A multi-layer waveguide assembly, and a method for manufacturing said multi-layer waveguide assembly

Abstract

The present disclosure relates to a multi-layer waveguide arrangement and a method for manufacturing a waveguide arrangement. The waveguide arrangement comprises a first layer (1) and a second layer (1), wherein the first and second layer (1, 2) comprises at least one throughgoing opening (11a, 11b, 21a, 21b) and wherein the at least two layers (1, 2) are arranged together such that the throughgoing openings (11a, 21a) form a respective channel (9a) that extends from an exterior surface (1a) of the first layer (1) to a an exterior surface (2a) of the second layer (2). The at least two layers (1, 2), when arranged together, form a waveguide for an operational wavelength λ, and the arrangement further comprises a monolithic holding element (8') extending through the at least one channel (9a).

Description

[0001] A MULTI-LAYER WAVEGUIDE ASSEMBLY, AND A METHOD FOR MANUFACTURING SAID MULTI-LAYER WAVEGUIDE ASSEMBLY

[0002] TECHNICAL FIELD OF THE INVENTION

[0003]

[0001] The present invention relates to a method for manufacturing a multi-layer waveguide and a multi-layer waveguide formed by said method.

[0004] BACKGROUND OF THE INVENTION

[0005]

[0002] Waveguiding arrangements, such as antenna arrangements for transmitting and receiving electromagnetic radiation or filters for filtering of electromagnetic signals are of great importance in modern society. For example, antennas are essential for wireless communication and are also used in RADAR applications for transmitting and detecting RADAR signals. To this end, multiple antennas are integrated into most modern automobiles (as well as other vehicles) for both wireless communication purposes and RADAR detection of the surroundings.

[0006]

[0003] In many applications, and especially for automotive, it is important that the antennas are cost efficient to manufacture, made small and thin to enable simple integration and offer excellent radiation performance at high frequencies. These requirements have made waveguide structures utilizing multiple layers forming gap waveguides popular.

[0007]

[0004] However, a problem with multi-layer waveguide structures is that the manufacturing process can be costly and time consuming since the multiple layers must be riveted or glued together at a large number or locations.

[0008]

[0005] When using rivets, multiple through-holes must be formed through the layers and the rivets are installed one-by-one. In some cases riveting risks damaging the delicate layers when the tail is deformed. In international application WO21151538 by the same applicant a multi-layer waveguide arrangement with rivets integrated into one layer is proposed. According to this implementation, the rivets can be integrated with one of the layers whereby they are deformed or melted to hold all layers together. A drawback however is that the integrated rivets are fragile and must be formed by the same material as that of the layer with which they are integrated whereas it may be desirable to use a different material. Additionally, the rivets and necessary surrounding geometry is space consuming and cannot be placed at all wanted locations.

[0006] A drawback with using an adhesive is that it generally does not provide an as secure mounting as rivets. Additionally, providing an adhesive between the layers will increase the spacing between the layers which may be detrimental for waveguiding performance in some implementations.

[0009] GENERAL DISCLOSURE OF THE INVENTION

[0010]

[0007] It is a purpose of the present invention to overcome at least some of the shortcomings of the prior solutions and provide a method for manufacturing a multi-layer waveguide arrangement that is accurate and reliable whereby the resulting multi-layer waveguide arrangement is securely assembled.

[0011]

[0008] According to a first aspect of the invention there is provided a multi-layer waveguide assembly comprising at least two layers, a first layer and a second layer. The first and second layer each comprises at least one throughgoing opening, respectively, wherein the at least two layers are arranged together such that the throughgoing openings of each layer form a respective channel that extends from an exterior surface of the first layer to an exterior surface of the second layer. The at least two layers, when arranged together, form a waveguide for an operational wavelength and the arrangement further comprises a monolithic holding element extending through the at least one channel, wherein the monolithic holding element has been formed directly in the channel by a moulding process with the at least one channel acting as a part of the mould.

[0012]

[0009] A monolithic holding element formed by a moulding process using the channel as a part of the mould is a completely new type of holding element for holding the delicate layers of a multi-layer waveguide together. The monolithic holding element is integrally formed (i.e. formed as a single piece) which enhances the strength of the monolithic holding element. Additionally, since the monolithic holding element has been formed by e.g. injection moulding directly inside the channel, the monolithic holding element will in general fill the entire channel to enable more reliable holding of the layers. At the same time, this enables the channels themselves to be designed with curves or bends that would not be possible for other types of fastening means.

[0013]

[0010] In some implementations, each opening that together form a channel when the layers are held together will act as a mould for the monolithically formed holding element.

[0014] [OH] In some embodiments, at least one channel is curved or bent, and the monolithic holding element provided in the channel is also curved or bent. Accordingly, the channels may be formed in shapes which would not allow a rigid and straight rivet to pass through the channels.

[0015]

[0012] In some implementations, the monolithic holding element completely fills the inside of at least one channel.

[0016]

[0013] Comparison can e.g. be made to conventional meltable rivets which can be used to hold the layers of a multi-layer waveguide together. Meltable rivets may as such be monolithic and manufactured in an injection moulding process using an external mould. However, the meltable rivets necessarily comprise a tail which has a diameter that is smaller than the diameter of the channel. When in use, the meltable rivets are introduced into the channel formed by the layers such that the tail protrudes out of the channel, whereby the tail can be melted to form a head for holding the layers together. However, with traditional meltable rivets the pressure is mainly exerted by the rivet heads which exerts a clamping force on the layers which risks damaging or deforming the layers. Additionally, even after formation of the head by melting an end portion of the tail, the tail will still be smaller than the channel which introduces a risk that the layers slide relative to each other.

[0017]

[0014] With the monolithic holding elements according to present disclosure, which have been formed with the channel forming a part of the mould, the pressure on the layers will be more evenly distributed coming from both the heads as well as from the inside of the channel which enables a more reliable fastening with lower risk for damaging the layers or the layers sliding relative to each other.

[0018]

[0015] While injection moulding of a mouldable material into the channel is one example of how the monolithic holding element can be formed other moulding techniques such as compression moulding or resin (e.g. epoxy) transfer moulding can also be used to form the monolithic holding element. For example, in compression moulding a (e.g. solid) moulding material is placed in the channel wherein pressure (and optionally heat) is applied to form a monolithic holding element which fills the channel.

[0019]

[0016] In some implementations each throughgoing opening comprises a respective throat section with a minimum opening dimension, and wherein the monolithic holding element comprises a first head portion at the first layer and second head portion at the second layer whereby the first and second head portion are connected via a neck portion. The neck portion extending through the throat sections and wherein a dimension the first and second head portion is greater than the minimum opening dimension in the respective throat section.

[0020]

[0017] That is, by forming monolithically formed holding elements having comparatively wide head portions and a comparatively narrow neck portion the layers will be held together in a highly reliable manner with a very low risk of the layers coming loose. Since the monolithic holding elements may be formed by injection directly into the channel or by compression moulding the throat sections and general profile of the throughgoing openings can be realized with arbitrary shapes. Especially when injection moulding is used the liquid mouldable material can creep around corners and fill even the most complex geometries (which is different from fastening with rivets, screws or the like).

[0021]

[0018] In some implementations, the first and second layer each comprises at least two throughgoing openings, respectively, forming at least two channels when the layers are arranged together, and the monolithic holding element comprises a first structure extending between at least two channels on the exterior surface of the first layer and wherein the monolithic holding element extends through the at least two channels.

