EP1152487A1 - Monolithic antenna with orthogonal polarisation - Google Patents

Abstract

The monolithic cross polarised antenna has a rectangular reflector (2) with radiating elements (11) and feed system (20). The feed circuit has two line conductors connecting two elements. Each conductor element has a folded foot (17) connected between the upper element and the feed lines.

Description

The present invention relates to a monolithic polarization antenna crossover, intended in particular for cellular telephony.

Document FR-A-2 766 626 discloses a cross-polarized antenna having dipoles mounted on a reflector, being two by two orthogonal and thus defining at least one radiating cell with polarization crossed. This antenna preferably comprises several radiating cells with cross polarization, which are made identically to each other and arranged in the same alignment along the reflector.

In this known antenna, the two conductive elements of each of the dipoles are identical. They have the shape of a Vé and are mounted back to back, the bases of the Vés being opposite. Each of them has an integral jamb to the reflector and provided with two end lateral arms opposite the reflector. he is advantageously made in one piece in the form of a plate suitably cut and then folded into a Vee.

In this same known antenna, two dipoles are arranged orthogonally to each other by having the two conductive elements of one inserted between the two conductive elements of the other dipole, to thus define one of the radiating cells with cross polarization which constitutes a compact and robust radiant module.

This known antenna also includes a power supply system. its radiating cells with cross polarization. This feeding system is double for supplying the two cell dipoles from two sources external energy. It is constituted in an analogous manner whatever the dipole of each cell. It includes a first section of coaxial cable connected to a coaxial connector for connection to one of the sources, second sections of coaxial cable each connected to one of the cell dipoles and a power divider coupling the first section to the second sections of coaxial cable.

It turns out that such a power system induces losses and can generate unwanted intermodulation products, which are mainly due to numerous welded connections that this power system has, particularly for its connection to the dipoles.

The object of the present invention is to minimize the drawbacks and to simplify the feed system of a polarized cell antenna compact crossover as above, and consequently simplify the structure assembly of the antenna, making it possible to considerably reduce its cost.

Its object is a monolithic cross-polarized antenna, comprising a substantially rectangular reflector, cells radiant mounted aligned with said reflector and each formed by two orthogonal dipoles, and a power supply system connecting the two dipoles of said radiating cells to two external energy sources, each of the dipoles comprising two flat V-shaped conductive elements, arranged back to back and each having a central folding branch fixed to the reflector by a first end part of said branch and two protruding end lateral arms on either side on one second end part of said branch, the two conductive elements of one of the dipoles of each of the cells being each arranged between those of the other dipole of the same cell, characterized in that said circuit supply comprises two flat conductive supply lines, mounted opposite said reflector and connected to both of said sources respectively, and in that only one of the two conductive elements of each of said dipoles has a folded conductive tab having a first end secured to the second end part of the branch central of said first conductive element, extending inside the Vee and substantially along the central branch of the second element dipole conductor and having a second end connected to one of said supply lines.

• lesdites lignes conductrices plates sont situées en regard d'une face dite arrière dudit réflecteur, lesdites cellules étant montées sur une face dite avant dudit réflecteur,
• les pattes solidaires des premiers éléments conducteurs des deux dipôles de la même cellule rayonnante se croisent, sans contact entre elles, dans une partie avant de la cellule et ont les mêmes orientations que l'une et l'autre des polarisations croisées de la cellule,
• la patte est partie intégrante dudit premier élément conducteur,
• la patte est solidaire de l'extrémité avant de la branche centrale dudit premier élément conducteur et s'étend à l'intérieur du Vé et en regard de la branche centrale du deuxième élément conducteur du dipôle,
• la patte est solidaire d'une portion intermédiaire de la deuxième partie terminale de la branche centrale dudit premier élément, est constituée par une partie de découpe axiale de ladite branche centrale, non complétement détachée de celle-ci, et s'étend le long de la partie axiale fendue de la branche centrale du deuxième élément conducteur du dipôle,
• chacune des lignes conductrices présentent des bifurcations en T à deux branches latérales soudées aux pattes des deux premiers éléments de dipôles de deux cellules consécutives sur ledit réflecteur, respectivement,
• chacune desdites lignes conductrices présente une extension centrale, de liaison de la ligne conductrice à l'une des sources extérieures.

