EP0598656B1 - Radiating element for an antenna array and sub-set with such elements - Google Patents

Description

The field of the invention is that of antennas networks, and more particularly network antennas broadband (5 to 10%), especially for the space sector. These network antennas include many sources radiant elementals, and the nourishment of these sources, in an appropriate relative provision to give to radiated fields the desired shape for application specific envisaged. So we are looking for a cheap item at manufacture (because it requires a large number, which can reach a few thousand), neither heavy nor bulky (because on board), and easy to integrate into the antenna (geometry implantation and food). In addition, for new antenna designs, we want to be able to arrange these elements on a shaped surface, possibly deformable.

In the field of satellites, it is common to use fine radiated beams, which are called "paint brushes". This means that the main lobes of radiated fields of the brushes are relatively narrow, and that brushes of this type have a fairly small footprint limited. But we can form the main lobe of several ways, to create elongated brushes for example, or asymmetrical. In general, we try to adapt the footprint on the ground to the geographic area that we would actually like light, so as not to waste radiated power unnecessarily outside this area. A lobe of an antenna network is formed by geometry or relative arrangement radiating elements, as well as by the amplitude and the phase of the excitation signals applied to these elements radiant through a power network and its control electronics.

Often in the practical realization of antennas networks, where possible, multiple sources elementary will be grouped into subsets, so that these sources share a control point common in the amplitude and phases. An example is shown in Figure 1 of a network printed feed from four elementary sources printed. An elementary source of this type is commonly known to those skilled in the art under the English name "Patch". In the absence of a monolithic and global realization, a subset can be made up purely mechanically, forming the basic brick of a modular construction of antenna, which facilitates maintenance and repairs possible.

1) MICROSTRIP ANTENNA TECHNOLOGY, K. Carver, J.W Mink, IEEE. AP vol AP 29. - n°1 janvier 1981

2) ANNULAR SLOT ANTENNA WITH A STRIPLINE FEED, M.FASSET, 23 juin 1989 - US Patent.

3) A NEW BROADBAND STACKED TWO LAYER MICROSTRIP ANTENNA - A. Sabban - APS 1983 - P63 - 66 IEEE.

4) ANTENNE PLANE - T. Dusseux, M. Gomez-HENRI, G. RAGUENET - French Patent n° 89 11829, 11 sept. 1989. - Publ. FR 2 651 926.

Printed or planar array antennas with elementary sources have been known for about fifteen years and are used in increasingly varied fields of application. Many publications as well as patents situate the state of the art in this field. We quote below, some of the best known references, which form an integral part of the present application as a description of the prior art:

1) MICROSTRIP ANTENNA TECHNOLOGY, K. Carver, JW Mink, IEEE. AP vol AP 29. - n ° 1 January 1981

2) ANNULAR SLOT ANTENNA WITH A STRIPLINE FEED, M.FASSET, June 23, 1989 - US Patent.

3) A NEW BROADBAND STACKED TWO LAYER MICROSTRIP ANTENNA - A. Sabban - APS 1983 - P63 - 66 IEEE.

4) ANTENNA PLANE - T. Dusseux, M. Gomez-HENRI, G. RAGUENET - French Patent n ° 89 11829, Sept. 11, 1989. - Publ. FR 2 651 926.

These printed antenna systems are therefore well known in their single or multi-resonant versions. Their main advantages, compared to old ones network antennas made up of elementary sources of the type cones or propellers, are their small size and mass. For the space sector, we can also cite their large robustness. In return, the bandwidth of patch-type elementary sources is relatively limited, only in the range of 1% to a few percent, in its simplest version. An object of the invention is to obtain a wide operating band, normally excluded for simple patch type radiant sources, simultaneously with the known advantages of this type of element.

It is known in the prior art, to widen the bandwidth, to use a resonant cavity placed behind the patch, as described in document D1 = EP-A- 355 898 to Rammos. Such a radiant source, according to the assembly of the prior art is generally powered by "triplate" technology, which consists in a conductive (supply) track suspended between two ground planes, as described in document D2 = US-A-5,087,920 in the name of Shinobu Tsurumare et al., Of SONY. This solution generally has disadvantages with a larger mass and size than those of networks printed materials, as well as higher production costs. In D2, to overcome these problems, we propose the use of the possible ground plans by the metallization of plastic panels, in which holes are made to form radiant slots around the patches engraved on the dielectric substrate. In D1, this drawback is overcome by using engraved coplanar supply lines.

