EP1702388A1

EP1702388A1 - Configurable and orientable antenna and corresponding base station

Info

Publication number: EP1702388A1
Application number: EP04805862A
Authority: EP
Inventors: André DE LUSTRAC; Kouroch Mahdjoubi; Anne-Claude Tarot; Halim Boutayeb; Claude Terret
Original assignee: Centre National de la Recherche Scientifique CNRS; Universite de Rennes 1; Universite Paris Sud Paris 11
Current assignee: Centre National de la Recherche Scientifique CNRS; Universite de Rennes 1; Universite Paris Sud Paris 11
Priority date: 2003-11-27
Filing date: 2004-11-26
Publication date: 2006-09-20
Also published as: US20070080891A1; US7636070B2; JP2007512747A; WO2005055365A1; FR2863109A1; FR2863109B1; CN1906809A

Abstract

The invention relates to an antenna, permitting the configuration of at least one radioelectric wave beam (4, 5, 61, 62, 91, 92) of at least one fixed wavelength, of the type comprising at least one transmitting element (2), preferably of the passive type, arranged in a set of essentially parallel, wave-reflecting wires or bars (1), made from a photonic band gap (BIP) material and forming a given structure. Said given structure comprises faults for shaping said at least one beam in a direction as a function of the position and/or the configuration of said faults. According to the invention, said wires or bars and the faults are arranged on a set of N curves which are closed and concentric on a plane, N being greater than or equal to 1 and the transmitting element is arranged within the innermost curve. The curves are preferably circular and the wires/bars can be controlled to pass from a wave-conducting/reflecting state to a transparent state.

