Classifications

• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01Q—ANTENNAS, i.e. RADIO AERIALS
  • H01Q3/00—Arrangements for changing or varying the orientation or the shape of the directional pattern of the waves radiated from an antenna or antenna system
  • H01Q3/12—Arrangements for changing or varying the orientation or the shape of the directional pattern of the waves radiated from an antenna or antenna system using mechanical relative movement between primary active elements and secondary devices of antennas or antenna systems
  • H01Q3/16—Arrangements for changing or varying the orientation or the shape of the directional pattern of the waves radiated from an antenna or antenna system using mechanical relative movement between primary active elements and secondary devices of antennas or antenna systems for varying relative position of primary active element and a reflecting device
  • H01Q3/20—Arrangements for changing or varying the orientation or the shape of the directional pattern of the waves radiated from an antenna or antenna system using mechanical relative movement between primary active elements and secondary devices of antennas or antenna systems for varying relative position of primary active element and a reflecting device wherein the primary active element is fixed and the reflecting device is movable
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01Q—ANTENNAS, i.e. RADIO AERIALS
  • H01Q1/00—Details of, or arrangements associated with, antennas
  • H01Q1/27—Adaptation for use in or on movable bodies
  • H01Q1/28—Adaptation for use in or on aircraft, missiles, satellites, or balloons
  • H01Q1/288—Satellite antennas

