Classifications

• • 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
  • H01Q19/06—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 refracting or diffracting devices, e.g. lens
  • H01Q19/062—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 refracting or diffracting devices, e.g. lens for focusing
• • 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
  • H01Q19/06—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 refracting or diffracting devices, e.g. lens

Definitions

• the field of the invention is that of focusing systems of the lens type, usable in the microwave and in particular in millimeter waves.
• the invention relates to an index-index inhomogeneous lens of the Maxwell Poisson's Eye type.
• the invention also relates to an antenna system associating such a lens with one or more source antennas.
• the invention has many applications, such as, for example, high speed satellite communications, digital satellite television, anti-collision radar applications in the automobile, etc.
• the antenna system according to the invention can be used as a source of a reflector (for example in the 50 GHz band).
• the antenna system according to the invention in one of its configurations, can be used to detach the beam to replace these two sources by one.
• an antenna system according to the invention (that is to say a “lens antenna”) can make it possible to reach the necessary directivity and the index gradient aspect can bring about a reduction in size and weight interesting.
• the beam of the antenna located at the front of the car is fixed, but it would be interesting to detach the beam slightly to follow more precisely the routes of the road.
• the antenna system according to the invention in one of its configurations, can make it possible to change the direction of the beam on a sufficient angle.
• each point of the surface is an ideal focal point.
• the distribution of Eaton-Lippman reacts like a mirror: the points objects and images are perfectly confused. It is an omnidirectional reflector.
• Emerson & Cumming made a L ⁇ neburg lens by interweaving several homogeneous, sphere-shaped concentric shells with different indices. It has also been proposed to make lenses L ⁇ neburg by inserting air holes in a Teflon sphere (marked deposited). The number of holes and their diameters are optimized so that the artificial law follows at best the theoretical law. However, the latter technique is also complex in terms of mechanics because the number of holes is prohibitive. None of these two known solutions, specific to the L ⁇ neburg lens, can be transposed to the production of a Maxwell Fish Eye lens.
• the invention in at least one embodiment, is intended in particular to overcome these various disadvantages of the state of the art.
• one of the objectives of the present invention in at least one embodiment, is to provide a technique for manufacturing an eyeglass lens.
• Maxwell's fish which is simple in terms of mechanics and inexpensive.
• the invention also aims to theoretically give the manner of choosing the number and nature of the materials used to make a Maxwell Fish Eye lens, and thus generalize the production technique.
• the invention also aims to provide an antenna system comprising a lens thus manufactured, and which is itself simple to achieve and inexpensive.
• Another object of the invention is to provide such an antenna system which, in one embodiment where the source is constituted by one or more printed antennas, makes it possible to obtain an interesting directionality while limiting the printed surfaces, which reduces the losses caused by the printed source.
• Another object of the invention is to provide such an antenna system which, in a particular embodiment, has a minimum compactness.
• Yet another object of the invention is to provide such an antenna system which, in a particular embodiment, allows scanning of the focused beam at the exit of the lens, making this antenna system usable in all applications. requiring a misalignment of the beam or obtaining a multibeam radiation pattern. 4. Presentation of the invention
• the lens comprises N concentric shells in the shape of a half-sphere, different discrete dielectric constants and interleaved with each other without empty space between two successive shells, with 3 ⁇ N ⁇ 20, the discrete dielectric constants of the N shells being as they define a discrete distribution approaching the theoretical distribution of the index inside the lens.
• the shells do not all have the same dielectric constant and there is no space filled with air between two successive shells.
• the lens comprises three shells, said shell central, intermediate and outer eggshell, the standardized external radii are respectively: d u U 2 and 3, and whose standard radial thicknesses are respectively equal to: d ls U 2 - d 1 and d 3 - U 2 to the nearest hundredth.
• a lens according to the invention consists of three shells only allows for example a side lobe level of about - 20 dB relative to the main lobe which proves that the focus is done correctly.
• the invention also relates to an antenna system comprising a lens according to the invention (as mentioned above) associated with at least one source antenna.
• said at least one source antenna belongs to the group comprising: printed antennas; waveguides; cornets; and - wire antennas.
• the system comprises positioning means for placing said at least one source antenna at a distance h from the lens, and in a position included in a focal spot that this lens has.
• said lens has a focal spot because the index distribution obtained with said concentric shells is discrete (and is therefore only an approximation, with a limited number of shells, of the theoretical continuous distribution.
• focal length is located outside the lens and at a determined distance h from the lens.
• the positioning means comprise at least one shim made of a dielectric material whose dielectric permittivity is close to that of the air and for positioning the lens relative to said at least one source antenna.
