EP2449622B1 - High frequency filter - Google Patents

Description

The invention relates to a high-frequency filter, i.e. a so-called high-pass filter, according to the preamble of claim 1.

In radio-technical systems, for example in the mobile radio sector, it is often desirable to use only one common antenna for the transmitted and received signals. Transmit and receive signals use different frequency ranges. The antenna used must be suitable for transmitting and receiving in both frequency ranges. To separate the transmitted and received signals, a suitable frequency filtering is required, which ensures that on the one hand the transmitted signals from the transmitter only to the antenna (and not in the direction of the receiver) and on the other hand, the received signals from the antenna are only forwarded to the receiver.

For this purpose, a pair of high-frequency filters can be used, both of which allow a specific (i.e. the respectively desired) frequency band to pass through (bandpass filter) or a pair of high-frequency filters which both block a certain (i.e. the respectively undesired) frequency band (band-stop filter), or a Pair of high-frequency filters, made up of a filter that passes frequencies below a frequency between the transmission and reception bands and blocks the frequencies above (low-pass filters), and a filter that blocks frequencies below this frequency between the transmission and reception bands and the above it lets through (high-pass filter). Other combinations of the filter types mentioned can also be used.

High-frequency filters of the type described can be constructed in different ways. A known high-pass filter can consist of a bore or a channel in a milled or cast housing, with inner conductor sections being arranged in the channel or in the bore, which are galvanically connected to the outer conductor via so-called stub lines. The inner conductor sections (if the entire arrangement should still have a compact structural size) generally have very small-dimensioned interruptions, as a result of which the corresponding inner conductor sections are capacitively coupled at their end faces. The size of the capacitive couplings between the line sections is inversely proportional to Change the distance. The frontal capacitive coupling between the inner conductors also increases with an increasing cross-sectional area of the lines and with an increasing dielectric constant of the material that can be located in the gap between the lines. Since the coaxial high-pass filters known and designed according to the state of the art generally require relatively high capacities, the distance between the end faces of the inner conductor sections positioned in an axial extension of one another is (if, as mentioned, comparatively compact outer dimensions are to be maintained ) usually smaller than 0.5 mm (for example when installing in a base station or other antenna device). The distance is often around 0.1 to 0.2 mm.

Based on Figure 12a is in a schematic axial longitudinal section (for example, in a plan view without showing the cover closing the outer conductor) and in Figure 12b a corresponding coaxial high-pass filter, as is known from the prior art, is shown in an axial cross-sectional view (with a cover closing the outer conductor). In a departure from this design, the housing can also be divided into two or more parts, for example it can comprise two housing sections or housing halves that can be joined together. Likewise, the outer conductor housing can also be completely closed, so that the inner conductor arrangement is only pushed axially into this outer conductor housing. There are no restrictions in this regard. It can be seen from this that such a coaxial high-pass filter comprises an outer conductor 1 which - as mentioned - usually consists of a milled or cast housing (metal, metal alloy) in which an axial bore or an axial channel 3 is formed. An inner conductor arrangement 5 is then provided along this bore or this channel 3, which consists of several inner conductor sections 5a. The inner conductor sections end with their inner conductor end face 5b at a small distance A, so that a capacitive coupling results between the inner conductor end faces 5b and thus the inner conductor sections 5a. Furthermore, a dielectric D can be inserted between these inner conductor end faces 5b, for example.

The individual inner conductor sections 5a are each galvanically coupled (as a rule in the middle) to the outer conductor 1 via a branch line 7 running transversely or perpendicularly to the associated inner conductor section 5a, the corresponding branch lines 7 in lateral branch line ducts 9 (i.e. branch line recesses 9). run in the material of the outer conductor 1 and are galvanically connected to the aforementioned outer conductor 1 on the branch line channel bottom 9a (the outer conductor 1 quasi represents the housing of the high-pass filter formed in this way).

Such a high pass in a coaxial structure is, for example, through Matthei, Young, Jones: "Microwave Filters, Impedance-Matching Networks, and Coupling Structures", McGraw - Hill Book Company 2001 , namely on page 414 ( Figure 7 .07-3) as known.

Based on Figure 12c is a corresponding equivalent circuit diagram for the prior art according to the Figures 12a and 12b known high frequency filter reproduced. It can be seen from this that a single inner conductor 5 with individual inner conductor sections 5a is provided, with a capacitance C _{1 being} formed between two inner conductor sections 5a and running from the inner conductor sections 5a, which are continuous to ground, or the outer conductor 1 Branch line 7 is connected in the form of an inductance I.

The desired response behavior of the high-pass filter formed in this way is generated by the paired capacitive coupling of several line sections or line pieces (whereby the coupling can take place via a dielectric consisting of air or some other material) and their galvanic connection with the outer conductor. The degree of capacitive coupling is determined by the size of the opposite two end faces of the inner conductor sections coupled above, by the distance A between the two end inner conductor sections and by the dielectric used between the two end inner conductor sections.

One according to the state of the art as shown Figures 12a and 12b comparable solution is also from the US 2009/0153270 A1 became known that the DE 10 2007 061 413 A1 corresponds to. A high-pass filter is shown with an inner conductor which comprises individual inner conductor sections. Two inner conductor sections following one another in an axial extension are at a distance from one another arranged, the mutually facing end faces as well as an adjoining inner conductor section dipping in a partial length into a tubular intermediate piece which has a closed wall section in the middle between the two end faces of the successive inner conductor sections. This creates a first coupling in the signal direction between the inner conductor end section dipping into the tubular intermediate section and the first tubular capacitor formed in this way, with a second at the opposite end of the tubular intermediate piece between the tubular jacket section and the end section of the adjoining next inner conductor section that plunges there Tube capacitor is formed. A spiral-shaped line section then runs from the inner conductor to the outer conductor at the end-side boundaries of the tubular intermediate piece, as a result of which coils are formed.

This structure results in an inner conductor path with a length compared to the exemplary embodiment according to FIG Figure 12a , intermediate and successive double capacitive coupling from the end of an inner conductor section to the tubular intermediate piece and from the tubular intermediate piece to the next inner conductor section etc ..

With increasing demands on the blocking characteristics of high-pass filters, however, several such inner conductor sections have to be connected in series in order to generate corresponding blocking attenuations.

The disadvantage of the previously known high-pass filters in a corresponding coaxial structure is that a corresponding number of line sections must be arranged one behind the other in order to be able to meet the corresponding requirements for high-pass filters, especially in the field of mobile radio technology. As mentioned, very small distances must be maintained between the line sections in order to ensure the sufficiently high capacitive coupling. This leads to a very high tolerance sensitivity of the structures.

