Dual-band radio antenna

Abstract

Disclosed is a dual-band radio antenna (100) comprising a single antenna array (103) comprising: – a first active antenna element (107A), intended to be excited by a radiofrequency signal; and – second parasitic antenna elements (107P) having geometries that are identical to one another and different from that of the first antenna element, each second antenna element being connected: A) to a reconfigurable parasitic load; or B) to a filtering and / or non-Foster parasitic load.

Description

B23006PCT – DD21860 SP DESCRIPTION Dual band radio antenna This application is based on, and claims priority from, French patent application FR2313515 filed on December 4, 2023 and entitled “Dual band radio antenna”, which is considered an integral part of this description within the limits provided by law. Technical field

[0001] The present description relates generally to electronic devices, more particularly to radio antennas. The present description relates in particular to dual-band antennas, i.e. capable of communicating on two different frequency bands, and to circular polarization, in other words intended to transmit and / or receive waves having circular polarization. Prior art

[0002] Circularly polarized antennas are used in many application areas, such as satellite positioning systems of the "GNSS" type (Geolocation and Navigation by a Satellite System). In these application areas, the antennas are subject to very strong dimensional and economic constraints, resulting from a desire to integrate these antennas into more compact and less expensive wireless communication devices to produce. Furthermore, the antennas used in these application areas generally have multi-band operation, for example dual-band, to be able to process waves simultaneously transmitted or received in different frequency bands. This improves the performance of navigation systems, by allowing B23006PCT – DD21860 SP in particular to obtain more reliable and more precise location data.

[0003] Other applications, such as so-called cognitive radio (CR) systems, use reconfigurable antennas that can adapt to the wireless environment. These applications could benefit from reconfigurable circularly polarized antennas to change the communication frequency based on available propagation channels while reducing losses.

[0004] Furthermore, fifth and sixth generation (5G and 6G) ​​mobile telephone networks are likely to implement base stations incorporating circularly polarized antennas and presenting reconfigurable radiation patterns.

[0005] Among existing circularly polarized radio antennas, compact antennas having, for example, dimensions smaller than half the antenna's transmission wavelength have been proposed. These antennas can be produced in different ways, in particular by forming structures called microarrays comprising several antennas of sub-wavelength dimensions arranged and controlled so as to be able to jointly transmit and / or receive radiofrequency waves having circular polarization.

[0006] A first category of microarray radio antennas includes fully driven antennas, in which all the elements of the array are directly excited by radiofrequency signals. These signals, for example, have the same amplitude but are out of phase with each other. In this category, arrays comprising four inverted-F antennas (IFA), each inverted-F antenna being directly excited by a B23006PCT – DD21860 SP signal 90° out of phase with adjacent antennas, have been proposed. Inverted-F antennas are used in this type of application due to their low thickness (low profile) and their mainly sectoral radiation above the antenna. These characteristics are particularly required for the GNSS application. Other arrays comprising N inverted-F antennas directly excited by signals 360° / N out of phase, for example three inverted-F antennas directly excited by signals 120° out of phase, have also been realized. This thus ensures phase rotation to generate circular polarization. Antennas in this category have the advantage of offering broadband operation, obtained however at the expense of simplicity, compactness and efficiency of the antenna due in particular to the presence of complex excitation circuits.

[0007] A second category of microarray radio antennas includes so-called parasitic element antennas, in which only some active elements of the array are directly excited by a radio frequency signal. The other elements, called parasitic elements, are excited indirectly by coupling with the active elements directly excited by the radio frequency signal. In this category, dual-band antennas have been proposed whose array comprises eight identical inverted-F antennas distributed in two concentric groups of four antennas. In these dual-band antennas, only one of the inverted-F antennas is an active antenna directly excited by the radio frequency signal, the other inverted-F antennas being connected to parasitic loads optimized so that the array emits or receives a circularly polarized wave.Each group of inverted F antennas allows communication using a different frequency band than the other group of antennas. B23006PCT – DD21860 SP

[0008] Parasitic element antennas are simpler and less expensive to produce, but have a narrower bandwidth than fully fed antennas, particularly in the case of compact antennas having a radiation pattern sensitive to variations in parasitic loads as a function of the antenna's transmission frequency. Summary of the invention

[0009] There is a need to overcome some or all of the disadvantages of existing radio antennas. In particular, it would be desirable to produce dual-band circularly polarized antennas capable of achieving similar performance to existing antennas, while having lower size, weight and manufacturing costs.