Description

CONFIGURABLE AND ADJUSTABLE ANTENNA, CORRESPONDING BASE STATION

The present invention relates to a radio antenna which makes it possible to configure in space one or more lobes or beams, these terms being here equivalent, of emission / reception of electromagnetic waves and therefore of configuring its radiative diagram. It finds 10 applications in the field of transmission / reception in radio electromagnetic waves and in particular as a mobile telephone antenna. It allows in particular the conformation and switching of radioelectric beams or lobes within a base station of a telephone network or of radiocommunication data transmissions with mobile stations both in transmission and in reception (E / R). In general, to produce a steerable directional antenna, a structurally directional antenna is produced on the one hand and, on the other hand, it is moved to orient it in space, generally in rotation, so that its diagram of electromagnetic radiation is oriented in the desired direction. In addition to the fact that the mechanical displacement of the antenna requires mechanical means which can be expensive, wear out and are complex to maintain, the antennas generally being at high points and in a harsh climatic environment, the radiation pattern remains identical in shape throughout the rotation. It is therefore desirable to have non-mechanical means making it possible to modify the orientation of the radiation pattern in space. In addition, it also appears desirable to be able to modify the structure of the radiation diagram, in particular the number of emission / reception lobes and / or their shapes in space. Indeed, for example in the case of new high-speed radiocommunication services, it appears that only dynamic systems provided with intelligent antennas will allow an optimal use of the radio spectrum by using capacities of adaptation of spatial configuration of transmission / reception as shown in the articles "The path towards UMTS - Technologies for the information society", UMTS Forum 1998 and, "A global view of the concept of UMTS", S. Breyer, G. Dega, V. Kumar and L. Szabo, from Alcatel. These intelligent antennas offer the possibility of increasing the capacity of systems operating in particular in CDMA ("Code-Division-Multiple-Access") thanks to the use of a pseudo-SDMA ("Spatial- Division-Multiple Access") technique. ) according to known methods as described in the article "Smart antennas enhance cellular / PCS performance, part 1 & 2", CB Dietrich Jr. and WL Stuztman, in Microwaves & RF, April 1997. This technique makes it possible to reduce interference "co-channel" in the downlink (base station to mobile) of cellular networks by forming a directional beam directed towards the mobile. It also allows rejection of interference in the uplink (mobile to base station) with the additional possibility of forming the antenna diagram of the base station so that it presents a receiving trough in the direction of the interference. A distinction is generally made between two categories of so-called intelligent antennas which have a modular radiation pattern: those carried out with beam-switched antenna arrays and those carried out with adaptive antennas as was presented in "Experiments on adaptive array diversity transceiver for base station application in W-CDMA mobile radio "by M. Sawahashi and S. Tanaka during AP-S 2000, Sait Lake City, USA, July 2000. Smart antennas made with adaptive antennas generally consist of a network of radiating elements controlled by a digital signal processor (or DSP, for "Digital Signal Processor"). They can automatically adapt their radiation pattern according to the external signals received. Unfortunately, current digital technology does not appear mature enough to support the multiple frequency bands necessary in mobile telephony, as well as the powers necessary to control this radio spectrum. In addition, the technology of adaptive and digital intelligent antennas is not very adapted to the existing technology in base stations (or BTS, for "Base Tranceiver Station") and therefore would require too much investment to renew the latter like this. was noted in Mr. Sawahashi's presentation cited above. Intelligent antennas made with beam switching antennas use analog synthesis of multiple beams. This approach retains most of the characteristics of digital smart antennas, but with much lower complexity and cost. It is compatible with existing infrastructures (in particular base stations) and allows a significant increase in network capacity in relation to investment. Traditionally, beam-switching antennas use a pre-defined phase feed network that provides multiple output ports, each corresponding to a fixed direction beam. Base stations of this type have been tested by numerous companies in the United States and in Europe, in particular by: Celwave associated with BellSouth, Hazeltine Corp., Metawave Communications, ArrayConun Inc., Ericsson, Nortel, ... Besides previously mentioned articles and presentation, information on this is also available in "Novel multiple-beam antenna array serves mobile BTS, part 1", L. Cellai and A. Ferrarotti, Microwaves & RF, August 1999 or in "Array antenna design for base station applications", B Johannisson and A. Derneryd, Ericsson Microwave Systems AB. The main drawback of this beam switching technology is the high number of radiating elements and therefore its cost. It has therefore been proposed to use an alternative solution for producing beam switching type antennas by placing a passive radiating element at the heart of a set of rods made of photonic band gap material (abbreviated as BIP), some of these rods being made active by the insertion of switching components allowing, by appropriate control, to force the rods to behave for some like discontinuous rods and for others like continuous rods which have radioelectric characteristics different from the previous ones . Information on this subject is available in the presentation "Beam switching smart antenna for hyperlan terminais" by A. Chelouah, A. Sibille, C. Roblin, during AP2000, Davos, April 2000, or, in the article by E. Yablonovitch in Physical Review Letters, vol. 58, n'20, 1987, p2059-2062. This alternative solution does not imply direct action on the excitation circuit of the radiating element but only on elements of its close environment, thus limiting losses. It is obtained by using the properties of Photonic Forbidden Band (BIP) materials which are already known and for which articles have been published, in particular: "Photonic Band Gaps in experimentally realizable periodic dielectric structures", CT Chan, KM Ho and CM. Soukoulis, Europhysics Letters, 16 (6), pp563-568, October 7, 1991; or "Metallic Photonic band-gap materials", M. M. Sigalas, C.T. Chan, K.M. Ho and CM. Soukoulis, Physical Review B, vol. 52, n'16, October 15, 1995; or, finally, "Active Metallic Photonic B and Gap materials (MPBG): experimental results on beam shaper ", G. Poilasne, P. Pouliguen, K. MahdJoubi, L. Desclos and C. Terret, IEEE Trans. On Antennas and Propagation, January 1999. L ' set of rods forming the BIP material of this type of antenna is a periodic structure, called BIP structure, mainly composed of parallel conductors and in which a radiating element acts.The electromagnetic characteristics of this BIP structure depend mainly on the emission frequency / reception of the radiating element. Its frequency response to a plane wave alternately presents frequency bands authorizing or not the propagation through the BIP structure. The duality of response between a BIP structure composed of continuous rods and a BIP structure composed of discontinuous rods was studied. These differences were exploited to obtain the switching and the spatial conformation of the diagram radiation by passing from one to the other, continuous or discontinuous rods, of these BIP structures. This is how presentations and articles were produced on this subject, in particular: "Numerical and experimental demonstration of an electronically controllable PBG in the frequency range 0 to 20 GHz", by A. De Lustrac.T. Bri llât, F. Gadot, E. Akmansoy, during AP2000, Davos, April 2000; and in "Experimental radiation pattern of dipole inside metallic photonic band-gap materials", by G. Poilasne, P. Pouliguen, K. MahdJoubi, C. Terret, P. Gelin and L. Desclos, in Microwave and Optical Technology Letters, vol . 22, issue 1, July 1999. Currently, BIP square mesh structures are used. In other words, and as illustrated in FIG. 1 (cross section relative to the axis of the rods), the rods 1 form a grid with square meshes at the center of which is the passive radiating element 2. It appears that this BIP square mesh structure has two major drawbacks. First of all, it is poorly adapted to excitations by cylindrical waves, hence a difficult study when a radiating element is placed in the middle of a BIP structure with square meshes. Furthermore, it does not make it possible to create a constant beam rotating over 360 ° with any step and any angle. The invention which is proposed has in particular the objective of overcoming the drawbacks of the state of the art concerning antennas of the type using a material with Photonic Forbidden Band (BIP material) and forming a determined structure which can be qualified of photonic crystal. The antenna of the invention can be used to orient (direction) and / or shape (shape) a single beam or several simultaneous beams. It can also be used to conform and switch different beams: we can then speak of beam-switching antenna. Basically, the antenna of the invention differs from antennas with a BIP structure known by the fact that the implantation of the elements (wires / bars) within the antenna and around the radiating element is not done. according to a square mesh but according to a distribution along closed curves concentric to each other at the center of which is the radiating element. The shape of the closed curves is preferably circular (circles) but it can be more complex in particular with the type of ellipse, cycloid or other rounded curves. The shape of the elements making up the antenna (radiating element and / or the wires / bars) is preferably linear but it can be different and in particular curved for the wires / bars. Thus, the invention relates to an antenna allowing the conformation of at least one beam of radio waves of at least one determined wavelength, of the type comprising at least one element radiating the waves, preferably passive, placed in a set of wires or bars reflecting the wave and substantially parallel to each other, made of a material with Photonic Forbidden Band (BIP) and forming a determined structure, said determined structure having defects so as to conform said at least one beam in a direction depending on the position and / or the configuration of said faults. According to the invention, the wires or bars and the faults are arranged on a set of N closed concentric curves of a plane, N being greater than or equal to one, the radiating element being disposed inside the most curved internal. In various embodiments of the invention, the following means which can be combined according to all the technically possible possibilities, are used: - the curves are chosen from circles, ellipses, cycloids and, preferably, are all circles, the radiating element being placed substantially at the common center of the circles; - the maximum distance separating the innermost curve (in practice a wire / bar on the innermost curve) and the radiating element is less than or equal to a quarter of the wavelength (of the shortest wavelength in the case where several wavelengths are possible), - the distance separating the innermost curve and the radiating element is greater than a quarter of the wavelength (of the shortest wavelength in the case where several wavelengths are possible), in order to reduce the weight and / or the production cost and / or to facilitate the impedance adaptation, etc. - the maximum distance separating two successive contiguous curves (in practice two wires / bars adjacent to two curves along a direction passing through the radiating element) is less than or equal to a quarter of the length wavelength (of the shortest wavelength in the case where several wavelengths are possible), - the adjacent wires / bars or faults along a given curve are arranged at equidistant points transversely (corresponds to a constant transverse period in the case of a curve which is a circle); - the transverse distances of the adjacent wires / bars or defects are all equal for all the curves (corresponds to a constant and equal transverse period for all the circles in the case of curves which are circles); - The curves are circles and the wires / bars or defects are arranged in at least two concentric circles around the radiant element that is substantially central according to a periodic transverse distribution which is constant and equal for all the circles; - the wires / bars or faults are arranged along distribution axes passing through the radiating element and in the plane, at points corresponding to the intersection of the curves and the distribution axes (corresponds to a constant angular period and the wires / bars or faults are systematically or not arranged at the crossing points of the distribution axes and curves); the distribution axes are regularly distributed in the plane over 360 ° and divide it into equal angular sectors, the value of an angular sector being preferably 22.5 ° or a multiple of 22.5 °; the curves are circles and that the wires / bars or defects are arranged in at least two concentric circles around the radiant element that is substantially central according to a constant and equal angular periodic distribution for all the circles; - the wires / bars or faults are arranged according to a combination of arrangement with constant transverse period and arrangement with constant angular period, - the radiating element is directional; - The radiating element is omnidirectional and is preferably a dipole, said dipole then being arranged substantially parallel to the wires / bars; the radiating element is omnidirectional and is preferably a monopole arranged on a ground plane, said monopole then being disposed substantially parallel to the wires / bars, each of the wires / bars being connected at one of its two ends to the ground plane, - in the case of a monopole and of wires / bars with conductive segments separated by insulators comprising or formed of switchable active components, the wires / bars are connected to the ground plane by the insulators, - in the case of a monopole and of wires / bars with conductive segments separated by insulators comprising or formed of switchable active components, the wires / bars are connected to the ground plane by the segments; - the wires / bars are straight; - the wires / bars are curved; - the wires / bars have straight parts, in circles, ellipses, triangles, squares or rectangles; - The faults are achieved by the at least partial withdrawal of some of said wires / bars, the at least one beam being shaped in a direction depending on the position and / or the configuration of the wires / bars removed; - at least some of the wires / bars each consist of at least two conductive segments, the maximum length of a segment being less than a quarter of the wavelength (of the shortest wavelength in the case where several wavelengths are possible) and preferably less than or equal to one tenth of the wavelength, the adjacent segments of a wire / bar being separated