A waveguide arrangement

TEHCNICAL FIELD

The present disclosure relates to a waveguide arrangement comprising a first waveguide port, a second waveguide port and a waveguide conductor that extends between the waveguide ports.

BACKGROUND

Traditionally, microwave radios and radars are using waveguide filters due to the low losses. There are waveguide ports used as interfaces to receivers, to transmitters and to antennas. These waveguide filters are often manufactured of milled or cast aluminum that is surface-treated with silver, gold or copper to lower the insertion losses. These solutions are common on S-, C-, X-, Ku- and Ka-bands. It is common that there are waveguide ports that are perpendicular to the rest of the waveguide structures which results in H- or E-bends in the design to connect the waveguide ports to the rest of the waveguide structure.

At higher frequencies that are used in different applications where physical sizes become smaller, it is obvious that it is difficult to scale the traditional technology to meet the tolerances needed for high performance applications. When using a metal body that is surface-treated with high conductive metal such as silver or gold, it is not critical if there are small areas with no, or thinner, surface treatments at lower frequencies. For higher frequencies, such a V-, E-, W- and D-Band, the electrical performance is more sensitive for these types of discontinuities, and this has become a major problem since many high precision technologies are based on non-conductive or semi- conductive materials. Even relatively small discontinuities in the electrically conducting layer will then be devastating with low performance regarding for example return loss and insertion loss.

Even thinner surface treatment could worsen the electrical performance since the concentration of currents will increase, which in turn increases the losses. For higher frequencies, the skin depth could be just a fraction of a pm, and therefore a thin layer of gold and silver will have a significant effect on the electrical performance.

One solution today to avoid gaps in the surface treatment and/or too thin surface treatment is to make the surface treatment thicker, which will increase manufacturing cost. Both gold and silver as well as copper are expensive raw materials and costly to deploy as surface treatments. Process manufacturing might also be more complex.

In solutions based on MEMS (Micro Electro-Mechanical Systems), a common problem lies in realizing a multi-substrate silicon-based RF device with robust electrical connections through substrate layers. When metal needs to be deposited in such a way that it connects to metal on the opposing side of a substrate after a subsequent silicon etch, creating for example an opening to a waveguide, it is difficult to make a proper electrical connection since there may be gaps in the metallization, or thin metal membranes or flakes that are left suspended in air. This is also the case for metallization on other materials.

It is therefore an object of the present disclosure to provide an increased electrical performance in a waveguide arrangement, in particular at higher frequencies, such a V-, E-, W- and D-Band.

SUMMARY

The above object is achieved by means of a waveguide arrangement comprising a first waveguide port, a second waveguide port and a waveguide conductor that extends between the waveguide ports. The waveguide conductor has an extension and comprises at least one electrically conducting inner wall. At least one inner wall at least partly comprises a plurality of grooves that run along the extension, where said grooves are covered by a metal layer that has been applied by means of a metallization.

This will ensure that the electrical contact in the metal layer, which coats at least those inner walls that comprise the plurality of grooves, is less prone to discontinuities and more uniform and reliable as a manufacturing process than previous waveguide arrangements.

According to some aspects, the grooves are uniformly spaced. In this way, the grooves can be easily designed and manufactured.

According to some aspects, the grooves have a maximum height that runs perpendicular to the extension and a maximum width that runs parallel to the extension. The maximum height falls below a tenth of a largest distance between either two opposite electrically conducting inner walls or a largest diameter of an oval electrically conducting inner wall.

According to some aspects, the maximum width falls below a tenth of a largest distance between either two opposite electrically conducting inner walls or a largest diameter of an oval electrically conducting inner wall.

According to some aspects, the grooves have at least one of a triangular cross-section, an arcuate cross-section, a sinusoidal cross-section or a rectangular cross-section. The grooves can in other words be formed to have many different shapes.

According to some aspects, the extension runs along at least one discontinuous bend. According to some aspects, the extension runs along an arcuate path. This means that the grooves can be formed to follow many different shapes.

According to some aspects, the grooves are formed on a plurality of inner walls.

According to some aspects, the waveguide arrangement is formed in at least one layer of material, where the waveguide ports and waveguide conductor are formed by means of the metal layer that has been applied by means of a metallization on the material.

According to some aspects, the metallization can be formed by means of PVD (Physical Vapor Deposition), CVD (Chemical Vapor Deposition), ALD (Atomic Layer Deposition), Inkjet Technology, evaporation and electro- or electroless plating.

According to some aspects, the waveguide conductor is formed by means of chemical removal of the material followed by the metallization such that the metal layer is formed.

