EP0372451B1 - Multifrequency radiating device - Google Patents

Description

The invention relates to a multi-frequency radiating device.

• le nombre de pinceaux ;
• le gain sur la ou/les couvertures ;
• l'isolation interfaisceaux.

The general development in the field of telecommunications satellites is going in the direction of an increase in capacities in terms of power, traffic, number of missions. The same satellite must, for economic reasons, be able to carry several payloads. These use antenna systems whose gains are constantly increasing, this in order to guarantee ever more stringent specifications on the parameters in force, namely:

• the number of brushes;
• the gain on the cover (s);
• inter-beam insulation.

The new payloads use antenna systems whose projected opening can vary from 3 to 6 meters, or even more. It is easily understood that for various reasons, and in particular of location and of mass, it is not possible to multiply the number of these large antennas on the same satellite body.

In general, whether in the case of a direct radiation array or a reflector antenna using a primary array, it is attractive to use the same radiating surface: this going in the direction of maximum integration functions and better optimization of the payload at the satellite level.

Document EP-A-0 188 345 discloses a multi-frequency network antenna, constituted by the production of a network antenna operating at a first frequency, and a second network antenna operating at a second frequency, this primary antenna being composed of 'radiating elements of a first type, either slots or printed paving stones; and this second antenna being composed of radiating elements of a second type, which are in this document "patches". This document teaches the construction of a second virtually transparent antenna at the operating frequency of the first antenna, so that the juxtaposition side by side of the two antennas does not interfere too much with the operation of the first antenna. This nevertheless constitutes an important constraint in the design of the two antennas, since they cannot be optimized separately due to inevitable couplings between the two antennas.

The object of the invention is to provide a solution to this kind of problem and thus to achieve, on the same physical surface, the optimization of sets of different radiating elements working at different frequencies.

To this end, the invention provides a multifrequency radiating device, comprising at least a first radiating element of a first type, and at least one radiating element of a second type associated, side by side, on the same surface to form an antenna. array, the radiating elements of the first type acting in a first frequency range, and the radiating elements of the second type acting in a second frequency range, characterized in that the elements of the first type are elements of the microstrip type and the elements of the second type are elements of the wire type, and in that these elements are associated two by two to form at least one compound radiating element.

Advantageously, networking can be done optimally for different missions, at different frequencies and this on the same radiating antenna.

In addition, the possibility of using third radiating elements makes it possible to solve the delicate problem of the networking of elements having fundamentally different spacing needs due to their directivity or to their operating frequency.

• l'un utilisant les premiers éléments rayonnants ;
• l'autre utilisant la combinaison des seconds et des troisièmes éléments rayonnants.

The non-interaction between the different types of radiating elements makes it possible, finally, to treat and optimize the complete network as two independent networks, each of them being optimally produced:

• one using the first radiating elements;
• the other using the combination of the second and third radiating elements.

• les figures 1 et 2 représentent schématiquement deux réalisations respectives du dispositif selon l'invention ;
• les figures 3 et 4 représentent deux vues en coupe d'éléments d'une réalisation du dispositif selon l'invention ;
• les figures 5 et 6 représentent schématiquement deux réalisations du dispositif selon l'invention.

The characteristics and advantages of the invention will become apparent from the description which follows, by way of nonlimiting example, with reference to the appended figures in which:

• Figures 1 and 2 schematically represent two respective embodiments of the device according to the invention;
• Figures 3 and 4 show two sectional views of elements of an embodiment of the device according to the invention;
• Figures 5 and 6 schematically represent two embodiments of the device according to the invention.

• des premiers éléments 11 rayonnants de type microrubans ou de type imprimés ("Patch" en anglais) ;
• de second éléments 12 rayonnants de type filaire.

The radiating device of the invention, as shown in FIG. 1, comprises, associated on the same surface 10, at least two types of radiating elements operating according to different principles:

• first radiating elements 11 of microstrip type or printed type ("Patch" in English);
• second radiating elements 12 of wired type.

