EP2469649B1 - Radiofrequency antenna with multiple radiating elements for transmission of a wave with variable propagation direction - Google Patents

Description

The present invention relates to a radiofrequency antenna, of the type comprising a frame and an emission surface carrying a set of radiating antenna elements, each in a direction of emission own.

Network antennas for which the helical type emissive elements are known, in particular by the patent US 6,115,005 . Similarly this type of compact antenna is capable of transmitting very high peak powers as described for example in the document Li, XQ; Liu, QX; Zhang, JQ; Zhao, L .; Zhang, ZQ; , "The High-Power Radial Line Helical Circular Array Antenna: Theory and Development," Microwave and Millimeter Wave Technology (ICMMT), 2010, International Conference on, vol., No., Pp. 671-674, 8-11 May 2010 , doi: 10.1109 / ICMMT.2010.5525020. However, the pointing possibilities of such a very high power antenna remain limited because of the direct connection, generally under vacuum, between the power source and the antenna. In general, a radial antenna based on helical radiating antenna elements consists of a radial transmission line, which can be powered by its center or by its periphery, and a set of antenna elements. radiating regularly distributed. Each antenna element comprises a helically radiating strand projecting from the emission face. The strand is connected to a capture loop present inside the radial transmission line of the antenna, on the other side of the emission surface. Each of the helically radiating strands is positioned with an initial angle so as to form, for example, a coherent electromagnetic field whose direction of propagation is perpendicular to the emission surface.

The starting angle of the helices of each antenna element is fixed once and for all so that the phase shift between the different antenna elements allows the coherent addition in the desired transmission direction.

In order to change the direction of transmission of the antenna, it is known to mount the antenna on an articulated and motorized support for moving the entire antenna, including its transmitting surface and all the elements. antennas that are present, as well as the support frame of the transmitting surface.

It is alternately known patents US 6552695 , US 6407714 and US 4427984 to angularly move the emissive elements of helical type.

The source of electromagnetic radiation used to power the antenna with very high power is generally a relativistic source (high power magnetron, "Magnetically Insulated Line Oscillator" (MILO), carcinotron, relativistic klystron for example). The source assembly, connection guide, antenna must then be kept under vacuum and is difficult to deform, because of the risk of breakdown limiting the technologies and architectures that allow pointing of the antenna in a particular direction, other than by moving the assembly.

The object of the invention is to propose a radiofrequency antenna that can be used in an arrangement where the direction of the field radiated by the antenna is angularly movable in one or two directions, without requiring complex deformable guide elements or displacement. large masses.

For this purpose, the subject of the invention is a radiofrequency antenna of the aforementioned type, according to claim 1. Each antenna element is at least partially displaceable with respect to the emission surface in order to modify its own emission direction and it comprises means for moving the antenna elements in a coordinated manner along said surface to form, from the elementary waves produced by the antenna elements, a coherent wave propagating in a direction angularly offset relative to the normal to the emission surface.

The antenna elements each having a transmission strand rotatably mounted relative to the emission surface and the means for moving the antenna elements are adapted to drive the rotating antenna elements, the displacement means comprise racks slidably mounted relative to the emission surface and the transmission strands are integral with driving gears engaged with the racks and in that the displacement means comprise a mechanism for synchronized movement of the racks, the displacement mechanism synchronized comprises a rotary control ring relative to the frame and provided with control cams of the racks, the racks being each equipped with at least one cam follower cooperating with a cam, and a drive motor in rotation of the ring.

