Polarising cell, transmitting network and radio transmitting and receiving antennas

Abstract

The invention relates to a polarising cell (C) suitable for receiving radiation incident on a first side of the cell, and for producing, from the incident radiation, on a second side of the cell opposite the first side, re-emission radiation that has a circular polarisation. Such a cell can be used in a transmitting network, in particular as a component of a radio transmitting antenna or a radio receiving antenna. A beamforming function can be performed simply and without causing energy losses, by adapting orientations of a pattern of metal wafers that generates the circular polarisation.

Description

[0001] POLARIZING CELL, TRANSMITTER NETWORK AND RADIO TRANSMISSION AND RECEIVING ANTENNAS

[0002] TECHNICAL FIELD OF THE INVENTION

[0003] This description relates to a polarizing cell, a transmitter network and radio transmitting and receiving antennas.

[0004] PRIOR TECHNIQUE

[0005] Transmit-arrays are components that are increasingly being considered or used to produce efficient radio antennas for electromagnetic radiation wavelengths in the order of several millimeters. The X and Ka radio communication bands are particularly targeted with this new antenna technology. Indeed, transmit-arrays make it possible to provide high-gain radio antennas at much lower cost than array antennas, because the latter are each made up of multiple radiation sources that are out of phase with each other, instead of a single radiation source for each radio antenna with a transmit-array. The article entitled “Hybrid Numerical Methodology for Efficient Design and Optimization of Transmit-Array Antennas, X-Band Application” by J. Pages-Mounic et al., IEEE Access, 2021, Vol. 9, pp. 148302-148314, DOI 10.1109 / ACCESS.2021.3124287, describes a transmitter network capable of transforming radiation that comes from a source with linear polarization into a re-emission beam that is also linearly polarized, but with a linear polarization direction that is orthogonal. This transmitter network consists of juxtaposed cells that are each capable of absorbing at the input a part of the linearly polarized radiation that is produced by the source, and capable of re-emitting radiation that is also linearly polarized but whose re-emission polarization direction can be changed simply by modifying an orientation of a re-emitting part of each cell.

[0006] But to achieve high communication efficiency between a radio transmitting antenna with transmitted radiation that is linearly polarized and a radio receiving antenna adapted to receive radiation that is also linearly polarized, it is necessary that the polarization directions of the two antennas are identical or substantially identical. In other words, a step of angular alignment of the two radio antennas relative to each other around the transmission direction is necessary, which can be particularly penalizing or difficult to achieve in certain circumstances, for example when dealing with satellite communications. The use of radio antennas with radiation beams that are circularly polarized eliminates this difficulty.

[0007] Furthermore, the transmitter array design described in the aforementioned article by J. Pages-Mounic only allows a beamforming function to be achieved by rotating some of the cell patterns by 180° (degrees), which limits the finesse with which this beamforming function can be achieved. Variable rotations of the cell patterns, by angles that are different from 180°, in a transmitter array as described in this article, allow phase compensation to be produced, but the resulting re-emission radiation has a circular polarization with an efficiency that is low, and with an ellipticity ratio that is not controlled.

[0008] Finally, most radiation sources used for radio transmitting array antennas produce radiation that is linearly polarized (see Lee ln-gon et al: “Design of Multi-Functional Transmitarray with Active Linear Polarization Conversion and Beam Steering Capabilities,” Applied Sciences, vol. 12, no. 9, April 25, 2022). This is particularly the case for horn antennas. TECHNICAL PROBLEM

[0009] From this situation, an aim of the present invention is to propose a new transmitter network which is capable of re-emitting electromagnetic radiation with circular polarization.

[0010] More specifically, the invention aims to ensure that the electromagnetic radiation which is re-emitted by the transmitting network has an ellipticity rate which is low or as low as possible, that is to say that this re-emitted radiation has a determined circular polarization, right or left, with a power level in the other circular polarization which is low or as low as possible.

[0011] This goal is particularly sought when incident radiation that is linearly polarized is used.

[0012] Another object of the invention is that the transmitting array provides a radio transmitting antenna incorporating it with low, or the lowest possible, beam divergence for the radiation that is re-emitted with circular polarization. In other words, a transmitting array design is sought that allows the beamforming function to be performed with an increased level of finesse.

[0013] SUMMARY OF THE INVENTION

[0014] To achieve at least one of these aims or another, a first aspect of the invention provides a novel polarizing cell which is adapted to receive incident radiation on a first side of the cell during use thereof, and to produce, from the incident radiation, re-emission radiation on a second side of the cell opposite the first side, the cell comprising at least:

[0015] - a portion of a metal film, which is intended to constitute a ground plane for the cell when using this cell, and which is provided with a hole;

[0016] - a first metal plate ("patch" in English), which is located on the first side of the cell relative to the portion of metal film, which is parallel to this portion of metal film and electrically insulated from the latter, and which is intended to absorb at least partially the incident radiation during use of the cell;

[0017] - a second metal plate, which is located on the second side of the cell with respect to the portion of metal film, which is parallel to this portion of metal film and electrically insulated from the latter, and which is intended to produce the re-emission radiation during use of the cell; and - an electrical connection, which connects the first metal plate to the second metal plate by passing through the portion of metal film through the hole, while being electrically insulated with respect to this portion of metal film.

