FR2840455A1 - WIDE RADIATION ELEMENT WITH DOUBLE POLARIZATION, OF GENERAL SQUARE FORM - Google Patents

Abstract

The radiating element (l) comprises two crossed dipoles (2), arranged to operate in broadband and in double polarization. Each dipole includes a pair of coplanar conductive plates (2a, 2c; 2b, 2d), with the same geometry in the general shape of squares. The two plates of each pair (2a, 2b; 2c, 2d) are positioned with their diagonals substantially aligned on the same alignment axis (3, 4) for each pair. The alignment axes (3, 4) of the two pairs of plates intersect at right angles at a crossing point (O) located between the plates of each dipole. Applications: Cellular radio networks.

Description

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  Lovely broadband element with double polarization. generally square.

  The invention relates to antennas and their radiating elements. A radiating element with double polarization can be formed of two radiating dipoles, each dipole being constituted by two strands of colinear conductors. The length of each strand is approximately equal to a quarter of the working wavelength. The wind dipoles are mounted on a structure allowing them to be fed and positioned above a reflector (ground plane). This allows, by reflection of the rear radiation of the dipoles,

  to set the directivity of the radiation pattern of the whole thus formed.

  Depending on their orientation in space, the dipoles can radiate or receive electromagnetic waves according to two polarization flights, for example a horizontal polarization flight and a vertical polarization flight or even according to two polarization sati on

  offset by an angle of 45 from horizontal or vertical.

  However, when assembling such a structure, it is generally difficult to obtain a good decoupling of the bias channels, for example 30dB, combined with a good impedance matching of the channels, for example a rate of standing wave at 50 Ohms less than 1.5: 1 while allowing a unidirectional radiated opening diagram at ml-power substantially constant in a wide frequency band,

  for example 65 of opening in a bandwidth of 24%.

  It therefore remains difficult to obtain a simple to manufacture radiating element having two orthogonal linearly polarized channels strongly 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

  +/- 45 of the main planes E and H of each dipole. is substantially less than 90.

  The invention aims to improve the situation.

  According to the invention, each dip81e comprises a pad of coplanar conductive plates, of the same geometric in general square shape, the two plates of each padre are positioned with their diagonals substantially aligned on the same alignment axis for each padre; and the alignment axes of the two pad pads intersect at an angle

  right at a crossing point located between the plates of each dipal.

  In other words, the wind plates are arranged with respect to each other so that two vertices of a square of a plate, opposed on a diagonal of the square, are aligned along the same axis of alignment with two vertices opposite on a diagonal of the square of

the other plate of the same padre.

  Other characteristics and advantages of the invention will appear in the detailed description

  below, made with reference to the accompanying drawings, in which: - Figure 1 is a top view of a first embodiment of a radiating element according to the invention, - Figure 2 is a view along the section AA of the radiating element of FIG. 1, FIGS. 3, 4 and 5 illustrate in top view three variant embodiments of the radiating element represented in FIGS. 1 and 2, and - FIG. 6 is a view in perspective of a linear network composed of several elements

radiant according to the invention.

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

  2 5 therefore not only serve to make the description better understood, but also contribute

  to the definition of the invention, if applicable.

  Figure 1 shows a virtual square outline in dotted lines 1, the length of the side of which is "a". Inside this virtual square, the radiating element represented comprises four metallic radiating plates 2a, 2b, 2c, 2d, of square shape, the length of the edge of which is "c". These four plates are juxtaposed in the same plane inside the virtual square 1. Preferably, the plates have identical dimensions and are separated from one another.

same deviation "b", with a = 2 c + b.

  The square plates 2a and 2c have a common diagonal, that is to say located substantially on the same alignment axis 3; similarly, plates 2b and 2d have a diagonal

  common, that is to say located substantially on the same alignment axis 4.

  These alignment axes 3, 4, which constitute diagonals common to one and the other padres of plates, intersect at right angles at a crossing point "O" located between the plates of each padre or dipale. In Figure 1, the alignment axes 3 and 4 form

  also the diagonals of the virtual square in dotted line 1.