• les éléments d'antenne sont répartis par groupes d'éléments d'antenne, les éléments d'un même groupe étant présents dans une bande de la surface d'émission s'étendant perpendiculairement à la projection de la direction d'émission sur la surface, les éléments d'antenne d'un même groupe étant positionnés pour produire des ondes élémentaires ayant un même déphasage par rapport aux ondes produites par des éléments d'antenne d'un autre groupe,
• les moyens de déplacement des éléments d'antenne sont propres à positionner les éléments d'antenne pour qu'ils produisent chacun une onde élémentaire déphasée d'un déphasage δΦ par rapport aux autres éléments d'antenne défini par : $$\mathrm{\delta \Phi }\mathrm{=}\mathrm{2}\mathrm{\pi h\; tg\theta }\mathrm{/}\mathrm{\lambda }$$
  
  
  où θ est l'angle d'inclinaison de la direction d'émission par rapport à la normale à la surface d'émission, À est la longueur d'onde du rayonnement électromagnétique ; et h est la distance de l'élément d'antenne à un axe de référence mesurée suivant la direction d'émission sur la surface d'émission,
• la surface d'émission portant les éléments d'antenne rayonnants est rotative par rapport au châssis et en ce qu'elle comporte des moyens d'entraînement en rotation de la surface d'émission.
• le châssis délimite un espace clos sous vide dans lequel sont contenus les éléments d'antenne et en ce qu'elle comporte des colonnettes de reprise d'effort entre le châssis et la surface d'émission.

According to particular embodiments, the radiofrequency antenna comprises one or more of the following characteristics:

• the antenna elements are distributed in groups of antenna elements, the elements of the same group being present in a band of the emission surface extending perpendicular to the projection of the emission direction on the surface the antenna elements of one and the same group being positioned to produce elementary waves having the same phase shift with respect to the waves produced by antenna elements of another group,
• the means for moving the antenna elements are adapted to position the antenna elements so that they each produce an elementary wave phase-shifted by a phase shift δΦ with respect to the other antenna elements defined by: $$\mathrm{\delta \Phi }\mathrm{=}\mathrm{2}\mathrm{\pi h\; tg\theta }\mathrm{/}\mathrm{\lambda }$$
  
  
  where θ is the angle of inclination of the emission direction with respect to the normal to the emission surface, λ is the wavelength of the electromagnetic radiation; and h is the distance of the antenna element to a reference axis measured in the direction of emission on the emission surface,
• the transmitting surface carrying the radiating antenna elements is rotatable relative to the frame and in that it comprises means for driving the emission surface in rotation.
• the frame delimits a vacuum-enclosed space in which the antenna elements are contained and in that it comprises balancing columns of force between the frame and the emission surface.

• les éléments d'antenne comportent un brin d'émission déformable et en ce que les moyens de déplacement comportent un mécanisme propre à assurer la déformation de chaque brin d'émission pour modifier la direction d'émission propre,
• les éléments d'antenne comportent chacun une lentille de focalisation de l'onde électromagnétique élémentaire produite par l'élément d'antenne et en ce que les moyens de déplacement comportent un mécanisme de déplacement angulaire de chaque lentille de focalisation,

According to examples, the radiofrequency antenna comprises one or more of the following features:

• the antenna elements comprise a deformable transmission strand and in that the displacement means comprise a mechanism capable of ensuring the deformation of each transmission strand to modify the own emission direction,
• the antenna elements each comprise a focusing lens of the elementary electromagnetic wave produced by the antenna element and in that the displacement means comprise a mechanism for angular displacement of each focusing lens,

• la figure 1 est une vue en coupe d'une antenne selon l'invention, vue de dessus, prise suivant la ligne I-I de la figure 2 ;
• la figure 2 est une vue en coupe transversale de l'antenne selon l'invention prise suivant la ligne II-II de la figure 1 ;
• la figure 3 est une vue en coupe de détail d'un élément d'antenne de l'antenne selon l'invention ; et
• les figures 4, 5 et 6 sont des vues en élévation de variantes de réalisation d'éléments d'antenne selon l'invention.

The invention will be better understood on reading the description which follows, given solely by way of example and with reference to the drawings in which:

• the figure 1 is a sectional view of an antenna according to the invention, seen from above, taken along line II of FIG. figure 2 ;
• the figure 2 is a cross-sectional view of the antenna according to the invention taken along line II-II of FIG. figure 1 ;
• the figure 3 is a detail sectional view of an antenna element of the antenna according to the invention; and
• the figures 4 , 5 and 6 are elevational views of alternative embodiments of antenna elements according to the invention.

