Classifications

• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01Q—ANTENNAS, i.e. RADIO AERIALS
  • H01Q15/00—Devices for reflection, refraction, diffraction or polarisation of waves radiated from an antenna, e.g. quasi-optical devices
  • H01Q15/02—Refracting or diffracting devices, e.g. lens, prism
  • H01Q15/10—Refracting or diffracting devices, e.g. lens, prism comprising three-dimensional array of impedance discontinuities, e.g. holes in conductive surfaces or conductive discs forming artificial dielectric
• • 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
  • H01Q3/14—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 the relative position of primary active element and a refracting or diffracting device

Definitions

• the invention relates to the treatment of microwave waves, and in particular the deflection of a microwave beam. More specifically, the invention relates to a configurable deflection system.
• the invention applies for the treatment of a microwave beam, corresponding to frequencies between 300 MHz and 300 GHZ, typical wavelength of 1 mm to 1 m.
• the antenna For pointing, the antenna must be configured to transmit / receive a wave in a direction of the given space.
• it is increasingly necessary to redirect an antenna following the update of the coverage of the territory. For example, each antenna withdrawal is followed by a repositioning of neighboring antennas.
• the coverage of the territory is in perpetual change because we constantly seek to improve coverage while optimizing costs, thus minimizing the number of antennas. It also happens that some antennas must be removed or moved, which gives rise to a reorientation of neighboring antennas.
• an antenna called “smart” and “remote”, “intelligent” for their ability to orient themselves to cover different areas in space and “remote” for their ability to be remotely controllable to from a central office.
• the antenna For “tracking” or tracking, the antenna must be configured to follow a target, such as a satellite.
• a first solution is mechanical.
• the disadvantages are the addition of an additional mechanical system, in mass / volume (compared to the rental of a mast), a sphere of large size, seen from the outside, which changes volume according to its orientation, reliability (especially if you want a "remote” antenna), maintenance costs and preventive maintenance.
• Another type of antenna called “electronic scanning” are electrically adjustable.
• the antenna consists of different radiating elements or elementary antennas mounted in a network and to each of which is associated a phase shifter. These phase shifters make it possible to inject different phases so as to generate a deflection of the beam.
• a complex system an elementary antenna phase shifter and a phase shifter are required, hence an associated power supply.
• elementary phase shifter which requires good cable management.
• the wires are often integrated into printed circuits to facilitate the "management" of the cables;
• Phase shifters in some cases have difficulty supporting the power from which a limitation in power
• FIG. 1 describes the operating principle of such a deflector.
• An antenna emits radiation to two prisms arranged "back to back”, rotated relative to each other along an axis ZZ 'perpendicular to the emission surface, and independently.
• the incident radiation is deflected in a given direction, depending on the index of the material or materials constituting the prism and its apex angle.
• the total deflection angle ⁇ provided by the set of two prisms depends on the rotation angles of the two prisms.
• a disadvantage of this system for its microwave application is the size of the deflector resulting from the thickness of the prisms.
• the document FR 2945674 discloses the use of discs of constant thickness, refractive index increasing linearly from one end to the other end of the disc to obtain the deflection of the electromagnetic wave passing through the disc.
• This solution makes it possible to have two flat-faced components and thus to avoid unbalance effects.
• this solution offers a footprint related to the thickness similar to that of a solid prism for an equivalent deflection.
• the greater the diameter (or opening) of the deflection system the greater the diameter of the components, which will increase their thickness (with fixed material) for get the desired deviation, resulting in a component that is more cumbersome.
• the document FR 2570886 also describes the use of structures on the faces of the prisms, to produce a matching layer providing an antireflection function.
• the documents FR 2570886 and FR 2945674 also describe the possibility of replacing the prism by a diffraction grating in echelettes, called "zoned prism".
• the thickness of the prism is reduced by the creation areas for which the differential phase difference between the material constituting the prism, a dielectric material with a high refractive index (greater than the index of air), and air, is equal to 2 ⁇ between each zone.