Advantageously, this antenna also has at least one of the following characteristics:

• said flat conducting lines are located opposite a so-called rear face of said reflector, said cells being mounted on a so-called front face of said reflector,
• the tabs integral with the first conductive elements of the two dipoles of the same radiating cell cross, without contact with each other, in a front part of the cell and have the same orientations as both of the crossed polarizations of the cell,
• the tab is an integral part of said first conductive element,
• the tab is integral with the front end of the central branch of said first conductive element and extends inside the V and opposite the central branch of the second conductive element of the dipole,
• the tab is integral with an intermediate portion of the second end portion of the central branch of said first element, is formed by an axial cutting portion of said central branch, not completely detached from the latter, and extends along the split axial part of the central branch of the second conductive element of the dipole,
• each of the conductive lines have T-shaped bifurcations with two lateral branches welded to the legs of the first two dipole elements of two consecutive cells on said reflector, respectively,
• each of said conductive lines has a central extension, connecting the conductive line to one of the external sources.

• la figure 1 est une vue de face d'une antenne selon l'invention,
• la figure 2 est une vue de dessus d'une cellule rayonnante de l'antenne de la figure 1,
• les figures 3 et 4 sont deux vues en perspective de deux premiers éléments conducteurs de l'un et l'autre des dipôles de chacune des cellules rayonnantes,
• la figure 5 est une vue de face de l'un des dipôles de chacune des cellules rayonnantes,
• la figure 6 est une vue de la face arrière de l'antenne,
• les figures 7 et 8 montrent une variante de réalisation des deux premiers éléments conducteurs des figures 3 et 4,
• la figure 9 montre le deuxième élément conducteur, à associer au premier élément de la figure 7 pour constituer l'un des dipôles des cellules rayonnantes,
• la figure 10 montre l'un des dipôles selon cette variante.

The characteristics and advantages of the present invention will emerge from an embodiment illustrated by way of a preferred but non-limiting example in the accompanying drawings. In these drawings:

• FIG. 1 is a front view of an antenna according to the invention,
• FIG. 2 is a top view of a radiating cell of the antenna of FIG. 1,
• FIGS. 3 and 4 are two perspective views of two first conductive elements of one and the other of the dipoles of each of the radiating cells,
• FIG. 5 is a front view of one of the dipoles of each of the radiating cells,
• FIG. 6 is a view of the rear face of the antenna,
• FIGS. 7 and 8 show an alternative embodiment of the first two conductive elements in FIGS. 3 and 4,
• FIG. 9 shows the second conducting element, to be associated with the first element in FIG. 7 to constitute one of the dipoles of the radiating cells,
• Figure 10 shows one of the dipoles according to this variant.

Referring to Figure 1, we see that the antenna has several identical radiating cells 1 with cross polarization which are mounted in being aligned axially on a reflector 2. These cells are four in the example illustrated but their number could be different. The reflector 2 is flat with two longitudinal rebounds 3 and 4 folded at 90 ° from the same side as the radiating cells 1.

With reference to FIG. 2, it can be seen that each radiating cell 1 has two orthogonal dipoles 11 and 12. Each of the dipoles is formed by a pair of conductive elements 11A and 11B or 12A and 12B having the form a Vé, whose Vés are mounted back to back at a short distance from each other. We illustrated in dashed lines the two main components of polarization of powered dipoles, which are the two orthogonally crossed polarizations 5 and 6 and are in phase from one to the other of the elements of the same dipole. We also have shown on only one of the conductive elements, the secondary components of polarization 7A and 7B, which are orthogonal to the main polarization of the dipole and are in phase opposition with each other and therefore cancel each other directly. We also noted by + and - the polarities of the dipole elements for their radiation in radiofrequency waves according to a wide diagram strip from electrical energy supplied by two non-external sources represented.

