EP2532046B1 - Flat-plate scanning antenna for land mobile application, vehicle comprising such an antenna, and satellite telecommunication system comprising such a vehicle - Google Patents

Description

The present invention relates to a planar scanning antenna, a vehicle comprising such an antenna and a satellite telecommunications system comprising such a vehicle. It applies in particular to the field of satellite telecommunications and more particularly to telecommunications equipment installed on mobile vehicles such as land, sea or aeronautical means of transport to ensure a two-way connection between a mobile terminal and a land station by through a repeater installed on a satellite.

In means of transport, such as trains and buses, the need for connections to a broadband Internet service and the need for high-performance, low-cost and small antennae are increasing.

Currently, it is known to make a satellite link between a mobile terminal and a land station to, for example, provide an internet connection to the passengers of a train or a bus, by using a very directive antenna operating in L-band The problem is that in L band, there are very few frequencies available and that the communication transmission rate is therefore very low. To increase the speed, it is necessary to establish links with satellites operating in the Ku band (10.5 GHz to 14.5 GHz) or Ka (20 to 30 GHz) and to provide directional antennas. However, with a directional antenna, it is necessary to continuously point the satellite regardless of the position of the vehicle.

To cover a territory such as Europe, the specifications for transmission and reception of the mobile terminal capable of ensuring the required transmission qualities lead, in the Ku band, to antenna gains typically of the order of 34 to 35 dB on the covered area and the antenna must be able to ensure, in transmission and reception, pointing in an angular range between 0 ° and 360 ° in azimuth and between 20 ° and 60 ° on average in elevation.

These performances can be obtained by using an array antenna comprising elementary radiating elements whose phase is adjusted to obtain a precise pointing in a chosen direction. These array antennas have the advantage of being flat and therefore of small overall dimensions in the direction of their height, however the angular range to be covered is very large, in order to obtain good performance and avoid the appearance of array lobes in the diagram. radiation from the antenna, it is necessary to use a beam forming network comprising a very large number of phase controls, which is prohibitive. For example, for a Ku-band antenna having a surface area of the order of 1 m 2, the number of radiating elements of the antenna must be greater than 15,000, which is prohibitive in terms of cost and complexity of the antenna for application to means of transport.

It is also possible to achieve pointing in a wide angular range using a mechanical pointing antenna. In this type of antenna, the pointing of the antenna towards the satellite is carried out by a combination of two mechanical movements. A first mechanical movement is obtained by means of a rotating platform arranged in an XY plane and ensuring the orientation of the antenna in elevation and in azimuth. A second movement in elevation is carried out by an annex device, for example a plane mirror, integral with the platform. The antenna conventionally comprises a parabolic reflector and a radiating source illuminating the reflector. To reduce the size of the reflector and reduce the height of the antenna, its periphery is elliptical instead of circular. Typically, such an antenna currently deployed on high-speed trains has a height of the order of 45 cm. Although this height is compatible with current trains, it is too great for future high-speed trains with two bridges for which the height available for the installation of an antenna, between the roof of the train and the overhead lines, is much more low.

Similarly, for an application in the aeronautical field, the height of the antenna has an influence on the drag generated by the aircraft as well as on the fuel consumption. For example, the current reflector antennas installed on aircraft have a height of the order of 30cm and lead to overconsumption of fuel equivalent to eight additional passengers.

There are architectures making it possible to reduce the height of the antenna with mechanical pointing. According to a first architecture, the antenna is composed of two parallel plates between which circulate longitudinal current components and an array of one dimension of continuous transverse grooves which couple and radiate energy in space. The two plates and the network of grooves are mounted on two coplanar plates mechanically rotating independently of one another, the two rotational movements being superimposed and produced in the same plane of the plates. The orientation of the lower plate makes it possible to adjust the pointing direction in azimuth, the orientation of the upper plate makes it possible to obtain a variable inclination of the grooves and thus to modify the pointing direction in elevation of the beam generated by the antenna. However, this antenna initially operating in linear polarization, it is necessary to add an additional orientable polarization grid mounted on the upper face of the antenna to control the plane of polarization of the antenna which increases the complexity of implementation. and the height of the antenna which is then not planar.

