Multilayer waveguide having a metasurface, arrangement, and method for manufacturing the same

Abstract

A multilayer waveguide (1) comprising at least three physical layers (21, 2a, 2b, 2c, ... 2n, 22) assembled as a multilayer waveguide (1), the layers being a top layer (21), one or more intermediate layers (2a, 2b, ... 2n), and a bottom layer (22). The multilayer waveguide (1) comprises a waveguide channel (77) which is an elongated aperture (7) in at least one intermediate layer (2a, 2b, ... 2n). At least one layer (21, 2a, 2b, ... 2n, 22) has a metasurface (3) on a first surface (5a) facing a first adjacent layer, the metasurface (3) surrounding the elongated aperture (7) and comprising a thick section (3a) and a thin section (3b).

Description

Technical Field

[0001] The present invention generally relates to a multi-layer waveguide transmission line having a layer with an electromagnetic metasurface.

Background Art

[0002] Waveguides are well known in the art and are common components used to transmit electromagnetic waves from a starting point to an ending point. A waveguide can be, in its most common designation, a hollow metal pipe.

[0003] For waves propagating in free space, power is lost with distance, reducing both the transmission distance and the wave quality. For this reason, a waveguide is a structure adapted to guide waves by restricting the spreading direction of the waves at least in one dimension. This concept is to reduce losses by forcing the waves to propagate in a specific direction. Ideally, this would result in the waves losing no power at all, but this rarely, if ever, happens. There are losses and leakage in waveguide transmission lines, and energy loss occurs when the waves connect to the edges of the waveguide. The concept of waveguides has been known for a long time and is used for the transmission of signals, sounds, light, etc.

[0004] At the same time, the use of wireless communication has increased, and waveguides and antenna arrays based on such technologies are in demand in the market. The market demand further requires compact and inexpensive waveguides.

[0005] One available solution is the substrate integrated waveguide (SIW). This is a compact waveguide that uses via holes to connect the top layer and the bottom layer based on printed circuit board (PCB) technology. A via hole is a hole that extends between the layers of the waveguide and connects at least the top layer and the bottom layer. There are cost-effective manufacturing methods for substrate integrated waveguides, but because a high-frequency dielectric is required, the cost increases as the frequency increases.

[0006] Another available solution is the so-called gap waveguide technology. A gap waveguide generally consists of two components. One component has pins that form a barrier to prevent electromagnetic waves from propagating in directions other than the intended waveguide direction. This reduces leakage in such a structure. Gap waveguides are suitable for some applications but are limited in terms of size. The typical height of the pins is a value obtained by dividing the wavelength by 2 to 6, i.e., λ / 2 to λ / 6. Summary of the Invention

[0007] Technologies for compact waveguides can be utilized, but there is a need for compact components with good reduction of losses and leakage and low losses. As an example, SIW has inherent losses, which are higher than the corresponding losses of, for example, a hollow waveguide filled with air. Therefore, although SIW provides a cost-effective alternative, other solutions are needed. Hollow waveguides generally have other drawbacks. For example, leakage occurs because the magnetic field penetrates the metal over a short distance. This leakage can be significant when fabricating a hollow waveguide structure with split blocks, especially when the gap is in the horizontal direction. This is because the electromagnetic waves are well-confined and are made to penetrate the metal only over a very short distance.

[0008] Dielectric waveguides are another option for reducing leakage, but the nature of the problems for such waveguides is different, for example, due to non-propagating evanescent waves. This is also the reason why such waveguides require a high level of conductivity between layers to reduce leakage. Due to the high level of conductivity, the production cost increases significantly and a very high accuracy during manufacturing is required. In addition, the losses are generally still higher than those of air-filled waveguides.

[0009] Gap waveguides have limitations in both design and the size of the pin irregularities, so although they are a useful solution, they are not applicable to some applications.

[0010] There are further problems with the manufacture of waveguides. This is that, at the current levels of CNC milling and forming, the manufacturing methods often have poor tolerances compared to other methods such as laser cutting, etching, or chemical etching. This makes the manufacture of waveguide structures difficult and / or expensive. This problem becomes more prominent for certain frequency ranges. For example, CNC milling and forming are both common manufacturing methods for waveguides adapted to frequencies below 60 GHz. In the higher E-band and D-band frequency ranges, i.e., 71 GHz to 86 GHz and 110 GHz to 170 GHz, CNC milling and forming are very expensive because all aspects of how the production technology works are very small. Therefore, it may not be suitable in some cases and may not be able to obtain the desired results in some cases.