The proposed invention relates to an embodiment of an elementary source for radiating device of the flat antenna type, and radiating sub-assemblies including such sources. The device according to the invention can therefore be integrated in a flat array antenna, but moreover, is particularly suitable for installing such a radiant sub-assembly on a surface consistent.

As will be explained in more detail below, a means known from the prior art to increase the bandwidth of type printed radiating elements patch is to increase the thickness of dielectric between the patch and the ground plane. This method suffers from the drawback that the network of elements thus constructed is more difficult to integrate on the radiating face of the antenna, all the more if this surface is not flat but conformed. Furthermore the characteristics of radiation from a thick planar antenna degrades very quickly, which does not provide only limited operational interest. Another object of the invention is therefore to overcome this disadvantage of the prior art, to obtain a strip wide bandwidth without complicating the integration of the antenna on a shaped surface.

The basic principle of the elementary source radiant according to the invention is described in FIG. 2.

The radiating element consists, in part of a metallic cavity, whose fine geometry results from a optimization in relation to the mission of the antenna, other part of a patch-type resonator etched on a substrate thin dielectric.

The structure can therefore be considered as a element in technology known as buried microstrip.

The printed elements known from the prior art, if simple as they are, offer only limited possibilities in bandwidth and quality of radiation. Failure main concerns the impact of using a substrate dielectric whose thickness is increased to increase bandwidth.

The bandwidth (BP) of an etched microstrip antenna is inversely proportional to its cavity overvoltage, also known as quality factor Q. The cavity of the printed element of the prior art is closed by the patch, the dielectric between the patch and the ground plane, and the mass itself.

The bandwidth can be expressed as a function of the Q overvoltage and the ROS (standing wave ratio). The relationship between these parameters is as follows: BP = ROS - 1 Q ROS

This same quality factor Q is (approximately) inversely proportional to the normalized height of the patch t / λ _ε , where t is the thickness of dielectric between the patch and the ground plane, and λ _ε is the electrical wavelength in the dielectric characterized by the dielectric constant ε, at the operating frequency of the antenna. It follows that in the major part of the curve which describes the bandwidth as a function of the normalized height, and this up to reasonable thicknesses, the bandwidth BP is linear with respect to t / λ _ε as shown by it the abacuses from the publication of Carver and Mink (1), and reproduced in FIG. 3.

Few missions or applications use only a few percent of the band (radar, for example). More generally, we need 6 to 10% of bandwidth, or even more, so that the simple resonator approach leads to thicknesses greater than 15 λ _ε for ROS in the vicinity of 1.20.

• pertes de rendement : pertes ohmiques, diélectriques ;
• médiocre qualité de la polarisation principale ;
• accroissement à des niveaux inacceptables de la polarisation croisée ;
• propagation et rayonnement des ondes de surface, d'ou des couplages indésirés entre des éléments voisins.

The impact of such a height is quite often dramatic, and includes undesirable effects such as:

• yield losses: ohmic, dielectric losses;
• poor quality of main polarization;
• increase to unacceptable levels of cross polarization;
• propagation and radiation of surface waves, hence unwanted couplings between neighboring elements.

We generally accept as an upper limit using a simple resonator etched a band of 4 to 5% at ROS of 1.20. Beyond this bandwidth, the solution also becomes penalizing en masse, so that it he has almost none of the desired benefits of printed antenna technology.

The man of art who wants to increase the band inherently low bandwidth of a printed antenna knows the use of multiresonator techniques coupled (ref. 3 - Albert Sabban). We thus obtain multi-pole structures that offer capacities ranging from a few percent to a few tens of percent of tape, in the case where an optimization has been pushed in this meaning. However, these advantages are obtained at the cost of one greater complexity of implementation, as well as a weight of the antenna which increases in proportion to the number of resonators employees.

The invention will therefore remedy the drawbacks of the prior art, and allow a wide band to be obtained busy using simple technology derived from that printed "patch" antennas, while retaining the advantages of this technology.

