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Title:
CASING STRUCTURE OF RF FILTER AND METHOD FOR ITS MANUFACTURING
Document Type and Number:
WIPO Patent Application WO/2018/162795
Kind Code:
A1
Abstract:
The invention relates to a casing structure for an RF filter. The casing structure is such that in addition to the first wall structure (WS1) and one or more resonators (R1-R6) protruding therefrom towards the second wall structure (WS2), the opposite second wall structure (WS2) and a connecting structure (MW1-MW5; EW1,EW2) between the wall structures (WS1, WS2) are also of the same one-piece integral part, and that in such a case each resonator (R1-R6) belongs to the same one-piece entity formed by casting, injection moulding, or 3D printing as both of said wall structures (WS1, WS2) directed towards each other and the connecting structure (MW1-MW5, EW1-EW2) between them, each resonator (R1-R6) extending in the direction between said wall structures (WS1, WS2) in the casing structure.

Inventors:
PENTTILĂ„, Janne (Lars Sonckin kaari 14, Espoo, 02600, FI)
Application Number:
FI2018/050151
Publication Date:
September 13, 2018
Filing Date:
March 01, 2018
Export Citation:
Click for automatic bibliography generation   Help
Assignee:
TONGYU TECHNOLOGY OY (Lars Sonckin kaari 14, Espoo, 02600, FI)
International Classes:
H01P1/205; H01P1/208; H01P11/00
Domestic Patent References:
WO2004105173A12004-12-02
Foreign References:
EP0823746A21998-02-11
US4034319A1977-07-05
US20120084968A12012-04-12
Other References:
None
Attorney, Agent or Firm:
KOLSTER OY AB (P.O.Box 204, Helsinki, Helsinki, 00181, FI)
Download PDF:
Claims:
Claims

1. A casing structure for an RF filter, comprising a first wall structure (WS1), an opposite second wall structure (WS2) pointing towards the first wall structure, and between the wall structures (WS1, WS2) a connecting structure (MW1-MW5; EW1, EW2) connecting the wall structures (WS1, WS2), the casing structure containing one or more resonator compartments (C1-C6 ) in an area between the wall structures (WS1, WS2), and that one or more resonators (R1-R6) extend from the first wall structure (WS1) towards the opposite second wall structure (WS2) so that an inductive end (IE1) of the resonator is on the side of the base (Bl) of the resonator where the resonator (Rl) is short-circuited to the first wall structure (WS1), and the capacitive free end (CE1) of the resonator is closer to the opposite second wall structure (WS2), c h a r a c t e r i z e d in that in addition to the first wall structure (WS1) and one or more resonators (R1-R6) protruding therefrom towards the second wall structure (WS2), the opposite second wall structure (WS2) and the connecting structure (MW1-MW5; EW1,EW2) between the wall structures (WS1, WS2) are also of the same one- piece integral part, and that in such a case each resonator (R1-R6) belongs to the same one-piece integral entity formed by casting, injection moulding, or 3D printing as both of said wall structures (WS1, WS2) directed towards each other and the connecting structure (MW1-MW5, EW1-EW2) between them, each resonator (R1-R6) extending in the direction between said wall structures (WS1, WS2) in the casing structure.

2. A casing structure as claimed in claim 1, c h a r a c t e r i z e d in that at the capacitive end (CE1-CE6) of one or more resonators (R1-R6) there is a widening (CA1-CA6) adding to the cross- sectional area of the resonator to increase capacitive coupling in relation to the second wall structure (WS2), and in that the widening (CA1-CA6) belongs to the same one-piece integral entity formed by casting, injection moulding, or 3D printing, which has the resonator (R1-R6) in question and both of said wall structures (WS1, WS2) directed to- wards each other and the connecting structure (MW1-MW5; EW1-EW2) between them, each resonator (R1-R6) with its widening (CA1-CA6) extending in the direction between said wall structures (WS1, WS2) in the casing structure.

3. A casing structure as claimed in claim 1 or 2, c h a r a c t e r i z e d in that to separate the compartments (C1-C6) of the casing structure, the casing structure comprises partition walls (MW1-MW5) extending between the first wall structure (WS1) and the opposite second wall structure (WS2) and which are said connecting structures which connect the first wall structure (WS1) and the opposite second wall structure (WS2), and in that the partition walls (MW1-MW5) also belong to the same one-piece integral entity formed by casting, injection moulding, or 3D printing, which has both the resonators (R1-R6) extending in the direc- tion of the partition walls (MW1-MW5) in question and both of said wall structures (WS1, WS2) directed towards each other, the resonators (R1-R6) extending in the direction between them in the casing structure.