• the height h of the echelette is given by the formula:
• ⁇ design wavelength of the device typically equal to the wavelength of the incident microwave beam and n index of the material.
• the period P of the network determines the angle at which diffraction of the grating occurs.
• the diffraction angle ⁇ that the first-order diffracted beam, called the main diffracted beam, F0 with the normal to the grating
• the component thus has a smaller footprint than the prism.
• the thickness of the component no longer depends on the size of the system (diameter or opening of the system), which is a major advantage when the opening of the system is large.
• this solution is suitable when the total deflection angle is less than about 10 °, ie an angle of 5 ° per grating.
• this solution is no longer suitable because it induces increasing losses with the diffraction angle, because of the effect of 'shady.
• the shadow or masking effect is illustrated in Figure 2 by a ray pattern. The part of the Fine incident beam corresponding to zone 21 is not diffracted in the direction ⁇ of the main diffracted beam FO, and a portion 22 of the diffracted beam is lost, inducing a loss.
• the angle of the first-order diffracted beam increases, which corresponds to a period P of the network which decreases, the energy diffracted in the other orders of the network or secondary orders increases, also inducing a loss on the efficiency of diffraction of the grating, and thus on the intensity of the microwave beam deflects.
• the object of the invention is to overcome the aforementioned drawbacks, by proposing a compact and light deflection system, making it possible to obtain high angles of deflection, a high efficiency on the main diffraction order corresponding to the main direction of the deflection , and a strong attenuation of the other orders of diffractions.
• a configurable deflection system of an incident microwave beam having a wavelength in a wavelength range corresponding to the microwave frequencies comprising:
• a first and a second diffractive dielectric component each capable of rotating about an axis of rotation Z
• the deflection system being able to generate a microwave beam by diffraction of the incident microwave beam on the first and second components, the microwave beam being oriented at an angle depending on the angular positioning between the first and the second diffractive components,
• the first and second components respectively having a first and second periodic structure of first and second periods along a first and second axis, the first and second structures respectively comprising a plurality of first and second primary microstructures formed respectively on a first and a second second first index substrate and second substrate refractive index,
• the first and second primary microstructures respectively having at least a first and a second primary size less than the ratio between a target wavelength chosen in the range and respectively the first and second refractive index substrate, the first and second primary microstructures; being arranged to form an artificial material respectively having a first variation of a first effective refractive index and a second variation of a second effective refractive index respectively following said first and second periods.
• the primary microstructures are formed in the body of the first and second substrates.
• the first primary microstructures have a pillar shape and / or a hole shape.
• the second primary microstructures have a pillar shape and / or a hole shape.
• the primary microstructures have a hexagonal, circular or square section.
• At least one of the periods is sampled according to a sampling period defining sampling intervals, the primary microstructures being arranged within each interval so as to correspond to a given value of effective index. in the meantime.
• the first and / or second primary microstructures respectively have a plurality of first and / or second primary variable sizes respectively along the first period and / or the second period respectively.
• At most one primary microstructure is arranged per sampling interval.
• the first and / or second primary microstructures respectively have a first and / or a second principal size given and a density per unit of variable area along respectively the first and the second period.
• the system according to the invention further comprises at least a plurality of secondary microstructures of secondary sizes smaller than the primary sizes.
• a secondary microstructure at most is arranged by sampling interval.
• the first component and / or the second component is perpendicular to the axis of rotation Z.
• the first period is less than or equal to the second period.
• the incident beam is a collimated beam.
• the generated microwave beam comprises a deflected main beam of main lobe relative gain and a plurality of diffracted beams parasitic relative gains of lobes, and the first and second variations respectively of the first and second effective indices are adapted so that each of the differences between the relative gain of the main lobe and one of the relative gains of the spurious lobes is greater than or equal to 10 dB when the incident microwave beam has a wavelength equal to said target wavelength.
• an antenna comprising a microwave source disposed substantially at the focus of a dielectric lens so as to generate a collimated beam and a deflection system according to one of the aspects of the invention. invention.