[0011] One objective is to provide a new realization regarding air-filled waveguide transmission lines that are easy to produce.

[0012] Another objective is to provide a waveguide with high manufacturing cost-effectiveness.

[0013] Another objective is to provide a waveguide and design that can be conveniently used in an antenna array.

[0014] Another objective is to provide a waveguide that can be conveniently used in the design of waveguide filters and diplexers.

[0015] Another objective is to provide a waveguide that can be conveniently used in the packaging and integration of active electronic circuits, i.e., passive components such as power amplifiers (PAs) and array antennas.

[0016] Another objective is to provide a leaky small multilayer waveguide having layers that are laminated while not connected.

[0017] Another object is to provide a multilayer waveguide that reduces leakage without requiring galvanic contact between layers.

[0018] Another object of the present invention is to provide a multilayer waveguide that reduces leakage without requiring an interlayer connection.

[0019] Yet another object of the present invention is to provide a multilayer waveguide that is more compact compared to prior art solutions.

[0020] Therefore, a waveguide that is compact and overcomes at least some of the drawbacks of the prior art would be beneficial.

[0021] Therefore, the present solution relates to a cost - effective and easily manufacturable multilayer waveguide transmission line having an electromagnetic metasurface arranged in a specific configuration. This solution is a compact air - filled waveguide having thin layers that are laminated together but not connected, overcoming many of the drawbacks of prior art solutions. This solution can advantageously be used with a metal layer having a typical thickness of λ / 10 or λ / 15 and a depth of the leakage suppression structure of λ / 20 or less than λ / 30. The multilayer waveguide comprises at least three physical layers assembled as a multilayer waveguide. The layers are at least one top layer, one or more intermediate layers, and one bottom layer. The multilayer waveguide comprises a waveguide channel that is an elongated aperture in at least one intermediate layer. At least one layer has a metasurface on a first face facing a first adjacent layer, and the metasurface surrounds the elongated aperture. The metasurface comprises a thick section and a thin section.

[0022] In various embodiments, the waveguide channels are arranged in the layers as elongated apertures of different sizes. In one embodiment, all layers have elongated apertures of different sizes. In other embodiments, some of the layers have corresponding apertures.

[0023] The metasurface is an uneven surface having a sub-wavelength thickness usually less than λ / 10 in this specific example. The uneven surface includes a thick section and a thin section that form the unevenness.

[0024] One advantage is that the meta-structure in the multilayer arrangement produces a leakage reduction effect due to a small gap between the layer and the metasurface. This effect is derived from the electromagnetic bandgap. Compared with conventional multilayer waveguides, the metasurface structure has the advantages of small size and low-cost manufacturing.

[0025] According to one embodiment, the first surface has a flat portion surrounding the metasurface. The thick section has a thickness corresponding to the thickness of the layer in the flat portion, and the thin section has a thickness smaller than the thickness in the flat portion.

[0026] According to one embodiment, the second surface of the intermediate layer faces a second adjacent layer that is a flat surface except for the elongated aperture.

[0027] The metasurface faces the flat surface to form a small air-filled space between the surfaces of the layers, and an electromagnetic bandgap structure is formed.

[0028] According to one embodiment, the layer is a separate layer laminated without elements extending between the layers.

[0029] One advantage of this solution is that a small gap can be received between all or some of the layers without increasing leakage.

[0030] According to one embodiment, each thick section has a shape of any one of a circle, an ellipse, a triangle, a square, a pentagon, a rectangle, a quadrilateral, a square, a hexagon, or a rectangle.

[0031] One advantage is that the shape of the thick section can be changed between different layers or different waveguides.

[0032] According to one embodiment, the thick sections are arranged in a row parallel to the elongated aperture.

[0033] According to one embodiment, the thick sections are arranged at irregular distances from the elongated aperture.

[0034] According to one embodiment, the thick sections are arranged in a random pattern surrounding the elongated aperture.