[0018] According to the invention, the second metal plate has a pattern that comprises the following parts of the second metal plate:

[0019] - a peripheral portion, which is comprised between an outer edge and a circular inner edge, the circular inner edge delimiting an inner pattern area of ​​the second metal plate, and the electrical connection terminating at a center of the circular inner edge; and

[0020] - a first power segment, which radially connects the circular inner edge to the electrical connection, in the inner pattern area,

[0021] - the pattern of the second metal plate further comprising the following other parts of the second metal plate, which are also in the internal pattern area:

[0022] - a second feed segment, which terminates radially at the circular inner edge at an angle of between 80° (degree) and 100° with the first feed segment, the angle being measured at the center of the circular inner edge; and

[0023] - an intermediate strip, which connects the first power segment at the electrical connection to one end of the second power segment opposite the circular inner edge.

[0024] By this patterning of the second metal plate, the first and second feed segments transmit first and second electric currents, respectively, to the peripheral portion during use of the cell. Furthermore, according to a further feature of the invention, the intermediate strip has a length such that the second electric current is delayed in phase quadrature with respect to the first electric current at the circular inner edge, when the incident radiation has a frequency value which belongs to a resonance band of the cell to produce the re-emission radiation from the incident radiation.

[0025] Such a polarizing cell can be manufactured using one of the available technologies, in particular based on printed circuits. Its cost price, as well as that of a transmitter network which is constituted by such cells, can therefore be low. When using the polarizing cell of the invention, the electrical connection transmits to the second metal plate a variable electric current which results from the absorption of the incident radiation by the first metal plate. This electric current is then transmitted to the peripheral portion of the second metal plate simultaneously for a part by the first power supply segment of the second metal plate, and for an additional part by its second power supply segment.Due to the quadrature phase shift produced by the pattern of this second metal plate between the respective portions of electric current that are transmitted by the two feed segments, and due to the angle between the respective connections of these two feed segments to the circular inner edge of the peripheral portion of the second metal plate, these transmitted portions of electric current generate in the peripheral portion an electric current that rotates around the inner pattern area. This rotating electric current then produces the field of re-emission radiation with a circular polarization and a determined direction of rotation, and with a high level of purity compared to the other direction of rotation of circular polarization.

[0026] A polarizing cell which is in accordance with the invention can be used as a circular polarizer. Furthermore, if the first metal plate is adapted to absorb the incident radiation when it has a determined polarization, different from the re-emission circular polarization produced by the pattern of the second metal plate, the polarizing cell performs a polarization conversion function. In particular, if the first metal plate is adapted to absorb the incident radiation when it has a determined linear polarization, the polarizing cell of the invention performs a function of converting this linear polarization into circular polarization.

[0027] Furthermore, when several polarizing cells which are each in accordance with the invention and identical are juxtaposed to form a transmitting network, an angular difference between the respective orientations of the second metal plates of two of these polarizing cells, within a plane common to these second metal plates, produces the same angular difference between the respective instantaneous fields which are re-emitted by the two cells. Due to the circular polarization of the re-emitted field, this angular difference is equivalent to a phase shift of the same value between the radiations which are re-emitted separately by the two cells. An appropriate selection of the respective orientations of the second metal plates of all the cells of this transmitting network therefore makes it possible to simply produce beam formation for the radiation which is re-emitted by the entire transmitting network.Since the orientation angle of each second metal plate is a continuous variable, the beam-forming function can be performed with great finesse using cells that conform to the invention. The beam of re-emitted radiation can thus have a divergence that is low, and have a radiative power in secondary lobes of the beam that is reduced. In addition, this possibility of producing the beam-forming function by rotating the second metal plates makes it unnecessary to associate a retarder with each cell of the transmitting network, at the electrical connection of this cell. The additional cost and energy losses associated with retarders are thus eliminated.

[0028] In preferred embodiments of the invention, the intermediate strip may have a connecting portion and a curved portion, the connecting portion connecting the first feed segment at the electrical connection to a first end of the curved portion, and a second end of this curved portion being connected to the end of the second feed segment which is opposite the circular inner edge. With such a shape, the intermediate strip may have a characteristic impedance which is continuous or constant throughout this intermediate strip, so that it does not produce significant reflection for the portion of electric current which it transmits to the second feed segment. The polarizing cell thus has an effective reflection rate for the incident radiation, which is lower. In other words, a greater proportion of the incident radiation is converted into re-emitted radiation.Furthermore, this two-part design of the intermediate strip, i.e. with the connection part and the curved part, makes it possible to easily adjust the total length of the intermediate strip to produce the quadrature phase shift between the two parts of electric current which are transmitted separately by the two feed segments to the peripheral portion of the second wafer. Preferably, the curved part of the intermediate strip may have an arcuate shape inside the pattern area, with an angular extension which is between 210° and 270°. Such an arcuate shape of the curved part also makes it possible to reduce parasitic inductances which would be likely to degrade the operation of the polarizing cell.

