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
  • H01Q9/16—Resonant antennas with feed intermediate between the extremities of the antenna, e.g. centre-fed dipole
  • H01Q9/26—Resonant antennas with feed intermediate between the extremities of the antenna, e.g. centre-fed dipole with folded element or elements, the folded parts being spaced apart a small fraction of operating wavelength
  • H01Q9/27—Spiral antennas
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01Q—ANTENNAS, i.e. RADIO AERIALS
  • H01Q17/00—Devices for absorbing waves radiated from an antenna; Combinations of such devices with active antenna elements or systems
  • H01Q17/008—Devices for absorbing waves radiated from an antenna; Combinations of such devices with active antenna elements or systems with a particular shape
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01Q—ANTENNAS, i.e. RADIO AERIALS
  • H01Q11/00—Electrically-long antennas having dimensions more than twice the shortest operating wavelength and consisting of conductive active radiating elements
  • H01Q11/02—Non-resonant antennas, e.g. travelling-wave antenna
  • H01Q11/10—Logperiodic antennas
  • H01Q11/105—Logperiodic antennas using a dielectric support
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01Q—ANTENNAS, i.e. RADIO AERIALS
  • H01Q17/00—Devices for absorbing waves radiated from an antenna; Combinations of such devices with active antenna elements or systems

Definitions

• the present invention relates to a wire antenna capable of operating in at least one predetermined frequency band, comprising a plurality of superposed layers.
• the invention finds applications in particular in the field of electromagnetic listening systems.
• the antennas which are used either singly or in a goniometric network, must operate in a very wide frequency band and in a circular polarization, linear or double linear, respectively corresponding to the ranges of interest of electromagnetic signals in frequency and polarization. It should be noted that the characteristics of an antenna being the same in reception and transmission, an antenna can be characterized either in transmission or in reception.
• These antennas must have the smallest possible footprint and, in particular, a low thickness, in particular to be more easily integrated on carriers. They must also have radiation performance (gain, quality of radiation patterns, etc.) reproducible from one antenna to another, especially for network applications or to allow replacement during a maintenance operation. .
• the radiating element consists of a wire which is shaped to describe, in a so-called radiation surface, a spiral-type or log-periodic pattern.
• the wire is wound on itself so as to form a spiral view in top view.
• This spiral can for example be an Archimedean spiral, a logarithmic spiral, or other.
• the wire is shaped so as to have, in top view, several strands.
• Each strand is inscribed in an angular sector, extends radially and has indentations. The length of each tooth and the distance between two successive teeth of a strand follow a logarithmic progression.
• the radiating element is produced by etching a thin metal layer, for example a copper layer with a thickness of between 2 and 20 ⁇ (micrometers), deposited on a thin support layer. .
• first wired antennae with an absorptive cavity in which the radiating element, etched on a surface of radiation. planar or shaped, is located above an absorbent cavity delimited by metal walls, and filled with a material absorbing electromagnetic waves.
• the radiating element is adapted to emit a wave propagating towards the front of the radiating surface (away from the absorbing cavity) and a wave propagating towards the rear of the radiating surface (towards the absorbent cavity). The latter is absorbed by the absorbent cavity.
• Such an antenna has a large footprint because of the dimensions of the absorbent cavity. It also has a low efficiency since half of the power emitted by the radiating element is absorbed in the absorbent cavity. Finally, the reproducibility of the radio performance of such an antenna is difficult to obtain because of a lack of control of the electromagnetic characteristics of the absorbent material filling the cavity.
• the radiating elements are placed on a charged band electromagnetic structure, called LEBG (for Loaded Electromagnetic Band Gap), on a lower ground plane.
• LEBG for Loaded Electromagnetic Band Gap
• a surface composed of periodic metal patterns connected by resistors is placed in the cavity of the antenna.
• the wave emitted backwards by the radiating element is absorbed in a thin layer consisting of a metallic reflector plane surmounted by metal and LEBG material charged by resistors.
• the radiating element In a third wire antenna of the state of the art, the radiating element, etched on a plane radiation surface, is located above a reflective plane of metal. In this antenna, the wave emitted towards the rear of the radiating surface by the radiating element is reflected towards the front by the reflective plane. During this reflection, the wave is out of phase by an angle ⁇ . The reflected wave propagates forward and interferes, beyond the radiation surface, with the wave emitted forward by the radiating element. This interference is constructive when, for a position of the wavefront, the phases of the waves emitted towards the front and reflected towards the front are close.