An adjustable filter arrangement is, for example, also from the US 2006/0170522 A1 known. In this filter arrangement, coaxial inner conductor sections are arranged within a coaxial conductor at a distance therefrom, the end faces of which are spaced apart from one another. Over a certain axial length of these inner conductor ends, they are surrounded by an insulating sleeve, which in turn is located in a conductive sleeve. On the one hand, there is a capacitive coupling between the end faces of the inner conductor sections that face one another and are spaced apart from one another, as well as a further capacitive coupling connected in parallel, namely from the one inner conductor section to the coupling sleeve surrounding the inner conductor section and from the coupling sleeve via a further capacitive coupling Coupling to the next inner conductor section.

According to the U.S. 3,792,385 a high-frequency filter with a sleeve tuning element is shown which, in addition to an outer conductor, comprises a continuous inner conductor arrangement. On the continuous inner conductor arrangement are in axial Distances provided as parallel elements capacitances that represent a capacitive connection between the inner conductor and the outer conductor. As a result, a distance filter with a low-pass behavior is generated, specifically by the formation of capacitances which, in contrast to the above-mentioned prior publication US 2006/0170522 A1 are not arranged as series elements, but as parallel elements.

Finally from the U.S. 2,516,529 A Another capacitive connector for coaxial conductors can be seen as known, which has an intermediate structure between two spaced inner conductors in a coaxial outer conductor arrangement, namely with a conductive coupling sleeve which extends over almost the entire distance between the two spaced inner conductor sections and which is provided with an insulating cylinder Dielectric is surrounded.

A ring capacitor is formed at each of the two opposite ends, one ring capacitor being galvanically connected to the one inner conductor section via a connecting line and the other ring capacitor being galvanically connected to the spaced-apart second inner conductor section via a further connecting line.

Between the two ring capacitors, a further separate ring capacitor is provided, which is galvanically connected to the outer conductor via a radial grid arrangement.

This results in an overall structure in which two capacitances are formed by the outer ring capacitors which are connected in series, with a further capacitive connection between the inner conductor and the outer conductor being implemented between these two capacitors connected in series.

From the US 2009/0153270 A1 a high-frequency filter can also be seen as known, which has an intermediate inner conductor between the input and output-side inner conductor section. A two-stage capacitive transmission is provided between the input-side inner conductor section and this intermediate inner conductor as well as from the intermediate inner conductor to the output-side inner conductor section.

Finally, from the pre-publication RIZZI, Peter A., Microwave Engineering (1988, ISBN 0-13-586702-9 ) A high-frequency filter can also be found, which has a coupling element between the input and output-side inner conductor, which ultimately has the same width as the inner conductor sections. This brings about a capacitive coupling from an inner conductor section to the coupling element located between the inner conductor sections and from this to the opposite inner conductor section, that is to say a two-stage capacitive coupling connected in series. The inner conductor intermediate piece is connected to the outer conductor via a branch line.

In contrast, it is the object of the present invention to provide an improved high-frequency filter (a so-called high-pass filter) to create which, with a preferably more compact design, enables the blocking area to be steepened.

The object is achieved according to the invention in accordance with the features specified in claim 1. Advantageous refinements of the invention are given in the subclaims.

It can and must be described as extremely surprising that, compared to the prior art, a significantly improved high-pass filter can be implemented within the scope of the invention, which enables improved electrical properties and a space-saving structure. In addition, the high-pass filter according to the invention is distinguished by a tolerance sensitivity that is significantly improved compared to the prior art.

The high-pass filter according to the invention can also be used as a single filter, but also in combination with one or more similar or different high-frequency filters. The use of the high-frequency filter (RF filter) according to the invention in mobile radio technology, and there in particular with duplex filters, which - as explained at the beginning - are required to divert the transmitted signals fed to an antenna from those received via the same antenna, also results as a favorable application To separate received signals that are sent or received in offset frequency ranges.

The solution according to the invention consists essentially in that an additional inner conductor coupling element is built into the high-frequency filter track, this additional inner conductor coupling element either being metallic and therefore electrically conductive or consisting of or comprising a metallic or electrically conductive coated dielectric . The inner conductor coupling element additionally attached according to the invention is provided in the area of the frontal coupling of the inner conductor sections. If this inner conductor coupling element is, for example, hollow-cylindrical or generally provided with an inner recess, the ends of the adjacent inner conductor sections, i.e. the respective inner conductor end faces, can face each other wholly or at least partially within the inner conductor coupling element in this inner conductor coupling element. However, it is also possible that the inner conductor coupling element with the inner conductor sections interacting with it is arranged so as to overlap only in a partial circumferential area, i.e. for example only over an axial length away from the respective end face of the inner conductor section with the end area of the associated inner conductor -Section covered in order to realize the additional coupling here.

In contrast to the prior art, the electrical connection of the inner conductor to the outer conductor is then not made from the inner conductor sections, but rather with corresponding branch lines from the inner conductor coupling elements.

In the context of the invention, a number of surprising advantages can be achieved through such a structured construction of a high-pass filter.

It is possible within the scope of the invention to generate blocking poles below the frequency pass band, which thus contribute to a considerable steepening of the filter characteristic below the pass band.

A blocking pole can be achieved with each high-pass filter according to the invention using a corresponding inner conductor coupling element. In other words, several such structures can be connected one behind the other (in series), with several additional blocking poles being able to be generated by appropriate coordination. For the sake of completeness, it is already mentioned at this point that the high-pass filter according to the invention can also be assembled with conventional further high-pass filter structures while generating one or more blocking poles. There are also no restrictions in this respect.

In addition, within the scope of the invention, the design of the high-frequency filter can be significantly shortened compared to the prior art. This results in overall more compact overall dimensions.

Furthermore, the sensitivity of the capacitive electrical coupling is reduced by the inserted inner conductor coupling element.

There is also a cost advantage within the scope of the invention. This is because the invention leads to only lower additional costs for the additionally provided inner conductor coupling elements, these additional costs being lower compared to the additional costs of the series connection of additional inner conductor sections, as are necessary today according to the state of the art.

Finally, within the scope of the invention, the mechanical stability can also be increased by the inner conductor coupling elements used. This is especially true when a dielectric is used in solid form, i.e. not in air. This is because the inner conductor sections, the inner conductor coupling elements and / or the branch lines can also be stabilized and held in this way.

In other words, the dielectric, which is at least partially in the inner conductor coupling element in which the inner conductor sections end, can take on an additional positioning function of the inner conductor coupling element and thus also of the inner conductor sections, especially when the dielectric is also outside the Inner conductor coupling element is provided in the corresponding receiving space (bore, channel) of the outer conductor arrangement. Further dielectrics for mechanical stabilization within the structures are also possible, for example also layered dielectrics.