[0035] According to one embodiment, the metasurface surrounds the elongated aperture.

[0036] According to one embodiment, the multi-layer waveguide includes a first intermediate layer, a second intermediate layer, and a third intermediate layer, each including an elongated aperture, and the second intermediate layer further includes a central member disposed within the elongated aperture.

[0037] In various embodiments, all or some of the layers have a metasurface. In one embodiment, only the intermediate layer has a metasurface. In another embodiment, at least one of the top layer and the bottom layer has a metasurface. In one embodiment, the metasurfaces are arranged to face the flat surfaces of adjacent layers. That is, in such an embodiment, the two metasurfaces do not face each other.

[0038] According to one embodiment, the multi-layer waveguide includes a first intermediate layer, a second intermediate layer, and a third intermediate layer, and the second intermediate layer is a non-convex and non-concave layer for an integrated electronic chipset.

[0039] One advantage is that a non-convex and non-concave layer, that is, a layer without a metasurface, can be used for the integration of an electronic chipset.

[0040] According to one embodiment, the thickness difference between the thick section and the thin section of the metasurface is smaller than a value obtained by dividing the wavelength by 10.

[0041] According to one embodiment, the thickness difference between the thick section and the thin section of the metasurface is smaller than the value obtained by dividing the wavelength by 20.

[0042] According to one embodiment, the thickness difference between the thick section and the thin section of the metasurface is smaller than the value obtained by dividing the wavelength by 30.

[0043] One advantage of this solution is that the metasurface enables a waveguide of a smaller size compared to other available alternatives without increasing leakage. Another advantage is that in a multilayer structure combined with the metasurface, leakage between layers is significantly reduced. Large metasurfaces are also possible, but one clear advantage is that small metasurfaces are easier to manufacture than alternatives for the corresponding frequencies.

[0044] According to one aspect, a method of manufacturing a multilayer waveguide described herein is disclosed.

[0045] According to an embodiment, the metasurfaces of different layers in the multilayer waveguide have an asymmetric configuration.

[0046] One advantage of this solution is that the metasurfaces of each layer in a multilayer waveguide having a metasurface do not have to be the same. For example, the metasurfaces can be arranged such that the thick sections and the thin sections are aligned with each other between the layers, or can be arranged in an asymmetric configuration where the thick sections and the thin sections are not aligned.

[0047] According to an embodiment, the thick sections and the thin sections are periodically arranged along the periphery outside the elongated aperture of each layer.

[0048] According to one embodiment, the metasurface is not the same in each layer.

[0049] According to one embodiment, the central member of the elongated aperture is connected to the rest of the layer using one connection tab that spans the aperture. The connection tab is part of what is incorporated into the layer.

[0050] According to one embodiment, the distance between layers of the multilayer waveguide is from 0 to 20 μm.

[0051] According to one embodiment, the distance between layers of the multilayer waveguide is from 0 to 50 μm.

[0052] According to one embodiment, the multilayer waveguide is a transmission line realized as any one of an antenna, an antenna array, and a filter.

[0053] One advantage of this solution is that the multilayer waveguide can be realized, for example Waveguide slot antenna in such a way.

[0054] Another advantage of this solution is that the multilayer waveguide can be realized for packages of chip sets such as packages of MMIC (Monolithic Microwave Integrated Circuit).

[0055] According to one embodiment, the waveguide is made of a single material.

[0056] According to one embodiment, the waveguide is made of a layer of a single material coated with metal.

[0057] According to one embodiment, the multilayer waveguide is assembled using a non-conductive adhesive.

[0058] According to one embodiment, the layers are directly laminated.

[0059] According to one embodiment, the layers are thin films laminated without being connected.

[0060] One advantage is that the multi-layer waveguide does not require any galvanic, electrical, or physical connections between the layers. That is, there may be a small gap between the layers. This gap can be, for example, an air gap that is not controlled from the manufacturing of the layers. Also, the gap can be, for example, at the micron (μm) level or even at the atomic level.

[0061] According to an embodiment, the layers are thin metal layers laminated without connection.

[0062] According to an embodiment, the layers of the multi-layer waveguide are held together by either a conductive glue, an insulating glue, or one of two screws.