• the frequency band of such an antenna is restricted because of the relationship between the operating frequency of the antenna and the distance between the radiation surface and the reflective plane.
• the multiple interactions between the radiating element and the lower ground plane cause degradation of the radiation patterns of the antenna, rendering them unusable for amplitude direction finding applications, for example.
• the radiating element is etched on a high impedance surface (SHI), resting on spaced periodic metal patterns, placed in the antenna cavity and connected to the ground plane by links, also called vias, metallized.
• SHI high impedance surface
• the efficiency band of such an antenna in which the interference between the incident wave and the reflected wave is constructive corresponds substantially to an octave. Therefore, this type of antenna is limited to narrow bands of operation, and does not cover simultaneously a multi-octave frequency band.
• the radiating element etched on a plane radiation surface, is disposed above a plane of a perfect magnetic conductive material (PMC).
• PMC perfect magnetic conductive material
• the wave emitted by the radiating element towards the rear of the radiating surface is reflected towards the front by the material PMC, with a zero phase shift.
• This wave reflected backwards interferes, beyond the radiation surface, with the wave emitted forward by the radiating element.
• This interference is constructive provided that, for a wavefront position, the phases between the forward and forwardly reflected waves are close. This condition is fulfilled if the distance between the radiation surface and the PMC plane is very small compared to the wavelength ⁇ .
• the thickness of such an antenna is greatly reduced compared to that of an absorbent cavity antenna.
• the frequency band accessible by means of such an antenna is restricted. Indeed, if the distance between the radiation surface and the PMC plane is very small, there is a limitation at low frequencies because of a sharp decrease in impedance and the establishment of a short circuit between the radiating element and the PMC plane. On the other hand, if this distance is chosen greater, for each operating frequency such that h / 4 is a multiple of the distance between the radiating surface and the PMC plane, the radiated power forward of the radiating surface is nothing.
• the radiating elements are placed on a progressive magneto-dielectric substrate.
• the radiating elements are placed on a dielectric substrate of high relative permittivity and pierced with thin vertical holes.
• an eighth wire antenna of the state of the art comprises, interposed between the radiating element considered and the lower metal reflector plane (or ground plane) of the cavity, a layer consisting of resistive units with a fixed resistance value, arranged in the so-called radiation zone in the near field of the radiating element or elements.
• the resistive patterns form a partial resistance layer, spaces being arranged between neighboring patterns, and can be made from a resistive ink.
• this solution provides an improvement in the polarization axis gain adapted to the first and second antennas mentioned above, this gain can be improved typically about 5 dB (decibels).
• this type of antenna has a significant decrease in axis gain in polarization adapted for low frequencies, and the axial ratio, in the case of a spiral antenna, remains degraded for low frequencies, typically greater than 3 dB for frequencies below 1 GHz (GigaHertz), reflecting a non-circular character of the polarization of the electromagnetic wave at these frequencies.
• ⁇ ⁇ and ⁇ ⁇ denote the electric field components along the main axes of the reference frame considered:
• an axial ratio typically less than 3 dB is sought (theoretical circular polarization: axial ratio of 1, ie 0 dB).
• the aim of the invention is to correct the aforementioned problems by proposing a high gain, low axial ratio wire antenna and stable radiation patterns over a wide frequency band.
• the invention proposes a wire antenna capable of operating in at least one predetermined frequency band, comprising a plurality of superimposed layers, comprising at least one radiating element placed on a support layer, said support layer being placed on a spacer substrate, said spacer substrate being placed on a reflective plane, comprising at least one resistive layer between the support layer of the radiating element (s) and said spacer substrate, the resistive layer comprising at least two sets of nested resistive patterns.
• This antenna is such that the sets of resistive patterns have resistance values gradually varying between a central antenna point and an outer edge of the antenna, so as to achieve a resistance gradient.
• the wire antenna according to the invention allows an optimal interaction between the radiating element (s) and the reflector plane or ground plane, over a widest possible frequency band.
• the wire antenna according to the invention may have one or more of the following characteristics, taken independently or in combination, in any technically acceptable combination.
• the antenna comprises a first continuous peripheral resistive portion disposed in a peripheral zone of the resistive layer and surrounding the resistive pattern assembly (s) of said resistive layer.