The structures according to the invention allow high powers to be transmitted. There is also an overall good intermodulation behavior - which is also of great importance in mobile radio technology in particular. Finally, it can and must be noted that, within the scope of the solution according to the invention, good heat dissipation is still achieved via the inner conductor coupling elements and, for example, the galvanic coupling to the outer conductor.

A further improvement can also be achieved within the scope of the invention in that the coupling of the inner conductor structures between the inner conductor coupling elements and the outer conductor does not necessarily have to take place in that the corresponding branch lines are galvanically connected to the outer conductor. It is also possible that the branch lines are capacitively coupled to the outer conductor. In this case too, the solid dielectric that may be located in the interior of the outer conductor can also be used to position and fix the branch lines capacitively coupled to the outer conductor.

In summary, it can be stated that a high-frequency filter is created within the scope of the invention, namely a so-called high-pass filter, in which a blocking pole can be generated below the pass band by specifically introducing a structure, also referred to below as an inner conductor coupling element. If several such structures are connected in series, several blocking poles can be generated below the pass band. Such an inner conductor coupling element can be electrically conductive because it consists, for example, of a metal or a metallic structure, or it can be formed from or comprise a dielectric, which for example is coated electrically conductive. Such a design according to the invention of one or more additional blocking poles leads to a significant steepening of the blocking range and to a shortened design while at the same time the high-pass filter is insensitive to tolerances compared to previous solutions. The invention can be used both as an individual filter and in combination with one or more high-frequency filters of the same type or of different types. In addition to the single filter, one of the main applications is the use of so-called duplex filters or, for example, triplexers.

Figur 1a:

eine schematische axiale Längsschnittdarstellung durch ein erstes Ausführungsbeispiel der Erfindung;

Figur 1b:

eine axiale Querschnittsdarstellung längs der Linie I-I in Figur 1a;

Figur 1c:

ein Ersatzschaltbild für das Ausführungsbeispiel gemäß den Figuren 1a und 1b;

Figur 1d:

ein entsprechendes Ersatzschaltbild grundsätzlich wie dargestellt anhand von Figur 1c, jedoch in gegenüber Figur 1c kompakterer Form;

Figur 1e:

ein Diagramm zur Darstellung des Dämpfungsverlaufes bei einem Ausführungsbeispiel entsprechend den Figuren 1a bis 1d unter Ausbildung zweier Sperrpole, hervorgerufen durch die Kapazitäten auf den beiden Signalpfaden;

Figuren 2a

elf weitere schematisch wiedergegebene bis 2k: ..Querschnittsdarstellungen längs der Linie II-II in Figur 1a zur Verdeutlichung unterschiedlicher Innenleiter- und Außenleiter-Querschnittsformen sowie unterschiedlicher Querschnittsdarstellungen des beispielsweise zwischen den Innenleiter-Abschnitten und den Innenleiter-Koppelelementen vorgesehenen (festen) Dielektrikums;

Figur 3a:

eine axiale Längsschnittsdarstellung ähnlich zu Figur 1a bzgl. eines weiteren Ausführungsbeispiels, bei welchem unter anderem die Zweigleitungen kapazitiv mit dem Außenleiter gekoppelt sind;

Figur 3b:

eine Querschnittsdarstellung durch das Ausführungsbeispiel gemäß Figur 3a längs III-III;

Figuren 4a:

acht unterschiedliche Ausführungsbeispiele bis 4h: in schematischem axialen Längsschnitt zur Verdeutlichung der Verkopplung zweier Innenleiter-Endabschnitte unter Verwendung eines Innenleiter-Koppelelementes;

Figur 5a:

eine weiteres erfindungsgemäßes Ausführungsbeispiel in schematischem Axialschnitt mit abweichender Verkopplung zwischen den Innenleiter-Abschnitten und den Innenleiter-Koppelelementen;

Figur 5b:

eine schematische axiale Querschnittsdarstellung längs der Linie V-V in Figur 5a;

Figur 6a:

eine weitere schematische Axialschnittdarstellung durch ein gegenüber Figur 5a abweichendes Ausführungsbeispiel, bei der die Zweigleitung zwischen Innenleiter-Koppelelement und Außenleiter im Bereich des Außenleiters nicht galvanisch, sondern kapazitiv realisiert ist;

Figur 6b:

eine Querschnittsdarstellung längs der Linie VI-VI in Figur 6a;

Figur 7a:

eine Längsschnittdarstellung durch einen Hochpass mit zwei Sperrpolen, bei welchem zwei unterschiedliche erfindungsgemäße Koppeleinrichtungen verwendet werden;

Figur 7b:

eine Querschnittsdarstellung längs der Linie VII-VII in Figur 7a;

Figur 8a:

eine schematische Längsschnittsdarstellung durch einen Hochpass, der ein erfindungsgemäßes Hochfrequenzfilter umfasst, welches in Reihe geschaltet ist mit einem herkömmlichen Hochpass nach dem Stand der Technik;

Figur 8b:

eine Querschnittsdarstellung längs der Linie VIII-VIII in Figur 8a;

Figur 9:

eine Längsschnittdarstellung durch ein weiteres abgewandeltes Ausführungsbeispiel zur Verdeutlichung, dass ein erfindungsgemäßes Hochpassfilter keine Außenleitererweiterung zur Verlängerung einer Zweigleitung benötigt;

Figur 9b:

eine Querschnittsdarstellung längs der Linie IX-IX in Figur 9a;

Figur 10a

drei schematische Querschnittsdarstellunbis 10c: .gen durch einen Hochpassfilter, zur Erläuterung, dass auch weitere TuningElemente zur Veränderung der elektrischen Eigenschaften der entsprechenden Leitungsabschnitte bzw. der Innenleiterkoppelelemente vorgesehen sein können;

Figur 11:

ein Diagramm unter Darstellung eines Vergleichs S-Parameter zwischen dem erfindungsgemäßen Hochpass-Filtergrad 5 mit zwei Innenleiterkoppelelementen und einem Hochpass-Filtergrad 5 nach dem Stand der Technik gemäß Figur 8a und 8b (aufgetragen über die Frequenz);

Figuren 12a

eine schematische axiale Längsschnittdar- und 12b: . stellung und eine Querschnittsdarstellung längs der Linie X-X in Figur 12a für einen Hochpassfilter in koaxialer Struktur nach dem Stand der Technik; und

Figur 12c:

ein Ersatzschaltbild bezüglich eines Hochpassfilters in koaxialer Struktur nach dem Stand der Technik, wie es anhand der Figuren 12a und 12b wiedergegeben ist.

