Passive radiofrequency device comprising axial attachment openings

Abstract

The invention relates to a radiofrequency device (1) comprising at least: a tube through which a channel (3) passes, a front face (4) and / or a rear face (5) forming a support surface passed through by the channel (3), the support surface forming an annular frame around one end of the tube and integral with the tube, the support surface comprising a plurality of axial attachment openings (7) passing through the support surface and opening to the outside of the channel (3) in order to allow the attachment of the device, the width of the frame being greater at and in the immediate proximity of the axial attachment openings than at a distance from these axial attachment openings.

Description

technical field

[0001] The present invention relates to a radio frequency device comprising axial fixing openings. State of the art

[0002] Passive radio frequency devices are used to propagate or manipulate radio frequency signals without using active electronic components. Examples of passive radio frequency devices include passive waveguides based on wave guidance within hollow metallic channels, filters, antennas, mode converters, and so on. Such devices can be used for signal routing, frequency filtering, signal separation or recombination, signal transmission or reception into or from free space, and other applications.

[0003] Conventional waveguides used for radio frequency signals have internal openings with cross-sections such as rectangular or circular shapes. They allow the propagation of electromagnetic modes corresponding to different electromagnetic field distributions along their cross-section.

[0004] Radio frequency devices are used, for example, in aerospace (airplanes, helicopters, drones), to equip spacecraft in space, on ships at sea or on underwater vehicles, and on vehicles operating in deserts or high mountains—each time in hostile or even extreme conditions. In these environments, radio frequency devices are particularly exposed to: extreme pressures and temperatures that vary significantly, leading to repeated thermal shocks; mechanical stress, as the waveguide is integrated into a craft that is subjected to shocks, vibrations and loads that impact the waveguide; hostile weather and environmental conditions in which craft equipped with waveguides operate (wind, frost, humidity, sand, salts, fungi / bacteria).

[0005] Furthermore, weight-related requirements are often critical for space or aeronautical applications.

[0006] To address these constraints, waveguides made from pre-machined metal plates are known, allowing the production of waveguides capable of operating in harsh environments. However, manufacturing these waveguides is often difficult, expensive, and hard to adapt to the production of lightweight waveguides with complex shapes.

[0007] Waveguides manufactured by assembling plates of aluminum, copper, titanium, etc., with or without surface treatments, are therefore often produced as standardized parts that must then be assembled together. Furthermore, it is often useful to be able to connect two or more passive radio frequency devices, for example, a waveguide with an antenna or several waveguide sections, in order to create various types of configurations. These assemblies are most often made using flanges or brackets to create the desired system. The presence of these connecting elements increases the weight of the system, which is particularly problematic for aerospace applications.

[0008] For example, document WO2018029455 describes a waveguide connector comprising a flange and a plurality of ports. The flange includes means for coupling to another waveguide connector, each port of the plurality of ports being configured to interface with a respective waveguide. The flange's volume and weight are significant compared to the connector.

[0009] As an example, Huikin LI's dissertation, "Waveguide flange design and characterization of misalignment at submillimeter wavelengths", May 2013, pages 4, 22, 23, 24, 26, 62, 152, describes various embodiments of waveguide connectors, for example flanges with complementary holes and rods, flanges with complementary male / female profiles, or flanges with an alignment ring that fits between them.

[0010] Examples of such flasks are presented at figures 1a, 1b and 1cfrom this document. It is observed that known interfaces use flanges of significant dimensions and mass compared to the effective area of ​​the waveguides. In order to achieve highly precise connections, with accurate alignment and durable fixings, the flanges occupy particularly large surfaces.

[0011] WO2017 / 192071 discloses a waveguide interconnection system that enables fast and reliable interconnection with a minimum number of interconnects. The interconnection system includes a flange adapter element designed to be placed between two waveguide flanges. Connecting the two waveguides therefore requires an additional component to join them, increasing the complexity and cost of waveguide assembly.

