EP3664214B1 - Multiple access radiant elements - Google Patents

Description

The invention relates to the general field of antennas, in particular satellite antennas, in particular active antennas, array antennas or multibeam antennas. Such antennas comprise several radiating elements, the invention relates more specifically to radiating elements with compact multiple accesses and high radiation efficiency.

An array antenna is made up of radiating elements which must respect certain characteristics. They must in particular have a radiating surface whose maximum dimensions depend on the operating frequency and on the desired angular spacing between the main lobe generated by the antenna and its array lobes. Taking these dimensional constraints into account, they must have the maximum surface efficiency, ie close to 100%. The surface efficiency characterizes the coefficient between the directivity of the radiating element and that which would be obtained by a radiating aperture occupying the space allocated to the radiating element, and on which a uniform distribution of the electric field is imposed. Maximizing the area efficiency of the radiating elements helps to optimize array antenna gain and reduce sidelobe and arraylobe levels.

By respecting these constraints, for a given antenna surface, the gain will be maximized, and it will thus be possible to minimize the power of the amplifiers of the transmitting antennas or to maximize the G/T ratio of the receiving antennas.

The radiating elements must also have a small size and a low mass and/or the ability to be excited in a compact manner in single or bi-polarization and a passband compatible with the intended application.

Thus, a general problem which the invention seeks to solve consists in designing radiating elements which make it possible to obtain at the output of the radiating aperture an electric field which is as uniform as possible while respecting the imposed sizing constraints. In particular, each radiating element must be compact and have a short profile.

Different solutions exist in the state of the art for designing radiating elements for satellite antennas. Generally, they all use metallic structures in order to minimize insertion losses. We know in particular the solutions described in the patent documents EN 2477785 , EP1930982 And FR2739226 .

There figure 1 schematizes a first example of radiating element 100 according to the prior art. The radiating element of the figure 1 comprises a first access waveguide 101 and a second waveguide 102 in the shape of a flared horn towards the radiating opening. On the example of the figure 1 , the section of the horn is square in shape. This type of known radiating element makes it possible to ensure a smooth transition between the signal guided via the access guide 101 and the signal radiated at the output of the horn 102.

The radiating element 100 of the figure 1 however, has the disadvantage of low radiation efficiency because it does not make it possible to obtain an electric field uniformly distributed over its opening. Indeed, the structure of the horn 102 only favors the propagation of the fundamental mode of the wave excited at the level of the access guide 101.

There figure 2 schematically represents a profile sectional view of the radiating element 100. The curve 103 schematizes the distribution of the density of the electric field radiated at the opening of the horn 102. As indicated on the figure 2 , the maximum energy of the radiated electric field is reached at the center of the opening while the energy decreases progressively from the center towards the edges of the opening.

In order to try to obtain a more homogeneous distribution of the electric field on the opening of the radiating element, the profile of the horn can be modified in the way described on the example of the picture 3 . In this example, the horn 302 no longer has a straight linear profile but an undulating profile or so-called “spline” profile. Such a profile consists in producing undulations on the wall of the horn 302 in order to excite and control the propagation of higher modes of the wave radiated inside the horn. This example is described in publication (1). Thanks to this type of profile, an adequate combination of the different propagation modes of the wave is obtained on the radiating aperture of the horn 302 which leads to a distribution more homogeneous of the electric field 303 as schematized on the picture 3 . However, the distribution of the electric field is still not uniform because the energy decreases, in this imaged example, towards the center of the opening. In other variant embodiments of this type of horn, the electric field may have more than two energy maxima but in all cases the distribution of the electric field is not uniform.

There figure 4 schematizes another example of radiating element 400 as described in publication (2). In this example, an array of horns each having a small aperture is used in an attempt to achieve better overall radiation efficiency for the radiating aperture of the antenna. The radiating element 400 thus consists of several sub-elements each comprising an access guide 401.411 and a horn 402.412 of the type described in figure 1 . A power splitter 404 ensures the uniform and phased supply of the various sub-elements of the network. The distribution 403 of the density of the electric field radiated at the opening of the horn array is also not uniform. In particular, it has a minima close to 0 at the center of the distribution.

