Microwave or millimeter wave RF part realized by die-forming

Abstract

A method and apparatus for producing an RF part of an antenna system is disclosed, as well as thereby producible RF parts. The RF part has at least one surface provided with a plurality of protruding elements. In particular, the RF part may be a gap waveguide. The protruding elements are monolithically formed and fixed on a conducting layer, and all protruding elements are connected electrically to each other at their bases via the conductive layer. The RF part is produced by providing a die having a plurality of recessions forming the negative of the protruding elements of the RF part. The die may be a multilayer die, having several layers, at least some having through-holes to form the recessions. A formable piece of material is arranged on the die, and pressure is applied, thereby compressing the formable piece of material to conform with the recessions of the die.

Claims

1. A radio frequency (RF) part of an antenna system, comprising at least two conducting layers arranged with a gap there between, and a set of periodically or quasi-periodically arranged protruding elements 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 said protruding elements are monolithically formed on said at least one conducting layer, whereby each protruding element is monolithically fixed to the at least one conducting layer, all protruding elements being connected electrically to each other at their bases via said at least one conductive layer on which they are fixedly connected, further comprising at least one integrated circuit module arranged between said at least two conducting layers, the texture to stop wave propagation thereby functioning as a means of removing resonances within a package for said at least one integrated circuit module.

2. The RF part of claim 1, wherein the protruding elements being monolithically formed on said at least one conducting layer are formed by coining.

3. The RF part of claim 1, wherein the RF part is a waveguide, and wherein the protruding elements are further in contact with also another conducting layer of the at least two conducting layers, and wherein the protruding elements are arranged to at least partly surround a cavity between said at least two conducting layers, said cavity thereby functioning as the waveguide.

4. The RF part of claim 1, wherein the RF part is a gap waveguide, and further comprising at least one groove, ridge or microstrip line along which waves are to propagate.

5. The RF part of claim 1, wherein the RF part is a gap waveguide, and further comprising at least one ridge along which waves are to propagate, said at least one ridge being arranged on the same conducting layer as the protruding elements, and also being monolithically formed on said at least one conducting layer.

6. The RF part of claim 1, wherein each of the protruding elements have maximum cross-sectional dimensions of less than half a wavelength in air at the operating frequency, and/or wherein each of 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.

7. The RF part of claim 1, wherein the protruding elements forming said texture to stop wave propagation are only in contact with one of the at least two conducting layers.

8. The RF part of claim 1, wherein one of the at least two conducting layers is provided with at least one opening, said at least one opening allowing radiation to be transmitted to and/or received from said RF part.

9. The RF part of claim 1, wherein one of the at least two conducting layers is a conducting layer not being provided with said protruding elements, wherein the at least one integrated circuit module is arranged on the conducting layer not being provided with said protruding elements, and wherein protruding elements overlying the at least one integrated circuit module are shorter than protruding elements not overlying said at least one integrated circuit module.

10. A flat array antenna comprising a corporate distribution network realized by the RF part in accordance with claim 1.

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) FIGS. 3a, 3b, and 3c show 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 usable 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) FIG. 10 is a schematic exploded view of a manufacturing equipment in accordance with one embodiment of the present invention;

(11) FIG. 11 is a top view of the die forming layer in FIG. 10;

(12) FIG. 12 is a perspective view of the assembled die of FIG. 10;

(13) FIG. 13 is a perspective view of the manufacturing equipment of FIG. 10 in an assembled disposition;

(14) FIG. 14 is a schematic exploded view of a manufacturing equipment in accordance with another embodiment of the present invention;

(15) FIGS. 15 and 16 are top views illustrating the two die forming layers in the embodiment of FIG. 14; and

(16) FIG. 17 is a perspective view showing an RF part producible by the manufacturing equipment of FIG. 14.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

(17) 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 e 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.

(18) 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.

(19) 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 metallized via holes are replaced with a monolithic part comprising a conductive layer and protruding elements 3 extending from, and fixedly monolithically integrated with this first conducting layer. The second conducting layer 2 rest on the protruding elements 3, and is also connected to these, e.g. by means of soldering. The protruding elements 3 are made of conducting material, such as metal. They can also be made of metallized plastics or ceramics.

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

(21) 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.

(22) 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 are monolithically connected to one of the conducting 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 a X-shaped radiating slot opening 5 is provided.

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

(24) With reference to FIGS. 3a, 3b, and 3c, 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.

(25) 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.

(26) 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.

(27) 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.

(28) 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 monolithic 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.

(29) 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 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. The ridge structure may be formed in the same way, to be monolithically arranged on the conductive layer. 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.

(30) 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, monolithically manufactured in the above-discussed manner 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.

(31) 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 provides a distribution network realized as a monolithically formed gap waveguide, which entails many advantages, as has been discussed thoroughly in the foregoing sections of this application.

(32) 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, monolithically connected to a conducting layer 62 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.

(33) 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 a lower conducting layer 72 are here formed by monolithically and integrally formed protruding elements in the above-discussed fashion. 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.

(34) 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 a surface having protruding elements, in which protruding elements 81 provided on a conducting layer 82 are realized in the above-described way. Two alternative lids, comprising different number and arrangement of the protruding elements 81 are illustrated.

(35) 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.

(36) The lid is further provided with protruding elements 96, 97, protruding towards the lower plate 92. 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 are preferably of different heights, so that the elements overlying the integrated circuits 91 are of a lower height, and the elements overlying 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. The protruding elements are in electric contact with the upper layer 95, and electrically connected to each other by this layer. However, the protruding elements are preferably not in contact neither with the lower plate 92, nor the integrated circuit modules 91.

(37) Here, and contrary to the disclosure in [16], the protruding elements are formed on the upper layer 95 monolithically. This packaging is consequently an example of using the gap waveguide as discussed above as a packaging technology, according to the present invention.

(38) An equipment and method for manufacturing of the monolithically formed RF part will next be described in further detail, with reference to FIGS. 10-17.

(39) With reference to FIG. 10, a first embodiment of an apparatus for producing an RF part comprises a die comprising a die layer 104 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 104 is illustrated in FIG. 11. This die layer 104 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.

(40) The die further comprises a collar 103 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. 12, the die layer arranged within the collar is illustrated.

(41) The die further comprises a base plate 105 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.

(42) A formable piece 102 of material is further arranged within the collar, to be depressed onto the die layer 104. Pressure may be applied directly to the formable piece of material, but preferably, a stamp 101 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. 13, the stamp 101 arranged on top of the formable piece of material in the collar 103 is illustrated in an assembled disposition.

(43) 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.

(44) 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.

(45) 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. 14-17.

(46) With reference to the exploded view of FIG. 14, this apparatus comprises the same layers/components as in the previously discussed embodiment. However, here two separate die layers 104a and 104b are provided. Examples of such die layers are illustrated in FIGS. 15 and 16. The die layer 104a (shown in FIG. 15) being arranged closest to the formable piece of material 102 is provided with a plurality of through-holes. The other die layer 104b (shown in FIG. 16), being farther from the formable piece of material 102 comprises fewer recessions. The recessions of the second die layer 104b are preferably correlated with corresponding recessions in the first die layer 104a. 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,

(47) An example of an RF part having protruding elements of varying heights, in accordance with the embodiments of the die layers illustrated in FIGS. 15 and 16, is shown in FIG. 17.

(48) In the foregoing, the stamp 101, collar 103, die layer(s) 104 and base plate 105 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 105 and collar 103 may be provided as a combined unit, the die layer may be connected to the collar and/or the base plate, etc.

(49) 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.

(50) 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.

(51) 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, 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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