[0010] For this, one embodiment provides a dual-band radio antenna comprising a single antenna array comprising: – a first active antenna element, intended to be excited by a radiofrequency signal; and – second parasitic antenna elements having geometries identical to each other and different from that of the first antenna element, each second antenna element being connected: A) to a reconfigurable parasitic load; or B) to a filtering and / or non-Foster parasitic load.

[0011] According to one embodiment, the second antenna elements each comprise an inverted F antenna.

[0012] According to one embodiment, the first antenna element comprises an inverted F antenna.

[0013] According to one embodiment, the first antenna element and the second antenna elements are formed on a tubular-shaped support substrate. B23006PCT – DD21860 SP

[0014] According to one embodiment, the support substrate is a flexible substrate intended to be rolled up on itself to present said tubular shape.

[0015] According to one embodiment, the first antenna element and the second antenna elements are separate and distributed around the perimeter of the same circle.

[0016] According to one embodiment, the antenna further comprises a support and interconnection substrate, the support substrate having an axis of revolution substantially orthogonal to a face of the support and interconnection substrate.

[0017] According to one embodiment, the reconfigurable parasitic load or the filtering and / or non-Foster parasitic load connected to each second antenna element is located on the upper face of the support and interconnection substrate.

[0018] According to one embodiment, the antenna comprises exactly two second antenna elements.

[0019] According to one embodiment, the first antenna element is a monopole wire-plate antenna.

[0020] According to one embodiment, the second antenna elements surround the first antenna element.

[0021] According to one embodiment, each reconfigurable parasitic load comprises: – a first parasitic load having a first reactance; – at least one second parasitic load having a second reactance; and – a switch configured to select the first parasitic load or one of the second parasitic loads. B23006PCT – DD21860 SP Brief description of the drawings

[0022] These and other features and advantages will be set forth in detail in the following description of particular embodiments given without limitation in relation to the attached figures, among which:

[0023] Figure 1A is a schematic and partial isometric view illustrating an example of a radio antenna according to one embodiment;

[0024] Figure 1B is a schematic and partial top view of the antenna of Figure 1A;

[0025] Figure 1C is a schematic and partial side and sectional view of a support substrate on which elements of the antenna of Figure 1A are formed;

[0026] Figure 1D is a schematic, partial top view of the planar support substrate of Figure 1C;

[0027] Figure 2 is an equivalent electrical diagram of a radio antenna according to one embodiment;

[0028] Figure 3 is a graph illustrating variations of an axial ratio of a radio antenna as a function of a communication frequency;

[0029] Figure 4 is an equivalent electrical diagram of a radio antenna according to one embodiment;

[0030] Figure 5 is a graph illustrating variations of an axial ratio of a radio antenna as a function of a communication frequency;

[0031] Figure 6 is a schematic and partial top view of a radio antenna according to one embodiment; and

[0032] Figure 7 is a schematic and partial top view of a radio antenna according to one embodiment. B23006PCT – DD21860 SP Description of embodiments

[0033] The same elements have been designated by the same references in the different figures. In particular, the structural and / or functional elements common to the different embodiments may have the same references and may have identical structural, dimensional and material properties.

[0034] For the sake of clarity, only the steps and elements useful for understanding the embodiments described have been represented and are detailed. In particular, the circuits for producing, filtering, amplifying, etc. radiofrequency waves emitted and / or captured by the antennas described will not be detailed, the antennas described being compatible with all or most of the circuits usually used in communication systems implementing antennas, possibly subject to adaptations within the scope of the person skilled in the art upon reading this description.