The solution of the figure 4 has the advantage of using radiating sub-elements with a small opening and which therefore have a length that is markedly less than that of a radiating element of the type of figure 1 . This solution thus makes it possible to develop compact radiating elements. However, it does not make it possible to obtain a uniform distribution of the electric field on the radiating opening because, as schematized by the curve 403 on the figure 4 , the tangential electric field is canceled on the metal walls of this radiating element, and minimum levels of the electric field are identified between the various horns 402,412 which penalizes the overall radiation efficiency. Another disadvantage of the solution of the figure 4 is that it requires the use of a power splitter 404 connected to the radiating sub-elements to supply them in phase. The splitter 404 must respect the mesh of the antenna and be very compact so as not to penalize the overall profile of the antenna.

There figure 5 diagrams yet another example of radiating element 500 as described in US patent US6211838 . This solution consists of a radiating aperture network supplied by a power splitter integrated in the horn 502 as the latter flares out. This solution has a radiation efficiency comparable to that of the example of the figure 4 with the same drawback of electric field level minima between the different openings as illustrated by the electric field curve 503.

There figure 6 schematizes yet another example of radiating element 600 described in the application for French patent FR3012917 . In this example, the radiating element 600 consists of several Fabry-Pérot cavities 603,613,604 which are superimposed, the assembly being fed by several access guides 602,612. Each Fabry-Pérot cavity 603,613,604 is a metal cavity closed by a gate 606,616,626 which is configured to reflect part of the signal injected at the center of the cavity towards its periphery. This approach achieves better surface radiation efficiency than the solutions described previously, as illustrated by the electric field curve 605. However, it has the disadvantage of being difficult to apply over a wide frequency band while guaranteeing a good adaptation to the accesses.

None of the solutions of the state of the art makes it possible to obtain a truly uniform electric field density at the horn output while retaining the compactness necessary for active antenna applications.

The invention proposes a new type of radiating element which is based on the excitation of a single radiating opening by several accesses. Unlike a known array of radiating elements, the proposed radiating element comprises a horn common to all the ports which are coupled to the common horn at an excitation interface and via excitation guides.

The use of a common horn with several accesses makes it possible to promote the excitation of the higher modes of the wave on the radiating surface, unlike a network of conventional radiating elements. In order to control the excitation and combination levels of the different wave propagation modes on the radiating aperture, the excitation guides also work in several modes. The excitation and the control of these modes in the excitation guides are obtained in particular thanks to their asymmetry.

The association of the excitation at several points of a radiating element (naturally allowing a more homogeneous distribution of the electric field) with the numerous optimization parameters provided by the proposed solution makes it possible to more effectively control the combination of the different modes of propagation in exit from the radiating aperture over a shorter distance in the signal propagation axis than the known solutions. It follows that the proposed solution makes it possible to develop radiating elements which are both very efficient and very compact.

The subject of the invention is a radiating element comprising at least two supply guides and a horn common to the at least two supply guides and having an excitation interface, each supply guide being separate from the other supply guides. , each power guide consisting of an access guide and an excitation guide connected to the access guide by an access interface and connected to the common horn by the excitation interface, each guide excitation being flared in the direction of the access interface towards the excitation interface, each excitation guide having no axis of symmetry, the at least two supply guides being identical and arranged symmetrically 'one with respect to the other with respect to a plane of symmetry of the radiating element, and the flare profile of each excitation guide is configured so as to control, in amplitude and in phase, the modes of propagation of a radiating wave propagated from each access guide to the output of the horn, so that the electric field obtained at the output of the horn is substantially uniform.

According to a particular aspect of the invention, the splaying profile of each excitation guide is configured in such a way as to promote the propagation of a fundamental mode of propagation and of a higher propagation mode of order two in the guide. of excitement.

According to a particular aspect of the invention, the widening profile of each excitation guide is configured so as to favor the propagation, in the horn, of several modes of propagation of odd orders, from the mode of fundamental propagation and of the second order upper propagation mode propagated in each excitation guide.

According to a particular aspect of the invention, the flare profile of each excitation guide is configured so as to control the amplitude and the phase of each mode of propagation propagated in the horn so that the electric field resulting from the combination of all the propagation modes propagated in the horn is uniform at the output of the horn.

According to a particular variant, the radiating element according to the invention comprises at least four supply guides, the horn being common to four supply guides, the four supply guides being arranged symmetrically with one another with respect to two planes of orthogonal symmetry.

According to a particular aspect of the invention, each supply guide is configured so that the longitudinal axis of an access guide is off-center with respect to the center of the opening of the excitation guide connected to the interface of excitement.