• the positioning means comprise an additional shell, whose dielectric permittivity approaches that of the air, having a shape matching the external surface of the lens, and at least a part of said source antenna being shaped directly to the outer surface of said additional shell.
• the size of the antenna system is reduced.
• the system comprises a single source antenna, which is an antenna printed on air and powered by slot.
• a single source antenna of this type the dielectric losses are missing and the directivity of this type of antenna (pellet) is very important (9 - 10 dBi) because of the very low permittivity of the substrate (air).
• this solution provides very good radiation characteristics (openings, lobes, directivity) compared to the solution comprising a source network.
• the focal spot possessed by said lens is used because the index distribution obtained with said concentric shells is discrete. This focal spot is located outside the lens and at a determined distance h from the lens.
• the system further comprises means for decentering said at least one source antenna with respect to the axis of the lens, allowing said at least one source antenna to occupy successively at least two different positions included in said spot focal, in order to allow scanning, on an angular sector, the focused beam at the exit of the lens.
• the lens according to the invention has a focal spot (and not a single focal point). , which allows to detach the beam or to obtain multibeam diagrams.
• the fact that there is a focal spot makes it possible to move the source under the lens and thus obtain a scanning, on a determined angular sector, of the focused beam.
• the invention also relates to an application of the antenna system according to the invention to the misalignment of the beam at the exit of the lens.
• FIGS. 1a and 1b show a perspective view and a sectional view, respectively, of a first particular embodiment of an antenna system according to the invention, associating a lens of the Poisson's Eye type;
• FIG. 2 shows a view from above of a particular embodiment of a Maxwell Poisson's Eye lens according to the invention, which can be used in the antenna system of FIGS. 1a and 1b;
• FIG. 3 shows the curve of a polynomial of degree 3 approximating the theoretical distribution of the index inside an eye-type lens.
• FIGS. 4a and 4b illustrate the results of a first example of a Maxwell Poisson's Eye lens according to the invention, in terms of electric field and power density respectively
• FIGS. 5a and 5b illustrate the results of a second example of a Maxwell Poisson's Eye lens according to the invention, in terms of electric field and power density respectively
• Figures 6a, 6b and 6c show a top view, a bottom view and a sectional view respectively of a particular embodiment of the antenna array appearing in Figures la and Ib;
• FIG. 7a and 7b show a bottom view and a cross-sectional view respectively of a first embodiment of a pellet on air (unconformed, vertical linear polarization), which can be associated with a Poisson's eye-type lens; Maxwell according to the invention;
• Figure 8 shows a bottom view of a second embodiment of a pellet (unconformed, bipolarization), which can be associated with a lens of the type of Fish Eye Maxwell according to the invention;
• FIG. 9 is a bottom view of a third embodiment of a pellet (unconformed, circular polarization), which can be associated with a Maxwell Poisson's Eye lens according to the invention;
• FIG. 10 shows a sectional view of a second particular embodiment of an antenna system according to the invention, associating a lens of Maxwell Poisson's eye type according to the invention and a shaped antenna array. 6.
• the invention thus relates to a non-homogeneous gradient-index lens of the Maxwell Poisson eye type, as well as an antenna system associating this lens with one or more source antennas.
• the Maxwell Poisson Eye lens according to the invention comprises N shells in the form of half-spheres, with 3 ⁇ N ⁇ 20. N directly depends on the size of the lens. The larger the lens, the higher the number N of shells must be in order to approach the theoretical distribution law of the index inside the lens.
• the shells are concentric, different discrete dielectric constants and nested with each other without empty space between two successive shells.
• FIGS. 1a and 1b respectively, a first particular embodiment of the antenna system according to the invention is presented. For the sake of simplification of FIG. positioning means of the lens relative to the source are shown only in Figure Ib.
• the Maxwell 1 Fish Eye lens 1 comprises three shells, said central shell 2, intermediate shell 3 and outer shell 4.
• the standardized external radii of these shells 2 to 4 are respectively: d ls U 2 and d 3.
• Their normalized radial thicknesses are respectively equal to: d u U 2 - & ⁇ and d 3 - U 2 to the nearest hundredth.
• Their dielectric constants are respectively equal to: ⁇ ls ⁇ 2 and ⁇ 3 .
• the inventors have carried out an optimization calculation of the parameters of the three shells forming the Maxwell Poisson's Eye lens in this particular embodiment of the invention.
• this first cost function is original because the optimization is done on the volume of the half-sphere and not on a 2D sectional view (steps).
