Waffle Iron Filter Arrangement For High-Frequency Signals

Abstract

A filter arrangement for high frequency signals, HF signals, is described. The filter arrangement includes a housing in which there is a cavity that extends in the longitudinal direction of the housing. The waffle-iron arrangement is arranged in the cavity and includes a carrier plate having a plurality of recesses, wherein there is an electrically conductive material arranged in at least some of the recesses, wherein the electrically conductive material in each case forms a pin in the at least some recesses. This structure makes it possible to provide a filter arrangement for very high frequencies, because the structure allows the carrier plate and the pins arranged therein to be provided with very small geometrical dimensions.

Claims

1. A filter arrangement for high-frequency signals (HF-signals) comprising: a housing having a cavity extending in a longitudinal direction of the housing; a waffle-iron arrangement arranged in the cavity; wherein the waffle-iron arrangement comprises: a carrier plate having a plurality of recesses; and an electrically conductive material arranged in at least some of the plurality of recesses, wherein the electrically conductive material in each case forms a pin in the at least some recesses; wherein the cavity of the housing includes two transformer portions and a waffle portion, wherein the waffle portion is arranged between the two transformer portions; wherein the carrier plate is arranged in the waffle portion; wherein the carrier plate includes a material that is permeable to HF signals.

2. The filter arrangement as claimed in claim 1, wherein the recesses in the carrier plate extend over an entire plate thickness of the carrier plate; wherein the pin completely fills the respective recess.

3. The filter arrangement as claimed in claim 1, wherein the pins in the recesses contain an electrically conductive epoxy resin.

4. The filter arrangement as claimed in claim 1, wherein at least some of the recesses in which the pins are arranged have a circular cross-section.

5. The filter arrangement as claimed in claim 1, wherein a surface of the carrier plate from which the recesses extend into the carrier plate has a coating; wherein the coating comprises an electrically conductive material.

6. The filter arrangement as claimed in claim 1, wherein the waffle-iron arrangement is connected to the housing in such a way that the pins in the recesses are galvanically connected to the housing.

7. The filter arrangement as claimed in claim 1, wherein the waffle-iron arrangement is bonded to the housing by an adhesive layer comprising an electrically conductive adhesive.

8. The filter arrangement as claimed in claim 1, wherein the carrier plate is a printed circuit board that is permeable to HF signals.

9. The filter arrangement as claimed in claim 1, further comprising a second waffle-iron arrangement connected to the housing; wherein the second waffle-iron arrangement is opposite the first waffle-iron arrangement and is spaced from the first waffle-iron arrangement by a predefined distance.

10. The filter arrangement as claimed in claim 9, wherein the pins of the waffle-iron arrangement extend in a direction of the second waffle-iron arrangement.

11. The filter arrangement as claimed in claim 1, wherein the housing is an integral housing or is composed of two half-shells.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0049] In the following, exemplary embodiments are described in more detail on the basis of the appended drawings. The representations are schematic and not to scale. Elements that are the same or similar are denoted by the same reference signs. In the drawings:

[0050] FIG. 1 shows a schematic representation of a part of a waffle-iron filter.

[0051] FIG. 2 shows a schematic representation of a half-shell of a filter arrangement according to an exemplary embodiment.

[0052] FIG. 3 shows a schematic representation of the cavity and two waffle-iron arrangements of a filter arrangement according to a further exemplary embodiment.

[0053] FIG. 4 shows a schematic representation of two waffle-iron arrangements of a filter arrangement according to a further exemplary embodiment.

[0054] FIG. 5 shows a schematic representation of two half-shells of a filter arrangement according to a further exemplary embodiment.

[0055] FIG. 6 shows a schematic representation of the pins and the coating of a waffle-iron arrangement for a filter arrangement according to a further exemplary embodiment.