This means that well-known metallization methods can be used together with the grooves according the present disclosure. For example, MEMS technology can be used for forming the material with the grooves followed by the metallization for obtaining the waveguide arrangement. The material can then for example be a silicon material that is formed by means of etching.

According to some aspects, the waveguide conductor is in the form of a coaxial conductor that comprises an inner conductor and an outer conductor. The inner conductor at least partly comprises a plurality of the grooves, and/or the outer conductor comprises an inner wall that at least partly comprises a plurality of the grooves.

This means that either the inner conductor or the outer conductor, or both, comprises a plurality of the grooves.

The above object is also achieved by means of a method that is associated with the above advantages.

BRIEF DESCRIPTION OF THE DRAWINGS

The present disclosure will now be described more in detail with reference to the appended drawings, where:

Figure 1 shows a perspective view of a waveguide arrangement according to a first example,

Figure 2 shows an enlarged side view of the waveguide arrangement according to the first example; Figure 3 shows an enlarged perspective view of the waveguide arrangement according to the first example;

Figure 4 shows a cut-open longitudinal cross-section side view of a waveguide arrangement according to a second example;

Figure 5 shows a cut-open longitudinal cross-section side view of a waveguide arrangement according to a third example;

Figure 6A shows a top view of a waveguide arrangement according to a fourth example;

Figure 6B shows a longitudinal cross-section side view of the waveguide arrangement according to the fourth example;

Figure 7A shows a top view of a waveguide arrangement according to a fifth example;

Figure 7B shows a top view of a waveguide arrangement according to a sixth example;

Figure 8A shows a top view of a waveguide arrangement according to a seventh example;

Figure 8B shows a top view of a waveguide arrangement according to an eighth example;

Figure 9 shows a top view of a different types of waveguide profiles;

Figure 10A shows a first perspective view illustrating manufacturing of a waveguide arrangement using MEMS technology;

Figure 10B shows a second perspective view illustrating manufacturing of a waveguide arrangement using MEMS technology;

Figure IOC shows a third perspective view illustrating manufacturing of a waveguide arrangement using MEMS technology;

Figure 10D shows a fourth perspective view illustrating manufacturing of a waveguide arrangement using MEMS technology;

Figure 11 A shows a top view of an enlarged detail of the third perspective view; Figure 1 IB shows a top view of an enlarged detail of the fourth perspective view;

Figure 12 is a flowchart illustrating methods according to the present disclosure;

Figure 13 shows a perspective view of a waveguide arrangement in the form of a coaxial conductor; and

Figure 14 shows an enlarged cross-section view of a waveguide arrangement that exemplifies different types of grooves as well as different distributions and configurations of grooves.

DETAILED DESCRIPTION

Aspects of the present disclosure will now be described more fully hereinafter with reference to the accompanying drawings. The different devices, systems, computer programs and methods disclosed herein can, however, be realized in many different forms and should not be construed as being limited to the aspects set forth herein. Like numbers in the drawings refer to like elements throughout.

The terminology used herein is for describing aspects of the disclosure only and is not intended to limit the invention. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise.

With reference to Figure 1-3 there is a first example of a waveguide arrangement 100 comprising a first waveguide port 101, a second waveguide port 102 and a waveguide conductor 103 that extends between the waveguide ports 101, 102. The waveguide conductor 103 has an extension E and comprises at least one electrically conducting inner wall 104, 105, 106, 107.

In this example, there are four electrically conducting inner walls 104, 105, 106, 107 that enclose the waveguide conductor 103, and the extension E runs along a straight line, but can, as will be exemplified in the following, run in any suitable manner. According to some aspects, the waveguide conductor 103 constitutes an air-filled tube, but can also constitute a tube that at least partly is filled with at least one other dielectric material.

According to the present disclosure, at least one inner wall 104 at least partly comprises a plurality of grooves 108 that either run along, or perpendicular to, the extension E. The grooves 108 are covered by a metal layer 122 that has been applied by means of a metallization.

It is to be appreciated that the Figures illustrate the grooves 108 in different ways in a schematic manner, for example in Figure 1, the grooves 108 are not explicitly shown for reasons of clarity. According to some aspects, the grooves 108 form a micro structure. Examples of actual sizes will be discussed later.

These grooves 108 will ensure that the electrical contact in the metal layer 122, which coats at least those inner walls that comprise the plurality of grooves 108, is more uniform and reliable than previous waveguide arrangements 100. This is due to the inventors realizing that the metal that is deposited during normal metallization processes will be more likely to attach to the grooves 108 than to a smooth surface. This is in particular the case where the extension E runs in a vertical manner. There will furthermore be possible to achieve more metal coating per area unit of the wall, which will lead to a better electrical conduction of the wall.