Definitions

• the field of the invention relates to montages of mobile beam antennas, including antennas embedded on telecommunication satellites.
• Telecommunication satellites embed antennas that can generate mobile beams for broadcasting multimedia services. These services require that communication networks can cover large geographical areas and maintain a sufficiently high signal quality over the entire area to be covered. For this, there are mobile beam antennas that can change the pointing direction of the beam to meet the needs of telecommunication services.
• the telecommunication satellites receive data from the ground stations and transmit these data to the earth by means of antennas positioned in front of the Earth.
• Passive double reflector antennas are preferentially used because they present the best compromise between the constraints of mass, size, performance and cost. Indeed, these antennas with double reflectors allow, given equivalent focal length, to reduce the size of the antenna in comparison with a simple reflector antenna. This has a particularly advantageous advantage to reduce the size of a satellite in a launcher.
• the known passive antenna solutions for moving a beam of radio frequency signals on the earth's surface are antennas comprising means allowing the movement of either the complete antenna assembly or only the reflector by the change of orientation of the reflecting surface.
• the existing passive antenna mounting solutions comprises a source for transmitting and / or receiving RF signals, one or more reflectors and a supporting base for carrying all the radiofrequency components of the antenna.
• the object of the invention is to overcome the aforementioned problems and to propose an antenna assembly for transmitting and / or receiving a moving beam, comprising a simplified kinematic mechanism and having better radiofrequency performance. More specifically, the invention relates to a mobile beam antenna assembly comprising a support base, a parabolic primary reflector having a focus and a secondary reflector ellipsoid type having two focal points, a source of transmission and / or reception of signals RF forming a beam mounted in the fixture so as to be stationary relative to the supportive base, a movable support carrying the primary reflector and the secondary reflector, said reflectors being stationary with respect to each other, the mobile support being mounted on the support base with connecting means able to move the reflectors around at least one fixed displacement axis passing through the phase center of the source.
• the focus of the primary reflector is maintained positioned on a first focus of the secondary reflector and the second focus of the secondary reflector is maintained positioned on the phase center of the source in any position of the movable support.
• the movable support, the primary reflector and the secondary reflector form a moving assembly relative to the supportive base.
• the connecting means are able to put said moving assembly in motion about two axes of rotation concurrent with the phase center of the source.
• the surface of at least one reflector is substantially greater than the surface of the beam reflected on the surface of said reflector.
• the antenna assembly according to the invention solves the connection problems between the RF source and the payload of the satellite.
• the immobility of the source in the assembly does not require the use of flexible waveguides and complex kinematic means for deforming this type of waveguide. This also results in better radio frequency performance.
• the displacement of the assembly consisting of the movable support and the reflectors, immobile with each other, around the source makes it possible to maintain the most optimal RF signal propagation geometry and to reduce, or even to render non-existent, focusing aberrations. of antenna mounting.
• the assembly allows the beam to move on the Earth without any deformation of the beam.
• FIG. 1 represents a schematic diagram of the antenna assembly according to the invention symbolizing the source, the primary reflector and the secondary reflector.
• Figure 2 shows a simplified diagram of the antenna assembly according to a front view.
• Figure 3 shows a simplified diagram of the antenna assembly in a profile view.
• FIG. 4 represents a diagram of a reflector according to two positions as well as the reflected beam for each position.
• FIG. 5a shows radio frequency simulations of transmission of moving beams distributed on the terrestrial surface by means of an antenna assembly comprising a single movable reflector.
• FIG. 5B represents radio frequency simulations of transmission of moving beams distributed on the terrestrial surface by means of an antenna assembly according to the invention.
• Telecommunication satellites generally have a parallelepipedal shape with a terrestrial face permanently directed towards the Earth.
• An RF signal transmission system is mounted on this face Earth for the realization of the mission of the satellite such as the offer of telephone service and data and video transmission.
• these antennas comprise a paraboloidal reflector based on the geometric properties of the curve named parabola and the named paraboloid surface of revolution.
• the parabolic reflector is responsible for concentrating the waves received or emitted towards the source antenna, commonly called the source, which is located at the focus of the dish.
• Several types of paraboloid reflector antennas can be used in the context of the invention.
• antenna assemblies comprising a single reflector and multi-reflector assemblies, commonly known as Cassegrain-type antenna or Gregorian-type antenna mounting.
• the object of the invention is described later on the basis of the example of an antenna assembly particularly well suited for a spatial application. It is a Gregorian antenna type montage.
• the scope of the invention is not limited to this type of antenna mounting.
• the person skilled in the art knows how to adapt the concept of the invention to other types of antenna assembly comprising an ellipsoidal secondary reflector.
• FIG. 1 represents a simplified diagram of the functional elements participating in the transmission and / or reception function of a Gregorian antenna type assembly.
• the antenna comprises a primary reflector 2 and a secondary reflector 1.
• the primary reflector 2 has a paraboloidal shape concentrating the RF signals to the focus 21 of the dish.
• the secondary reflector 1 has an ellipsoidal shape.
• the source is off-center of the central axis of the secondary reflector 1.
• This type of assembly comprising an off-center source is a so-called "Offset" assembly and has the advantage of not positioning the source in the field of the radiofrequency beam, thus avoiding a loss of efficiency.
• the use of a secondary reflector 1 of ellipsoidal shape, for off-centering the source, has two foci, a primary focus 32 and a secondary focus 31.
• the primary reflector and the secondary reflector are mounted together in the antenna assembly so that the secondary focus 31 of the secondary reflector is coincident with the focal point 21 of the antenna.
• primary reflector 2 whatever the orientation of the beam 10.
• the antenna comprises a source 3 radiating towards the secondary reflector 1.
• the source is mounted so that the primary focus 32 of the secondary reflector 1 coincides with the phase center of the source 3, whatever the orientation. beam.
• the source 3 is mounted immobile in the mounting of the antenna.
• the source 3 is preferably fixed on the support base 6.
• FIGS. 2 and 3 show a simplified diagram of the antenna assembly of the Gregorian antenna type according to FIG. invention in front view and side view. For reasons of clarity of the drawings, the source is not shown.
• the phase center of the source is represented by reference 41.
• the antenna assembly comprises a supporting base 6 and a movable support 7.
• the supportive base 6 is mounted on a repository 8 so as to be immobile with respect to this reference frame.