According to a particular variant, the radiating element according to the invention further comprises a power splitter to excite the access guides in phase.

According to a particular aspect of the invention, a cross section of the excitation guide is of square, rectangular or circular shape.

According to a particular aspect of the invention, the radiating element operates in mono-polarization or in bi-polarization.

According to a particular aspect of the invention, each excitation guide has a continuous or discontinuous widening profile.

According to a particular aspect of the invention, the common horn is axisymmetric.

According to a particular aspect of the invention, each excitation guide has a flared profile on a first plane and an invariant profile on a second plane orthogonal to the first plane.

The invention also relates to a radiating device comprising at least four radiating elements according to one of the preceding claims and a secondary horn common to the four radiating elements and connected via a input interface to the openings of the respective horns of each radiating element.

The invention also relates to an antenna comprising a plurality of radiating elements or a plurality of radiating devices according to the invention.

• [Fig.1] la figure 1 représente un premier exemple d'élément rayonnant selon l'art antérieur,
• [Fig.2] la figure 2 représente un deuxième exemple d'élément rayonnant selon l'art antérieur,
• [Fig.3] la figure 3 représente un troisième exemple d'élément rayonnant selon l'art antérieur,
• [Fig.4] la figure 4 représente un quatrième exemple d'élément rayonnant selon l'art antérieur,
• [Fig.5] la figure 5 représente un cinquième exemple d'élément rayonnant selon l'art antérieur,
• [Fig.6] la figure 6 représente un sixième exemple d'élément rayonnant selon l'art antérieur,
• [Fig.7] la figure 7 représente une vue de profil schématique d'un exemple d'un élément antennaire selon un mode de réalisation de l'invention,
• [Fig.8] la figure 8 représente une vue de profil schématique d'un guide d'alimentation d'un élément antennaire selon un mode de réalisation de l'invention,
• [Fig.9] la figure 9 représente une vue en perspective d'un élément antennaire selon un mode de réalisation de l'invention,
• [Fig.10] la figure 10 représente une vue schématique d'un champ électrique uniforme sur l'ouverture rayonnante de l'élément antennaire de la figure 9,
• [Fig.11] la figure 11 représente une vue schématique d'un champ électrique résultant uniquement de la propagation d'un mode fondamental TE₁₀,
• [Fig.12] la figure 12 représente une vue schématique d'une combinaison souhaitée des composantes des modes TE₁₀, TE₃₀ et TE₅₀ pour obtenir un champ électrique sensiblement uniforme,
• [Fig.13] la figure 13 représente une vue schématique des composantes d'un mode fondamental du champ électrique générés dans les guides d'accès de l'élément antennaire,
• [Fig. 14] la figure 14 représente une vue schématique des composantes d'un mode d'ordre deux du champ électrique générés dans les guides d'excitation de l'élément antennaire,
• [Fig. 15] la figure 15 représente une variante de réalisation de l'élément antennaire décrit à la figure 7,
• [Fig. 16] la figure 16 représente une vue en perspective d'une autre variante de réalisation de l'élément antennaire décrit aux figures 7 et 9,
• [Fig. 17] la figure 17 représente une vue schématique des composantes d'un mode fondamental du champ électrique générés dans un guide d'accès de section carrée,
• [Fig. 18] la figure 18 représente une vue en perspective d'encore une autre variante de réalisation de l'invention,
• [Fig. 19] la figure 19 représente une vue en perspective d'encore une autre variante de réalisation de l'invention,
• [Fig. 20] la figure 20 représente une vue de profil de la variante de réalisation de la figure 19,
• [Fig. 21] la figure 21 représente un autre mode de réalisation de l'invention intégrant un répartiteur de puissance,
• [Fig. 22] la figure 22 représente une variante de réalisation de l'élément antennaire de la figure 21,
• [Fig. 23] la figure 23 représente encore une autre variante de réalisation de l'élément antennaire de la figure 22.