[0029] Generally, the polarizing cell of the invention can be sized so that the resonance band of this cell is contained between 8 GHz (Gigahertz) and 12 GHz, corresponding to the X band, or between 26.5 GHz and 40 GHz, corresponding to the Ka band. However, the polarizing cell of the invention can be alternatively sized so that its resonance band is in other spectral domains assigned to listed types of radio communication.

[0030] Possibly, the polarizing cell of the invention may further comprise, on its second side, and on one side of the second metal plate which is opposite the portion of metal film:

[0031] - a third metal plate which is parallel to the portion of metal film, and which is electrically insulated from each of the portion of metal film and the first and second metal plates, the third metal plate having a shape with rotational symmetry around an axis, called the cell axis, which passes through the center of the circular inner edge of the second metal plate and which is perpendicular to the portion of metal film.

[0032] Such a third metal plate is therefore electromagnetically coupled remotely to the second metal plate. It makes it possible to broaden the frequency band within which the polarizing cell is effective. In particular, the third metal plate may have dimensions which are adapted to broaden the resonance band of the cell, compared to this same cell when it is devoid of a third metal plate. Advantageously, the third metal plate may be an annular strip which is centered relative to the cell axis. The radii of the inner and outer circular edges of the annular strip are then two dimensional parameters which can be adjusted to control the broadening of the resonance band of the cell.

[0033] In embodiments of the invention that are intended to be used with linearly polarized incident radiation, the first metal plate may have a pattern adapted so that it exhibits, during use of the cell, an absorption efficiency that is higher for a first linear polarization of the incident radiation, compared to a second linear polarization of this incident radiation perpendicular to the first polarization. In particular, the pattern of the first metal plate may comprise the following portions of the first metal plate, independent of the portions of the second metal plate:

[0034] - a peripheral portion, which is comprised between an outer edge and a circular inner edge, the circular inner edge delimiting an inner pattern area of ​​the first metal plate, and the electrical connection terminating at a center of this circular inner edge; and - a feed segment, which radially connects the circular inner edge to the electrical connection, in the inner pattern area of ​​the first metal plate.

[0035] A second aspect of the invention provides a transmitter array which comprises a plurality of identical cells each in accordance with the first aspect of the invention. These cells are juxtaposed with each other so that their conductive film portions extend continuously between neighboring cells, to constitute a plane perforated screen. The cells are rotated so that their respective first metal plates are all on the same side of the transmitter array, and are spaced parallel to the plane perforated screen so that these respective first metal plates are disjointed, and the respective second metal plates are also disjointed, and the respective third metal plates, when present in the cells, are also disjointed.

[0036] In preferred embodiments of such a transmitter array according to the invention, the respective first metal plates of the cells may all be oriented identically within an input plane which is parallel to the plane hole screen, and the respective second metal plates of the cells may have varying orientations within another plane which is also parallel to the plane hole screen. These varying orientations may be adapted to produce a beamforming function for the radiation which is re-emitted by the transmitter array.

[0037] In this transmitting network, the cells can be arranged in a matrix arrangement, being located at intersections of rows and columns of a matrix. A pitch of the matrix, parallel to the rows and columns, can be substantially equal to half of a wavelength value which is associated with a frequency value belonging to the bandwidth of the cells. The relationship between a wavelength value, denoted λ, and the associated frequency value, denoted f, is: λ = C / f where C is the propagation speed of electromagnetic radiation in a vacuum.

[0038] A third aspect of the invention provides a radio transmitting antenna which comprises:

[0039] - a source, adapted to produce electromagnetic radiation which has a polarization state during use of the radio transmitting antenna; and

[0040] - a transmitter network which is in accordance with the second aspect of the invention, and which is arranged in front of a radiation outlet of the source, with the first side of the transmitter network, which comprises the first metal plates, facing the source.

[0041] In this radio transmitting antenna, the pattern of the first metal plates is adapted to absorb the radiation produced by the source, as incident radiation for each cell of the transmitting array, in accordance with the polarization state of this incident radiation as produced by the source.

[0042] Finally, a fourth aspect of the invention provides a radio receiving antenna which comprises:

[0043] - a detector, adapted to detect electromagnetic radiation which has a polarization state prescribed for this detector; and

[0044] - a transmitter network which is in accordance with the second aspect of the invention, and which is arranged in front of the detector, with the first side of the transmitter network, which comprises the first metal plates, facing the detector,

[0045] In this radio receiving antenna, the pattern of the first metal plates is adapted to the polarization state prescribed for the detector. Thus, when external radiation which has a circular polarization allowing absorption of this external radiation by the second metal plates of the transmitting network, arrives on the second side of the latter, the first metal plates re-emit towards the detector a reception radiation which has the polarization state prescribed for this detector.