by insulators (at least insulator for the wave), each wire / bar with several isolated segments (at least for the wave) between them, called discontinuous wire / bar, being transparent for the wave and equivalent to the defect of a wire / bar at least partially removed; - a wire / bar may comprise at least one part formed by a succession of segments separated by insulators and at least one other part consisting of a continuous reflective conductor, - the use of the addition / removal of wires / bars for the implementation of wires / bars with segments; - all the wires / bars are wires / bars with several segments; - at least one of the insulators separating two adjacent segments in a wire / bar comprises or is formed of a switchable active component which can take at least a first state, conductive for the wave, in which the wire / bar with several segments behaves as a conductor / reflector for the wave called continuous wire / bar, and a second insulating state for the wave in which the wire / bar with several segments is transparent for the wave and equivalent to the defect of a wire / bar at less partially removed, and in that said antenna further comprises means for controlling the active components, making it possible to force certain of the wires / bars with several segments to behave like discontinuous wires / bars, the at least one beam being shaped in a direction depending on the position and / or configuration of the discontinuous wires / bars; - in a wire / bar with segments and active switching components, the control is carried out by section (s) formed by a subset of adjacent segments of the set of segments of the wire / bar, the subassembly being able to consist of two to the total number of segments of the wire / bar, the components separating the segments of a section being put in their first state, the others components being in the second state, in order to be able to further orient in height with respect to the plane the beam (s); the means for controlling the active components form means for shaping and switching between at least a first beam and at least a second beam, so that the antenna is a beam-switching antenna; - the antenna is applied to a public or private civil telecommunications network. The invention finally consists of a base station which comprises at least one beam-switching antenna according to one or more of the preceding characteristics. The invention therefore consists of a tunable electromagnetic material derived from photonic band gap materials (BIP) and preferably having a cylindrical symmetry. This material will hereinafter be called BIP Accordable Conformé material (BIPAC). The main destination of this material is the use as an active deflector in base station antennas, in particular for civil telecommunications networks (GSM and UMTS). According to another presentation of a modality of the invention, the antenna is produced by surrounding an element radiating electromagnetic waves (preferably omnidirectional at least in an xy plane) with a structure of Faraday cage type with bars (or wires) which are perpendicular to the xy plane (and parallel to the radiating element), each of the bars of the cage being able to selectively be made conductive of the waves, it then appears as a reflector of the electromagnetic waves, in whole or by section (s) very long (continuous state) or be conductive only on very small segments (discontinuous state), the segments being separated from each other by insulators and the segments being of a length such that the bar then appears substantially transparent for the waves. From a theoretical point of view it is preferable that the total length of the bars in the continuous state is large compared to the wavelength of the waves to be emitted or received because they then appear to be in a conductive state vis-à-vis -vis these waves which prevents (or limit) by reflection their exit outside the antenna. It is understood that in this very long case with controllable wires / bars (in particular by components which are diodes), it is necessary to use many components. However, it has been observed in practice that, surprisingly, shorter lengths of the wires / bars could be used advantageously and it is thus possible to use lengths of wires / bars greater than or equal to half the length d 'wave. The use of shorter lengths than from a theoretical point of view makes it possible to reduce the number of components without consequent degradation of the characteristics of the antenna. It was thus possible to make, by way of example, an antenna intended to operate at 1 GHz, the length of each wire / bar is approximately 17 cm. Thus, the term “large” for the length of the wires / bars (or continuous conductive parts / reflectors of the waves) must be considered more in a functional aspect than in pure length since one can make antennas with wires / bars of a length which can be reduced to half the wavelength and whose continuous wires / bars behave well as wave conductors / reflectors. The length of the segments is described as very small compared to a quarter of the wavelength of the waves to be emitted or received, the segments being isolated from each other, the bars in this state are generally non-conductive with respect to vis these waves and then appear substantially transparent to these waves. In one embodiment, each of the bars can thus be made conductive / reflective (continuous state) or non-conductive / transparent (discontinuous state) vis-à-vis the waves is of the type with very small segments separated by radioelectric insulators with, in parallel with the insulators, switching means making it possible to connect electrically continuously and alternately or only alternately (capacitive connection for example) two by two adjacent segments of an insulator. Note that the mean term of parallel switching of the insulator corresponds as well to the case where an insulator is always present (switch controlled in parallel with an insulating spacer), as to the case where the insulator becomes conductive (diode for example ). For reasons of simplicity, it is preferred to use between the segments a component which switches on command from a conducting state to an insulating state from electromagnetic waves, such as a diode. In the following, the terms wire or bar will be used interchangeably to designate conductive / reflective or non-conductive / transparent (radio) electric elements of the antenna structure. In practice, depending on the frequencies used by the antenna, it may be preferable to use bars for very high frequencies for which skin effects are present rather than wires. In addition, the bars can be hollow and internally allow the passage of in particular electrical connections for the control of active switching components between isolated segments of the bar, these connections can thus be partially shielded by the presence of the bar. On the other hand, the term (radio) electric is used to define the conductive / reflective or non-conductive / transparent state of the wires / bars overall and conductive or non-conductive of the active switching components specifically because if, at a minimum, conduction or non-conduction must concern radio waves (alternating), these elements can be more conductive or non-conductive towards a possible direct current. In fact, a capacitive link, for example in an active switching element, is conductive for radio waves but insulating for DC, so a switching can be obtained by varying the value of the capacitance (varicap). Likewise, an inductive link, for example in an active switching element, is non-conductive for radio waves but conductive for direct current, a switching can therefore be obtained by varying the value of the inductor. It is also possible to associate capacitive and inductive components in plug circuits (non-conductive) forming active switching elements and the values of the components of which can be varied in order to make them conductive. In order to improve the behavior of the antenna, it is also possible to correct the presence of stray capacitances (in particular for the diodes) or stray self (in particular for the connections of the diodes), by additional corrective components, in particular chokes parasitic capacities and capacity against parasitic coils, see combinations of these components. These active switching components can for example be diodes which are turned on or off depending on whether or not a current is applied. Depending on their type, the active switching components can be conductive or non-conductive at rest (a non-polarized diode, at rest, is non-conductive, neglecting its parasitic capacity). The antenna of the invention in the preferred case of a distribution of the layers of wires / bars in concentric circles is particularly well suited to excitations by cylindrical waves produced by a radiating element of the dipole type placed in its center. Depending on its configuration, it makes it possible to produce at least one radio beam (lobe) of any opening, which can rotate 360 °. Indeed, in particular for the UMTS network, the antennas must be capable of having a directional radiating beam orientable through 360 °, capable of following a user during his movement. The antenna of the invention, in particular in its preferred configuration of circular (cylindrical) layers, is simple to implement and inexpensive. It is recalled that in the current antennas of the base stations, the direction of the beams is fixed and does not allow the operators to adapt to telephone traffic. The BIP structure according to the invention and preferably in its form with a cylindrical BIP structure and in the case where it can be controlled, makes it possible to obtain beam agility. This makes it possible to follow the mobiles, to dynamically modify the coverage areas according to the needs of the moment, to give priority to particular sectors during peak hours, etc. The present invention will now be exemplified by the description which follows, without however being limited thereto, and in relation to: FIG. 1 which represents a cross-sectional view of an antenna comprising a BIP structure of the state of the art square mesh; FIG. 2 which represents a first particular embodiment of a cylindrical BIP structure according to the invention; FIG. 3 which represents a second particular embodiment of a cylindrical BIP structure according to the invention; FIG. 4 which represents an example of antenna according to the invention comprising a cylindrical BIP structure according to the first embodiment illustrated in FIG. 2 and with faults obtained by withdrawal of wires / bars; FIG. 5 which represents an example of antenna according to the invention comprising a cylindrical BIP structure according to the second embodiment illustrated in FIG. 3 and with faults obtained by withdrawal of wires / bars; FIG. 6 which represents radiation patterns obtained for the antennas of FIGS. 4 and 5; FIG. 7 which represents a schematic perspective view of an antenna according to the invention comprising a cylindrical BIP structure; FIG. 8 which represents a real perspective view of an exemplary antenna according to the invention comprising a cylindrical BIP structure; FIG. 9 which illustrates the operation of a beam switching antenna, FIG. 10 which represents in (a) a perspective view of an antenna formed from a 90 ° BIPAC material, the wires / bars being arranged on spokes separated angularly by 90 ° and in (b) a top view of an antenna formed of a BIPAC material 30 °, the wires / bars being arranged on spokes separated angularly by 30 °, Figure 1 1 (a) to (d) which represents simulations of 45 ° BIPAC antennas for different distributions of continuous and discontinuous wires / bars, FIG. 12 (a) to (d) which represents a simulation of a radiating element of dipole type alone, FIG. 13 (a) to (d) which represents the simulation of a radiating element such as that of FIG. 12 but placed within an antenna in a 45 ° BIPAC material, FIG. 14 (a) to (d) which represents the simulation of a radiating element such as that of Figure 12 but placed within an ante nne in 22.5 ° BIPAC material. In contrast to known antennas and in particular as we have seen in the part relating to the prior art concerning an antenna with a BIP structure with square meshes as shown in FIG. 1 where the rods 1 form a grid (of seven rows by seven columns ) with square meshes in the center of which is the passive radiating element 2, the antennas of the invention have a structure based on a distribution on circular curves (circle, ellipse or another circular closed curve) concentric son or bars each forming a layer around a radiating element substantially central to the curves. Typically, in an antenna of the invention, a radiating element (in particular a simple dipole antenna) is arranged along a z axis and is surrounded by a structure of wires or bars typically linear and parallel to each other and to the z axis. Preferably and as shown in the figures, a BIP structure is used, the distribution of the wires or bars of which is carried out on concentric circles around a center where the radiating element is substantially located. The radiating element and the wires / bars are perpendicular to a median xy plane of the structure which, in a basic operating mode, carries the major axes of the transmission / reception beams (lobes) which can be created (in other modes of operation, the main axes can be above or below), with a particular lobe shape and an angular position around the particular z axis depending on the distribution and the conductor / reflector or non-conductor states conductor / transparent wires / bars. The term radiating element is used here to designate both the final device for transmitting in the radio wave space of a transmitter and the device for collecting in space the electromagnetic waves of a receiver, devices which are of preferably assembled in a single structure (same device for emission and reception) but which, in certain configurations, can be formed of two distinct devices or be used only for emission or for reception (in the case of the creation of an antenna specializing in transmission or reception). The radiating element is for example a dipole, preferably passive. To cover a large bandwidth (for example the UMTS band), the radiating element can be a thick dipole or a folded dipole in printed technology. Each wire or bar is preferably made up of adjacent electrically conductive segments separated from each other by insulators comprising in parallel active switching components (active controlled components) capable of placing (radio) electrical continuity in the adjacent electrically conductive segments. Thus, each wire or bar can be conductive in sections or in its entirety (continuous state appearing conductive / reflective for the waves) or be left consisting of conductive segments isolated from each other (discontinuous state, appearing non-conductive / transparent for the wave). The possibility of conduction or not by sections of the wires / bars also makes it possible to orient the major axis of the lobe (s) in height with respect to the xy plane for volume scanning of the space. As indicated, this reflection or transparency effect concerns the waves and the lengths of the wires / bars, of the segments and of the sections are adapted to the wavelengths involved so that these effects are indeed present vis-à-vis -vis waves. In certain embodiments, only part of the wires or bars is of the previous type consisting of conductive segments which can be connected

