Passive RF device including first and second core parts configured to be joined at mounting faces to each other by using an alignment pin and glue

Abstract

A passive radiofrequency device includes a core formed by the gluing of multiple parts in direct contact against one another. At least one of the parts includes a housing for glue. At least some of the parts are manufactured individually by additive manufacturing. A conductive metal jacket surrounds the core without separating the parts from one another.

Claims

1. A passive radiofrequency device comprising: a core formed by an assembly of a first part and a second part, each of the first and second parts having a respective mounting face configured to be in direct contact against one another in an assembled state, at least one of said mounting faces having a respective cavity for receiving glue therein, at least one of said mounting faces having a pin extending perpendicularly therefrom, and at least one of the first and second parts being manufactured individually by additive manufacturing; and a conductive metal jacket surrounding said core without separating said first and second parts from one another, wherein the first and second parts are aligned with one another via the pin.

2. The device according to claim 1, wherein said first and second parts being glued together by means of a glue filled with metal or ceramic particles to facilitate the assembly.

3. The device according to claim 1, said cavity not emerging on a surface of the core intended for the deposition of said metal jacket.

4. The device according to claim 1, wherein said first and second parts being glued together by means of the glue.

5. The device according to claim 1, wherein at least one of said mounting faces has an aperture configured to receive the pin therein in the assembled state.

6. The device according to claim 1, wherein said first and second parts being provided with screw holes for securing said first and second parts together at least during the gluing.

7. The device according to claim 1, wherein said conductive metal jacket covers surfaces of the core without a interruption and without joint between said first and second parts.

8. The device according to claim 1, wherein a thickness of said conductive metal jacket being at least equal to five time a skin depth , wherein the skin depth $=\sqrt{\frac{2}{2f}}$ wherein is a magnetic permeability of the conductive metal jacket, wherein f is a radiofrequency of a signal to be transmitted, and wherein a is an electrical conductivity of the conductive metal jacket.

9. The device according to claim 1, wherein said first and second parts being mirror image shapes of one another about an imaginary plane being perpendicular to a longitudinal axis of the core.

10. The device according to claim 1, further comprising a smoothing layer intended to at least partially smooth irregularities in a surface of the core, the conductive metal jacket being deposited on top of the smoothing layer.

11. The device according to claim 10, wherein said smoothing layer surrounding said core without separating said first and second parts from one another.

12. The device according to claim 1, further comprising an adhesion layer deposited after assembly of the core so as to cover the core without interruption, the conductive metal jacket being deposited on top of the adhesion layer.

13. A method for manufacturing a passive radiofrequency device, the method comprising: additive manufacturing of first and second parts, each of the first and second parts having a respective mounting face, at least one of said mounting faces having a respective cavity for receiving glue therein; insertion of the glue into said cavity; insertion of a pin into at least one of the mounting faces; assembly of the first and second parts together, so as to form a core of the device, the respective mounting faces of the first and second parts being in direct contact with one another, and the pin promoting correct alignment between the first and second parts; and deposition on the core of a conductive layer, without separating said first and second parts from one another.

14. The method according to claim 13, wherein the step of assembly of the first and second parts together further includes inserting the pin into an aperture formed in at least one of the mounting faces.

15. The method according to claim 13, wherein said glue being inserted only into said cavity, without emerging on a surface of the core intended for the deposition of said conductive layer.

16. The method according to claim 13, further comprising a step of deposition of an adhesion layer around said core.

17. The method according to claim 13, further comprising a step of deposition of a smoothing layer around said core.

18. The method according to claim 17, wherein said smoothing layer being deposited after assembly and thus not separating said first and second parts from one another.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Examples of implementation of the invention are indicated in the description illustrated by the attached figures, where like features are denoted by the same reference numerals throughout the drawings, and in which:

(2) FIG. 1A illustrates a perspective view of two parts intended to be assembled along a joining plane at right angles to the signal propagation direction in order to form a waveguide core.

(3) FIG. 1B illustrates a perspective view of the two parts of FIG. 1A after assembly in order to form a waveguide core.

(4) FIG. 1C illustrates a perspective view of a device comprising a core made of two parts assembled and covered by a conductive jacket on the inner and outer walls.

