Waveguides and transmission lines in gaps between parallel conducting surfaces

Abstract

A microwave device is based on gap waveguide technology, and comprises two conducting layers (101, 102) arranged with a gap there between, and protruding elements (103, 104) arranged in a periodically or quasi-periodically pattern and fixedly connected to at least one of said conducting layers, thereby forming a texture to stop wave propagation in a frequency band of operation in other directions than along intended waveguiding paths. Sets of complementary protruding elements are either each formed in said pattern and arranged in alignment and overlying each other, the complementary protruding elements of each set forming part of the full length of each protruding element of the pattern, or the sets of complementary protruding elements are arranged in an offset complementary arrangement, the protruding elements of one set thereby being arranged in between the protruding elements of the other set.

Claims

1. A microwave device comprising two conducting layers arranged with a gap there between, and protruding elements arranged in a periodically or quasi-periodically pattern and fixedly connected to at least one of said conducting layers, thereby forming a texture to stop wave propagation in a frequency band of operation in other directions than along intended waveguiding paths, wherein at least one of the conducting layers comprises a waveguiding path, the waveguiding paths comprising at least one of a conducting ridge and a groove with conducting walls, and wherein the protruding elements are arranged along at least one row on each side of the waveguiding paths, wherein each of said conducting layers comprises a thereto fixedly connected set of complementary protruding elements, said sets in combination forming said texture, the sets of complementary protruding elements being each formed in said pattern and arranged in alignment and overlying each other, the complementary protruding elements of each set forming part of the full length of each protruding element of the pattern, and wherein the complementary protruding elements of each set being arranged in contact with each other or with a small gap there between.

2. The microwave device of claim 1, wherein the sets of complementary protruding elements are formed in said pattern and arranged in alignment with each other, and wherein the protruding elements of both sets are all of the same length, said length being half the length of the full-length protruding elements of the texture.

3. The microwave device of claim 1, wherein the protruding elements in at least one of the conducting layers are arranged to at least partly surround a cavity between said conducting layers, said cavity thereby forming said groove functioning as a waveguide.

4. The microwave device according to claim 1, wherein the sets of protruding elements are monolithically formed on said conducting layers.

5. The microwave device of claim 1, wherein all protruding elements of each of said conducting layers are connected electrically to each other at their bases at least via said conductive layer on which they are fixedly connected.

6. The microwave device of claim 1, wherein the waveguiding path is a conducting ridge.

7. The microwave device of claim 6, wherein the waveguiding path is for a single-mode wave.

8. The microwave device of claim 1, wherein each of the protruding elements has a maximum width dimension in the range 0.05-1.0 mm.

9. The microwave device of claim 8, wherein each of the protruding elements has a maximum width dimension in the range 0.1-0.5 mm.

10. The microwave device according to claim 1, wherein the two conducting layers are connected together for rigidity by a mechanical structure at some distance outside the region with guided waves.

11. The microwave device of claim 10, wherein the mechanical structure is integrally and monolithically formed on at least one of the conducting materials defining one of the conducting layers.

12. The microwave device of claim 1, wherein the protruding elements are in form of posts or pins, the posts/pins having a circular or rectangular cross-section.

13. The microwave device of claim 1, wherein a full length of the protruding elements is greater than a width and thickness of the protruding elements.

14. The microwave device of claim 13, wherein the full length of the protruding elements is greater than double the width and thickness of the protruding elements.

15. The microwave device according to claim 1, wherein at least one of the conducting layers is provided with at least one opening, in the form of rectangular slot(s), said opening(s) allowing radiation to be transmitted to and/or received from said microwave device.

16. The microwave device according to claim 1, wherein the protruding elements have maximum cross-sectional dimensions of less than half a wavelength in air at an operating frequency, and/or wherein the protruding elements in the texture stopping wave propagation are spaced apart by a spacing being smaller than half a wavelength in air at the operating frequency.