Further advantages, details and features of the invention emerge from the exemplary embodiments explained with reference to the drawings. The following show in detail:

Figure 1a:

a schematic axial longitudinal section through a first embodiment of the invention;

Figure 1b:

an axial cross-sectional view along the line II in Figure 1a ;

Figure 1c:

an equivalent circuit diagram for the embodiment according to FIG Figures 1a and 1b ;

Figure 1d:

a corresponding equivalent circuit basically as shown on the basis of Figure 1c , but in opposite Figure 1c more compact shape;

Figure 1e:

a diagram to illustrate the attenuation curve in an embodiment according to FIG Figures 1a to 1d with the formation of two blocking poles, caused by the capacitances on the two signal paths;

Figures 2a

eleven further schematically reproduced up to 2k: .. Cross-sectional views along the line II-II in Figure 1a to illustrate different inner conductor and outer conductor cross-sectional shapes as well as different cross-sectional representations of the (solid) dielectric provided, for example, between the inner conductor sections and the inner conductor coupling elements;

Figure 3a:

an axial longitudinal section view similar to Figure 1a Regarding a further exemplary embodiment in which, among other things, the branch lines are capacitively coupled to the outer conductor;

Figure 3b:

a cross-sectional view through the embodiment according to Figure 3a along III-III;

Figures 4a:

eight different exemplary embodiments up to 4h: in a schematic axial longitudinal section to illustrate the coupling of two inner conductor end sections using an inner conductor coupling element;

Figure 5a:

a further exemplary embodiment according to the invention in a schematic axial section with a different coupling between the inner conductor sections and the inner conductor coupling elements;

Figure 5b:

a schematic axial cross-sectional view along the line VV in Figure 5a ;

Figure 6a:

a further schematic axial section through an opposite Figure 5a different embodiment in which the branch line between the inner conductor coupling element and the outer conductor in the area of the outer conductor is not implemented galvanically, but capacitively;

Figure 6b:

a cross-sectional view along the line VI-VI in Figure 6a ;

Figure 7a:

a longitudinal sectional view through a high pass with two blocking poles, in which two different coupling devices according to the invention are used;

Figure 7b:

a cross-sectional view along the line VII-VII in Figure 7a ;

Figure 8a:

a schematic longitudinal section through a high-pass filter comprising a high-frequency filter according to the invention, which is connected in series with a conventional high-pass filter according to the prior art;

Figure 8b:

a cross-sectional view along the line VIII-VIII in Figure 8a ;

Figure 9:

a longitudinal sectional view through a further modified embodiment to illustrate that a high-pass filter according to the invention does not require an external conductor extension to extend a branch line;

Figure 9b:

a cross-sectional view along the line IX-IX in Figure 9a ;

Figure 10a

three schematic cross-sectional representations to 10c: .gen through a high-pass filter, to explain that further tuning elements can also be provided for changing the electrical properties of the corresponding line sections or the inner conductor coupling elements;

Figure 11:

a diagram showing a comparison of S parameters between the high-pass filter degree 5 according to the invention with two inner conductor coupling elements and one High-pass filter degree 5 according to the prior art Figures 8a and 8b (plotted against the frequency);

Figures 12a

a schematic axial longitudinal section and 12b:. position and a cross-sectional view along the line XX in Figure 12a for a high-pass filter in a coaxial structure according to the prior art; and

Figure 12c:

an equivalent circuit diagram with regard to a high-pass filter in a coaxial structure according to the prior art, as shown with reference to FIGS. 12a and 12b.

The following is based on the Figures 1a and 1b reference is made to a first exemplary embodiment according to the invention.

This exemplary embodiment according to the invention differs from the high-frequency filter in coaxial construction according to the prior art according to FIGS Figures 12a and 12b Among other things, in that an inner conductor coupling device 15 in the manner of an inner conductor coupling element 115 is now provided in the area of the inner conductor end sections 5c, over which the inner conductor end sections 5c overlap with the inner conductor coupling element 115 with a certain axial length.

In the embodiment shown according to Figures 1a and 1b is the inner conductor coupling device 15 as an inner conductor Koppelyzlinder 15a, in which the inner conductor end sections 5c immerse with a certain axial length, wherein the inner conductor end faces 5b of the inner conductor sections 5a positioned in an axial extension of one another come to lie at a distance A from one another.

In the exemplary embodiment shown, the inner conductor sections 5a are arranged on a common axis line X1 in a direct axial extension of one another and in the process plunge coaxially into the inner conductor coupling cylinder 15a.

In principle, the individual inner conductor sections can be held and anchored by dielectric spacers in the inner conductor space 21, designed as a channel 3, for example, opposite the outer conductor 1 (i.e. the outer conductor housing 10), for example also in that the entire inner conductor space 21 or only certain sections of the Inner conductor space is filled, poured, etc. with a solid dielectric. Likewise, several dielectric structures can also be provided, for example at an axial distance, in the inner conductor space 21, via which individual areas of the inner conductor sections can be mechanically held and supported with respect to the outer conductor.

In the embodiment shown, a dielectric 23 is provided in the area of the inner conductor coupling device 15, ie in the interior of the inner conductor coupling cylinder 15a, preferably not from air, but from a solid material (for example plastic, ceramic, etc.) over what the individual inner conductor sections 5a are held and positioned by the inner conductor coupling cylinder 15a.

The branch lines 7 already explained in the prior art are not coupled to the individual inner conductor sections 5a in the embodiment according to the invention, but are electrically-galvanically connected to the respective inner conductor coupling device 15, ie to the inner conductor coupling element 115 and preferably run across and in shown embodiment perpendicular to the axial extension X1 of the inner conductor 5 in a corresponding branch line channel 9 to the branch line channel bottom 9a in the outer conductor housing 10 and are opposite to the inner conductor coupling device 15 electrically-galvanically connected to the outer conductor 1, ie the outer conductor housing 10.

The individual branch lines can, however, also be located in a second line channel located in the bottom of the outer conductor housing or on opposite sides of the outer conductor. There are no restrictions in this regard.

As can be seen from the axial longitudinal section according to Figure 1a also results, the dielectric preferably formed from a solid dielectric 23 in this embodiment does not have to extend over the entire axial length of the inner conductor coupling cylinder 15a, but can end in front of the front end of the inner conductor coupling cylinder 15a (as in Figure 1a is shown for the example of the coupling on the right) or can even use the inner conductor coupling cylinder 15a in the axial direction survive (as shown in the exemplary embodiment according to FIG. 1a for the left-hand coupling).