For these purposes, the invention proposes a radiating element high bandwidth patch type for an antenna network, as defined in claim 1.

According to a variant, said cavity of the embodiment previous is partially closed in the direction of radiation by a second resonator which consists of a conductive patch engraved on a support which is then placed on the front face of said conductive cavity. According to different variants, the microstrip supply line can be carried out either in simple microstrip, or in shielded microstrip or channel, and enters said cavity either by a channel dug in the metal cavity, either through a recess in the wall of said cavity.

Different forms of patch can be used, for example: circle, square, polygon, ...; as well as different forms of cavity: circular cylinder, square, octagonal, pentahexagonal, ...

The invention also provides a subset of radiating elements for a network antenna, known as a sub-network, said sub-network comprising in particular a mechanical support, several patches and their supplies in microstrip technology, with their dielectric substrate and their associated ground plane. , characterized in that said mechanical sub-array support is placed on the front face of said dielectric substrate, on the radiation side of the antenna. According to a variant of the sub-network, the radiating elements conform to one of the preceding descriptions, and further comprise a resonant system around each patch, said resonant system possibly being a cavity, for example. According to a preferred embodiment, said mechanical support comprises said cavities. According to a particularly advantageous embodiment, said sub-assembly is supplied by a single supply point, common to all the elements of said sub-network. According to an important geometric variant, said sub-network is not planar, but conformed, that is to say that the patches of a sub-network can have different angular orientations.

The invention also relates to the integration of subnets according to the previous descriptions in an antenna network. According to different variants, said antenna can be placed on a flat surface, of revolution, or of a any curvature. Advantageously, the subnets used to make the network antenna will be of geometry identical, allowing the production of series of components of said subnets, as well as subnets themselves.

La figure 1, déjà décrite, montre schématiquement en plan un sous-réseau de quatre patches rayonnants selon l'invention, avec leur alimentation en technologie microruban ;

La figure 2, déjà évoquée, montre schématiquement en plan et en coupe un exemple d'un élément rayonnant selon l'art antérieur;

La figure 3, déjà évoquée, montre des courbes de Bande Passante (BP) en fonction de la hauteur normalisée de diélectrique pour des patches carrés et rectangulaires, pour ROS=2 et aux fréquences de 1 GHz et 10 GHz (référence 1) ;

Les figures 4a et 4b montrent schématiquement en coupe une ligne d'alimentation microruban simple (4a) et une ligne d'alimentation en microruban blindé (4b) ;

La figure 5 montre schématiquement en coupe une variante d'un élément rayonnant selon l'invention ;

La figure 6 montre schématiquement en coupe une autre variante d'un élément rayonnant selon l'invention, avec un deuxième résonateur ;

La figure 7 montre schématiquement en perspective éclatée un mode de réalisation de la variante de la figure 6 ;

La figure 8 montre schématiquement et en perspective un exemple d'une structure mécanique pour la réalisation d'un sous-ensemble rayonnant selon l'invention ;

La figure 9 montre schématiquement en plan la réalisation d'une antenne réseau sur une surface conformée utilisant des sous-réseaux d'éléments rayonnants selon l'invention ;

Other characteristics, variants and advantages will emerge from the detailed description which follows with its annexed drawings, including:

FIG. 1, already described, schematically shows in plan a sub-network of four radiating patches according to the invention, with their supply in microstrip technology;

Figure 2, already mentioned, shows schematically in plan and in section an example of a radiating element according to the prior art;

Figure 3, already mentioned, shows Bandwidth curves (BP) as a function of the normalized dielectric height for square and rectangular patches, for ROS = 2 and at frequencies of 1 GHz and 10 GHz (reference 1);

Figures 4a and 4b schematically show in section a single microstrip supply line (4a) and a shielded microstrip supply line (4b);

FIG. 5 schematically shows in section a variant of a radiating element according to the invention;

FIG. 6 schematically shows in section another variant of a radiating element according to the invention, with a second resonator;

Figure 7 shows schematically in exploded perspective an embodiment of the variant of Figure 6;

Figure 8 shows schematically and in perspective an example of a mechanical structure for the production of a radiating sub-assembly according to the invention;

FIG. 9 schematically shows in plan the production of an array antenna on a shaped surface using sub-arrays of radiating elements according to the invention;

In the different figures, the same references designate the same elements, and the realizations therein described and drawn are given by way of nonlimiting examples.