[0035] Furthermore, the manufacturing processes of the antennas described will not be detailed, the production of these antennas being within the reach of the person skilled in the art from the indications of this description, for example by implementing standard techniques for manufacturing radiofrequency printed circuits.

[0036] Unless otherwise specified, when referring to two elements connected together, this means directly connected without intermediate elements other than conductors, and when referring to two elements connected (in English "coupled") together, this means that these two elements can be connected or be connected by means of one or more other elements. B23006PCT – DD21860 SP

[0037] In the following description, when reference is made to absolute position qualifiers, such as the terms "front", "back", "top", "bottom", "left", "right", etc., or relative position qualifiers, such as the terms "above", "below", "upper", "lower", etc., or to orientation qualifiers, such as the terms "horizontal", "vertical", etc., reference is made, unless otherwise specified, to the orientation of the figures.

[0038] Unless otherwise specified, the expressions “about”, “approximately”, “substantially”, and “in the order of” mean to within 10%, preferably to within 5%.

[0039] In the following description, the terms "insulator" and "conductor" mean respectively, unless otherwise specified, electrically insulating and electrically conductive.

[0040] Figure 1A is a schematic and partial isometric view illustrating an example of a radio antenna 100 according to one embodiment.

[0041] In the example shown, the antenna 100 comprises a support and interconnection substrate 101 on which a single antenna array 103 is arranged. For the sake of simplification, the antenna array 103 is symbolized, in FIG. 1A, by a hollow cylinder, or a tube, of substantially circular section and whose axis of revolution is substantially orthogonal to one face of the support and interconnection substrate 101 (the upper face of the substrate 101, in the orientation of FIG. 1A). Although this has not been detailed in FIG. 1A, the support and interconnection substrate 101 is for example a printed circuit board. The support and interconnection substrate 101 comprises for example metal layers located on either side of an insulating layer. Contact recovery elements and conductive tracks, not detailed in FIG. B23006PCT – DD21860 SP 1A, are for example formed in the metal layers of the support and interconnect substrate 101.

[0042] Figure 1B is a schematic and partial top view of the antenna 100 of Figure 1A.

[0043] In the example shown, the antenna array 103 comprises a support substrate 105 at the periphery of which are arranged an active antenna element 107A and two parasitic antenna elements 107P. The support substrate 105 has for example, as illustrated in FIG. 1B, a generally hollow cylindrical, or tubular shape. The substrate 105 has for example a periphery of substantially circular shape and an axis of revolution substantially orthogonal to the upper face of the support and interconnection substrate 101. This example is however not limiting, the substrate 105 being able, as a variant, to have any general shape, for example a tubular shape of oval, triangular, rectangular, square section, etc.

[0044] The active antenna element 107A is intended to be excited by a radiofrequency signal, for example directly, while the parasitic antenna elements 107P are intended to be excited indirectly by the active antenna element 107A. Figure 1B illustrates an example in which the antenna array 103 comprises two parasitic antenna elements 107P. This example is however not limiting, the antenna array 103 being able, as a variant, to have any number, strictly greater than two, of parasitic antenna elements 107P.

[0045] According to one embodiment, the parasitic antenna elements 107P have geometries identical to each other and different from that of the active antenna element 107A. To facilitate understanding of the drawing, the active antenna element 107A has been symbolized, in FIG. 1B, by a shape comprising an arc of a circle in a stronger line than the B23006PCT – DD21860 SP parasitic antenna elements 107P, in order to highlight the fact that the geometry of the active antenna element 107A is different from that of the parasitic antenna elements 107P. In the example shown, the active antenna elements 107A and parasitic antenna elements 107P are disjoint and distributed around the periphery of the same circle.