[0063] One advantage of this solution is that any form of bonding or adhesive means can be used to hold the layers together. This is because electrical conductivity is not required between the layers to suppress leakage. However, it should be noted that conductivity does not have an adverse effect on performance. That is, the multi-layer waveguide according to the solution described herein functions well regardless of the conductive characteristics between the layers.

[0064] Next, the present invention will be exemplarily described with reference to the accompanying drawings.

Brief Description of the Drawings

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DETAILED DESCRIPTION OF THE INVENTION

[0066] In the following, with reference to the accompanying drawings, a detailed description of various embodiments of the present invention will be disclosed. All examples in this specification should be regarded as part of a general description and can thus be combined in any way from a general perspective. The individual features of the various embodiments and aspects can be combined or exchanged as long as such combinations or exchanges do not clearly conflict with the overall function of the multi-layer waveguide, arrangement, or its manufacturing method.

[0067] Briefly stated, the present solution relates to a compact multi-layer waveguide that does not require electrical and galvanic contact between layers. The multi-layer waveguide has a metasurface in the layers as a leakage suppression structure for reducing energy leakage between the layers of the waveguide. The metasurface comprises a plurality of thick sections and thin sections surrounding the waveguide channel.

[0068] FIG. 1 shows an embodiment of a multi-layer waveguide 1 having a plurality of layers 21, 1a, 2b, 2c, 22 of the multi-layer waveguide. The intermediate layers, 2a, 2b, 2c, 2d, 2e each have an elongated aperture 7. The elongated apertures 7, alone or together with the elongated apertures of other layers, form a waveguide channel 77. The elongated apertures 7 are in part or all of the intermediate layer surrounded by the metasurface.

[0069] FIG. 2 shows a cross-section of a part of the intermediate layer 2b. The layer has an elongated aperture 7, only part of which is visible in FIG. 2. The elongated aperture 7 is surrounded by a metasurface 3 comprising a thick section 3a and a thin section 3b. Both the thick section 3a and the thin section 3b form the metasurface. The metasurface suppresses leakage in a manner that aids in guiding the wave and in holding the wave in the waveguide channel 77 of which the elongated aperture 7 forms part.

[0070] Figure 2 further shows a flat portion 4 surrounding the meta-surface meta-surface 3. The flat portion 4 in one embodiment has the same thickness as the thick section 3a. In the embodiment shown in Figure 2, the thick sections 3a are arranged in straight rows 6a, 6b, 6c. In one embodiment, the number of straight rows 6a, 6b, 6c can be one, two, three, or more on any or all sides of the elongated aperture 7.

[0071] Figure 3 shows an embodiment of the multi-layer waveguide 1 in which the layers are spaced apart. This exploded view shows an important feature of the multi-layer waveguide 1 that no galvanic, electrical, or physical connection is required between the layers. That is, a small gap can exist between the layers. This gap can be, for example, an air gap that is not controlled from the manufacturing of the layers. Also, the gap can be, for example, at the micron level or even at the atomic level. However, note that the size of the gap shown in Figure 3 is for illustration only, and the gap between the layers can typically be any value between 0 and 15 micrometers.

[0072] Figure 4 shows a cross-section of an embodiment of the multi-layer waveguide 1 in which the inlet opening 30 and the outlet opening 31 can be seen. These openings 30, 31 are the openings through which waves enter and exit the waveguide channel 77. Figure 4 further shows a first surface 5a and a second surface 5b specified for one intermediate layer 2b. Note that each layer has a first surface 5a and a second surface 5b. The inlet opening 30 and the outlet opening 31 do not need to be arranged in the bottommost layer 22. In another embodiment, the inlet opening 30 and the outlet opening 31 are instead arranged in the topmost layer 21. In yet another embodiment, the inlet opening 30 and the outlet opening 31 are arranged in different layers. For example, the inlet opening 30 can be arranged in the topmost layer 21 while the outlet opening 31 can be arranged in the bottommost layer 22. The reverse can also be true.

[0073] FIG. 5 shows a part of the intermediate layers 2a, 2b, … 2n having the meta - surface 3, or a part of the uppermost layer 21 or the lowermost layer 22. FIG. 5 shows the thick - section 3a, the flat part 4, and the thin - section 3b and the difference in thickness. This difference can be, for example, 50 - 70%, 50 - 60%, 55 - 65%, or 60 - 70% of the total thickness of the layer, but the difference in thickness can also vary outside this range.

