Classifications

• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01Q—ANTENNAS, i.e. RADIO AERIALS
  • H01Q9/00—Electrically-short antennas having dimensions not more than twice the operating wavelength and consisting of conductive active radiating elements
  • H01Q9/04—Resonant antennas
  • H01Q9/30—Resonant antennas with feed to end of elongated active element, e.g. unipole
  • H01Q9/32—Vertical arrangement of element
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
  • H01F21/00—Variable inductances or transformers of the signal type
  • H01F21/005—Inductances without magnetic core
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
  • H01F21/00—Variable inductances or transformers of the signal type
  • H01F21/02—Variable inductances or transformers of the signal type continuously variable, e.g. variometers
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
  • H01F5/00—Coils
  • H01F5/003—Printed circuit coils
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01Q—ANTENNAS, i.e. RADIO AERIALS
  • H01Q1/00—Details of, or arrangements associated with, antennas
  • H01Q1/36—Structural form of radiating elements, e.g. cone, spiral, umbrella; Particular materials used therewith
  • H01Q1/364—Structural form of radiating elements, e.g. cone, spiral, umbrella; Particular materials used therewith using a particular conducting material, e.g. superconductor
  • H01Q1/368—Structural form of radiating elements, e.g. cone, spiral, umbrella; Particular materials used therewith using a particular conducting material, e.g. superconductor using carbon or carbon composite
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01Q—ANTENNAS, i.e. RADIO AERIALS
  • H01Q21/00—Antenna arrays or systems
  • H01Q21/0006—Particular feeding systems

Definitions

• the field of the invention is that of microwave devices, such as array antennas.
• Such devices can be used in various applications such as radar applications in avionics and aerospace, high speed communication, space technologies.
• An array antenna is formed by a two-dimensional array of radiating elements.
• the present invention relates to a radiating element, an antenna comprising such a radiating element and a method of manufacturing such a radiating element.
• antennas exist, varying according to the intended applications, for example according to the wavelength and the power, or else the spectral characteristics of the desired emission.
• many types of antennas include a set of radiating elements, also called elementary antennas.
• the radiating elements make it possible, by controlling their arrangement, their conformation or the electrical signal which feeds each of them, to improve the gain of the antenna or to control its directivity or the shape of the emitted beam.
• the existing antennas have relatively large dimensions, of the order of several centimeters to several tens of centimeters depending on the frequency and power required by the intended application, and therefore a large volume and weight .
• the large dimensions are inconvenient for certain applications, for example for mobile devices, since an increase in the volume and / or weight of the devices results.
• devices containing large antennas are more difficult to transport.
• the integration of antennas in devices whose geometry is fixed for functions other than communication is, moreover, made difficult.
• a radiating element having a smaller size than the radiating elements of the state of the art.
• a radiating element is proposed for an antenna comprising a set of at least one wire nanostructure, each wire nanostructure extending in the same direction, called the common direction, between a first end and a second end .
• the radiating element also comprises an inductance connected to each first end of a nanostructure, the inductance being made from a first conductive material, the inductance extending in a plane normal to the common direction.
• the first conductive material has an electrical conductivity varying under the effect of a variation in an electric field applied within the first conductive material.
• the inductance is configured so as to have a tunable inductance value with a capacitance of the set of at least one wire nanostructure.
• the first conductive material comprises a semimetal.
• the first material is, for example, graphene, or a transition metal dichalide.
• At least one wire nanostructure is a carbon nanotube.
• the set of at least one wire nanostructure comprises several wire nanostructures.
• each wire nanostructure has an aspect ratio of greater than 20.
• the inductance has a spiral shape.
• the set of at least one wire nanostructure comprises several wire nanostructures.
• the inductance is configured so as to have an inductance value tunable with a capacitance of the set of wire nanostructures.
• the invention also relates to an elementary antenna comprising a first radiating element according to the invention.
• the antenna also comprises a transmission line comprising an area made of a second conductive material and two ground planes, the transmission line extending into the same plane as the inductance and the area being connected to the inductance, each ground plane being made of a third conductive material, the area being arranged between the two ground planes.
• the antenna comprises a variable DC voltage generator capable of applying the electric field within the first conductive material.
• the DC voltage generator is a variable DC voltage generator
• the DC voltage generator is able to apply a variable electric field within the first conductive material.
• the elementary antenna comprises an electrode in physical contact with the inductance, the voltage generator applying the electric field within the first conductive material through the electrode.
• the invention also relates to an array antenna. It comprises a network of several radiating elements according to the invention. In other words, it comprises several elementary antennas according to the invention arranged so that the radiating elements of the different elementary antennas form an array of radiating elements.
• the inductances of the radiating elements are coplanar or capable of being coplanar.
• the array antenna comprises, for example, several radiating elements including a first radiating element according to the invention and a second radiating element according to the invention, the first radiating element and the second radiating element having sets of at least a wire nanostructure with different capacities.