4. A casing structure as claimed in any of the preceding claims 1-3, c h a r a c t e r i z e d in that the casing structure comprises end walls (EW1, EW2) which are said connecting structures which connect the first wall structure (WS1) and the opposite second wall structure (WS2), and in that the end walls (EW1, EW2) are at the ends of the casing structure between the first wall structure (WS1) and the opposite second wall structure (WS2) of the casing structure, and in that also these end walls (EW1, EW2) belong to the same one-piece inte- gral entity formed by casting, injection moulding or 3D printing, which has the resonators (R1-R6) extending in the direction of the end walls (EW1, EW2) in question and both of said wall structures (WS1, WS2) directed towards each other, the resonators (R1-R6) extending in the direction between them in the casing structure.

5. A casing structure as claimed in any of the preceding claims 1-4, c h a r a c t e r i z e d in that to cover the open sides of the one-piece part of the casing structure, the part including the first wall structure (WS1), opposite second wall structure (WS2), connecting structure (MW1-MW5; EW1-EW2) connecting the wall structures (WS1, WS2) and resonators (R1-R6) extending in the di- rection between the wall structures (WS1, WS2), the casing structure comprises separate side plate pieces (SP1, SP2) or similar cover pieces (SP1, SP2).

6. A method for manufacturing a casing structure of an RF filter, in which a casing structure of one or more compartments and comprising a first wall structure (WS1), an opposite second wall structure (WS2), a connecting structure (MW1-MW5, EW1-EW2) connecting said wall structures (WS1, WS2), and one or more resonators is manufactured, c h a r a c t e r i z e d in that in the method:

- the casing structure is cast, injection-moulded, or 3D printed as a one-piece integral part so that the first wall structure (WS1), opposite second wall structure (WS2), resonators (R1-R6) extending in the direction between said wall structures, and said connecting structure (MW1-MW5; EW1-EW2) connect- ing the wall structures (WS1, WS2) belong to the same one-piece integral part, and

- to form a capacitive end for each resonator (R1-R6), each resonator is separated from the second wall structure (WS2) by cutting the resonator.

7. A method as claimed in claim 6, characterized in that on each resonator (R1-R6) in the same context, by casting, injection moulding or 3D printing, a widening (CA1-CA6) increasing the cross-sectional area of the resonator is formed.

8. A method as claimed in claim 7, characterized in that, to form the capacitive end (CA1-CA6) for each resonator (R1-R6), the resonator is cut between each widening (CA1-CA6) and the second wall structure (WS2).

9. A method as claimed in any one of the preceding claims 6-8, characterized in that the method works in such a way that the partition walls (MW1-MW5) separating the compartments of the casing structure are cast, injection moulded, or 3D printed as the connecting structure connecting the opposite wall structures (WS1, WS2) and extending in the direction of the resonators.

10. A method as claimed in any one of the preceding claims 6-9, characterized in that the method works in such a way that the end walls (EW1-EW2) at the ends of the casing structure are cast, injection moulded, or 3D printed as the connecting structure connecting the opposite wall structures (WS1, WS2) and extending in the direction of the resonators.

Description:
Casing structure of RF filter and method for its manufacturing

Background of the invention

RF filters, i.e. radio frequency filters, are used in connection with RF devices, such as transmitters, receivers or transceivers, used in base stations of mobile phone networks, for example, in particular in the amplifiers therein as filtering and adapting circuits.

Resonator type filters comprise a casing structure with one or more compartments whose shape is defined by the walls of the casing structure.

Typically, a compartment of the casing structure may contain an inner conductor, referred to as a resonator or a resonator pin, extending from the bottom of the compartment or cavity, a common structure being a coaxial resonator in which the inner conductor, or the resonator, shares a common axis, i.e. is coaxial, with the surrounding compartment or cavity. The metallic or conductively coated walls of a compartment of a casing structure and the metallic or conduc- tively coated inner conductor together form a resonant circuit. In more complex RF filters, the casing structure consists of plural compartments, each compartment having a separate inner conductor, or resonator, whereby a plural number of resonant circuits is formed and, with a suitable intercoupling of these, desired frequency responses, i.e. stopbands and passbands, are obtained.