In Figure 1, we see an example of a subnet of four radiating elements 2 of the patch type, printed on one dielectric substrate 1. The four radiating elements or "patches" are powered by a power network realized in microstrip technology, which consists of conductive tracks printed or engraved on the same dielectric substrate 1. In the present example, the feeding of the four patches is from a point common 5, which feeds two branches 3a, 3b which are then still branched into sub-branches 4a, 4b, 4c, 4d. According to relative length of the electrical paths traveled by signals applied to input 5 of the supply network, until each patch, the relative phase of excitation of four patches can find an adjustment parameter. The relative amplitude of excitation can also be controlled by the management of the various impedances of the different paths. These considerations belong to the field of antenna design well known to humans art, and will not be explained further in the context of this application.

In Figure 2, we see an example of embodiment of a radiating element according to the prior art. As example, we assume that this element includes a patch etched conductor 2 on a dielectric substrate 1 covered on its back side by a ground plane 6. Patch 2 is powered by microstrip 4b, which is an engraved track conductive, usually of the same material as the patch. According to the invention, patch 2 is placed at the bottom of a system closed which consists for example of a cavity 7 defined by conductive walls 8 delimiting the radial extent of the cavity 7 around patch 2. The dimensions of this cavity 7 determine its radio characteristics according to rules known to those skilled in the art; as a result, these dimensions can be chosen by the designer in order to provide the desired bandwidth at the frequency of operation of the radiating element, and this without increase in the thickness of dielectric 1 behind the patch 2. It follows that the dimensioning of the element radiating from the antenna according to the invention and as described as simply as possible in Figure 5 is not governed by the same mechanisms as sizing practical in the prior art.

In particular, in FIG. 3, we see in the case of a construction according to the prior art, the bandwidth curves Δf / f as a function of the normalized height t / λ _ε of dielectric, that is to say to say that the thickness of dielectric is "normalized" or divided by the wavelength in the dielectric λ _ε , indicates to us that an unacceptable thickness of dielectric is necessary to provide a bandwidth beyond a few percent. By way of example, curve 9 represents the frequency response of a square patch of dimensions equal to 0.3 λ ₀ or λ ₀ is the wavelength in vacuum, on a dielectric substrate having a dielectric constant of ε _r = 2.76 and for an ROS (standing wave ratio) of 2. Curve 10 represents the frequency response of a rectangular patch of dimensions equal to 0.3 x 0.5 λ ₀ , with the same dielectric constant parameters and from ROS. We see that for microwaves of the order of 1 to 10 GHz, indicated respectively on curves 9, 10 by a solid line and a dotted line, the relationship remains approximately linear between the bandwidth and the normalized height for widths of band between 1% and 10%.

In the case of the invention, and as described in Figure 5 on the other hand, we are more in a situation analogous to a propagation line transition microstrip towards a mini-guide, the fundamental elements of behavior therefore follow specific rules whose description follows.

The main propagation line is therefore of microstrip type and typically involves a conductor track etched on a thickness of dense substrate. The thickness of this one is dimensioned by integrating the radioelectric criteria of use (ε _r , w, h, Ze) as well as more specific constraints which can come from the envisaged mission. The advantage of thin substrate thickness (of the order of 20 mils, 30 mils maximum, or 0.5 to 0.75 mm) is that it makes it entirely manageable in terms of industrial production the use of radiating elements as well as their associated distribution circuits on surfaces of course flat, but above all shaped in three dimensions, as will be seen below.

We will describe in more detail an example of antenna network on a conformed surface, the implementation of which using radiating elements designed according to the invention is excessively attractive.

FIGS. 4a, 4b show two examples of microstrip technology which can be used for the production of supply lines for the radiating elements according to the invention. In the case of FIG. 4a, the microstrip line consists of a conductive track 22 etched on a dielectric substrate 1 having a ground plane 6 behind the substrate (on the opposite face of the face comprising the etched track). The physical parameters characterizing this system are the dielectric constant ε and the height or thickness of dielectric h ₁ .

