SE543085C2

SE543085C2 - Sheet metal rf cavity filter

Info

Publication number: SE543085C2
Application number: SE1950508A
Authority: SE
Inventors: Markku Tiihonen; Marko Määttä; Mattias Aquilon; Pasi Tiitto
Original assignee: Microdata Telecom Innovation Stockholm Ab
Priority date: 2019-04-26
Filing date: 2019-04-26
Publication date: 2020-10-06
Also published as: SE1950508A1; CN212303856U

Abstract

There is provided a sheet metal RF cavity filter (100) comprising: a housing (110) having a bottom (B), four side walls (W1, W2, W3, W4), and a cover (T); and a plurality of resonators (120) arranged within the housing (110), wherein at least some of the resonators (120) comprise integrated capacitive coupling tuning members (130) arranged for tuning a capacitive coupling between adjacent resonators (120). The sheet metal RF cavity filter (100) is characterized in that the resonators (120) extend from the bottom (B) of the housing towards the top (T) of the housing, so that they extend substantially in parallel with the side walls (W1, W2, W3, W4) of the housing (110); and that the resonators (120) that comprise integrated capacitive coupling tuning members (130) each have an upper section (124) that extends out from a lower section (122) in a direction towards at least one adjacent resonator (120), wherein at least one capacitive coupling tuning member (130) extends downwards from the upper section (124) towards the bottom (B) of the housing (110), substantially in parallel with the extension of the lower section (122) of the resonator (120) .

Description

l0 SHEET METAL RF CAVITY FILTER TECHNICAL FIELD The present disclosure relates to a sheet metal RF cavity filter and a method of manufacturing a sheet metal RF cavity filter.

BACKGROUND Radio frequency (RF) cavity filters are widely used in telecommunicationapplications. RF cavity filters are generally designed by arranging aplurality of resonators, where each resonator is tuned to a particularfrequency to achieve a combined filter characteristic, in a housing. Theresonators within the housing will interact to form a resulting filter characteristic acting on an input signal to generate an output signal.

Traditional RF cavity filters are quite bulky, but there is an increasingneed in new applications such as e.g. 5G for smaller RF cavity filters.One way of producing small RF cavity filters is by manufacturing the filters from sheet metal. However, for sheet metal RF cavity filters, traditional tuning methods are not applicable.

US 2017/0084972 describes a sheet metal RF cavity filter where the resonators ll0, ll2, ll4, ll6 and the coupling lines l20, l22, 124between them are integrated and manufactured from a uniform copper plate.The bottom parts of the resonators are attached to and extend from theside wall Cl towards the side wall C2 of the housing C. This provides a high degree of integration of the construction.

According to US 20l7/0084972, a resonator may comprise an integral bendable adjustment member 6l0a (shown in Fig. 4) extending towards thecover T of the housing C for frequency tuning. 722, There may also be bendable adjustment members 720, 724 in the cover T that coincide with the coupling lines l20, l22, l24 for adjusting the inductive coupling between the resonators. The capacitive coupling between the resonators may betuned using a metal piece l64 that is attached (shown in Fig. l) (with l (20) l0 insulation) to two adjacent resonators and has bendable adjustment protrusions l60, l62 extending above the resonators. Alternatively, thecapacitive coupling may be tuned using integral bendable adjustmentmembers 4l0a, 4l2a (shown in Fig. 3) that extend transversely from a resonator side towards an adjacent resonator.

PROBLEMS WITH THE PRIOR ART US 2017/0084972 describes two alternative ways of tuning the capacitivecoupling between resonators. The first alternative is implemented bysupplementary parts and thus rather complicated to manufacture. Thesecond alternative provides a rather weak tuning of the capacitivecoupling between the resonators, since the bendable adjustment members are located far from the free end of the resonators.

There is thus a need for a sheet metal RF cavity filter with improved tuning capabilities.

SUMMARY One of the objects of the present disclosure is to address the problemmentioned above. This is achieved by the sheet metal RF cavity filter andthe method of manufacturing a sheet metal RF cavity filter defined in the claims.