In the known casing structures of RF filters, the structural integration is not optimal, which due to imprecision of manufacturing tolerances causes problems in the application of the casing structure, that is, the RF filter, such as imprecision regarding the operation of the filter, such as the realization of a stop- band or passband as desired. The problems are getting worse because higher and higher frequency ranges, such as 3.5 GHz, are used.

Summary of the invention

An object of the invention is thus to provide a new type of casing structure and manufacturing method of an RF filter so as to enable the aforementioned problems to be solved or alleviated. The object of the invention is achieved with a casing structure and method which are characterized by what is stated in the independent claims. Preferred embodiments of the invention are disclosed in the dependent claims.

The invention is based on a new type of structural integration and a method implementing it. The advantage of the inventive casing structure and method is a new type of structural integration and an improved manufacturing precision it allows, which in turn provides a better frequency stabilization for the application of the casing structure, such as an RF filter. The advantage results from the fact that the surface of the casing structure and, in particular, the transverse resonators included in it, is of high quality and not porous. The integration of a resonator "hat", that is, a widening increasing the cross-sectional area of the resonator in accordance with an embodiment, into the resonator and the remaining structural entity further increases the degree of integration.

Brief description of the figures

The invention will now be described in more detail in connection with preferred embodiments and with reference to the accompanying drawings, in which:

Figure 1 shows a casing structure before separating resonator ends from a second wall structure,

Figure 2 shows a casing structure where resonator ends have already been separated from the second wall structure,

Figure 3 shows a casing structure and two cover plates that close its open sides.

Detailed description of the invention

With reference to Figures 1 to 3, a casing structure FR is thus described

for an RF filter. The material of the casing structure FR is aluminium or magnesium, for example. To improve electrical conductivity, the aluminium casing structure may towards the final stages of manufacturing be coated with a coating having a better conductivity, such as silver.

The casing structure FR comprises a first wall structure WS1, an oppo- site second wall structure WS2 pointing towards the first wall structure WS1, and between the wall structures WS1, WS2 a connecting structure MW1-MW5 and/or EW1, EW2 connecting the wall structures WS1, WS2.

As noted in the above, there are two options for the connecting structure, either as alternatives but preferably, that is, in an embodiment as comple- mentary to each other, that is, the connecting structure comprises end walls EW1, EW2 and/or partition walls MW1-MW5, so preferably both as in the examples of the drawings.

In addition, the casing structure FR comprises, in the area between the wall structures WSl, WS2, one or more resonator compartments C1-C6, separat- ed from each other by the partition walls MW1-MW5, and furthermore the end walls EW1, EW2 also contribute to forming the outmost compartments CI and C6. The compartments C1-C6 are finally closed by separate side plate parts SP1, SP2 for covering the open sides SI, S2 of the casing structure, or other similar cover pieces, shown in Figure 3.

This is a casing structure for a resonator-type filter, so

there is one or more resonators R1-R6 extending from the first wall structure WSl towards the opposite second wall structure WS2 so that the inductive end IE1-IE6 of the resonators, such as R1-R6, is on the side of the resonator base Bl- B6 where the resonators R1-R6 are short-circuited to the first wall structure WSl, whereas the capacitive free end CE1-CE6 of the resonators is closer to the opposite second wall structure WS2.

Insofar as the actual invention is concerned, it may be noted that in addition to the first wall structure WSl and the one or more resonators R1-R6 extending from the first wall structure WSl towards the opposite second wall struc- ture WS2, also the opposite second wall structure WS2 and the connecting structure MW1-MW5 and/or EW1-EW2 between the wall structures WSl, WS2 are of the same integral one-piece part.

In such a case, each resonator R1-R6 belongs to the same one-piece integral entity formed by casting, die-casting i.e. injection moulding, or 3D printing as both of said wall structures WSl, WS2 directed towards each other and the connecting structure MW1-MW5, EW1-EW2 between them, each resonator R1-R6 extending in the direction between said wall structures WSl, WS2 in the casing structure FR.

These manners of manufacturing methods have in common that the material forming the casing structure flows forward and forms the desired shape. In casting and injection moulding, the material is molten, in 3D printing the matter forming the casing structure is melted from powder, for example. In casting and injection moulding, a casting machine with its mould may be used.

The manufacturing method will be examined in closer detail below, but even at this stage it may be noted that after the first stage of the manufacturing method a structure of Figure 1 is reached, where the resonators (or resonator preforms, in a way) are connected to both the long wall structures WS1, WS2, in other words, not only to the first wall structure WS1 which is, in a way, the bottom/base, but also to the opposite or the second wall structure WS2.