According to a second planar antenna architecture at reduced height, the antenna comprises several alternating planes of substrates and metal planes superimposed one above the other. The antenna comprises a first lower metallic plane, then a first substrate plane comprising several sources, the first substrate plane comprising a lateral end forming a parabolic surface on which the waves emitted by the sources are reflected. Above the first substrate plane is a second metallic plane having slots for coupling the reflected wave plane, each coupling slot opening into respective slot wave guides arranged side by side parallel to each other in the same second substrate plane. The guided waves are then emitted in the form of a beam radiated through a plurality of radiating openings formed in a third upper metallic plane. A sweep and a deflection of the beam in elevation, in a plane perpendicular to the plane of the antenna, is obtained by switching the different sources but no modification of pointing in azimuth is not possible. Furthermore, this type of very compact antenna has the drawback of requiring high-power switching means, which is never easy to achieve. In addition, the switching of the sources is discrete which does not make it possible to obtain a continuous pointing of the beam. Finally, this very compact antenna is supplied by a single power source which requires the use of bulky power amplifiers which considerably increase the volume of the antenna which becomes too large for an application to means of transport.

To solve the problem of discreet pointing of this planar antenna, it has been proposed to use only one source and to place the planar antenna on a rotating platform making it possible to adjust the pointing in azimuth, the platform comprising an articulated mirror. on the platform whose angle of inclination relative to the plane of the platform is variable by rotation. The plane wave emitted by the source illuminates the mirror which reflects this wave in a chosen pointing direction, the angle of inclination of the mirror making it possible to adjust the elevation angle of the emitted beam. This antenna is very elliptical, the dimension of the mirror in its region articulated on the platform being much greater than the dimension of the mirror in its region inclined above the platform, which makes it possible to reduce the height of the antenna to 20 or 30cm, but this height is still too large for an application to means of transport.

We know the document WO 2009/144763 and document US 6,873,301 antenna systems comprising a plurality of waveguides equipped with radiating slots, and the document WO 03/043124 an antenna system comprising a pivoting mechanism for part of the radiating elements. We also know of the document JP 2002 033612 a planar antenna equipped with a network of radiating slit waveguides comprising two superimposed layers of waveguides.

The object of the invention is to produce a planar scanning antenna which does not have the drawbacks of existing antennas and which can be installed on a mobile means of transport. In particular, the purpose of the invention is to provide a directional planar antenna, operating in the Ku band, very compact in the direction of its height, simple to implement and low cost, capable of remaining pointed at a satellite continuously whatever the position of the means of transport and allowing control of the plane of polarization without adding an orientable grid.

For this, the invention relates to a planar scanning antenna comprising at least one network of waveguides with radiating slits, the network of waveguides with radiating slits comprising two substrates of dielectric, respectively lower and upper, superimposed one above the other. The two substrates Sub1, Sub2, lower and upper, have identical waveguides which correspond and each waveguide of the upper substrate communicates with a single corresponding waveguide of the lower substrate by means of a coupling slot (13). Each waveguide of the upper substrate Sub2 further comprises a plurality of radiating slots, all the radiating slots being parallel to each other and oriented in the same direction parallel to a longitudinal axis of the waveguides and each waveguide of the substrate Lower Sub1 has an internal individual supply circuit comprising an individual electronic phase shift and amplification circuit.

According to one embodiment, in each dielectric substrate, the waveguides are placed parallel next to each other and have lower and upper metal walls parallel to a plane of the antenna. In this case, advantageously, the upper and lower walls of all the waveguides can be formed by three flat metal plates, respectively lower, intermediate and upper, parallel to the plane of the antenna, the coupling slots passing through the metal plate intermediate, the radiating slots passing through the upper metal plate.