In embodiments, there is provided a sheet metal RF cavity filter that may comprise: a housing having a bottom, four side walls, and a cover; and aplurality of resonators arranged within the housing, wherein at leastsome of the resonators comprise integrated capacitive coupling tuningmembers arranged for tuning a capacitive coupling between adjacentresonators. Such a sheet metal RF cavity filter may be characterized inthat the resonators extend from the bottom of the housing towards the topof the housing, so that they extend substantially in parallel with theside walls of the housing; and that the resonators that comprise integrated capacitive coupling tuning members each have an upper section 2 (20) l0 that extends out from a lower section in a direction towards at least oneadjacent resonator, wherein at least one capacitive coupling tuningmember extends downwards from the upper section towards the bottom of thehousing, substantially in parallel with the extension of the lowersection of the resonator. Such a sheet metal RF cavity filter fits into small places while still being easily tunable.

In embodiments, the sheet metal RF cavity filter also comprises a plurality of coupling lines arranged between adjacent resonators, whereina number of the resonators and coupling lines are in one piece,manufactured from a single metal sheet. This simplifies the assembly of the sheet metal RF cavity filter.

In embodiments, the resonators are attached to the bottom of the housing.The resonators may e.g. be inserted through openings in the bottom of thehousing and then fixed in place by e.g. soldering or welding. This further simplifies the assembly of the sheet metal RF cavity filter.

In embodiments, the cover of the housing comprises a plurality of frequency tuning tabs, arranged to be positioned above at least some ofthe resonators when the cover is attached to the side walls of thehousing. The provision of such frequency tuning tabs enables an efficient tuning of the frequency.

In embodiments, the bottom and the side walls of the housing are in one piece, manufactured from a single metal sheet. If the bottom and sidewalls of the housing are manufactured in the form of a flat piece, thisenables an easy assembly of the housing by folding up the side walls fromthe bottom. However, the bottom and side walls of the housing may also bemanufactured directly into the desired shape by being e.g. deep-drawn, punched, extruded or die-casted.

The sheet metal RF cavity filter may comprise at least one cross-couplingbetween the resonators on the input side and the resonators on the outputthe sheet metal RF cavity filter comprises at least side. In embodiments, two cross-couplings integrated into a single part between the resonators 3 (20) lO on the input side and the resonators on the output side. This simplifies the assembly of the sheet metal RF cavity filter. The cross-couplings maye.g. be arranged on an interior wall in the housing, which interior wallseparates the resonators on the input side from the resonators on the output side.

In embodiments, the sheet metal RF cavity filter also comprises input means arranged on the exterior of the housing, which input means isconnected to one of the resonators via an in-coupling, wherein the in-coupling has a shape that low-pass filters an incoming signal. This makesthe arrangement even more compact, since no external low-pass inputfilter is needed. Such an in-coupling may be in one piece with the inputresonators and coupling lines, manufactured from a single metal sheet.This simplifies the assembly of the sheet metal RF cavity filter, sincethe whole input piece may then be attached to the bottom of the housing, after folding the in-coupling into position.

In embodiments, the sheet metal RF cavity filter also comprises output means arranged on the exterior of the housing, which output means isconnected to one of the resonators via an out-coupling, wherein the out-coupling has a shape that low-pass filters an outgoing signal. This makesthe arrangement even more compact, since no external low-pass outputfilter is needed. Such an out-coupling may be in one piece with theresonators and coupling lines on the output side, manufactured from asingle metal sheet. This simplifies the assembly of the sheet metal RFcavity filter, since the whole output piece may then be attached to the bottom of the housing, after folding the out-coupling into position.

