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
  • H01Q3/26—Arrangements for changing or varying the orientation or the shape of the directional pattern of the waves radiated from an antenna or antenna system varying the relative phase or relative amplitude of energisation between two or more active radiating elements; varying the distribution of energy across a radiating aperture
  • H01Q3/2658—Phased-array fed focussing structure
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01Q—ANTENNAS, i.e. RADIO AERIALS
  • H01Q19/00—Combinations of primary active antenna elements and units with secondary devices, e.g. with quasi-optical devices, for giving the antenna a desired directional characteristic
  • H01Q19/10—Combinations of primary active antenna elements and units with secondary devices, e.g. with quasi-optical devices, for giving the antenna a desired directional characteristic using reflecting surfaces
  • H01Q19/12—Combinations of primary active antenna elements and units with secondary devices, e.g. with quasi-optical devices, for giving the antenna a desired directional characteristic using reflecting surfaces wherein the surfaces are concave
  • H01Q19/17—Combinations of primary active antenna elements and units with secondary devices, e.g. with quasi-optical devices, for giving the antenna a desired directional characteristic using reflecting surfaces wherein the surfaces are concave the primary radiating source comprising two or more radiating elements
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01Q—ANTENNAS, i.e. RADIO AERIALS
  • H01Q25/00—Antennas or antenna systems providing at least two radiating patterns
  • H01Q25/007—Antennas or antenna systems providing at least two radiating patterns using two or more primary active elements in the focal region of a focusing device