The antenna 20 according to the invention is shown in plan view and in section on the figure 1 and in cross section on the figure 2 . It has a general shape of disk axis X1-X1. According to the invention, each antenna 20 is able to emit in a direction TT angularly offset by an angle θ with respect to the axis X1-X1 of the antenna.

Its planar emission surface consists of a circular plate 22 rotatable about the axis X1-X1 and on which is disposed a set of radiating antenna elements 24 regularly distributed on the surface of the plate 22. The antenna elements are each able to produce an elementary wave, each following a own emission direction and with a proper phase shift so that the addition of the elementary waves produce a coherent wave in the direction TT.

These antenna elements each have an axis X2-X2 normally perpendicular to the plate 22.

The antenna is equipped according to the invention means 25 for moving the antenna elements relative to the emission surface to change their direction of emission and / or their phase. In the embodiment described here, the means 25 are able to produce a rotational movement on themselves of all or part of the antenna elements.

The plate 22 is carried by a frame 26 in the general shape of a bell flaring progressively from an inlet 27 for collecting the magnetic radiation from the source to a mouth 28 of the radiation output from the antenna elements 24. The mouth is closed by an airtight protective wall 30 for creating the vacuum inside the frame 26. The wall 30 is transparent to the electromagnetic radiation and radome form.

The inlet end 27 of the frame 26 is formed of a tube extended by a ring 34 forming the bottom of the frame. This ring is of axis X1-X1. The bottom is extended by a first peripheral wall 36 having at its end facing the mouth 28 a diverging shoulder 38 forming a support. This shoulder is bordered by a second peripheral wall 40 carrying the protective wall 30.

The plate 22 is supported on an inner peripheral rim 44 of the side wall 34. This flange 44 forms a bearing guide for rotation of the plate 22 about the axis X1-X1. For this purpose, it is advantageously equipped with a ball bearing 46.

Between the plate 22 and the bottom 34 is disposed an intermediate partition wall 48 extending parallel to the plate 22 and separating the annular space defined by the side wall 36 into two adjacent spaces. The wall 44 is carried, like the plate 22, by an abutment flange 50 advantageously equipped with a ball bearing 52.

Columns of connection and recovery of effort 54 are arranged between the plate 22 and the wall 48. They extend parallel to the axis X1-X1 and are equi-parts along one or more circles of axis X1-X1 on the plateau surface to ensure the mechanical strength of the assembly when the antenna is under vacuum. These columns rigidly connect the plate 22 and the wall 48.

Columns 56 extending the columns 44 extend between the wall 48 and the bottom 34 in the extension of the columns 56. The columns 56 are connected to the wall 48 at one of their ends and have a sliding contact 58 at their other ends resting on the surface of the bottom 34.

Likewise, columns 60 extend the columns 54 from the plate 22 to the protection wall 30. These columns are fixed to the plate 22 and bear in a sliding contact 62 on the wall 30.

The sliding support of the columns 52 and 60 on the bottom 34 and the wall 30 is provided for example by interposition of a free ball rotating at the end of each column.

The intermediate wall 48 carries, next to the duct 32, along the axis X1-X1, a metal cone 70 capable of modifying the propagation mode of the electromagnetic flux, while passing from a flow in TM01 mode along the axis X1-X1 at a centripetal flow according to the TEM mode extending from the axis X1-X1 outwards in the direction of the arrows 72.

The intermediate wall 48 is provided with through loops 74 regularly distributed in a circle centered along the axis X1-X1. These loops 74 are formed of a metal conductor closed on itself and have two lobes 74A, 74B protruding on either side of the intermediate wall 48. The antenna elements 24 are represented on a larger scale on the figure 3 . According to the invention, these antenna elements are able to rotate on themselves about their axis X2-X2 parallel to the axis X1-X1.

On the figure 3 , there is the plate 22 carrying the antenna element 24. Each antenna element comprises a transmission strand 80 disposed on the side of the antenna transmission port and a capture loop 82 disposed between the panel 22 and the intermediate wall 48.

The loop 82 is rigidly and fixedly connected to the wall 22 at one of its ends while remaining electrically isolated from the wall 22 in its passage towards the emission strand 84. The loop has a shape known per se and is obtained by curvature on itself of a metal conductor.

