EP3001504B1 - Assembly device for attaching an element provided with a flat flange on a substrate - Google Patents

Description

FIELD

The present invention relates to an assembly device for fixing a radome on a reflector, intended for use in concave reflector antennas having for example the shape of at least one parabola portion, the reflector being possibly equipped with a skirt.

BACKGROUND

Parabolic reflector antennas are usually used for mobile communication networks. Such an antenna comprises a main reflector having a concavity having for example the shape of a paraboloid of revolution about the axis of symmetry of the antenna, and a feeding device located along the axis of symmetry of the antenna. antenna for transmitting electromagnetic waves transmitted or received by the antenna. The periphery of the parabola is most often provided with a cylindrical wall, also called skirt or screen, which limits the lateral radiation of the antenna and thus improves its performance.

A radome is associated with an impervious protective surface which partitions the space defined by the reflector vis-à-vis the outside. This radome can be flexible or relatively rigid. A radome composed of a flexible material such as a fabric has a limited production cost and a small footprint prior to installation on the antenna. However, such a flexible radome has disadvantages related to a relative fragility and a complex system of attachment to the skirt of the antenna, requiring self-tensing elements for its setting and its maintenance under tension, such as springs.

A rigid but flexible radome, made of a non-flexible material, the most used today, has the advantage of good resistance to the external climatic environment such as rain, wind or snow. It is therefore essential to ensure a solid attachment capable of withstanding the wind force, particularly for reflectors of large diameter. The fastening system must also allow rapid disassembly / reassembly and without degradation of the radome on the reflector.

The rigid radome, is most often fixed on the reflector by means of different devices having in common to require a plurality of screws or bolts placed on the periphery of the radome. In order to meet the standards of resistance to environmental conditions, the number of bolts is high. However, the presence of such a quantity of metal bolts and the asperities they form on the radome can cause degradation of the radio performance of the antenna. A thermoforming method is usually used in the case of materials capable of withstanding a high temperature and whose thermal expansion coefficient is adapted, to give the rigid radome a lid shape having a folded flange facilitating attachment to the skirt of the reflector .

However, for rigid radomes made of a non-homogeneous material, such as a sandwich-type material for example, this method is generally not applicable, in particular because the high temperature would destroy the sandwich structure. In order to close the open-cell structure on the edge of the radome, a covering piece is necessary. To allow the fixing of the flat radome on the rim of the reflector, or its skirt, which is substantially perpendicular thereto, it is necessary to have a workpiece whose surface forms an angle with the plane of the radome.

In the past, various solutions comprising several pieces of plastic material have been proposed. The disadvantage of these solutions is the number of parts used and the number of corresponding perforations to be made in the skirt of the reflector. In other cases, an additional edge added to fix the radome on the edge of the reflector is necessary. In order to obtain the required mechanical strength, this rim is firmly fixed to the radome by means of several screws for example. The cost and the time of realization of the radome are increased by the additional steps introduced in the manufacturing process, such as in particular a step of drilling the holes for receiving the screws for fixing the rim.

The document EP1762860 discloses a radar device with a flat support comprising antennas, the support being covered by two halves of a cover, the upper half acting as a radome. The upper half, the flat support, and the lower half are stacked in this order, and their peripheries are in direct contact. Two watertight rings are attached to the contact surfaces of the two halves of the cover with the flat support. The stack is held together by means of metal clips.

The document EP2772985 discloses a fixation of a flat radome of a parabolic antenna, consisting of two annular metal parts pinching the stacked peripheries of the radome and the reflector. The lower annular part has grooves for better adhesion to the periphery of the reflector.

ABSTRACT

The technical problem that arises then is to find an assembly solution suitable for fixing a radome consisting of a rigid material such as a non-thermoformable material, for example a low density multilayer material or "honeycomb", and having a flat flange on a reflector. In addition the device assembly must be inexpensive and easy to implement, whether assembly or disassembly.

• le radôme fixé sur le réflecteur doit être capable de supporter des forces élevées, en particulier des vitesses de vent allant jusqu'à 250 kilomètres par heure,
• la fabrication du radôme en usine doit être simple et rapide,
• l'installation du radôme sur le site doit être simple et rapide,
• la solution proposée doit être de faible coût, ce qui signifie qu'il est nécessaire de réduire le nombre de points de fixation du radôme sur le réflecteur étant donné que chaque point de fixation nécessite la réalisation d'un trou,
• pour faciliter l'assemblage et maintenir un coût d'assemblage faible, le nombre total de pièces doit être réduit,
• la solution proposée doit avoir un impact minimum sur les performances radiofréquences.