[0046] In the example illustrated in Figure 1B, each active antenna element 107A or parasitic antenna element 107P comprises an inverted F antenna. In this example, the vertical bar of the F formed by the antenna, included in the plane of Figure 1B, is symbolized by an arc of a circle matching the curvature of the external face of the support substrate 105, and the central horizontal bar of the F formed by the antenna, extending along a direction orthogonal to the plane of Figure 1B, is symbolized by a disc, for the active antenna element 107A, or by a circle, for each parasitic antenna element 107P. In the present description, the expression “central horizontal bar” designates a part of the F antenna substantially orthogonal to the vertical bar of the F formed by the antenna and different from the upper horizontal bar of the F, it being understood that the central horizontal bar of the F does not necessarily intersect the vertical bar of the F in its middle.In the example shown, the central horizontal bar of each inverted F antenna is substantially orthogonal to the upper face of the support and interconnection substrate 101.

[0047] In the example shown, the antenna 100 is intended to transmit and / or receive waves having circular polarization.

[0048] For the sake of readability, the antenna elements 107A and 107P have not, in FIG. 1B, been shown in contact with the external wall of the support substrate 105. However, in practice, the antenna elements 107A and 107P may be B23006PCT – DD21860 SP located on and in contact with the outer wall of the support substrate 105. Alternatively, the antenna elements 107A and 107P may be located inside the tube formed by the support substrate 105, and are then for example located on and in contact with the inner wall of the support substrate 105.

[0049] Although this has not been illustrated in FIG. 1B, the radio antenna 100 may further comprise a connector, for example an SMA connector (from the English “SubMiniature version A”), intended to connect the antenna 100 to a communication circuit (not shown), for example a circuit making it possible to transmit signals intended to be emitted by the antenna 100 in the form of waves and / or to receive signals originating from waves picked up by the antenna 100. In this case, the connector is for example located on the side of a face of the support and interconnection substrate 101 opposite the antenna array 103 (the lower face of the substrate 101, in the orientation of FIG. 1B). For example, the connector is connected to the central bar of the F of the active antenna element 107A by a microstrip line formed on the support and interconnection substrate 101.

[0050] Figure 1C is a schematic and partial side and sectional view of the support substrate 105 on which the active antenna element 107A and the parasitic antenna elements 107P of the antenna 100 of Figure 1A are formed.

[0051] In the example shown, the support substrate 105 is coated with a conductive layer 109. The conductive layer 109 is, in the orientation of FIG. 1C, located on and in contact with the upper face of the support substrate 105. By way of example, the conductive layer 109 is made of a metal, for example copper, or a metal alloy. B23006PCT – DD21860 SP

[0052] The antenna elements 107A and 107P are for example formed in the conductive layer 109, for example by photolithography then etching the layer 109. Alternatively, the antenna elements 107A and 107P can be formed on and in contact with the upper face of the support substrate 105 by selective deposition of a conductive material.

[0053] In the illustrated example, the conductive layer 109 is coated with an insulating layer 111. In this example, the insulating layer 111 is located on and in contact with a face of the conductive layer 109 in which the antenna elements 107A and 107P are formed (the upper face of the conductive layer 109, in the orientation of FIG. 1C). By way of example, the insulating layer 111 is a so-called cover layer intended to protect the antenna elements 107A and 107P against mechanical and / or chemical attacks. In the example shown, the antenna elements 107A and 107P are interposed vertically between the support substrate 105 and the insulating layer 111.

[0054] For example, the support substrate 105 and the layers 109 and 111 have thicknesses respectively equal to approximately 70 µm, 35 µm and 38 µm.

[0055] The substrate 105 is for example a flexible substrate (“flex” in English) intended to be wound on itself to form a tubular structure, for example as explained previously in relation to FIGS. 1A and 1B, then fixed to the support and interconnection substrate 101 in order to make it mechanically integral with the latter and to maintain it in the form of a tube. For example, the support substrate 105 is wound so that the layers 109 and 111 are located outside the tube formed by the substrate 105. Alternatively, the support substrate 105 can be wound so that the layers 109 and 111 are located inside the tube formed by the substrate 105. B23006PCT – DD21860 SP

[0056] Figure 1D is a schematic, partial top view of the planar support substrate 105 of Figure 1C.