The accompanying drawings illustrate the invention:

• [ Fig.1 ] there figure 1 represents a first example of a radiating element according to the prior art,
• [ Fig.2 ] there picture 2 represents a second example of a radiating element according to the prior art,
• [ Fig.3 ] there picture 3 represents a third example of a radiating element according to the prior art,
• [ Fig.4 ] there figure 4 represents a fourth example of a radiating element according to the prior art,
• [ Fig.5 ] there figure 5 represents a fifth example of a radiating element according to the prior art,
• [ Fig.6 ] there figure 6 represents a sixth example of a radiating element according to the prior art,
• [ Fig.7 ] there figure 7 represents a schematic profile view of an example of an antenna element according to one embodiment of the invention,
• [ Fig.8 ] there figure 8 represents a schematic profile view of a feed guide of an antenna element according to one embodiment of the invention,
• [ Fig.9 ] there figure 9 represents a perspective view of an antenna element according to one embodiment of the invention,
• [ Fig.10 ] there figure 10 shows a schematic view of a uniform electric field on the radiating aperture of the antenna element of the figure 9 ,
• [ Fig.11 ] there figure 11 represents a schematic view of an electric field resulting solely from the propagation of a fundamental mode TE ₁₀ ,
• [ Fig.12 ] there figure 12 represents a schematic view of a desired combination of the components of the TE ₁₀ , TE ₃₀ and TE ₅₀ modes to obtain a substantially uniform electric field,
• [ Fig.13 ] there figure 13 represents a schematic view of the components of a fundamental mode of the electric field generated in the access guides of the antenna element,
• [ Fig. 14 ] there figure 14 represents a schematic view of the components of a second order mode of the electric field generated in the excitation guides of the antenna element,
• [ Fig. 15 ] there figure 15 represents a variant embodiment of the antenna element described in figure 7 ,
• [ Fig. 16 ] there figure 16 shows a perspective view of another alternative embodiment of the antenna element described in figure 7 And 9 ,
• [ Fig. 17 ] there figure 17 represents a schematic view of the components of a fundamental mode of the electric field generated in a square section access guide,
• [ Fig. 18 ] there figure 18 shows a perspective view of yet another alternative embodiment of the invention,
• [ Fig. 19 ] there figure 19 shows a perspective view of yet another alternative embodiment of the invention,
• [ Fig. 20 ] there figure 20 shows a side view of the variant embodiment of the figure 19 ,
• [ Fig. 21 ] there figure 21 represents another embodiment of the invention integrating a power splitter,
• [ Fig. 22 ] there figure 22 represents a variant embodiment of the antenna element of the figure 21 ,
• [ Fig. 23 ] there figure 23 represents yet another alternative embodiment of the antenna element of the figure 22 .

There figure 7 shows a diagram, in side view according to a longitudinal section, of an example of an antenna element according to a first embodiment of the invention.

In this first embodiment, the antenna element 700 comprises two supply guides coupled to a common horn 703 via an excitation interface 704. The common horn 703 is, for example, an axisymmetric horn of square or rectangular section or circular, the choice of the section being made according to the dimensioning constraints of the network of antenna elements, in particular the mesh of the network. Each power guide includes an access guide 701.711 coupled to an excitation guide 702.712. The access guides and the excitation guides are, for example, produced in waveguide technology. Each excitation guide is flared in the direction of the access guide towards the excitation interface 704. As will be explained in more detail later, an important characteristic of the antenna element is that each excitation guide has no axis of symmetry, in particular its longitudinal section (as shown in the figure 7 ) is asymmetric. Furthermore, the two supply guides are identical and arranged symmetrically with respect to each other with respect to a plane of symmetry 706 and coupled to the excitation interface 704 as illustrated in the figure 7 . The access guides 701.711 are, for example, guides with a square or rectangular or circular section with a straight profile. The excitation guides 702.712 may likewise have a square, rectangular or circular profile, but they have an asymmetric widening profile. The widening profile of an excitation guide is dimensioned so as to effectively excite and control a combination of propagation modes of the wave at the exit of the radiating aperture 705 of the common horn 703.

There figure 8 diagrams a side view of an 800 feed guide identical to one of the feed guides described in figure 7 . The 800 feed guide has the particularity of having an asymmetrical profile. More precisely, the axis 806 of symmetry of the access guide 801 is offset with respect to the axis 805 passing through the center of the opening 804 of the excitation guide 802, the axis 805 being orthogonal to the interface of excitement. In other words, the axis 806 of symmetry of the access guide 801 intersects the surface defined by the opening 804 of the excitation guide at a point which is not the center of the surface. By asymmetrical profile, it is also meant that the excitation guide 802 has no axis of orthogonal symmetry, unlike the horns usually used in the known solutions. In other words, a longitudinal section of an excitation guide (as shown in figure 8 ) has no axis of symmetry along the length. In particular the axis 805 is not an axis of symmetry since the flare profiles on the two sides of the axis 805 are not identical. The splay profile of an excitation guide can be obtained by setting increasing values for the perimeters of the cross-sections of the guide according to planes orthogonal to the view of the figure 8 and which intersect the axis 805 in an increasing direction from the access guide 801 towards the excitation interface. The asymmetry of the excitation guide requires that the centers of the cross sections of the excitation guide are not aligned on the same straight line perpendicular to the sections. In certain variant embodiments, the cross-section of the excitation guide may have a variable perimeter with globally increasing values in the direction of the aforementioned axis 805 although locally the perimeter may decrease slightly.