[0022]

[0019] With multiple thoroughgoing openings in each layer multiple channels are formed when the layers are arranged together and the monolithic holding element can hold the layers together at multiple locations which enables the clamping pressure on the layers to be distributed more evenly across the layers. This ensures e.g. contact between the layers at more locations and reduces the risk of the layers deforming due to unevenly distributed clamping pressure. The first structure of the monolithic holding element connects the parts of the monolithic holding element that goes through the channels whereby the first structure further enhances the structural stability of the multi-layer waveguide arrangement.

[0023]

[0020] The thoroughgoing openings of the first layer are arranged so as to match, i.e. communicate, with the throughgoing openings of the second layer when the layers are arranged together. Similarly, if more than two layers are provided, the throughgoing openings of each layer matches the throughgoing openings of the other layers when the layers are arranged together so as to form, optionally curved or bent, channels.

[0024]

[0021] In some implementations, the first and second layer each comprises at least two throughgoing openings, forming at least two channels when the layers are arranged together. Wherein the monolithic holding element comprises a second structure extending between at least two channels on the exterior surface of the second layer.

[0025]

[0022] Similar to the first structure extending over the first exterior surface the second structure extends over the second exterior surface to connect the parts of the monolithic holding element that extends through the at least two channels. The first and second structure are both optional, and embodiments with only the first structure, only the second structure or both are envisaged. The first and / or second structure is formed with a part of the exterior surface of the first and / or second layer acting as a part of the mould.

[0023] When both the first and second structure are provided, the first and second structure may be monolithically attached through the at least two channels. That is, the monolithic holding element may be formed as a single piece covering a portion of the first exterior surface, covering a portion of the second exterior surface and extending through at least two channels.

[0026]

[0024] In some implementations, the second structure forms a stand-off configured to be mounted against a PCB so as to hold the second layer of the multi-layer waveguide assembly at some distance from the PCB.

[0027]

[0025] The second structure may therefore double as a mounting arrangement for mounting towards a PCB. Accordingly, the same monolithically formed holding element may also comprise features for facilitating mounting against a PCB. For example, the stand-offs may be pins or protruding sections that can be mounted against a PCB while allowing sufficient space for the electronic components of the PCB to be placed between the PCB and the second structure.

[0028]

[0026] According to a second aspect of the invention there is provided a multi-layer waveguide system, comprising a PCB and the multi-layer waveguide assembly according to the first aspect, wherein the multi-layer waveguide assembly is mounted onto a PCB with the standoff contacting the PCB.

[0029]

[0027] Optionally, the second structure may comprise at least one opening that exposes the exterior surface of the second layer whereby electronic components of the PCB can be in direct thermal contact with the second layer. Since the layers may be made of metal (or at least coated with a metal) they may serve as a heatsink for components on the PCB.

[0030]

[0028] In some implementations, at least one structure forms a substantially flat layer. Depending on the material used for the monolithic holding element the substantially flat layer may e.g. act as an absorber layer that absorbs electromagnetic radiation when the multi-layer waveguide is used as an antenna. As a further example, the substantially flat layer may be made of an electrically conductive material (such as a conductive plastic material) wherein the substantially flat layer may be provided with corrugations and act a corrugation layer that enhances radiation performance when the multi-layer waveguide is used as an antenna.

[0031]

[0029] In some implementations, the substantially flat layer covers at least 50%, and preferably at least 70%, of the exterior surface of the first or second layer.

[0032]

[0030] Put differently, the substantially flat layer may cover a majority of the exterior surface of at least one of the first and second layer.

[0031] In some implementations, the first layer comprises one or more antenna apertures, wherein the first structure forms a substantially flat layer and wherein the substantially flat layer comprises at least one opening, surrounding the one or more antenna apertures.

[0033]

[0032] To allow the one or more antennas to communicate with the environment, the substantially flat layer may comprise one or more openings around the one or more antennas. The opening may be formed at the same time as the monolithically formed holding element. Alternatively, the one or more openings are formed in the substantially flat layer after it has been formed.

[0034]

[0033] In some implementations, the substantially flat layer, or at least a portion thereof overlapping with the one or more antenna openings, is made of a radiation transparent material which allows electromagnetic radiation at the operating frequency to pass through.

[0035]

[0034] In some implementations, the first and second layer each comprises at least three throughgoing openings, forming at least three channels when the layers are arranged together, wherein at least one structure is a shaped like a web extending between at least three channels.

[0035] When three or more channels is provided the first structure may form a web, which may also be referred to as a net or mesh, that extends over the exterior surface of the first layer to connect the parts of the monolithic holding element that goes through the at least three channels. Compared to a substantially flat, solid, layer covering a majority of the exterior surface a net may still connect the parts of the parts of the monolithic holding element extending through the channels while still leaving a large portion (e.g. a majority) of the first exterior surface exposed which decreases the material needed to form the monolithic holding element and / or enhances heat dissipation from the layers if the monolithic holding element is formed of a thermally insulating material.

[0036]

[0036] In some implementations, the multi-layer waveguide further comprises a third layer, wherein the third layer comprises at least one throughgoing opening and wherein the first layer further comprises an additional throughgoing opening. The third layer is arranged on the exterior side of the first layer, opposite the second layer, such that the throughgoing opening of the third layer forms an additional channel that extends from an exterior surface of the third layer to an interior surface of the first layer. Wherein the multi-layer waveguide further comprises an additional monolithic holding element extending through the additional channel, wherein the additional monolithic holding element has been formed directly in the second channel by injection moulding or compression moulding with the additional channel and the second layer acting as a part of the mould.

[0037] That is, when three or more layers are used it is not necessary for each monolithic holding element to pass through all layers. By using an additional monolithic holding element that extends through (and fastens) the third layer to the first layer in addition to the monolithic holding element that fastens the first layer to the second layer, a multi-layer waveguide assembly with all layers directly of indirectly attached to each other may still be realized. A benefit with this arrangement is that more space is provided for routing between the layers, when many layers are used, since the same channel does not need to through all, at least three, layers.

[0037]

[0038] In some implementations, at least one intermediate layer is arranged between the first and second layer, wherein the at least one intermediate layer comprises a throughgoing opening that forms the channel together with throughgoing openings of the first and second layer.

[0038]

[0039] In general, any number of layers may be used, and it is envisaged that one or more, two or more, three or more or even four or more intermediate layers may be added between the first and second layer to form a multi-layer waveguide with at least three, at least four, at least five, or even at least six layers in total.

[0039]

[0040] In some implementations, the first and second layer each comprises at least two throughgoing openings, forming at least two channels when the layers are arranged together, and wherein the multi-layer waveguide assembly comprises at least two separate monolithic holding elements, each monolithic holding element extending through a respective channel.

[0040]

[0041] Accordingly, multiple individual monolithic holding elements may be provided instead of or in addition to one or more monolithic holding element that extends through multiple channels. That is, it is envisaged that a monolithic holding element may be a single-channel monolithic holding element (that only extends through one channel) or a multiple-channel monolithic holding element (that extends through at least two channels and comprises a structure on the first or second exterior surface that runs between the at least two channels). A benefit with multiple single-channel monolithic holding elements is that the amount of material used is very small and / or that very little of the exterior surface will be covered by the monolithic holding element.