According to another embodiment, in each dielectric substrate, the waveguides are placed parallel to one another and have lower and upper metal walls inclined relative to a plane of the antenna,

Advantageously, the network of guides with radiating slits is mounted on a platform rotating in azimuth.

Preferably, the antenna comprises two identical arrays of radiating slit waveguides dedicated respectively to transmission and to reception.

• un réseau principal de guides d'onde à fentes rayonnantes et un réseau auxiliaire de guides à fentes rayonnantes, les deux réseaux comportant chacun un premier circuit de déphasage interne réglé à une même valeur de phase, le réseau auxiliaire comportant des fentes rayonnantes orientées avec un angle incliné non nul par rapport aux fentes du réseau principal,
• un deuxième circuit de déphasage placé en entrée du réseau auxiliaire, le deuxième circuit de déphasage étant destiné à compenser une rotation du plan de polarisation d'une onde émise par le réseau principal et comportant un déphaseur à phase variable entre 0° et 180° et un amplificateur à gain variable.

According to the invention, the antenna comprises on transmission and on reception,

• a main network of radiant slot waveguides and an auxiliary network of radiating slot guides, the two networks each comprising a first internal phase shift circuit adjusted to the same phase value, the auxiliary network comprising radiating slots oriented with a non-zero inclined angle relative to the slots of the main network,
• a second phase shift circuit placed at the input of the auxiliary network, the second phase shift circuit being intended to compensate for a rotation of the plane of polarization of a wave emitted by the main network and comprising a phase shifter with variable phase between 0 ° and 180 ° and a variable gain amplifier.

Preferably, the angle of inclination of the radiating slots of the main network is between 20 ° and 70 °.

The invention also relates to a vehicle comprising at least one such antenna and to a satellite telecommunications system comprising at least one such vehicle.

• figures 1a et 1b: deux schémas, respectivement en perspective et en coupe parallèle au plan XZ, d'un premier exemple d'antenne plane ;
• figure 1c : une vue schématique en coupe transversale, d'un exemple d'implantation des guides d'onde dans lequel les parois des guides d'onde sont parallèles au plan XY de l'antenne;
• figure 1d : une vue schématique en coupe transversale parallèle au plan YZ, d'un exemple d'implantation des guides d'onde dans lequel les parois des guides d'ondes sont inclinées par rapport au plan XY de l'antenne ;
• figure 2 : un schéma d'un deuxième exemple d'antenne plane comportant des fonctions d'émission et de réception séparées ;
• figures 3a, 3b : un exemple de dimensionnement d'un réseau de guides d'onde à fentes rayonnantes et un diagramme de rayonnement obtenu avec une antenne plane comportant ce réseau ;
• figure 4 : un schéma d'un troisième exemple d'antenne plane comportant des fonctions d'émission et de réception séparées et un plan d'onde optimisé à l'émission, selon l'invention ;

Other features and advantages of the invention will appear clearly in the following description given by way of purely illustrative and nonlimiting example, with reference to the appended schematic drawings which represent:

• Figures 1a and 1b : two diagrams, respectively in perspective and in section parallel to the XZ plane, of a first example of a planar antenna;
• figure 1c : a schematic view in cross section, of an example of installation of the waveguides in which the walls of the waveguides are parallel to the plane XY of the antenna;
• figure 1d : a schematic view in transverse section parallel to the YZ plane, of an example of installation of the guides wave in which the walls of the waveguides are inclined relative to the XY plane of the antenna;
• figure 2 : a diagram of a second example of a planar antenna comprising separate transmission and reception functions;
• Figures 3a, 3b : an example of sizing of a network of radiating slit waveguides and a radiation diagram obtained with a planar antenna comprising this network;
• figure 4 : a diagram of a third example of a planar antenna comprising separate transmission and reception functions and a wave plane optimized for transmission, according to the invention;