[0057] In the example shown, the support substrate 105 has, in top view, a periphery of substantially rectangular shape, it being understood that the substrate 105 may, as a variant, have any shape. In the example shown, the antenna elements 107A and 107P are inverted F antennas. The horizontal bars of the Fs formed by the antenna elements 107A and 107P, arranged vertically in the orientation of FIG. 1D, are substantially parallel to each other and substantially orthogonal to the length of the rectangle formed by the substrate 105, and the vertical bars of the Fs formed by the antenna elements 107A and 107P, arranged horizontally in the orientation of FIG. 1D, are substantially parallel to each other and substantially parallel to the length of the rectangle formed by the substrate 105.For example, antenna elements 107A and 107P include strips of conductive material extending laterally in directions substantially parallel to the upper face of support substrate 105.

[0058] In the example illustrated in Figure 1D, the end of the upper horizontal bar of the F formed by each antenna element 107A and 107P opposite the vertical bar of the F is located on and in contact with a portion of the support substrate 105 forming a projection. This makes it possible, for example, to fix the support substrate 105 to the support and interconnection substrate 101, for example by soldering on the side of the lower face of the substrate 101 the portions of the substrate 105 forming a projection. For example, notches or slots intended to cooperate with the portions of the support substrate 105 forming a projection are formed in the thickness of the substrate. B23006PCT – DD21860 Support and interconnection SP 101. In the example shown, each portion of the support substrate 105 forming a projection extends parallel to the width of the substrate 105 over a distance L1, for example equal to approximately 2.5 mm.

[0059] Noting λ0 as a transmission and / or reception wavelength of the antenna 100: – the support substrate 105 has for example a length L sub equal to approximately 0.6 λ0 and a width W sub equal to approximately 0.11 λ0; – the F formed by the active antenna element 107A has for example a height H A equal to approximately 0.16 λ0 and a width W A equal to approximately 0.11 λ0; and – the F formed by each parasitic antenna element 107P has for example a height H P equal to approximately 0.2 λ0 and a width W P equal to approximately 0.09 λ0.

[0060] In a case where the wavelength λ0 is expressed in meters, the dimensions L sub , W sub, H A , W A , H P and W P above are expressed in millimeters.

[0061] For example, in a case where the wavelength λ0 is equal to approximately 0.19 m, corresponding to a frequency of the order of 1.575 GHz: – the length L sub is equal to approximately 150 mm; – the width W sub is equal to approximately 28 mm; – the height H A is equal to approximately 40 mm; – the width W A is equal to approximately 26 mm; – the height H P is equal to approximately 50 mm; and – the width W P is equal to approximately 22 mm.

[0062] Figure 2 is an equivalent electrical diagram 200 of a radio antenna, for example the antenna 100 described above in relation to Figures 1A to 1D, according to one embodiment. The electrical diagram 200 of Figure 2 illustrates more precisely an example in which the antenna 100 has reconfigurable dual-band operation. B23006PCT – DD21860 SP

[0063] In the example shown, the radio antenna 100 is symbolized by an impedance matrix [Z A ] 3x3 connected to a signal source 201. The signal source 201 is for example configured to produce a radiofrequency signal to be transmitted by the radio antenna 100.

[0064] In the illustrated example, one of the parasitic antenna elements 107P is connected either to a parasitic load of reactance X2, or to a parasitic load of reactance X′2, different from the reactance X2. Similarly, the other parasitic antenna element 107P is connected either to a parasitic load of reactance X3, or to a parasitic load of reactance X′3, different from the reactance X3.

[0065] In the example shown, each parasitic antenna element 107P comprises a switch 203 for activating the parasitic reactance load X2, X3 or the parasitic reactance load X'2, X'3. The switches 203 are for example of the SPDT type ("Single Pole Double Throw" in English) and each comprise an input connected to a node for applying a potential V ref , for example ground, one output connected to the parasitic load of reactance X2, X3, and another output connected to the parasitic load of reactance X'2, X'3. Each switch 203 is for example controlled by a control circuit, not shown in figure 2.