The solution must necessarily fulfill the following conditions:

• the radome attached to the reflector must be capable of withstanding high forces, in particular wind speeds of up to 250 kilometers per hour,
• the manufacturing of the radome in the factory must be simple and fast,
• the installation of the radome on the site must be simple and fast,
• the solution proposed must be of low cost, which means that it is necessary to reduce the number of fixing points of the radome on the reflector since each fixing point requires the realization of a hole,
• to facilitate assembly and maintain a low assembly cost, the total number of parts must be reduced,
• the proposed solution must have a minimum impact on radio frequency performance.

The object of the present invention is an antenna according to claim 1.

In one aspect, the half-flanges are plastic. The half-flanges are made of a rigid dielectric material having nevertheless a certain flexibility, such as for example a polymer. Suitable polymers include polycarbonate PC, polypropylene PP, polystyrene PS, PVC polyvinyl chloride, acrylonitrile-butadiene-styrene ABS, etc.

In another aspect, the rim is metallic. For example, the rim may be made by folding a sheet of metal, for example aluminum or stainless steel.

According to one embodiment, the rim is circular and its ends are connected by a clamping means.

According to another embodiment, the upper half-flange and the lower half-flange bear protuberances capable of cooperating with a housing formed in the flat flange. During assembly, these protuberances facilitate and improve the positioning accuracy of the half-flanges relative to the flanged element.

According to yet another embodiment, the second section of the lower half-flange comprises orifices intended to receive means for fixing the lower half-flange on the support. When these orifices exist, they are arranged so as to be in vis-à-vis perforations previously made in the support.

The present solution has the advantage of providing a device for assembling a radome on a light reflector and at low cost with high mechanical and radioelectric performance. It should be noted that the cost of the radome and its installation on the reflector is an important part of the total cost of the antenna. In addition, it can allow assemblies that could not be made using currently known devices.

The invention also relates to a method of assembling the antenna described above. The method comprises steps according to claim 7.

The value of this solution is to avoid drilling many holes in the radome, as well as the corresponding manufacturing process steps and the time required. It also does not require perforations in the metal rim. The solution takes advantage of the density of the material chosen for the radome to achieve a pressure assembly so as to incorporate protruding reliefs, for example in the form of teeth, in this lightweight material, solid and soft. The number of parts to make the assembly is also reduced. The step of shaping the rim replaces the steps of drilling holes, reduces the time and complexity of assembly, and therefore the associated costs.

BRIEF DESCRIPTION

• la figure 1 illustre une coupe partielle en perspective d'un matériau de type sandwich,
• la figure 2 illustre une vue partielle éclatée d'un mode de réalisation du dispositif d'assemblage,
• la figure 3 illustre une vue partielle assemblée d'un mode de réalisation du dispositif d'assemblage,
• la figure 4 illustre une vue en coupe d'un mode de réalisation du dispositif d'assemblage,
• la figure 5 illustre une vue de détail d'un mode de réalisation du dispositif d'assemblage,
• la figure 6 illustre le procédé de fixation d'un élément muni d'un rebord plat sur un support,
• la figure 7 illustre schématiquement le phénomène de diffraction au bord d'un radôme adjacent au réflecteur d'une antenne,
• la figure 8 illustre le diagramme de rayonnement d'une antenne comportant un dispositif d'assemblage ne comprenant que des pièces en plastique,
• la figure 9 illustre le diagramme de rayonnement d'une antenne comportant un dispositif d'assemblage comprenant une pièce en métal.

Other characteristics and advantages will appear on reading the following description of an embodiment, given of course by way of illustration and not limitation, and in the accompanying drawing in which:

• the figure 1 illustrates a partial perspective section of a sandwich-type material,
• the figure 2 illustrates an exploded partial view of an embodiment of the assembly device,
• the figure 3 illustrates an assembled partial view of an embodiment of the assembly device,
• the figure 4 illustrates a sectional view of an embodiment of the assembly device,
• the figure 5 illustrates a detail view of an embodiment of the assembly device,
• the figure 6 illustrates the method of fixing an element provided with a flat rim on a support,
• the figure 7 schematically illustrates the phenomenon of diffraction at the edge of a radome adjacent to the reflector of an antenna,
• the figure 8 illustrates the radiation pattern of an antenna comprising an assembly device comprising only plastic parts,
• the figure 9 illustrates the radiation pattern of an antenna comprising an assembly device comprising a metal part.

On the figures 8 and 9 , the intensity of the radiation I in dB is given on the ordinate, and on the abscissa the emission / reception angle β in degrees.