The strand 80 has an emission portion 84 consisting of a solid wire describing a helix shape. This strand is extended by a core 86 engaged inside the hollow conductor constituting the loop 82 while providing an electrical connection.

A sliding contact 88 is provided between the conductor 83 and the core 86 according to an arrangement of any suitable type thus allowing rotation of the emission strand 80 with respect to the loop 82 while ensuring an electrical connection.

A drive gear 90 is disposed around the strand 80 at the connection between the helical emission portion 84 and the core 86. This pinion extends perpendicular to the axis X2-X2 rotation of the emission strand and is arranged along the panel 22 on the side of the mouth 28 of emission. It is integral in rotation with the strand 80.

As illustrated on the figure 1 , the mechanism 25 for rotating the antenna elements 24 themselves comprises a set of racks 102 arranged parallel to one another on the surface of the plate 22 facing the mouth 28. These racks thus extend according to cords of the disk forming the plate 22. They are perpendicular to the component of the direction TT according to the emission plane defined by the plate 22.

These racks have on each side rectilinear teeth engaged with the gables 90 of the adjacent antenna elements. Thus, the antenna elements associated with the same rack are distributed alternately on both sides of the rack.

The racks 102 are mounted slidably movable along the surface of the plate 22. They are held laterally by the antenna elements arranged on either side.

The drive mechanism 25 further comprises a ring 104 for controlling the racks and a drive motor 106 of the control ring 104.

The ring 104 bears on the shoulder 38 and is guided laterally by the peripheral wall 40. The ring is of axis X1-X1. It is angularly movable relative to the plate 22 about its axis following an angular deflection of the order of 60 °.

The motor 106 is attached to an extension of the plate 22 denoted 108. The extension extends outside the enclosed space delimited by the frame 26 and the protective wall 30. The output shaft of the engine is equipped with a pinion 110 received in a groove 112 of the crown 104. This groove is in the shape of a circular arc centered on the axis X1-X1 and has on a cylindrical surface a toothing 114 engaged with the pinion 110 for the drive of the crown under the action of the engine 106.

Each rack 102 is extended in the space defined between the shoulder 38 and the crown 104. At its two ends, each rack has a drive pin 120 received in a groove 122 forming a cam of the control ring 104.

The grooves 122 forming a cam have a curved shape and have a width equal to the thickness of the drive finger 120. They generally extend in an angular opening around the crown 104 equal to the angular displacement of the crown 104 relative to the tray 22.

The grooves 122 are symmetrical to one another for the same rack with respect to a diameter of the disk forming the plate, this diameter extending perpendicularly to the racks 102.

où θ est l'angle d'inclinaison par rapport à la normale de la direction d'émission T-T de l'antenne et À est la longueur d'ondes du rayonnement électromagnétique à émettre. De manière générale, l'inclinaison des gorges formant la came 22 augmentent d'un côté noté A à l'autre de la couronne suivant le sens de la flèche F comme cela est visible sur la figure 1.The profile of the cam grooves 122 is such that for a given rack located at a distance Rh from the center of the plate 22, R being the radius of the plate, the movement of the rack is such as to produce an angular displacement of the element. of antenna 24 which is geared to it equal to δΦ according to the formula: $$\mathrm{\delta \Phi }\mathrm{=}\mathrm{2}\mathrm{\pi h\; tg\theta }\mathrm{/}\mathrm{\lambda }$$

where θ is the angle of inclination with respect to the normal of the transmission direction TT of the antenna and λ is the wavelength of the electromagnetic radiation to be emitted. In general, the inclination of the grooves forming the cam 22 increases from one side noted A to the other of the ring in the direction of the arrow F as is visible on the figure 1 .

The antenna elements are thus distributed in groups by being associated with the same rack. All the antenna elements of the same group are thus located in a band extending in the plane of the plate 22 perpendicular to the transmission direction T-T. These antenna elements are all able to be moved by the same angular offset during a movement of the associated rack. The initial angular offset of the helices is calculated to allow coherent addition in the main axis of the antenna for positioning in the center of this rack to allow a deflection of the beam on either side of this axis. A variant, favoring only a deflection of one side, would correspond to an initial setting of the propellers to allow coherent addition along the main axis for a positioning of the racks in abutment.