(radio) electrically to each other by controlling switching components, the others being either non-conductive / transparent or, more simply, being omitted, or conductors / reflectors on all or a large part (large relative to the length d 'wave) of their total length. It is understood that in the case where the wires / bars are of a fixed type, conductive / reflective or non-conductive / transparent, it is no longer possible to control them and, that apart from manual operations, there n It is not possible to modify by command the shape and the orientation of the lobe (s) on all (if all the wires / bars of the antenna are of a fixed type) or part of the antenna (if only part of the antenna wires / bars is of a fixed type, the others can be ordered). An additional advantage of having separate electrically conductive segments of insulators which can be made conductive by section switching elements is to allow the creation of a broadband antenna or of the logarithmic type, the length of the section made conductive being suitable for a particular frequency. Thus, in addition to being able to orient the lobe in height relative to the xy plane, the operation of the antenna can optionally be adapted to a wide range of frequencies. We have therefore seen that the wires / bars of the antenna structure of the invention are arranged in concentric layers and, preferably, each circular (circle in the xy plane or cylinder in the xyz space) whose single center of the structure and circles correspond substantially to the radiating element. In one embodiment, the wires / bars are arranged from one layer to the other in the xy plane along carrier axes in rays (distribution axes) passing through the center of the structure (or in zw planes in xyz space; w being a line centered in the xy plane). Preferably, these bearing axes in radii are regularly angularly arranged in the xy plane, for example every 90 °, 45 °, 30 ° or 22.5 °, or even more or less and more generally any value corresponding to a division of the plane xy around the center in equal angular portions. If it is preferred that the wires / bars of a layer are distributed around the center in equiangular positions (for example every 30 °), it is however considered the case of non-equiangular distributions, the wires / bars being able to be more tightened angularly in certain parts of the xy plane in order to increase the pointing accuracy of the lobe (s) in said parts relative to the others. Thus at each intersection of a bearing axis in radius and a circle of a layer, a wire or bar is present. It is understood that these circles (cylinders) and axes (planes) are virtual and intended to facilitate the explanation of the location of the wires or bars to form the structure. In a variant, the wires / bars are arranged regularly with transverse distances between two adjacent wires / bars (distance along the straight line joining the two) of a given circle equal all along said circle and, possibly, for all circles. As previously, however, it is envisaged that in certain sectors the transverse distances are different. In practice, the wires or bars as well as the radiating element are held together by material means in order to keep a stable structural configuration. These means are typically spacers joining the wires / bars and the antenna or a common support. These means can be drilled discs through which the wires / bars are held relative to the radiating element. These means can still completely fill the structure of the antenna. These means are made of materials with low loss for the frequencies involved by the antenna and are in particular plastics, special glasses or special ceramics and, for example foams, expanded polystyrene, resins,