[0046] BRIEF DESCRIPTION OF THE FIGURES

[0047] The characteristics and advantages of the present invention will appear more clearly in the detailed description below of non-limiting exemplary embodiments, with reference to the appended figures among which:

[0048] - Figure 1 is a sectional view of a polarizing cell which is in accordance with the invention;

[0049] - Figure 2 is a perspective view of metal parts of the polarizing cell of Figure 1;

[0050] - Figure 3a is a plan view of a first metal part of the polarizing cell of Figure 1;

[0051] - Figure 3b is a plan view of a second metal part of the polarizing cell of Figure 1;

[0052] - Figure 3c is a plan view of a third metal part of the polarizing cell of Figure 1; - Figure 3d is a plan view of a fourth metal part of the polarizing cell of Figure 1;

[0053] - Figure 4a is a view of an input plane of a transmitter network which is in accordance with the invention;

[0054] - Figure 4b is a view of a part of another plane of the transmitter network of Figure Fig. 4a;

[0055] - Figure 5a is a schematic view of a transmitting array antenna which is in accordance with the invention; and

[0056] - Figure 5b is a schematic view of a receiving antenna with a transmitting array which is in accordance with the invention.

[0057] DETAILED DESCRIPTION OF THE INVENTION

[0058] For the sake of clarity, the dimensions of the elements shown in these figures do not correspond to actual dimensions or to actual dimensional ratios. In addition, some of these elements are represented only symbolically, and identical references indicated in different figures designate identical elements or those having identical functions.

[0059] For illustration purposes, all numerical values ​​given first with reference to Figure 1, Figure 2 and Figure 3a-Figure 3d relate to a polarizing cell sized to operate within the X band, with a bandwidth center wavelength value, denoted λ, which is substantially equal to 28.6 mm (millimeter), corresponding to an electromagnetic radiation frequency value, denoted f, which is equal to 10.5 GHz.

[0060] In accordance with Figure 1 and Figure 2, a polarizing cell according to the invention and generally designated by C can be produced in the form of a superposition of three planar printed circuit substrates. In this embodiment, substrates 5 and 7 each carry a metal layer on only one of their respective faces, and substrate 6 carries a metal layer on each of its faces. Each metal layer, which can be made of copper (Cu), is etched according to a pattern which will be described later to form the following metal parts of cell C, listed in order from an input plane Pin of cell C to its output plane Pout:

[0061] - a first metal part, designated by the reference 1, which is superimposed on the input plane Pin and which has been called the first metal plate in the general part of this description, is carried by the substrate 5, - a second metal part, designated by the reference 2 and which has been called the portion of metal film in the general part of this description, is carried by the face of the substrate 6 which is turned towards the input plane Pin,

[0062] - a third metal part, designated by the reference 3 and which has been called second metal plate in the general part of the present description, is carried by the other face of the substrate 6, which is turned towards the output plane Pout, and

[0063] - a fourth metallic part, optional and designated by the reference 4, which is superimposed on the output plane Pout and which has been called third metallic plate in the general part of the present description, is carried by the substrate 7.

[0064] The substrates 5-7 are bonded together by the assembly layers 56 and 67, commonly called pre-preg. The following numerical values ​​can be adopted:

[0065] - respective thicknesses of metal plates 1, 3 and 4: 43 pm (micrometer), 43 pm and 35 pm

[0066] - thickness of the portion of metallic film 2: 17 pm

[0067] - thickness of substrates 5 and 6: 1.524 mm

[0068] - relative dielectric permittivity of substrates 5 and 6: 3.55

[0069] - thickness and relative dielectric permittivity of substrate 7: 1.575 mm and 2.2

[0070] - thickness and relative dielectric permittivity of the pre-preg layer 56: 90 pm and 3.52

[0071] - thickness and relative dielectric permittivity of the pre-preg layer 67: 50 pm and 2.7

[0072] Cell C has a square shape parallel to the planes Pin and Pout, with sides equal to approximately λ / 2 = 14.3 mm. It is intended to receive on its input plane Pin an incident electromagnetic radiation Rin which has the wavelength λ, and it then produces, from this incident radiation Rin, a re-emission electromagnetic radiation Rout from the output plane Pout.

[0073] As shown in Figure 1 and Figure 2, the metal pads 1 and 3 are electrically connected to each other by a metal via 8. The via 8 is superimposed on a central axis AA of the cell C, which is perpendicular to the Pin and Pout planes. The via 8 may be made of a copper-based alloy, and have an outer radius of 0.15 mm.