• the second cost function is minimized as follows:
• the materials marketed by Emerson & Cuming whose names are:
• one or two dielectric constants are fixed and the rays are optimized
• the dielectric constants are all variable as well as the rays.
• a second example of a Maxwell Poisson's Eye lens according to the invention (after optimization with the second cost function), in accordance with the last line of the table above, was tested in terms of electric field and laser density. power.
• the rays u U 2 and 3 are respectively 6.84, 9.48 and 12 mm.
• the dielectric constants are 2.77, 1.81 and 1.19, respectively.
• the lens 1 is associated with a printed antenna array 5.
• the latter is for example optimized around 48.7 GHz.
• the antenna system according to the invention further comprises means for positioning the lens relative to the printed antenna array.
• These positioning means comprise for example: a support (or base) 7, made of foam material (whose dielectric permittivity is close to that of air) and in which is embedded the lens 1; a metal base 8 on which rests the printed antenna array 5; shims 9a, 9b made of foam material and for maintaining a distance h between the outer surface of the lens 1 and the pellets of the printed antenna array 5. The distance h is discussed in detail later; and - screws 10a, 10b for assembling the support 7, metal plate 8 and shims 9a, 9b.
• the printed antenna array 5 i.e., the excitation source of the lens
• the printed antenna array 5 is example realized in the form of a structure comprising: a feed line 65 printed on the underside of a first substrate layer 67; a ground plane 69 with slot 68, interposed between the first substrate layer 67 and a second substrate layer 66; four pastilles (or patches) 61 to 64 printed on the upper face of the second substrate layer 66.
• the height h between the source and the lens varies because the zone focus does not necessarily lie in the same place.
• the lenses have relatively limited surface yields because of their large size.
• To calculate the surface efficiency of the lens it is necessary to consider a radiating aperture of the same dimension as the lens, namely 24 mm, and calculate the associated directivity. The latter is given by the following formula:
• ⁇ is the wavelength in the vacuum and d is the diameter of the opening.
• the yield due to losses is lower. But the losses introduced are essentially by the printed network which serves as a source for the lens.
• the solution to increase the overall efficiency is therefore to use a very low loss substrate such as quartz for example or to limit the line lengths of the network tree.
• This last remark led the inventors to study an original solution for the source of the lens. Indeed, they decided to use only one printed pellet to feed the lens.
• the source diagram is very wide, which implies problems of spill-over and backward radiation.
• the overall directivity is much lower than with a network of four elements.
• FIGS. 7a and 7b show a bottom view and a sectional view respectively of a first embodiment of an air-printed pellet (unconformed, vertical linear polarization), which can be associated with a Poisson-like lens. Maxwell according to the invention.
• the printed pellet 70 is in the form of a structure comprising: a feed line 73 printed on the underside of a first substrate layer 74; a ground plane 75 with slot 76, interposed between the first substrate layer 74 and a second substrate layer 77; an air cavity 78 formed in the second substrate layer 77; a third layer of foam substrate 72 of very low permittivity (1.45), used as a support for the chip 71, so that the chip is above the air cavity 78.
• the input impedance of this printed chip 70 has been simulated with the CST Microwave Studio software, between 40 and 55 GHz. As a result of this simulation, the printed chip 70 is well adapted to the band in question (47.2 GHz - 50.2 GHz). The directivity obtained is stable in the frequency band and equal to 9 dBi. The latter is strong because the pellet is printed on air.
• the next step was to associate this printed chip 70 with an example of inhomogeneous lens according to the invention (that of diameter 24 mm).
• the support of the printed pellet here has a height h of 1 mm because this height h between pellet and lens makes it possible to obtain a directivity that is interesting for the whole and almost stable over the frequency band considered.
• the complete structure was simulated on CST.
• the radiation diagrams calculated at 48.7 GHz show the very clear effect of focusing. Indeed, the half-power openings obtained are respectively 23.1 ° and 19.1 °.
• the level of the secondary lobes is satisfactory, of the order of -18 dB compared to the main lobe.
• the directivity is therefore stable on the band of interest.
• the lens excited by a single printed chip is a very interesting device because it provides very good radiation characteristics (openings, lobes, directivity) compared to the solution comprising a network of four sources.
• the losses due to the substrate of the source are reduced because the printed areas are smaller. This increases the overall performance of the structure, which was one of the objectives.
• the printed pellet that excites the lens sets the type of polarization.
• the polarization obtained is vertical linear.
• Other polarizations can be envisaged.
• the patch 91 is almost square and two orthogonal slots 96a and 96b (cross slots) are etched in the ground plane and fed by a single power supply line 93, which makes it possible to create out of phase modes of 90 ° at a frequency and thus create a circular polarization.