[0056] FIG. 7 shows a schematic representation of a half-shell with adhesive layer and waffle-iron arrangement for a filter arrangement according to a further exemplary embodiment.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

[0057] Shown schematically in FIG. 1 is the typical structure of a half-shell 20 of a filter arrangement 10 in a waffle-iron structure. Usually, a filter arrangement is composed of two such half-shells 20 joined together at the surface that faces toward the viewer, such that a cavity (or two such cavities 18, as shown in FIG. 1, extending from bottom to top) and a waffle-iron structure is are realized between the half-shells.

[0058] The half-shell 20 has a first connector 11 (the end at the top in the representation) and a second connector 12 (the end at the bottom in the representation). An external waveguide is connected to these connectors 11, 12, but is not shown in FIG. 1. The connectors 11, 12 each have a flange 13 to which a respective waveguide may be connected.

[0059] Starting from the first connector 11 and the second connector 12, a cavity (or, also, two cavities) extends (extend) toward the waffle portion 15, the cavity 18 forming a transformer portion 14 on both sides of the waffle portion 15. The waffle portion 15 has a multiplicity of teeth 16. The dimensions of the teeth 16 decrease as the frequency of the signals to be processed increases. In the example of FIG. 1, the teeth and the entire structure of the half-shell are milled into a metallic block. However, as the size of the teeth 16 decreases, greater demands are placed on the production of the tooth structure in the waffle portion 15, because at very high frequencies the teeth may have cross-sections of a few tenths or hundredths of a square millimeter.

[0060] Arranged along the half-shell 20 are a number of recesses 17 that enable the two half-shells to be assembled, for example by the insertion and fastening of screws in these recesses 17.

[0061] The transformer portion 14 has a cross-section that tapers from the ends toward the waffle portion 15.

[0062] Given this general description of a waffle-iron filter structure of FIG. 1, alternative structures of a filter arrangement are now described with reference to FIGS. 2 to 7.

[0063] FIG. 2 shows a schematic representation of a half-shell 20. There are two fasteners 19 arranged at each of the ends, on the left and right, for the purpose of connecting an external waveguide (not shown) to the filter arrangement. In this example, the fastenings are internally threaded borings. However, it is of course possible to select other types of fastening, for example clamp connections or other suitable types of connection.

[0064] The cavity 18 extends centrally in the half-shell from left to right, starting from the first connector 11 and toward the second connector 12, initially forming a transformer portion 14, this transformer portion leading into the waffle portion 15, which is again followed by a transformer portion.

[0065] The transformer portions 14 are designed in such a way that their cross-section reduces from the respective end face to the waffle portion 15. In this case, this is achieved in that the depth of the cavity decreases nearer to the waffle portion 15. Arranged for this purpose in the example of FIG. 2 are a plurality of steps, the height of which increases the closer they are arranged to the wafer portion 15. This change in the cross-section already filters out some signal components of the signal.

[0066] A waffle-iron arrangement 100 is arranged in the waffle portion 15 and is electrically conductively connected to the half-shell, namely on the underside of the waffle-iron arrangement 100.

[0067] FIG. 3 shows a detailed representation of the cavity 18 (represented here as a negative without the surrounding half-shells) and of two waffle-iron arrangements 100, 200. The cavities 18 located on both sides of the waffle-iron arrangements 100, 200 show a tapering cross-section starting from the first connector 11, or the second connector 12, in the direction of the waffle-iron arrangements 100, 200. The transformer portions 14 of the cavity 18 may be of the same design in respect of their dimensions and shape.

[0068] Between the transformer portions 14, the waffle portion 15 is arranged with two waffle-iron arrangements 100, 200. The waffle-iron arrangements are each connected in an electrically conductive manner to a half-shell and are spaced apart from each other.

[0069] FIG. 4 shows a detailed representation of the two waffle-iron arrangements 100, 200 from FIG. 3. Each waffle-iron arrangement 100, 200 has a carrier plate 102, 202 having a corresponding plate thickness 120, 220. It can be seen that the two waffle-iron arrangements 100, 200 do not touch, but are spaced apart by a predefined distance, such that the cavity 18 extends between them. The first waffle-iron arrangement 100 is described here, the second waffle-iron arrangement being of a similar structure.