• Figure 1 is a diagram of an antenna comprising a set of radiating elements and a set of transmission lines
• Figure 2 is a sectional view of a radiating element of the invention and a transmission line of Figure 1, the radiating element comprising a bundle of nanostructures
• Figure 3 is a top view of a bundle of nanostructures
• Figure 4 is a top view of the radiating element and the transmission line of Figure 2,
• FIG. 5 schematically represents a curve of values of the kinetic inductance of an inductor formed of a plurality of monoatomic layers of graphene as a function of a voltage applied to the terminals of the inductance
• FIG.6 is a schematic representation of a radiating element according to the invention associated with an adjustable DC voltage generator, the radiating element comprising a beam of nanostructures,
• FIG. 7 is a schematic representation of curves of real (solid lines) and imaginary (dotted lines) values of an input impedance of an antenna as a function of frequency
• Figure 8 shows a curve representing the reactance of a beam of nanowire nanostructures as a function of frequency
• Figure 9 shows a first embodiment of an array antenna comprising a one-dimensional array of radiating elements according to the second embodiment.
• Figure 10 shows a first embodiment of an array antenna comprising a one-dimensional array of radiating elements according to the second embodiment.
• FIG. 11 is a flowchart of the steps of a method for manufacturing a radiating element.
• An antenna 10 is shown in Figure 1.
• the antenna 10 is configured to emit and / or receive a set of electromagnetic waves.
• antenna 10 is configured to transmit and receive a set of electromagnetic waves.
• the electromagnetic wave has a frequency between 3 kilohertz (KHz) and 300 gigahertz (GHz). It should be noted that the frequency of the electromagnetic wave is liable to vary according to the applications envisaged for the antenna 10.
• the antenna 10 comprises a substrate 15, radiating elements 20 and transmission lines 25.
• the antenna 10 has a transmission line 25 for each radiating element 20.
• the antenna 10 comprises a single radiating element 20 and a single transmission line 25.
• the antenna 10 further comprises an electrical ground such as a metal frame.
• the electrical ground is an electrical circuit connected to the earth.
• the substrate 15 is provided to support the radiating elements 20 and the transmission lines 25.
• the substrate 15 has a support face 30.
• the support face 30 is flat.
• a normal direction Z is defined as being the direction perpendicular to the support face 30.
• the Z axis defined by the Z direction and oriented in the direction of the substrate towards the radiating elements is also defined.
• the substrate 15 comprises a support plate 35 and a buffer layer 40.
• the support plate 35 is configured to serve as a support for the buffer layer 40, the radiating elements 20 and the transmission lines 25.
• the support plate 35 is, for example, made of silicon. According to one variant, the support plate 35 is made of alumina.
• the support plate 35 has, for example, a thickness between 200 micrometers (pm) and 500 pm.
• the support plate 35 is made of a material having electrical resistivity.
• the electrical resistivity is, for example, greater than or equal to 10,000 Ohm. centimeter. Such an electrical resistivity makes it possible to limit the radiofrequency losses in the support plate 35. It should be noted that a material other than silicon is likely to be used to make the support plate 35.
• the buffer layer 40 is interposed between, on one side, the support plate 35 and, on the other hand, on the other hand, the radiating elements 20 and the transmission lines 25.
• the buffer layer 40 is delimited in the normal direction Z by the support plate 35 and by the support face 30.
• the buffer layer 40 is made of an electrically insulating material.
• the buffer layer 40 is, for example, made of silicon oxide.
• the buffer layer 40 has a thickness, in the normal direction Z, of between 500 nanometers and 5 micrometers.
• the thickness of the buffer layer 40 is equal to 2 micrometers.
• FIG. 1 A sectional view of a radiating element 20 in a plane parallel to the normal direction Z is shown in Figure 2.
• Each radiating element 20 is configured to emit and / or receive an electromagnetic wave.
• Each radiating element 20 comprises a beam F of nanostructures 45 and an inductor 50.
• the bundle or bundle F comprises at least ten nanostructures 45.
• the bundle comprises for example thousands or millions of nanostructures 45.
• the radiating element 20 comprises a single nanostructure 45.
• nanostructure is understood to mean a structure having at least one nanometric dimension.
• a dimension of an object, measured in one direction, is the distance between the two points of the object furthest from each other in said direction.
• a nanometric dimension is a dimension strictly less than 1 micrometer, preferably strictly less than 100 nanometers.
• a direction D is defined for each nanostructure 45. This means that each nanostructure 45 extends in the direction D defined for the nanostructure 45 considered.
• the direction D of each nanostructure 45 is parallel to the normal direction Z.
• Each nanostructure 45 has a first end 55 and a second end 60. Each nanostructure 45 extends between the first end 55 and the second end 60.
• the direction D is, for example, parallel to the normal direction Z.
• the direction D is common to all the nanostructures 45 of the same radiating element 20.