[0074] Figure 3a shows the pattern of the metal film portion 2. This metal film portion 2 is continuous throughout the cell extension C, parallel to the Pin and Pout planes, except at a hole 20 which is centered on the AA axis. This hole 20, which can have a radius of 0.3 mm, ensures that the metal film portion 2 is electrically isolated from the via 8.

[0075] Figure 3b shows an example of a pattern of the metal wafer 1, which is suitable when the incident radiation Rin has a linear polarization. This wafer pattern 1 is described in the article by J. Pages-Mounic et al. which was cited at the beginning of this description. According to this pattern, the wafer 1 comprises a peripheral portion 10 which is continuous between a rectangular outer edge 11 and a circular inner edge 12. The circular inner edge 12 is centered on the axis AA. The wafer pattern 1 further comprises a rectilinear feed segment 13 which connects the circular inner edge 12 to the via 8. The metal layer has been removed by chemical etching outside the peripheral portion 10 and the feed segment 13. The following dimensions can be adopted for the wafer 1:

[0076] - dimensions Lpatchl x Wpatchl of the external edge 11: 6.13 mm x 6.13 mm

[0077] - radius Rcyll of the circular internal edge 12: 2 mm

[0078] - Wlinel width of power segment 13: 0.46 mm

[0079] Such a metal plate 1 is adapted to absorb the incident radiation Rin when this incident radiation has a linear polarization of its electric field which is parallel to the longitudinal extension direction of the power supply segment 13.

[0080] Figure 3c shows an example of a pattern of the metal wafer 3, which is adapted to produce the re-emission radiation Rout with circular polarization. This wafer pattern 3 comprises a peripheral portion 30 which is continuous between a square outer edge 31 and a circular inner edge 32, a first straight feed segment 33, a second feed segment 34 also straight, and an intermediate strip 35. The circular inner edge 32 is centered on the axis AA. The first feed segment 33 connects the circular inner edge 32 to the via 8. The second feed segment 34 connects the circular inner edge 32 by making an angle 0 which is equal to 90° with the longitudinal direction of the first feed segment 33, around the axis AA. The intermediate strip 35 connects to each other two respective ends 33e and 34e of the supply segments 33 and 34, which are opposite the circular internal edge 32.In the embodiment shown, the intermediate strip 35 is constituted by a connecting portion 35a and a curved portion 35b. The curved portion 35b may have an angular extension of approximately 240° around the axis AA, and the two portions 35a and 35b are arranged in series to connect the end 33e of the first feed segment 33 to the end 34e of the second feed segment 34. How to determine the total length of the intermediate strip 35 will be described later. The following dimensions may be adopted for the wafer 3:.

[0081] - dimensions Lpatch3 x Wpatch3 of the external edge 31: 6.13 mm x 6.13 mm

[0082] - radius Rcyl3 of the circular internal edge 32: 2 mm

[0083] - Wline3 width of power segment 33: 0.44 mm

[0084] - common width Wstrip3 of the power segment 34 and the intermediate strip 35 in its two parts 35a and 35b: 0.43 mm

[0085] Figure 3d shows an example of a pattern of the metal plate 4, which is suitable for enlarging a bandwidth of the cell C. This plate pattern 4 may be an annular strip which is limited between a circular outer edge 41 and a circular inner edge 42. Both edges 41 and 42 are centered on the axis AA and may have the radius values ​​Rcyl_ext4 = 3.7 mm and Rcyl_int4 = 1.2 mm, respectively. This metal plate 4 is electrically isolated from all other metal parts of the cell C. Its effect on the operation of the cell C results from a remote electromagnetic coupling which exists between the plates 3 and 4.

[0086] When the cell C just described receives the incident radiation Rin on the wafer 1, in the input plane Pin, this radiation Rin induces electric currents inside the wafer 1, which cause at least partial absorption of the power of the radiation Rin. For the wafer pattern 1 described above, this absorption is maximum when the incident radiation Rin is linearly polarized with its electric field which is parallel to the longitudinal direction of the feed segment 13. The metal film portion 2 produces a screening effect, for a residual part of the incident radiation Rin which has not been absorbed by the wafer 1. To improve this screening effect of the metal film portion 2, the latter can be connected to an electrical ground terminal. Thus, the metal film portion 2 constitutes a ground plane of the cell C.The electric currents that have been generated by the incident radiation Rin in the wafer 1 are transmitted to the wafer 3 by the via 8, through the portion of metal film 2. By an electrical operation inverse to that which occurred in the wafer 1, these electric currents that arrive at the wafer 3 by the via 8 are transmitted to the peripheral portion 30 thereof by each of the power supply segments 33 and 34. The part of these electric currents that is transmitted by the power supply segment 33 produces a component of the re-emission radiation Rout which has a linear polarization parallel to this segment 33. Simultaneously, the other part of the electric currents, transmitted by the power supply segment 34, produces another component of the re-emission radiation Rout which has a polarization parallel to this other segment 34.The intermediate strip 35 is designed to have a total length that produces a transmission delay of a phase quadrature for the electric currents it transmits. This total length can be easily adjusted by selecting the angular orientation of the connecting portion 35a relative to the longitudinal direction of the feed segment 33, and by adapting accordingly the angular length of the curved portion 35b to join the feed segment 34.Since the two feed segments 33 and 34 are perpendicular (0=90°), and the intermediate strip 35 delivers to the peripheral portion 30, via the feed segment 34, the part of the electric currents that it transmits with a delay of one quadrature with respect to the part of the electric currents that is transmitted by the feed segment 33, the two components of the re-emission radiation Rout combine to produce this re-emission radiation with circular polarization. The widths Wline3 and Wstrip3 can be selected so that the electric currents that are transmitted respectively by the feed segments 33 and 34 have equal amplitudes. The complementary effect of the optional plate 4 has already been indicated above.