[0070] The waffle arrangement 100 comprises a carrier plate 102, which may be, for example, a printed circuit board (PCB). The carrier plate may have side lengths of a few millimeters. A plurality of recesses 115 are arranged in the carrier plate 102, extending over the entire thickness 120 of the plate from one surface 105 to the opposite surface at the cavity 18. An electrically conductive material is inserted into the recesses 115 in order to form the teeth of the waffle-iron filter.

[0071] The surface 105 of the carrier plate 102 is the face that is fastened to the half-shell. In this example, the surface 105 has a metallic coating, the coating 110 being represented as hatching to reveal the structure of the carrier plate 102 with the recesses 115. The coating 110 thus constitutes a metallic plane on the surface 105 of the carrier plate 102. The coating 110 is galvanically connected to the teeth in the recesses 115.

[0072] It is to be noted that the number and arrangement of the recesses in the representation of FIG. 4 has been selected merely by way of example. Both the number and the arrangement of the recesses can be freely selected in dependence on the required filter properties of the filter arrangement.

[0073] FIG. 5 shows a schematic representation of the first half-shell 20 and the second half-shell 25 when the filter arrangement is in a non-assembled state. The first waffle-iron arrangement 100 is arranged centrally in the first half-shell 20, and the second waffle-iron arrangement 200 is arranged centrally in the second half-shell 25 is, such that the two waffle-iron arrangements are opposite each other when the second half-shell 25 is assembled with the first half-shell 20. The cavity 18 extends along the half-shells 20, 25 in the longitudinal direction 40.

[0074] FIG. 6 shows a schematic representation of the metallic coating 100 and of the pins 112 of the waffle-iron arrangement 100. This is the negative of the carrier plate 102, although for illustrative and simplification purposes only four pins 112 are shown in FIG. 6. The coating 110 forms a continuous planar element along the surface 105. The pins 112 adjoin the coating and extend perpendicularly with respect to it. Accordingly, the recesses 115 also extend perpendicularly with respect to the surface 105.

[0075] Shown schematically in FIG. 7 is the connection between the half-shell 20, the adhesive layer 30 and the waffle-iron arrangement 100. The rest of the structure of the half-shell has not been shown here. In any case, the waffle-iron arrangement 100 is bonded in an electrically conductive manner to the half-shell 20 by means of an adhesive layer 30, namely at the point that forms the waffle portion 15 in FIG. 2.

[0076] The filter arrangement 10 as described herein enables the waffle-iron filter structure to be used for high frequencies at 20 GHz and above. Waffle-iron filters used as low pass filters have advantageous properties because they have a very high return frequency at which they again become permeable to high-frequency signals. However, a disadvantage for conventional waffle-iron filters as shown in FIG. 1 is that they cannot easily be manufactured for high frequencies because the tooth structure cannot be manufactured in the required geometries for high frequencies. With the structure described here, however, it is easy to offer a waffle-iron filter even for frequencies in the HF range, because this structure affords a particularly precise and miniaturized shape of the waffle-iron arrangement.

[0077] In addition, it is to be noted that “comprising” or “having” does not exclude other elements or steps, and “one” or “a/an” does not exclude a multiplicity. Further, it is to be noted that features or steps that have been described with reference to any of the above exemplary embodiments may also be used in combination with other features or steps of other exemplary embodiments described above. Reference signs in the claims are not to be regarded as a limitation.

LIST OF REFERENCES

[0078] 10 filter arrangement, waffle-iron filter [0079] 11 first connector [0080] 12 second connector [0081] 13 flange [0082] 14 transformer portion [0083] 15 waffle portion [0084] 16 tooth [0085] 17 recess [0086] 18 cavity [0087] 19 fastening [0088] 20 first half-shell [0089] 25 second half-shell [0090] 30 adhesive layer [0091] 40 longitudinal direction [0092] 100 waffle-iron arrangement [0093] 102 carrier plate [0094] 105 surface [0095] 110 coating [0096] 112 pin [0097] 115 recess [0098] 120 plate thickness [0099] 200 waffle-iron arrangement [0100] 202 carrier plate [0101] 220 plate thickness