The orientation in Figure 1 of the radiating cells 1 on the reflector 2 is advantageously chosen so that the crossed polarizations 5 and 6 are not not horizontal or vertical, this in order to optimize the characteristics of transmission of dipoles. These crossed polarizations are preferably at + and - 45 ° relative to the longitudinal axis of the reflector, corresponding to the vertical.

Referring to Figures 2 to 5, it appears that the conductive elements dipoles advantageously consist of plates suitably cut and folded in Vee.

Each of these conductive elements presents identically, as well as referenced in Figure 3 for element 12A, a central branch 13 folded longitudinally and two end lateral arms 14 and 15, projecting on one so-called terminal parts before this branch. At least one tooth 16 is provided on the other end of the branch for mounting the element conductor on the reflector. The central branch present in this realization two longitudinal folds thus dividing it into a planar axial part 13A, constituting an axial flat, and two fins such as 13B folded on the same side along the flat. Alternatively, it may have only one axial line folding.

Only one of the two conductive elements of the same dipole, such as element 12A of dipole 12 and element 11A of dipole 11, further comprises a tab 17 or 17 'which starts from the slightly indented front end of the central branch 13, or corresponding 13 ′ for element 11A. This leg is centered on the end of the branch and is folded to extend opposite and the along the central branch, being outside the Vé that this element defines 12A or 11A. This tab is received inside the V that defines the other element 12B of dipole 12 or 11B of dipole 11, where it extends along and opposite the central branch of this other element as seen in Figure 2 or 5. This tab is an integral part of this conductive element or alternatively is brought back and welded at the front end of its central branch.

With reference to FIGS. 3 and 4, it is noted that the two conductive elements 12A and 11A differ from each other only by their notch before 13C or 13'C from where the 17 or 17 'tab starts. These two notches although little deep have different depths from each other. They thus allow legs 17 and 17 'to cross in the front part of the radiating cell, as shown in figure 2, but without contact with each other.

The length of the central branch and the two arms of the different conductive elements is equal to a quarter of the wavelength of energy radiated by each dipole. The different parts of the conductive elements of each of the dipoles constitute a symmetrizing arrangement for their supply of electrical energy from two non-external sources shown, to which the dipoles are coupled as described below.

The mounting teeth 16 provided on the conductive elements are received in the reflector 2 and welded thereto, each by a welding point such as 18 in FIGS. 5 and 6. The end of the tab 17 or 17 ', provided on one only one of the two conductive elements of each dipole, is received through the reflector, but remains isolated from it and is connected by a solder point 19 to a supply circuit 20 for the dipoles.

This supply circuit 20 is advantageously made at the rear of the reflector 2, as shown in FIGS. 5 and 6. As a variant, it can be produced at the front of the reflector, but is then associated with additional elements of decoupling between its different parts connected to the cell dipoles radiant.

It is formed symmetrically with respect to the longitudinal axis of the reflector 2, being at a short defined distance from the reflector. It thus comprises two supply lines 21 and 22, each coupled to one of the two sources exterior not shown. These two lines are parallel to the alignment of the radiant cells and located on either side of the direction of this alignment. Each of them has two T-shaped bifurcations which are provided, in this example at both ends of this line. So by referring to same time in Figure 1 or 2, we understand that the two side branches 23 and 24 of one of the two bifurcations and similar ones of the other bifucartion on line 21 are each connected to the conductive element 11A of dipoles 11 of the four cells 1. Similarly the two branches of the bifurcations on line 22 are connected to the conductive elements 12A of the dipoles 12 of the cells 1. The other conducting elements 11B and 12B of the dipoles 11 and 12 are in turn electrically connected to the reflector 2, grounded to the two external sources of energy.