[0012] Recent work has demonstrated the possibility of manufacturing passive radio frequency devices, including antennas, waveguides, filters, converters, etc., using additive manufacturing methods, for example 3D printing. In particular, the additive manufacturing of waveguides comprising both a core of non-conductive material, such as polymers or ceramics, and a shell of conductive metal is well known.

[0013] Waveguides with ceramic or polymer walls manufactured using an additive manufacturing process and then coated with a metallic layer have been suggested. The internal surfaces of the waveguide must be electrically conductive to function. Using a non-conductive core reduces the weight and cost of the device and allows for the implementation of 3D printing methods adapted to polymers or ceramics, enabling the production of high-precision parts with low surface roughness.

[0014] As an example, the article by Mario D'Auria et al, "3-D PRINTED METAL-PIPE RECTANGULAR WAVEGUIDES", August 21, 2015, IEEE Transactions on components, packaging and manufacturing technologies, Vol. 5, No. 9, pages 1339-1349, describes in paragraph III a process for manufacturing the core of a waveguide by fused deposition modeling (FDM).

[0015] Waveguides manufactured by additive manufacturing are known to have a non-conductive core produced, for example, by stereolithography, selective laser melting, selective laser sintering, or another additive process. This core typically has an internal aperture for the propagation of the radio frequency signal. The internal walls of the core around the aperture can be coated with an electrically conductive material, such as a metallic plating.

[0016] Additive manufacturing of passive radio frequency devices makes it possible to create devices with complex shapes that would be difficult or even impossible to produce by machining. However, additive manufacturing has its own limitations and does not allow the production of certain shapes or large parts.

[0017] The need to make effective connections between several parts is therefore a recurring one.

[0018] US2012 / 0084968A1 describes a method for manufacturing passive waveguides in multiple parts produced by 3D printing, then metallized before assembly. Manufacturing in multiple parts makes the process more flexible and allows for the creation of complex shapes that would be impossible to print in a single operation. However, this process creates discontinuities in the metal layer at the junctions between the metallized parts, which disrupt signal transmission in the waveguide. Furthermore, precise alignment of the parts is difficult to guarantee and can hardly be improved by polishing or adjusting the metal layer, which is generally too thin.

[0019] The same weight and bulk problems of the flanges are also found on active radio frequency equipment, for example semiconductor equipment such as low noise amplifiers, power amplifiers, filters, etc. when this equipment has to be connected to waveguides.

[0020] Document WO 2014 / 174494 A2 discloses a gender-neutral, self-aligning flange with a corrugated structure that limits the introduction of discontinuities in the corrugation profile at the interface with another flange. These flanges suffer from the same bulkiness issue and therefore remain heavy. Brief summary of the invention

[0021] One aim of the present invention is to provide a passive or active radio frequency device that is free from or minimizes the limitations of known devices.

[0022] One aim of the invention is in particular to provide a radio frequency device, for example a passive device, for example a waveguide, easily connectable to other elements, for example other waveguides, antennas, polarizers, etc.

[0023] Another objective of the invention is to provide a radio frequency device that is easy to assemble and of reduced mass, suitable for uses where mass reduction is a critical objective.

[0024] According to the invention, these goals are achieved in particular by means of a radio frequency device comprising at least: a tube through which a channel passes, a front face and / or a rear face forming a support surface through which the channel passes, said support surface forming an annular frame around one end of the tube and integral with the tube, said support surface comprising a plurality of axial fixing openings passing through the support surface and opening out to the outside of said channel in order to allow the fixing of the device, the width of said frame being greater at the level and in the immediate vicinity of the axial fixing openings than at a distance from these axial fixing openings.

[0025] The front face and / or the rear face thus form a lighter flange.

[0026] The term "annular" and the expression "annular frame" refer to any closed and not solid shape, including for example a rectangular, square, circular, oval, elliptical ring, etc. The shape of the outer circumference may be different from the shape of the opening.

[0027] The support surface(s) allow the device to be aligned and pressed against another device fixed by means of the axial fixing openings.

[0028] At least one of the axial fixing openings can be reinforced.