TEFLON® ... We have seen that in certain configurations it is possible to have a ground plane at an axial end of the antenna and in particular when the radiating element is a monopole (radiating element with ground plane), the radiating element then being placed substantially perpendicular to the ground plane and isolated from it. In such a configuration, it is possible to use this ground plane as a means of holding the wires / bars which will then be fixed to one (lower) of their two ends. to said ground plane and preferably connected (or which can be electrically connected in particular by the switching components in the case of segment wires / bars) to the ground plane. Since it is also possible to have one or, preferably, two ground planes (at the two axial ends, at the bottom and at the top of the antenna), whatever the type of the radiating element (dipole, monopoly or other), this / these end ground planes can also serve mechanically as a means of holding the wires / bars. In the case of simultaneous electrical connection of all the wires / bars to the two ground planes (top and bottom) prevents the control of the wires / bars with controlled segments (in particular with diodes) by a direct voltage ("DC"), control which would allow them to pass from a continuous state, to a discontinuous state and vice versa. It is therefore preferable to provide electrically insulating spacers for the wires / bars of one of the two ground planes while ensuring mechanical support, the spacers ensuring at least insulation for direct current (any electrical insulating material can be used, remembering that a capacity is insulating for direct current). It should be noted that the term ground plane signifies both a continuous surface and a discontinuous surface. Indeed, if from a theoretical point of view a continuous surface is ideal, it is also possible to implement wired or meshed ground planes without net degradation of the characteristics of the antenna. These wired ground planes are presented as continuous horizontal conductive wires / bars, that is to say perpendicular to the radiating element and to the wires / bars of the BIP / BIPAC structure, joining the latter and grounded. We will see later in the description such an antenna structure with Figure 11. The presence of ground planes at both high and low axial ends of the antenna makes it possible to limit the propagation of waves in these two directions. The distance between the layers of wires / bars and the length of the segments along the wires / bars depends on the emission wavelength of the antenna. If the antenna transmits at a given wavelength, the distances between the concentric layers will be equal to or different from each other, provided that these distances are clearly less than the wavelength and better still, less than a quarter of the length d 'wave. For example, for a frequency f = 1 GHz, the wavelength in air is 30 cm. The length of a segment of a wire / bar is of the order of a few centimeters (2.5 cm in the example considered here). These wires / bars are arranged in concentric layers starting from the central axis of the antenna. These layers are separated by a distance which must be less than a quarter of a wavelength (7.5 cm for the example at 1 GHz). The wires / bars are preferably arranged along the radii of concentric cylinders. The number of these rays, and therefore the angle which separates them, is chosen according to the intended application and, in practice, the smaller the angle the more precision can be obtained on the shape and angular orientation of the / lobes. A radiating element is placed in the center of the antenna. The radiation of the antenna will be controlled by the BIPAC material. The arrangement of the rays, the number of layers and the number of wires / bars switched determine the shape (width) of the beam radiated by the antenna. In the case of switching components with a diode type, the metal wires / bars have diodes between the segments which can be made conductive (state of a continuous wire / bar therefore conductive / reflective for waves) or non-conductive ( state of a discontinuous wire / bar therefore non-conductive / transparent for waves) by acting on the polarization of these diodes. Direct current polarizes these diodes. When the current is sufficient, the diodes are in the passing state, their internal resistance is low and the wire / bar is in a continuous state (conductor / radioelectric reflector). When this current is interrupted, the diodes are blocked and the wire becomes in a discontinuous state (non-conductive radioelectric, transparent for waves). The operating principle is as follows. The material behaves like a metallic BEEP operating in its first prohibited band. When the metallic wires / bars that compose it are in the continuous state (passing diodes for example), the material is reflective and the radiation from the antenna placed in the center is confined inside. When the wires / bars are in the discontinuous state (blocked diodes for example) the material becomes transparent for this radiation only in the region where these wires / bars are in the discontinuous state. If we can control the state of the switching components (diodes for example) between the adjacent segments of the wires / bars on the whole material, we can make all or part of this material transparent and therefore control the direction in which the antenna will transmit or receive. Modelings carried out using two industrial electromagnetic simulators (NEC® and HFSS®) have shown the validity of this operating principle and of the material design. When the radiating element of dipolar type is only, its radiation diagram is omnidirectional in the direction normal to the radiating element which is along the axis z. We were able to simulate antennas with circular (cylindrical) layers with an increasing number of layers from 1 to 6, the dipolar radiating element being central, and with wires / bars arranged every 45 ° along the circles (the wires / bars are aligned on the shelves). To control the direction of emission, the wires / bars arranged along a single ray are all placed in the discontinuous state (transparent for the waves), the others being in the continuous state (conductor / reflector for the waves ). The antenna simulated uses a central radiating element of the dipole type operating at 1 GHz. The radiation pattern has a lobe which becomes thinner in the direction of radiation when the number of layers of wires / bars of the material is increased. The wires / bars can also be placed every 30 ° and made discontinuous along two directly adjacent spokes. If the number of layers is sufficient, the beam will be more directive than in the previous case of an angular arrangement at 45 °. Other simulations have been carried out for operation at 2 GHz and dipolar radiating element, for angular distributions at 45 ° and 22.5 "on the circular layers. As before, the radiation diagram only includes a lobe in the direction of the wires / bars of a spoke in a discontinuous state. Thus, in the antenna of the invention, the radioelectric radiating element is preferentially passive and it is placed at the heart of a set of wires / bar conductors substantially parallel to each other and made of a Photonic Forbidden Band (BIP) material and forming a determined structure of wires / bars. This antenna structure formed of wires / bars surrounding a radiating element has defects in the type of wires / bars having (radio) electrical characteristics different from the others, in particular conduction / reflection or non-conduction / transparency, so as to conform at least one beam (or lobe) in a direction depending on the position and / or configuration of said defects. The defect corresponding to characteristics