Definitions

• the field of the invention is that of multi-beam antennas for satellite telecommunications applications.
• Such an antenna can serve several areas on the ground ("spots" in English) with fine radiation brushes ("spot beams" in English).
• the invention relates to an antenna having one or more focusing reflectors, with an array of elementary sources placed in the focal zone.
• Such an antenna geometry is known to a person skilled in the art as a “FAF.R. "(" Focal Array Fed Reflector "in English).
• each spot is produced by the coherent grouping of the signals from a subset of the elementary sources, with appropriate amplitudes and phases to obtain the desired antenna diagram, in particular the size and the direction of sight of the main radiation lobe. 5
• the antenna comprises a flat panel 30 of radiating elements associated with a beam forming network (not shown) for controlling the phase o of the signals applied to the radiating elements.
• the beam 42 reflected by the reflector 34 is directed towards a second concave reflector 44 arranged opposite the axis 38 with respect to the reflector 34 and to the panel 30.
• This reflector 44 is also an element of a fictitious surface 46, which in the plane of the FIG. 1 is a parabola with the same focus 40 as the parabola 36 and with the same axis 38.
• the surface 46 is also a paraboloid. 0
• the concavity of the reflector 44 faces the concavity of the reflector 34.
• the focal length of the reflector 44 is for example four times less than the focal distance of the reflector 34.
• the axis 38 does not form an intersection with the reflectors 34 and 44.
• the edge 44-] of the reflector 44 closest to the axis 38 is at a distance from the axis substantially less than the distance from the edge 34 ⁇ corresponding from reflector 34 to axis 38.
• the network 30 has a general external shape of a circle of diameter 30 cm (or 12 ⁇ ) approximately with 37 radiating elements separated from each other by 42 mm, that is 1.7 ⁇ , ⁇ being the wavelength of the radiation
• Each of the reflectors is cut out in a circle.
• the diameter of the circle limiting the reflector 34 is, in this example, of the order of 28 ⁇ , while the diameter of the circle limiting the reflector 44 is of the order of 30 ⁇ .
• the distance between the edge 34 ⁇ of the axis 38 is 24 ⁇ and the distance between the edge 44-j of the reflector 44 and the axis 38 is 4 ⁇ .
• the beam 32 ⁇ reflected by the reflector 34 converges at a point 50 close to the focal point 40 and the beam 327 reflected by the reflector 44 is inclined by an angle which is about n times the angle ⁇ , n being the ratio of the focal distance f of the reflector 34 to the focal distance f of the reflector 44.
• this ratio between the focal distances being four, the beam 327 is therefore inclined at an angle 4 ⁇ with respect to the axis 38.
• This geometry has many advantages for the installation on board 5 of a satellite, among which we would mention its compactness, its relatively reduced dimensions resulting in a lower weight, and the possibility of mounting the electronics associated with each elementary source directly. on the body of the satellite.
• FIG. 3 An example of a plane focal network 110 of elementary sources (A, B, C, D) is shown in FIG. 3 (from the same document D2) where we see a hexagonal arrangement of 61 elementary sources 31 distributed over a planar network 110 intended to be positioned on the focal plane of a focusing reflector 100.
• the sources supplied from each group A, B, C, D are indicated by the corresponding letter. It can be seen that no source of a given group is located adjacent to another source of the same group.
• the document D3 US 5,202,700 relates to a FAFR radar antenna for air traffic control.
• this antenna is multi-brushes but only in elevation, with the sources deployed on the surface of a convex cylinder for phase correction and for reduction of the lateral i o lobes.
• This antenna can operate in circular polarization.
• Document D4 US 4,535,338 describes a multi-spot antenna having a Cassegrain type geometry, with a first “sub” convex reflector 12 in front of a second concave main parabolic reflector 10. This arrangement is shown diagrammatically in FIG. 4.
• each beam comprising a single horn source, and the sources are spaced in the focal plane and oriented so that a ray central of each horn, after reflection on the first reflector 12, falls on a single point C of the main reflector 10.
• the antenna of the invention is designed to perform the reception function for a cover consisting of a multiplicity of contiguous spots of small size.
• An antenna solution associating a source with each spot cannot be envisaged, because it leads to an overlap of the sources.
• the antenna of the invention will be designed to operate at high frequencies, ranging from the Ku band (approximately 11 to 15 GHz) to the Ka band (approximately 20 to 40 GHz) and beyond. Hence, the dimensions of the resonant elementary sources become very small, of the order of a centimeter. As in documents D1 to D3, each brush of the antenna according to the invention is formed by the excitation of a
• each elementary source is associated with a variable phase shifter and a variable attenuator or amplifier, as well as their control electronics. The phase shift and attenuation or amplification values are applied upstream of the beam-forming networks to create each spot on the cover.
• the antenna according to the invention seeks to solve these various problems
• the invention provides a reception antenna for multispot coverage, comprising at least one focusing reflector (34, 44, 100), and a focal network (30, 110) of elementary sources (31) arranged in the focal zone. of said focusing reflector (34, 44, 100), characterized in that said sources (31) are substantially contiguous and arranged on a concave surface S and
• a plurality of elementary sources is used to form each beam which illuminates each respective spot of said cover.
• a single elementary source can be used in the formation of several different beams.
• the number of elementary sources used in the formation of a single The beam is greater than or equal to seven.
• the number of elementary sources contributing to a beam is not the same for all the beams, this number being determined as a function of the desired characteristics of each beam.
• the antenna comprises two concave reflectors (34, 44) in a so-called “Gregory” type geometry.
• the antenna comprises a single concave reflector (100), in a geometry called "offset".
• the antenna further comprises polarization duplexers (20) behind each elementary source.
• the antenna is designed to operate with a single polarization, and there is no polarization duplexer.
• the elementary sources are of a dimension not exceeding 1.2 times the wavelength.
• FIG. 6 which schematically shows a second example of a focal network 5 of elementary sources 31, substantially contiguous and arranged on a concave surface S approximately spherical, capable of being integrated into the antenna according to the invention.
• FIG. 7 shows schematically an example of a focal array antenna according to the invention, with a Gregorian type geometry with a first concave ellipsoid reflector and a second concave and confocal parabolic reflector with the first reflector o.
• FIGS. 1 to 3 represent realizations known in the art
• the antenna of the invention comprises an array (30, 11) of N th elementary sources 31; optical means forming a reflector (10, 34, 44) and focusing the energy; the grating being located in the focal zone of said focusing means, as shown in FIGS. 1 and 2.
• the elementary sources are contiguous, either in hexagonal mesh as shown in Figure 3, or in rectangular mesh.
• several sources contribute to a single beam, while each source can contribute to a plurality of beams.
• the sources can be divided into groups A, B, C, D which will be excited and amplified separately; this arrangement in groups improving the isolation between sources
• FIG. 4 shows a teaching contrary to that of the invention. Only one source is used for each corresponding brush. There is no focal network, and the sources are distinct and not contiguous. On the other hand, they are placed in front of a divergent convex reflector 12, which contributes to increasing the distance between the
• FIG. 5 schematically shows a first example of a focal array of elementary sources 31, substantially contiguous and arranged on a concave surface S approximately spherical, capable of being integrated into the antenna according to the invention.
• the shape of the surface S makes it possible to improve the efficiency of the antenna on the one hand, according to a consequence of the geometric optics; on the other hand, this shape makes it possible to have the sources very tight against each other on the front face of the network, but to have more space between the output waveguides 112 on the rear face of the network.
• the elementary sources can be divided into groups, for example A, B, C, D as explained above during the description of FIG. 3. They can be arranged in a hexagonal mesh as shown here; or any other mesh chosen by the designer.
• the sources are horns, connected to the output waveguides 112 by means of flanges 111.
• FIG. 6 schematically shows a second example of a focal network of elementary sources 31, substantially contiguous and arranged on a concave surface S approximately spherical, capable of being integrated into the antenna according to the invention.
• polarization duplexers 20 also known as “orthomode”.
• These duplexers 20 make it possible to separate the signals into two orthogonal polarizations, for example Horizontal and Vertical (H, V), which will then be conveyed in respective waveguides, for example guide 21 for H, guide 22 for V.
• H, V Horizontal and Vertical
• FIG. 7 schematically shows an example of a focal array antenna according to the invention, with geometry of the Gregorian type.
• This antenna comprises a first concave ellipsoid reflector 54 having two focal points F1 and F2.
• a focal network 110 of active elements is placed in the vicinity of the first focus F1.
• a property of the geometry of an ellipsoid is that all the rays emitted from one of the focal points (F2 by example) and reflected by the ellipsoid reflector 54 will be focused in the other focal point. (F1).
• a second concave paraboloid reflector 44 is positioned with its focal point at the same location as the second focal point F2 of said first reflector, the two reflectors
• This geometry represents a preferred embodiment of the invention, however, other antenna geometries, with other types and arrangements of reflectors can be considered in order to obtain a large number of variants.

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• Aerials With Secondary Devices (AREA)

Applications Claiming Priority (3)

Publications (1)

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ID=27619772

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• 2002
  • 2002-01-31 FR FR0201140A patent/FR2835356B1/fr not_active Expired - Lifetime
• 2003
  • 2003-01-17 WO PCT/FR2003/000140 patent/WO2003065507A1/fr not_active Ceased
  • 2003-01-17 US US10/503,097 patent/US7119754B2/en not_active Expired - Lifetime
  • 2003-01-17 EP EP03712252A patent/EP1472760A1/de not_active Withdrawn
  • 2003-01-17 CA CA2474126A patent/CA2474126C/fr not_active Expired - Lifetime

Non-Patent Citations (1)

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