The antenna finally comprises a mechanism 150 for global drive in rotation of the plate 22 and all the antenna elements around the axis X1-X1 relative to the frame 26. This mechanism comprises a motor 152 carried by the chassis 26. It has on its output shaft a pinion 154 adapted to drive the plate 22. For this purpose, the plate 22 has in the extension 108, a slot 156 of semi-circular shape centered on the axis X1-X1 including a wall 158 has a toothing 160 engaged with the pinion 154.

In operation, in such an antenna, the electromagnetic flux arriving along the axis X1-X1 through the inlet 27 is distributed along the surface of the intermediate wall 28 by the mode converter 70.

The centripetal flow is then captured by the lobes 74A of the loops and reemitted by the lobes 74B in the space between the plate 22 and the intermediate wall 48. loops 82 of the antenna elements 24 capture again the electromagnetic wave inducing a current to the transmission strand 84, which re-emits the electromagnetic wave in a direction and with a phase which are specific to the angular positioning of the elements of antenna.

When the ring gear 104 is in an extreme position, all the antenna elements are oriented in the same direction, so that they produce elementary electromagnetic waves with zero relative phase shifts.

When under the action of the motor 106, the control ring 104 is angularly displaced, the racks 102 are moved parallel to each other by being driven by their two ends by the driving fingers urged by a wall of the grooves 122 forming cam.

The amplitude of the displacement applied to each rack is defined by the shape of the cam groove 122 present at each end so that the more the rack is away from the point A, the greater the amplitude of its displacement is important.

During the movement of the racks, the associated antenna elements are moved angularly, the rack driving the pinion 90 integral with the emission strand 80. Under these conditions, it is understood that all the transmission strands associated with the same rack and belonging to the same group are moved angularly of the same amplitude, thus producing a phase shift between the elementary electromagnetic waves emitted by these antenna elements and those of the antenna elements associated with other racks which undergo a different displacement.

It can be understood from formula (1) that the phase shifts applied to the antenna elements are such that, depending on their position, the antenna elements produce an electromagnetic wave whose phase shift corresponds to the phase difference existing between the wave actually emitted and the wave that would have been emitted by antenna elements located in a plane angularly offset by an angle θ with respect to the plane of the plate 22. Thus, the electromagnetic wave resulting from the elementary waves produced by the elements is coherently, the elementary waves being in phase in a plane perpendicular to the propagation direction TT and that this coherent antenna wave propagating along the direction TT is angularly offset by an angle θ relative to the normal of the plate 22.

It is understood that such an arrangement makes it possible to modify the direction of propagation of the wave along an angle θ which depends on the position of the control ring 104, which is controlled by the motor 106. During a rotation of 360 ° of the ring gear 104, the propagation direction TT describes a cone of revolution along the axis X1-X1 and with a half-angle at the apex θ. The angle θ is adjustable independently of the movement overall and thus allows the realization of a two-dimensional pointing on a solid angle of half-angle at the apex θmax (θmax being the angle at the maximum deflection of the racks)

Similarly, the motor 152 acting on the plate 22 through the gear 154 meshing with the toothing 158 allows an overall displacement of all the antenna elements of the same angular offset around their axis X2-X2 by displacement of the plate 22, thus allowing phase shifting of all the antenna elements and therefore of the antenna. This phase shifter is able to operate over a wide range of frequencies and at very high power.

The antenna thus formed thus allows, without articulated element in the wave supply guide duct, to emit an angularly offset wave.

This angular offset is obtained without the need to angularly move the frame of the antenna and its radome.

Following an example, illustrated next to the figure 4 each antenna element 24 is formed of a radiating strand 184 fixedly fixed in rotation with respect to the panel 22. All the strands are identical and are oriented identically. Each strand is associated with a focusing lens 186 disposed in line with the corresponding strand. This lens is able to focus the electromagnetic wave produced the strand.