[0041]

[0042] In some implementations, the spatial density of channels populated by a same monolithic holding element or different monolithic holding elements is less than 6 channels per X2, preferably less than 3 channels per X2, more preferably less than 2 channels per X2, and most preferably less than 1 channel per X2.

[0042]

[0043] The monolithically formed holding element(s) are efficient at reliantly holding layers together whereby the channels may be arranged with comparatively low density relative to the wavelength. This ensures that much space is left between the layers for routing without being obstructed by the channels.

[0043]

[0044] In some implementations, at least one throughgoing opening has an opening dimension which increases in a direction towards the respective exterior surface.

[0044]

[0045] Preferably, this applies to at least one throughgoing opening in the outermost layers (i.e. at least the first and second layer if one or more intermediate layers is arranged therebetween and / or at least the first and third layer, if the third layer is present and adjacent to the second layer opposite the first layer). With this type of throughgoing opening the monolithic holding element does not need to protrude out beyond the exterior surface to fixate the layers. In fact, the monolithic holding element may end flush with exterior surface or even end at some distance inside the throughgoing opening. Accordingly, it is envisaged that the fixating elements do not add to the total thickness of the stack of layers forming the multi-layer waveguide.

[0045]

[0046] In some implementations, at least one of the layers comprises a metasurface (4) arranged on a surface facing another layer, wherein the metasurface delimits a waveguide and prohibits electromagnetic radiation with the operational wavelength to propagate between the layers in directions other than along the waveguide.

[0046]

[0047] The metasurface is configured to contain the electromagnetic signals so as to confine them between the layers and along the waveguide. In some implementations, the metasurface is a textured surface comprising a plurality of thick sections and thin sections. Specifically, the height difference between the thick and thin sections can be made very small, such as less than divided by five, or less than divided by six, or less than divided by eight, or even less than divided by ten.

[0047]

[0048] In some implementations, the monolithic holding element is made of a plastic material, such as polypropylene, polybutylentereftalat, a polycarbonate, an electrically conductive plastic material, mixtures thereof, or blends thereof.

[0048]

[0049] Other suitable materials can also be used. The monolithic holding element may be realized with an electrically and / or thermally conductive or insulating material. For example, the monolithic holding element may be made by a plastic material with metal additives that makes it electrically and / or thermally conductive.

[0049]

[0050] According to a third aspect of the invention there is provided a method for manufacturing a multi-layer waveguide assembly. The method comprises providing at least two layers, including a first layer and a second layer, wherein each of the first and second layer comprises at least one throughgoing opening. The method further comprises holding the at least two layers together such that the throughgoing openings form a respective channel that extends from a first aperture in an exterior surface of the first layer to a second aperture in an exterior surface of the second layer wherein the at least two layers, when arranged together, form a waveguide for an operational wavelength X. The method further comprises forming a monolithic holding element extending through the at least one channel, wherein the monolithic holding element has been formed directly in the channel by a moulding process with the at least one channel acting as a part of the mould.

[0050]

[0051] For an injection moulding process, forming a monolithic holding element may comprise placing a first nozzle in communication with the first aperture of at least one channel. The method further comprises injecting, via the first nozzle, a fluid mouldable material such that the fluid mouldable material fills the channel and curing or solidifying the mouldable material such that it solidifies. For example, the mouldable material may be solidified by cooling such that it transitions from a liquid phase to a solid phase, or the mouldable material may be cured by heat or light (e.g. UV light).

[0051]

[0052] That is, the layers of the multi-layer waveguide arrangement can be fixated together by injecting the liquid mouldable material directly into the channel. The step of curing and solidifying the mouldable material may involve actively or passively cooling the layers such that the mouldable material solidifies.

[0052]

[0053] The invention according to the third aspect features the same or equivalent benefits as the invention according to the first or second aspect. Any functions described in relation to the method may have corresponding features in a multi-layer waveguide, and vice versa.

[0053] BRIEF DESCRIPTION OF THE DRAWINGS

[0054]

[0054] Aspects of the present invention will be described in more detail with reference to the appended drawings, showing currently preferred embodiments.

[0055]

[0055] Figures la-d show cross-sections of a multi-layer waveguide arrangement with two layers according to some implementations.

[0056]

[0056] Figure 2 is a flowchart illustrating a method for manufacturing a multi-layer waveguide according to some implementations.

[0057]

[0057] Figures 3a-d show cross-sectional views of multi-layer waveguide arrangements with different types of monolithically formed holding elements according to some implementations.

[0058]

[0058] Figures 4a-b show different views of an assembled multi-layer waveguide assembly with a monolithically formed holding element having a first structure that covers a majority of the first layer, according to some implementations.

[0059] Figure 5 illustrates an example of a net shaped structure of the monolithically formed holding element according to some implementations.

[0059]

[0060] Figures 6a and 6b show close-up cross-sectional views of monolithically formed holding elements according to some implementations.

[0060]

[0061] Figures 7a-c show cross-sectional views of a three layer multi-layer waveguide arrangement according to some implementations.

[0061]

[0062] Figures 8a-b show cross-sectional views of a three layer multi-layer waveguide arrangement held together by different types of monolithically formed holding elements that do not extend fully through more than two layers, according to some implementations.

[0062]

[0063] Figure 9 is a cross-sectional view of a multi-layer arrangement with five layers, according to some implementations.

[0063] DETAILED DESCRIPTION OF CURRENTLY PREFERRED EMBODIMENTS

[0064]

[0064] Fig. la depicts a cross-sectional and side view of two layers 1, 2 that may be held together to form a multi-layer waveguide 10 for guiding electromagnetic signals. The multi-layer waveguide 10 is configured for an operational frequency associated with an operational wavelength X. The multi-layer waveguides presented herein are especially suitable for high frequencies above 10 GHz, above 50 GHz or even above 60 GHz. However, the same general structure of the multi-layer waveguide 10 may also be used for lower frequencies.

[0065]

[0065] The multi-layer waveguide 10 shown in fig. la comprises two layers 1, 2, however, as will be described below, this is merely an exemplary embodiment and the present disclosure generally covers many types of multi-layer waveguides 10 with two, three, four or more layers 1, 2.

[0066]

[0066] Each layer 1, 2 may be made of a metal, such as copper, aluminum, brass or alloys thereof. Alternatively, one or more layers 1, 2 may be made of a non-metal material, such as a plastic material, and coated with a metal on at least one side or completely covered with a metal. It is envisaged that different types of layers 1, 2 can be combined, for example at least one layer 1 made of metal is combined with at least one layer 2 made of a non-metal material coated with a metal.

[0067]

[0067] The second layer 2 in fig. la comprises two main surfaces 2a, 2b that are opposite to each other. The second layer 2 also comprises a minor edge surface that defines the thickness of the second layer 2. Similarly, the first layer 1 also comprises two opposite main surfaces la, lb and a minor edge surface. In general, in each layer 1, 2 used in the multi-layer waveguides 10 described herein will feature two respective main surfaces la, lb, 2a, 2b and a minor edge surface wherein waveguiding structures or openings (to e.g. form an antenna) are arranged on one or more of the main surfaces la, lb, 2a, 2b or, in the case of an opening being provided, extending between the two main surfaces la, lb, 2a, 2b.

[0068]

[0068] When the two layers 1, 2 of fig. la are held together as shown in fig. lb, each layer 1, 2 will exhibit a respective internal main surface lb, 2b (facing another layer) and each layer will exhibit a respective exterior main surface la, lb (facing away from another layer).