17. A microwave device comprising two conducting layers arranged with a gap there between, and protruding elements arranged in a periodically or quasi-periodically pattern and fixedly connected to at least one of said conducting layers, thereby forming a texture to stop wave propagation in a frequency band of operation in other directions than along intended waveguiding paths, wherein at least one of the conducting layers comprises a waveguiding path, the waveguiding paths comprising at least one of a conducting ridge and a groove with conducting walls, and wherein the protruding elements are arranged along at least one row on each side of the waveguiding paths, wherein each of said conducting layers comprises a thereto fixedly connected set of complementary protruding elements, said sets in combination forming said texture, the sets of complementary protruding elements being arranged in an offset complementary arrangement, the protruding elements of one set thereby being arranged in between the protruding elements of the other set.

18. The microwave device of claim 17, wherein the sets of complementary protruding elements are arranged in an offset complementary arrangement, the protruding elements of each set being arranged in rows, wherein the protruding elements in each row being arranged in a staggered disposition in relation to adjacent rows, the protruding elements of the sets thereby being interleaved between each other both within each row.

19. The microwave device of claim 17, wherein the sets of complementary protruding elements are arranged in an offset complementary arrangement, the protruding elements of each set being arranged in rows, wherein the distance between the rows are double the distance between neighboring protruding elements within the rows, the rows of the sets thereby being interleaved between each other.

20. The microwave device of claim 17, wherein at least some of the protruding elements are in mechanical contact with said other conducting layer.

21. The microwave device of claim 20, wherein all of the protruding elements are in mechanical contact with the other conducting layer.

22. A microwave device comprising two conducting layers arranged with a gap there between, and protruding elements arranged in a periodically or quasi-periodically pattern and fixedly connected to at least one of said conducting layers, thereby forming a texture to stop wave propagation in a frequency band of operation in other directions than along intended waveguiding paths, wherein at least one of the conducting layers comprises a waveguiding path, the waveguiding paths comprising at least one of a conducting ridge and a groove with conducting walls, and wherein the protruding elements are arranged along at least one row on each side of the waveguiding paths, wherein each of said conducting layers comprises a thereto fixedly connected set of complementary protruding elements, said sets in combination forming said texture, the sets of complementary protruding elements being either each formed in said pattern and arranged in alignment and overlying each other, the complementary protruding elements of each set forming part of the full length of each protruding element of the pattern, or the sets of complementary protruding elements being arranged in an offset complementary arrangement, the protruding elements of one set thereby being arranged in between the protruding elements of the other set, wherein at least some of the protruding elements are in mechanical contact with said other conducting layer.

23. The microwave device of claim 22, wherein all of the protruding elements are in mechanical contact with the other conducting layer.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) For exemplifying purposes, the invention will be described in closer detail in the following with reference to embodiments thereof illustrated in the attached drawings, wherein:

(2) FIG. 1 is a perspective side view showing a gap waveguide in accordance with one embodiment of the present invention;

(3) FIG. 2 is a perspective side view showing a circular cavity of a gap waveguide in accordance with another embodiment of the present invention;

(4) FIG. 3 is a schematic illustration of an array antenna in accordance with another embodiment of the present invention, where FIG. 3a is an exploded view of a subarray/sub-assembly of said antenna, FIG. 3b is a perspective view of an antenna comprising four such subarrays/sub-assemblies, and FIG. 3c is a perspective view of an alternative way of realizing the antenna of FIG. 3b;

(5) FIG. 4 is a top view of an exemplary distribution network realized in accordance with the present invention, and useable e.g. in the antenna of FIG. 3;

(6) FIG. 5 is a perspective and exploded view of three different layers of an antenna in accordance with another alternative embodiment of the present invention making use of an inverted microstrip gap waveguide;

(7) FIG. 6 is a close-up view of an input port of a ridge gap waveguide in accordance with a further embodiment of the present invention;

(8) FIGS. 7 and 8 are perspective views of partly disassembled gap waveguide filters in accordance with a further embodiments of the present invention;

(9) FIG. 9 is an illustration of a gap waveguide packaged MMIC amplifier chains, in accordance with a further embodiment of the present invention, and where FIG. 9a is a schematic perspective view seen from the side and FIG. 9b is a side view;

(10) FIGS. 10 and 11 are schematic illustrations of embodiments where the protruding elements are formed by a combination of protruding elements from two sets, in accordance with one line of embodiments of the present invention;

