well to the emission and / or reception of electromagnetic waves from and / or to two different directions, while allowing, simultaneously, a double polarization.

Claims (17)

Flat microwave network antenna comprising a plurality of radiant slotted elements (Er _i ), arranged in space according to a predetermined configuration, the antenna (1) consisting of a multilayer stack comprising first (12), second ( 11) and third (10) ground plates, substantially parallel to each other, each provided with recesses (120, 110, 100) of determined shape and aligned in pairs along an axis orthogonal to the planes formed by the three plates (12, 11 , 10), and first (140) and second (130) independent excitation circuits, arranged in first and second planes, the first plan being located between the first (12) and second (11) ground plates and the second plane being located between the second (11) and third (10) ground plates, these excitation circuits (140, 130) being made up of suspended lines of signal transmission, cooperating with the recesses (120, 110, 100) by coupling electromagnetic to form said radiating elements (Er _i ), the excitation circuits (140, 130) being arranged so that the antenna (1) emits and / or receives first and second beams of electromagnetic waves, towards and / or two directions inclined with respect to one another, characterized in that said stack comprises at least third (170) and fourth (160) independent excitation circuits, arranged in third and fourth planes, in that these excitation circuits (170, 160) consist of suspended lines for transmitting signals and in that they are arranged so as to cooperate with said recesses (120, 110, 100) and the first ones (140) and second (130) excitation circuits, by electromagnetic coupling, so as to obtain a double polarization for each of said first and second beams of electromagnetic waves. Antenna according to claim 1, characterized in that said third and fourth planes containing the third (170) and fourth (160) excitation circuits are located, respectively, above and below said first (12) and third (10) mass plates of the multilayer stack. Antenna according to claim 2, characterized in that it further comprises fourth (12a) and fifth (10a) ground plates, substantially parallel to each other and parallel to said first (12), second (11) and third (10) ground plates, each provided with recesses (120a, 100a) of determined shape, in that the recesses (120a, 120, 110, 100, 100a) of all the ground plates (12a, 12, 11, 10, 10a ) are aligned in pairs along an axis orthogonal to the planes formed by these plates, and in that said fourth (12a) and fifth (10a) ground plates are disposed, respectively, above said third excitation circuits (170) and below said fourth excitation circuits (160). Antenna according to claim 1, characterized in that said third plane containing the third excitation circuits (170) is located between said first ground plate (12) and said first excitation circuits (140) and in that said fourth plane containing the fourth excitation circuits (160) is located between said third ground plate (10) and said second excitation circuits (130). Antenna according to any one of the preceding claims, characterized in that said excitation circuits (170, 140, 130, 160) are supported by sheets of dielectric material (17, 14, 13, 16) and in that spacing means (101, 102, 18) are provided arranged between two successive support sheets or between a support sheet and a ground plate. Antenna according to claim 5, characterized in that said spacing means are constituted by bosses (101, 102) produced by stamping said ground plates (10). Antenna according to claim 5, characterized in that said spacing means consist of a layer of dielectric foam. Antenna according to claim 5, characterized in that said spacing means consist of spacers (18). Antenna according to claim 5, characterized in that said spacing means are constituted by the dielectric material of said sheets (13, 16) supporting the excitation circuits (130, 160), in that at least a part of these sheets constitutes double-sided printed circuits and in that at least a part of said ground plates (10) is formed by a metallic film comprising recesses (100), supported by at least one of the faces. Antenna according to any one of claims 1 to 4, characterized in that said suspended signal transmission lines are constituted by ribbons (131m, 161m) extending by a solid metal area (132m, 162m), of determined shape, aligned with said recesses (100), and in that two successive ribbons are arranged in orthogonal directions therebetween. Antenna according to any one of claims 1 to 4, characterized in that said suspended signal transmission lines are constituted by co-planar waveguides (13c, 16c), in that each co-planar waveguide (13c, 16c) comprises an elongated central conductor (131c, 161c) opening into a recessed area (163c or 133c) of a metal area (162c or 132c), and in that the elongated central conductors (131c, 161c) of two successive co-planar waveguides (13c, 16c) are arranged in directions orthogonal to each other. Antenna according to any one of claims 1 to 4, characterized in that said suspended signal transmission lines are constituted by slotted lines (13s, 16s), in that each slotted line (13s, 16s) comprises a central groove (131s, 161s) opening into a recessed area (163s or 133s) of a metal area (162c or 132c), and in that the central grooves (131s, 161s) of the slotted lines (131s, 161s) of two successive co-planar waveguides (13s, 16s) are arranged in orthogonal directions therebetween. Antenna according to any one of claims 1 to 4, characterized in that said suspended signal transmission lines are constituted by two-wire lines with a dipole element (13d, 16d), in that each two-wire line with a dipole element ( 13d, 16d) includes two parallel ribbons (161d1 - 161d2 and 131d1 - 131d2) is extended by two branches (162d1 - 162d2 and 132d1 - 132d2) forming an angle of 90 ° with the ribbons (162d1 - 162d2 and 132d1 - 132d2) and in that the parallel strips (162d1 - 162d2 and 132d1 - 132d2) of two successive dipole lines (13d, 16d) are arranged in orthogonal directions between them. Antenna according to any one of Claims 1 to 4, characterized in that the said suspended signal transmission lines are constituted by two-wire lines with a loop element (13b, 16b), in that each two-wire line with an element in loop (13b, 16b) comprises two parallel ribbons (161b1 - 161b2, 131b1 - 131b2) extended by a loop of determined shape (163b, 133b) and in that the parallel ribbons (161b1 - 161b2, 131b1 - 131b2) successive two-wire with a loop element (13b, 16b) are arranged in orthogonal directions therebetween. Antenna according to any one of the preceding claims, characterized in that there is further provided an additional external ground plate (15) forming a reflector and in that this external ground plate is located at a distance from said stack substantially equal to quarter of the wavelength of the beams emitted and / or received by the antenna. Antenna according to claim 15, characterized in that said stack (A) is disposed in a metal case (19), the bottom (15) of which constitutes said reflector. Application of an antenna (1, 1 ', 1 ") according to any one of the preceding claims to the individual reception of two geostationary television satellites placed on different orbital positions.

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