FR2841391A1 - DUAL POLARIZATION TWO-BAND RADIANT DEVICE - Google Patents

Abstract

The invention concerns a device comprising a first radiating element operating in a first frequency band F1, consisting of four dipoles (1, 2, 3, 4) in square arrangement and a second radiating element (23) operating in a second frequency band F2 consisting of at least one dipole arranged in the center of the square of dipoles (1, 2, 3, 4) forming the first radiating element, each dipole being center-fed by a balun. The set of radiating elements is arranged above a reflector (24). The dipoles (1, 2, 3, 4) forming the first radiating element and the baluns (8, 9, 10, 11) associated therewith are produced in a common metal plate (5), each balun of a dipole consisting of a close-circuit slotted line cut out in the metal plate (5) along a direction perpendicular to the dipole axis. The second radiating element (23) consists of at least one dipole arranged inside a metal cavity (7) located in the center of the metal plate (5). The invention is applicable to cellular radio communication networks.

Description

with respect to the vertical direction in each frequency band.

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JACQUELOT3 -PI.frd

  Rare dual-band device with double polarization.

  The invention relates to antennas and their radiating elements which can be used in particular in base stations of cellular radiocommunication networks of the GSM or UMTS type.

for example.

  A radiating element with double polarization can be formed of two radiating lines, each line being constituted by two strands of linear conductors. The length of each strand is approximately equal to a quarter of the working wavelength. The dip81es wind mounted on a structure allowing their supply and their positioning above a reflector (ground plane). This allows, by reflection of the rear radiation of the dip81es,

  to refine the directivity of the radiation pattern of the assembly thus formed.

  I1 is known to make a radiating device operating in two frequency bands and orthogonal apolarizations, to have a first radiating element, formed by four dipoles in quadrature operating on a first frequency F1, around a second radiating element formed by two crossed dipoles in quadrature operating on a

  2 0 second frequency F2, ['all of these elements being arranged above a reflector.

  According to their orientation in space, the dip81es can radiate or receive electromagnetic waves according to two depolarization paths, for example a horizontal polarization fly and a vertical polarization fly or even according to two polarization tracks

  2 5 offset by an angle of 45 from the horizontal or the vertical.

  However, inter-band decoupling basically depends on the relative orientation of the second radiating element placed in the center of the first. In particular, the parallel dipoles of the elements operating in the frequency bands F1 and F2 are insufficiently 30 decouples in the higher frequency band of frequency F2 for which the peripheral dipoles have a large dimension in relation to the wavelength correspond to the frequency F2. Indeed, the interaction between the peripheral dipoles operating at the frequency F1 and the crossed dipoles operating at the frequency F2 is due both to direct radiation, the dipoles being in direct visibility, but also to the radiation reflected by the reflector. On the other hand, the perpendicular channels of the two radiating elements are well decoupled by virtue of this geometric orthogonality. But if this orthogonality is no longer respected, in particular if the dipoles of the central radiating element have arbitrary orientations with respect to those of the peripheral dipoles forming the first radiating element then a fairly strong inter-band coupling appears between the

  different transmission or reception channels of the two radiating elements.

  Another disadvantage of this structure is that the radiation of the central radiating element is disturbed by the peripheral radiating element. Indeed this radiation is partially diffracted in particular by the dipoles of the peripheral radiating element, so that the resulting radiation diagram presents in the best of the cases ripples and, for an arbitrary relative orientation of the dipoles of the central radiating element , this diagram is asymmetrical with respect to the main axis of radiation

  perpendicular to the plane of the dipoles.

  It therefore remains difficult to obtain a simple to manufacture dual-band radiating element having two orthogonal channels with linear polarization highly decoupled in a wide frequency band. It is a fortiori difficult to realize a bipolarized directive network comprising

  several radiating elements of this kind, and offering a good purity of polarization.

  On another plane, it would be desirable to obtain a radiating element with two orthogonal polarization pathways each having a unidirectional radiation pattern and whose aperture at ml-power in the diagonal planes, ie planes located at

   principal planes E and H of each dip81e, that is to say substantially lower than 90.

  The invention aims to improve the situation.