(11) FIG. 12-14 are schematic illustrations of embodiments where the protruding elements are formed by a combination of protruding elements from two sets, in accordance with another line of embodiments of the present invention;

(12) FIG. 15 is a schematic exploded view of a manufacturing equipment in accordance with one embodiment of the present invention;

(13) FIG. 16 is a top view of the die forming layer in FIG. 10;

(14) FIG. 17 is a perspective view of the assembled die of FIG. 10;

(15) FIG. 18 is a perspective view of the manufacturing equipment of FIG. 15 in an assembled disposition;

(16) FIG. 19 is a schematic exploded view of a manufacturing equipment in accordance with another embodiment of the present invention;

(17) FIGS. 20 and 21 are top views illustrating the two die forming layers in the embodiment of FIG. 19; and

(18) FIG. 22 is a perspective view showing an RF part producible by the manufacturing equipment of FIG. 19.

DETAILED DESCRIPTION

(19) In the following detailed description, preferred embodiments of the present invention will be described. However, it is to be understood that features of the different embodiments are exchangeable between the embodiments and may be combined in different ways, unless anything else is specifically indicated. Even though in the following description, numerous specific details are set forth to provide a more thorough understanding of the present invention, it will be apparent to one skilled in the art that the present invention may be practiced without these specific details. In other instances, well-known constructions or functions are not described in detail, so as not to obscure the present invention.

(20) In the following, some exemplary microwave devices in accordance with the present invention will first be generally discussed. The protruding elements forming a stop band are here formed in the novel way discussed in the last sections.

(21) In a first embodiment, as illustrated in FIG. 1, an example of a rectangular waveguide is illustrated. The waveguide comprises a first conducting layer 1, and a second conducting layer 2 (here made semi-transparent, for increased visibility). The conducting layers are arranged at a constant distance h from each other, thereby forming a gap there between.

(22) This waveguide resembles a conventional SIW with metallized via holes in a PCB with metal layer (ground) on both sides, upper (top) and lower (bottom) ground plane. However, here there is no dielectric substrate between the conducting layers, and the metalized via holes are replaced with a plurality of protruding elements 3 extending from one or both of the conducting layers. The protruding elements 3 are made of conducting material, such as metal. They can also be made of metallized plastics or ceramics.

(23) Further, the first and second conductive layers may be attached to each other by means of a rim, extending around the periphery of one of the conducting layers. The rim is not illustrated, for increased visibility.

(24) Similar to a SIW waveguide, a waveguide is here formed between the conducting elements, here extending between the first and second ports 4.

(25) In this example, a very simple, straight waveguide is illustrated. However, more complicated paths may be realized in the same way, including curves, branches, etc.

(26) The waveguide path may, as is per se known in the art, be formed as a conducting ridge, a conducing grove, or as a microstrip.

(27) The protruding elements may have circular cross-section geometry (as shown in FIG. 1) or rectangular or square cross-sectional geometry. Other cross-sectional geometries are also feasible.

(28) FIG. 2 illustrates a circular cavity of a gap waveguide. This is realized in a similar way as in the above-discussed straight waveguide of FIG. 1, and comprises first and second conducting layers 1, 2, arranged with a gap there between, and protruding elements extending between the conducting layers, and connected to these layers. The protruding elements 3 are here arranged along a circular path, enclosing a circular cavity. Further, in this exemplary embodiment, a feeding arrangement 6 and an X-shaped radiating slot opening 5 is provided.

(29) This circular waveguide cavity functions in similar ways as circular SIW cavity.

(30) With reference to FIG. 3, an embodiment of a flat array antenna will now be discussed. This antenna structurally and functionally resembles the antenna discussed in [13], said document hereby being incorporated in its entirety by reference.