• the first continuous peripheral resistive portion has a circular or square crown shape.
• the antenna comprises a second continuous peripheral resistive portion disposed on the support layer of said radiating element and surrounding said radiating element, said second portion having characteristics of shape and resistance similar to the characteristics of said first continuous peripheral resistive portion.
• the antenna comprises a plurality of sets of resistive patterns, each set of resistive patterns being composed of non-contiguous elementary resistive patterns and having an associated resistance value, said resistance value being the same for all elementary resistive patterns of a set of resistive patterns.
• the antenna comprises a plurality of sets of resistive patterns, each set of resistive patterns being composed of non-contiguous elementary resistive patterns, each elementary resistive pattern having gradually varying resistance value over its surface, the resistance variation having the same sense of resistance. variation than that of said gradual variation between the central antenna point and the outer edge of the antenna.
• All the elementary resistive patterns of the same set of patterns have the same geometric shape and are regularly spaced.
• the sets of resistive patterns are concentric and have a square or circular topology.
• the resistive patterns are made in resistive ink.
• the antenna comprises a plurality of resistive layers with sets of resistance resistive patterns with resistance values gradually varying between a central antenna point and an outer edge of the antenna, two successive resistive layers being separated by at least one substrate layer. .
• FIG. 1 is a cross-sectional view of a wire antenna according to a first embodiment of the invention
• FIG. 2 is a perspective representation of a wire antenna according to FIG. 1;
• FIG. 3 is a view from above of the resistive layer according to a first embodiment
• FIGS. 4 and 5 illustrate performances of an exemplary antenna according to the first embodiment
• FIG. 6 is a view from above of the resistive layer according to a variant of the first embodiment
• FIG. 7 is a cross-sectional view of a wire antenna according to a second embodiment of the invention.
• FIG. 8 is a view from above of an implementation of a wire antenna according to FIG. 7;
• FIG. 9 is a cross-sectional view of a wire antenna according to a third embodiment of the invention.
• FIG. 10 is a cross-sectional view of a wire antenna according to a fourth embodiment of the invention.
• Figures 1 and 2 respectively show a cross-sectional view and a perspective view of a wire antenna 2 according to a first embodiment of the invention.
• the wired antenna 2 is a broadband antenna capable of operating over a decade, for example, typically in a frequency range of 1 GHz to 10 GHz.
• the wire antenna 2 is in the form of a disk of circular circumference C, of center O and several concentric layers stacked along an axis A.
• the first substrate 6 is made of dielectric material with a relative permittivity.
• the first substrate is made of a dielectric material of low relative permittivity (e.g. foam) or a dielectric material of Duroid type (trademark) or a possibly multilayer composite material.
• the first substrate is made of a pure magneto-dielectric or magnetic material.
• the first substrate 6 is formed of a progressive dielectric material or drilled, recessed in its center, so as to achieve a relative permittivity increasing from the center to the outer edge of the antenna.
• the spacer substrate 8 is disposed on a reflective plane 10.
• the reflective plane 10 is preferably metallic, and is located at a distance h1 below the radiation surface S. It has the function of reflecting any incident wave whatever its frequency in a given frequency interval.
• the metal reflector plane 10 is not full but has perforations, for example slits.
• the spacer substrate 8 has the general external shape of a flat cylinder of axis A and of substantially constant thickness h2.
• the thickness h2 of the spacer substrate 8 is greater than the thicknesses of the other layers forming the antenna 2, and forms an antenna cavity.
• the thickness h 2 is chosen so that the total thickness of the antenna satisfies, without resistive patterns, the following phase shift relationship, reflecting a constructive interference (in terms of electromagnetic waves) between the radiating circuit and the reflective plane (phase shift between -120 ° and + 120 °):
• the term F designates the frequency.
• c represents the speed of propagation of the waves in the vacuum and e eff and pie f t denote, respectively, the effective relative permittivity and the effective relative permeability, a function of the constituent materials of the antenna.
• This spacer substrate 8 is made of a dielectric material of given permittivity.
• the spacer substrate is made of a dielectric material of low relative permittivity (e.g. foam) or a dielectric material of Duroid type (trademark) or a possibly multilayer composite material.
• the spacer substrate 8 is made of a pure magneto-dielectric or magnetic material.
• the spacer substrate 8 is formed of a progressive dielectric material or drilled, recessed at its center, so as to achieve a relative permittivity increasing from the center to the outer edge.