According to some aspects, as shown in Figure 2 and Figure 3, the grooves 108 are uniformly spaced. In this way, the grooves can be easily designed and manufactured.

According to some aspects, as illustrated in Figure 4 that shows a cut-open side view, there is a second example of a waveguide arrangement 400 where the waveguide conductor 403 extends between a first waveguide port 401 and a second waveguide port 402. The extension E’ of the waveguide conductor 403 runs along at least one discontinuous bend 430, 431. Here, there are two bends 430, 431 such that the waveguide arrangement 400 comprises a first part 440, a second part 441 and a third part 442, where the first part 440 is positioned between the second part 441 and the third part 442, where the parts 440, 441, 442 are divided by the bends 430, 431. This results in that the extension E’ in the second part 441 and the third part 442 present an angle to the extension E’ in the first part 440, here the angle is about 90°.

The bends 430, 431 have corresponding inner corners 430a, 431a, and as marked with solid lines the groves 408 run along an inner wall of the second part 441 and the third part 442 until the corresponding inner corners 430a, 431a is reached. In this way, a reliable electrical contact is obtained at the inner comers 430a, 43 la of the bends 430, 431. The grooves 408 can run along any number of inner walls of the second part 441 and the third part 442, but most important is the inner walls that meet the corresponding inner comers 430a, 431a.

As indicated with dashed lines, one or more inner walls of the first part 440 may also comprise the grooves 408’.

According to some aspects, as illustrated in Figure 5, showing a cut-open side view, there is a third example of a waveguide arrangement 500, where a waveguide conductor 503 has an extension E” an extends between a first waveguide port 501 and a second waveguide port 502, where the extension E” runs along an arcuate path. The waveguide conductor 503 comprises only one circumferentially running electrically conducting inner wall 504. As indicated in Figure 5, the inner wall 504 at least partly comprises grooves 508, but can of course be completely covered with grooves.

According to some aspects, as illustrated in Figure 6A that shows a top view and Figure 6B that shows a longitudinal cross-section side view, there is a fourth example of a waveguide arrangement 600 that corresponds to the second example. The extension E’ of the waveguide conductor 603 runs between a first waveguide port 601 and a second waveguide port 602 along two bends 630, 631 with inner comers 630a, 631a such that the waveguide arrangement 600 comprises a first part 640, a second part 641 and a third part 642 in the same way as for the second example. The grooves may change character along the extension E’ of the waveguide conductor 603, for example regarding shape and/or size.

The grooves 608 run along inner walls that meet the corresponding inner corners 630a, 63 la in the same way as for the second example in the case where one or more inner walls of the first part 440 do not comprise any grooves 408’.

Furthermore, in this example, the waveguide arrangement 600 is formed in at least one layer 610, 611, 612 of material, here three layers 610, 611, 612 of material, where the waveguide ports 601, 602 and the waveguide conductor 603 are formed by means of a metal layer 622 that has been applied by means of a metallization on the material.

In this case, it is very important that the wall metallizations of the waveguide conductor 603 that mainly runs in an intermediate layer 611 makes a reliable electrical connection to the inner walls of the ports 601, 602, and by means of the grooves 608, this is accomplished.

According to some aspects, the metallization is formed by means of at least any one of PVD (Physical Vapor Deposition), CVD (Chemical Vapor Deposition), ALD (Atomic Layer Deposition), Inkjet Technology, evaporation and electro- or electroless plating. This means that metal particles are deposited on the walls of the waveguide conductor, and where grooves are applied, they enhance the corresponding surface’s ability to receive the metallization in a more efficient manner.

According to some aspects, the waveguide conductor 603 is formed by means of chemical removal of the material followed by the metallization such that the metal layer 622 is formed.

According to some aspects, it is conceivable that the waveguide arrangement 600 is formed in several dielectric pre-metallized layers 610, 611, 612. Then the waveguide ports 601, 602 are formed by means of partial removal of the existing metallization on a port layer 612, into which the waveguide ports 601, 602 are to be formed, followed by an etch of the waveguide ports 601, 602 such that they are formed, and then a subsequent metallization of the waveguide ports 601, 602 such that the metal layer 622 is safely joined electrically in the corners 630a, 63 la by means of the grooves 608.

According to some further aspects, the material comprises at least one of dielectric material, substrate material, semiconductor material and metal material.

This means that for example MEMS (Micro Electro-Mechanical systems) technology can be used for forming the material with the grooves followed by the metallization for obtaining the waveguide arrangement 600. The material can then for example be a silicon material that is formed by means of etching.