There figure 9 schematizes a perspective view of a first embodiment of the antenna element according to the invention. This example is given by way of non-limiting illustration in order to explain the way in which the flare profile of an excitation guide is determined. In this example, the excitation guides 902.912 have a widening profile along a first plane and a straight profile along a second plane orthogonal to the first plane. Thus, the radiating opening of the horn 903 is rectangular in shape with length a and width b. In this example, an excitation guide 902.912 has no axis of symmetry, i.e. it does not exhibit invariance by rotation through an angle of 180° although it exhibits a plane of symmetry parallel to side a.

As explained in the preamble, a general objective of the invention is to obtain, on the radiating aperture 903 of the radiating element 900, a uniform distribution of the electric field of the radiated wave.

We now develop, for the particular example of the figure 9 , how the particular arrangement of the radiating element, and in particular the shape of the 902,912 excitation guides, makes it possible to tend towards a uniform distribution of the electric field on the radiating opening 903.

In the example of the figure 9 , the width b of the horn is less than λ/2, with λ the wavelength of the signal. With this configuration, only the transverse electric propagation modes TE _m0 are propagated in the horn, that is to say the components of the electric field which are parallel to the side of the horn of width b. Indeed, the propagation modes TE _0n corresponding to components of the electric field parallel to the side of length a cannot propagate.

It is recalled that the cut-off wavelength of a propagation mode TE _mn is given by the relationship:
[Math. 1] $${\left({\lambda }_{\mathrm{vs}}\right)}_{\mathit{min}}=\frac{2}{\sqrt{{\left(\frac{m}{\mathrm{To}}\right)}^2+{\left(\frac{\mathrm{not}}{b}\right)}^2}}$$

There figure 10 schematically represents the radiating aperture of the antenna element of the figure 9 with a uniform distribution of the electric field over the entire aperture. This uniform distribution is represented by arrows of the same thickness which reflect transverse components of the electric field of the same intensity. There figure 10 represents the desired distribution of the electric field on the radiating aperture.

There figure 11 represents a distribution of the electric field on the same radiating aperture but this time considering that only the fundamental mode TE ₁₀ is propagated. In this case, the energy of the electric field presents a higher level in the center of the opening than on the edges as it is represented on the figure 11 by means of arrows whose thickness, which reflects the intensity of the electric field, decreases from the center towards the edges of the opening, each arrow representing a transverse component of the electric field. Thus, it is seen that it is not possible to obtain a uniform distribution of the electric field if only the TE ₁₀ mode is propagated.

There figure 12 schematically represents a combination of several modes making it possible to obtain a substantially uniform distribution 1200 of the electric field. It is a question of combining in phase several modes TE _m0 , with m an odd integer, with an amplitude ratio equal to 1/m between the upper mode TE _m0 , m being at least equal to 3, and the fundamental mode TE ₁₀ . Ideally, to arrive at a strictly uniform electric field, it would be necessary to combine an infinity of modes TE _m0 , m being odd and varying from 1 to infinity. However, each higher mode is associated with a decreasing cutoff wavelength (λ _c ) _mn (given by relation (Eq.1)). Thus, the modes whose cut-off wavelength is greater than the wavelength of the signal cannot propagate. Also, the number of modes that can be propagated is limited by the dimensions (a,b) of the horn. For example, for a rectangular opening of length a=2.6λ (with λ the wavelength of the signal), only the odd modes with m less than or equal to 5 can propagate. So, in the example of the figure 12 , it is necessary to combine in phase the modes TE ₁₀ , TE ₃₀ and TE ₅₀ with an amplitude ratio equal to 1/3 between the higher mode of order 3 and the fundamental mode and an amplitude ratio equal to 1/5 between the higher mode of order 5 and the fundamental mode. There figure 12 illustrates, on a diagram, the distribution of the electric fields of the TE ₁₀ , TE ₃₀ and TE ₅₀ modes as well as the result 1200 of the aforementioned combination. The direction of the arrows gives the orientation of the electric field.