In embodiments, there is provided a method of manufacturing a sheet metal RF cavity filter. The method may comprise: manufacturing a housing havinga bottom, four side walls and a cover from sheet metal; manufacturingresonators that comprise integrated capacitive coupling tuning members,arranged for tuning a capacitive coupling between adjacent resonators,from sheet metal so that they each have an upper section that extends out from a lower section in a direction towards at least one adjacent 4 (20) l0 resonator, wherein at least one capacitive coupling tuning member extendsdownwards from the upper section towards the bottom of the housing, substantially in parallel with the extension of the lower section of theresonator; assembling the housing without attaching the cover to the sidewalls; arranging a plurality of resonators manufactured from sheet metalwithin the housing, so that they extend from the bottom of the housingtowards the top of the housing, substantially in parallel with the sidewalls of the housing, wherein at least some of the resonators compriseintegrated capacitive coupling tuning members; and assembling and closingthe housing. A sheet metal RF cavity filter manufactured in this way fits into small places while still being easily tunable.

In embodiments, the method further comprises arranging a plurality ofcoupling lines manufactured from sheet metal between adjacent resonators,wherein the manufacturing of the resonators further comprises manufacturing a number of the resonators and coupling lines from a singleThis simplifies the assembly metal sheet, so that they are in one piece. of the sheet metal RF cavity filter.

In embodiments, the arranging of the resonators further comprises attaching the resonators to the bottom of the housing. This simplifies the assembly of the sheet metal RF cavity filter.

In embodiments, the arranging of the resonators further comprisesinserting the resonators through openings in the bottom of the housing.

This further simplifies the assembly of the sheet metal RF cavity filter.

In embodiments, the manufacturing of the cover comprises manufacturing a plurality of frequency tuning tabs in the cover, arranged to bepositioned above at least some of the resonators when the cover isattached to the side walls of the housing. The provision of such frequency tuning tabs enables an efficient tuning of the frequency.

In embodiments, the manufacturing of the bottom and the side walls of thehousing comprises manufacturing them from a single metal sheet, so thatthey are in one piece. If the bottom and side walls of the housing are (20) l0 manufactured in the form of a flat piece, this enables an easy assemblyof the housing by folding up the side walls from the bottom. However, thebottom and side walls of the housing may also be manufactured directlyextruded or into the desired shape by being e.g. deep-drawn, punched, die-casted.

The method may comprise arranging at least one cross-coupling between theresonators on the input side and the resonators on the output side. Inembodiments, the method comprises arranging at least two cross-couplingsintegrated into a single part between the resonators on the input sideand the resonators on the output side. This simplifies the assembly ofthe sheet metal RF cavity filter. The cross-couplings may e.g. bearranged on an interior wall in the housing, which interior wallseparates the resonators on the input side from the resonators on the output side.

In embodiments, the method further comprises manufacturing an in- coupling, having a shape that low-pass filters an incoming signal, from sheet metal; arranging input means on the exterior of the housing; andarranging the in-coupling between the input means and one of theresonators, so that the in-coupling connects the input means to the resonators. This makes the arrangement even more compact, since no external low-pass input filter is needed. Such an in-coupling may be inone piece with the resonators and coupling lines on the input side, manufactured from a single metal sheet. This simplifies the assembly ofthe sheet metal RF cavity filter, since the whole input piece may then beattached to the bottom of the housing, after folding the in-coupling into position.

In embodiments, the method further comprises manufacturing an out- coupling, having a shape that low-pass filters an outgoing signal, from sheet metal; arranging output means on the exterior of the housing; andarranging the out-coupling between the output means and one of theresonators, so that the out-coupling connects the resonators to the output means. This makes the arrangement even more compact, since no 6 (20) lO external low-pass output filter is needed. Such an out-coupling may be inone piece with the resonators and coupling lines on the output side, manufactured from a single metal sheet. This simplifies the assembly ofthe sheet metal RF cavity filter, since the whole output piece may thenbe attached to the bottom of the housing, after folding the out-coupling into position.