• a resistive layer 12 Between the support layer 6 and the spacer substrate 8 is disposed a resistive layer 12, with regular resistive patterns on at least one crown O center.
• the resistive layer 12 is composed of a plurality of sets 12a, 12b, 12c of resistive patterns having different resistance values, gradually varying between the central antenna point O and an outer edge C of the antenna.
• the set of patterns 12c is placed centrally around the axis A of the antenna, the set of patterns 12b is placed around the set of patterns 12c, and the pattern set 12a is placed around the pattern set 12b.
• the sets of patterns are concentric and nested.
• the number of sets of patterns forming the antenna is not limited.
• the resistive layer 12 is, according to a first embodiment, disposed on a first face 14, or upper face, of the spacer substrate 8 oriented towards the radiating element 4 and opposite the second face 16, or lower face, in contact with the the metal reflector 10.
• the resistive layer 12 is disposed on a second face 20 or lower face of the support layer 6, the radiating element 4 being disposed on the first face 18 or upper face of the support layer 6.
• the resistive layer 12 is disposed in a field zone close to the radiating element 4, spaced from the reflector plane 10 by the spacer substrate 8 of thickness h2.
• the resistive layer 12 is made from a resistive ink by serigraphic process, the resistive patterns being deposited on the support surface chosen according to the first or the second variant described above.
• resistive ink deposition by screen printing a resistive ink having a resistivity characteristic expressed in ⁇ per square is used.
• the radiating element 4 comprises first and second metal wires 22 and 24 which are respectively shaped according to a pattern of the spiral type or serpentine log-periodic type, for example. More particularly, the pattern forms an Archimedean spiral in the embodiment of FIG.
• Each wire, 22, 24, is wound around the origin point O, which corresponds to the intersection of the axis A and the radiation surface S.
• the radiating element 4 is for example made by an etching operation, directly on the upper face 18 of the support layer 6.
• a supply device (not shown) for the radiating element 4 is placed below the reflector plane 10, which is electrically connected to ground.
• the reflector plane 10 and the layers 8, 12, 6 placed above are provided with a recessed passage 28, along the axis A, for the passage of a clean conductor wire to be connected to the radiating element 4, to power the latter electrically.
• an active zone of the radiating element 4 emits a first direct wave propagating forwards, that is to say away from the spacer substrate 8, and a second wave propagating towards the rear , that is to say in the direction of the spacer substrate 8.
• the second wave passes through the resistive layer 12, the spacer substrate 8, is reflected by the reflector plane 10, then crosses again the spacer substrate 8, and the resistive layer 12.
• the resistive layer 12 comprises resistive patterns arranged in several sets, each set being arranged on at least one crown of center O.
• FIG. 3 illustrates an embodiment of the resistive layer 12, when the antenna has the shape of a disk of circumference C.
• the resistive layer comprises six sets of resistive patterns, 30a to 30f, each pattern set being formed of elementary resistive patterns 32a to 32f, the assembly 30a being closest to the outer edge C and the entire 30f being closest to the center 0 of the antenna.
• More generally 30n is a set of resistive patterns, and 32n an elementary resistive pattern associated.
• the size of the elementary resistive patterns of two sets of different patterns may be the same or different as shown in Figure 3.
• the elementary resistive patterns are equally square and evenly spaced.
• the elementary resistive patterns 32n of the same set of patterns 30n have the same size and the same resistance value Rn, called the resistance value associated with the set of patterns 30n.
• Two sets of adjacent patterns have different resistance values, and therefore sets of resistive patterns are frequency selective. In other words, the gradual difference in resistance value between sets of adjacent patterns, coupled with the fact that a spiral antenna has a frequency-dependent near-field radiation region, produces a frequency-selective effect.
• the resistance values are chosen to vary gradually between an antenna center point O and the periphery of the antenna, so as to achieve a resistance gradient.
• a resistance gradient is here called a variation of the resistance values between a minimum value and a maximum value.
• the gradient is substantially continuous if the variation is almost monotonous.
• the minimum resistance value is the value associated with the set of resistive patterns 30a, located at the periphery of the antenna, and the maximum resistance value at the set of resistive patterns 30f closest to the center O.
• the resistance values in ohms ( ⁇ ) are as follows, noting C, the square corresponding to the elementary resistive pattern 32i.