  The dual-polarized dual-band radiating device according to the invention comprises a first radiating element operating in a first frequency band F1 which is in the form of four dipoles arranged in a square and a second radiating element operating in a second frequency band F2 which is formed of at least one dip81e has at the center of the square dip81s forming the first radiating element, each dip81e being fed in its center by a symmetrizer. The first and second radiating element

  wind arranged above a reflector.

  According to an advantageous arrangement, the dip81s forming the first radiating element and the wind symmetrizers produced in the same metal plate, each symmetrizator of a dip81e being formed by a short slit line cut in the metal plate in a direction perpendicular to the axis of the dip801e. The second radiating element is formed by at least one dipole arranged inside a cavity opening in the center of the

metal plate.

  According to another advantageous embodiment of the invention, the metal plate and the cavity can be produced in one piece, by stamping for example. The second radiating element operating in the frequency band F2 is then fixed inside and in the center of the cavity, the bottom of which serves as an electric short-circuit plane for at least one balun or balun used to supply the second element. radiant Thus realized the first radiating element and the second radiating element present a very weak electromagnetic interaction. This is only due to the diffraction of the edge of the cavity. In this way the decoupling between the two frequency bands is very strong regardless of the relative orientation of the dipole (s) forming the second radiating element at

  inside the cavity, ie its polarization.

  Other features and advantages of the invention will become apparent from the detailed description.

  below, made with reference to the accompanying drawings, in which: FIG. 1 represents a first embodiment of a first radiating device with double polarization capable of operating in two different frequency bands according to the invention,

  2 5 - Figure 2 shows a view along section AA of Figure1.

  FIG. 3 is a perspective view of the device represented in FIGS. 1 and 2.

  FIG 4 is an alternative embodiment of the first radiating element of Figure 1

  FIG. 5 represents a second embodiment of a device according to the invention.

  FIG. 6 is a view along section AA of the device in FIG. 5.

  FIG. 7 is a perspective view of the device of FIGS. 5 and 6.

  FIG. 8 is a partial perspective view of a colinear network formed on the one hand of dual-band and bipolarized radiating elements of the type described in FIG. 7 and of single-band and bipolarized radiating elements of the same type as the elements central radiant

in Figure 7.

  The drawings essentially contain elements of a certain character. They could

  done not only serve to better understand the description, but also conkibuer

  to the definition of the invention, if applicable.

  The device represented in FIGS. 1, 2 and 3 or the homologous elements wind represented with the same references, shows four dipoles referenced from 1 to 4 forming a square, cut out from a metal plate 5 comprising a central hole 6 into which opens out the open end of a radiating cavity 7. The dimension of the square formed by each dipole at a typical length equal to the half wavelength of the wave of frequency F1 radiated by the dipoles for an opening at ml - power of the beam close to 65 in

the horizontal plane.

  It should be noted, however, that ct is the distance (d) between two parallel dipoles of the radiating plate 5 and consequently the length of the sides of the square formed by the four dipoles 1 to 4 which largely determines the directivity of the diagram. of radiation in the horizontal plane of these dipoles, ie the aperture at ml-power of this diagram and that this aperture depends little on the length (1) of the dipoles. The length (1) of a dipole determines its impedance and can be greater or less depending on the thickness and width of the dipole. The greater this thickness, the longer the length of the dipole. In other words, the dimension (d) of the square is determined as a function of the aperture at ml-power which is sought and which may have a value different from 65 and the length of the dipoles is adjusted to ensure adaptation. impedance, generally 50 Ohms, of the padre of the parallel dipoles associated to form a polarization fly with directional diagram. Next before an advantageous embodiment dipoles 1 to 4 and cavity 7 can be realized

  2 5 in one piece by cutting and stamping the metal plate 5.

  Each dipole 1 to 4 is supplied by a reference symekizer from 8 to 11 respectively, of the "balun" type formed by a slit line in short circuit cut in the metal plate 5. Each symmetrizator constitutes a support arm of the corresponding dip81e. To do this, the plate 5 is formed around the hole 6 for the passage of the cavity 7 by a concentric crown 12 comprising on its outer periphery and in two directions at right angles, protrusions or arms 13 to 16 of shapes for example, rectangular, bevelled or trapezoidal, respectively connecting the crown 12 to dipoles 1 to 4. The radial length (h) of the arms is preferably non-zero, for example greater than 0.0511 so as to avoid direct contact of the interior edge of the dipoles with the edge outside of the crown 12 and thus minimize the interaction between the current flowing on the dipOles and the currents flowing on the crown 12. The average width (w) of the arms is typically 5 to 10 times the width of the slotted line which is also very small compared to the wavelength i1

correspond to the frequency F1.