(radio) different electric (wire / conductive bar / reflector or non-conductive / transparent to waves) can be obtained in various ways, several modes of implementation are possible and two are given as main 'example. We understand that the term default can have two meanings depending on the context. The first, which will be used later, corresponds to the case where in an antenna that initially comprises conductive wires / bars / reflectors, the defect is the presence of non-conductive / transparent wires / bar or the omission of wires / bars conductive / reflective. The second, opposite to the previous one, corresponds to the case where the defect is a conductive wire / bar / reflector. In a first implementation of the invention, said defects are achieved by the withdrawal of some of said conductive wires / bars, said at least one bundle being shaped in a direction depending on the position and / or configuration of the wires / bars removed. The withdrawal of a wire / bar can be carried out in whole or in part in order to also be able to orient the beam in height with respect to the xy plane. The conductive wires / bars are either actually continuous, or of the type with separate segments of insulators with active switching components and placed in a continuous state (conductor / reflector with respect to waves). In a second implementation of the invention, at least some of the wires / bars are in several segments separated by insulators which can be short-circuited by active active components and allowing when the active components are in a passing state, in short -circuit (radio) electric, that the wire / bar behaves like a conductor / reflector (radio) electric (continuous state) and when the active components are in an insulating state, the wire / bar behaves like a non-conductor / transparent (radio) electric (discontinuous state) equivalent to a wire / bar at least partially removed. The antenna preferably comprises means for controlling said active switching components, making it possible to force certain of the segment wires / bars to behave like discontinuous wires / bars (non-conductive of waves, transparent) and others like continuous wires / bars (conductor / wave reflector). The defects here are wires / bars behaving like discontinuous wires / bars and a bundle can be shaped in a direction depending on the position and / or configuration of the discontinuous wires / bars. In this second implementation of the invention, the BIP structure of the antenna is therefore active in that it makes it possible to dynamically and easily conform one or more beams or lobes (radiation patterns). No manual manipulation of wire / bar removal is necessary here. Note that these two possibilities of implementation can be combined, part of the wires / bars being able to be controlled, the rest having to be handled for removal or addition in order to be able to modify the radiation diagram. Indeed, if, advantageously, all the wires / bars of the BIP structure of the antenna are with several segments isolated from each other and with active components for switching insulators in parallel, it is however clear that the invention covers also the case where only certain wires / bars are active, that is to say formed from several isolated segments whose insulator comprises in parallel an active switching component. Advantageously, said means for controlling the active switching components form shaping and switching means between at least a first beam and at least a second beam, so that said antenna is a beam switching antenna. The beam switching antenna according to the invention makes it possible to produce one or more beam (s) of any opening, which can rotate (that is to say switchable) over 360 °, with a pitch and an angle of any function the angular distribution of the wires / bars within the BIP structure of the antenna. Preferably, the wires / bars are arranged on circles according to an angular period constant, and consequently according to a variable transverse period, for each concentric layer. Many arrangements of the wires / bars, according to concentric layers along closed circular curves can be envisaged without departing from the scope of the present invention and we will now describe in more detail antennas with concentric circles layers of the BIP structure type cylindrical. In FIGS. 2 to 5 and 9 discussed below, the radiating element 2 and the wires / bars 1 are seen in cross section from above (or below) the xy plane, said plane being in the plane of the sheet on which the figures are made. In these same figures, the wires / bars are arranged along concentric circles or layers around the radiating element 2. In general, the different parameters of the cylindrical BIP structure are: - Pθ: the angular period (in °), that is to say the angular distance between two adjacent wires / bars of a given circle; - Pt: the transverse period (in mm), that is to say the interval between two adjacent wires / bars of a given circle; - P r: the radial period (in mm), that is to say the interval between two adjacent circles; - d: the diameter of the conductive wires / bars (in mm); - n: the number of concentric circles (layers). In the following description, it is assumed that the wires / bars are arranged periodically according to a constant radial period Pr and, for each concentric circle, according to a constant angular period Pθ (and consequently according to a variable transverse period Pt). As illustrated in FIG. 2, in a first embodiment of the cylindrical BIP structure according to the invention, the angular period Pθ is identical for all the concentric circles. Consequently, the transverse period Pt varies from one circle to another (Pt1 <Pt2). In this Figure 2 we can notice that the inner circle has particularly tight wires / bars and in this type of configuration it is this inner circle which essentially controls the frequency characteristics of the antenna. Such an antenna structure is rather intended for single-band applications. In a second embodiment, illustrated in FIG. 3, it is the transverse period Pt which is identical for all the concentric circles. The angular period Pθ therefore varies from one circle to another. In this type of structure, all of the circles influence the frequency response of the antenna and such an antenna is rather intended for multiband applications. It should also be noted that the number of transmission peaks is proportional to the number of concentric layers. The cylindrical BIP structure must also contain faults (wires / rod in a discontinuous state, non-conductive of the waves and therefore transparent for these waves) so as to create (at least) a beam in a direction depending on the position and / or the configuration of these faults within a BIP structure essentially made up of wires / bars in a continuous state (conductor / reflector of waves). A first, simple technique for producing faults in the cylindrical BIP structure consists in removing metallic wires / bars locally. Depending on the position and configuration of the wires / bars removed (faults), the width, direction and number of useful beams can be chosen. Figures 4 and 5 illustrate the structures obtained by removing wires / bars in an angular sector of the BIP structure. The radiation diagram obtained for the antenna in FIG. 4 is referenced 61 in FIG. 6. The radiation obtained for the antenna of FIG. 5 is referenced 62 in FIG. 6. It will be seen from these diagrams that the antenna of FIG. 5 offers better directivity than that of FIG. 4. A second technique for producing faults in the cylindrical BIP structure consists in using metallic wires / bars which can be controlled, known as active wires / bars, by using active wires / bars comprising at least two conductive segments between which an insulator is inserted and in parallel from the insulator to the at least one active switching component (diode, transistor, MEMS, etc.) making it possible, depending on the state of the component (conductive or non-conductive) to connect (radio) the two segments electrically. Thus, depending on the control of the active component and therefore its state, the active wire / bar behaves as if it were in a continuous state (conductor / wave reflector) or a discontinuous state (non-conductor of waves and therefore transparent for waves). The wires / bars behaving like wires / bars of discontinuous state, therefore non-conductive at least for radio waves, constitute the faults. Depending on their position and configuration, you can choose the width, the direction and the number of useful beams. The antenna therefore comprises means for controlling the active switching components, making it possible, depending on the beam (s) to be created, to force certain of the active wires / bars to behave like wires / bars in a state discontinuous while the others are in a continuous state. As active switching components, networks of PIN diodes polarized by a direct current flowing in the metal wires / bars can be used. The control of these components (and therefore of the wires / bars in which they are included) can be carried out by angular sectors (for example three sectors separated by 90 ° to produce three lobes in three directions) of the cylindrical BIP structure. For example, all the wires / bars of a sector commute together. This reduces the number of independent control circuits to the number of switchable sectors. Photodiodes (possibly phototransistor) can also be used, the switching of which is obtained by light supplied by optical fiber. In order to increase the possibilities in terms of beam conformation and angular positioning in the xy plane, all the wires / bars can be of the type that can be controlled. On the other hand, within each wire / bar that can be controlled, the active switching components can be controlled as a block or individually or in sections. In the first case, all the wire / bar will be made conductive / reflective or non-conductive / transparent depending on the order. In the latter case, it will be the section (s) ordered which will be made conductive / reflective or non-conductive / transparent according to the order (as indicated above, the length of the section must be large relative to the wavelength). Thus, depending on the position of the section in height relative to the xy plane, it will be possible, in addition, to orient the lobe (s) created in height. In the intermediate case with independent controls of each active switching component of a wire / bar, it is possible to carry out both a block action and a sectional action (the controlled components will be adjacent and defining a sufficiently long section length vis-à-vis screw waves). The wires / bars arranged in the outer circle (with the largest radius) form a cylindrical envelope 3 of the structure, as illustrated in the schematic perspective view of FIG. 7. For the sake of simplification, only the external envelope 3 (without representation of the wires / bars themselves), the radiating element 2 and two beams 4 and 5 have been shown. The cylindrical BIP structure also appears in FIG. 8, which is a real perspective view of an exemplary antenna according to the invention. In this example, the cylindrical BIP structure comprises three concentric circles on each of which are arranged a plurality of wires / bars 1. The conductive wires / bars are for example metallic wires / bars, placed in air or in a dielectric (in view of reducing the dimensions). In the case of air, as illustrated in FIG. 8, the wires / bars are held by means