[0029] An axial opening is said to be reinforced, for example, if the bearing surface uses more material near the axial fixing openings than between these axial fixing openings.

[0030] An axial opening is considered reinforced, for example, when the supporting surface forms an annular surface around the canal, and the width of this annular surface is greater at the opening than between any two openings. The opening is also considered reinforced when this axial opening is located within an atrium or another prominent portion surrounding the annular surface of the canal.

[0031] An axial opening is also said to be reinforced when the bearing surface forms an annular surface around the axial channel, which this bearing surface comprises except for a portion, for example of a ring, around the axial opening.

[0032] Reinforcing the bearing surface at the axial fixing openings allows for a comparatively lighter bearing surface between these fixing openings, ultimately resulting in a lighter bearing surface.

[0033] The support surface may be provided with an opening corresponding to said channel, and an annular surface around this opening.

[0034] The radial openings pass through this support surface and emerge at the rear of the support surface, but outside the channel.

[0035] The width of the bearing surface can be wider at and in the immediate vicinity of the axial fixing openings than at a distance from these axial fixing openings.

[0036] The bearing surface can be thinned between the axial fixing openings.

[0037] The support surface can be provided with recesses between the axial fixing openings.

[0038] Advantageously, all or part of the bearing surfaces of the front or rear faces incorporate a lattice structure. The use of such a structure, easily produced by additive manufacturing, makes it possible to lighten the bearing surfaces, particularly between the earcups or mounting openings, in order to further reduce the mass while maintaining sufficient rigidity of the bearing portions.

[0039] According to one aspect, at least one of the support surfaces comprises a plurality of fixing lugs, each of the lugs comprising at least one said axial fixing opening.

[0040] Reinforced earcups prevent deformation of the device when it is attached to another device by means of screws or pins engaged in the axial fixing openings.

[0041] Each of the earpieces can be independent and separate from the others, thus forming inter-earpiece spaces devoid of material, allowing the structure of the device to be lightened.

[0042] The device may include exactly three axial fixing openings on one or more faces, in order to allow isostatic fixing.

[0043] The device can have exactly three earpieces per support surface, defining a fixation plane in an isostatic manner.

[0044] However, it is also possible to have two fixing points, four fixing points, or another number of fixing points.

[0045] The devices can be fixed together using at least one screw or pin engaged in each axial fixing opening. The screw or screws can be metallic or made of other materials.

[0046] The device may be a waveguide, more specifically a waveguide for a satellite antenna.

[0047] Advantageously, the bearing surface is flat. Securing two elements with flat faces allows for a simple, reliable, and quick-to-install connection.

[0048] In another advantageous embodiment, the bearing surface is in a plane perpendicular to the canal axis. This allows for the easy production of devices with standard profiles and aligned flanges, enabling simple and precise assembly.

[0049] Also advantageous is that the support surface can be manufactured as a single unit with the device. This single-piece manufacturing simplifies production and facilitates the achievement of consistent and precise dimensions.

[0050] In yet another advantageous embodiment, the device and its bearing surfaces are produced by additive manufacturing. This manufacturing method is particularly advantageous for producing custom or standard parts with consistent quality.

[0051] The channel may comprise a non-conductive core and a conductive sheath around that core, said core and said conductive sheath extending into said support surface.

[0052] The thickness of the metallic conductive layer is advantageously at least five times the skin depth δ, preferably at least twenty times the skin depth δ. This significant thickness is not necessary for signal transmission, but contributes to the rigidity of the device, which is thus guaranteed by the metallic casing despite a multi-piece core potentially less rigid than a monolithic core, and despite a reduced bearing surface of the flanges.

[0053] The skin depth δ is defined as: δ = 2 μ 2 πf σ where µ is the magnetic permeability of the plated metal, f is the radio frequency of the signal to be transmitted, and σ is the electrical conductivity of the plated metal. Intuitively, this is the thickness of the region where the current is concentrated in the conductor at a given frequency.

[0054] This solution has the advantage over the previous art of providing waveguides assembled by additive manufacturing that are more resistant to the stresses to which they are exposed (thermal, mechanical, meteorological and environmental stresses).