  Each plate padre, respectively; 2b, 2d, is powered by means of a balun. Thus, the pad of plates 2a, 2c forms a symmetrical dipal radiating a polarized electric field, and this in a plane perpendicular to that of the plates 2a, 2b, 2c, 2d, and containing the common diagonal 3 to the cited plates. Similarly, the pad of plates 2b, 2d forms a symmetrical dipal radiating a polarized electric field, and this in a plane perpendicular to that of plates 2a, 2b, 2c, 2d, and containing the diagonal

common 4 to the cited plates.

  The two orthogonal padres of plates thus generate two electric fields orthogonal to one another. The polarization planes make an angle of +/- 45 with respect to the vertical axis VV 'of FIG. 1, which passes in the interval between the plates 2a, 2b of a

part, and 2c, 2d on the other hand.

  As shown in the section in Figure 2, the plane of the four plates is arranged parallel to a plane reflector 5. Each of the plates 2a, 2b, 2c, 2d can be mounted and supported on the reflector 5 by means of conductive tubes references respectively 6a, 6b, 6c, 6d. Each tube is fixed at one of its ends to the plane reflector 5, and oriented in a general direction perpendicular to the plane of the plates and to

reflector plane 5.

  In the sectional view of FIG. 2, only the plates 2a, 2b and 2d as well as the tubes 6a, 6b, 6d are visible. These tubes 6a, 6b, 6c, 6d serve as a spacer to keep the plates 2a, 2b, 2c, 2d of the reflector 5 separate; they also provide or support the function of

  balun or "balun" for the electrical supply of the plates.

  The reflector 5 allows the back radiation from the plates to be reflected by reflection.

  It is positioned so that the resulting global radiation corresponds to a unidirectional diagram, directs towards the half-space which contains the radiating plates (compared

reflector).

  In FIG. 1, the ends of the conductive tubes 6a, 6b, 6c, 6d in contact with the plates 2a, 2b, 2c, 2d wind fixed respectively on the right angle (or "corner") portion of the plates 2a, 2b, 2c, 2d which is located in the vicinity of the crossing point "O" of the axes

alignment 3 and 4.

  The pad of tubes 6a, 6c forms the symmetrizer of the pad of diagonally opposite plates 2a, 2c. The pad of tubes 6b, 6d forms the symmetrizer of the pad of diagonally opposite plates

opposite 2b, 2d.

  Each balun can be seen as a two-wire line, the high wind ends of which are electrically connected to the plates and the low wind ends of which are connected

  electrically at reflector 5, as well as at a hot supply point.

  More precisely, one of the tubes 6b or 6c of a balun can be crossed by a central conductor 7b or 7c, one end of which is connected to the diagonally opposite plate 2d or 2a, and the other end of which is connected to the central conductor of a power connector 8 or possibly to the central conductor of a coaxial cable not shown, the sheath of which would be welded to the reflector S. The tube 6b or 6c thus forms, with its central conductor 7b or 7c, a transforming coaxial line of impedance for the dipole 2 5 formed by the pad of plates connected to the symmetrizor, in each cast In addition, the two orthogonal symmetrizers thus formed by the tubes, which also serve as support for the radiating plates, can be realized in one piece

  conductive in the form of a foot supporting the radiating plates.

  Each central conductor 7b or 7c passing through a tube 6b or 6c can be of section

  circular, square, rectangular or other.

  The section of the tubes 6a, 6b, 6c, 6d of the symmetrizers can be circular, square, rectangular.

  milk, trapezoidal, almost triangular or of another shape, preferably substantially regular. The tube section may also not be closed, for example by being open on one side. The main thing is that the tubes can receive the central conductor, which can possibly have the shape of a conductive strip (strip) to allow the supply of the hot spot and the impedance transformation. The tubes can also be filled with a dielectric to facilitate the mechanical behavior of the central conductor or to achieve the necessary length of the central conductor for the adaptation of impedance. Furthermore, the tubes not receiving a central conductor can be hollow or solid. The transverse dimension of this section is chosen to achieve a suitable excitation of the plate concerned (that which receives the end of the central conductor concerned, 7b or 7c), and, by symmetry of the plate opposite on the same diagonal

3 or 4.

  According to another embodiment, represented in FIG. 3, the plates 2a, 2b, 2c, 2d can be hollowed out, and each have a hole 9, substantially of the same shape, for example a circular hole centered at the point of intersection of the diagonals of the square that each plate defines. This makes it possible to lighten their weight; and it has been observed that this does not change

  substantially the radioelectric properties of the radiating elements.