In embodiments, the upper section of the resonators is a short but widetop section that extends out from a much longer but narrower lowersection. The resonators may e.g. be T-shaped, with the capacitivecoupling tuning members extending downwards from both edges of the T.However, the resonators may also e.g. be shaped like an upside down L,with just one capacitive coupling tuning member extending downwards fromthe edge of the upside down L. Other shapes are also possible, as well as combinations of resonators of different shapes.

The sheet metal RF cavity filter may be manufactured from any type ofmetal sheet or metal plate, and may comprise pieces or componentsmanufactured from different types of metal sheets or metal plates, e.g. metal sheets or metal plates of different thickness.

The scope of the invention is defined by the claims, which areincorporated into this section by reference. A more completeunderstanding of embodiments of the invention will be afforded to thoseskilled in the art, as well as a realization of additional advantagesthereof, by a consideration of the following detailed description of oneor more embodiments. Reference will be made to the appended drawings that will first be described briefly.

BRIEF DESCRIPTION OF THE DRAWINGS Figs. la and lb show the exterior of a sheet metal RF cavity filter, in accordance with one or more embodiments of the disclosure.

Figs. 2a and 2b show the interior of a sheet metal RF cavity filter, in accordance with one or more embodiments of the disclosure. 7 (20) lO Fig. 3a is shows an out-coupling, in accordance with one or more embodiments of the disclosure.

Fig. 3b shows resonators, coupling lines and in-coupling integrated into one piece, as well as resonators, coupling lines and out-coupling integrated into one piece, in accordance with one or more embodiments of the disclosure.

Figs. 4a and 4b show two different embodiments of resonators, in accordance with one or more embodiments of the disclosure.

Fig. 5 shows a flow diagram for a method of manufacturing a sheet metal RF cavity filter, in accordance with one or more embodiments of the disclosure.

Embodiments of the present invention and their advantages are bestunderstood by referring to the detailed description that follows. Itshould be appreciated that like reference numerals are used to identify like elements illustrated in one or more of the figures.

DETAILED DESCRIPTION There is an increasing need in new applications such as e.g. 5G for smaller RF cavity filters. One way of producing small RF cavity filters is by manufacturing the filters from sheet metal. However, for sheet metal RF cavity filters, traditional tuning methods are not applicable.There is thus a need for a sheet metal RF cavity filter with good tuning capabilities.

Figs. la and lb show the exterior of a sheet metal RF cavity filter l00, in accordance with one or more embodiments of the disclosure. Fig. la is a perspective view of the exterior of the housing ll0, where the side walls W1, W4 and the cover T can be seen. Fig. lb is a bottom view of the exterior of the housing ll0, where the bottom B can be seen. The bottom Bmay comprise openings l60 where interior components of the sheet metal RF cavity filter l00 may be inserted. lO In the housing ll0 shown in Figs. la and lb, the bottom B and the side walls W1, W2, W3, W4 of the housing ll0 are in one piece, manufactured from a single metal sheet. If the bottom B and side walls Wh Uh, W3, W4of the housing ll0 are manufactured in the form of a flat piece, thisenables an easy assembly of the housing ll0 by folding up the side wallsW1, W” Uh, W4 from the bottom B. However, the bottom B and side walls WhW2, W3, W4 of the housing ll0 may also be manufactured directly into thedesired shape by being e.g. deep-drawn, punched, extruded or die-casted.

Alternatively, the bottom B and the side walls W1, W2, W3, W4 of the housing ll0 are separate pieces that are e.g. soldered or welded together.

As shown in Fig. la, the cover T may comprise a number of frequency tuning tabs l50, arranged to be positioned above at least some of theresonators l20 when the cover T is attached to the side walls W1, W2, WyW4 of the housing ll0. The provision of such frequency tuning tabs l50 enables an efficient tuning of the frequency.

The sheet metal RF cavity filter l00 shown in Figs. la and lb furthercomprises input and output means in the form of an input connector l80 and an output connector l90 arranged on the exterior of the housing ll0.The connectors l80, l90 may e.g. be coaxial cable connectors. However, other types of input/output means may alternatively be used, such as e.g. direct surface mounting via e.g. soldering.