A connection extension 25 is provided on the middle part of each supply line such as 21. This extension is used for direct connection from one of the external sources in the middle of this line 21. Alternatively it is used for connection, via a section of coaxial cable, from the power line to a coaxial connector mounted at one end of the reflector and connected to one of the sources. Energy from sources outside is thus distributed in a suitable way on the various dipoles 11 and 12, the amplitude and phase weights being obtained by variations in the parameters of the supply system, namely the distance of the lines 21 and 22 and their bifurcations with respect to reflector 2 and the length and width of these lines and bifurcations.

These lines are flat electrical conductors of the same type as that of the reflector and of the conductive elements of the dipoles 11 and 12, in especially aluminum or aluminum alloy. They are maintained in sight and at the required distance from the reflector by insulating spacers, not shown, which are provided between them and the reflector.

To complete the description of the antenna according to the invention, we have shown in Figure 6 the welding points 18 of the ends of the central branches of the various conducting elements of the dipoles and the points 19 of the additional tabs provided on two of the four conductive elements of each radiating cell. We have schematized in the Figure 2 the holes 29 for passage of the legs such as 17 and 17 'through the reflector, without contact between these legs and the reflector.

Finally, it is specified that insulating shims, not shown, can be advantageously provided between each of the legs, such as 17 and 17 ′, and the central branch of the conductive element which receives the tab.

Similarly, one or more insulating shims not shown are advantageously provided between the tab integral with the conductive element 11A and that integral with the conductive element 12A, which cross one below on the other but without electrical contact between them at the front of each cell 1 (figure 2). The portions of these legs that cross at the front of the cell are oriented according to crossed polarizations 5 and 6.

The advantages of the structure of the antenna made monolithic, in integrating the dipole supply system and thus eliminating many welding points, emerge directly from the description of this mode preferential realization. These advantages include robustness improved, losses in the supply system and unwanted products intermodulation minimized, and the cost significantly reduced by the antenna.

In the alternative embodiment given in FIGS. 7 and 8, with respect to in FIGS. 3 and 4, the first two conductive elements respectively of two dipoles of the same radiating cell are designated by 32A and 31A. Their only differences compared to the conducting elements 12A and 11A of the Figures 3 and 4 are specified below.

In this variant, the front end of the central branch 33 or 33 ' is not indented. By cons an axial slot 38 or 38 'is provided in this central branch, and extends from an intermediate portion of its part front terminal to its rear end, across the width of the initial flat between the two fins 33B or 33'B.

The tab 37 or 37 'of each of the conductive elements is constituted by the axial cutting portion of the slot, without its detachment from the part before 33 or 33 'only remaining of the initial flat, and by folding twice of this axial cutting portion. This leg thus extends outside the Vé and opposite the conductive element to which it is integral.

These Figures 7 and 8 show that the folding point closest to the central branch is on a slightly different level on the two legs 37 and 37 '. This allows the crossing of these legs, without contact, in the part front of the radiant cell.

FIG. 9 shows the second conductive element 32B associated with the conducting element 32A of FIG. 7 to then constitute one of the dipoles denoted 32 and illustrated in FIG. 10. It appears that this second element 32B is analogous to the conductive element 32A, except that it is without the tab 37 of this one. In particular, its central branch has a slot 38B extending over almost its entire length, to receive the tab 37 without contact between this tab and the conductive element 32B.

As an alternative, not shown, shown with reference to FIG. 9, instead of the aforementioned slot 38B, a simple light can be provided in a portion intermediate of the front part of the flat part of the central branch, to the insertion through this light of the tab 37 of the element 32A of FIG. 7 inside the V of the conductive element 32B thus modified. This paw 37 then remains without contact with this conductive element which receives it.

When the dipole 32 of FIG. 10 is mounted on the reflector and then powered, as described above for dipoles 11 and 12 opposite the Figures 2, 5 and 6, tab 37 is at the polarity + of one of the two sources to give this polarity + to the conductive element 32A, while the conductive element 32B has the polarity - given by the reflector grounded from outside sources. By this tab 37 located in or practically in slot 38B, this results in a feeding mode coplanar or quasi-coplanar radioelectric of the two conductive elements of this dipole 32.