[0066] The activation of the parasitic loads of reactances X2 and X3 allows for example the antenna 100 to emit a wave at a first frequency f1, and the activation of the parasitic loads of reactances X'2 and X'3 allows the antenna 100 to emit a wave at a second frequency f2, different from the first frequency f1. In the example shown, the parasitic loads of reactances X2 and X'2 and the switch 203 connected to these loads form a reconfigurable parasitic load 205-2. Similarly, the parasitic loads of reactances X3 and X'3 and the switch 203 B23006PCT – DD21860 SP connected to these loads form a reconfigurable parasitic load 205-3.

[0067] The values ​​of the reactances X2, X′2, X3 and X′3 of the parasitic loads are for example defined by simulation, for example by implementing a so-called "SWE" (from the English "Spherical Wave Expansion") method, for example as described in the publication by H. Jaafar et al. entitled "Synthesis of Circularly Polarized Parasitic Micro-Array Using Spherical Wave Expansion" and published in "Proc. 15th European Conference on Antennas and Propagation (EuCAP 2023)", Florence, Italy, March 2023, pp. 1-4.

[0068] For example, for first and second frequencies f1 and f2 respectively equal to approximately 1.225 GHz, corresponding to the GPS-L2 band, and 1.575 GHz, corresponding to the GPS-L1 band: – the reactances X2 and X3 are respectively equal to approximately -21 Ω and -43 Ω; and – the reactances X'2 and X'3 are equal to approximately -120 Ω each.

[0069] The parasitic charges of reactances X2, X′2, X3 and X′3 are for example formed on the upper face of the support and interconnection substrate 101, and the node of application of the potential V ref corresponds to a ground plane formed on the side of the lower face of the substrate 101.

[0070] Figure 3 is a graph 300 illustrating variations of an axial ratio AR, expressed for example in decibels (dB), of a radio antenna, for example the antenna 100 of Figures 1A to 1D comprising the reconfigurable parasitic loads 205-2 and 205-3, as a function of a communication frequency f, expressed for example in gigahertz (GHz). B23006PCT – DD21860 SP

[0071] In the example shown, a curve 301 illustrates variations in the axial ratio AR of the antenna 100 as a function of the frequency f in the case where the parasitic loads of reactances X2 and X3 are connected to the parasitic antenna elements 107P. The curve 301 corresponds to a first frequency band usable by the antenna 100. Furthermore, in this example, a curve 303 illustrates variations in the axial ratio AR of the antenna 100 as a function of the frequency f in the case where the parasitic loads of reactances X′2 and X′3 are connected to the parasitic antenna elements 107P. The curve 303 corresponds to a second frequency band, higher than the first frequency band, usable by the antenna 100.

[0072] The equivalent diagram 200 and the graph 300 correspond for example to a case in which the antenna 100 is intended to be used in a smart radio type device (“Cognitive Radio” - CR, in English).

[0073] Figure 4 is an equivalent electrical diagram 400 of a radio antenna, for example the antenna 100 described above in relation to Figures 1A to 1D, according to one embodiment. The electrical diagram 400 of Figure 4 illustrates more precisely an example in which the antenna 100 has dual-band operation.

[0074] The electrical diagram 400 of Figure 4 includes elements in common with the electrical diagram 200 of Figure 2. These common elements will not be described again below. The electrical diagram 400 differs from the electrical diagram 200 in that the electrical diagram 400 includes filtering and / or non-Foster parasitic loads of impedances Z L2 and Z L3 instead of reconfigurable parasitic loads 205-2 and 205-3.

[0075] In this description, the expression "parasitic filter load" means a load whose reactance B23006PCT – DD21860 SP grows in an optimized manner with frequency to achieve desired impedance variations, and the term "non-Foster load" refers to a non-Foster type load, i.e. a load whose reactance decreases with frequency.

[0076] Figure 5 is a graph 500 illustrating variations of an axial ratio AR, expressed for example in decibels (dB), of a radio antenna, for example the antenna 100 of Figures 1A to 1D including the filtering and / or non-Foster parasitic loads of impedances Z L2 and Z L3 , as a function of a communication frequency f, expressed for example in gigahertz (GHz).