• the resistive patterns have a geometric shape and a thickness, and are made of a resistive material, which is a resistive ink in the case of a screen printing deposit, having a given resistivity value p, expressed in ⁇ . ⁇ .
• the effective resistance obtained for a pattern for example for a square-shaped pattern of side a and of thickness e, taken between two opposite sides of the square, is:
• FIGS 4 and 5 illustrate the radio frequency performance of an antenna having the following characteristics:
• the elementary resistive patterns 32a, 32b are squared on the side equal to 0.098 Fc
• the resistive patterns 32c-32f are square on the side equal to 0.049 Fc , with Fc the wavelength in the vacuum, at the center frequency of the band frequency of operation of the antenna (here 0.8 GHz to 10 GHz).
• the center frequency is calculated by the arithmetic mean of the extreme frequencies of the frequency band.
• Each set of patterns 30i is formed of square elementary resistive patterns, the center of each elementary square being disposed on the contour of a support square associated with the set of patterns 30i having a side equal to 2Di, the respective values of Di being the following :
• the shape and size are variable and defined, for each embodiment, using a 3D electromagnetic simulation software or electromagnetic simulator. During an electromagnetic optimization step.
• antenna size cavity size and thickness
• a set of materials of the various layers a number and a topology of the sets of resistive patterns, and the associated resistance values
• Such simulation software is known, for example software that solves the Maxwell equations in integral form, using the finite integral method.
• the size and topology of the patterns are chosen to improve the stability of the radiation pattern.
• the choice of the values of the resistors associated with the pattern sets of the resistive layer 12 and the pattern shape is guided by a compromise to be found between the far-field gain radiated in the radio axis, thus the radiation efficiency, and the shape or stability of the radiation pattern (angular aperture of the lobe according to the frequency).
• the choice of the various values of resistance, elementary pattern size and associated distances is done by implementing several simulations and comparing the results to select the values and patterns best suited for a targeted application.
• FIG. 4 represents the axis gain expressed in decibels as a function of frequency, for a right circular polarization (RHCP) and a left circular polarization (LHCP) for the example antenna detailed above (of theoretical adapted polarization RHCP) .
• RHCP right circular polarization
• LHCP left circular polarization
• Figure 5 shows the axial ratio, which is the ratio in the radio axis, in decibels, as a function of frequency.
• the frequency band considered is [0.5 GHz - 10 GHz]
• the radiation patterns are stable.
• the first embodiment has been described above with a topology of resistive patterns arranged in a square and formed of square elementary resistive patterns.
• the resistive layer comprises concentric resistive ring unit assemblies, elementary resistive square units and the same size being regularly arranged radially and angularly to form O-centered rings.
• the topology is called radial topology.
• the sets of patterns have a radial topology, distributed in concentric rings 34a, 34b,..., Each being formed of elementary patterns 36, which are ring portions in FIG. isosceles trapezium shape.
• each set of ring patterns is composed of patterns of the same dimensions and regularly spaced, the dimensions of the ring patterns varying depending on the radius of the ring, so the distance from the center O.
• the first embodiment has been described above with sets of elementary patterns, each set of elementary patterns having an associated resistance value, the resistance value being the same for each elementary resistive pattern of the set.
• a resistance gradient is applied for each elementary resistive pattern, which makes it possible to produce a resistance gradient within each set of patterns.
• the intramotif resistance gradient evolves in the same direction as the intermititive resistance gradient, the transition between adjacent resistive patterns is all the more gradual. It is then possible to produce a quasi-monotonic resistance gradient between the center and the periphery of the antenna produced.
• the first embodiment has been described above with reference to FIGS. 3 to 6 with sets of resistive patterns forming a resistance gradient that increases from the periphery of the antenna to its center.
• Figure 7 is a cross-sectional view of a wire antenna 40 according to a second embodiment of the invention.
• FIG. 8 is a view from above of an embodiment of the resistive layer 12 of the wired antenna 40.
• the common elements of the antenna 40 with the antenna 2 of the first embodiment are denoted by the same references, and are not described further.
• the resistive layer comprises sets of resistive resistor units of variable resistance as described above and also comprises, in this second embodiment, a continuous peripheral resistive portion 44 surrounding the sets of resistive patterns.
• this resistive portion is produced according to the same method as that of sets of resistive patterns, for example by screen printing, aerosol deposition or 3D printing.