The invention consists, in particular, in generating and controlling the level of the fundamental mode and of the higher modes of odd orders at the output of the common horn to obtain a substantially uniform electric field 1200 on the radiating aperture. To achieve this result, the common horn is excited via an excitation interface fed by several excitation guides which each promote the propagation of several modes.

Returning to the example of the figure 7 , the operation of the propagation of the various modes of propagation of the electric field in the antenna element is now described in more detail. The access guides 701,711 are powered in phase via an excitation source (not shown on the figure 7 ). The access guides 701,711 are dimensioned so that only the fundamental modes TE ₁₀ propagate in the access guides. For example, the access guides 701,711 are waveguides having a rectangular section and a straight profile, the section being dimensioned in such a way that only the fundamental modes can propagate. There figure 13 represented schematically the electric fields corresponding to the fundamental modes TE _10.1 , TE _10.2 respectively observed at the output of the first access guide 701 and of the second access guide 711. These fundamental modes are excited in phase.

The gradual widening of the excitation guides 702,712 then allows the higher order two-order mode TE ₂₀ to propagate. Thus, from the fundamental modes TE _10.1 , TE _10.2 from the access guides 701.711, a fundamental mode TE ₁₀ and a higher mode of order two TE ₂₀ are propagated in each of the excitation guides 702.712 . There figure 14 schematically represents the electric fields corresponding to the two-order modes TE _20.1 , TE _20.2 generated in the excitation guides 702.712. The two-order modes TE _20.1 , TE _20.2 are excited in phase opposition due to the plane of symmetry 706 between the two excitation guides 702.712. The propagation of the second order modes in the excitation guides 702,712 is favored by the asymmetrical shape of the excitation guides and the misalignment between an access guide and the opening of an excitation guide (such as illustrated at figure 8 ).

From the fundamental and second-order modes generated in the excitation guides 702,712, a suitable combination of the odd-order modes (in the present example, fundamental, third-order and fifth-order modes) is obtained. in the common horn 703. Indeed, the even order modes (for example of order two or four) cannot be excited in the common horn due to the excitation symmetry of the common horn which is linked to the symmetry of the antenna element with respect to the plane 706. Indeed, the second order modes generated in the excitation guides are in phase opposition and require an asymmetrical structure to propagate. Naturally, they cannot propagate into the common turbinate 703.

Thus, each of the modes TE _10.1 , TE _10.2 , TE _20.1 , TE _20.2 , generated in the excitation guides 702.712 makes it possible to generate modes TE _10, TE _30, TE _50, in the horn common 703 (due in particular to the larger section of the common horn compared to the section of an excitation guide).

The levels of the TE _10, TE _30, TE ₅₀ modes generated in the horn 703 from only the fundamental modes TE _10.1 , TE _10.2 generated in the guides of excitation 702,712 alone do not make it possible to respect the ratios 1/3 and 1/5 between these different modes to obtain a uniform electric field.

On the other hand, the controlled association of the modes TE _10, TE _30, TE ₅₀ generated on the one hand from the fundamental modes TE _10.1 , TE _10.2 and the modes TE _10, TE _30, TE ₅₀ generated from on the other hand, from the fundamental modes TE _20.1 , TE _20.2 , makes it possible to approach the desired amplitude ratios between the different modes: |TE ₃₀ | / | TE ₁₀ | = 1/3 and |TE ₅₀ | / | TE ₁₀ | = 1/5 and also allows correct phase alignment of these different modes.

The control of the amplitudes and phase of the TE _10, TE _30, TE ₅₀ modes generated in the horn 703 from the TE _10, TE ₂₀ modes generated in the excitation guides 702,712 is obtained by the asymmetrical widening profile of a excitement guide. More precisely, the flare profile can be obtained by numerical optimization by means of a software simulator making it possible to simulate the propagation of the various modes of the electric field as well as their phase and their amplitude, as a function of the flare profile. Thus, it is possible by optimization to determine the widening profile which makes it possible to apply the combinations of modes described above.