[0087] A transmitter array 100 is manufactured by producing in large printed circuit boards a large number of cells C, each identical to the one previously described. For example, the cells C are arranged in a matrix arrangement, which has the pitch λ / 2 = 14.3 mm in both the row and column directions. The metal film portions 2 extend continuously between cells that are neighboring in the matrix. Within the input plane Pin, the pads 1 of all the cells C of the transmitter array 100 are oriented so that their respective power supply segments 13 are all parallel, as shown in Figure 4a. Parallel to the output plane Pout, the pads 3 of all the cells C of the transmitter array 100 may also be oriented so that their respective power supply segments 33 are all parallel.However, when two cells C of the transmitter array 100 are oriented parallel to the output plane Pout so that their respective feed segments 33 form an angle a, these two cells C produce respective contributions to the radiation Rout as re-emitted by the entire transmitter array 100, which have between them a phase shift equal to a. This phase shift arises from the equivalence between a rotation of the electric field and a phase delay for circular polarization. It is then possible to select the respective orientations of the plates 3 of all the cells C of the transmitter array 100, parallel to the output plane Pout, in order to obtain a beam-forming effect for the re-emission radiation Rout.A person skilled in the art will be able to determine by numerical simulations an appropriate distribution of the angle values ​​a in the matrix of the transmitter network 100, to reduce or adapt a divergence of the beam of the re-emitted radiation Rout. Figure 4b symbolically shows a distribution of variable angle values ​​a in a part of the transmitter network 100.

[0088] As shown in Figure 5a, the transmitting array 100 can be used with a radiation source 200 to constitute a radio transmitting antenna 300, called a transmitting array transmitting antenna. The source 200 can be of the horn type, which produces the Rin radiation in the X band, with a central transmission frequency which is equal to 10.5 GHz. Such a source 200 produces the Rin radiation with a linear electric field polarization which is parallel to the x axis, and with a nominal gain of 15.5 dBi, being effective throughout the entire spectral transmission interval 8 GHz - 12 GHz. Usually, the nominal gain of a radio transmitting source is understood to mean the value expressed in decibels (dB) of the ratio between the power which is emitted by this source in its main direction of transmission and the power value which would be produced in this direction by an isotropically emitting source, for the same total power value emitted.The z axis designates the main emission direction of the source 200. The transmitter network 100 is then arranged perpendicular to the z axis, at a distance D = 214 mm from the emission focus of the source 200, and is oriented around the z axis so that the feed segments 13 are all parallel to the x axis. Furthermore, the transmitter network 100 is rotated so that the source 200 is on the side of the first metal plates 1.

[0089] In the exemplary embodiment of a transmitting array antenna 300 reported herein, the transmitting array 100 has a square perimeter in the xy plane of 285.5 mm on each side, and comprises 20 x 20 C cells juxtaposed in a matrix arrangement parallel to the x and y axes. These dimensions correspond to the individual size of the C cells of 14.275 mm x 14.275 mm, i.e., a matrix pitch which is equal to λ / 2 for the transmission frequency of 10.5 GHz. The pattern of the plates 3 of the transmitting array 100 is selected to produce the radiation Rout with left-hand circular polarization. Furthermore, a distribution of angle values ​​α for all the plates 3 parallel to the xy plane has been determined to provide a maximum value of nominal gain for the transmitting array antenna 300.This maximum nominal gain value as calculated is equal to 26.5 dBi, or 26 dBi taking into account losses occurring in the system, while measurements carried out in an anechoic chamber provided the value of 25.5 dBi. The transmitter array 100 therefore provides an increase of 10 dBi compared to the source 200. In other words, the beamforming function of the transmitter array 100 makes it possible to reduce the divergence of the re-emitted radiation beam Rout which is transmitted outwards by the transmitting antenna 300, compared to the divergence of the beam Rin as it emerges directly from the source 200. The ellipticity ratio of the re-emitted radiation Rout is 0.3 dB at the transmitting frequency of 10.5 GHz, which shows the high purity of the left-hand circular polarization in this re-emitted radiation Rout. Finally, the transmitting antenna with transmitter array 300 has the following additional characteristics:.