(5) FIG. 1D illustrates a longitudinal cross-sectional view of a device comprising a core in two parts assembled and covered with a conductive jacket on the inner and outer walls.

(6) FIG. 2A illustrates a perspective view of two parts intended to be assembled along a joining plane parallel to the signal propagation direction, in order to form a waveguide core.

(7) FIG. 2B illustrates a perspective view of the two parts of FIG. 2A after assembly in order to form a waveguide core.

(8) FIG. 2C illustrates a transverse cross-sectional view of a device comprising a core in two parts assembled and covered by a conductive jacket on the inner and outer walls.

(9) FIG. 3A illustrates a transverse cross-sectional view of a device according to the invention, comprising a core in two parts coated with a smoothing layer and a conductive jacket.

(10) FIG. 3B illustrates a longitudinal cross-sectional view of a device comprising a core in two parts assembled and covered with a smoothing layer and a conductive jacket on the inner and outer walls.

DETAILED DESCRIPTION OF THE INVENTION

(11) FIG. 1A illustrates two parts 1A and 1B intended to be assembled together to form the core 3 of a passive radiofrequency device, here a waveguide. The parts are provided with a longitudinal aperture 2 of rectangular section defining a channel for the transmission of the radiofrequency signal. The section of the aperture is determined according to the frequency of the electromagnetic signal to be transmitted. The dimensions of this inner channel and its form are determined as a function of the operational frequency of the device 1, that is to say the frequency of the electromagnetic signal for which the device is manufactured and for which a transmission mode that is stable and optionally with minimum attenuation is obtained.

(12) The two parts 1A and 1B are intended in this example to be juxtaposed one after the other in the direction of transmission of the signal, thus forming a continuous longitudinal channel. The surfaces 31 intended to be placed in contact are planar and at right angles to the direction of transmission of the radiofrequency signal. At least one of these surfaces comprises one or more housings 30 to house glue therein in order to secure the two parts 1A, 1B glued to one another. The housings 30 are provided on the surface 31 of a part (here the part 1B) intended to be placed in contact with another part (1A) during assembly. These housings do not preferably emerge on the outer faces or inner faces intended to be covered with a metal deposition. Thus, the metal layer is deposited only on the core, and not on the glue, which guarantees a regular deposition.

(13) This core 3 delimits an inner channel 2 intended for guiding waves.

(14) The parts 1A, 1B intended to form the core 3 can for example be made of polymer, of epoxy, of ceramic, of organic material or of metal (preferably aluminium, titanium, steel or Invar, i.e., a nickel-iron alloy).

(15) The parts 1A and 1B are manufactured by additive manufacturing, preferably by stereolithography or by selective laser melting in order to reduce the roughness of the surface. The material of the core can be non-conductive or conductive. The thickness of the walls is for example between 0.5 and 3 mm, preferably between 0.8 and 1.5 mm.

(16) The form of the parts 1A, 1B can be determined by a computer file stored in a computer data medium and making it possible to control an additive manufacturing device.

(17) After manufacture, and before assembly, each of the parts 1A, 1B can be dried, cleaned and/or polished to improve the surface condition. It is also hardened, at least partially. The drying, cleaning, polishing and/or hardening before assembly makes it possible to more easily access the portions of the device that are difficult to access after assembly, for example at the centre of the channel 2. As will be seen, it is also possible to deposit a smoothing layer before assembly.

(18) FIG. 1B illustrates the two parts 1A, 1B after assembly so as to form a core 3. The parts are secured by gluing by means of glue deposited in the glue housings 30. The presence of glue on the contact surfaces 31 (shown in FIG. 1A) is preferably avoided, which improves the accuracy of assembly. A glue will however preferably be chosen which allows the deposition of metal with the deposition methods to be retained; thus, the possible presence of traces of glue close to the joint will not cause irregularities in the deposition.

(19) In one embodiment, the different parts forming the core are pre-hardened, for example by heating and/or exposure to an ultraviolet radiation, before the assembly thereof. The different parts forming the core are then juxtaposed, then a final hardening step is performed by once again placing the parts under ultraviolet radiation or in an oven. This solution makes it possible to fuse the parts 1A, 1B together to facilitate the assembly thereof.