Figs. 2a and 2b show the interior of a sheet metal RF cavity filter l00, in accordance with one or more embodiments of the disclosure. As shown in Figs. 2a and 2b, an interior wall ll5 may be arranged in the interior ofthe housing ll0 to separate the resonators l20 on the input side from theresonators l20 on the output side. Such an interior wall ll5 may be inserted into openings l60 in the bottom B of the housing, but it mayalso be attached to the bottom B entirely by e.g. soldering or welding.On the interior wall ll5, one or more cross-couplings l70 between resonators l20 on the input side and resonators l20 on the output side lO may be arranged. In embodiments, the sheet metal RF cavity filter l00 comprises at least two cross-couplings l70 integrated into a single part.

A plurality of resonators l20 may be arranged within the housing ll0, anda plurality of coupling lines l40 may be arranged between adjacentresonators l20. The resonators l20 and coupling lines l40 on each side ofthe interior wall ll5 may be in one piece, manufactured from a singlemetal sheet, since this simplifies the assembly of the sheet metal RFcavity filter l00. The resonators l20 and/or coupling lines l40 may however also be separate pieces.

The resonators l20 may extend from the bottom B of the housing ll0towards the top T of the housing ll0, so that they extend substantiallyin parallel with the side walls W1, W2, W3, W4 of the housing llO. Theresonators l20 are preferably attached to the bottom B of the housingll0, e.g. by soldering or welding. The resonators l20 may be insertedthrough openings l60 in the bottom B of the housing ll0, since this simplifies the assembly of the sheet metal RF cavity filter l00.

At least some of the resonators l20 may comprise integrated capacitivecoupling tuning members l30 arranged for tuning a capacitive couplingbetween adjacent resonators l20. The resonators l20 shown in Fig. 2a areT-shaped, with capacitive coupling tuning members l30 extending downwardsfrom both edges of the T. However, other shapes are also conceivable, aslong as each resonator l20 that comprises at least one integratedcapacitive coupling tuning member l30 has an upper section l24 thatextends out from a lower section l22 in a direction towards at least oneadjacent resonator l20, as illustrated in Figs. 4a and 4b. This enablesthe at least one capacitive coupling tuning member l30 to extenddownwards from the upper section l24 towards the bottom B of the housingll0, substantially in parallel with the extension of the lower sectionl22 of the resonator l20. This provides for an efficient tuning of thecapacitive coupling between the resonators l20. The upper section l24 ofthe resonators l20 may e.g. be a short but wide top section l24 that extends out from a much longer but narrower lower section l22. l0 (20) The sheet metal RF cavity filter 100 may also comprise one or more integrated low-pass filters. Figs. 2a and 2b illustrate such integrated low-pass input and output filters in the form of an in-coupling 310 and190 with the an out-coupling 320, arranged to connect the connectors 180, resonators 120. This makes the arrangement even more compact, since no external low-pass input or output filters are needed.Fig. 3a shows an out-coupling 320 that has a shape that low-pass filtersan outgoing signal. Such a shape could e.g. be in the form of alternatingsections of different characteristic impedance lines, and/or resonatingline sections forming attenuation notches to desired frequencies. In theout-coupling 320 shown in Fig. 3a, there is a section 330 of highimpedance between two sections 340 of low impedance. Such filters are often referred to as stepped impedance filters.

Fig. 3b shows resonators 120, coupling lines 140 and in-coupling 310 integrated into one input piece, which may be manufactured from a single metal sheet, as well as resonators 120, coupling lines 140 and out- coupling 320 integrated into one output piece, which may be manufacturedfrom a single metal sheet, in accordance with one or more embodiments ofthe disclosure. This simplifies the assembly of the sheet metal RF cavityfilter 100, since the whole input piece may then be attached to thebottom B of the housing 110, after folding the in-coupling 310 intoposition, and the whole output piece may also be attached to the bottom Bof the housing 110, after folding the out-coupling 320 into position.