[0055] The core of the device can be made of a polymer material.

[0056] The core of the device can be made of a metal or an alloy, for example aluminium, titanium or steel.

[0057] The core of the device can be made of ceramic.

[0058] The core of the device can be produced by stereolithography, selective laser melting or selective laser sintering.

[0059] The metallic layer forming the envelope can comprise a choice of metals from Cu, Au, Ag, Ni, Al, stainless steel, brass or a combination of these metals.

[0060] The resistance of the device, chosen from tensile, torsional, flexural, or a combination of these resistances, can be conferred mainly by the conductive layer.

[0061] According to one embodiment, the conductive layer is deposited on the core by electrolytic deposition or electroplating, chemical deposition, vacuum deposition, physical vapor phase deposition (PVD), printing deposition, sintering deposition.

[0062] In one embodiment of the process, the conductive layer comprises several layers of metals and / or non-metals deposited successively.

[0063] The core manufacturing process includes an additive manufacturing step. Additive manufacturing refers to any process for manufacturing parts by adding material, based on computer data stored on a computer and defining a model of the part. Besides stereolithography and selective laser melting, the term also encompasses other manufacturing methods involving the hardening or coagulation of liquid or powder, including but not limited to methods based on inkjet printing (binder jetting), DED (Direct Energy Deposition), EBFF (Electron beam freeform fabrication), FDM (fused deposition modeling), PFF (plastic freeforming), aerosol deposition, BPM (ballistic particle manufacturing), powder bed fusion, SLS (Selective Laser Sintering), ALM (Additive Layer Manufacturing), polyjet, EBM (electron beam melting), photopolymerization, etc.However, manufacturing by stereolithography or selective laser melting is preferred because it allows for parts with relatively clean surface finishes and low roughness.

[0064] The manufacturing of the core may involve an additive manufacturing step by stereolithography, selective laser melting or selective laser sintering.

[0065] In the context of the invention, the terms "conductive layer", "conductive coating", "metallic conductive layer" and "metallic layer" are synonymous and interchangeable. Brief description of the figures

[0066] Examples of implementation of the invention are given in the description illustrated by the accompanying figures, in which: THE figures 1a, 1b and 1cillustrate examples of prior art waveguides, featuring a flange surrounding the waveguide and allowing two waveguides with compatible flanges to be joined together; The figure 2 is a perspective view of two parts intended to be joined along a junction plane perpendicular to the direction of signal propagation in order to form a longer waveguide; The figure 3 shows an enlarged view of an earpiece from a variant of the device in which the attachment earpieces are made with a lattice structure; The figure 4 illustrates a front view of the front or rear face of a waveguide device forming a support surface (flange) with an opening corresponding to said channel, said support surface being made of lattice and comprising four reinforced axial openings. figure 5illustrates a cross-sectional view of a device comprising a core covered with a conductive sheath on the internal and external walls. Example(s) of an embodiment of the invention

[0067] THE figures 1a to 1cThese illustrations depict examples of flanges belonging to prior art radio frequency devices. These flanges are designed to facilitate the assembly of multiple devices, for example, several waveguide sections of identical or different shapes. The connection is achieved by bringing the flanges into contact at the ends of the waveguide sections. The flanges have openings for the insertion of fasteners such as screws or pins. Known flanges are large in size, and their surface area is significantly greater than that of a waveguide section. The large surface areas allow for high-quality assemblies with precise alignment, without risk of compromising the performance of the assembled components.However, the large surfaces used considerably increase the weight of the parts, making them unsuitable for certain applications where mass is a critical factor.

[0068] An example of a device according to the invention is illustrated on the figure 2 As illustrated, the radio frequency device 1, here a passive radio frequency device, for example a waveguide, comprises a tube 2 elongated along a longitudinal axis AA. A channel 3, for the transmission of the radio frequency signal, is also aligned along the axis AA and passes through the tube. In the illustrated example, the longitudinal opening 3 has a rectangular cross-section and defines a channel for the transmission of the radio frequency signal. Other channel shapes, including round, square, elliptical, semi-circular, semi-elliptical, hexagonal, octagonal, etc., can be used.