In these figures, the identical elements bear the same reference numbers.

Directional terminology such as "left", "right", "up", "down", "forward", "backward", "vertical", horizontal ", etc. is used with reference to the orientation of the figures here described. Because the elements composing the embodiments of the present invention can be placed in different orientations, the directional terminology is only used here for purposes of illustration and is in no way limiting.

DETAILED DESCRIPTION

A rigid radome is made of a light and solid but non-flexible material, such as a sandwich-type material. The radome is usually made of a flexible dielectric material such as a polymer, fiberglass, etc. Suitable polymers are in particular PC polycarbonate, polypropylene PP, polystyrene PS, PVC polyvinyl chloride acrylonitrile-butadiene-styrene ABS, etc.

The figure 1 illustrates a partial perspective view of an example of material 1 used for the realization of the rigid radome of a concave reflector antenna. This material, sandwich type, comprises an upper layer 2 consisting of a flat plate of polymeric material, such as polypropylene, and a lower layer 3 consisting of a plate of polymeric material which may be similar or different from that of the upper layer 2. To optimize the broadband characteristics of the antenna, the outer layers 2, 3 must be thin (eg 0.55 mm) and have a very low dielectric constant. The layers 2 and 3 surround an intermediate layer 4, formed of cells 5 of low dielectric constant (eg ε _r ~ 1). The For example, the cells 5 are of substantially conical shape and filled with air. Their walls are made of polymer material, such as polypropylene. Thanks to this material, the radome 1 obtained is light and strong, while maintaining a certain flexibility that prevents it from breaking under a moderate stress.

To fix the rigid radome on the edge of a reflector, the means used must ensure a solid attachment capable of withstanding the force of the wind, especially for antennas of large diameter. Some materials are not thermoformable, which is particularly the case of the sandwich type material illustrated by the figure 1 . It is therefore not possible to give them a shape that would easily fix the flat radome on the edge of the reflector or skirt.

The figure 2 illustrates, in exploded view, an embodiment of an assembly device for allowing the attachment of an element 20 having a flat flange 21 on a support. The assembly device comprises an upper half-flange 22 and a lower half-flange 23.

The upper half-flange 22 has a first face 24 facing outwards, and a second face 25 which is intended to be brought into contact with a face 26 of the flat flange 21. The second face 25 comprises reliefs 27, which can have for example the shape of teeth, having a suitable profile and sufficient hardness to be able to penetrate into the material constituting the flat rim 21 without damaging it when sufficient pressure is imposed. The upper half-flange 22 also comprises protuberances 28 of shape adapted to the form of housings 29 formed in the flat flange 21. The protuberances 28 cooperating with the corresponding housing 29 serve as guides to allow precise positioning of the upper half-flange 22 with respect to the element 20.

The lower flange half 23 has a first pane 30 having a first face 31 facing outwards, and a second face 32 which is intended to be brought into contact with the opposite face 35 of the flat edge 21. The second side 3 2 comprises reliefs 27 able to penetrate into the material constituting the flat rim 21, similar to those described above. The lower half-flange 23 comprises protuberances 28 of shape adapted to the housing form 29 formed in the flat flange 21, similar to those described above.

The lower half-flange 23 also comprises a second flange 33. In the embodiment illustrated here, the second flange 33 forms an angle α that is non-zero with the first flange 30, which may be for example approximately 90 °, thereby forming L. The second pan 33 must allow the docking of the lower half-flange 23 on the chosen support. Orifices 34 are adapted to receive means, such as screws, bolts or rivets, for fixing the lower half-flange 23 to the support.

On the figure 3 , the upper half-flange 22 and the lower half-flange 23 are brought together so as to sandwich the flat flange 21 of the element 20. By exerting a moderate pressure, the reliefs 27 carried by the upper half-flange 22 and the lower half-flange 23 penetrate into the flexible material constituting the element 20 on either side of the flat flange 21. Of course the material constituting the element 20 must be sufficiently flexible and soft or be composed of thin layers , as in the case of a sandwich type material, to be perforated without the need to exert too much pressure.

The protuberances 28 carried by the upper half-flange 22 and the lower half-flange 23 fit into the housings 29 formed in the flat flange 21 in order to ensure the connection between the upper half-flange 22 and the lower half-flange. 23, and to facilitate their positioning relative to the flat flange 21. In this case, a protuberance 28 carried by the upper half-flange 22 and another protrusion 28 carried by the lower half-flange 23 respectively insert by the top and bottom in the same housing 29, thus making integral the upper half-flange 22 and the lower half-flange 23 between them and with the flat flange 21.