(31) FIG. 3a shows the multilayer structure of a sub-assembly in an exploded view. The sub-assembly comprises a lower gap waveguide layer 31 with a first ground plane/conducting layer 32, and a texture formed by protruding elements 33 and a ridge structure 34, together forming a gap waveguide between the first ground plane 32 and a second ground plane/conducting layer 35. The second ground plane 35 is here arranged on a second, upper waveguide layer 36, which also comprises a third, upper ground plane/conducting layer 37. The second waveguide layer may also be formed as a gap waveguide layer. A gap is thus formed between both the first and second ground planes and between the second and third ground planes, respectively, thereby forming two layers of waveguides. The bottom, second ground plane 35 of the upper layer has a coupling slot 38, and the upper one has 4 radiating slots 39, and between the two ground planes there is a gap waveguide cavity. FIG. 3a shows only a single subarray forming the unit cell (element) of a large array. FIG. 3b shows an array of 4 such subarrays, arranged side-by-side in a rectangular configuration. There may be even larger arrays of such subarrays to form a more directive antenna.

(32) Between the subarrays, there is in one direction provided a separation, thereby forming elongated slots in the upper metal plate. Protruding elements/pins are arranged along both sides of the slots. This forms corrugations between the subarrays in E-plane.

(33) In FIG. 3c, an alternative embodiment is shown, in which the upper conducting layer, including several sub-arrays, is formed as a continuous metal plate. This metal plate preferably has a thickness sufficient to allow grooves to be formed in it. Hereby, elongate corrugations having similar effects as the slots in FIG. 3b can instead be realized as elongate grooves extending between the unit cells.

(34) Either or both of the waveguide layers between the first and second conducting layer and the second and third conducting layer, respectively, may be formed as gap waveguides as discussed in the foregoing, without any substrate between the two metal ground planes, and with protruding elements extending between the two conducting layers. Then, the conventional via holes, as discussed in [13], will instead be metal pins or the like, which are monolithically formed between the two metal plates, within each unit cell of the whole antenna array.

(35) In FIG. 4, a top view of an example of the texture in the lower gap waveguide layer of the antenna in FIG. 3 is illustrated. This shows a distribution network 41 in ridge gap waveguide technology in accordance with [13], for waves in the gap between the two lower conducting layers. The ridge structure 45 forms a branched so-called corporate distribution network from one input port 42 to four output ports 43. The distribution network may be much larger than this with many more output ports to feed a larger array. In contrast to the antenna of [13], the via-holes arranged to provide a stopping texture are here formed as protruding elements 44 monolithically formed in the above-described manner. Hereby, there is no or partly no substrate and the via holes are replaced by the protruding elements/pins. Hereby, the ridge becomes a solid ridge such as shown in the ridge gap waveguides in e.g. [4]. Alternatively, the ridge may be drawn as a thin metal strip, a microstrip, supported by pins.

(36) With reference to FIG. 5, another embodiment of an antenna will now be discussed. This antenna comprises three layers, illustrated separately in an exploded view. The upper layer 51 (left) comprises an array of radiating horn elements 52 formed therein. The middle layer 53 is arranged at a distance from the upper layer 51, so that a gap towards the upper layer is provided. This middle layer 53 comprises a microstrip distribution network 54 arranged on a substrate having no ground plane. The waves propagate in the air gap between the upper and middle layer, and above the microstrip paths. A lower layer 55 (right) is arranged beneath and in contact with the middle layer 53. This lower layer comprises an array of protruding elements 56, such as metal pins, preferably monolithically manufactured, on a conducting layer 57. The conducting layer may be formed as a separate metal layer or as a metal surface of an upper ground plane of a PCB. The protruding elements are integrally connected to the conducting layer in such a way that metal contact between the bases of all protruding elements is ensured. Thus, this antenna functionally and structurally resembles the antenna disclosed in [12], said document hereby being incorporated in its entirety by reference. However, whereas this known antenna was realized by milling to form an inverted microstrip gap waveguide network, the present example comprises protruding elements formed in the way discussed in the following, which entails many advantages.

(37) FIG. 6 provides a close-up view of an input port of a microstrip-ridge gap waveguide on a lower layer showing a transition to a rectangular waveguide through a slot 63 in the ground plane. In this embodiment, there is no dielectric substrate present, and the conventionally used via holes are replaced by protruding elements 61, preferably monolithically connected to the conducting layers in such a way that there is electric contact between all the protruding elements 61. Thus, a microstrip gap waveguide is provided. The upper metal surface is removed for clarity. The microstrip supported by pins, i.e. the microstrip-ridge, may also be replaced by a solid ridge in the same way as discussed above in connection with FIG. 4.