[0069] The cross-section of the aperture is determined according to the frequency of the electromagnetic signal to be transmitted. The dimensions and shape of this internal channel are determined based on the operating frequency of the device 1, that is, the frequency of the electromagnetic signal for which the device is manufactured and for which a stable transmission mode, optionally with minimal attenuation, is obtained. The tube 2 can be made of metal, or by metallizing a core 2, for example, of polymer, epoxy, ceramic, organic material, or metal.

[0070] A front face 4 and / or a rear face 5 define bearing surfaces for connecting two or more devices 1 along the axis AA. The bearing surfaces of the front face 4 and rear face 5 are in a plane perpendicular to the axis of the channel.

[0071] To secure two consecutive adjacent devices together, the front and / or rear faces of the device form an annular surface around channel 3. This annular surface has a plurality of mounting lugs 6. The width of the annular surface is therefore greater at the lugs around the mounting points than between these lugs, which reinforces the mounting points. The contact face of each lug is coplanar with the adjacent face 4 or 5 of the channel. The arrangements can be designed to maintain compatibility with existing flanges, whether standardized or not.

[0072] In the illustrated examples, exactly three fixing points are provided, thus enabling isostatic mounting. These three fixing points are located in three tabs 6 distributed around the opening, creating an isostatic mounting plane. The tabs 6 are positioned here with two tabs at the lower corners and one in the mid-zone of the opposite edge. Other arrangements with tabs 6 in the corners and / or along the edges are possible.

[0073] The earcups have seven axial openings for inserting fasteners such as screws, screw / nut assemblies, pins, etc. Additional openings may be provided in the earcups or bearing surfaces to reduce mass. Heat dissipation surfaces may also be included.

[0074] In order to best meet the desired mass reduction objectives compared to the use of flanges, the dimensions of the augers 6 are significantly reduced compared to those of device 1. For example, the augers 6 are dimensioned so that the total sum of the spans E is less than one-third and more preferably less than one-quarter of the external perimeter of the web 2 of device 1. By span, we mean the width of the auger at the point of intersection with the web 2 of the device, as illustrated for example in the figures 2 And 4 .

[0075] There figure 3This illustrates a variant embodiment in which at least one of the 6 auricles, and possibly the rest of the annular surface around the canal, consists of a lattice structure, i.e., one comprising beams separated by recesses. Such an architecture further contributes to the mass reduction objectives, without affecting the rigidity and / or durability of the attachment.

[0076] There figure 4This illustrates a front view of a bearing surface (flange) 4 made entirely of a lattice between the four axial mounting openings 7. The openings are reinforced by means of a reinforcing ring 70, denser than the rest of the lattice, around each opening. This embodiment makes it possible to increase the size of the bearing surface 4 without significantly increasing its mass, thus ensuring a perfectly flat bearing surface even after clamping against the corresponding bearing surface of an adjacent device. The density of the lattice can vary around the periphery of the bearing surface, and be, for example, greater near the mounting openings 7 than further away from them.

[0077] The tube and its bearing surfaces 6 are preferably manufactured by additive manufacturing, as described later. This manufacturing method makes it easy to produce a device with complexly shaped bearing surfaces (flanges), for example a tube with lugs, and / or a lattice structure.

[0078] There figure 2 illustrates two aligned devices 1, intended to be fixed together.

[0079] In this example, the two devices are intended to be placed end-to-end in the direction of signal transmission, thus forming a continuous, elongated longitudinal channel. The contacting surfaces are flat and perpendicular to the direction of radio frequency signal transmission.

[0080] The front or rear face of the device may have a central area that is very slightly recessed so that it does not touch the face of the device or connected equipment's flange, but is separated from it by a narrow gap. The recessed area is defined by a deeper groove in the flange's surface. This arrangement allows for short-circuit operation. This recessed central area may also be provided in the case of a lattice flange as described above.