(20) At least one pin 34 (shown in FIG. 1A) is preferably inserted into a housing for a pin in one of the contact surfaces 31, so as to extend at right angles to this contact surface. This pin is preferably driven into the housing, and intended to be inserted into a housing provided in the contact face of the facing part 1A. This or these pins guarantee(s) an alignment of the parts 1A, 1B with one another.

(21) Screws (not illustrated) can also be provided to secure the two parts together, at least during the gluing.

(22) A mechanical assembly by fitting in a clip-fastened or tenon-mortise type assembly can also be employed to fix the parts 1A, 1B to one another.

(23) FIG. 1C illustrates the device formed by coating the core 3 by a metal deposition forming a conductive jacket 4, 5 on the inner and outer surfaces of the core 3. The figure illustrates the different layers on the transverse face 32 (shown in FIG. 1A) at the front of the device; in another embodiment, this front face is also metallized such that the inner layers 3, 4 are not visible.

(24) In this embodiment illustrated, the inner surface and the outer surface of the core 3 are covered with a conductive metal layer 4, for example copper, silver, gold, nickel, etc., plated by chemical deposition without electrical current. The thickness of this layer for example lies between 1 and 20 micrometres, for example between 4 and 10 micrometres.

(25) The thickness of this conductive coating 4 must be sufficient for the surface to be electrically conductive at the chosen radiofrequency. This is typically obtained using a conductive layer whose thickness is greater than the skin depth .

(26) This thickness is preferably substantially constant over all the inner surfaces in order to obtain a finished part with precise dimensional tolerances for the channel.

(27) The deposition of conductive metal 4, 5 on the inner and possibly outer faces is done by immersing the core 3 after assembly of the parts 1A, 1B in a successive series of baths, typically 1 to 15 baths. Each bath involves a fluid with one or more reagents. The deposition does not entail applying a current to the core to be covered. A stirring and a regular deposition are obtained by stirring the fluid, for example by pumping the fluid into the transmission channel and/or around the device or by vibrating the core 3 and/or the fluid tank, for example with an ultrasound-vibrating device to create ultrasonic waves.

(28) In one embodiment, the thickness of this layer 4 is at least twenty times greater than the skin depth in order to improve the structural, mechanical, thermal and chemical properties of the device. The surface currents are thus concentrated for the most part, even almost exclusively, in this layer.

(29) The application of a metal deposition on the outer surfaces does not contribute to the propagation of the radiofrequency signal in the channel 2, but does however have the advantage of protecting the device from thermal, mechanical or chemical abuses. In an embodiment that is not illustrated, only the inner surface of the core, around the channel 2, is covered with a metal jacket; the outer surfaces are bare, or covered with a different coating.

(30) FIG. 1D illustrates a longitudinal cross-sectional view of the metal device along the plane A-A of FIG. 1C. Particularly visible are the two parts 1A, 1B secured against one another by gluing in the glue housings 30 (FIG. 1C). The securing is also ensured by the continuous metal jacket 4 on the inner and outer surfaces of the core.

(31) FIGS. 2A to 2C illustrate a variant device; all the features and steps described above in relation to FIGS. 1A to 1D apply also this variant, except when indicated otherwise.

(32) FIG. 2A illustrates a variant device in which the core is formed by assembly of two parts 1A and 1B along a plane of separation which extends longitudinally in the direction of propagation of the signal through the channel 2. In this example, the part 1A has a U-shaped section and the part 1B has a rectangular section forming a cover on top of the part 1A. It is also possible to produce a waveguide with rectangular section with two U-shaped parts mounted head-to-tail one on top of the other.

(33) The contact surface 31 of one of the parts 1A comprises housings 30 to house glue therein intended to secure the parts together.

(34) The two parts 1A, 1B are aligned with one another by means of pins 34 extending from, in other words protruding from the surface of one of the parts 1A and penetrating into a blind hole in the other part 1B. The pins are thus hidden after assembly.

(35) FIG. 2B shows the core of the device after assembly and gluing of the two parts 1A and 1B.

(36) The two parts 1A, 1B are preferably secured clamped to one another by means of screws 35 passing through holes 36 through one of the parts 1A and engaged in tapped holes 37 (as shown in FIG. 2A) in the other part. These screws can be inserted before gluing, and removed after the hardening of the glue. In a variant, it is possible to retain screws which do not disrupt the deposition of the metal jacket.