• a diameter measured in a plane perpendicular to the direction D is defined for each nanostructure 45,
• each nanostructure 45 is between 2 nanometers (nm) and 10 nm.
• each nanostructure 45 is between 300 ⁇ m and 1 millimeter (mm). In particular, the length of each nanostructure 45 is greater than or equal to 500 ⁇ m.
• each nanostructure 45 is measured along the common direction D.
• Each nanostructure 45 is a wire nanostructure.
• a wire structure is a structure having a length strictly greater than 10 times the diameter.
• the ratio of the length to the numerator and the diameter to the denominator is called the “aspect ratio” also called the aspect ratio.
• each nanostructure 45 is such that the aspect ratio is strictly greater than 20.
• Nanotubes are examples of wire nanostructures 45. Nanotubes are hollow wire structures having a diameter of less than 100 nanometers.
• a nanotube is a hollow wire nanostructure.
• beam is understood to mean a set of nanostructures 45 in which the nanostructures 45 are spaced from each other by a distance less than or equal to the length of the nanostructures 45.
• the distance between the nanostructures 45 is measured in a plane perpendicular to the common direction D.
• the distance is less than or equal to half the length, for example less than or equal to one fifth of the length, in particular less than or equal to one tenth of the length.
• a median value is defined for the length of the nanostructures 45 of the same beam F.
• the median value is a value such that half of the nanostructures 45 of the beam F considered have a length greater than or equal at the median value, the other half having a length less than or equal to the median value.
• the lengths of the nanostructures 45 of the beam considered vary between 50 percent (%) and 150% of the median value.
• the median value is, for example, greater than or equal to five hundred micrometers.
• a total length is defined for the beam F.
• the total length is, for example, defined as being the length of the longest nanostructure 45 among all of the nanostructures 45 belonging to the beam F.
• the total length is, for example, identical for each beam F.
• the total lengths of at least two F beams are different from each other.
• the beam has an envelope common to all the nanostructures.
• envelope is understood to mean a surface enveloping the nanostructures 45 and tangent to the nanostructures 45 which delimit the beam F in a plane perpendicular to the common direction D.
• a maximum lateral dimension is defined for the envelope.
• the maximum lateral dimension is the largest dimension of the envelope in a plane perpendicular to the common direction D.
• the maximum lateral dimension is between 10pm (or 20pm) and 1mm.
• An aspect ratio equal to the ratio between, in the numerator, the total length of the beam F and, in the denominator, the maximum lateral dimension, is defined for the beam F.
• the aspect ratio of the beam F is, for example, between 5 and 15. According to one embodiment, the aspect ratio of the beam F is less than or equal to 10. It is, for example, included between 9 and 10.
• the bundle F typically has a total length of between 100 micrometers and 1mm and a diameter of between 10 micrometers and 100 micrometers.
• the aspect ratio depends on the target transmission or reception frequency, that is to say depending on the target resonant frequency.
• the beam or bundle F is advantageously configured to resonate at a frequency between 1 GHz and 100 GHz.
• the beam F is shown seen in the common direction D in Figure 3.
• the envelope has a cross section to the common direction D of circular shape.
• the section of the beam F has a circular shape, or even a polygonal shape such as a rectangular or rectangular shape. crossed.
• the nanostructures 45 are all made of the same material.
• each nanostructure 45 is a carbon nanotube.
• each nanostructure 45 is a double-layered carbon nanotube.
• the carbon nanotubes are likely to be single-sheet carbon nanotubes, multi-wall carbon nanotubes or MWCNT with reference to the English expression “multi-wall carbon nanotubes” or even a mixture of Single-layered carbon nanotubes and multi-layered carbon nanotubes.
• other types of wire nanostructures 45 are likely to be used in place of carbon nanotubes.
• the carbon nanotubes are advantageously aligned vertically. In other words, the carbon nanotubes extend longitudinally in the same direction D. It should be noted that other types of wire nanostructures 45 are likely to be used instead of carbon nanotubes.
• the nanostructures 45 are nanowires, for example nanowires of silicon or of another semiconductor material.
• the nanostructures 45 are made of an electrically conductive material such as a metallic material.
• each radiating element 20 extends in a plane normal to the common direction D.
• Each inductor 50 is, for example, produced in the form of a conductive layer carried by the substrate 15.
• each inductor 50 is perpendicular to the normal direction Z and to the common direction D.
• the inductance 50 is carried by the buffer layer 40.
• the inductor 50 is made from a first conductive material.
• each inductor 50 has a first portion 65 and a second portion 70.
• the first portion 65 extends in a plane perpendicular to the normal direction Z.
• the first portion 65 is interposed between the beam F of nanostructures 45 and the substrate 15.
• the first portion 65 is connected to the first end 55 of each nanostructure 45.
• the first portion 65 has a triangular shape in a plane normal to the common direction D.
• first portion 65 has a circular or square shape.