• the antenna according to the invention comprises a microwave waveguide capable of generating a collimated beam and a deflection system according to one of the aspects of the invention.
• FIG. 2 already cited, illustrates the shading effect induced by a scaled grating at high diffraction angles.
• FIG. 3 illustrates an exemplary deflection system according to the invention.
• FIG. 4 describes an example of a diffractive component according to the invention
• FIG. 5 illustrates the notion of effective index for the example described in FIG. 4
• FIG. 6 describes another example of a diffractive component according to the invention
• FIG. 7 illustrates the notion of effective index for the example described in FIG. 6.
• FIG. 8 describes several variants (FIG. 8a, 8b and 8c) of the embodiment of a diffractive component according to the invention comprising secondary microstructures.
• FIG. 9 describes another variant of the embodiment comprising secondary microstructures
• FIG. 10 schematically illustrates the variation of effective index obtained with the microstructures described in FIG. 9.
• FIG. 11 illustrates the compared behavior, by numerical simulation, of three deflection systems.
• FIG. 12 describes the phase induced by the three deflection systems illustrated in FIG.
• FIG. 13 illustrates the comparative behavior of three deflection systems according to the invention.
• FIG. 14 illustrates an antenna variant comprising a deflection system according to the invention
• FIG. 15 describes another antenna variant comprising a deflection system according to the invention
• FIG. 3 represents an exemplary deflection system 1 of a Fine incident microwave beam according to the invention.
• Fine incident beam has a wavelength in a range of wavelengths corresponding to microwave frequencies, typically a wavelength of between 1 mm and 1 m.
• the deflection system 1 comprises at least two diffractive dielectric components, a first diffractive dielectric component C1 and a second diffractive dielectric component C2.
• the components C1 and C2 are able to perform each, and independently, a rotation about a Z axis.
• the deflection system 1 is capable of generating a microwave beam F from the incident microwave beam Fine.
• Components C1 and C2 are diffractive networks able to diffract a beam.
• the component C1 illuminated by the incident beam Fine diffracts a first beam, this beam then being itself diffracted by the second component C2, generating the beam F of the system 1.
• the beam F is oriented at an angle depending on the angular positioning between the first diffractive component C1 and the second diffractive component C2 according to the principle of the diasporameter.
• the first diffractive dielectric component C1 has a first periodic structure of first period P1 along an axis X1.
• the first structure comprises a plurality of first primary microstructures MS1 p formed on a first substrate S1 having a first refractive index substrate n1 s.
• microstructures MS2p in a period P2 is such that they form an artificial material having a second variation of the effective index n2eff.
• the effective index nl eff varies according to the period P1 as a function of an abscissa x n1 eff (x), between a first minimum value nl min and a first maximum value n1 max, with n1 min ⁇ n1 max. Since the network is in contact with the air, n1 min is greater than or equal to 1.
• the effective index n2eff varies according to the period P2 as a function of an abscissa x n2eff (x) between a second minimum value n2min and a second maximum value n2max, with n2min ⁇ n2max. Since the network is in contact with the air, n2min is greater than or equal to 1.
• the sub- ⁇ MS1 p and MS2p microstructures are formed in the body of their respective substrate S1 and S2.
• the microstructures are thus easier to manufacture, the manufacturing technique being, for example, mechanical or laser machining of the substrate, molding, sintering or 3D printing.
• the values of nl max and n2max can not exceed the index value of the corresponding substrate, thus:
• the beam F generated by the system 1 comprises several beams:
• the parasitic diffracted beams can be indexed by an index i corresponding to the order they correspond to, and denominated Fd (i) with i ⁇ 1.
• the set of these parasitic beams is denominated globally Fd, thus:
• the variation of the effective index induces a phase variation on the incident beam on the component.
• the periodic structure of the effective index variation induces a periodic structure of phase variation.
• phase variation induced by the effective index variation over a period P is substantially equal to 2 ⁇ (within 10%) between one end of the period and the other end of this same period.