In the embodiment illustrated in section on the figure 4 , the flat flange 21 is sandwiched between the upper half-flange 22 and the lower half-flange 23, themselves held tight by a rim 40. The rim 40 in the shape of a U comprises a first branch 41 contiguous to the first 24 facing outwardly of the upper half-flange 22, and a second branch 42 contiguous to the first face 31 facing outwardly of the first section 30 of the lower half-flange 23. The rim 40 secures the two half -brides 22 and 23 and makes their assembly more solid. It ensures a tight hold of the two half-flanges 22 and 23.

The use of a plastic material for producing the upper and lower half-flanges 22, 23, including the reliefs 27 and the protuberances 28, a the advantage of a lower cost. Advantageously, the rim 40 is metallic, which contributes to the strength of the assembly and to the improvement of the radiation pattern. For example, the rim 40 can be shaped by folding a sheet of metal.

If the element is circular for example, the half-flanges 22, 23 and the rim 40 may cover a portion of the circumference of the flange 21, or the entire circumference thereof. In the latter case, the two ends of the rim 40 may be connected by a clamping means 50 comprising for example a bolt or a screw 51, as illustrated in FIG. figure 5 .

In the case of a concave reflector antenna and rigid flat circular radome, the fixing is obtained by clamping the rim on the radome. This avoids creating multiple holes in the radome. The assembly is obtained by clamping so as to cause the reliefs carried by the half-flanges, such as teeth, to penetrate into the solid but soft material of the radome. The assembly device therefore comprises only three main parts: two half-flanges of plastic material and a metal rim without perforation, obtained for example by folding, to connect the two half-flanges.

The figure 6 illustrates the method of fixing the element provided with a flat flange on a support by means of the assembly device described above. This process comprises several steps which are as follows.

During a first step 60, a face of the flat flange is contiguous to the second face provided with reliefs and protuberances of the upper half-flange. To ensure positioning of the upper half-flange, the protuberances are placed opposite the corresponding housing formed in the flat flange.

During a second step 61, the opposite face of the flat flange is contiguous to the second face provided with reliefs and protuberances of the first section of the lower half-flange. In order to ensure the positioning of the lower half-flange, the protuberances are placed opposite the corresponding housing formed in the flat flange.

During a third step 62, a pressure is exerted simultaneously on the first outwardly facing face of the upper half-flange and on the first outwardly facing face of the first flange of the lower half-flange, so that to make penetrate the reliefs in the material constituting the flat edge. At the same time, protuberances of the upper half-flange and the lower half-flange penetrate into the corresponding housing formed in the flat flange.

During a fourth step 63, a U-shaped rim is disposed around the upper half-flange and the lower half-flange so as to ensure a tight hold of the two half-flanges. Preferably the rim may be composed of two distinct parts which are joined and secured around the upper half-flange and the lower half-flange. Alternatively, the rim is made of a thin and malleable metal that allows a slight elastic deformation to fit around the upper half-flange and the lower half-flange. This has resulted in a solid assembly around the flat flange which will allow its attachment to a support. It should be noted that steps 60 to 63 can be performed in the factory.

During a fifth step 64, fastening means are inserted into the orifices of the second panel of the lower half-flange in order to fix the element provided with a flat flange on the support. It can include screws, bolts or rivets. Thanks to the precise positioning obtained by means of the protuberances, the orifices of the second part of the lower half-flange are opposite the perforations previously drilled in the support.

The figure 7 is a diagram showing an antenna 70 comprising a concave primary reflector 71 , provided with a skirt 72, and a secondary reflector 73. The antenna 70 is powered by a waveguide 74 which may be a hollow metal tube, for example in aluminium. The antenna is covered with a flat rigid radome 75 . The waveguide 74 emits incident radiation towards the secondary reflector 73 which is reflected towards the primary reflector 71. Most of the incident radiation is reflected on the primary reflector 71 and forms the radiation emitted by the antenna 70. direction of a receiver. However, a portion 76 of the incident radiation reaches the edges of the primary reflector 71 where diffraction 77 occurs , which increases the field at the rear of the primary reflector 71 and contributes to deterioration of the forward / backward ratio of the antenna.

The figures 8 and 9 illustrate the radiation diagram of an antenna comprising an assembly device as described above. In these two figures, the line 80 continues to reference represents the standard profile corresponding to the model class 3 ETSI.

The figure 8 relates to an antenna comprising an assembly device, all parts of which are made of plastic. It is observed that the side lobes 81 exceed the ETSI standard.