• second portion 70 extends in a plane perpendicular to the normal direction Z.
• a maximum dimension is defined for the second portion 70.
• the maximum dimension is measured in a plane perpendicular to the normal direction Z between the two points of the second portion 70 which are the most distant from each other.
• the maximum dimension 70 is between 100 ⁇ m and 1 mm.
• the maximum dimension 70 is between 200 ⁇ m and 500 ⁇ m. It should be noted that the maximum dimension 70 is liable to vary.
• the second portion 70 has a spiral shape in a plane perpendicular to the normal direction Z.
• the second portion 70 surrounds the first portion 65 in a plane perpendicular to the normal direction Z.
• the second portion 70 is formed by a succession of straight segments.
• each line segment is perpendicular to the line segments to which it adjoins.
• a curved part of the second portion 70 is interposed between two contiguous straight line segments.
• the second portion 70 is formed by a single curve wound on itself.
• the second portion 70 has a third end 75 and a fourth end 80.
• the second portion 70 extends spirally from the third end 75 to the fourth end 80.
• the third end 75 is the end of the second portion 70 which is located on the periphery of the second portion 70 in a plane perpendicular to the normal direction Z.
• the fourth end 80 is the end of the second portion 70 which is located at the periphery of the first portion 65 in a plane perpendicular to the normal direction Z.
• the fourth end 80 is therefore surrounded by the rest of the second portion 70 in a plane perpendicular to the normal direction Z.
• the fourth end 80 is connected to the first portion 65.
• the transmission line 25 extends in the same plane as the inductor 50.
• the transmission line 25 is produced in the form of a layer carried by the substrate 15.
• the transmission line 25 comprises a conductive zone 85 and at least one ground plane 90.
• the transmission line 25 shown in FIG. 4 comprises two ground planes 90.
• the conductive zone 85 is connected to the inductor 50.
• the conductive zone 85 is connected to the third end 75 of the inductor 50.
• the conductive zone 85 is configured to receive an electric current from the inductor 50. Such a current is generated in particular by the inductor 50 following the reception of an electromagnetic wave.
• the conductive zone 85 is further configured to receive an electric current from an external electric source to the antenna 10 and to supply the inductor 50 with said electric current.
• the conductive zone 85 has, for example, a rectangular shape.
• the conductive zone 85 has a thickness measured in the normal direction Z.
• the thickness of the conductive zone 85 is between 100 nanometers and 1 micrometer.
• the thickness of the conductive zone 85 is equal to 600 nanometers.
• the conductive zone 85 is made of a second conductive material.
• the second conductive material is, for example, a metallic material.
• the second conductive material is, for example, molybdenum.
• the second conductive material is the same material as the first conductive material.
• Each ground plane 90 is connected to the ground of the antenna 10.
• Each ground plane 90 has a thickness measured in the normal direction Z.
• the thickness of each ground plane 90 is between 100 nanometers and 1 micrometer.
• each ground plane 90 is equal to 600 nanometers.
• Each ground plane 90 is made of a third conductive material.
• the third conductive material is, for example, a metallic material.
• the third conductive material is, for example, molydbdenum.
• the third conductive material is the same material as the first conductive material.
• each ground plane 90 It should be noted that other conductive materials can be envisaged for each ground plane 90.
• the conductive zone 85 is arranged between the two ground planes 90.
• a distance, in a plane perpendicular to the normal direction Z, between the conductive zone 85 and the ground plane 90 closest to the conductive zone 85 is between 50 ⁇ m and 250 ⁇ m.
• the conductive zone 85 is equidistant from the two ground planes 90.
• the inductance 50 is at least partially interposed between the two ground planes 90.
• a distance between the inductance 50 and the ground plane (s) 90 is between 20 pm and 300 pm.
• each ground plane 90 has an “L” shape. Each ground plane 90 then has a first branch and a second branch, the two branches being perpendicular to each other.
• the first branch of each ground plane 90 extends in the direction of the other ground plane 90 belonging to the same transmission line 25.
• the first two branches of the same transmission line 25 are aligned with each other.
• each transmission line 25 is, for example, interposed between the two first branches of the transmission line 25 considered.
• the two first branches of the same transmission line 25 are, for example, interposed between the two corresponding second branches.
• Each inductor 50 is, for example, interposed between the two second branches of the ground planes 90 between which the inductor 50 is interposed.
• the inductor 50 is housed in a rectangular area delimited on a first side of the rectangular area by the first two branches, on a second side of the rectangular area by one of the second branches and on a third side of the rectangular area by the other second branch, the first side being perpendicular to the second side and 5 to the third side.
• At least one transmission line 25 receives a first electric current.
• the first electric current is transmitted, from a device external to the antenna 10, to the conductive zone 85.
• the conductive zone 85 transmits the first electric current to the inductor 50 of the radiating element 20 connected to the transmission line 25 in question.