The flat antenna shown on the Figures 1a, 1b , 1 C comprises a network 5 of radiating slit waveguides comprising two dielectric substrates Sub1, Sub2, respectively lower and upper, superimposed one above the other. The upper dielectric substrate Sub2 supports waveguides with radiating slits 10, the lower substrate Sub1 supports waveguides 11 intended to supply each waveguide with radiating slits 10 by a microwave signal. Three radiating slit waveguides are shown in the figure 1a and four radiating slit waveguides are shown on the Figures 1c and 1d , but these numbers are not limitative and can have any value greater than or equal to one. Preferably, the waveguides have a cross section of rectangular shape. In the example corresponding to Figures 1a, 1b , 1 C , the planes of the different layers of the antenna are parallel to an XY plane and in each substrate layer, the waveguides are placed next to each other parallel to the XY plane. The upper and lower walls of all the waveguides are then constituted by three metal plates M1, M2, M3 respectively lower, intermediate and upper, parallel to the plane XY and delimiting the two dielectric substrates equipped with the waveguides, the two dielectric substrates Sub1, Sub2 being interposed between two consecutive metal plates. The height of the antenna is along an axis Z orthogonal to the plane XY. The radiating slit waveguides 10 of the upper substrate and the waveguides 11 of the lower substrate are identical in number, correspond in pairs and communicate with each other in pairs by means of coupling slots in the M2 intermediate metal plate. So on the figure 1a , each waveguide 11 of the lower substrate Sub1 has two metal walls, lower and upper, respectively formed by the lower metal plates M1 and intermediate M2 and lateral metal walls connecting the two lower metal plates M1 and intermediate M2. Each waveguide 11 of the lower substrate Sub1 further comprises a coupling slot 13 passing through the intermediate metal plate M2 and opening into a single corresponding waveguide 10 of the upper substrate Sub2. The coupling slots 13 which feed each waveguide 10 of the upper substrate Sub2, can open for example in the middle of each waveguide 10 or at one end 16 of these waveguides as on the Figures 1a and 1b or at another location of these waveguides 10. Each waveguide 10 of the upper substrate Sub2 has two metallic walls, lower and upper, respectively formed by the intermediate metallic plates M2 and upper M3 and lateral metallic walls connecting the two intermediate metal plates M2 and upper M3. The waveguides 10, 11 extend along a longitudinal axis parallel to the same direction, which can correspond, for example, to the axis X and have two opposite ends 15, 16 on this axis. As shown in the figure 1b , the waveguides of the upper substrate Sub2 are closed at their two ends 15, 16 by two metal walls 17, 18 transverse connecting the three metal plates M1, M2, M3, while the waveguides of the lower substrate are not closed at only one end 16 by the transverse wall 17, their open end 15 corresponding to a signal input 19. Each waveguide 10 of the upper substrate Sub2 further comprises a plurality of radiating slots 20 passing through the upper metal plate M3, all the radiating slots 20 being parallel to each other and oriented in the same direction parallel to the longitudinal axis of the waveguides, for example the direction X, the direction Y orthogonal to the direction X in the XY plane of the corresponding slots to a linear polarization wave plane. The slots can be aligned along the longitudinal axis X of the waveguides or offset by a distance ds with respect to this axis, as shown in the example of the figure 3a . Each waveguide 11 of the lower substrate Sub1 comprises an internal individual supply circuit 25 capable of receiving an incoming microwave signal 19 applied to its open end, this internal individual supply circuit 25 comprising an internal individual electronic phase shift circuit and amplification comprising an internal phase shifter 21 for controlling the phase of the signal to be transmitted and an internal amplification device 22 of the incoming signal making it possible to control the radiation emitted by the antenna. The incoming signal 19 can be emitted for example by an external source 24, for example unique, then divided by a divider 26 connected at the input of each of the waveguides 11 of the lower substrate Sub1. After phase shift 21 and amplification 22, the incoming signal 19 in one of the waveguides 11 of the lower substrate Sub1 is transmitted in a corresponding waveguide 10 of the upper substrate Sub2 via the coupling slots 13 in the intermediate metal plate M2 then radiated by the radiating slots 20. A scanning and a deflection of the beam in elevation, in a plane YZ perpendicular to the plane XY of the antenna, is obtained by checking the law of phase and amplitude applied electronically by the internal supply circuits of each waveguide 11 of the lower substrate corresponding to each of the waveguides 10 with radiating slits. The waveguides shown on the figure 1a all have an arrangement parallel to the metal plates M1, M2, M3. According to a particular example shown schematically in cross section along a section plane parallel to the YZ plane on the figure 1d , to achieve very large deviations, for example greater than 50 °, it is also possible to tilt each waveguide by a predetermined angle, for example between 10 ° and 20 °, relative to the XY plane of the antenna. In this case, the lower and upper walls of the different waveguides are not formed by flat metal plates M1, M2, M3 but by metal walls inclined relative to the plane XY, the metal plates M1, M2, M3 being replaced by sawtooth metal walls.