[0090] - Af / f bandwidth at -1 dB gain: 16%, corresponding to the bandwidth Af = 1.6 GHz for the 300 transmitter array transmitting antenna

[0091] - bandwidth at -1 dB ellipticity ratio: greater than 30%, corresponding to a spectral width greater than 3 GHz for this polarization criterion

[0092] - quotient of the directivity of the transmitting antenna with transmitting array 300 on the maximum theoretical directivity which can be obtained with the same antenna surface, called aperture efficiency: 44%

[0093] - quotient of the power which is actually radiated by the transmitting array antenna 300 over the feed power of the source 200, called power efficiency: 77%.

[0094] Another transmitter array has been made in accordance with the present invention, being dimensioned for use within the Ka band, with a central frequency value equal to 30 GHz. This other transmitter array has a matrix of 70 x 70 cells C, resulting in a square perimeter of 350 mm x 350 mm for the transmitter array. The radiation source which is used with this other transmitter array to make another transmitting antenna effective in a part of the Ka band, has a nominal gain of 15.5 dBi, being effective in the entire spectral transmission interval 26 GHz - 40 GHz. The value adopted for the distance D is then 300 mm. The characteristics of the transmitting antenna with transmitter array which is thus made are as follows:

[0095] - polarization of Rin radiation: linear

[0096] - polarization of the re-emitted radiation Rout: left circular

[0097] - calculated value of the nominal gain of the transmitting array antenna: 39.5 dBi

[0098] - value measured in an anechoic chamber of the nominal gain of the transmitting network antenna: 39 dBi, i.e. an increase of approximately 24 dB compared to the nominal gain value of the source used

[0099] - ellipticity ratio at the central frequency: 0.3 dB

[0100] - Af / f bandwidth at -1 dB gain: 8%, corresponding to Af = 2.4 GHz - bandwidth at -1 dB ellipticity ratio: greater than 20%, corresponding to a spectral width greater than 6 GHz for this polarization criterion

[0101] - opening efficiency: 62%

[0102] - power efficiency: 80%.

[0103] The inventors emphasize that the invention therefore makes it possible to obtain aperture efficiency and power efficiency values ​​never previously achieved for transmitter networks which convert linear polarization into circular polarization.

[0104] Finally, a transmitter array 100 which is in accordance with the invention can also be used to constitute a radio reception antenna, as shown in [Fig. 5b]. The receiving antenna with a transmitter array is generally designated by the reference 500. In addition to the transmitter array 100, the receiving antenna 500 comprises a radiation detector 400, which is located on the side of the transmitter array 100 which comprises the first metal plates 1. In the receiving antenna 500, the transmitter array 100 has an operation inverse to that which has been described previously: external radiation Rext which is circularly polarized and which is incident on the transmitter array 100, on the side of the second metal plates 3, is absorbed by the latter when its direction of polarization rotation is appropriate.The electrical currents that are produced by this absorption are transmitted by the vias 8 to the plates 1, which then emit a reception radiation Rrecep towards the detector 400. The transmitter array 100 is selected to have a pattern of its plates 1 which is compatible with a polarization state required by the detector 400. For example, the detector 400 may require that the reception radiation Rrecep has a suitably oriented linear polarization, in order to provide optimal detection efficiency. In particular, the detector 400 may be constituted by a horn antenna which is used for reception. For such a reception antenna with a transmitter array 500, the beamforming function of the transmitter array 100 makes it possible to converge the reception radiation Rrecep onto the detector 400.

[0105] It is understood that the invention may be reproduced by modifying secondary aspects of the embodiments which have been described in detail above, while retaining at least some of the advantages cited. In particular, all the numerical values ​​which have been cited have been cited only for illustration purposes, and may be changed depending on the application considered and the radio transmission band concerned.