(38) FIG. 7 illustrates an exemplary embodiment of a gap waveguide filter, structurally and functionally similar to the one disclosed in [14], said document hereby being incorporated in its entirety by reference. However, contrary to the waveguide filter disclosed in this document, the protruding elements 71 arranged on the conducting layers (here all being arranged on the lower conducting layer for simplicity) are arranged in the way to be discussed in the following. An upper conducting layer 73 is arranged above the protruding elements, in the same way as disclosed in [12]. Thus, this then becomes a groove gap waveguide filter.

(39) FIG. 8 provides another example of a waveguide filter, which may also be referred to as gap-waveguide-packaged microstrip filter. This filter functionally and structurally resembles the filter disclosed in [15], said document hereby being incorporated in its entirety by reference. However, contrary to the filter disclosed in [15], the filter here is packaged by surfaces having protruding elements, in which protruding elements 81 provided on conducting layers 82 are realized in the above-described way. Two alternative lids, comprising different number and arrangement of the protruding elements 81 are illustrated. Again, the protruding elements are here shown as arranged only on one of the surfaces, for simplicity.

(40) With reference to FIG. 9, an embodiment providing a package for integrated circuit(s) will be discussed. In this example, the integrated circuits are MMIC amplifier modules 91, arranged in a chain configuration on a lower plate 92, here realized as a PCB having an upper main substrate, provided with a lower ground plane 93. A lid is provided, formed by a conducting layer 95, e.g. made of aluminum or any other suitable metal. The lid may be connected to the lower plate 92 by means of a surrounding frame or the like.

(41) The lid as well as the PCB are further provided with protruding elements 96, 97 (in the FIG. 9 shown only on the lid, for simplicity). This is functionally and structurally similar to the package disclosed in [16], said document hereby being incorporated in its entirety by reference. The protruding elements may be of different heights, so that the elements overlying the integrated circuits 91 are of a lower height, and the elements at other areas laterally outside the integrated circuits are of a greater height. Hereby, holes are formed in the surface presented by the protruding elements, in which the integrated circuits are inserted. This packaging is consequently an example of using the gap waveguide as discussed above as a packaging technology, according to the present invention.

(42) All the protruding elements as discussed above, or at least all protruding elements in certain parts or areas of the microwave device, are further arranged and distributed on both the conducting layers, and some preferred realizations of this will now be discussed in more detail.

(43) Hereby, each conducting layer comprises a thereto attached and fixedly connected, and preferably monolithically integrated, set of protruding elements. These two sets are complementary to each other, so that the two sets together form the desired periodical or quasi-periodical pattern forming the stop band, thereby in combination forming the texture to stop wave propagation in a frequency band of operation in other directions than along intended waveguiding paths.

(44) In a first line of embodiment, illustrated in FIGS. 10 and 11, the sets of complementary protruding elements are each formed in said pattern, i.e. each conducting layer comprises a set of protruding elements arranged in the intended periodical or quasi-periodical pattern. However, the protruding elements of each set are each much too low in height to form the stop band. Instead, the protruding elements of the two sets are aligned and arranged overlying each other, so that the protruding elements of the two sets in combination form the required full length of the protruding elements to form the texture.

(45) In the embodiment of FIG. 10, the first conducting layer 101 is provided with a first set of protruding elements 103, and the second conducting layer 102 is provided with a second set of protruding elements 104. At the interface 105 between the protruding elements 103 and 104, a narrow gap may be provided. However, alternatively the protruding elements may be arranged in mechanical and possibly even electrical contact with each other. There will normally not be any need for fixating the protruding elements together. However, should this be desirous, the abutting ends of some or all of the protruding elements may be connected to each other, e.g. by means of soldering, adhesion or the like.

(46) It is normally preferred that the protruding elements of the two sets are all of the same height, so that each protruding element has half the total length of the protruding elements necessary to form the desired stop band. However, sometimes or at certain areas it may be advantageous to use different heights in the two sets. For example, one set may have protruding elements of a first height, and the other set may have protruding elements of a different, second height. However, the height of the protruding elements may also vary within each set. Such an embodiment is illustrated schematically in FIG. 11.