When the resonators R1-R6 (their preforms, in a way) are cut, the res- onators R1-R6 develop free ends, that is, capacitive ends CE1-CE6, and thus the situation and structure of Figure 2 has been reached.

The structure of the type referred to is considerably better than the prior art structure, in which the resonators rising from the bottom (which would be a certain kind of first wall structure) are faced with, so also directed against the bottom, a cover plate of a separate piece and not the integral wall structure belonging to the same casing structure piece FR as in the invention.

In the invention, the resonators are transversely, in a right angle, for example, in relation to the direction of the cover plates SP1, SP2 closing the casing structure at its sides SI, S2, but parallel to the direction between the wall struc- tures SW1, WS2. If the direction of extension of the compartments C1-C6 is interpreted to be the direction between the separate cover plates SP1, SP2 closing the compartments C1-C6, then the resonators R1-R6 are transverse in relation to the extension direction of the compartments C1-C6. The cover plates SP1, SP2 in Figure 3 may also be seen as a bottom and lid, due to the position of the main part of the casing structure FR in Figure 3. If cover plates according to Figure 3 had been installed in the casing structure FR that is in the position of Figures 1-2, they could be seen as side surfaces for the casing structure FR.

In an embodiment, at the capacitive end CE1-CE6 of one or more resonators R1-R6 there is a widening CA1-CA6 that adds to the cross-sectional area of the resonator to increase capacitive coupling in relation to the opposite adjacent second wall structure WS2. It may be said that each widening CA1-CA6 together with the opposite wall structure WS2 forms, in a way, a capacitor structure where plate surfaces face each other.

In such a case, each widening CA1-CA6 belongs to the same one-piece integral entity formed by casting, injection moulding, or 3D printing, which has the resonator R1-R6 in question and both of said wall structures WS1, WS2 directed towards each other and the connecting structure MW1-MW5, EW1-EW2 between them, each resonator R1-R6 with its widening CA1-CA6 extending in the direction between said wall structures WS1, WS2 in the casing structure FR.

By cutting the resonators R1-R6, other things may be achieved in addition to merely the issue referred to in the above, that is, forming free/capacitive ends CA1, CA2 to the resonators R1-R6. In an embodiment, cutting the resonators R1-R6 by milling, for example, is performed between the widenings CA1-CA6 and the second wall structure 2 so that, for example, the cutting width approximately corresponds to the distance of the widening such as CA1 from the second wall structure WS2, because by doing so the connecting bridge MP1 between the widening CA1 and the second wall structure WS2 may be altogether removed and in addition the surface of the widening such as CA1 towards the second wall structure WS2 as well as the surface of the wall structure WS2 towards the widening CA1 may be made even and smooth.

As mentioned in the above, the connecting structure between the wall structures WS1, WS2 may be the partition walls MW1-MW5 between the compartments C1-C6 and/or the end walls EW1, EW2 of the ends.

This being the case, in an embodiment in order to separate the compartments C1-C6 of the casing structure, the casing structure comprises, extend- ing between the first wall structure WS1 and the opposite second wall structure WS2, partition walls MW1-MW5 which are said connecting structures connecting the first wall structures WS1 and the opposite second wall structure WS2. In this case, also the partition walls MW1-MW5 in this embodiment belong to the same one-piece integral entity formed by casting, injection moulding, or 3D printing, which has the resonators R1-R6 extending in the direction of the partition walls MW1-MW5 and both of said wall structures WS1, WS2 directed towards each other, the resonators R1-R6 extending in the direction between them in the casing structure FR.

Alternatively or additionally, the connecting structure may be the end walls EW1, EW2 of the ends of the casing structure. Therefore, in an embodiment the casing structure comprises end walls EW1, EW2 which are said connecting structures which connect the first wall structure WS1 and the opposite second wall structure WS2, and the end walls EW1, EW2 are at the ends of the casing structure between the first wall structure WS1 and the opposite second wall structure WS2 of the casing structure, and also these end walls EW1, EW2 belong to the same one-piece integral entity formed by casting or 3D printing, which has the resonators R1-R6 extending in the direction of the end walls EW1, EW2 in question and both of said wall structures WS1, WS2 directed towards each other, the resonators R1-R6 extending in the direction between them in the casing struc- ture. By comparing Figures 1 and 2, it may be noted that in Figure 1 also the resonators R1-R6 are at first, so at the initial stage of manufacturing, as a connecting structure or a third connecting structure type, but in accordance with Figure 2 the resonators are cut off from the second wall structure WS2, whereby they no longer act as a connecting structure between the wall structures WS1, WS2.