Each waveguide 11 of the lower substrate Sub1 being supplied individually by an internal circuit 25 and comprising a circuit individual internal electronic phase shift 21 and amplification 22, the phase control is carried out continuously which allows to continuously control the direction of radiation of the antenna in elevation. Furthermore, the amplification is distributed in each waveguide 11 which allows the use of low power amplifiers and to overcome a complex and bulky external amplification circuit. In addition, no high energy source switching means is required to achieve continuous scanning of the beam.

By placing the flat antenna 6 thus obtained on a platform 7 rotating in azimuth, the pointing of the beam in azimuth is achieved by rotation of the platform and the pointing of the beam in elevation is given by the phase law applied to the incoming signals 19 This phase law is obtained by controlling the internal phase shifters 21 and the internal amplifiers 22 integrated in each of the waveguides 11 of the lower substrate Sub1. Advantageously, the waveguides 10 with radiating slits operating in a low bandwidth, it is possible to split the transmission and reception functions and to use as shown in the figure 2 , a system of planar antennas 6, 8 comprising a first array of slot wave guides dedicated to transmission and a second array of slot wave guides, not shown, dedicated to reception, the two array of slotted waveguides being identical and mounted on the same platform 7 rotating in azimuth. The pointing in elevation of each of the transmitting and receiving antennas of the planar antenna system mounted on the rotating platform is carried out by amplification and electronic control of the phases of each of the signals flowing in the slot guides forming the arrays of radiation from the two antennas.

The figure 3b shows a nonlimiting example of a radiation diagram obtained with a planar antenna having a structure in accordance with Figures 1a and 1b and comprising an array of Ny = 21 slot wave guides and Nx = 70 slots per wave guide, the slots being distributed uniformly along each wave guide. As shown in the figure 3a , in this example, the waveguides have a dielectric constant ε _r of 2.2 and a rectangular section of a = 12mm long and b = 1.575mm high. The slots are rectangular and their dimensions are ls = 15mm long in the X direction and ws = 1mm wide in the Y direction. The spacing between two consecutive slots is dx = 11.82mm lengthwise in the X direction. Two consecutive slots can be offset from each other in the Y direction. figure 3 , the offset is ds = 0.14mm compared to the median separating two slits. The antenna thus obtained has dimensions of 840mm long and 242mm wide. The height of the antenna without the rotating platform on which it is mounted is a few millimeters. The total height of the antenna with the rotating platform is almost equal to the height of the rotating platform, ie of the order of 2 to 3 cm. This antenna radiates a linearly polarized wave, the radiated wave plane being parallel to the slits. The radiation diagram obtained with this antenna comprises a main lobe having a maximum amplitude at 36.2 dB corresponding to the maximum directivity of the antenna and a bandwidth at 3dB of angle Theta equal to 1.5 ° in the XZ plane and at 5 ° in the YZ plane.