In the case of Figure 4b, it is a line shielded microstrip which is shown diagrammatically. As in the previous case, the microstrip line itself consists of a conductive track 22 etched on a dielectric substrate 1 having a ground plane 6 behind the substrate 1. Shielding around this line is constituted by conductive walls 18 which surround the track 22 and which are electrically connected to earth 6.

The physical parameters which characterize the system are the dielectric constant ε and the height or thickness of dielectric h ₁ , as well as the dimensions of the shielding h ₂ for the height or the distance between the surface of the dielectric 1 and the conductive wall 18 which is oriented parallel to this surface, and the width d between the conductive walls 18 on each side of the track 22. The space 17 inside the shield formed by the conductive walls 18 is assumed to be filled with air, and therefore will have a dielectric constant close to 1. The radio propagation characteristics on such a line are calculated from the physical parameters cited according to methods well known to those skilled in the art.

In a practical embodiment of a radiating element according to the invention, this simple or "shielded" line using channel technology opens into a cavity and deforms significantly, so as to form a geometry of patch.

The simplest form of the cavity is that of a cylinder, but other geometries can be used in function of the application: square, pentagonal, hexagonal etc ... without aspect or limiting character.

It is the same for the geometry of the patch which can be limit to a circle or a square in its most simple, and undergo deformations which lead to geometries as varied as the designer's imagination. This is the case, for example, of knowingly deformations sized to radiate a polarized wave circular, for example notches or chamfers, even more exotic geometries.

• compacité
• large bande passante.

The characteristics of this patch as well as those of the surrounding metallic cavity, or rather those fulfilling a metallic type condition on fields E and H; allow therefore to achieve, thanks to a carefully dimensioned assembly of the two, respective size, size, processing, etc., an orthogonal type transition from the microstrip line to the mini-guide having the desired characteristics:

• compactness
• wide bandwidth.

• la taille moyenne de la cavité
• la hauteur moyenne de la cavité.

Many parameters, which were not available in a patch without cavity situation, can be implemented to optimize this or that performance, whether in impedance or in radiation. These include:

• the average size of the cavity
• the average height of the cavity.

For example, the directivity of radiation of a element according to the invention is determined by the dimensions relative of the patch and the surrounding cavity.

Such flexibility and sizing flexibility is inconceivable in a simple resonator situation according to art anterior, but becomes possible by combining patch and cavities according to the invention. It is therefore clear that the laws which govern its behavior are modified and that new multivariable charts can be empirically established, similar to those presented on Figure 3.

Adaptation performance is also not managed by the same laws and the implementation of the cavity more than significantly improves the performance of ROS. In an example of practical realization carried out by the inventor, a typical performance of 6 to 8% of tape to was obtained with a ROS = 1.20 in L-band (1.5 GHz) and this at using a structure whose total thickness does not exceed 10 mm, typically 6 mm which categorizes the achievement as belonging to thin antennas.

• sécurisation de la qualité du rayonnement ainsi que de la mise en réseau, la situation à cavités minimise les couplages mutuels interéléments.
• absence du mécanisme perturbateur lié à la génération d'ondes de surface dans le diélectrique. Classiquement ces ondes de surface se propagent dans la structure et peuvent perturber le comportement des éléments adjacents. De fait, dans une réalisation selon l'invention, les ondes de surface sont "piégées" dans le volume de la cavité et participent au mécanisme d'adaptation général de l'antenne.

Such a cavity patch environment provides shielding which has two main consequences:

• securing the quality of radiation as well as networking, the cavity situation minimizes mutual interelement coupling.
• absence of the disturbing mechanism linked to the generation of surface waves in the dielectric. Conventionally, these surface waves propagate in the structure and can disturb the behavior of adjacent elements. In fact, in an embodiment according to the invention, the surface waves are "trapped" in the volume of the cavity and participate in the general adaptation mechanism of the antenna.

We can consider two technological achievements of concept of the invention, which consists in assembling a cavity and the radiating element produced in microstrip technology buried.