[0069] Generally, the exterior main surfaces la, lb are said to face outwards since they face away from the internal structures of the multi-layer waveguide 10. If more than two layers are used to form the stack of layers that constitutes the multi-layer waveguide 10, there will in general still be two exterior surfaces la, 2a with at least one layer (arranged between two other layers) featuring only internal surfaces.

[0070]

[0069] At least one of the layers 1, 2, comprises structures facing another layer 1, 2 that, when the layers 1, 2 are held together, forms a waveguide for guiding electromagnetic radiation. In the embodiment shown in fig. la, the second layer 2 comprises a recess provided with a metasurface 4 comprising thick and thin sections 41, 42. The thick and thin sections 41, 42 of the metasurface 4 are configured to stop electromagnetic signals from propagating between the layers in directions other than along a path formed in the metasurface 4. The path is defined by a region devoid of metasurface 4 that defines the waveguide 33. When electromagnetic signals are guided by the waveguide 33 they will travel between the metasurface 4, in the region devoid of metasurface, and between the first and second layer 1, 2. Optionally, a ridge 5 may be arranged in the region devoid of metasurface wherein the ridge 5 may facilitate waveguiding properties.

[0070] The thick sections 41 and thin 42 sections of the metasurface 4 may be arranged in a regular pattern, e.g. a matrix pattern with multiple rows of thick and thin sections 41, 42 on either side of the waveguide, or in a random pattern. Preferably, the height difference between the thick and thin sections 41, 42 is less than divided by five, or less than divided by six.

[0071] Even more preferably, the height difference between the thick and thin sections 41, 42 is less than divided by eight or divided by ten. Accordingly, since the minimum depth of the recess comprising the metasurface 4 is equal to the height difference between the thick and thin sections 41, 42 the recess can be made very shallow. In turn, this enables the entire second layer 2 to be made very thin, having a maximum thickness of less than divided by four, or even smaller, such as less than divided by five or less than I divided by six.

[0072]

[0071] For example, at least one or all layers 1, 2 forming the multi-layer waveguide may have a thickness which is less than divided by four, or less than divided by five. It is also envisaged that all layers 1, 2 may have the same thickness, or that the layers 1, 2 have different thicknesses.

[0073]

[0072] Each layer 1, 2 further comprises at least one throughgoing opening I la, 1 lb, 21a, 21b, that extends through the layer 1, 2 to form a channel 9a, 9b between the two major (exterior) surfaces of each layer 1, 2. The throughgoing openings I la, 1 lb, 21a, 21b of the layers 1, 2 are arranged to align when the layers 1, 2 are held together to form the waveguide. That is, each layer 1, 2 comprises at least one throughgoing opening I la, 1 lb, 21a, 21b that corresponds to, or is associated with, a throughgoing opening I la, 1 lb, 21a, 21b of an adjacent layer such that, when the layers 1, 2 are arranged together, the corresponding throughgoing openings form a channel 9a, 9b that extends through all layers 1, 2 of the stack.

[0074]

[0073] As seen in fig. lb the throughgoing openings 21a, I la form a channel 9a and throughgoing openings 21b, 1 lb form a channel 9b wherein each channel extends between the two exterior surfaces of the stack of layers 1, 2.

[0075]

[0074] It is also understood that even if the stack of layers 1, 2 comprises three or more layers 1, 2, throughgoing openings I la, 1 lb, 21a, 21b may be arranged in each layer to form channels 9a, 9b extending through all layers 1, 2 in the stack of layers.

[0076]

[0075] The channels 9a, 9b depicted in fig. lb are straight and extend perpendicular to the plane in which the layers 1, 2 extend. For example, this means that when the layers 1, 2 are held together it is possible to see through the channel 9a, 9b. This is however merely exemplary, and the channels 9a, 9b may be arranged at a non-perpendicular angle through the layers 1, 2 and / or the channels 9a, 9b may comprise at least one curve or bend such that the channels 9a, 9b cannot be seen through.

[0077]

[0076] Straight channels 9a, 9b provided in the layers are as such known for multi-layer waveguide arrangements since they are used for the insertion of screws or rivets to hold the layers 1, 2 together. However, according to implementations of the present invention, the layers are held together by one or more monolithically formed holding element(s) that has been formed directly in the channel 9a, 9b by an injection moulding or compression moulding process with the channel 9a, 9b acting as a part of the mould.

[0078]

[0077] The process for forming a multi-layer waveguide with this type of monolithically formed holding element(s) holding the layers 1, 2 together will now be described with reference to figs, la-d and the flowchart in fig. 2.

[0079]

[0078] At step SI at least two layers 1, 2 are provided. As mentioned above, the layers 1, 2 feature structures that, when the layers 1, 2 are held together, form a waveguide for electromagnetic signals at an operational frequency X. Each layer 1, 2 comprises at least one throughgoing opening I la, 1 lb, 21a, 21b. At step S2 the at least two layers 1, 2 are held together such that the multi-layer waveguide is formed and throughgoing openings I la, 1 lb, 21a, 21b comes into communication with each other, to form one or more channels 9a, 9b extending through the stack of layers 1, 2.

[0080]

[0079] At step S3 a nozzle 6 is placed in communication with one channel 9a as seen in fig. lb. Optionally, a stopper 7 or second nozzle (not shown) is placed to cover the other opening of the channel 9a. A mouldable material 8 (e.g. in a liquid phase) is then ejected from the nozzle 6 at step S4 as seen in fig. 1c. The mouldable material 8 enters into the channel 9a and fills at least a portion the channel 9a. The nozzle 6 may comprise a nozzle skirt 61 that allows the mouldable material 8 to also fill an area outside of the channel 9a, between the skirt 61 and the exterior surface la of the first layer 1. Similarly, the stopper 7 may define a closed space between the stopper allowing the mouldable material 8 to also fill an area outside the channel 9a between the exterior surface 2a of the second layer 2.

[0081]

[0080] The mouldable material 8 may be any suitable type of material which melts at elevated temperatures, typically in excess of 100 degrees Celsius, but is a solid at lower temperatures, typically at temperatures below 80 degrees Celsius. For example, the mouldable material is a plastic material such as polypropylene, polybutylentereftalat, a polycarbonate, an electrically conductive plastic material, mixtures thereof, or blends thereof.

[0082]

[0081] When the mouldable material 8 is injected, it may be heated and may exhibit a lower viscosity compared to when it is cured or solidified. For example, the mouldable material 8 is heated such that it is melted when it is injected and the allowed to cool such that it solidifies inside the channel 9a. This allows the mouldable material 8 to fill out the channel 9a as well as any space that is in fluid communication with the channel 9a during mouldable material injection, such as a space between the first layer exterior surface la and the nozzle skirt 61 or between the second layer exterior surface 2a and the stopper 7.

[0083]

[0082] If compression moulding is used the mouldable material (e.g. slab thereof) is placed inside the channel 9a and two (optionally heated) stoppers 7 are brought down from either side to put pressure on the mouldable material in such a way that it deforms to fill the channel 9a and form a monolithically formed holding element. Accordingly, when using compression moulding a nozzle 6 is not strictly necessary. For example, steps S3 and S4 can be replaced with a step of introducing a mouldable material into the channel and compressing (and optionally heating) the mouldable material to form the monolithic holding element.