(47) In an alternative line of embodiments, the complementary protruding elements of each set all have the required length of to form the desired stop band, but each set only comprises a subset of the elements forming the intended pattern, so that the complementary sets of protruding elements in combination form the intended pattern.

(48) Such an embodiment is illustrated in FIG. 12. Here, a first set of protruding elements 103 is arranged on the upper conducting layer 101, and a second set of protruding elements 104 is arranged on the lower conducting surface. At the interface 105 between the protruding elements 103 and 104 and the overlying/underlying conducting layer to which they are not attached, a narrow gap may be provided. However, alternatively the protruding elements may be arranged in mechanical and possibly even electrical contact with the other conducting layer. There will normally not be any need for fixating the protruding elements to both conducting layers. However, should this be desirous, the ends of some or all of the protruding elements may be connected to the other conducting layer, e.g. by means of soldering, adhesion or the like.

(49) The protruding elements of the two sets are preferably offset in a complementary arrangement, so that protruding elements or rows of protruding elements of the sets are interleaved between each other. However, other ways of dividing the protruding elements in two complementary subsets are also feasible.

(50) In FIG. 13, an embodiment is schematically illustrated. Here, the protruding elements 104 of the lower conducting surface 102 are arranged in rows, and the protruding elements of each row are offset or staggered in relation to adjacent rows. The complementary subset of protruding elements 103 (illustrated in dashed lines) of the other conducting layer fills the gaps between the protruding elements 104.

(51) In FIG. 14, an alternative way of separating the protruding elements between the subsets is provided. Here, the each subset contains full rows of protruding elements, but every other row is arranged in the second subset instead of the first subset, so that the rows are interleaved between each other. Thus, the distance between the rows is double the distance between neighboring protruding elements within the rows. Thus, here the distance between each protruding element in each set is greatly increased in one direction, viz. the direction transversal to the rows, but remains the same in one direction, viz. the direction along the rows. Increased separation between the protruding elements dramatically lowers the manufacturing costs.

(52) In experimental simulations, the Ku and V band have been studied, and the obtained stop band been analyzed. The simulations were made on: a) A conventional gap waveguide, where all the pins (protruding elements) are arranged on the same conducting layer, and where a small gap is provided between the ends of the pins and the overlying second conducting layer. These waveguides are below referred to as Conventional pin. b) A gap waveguide in accordance with the FIG. 10 embodiment discussed above. These waveguides are below referred to as Middle gap pin. c) A gap waveguide in accordance with the FIGS. 12 and 13 embodiment discussed above. These waveguides are below referred to as Staggered pin.

(53) When evaluating the stop band for Ku and V band, respectively, the total width and height of the pins were all the same in the embodiments, and the period of the pins were also the same. More specifically, when evaluating the Ku band the width was 3 mm, the height 5 mm and the period 6.5 mm. Simulations were made with a relatively large gap of 1 mm (Conventional gap), a relatively narrow gap of 0.13 mm (Reduced gap), and a narrow gap of 0.13 mm filled with dielectric (Dielectric filled reduced gap), respectively. When evaluating the V band the width was 0.79 mm, the height 1.31 mm and the period 1.71 mm. Simulations were made with a relatively large gap of 0.26 mm (Conventional gap), a relatively narrow gap of 0.13 mm (Reduced gap), and a narrow gap of 0.13 mm filled with dielectric (Dielectric filled reduced gap), respectively.

(54) The results of these experimental simulations are as presented in table 1 and table 2 below.

(55) TABLE-US-00001 TABLE 1 Comparison at Ku band Stop bandwidth (relative bandwidth: f.sub.max/f.sub.min) Conventional pin Middle gap pin Staggered pin Conventional gap 9.3-22 GHz 11-25 GHz 12-22 GHz (2.4) (2.3) (1.8) Reduced gap 5.2-28 GHz 5.6-29 GHz 6.3-28 (5.4) (5.2) (4.4) Dielectric filled 3.2-25 GHz 3.3-27 GHz n/a reduced gap (7.8) (8.2)