The inventive solution using the coupling device 15 results in two capacitive couplings connected in series, namely, for example, a first coupling from one inner conductor end section 5b to the inner conductor coupling device 15 and from the inner conductor coupling device 15 to the next adjacent inner conductor end section 5c of a subsequent adjacent inner conductor end section 5b. In terms of their function, these capacitive couplings correspond to the end-side coupling between the end faces 5b in the high-pass filter according to the prior art, as shown on the basis of FIG Figures 12a and 12b is explained. In the invention, the capacitive coupling provided between the end faces 5b is now additionally generated by the aforementioned capacitive coupling in series via the new inner conductor coupling device 15, which is now shown in this structure according to FIG Figures 1a and 1b the generation of additional blocking poles is used to improve the flank of the high pass compared to the prior art.

Figure 1c shows an equivalent circuit diagram of the solution according to the invention according to FIG Figures 1a and 1b , where in Figure 1d the equivalent circuit diagram in a more compact representation compared to the representation in Figure 1c is reproduced.

It can be seen from this that within the scope of the invention, by introducing new capacitances C _2, a further capacitive coupling is now created through which ultimately two blocking poles can be realized by two signal paths P1 and P2.

When Figure 1e a diagram is then shown in which the transmission loss in dB is shown on the vertical Y-axis and the frequency in GHz for a high-frequency filter is shown on the horizontal X-axis. The attenuation curve relates to an embodiment as it is for the solution according to the invention according to FIGS Figures 1a to 1d was implemented, with an attenuation of, for example, 200 MHz to 960 MHz, the attenuation being greater than 60 dB. It can be clearly seen in the diagram according to FIG Figure 1e the formation of two blocking poles, which are caused by the capacitive couplings on the two signal paths. These improvements according to the invention are neither possible nor known with conventional solutions.

As can be seen from the schematic cross-sectional representation according to Figures 2a to 2k results, both the cross-sectional shape of the outer conductor, the cross-sectional shape of the inner conductor, the cross-sectional shape of the inner conductor coupling device and the cross-sectional shape of the dielectric 23 provided, for example, between the inner conductor end sections and the inner conductor coupling device 15 can have a wide variety of shapes, in particular cross-sectional shapes.

In the schematic cross-sectional representations according to FIGS. 2a to 2k, the outer conductor housing extensions 1 'are shown with a larger material extension, in which the mentioned branch line recesses or channels 9 for receiving the branch lines are accommodated. If necessary, however, the outer conductor housing does not have to be included an outer conductor housing extension 1 ', but can generally be tubular (with any cross-sectional shape) so that the branch lines 7 are connected directly to the inner wall of the outer conductor housing or outer conductor tube, generally the outer conductor.

The branch line recesses can also be located in the outer conductor area or in the correspondingly recessed cover.

They show Figures 2a to 2k that, for example, the outer contour of the outer conductor 1 can be rectangular or square or generally n-polygonal. Likewise, however, the outer conductor can ultimately also have a round or partially round cross-sectional shape, at least on its outside. It can be designed oval or cylindrical. There are no restrictions on certain cross-sectional shapes or external contours.

The Figures 2a to 2d also show that, for example, the cross-sectional shape of the inner conductor space 21, at least outside the area in which the branch line recesses or channels 9 are provided in the outer conductor 1, can have a square or rectangular, cylindrical or generally n-polygonal cross-sectional shape, which is defined by the outer conductor inner surface 1a is formed.

Also show the Figures 2a to 2k also that the inner conductor 5, ie the inner conductor sections 5a and in particular the inner conductor end sections 5c, can have different cross-sectional shapes, for example round cross-sectional shapes, square or rectangular cross-sectional shapes, generally n-polygonal cross-sectional shapes. However, oval cross-sectional shapes or mixed shapes are also possible for the inner conductor cross-section, as well as a cross-sectional shape in which rounded transition areas are provided between the different side surfaces. However, elliptical cross-sectional shapes etc. are also conceivable. There are no restrictions in this regard.

The cross-sectional representations according to Figures 2a to 2k furthermore show that, above all, the inner conductor coupling devices 15 can also have a wide variety of cross-sectional shapes, for example in the manner of a hollow cylinder with a round cross-sectional shape or with an angular cross-sectional shape or at least partially or in sections with an angular or square outer surface 15b and an inner surface, also partly or in sections round, square or generally n-polygonal inner surface 15c etc .. Here, too, the individual wall sections, ie the individual surfaces on the outside or inside of the inner conductor coupling element 115, can merge into adjacent wall sections via corners or roundings.

Based on Figure 2j it is shown that, for example, the inner conductor coupling device 15 can have an oval cross-sectional shape with respect to its outer surface 15b, and in FIG Deviating from this, the surfaces 15c lying on the inside facing the inner conductor end sections can have a cross-sectional shape that differs therefrom, for example a cross-sectional shape approximating a square or rectangle.

The example according to Figure 2f also shows that the inner conductor coupling element 115 is not completely closed in the circumferential direction, but can be provided with an opening section 15d, similar to the embodiment according to FIG Figure 2g . It is in the embodiment according to Figure 2g the opening area 15d as well as the distance between the inner conductor end section 5b and the inner conductor coupling device 15 are filled with a dielectric 23.

The examples according to Figures 2h and 2i also show that the inner conductor coupling element 115 can be arranged, for example, only in a side area or a partial circumferential area - in relation to the inner conductor sections - generally parallel or generally more or less in the overlapping direction to the inner conductor end sections 5c, in order to be next to the capacitive coupling between the inner conductor end faces 5b of two inner conductor sections 5a arranged in extension to one another, an additional coupling between the respective inner conductor end section 5b to the inner conductor coupling element 115 and from the inner conductor coupling element 115 to the next adjacent inner conductor end section of a to generate the next inner conductor section 5a.

They show Figures 2f, 2g, 2h or 2i or 2j that the inner conductor coupling device 15 is to be coupled Inner conductor end sections 5c in a circumferential range of more than 10 °, in particular more than 20 °, 30 °, 40 °, 50 °, 60 °, 70 °, 80 °, 90 °, 100 °, 110 °, 120 °, 130 °, 140 °, 150 °, 160 °, 170 °, 180 °, 190 °, 200 °, 210 °, 220 °, 230 °, 240 °, 250 °, 260 °, 270 °, 280 °, 290 °, 300 °, 310 °, 320 °, 330 °, 340 °, 350 °.