[0077] In the example shown, a curve 501 illustrates variations in the axial ratio AR of the antenna 100 as a function of the frequency f in the case where the two filtering and / or non-Foster parasitic loads have reactances substantially equal to the reactances X2 and X3 respectively at the frequency f1. The curve 501 corresponds to a first frequency band usable by the antenna 100. Furthermore, in this example, a curve 503 illustrates variations in the axial ratio AR of the antenna 100 as a function of the frequency f in the case where the filtering and / or non-Foster parasitic loads have reactances substantially equal to the reactances X′2 and X′3 respectively at the frequency f2. Curve 503 corresponds to a second frequency band, higher than the first frequency band, usable by the antenna 100. Curves 501 and 503 of graph 500 are for example identical or analogous to curves 301 and 303 of graph 300.

[0078] Furthermore, graph 500 includes curves 505 and 507 illustrating respectively the frequency variations of the reactances in the case of non-Foster parasitic loads. In the example shown, the reactance of one of the loads, for example the load of impedance Z L2 , decreases B23006PCT – DD21860 SP between the value X2, for the first frequency band centered around the frequency f1, and the value X′2, for the second frequency band centered around the frequency f2. Furthermore, in this example, the reactance of the impedance load Z L3 decreases between the value X3, for the first frequency band, and the value X′3, for the second frequency band.

[0079] The equivalent diagram 400 and the graph 500 correspond for example to a case in which the antenna is intended to be used in a satellite positioning device of the “GNSS” (Geolocation and Navigation by a Satellite System) type using the first and second bands L1 and L2.

[0080] Figure 6 is a schematic and partial top view of a radio antenna 600 according to one embodiment.

[0081] The antenna 600 of Figure 6 includes elements in common with the antenna 100 of Figures 1A to 1D. These common elements will not be described again below. The antenna 600 differs from the antenna 100 in that the antenna 600 includes a fed antenna element 607A and three parasitic antenna elements 607P.

[0082] The active antenna elements 607A and parasitic antenna elements 607P of the antenna 600 are for example analogous respectively to the active antenna elements 107A and parasitic antenna elements 107P of the antenna 100. For example, each antenna element 607A, 607P comprises an inverted F antenna. In the example shown, the active antenna elements 607A and parasitic antenna elements 607P are disjoint and distributed around the periphery of the same square, for example at the periphery of a support substrate analogous to the support substrate 105. B23006PCT – DD21860 SP

[0083] An advantage of the antenna 600 over the antenna 100 is that the antenna 600 has a number of parasitic elements 607P strictly greater than the number of parasitic elements 107P of the antenna 100. This allows the antenna 600 to emit a wave having a purer circular polarization than the polarization of the wave emitted by the antenna 100.

[0084] Figure 7 is a top view, schematic and partial, of a radio antenna 700 according to one embodiment.

[0085] The antenna 700 of Figure 7 includes elements in common with the antenna 100 of Figures 1A-1D. These common elements will not be described again below. The antenna 700 differs from the antenna 100 in that the antenna 700 includes a fed antenna element 707A and five parasitic antenna elements 707P.

[0086] The fed antenna elements 707A and parasitic antenna elements 707P of the antenna 700 are for example analogous respectively to the active antenna elements 107A and parasitic antenna elements 107P of the antenna 100. For example, the active antenna element 707A comprises a central radiating element in the form of a disc and each parasitic antenna element 707P comprises an inverted F antenna. The fed antenna element 707A is for example more precisely a “wire-plate” type antenna comprising a circular roof constituting a capacitive load making it possible to miniaturize the antenna, for example an antenna of the type described in the European patent application EP 3671953A1. Arranging the active antenna element 707A at the center of the antenna 700 allows the quasi-omnidirectional radiation emitted by the element 707A to be coupled in a substantially equivalent manner with the parasitic antenna elements 707P.In the illustrated example, the parasitic antenna elements 707P surround the active antenna element. B23006PCT – DD21860 SP 707A. In the example shown, the parasitic antenna elements 707P are disjointed and distributed on the faces of the same pentagon, for example at the periphery of a support substrate similar to the support substrate 105. The active antenna element 707A is for example placed substantially in the center of the pentagon formed by the parasitic antenna elements 707P.