[0084]

[0083] At step S5 the mouldable material 8 is allowed to cure or solidify. The curing or solidifying may be passive or expedited using active cooling of the layers 1, 2, the nozzle 6 and / or the stopper. The solidified or cured mouldable material forms a monolithically formed holding element 8’ that has been formed directly in the channel 9a by injection moulding with at least one channel 9a acting as a part of the mould, as seen in fig. Id.

[0085]

[0084] When the monolithically formed holding element 8’ has been formed, the nozzle 6 and the optional stopper 7 can be removed leaving a multi-layer waveguide held together with a monolithically formed holding element 8’.

[0086]

[0085] The process can be repeated for each channel 9a, 9b in through the stack of layers 1, 2 wherein a single-channel monolithic holding element 8’ is formed in each channel 9a, 9b. A benefit with multiple single-channel monolithic holding elements 8’ is that the clamping force pressing the layers together becomes more evenly distributed across the layers, which decreases the tendency for the sometimes delicate layers to deform or crack.

[0087]

[0086] In some implementations, to achieve a proper fixation of the layers 1, 2, the channels 9a, 9b are provided with a comparatively low spatial density.

[0088]

[0087] Preferably, the spatial density of channels 9a, 9b in which monolithically formed holding elements 8’ are provided is kept small since too densely packed channels 9a, 9b generally makes it more difficult to design waveguides around the channels and may introduce excessive strain on the layers 1, 2. The spatial density of channels 9a, 9b populated by one or more monolithically formed holding elements 8’ is determined as the number channels 9a, 9b divided by the surface area of the exterior surface la, 2a (wherein the surface optionally is expressed in the operational wavelength squared). The spatial density may be below 6 channels 9a, 9b per2, preferably below 4 channels 9a, 9b per2, more preferably below 2 channels 9a, 9b per2and most preferably below 1 channel 9a, 9b per2. Even lower spatial densities may be used and, in some implementations, the spatial density is below 0.5 or 0.25 channels 9a, 9b per .

[0089]

[0088] The smallest spacing between two neighboring channels 9a, 9b could vary. In some implementations, the center-to-center distance between each pair of channels 9a, 9b is at least X divided by six, preferably at least X divided by four and most preferably at least X divided by two.

[0090]

[0089] By altering the design of the nozzle skirt 61 and / or the stopper 7 different types of monolithically formed holding elements 8’ may be formed with the same general process. Fig. Id shows a single-channel monolithically formed holding element 8’ that extends through one channel, however other types of monolithically formed holding elements 8’ are also envisaged.

[0090] Turning to figs. 3a and 3b an implementation is shown wherein two layers 1, 2 are held together by a single multi-channel monolithically formed holding element 8’ that extends through two channels 9a, 9b between the channels 9a, 9b along the exterior surface la of the first layer 1. The portion of the monolithically formed holding element 8’ that extends over the first exterior surface la is referred to as a first structure and it is understood that while different “parts” of a single monolithically formed holding element 8’ may be discussed the monolithically formed holding element 8’ is still a single piece formed in a single moulding process.

[0091]

[0091] The first structure is in this embodiment shaped like a substantially flat layer covering, at least partially, the first layer exterior surface la. Optionally, the substantially flat layer has a substantially constant thickness tcwhich may be below 10 mm or below 5 mm. For example the substantially flat layer has a thickness between 0.5 mm and 3 mm, such as a thickness between 1 mm and 2.5 mm.

[0092]

[0092] To create a monolithically formed holding element 8’ with this type of first structure a nozzle skirt 61 that extends so as to cover the inlets of two channels 9a, 9b may be used in combination with two stoppers 7a, 7b that stops the mouldable material form the exterior surface 2a of the second layer 2.

[0093]

[0093] Using such a nozzle skirt 61 a multi-channel monolithically formed holding element 8’ with a large first structure overlaying a portion of the first exterior surface la may therefore be formed. For example, the first structure covers the majority of the exterior surface la of the first layer 1, such as at least 50% of the surface or at least 70% of the surface.

[0094]

[0094] Fig. 4a shows one example of a multi-channel monolithically formed holding element 8’ with a first structure that covers a large portion of the first layer exterior surface la. Although not seen in fig. 4a, the monolithically formed holding element 8’ extends through one or more (typically two or more, such as ten or more) channels to hold the layers 1, 2 together. With a monolithically formed holding element 8’ that covers a large portion of the first exterior surface it is envisaged that the monolithically formed holding element 8’ may serve to protect the layers from the environment such as protecting the layers from weather or impact with other objects.

[0095]

[0095] In some implementations, one or more antenna slots 13 communicating with the waveguiding structures inside the multi-layer waveguide arrangement are arranged in one of the first and second layer 1, 2. Without loss of generality, it is assumed that the antenna slots 13 are arranged in the first layer 1, as seen in fig. 4a. The first structure of the monolithically formed holding element 8’ may therefore serve as an attenuation layer and / or antenna-pattern shaping layer that improves antenna performance. For example, the monolithically formed holding element 8’ may be of an electromagnetically absorbing material which reduces surface currents and reflections caused by signals being emitted by the antenna slots 13. As another example, the monolithically formed holding element 8’ is made of an electrically conductive material (e.g. a plastic material with conductive material additives) wherein the first structure of the monolithically formed holding element 8’ may be shaped to enhance the antenna pattern. For example, the electrically conductive material is provided with one or more corrugations that ma reduce surface currents.

[0096]

[0096] As also seen in fig. 4a, the first structure of the monolithically formed holding element 8’ may be formed with one or more openings 85 exposing parts of exterior surface la of the first layer 1. For example, these openings 85 may be arranged to expose the one or more antenna slots 13 and / or at other locations.

[0097]

[0097] In some implementations, an electromagnetic band gap (EBG) structure is formed by the first structure of the monolithically formed holding element 8’ which improves the antenna pattern. Accordingly, an EBG layer for antenna pattern is formed by the same monolithic structure that holds the layers together.

[0098]

[0098] When multiple stoppers 7a, 7b are used for each channel the pattern formed by the monolithically formed holding element 8’ on the exterior surface 2a of the second layer 2 may be a distribution of small heads or beads of cured or solidified mouldable material as seen in fig. 4b showing the second layer exterior surface 2a of the second layer 2. Depending on the shape of the stoppers 71a, 71b the shape of each head or bead can be adjusted. For example, each head may be substantially dome shaped, substantially polygonal or any other shape.

[0099]

[0099] Additionally or alternatively to using many discrete heads or beads a large substantially flat layer may be formed by the monolithically formed holding element 8’ also on the second layer exterior surface 2a. Accordingly, a second structure may be arranged to cover the second layer exterior surface 2a. Figs. 3c and 3d illustrate this schematically wherein a large stopper 71 covering at least two channels 9a, 9b is placed over the second layer exterior surface 2a to allow formation of a monolithically formed holding element 8’ with a second structure that covers a large portion of the exterior surface 2a of the second layer 2a in addition to a first structure covering a large portion of the exterior surface la of the first layer 1.