This design example therefore shows that the flat antenna thus produced meets the height conditions imposed for installation on a means of transport and in particular on a future high-speed train. However, when an antenna transmits a linearly polarized wave plane in a given direction, the satellite receives this wave in a direction which depends on the relative position of the satellite with respect to the local vertical of the vehicle equipped with the antenna and the relative position of the vehicle in relation to the local vertical on the ground. The satellite therefore sees a wave whose polarization has undergone a rotation of an angle Psi with respect to the plane of polarization of the wave emitted by the antenna. If the vehicle is traveling in a geographical area with slopes less than 10%, the Psi value remains at values less than 15 °. If this rotation is not compensated, it has the effect of generating two crossed energy components at the satellite level. The satellite then receives a main energy component parallel to the plane of polarization of the transmitted wave and an additional energy component in a direction perpendicular to the main polarization plane. Since this additional energy component can create interference for users using this other plane of polarization, it is necessary to compensate for the angle of rotation Psi so that the satellite receives only one wave whose polarization is perfectly aligned. This angle of rotation Psi varies continuously when the vehicle equipped with the antenna moves, compensation must be carried out continuously. To limit interference, this compensation must be carried out both on transmission and on reception.

To compensate for the rotation of the polarization plane on transmission, according to an additional feature of the invention, a planar auxiliary transmit antenna 9 and a planar auxiliary receive antenna 14, having the same structure as the main antennas 6 transmission and 8 reception are mounted on the rotating platform 7 as shown in the figure 4 .

Each auxiliary planar antenna 9, 14 comprises an auxiliary network 30 of slot guides supplied in an identical manner as that of the main transmission network, that is to say by a phase shift circuit 31 and internal amplification 32 installed in the guides wave of the lower substrate of the auxiliary network, the phase shift being set to the same value as that of the main network 5. The orientation of the radiating slots 33 of the auxiliary network 30 makes a non-zero angle α , preferably between 20 ° and 70 °, with respect to the radiating slots 20 of the main transmission network 5 so as to emit a secondary wave having a plane of polarization 2 inclined with respect to the plane of polarization 1 of the main wave emitted by the main network 5.

The auxiliary network 30 makes it possible to obtain, in the direction of the beam emitted by the main network, a secondary beam having amplitude, phase and polarization characteristics independent of the main network. The polarization components of the two wave planes 1, 2 emitted by the two main 5 and auxiliary 30 networks will combine vectorially into a global resulting wave having a polarization plane 3.

The plane wave emitted by the auxiliary antenna 9, 14 being polarized according to a wave plane perpendicular to the direction of orientation of the slots 33 of the auxiliary antenna 9, 14 it therefore comprises two polarization components parallel to the axes X and Y.

By adjusting the polarization, phase and amplitude parameters of the wave emitted by the auxiliary network 30, it is then possible to obtain, at satellite level, a global resulting wave whose polarization plane 3 is aligned with the plane of polarization 1 of the main wave emitted and of thus compensate for the angle of rotation Psi of the polarization of the main wave received by the satellite. For example, by applying a phase equal to 180 ° to the wave emitted by the auxiliary network 30, which corresponds to the plane of polarization 4, the overall resulting wave has a plane of polarization in direction 12.

For this, a second phase shift circuit intended to compensate for a rotation of the plane of polarization of a wave emitted by the main network, is placed at the input of the auxiliary network 30. The second phase shift circuit comprises a phase shifter 34 with variable phase between 0 ° and 180 ° and an amplifier 35 with variable gain.