The flare profile of an excitation guide can be obtained by determining, for different points on the longitudinal axis of the excitation guide, the dimension of the section of the guide at this point, this dimension increasing with the widening from the access guide to the excitation interface with the common horn.

The splay profile of an excitation guide can be obtained for a discrete number of sections, resulting in a discontinuous "step" shaped profile as shown in Fig. figure 7 or the figure 9 . But the profile can also be continuous as shown in the figure 15 which represents a variant embodiment 1500 of the antenna element described in figure 7 .

In the example described in figure 9 which served as the basis for the explanations above, the antenna element has a flared and asymmetrical profile only on one plane, with an invariant straight profile on the other perpendicular plane. In another embodiment illustrated in figure 16 , the antenna element 1600 can also have a flared and asymmetrical profile on the two orthogonal planes in order to increase the radiation aperture.

In the example of the figure 9 , the section of an excitation guide is rectangular. However, the section of an excitation guide can also be square or circular, then allowing operation of the antenna element in bipolarization. In this case, the excitation guides make it possible to propagate transverse modes TE _0n in addition to the transverse modes TE _m0 described previously for the case of a guide of rectangular section. In other words, the electric field can propagate with modes in the two perpendicular directions as shown in Fig. figure 17 for the case of the fundamental modes TE ₁₀ and TE ₀₁ and a square waveguide section.

According to a variant of the invention, the antenna element is not limited to operation with two ports as described so far. It may comprise a number greater than two of supply guides, preferably a number equal to a power of two.

According to an embodiment of the invention described in figure 18 , the antenna element 1800 may comprise four feed guides 1801,1802,1803,1804, arranged symmetrically with respect to two orthogonal planes of symmetry, and a common horn 1810. Each feed guide comprises an access guide and an asymmetrical excitation guide. An advantage to this embodiment is that it makes it possible to obtain a wider radiating aperture.

There figure 19 describes yet another embodiment of the antenna element 1900 this time comprising 16 supply guides arranged in groups of four. Each group of four feed guides is arranged as on the antenna element 1800 of the figure 19 . The horn is common to the eight feed guides making it possible to further increase the radiating aperture.

In a variant of the example of the figure 19 , advantageous for a large number of feed guides, typically a number at least equal to 16, the common horn may be composed of several levels or stages. This principle is illustrated in the figure 20 by a side view of an antenna element with sixteen feed guides. The antenna element 2000 of the figure 20 includes a common horn made up of five elementary horns, three of which are visible in the profile view of the figure 20 . Four elementary cones 2001,2002 are positioned above the four sets of four feed guides. Another elementary horn 2003 is positioned above the four horns 2001,2002 of the first level. Thus, the 2003 cone of the second level combines the four cones 2001,2002 of the first level. The principle described in figure 20 can easily be extended to cones arranged on more than two levels. For example, if the antenna element comprises 16x4=64 feed guides, it may comprise three levels of horns, a first level with 16 horns each being common to four feed guides, a second level with 4 horns and a third level with a cornet.

Without departing from the scope of the invention, other arrangements are possible, in particular concerning the number of supply or access guides per antenna element.

As explained previously, to obtain optimum operation of the multiple-access radiating element according to the invention, the access guides must be excited in phase. For this, a power splitter can be coupled to the inputs of the access guides.

There figure 21 represents an example of an antenna element 2100 with two ports and operating in mono-polarization. For this example, the in-phase excitation of the two access guides is carried out by means of a power splitter 2101 which mainly comprises an H-plane junction 2102 and matching sections 2103 to interface the H-plane junction with on the one hand the access guides of the antenna element and on the other hand the source of excitation.

There figure 22 represents another example of an antenna element 2200 with four ports operating in bi-polarization. For this example, the four access guides are coupled to a power distributor 2201 which distributes to each access guide a signal fraction of each of the two polarizations with the same amplitude and the same phase. An example of a power splitter adapted to fulfill this function is a splitter comprising four ortho-mode transducers of the type described in the Applicant's French patent application filed under the number FR1700993 .

In the examples described in figure 21 And 22 , the power splitter is separate from the antenna element and does not make it possible to generate higher order propagation modes.

In another embodiment described in figure 23 , the power splitter is integrated into the antenna element 2300. In other words, the functions of power splitting and excitation of the propagation modes are combined and provided jointly by the same device in waveguide technology. An advantage of this embodiment is that it makes it possible to add further optimization parameters to the simulations allowing precise adjustment of the profile of the antenna element with a view to obtaining a uniform electric field on the radiating aperture.