However, as shown in Fig. 4b, there does not have to be coupling lines 140 between adjacent resonators.

Fig. 5 shows a flow diagram for a method 500 of manufacturing a sheet metal RF cavity filter 100. In accordance with one or more embodiments of the disclosure, the method comprises the following steps: Step 510: manufacturing a housing 110 having a bottom B, four side walls W1, W2, W3, W4 and a cover T from sheet metal. 11 (20) Step 520: manufacturing resonators 120 that comprise integratedcapacitive coupling tuning members 130 from sheet metal so that they eachhave an upper section 124 that extends out from a lower section 122 in adirection towards at least one adjacent resonator 120, wherein at leastone capacitive coupling tuning member 130 extends downwards from theupper section 124 towards the bottom B of the housing 110, substantiallyin parallel with the extension of the lower section 122 of the resonator 120.

Step 540: arranging a plurality of resonators 120 manufactured from sheet metal within the housing 110, so that they extend from the bottom B ofthe housing towards the top T of the housing, substantially in parallelwith the side walls W1, WL VM, W4 of the housing 110, wherein at leastsome of the resonators 120 comprise integrated capacitive coupling tuningmembers 130 arranged for tuning a capacitive coupling between adjacent resonators 120.

Step 575: assembling and closing the housing 110.

A sheet metal RF cavity filter 100 manufactured in this way fits into small places while still being easily tunable.

In embodiments, the method further comprises arranging, in a step 550, aplurality of coupling lines 140 manufactured from sheet metal between adjacent resonators 120. The manufacturing 520 of the resonators 120 maythen further comprise manufacturing a number of the resonators 120 andcoupling lines 140 from a single metal sheet, so that they are in onepiece. This simplifies the assembly of the sheet metal RF cavity filter 100.

In embodiments, the arranging 540 of the resonators 120 further comprises attaching the resonators 120 to the bottom B of the housing 110. This simplifies the assembly of the sheet metal RF cavity filter 100.

In embodiments, the arranging 540 of the resonators 120 further comprises inserting the resonators 120 through openings 160 in the bottom B of the 12 (20) l0 housing ll0. This further simplifies the assembly of the sheet metal RF cavity filter l00.

In embodiments, the manufacturing 5l0 of the cover T comprisesmanufacturing a plurality of frequency tuning tabs l50 in the cover T,arranged to be positioned above at least some of the resonators l20 whenthe cover T is attached to the side walls W1, W” Uh, W4 of the housingll0. The provision of such frequency tuning tabs l50 enables an efficient tuning of the frequency.

In embodiments, the manufacturing 5l0 of the bottom B and the side wallsW1, W” Uh, W4 of the housing ll0 comprises manufacturing them from asingle metal sheet, so that they are in one piece. If the bottom B andside walls W1, W” Uh, W4 of the housing ll0 are manufactured in the formof a flat piece, this enables an easy assembly of the housing ll0 byfolding up the side walls W1, W” Uh, W4 from the bottom B. However, thebottom B and side walls W1, W2, W3, W4 of the housing ll0 may also bemanufactured directly into the desired shape by being e.g. deep-drawn, punched, extruded or die-casted.

The method may comprise arranging at least one cross-coupling l70 betweenthe resonators l20 on the input side and the resonators l20 on the outputside. In embodiments, the method comprises arranging, in a step 570, atleast two cross-couplings l70 integrated into a single part between theresonators l20 on the input side and the resonators l20 on the output side. l00.

This simplifies the assembly of the sheet metal RF cavity filterThe cross-couplings l70 may e.g. be arranged on an interior wall ll5in the housing, which interior wall ll5 separates the resonators l20 on the input side from the resonators l20 on the output side.