The same cross-sectional representations also show that the inner conductor coupling device 15 moves the inner conductor end sections 5c to be coupled by less than 360 °, 350 °, 340 °, 330 °, 320 °, 310 °, 300 °, 290 °, 280 °, 270 °, 260 °, 250 °, 240 °, 230 °, 220 °, 210 °, 200 °, 190 °, 180 °, 170 °, 160 °, 150 °, 140 °, 130 °, 120 °, 110 ° , 100 °, 90 °, 80 °, 70 °, 60 °, 50 °, 40 °, 30 ° and in particular less than 20 °.

In the exemplary embodiment according to FIG. 2h it is shown, for example, that the inner conductor coupling element 115 can be semicylindrical in cross-sectional form, the variant according to Figure 2i shows that the design of the coupling element 115, even if it encloses the inner conductor end sections only in a partial circumferential area or is arranged to do so, can have an outer contour 15b deviating from the inner contour 15c, for example, can be designed in the form of a semi-cylinder on the inside or a rectangular shape on the outside. These examples show that in this respect there are no restrictions with regard to the shape and / or arrangement of the inner conductor coupling device 15.

The exemplary embodiment according to FIG Figure 2k also that, for example, the corresponding inner conductor end sections 5b and the inner conductor coupling device 15, which usually runs parallel to it, can be plate-shaped, ie also plate-shaped, i.e. as flat material, preferably with an interposed dielectric 23, which is also again plate-shaped in cross-section is. In the embodiment shown according to Figure 2k a further dielectric 23 '(rectangular in cross section), which can also be provided on the coupling device, is provided below it again below the one inner conductor end section.

This exemplary embodiment, too, is ultimately understood in the sense of a high-frequency filter with a coaxial design.

Finally, some of the exemplary embodiments also show that the outer conductor can be designed as a closed overall housing, with a corresponding inner conductor channel 3. In the variants according to FIG Figures 2b, 2c, 2d, 2f, 2g, 2i and 2k it is also shown that the outer conductor housing is divided into two parts and comprises an actual housing section which is closed with a preferably detachable outer conductor housing cover 1a. Alternatively and additionally, for example, using Figure 2a shown that the housing can also consist of two housing halves 1b and 1c, which can be separated along a separation plane T, preferably centrally at the level of the inner conductor. This separation plane can, however, also be designed in a different position and does not have to be in the plane of the Inner conductor sections lie so that the two housing parts are designed to be of different sizes. Any modifications are possible here.

Finally, based on the explained Figures 2a to 2k noted that with regard to all contours, cross-sectional shapes, internal surfaces or outward-facing surfaces of the outer conductor, the inner conductor sections, the coupling elements, the dielectrics, etc., many mixed forms can be provided, and the schematic cross-sectional representations according to Figures 2a to 2k should only show a few of the possible variants.

Based on Figure 3a is in a schematic axial longitudinal section and in Figure 3b in a schematic axial section in deviation from Figure 1a and FIG. 1b shows that the electrical connection between the inner conductor coupling device 15 and the outer conductor 1 via the branch line 7 can be made not only galvanically, but also capacitively.

The branch line 7 is shown opposite the inner conductor coupling device 15 with a branch line coupling section 7a in the form of a branch line base 7a, which in the variant according to FIG Figure 3a on the left a cubic shape, for example a cube shape but also a cylindrical shape and in the variant according to FIG Figure 3a on the right can have a spherical shape or also a cylindrical shape. Correspondingly, the recess 1b is then also provided in the material of the outer conductor 1a, into which the corresponding branch line coupling section 7a intervenes. The outer conductor recess 1b is preferably adapted to the cross-sectional shape or contour of the branch line base section 7a (although here, too, deviations are possible and the cross-sectional shape of the outer conductor recess 1b deviates from the cross-sectional shape or contour of the branch line base section 7a or is completely different from it can be).

With the variant in Figure 3a On the left, a solid dielectric 23a is provided between the branch line coupling section 7a and the outer conductor recess 1b. This opens up the possibility that the branch line section 7 is held on the outer conductor 1 of the outer conductor housing 10 and the inner conductor coupling element 115 is also positioned firmly and stably in the inner conductor space 21. As mentioned, the inner conductor coupling element 15 is also provided with a solid dielectric 23, so that the inner conductor end sections 5a are also held and positioned over it and the actual inner conductor sections 5a are not held in the inner conductor space 21 via further dielectric spacers and need to be positioned. With the right variant in Figure 3a air is provided as a dielectric 23a between the branch line coupling section 7a and the outer conductor recess 1b.

The variant according to Figures 3a (shown in longitudinal section) and 3b (showing a cross section along the line III-III in FIG Figure 3a reproduces) further shows that the coupling devices 15 also in the axial longitudinal direction, that is, in the direction of extent X1 of the inner conductor sections 5a do not have to be of the same design, but can have different longitudinal extensions at different sections in the circumferential direction and thus overlap sections of different sizes with the associated inner conductor end sections 5c.

Furthermore, the inner conductor sections can also have different diameters, also include gradations in the axial longitudinal extent at which they transition from a smaller diameter to a larger diameter or vice versa. In addition, additional dielectrics can be provided in the area of the coupling elements (for example in the area of the inner surfaces of the outer conductors), which for example extend to the coupling element or end beforehand. For the sake of clarity, however, these variants are shown in Figures 3a and 3b not shown. It is partly due to the Figures 2a to 2k referenced, which represent and reproduce some variants.

Based on Figures 4a to 4h it is also shown how the coupling between the end faces 5d of the inner conductor sections 5a and the additional coupling via the inner conductor end sections 5b can be implemented via the inner conductor coupling device 15.

With the variant according to Figure 4a the inner conductor end sections 5c are designed with the same diameter and, for example, the same cross-sectional shape, roughly round, the inner conductor coupling element having a larger inner diameter than the outer diameter of the inner conductor end sections is formed so that the inner conductor end sections can dip into the interior 15e of the tubular inner conductor coupling device 15 in this embodiment in a certain axial length, so that the associated inner conductor end faces 5b end at the mentioned distance A from one another. In this exemplary embodiment, the interior 15e of the coupling device 15 is filled with a solid dielectric 23, for example also poured out, via which the inner conductor sections 5b can be held mechanically.

With the variant according to Figure 4b the outermost inner conductor end sections 5c adjacent to their end faces 5b are provided with a circumferential annular projection 5r, that is to say an area which has a larger outer diameter than the inner conductor end section 5c adjoining it. In particular when the inner conductor coupling element 115, which is completely or partially closed in the circumferential direction, is poured and / or filled with the dielectric 23, this results in a particularly favorable mechanical fixing of the inner conductor end sections 5c, which is not only in the radial direction but also in the axial direction are held against the dielectric.

With the variant according to Figure 4c a circumferential inner conductor groove 5n is formed in an end region of the inner conductor end section 5c shown on the right, whereby the same advantage is achieved. Here, too, there are good axial fixations with respect to the inner conductor and dielectric.