of a support. This support is for example made of foam (permittivity equivalent to that of air). In the example illustrated, it comprises a horizontal plate or disc 6. We now present, in relation to FIG. 9, the operation of a beam-switching antenna according to the invention, comprising a cylindrical BIP structure with defects obtained by wires / bars placed in a discontinuous state (therefore transparent for radio waves) by command. Only a part of each of the lobes 91, 92 has been shown, that closest to the antenna. It should be noted (Figure 9 does not represent the outermost part of the lobes) that it is preferable to obtain a narrow lobe to have a sector of defects or formed of discontinuous wires / bars (transparent for waves) sufficiently open rather than reduced to a minimum, that is to say for Figure 9 formed from several adjacent bearing rays (lobe 91) rather than a single one (lobe 92). We can compare the effects of this phenomenon of interaction of waves with structure with that of diffraction in optics. The control of the conformation of a beam is carried out as follows. The cylindrical BIP structure is excited in the center by an antenna with symmetry of revolution 2. At the start, all the active wires / bars 1 are in a continuous state (they are in this continuous state represented by a black patch in FIG. 9) and behave like (radio) electric conductors / reflectors. To create a beam in a given direction, faults are created in this cylindrical BIP structure by passing the active switching components between segments of certain wires / bars which are oriented in the desired beam direction to the insulating state. These wires / bars therefore pass in a discontinuous state (they are in this discontinuous state represented by a white patch in FIG. 9) and behave like electrical (radio) non-conductors and appear substantially transparent to radio waves. In this way we can direct the beam in all directions of space. There is also the possibility of having two or more beams simultaneously in different directions. Thus, in the example of FIG. 9, two beams 91 and 92 are created simultaneously. In Figure 10 there are shown two examples of antenna made from BIPAC materials, the first in (a) with circular and radial distribution of angular pitch of 90 ° and the second in (b) of pitch of 30 °. The wires / bars are formed of segments 7 conductors separated by diodes 9 and can therefore be placed in a continuous state (conductor / reflector of the waves) or discontinuous (transparent for the waves) depending on the polarization or not of the diodes. The central radiating element is a dipole. It is understood that this type of structure, in the case where the diodes can be controlled selectively (in a wire / bar: individually, by group or globally), makes it possible to produce a wire / bar of which one (or more) section (s) (Fri) t be made discontinuous with respect to the rest of the wire / bar, a section corresponding to a portion (or all) of a wire / bar whose adjacent (contiguous) segments are isolated from each other others (discontinuous) electrically radio, the rest of the wire / bar being continuous. In Figure 1 1 (a), the BIPAC 45 ° material of the antenna is seen in perspective and all the wires / bars of the two circular layers are in a continuous state 10 (wave conductors / reflectors), except those located along a radius which are in a discontinuous state 1 1 (transparent to waves). The radiation diagram for θ = 90 ° is given in Figure 11 (b) in dB. The major axis of the radiation diagram is in the direction of the radius having the discontinuous wires / bars. In Figure 1 1 (c), the BIPAC 45 ° material of the antenna is seen in perspective and all the wires / bars of the six circular layers are in a continuous state 10 (conductors / reflectors of the waves), except those located on along a ray which are in a discontinuous state 11 (transparent to the waves). The radiation diagram for θ = 90 ° is given in Figure 11 (b) in dB. The major axis of the radiation diagram is in the direction of the radius having the discontinuous wires / bars. It should be noted in Figure 11 (a) and (c) that conductors are arranged at the upper and lower ends of the spoke antenna structure from the (isolated) ends of the radiating element to the wires / bars of the first circle, they form a wired ground plane limiting the propagation of the waves up and down the antenna. In Figure 12 (a) to (d), the radiating element alone with a dipole type radiates at a frequency of 2 GHz and the length of the dipole is 75mm in total. For reasons of symmetry and with the HFSS® simulation software, only a quarter of the antenna is simulated (Figure 12 (d)). Figure 12 (a), the far field radiation diagram forms a torus in this perspective view. Figure 12 (b), the radiation diagram is seen in projection for φ = 0 ° and Figure 12 (c) for θ = 90 °. In Figure 13 (a) to (d), the dipole radiates at a frequency of 2 GHz within a BIPAC material whose wires / bars are arranged on concentric circles along rays spaced angularly by 45 °, all son being in a continuous state 10 (conductor / reflector of the waves) except those of a ray which are in a discontinuous state 1 1 (transparent for the waves) and in the direction of which ray will be formed a lobe of the radiation diagram. For reasons of symmetry and with the HFSS® simulation software, only a quarter of the antenna is simulated (Figure 13 (d)). Figure 13 (a), the far field radiation pattern forms a lobe in this perspective view. Figure 13 (b), the radiation diagram is seen in projection for φ = 0 ° and Figure 13 (c) for θ = 90 °. In Figure 14 (a) to (d), the dipole radiates at a frequency of 2 GHz within a BIPAC material, the wires / bars of which are arranged in concentric circles along rays spaced angularly by 22.5 °, all the wires being in a continuous state 10 (conductor / reflector of the waves) except those of two adjacent rays which are in a discontinuous state 1 1 (transparent for the waves) and in the direction of which rays will be formed a lobe of the radiation diagram . For reasons of symmetry and with the HFSS® simulation software, only a quarter of the antenna is simulated (Figure 14 (d)). In Figure 14 (a), the far field radiation pattern forms a lobe in this perspective view. Figure 14 (b), the radiation diagram is seen in projection for φ = 0 ° and Figure 14 (c) for θ = 90 °. Because they allow a dynamic change of beam conformation, the control means can also constitute beam switching means. In other words, by modifying the control signals applied to the active components of the wires / bars of several elements, it is possible to switch between at least a first beam and at least a second beam. The beam switching antenna thus obtained, according to the invention, can be implemented in particular, but not exclusively, in a base station of a radiocommunication system with mobile stations. In the detailed examples which have been given, a particular case of antenna has been considered, the BIP elements of which are arranged regularly and in a circular distribution in a circle coaxially around a radiating element (simple omnidirectional dipole antenna) in order to simplify the explanations. and calculations. Indeed, the radiating element being omnidirectional and the arrangement of the BIP elements regular in concentric circles, one can limit the modeling calculations to certain sectors of space, in particular angular. We can also deduce a symmetry in revolution of the behavior of the antenna. It is however considered that other antenna structures with BIP / BIPAC elements can be produced if one wishes different behaviors according to the angular directions considered although the continuous / discontinuous BIP elements are structured in an equivalent manner but angularly offset. : the radiating element alone can have a non-omnidirectional diagram and / or the BIP elements be arranged on elliptical curves (or even at the limit in a circle) with constant eccentricity or not as the element moves away radiant which is central. It is therefore understood that the simulation and the radiation patterns obtained can be more complex. This type of antenna can for example be used in a base station whose environment is inhomogeneous and includes obstacles to the waves and / or constructions with mirror effect on the waves (reflection, multiple paths) and / or promoting transmission (E / R by the sea: you can choose to favor / refine by default the transmission towards the interior of the land rather than towards the sea). On the other hand, we considered a BIP structure with linear wires / bars parallel to the radiating element (z axis) which allows the conformation of one or more lobes, the major axis is substantially perpendicular to the radiating element, thus allowing circular scanning of the major axis (s) of the lobe (s) in a plane also perpendicular to the radiating element. It is also considered in the context of the invention that the BIP structure is with parallel / non-linear wires / bars and, preferably, with wires / bars which are at least on part of their paths substantially parallel to each other and on a curve circular of the circle type (wires / bars in arcs of circles), elliptical (wires / bars in arcs of ellipses). Such a structure in concentric spherical or elliptical shells of wires / bars, in addition to the possibility of conformation of lobe (s) in a plane perpendicular to the radiating element (xy plane) allows better conformation of the lobes in height relative to the xy plane (the lobes are in zw planes; w being a centered axis traversing the xy plane), thus allowing a volume scanning of the major axis of the lobe (s) in space. In the latter case, the selection of the continuous or discontinuous state for a wire / bar is preferably carried out in sections according to a position determined in height. Thus, for example, antennas can be produced in which wires or bars are arranged in spherical layers around an omnidirectional antenna. As before, the antenna will only radiate in the directions in which wires / bars or sections of wires / bars are electrically non-conductive (radio). It is also possible, as we have seen, to sweep part of the space with one / several lobes even with linear wires / bars controlled by sections. It is clear that the general shape of the wires / bars, in particular towards their upper and / or lower ends, can depart from the forms indicated above (linear, circle or ellipse), in order to obtain an even more particular behavior of the / lobes up and / or down the antenna by implementing shapes of particular wires / bars and, for example, (associated or not with the preceding linear, circle, ellipse) in triangle, square or rectangle (in particular in the case where there are ground planes at the two axial ends of the antenna to limit the radiation up or down). It may in fact be necessary to have an angle of attack withstand which is improved in particular in the case of radome applications for omnidirectional antenna and in this case it is necessary to use a network with three-dimensional structure formed of planes of wires / bars crisscrossed at right angles. Likewise, the invention can be applied in combinations of antennas produced according to the distribution characteristics on circular curves (circle or ellipse or other curved closed shape) of wires / bars, wires / bars being common to two (or plus) separate radiating elements, the distribution curves for each of the radiating elements crossing at said common wires / bars.