The first approach is faithful to Figure 2. In this case, the cavity can be integrated into a structure carrier (such as the example shown in Figure 8) on which we will glue, screw, or assemble by any other means the microstrip circuit on a substrate thin dielectric 1 comprising patch 2 and the power line 4.

In Figure 5, we have a sectional view of a variant implementation of the invention. This figure is identical to Figure 2 except for the presence of conductive elements 13. According to this variant, one realizes a short circuit condition between the vertical wall 8 of the cavity 7 and the ground plane 6 of the microstrip line, by means of one or more conductive element (s) 13 which electrically connects the two. This achievement allows thereby a total shielding of the microstrip assembly and patch compared to other neighboring elements. The electrical continuity established by the element (s) conductor (s) 13 can be total or partial:

Total : We can very well weld or braze the metal structure 8 defining the cavity 7 on the ground plane bottom 6 in accordance with the geometry of the cavity.

Partial : One can imagine a discrete shielding using studs crossing the dielectric substrate 2 screwable on the cavity or even consider the technique of metallized holes in the dielectric substrate which one could weld in vapor phase for example to the continuous part of the cavity.

Another technique could also consist of achieve an equivalent electrical condition. So we could give geometry to the cavity facing the plane of mass such that it constitutes a reactive short circuit for microwave signals. Such a technique has already been described in the document referenced n ° 4 - French patent n ° 89 11-829.

a) un élément très large bande, développe en bande X.

b) un réseau conforme utilisant l'élément du type montré sur la figure 2.

From the basic concept, the association of a patch / microstrip power supply line with a cavity, it is possible to build many variants which are only specific applications or optimizations of the original concept. We will describe two examples to illustrate this point.

a) a very wide band element, develops in X band.

b) a conforming network using the element of the type shown in FIG. 2.

A first example of an antenna realization using a very wide band element according to the invention is shown in Figure 6. This element is intended for antenna operating at 8 GHz which has been produced and on which of the measurements made it possible to confirm the expected performance.

FIG. 6 illustrates the method of this realization, which consists in adding to a basic patch 2 radiator, a second resonator 12 positioned above the first resonator 2. The configuration is therefore that of the Figure 5, except that the resonant cavity 7 is partially closed on its front side by a second resonator 12 which can be for example a patch printed on a dielectric support 11. In this specific case the second element is implanted flush with cavity 7, but we could place it, with more elaborate constructions, either at a higher height or either at a lower height than the height of the conductive walls 8 of the cavity 7.

The approach, however, which is to make identical the interpatch distance and the height of the cavity makes it very simple technological achievement. The second resonator 12 can be etched on a carrier substrate 11 of low thickness and mass and its assembly can be done by simple bonding or screwing.

• Diamètre cavité 7 : 23 mm
• Hauteur cavité 7 : 2 mm
• Taille 1er résonateur 2 : ^~14 mm
• Permittivité substrat 1 ^~2.50
  (1er résonateur)
• Epaisseur 1Er substrat 1 : 20 mils = 0,508 mm
• Taille 2ème résonateur 12 : ^~14 mm
• Permittivité substrat 11 : ^~ 3.90
• Epaisseur 2ème substrat 11 : ^~125 µm

In our embodiment of Figure 6, the main characteristics of the radiator are as follows:

• Cavity 7 diameter: 23 mm
• Cavity height 7: 2 mm
• 1st resonator size 2: ^~ 14 mm
• Permittivity substrate 1 ^~ 2.50
  (1st resonator)
• Thickness 1 Er substrate 1: 20 mils = 0.508 mm
• 2nd resonator size 12: ^~ 14 mm
• Permittivity substrate 11: ^~ 3.90
• Thickness of 2nd substrate 11: ^~ 125 µm

As shown in Figure 7, which shows the exploded view in Figure 6, the two resonators can be deformed at using chamfers to generate polarization circular, if required, using a single access. The radiation patterns measured in a band 8.0 to 8.4 GHz application show excellent device behavior. The ellipticity rate (cross polarization) is excellent at frequency optimization (8.2 GHz) and remains well below 3 dB on the entire useful band.

In this figure 7, we also see the recess 19 fitted on one side of the conductive wall 8 of the cavity resonant, to allow penetration of the line feeding microstrip in the cavity.