• the continuous peripheral resistive portion 44 is, analogously to the sets of resistive patterns, disposed on the first face 14, or upper face, of the spacer substrate 8, is disposed on the second face 20 or lower face of the support layer 6.
• the resistance value of the continuous peripheral resistive portion 44 is equal to the resistance value of the peripheral assembly of resistive patterns, for example the assembly 12a of FIG. 7 or the assembly 30a of FIG. .
• the continuous peripheral resistive portion 44 has a ring shape for a circular antenna.
• the continuous peripheral resistive portion 44 has a square crown shape.
• the shape of the continuous peripheral resistive portion 44 is a function of the shape of the antenna cavity.
• it has a thickness dimension along the axis A for example between 10 and 20 ⁇ and a width in the plane of the resistive layer of the order of several mm, for example 6 mm.
• the continuous peripheral resistive portion 44 is joined to the peripheral elementary resistive patterns of the antenna 40, as illustrated in FIG. 8.
• this second embodiment allows a low axial ratio and a large gain in suitable polarization.
• Figure 9 is a cross-sectional view of a wire antenna 50 according to a third embodiment of the invention.
• a second continuous peripheral resistive portion 52 is added, in addition to the first continuous peripheral resistive portion 44.
• This second continuous peripheral resistive portion 52 is added on the upper face 18 of the first substrate, on the same side as the radiating element 4.
• the second continuous peripheral resistive portion 52 surrounds the radiating element and has the same shape and resistivity characteristics as the first continuous peripheral resistive portion 44.
• this second continuous peripheral resistive portion 52 makes it possible to improve the axial ratio at the bottom of the frequency band of the antenna, by making it possible to control the end-of-strand effects of the radiating element 4 in an open circuit.
• the axial ratio increases to 1.6 dB, and remains unchanged for the higher frequencies.
• the stability of the antenna pattern is maintained.
• Figure 10 is a cross-sectional view of a wire antenna 60 according to a fourth embodiment of the invention.
• the antenna 60 comprises a plurality of resistive resistor pattern layers having a progressive variation forming a resistance gradient.
• resistive layers 62, 64, 66 are illustrated, separated by substrate layers 68, 70, 72.
• the sets of resistive patterns are either deposited on the upper face (facing the radiating element) of the substrate located below the axis A, or on the lower face (in view of the reflective plane) of the substrate situated above it along the axis A.
• the structuring into a plurality of layers makes it possible to improve the gain in polarization adapted to the antenna, mainly in the lower part of the frequency band, and a better stabilization of the radiation patterns.
• an antenna 60 comprising:
• a first resistive layer 62 consisting of two sets 62a, 62b of resistive patterns consisting of non-contiguous square elementary units, respective resistances 20000 ⁇ per square, and 30000 ⁇ / square;
• a second resistive layer 64 consisting of two sets 64a, 64b of resistive patterns consisting of non-contiguous square elementary units, of respective resistances 10000 ⁇ / square and 15000 ⁇ / square; a second substrate 6 'of dielectric material of the type RO4350 (registered trademark) with a thickness of 0.254 mm;
• a third resistive layer 66 consisting of two sets 66a, 66b of resistive patterns consisting of non-contiguous square elementary units, respective resistances 1000 ⁇ / square and 5000 ⁇ / square;
• a third substrate 6 made of a dielectric material of the type RO4350 with a thickness of 0.254 mm;
• Peripheral resistive portions 74, 76 are also added, of 1000 ⁇ / square resistance.
• FIGS. 11 and 12 illustrate the performance of the antenna 60 with the numerical values of example given above, in the frequency band 0.5 GHz to 10 GHz.
• FIG. 11 represents the axis gain expressed in decibels as a function of frequency, for a right circular polarization (RHCP) and a left circular polarization (LHCP) for the example antenna detailed above (of theoretical circular adapted polarization RHCP).
• RHCP right circular polarization
• LHCP left circular polarization
• Figure 12 shows the axial ratio, which is the ratio in the radio axis, in decibels, as a function of frequency.
• the frequency band considered is [0.5 GHz - 10 GHz].
• This embodiment is useful if a wideband and high gain antenna is desired.
• the resistive patterns and the peripheral resistive portions are feasible in resistive ink, by an easy manufacturing process, for example by screen printing, aerosol deposition or 3D printing.
• all the embodiments described make it possible to improve the gain performance with respect to the resistive-layer antennas formed of resistive units of given fixed resistance value.

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