There is thus obtained a dual-frequency antenna which makes it possible to carry out radiation on the same useful surface at a first frequency using a printed antenna, radiation at a second frequency using a wire antenna. The operating impedance of these two antennas make it possible to optimize these at separate frequencies, the decoupling between them being ensured by the fact that the principles which contribute to radiation are of different natures.

FIG. 2 represents an alternative embodiment of the device of the invention, for which the layout of the first and second elements 11 and 12 has been modified. The number of second elements 12, for example of the wired type, located between the first elements 10, for example of the printed type depends on the optimization of the antenna. The network thus formed can also be of triangular, square, rectangular or hexagonal type.

If one thus associates on the same surface such radiating elements operating according to different principles, one obtains a dual-frequency antenna. This in fact makes it possible to produce radiation on the same useful surface at one frequency using a printed antenna, radiation at another frequency by means of a wire antenna.

• L'antenne filaire n'affecte pas les caractéristiques adaptation et rayonnement de l'antenne imprimée.
• Du fait de principes de rayonnement différents, le couplage entre les deux éléments reste très faible.

Such an embodiment has the following two characteristics:

• The wire antenna does not affect the adaptation and radiation characteristics of the printed antenna.
• Due to different radiation principles, the coupling between the two elements remains very weak.

A certain number of types of wire antennas can be envisaged as being able to be mounted on the printed antenna. The precise choice depends on an optimization in relation to a need, and directs the solution towards dipoles, monofilar propellers, quadrifilar propellers ...

Compared to nominal operation (without printed antenna) of the wired element there is no significant change in performance of this antenna when it is installed on a printed antenna; the ground plane seen by the wire antenna being produced by all of the printed conductor and the general ground plane of the printed antenna. As the operating frequency of the wire antenna does not correspond to a resonance of the printed antenna, the printed antenna does not play any particular role (field concentration, cavity, resonance).

• un plan de masse 13, un substrat diélectrique 14 et une piste métallique 15 qui forment une antenne imprimée plane 16 ; cette antenne étant percée en son centre d'un trou 17 de passage ;
• un câble coaxial 18 passant par ce trou 17 perpendiculairement au plan de l'antenne imprimée 16 ; ce câble se terminant à son extrémité libre par une antenne d'un autre type 19 ici un dipôle.

In another example of embodiment of the device of the invention, shown in FIG. 3, a first element 16 is associated with a second element 19 on the same projected surface to form a radiating element called "compound"; so we have:

• a ground plane 13, a dielectric substrate 14 and a metal track 15 which form a planar printed antenna 16; this antenna being pierced in its center with a through hole 17;
• a coaxial cable 18 passing through this hole 17 perpendicular to the plane of the printed antenna 16; this cable ending at its free end by an antenna of another type 19 here a dipole.

In the embodiment, shown in Figure 4, the coaxial cable 18 passing through the hole 17 ends with an antenna 19 which is then a helical antenna.

• un élément imprimé simple résonateur ;
• un élément imprimé double résonateur ;
• un élément double "patch" diplexant présentant des accès séparés pour deux gammes de fréquence par exemple un accès émission et un accès réception.

The printed antenna 16 thus defined is dimensioned so as to meet the general requirements of its mission. Depending on the case and depending on the desired application, it consists, for example, in:

• a simple resonator printed element;
• a double resonator printed element;
• a double diplexing "patch" element having separate accesses for two frequency ranges, for example a transmission access and a reception access.

For its part, the wire element 19 is defined due to specifications specific to the mission for which it is intended. Its geometry, whether it is a dipole or a propeller, is subject to optimization in order to obtain the desired performance.