• the use of sub- ⁇ microstructures thus makes it possible to achieve an optimized phase law so that the energy radiated in the main deflected beam is favored, and the energy diffracted in the parasitic diffracted beams is minimized.
• the optimization is performed on the complete system comprising at least two diffractive dielectric components.
• the period and phase law over one period is not necessarily identical for the first component C1 and the second component C2.
• the phase law, and therefore the effective index variation, over a period is almost monotonous.
• the phase law, and therefore the effective index variation, over a period is constant by subintervals, that is to say variable in steps.
• the primary microstructures are arranged according to different variants. These variants are applicable to the first diffractive dielectric component C1 and to the second diffractive dielectric component C2 independently.
• the primary microstructures MSp are arranged at a periodicity P along an axis X.
• microstructures are formed in a dielectric material either protruding, in the form of pillars, or hollow, in the form of holes. A combination of holes and pillars is also possible.
• the pillars and / or the holes are made directly in the substrate for example by the manufacturing methods described above.
• the microstructures are of any shape, preferably with axes of symmetry to make them independent of the polarization of the incident beam at normal incidence, which allows a behavior of the deflection system according to the invention which is not very sensitive to polarization.
• the microstructures according to the invention have a square, hexagonal or circular section, or a combination of different geometries.
• the period P of the network (P1 and / or P2) is sampled according to a sampling period Pe (P1e and / or P2e) less than P (P1 and / or P2) dividing the period P and defining intervals sampling li indexed by an index i.
• the primary microstructures (MS1 p, MS2p) are arranged within each interval li of dimension Pe so as to correspond to a given value of effective index neff (i) in said interval.
• the index variation effectiff neff (n1 eff and / or n2eff) according to the period P is thus sampled according to a period Pe.
• the sampling period Pe is chosen greater than or equal to Ao / 10.ns.
• FIG. 4 describes a diffractive dielectric network C according to the invention that may correspond to C1 or C2, composed of primary microstructures MSp in columns distributed periodically according to a period Pe, their primary size dp being variable. along the period P. It is the variation of their size which allows the variation of the effective index neff according to the period P.
• FIG. 4a corresponds to a profile view
• FIG. 4b to a view from above of the component vs.
• a primary microstructure MSp at most (MS1 p and / or MS2p) is arranged at sampling interval li.
• the size of the microstructure dp (dp1 and / or dp2) varies from one interval to another.
• the gap without microstructure is equivalent to an effective index equal to the refractive index of air.
• FIG. 5 illustrates the notion of effective index for the variant described in FIG. 4 and gives an example of a calibration curve for determining the dimension of the pillar corresponding to a chosen effective index value.
• FIG. 5 represents the variation of the effective index neff as a function of the surface filling ratio of the microstructures, which varies between 0 and 1.
• the target wavelength ⁇ is 7.14 mm, corresponding to a frequency of 42 GHz.
• the period Pe is in this example equal to 0.336x ⁇ .
• the points P1 to P5 shown in FIG. 5 correspond on the abscissa to five size values of microstructures, and therefore to five different values of surface filling ratio.
• the surface filling ratio is schematically represented by a top view of each square section pillar 38 centered per surface unit 40.
• the zone 38 represents the dielectric material constituting the pillar, the zone 42 corresponds to the air, ie the zone left empty around the pillars. On the ordinate one can read the value of the effective index corresponding to each case.
• the D0 side of the square section of each pillar is 0.322x ⁇ or 2.3 mm, which corresponds to an effective index of 2.28.
• the absence of a pillar corresponds to an effective index equal to the index of the air 1 and a complete covering of the surface by the microstructures corresponds to the value of the index of the substrate 2.54.
• the value of the effective index is a function of the surface filling ratio.
• a diffractive dielectric network C is composed of microparticles of pillar MSp 'of constant size, and of density per unit of variable area along the period P. It is the variation of their density which allows the variation of the effective index neff according to the period P. The method of manufacturing the component is thus facilitated.