  A variant applicable to the previous embodiments is shown in the figure

  4, or the elements homologous to those of FIG. 1 keep the same references. In this case, the four outer corners of the plates 2a, 2b, 2c, 2d located at the ends of the two alignment axes 3 and 4, can also be cut along cutting planes perpendicular to the alignment axes, this cutting is substantially identical on

  four corners to keep the geometrical symmetry of the two polari sati on roads.

  Another variant, not shown, consists in bending more or less the corner of each plate towards the teas or upwards relative to the horizontal plane of the plates at a certain angle "p". In this way the folded corner forms an isosceles triangle of dimension "w" inclined by ", B" relative to the plane of the plates (, B is between -90 and +90). Such an arrangement can be of interest in dense arrays of radiating elements to improve coupling.

  mutual between two adjacent elements.

  The depth w of the section shown in FIG. 4 or of the fold of the variant embodiment stated above, measured along a side of length "c" of the square of a plate from its angle at the top, can in these configurations to be at most equal to the length of the side "c" of the square, reducing the latter to the shape of a triangle, without the proper functioning of the radiating element being significantly affected. According to another variant represented in FIG. 5, it is also possible to combine the embodiments of the plates 2a, 2b, 2c, 2d of FIGS. 3 and 4 to produce a radiating element in the form of a "Maltese cross. In this mode for making the plates 2a, 2b, 2c, 2d wind drilled with a circular hole 9 and the outer corners located on the alignment axes

wind truncates.

  Thus, the weight of the radiating element is reduced, without the characteristics of the element

  radiant are significantly degraded.

  In Figure 6, several radiating elements of one of the types described with reference to Figures 1 to 4 wind aligned above a common reflector 5, to form an antenna array. In this configuration, the alignment axes 3 and 4 of the radiating plates of the wind dual inclined at an angle equal to 45 relative to the longitudinal axis w 'of the reflector 5. Other wind alignments can be envisaged, according to the needs. We can also

  plan to mix different types of radiant elements.

  For a large number of applications, in particular where directional diagrams with aperture at ml-power around 65c are sought in the horizontal plane, as is the case for antennas of GSM or UMTS type base stations, the range of variation of the main dimensions "a" and "h" can be as follows: 0.35 <a <0.6 0.147 <h <0.287 where the wavelength corresponds to the operating frequency of the element

3 0 radiant.

  The spacing between the plates "b" is typically a few millimeters or a few

hundredths of dimension "a".

  Radiant elements produced in accordance with those of the invention described above and operating in the GSM900 frequency band and in the GSM1800 and UMTS frequency bands combined have made it possible to obtain, between the two orthogonal channels: - an insulation greater than 30dB, - a stationary wave rate at 50 Ohms less than 1.5: 1, - a gain of the radiating element close to 9dBi for apertures at ml - power of the radiation diagram close to 65, - a cross polarization rate close to 28dB in the mid-power opening of the

radiation pattern.

  The use of radiant plates with square profes has different advantages, which can be considered independently: - possibility of a significant simplification of the dipole supply device, reduced size of the radiating element,

1 5 - amazing performances.

  - possibility of manufacturing by overmolding for example, the plates and the symmetrizers of a

one and the same room.

  As we have seen, the radiating element is particularly well suited to the creation of base station antennas for cellular radiocommunication networks such as GSM900 (870 to 960 MHz), GSM1800 (1710 to 1880 MHz) or the new UMTS system (1920 to 2170 MHz) for which the links with mobiles must be made

  according to two orthogonal polarizations inclined by 45 with respect to the vertical.

  2 5 However, the radiating element according to the invention can be used for other applications and other frequency bands requiring for example to transmit and receive electromagnetic waves with right or left circular polarization by combining the two channels

  of orthogonal polarization in phase quadrature.

  We can also constitute a planar network, that is to say bidirectional, with the radiating elements described above. In this case the radiating elements are aligned horizontally at a determined pitch and vertically with another determined pitch. For example, a subnetwork of two horizontal elements associated in parallel with equal supply allows an opening at -3dB of about 29 in the horizontal plane for a step of 0.91, or is the operating wavelength. A uniform vertical alignment of 8 such subnets gives an opening of about 7 in the vertical plane with the same pitch of 0.9X,

  the global network thus formed has a theoretical gain of approximately 22.5 dBi.