• FIG. 10 shows a sectional view of a second particular embodiment of an antenna system according to the invention, associating a Maxwell Poisson's Eye lens according to the invention 1 and an antenna array 106 .
• the positioning means of the lens 1 relative to the printed antenna array 106 comprise: an additional shell 101, having a shape matching the external surface of the lens 1, made in a substrate whose permittivity dielectric approximates that of air, and which is metallizable (so as to receive one or more radiating pellets); a support (or base) 102, made of foam material (whose dielectric permittivity is close to that of air) and in which is embedded the lens 1 surrounded by the additional shell 101; a metal sole 103; shims 104a, 104b made of foam material and making it possible to maintain a determined distance (not to be confused with the height h, as explained hereinafter) between the lens 1 and the metal plate 8; and screws 105a, 105b assembling the support 102, the metal sole 103 and shims 104a, 104b.
• the printed antenna array 106 is of the type shown above in connection with FIGS. 6a and 6b, but differs in that at least part of this network is shaped directly on the outer surface of the antenna. additional shell 101.
• the pellets 107, 108 are shaped on the outer surface of the additional shell 101.
• it is the thickness of the additional shell 101 that gives the height h between the lens 1 and the network of antennas printed. It is important to note that given the very small size of the pellets relative to the radius of the half-sphere constituting the lens 1, the curvature of the metal pellets is low and does not significantly modify the results of the planar case.
• the rest of the antenna array (namely a substrate layer 110 on the underside of which is printed a feed line 109 and on the upper face of which rests a ground plane 111 with slot 112) rests on the metal sole 103.
• the space filled with air between, on the one hand, the shaped pellets 107, 108 and, on the other hand, the ground plane 111 with slot 112 plays the same role as the referenced substrate layer. 66 in Figure 6c.
• the entire printed antenna array is shaped to the outer surface of the additional shell 101.
• the source associated with the lens is a single antenna printed on air, shaped at least in part to the outer surface of the additional shell 101.
• D ' the system of the invention (association of a lens with at least one source antenna) is not related to a particular type of antenna .
• this system can be implemented for example with one or more printed antennas (mono or multi-layer), one or more waveguides, one or more horns, one or more wire antennas, etc.
• the antenna system according to the invention further comprises means for off-centering the source (for example a printed antenna array or a single patch printed on air) with respect to the axis of the lens, allowing the source of successively occupying at least two different positions included in the focal spot. This allows scanning, on a small angular sector, the focused beam at the exit of the lens.
• the lens of the invention whatever its embodiment, has a focal spot because the index distribution obtained with the N concentric shells is discrete.
• This focal spot is located outside the lens and at a determined distance h from the lens.
• the decentering means are for example made in mechanical form (any means allowing a physical displacement of the source with respect to the lens) or in electronic form (displacement of the source beam by switching between elements of an antenna array, intelligent antenna type).
• the physical displacement of the source relative to the lens is achieved by a rotational movement or translation of the source relative to the lens.
• Maxwell Poisson's eye lens has only one focal point and does not allow detaching the beam or obtaining multibeam diagrams.
• the law of the index in the lens produced according to the invention is discrete, it is in fact a focal spot that is obtained (see FIGS. 4a and 5a). The fact that there is a focal spot makes it possible to move the source under the lens and thus obtain a misalignment of the beam or a multibeam diagram.
• the antenna structure according to the invention can for example be used in satellite reception (band 12-14 GHz). Indeed, when a customer wants to receive two different satellites, currently two switchable sources illuminating the dish are needed.
• the solution of the invention makes it possible to have only one source (lens illuminated by an array of printed antennas for example) whose diagram can detach to target the two satellites.
• the antenna structure according to the present invention (association of at least one source antenna with a Maxwell Poisson's Eye lens) can also make it easy to obtain multibeam diagrams by changing the position of the source with respect to the axis. of the lens.
• This aspect is particularly interesting because many applications may require the use of multibeam antennas: automobile collision radar (77 GHz), indoor communications (60 GHz), satellite television reception, high-speed space communications ...

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• 2005
  • 2005-07-05 FR FR0507188A patent/FR2888407B1/fr not_active Expired - Fee Related
• 2006
  • 2006-07-05 EP EP06764069.8A patent/EP1900064B1/de not_active Not-in-force
  • 2006-07-05 US US11/994,769 patent/US20100134368A1/en not_active Abandoned
  • 2006-07-05 WO PCT/EP2006/063912 patent/WO2007003653A1/fr active Application Filing

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