Claims

CLAIMS 1. Polarizing cell (C), adapted to receive incident radiation on a first side of the cell during use of said cell, and to produce, from the incident radiation, re-emission radiation on a second side of the cell opposite the first side, the cell comprising at least: - a portion of a metal film (2), which is intended to constitute a ground plane for the cell (C) when said cell is used, and which is provided with a hole (20); - a first metal plate (1), which is located on the first side of the cell (C) relative to the portion of metal film (2), which is parallel to said portion of metal film and electrically insulated from said portion of metal film, and which is intended to absorb at least partially the incident radiation during use of the cell; - a second metal plate (3), which is located on the second side of the cell (C) with respect to the portion of metal film (2), which is parallel to said portion of metal film and electrically insulated from said portion of metal film, and which is intended to produce the re-emission radiation during use of the cell; and - an electrical connection (8), which connects the first metal plate (1) to the second metal plate (3) by passing through the portion of metal film (2) through the hole (20), while being electrically insulated with respect to said portion of metal film, the second metal plate (3) having a pattern which comprises the following parts of second metal plate: - a peripheral portion (30), which is comprised between an outer edge (31) and a circular inner edge (32), the circular inner edge delimiting an inner pattern zone of the second metal plate (3), and the electrical connection (8) terminating at a center of the circular inner edge; and - a first feed segment (33), which radially connects the circular inner edge (32) to the electrical connection (8), in the inner pattern area, the cell (C) being characterized in that the pattern of the second metal plate (3) further comprises the following other parts of second metal plate, which are also in the inner pattern area: - a second feed segment (34), which ends radially at the circular inner edge (32) forming an angle of between 80° and 100° with the first feed segment (33), the angle being measured at the center of the circular inner edge; and - an intermediate strip (35), which connects the first power segment (33) at the electrical connection (8) at one end of the second power segment (34) opposite the circular inner edge (32), so that, during use of the cell (C), the first (33) and second (34) feed segments transmit to the peripheral portion (30) first and second electric currents, respectively, and the intermediate band (35) has a length such that the second electric current is delayed in phase quadrature with respect to the first electric current at the circular inner edge (32), when the incident radiation has a wavelength value which belongs to a resonance band of the cell to produce the re-emission radiation from the incident radiation.

2. Cell (C) according to claim 1, wherein the intermediate strip (35) has a connecting portion (35a) and a curved portion (35b), the connecting portion connecting the first power segment (33) at the electrical connection (8) to a first end of the curved portion, and a second end of said curved portion being connected to the end of the second power segment (34) opposite the circular inner edge (32).

3. Cell (C) according to claim 1 or 2, further comprising, on the second side of the cell, and on a side of the second metal plate (3) which is opposite the portion of metal film (2): - a third metal plate (4) which is parallel to the portion of metal film (2), and which is electrically insulated from each of said portion of metal film and from the first (1) and second (3) metal plates, the third metal plate having a shape with symmetry of revolution around an axis, called cell axis (AA), which passes through the center of the circular internal edge (32) of the second metal plate and which is perpendicular to the portion of metal film.

4. Cell (C) according to claim 3, in which the third metal plate (4) is an annular strip which is centered relative to the cell axis (AA).

5. Cell (C) according to claim 3 or 4, in which the third metal plate (4) has dimensions adapted to widen the resonance band of the cell, compared to said cell when it is without a third metal plate.

6. Cell (C) according to one of the preceding claims, in which the first metal plate (1) has a pattern adapted so that said first plate has, when using the cell, an absorption efficiency which is higher for a first linear polarization of the incident radiation, compared to a second linear polarization of said incident radiation perpendicular to the first polarization.

7. Transmitter network (100) comprising a plurality of identical cells (C) each according to one of the preceding claims, juxtaposed with each other so that the portions of conductive film (2) extend continuously between neighboring cells, to form a plane screen with holes, the cells being turned so that the respective first metal plates (1) of said cells are all on the same side of the transmitter network, and the cells being spaced parallel to the plane screen with holes so that the respective first metal plates are disjointed and the respective second metal plates (3) are disjointed, and the respective third metal plates (4), when said third metal plates are present in the cells, are also disjointed.

8. A transmitter array (100) according to claim 7, wherein the respective first metal plates (1) of the cells (C) are all oriented identically within an input plane (Pin) which is parallel to the plane perforated screen, and wherein the respective second metal plates (3) of the cells (C) have variable orientations within another plane which is also parallel to the plane perforated screen, said variable orientations being adapted to produce a beamforming function for radiation which is re-emitted by the transmitter array.

9. Radio transmitting antenna (300) comprising: - a source (200), adapted to produce electromagnetic radiation which has a polarization state during use of the radio transmission antenna (300); - a transmitter network (100) which is in accordance with claim 7 or 8, and which is arranged in front of a radiation outlet of the source (200), with the first side of the transmitter network, which comprises the first metal plates (1), facing the source, wherein the pattern of the first metal plates (1) is adapted to absorb the radiation produced by the source (200), as incident radiation for each cell (C) of the transmitter network, in accordance with the polarization state of said incident radiation as produced by the source.

10. Radio receiving antenna (500) comprising: - a detector (400), adapted to detect electromagnetic radiation which has a polarization state prescribed for said detector; and - a transmitter array (100) which is in accordance with claim 7 or 8, and which is arranged in front of the detector (400), with the first side of the transmitter array, which comprises the first metal plates (1), facing the detector, wherein the pattern of the first metal plates (1) is adapted to the polarization state prescribed for the detector (400), so that when external radiation which has a circular polarization allowing absorption of said external radiation by the second metal plates (3) of the transmitter array (100), arrives on the second side of said transmitter array, the first metal plates (1) re-emit towards the detector a reception radiation which has the polarization state prescribed for said detector.

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