• a second electromagnetic wave is received by at least one radiating element 20.
• the second electric current is then transmitted, via the transmission line 25 in question, to a device external to the antenna 10.
• the radiating element 20 has very small dimensions. In particular, the dimensions of the radiating element 20 are smaller than the dimensions of the radiating elements of the state of the art.
• the antenna 10 therefore has a volume and a lower weight than the antennas of the state of the art.
• the combination of the nanostructure (s) 45 and the inductance 50 makes it possible to minimize the length of the nanostructures 45 with respect to a radiating element 20 which does not include an inductance 50.
• An aspect ratio, for the beam F, of between 5 and 15 typically exhibits good mechanical strength while allowing good efficiency of converting electric current into electromagnetic wave and vice versa.
• An aspect ratio of between 9 and 10 is an example of a particularly advantageous aspect ratio for obtaining good mechanical strength and good conversion efficiency.
• the length of the nanostructures 45 and the inductance value of the inductor 50 which varies as a function of the dimensions of the inductor 50, allow the radiating element 20 to be easily adapted to different frequency values.
• antennas 10 having a wide transmission and / or reception band are obtained when total lengths or different inductance values are used for certain radiating elements 20.
• Nanostructures 45 having a median length value greater than or equal to 500 nanometers make it possible to obtain good conversion efficiency.
• the spiral shape is a shape making it possible to obtain a particularly compact inductor 50, and therefore a radiating element 20 of particularly small dimensions.
• An antenna 10 in which each inductor 50 is interposed at least partially between the two corresponding ground planes 90 is also particularly compact.
• the inductance 50 is made from a first conductive material.
• the first conductive material is chosen so as to have an electrical conductivity varying under the effect of a variation of an electric field applied within the first conductive material, that is to say within of inductance 50.
• the first material has an electrically controllable electrical conductivity.
• the inductance has an inductance value L which varies under the effect of the electrical conductivity of the first material and therefore under the effect of the variation of the electric field applied to the first conductive material.
• the inductance value varies under the effect of a variation in a voltage U1 applied between two terminals of the first material. It is the voltage U1 that generates an electric field within the inductor 50.
• the first conductive material is distinct from a metal. Metals exhibit a fixed electrical conductivity.
• the first conductive material is advantageously a semimetal.
• the first conductive material is graphene.
• Inductor 50 comprises, for example, a plurality of layers of a first conductive material or a single layer of graphene.
• each graphene layer is an atomic monolayer. In other words, it has a monoatomic thickness.
• Inductor 50 may include only the first conductive material or may include the first material and at least one other material.
• Inductance 50 comprises, for example, an alternation of layers of graphene and layers of another material.
• the other material advantageously has a lower electrical conductivity than that of graphene.
• the other material is, for example, graphene oxide.
• the inductance of an element made of a predefined material comprises a magnetic inductance essentially defined by the geometric characteristics of the element and a kinetic inductance due to the displacement of electrons within the material under tension.
• the inductance of graphene exhibits a remarkable property. The kinetic inductance of graphene is very much greater than its magnetic inductance, which distinguishes it from metals whose kinetic inductance is negligible.
• FIG. 5 there is shown the kinetic inductance L k defined in Hm 1 of an inductor 50 made of graphene. This kinetic inductance decreases as a function of the voltage U1 applied between two faces of the inductor 50.
• the first material may be a transition metal dichalide or TMD, which stands for "transition metal dichalcogenide”.
• the first conductive material is based on one semimetal or on several semimetals.
• a first topological semi-metal comprising the Dirac semi-metal (Cd3As2, Na3Bi) and the Weyl semi-metal (TaAs, NbAs).
• Each inductor 50 has a thickness measured in the normal direction Z.
• the thickness of the inductor 50 is between 100 nanometers and 1 micrometer.
• the thickness of inductor 50 is equal to 600 nanometers.
• Each inductor 50 has an adjustable inductance value by adjusting an electric field applied within the inductor, that is to say by adjusting a voltage applied between two terminals of the inductor 50.
• the antenna according to the invention advantageously comprises, as shown in FIG. 6, a generator G of variable direct voltage making it possible to apply a direct voltage U1 between two terminals F1, FS of the inductor so as to apply a electric field E within the first conductive material 50.
• the direct voltage U1 is applied so that a substantially uniform electric field E of variable value is applied within the first conductive material.
• the electrical conductivity of the first electrically conductive material varying as a function of the electric field to which it is subjected, the electric conductivity is adjustable by adjusting the electric field.
• the inductance value L of the inductor 50 varying as a function of the electrical conductivity of the first conductive electrical material, the inductance value L varies under the effect of a variation in the voltage U1, c 'that is to say the electric field E.
• the antenna advantageously comprises, as shown in Figure 6, an electrically conductive EL electrode in direct physical contact with the inductor 50.