(56) TABLE-US-00002 TABLE 2 Comparison at V band Stop bandwidth (relative bandwidth: f.sub.max/f.sub.min) Conventional pin Middle gap pin Staggered pin Conventional gap 35-85 GHz 43-96 GHz 46-84 GHz (2.4) (2.2) (1.8) Reduced gap 30-95 GHz 35-104 GHz 38-94 GHz (3.2) (3.0) (2.5) Dielectric filled 20-85 GHz 22-89 GHz n/a reduced gap (4.3) (4.0)

(57) From this it can be deduced that the provision of gaps at different sides, as in the Staggered pin embodiment, or in the middle, as in the Middle gap pin embodiment, works very well, and provides large and efficient stop bands. It can also be deduced that this works almost as good as conventional gap waveguides, in particular when narrow gaps are used.

(58) The above-discussed exemplary embodiments, such as other realizations of microwave devices in accordance with the invention, can be manufactured and produced in various ways. For example, it is possible to use conventional manufacturing techniques, such as drilling, milling and the like.

(59) It is also possible to use electrical discharge machining (EDM), which may also be referred to as spark machining, spark eroding or die sinking. Hereby, the desired shape is obtained using electrical discharges (sparks), and material is removed from the work piece by a series of rapidly recurring current discharges between two electrodes, separated by a dielectric liquid.

(60) However, it is also possible to use a special technique called die forming (which may also be referred to as coining or multilayer die forming). An equipment and method for manufacturing for such manufacturing of monolithically formed microwave devices and RF parts will next be described in further detail, with reference to FIGS. 15-22.

(61) With reference to FIG. 15, a first embodiment of an apparatus for producing an RF part comprises a die comprising a die layer 114 being provided with a plurality of recessions forming the negative of the protruding elements of the RF part. An example of such a die layer 114 is illustrated in FIG. 16. This die layer 114 comprises a grid array of evenly dispersed through-holes, to form a corresponding grid array of protruding elements. The recessions are here of a rectangular shape, but other shapes, such as circular, elliptical, hexagonal or the like, may also be used. Further, the recessions need not have a uniform cross-section over the height of the die layer. The recessions may be cylindrical, but may also be conical, or assume other shapes having varying diameters.

(62) The die further comprises a collar 113 arranged around said at least one die layer. The collar and die layer are preferably dimensioned to that the die layer has a close fit with the interior of the collar. In FIG. 17, the die layer arranged within the collar is illustrated.

(63) The die further comprises a base plate 115 on which the die layer and the collar are arranged. In case the die comprises through-holes, the base plate will form the bottom of the cavities provided by the through-holes.

(64) A formable piece 112 of material is further arranged within the collar, to be depressed onto the die layer 114. Pressure may be applied directly to the formable piece of material, but preferably, a stamp 111 is arranged on top of the formable piece of material, in order to distribute the pressure evenly. The stamp is preferably also arranged to be insertable into the collar, and having a close fit with the interior of the collar. In FIG. 18, the stamp 111 arranged on top of the formable piece of material in the collar 113 is illustrated in an assembled disposition.

(65) The above-discussed arrangement may be arranged in a conventional pressing arrangement, such as a mechanical or hydraulic press, to apply a pressure on the stamp and the base plate of the die, thereby compressing the formable piece of material to conform with the recessions of the at least one die layer.

(66) The multilayer die press or coining arrangement discussed above can provide protruding elements/pins, ridges and other protruding structures in the formable piece of material having the same height. Through-holes are obtainable e.g. by means of drilling. In case non-through going recessions are used in the die layer, this arrangement may also be used to produce such protruding structures having varying heights.

(67) However, in order to produce protruding structures having varying heights, it is also possible to use several die layers, each having through-holes. Such an embodiment will now be discussed with reference to FIGS. 19-22.

(68) With reference to the exploded view of FIG. 19, this apparatus comprises the same layers/components as in the previously discussed embodiment. However, here two separate die layers 114a and 114b are provided. Examples of such die layers are illustrated in FIGS. 20 and 21. The die layer 114a (shown in FIG. 20) being arranged closest to the formable piece of material 112 is provided with a plurality of through-holes. The other die layer 114b (shown in FIG. 21), being farther from the formable piece of material 112 comprises fewer recessions. The recessions of the second die layer 114b are preferably correlated with corresponding recessions in the first die layer 114a. Hereby, some recessions of the first die layer will end at the encounter with the second die layer, to form short protruding elements, whereas some will extend also within the second die layer, to form high protruding elements. Hereby, by adequate formation of the die layer, it is relatively simple to produce protruding element of various heights,

(69) An example of an RF part having protruding elements of varying heights, in accordance with the embodiments of the die layers illustrated in FIGS. 20 and 21, is shown in FIG. 22.