[0081] In the embodiment illustrated in the figure 5 The inner and outer surfaces of the core 2 are coated with a conductive metallic layer, for example copper, silver, gold, nickel, etc., plated by chemical deposition without electric current. The thickness of this layer is, for example, between 1 and 20 micrometers, or for example between 4 and 10 micrometers. figure 5illustrates the device in which a layer formed by a metallic deposition forms a conductive envelope 8 on the inner surface and 9 on the outer surface of the core 2. The coating can also be an assembly of layers and include, for example, a smoothing layer directly on the core, one or more bonding layers, etc.

[0082] In this example, the bearing surfaces (e.g. the auricles 6) also include a core covered by the external conductive layer 8.

[0083] The thickness of this conductive coating 8 or 9 must be sufficient for the surface to be electrically conductive at the chosen radio frequency. This is typically achieved using a conductive layer whose thickness is greater than the skin depth δ.

[0084] This thickness is preferably substantially constant on all internal surfaces in order to obtain a finished part with precise dimensional tolerances for the channel.

[0085] In one embodiment, the thickness of this layer 8 or 9 is at least five times, and preferably at least twenty times, greater than the skin depth, in order to improve the structural, mechanical, thermal, and chemical properties of the device. Surface currents are thus concentrated mainly, or even almost exclusively, in this layer.

[0086] Applying a metallic coating to the external surfaces does not contribute to the propagation of the radio frequency signal in channel 3, but it does have the advantage of protecting the device from thermal, mechanical, or chemical damage. In an embodiment not shown, only the inner surface of the core, around channel 3, is covered with a metallic coating. The external surfaces are bare or coated with a different material. Additive manufacturing

[0087] Device 1 is advantageously manufactured by additive manufacturing, preferably by stereolithography, selective laser melting, or selective laser sintering (SLS) to reduce surface roughness. The core material can be non-conductive or conductive. The wall thickness is, for example, between 0.5 and 3 mm, preferably between 0.8 and 1.5 mm.

[0088] The shape of the device can be determined by a computer file stored in a computer data medium and allowing control of an additive manufacturing device.

[0089] The deposition of conductive metal on the inner and possibly outer surfaces is achieved by immersing the core 2 in a series of successive baths, typically 1 to 15 baths. Each bath involves a fluid containing one or more reactants. The deposition does not require applying a current to the core being coated. Reference numbers used in the figures

[0090] 1 Passive radio frequency device 2 Soul 3 Channel 4 Front view 5 Back 6 Earpiece 7 Axial fixing opening 70 Reinforcement ring 8 Internal conductive coating 9 External conductive coating

Claims

1. Radiofrequency device (1) comprising at least: a tube traversed by a channel (3), a front face (4) and / or a rear face (5) forming a bearing surface traversed by the channel (3), said bearing surface forming an annular frame around one end of the tube and integral with the tube, said bearing surface comprising a plurality of axial fixing openings (7) passing through the bearing surface and opening to the outside of said channel (3) in order to allow fixation of the device, characterized in that the bearing surface forms a lattice structure and in that said lattice is reinforced around each axial opening (7) .

2. Radiofrequency device according to claim 1, said lattice being reinforced around each axial opening (7) by a reinforcement ring (70).

3. Radiofrequency device according to claim 1 or 2, the bearing surface being flat.

4. Radiofrequency device (1) according to one of claims 1 to 3, said front face or rear face comprising a recessed central portion delimited by a deep annular groove.

5. Radio frequency device (1) according to any of claims 1 to 4, the channel comprising a non-conductive core and a conductive envelope around this core, said non-conductive core and said conductive envelope extending into said bearing surface.

6. Radio frequency device (1) according to claim 5, wherein the core (2) is produced by additive manufacturing.

7. Radiofrequency device (1) according to any of claims 1 to 6, wherein the front (4) and / or rear (5) faces are in a plane perpendicular to the axis of the channel.

8. Radiofrequency device (1) according to any of claims 1 to 7, the device being a waveguide.

Images