[0074] FIG. 6 shows an embodiment of the meta - surface 3. The meta - surface 3 is manufactured by metal chemical etching that forms a characteristic shape at the edge of the meta - surface, and the shape of the edge at the meta - surface is rounded. Note that other manufacturing methods such as CNC and laser cutting are also possible.

[0075] FIG. 7 shows the coaxial multi - layer waveguide 1. The waveguide channel 77 includes a central member 8 disposed within the elongated aperture 7 of one of the intermediate layers 2a, 2b, 2c, …, 2n. The central member 8 is attached to the remaining part of the layer at one or more locations that connect the central member to the layer and maintain it in a predetermined position.

[0076] FIG. 8 shows an embodiment of the coaxial multi - layer waveguide 1. The uppermost layer 21 and the lowermost layer 22 have the meta - surface 3. Note that the uppermost layer 21 and the lowermost layer 22 in some embodiments have the meta - surface 3, but in some they do not. Further, in some embodiments, for example, as shown in FIG. 8, one or more intermediate layers do not have the meta - surface 3.

[0077] FIG. 9 shows another embodiment of the multi - layer waveguide 1. The uppermost layer 21 does not have a meta - surface, but the intermediate layers 2a, 2b, 2c and the lowermost layer 22 have a meta - surface.

[0078] Figure 10 shows an embodiment of the intermediate layers 2a, 2b, 2c, …, 2n, in which the thick section 3a has a rounded shape. This shape is not important for functionality, and it should be noted that the meta-surface 3 can have thick sections 3a of many different shapes, both on the same meta-surface 3 and on different meta-surfaces 3.

[0079] Figure 11 shows another embodiment in which the thick sections 3a of the meta-surface 3 are randomly placed around the elongated aperture 7. Figure 11 is a diagram showing how the thick sections 3a can be arranged, but what is described here is merely various possible embodiments, and it should be noted that other arrangements of the thick sections 3a are possible within the scope of the claims. A small gap between the layers and the meta-surface provides an electromagnetic bandgap (EBG) structure.

[0080] Figure 12 shows an exploded isometric view of a multilayer Waveguide slot antenna 40 as an example of the waveguide 1 described in this specification. In the embodiment shown in Figure 12, the top layer 21, the intermediate layer 2a, and the bottom layer 22 are shown. The top layer 21 includes an antenna slot 41 and a corrugated portion 42 disposed at one end of the waveguide 1. The intermediate layer 2a includes an elongated aperture 7 that provides a root shape to each waveguide 1. The bottom layer 22 and the top layer 21 include a meta-surface 3 disposed so as to surround the elongated aperture 7 of the intermediate layer 2a.

[0081] The elongated aperture 7 shown in Figure 12 includes a support structure for strengthening the mechanical support of the layer. The support structure is disposed within the elongated aperture 7. This provides an embodiment in which a plurality of elongated apertures 7 are arranged instead of a single aperture extending along the entire length. In one embodiment, this is merely for structural support.

[0082] FIG. 13 shows a bottom view of the uppermost layer 21 shown in FIG. 12. As shown, the uppermost layer 21 in one embodiment includes a metasurface 3 arranged to surround the elongated aperture 7 of the intermediate layer 2a. As will be appreciated, the embodiments shown in FIGS. 12 and 13 are merely illustrative of how the solution described herein can be Waveguide slot antenna realized as 40. FIGS. 12 and 13 further show how the route shape of the waveguide 1 can differ depending on the implementation aspect. For example, the route shape can be straight in one embodiment, while another embodiment can include one or more turns.

[0083] FIG. 14 shows Waveguide slot antenna one embodiment of the multilayer waveguide 1 realized as 40. FIG. 15 shows Waveguide slot antenna a somewhat more complex multilayer waveguide 1 realized as 40. Here, the corrugated portion 42 is arranged to reduce the ripple of the transmission pattern. The corrugated portion 42 improves the propagation pattern by reducing the surface current of the uppermost layer. As shown in FIG. 14, the corrugated portion 42 extends through the uppermost layer 21 and the intermediate layer 2a. Waveguide slot antenna In another embodiment where the multilayer waveguide realized as 40 includes additional intermediate layers 2b, 2c,... 2n, the corrugated portion 42 extends through the uppermost layer 21 and the intermediate layers 2a, 2b, 2c,... 2n. In yet another embodiment, the corrugated portion 42 extends through at least the uppermost layer 21 and at least some of the intermediate layers 2a, 2b, 2c,... 2n.