• variable DC voltage generator G is able to apply a potential difference between the conductive electrode EL and a mass M so that the first conductive material is subjected to a substantially uniform electric field.
• This electric field E extends for example along the Z axis as in the embodiment of Figure 2.
• the inductance 50 extends, along the Z axis, from a lower face F1 in direct physical contact with the substrate 15 and more particularly with the support face 30, to an upper face FS.
• the substrate 15 is attached to a lower conductive plate PC connected to the electrical ground.
• the substrate 15 is interposed, along the Z axis, between the conductive plate PC and the inductor 50.
• the EL electrode is electrically conductive, for example it is metallic.
• the EL electrode is deposited on the upper face FS of the inductor 50.
• the inductor 50 is interposed, along the Z axis, between the substrate 15 and the face. lower Fl of inductor 50.
• the variable direct voltage generator is able to apply a variable direct voltage U between the electrode EL and the lower conductive plate PC so that a voltage U1 is applied between the upper face FS and the lower face DI of the 'inductor 50.
• a voltage U1 is applied between the upper face FS and the lower face DI, the first conductive material is subjected to an electric field E extending along the Z axis.
• variable direct voltage generator is intended to apply a voltage between two coplanar terminals of the inductor 50 so that the first conductive material is subjected to an electric field extending in a plane perpendicular to the Z axis. There is then provided a coplanar electrode and a mass extending in the same transverse plane perpendicular to the Z axis as the inductor 50. The inductor is interposed between the electrode and the mass in this transverse plane according to a direction of the transverse plane. The generator is intended to apply a DC voltage between the electrode and the coplanar ground.
• the resonant mode of the radiating element 20 is mainly capacitive for the bundle F of wire nanostructures and inductive for the inductance.
• a wire nanostructure has a high resistance when it is alone while a bundle F of wire nanostructures has a very low resistance of up to 50 Ohms. It therefore becomes essentially capacitive.
• the wire nanostructures arranged in bundles form an element equivalent to a capacitor C. This distributed capacitance C depends on the number of wire nanostructures, on their diameter and on the form factor.
• inductance L of inductance 50 By matching the value of inductance L of inductance 50 to the capacitance C of the bundle of wire nanostructures 45 at the frequency fo, it is meant to choose the value of inductance L so that the radiating element 20 is resonant. at the frequency f 0 .
• the resonance inductance L value is linked to the frequency f 0 and to the capacitance C of the wire nanostructure F by the following formula:
• a transmitting antenna is a resonant electronic circuit of the RLC type: resistive (R) - inductive (L) - capacitive (C) series or parallel, at a resonant frequency fo.
• This circuit delivers a ZRLC impedance matched at the output to the air impedance (ie 377 Ohms and at the input a reference impedance Z 0 (generally 50 Ohms).
• Z 0 generally 50 Ohms
• the input impedance Z in of the antenna is connected to the ZRLC impedance of the RLC circuit and to the air impedance Z air by the following formula
• the real part of the input impedance is equal to 50 Ohms at the resonance frequency fo
• this real part is suitable for a radiofrequency emission from an input signal usually having a real part of this value.
• Its zero imaginary part is for its part suitable for transmission from the input signal usually exhibiting a zero imaginary part.
• the possibility of varying the inductance value of the inductor 50 makes it possible to obtain the resonance of the radiating element 20 even when the bundle F has, after its growth, a capacitance C which differs slightly from the capacitance. wanted.
• This solution therefore makes it possible to optimize the gain of the antenna by applying a voltage to the inductor 50, the value of which makes it possible to match the inductance value L of the inductance with the capacitance C of the bundle F.
• the electric field ensuring the tuning is advantageously applied during operation of the antenna, that is to say during the transmission or reception of a radiofrequency wave by the antenna in order to ensure tuning at the determined frequency.
• the invention also relates to a method of controlling the antenna in which the first conductive material is subjected to an electric field such that the inductance value of the inductor 50 is matched with the capacitance of the bundle. F at a predetermined frequency, when the antenna transmits or receives an electromagnetic wave at the predetermined frequency.
• the inductance value is matched with the capacitance of the bundle F at a predetermined frequency, it is possible to measure a reflection coefficient of a wave emitted or received by the antenna from which it is possible to deduce and, eg display, real part and imaginary part of antenna input impedance.
• a reflection coefficient of a wave emitted or received by the antenna from which it is possible to deduce and, eg display, real part and imaginary part of antenna input impedance.
• the antenna comprises means for measuring a reflection coefficient of a wave transmitted or received by the antenna and processing means making it possible to adjust the inductance value of an inductor in order to match the value of inductance at the capacitance of the bundle at a predetermined frequency, from measurements of the reflection coefficient measured by the measuring means for different values of a direct voltage applied by the variable direct voltage generator between two terminals of the inductor 50.
• the inductance adjustment can be done collectively for an array antenna.