In embodiments, the method further comprises: manufacturing 525 an in- coupling 3l0, having a shape that low-pass filters an incoming signal, from sheet metal; arranging, in a step 580, of input means l80 on the exterior of the housing ll0; and arranging 560 the in-coupling 3l0between the input means l80 and one of the resonators l20, so that the in-coupling 3l0 connects the input means l80 to the resonators l20. This l3 (20) l0 makes the arrangement even more compact, since no external low-pass input filter is needed. Such an in-coupling 3l0 may be in one piece with theresonators l20 and coupling lines l40 on the input side, manufacturedfrom a single metal sheet. This simplifies the assembly of the sheetmetal RF cavity filter l00, since the whole input piece may then beattached to the bottom B of the housing ll0, after folding the in- coupling 3l0 into position.

In embodiments, the method further comprises: manufacturing 530 an out- coupling 320, having a shape that low-pass filters an outgoing signal, from sheet metal; arranging, in a step 590, of output means l90 on the exterior of the housing ll0; and arranging 565 the out-coupling 320 between the output means l90 and one of the resonators l20, so that theout-coupling 320 connects the resonators l20 to the output means l90.This makes the arrangement even more compact, since no external low-passoutput filter is needed. Such an out-coupling 320 may be in one piecewith the resonators l20 and coupling lines l40 on the output side, manufactured from a single metal sheet. This simplifies the assembly ofthe sheet metal RF cavity filter l00, since the whole output piece maythen be attached to the bottom B of the housing ll0, after folding the out-coupling 320 into position.

The foregoing disclosure is not intended to limit the present inventionto the precise forms or particular fields of use disclosed. It iscontemplated that various alternate embodiments and/or modifications tothe present invention, whether explicitly described or implied herein,are possible in light of the disclosure. Accordingly, the scope of the invention is defined only by the claims. l4 (20)

Claims

1. l. A sheet metal radio frequency (RF) cavity filter (lOO) comprising: a housing (llO) having a bottom (B), four side walls (W1, WD 5 W3, W4), and a cover (T); and a plurality of resonators (l20) arranged within the housing(llO), wherein at least some of the resonators (l20) compriseintegrated capacitive coupling tuning members (l30) arranged for tuning a capacitive coupling between adjacent resonators (l20);lO characterized in: that the resonators (l20) extend from the bottom (B) of thehousing towards the top (T) of the housing, so that they extendsubstantially in parallel with the side walls (W1, W2, W3, W4) of thehousing (llO); and l5 that the resonators (l20) that comprise integrated capacitivecoupling tuning members (l30) each have an upper section (l24) thatextends out from a lower section (l22) in a direction towards atleast one adjacent resonator (l20), wherein at least one capacitivecoupling tuning member (l30) extends downwards from the edge of the 20 upper section (l24) towards the bottom (B) of the housing (llO),substantially in parallel with the extension of the lower section (l22) of the resonator (l20).

2. The sheet metal RF cavity filter (lOO) of claim l, furthercomprising a plurality of coupling lines (l40) arranged between adjacent25 resonators (l20), wherein a number of the resonators (l20) and coupling lines (l40) are in one piece, manufactured from a single metal sheet.

3. The sheet metal RF cavity filter (lOO) of claim l or 2, whereinthe resonators (l20) are attached to the bottom (B) of the housing (llO).

4. The sheet metal RF cavity filter (100) wherein the (160) of claim 3, resonators are inserted through openings in the bottom (B) of the housing (110).

5. The sheet metal RF cavity filter (100) (110) of any one of claims 1-4, wherein the cover (T)(150),(120) of the housing comprises a plurality of frequency tuning tabs arranged to be positioned above at least some of the resonators when the cover (T) is attached to the side walls (W1, W2, W3, W4) of the housing (110).

6. The sheet metal RF cavity filter (100) and the side walls (W1, W2, W3, Wm of any one of claims 1- 5, wherein the bottom (B) of the housing (110) are in one piece, manufactured from a single metal sheet.

7. The sheet metal RF cavity filter (100) of any one of claims 1- 6, further comprising at least two cross-couplings (170) integrated into a single part between the resonators (120) on the input side and the resonators (120) on the output side.