• FIG. 6a corresponds to a profile view
• FIG. 6b shows a front view of component C.
• Graph 72 corresponds to holes of the same size.
• the white areas correspond to the air, the hatched areas to the presence of material.
• the different surface densities are schematically described at different points on the curves.
• the value of the effective index is a function of the surface filling ratio. In order to obtain a component easy to manufacture, it is generally sought to minimize the height of the microstructures.
• the two geometries namely pillars and holes, are combined to reduce the height of the microstructures.
• the component C (C1 and / or C2) further comprises at least a plurality of secondary microstructures MSs (MS1 s and / or MS2s) of secondary size ds (di s and / or d2s) lower at the size DO (d1 p and / or d2p) corresponding primary microstructures MSp.
• the secondary microstructures are arranged in a second layer on the first layer of the primary structures MSp (MSI p and / or MS2p).
• the secondary microstructures are preferably pillars or holes or a combination of both, and preferably have shapes such as squares, hexagons or circles.
• Figure 8 illustrates several variants ( Figure 8a, 8b and 8c) of the embodiment including secondary microstructures.
• the component C (C1 or C2) comprises primary microstructures MSp of variable size in the form of a pillar in a first layer, and secondary microstructures MSs also in the form of a pillar arranged in a projection in a second layer.
• the secondary pillars of size ds are located on the primary pillars (8a, 8b, 8c) and / or between them (8a).
• FIG. 9 illustrates another variant of the embodiment comprising secondary microstructures.
• Figure 9a is the profile view and Figure 9b is the top view of component C (C1 and / or C2).
• the component C (C1 and / or C2) comprises primary microstructures MSp (MS1 p and / or MS2p) of variable size dp (d1p and / or d2p) along the period P (P1 and / or P2), such as 4, in the form of a square pillar.
• the period P is sampled according to a sampling period Pe (P1e and / or P2e), and there is at most one primary structure per interval li.
• the component C (C1 and / or C2) also comprises secondary microstructures MSs (MS1 s and / or MS2s) in the form of square holes of variable size ds (di s and / or d2s).
• At most one secondary microstructure is arranged at sampling interval li.
• a primary microstructure in the form of a square pillar is perforated by a secondary microstructure in the form of a hole of square section.
• the secondary microstructures are centered on the corresponding primary microstructure disposed in the same sampling interval.
• FIG. 10 schematically illustrates the variation of effective index neff (i) obtained with the microstructures described in FIG. 9.
• the actual index neff (i) given is generated for each interval.
• the plane X1 Y1 of the component C1 and / or the plane X2Y2 of the component C2 is / are perpendicular to the axis of rotation Z.
• the diffraction angle of the main order of the deflection system 1 is greater than or equal to 60 ° in absolute value, in order to obtain a total deflection amplitude comprised in a cone of at least 120 °.
• the periods P1 and P2 have distinct values, with P1 ⁇ P2, for a finer optimization of the deflection system 1.
• component P1 is illuminated by the incident beam at normal incidence
• component C2 is illuminated by the beam diffracted by component C1 at an angle of incidence greater than 0 °.
• the period P2 of the component C2 is greater than the period P1 of the component C1.
• the incident beam Fine illuminates the first component C1 at normal incidence for better operation of the deflection system according to the invention.
• ladder composed of two identical conventional ladder-type gratings.
• the phase ⁇ induced by a scaled network is illustrated in FIG. 12a.
• the index of the material is 1 .59 and the height of the echelette is 16.9 mm to induce a phase variation of 2 ⁇ over a period P.
• the effective index values neff (i) and the height of the microstructure are calculated to induce a phase variation close to 2 ⁇ over a period P in a linear stepwise manner.
• the sides of the pillars vary between about 0.8 mm and 2.5 mm increasing, and the sampling period Pe is equal to about 2.5 mm -a deflection system according to the invention called "optimisel" composed of two identical components C1 and C2 as shown schematically in FIG. 9, with also 9 sampling intervals.