• the antenna comprises means for measuring a reflection coefficient of a wave transmitted or received by the antenna and processing means making it possible to adjust the inductance values of the inductors 50 of the antenna to substantially match the inductance values to the capacitance of the bundle at a predetermined frequency, from measurements of the reflection coefficient measured by the measuring means for different values of a DC voltage or of applied DC voltages (s ) by one or more generators of variable direct voltage between two terminals of the inductors 50.
• the inductance has an inductance value capable of varying within an interval between 1 nanoHenry and 10 nanoHenrys.
• the inductance value is, for example capable of being equal to 5 nanoHenrys.
• the invention relates to an array antenna comprising two radiating elements each comprising a bundle or set of wire nanostructures).
• the bundles of the two radiating elements have distinct respective capacities.
• the inductance of each radiating element is tunable with the capacitance of the corresponding bundle, that is, with the capacitance of the set of at least one wire nanostructure of the same radiating element.
• FIG. 8 schematically represents the variation in the reactance of a bundle of carbon nanotubes as a function of the frequency of a first electrical signal which is applied to it, for example between 7 and 13 GHz.
• the reactance varies according to the frequency which means that the capacitance of this bundle also varies according to the frequency. Consequently, by varying the voltage U1 to vary the inductance value of the inductor 50, it is possible to tune the whole of the resonant cell formed of the inductor 50 and of a bundle F for several resonance frequencies. . This makes it possible to obtain an antenna emitting or receiving waves with a high gain at different frequencies and therefore exhibiting the behavior of a broadband antenna or a frequency tunable antenna.
• FIG. 9 represents an array antenna 100 comprising a one-dimensional array of radiating elements 20b, only one of which is referenced in FIG. 9 for greater clarity.
• the radiating element 20b differs from that of Figure 6 in that the EL electrode is coplanar with the inductor 50. Alternatively, the EL electrode is deposited on the inductor 50 as in Figure 6.
• the electrode may, as a variant, be partly deposited on the inductor 50 and be partly coplanar with the inductor 50.
• the network could be two-dimensional.
• the antenna 100 comprises a transmission line 25, as described above, for each radiating element 20b.
• the transmission lines 25, and more particularly the conductive zones 85 are electrically connected to a main transmission line LP making it possible to apply the first electric current to each of the conductive zones 85.
• the first electric current is advantageously a radiofrequency signal.
• the ground planes 90 are connected to a PC ground plane located on the rear face, that is to say contiguous to the face of the substrate 15 opposite to the support face 30.
• ground planes are, for example, connected to the ground plane PC by metallized holes VI.
• the EL electrodes of each of the radiating elements 20b are deposited in part on the support face 30.
• the electrodes can be controlled collectively by the same variable DC voltage generator or independently by different generators.
• the antenna may have radiating elements having F beams having different capacities and / or all identical capacities.
• the capacity of each beam is defined by its aspect ratio.
• the antenna 1000 of the embodiment of Figure 10 differs from that of Figure 9 in that the EL electrodes are connected to the ground planes 90 of the radiating elements 20c.
• the radiating elements 20c differ from the radiating elements 20b of Figure 9 in that they are devoid of metallized holes.
• the LP line makes it possible to apply a signal simultaneously comprising a radiofrequency signal and the direct voltage generating the electric field within the inductors 50 thus making it possible to adjust the inductance value of the inductor 50.
• This solution makes it possible to adjust the inductors 50 collectively.
• the capacity of a wire nanostructure depends on its aspect ratio. Therefore, the provision of radiating elements having wire nanostructures having different aspect ratios allows to obtain radiating elements resonating at different frequencies and thus to transmit and / or receive at several frequencies. It is thus possible to produce an antenna formed of radiating elements which radiate at different frequencies. The antenna therefore exhibits broadband antenna behavior.
• the antenna has, for example, a first radiating element having a wire nanostructure having a first aspect ratio and a second radiating element having a nanostructure having a second aspect ratio.
• the antenna has first means making it possible to vary the inductance value of the inductance of the first radiating element and of the second means making it possible to vary the value of the inductance of the second radiating element.
• the antenna has first means making it possible to vary the inductance value of the inductance of the first radiating element independently of the inductance value of the second radiating element and of the second means making it possible to vary the value. of the inductance of the second radiating element independently of the inductance of the first radiating element.
• the first and second means advantageously each comprise a variable direct voltage generator.
• Such an antenna is also easy to manufacture, as illustrated with reference to FIG. 11 which is a flowchart of a method for manufacturing a radiating element 20.
• the manufacturing process comprises a supply step 100, a deposition step 110, an etching step 120, a placement step 130 and a growth step 140.
• the substrate 15 is supplied.
• a layer of the first conductive material is deposited on the substrate 15.
• a transfer deposition comprises a step of exfoliation of a layer of graphene from a block of graphite, in which a carbon monolayer is extracted using an adhesive tape and a step of thermal transfer of the atomic monolayer of carbon onto the substrate 15.