As described, the casing structure comprises separate side plate parts SP1, SP2 for covering the open sides of the one-piece part of the casing structure, or other similar cover pieces SP1, SP2, which thus close the sides SI, S2 of the casing structure. So, the cover plates SP1, SP2 are placed as a cover for the one-piece integral casing part, which includes the first wall structure WS1, opposite second wall structure WS2, connecting structure MW1-MW5, EW1-EW2 connecting the wall structures WS1, WS2, and resonators R1-R6 with their widenings CA1-CA6, extending in the direction between the wall structures WS1, WS2.

In an embodiment, there are coupling apertures IR1-IR5 in connection with the partition walls, the size of which affects the mutual coupling between resonance circuits in adjacent compartments. These coupling apertures, too, have been formed in connection with casting, injection moulding, or 3D printing, so in practise the manufacturing method has determined the location and size of the edge determining the shape of the coupling apertures IR1-IR5 in the partition walls MW1-MW5. Therefore, partition walls comprise those coupling apertures. Alternative and not so optimal way, compared to forming the coupling apertures IR1-IR5 when casting, injection moulding or 3D printing the partition walls MW1- MW5, would be later to use drilling or machining for forming apertures on the already formed partition walls MW1-MW5.

The manufacturing method will be discussed next. The casing structure may be manufactured by die-casting out of metal such as aluminium or magnesium, or the casing structure may be manufactured by injection moulding i.e. extruding out of plastic, as long as the casing structure is coated with a conductive coating. It is also possible that 3D printing is used.

When casting metal, such as in die-casting, a die-casting machine with an appropriate mould is used. In injection moulding of plastic, or extruding, an injection-moulding machine is used with an appropriate mould, and in 3D printing of metal, metal powder is melted with laser layer by layer, a heated printing platform being used as additional help.

So, this is a method for manufacturing the casing structure of an RF filter In the method, a casing structure FR of one or more compartments and com- prising a first wall structure WSl, an opposite second wall structure WS2, a connecting structure MW1.MW5, EW1-EW2 connecting said wall structures WSl, WS2, and one or more resonators is manufactured.

In accordance with the essential feature of said method, the casing structure FR is cast, injection-moulded, or 3D printed as one-piece integral part so that the first wall structure WSl, opposite second wall structure WS2, resonators R1-R6 extending in the direction between said wall structures, and said connecting structure MW1-MW5, EW1-EW2 connecting the wall structures WSl, WS2 belong to the same one-piece integral part. This relates to the situation of Figure 1, where the resonators, such as resonator Rl, are connected, in addition to the first wall structure Wsl, also to the second wall structure WS2 through bridges, such as bridge MP1.

Next, at the second stage of the method, to form a capacitive end for each resonator R1-R6, each resonator is separated from the second wall structure WS2 by cutting the resonators. This leads to the situation in accordance with Figure 2.

To improve the method and to further increase the integration of the casing structure part, in an embodiment the method is such that

on each resonator R1-R6 in the same context, by casting, injection moulding or 3D printing as described in the above, a widening CA1-CA6 increasing the cross- sectional area of the resonator is formed.

The method is additionally such that to form the capacitive end CE1- CE6 for each resonator R1-R6, each resonator R1-R6 is cut between each widening CA1-CA6 and the second wall structure WS2.

Consequently, even the structure such as CA1 increasing the cross- sectional area, that is, capacitive coupling, of the resonator such as Rl, is united with its resonator Rl, as well as with the wall structures WSl, WS2, as well as partition walls MW1-MW5 and also end walls EW1, EW2.

It may further be noted that the method works in such a way that the partition walls MW1-MW5 separating the compartments of the casing structure are cast or 3D printed as the connecting structure connecting the opposite wall structures WSl, WS2 and extending in the direction of the resonators.

Additionally or alternatively, the method works in such a way that the end walls EW1-EW2 at the ends of the casing structure are cast or 3D printed as the connecting structure connecting the opposite wall structures WSl, WS2 and extending in the direction of the resonators. The casing structure FR, in the compartments CA1, CA6, for example, may be provided with a signal input port and output port by using apertures through the end walls EW1, EW2 and pilot cores, for example.

A person skilled in the art will find it obvious that, as technology ad- vances, the basic idea of the invention may be implemented in many different ways. The invention and its embodiments are thus not restricted to the above- described examples but may vary within the scope of the claims.




 
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