• This reference 8 represents, for example, the terrestrial side of a telecommunications satellite.
• the source 3 is mounted in the antenna assembly so as to be also stationary relative to the reference frame 8.
• the source 3 is fixed on the support base 6.
• the supportive base 6 comprises a part lower 61 covering a sufficient area to stabilize the entire assembly on the satellite.
• the two lateral parts 62 and 63 are connected together at their second ends by a longitudinal portion 64 also serving to fix connecting means 9 between the supportive base 6 and the mobile support 7.
• the mobile support 7 is articulated on the support base 6 with connecting means 9 making it possible to confer on the mobile support 7 a mobility capacity with respect to the source 3 and consequently with respect to the reference 8, the source 3 being in fact motionless with respect to the reference frame 8.
• the mobile support 7 holds the primary reflector 1 and the secondary reflector 2.
• the two reflectors are immobile relative to each other on the mobile support 7, fastening means for holding the two reflectors on the movable support.
• the connecting means 9 make it possible to move the mobile support 7 around at least one axis of rotation 4 passing through the phase center 41 of the source 3, and preferably around two axes of rotation. 4 and 5 concourant by the phase center 41 of the source 3.
• the two axes of rotation 4 and 5 are perpendicular to each other and allow to move the reflectors around the source 3, in several distinct positions in the assembly, according to the degrees of freedom necessary for the need of displacement of the beam.
• the propagation geometry of the RF signals emitted by the source 3 in the assembly consisting of the primary reflector 2 and the secondary reflector 1 is formed so that the main focus 32 of the secondary reflector 1 is located on the phase center of the source 3 and the secondary focus 31 of the secondary reflector 1 coincides with the focus 32 of the main reflector 2.
• the two reflectors are stationary relative to each other and the focus main 32 of the secondary reflector 1 is constantly maintained localized on the phase center 41 of the source 3.
• the geometric properties of the ellipsoidal shape of the secondary reflector 1 also maintain the secondary focus 31 at the same position regardless of the position of the secondary reflector around the axis or axes of rotation 4 and 5 concurrent at the center of phase 41 of the source.
• the focus of the main reflector 2 is also maintained at the secondary focus.
• connection means 9 consist for example of a cardan type mechanical articulation part.
• the gimbal is a mechanical articulation used to transmit one or two rotational movements between two axes of intersecting axes 4 and 5.
• the gimbal is preferably positioned at the source 3, itself fixed on the part 64 of the base support 6, so that the axes of rotation of the cardan contribute to the position of the phase center 41 of the source 3.
• the mobile support 7 may be a mechanical structure substantially of the shape of a U, having an elongate central portion 71 and two elongated lateral portions 72 and 73, at each end of the portion central 71, positioned perpendicular to the central portion.
• a lateral portion is substantially longer than the second lateral portion.
• the lateral portion 73 supporting the primary reflector 2, of greater circumference than the secondary reflector 1 consists of a length greater than the length of the lateral portion 72 supporting the secondary reflector 2.
• Unrepresented fastening means maintain the reflectors 2 and 1 on the mobile support 7.
• the connecting means 9 connect the central portion 71 of the movable support with the supportive base 6.
• the supportive base 6 is a mechanical structure sized to allow mobility of the assembly consisting of mobile support 7 and reflectors 2 and 1.
• the source 3 mounted on the supportive base 6 is connected to the electronic equipment of the payload of the satellite for example.
• the antenna assembly can be likened to a cradle in which the mobile support 7 is balanced between the elongated lateral portions 62 and 63 of the supportive base 6 which is stabilized on a reference frame 8.
• the reflectors 1 and 2 move around the source 3.
• the antenna assembly shows an improvement of the radio frequency performance and a use in frequency bands for which deformable waveguides are not qualified or do not exist.
• the antenna assembly also shows better power handling and no functional limitations related to the fatigue resistance of the deformable guides.
• simpler mechanisms can be used because the waveguides have weaker resistant torques.
• Figure 4 more precisely describes a reflector of the antenna assembly reflecting a beam in two different positions.
• the reflector in a first position 210 reflects a beam 21 1 according to a direction 212 and in a second position 220 reflects a beam 221 in a direction 222.
• the reflected beams have a given diameter.
• the reflector has a diameter substantially greater than the diameter of the beam so that the beam surface is constantly covered by the reflector regardless of the position of the reflector. Indeed, the source being immobile, the beam surface is positioned at the same location in the assembly.
• the orientation of the beam is modified by displacement of the reflecting surface.
• reflector means any type of surface exerting a reflection function of an RF beam, including reflector networks commonly called "Reflect Array” in English language.
• the Reflector Network is a periodic reflective surface composed of metallized cells placed above a ground plane. Detailed electromagnetic studies have identified the optimal profile of these cells, so that they can reflect an incident wave with a parameterizable electrical delay. It is then possible to produce with a Reflect Array of canonical surface the same radiation as that of a formed reflector.
• Figure 5a and 5b show emission simulations of several RF beams in several areas of the Earth's surface.
• the simulations of FIG. 5a are carried out with an antenna assembly as described in the state of the art comprising a mobile single reflector.
• the antenna assembly points and moves a beam 102 into several areas of the earth's surface.
• the circle 101 represents a circular surface targeted by the beam.
• the simulations show the deformation of the beam 102 in the East / West and North / South plane and the "delocalization" of the beam 102 in the North / South plane of the beams.
• the simulations of FIG. 5b are carried out with an antenna assembly according to the invention as claimed.
• the antenna assembly points and moves a beam 103 into several areas of the earth's surface.
• the circle 103 represents a circular surface targeted by the beam.
• the simulations show the absence of deformation and delocalization of the beam 104.
• Antenna mounting applies to satellite antenna fixtures with source shifted or not and having at least

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• General Physics & Mathematics (AREA)
• Remote Sensing (AREA)
• Aviation & Aerospace Engineering (AREA)
• Aerials With Secondary Devices (AREA)
• Variable-Direction Aerials And Aerial Arrays (AREA)

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• 2009
  • 2009-11-03 FR FR0905262A patent/FR2952238B1/fr not_active Expired - Fee Related
• 2010
  • 2010-10-20 IN IN3893DEN2012 patent/IN2012DN03893A/en unknown
  • 2010-10-20 US US13/505,434 patent/US8878745B2/en not_active Expired - Fee Related
  • 2010-10-20 CN CN201080056679.6A patent/CN102656746B/zh not_active Expired - Fee Related
  • 2010-10-20 CA CA2779657A patent/CA2779657A1/en not_active Abandoned
  • 2010-10-20 JP JP2012537338A patent/JP2013510479A/ja active Pending
  • 2010-10-20 WO PCT/EP2010/065778 patent/WO2011054669A1/fr active Application Filing
  • 2010-10-20 EP EP10766288A patent/EP2497150A1/fr not_active Ceased

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