As for the second example, the grooves can run along two or more inner walls, and in the first part as well.

As illustrated in the examples described, the grooves are shown to have a triangular shape, but many other shapes are of course possible.

Figure 7A and Figure 7B show a top view of a waveguide arrangement according to a fifth example and a sixth example, and correspond to Figure 6A.

As illustrated in Figure 7A, there is a waveguide arrangement 700A with waveguide ports 701 A, 702A where the grooves 708A have an arcuate shape, where the arcs can be directed in any suitable way. As illustrated in Figure 7B, there is a waveguide arrangement 700B with waveguide ports 70 IB, 702B where the grooves 708B have a sinusoidal shape.

Combinations of these shape of the grooves are also possible, and generally the grooves 108, 708 A, 708B have at least one of a triangular cross-section, an arcuate cross-section, a sinusoidal crosssection or a rectangular cross-section. Other shapes are of course possible.

Furthermore, as mentioned previously, the grooves can run on any number of available inner walls. Figure 8A and Figure 8B show a top view of a waveguide arrangement according to a seventh example and eighth example.

As illustrated in Figure 8A, there is a waveguide arrangement 800A with waveguide ports 801 A, 802A where the grooves 808A run along two opposing inner walls 804A, 807A. As illustrated in Figure 8B, there is a waveguide arrangement 800B with waveguide ports 80 IB, 802B where the grooves 808B run along all the inner walls 804B, 805B, 806B, 807B. This means that the grooves 808A, 808B are formed on a plurality of inner walls 804A, 805A, 806A, 807A; 804B, 805B, 806B, 807B.

As shown in Figure 9, the waveguide ports can have many different shapes. There is shown a circular waveguide port 911 with a diameter D, and oval or elliptical waveguide port 912 with a largest diameter D’, a U-shaped waveguide port 913 with a largest length a’, an I-shaped waveguide port 914 with a largest length a”. The oval waveguide port 912 has an oval electrically conducting inner wall 909.

As a further alternative, there is a coaxial waveguide port 915 with an outer diameter D”. This waveguide port is described and shown more in detail in Figure 13, where the waveguide conductor 900 is in the form of a coaxial conductor that comprises an inner conductor 940 and an outer conductor 941, where the inner conductor 940 at least partly comprises a plurality of the grooves 908, and/or the outer conductor 941 comprises an inner wall 904 that at least partly comprises a plurality of the grooves 908’.

This means that either the inner conductor 940 or the outer conductor 941, or both, comprises a plurality of the grooves. The details of the grooves 908, 908’ are only schematically indicated and the grooves 908, 908’ can cover more or less of the corresponding conductors 940, 941.

In the following, a manufacturing method for forming a waveguide arrangement will be described with reference to Figure 10A-10D, Figure 11 A-l IB and Figure 12.

Figure 10A shows a first perspective view illustrating manufacturing of a waveguide arrangement using MEMS technology, and Figure 10B-10D show corresponding second, third and fourth perspective views.

Figure 11 A shows a top view of an enlarged detail of the third perspective view, Figure 1 IB shows a top view of an enlarged detail of the fourth perspective view, and Figure 12 is a flowchart illustrating methods according to the present disclosure.

The method for forming a waveguide arrangement lOOOD comprises providing S100 a metallized material 1021 with a first metallization 1020 A formed on a first side 1023 of the material 1021, as illustrated in Figure 10A, and removing S200 metallization such that a first aperture 1022B is formed in the first metallization 1020A, as illustrated in Figure 10B. The material 1021 also has a second side 1024. The method further comprises removing S300 material such that a second aperture 1022C is formed in the material 1021, the second aperture 1022C comprising the first aperture 1022B and running along an extension L, where at least one inner wall 1025C is formed, as illustrated in Figure 10C. The first aperture 1022B is formed in the first metallization 1020A, and the second aperture 1022C is formed in the material 1021, where the apertures 1022B, 1022C at least partly correspond to each other such that a combined aperture is formed that runs through the first metallization 1020 A and the material 1021.

When removing the material, the method comprises forming S400 a plurality of grooves 1008C that run along the extension L such that at least one inner wall 1025C at least partly comprises a plurality of grooves 1008C. This is also illustrated in Figure IOC and in the detailed view in Figure 11 A, where a side of the first metallization 1020A that faces the material 1021 is shown, the first metallization 1020A following an inner edge of the grooves 1008C, which in this example are shown to have a triangular shape. This means that removing S300 material and forming S400 a plurality of grooves 1008C may be performed at the same time.