These lenses are associated with a mechanism 188 of angular displacement of each lens 186 about two axes 188A, 188B extending perpendicularly to each other and parallel to the plate 22. The mechanism 188 is such that all the lenses have a same orientation, thus allowing a deflection of an angle θ of the set of elementary electromagnetic waves normally initially transmitted to the plate 22 by each of the strands 184.

It is conceivable that with such an arrangement, the coherent wave produced by the addition of the elementary electromagnetic waves produced by each antenna element propagates at a predefined angle θ with respect to the normal to the plate 22.

On the figure 5 is shown again an example. The antenna strand noted 284, corresponding to the radiating strand 84, is helically wound around an elastically deformable mat 286. In the absence of stress, the mat 286 extends perpendicularly to the plate 22.

As previously, the mat 286 is connected to a mechanism 188 for moving its end, thus allowing the axis of the helix of the strand 284 to bend by deformation of the mat 286. Thus, the mechanism 188 ensures a transmission of the wave elementary produced by each strand in a direction angularly offset from the normal to the wall 22.

In the example shown on the figure 6 , a focusing lens 288 is added to the arrangement described with reference to FIG. figure 5 . This lens is placed at the free end of mat 286.

According to a variant of the embodiment of the figure 1 , the wall 48 is removed and the antenna elements are then fed from the center. The mode converter 70 is carried by the lower face of the wall 22.

Claims (5)

1. A radiofrequency antenna comprising a chassis (26) and an emission surface (22) supporting a set of radiating antenna elements (24), each radiating in a unique emission direction, each antenna element (24) being at least partially movable relative to the emission surface (22) to modify its phase shift and including an emission wire (30) rotatably mounted relative to the emission surface (22), the antenna comprising means (25) for moving the antenna elements (24) in a coordinated manner along said surface (22) to form, from the elementary waves produced by the antenna elements (24), a coherent wave propagating in a direction (T-T) that is angularly offset relative to the normal to the emission surface, characterized in that the movement means (25) comprising racks (102) slidingly mounted relative to the emission surface (22) and the emission wires (80) being integral with drive pinions engaged with the racks (102), the movement means (25) comprising a mechanism (104, 106) for synchronized movement of the racks (102) and being capable of rotating the antenna elements (24),
   the synchronized movement mechanism (104, 106) includes a rotary control crown (104) relative to the chassis (26) and provided with control cams (122) of the racks (102), the racks each being equipped with at least one cam follower (120) cooperating with a cam (122), and a motor (106) for rotating the crown (104).
2. The radiofrequency antenna according to claim 1, characterized in that the antenna elements (24) are distributed by groups of antenna elements, the elements of a same group being present in a strip of the emission surface extending perpendicular to the projection of the emission direction (T-T) on the surface, the antenna elements of a same group being positioned to produce elementary waves having a same phase shift relative to the waves produced by the antenna elements of another group.
3. The radiofrequency antenna according to claim 1 or 2, characterized in that the means (25) for moving the antenna elements are adapted to position the antenna elements (24) so that they each produce an elementary wave phase shifted by a phase shift δΦ relative to the other antenna elements (24) defined by: $$\mathrm{\delta \Phi }\mathrm{=}\mathrm{2}\mathrm{\pi htg\theta }\mathrm{/}\mathrm{\lambda }$$

   

   
   where θ is the incline angle of the emission direction (T-T) relative to the normal to the emission surface (22), λ is the wavelength of the electromagnetic radiation, and h is the distance of the antenna element (24) from a reference axis measured along the emission direction (T-T) on the emission surface (22).
4. The radiofrequency antenna according to any one of the preceding claims, characterized in that the emission surface (22) supporting the radiating antenna elements (24) is rotary relative to the chassis (26), and in that it comprises means (152) for rotating the emission surface (22).
5. The radiofrequency antenna according to any one of the preceding claims, characterized in that the chassis (26) delimits a closed vacuum space (26) in which the antenna elements are contained, and in that it comprises force-reacting guide pins between the chassis (26) and the emission surface (22).

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