  The width of the crown 12 is determined to be sufficient both on the mechanical plane to support the dipoles and on the radio plane to stabilize the directivity of the radiation patterns of cavity 7 in the second frequency band F2, making less fluctuating aperture to ml-power of radiation patterns as a function of frequency. This width is preferably greater than 5/100

  th of the wavelength 12 correspond to the frequency F2.

  The dipoles 1 to 4 are supplied at their base, that is to say at the open end of the slotted lines of the symmetrizers 8 to 11 by means, for example, of coaxial cables referenced respectively from 17 to 20. In the sectional view of figure 2 the dipoles 2 and 4 geometrically parallel on two opposite sides of the square wind supplied with equal phase and 20 amplitude by two identical coaxial lines 18 and 20 and a Te of association 21 to form a polarization flight with a directional diagram, like a classic network of two parallel dipoles. The coaxial supply lines 17, 18, 19, 20 of the wind dipoles arranged respectively along and on one side of the symmetrizers 8, 9, 10, 11. The external conductive sheath of the coaxial lines 17 to 20 is in electrical contact with the base of the first 2 5 half of the dipole which it feeds and with the plate 5, and the central conductor is connected to the base of the other half of the same dipal. Two orthogonal polarization paths are thus obtained, the substantially identical wind radiation diagrams of which. However

  this mode of association is not limiting, and other modes can be envisaged.

  The symmetrizers of the dipoles wind slit lines cut in the plate S in the form of meandres. The meanders of each slotted line must be in sufficient number so that the slotted line has a length substantially equal to a quarter of the wavelength of the wave of frequency F1 radiated by the first radiating element. However, the slotted lines can take other forms, they can for example as shown in FIG. 4 or the elements homologous to those of FIG. 1 bear the same references, be formed by a circular section followed by a straight section leading to at the supply base of a dipOle. The circular section can be anywhere on the crown 12. However to avoid coupling between the waves of frequencies F 1 and F2, it is preferable that it is not near the edge of the hole 6 but rather in the middle of the crown 12. The metal cavity 7 can have a cylindrical or slightly conical shape, of section

  circular or more generally polygonal with 2 power N equal dimensions with N = 2, 3, 4 ....

  The radiating plate S is in electrical contact with the edge 7a of the cavity.

  The cavity 7 is excited in its center by a radiating element 23 operating on the second frequency F2. This radiating element 23 can be of the simple dip81e type for the case of an operation in single polarization mode or of the crossed dipole type, or turnstile commonly called in English "turnstile", for the case of an operation in polarization mode orthogonal, or any other type of radiating elements adapted to other types of polarization including circular. The bottom 7b of the cavity 7 is closed so that the radiation from the internal radiating element 23 is unidirectional and

  directive towards the front of the cavity 7.

  The dipoles forming the radiating element 23 are supplied by means of balun type symmetrizers. In the sectional view of FIG. 2, each balun is formed by a first conductive tube 24 and a second conductive tube 25 of lengths substantially equal to a quarter of the wavelength of the frequency wave F2. The conductors 24 and 25 wind in electrical connection by their respective ends with the base 25 of supply of each half of a dipal of the radiating element 23 and the bottom 7b of the cavity. The first tube 24 is traversed along its longitudinal axis by a central conductor 26, one end of which is connected to the supply base of the half-dipole opposite to that in which it is connected by one of its ends and the other end of which can be connected to the central conductor of a power connector or possibly to the central conductor of a coaxial cable not shown. The tubes 24 and 25 thus form with the central conductor 26 a coaxial transforming line of impedance for the dipole to which they are connected. In a way, advantageously the depth of the cavity 7 is close to a quarter of the wavelength

  i2 of the radiated wave of frequency F2 of the radiating element 23 inside the cavity.