Claims

1. In a multi-layer waveguide (1) comprising at least three physical layers (21, 2a, 2b, 2c,... 2n, 22) assembled as a multi-layer waveguide (1), said layers are a top layer (21), one or more intermediate layers (2a, 2b,... 2n), and a bottom layer (22), and said multi-layer waveguide (1) comprises a waveguide channel (77) which is an elongated aperture (7) in at least one intermediate layer (2a, 2b,... 2n). In the multi-layer waveguide (1), at least one layer (21, 2a, 2b,... 2n, 22) has a metasurface (3) on a first surface (5a) facing a first adjacent layer, said metasurface (3) surrounds said elongated aperture (7) and comprises a thick section (3a) and a thin section (3b), A multi-layer waveguide (1), characterized in that.

2. Said first surface (5a) has a flat portion (4) surrounding said metasurface (3), Said thick section (3a) has a thickness corresponding to the thickness (L1) of said layer in said flat portion (4), Said thin section (3b) has a thickness (L2) smaller than said thickness in said flat portion (4), The multi-layer waveguide (1) according to claim 1.

3. A second surface (5b) of said layer (21, 2a, 2b,... 2n, 22) facing a second adjacent layer is a flat surface except for said elongated aperture (7), The multi-layer waveguide (1) according to claim 1 or 2.

4. Said layers (21, 2a, 2b, 2c,... 2n, 22) are separate layers laminated without elements extending between said layers (21, 2a, 2b, 2c,... 2n, 22), The multi-layer waveguide (1) according to any one of claims 1 to 3.

5. Each thick section (3a) has one of the shapes of a circle, an ellipse, a triangle, a square, a pentagon, a rectangle, a quadrilateral, a square, a hexagon, or a rectangle. The multi-layer waveguide (1) according to any one of claims 1 to 4.

6. The thick section (3a) is arranged in rows (6a, 6b, 6c,... 6n) parallel to the elongated aperture (7). The multi-layer waveguide (1) according to any one of claims 1 to 5.

7. The thick section (3a) is arranged at an irregular distance from the elongated aperture (7). The multi-layer waveguide (1) according to any one of claims 1 to 5.

8. The metasurface (3) surrounds the elongated aperture (7). The multi-layer waveguide (1) according to any one of claims 1 to 7.

9. The multi-layer waveguide includes a first intermediate layer (2a), a second intermediate layer (2b), and a third intermediate layer (2c), each having an elongated aperture (7). The second intermediate layer (2b) further includes a central member (8) disposed within the elongated aperture (7). The multi-layer waveguide (1) according to any one of claims 1 to 8.

10. The multi-layer waveguide includes a first intermediate layer (2a), a second intermediate layer (2b), and a third intermediate layer (2c). The second intermediate layer (2b) is a non-convex-concave layer for an integrated electronic chip set. The multi-layer waveguide (1) according to any one of claims 1 to 8.

11. The thickness difference (L3) between the thick section (3a) and the thin section (3b) of the metasurface (3) is smaller than the value obtained by dividing the wavelength by 20. The multi-layer waveguide (1) according to any one of claims 1 to 10.

12. The thickness difference (L3) between the thick section (3a) and the thin section (3b) of the meta-surface (3) is smaller than the value obtained by dividing the wavelength by 25. The multi-layer waveguide (1) according to any one of claims 1 to 11.

13. Either one of the uppermost layer (21) and the lowermost layer (22) includes a meta-surface (3). The multi-layer waveguide (1) according to any one of claims 1 to 12.

14. The multi-layer waveguide (1) is realized as a waveguide slot antenna (40). The multi-layer waveguide (1) according to any one of claims 1 to 13.

15. The uppermost layer (21) includes an antenna slot (41). The multi-layer waveguide (1) according to any one of claims 1 to 14.

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