• . à une distance d'environ $\text{da=0,67 λ OL}$
  
  pour une maille carrée ;
• . à une distance da de 0,70 à 0,72 λ OL pour une maille hexagonale ;

λ OL étant la longueur d'onde de la fréquence du centre de la première gamme de fréquence, par exemple la bande L (1,5 - 1,6 GHz).It is then possible to produce a network antenna made up of radiating elements composed as described. But this networking if it only uses the elements as described poses serious efficiency problems and the simultaneous optimization of the various missions proves difficult or even impossible to achieve. Thus, the antenna, represented in FIG. 5, notably comprises radiating elements printed 16 simple resonators to carry out for example a mission at 1.5 Ghz. This type of element having a typical directivity of the order of 7 to 8 dB, the knowledge of their mutual couplings makes it possible to envisage satisfactory use; that is to say at more than 80% yield per relation to the surface of the elementary cell. These elements are then located:

• . at a distance of about $\text{da = 0.67 λ OL}$
  
  for a square mesh;
• . at a distance da of 0.70 to 0.72 λ OL for a hexagonal mesh;

λ OL being the wavelength of the frequency of the center of the first frequency range, for example the L band (1.5 - 1.6 GHz).

These operating constraints on these first radiating elements 16 (optimum coupling / spacing) freeze the inter- "patch" spacing da and therefore the general layout of the network.

If it is desired to carry out a mission at 2.00 GHz using second radiating elements 19, as described above, dipoles 19 are implanted on the "patches" 16. Typically these have a directivity of 5.20 dB.

• de 0,51 λ OS environ pour une maille carrée ;
• de 0,55 λ OS environ pour une maille hexagonale ;

λ OS étant la longueur d'onde du centre de la seconde gamme de fréquences par exemple la bande S (2 GHz).L'implantation étant nominalement bloquée par les distances inter-patch, on a donc dans la configuration considérée une géométrie qui correspondrait à des distances inter dipôles da de :

• 0,89 λ OS (bande S) en maille carrée ;
• 0,96 λ OS en maille hexagonale :

Soit une perte à la mise en réseau de l'ordre de 4 à 5 dB pour les éléments dipôles 19 en bande S, trop fortement contraintes par l'implantation des éléments imprimés.This directivity requires a network of identical elements at a distance respectively:

• about 0.51 λ OS for a square mesh;
• about 0.55 λ OS for a hexagonal mesh;

λ OS being the wavelength of the center of the second frequency range for example the S band (2 GHz). The implantation being nominally blocked by the inter-patch distances, we therefore have in the configuration considered a geometry which would correspond at inter dipole distances da of:

• 0.89 λ OS (S band) in square mesh;
• 0.96 λ OS in hexagonal mesh:

Or a loss on networking of the order of 4 to 5 dB for the dipole elements 19 in S-band, too strongly constrained by the layout of the printed elements.

The solution to this subsampling for the band elements S consists in placing between the "patches" third elements 20 of the same type as the second radiators, therefore in the second frequency range.

The implantation of such elements 20 is made possible by the fact that in the areas considered the field densities of the printed elements are negligible. Measurements made by considering different installation distances confirmed these results and demonstrated the little impact of these additional elements on the nominal operation of dual-band composite elements 16-19.

Such a configuration, as shown in FIG. 6, therefore makes it possible to considerably densify the network of second radiating elements 19, the sampling of which is greatly improved, without any significant impact on the first radiating elements 16.

soit typiquement pour la maille hexagonale à $\text{db=0,96 λ OS/√3}$

, c'est-à-dire $\text{db=0,55 λ OS}$

. Cette distance correspond donc à un échantillonnage optimal pour l'utilisation des dipôles en bande S. La réalisation du réseau bande S par l'intermédiaire des éléments 19 et 20 permet donc une utilisation de la surface avec une efficacité maximum et correspondant à la mise en réseau de façon optimale des éléments bande S seule.On a hexagonal mesh, as shown in FIG. 6, the inter-dipole distances obtained correspond, including elements 19 and 20, to $\text{db = da / √3}$

either typically for the hexagonal mesh with $\text{db = 0.96 λ OS / √3}$

, that is to say $\text{db = 0.55 λ OS}$

. This distance therefore corresponds to an optimal sampling for the use of dipoles in S-band. The realization of the S-band network by means of elements 19 and 20 therefore allows use of the surface with maximum efficiency and corresponding to the setting in optimal network of S-band elements alone.

soit $\text{S = 0,798 λ OS²}$

.This result is explained, moreover, immediately by reasoning on the directivities: With such a type of mesh, a second radiating element 19 is surrounded by six third radiating elements 20. Each of these elements 20 is used jointly with three elements 19 so that, relative to the hexagonal mesh, everything happens as if these three elements 19 contributed to the radiation for a cell; this cell having a surface S such that: $\text{S = √}\overline{\text{3/2}}\text{. (0.96 λ OS) ²}$

is $\text{S = 0.798 λ OS²}$

.

soit DM=10 dB.The maximum DM directivity of such a cell is given by: $\text{DM = 4 S / λ OS²}$

or DM = 10 dB.