• phase ⁇ induced by an "optimized 1" network (C1 or C2) according to the invention is illustrated in FIG. 12c.
• the index of the material is 3.4 and the height of the component is about 10 mm.
• the sides of the pillars vary between about 1.8 mm and 2.5 mm non-linearly, and the sampling period Pe is about 2.5 mm.
• These pillars are holed with square side holes varying between 1 .4 mm and 2.4 mm.
• the arrangement of the structures is optimized to minimize diffracted energy in spurious diffraction orders.
• the planes of the substrates of the components are perpendicular to the Z axis.
• the axes X1 and X2 are parallel, there is no angular difference between the two components C1 and C2.
• the behavior of the deflection systems described above is simulated in FIG. 1 1 by calculating the angular distribution of the energy ⁇ ( ⁇ ) expressed in dB, referred to as the relative gain D, according to the formula:
• the figure gives the relative gain of the antenna in a maximum deflection configuration as a function of the angle ⁇ , which corresponds to the observation direction in the plane Oxz with respect to the axis Z (axis of rotation of the components) .
• a curve D (0) shows:
• Ls secondary lobes generally called Ls arranged on either side of the main lobe and lattice lobes, and attenuated with respect to the lobes around which they are arranged.
• Curve 1 corresponds to D (0) for the deflector constituted by conventional ladder gratings.
• the curve 1 1 1 corresponds to D (0) for the deflector according to the invention "pseudo echelette".
• Curve 1 12 corresponds to D (0) for the deflector according to the invention "optimisel".
• the efficiency D0 is defined as the value in dB of the relative gain of the main lobe L0, at the minimum of attenuation.
• Dd (0) corresponds to the rejection in the mechanical main axis.
• This relative difference is expressed in dBc (decibel relative to carrier) and corresponds to the level in dB relative to the main lobe.
• the ladder deflector has a main relative gain of -3 dB
• the "pseudo-ladder” deflector has a main relative gain of -3 dB
• the "optimized” deflector a major relative gain of -2 dB.
• the echelette network lobes are important and either not or only slightly more attenuated than the main lobe. These lobes are troublesome in some applications and must be minimized for proper operation of the deflector. In general, we try to attenuate all the lobes of networks.
• the deflectors according to the invention make it possible to obtain relative gain deviations which are greatly increased compared with the state of the art of the deflector ladder.
• the simulation of the behavior of the system according to the invention comprising sub- ⁇ microstructures makes it possible to identify variations n1 eff (x) and n2eff (x) resulting in performance of the deflection system according to the invention. higher than those of a deflection system obtained with conventional ladder type gratings.
• first and second variations respectively of the first and second effective index nl eff, n2eff are adapted to synthesize first and second phase law (each advantageously monotonic or near monotonic) to control the radiation of the antenna, and more particularly to maximize the level of the main lobe L0 and minimize the lobe lobe levels Ld.
• each of the differences between the relative gain of the main lobe DO and one of the relative gains of the spurious lobes Dd is greater than or equal to 15 dB when the incident microwave beam Fine has a wavelength equal to the target wavelength ⁇ .
• fO is equal to 30 GHz
• the bandwidth is equal to [28.5 GHz; 31.5 GHz].
• the table below gives the levels of the different lobes of the deflection system according to the invention "optimized 3" for three different values of the wavelength of the incident beam Fine.
• the minimum deviations are kept higher than 20 dB.
• Another aspect of the invention relates to an antenna comprising a deflection system according to the invention.
• the antenna comprises a microwave source S disposed substantially at the focus of a dielectric lens L so as to generate a collimated beam, and a deflection system according to the invention.
• the dielectric lens L is also manufactured from sub- ⁇ microstructures, as described in FIG. 14.
• the dielectric lens sub- ⁇ is manufactured on the face of the first component C1 facing the microwave source, the network type function for the deflector according to the invention being formed on the other side, as illustrated in FIG.
• the antenna comprises a microwave waveguide capable of generating a collimated beam, and a deflection system according to the invention.

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