(37) FIG. 2C shows a transverse cross-sectional view of the device after the coating of the inner and outer faces of the core 3 with a metal jacket.

(38) It is possible to produce a passive radiofrequency device core by assembling more than two parts. It is possible to assemble parts along planes which are neither longitudinal nor transversal, or along non-planar surfaces.

(39) FIGS. 3A and 3B illustrate a variant device; all the features and steps described above in relation to FIGS. 1A to 1D and 2A to 2C apply also to this variant, except when indicated otherwise.

(40) FIG. 3A shows a transverse cross-sectional view of another variant device in which the core 3 is coated by a first smoothing layer 9, 6 then by the conductive layer 4, 5. FIG. 3A shows a longitudinal cross-sectional view of this device.

(41) In the embodiment illustrated in FIG. 3A, the surfaces of the core 3 are covered after assembly with a smoothing layer 9, for example a layer of Ni. The thickness of the smoothing layer 9 is at least equal to the roughness Ra of the surface of the core, or at least equal to the resolution of the 3D printing method used to manufacture the core (the resolution of the 3D printing method determining the roughness Ra of the surface). In one embodiment, the thickness of this layer lies between 5 and 500 micrometres, preferably between 10 and 150 micrometres, preferably between 20 and 150 micrometres. This smoothing layer also determines the mechanical and thermal properties of the device 1. The layer of Ni is then covered with the conductive layer 4, for example of copper, silver, gold, etc.

(42) The smoothing layer makes it possible to smooth the surface of the core and therefore reduce the transmission losses due to the roughness of the inner surface.

(43) In this embodiment, the core 3 is therefore covered with a metal layer formed by a smoothing layer 9 and a conductive layer 4. The total thickness of this metal layer is preferably greater than or equal to five times, preferably twenty times the skin depth . The value of the Young's modulus of the device 1 is conferred by the most part by this metal layer. The thickness of the conductive layer 4 can also be on its own greater than or equal to twenty times the skin depth . The most conductive layer is preferably deposited last, at the periphery.

(44) The smoothing layer illustrated in this example is deposited after the assembly of the different parts 1A, 1B forming the core; it therefore does not separate the parts, and is not deposited on the joining surfaces 31 between parts.

(45) In an embodiment that is not illustrated, the smoothing layer is deposited before the assembly of the different parts 1A, 1B forming the core; it therefore separates the parts, by covering the joining surfaces 31 between parts. This embodiment makes it possible to obtain joining surfaces 31 between parts 1A, 1B of the core that are smoother, and therefore to improve the accuracy and the rigidity of the assembly.

(46) In an embodiment that is not illustrated, the device 1 comprises an adhesion layer, for example a coat made of Cu, on top of the inner surface and possibly the outer surface of the core 3; this adhesion layer facilitates the subsequent deposition of the smoothing layer 9 if such a layer is provided, or of the conductive layer 4. The thickness of this coat is advantageously less than 30 micrometres. This adhesion layer is preferably deposited after assembly, and does not therefore cover the joining surfaces 31 between parts.

(47) It is also possible to produce passive radiofrequency devices comprising a core formed by the assembly of multiple parts without gluing, at least some of said parts being manufactured individually by additive manufacturing and aligned using pins, a conductive metal jacket being deposited on said core without separating said parts from one another. The other features of the invention described above, apart from the gluing, can also be applied to these devices.

(48) It is also possible to produce passive radiofrequency devices comprising a core formed by the assembly of multiple parts, at least some of said parts being manufactured individually by additive manufacturing and aligned using pins, a conductive metal jacket being deposited on said core without separating said parts from one another, a smoothing layer being deposited on said parts before the assembly thereof. The other features of the invention described above, with or without gluing, can also be applied to these devices.

REFERENCE NUMBERS USED IN THE FIGURES

(49) TABLE-US-00001 1 Passive radiofrequency device 2 Waveguide channel 3 Core 30 Housing for glue 31 Contact surface 32 Outer face 34 Pin 35 Screw 36 Through-hole 37 Blind hole, for example tapped hole 4 Inner conductive coating 5 Outer conductive coating 6 Smoothing or structural layer 9 Smoothing layer