• the layer of the first conductive material is etched to form the inductor 50.
• the etching step 120 comprises, for example, a photolithography step and / or an ion beam etching step.
• Ion beam etching involves projecting a high energy beam of ions, in particular Argon ions, onto the layer to be etched to machine the layer to be etched.
• a catalyst C for the growth of nanostructures 45 is deposited on the inductor 50.
• Catalyst C is a metallic material.
• the most widely used C catalysts for growing nanotubes or nanowires are nickel, cobalt, iron and gold.
• catalyst C is iron.
• Catalyst C is made from an alloy of two or more metals.
• Catalyst C is, for example, in the form of a set of nanoparticles.
• the particles of catalyst C are nanoparticles.
• each particle has three nanometric dimensions.
• each dimension of each particle is strictly between 1 nanometer and 100 nanometers.
• the particles of catalyst C are, for example, obtained by lithography.
• Lithography makes it possible to obtain a perfectly periodic network of particles of catalyst C.
• the particles are obtained by fragmentation and controlled dewetting of a layer of catalyst C deposited on the inductor 50.
• the particles of catalyst C are obtained by spraying, on the inductor 50, a solution comprising these particles.
• the particles are deposited by electrostatic grafting on the inductor 50.
• the particles are, for example, liquid when the catalyst C is at the set temperature Te. This is the case, for example, with silicon nanowires, the growth of which is catalyzed with the help of gold particles.
• the particles are solid when the catalyst C is at the set temperature Te. This is the case, for example, with the growth of carbon nanotubes.
• catalyst C forms a homogeneous layer.
• the catalyst C is deposited so as to form a layer having, in a plane perpendicular to the normal direction Z, a shape identical to the shape of the section of the beam F.
• step 130 of placing a catalyst C by a step of depositing a layer preventing the growth of nanostructures other than on the inductor 50.
• this step of depositing a layer preventing growth comprises an etching step during which an opening is made at the level of the inductor 50 in the layer preventing the growth in order to allow the growth of. a beam F of nanostructures 45.
• At least one nanostructure 45 is obtained.
• the nanostructures 45 grow on the inductor 50 to form a beam F.
• a nanostructure 45 is obtained for each particle of catalyst C.
• the nanostructures 45 are, for example, obtained by chemical vapor deposition.
• Chemical vapor deposition (commonly referred to by the acronym CVD from “Chemical Vapor Deposition”) is a technique frequently used to deposit a material on a substrate. Chemical vapor deposition is carried out in a closed chamber, delimiting a chamber isolated from the outside atmosphere and containing at least one substrate, generally maintained at a high temperature. A so-called “precursor” gas is injected into the chamber and decomposes on contact with the heated substrate, releasing atoms of one or more predetermined elements onto the substrate.
• liberated atoms form between themselves chemical bonds leading to the formation, on the substrate, of the desired material.
• the thermal chemical vapor deposition process also known under the English name "Thermal Chemical Vapor Deposition" is a technique in which the substrate 15 is heated to a high temperature of the order of 600 degrees Celsius or more. is a type of CVD particularly suitable for the growth of carbon nanotubes.
• a plasma is generated in the growth chamber.
• Several radiating elements 20 are manufactured simultaneously. For example, during the etching step 120, the inductors 50 of several radiating elements are formed. During the placement step 130, a catalyst C is deposited on each inductor 50. During the growth step 140, at least one nanostructure 45 is formed on each inductor 50.
• each transmission line 25 is formed, in the layer of first conductive material, during the process. etching step 120.
• the manufacturing process comprises a step of depositing a layer of second conductive material and a step of etching of the layer of second conductive material to form the transmission lines 25.
• Molybdenum is a material which is resistant to the conditions which prevail in a growth frame of nanostructures 45, in particular a CVD frame.
• the inductance 50 and the transmission lines 25 are therefore not degraded during the growth of the nanostructures 45, in particular when the nanostructures 45 are carbon nanotubes.
• Cathodic sputtering is a deposition method for obtaining good quality molybdenum layers.
• the method can include a step of depositing one or more electrodes.
• the electrodes are made from a conductive material, for example molybdenum.
• the step of depositing an electrode comprises depositing the layer of molybdenum by sputtering.
• Cathodic sputtering (also designated under the English term “sputtering”) is a thin film deposition technique in which a target made of material to be deposited is supplied, generally in the form of a solid material, in a deposition chamber and a plasma is formed in a low pressure gas occupying the deposition chamber.
• the application of a potential difference between the target and the walls of the deposition chamber causes bombardment of the target with positively charged species of the plasma.
• the bombardment causes the target to sputter and thus the release into the atom deposition chamber of the material to be deposited.
• the condensation of the atoms thus released on a substrate then forms a layer of the material to be deposited.

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• 2019
  • 2019-11-29 FR FR1913566A patent/FR3103971B1/fr active Active
• 2020
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