  The height of the radiating element 23 with respect to the bottom 7b of the cavity is also close to a quarter of the wavelength i2 while being less than the depth of the cavity 7. The diameter of the cavity 7 can vary within large proportions, for example between 0.4512 and i2, for half-power openings of less than 90D, radiation patterns in the diagonal planes inclined at 45. relative to the main planes E and H of the dipole inside the cavity. However, according to the ratio of frequencies F1 / F2, the necessary spacing between the dipoles 1 to 4 of the radiating plate 5 operating at the frequency F1 can limit the maximum diameter of the cavity 7. For example, with a spacing of 1 70mm between two parallel dipoles of the radiating plate operating in the GSM900 band, a diameter of 80mm and a depth of cavity of 40mm are suitable for producing an opening diagram at ml-power about 65 in the

GSM1800 or UMTS band.

  As it appears in FIGS. 2 and 3 the cavity 7 which supports the plate 5 is fixed on a reflector 24 of sufficient dimensions to allow the electromagnetic fields 20 radiated behind the dipoles on the reflector to be returned to ['before. In addition to its mechanical role, the reflector 24 is intended to render the radiation of the dipoles of the radiating structure unidirectional. The reflector 24 may include low walls whose role is to stiffen the structure but also to act on the directionality of the radiated diagrams. The height of the dip81es of the radiating plate 5 relative to the reflector 24 may vary

  2 5 typically from 71/8 to 11/4 in the frequency band F1 of wavelength \ 1.

  According to another embodiment illustrated in Figures 5 to 7 where the elements homologous to those of Figures 1 to 4 bear the same references, the dip81es 1 to 4 of the plate 5 are partly raised relative to the plane formed by the opening of the cavity 7, each dip81e 30 being divided into three parts, a lower part 1b, 2b, 3b, 4b respectively located in the plane of the plate 5 and two upper parts respectively la, lc; 2a, 2c; 3a, 3c; 4a, 4c located on either side of the basset part This elevation which preferably must maintain the geometric symmetry of the structure, can also be done by tilting the parts of the dipoles located beyond the zones of the symmetrizers 8 to 1 corresponding . Various others

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  geometric shapes can be considered to make dipoles, the only condition being respect for the symmetry of the radiating structure, ie the identity of the dipoles, if not of the four at least two by two per padres of dipoles parallel. The symmetry of the dipoles per padre means that two parallel dipoles have the same total length so that they have the same impedance and that their respective radiation is substantially the same. The two padres of dipoles do not necessarily wind identical because each padre of dipoles generates a flight of independent polarization. The symmetry in question is a

  symmetry with respect to the cenke (O) of the square formed by the quake dipoles.

  The structures of the radiating elements of FIGS. 1 to 7 are very simple and make it possible to produce, at lower cost, dual-band radiating structures having two orthogonal polarization paths in each frequency band, inclined for example, as shown in FIGS. 1 and 5 , 45 with respect to a vertical direction w '. The four channels thus formed are strongly decoupled from each other, typically 30 dB, and radiate in each frequency band according to unidirectional directional patterns having

  apertures at ml-power less than 90 in the horizontal plane, for example 65.

  Advantageously, it will be able to perform linear alignments of a plurality of such radiating structures to form vertical linear networks of high gain, for example 1 8dBi, dual-band having two orthogonal polarization channels inclined by +45

  20 with respect to a vertical direction w 'in each frequency band.

  The embodiment of the network shown in FIG. 8 comprises on the one hand dual-band and bipolarized radiating elements of the type described in FIG. 7 operating in the bands F1 (GSM900) and F2 (UMTS and / or DCS) and d auke part of radiating elements mono band 2 5 bipolarized functioning in the band F2 of the same type as the central elements of the

  figure 7. The network pitch for band F2 is half the network pitch for band F 1.

  It is thus possible to build a highly directional network with a regular pitch, dual-band and bipolarized having a good polarization purity and a strong decoupling in the different flights. It will be noted that all the radiating elements operating in the band F2 have substantially the same phase center because of their identity, this being located on the central axis of the cavity, axis perpendicular to the plane of the opening of the cavity . This property greatly facilitates the electrical pointing (or tilt) of the beam by action on the phase shifts between radiating elements and also allows better alignment of the phases of the elements.

  radiating in the frequency band for greater directivity of the antenna.