Claims

1. Antenna allowing the conformation of at least one beam (4, 5, 61, 62, 91, 92) of radio waves of at least one determined wavelength, of the type comprising at least one radiating element (2 ) the waves, preferably passive, placed in a set of wires or bars (1) reflectors of the wave and substantially parallel to each other, made of a material with Photonic Forbidden Band (BIP) and forming a determined structure, said determined structure comprising defects so as to conform said at least one beam in a direction depending on the position and / or the configuration of said defects, characterized in that said wires or bars and the defects are arranged on a set of N concentric closed curves of a plane, N being greater than or equal to two, the radiating element being placed inside the innermost curve and the distance between the curves is less than a quarter of the length of, the length of a wire / bar being greater than or equal to half the wavelength.

2. Antenna according to claim 1, characterized in that the curves are chosen from circles, ellipses, cycloids and, preferably, are all circles, the radiating element being placed substantially at the common center of said circles.

3. Antenna according to claim 1 or 2, characterized in that the son / bars or adjacent faults along a given curve are arranged at equidistant points transversely.

4. Antenna according to claim 3, characterized in that the transverse distances from the adjacent wires / bars or faults are all equal for all the curves.

5. Antenna according to claim 4, characterized in that the curves are circles and that the wires / bars or faults are arranged in at least two concentric circles around the substantially central radiating element according to a constant and equal transverse periodic distribution for all the circles.

6. Antenna according to claim 1 or 2, characterized in that the wires / bars or faults are arranged along distribution axes passing through the radiating element and in the plane, at points corresponding to the intersection of the curves and distribution axes.

7. Antenna according to claim 6, characterized in that the distribution axes are regularly distributed in the plane over 360 ° and divide it into equal angular sectors, the value of an angular sector being preferably 22.5 ° or a multiple 22.5 °.

8. Antenna according to claim 7, characterized in that the curves are circles and that the wires / bars or defects are arranged in at least two concentric circles around the radiant element which is substantially central according to a constant and equal angular periodic distribution for all circles.

9. An antenna according to any one of the preceding claims, characterized in that the radiating element is omnidirectional and is preferably a dipole, said dipole then being disposed substantially parallel to the wires / bars.

10. Antenna according to any one of the preceding claims, characterized in that the wires / bars are straight.

1 1. Antenna according to any one of claims 1 to 9, characterized in that the wires / bars are curved.

12. Antenna according to any one of the preceding claims, characterized in that the said defects are produced by the at least partial withdrawal of some of the said wires / bars, the said at least one beam being shaped in a direction depending on the position and / or configuration of the wires / bars removed.

13. An antenna according to any one of the preceding claims, characterized in that at least some of said wires / bars each consist of at least two conductive segments, the maximum length of a segment being less than a quarter of the length d wave and preferably less than or equal to one tenth of the wavelength, the adjacent segments of a wire / bar being separated by insulators, each wire / bar with several segments isolated from each other, called discontinuous wire / bar (1 1), being transparent to the wave and equivalent to the defect of a wire / bar at least partially removed.

14. Antenna according to claim 13, characterized in that all the wires / bars are wires / bars with several segments.

15. An antenna according to claim 13 or 14, characterized in that at least one of the insulators separating two adjacent segments in a wire / bar comprises or is formed of a switchable active component which can take at least a first state, conductive for the wave, in which the wire / bar with several segments behaves like a reflector, called continuous wire / bar (10), and a second insulating state for the wave in which the wire / bar with several segments is transparent to the wave and equivalent to the defect of a wire / bar at least partially withdrawn, and in that said antenna further comprises means for controlling said active components, making it possible to impose on some of said wires / bars with several segments to behave as discontinuous wires / bars (1 1), said at least one beam being shaped in a direction depending on the position and / or the configuration of discontinuous wires / bars.

16. Antenna according to claim 15, characterized in that in a wire / bar with segments and active components switching, the control is carried out by section (s) formed of a subset of adjacent segments of the set of segments of the wire / bar, the subset being able to comprise from two to the total number of segments of the wire / bar, the components separating the segments of a section being put in their first state, the other components being in the second state, so that the beam (s) can also be oriented in height relative to the plane.

17. Antenna according to claim 15 or 16, characterized in that the means for controlling the active components form conformation and switching means between at least a first beam and at least a second beam, so that said antenna is a beam antenna. beam switching.

18. An antenna according to any one of the preceding claims, characterized in that it is in a public or private civil telecommunications network.

19. Base station of a radiocommunication system with mobile stations, characterized in that it comprises at least one beam-switching antenna according to claim 17 or 18.