In comparison, the side lobes 82 of an antenna comprising an assembly device whose rim is metallic are very clearly below the reference line 80 of the ETSI standard. This highlights the influence of the metal rim on the radio behavior of the antenna. The radiation pattern illustrated by the figure 8 shows that the phenomenon of diffraction is less in this case. Indeed, the thickness of the parts and the discontinuities between different materials create a diffraction on the edge of the primary reflector of the antenna in the case where only the plastic is used. The presence of the metal rim masks the discontinuities between the plastic parts, and contributes to reducing the level of diffraction on the edge of the reflector.

Of course, the present invention is not limited to the embodiments described. In particular, the number and shape of the reliefs and protuberances can be varied. It may also be modified to adapt to the chosen support shape and position of the second panel of the lower half-flange, and the fastening means on the support (clip, rivet, glue, ...). The description of the assembly device has been particularly illustrated in the case of the fixation of a rigid plane radome on a concave antenna reflector, but such a device can also be used for any type of radome equipped with a flat rim and any type of reflector.

Claims (9)

1. Antenna having a radome made of low-density material provided with a flat lip (21) and an assembly device for fastening said radome to a support, said assembly device comprising

   - an upper half flange (22) having a first face (24) and a second face (25) that is able to engage with a face (26) of the flat lip (21),

   - a lower half flange (23) having a first section (30) that has a first face (31) and a second face (32) that is able to engage with an opposite face (35) of the flat lip (21),

   - a U-shaped rim (40), a first leg (41) of which engages with the first face (24) of the upper half flange (22) and the second leg (42) of which engages with the first face (31) of the first section (30) of the lower half flange (23) so as to secure the upper half flange (22) to the lower half flange (23),

   characterized in that

   - the second face (25) of the upper half flange (22) has reliefs (27) that are sufficiently hard to be able to penetrate by exertion of pressure into the constituent material of the flat lip (21),

   - the second face (32) of the first section (30) of the lower half flange (23) has reliefs (27) that are sufficiently hard to be able to penetrate into the constituent material of the flat lip (21),

   and in that the lower half flange (23) has a second section (33) that is able to engage with the support, said second section (33) making a non-zero angle α with the first section (30).
2. Antenna according to Claim 1, wherein the half flanges (22, 23) are made of plastics material.
3. Antenna according to either of Claims 1 and 2, wherein the rim (40) is metallic.
4. Antenna according to one of the preceding claims, wherein the rim (40) is circular, and the ends thereof are linked by a clamping means (50).
5. Antenna according to one of the preceding claims, wherein the assembly device has positioning means made up of at least one protuberance (28) borne by the upper half flange (22) and the second lower half flange (23) that is able to cooperate with at least one housing (29) formed in the flat lip (21).
6. Antenna according to one of the preceding claims, wherein the second section (33) of the lower half flange (23) has orifices (34) intended to receive means for fastening the lower half flange (23) to the support.
7. Method for assembly an antenna according to one of Claims 1 to 6, having the following steps:

   - a face (26) of the flat lip (21) is placed next to the second face (25) provided with reliefs (27) of the upper half flange (22),

   - the opposite face (35) of the flat lip (21) is placed next to the second face (32) provided with reliefs (27) of the first section (30) of the lower half flange (23),

   - a pressure is exerted simultaneously on the outwardly facing first face (24) of the upper half flange (22) and on the outwardly facing first face (31) of the first section (30) of the lower half flange (23) in order to make the reliefs (27) penetrate into the constituent material of the flat lip (21),

   - a U-shaped rim (40) is disposed around the upper half flange (22) and the lower half flange (23) so as to ensure that the two half flanges (22, 23) are kept clamped together.
8. Method according to Claim 7 for assembling an antenna according to Claim 5, also having the following positioning steps:

   - a face (26) of the flat lip (21) is placed next to the second face (25) provided with protuberances (28) of the upper half flange (22) so as to position the protuberances (28) adjacent to the housing (29) formed in the flat lip (21),

   - the opposite face (21) is placed next to the second face (32) provided with protuberances (28) of the first section (30) of the lower half flange (23) so as position the protuberances (28) adjacent to the housing (29) formed in the flat lip (21),

   - a pressure is exerted simultaneously on the outwardly facing first face (24) of the upper half flange (22) and on the outwardly facing first face (31) of the first section (30) of the lower half flange (23) so as to make the protuberances (28) penetrate into the housing (29) formed in the flat lip.
9. Method according to either of Claims 7 and 8 for assembling an antenna according to Claim 6, also having the following fastening step:

   - fastening means are inserted into the orifices (34) in the second section (33) of the lower half flange (23) so as to fasten the lower half flange (23) to the support.

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