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  Radiant elements produced in accordance with those of the invention described above

  and operating in the frequency bands GSM1800, GSM 1900 and UMTS have made it possible to obtain an insulation between the channels close to 30dB, with standing wave ratios compared to 50 Ohms for all the radiating elements lower than 1.7 : 1 and apertures to ml-power of directivity diagrams close to 65 in the plane

  horizontal for gains close to 9dBi in the two frequency bands.

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Claims (4)

claims   1. Radiant device of the type comprising a first radiating element operating in a first frequency band F1, formed by four dipoles (1, 2, 3,4) arranged in a square and a second radiating element (23) operating in a second frequency band F2 forms at least one dipale which has at the center of the square dipales (1, 2, 3, 4) forming the first radiating element, each dip81e being fed in its center by a symekizer, ['all the radiating elements being disposed at the above a reflector (24), characterized in that the dipoles (1, 2, 3, 4) forming the first radiating element and the symmetrizers (8, 9, 10, 11) which are associated with them in the same wind metal plate (S), each symmetrizer of a dipole being formed by a slit line in short circuit, cut in the metal plate (5) in a direction perpendicular to the axis of the dipal, and in that the second radiating element ( 23) is formed by at least one dipale which has   the interior of a metal cavity (7) placed in the center of the metal plate (5).   2-Device according to claim 1, characterized in that the cavity (7) is of cylindrical, conical shape or of polygonal section at 2 power N equal dimensions with N = 2, 3, 4, ... etc.   3-Device according to claims 1 and 2, characterized in that the cavity is made by   stamping of the metal plate (S).   4- Device according to one of claims 1 to 3, characterized in that the symmetrizers (8,   2 5 9, 10, 11) wind formed by short slotted lines of substantially equal length   a quarter of the operating length of the first radiating element.   - Device according to claim 4, characterized in that the slotted lines (8, 9, 10, 11) wind shaped meandres.   6- Device according to claim 4, characterized in that the slotted lines (8, 9, 10, 11)   have a first rectilinear section followed by a second circular section. 2841 391   7- Device according to one of claims 1 to 6, characterized in that the dipoles (1, 2, 3,   4) forming the first wind radiating element supplied by coaxial cables (17,18,19,) arranged along the symmetrizers, the external conductive sheath of each cable being in eleckic contact with the first half of the dipole which it supplies, its central conductor being connected to the base of the other half of this same dipole.   8-Device according to one of claims 1 to 7, characterized in that the dip61es (1, 2, 3,   4) forming the first wind radiating element partly raised relative to the plane form through the opening of the cavity (7).   9-Device according to one of claims 1 to 8, characterized in that the cavity (7) comprises   a bottom (7b) on which the second radiating element (23) rests by means of support tubes (24, 25).   10-Device according to claim 9, characterized in that the support tubes (24, 25) form two-wire lines of the "Balun" type for feeding the dipoles of the second radiating element (23).   11 -A device according to claim 10, characterized in that the second radiating element   2 0 (23) is formed by two dipoles crossed at right angles.   12-Device according to one of claims 9 and 10, characterized in that the height of   [The radiating element (23) relative to the bottom (7b) of the cavity (7) is close to a quarter of the wavelength radiated by the second radiating element while being less than the 2 5 depth of the cavity (7).   13-Device according to one of claims 1 to 12, characterized in that the depth of   the cavity (7) is substantially equal to a quarter of the wavelength of the wave radiated by the second radiating element (23).   14-Device according to claim 13, characterized in that for the cylindrical cavities with circular section, or for the cavities with polygonal section, the diameter of the cavity (7) or that of the circle circumscribed in the polygonal section, is substantially between 0.452 and 2841 391   i2, X2 designating the wavelength of the wave radiated by the second radiating element (23).   1 5-Device according to one of claims 1 to 14, characterized in that the first element   radiating (1, 2, 3, 4) and the second radiating element (23) wind oriented in space to radiate respectively two waves with orthogonal polarizations inclined by 45 by vertical.   1 6-Antenna network, characterized in that it comprises several devices according to one of the   claims 1 to 15, aligned vertically on the same reflector (24) and arranged on the   reflector (24) so as to form two orthogonal polarization channels inclined by +45