By way of nonlimiting example, as shown in the figure 4 , the radiating slots 33 of the auxiliary network 30 can be chosen oriented at 45 ° relative to the radiating slots 20 of the main network 5. The input phase shifter 34 with variable phase between 0 ° and 180 ° and the input amplifier 35 with variable gain make it possible to adjust the amplitude and the phase of the signal delivered by the source of emission and derivative, via a power divider 36, towards the auxiliary network 30 and thus to control the orientation of the plane of polarization 3 of the resulting emitted wave which results from the combination of the two waves radiated by the two main radiating networks 5 and auxiliary 30. The secondary wave being only intended to compensate for the angle of rotation Psi, it does not has the sole purpose of creating a wave plane component perpendicular to the main wave plane and the amplitude of the wave it emits can therefore be much lower than the amplitude of the main wave. The auxiliary antenna 9, 14 can therefore be of much smaller dimensions than those of the main antenna 6, 8 and therefore, the numbers of waveguides and slots of the secondary antenna can be much lower than those from the main antenna.

Although the invention has been described in connection with specific examples and embodiments, it is obvious that it is in no way limited thereto and that it includes all the technical equivalents of the means described as well as their combinations if these are within the scope of the invention, which is defined by the claims.

Claims (9)

1. Flat scanning antenna comprising, at transmission and at reception, at least one main array (5) having waveguides with radiating slots, wherein the main array (5) having waveguides with radiating slots comprises two dielectric substrates, namely the lower substrate (Sub1) and the upper substrate (Sub2) respectively, one superposed above the other, the two, lower (Sub1) and upper (Sub2) substrates comprising the same number of waveguides (10, 11) corresponding thereto, each waveguide (10) of the upper substrate (Sub1) communicating with a corresponding single waveguide (11) of the lower substrate (Sub2) via a coupling slot (13), characterized in that:

   - each waveguide (10) of the upper substrate (Sub2) further includes a plurality of radiating slots (20), all the radiating slots (20) being mutually parallel and oriented in the same direction parallel to a longitudinal axis (X) of the waveguides;

   - each waveguide (11) of the lower substrate (Sub1) includes an individual internal supply circuit (25) comprising an individual internal phase-shift (21)/amplification (22) electronic circuit,

   - the antenna further includes, at transmission and at reception:

   ∘ an auxiliary array (30) having waveguides with radiating slots, the main array (5) and the auxiliary array (30) each comprising a first internal phase-shift circuit (21, 22), (31, 32) set to the same phase value, the auxiliary array (30) having radiating slots (33) oriented at a non-zero angle (α) inclined to the slots (20) of the main array (5);

   ∘ a second phase-shift circuit placed at the input of the auxiliary array (30), the second phase-shift circuit being intended to compensate for a rotation of the plane of polarization of a wave transmitted by the main array (5) and comprising a phase shifter (34) having a variable phase between 0° and 180°, and a variable-gain amplifier (35).
2. Flat antenna according to claim 1, characterized in that, in each dielectric substrate, the waveguides are placed so as to be mutually parallel, one beside another, and comprise upper and lower metal walls parallel to a plane (XY) of the antenna.
3. Flat antenna according to claim 2, characterized in that the upper and lower walls of all the waveguides are formed by three flat metal plates, a lower metal plate (M1), an intermediate metal plate (M2) and an upper metal plate (M3) respectively, which are parallel to the plane (XY) of the antenna, the coupling slots (13) passing through the intermediate metal plate (M2) and the radiating slots (20) passing through the upper metal plate (M3).
4. Flat antenna according to claim 1, characterized in that, in each dielectric substrate, the waveguides are placed so as to be parallel, one beside another, and comprise upper and lower metal walls inclined to a plane (XY) of the antenna.
5. Flat antenna according to one of the preceding claims, characterized in that the main array (5) and the auxiliary array (30) are mounted on a platform (7) rotating azimuthally.
6. Flat antenna according to claim 1, characterized in that the two arrays (5, 30), having waveguides with radiating slots which are dedicated to transmission and to reception respectively, are identical,
7. Antenna according to one of the preceding claims, characterized in that the angle (α) of inclination of the radiating slots (33) of the auxiliary array (30) is between 20° and 70°.
8. Vehicle having at least one antenna according to one of the preceding claims.
9. Satellite telecommunication system comprising at least one antenna mounted on a vehicle according to claim 8.

Images