(70) In the foregoing, the stamp 111, collar 113, die layer(s) 114 and base plate 115 are exemplified as separate elements, being detachably arranged on top of each other. However, these elements may also be permanently or detachably connected to each other, or formed as integrated units, in various combinations. For example, the base plate 115 and collar 113 may be provided as a combined unit, the die layer may be connected to the collar and/or the base plate, etc.

(71) The pressing in which pressure is applied to form the formable material in conformity with the die layer may be performed at room temperature. However, in order to facilitate the formation, especially when relatively hard materials are used, heat may also be applied to the formable material. For example if aluminum is used as the formable material, the material may be heated to a few hundred degrees C., or even up to 500 deg. C. If tin is used, the material may be heated to 100-150 deg. C. By applying heat, the forming can be faster, and less pressure is needed.

(72) To facilitate removal of the formable material from the die/die layer after the forming, the recessions can be made slightly conical or the like. It is also possible to apply heat or cold to the die and formable material. Since different materials have different coefficients of thermal expansion, the die and formable material will contract and expand differently when cold and or heat is applied. For example, tin has a much lower coefficient of thermal expansion than steel, so if the die is made of steel and the formable material of tin, removal will be much facilitated by cooling. Cooling may e.g. be made by dipping or in other way exposing the die and/or formable material to liquid nitrogen.

(73) Some examples of microwave devices and RF parts have been discussed in the foregoing. However, many other types of e.g. per se known RF parts and microwave devices can be produced by using a pattern of protruding elements made by complementary subsets arranged on the two conductive layers, as discussed above.

(74) For example, it is also possible to produce RF parts to form flat array antennas with this technology. For example, antennas structurally and functionally resembling the antenna disclosed in [12] and/or the antenna discussed in [13] can be cost-effectively produced in this way, said documents hereby being incorporated in its entirety by reference. One or several of the waveguide layers of such an antenna may be made as a waveguide as discussed in the foregoing, without any substrate between the two metal ground planes, and with protruding fingers/elements extending between the two conducting layers, formed by waveguide elements with bases attached to the substrate. Then, the conventional via holes, as discussed in [13], will instead be fingers, such as metal pins or the like, forming a waveguide cavity between the two metal plates, within each unit cell of the whole antenna array.

(75) The RF part may also be a gap waveguide filter, structurally and functionally similar to the one disclosed in [14], said document hereby being incorporated in its entirety by reference. However, contrary to the waveguide filter disclosed in this document, the protruding fingers/elements are now then arranged on a lower conducting layer by use of the above-discussed waveguide elements. Another example of a waveguide filter producible in this way is the filter disclosed in [15], said document hereby being incorporated in its entirety by reference.

(76) The RF part may also be used to form a connection to and from an integrated circuit, and in particular MMICs, such as MMIC amplifier modules.

(77) Further, grids of protruding fingers may also be provided by waveguide elements of the general type discussed above, for use e.g. for packaging. Such grids may e.g. be formed by providing waveguide elements having one, two or more rows of protruding fingers side-by-side on a substrate.

(78) The invention has now been described with reference to specific embodiments. However, several variations of the technology of the waveguide and RF packaging in the antenna system are feasible. For example, a multitude of different waveguide elements useable to form various types of waveguides and other RF parts are feasible, either for use as standardized elements, or for dedicated purposes or even being customized for certain uses and applications. Further, even though assembly by means of pick-and-place equipment is preferred, other types of surface mount technology placement may also be used, and the waveguide elements may also be assembled in other ways. Further, the here disclosed realization of protruding elements can be used in many other antenna systems and apparatuses in which conventional gap waveguides have been used or could be contemplated. 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. Further, a single unit may perform the functions of several means recited in the claims.

REFERENCES

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