[0100]

[0100] In some implementations, as mentioned above, at least one of the layers comprises an antenna aperture. In the exemplary implementation shown in figs. 4a and 4b the first layer acts as a radiating layer with antenna apertures 13 wherein the exterior surface of the second layer 2 faces rearwardly. The multi-channel monolithically formed holding element 8’ extending to cover a portion of the second exterior surface 2a may therefore be used to aid thermal dissipation, electrical insulation and / or provide structures for housing electrical components of a PCB that is mounted towards the stack of layers. Typically, to lead electromagnetic signals into / out of the multi-layer waveguide arrangement one or more feeding ports (not shown) for communication with a PCB may be arranged in the second layer.

[0101]

[0101] As a first example, the monolithically formed holding element 8’ is made of an electrically insulating material, wherein the stack of layers can be mounted against e.g. a PCB with the second structure facing the PCB and still be electrically insulated. The second structure may e.g. form standoffs that aid mounting the PCB against the stack of layers.

[0102]

[0102] As a second example, the monolithically formed holding element 8’ is made of thermally conductive material wherein the second structure of the monolithically formed holding element 8’ may aid in dissipating heat from the stack of layers to a structure behind the stack and / or in dissipating heat from an object behind the stack (e.g. an electrical component on a PCB) to the stack itself.

[0103]

[0103] As a third example, the second structure of the monolithically formed holding element 8’ comprises at least one of a stand-off for holding a PCB and an indentation or opening configured to receive an electrical component extending from the substrate of the PCB. This may allow a PCB to be arranged close to the stack of layers. For instance, since the layers are made of metal or at least coated with a metal they are thermally conducive. By providing an opening in the monolithically formed holding element 8’ exposing a part of the second layer 2 an active component of a PCB may be arranged in thermal contact with the second layer 2 whereby the second layer, and also other layers thermally linked to the second layer, may act as a heat dissipator for the active component.

[0104]

[0104] As a fourth example, the second structure is made of a conductive material and shaped to prohibit resonance between the PCB and the second layer. For example, the second structure is provided with an electromagnetic band gap (EBG) structure that supresses the resonance. A thermally and / or electrically conductive material may also result in the second structure serving as electromagnetic interference (EMI) shielding. Additionally, an electrically conductive material may form a channel for guiding electromagnetic signals to / from the PCB into the multi-layer waveguide via a port provided in the second layer.

[0105]

[0105] The alternatives shown in fig. 3a-3d and figs. 4a and 4b are merely exemplary and may be combined in any way. For example, the monolithically formed holding element 8’ of fig. 3b may be reversed, having the isolated heads of the monolithically formed holding element 8’ visible on the exterior surface la on the first layer 1 and a large substantially flat layer structure on the exterior surface of the second layer 2. Additionally, it is not necessary that only one multichannel holding element is used and it is envisaged that the single-channel monolithically formed holding element 8’ shown in fig. Id may be formed in one or more (or all) channels 9a, 9b in addition to, or as an alternative to, one or more multi-channel monolithically formed holding element 8’ extending through one or more (or all) channels 9a, 9b.

[0106]

[0106] Turning to fig. 5 another configuration of a multi-channel monolithically formed holding element 8’ is shown. Here, a net structure of the multi-channel monolithically formed holding element 8’ is arranged on the exterior surface 2a of the second layer but it is understood that the same net structure may be used on the exterior surface la of the first layer 1 as well. The structure is shaped like a web, net or mesh due to the different channels being connected via elongated pathways 84b’ of the monolithically formed holding element 8’. Optionally, heads 84a’ of the monolithically formed holding element 8’ may be arranged at the opening of each channel wherein the heads 84a’ are connected via one or more elongated pathways 84b’. To form the desired net structure shape of the nozzle skirt or stopper is adjusted accordingly. Compared to a substantially flat layer structure a net structure can be realized with much less material and it is envisaged that the net structure convers less than 50%, or less than 30%, of the exterior surface of the layer on which it is provided.

[0107]

[0107] Figs. 6a and 6b show close up cross-sectional views of monolithically formed holding element 8’ according to some implementations.

[0108]

[0108] Fig. 6a shows a single channel monolithically formed holding element 8’ that comprises two head portions 81’, 82’, a first head portion 81’ and a second head portion 82’. Each channel (formed by communicating throughgoing openings) goes through at least two layers 1, 2 and it is envisaged that an opening dimension (e.g. an opening diameter) Di, D2 of each throughgoing opening may be constant or vary as it extends through its respective layer 1, 2. In the embodiment of fig. 6a, the dimension of thoroughgoing opening in the first layer 1 has an approximately constant dimension Di. To enable reliable retention of the layers 1, 2 with the monolithically formed holding element 8’ the monolithically formed holding element 8’ may therefore comprise a first head portion 81’ that protrudes beyond the first layer exterior surface la and has a dimension which is larger than Di. The first head portion 81’ therefore extends beyond the exterior surface la of the first layer so as to partially overlay the exterior surface la in a vicinity of the channel.

[0109]

[0109] On the other hand, the dimension D2 of the throughgoing opening in the second layer 2 varies so as to feature a larger dimension D2 closer to the second layer exterior surface 2a and a smaller dimension further from the second exterior surface 2a. In this way, the second head portion 82’ of the monolithically formed holding element 8’ can be fully integrated into the second layer 2 such that it does not protrude out beyond the exterior plane of the second layer exterior surface 2a.

[0110] [HO] In other words, the monolithically formed holding element 8’ here comprises two head portions 81’, 82’ that are connected via a neck portion 83’ wherein the neck portion 83’ has a dimension in plane parallel to the layers that is smaller than a dimension of the first and second head portion 82’, 83’. The neck portion 83’ also extends through the minimal opening dimension of each throughgoing opening while the dimension of the first head portion 81’ is larger than the minimum dimension Di of the throughgoing opening in the first layer 1 and the dimension of the second head portion 82’ is larger than the minimum dimension D2 of the throughgoing opening in the second layer.

[0111] [Hl] In some implementations, the dimension of each Di, D2 of the throughgoing opening is at least 1 mm or at least 1.5 mm.

[0112]

[0112] This configuration of the monolithically formed holding element 8’ will reliantly hold the layers 1, 2 together, such that the layers do not accidentally become disconnected. Generally, constant dimension throughgoing openings, such as the one in the first layer 1 in fig. 6a, are preferred for thinner layers 1, 2 whereas varying dimension throughgoing openings, such as the one in the second layer in fig. 6a, are preferred for thicker layers. This is because throughgoing openings with varying opening dimensions may be challenging to realize in thin layers.

[0113]

[0113] Turning to fig. 6b a cross-sectional close-up view of a multi-channel monolithically formed holding element 8’ according to some implementations is shown. The multi-channel monolithically formed holding element 8’ has a first structure extending between to two or more channels (and e.g. forms a substantially flat surface on the exterior surface of the first layer 1). As seen, the head portion 81’ of monolithically formed holding element 8’ is constituted by the first structure of the multi-channel monolithically formed holding element 8’ that extends between different channels. To prohibit the second layer 2 from coming loose from the first layer 1 and the monolithically formed holding element 8’ a second head portion 82’ is formed so as to overhang the second exterior surface 2a.

[0114]

[0114] Accordingly, when a multi-channel monolithically formed holding element 8’ enters into two or more channels the same head portion 81’ is shared among multiple channels while there may be an individual second head portion 82’ for each channel.