  It is also possible to produce the radiating plates by etching on a thin dielectric support, for example of "Glass-Teflon" or "Duroid" type. This printed technology will find its application in particular at high frequencies going

from S Ghz to 24 GHz.

Claims (16)

claims   1. Radiating device (1), comprising two crossed dipals (2), agencies for operating in broadband and in double polarization, characterized in that each dipole comprises a pad of coplanar conductive plates (2a, 2c; 2b, 2d), of the same geometric in general shape of squares, the two plates of each padre (2a, 2b, 2c, 2d) being positioned with their diagonals substantially aligned on the same alignment axis (3, 4) for each padre, and in this that the alignment axes (3,4) of the two padres of plates intersect at right angles at a point   crossing point (O) located between the plates of each padre.   2. A radiating device according to claim 1, characterized in that the plates (2a, 2c; 2b, 2 d) of the two pads have surfaces substantially i dentic and wind di spo sees adjacent to each other in being inscribed inside a square of which each   dimension "a" contains two dimensions in alignment of two adjacent plates of the two padres.   3. Radiating device according to one of claims 1 and 2, characterized in that each   padre of plates is fed between the two ends of the plates located near the crossing point by a balun comprising two tubes (6a, 6c, 6b, 6d) forming   2 0 two-wire line of type "Balun".   4. Radiating device according to claim 3, characterized in that the wind plates   fixed to a reflector (5) by means of said tubes (6a, 6b, 6c, 6d).   2 5 5. A radiating device according to claim 4, characterized in that the ends of the tubes forming a two-wire wind line electrically connected to the reflector (5) and to the ends of the plates (2a, 2b, 2c, 2d) located near the crossing point " O "of the axes of alignment of the two padres of plates, and in that one of the tubes (6b, 6c) of each symmetrizer is crossed by a central conductor (7b, 7c) of which an end is connected 3 0 has a plate (2d, 2a).   6. Radiating device according to claim 5, characterized in that the other end of the central conductor (7b, 7c) is connected to the central conductor of a coaxial connector   supply (8) mounted on the reflector (S).   7. A radiating device according to claim 5, characterized in that the other end of the central conductor (7b, 7c) is connected to the central conductor of a coaxial cable mounted on the reflector (5).   8. Radiating device according to any one of claims 3 to 7, characterized in that   that the symmetrizers (6a, 6b, 6c, 6d) are made in one piece forming a foot   support for radiant plates.   9. Radiating device according to one of claims 3 to 8, characterized in that the sections   tubes of the symmetrizers (6a, 6b, 6c, 6d) are at least partly circular.   10. Radiating device according to one of claims 3 to 8 characterized in that the   tube sections (6a, 6b, 6c, 6d) are at least partly rectangular.   11. Radiating device according to one of claims 1 to 10, characterized in that the   radiant plates (2a, 2b, 2c, 2d) internally hollowed out (9).   12. Radiating device according to one of claims 1 to 10, characterized in that the   four outer corners of the radiating plates (2a, 2b, 2c, 2d) located on the axes   2 0 of wind-up warnings.   13. Radiating device according to one of claims 1 to 10, characterized in that the   four outer corners of the radiating plates (2a, 2b, 2c, 2d) are folded at an angle   determined relative to the plane of the plates.   14. Radiating device according to one of claims 1 to 10, characterized in that the   radiating plates (2a, 2b, 2c, 2d) assembled create a motif in the shape of a "Maltese cross".   15. Radiating device according to one of claims 1 to 14, characterized in that the   length "a" on the side of the square formed by the edges of the edges of two adjacent radiating plates is approximately between 0.35 and 0.6 X, and in that the radiating plates are located at a distance "h" from the reflector ( 5) included approximately   between 0.14 and 0.28 1, or is the working wavelength.   16. Radiating device, forming an antenna-network, characterized in that it comprises several   radiating elements (1) according to one of claims 1 to 15, places aligned on the same   reflector (5), and arranged so that the alignment axes (3,4) of the radiating plates 2a, 2b, 2c, 2d) of each dipole are inclined by 45 relative to the alignment axis