With the variant according to Figure 4d it is shown that the one inner conductor end section 5c is designed, for example, with a blind hole (generally an inner conductor receptacle 5 "c) into which the second inner conductor end section 5c, which is designed with a smaller outer diameter, engages in a contact-free manner in a certain axial length In this variant, on the one hand, a direct capacitive coupling is realized between the two end sections 5c between the two inner conductor sections 5a positioned in this way and, on the other hand, a capacitive coupling of one inner conductor section 5a or inner conductor end section 5c (the one with the mentioned inner conductor Receptacle 5 ″ c) to the inner conductor coupling device 15 arranged so as to be overlapping, as well as the further capacitive coupling from this inner conductor coupling device 15 to the in Figure 4d inner conductor end section 5c lying on the right. Finally, the dielectric 23 projects on the right-hand side over the coupling device in the radial direction.

In the example according to Figure 4e the diameters of the inner conductor sections 5a are different and so are the central axes of the two inner conductor end sections shown. Because in Figure 4e the central axes X2 and X3 are offset to one another, so that the distance between the outer circumference of the inner conductor end section 5c on the right does not come to lie coaxially with the, for example, tubular or hollow-cylindrical inner conductor coupling element. Furthermore, the in Figure 4e Inner conductor end section 5c lying on the left into a tapered end section 5'c which has a smaller outer diameter. The inner conductor end section on the right has here, adjacent to the dielectric 23, a circumferential annular shoulder 5r which has a larger outer diameter than the inner conductor end section which dips into the dielectric.

The variant according to Figure 4f shows only a plate-shaped coupling element 115 which, with the interposition of a dielectric 23, is arranged in an overlapping manner and connected to the inner conductor end sections 5c (parallel position to this) running towards one another and ending at a short distance A from one another.

The variant according to Figure 4g further shows that the coupling element (even if it is, for example, completely or partially closed in the circumferential direction) does not have to have the same outer or inner diameter over its axial length. In this embodiment according to Figure 4g it is designed conically. Finally, however, other gradations can also be provided not only on the inner conductor, but also on the coupling device 15, as shown, for example, on the basis of FIG Figures 4c and 4e is shown with respect to an elevation 15e or 15s for the gradation.

Figure 4h shows only schematically that, in general, the inner conductor end sections to be coupled directly capacitively do not necessarily have to be in an axial extension of one another, but can generally end next to one another. Here are according to Figure 4h two opposite inner conductor end sections 5d tapering in the form of a fork in cross-section for the inner conductor end section on the left, in which a tapered inner conductor end section 5e of the inner conductor end section 5c on the right engages (coaxially or eccentrically), the overall arrangement in this exemplary embodiment dipping into the inner conductor coupling device with the end sections directly coupled to one another.

The embodiment according to FIG Figure 5a (in longitudinal section) and Figure 5b (in cross section along the line VV in Figure 5a ) shows a further similar modification to the previous exemplary embodiments, quasi in the sense of a reversal to the embodiment variant according to FIG Figures 1a and 1b . Because in this embodiment after Figures 5a and 5b the inner conductor end sections 5c of the inner conductor sections 5b to be coupled at the end end fork-shaped or pot-shaped or in mixed forms, the actual inner conductor coupling element 115 then being arranged on the inside between the fork-shaped or pot-shaped inner conductor end section. This also results in the multiple capacitive coupling directly between the inner conductor end sections on the one hand and between the respective inner conductor end section and the associated inner conductor coupling element on the other hand.

Figure 6a shows one to Figure 5a corresponding embodiment, however, again with the difference that - similar to in Figure 3a the branch lines 7 are not galvanically connected to the outer conductor, but rather capacitively in the area of the branch line base sections 7a. Figure 6b shows a corresponding cross-sectional view along the line VI-VI in FIG Figure 6a . In this exemplary embodiment, too, a solid dielectric or air can be provided as the dielectric.

In particular, according to the cross-sectional illustration Figure 6b It can also be seen that the branch line coupling section 7a can be designed in the shape of a pin or preferably plate and comes to lie at a small distance A1 from a correspondingly shaped, here flat coupling plane to the outer conductor 1. If necessary, a dielectric 23 ′ made of solid material and not of air can again be provided here. The coupling surface of the outer conductor here runs perpendicular to the extension of the outer conductor.

On the basis of the axial longitudinal section according to Figure 7a and the cross-sectional view along the line VII-VII in Figure 7a It is intended to show that in principle any high-pass filter structure according to the invention can be interconnected in series to form a common high-pass filter in accordance with one of the variants or modifications explained. With the variant according to Figure 7a For example, two high-pass filters are connected in series, with one high-pass filter depending on the structure of that example Figure 5a and the high-pass filter on the right according to a variant Figure 1a corresponds to. This results in a high pass with two additional blocking poles.

The variant according to Figures 8a and 8b shows only that, for example, even individual high passes, as shown in accordance with the solution according to the invention using one of the examples explained above, with a conventional one High-pass filter structure can be interconnected, as was explained at the beginning with regard to the prior art.

With the variant according to Figures 9a and 9b it is only shown that the branch lines 7 do not necessarily have to end in branch line channels 9 in the outer conductor housing 1, i.e. the outer conductor housing does not necessarily have to be provided with an outer conductor housing extension 1 ', as explained in one of the previous exemplary embodiments. With the variant according to Figures 9a, 9b For example, an outer conductor housing with a square or tubular cross-section is used, in which the inner conductor sections with the coupling elements and the branch lines extending therefrom are arranged in the corresponding inner conductor space 21, which are galvanically or capacitively connected to the outer conductor housing at the end.

The individual branch lines can also be galvanically or capacitively connected on opposite sides to the outer conductor housing or also to the base or cover at the end.

As already mentioned, the individual branch line ducts 9 can, however, also be provided in a corresponding cover construction, so that the branch lines can be provided and accommodated here.

Based on Figures 10a and 10b it is also shown that additional tuning elements T at one or more points of the outer conductor housing, preferably from the outside adjustable (for example by turning them in and out of different lengths into the interior space 21). With the variant according to Figure 10b A tuning element T on the right is formed in the shape of a rod and even protrudes over the opening section 15d into the space within the coupling element 115 into a space provided there in the dielectric and can also be moved differently into the dielectric from the outside, preferably by further turning it in and out Outer conductor housing can be adjusted protruding.

By means of these measures, known per se, the electrical properties or individual line sections or inner conductor coupling elements can be changed and thus the frequency profile of the high-pass filter can be set differently according to the specifications and wishes.