An antenna project in which the radiator fits according to the invention and presented in FIGS. 2 and 5 to 7, concerns the creation of a scanning antenna electronics as shown in Figures 8 and 9. The Figure 8 shows schematically in perspective a structure mechanics of a radiating sub-assembly according to the invention, this sub-assembly being intended to be assembled with numerous similar sub-assemblies to form a network antenna as shown in Figure 9.

The operating principle of the antenna is exposed in Figure 9. The example of a complete network therefore consists by installing it on a surface with symmetry of revolution around an axis z of identical subsets, such as shown in Figure 8. The subsets are composed in this exemplary embodiment, four radiators identical patch type according to one of FIGS. 2, 5 to 7, supplied by a common distributor as shown on the Figure 1. The mechanical structure 14 shown schematically in plan in Figure 8 has the conductive walls of four cavities 8 and fixing pads 15 of the circuit microstrip and its dielectric substrate 1 as shown on Figure 1. Recesses 19 are arranged in the conductive walls 8 for the passage of microstrip lines supply of radiant elements.

The topology of these radiators is particular in the example shown in these figures 8 and 9 insofar as one of them undergoes an inclination of  = 10 ° relative to the three others. In Figure 8, we see that the three axes 20 of the first three cavities are parallel, while that the axis 30 of the fourth cavity is inclined at 10 ° by compared to others. The subnet is therefore not planar but consistent. Thanks to the small thickness of the dielectric 1 which results from the use of the invention, the circuit microstrip can be easily deformed to stick to the mechanical structure 14, once fixed to the latter by means of the fixing studs 15.

In Figure 9, we see an example of an antenna network made from subnets as shown in Figure 8. The subnets are themselves composed of a number of radiating elements 28 according to the invention (four in this example), aligned on axis 21 the subnet; to build the antenna, each subnet is arranged with its axis 21 in the same plane with the main axis of the antenna z, and with an angular deviation constant between two successive planes thus defined. The angle  is 10 ° as in figure 8. The interest of this particular topology is to assist in lobe formation antenna radiation, as described in the application French patent no. 91 05510 of May 6, 1991, on behalf of the plaintiff (which is an integral part of this request as description of prior art concerning lobe antennas with formed lobes).

1) La cavité assure un blindage qui élimine tout problème de couplage mutuel et permet la mise en réseau à efficacité maximale, à pas interélément optimum.

2) La technologie microruban permet en outre deux avantages majeurs :

a) réaliser la transition rayonnante de manière très compacte ;

b) rendre possible la réalisation du répartiteur d'alimentation sur la surface conformée.

So we can see all the interest of the new concept of radiation element to realize this kind of antenna. Among the advantages obtained, there may be mentioned in particular:

1) The cavity provides shielding which eliminates any problem of mutual coupling and allows networking at maximum efficiency , with optimum inter-element pitch.

2) The microstrip technology also allows two major advantages:

a) achieve the radiant transition in a very compact manner;

b) make it possible to produce the feed distributor on the shaped surface.

Indeed, because of its thinness (20 mils), the dielectric etching support can be easily formed hot for example without operating problems radioelectric. Another technology, triplate type for example, would have been either inapplicable or very delicate to implement.

a) réalisation sans difficulté d'éléments rayonnants bande large très compacts sur des surfaces pouvant être conformées : cône, sphère ou autres dépendant de l'application. Par principe ces radiateurs sont blindés par des murs électriques : cavités qui sécurisent leur fonctionnement propre, ainsi que leur mise en réseau.

b) facilité de la réalisation d'un répartiteur sur une surface non plane. Par essence, une technologie de type microruban est très adaptée à être conformée et de ce fait se trouve très utile dans les exemples d'application que nous venons d'évoquer. A titre d'exemple, la figure 1 montre le masque de réalisation d'un circuit microruban inférieur, pouvant servir à la réalisation d'un sous-ensemble rayonnant selon l'invention. On y voit les quatre radiateurs circulaires (en bande X dans cet exemple) ainsi que les divers éléments du circuit de distribution comportant une succession de transformateurs et d'éléments de diviseur de puissance. La propagation de type microruban s'appuie sur une disymétrie de répartition de champs et concentre ceux-ci entre la piste et le diélectrique. De ce fait, elle s'accommode tout à fait d'une topologie non planaire, et la distribution de l'alimentation se fait sans perturbation notable et sans problème technologiques majeurs.