The method further comprises applying S500 a second metallization 1020B along the second aperture 1022C such that a metallized aperture 1022D is formed where the first metallization 1020A is electrically connected to the metallized aperture 1022D. This is illustrated in Figure 10D and in the detailed view in Figure 1 IB, where it is apparent that the metallizations 1020A, 1020B on the corresponding sides are connected via the metallized aperture 1022D that comprises metallized grooves 1008D.

According to some aspects, the second metallization 1020B is applied not only along the second aperture 1022C, but also to the second side 1024 of the material 1021. This means that the first metallization 1020 A is electrically connected to the second metallization 1020B via the metallized aperture 1022D. In other words, the applying S500 comprises applying the second metallization 1020B to the second side 1024 of the material 1021 such that the first metallization 1020A is electrically connected to the second metallization 1020B via the metallized aperture 1022D.

In Figure 11B, the second metallization 1020B is indicated both for having been applied to the second aperture 1022C and thus the grooves 1008C such that a metallized inner wall 1025D has been formed, and for having been applied to the second side 1024 of the material 1021. The second metallization 1020B is at least applied to the second aperture 1022C and thus the grooves 1008C.

It should be noticed that at least some of the method steps above can be performed in another order than described above. For example, removing S300 material can be performed before removing S200 metallization.

As in particular shown in Figure 11A and Figure 11B, when the grooves 1008C in the material 1021 are metallized, the surface of the first metallization 1020A that faces the material 1021 is partly exposed by means of the grooves 1008C, ensuring that the metallization in the second aperture 1022C reaches and makes electrical contact with the first metallization 1020 A.

Here, a structure is introduced that may have grooves incorporated on a micro scale that will ensure perfect electrical contact between ground planes. The metallized aperture 1022D can for example constitute the inner wall 904 of the outer conductor 941 comprised in the coaxial conductor with the coaxial waveguide port 915 that has been discussed above with reference to Figure 9 and Figure 13.

According to some aspects, micro structuring is applied in the form of grooves that allow subsequent metallization steps to join metal surfaces without the risk of an open connection or too large metal layer membrane areas protruding without support and therefore being likely to break off during processing or interfere with RF precision. If noble metals are used such as gold, it is desirable to have as thin metal as RF properties allow for cost reasons. The thinner the metal, the more likely it is to break without the supporting micro structuring of the wall surface. If there is thin metal or even no metal in the “bottom” of the groves, the thicker metal on the protruding edges of the grooves will work as a Faraday cage, as long as the number of grooves is at least 3-4 per wavelength.

An etch selectivity difference between metallizations and a material, such as silicon, is presented where a robust residual metal membrane is supported by a micro structured wall pattern on one side by means of the groves to constitute a landing pad for an ohmic connection established with a subsequent metallization from any side of the material overlapping the interface between the micro structures and the etched membrane.

According to some aspects, the material 1021 comprises a plurality of layers, such as the layers 610, 611, 612 in the fourth example. According to some further aspects, the material comprises at least one of dielectric material, substrate material, semiconductor material and metal material.

The present disclosure is not limited to the above, but may vary freely within the scope of the appended claims. For example, the grooves can have any compositions and forms, as illustrated in Figure 14 where there is a waveguide arrangement 1400 with an inner wall 1404 that comprises a plurality of different types of grooves 1408. The grooves 1408 have widths that differ between a minimum width wi and a maximum width W2, and heights that differ between a minimum height hi and a maximum height 112. It is to be noted that Figure 14 is intended to illustrate different types and sizes of grooves, not necessarily a typical groove configuration of a waveguide arrangement 1400. According to some aspects, with reference to Figure 1, Figure 2 and Figure 9, the grooves 108 have a maximum height h that runs perpendicular to the extension E and a maximum width w that runs parallel to the extension E, where the maximum height h falls below a tenth of a largest distance a, a’, a” between either two opposite electrically conducting inner walls 105, 106 or a largest diameter D, D’, D” of an oval electrically conducting inner wall 909.

According to some aspects, the maximum width w falls below a tenth of a largest distance a, a’, a” between either two opposite electrically conducting inner walls 105, 106 or a largest diameter D, D’, D” of an oval electrically conducting inner wall 904, 909.

According to some aspects, micro structured walls with grooves can generally be applied to microwave cavity walls to create a thicker equivalent thickness of a metal coating. In general metal deposition, assuming a micro scale addition of a thin layer of metal on top of a micro structured wall, the total amount of metal carried by a micro structured surface will be proportionally higher than an absolutely flat wall and hence hold more metal and finally lead to a lower total resistance in the same equivalent wall area on the macro scale.