[0115]

[0115] In figs. 7a-c a cross-sectional view of a three layer multi-layer waveguide arrangement is shown. As indicated above, the multi-layer waveguide may comprise more than two layers 1, 2, 3 and in the embodiment shown in fig. 7a the multi-layer waveguide comprises three layers 1, 2, 3 the first layer 1, the second layer 2, and a third layer 3 arranged adjacent to the first layer 1 and opposite the second layer 2. Each layer has a throughgoing opening 21a, 3 la that, when the layers 1, 2, 3 are held together, form a channel 9a, 9b that extend to the exterior surface of the outermost layers (here the second and third layer 1, 3).

[0116]

[0116] In the same way as when only two layers 1, 2 are used, one or more nozzles 6a, 6b, optionally with respective skirts 61a, 61b, are brought into communication with each channel 9a, 9b whereby the monolithically formed holding element 8’a, 8’b is formed by injecting a mouldable material fluid 8 and allowing it to cure or solidify, as shown in fig. 7b and 7c. In this example, two separate single-channel monolithically formed holding elements 8’a, 8’b are formed but it is envisaged that multiple-channel monolithically formed holding element 8’ may be formed in the analogous manner.

[0117]

[0117] The layers depicted in fig. 7a-7c comprises structures that form a waveguide when the layers are held together. In this example, a waveguide 33 is formed by providing an elongated aperture that forms a channel in the first layer 1 that is intermediate of the second and third layer 2, 3. A metasurface 4 is arranged on the interior surfaces of the of the second and third metal layers 2, 3 to surround the channel in the first layer 1. Additionally, in a region overlapping with the channel of the first layer 1, the second and third layer 2, 3 is devoid of any metasurface 4 whereby a waveguide 33 extending parallel to the layers 1, 2, 3 is formed by the channel in the first layer, the second and third layer 2, 3 and the metasurface 4 arranged on each of the second and third layers 2, 3. Optionally, a central conductor 34 is arranged inside the channel of the first layer 1 whereby a coaxial waveguide channel is realized. The central conductor may be suspended by support stubs extending from the periphery of the channel.

[0118]

[0118] This type of three-layer waveguide arrangement may be realized with very thin layers. For example, at least one of the layers 1, 2, 3 has a total thickness below X divided by four, below X divided by five or below X divided by six. Preferably, each layer 1, 2, 3 has a total thickness below X divided by four, below X divided by five or below X divided by six.

[0119]

[0119] The thickness of each individual layer is preferably less than 1 mm, although larger thicknesses are possible. In some implementations, the thickness of each layer is between 500 pm and 300 pm. All layers could have the same thickness, but it is also envisaged that the metal layers 1, 2, 3 may have different thicknesses. For example, the second layer 2 and third layer 3 may have a same thickness between 500 pm and 300 pm and the first layer 1 is thinner, having a thickness between 50 pm and 200 pm, e.g. about 100 pm. The above exemplary thicknesses are suitable for simple and cost effective manufacturing but are merely exemplary and can vary outside of these ranges, e.g. depending on the operational frequency. The above exemplary thicknesses are suitable for an operational frequency around 77 GHz. These exemplary thicknesses are also applicable to the two layer waveguide shown in figs, la.d and may also be used for multi-layer waveguide arrangements with more than three layers.

[0120]

[0120] When at least three layers 1, 2, 3 are used in the stack of layers to form a multilayer waveguide it is no longer necessary that each monolithically formed holding element 8’ holds together all layers. For example, as will be described with reference to fig. 8a and 8b, for a three layer arrangement it is envisaged that at least two monolithically formed holding elements 8”a, 8”b are used wherein one of the monolithically formed holding elements 8”a fixates the first layer 1 and the second layer 2 and the other one of the monolithically formed holding elements 8”b fixates the third layer 3 and the first layer 1.

[0121]

[0121] In fig. 8a the third layer 3 has been provided with a recess 32 that is in communication with the channel 9a formed by throughgoing openings I la and 21a in the first and second layers 1, 2. The recess 32 is optional and may be omitted if the outgoing opening in the first layer 1 has a varying opening dimension that allows the monolithically formed holding element 8”a to hold the first and second layer 1, 2 together without going beyond the extent of the first layer 1 (see throughgoing opening of the second layer in fig. 6a which allows retention with a monolithically formed holding element that ends flush with the layer). The monolithically formed holding element 8”a is then formed through the channel 9a as seen in fig. 8b to hold the first and second layer 1, 2 together.

[0122]

[0122] The third layer 3 can now be fixated to the first and second layer 1, 2 by a second monolithically formed holding element 8”b is arranged to hold the third layer 3 to the first layer 2 as seen in fig. 8b.

[0123]

[0123] In fig. 8b two monolithically formed holding elements 8” a, 8”b has been formed. Each monolithically formed holding element 8”a, 8”b holds at least two layers together and for at least one of the monolithically formed holding element 8”a, 8”b the channel formed by the two layers it holds together has acted as a mould for the monolithically formed holding element 8”a, 8”b and, additionally, one other layer has acted as a stopper. For example, when monolithically formed holding element 8”b in fig. 8b is formed with injection moulding the nozzle injects a fluid (e.g. molten or light / heat curable) mouldable material into a mould formed by the throughgoing opening 31 of the third layer 3, the throughgoing opening 11 of the first layer 1 and the second layer 2, and optionally a recess 22 of the second layer.

[0124]

[0124] Turning to fig. 9 an exemplary multi-layer waveguide with five layers 1, 2, 3’, 3”, 3”’ according to some implementations is shown. The multi-layer waveguide arrangement comprises the first layer 1 and the second layer 2 acting as the outermost layers, wherein three intermediate layers 3’, 3”, 3”’ are arranged between the first and second layer 1, 2. For example, by providing matching channels through all intermediate layers 3’, 3”, 3”’ a comparatively larger waveguide 33 (compare to fig. 8b) can be realized. Optionally, a central conductor 34 is also introduced to make it a coaxial waveguide.

[0125]

[0125] Regardless of the number of layers 1, 2, 3’, 3”, 3”’, one or more channels extending through two or more layers 1, 2, 3’, 3”, 3”’ may be formed by throughgoing channels in the layers 1, 2, 3’, 3”, 3”’ wherein the layers in turn are held together by one or more monolithically formed holding elements 8’ formed in each channel, wherein each channel has formed a part of the mould for forming the monolithically formed holding element 8’. Various waveguiding structures can therefore be realized with the layers 1, 2, 3’, 3”, 3”’. For example, multiple three-layer stacks as shown in fig. 7a-7c can be stacked on top of each other which allows sophisticated waveguide routing along the plane of the layers as well as transversely to the plane of the layers by leading the electromagnetic radiation up / down between the three-layer stacks.

[0126]

[0126] The person skilled in the art realizes that the present invention by no means is limited to the preferred embodiments described above. On the contrary, many modifications and variations are possible within the scope of the appended claims. For example, various number of layers may be used and the layers may be held together with a single multi-channel monolithically formed holding element or multiple, single-channel or multi-channel monolithically formed holding elements. Additionally, when more than two layers are used, it is envisaged that it is not necessary that each monolithic holding element extends through all layers. Instead at least two monolithic holding elements may be used, each extending through a an individual subset of the layers. Wherein the individual subsets comprise at least one common layer.

[0127]

[0127] Such and other obvious modifications must be considered to be within the scope of the present invention, as it is defined by the appended claims. It should be noted that the above- mentioned embodiments illustrate rather than limit the invention, and that those skilled in the art will be able to design many alternative embodiments without departing from the scope of the appended claims. In the claims, any reference signs placed between parentheses shall not be construed as limiting to the claim. The word "comprising" does not exclude the presence of other elements or steps than those listed in the claim. The word "a" or "an" preceding an element does not exclude the presence of a plurality of such elements.