References

1. (1) Design, manufacturing and testing of a spline-profile square horn for focal array applications Isabelle Albert; Maxime Romier; Daniel Belot; Jean-Pierre Adam; Pierrick Hamel, 2012 15 International Symposium on Antenna Technology and Applied Electromagnetics, Year: 2012
2. (2) Multibeam antennas based on phased arrays: An overview on recent ESA developments; Giovanni Toso; Piero Angeletti; Cyril Mangenot; The 8th European Conference on Antennas and Propagation (EuCAP 2014); Year: 2014

Claims (15)

1. Radiating element (700, 800) comprising at least two feeding guides and one horn common (703) to the at least two feeding guides and having an excitation interface (704), each feeding guide being distinct from the other feeding guides, each feeding guide consisting of a port guide (701, 711, 801) and an excitation guide (702, 712, 802) connected to the port guide (701, 711, 801) by a port interface and connected to the common horn (703) by the excitation interface (704), each excitation guide (702, 712, 802) being flared in the direction from the port interface to the excitation interface (704), each excitation guide (702, 712, 802) not having an axis of symmetry, the at least two feeding guides being identical and disposed symmetrically relative to one another relative to a plane of symmetry of the radiating element.
2. Radiating element (700, 800) according to claim 1, wherein the flaring profile of each excitation guide (702, 712, 802) is configured so as to control, in amplitude and in phase, the propagation modes of a radiating wave propagated from each port guide (701, 711, 801) to the output of the horn (703), so that the electrical field obtained at the output of the horn (703) is substantially uniform.
3. Radiating element (700, 800) according to any one of the preceding claims, wherein the flaring profile of each excitation guide (702, 712, 802) is configured so as to favour the propagation of a fundamental propagation mode (TE₁₀) and of a second order higher propagation mode (TE₂₀) in the excitation guide (702, 712, 802).
4. Radiating element (700, 800) according to any one of the preceding claims, wherein the flaring profile of each excitation guide (702, 712, 802) is configured so as to favour the propagation, in the horn (703), of several odd order propagation modes (TE₁₀, TE_30, TE₅₀), from the fundamental propagation mode (TE₁₀) and from the second order higher propagation mode (TE₂₀) propagated in each excitation guide (702, 712, 802).
5. Radiating element (700, 800) according to claim 3, wherein the flaring profile of each excitation guide (702, 712, 802) is configured so as to control the amplitude and the phase of each propagation mode (TE₁₀, TE_30, TE₅₀) propagated in the horn (703) so that the electrical field resulting from the combination of all of the propagation modes (TE₁₀, TE_30, TE₅₀) propagated in the horn is uniform at the output of the horn (703).
6. Radiating element (1800, 1900, 2000) according to any one of the preceding claims, comprising at least four feeding guides, the horn (1804) being common to four feeding guides, the four feeding guides being disposed symmetrically to one another relative to two orthogonal planes of symmetry.
7. Radiating element (800) according to any one of the preceding claims, wherein each feeding guide is configured so that the longitudinal axis (806) of a port guide (801) is off-centre relative to the centre of the aperture (804) of the excitation guide (802) connected to the excitation interface.
8. Radiating element (2100, 2200, 2300) according to any one of the preceding claims, further comprising a power splitter (2101, 2201) for exciting the port guides in phase.
9. Radiating element according to any one of the preceding claims, wherein a transverse section of the excitation guide is of square, rectangular or circular shape.
10. Radiating element according to any one of the preceding claims, wherein the radiating element offers operation in single-polarisation or bi-polarisation mode.
11. Radiating element according to any one of the preceding claims, wherein each excitation guide has a continuous or discontinuous flaring profile.
12. Radiating element according to any one of the preceding claims, wherein the common horn is axisymmetrical.
13. Radiating element according to any one of the preceding claims, wherein each excitation guide has a flared profile on a first plane and an unchanging profile on a second plane orthogonal to the first plane.
14. Radiating device (2000) comprising at least four radiating elements according to any one of the preceding claims and a secondary horn (2003) common to the four radiating elements and connected via an input interface to the apertures of the respective horns (2001, 2002) of each radiating element.
15. Antenna comprising a plurality of radiating elements according to any of claims 1 to 13 or a plurality of radiating devices according to claim 14.

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