[0087] An advantage of the antenna 700 over the antenna 100 is that the antenna 700 has a number of parasitic elements 707P strictly greater than the number of parasitic elements 107P of the antenna 100. This allows the antenna 700 to emit a wave having a purer circular polarization than the circularly polarized wave emitted by the antenna 100.

[0088] An advantage of the 100, 600 and 700 antennas described above is that these antennas have dual-band operation and each have only a single antenna array. This allows them to have lower complexity, size and cost than existing fully fed antennas and dual-band parasitic element antennas.

[0089] Various embodiments and variations have been described. Those skilled in the art will understand that certain features of these various embodiments and variations could be combined, and other variations will occur to those skilled in the art. In particular, those skilled in the art are able to adjust the number of parasitic elements of the antenna depending on the intended application.

[0090] Furthermore, although the above description takes as an example cases in which each reconfigurable parasitic load 205-2, 205-3 comprises two parasitic loads, the embodiments are not limited to this example. Alternatively, each reconfigurable parasitic load may B23006PCT – DD21860 SP include any number, strictly greater than two, of parasitic loads.

[0091] Finally, the practical implementation of the embodiments and variants described is within the reach of the person skilled in the art from the functional indications given above. In particular, the person skilled in the art is capable of defining the values ​​of the impedances of the parasitic loads, in particular of their reactances, according to the intended application from the indications above.

Claims

B23006PCT – DD21860 SP CLAIMS 1. Dual-band radio antenna (100; 600; 700) comprising a single antenna array (103) comprising: – a first active antenna element (107A; 607A; 707A), intended to be excited by a radiofrequency signal; and – second parasitic antenna elements (107P; 607P; 707P) having geometries identical to each other and different from that of the first antenna element, each second antenna element being connected: A) to a reconfigurable parasitic load (205-2, 205-3); or B) to a filtering and / or non-Foster parasitic load.

2. Antenna (100; 600; 700) according to claim 1, wherein the second antenna elements (107P; 607P; 707P) each comprise an inverted F antenna.

3. Antenna (100; 600) according to claim 2, wherein the first antenna element (107A; 607A; 707A) comprises an inverted F antenna. 4.Antenna (100; 600) according to claim 3, wherein the first antenna element (107A; 607A) and the second antenna elements (107P; 607P) are formed on a support substrate (105) of tubular shape.

5. Antenna (100; 600) according to claim 4, wherein the support substrate (105) is a flexible substrate intended to be wound on itself to have said tubular shape.

6. Antenna (100) according to claim 4 or 5, wherein the first antenna element (107A) and the second antenna elements (107P) are disjoint and distributed around the periphery of the same circle. B23006PCT – DD21860 SP 7. Antenna (100; 600) according to claim 4, 5 or 6, further comprising a support and interconnection substrate (101), the support substrate (105) having an axis of revolution substantially orthogonal to a face of the support and interconnection substrate.

8. Antenna (100; 600) according to claim 7, wherein the reconfigurable parasitic load (205-2, 205-3) or the filtering and / or non-Foster parasitic load connected to each second antenna element (107P; 607P) is located on the upper face of the support and interconnection substrate (101).

9. Antenna (100; 600) according to any one of claims 1 to 8, comprising exactly two second antenna elements (107P; 607P).

10. The antenna (700) of claim 2, wherein the first antenna element (707A) is a monopole wire-plate antenna. 11.Antenna (700) according to claim 10, wherein the second antenna elements (707P) surround the first antenna element (707A).

12. Antenna (100; 600; 700) according to any one of claims 1 to 11, in its option A), wherein each reconfigurable parasitic load (205-2, 205-3) comprises: – a first parasitic load having a first reactance (X. 2 , X 3 ); – at least one second parasitic load having a second reactance (X′ 2 , X′ 3 ); and – a switch (203) configured to select the first parasitic load or one of the second parasitic loads.

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