Claims

CLAIMS1. A multi-layer waveguide assembly comprising: at least two layers (1, 2), including a first layer (1) and a second layer (1), wherein the first and second layer (1, 2) each comprises at least one throughgoing opening (I la, 1 lb, 21a, 21b), respectively, wherein the at least two layers (1, 2) are arranged together such that the throughgoing openings (1 la, 21a) form a respective channel (9a) that extends from an exterior surface (la) of the first layer (1) to a an exterior surface (2a) of the second layer (2), wherein the at least two layers (1, 2), when arranged together, form a waveguide for an operational wavelength; and a monolithic holding element (8’) extending through the at least one channel (9a), wherein the monolithic holding element (8’) has been formed directly in the channel (9a) by a moulding process with the at least one channel (9a) acting as a part of the mould.

2. The multi-layer waveguide assembly according to claim 1, wherein each throughgoing opening comprises a respective throat section with a minimum opening dimension (Di, D2), and wherein the monolithic holding element (8’) comprises a first head portion (8L) at the first layer (1) and second head portion (82’) at the second layer (2) whereby the first and second head portion (8L, 82’) are connected via a neck portion (83’), wherein the neck portion (83’) extends through the throat sections and wherein a dimension the first and second head portion (81’, 82’) is greater than the minimum opening dimension (Di, D2) in the respective throat section.

3. The multi-layer waveguide assembly according to claim 1 or claim 2, wherein the first and second layer (1, 2) comprise at least two throughgoing openings (I la, 1 lb, 21a, 21b), respectively, forming at least two channels (9a, 9b), and wherein the monolithic holding element (8’) comprises a first structure extending between at least two channels (9a, 9b) on the exterior surface (la) of the first layer (1) and wherein the monolithic holding element (8’) extends through the at least two channels (9a, 9b).

4. The multi-layer waveguide assembly according to any of the preceding claims, wherein the first and second layer (1, 2) each comprises at least two throughgoing openings (I la, 1 lb, 21a, 21b), forming at least two channels (9a, 9b), andwherein the monolithic holding element (8’) comprises a second structure extending between at least two channels (9a, 9b) on the exterior surface (2a) of the second layer (2).

5. The multi-layer waveguide assembly according to claim 4 when depending on claim 3, wherein the first and second structure are attached through the at least two channels (9a, 9b).

6. The multi-layer waveguide assembly according to claim 4 or claim 5, wherein the second structure forms a stand-off configured to be mounted against a PCB so as to hold the second layer (2) of the multi-layer waveguide assembly at some distance from the PCB.

7. A multi-layer waveguide system, comprising a PCB and the multi-layer waveguide assembly according to any of claims claim 4 - 6, wherein the multi-layer waveguide assembly is mounted onto the PCB with the stand-off contacting the PCB.

8. The multi-layer waveguide assembly according to any of claims 3-7, wherein at least one structure forms a substantially flat layer.

9. The multi-layer waveguide assembly according to claim 8, wherein the substantially flat layer covers at least 50%, and preferably at least 70%, of the exterior surface (la, lb) of the first or second layer (1, 2).

10. The multi-layer waveguide assembly according to claim 8 or claim 9, wherein the first layer comprises one or more antenna apertures, wherein the first structure forms a substantially flat layer and wherein the substantially flat layer comprises at least one opening (85), surrounding the one or more antenna apertures (13).

11. The multi-layer waveguide assembly according to any of claims 3-10, wherein the first and second layer, each comprises at least three throughgoing openings (I la, 1 lb, 21a, 21b), forming at least three channels (9a, 9b), and wherein at least one structure is a web extending between said at least three channels (9a, 9b).

12. The multi-layer waveguide assembly according to according to claim 1 or claim 2, further comprising: a third layer (3), wherein the third layer (3) comprises at least one though-going opening (31c), wherein the first layer (1) further comprises an additional throughgoing opening (11c), and wherein the third layer is arranged on the exterior side (la) of the first layer (1), opposite the second layer (2), such that the throughgoing opening of the third layer (3) forms an additional channel that extends from an exterior surface (3 a) of the third layer (3) to an interior surface (lb) of the first layer (1), the multi-layer waveguide further comprising: an additional monolithic holding element (8”b) extending through the additional channel, wherein the additional monolithic holding element (8”b) has been formed directly in the second channel by a moulding process with the additional channel (9) and the second layer (2) acting as a part of the mould.

13. The multi-layer waveguide assembly according to any of the preceding claims, further comprising: at least one intermediate layer (3 la, 3 lb, 31c) arranged between the first and second layer (1, 2), wherein the at least one intermediate layer comprises a throughgoing opening that forms the channel (9a) together with throughgoing openings (I la, 1 lb) of the first and second layer (1, 2).

14. The multi-layer waveguide assembly according to any of the preceding claims, wherein the first and second layer each comprises at least two throughgoing openings (I la, 1 lb, 21a, 21b), forming at least two channels, and wherein the multi-layer waveguide assembly comprises: at least two separate monolithic holding elements (8’a, 8’b), each monolithic holding element extending through a respective channel (9).

15. The multi-layer waveguide assembly according to any of the preceding claims, wherein the spatial density of channels populated by a same monolithic holding element (8’) or different monolithic holding elements (8’a, 8’b) is less than 4 channels per X2, preferablyless than 3 channels per X2, more preferably less than 2 channels per X2, and most preferably less than 1 channel per X2.

16. The multi-layer waveguide assembly according to any of the preceding claims, wherein at least one throughgoing opening (1 la, 21a) has an opening dimension which increases in direction towards the respective exterior surface (la, 2a).

17. The multi-layer waveguide assembly according to according to any of the preceding claims wherein at least one of the layers (1, 2, 3) comprises a metasurface (4) arranged on a surface facing another layer, wherein the metasurface (4) delimits a waveguide and prohibits electromagnetic radiation with the operational wavelength X to propagate between the layers in directions other than along the waveguide.

18. The multi-layer waveguide assembly according to claim 17, wherein the metasurface (4) is a textured surface comprising a plurality of thick sections (41) and thin sections (42).

19. The multi-layer waveguide assembly according to any of the preceding claims, wherein the monolithic holding element (8’) is made of a plastic material, such as polypropylene, polybutylentereftalat, a polycarbonate, an electrically conductive plastic material, mixtures thereof, or blends thereof.

20. A method for manufacturing a multi-layer waveguide assembly comprising: providing (SI) at least two layers (1, 2), a first layer (1) and a second layer (1), wherein the first and second layer (1, 2) each comprises at least one throughgoing opening (I la, 1 lb, 21a, 21b); holding (S2) the at least two layers (1, 2) together such that the throughgoing openings (I la, 1 lb, 21a, 21b) form at least one channel that extends from a first aperture in an exterior surface (la) of the first layer (1) to a second aperture in an exterior surface (2a) of the second layer (2), wherein the at least two layers (1, 2), when arranged together, form a waveguide for an operational wavelength , and ; forming a monolithic holding element (8’) extending through the at least one channel (9a), wherein the monolithic holding element (8’) is formed directly in the channel (9a) by a moulding process with the at least one channel (9a) acting as a part of the mould.

Images