We therefore perceive all the interest of the proposed approach which allows to simultaneously solve all the technical problems posed:

a) production without difficulty of very compact wide band radiating elements on surfaces which can be shaped: cone, sphere or others depending on the application. In principle, these radiators are shielded by electrical walls: cavities which secure their proper functioning, as well as their networking.

b) ease of making a distributor on a non-planar surface. In essence, a microstrip type technology is very suitable for conforming and therefore is very useful in the application examples that we have just mentioned. By way of example, FIG. 1 shows the mask for producing a lower microstrip circuit, which can be used for producing a radiating sub-assembly according to the invention. We can see the four circular radiators (in X band in this example) as well as the various elements of the distribution circuit comprising a succession of transformers and power divider elements. Microstrip type propagation is based on a field distribution asymmetry and concentrates these between the track and the dielectric. Therefore, it accommodates quite a non-planar topology, and the distribution of food is done without significant disturbance and without major technological problems.

It is quite clear that the configurations which have been described are not limiting and that the use of the concept can be done by imagining as many variations as of potential applications.

So with regard to the examples of antennas proposed networks, can they include more of elements, to be established in a plane way, or to be used to sample a reflector antenna and set up in this case according to a surface type geometry of Petzwald which optimizes the efficiency of the device.

Claims (13)

1. Broadband patch type antenna element for an array antenna comprising a ground plane (6), a dielectric substrate (1), a conductive patch (2) and a probe (4a, 4b, 4c, 4d) for feeding signals to said element, said patch (2) and said probe (4a, 4b, 4c, 4d) being produced by etching conductive microstrips on said dielectric (1), said patch (2) and said feed probe (4a, 4b, 4c, 4d) being disposed on a surface referred to as the front surface of said substrate (1) relative to the radiation direction, said ground plane (6) being disposed on the rear face of said substrate (1), said antenna element further including a radially closed cavity-type system (7) defined by conductive walls (8), said cavity being disposed on said front face of said dielectric substrate (1), with said patch (2) disposed on the bottom of said cavity (7), said cavity (7) being at least partly open in the radiation direction of said element, characterized in that said conductive walls (8) of said cavity (7) extend through said substrate (1) to the ground plane (6) on the rear surface of said substrate (1).
2. Antenna element according to claim 1, characterized in that said cavity (7) is partially closed in the radiation direction by a second resonator which comprises an etched conductive patch (12) on a second thin dielectric substrate (11) disposed on the front surface of said cavity (7).
3. Antenna element according to claim 1 or claim 2, characterized in that said microstrip feed array is a simple microstrip.
4. Antenna element according to claim 1 or claim 2, characterized in that said microstrip feed array is a screened microstrip.
5. Subarray of antenna elements for an array antenna according to any one of the above claims, said subarray in particular including a mechanical support (14), a plurality of patches (2) and their microstrip technology feed arrangements with their associated dielectric substrate (1) and their associated ground plane (6), characterized in that said mechanical support (14) of the subarray is disposed on the front surface of said dielectric substrate on the radiating side of the antenna.
6. Antenna subarray according to claim 5, characterized in that said mechanical support (14) comprises the conductive walls (8) of said cavities (7).
7. Antenna subarray according to claim 5 or claim 6, characterized in that said subarray is fed from a single feed point (5) common to all the antenna elements of said subarray.
8. Antenna subarray according to any one of claims 5 to 7, characterized in that said subarray is conformed rather than planar.
9. Array antenna characterized in that it comprises antenna subarrays according to any one of claims 5 to 8.
10. Array antenna according to claim 9, characterized in that said antenna is disposed on a plane surface.
11. Array antenna according to claim 9, characterized in that said antenna is disposed on a surface in the shape of a body of revolution.
12. Array antenna according to claim 9, characterized in that said antenna is disposed on a conformed surface having any curvature.
13. Array antenna according to any one of claims 9 to 12, characterized in that said antenna is made up of subarrays having exactly the same geometry.

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