   Une antenne réseau multifréquence peut donc être réalisée de façon optimale pour les diverses missions en faisant appel à :

• d'une part des éléments rayonnants composés tels que représentés aux figures 3 et 4 ;
• d'autre part des éléments additionnels 20 implantés entre ces éléments rayonnants composés.

The association of three radiating elements 19 of 5.2 dB in amplitude and phase corresponds to a directivity diagram.

A multi-frequency network antenna can therefore be optimally realized for the various missions by calling on:

• on the one hand, composed radiating elements as shown in FIGS. 3 and 4;
• on the other hand, additional elements 20 located between these compound radiating elements.

Figure 6 shows the layout of these elements on a hexagonal mesh while Figure 7 gives an example for a square mesh.

Networking can thus be done optimally for different missions, at different frequencies and this on the same radiating antenna.

The possibility of using third radiating elements 20 therefore makes it possible to solve the delicate problem of networking elements having fundamentally different spacing needs due to their directivity or to their operating frequency.

• l'un utilisant les premiers éléments rayonnants 16 ;
• l'autre utilisant la combinaison des seconds et des troisièmes éléments rayonnants 19 et 20.

The non-interaction between the different types of radiating elements makes it possible to treat and optimize the entire network as two independent networks. Each being carried out optimally:

• one using the first radiating elements 16;
• the other using the combination of the second and third radiating elements 19 and 20.

It is understood that the present invention has only been described and shown as a preferred example and that its constituent elements can be replaced by equivalent elements without, however, departing from the scope of the invention.

Thus the shape of the radiating device of the invention may, of course, not be planar and be provided with a certain curvature (cylindrical, spherical, etc.), depending on its particular location on a structure: for example location on concave surfaces.

Claims (8)

1. A multifrequency radiating device comprising at least one first radiating element (11, 16) of a first type and at least one radiating element (12, 19, 20) of a second type, the elements being associated on a common surface (10) in order to constitute an array antenna, the radiating elements of the first type (11, 16) acting in a first frequency range and the radiating elements of the second type (12, 19, 20) acting in a second frequency range, the device being characterized in that the elements of the first type (11, 16) are elements of the microstrip type and the elements of the second type (12, 19, 20) are elements of the wire type; and in that the elements are associated in pairs in order to form at least one composite radiating element (16, 19).
2. A device according to claim 1, characterized in that said composite radiating element comprises a first radiating element of said first type (11, 16) constituted by a ground plane (13), a dielectric substrate (14) and a metal track (15) deposited thereon, together with a second radiating element of said second type (19) of the wire type which passes through the first element via a hole (17) passing through the center of the metal track (13), with the ground plane as seen by the wire element being built up from the metal track (15) and from the general ground plane (13) of the first element.
3. An array antenna constituted at least in part from a plurality of composite elements (16, 19) according to any preceding claim, with a plurality of said composite elements disposed on a structure serving as a support and forming the general ground plane (13).
4. An array antenna according to claim 3, characterized in that it further comprises intermediate radiating elements (20) of a third type associated side-by-side with the composite radiating elements (16, 19).
5. An array antenna according to claim 4, characterized in that said intermediate radiating elements (20) are elements of the wire type.
6. A device according to claim 1, characterized in that the two frequency bands are the L band and the S band.
7. A device according to claim 1, characterized in that the radiating elements (16, 19, 20) constitute a hexagonal lattice array.
8. A device according to claim 1, characterized in that the radiating elements (16, 19, 20) constitute a square lattice array.

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