8. The sheet metal RF cavity filter (100) of any one of claims 1- 7, further comprising input means (180) arranged on the exterior of thehousing (110), which input means (180) is connected to one of theresonators (120) via an in-coupling (310), wherein the in-coupling (310) has a shape that low-pass filters an incoming signal.

9. The sheet metal RF cavity filter(190)(190) (100) of any one of claims 1- 8, further comprising output means arranged on the exterior of the housing (110), which output means is connected to one of the resonators (120) (320), wherein the out-coupling (320) via an out-coupling has a shape that low-pass filters an outgoing signal.

10. A method (500) of manufacturing a sheet metal radio frequency (RF) cavity filter (100), wherein the method comprises: 16 manufacturing (510) a housing (110) having a bottom (B), fourside walls (W1, W2, W3, W4), and a cover (T) from sheet metal;arranging (540) a plurality of resonators (120) manufactured from sheet metal within the housing (110), wherein at least some of the resonators (120) comprise integrated capacitive coupling tuning members (130) arranged for tuning a capacitive coupling betweenadjacent resonators (120); and assembling (575) and closing the housing (110); characterized in: manufacturing (520) the resonators (120) that compriseintegrated capacitive coupling tuning members (130) from sheetmetal so that they each have an upper section (124) that extends out from a lower section (122) in a direction towards at least oneadjacent resonator(130) towards the bottom (B) (120), wherein at least one capacitive couplingtuning member (124) extends downwards from the edge of the upper section of the housing (110), substantially in parallel with the extension of the lower section (122) of the resonator (120); and arranging (540) the resonators (120) so that they extend from the bottom (B) of the housing towards the top (T) of the housing,substantially in parallel with the side walls (W1, W2, W3, Wm (110). of the housing

11. The method (500) of claim 10, (140) further comprising arranging(550) manufactured from sheet metal (520) a plurality of coupling lines between adjacent resonators (120), of the(120) (120) wherein the manufacturingresonators further comprises manufacturing a number of the resonators and coupling lines (140) from a single metal sheet, so that they are in one piece. 17

12. The method (500) of claim 10 or 11, Wherein the arranging (540)of the resonators (120) further comprises attaching the resonators (120)to the bottom (B) of the housing (110).

13. The method (500) of claim 12, Wherein the arranging (540) ofthe resonators (120) further comprises inserting the resonators (120)through openings (160) in the bottom (B) of the housing (110).

14. The method(510) (500) of any one of claims 10-13, wherein thecomprises manufacturing a plurality(T), positioned above at least some of the resonators of the cover (T) (150) manufacturing of frequency tuning tabs in the cover arranged to be (120) when the cover (T) is attached to the side walls (W1, W2, W3, W4) of the housing (110).

15. The method(510)(110) (500)of the bottom (B) of any one of claims 10-14, wherein themanufacturing and the side walls (W1, W2, W3, Wmof the housing comprises manufacturing them from a single metal sheet, so that they are in one piece.

16. The method(570) (500) of any one of claims 10-15, (170) further comprisingat least two cross-couplings integrated into a (120) arranging single part between the resonators on the input side and the resonators (120) on the output side.

17. The method (500) of any one of claims 10-16, furthercomprising:manufacturing (525) an in-coupling (310), having a shape that low-pass filters an incoming signal, from sheet metal; (580) on the exterior of the (110); and arranging input means (180) housing 18 arranging (560) the in-coup1ing (310) between the input means(180) and one of the resonators (120), so that the in-coup1ing (310) connects the input means (180) to the resonators (120).

18. The method (500) of any one of c1aims 10-17, further 5 comprising: manufacturing (530) an out-coup1ing (320), having a shape that low-pass filters an outgoing signal, from sheet meta1; arranging (590) output means (190) on the exterior of the housing (110); and 10 arranging (565) the out-coup1ing (320) between the output means(190) and one of the resonators (120), so that the out-coup1ing(320) connects the resonators (120) to the output means (190). 19