Comparatively, the mode of supply of the two elements of each previous dipoles 11 and 12, like the dipole resulting from the variant suggested with regard to figure 9, is of the “microstrip” type, with a layer air dielectric of thickness defined between the conductive parts which have the + and - polarities and are opposite.

The advantage of the variant embodiment described with reference to FIGS. 7 and 10 is that the radiant cells thus obtained are lighter and less expensive, since the tab of one of the two conductive elements of each dipole mainly comes from cutting its central branch and that the other element is itself split.

Claims (13)

Monolithic cross-polarized antenna, comprising a substantially rectangular reflector (2), radiating cells (1) mounted aligned with said reflector and each formed by two orthogonal dipoles (11; 12, 32), and a feed system (20) connecting the two dipoles of said radiating cells to two external energy sources, each of the dipoles comprising two flat conductive elements (11A, B; 12A, B; 31A, B; 32A, B) folded in V, arranged back to back and having each a central folding branch (13, 33) fixed to the reflector by a first end portion of said branch and two end lateral arms (13, 14) projecting on either side on a second opposite end portion of said branch, the two conductive elements of one of the dipoles of each of the cells being each disposed between those of the other dipole of the same cell, characterized in that said supply circuit (20) comprises d them flat conductive supply lines (21, 22), mounted opposite said reflector (2) and connected to one and the other of said sources respectively, and in that only one first (11A, 12A, 31A, 32A) of the two conductive elements of each of said dipoles comprises a folded conductive tab (17, 37), having a first end integral with the second end portion of the central branch (13, 33) of said first conductive element, extending to the 'interior of the V and substantially along the central branch of the second conductive element (11B, 12B, 32B) of the dipole and having a second end connected to one of said supply lines (21, 22). Antenna according to claim 1, characterized in that said flat conductive lines (21, 22) are located opposite a rear face of said reflector (2), said cells being mounted on a so-called front face of said reflector. Antenna according to claim 2, characterized in that the legs (17, 17 '; 37, 37') integral with the first conductive elements of the two dipoles of the same radiating cell (1), intersect, without contact with each other, in a front part of the cell and have the same orientations as both of the crossed polarizations (5, 6) of the cell. Antenna according to claim 3, characterized in that the crossed polarizations are substantially at + and - 45 ° relative to the vertical, respectively. Antenna according to one of claims 1 to 4, characterized in that said legs (17) pass through said reflector (2) without contact therewith, each through a hole (29) in the reflector, and are each welded to the 'one of said flat conductive lines (21, 22). Antenna according to one of claims 1 to 5, characterized in that the tab (17; 37) is an integral part of said first conductive element (11A; 32A). Antenna according to one of claims 1 to 6, characterized in that the central branch of each conductive element has at least one end tooth (16) on said first end part thereof, which is engaged in said reflector and is welded to this one. Antenna according to one of claims 1 to 6, characterized in that each of said conductive lines have T-shaped bifurcations, each with two lateral branches (23, 24) welded to the legs of the first two elements of the dipoles of two consecutive cells on said reflector, respectively. Antenna according to claim 8, characterized in that each of said conductive lines (21, 22) has a central extension (25), connecting the conductive line to one of the external sources. Antenna according to claim 1, characterized in that the tab (17) is integral with a front end of the central branch (13) of said first conductive element (11A; 12A). Antenna according to claim 1, characterized in that the central branch (33) of each of said first and second conductive elements (32A; 32B) has an axial slot (38, 38B), extending between a rear end and an intermediate portion of said second terminal part thereof. Antenna according to claim 11, characterized in that the tab (37) of said first conductive element (32A) is integral with said intermediate portion of said second end portion of the central branch (33) thereof and consists of a axial portion for cutting said slot (38) in said branch. Antenna according to one of claims 10 to 12, characterized in that the central branch (13, 33) of each of said first and second conductive elements has an axial flat and two lateral fins folded on the same side of the flat.

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