In the exemplary embodiments shown, all electrically conductive structures can consist of metal, metal alloys, for example cast, milled, turned, deep-drawn and / or sheet metal or bent parts. It is also possible, however, for the correspondingly explained electrically conductive parts to consist of an insulator, plastic, generally a dielectric, and for the electrically conductive parts or surfaces to be covered with an electrically conductive surface. Mixed forms of metallic components (for example for the outer conductors) as well as parts arranged inside such as the coupling element, inner conductor sections or branch lines can also consist of electrically conductive surfaces provided with or formed on electrically conductive surfaces Tracks can be formed which are also made of dielectric materials, for example.

As can be seen on the basis of the exemplary embodiments explained, a high-pass filter with a coaxial structure (i.e. with an inner conductor or inner conductor section running into an outer conductor) can basically be implemented within the scope of the invention, which at least one additional metallic or electrically conductive inner conductor coupling element or comprises the corresponding inner conductor coupling device for generating additional blocking poles below the passage area. In this case, a blocking pole can be achieved per inner conductor coupling element 115 used, that is to say generally per inner conductor coupling device 15 used. By corresponding multiple interconnection of the high-pass filter structures according to the invention, a high-pass with several blocking poles that are offset from one another can thus be built up.

Based on Figure 11 are in comparison the S parameters for the case of a high-pass filter according to the invention with degree 5 with two inner conductor coupling elements and the resulting S parameters with regard to a solution according to the prior art ( Figures 12a and 12b ), namely plotted against the frequency. The curves marked with a triangle and a square relate to the high-pass filter according to the invention, whereas those marked with a | or measuring points marked with a circle which relate to a high-pass filter according to the prior art according to FIGS. 8a and 8b. From this it can therefore be clearly seen how the invention, when using two inner conductor coupling elements, creates two additional blocking poles arise below the pass band f lock, whereby a considerable steepening of the filter characteristic is produced below the pass band f lock. The size of the blocking attenuation is then obtained on the y-axis, which increases in the direction of the arrow downwards.

The explained high-pass filter can typically be used in the frequency range from 100 MHz to 10 GHz.

The electrical coupling of the individual conductor sections, i.e. the individual conductor sections 5b to one another, can be achieved via the distance between the end faces of the directly coupled inner conductor sections and via the distance between the inner conductor end section 5c (or its outer surface 5d) and the adjacent upper and / or inner surface 15c of the inner conductor coupling device 15, in particular of the inner conductor coupling element 115, as well as through the use of a dielectric, or their size can be set differently. The frontal capacitive coupling of the line sections creates a blocking pole below the pass band. The inner conductor coupling elements are galvanically connected or capacitively coupled to the outer conductor.

Finally, it is also mentioned that the inner conductors as well as the coupling devices can be made from a wide variety of inherently electrically conductive materials or from dielectrics with electrically conductive coatings, with the inner conductor also being able to be made from a flat or sheet material, for example such as the branch line. There are no restrictions in this respect either. With one of the explained high-pass filter structures, for example, a duplexer consisting of low-pass and high-pass filters can also be constructed, with the high-frequency filter structure according to the invention being used for a high-pass and a conventional filter structure for the low-pass.

Claims (19)

1. Radio frequency filter for mobile communications technology having a coaxial design, comprising the following features:

   - an outer conductor (1),

   - an inner conductor arrangement (5),

   - at least one branch line (7), via which there is an electrical connection between the inner conductor arrangement (5) and the outer conductor (1),

   - at least two inner conductor portions (5a) which have a distance (A) between the inner conductor end faces (5b) thereof or the inner conductor end portions thereof (5c), so as to form a capacitive coupling,

   - at least one further inner conductor coupling device (15) having an inner conductor coupling element (115) is provided in addition to the capacitive coupling between the at least two inner conductor end faces (5b) or the capacitively coupled inner conductor end portions (5c),

   - the inner conductor coupling device (15) having the inner conductor coupling element (115) is either metallic or consists of a metallically or electrically conductively coated dielectric,

   - the inner conductor coupling element (115) is arranged in at least partly overlapping arrangement with the inner conductor end portions (5c) of the coupled inner conductor portions (5b), as a result of which two capacitive couplings are connected in series, specifically a first coupling between the one inner conductor end portion (5b) and the inner conductor coupling device (15) and a second coupling between the inner conductor coupling device (15) and the next adjacent inner conductor end portion (5c) of a subsequent adjacent inner conductor end portion (5b),

   - the branch line (7) extends between the inner conductor coupling element (115) and the outer conductor (1),

   - the branch line (7) is electrically-galvanically connected to the inner conductor coupling element (115), and

   - the branch line (7) is galvanically connected or capacitively coupled to the outer conductor (1) at the end thereof opposite the inner conductor coupling element (115).
2. Radio frequency filter according to claim 1, characterised in that the inner conductor coupling device (15) is tubular, the inner conductor end portions (5c) to be coupled entering the interior space (15b) of the inner conductor coupling device (15).
3. Radio frequency filter according to either claim 1 or claim 2, characterised in that the inner conductor coupling device (15) extends only partly in the circumferential direction and has an opening portion (15d).
4. Radio frequency filter according to claim 3, characterised in that the inner conductor coupling device (15) surrounds the inner conductor end portions (5c) to be coupled in a circumferential range of more than 10°, in particular more than 20°, 30°, 40°, 50°, 60°, 70°, 80°, 90°, 100°, 110°, 120°, 130°, 140°, 150°, 160°, 170°, 180°, 190°, 200°, 210°, 220°, 230°, 240°, 250°, 260°, 270°, 280°, 290°, 300°, 310°, 320°, 330°, 340°, or 350°.
5. Radio frequency filter according to either claim 3 or claim 4, characterised in that the inner conductor coupling device (15) surrounds the inner conductor end portions (5c) to be coupled by less than 360°, 350°, 340°, 330°, 320°, 310°, 300°, 290°, 280°, 270°, 260°, 250°, 240°, 230°, 220°, 210°, 200°, 190°, 180°, 170°, 160°, 150°, 140°, 130°, 120°, 110°, 100°, 90°, 80°, 70°, 60°, 50°, 40°, 30° and in particular less than 20°.
6. Radio frequency filter according to any of claims 1 to 5, characterised in that the inner conductor end portions (5c) to be coupled enter an associated inner conductor coupling device (15) to different extents or overlap with the associated inner conductor coupling device (15) to different lengths.
7. Radio frequency filter according to any of claims 1 to 6, characterised in that the inner conductor end portions (5c) to be coupled are arranged coaxially to one another and therefore coaxially or eccentrically to the inner conductor coupling device (15).
8. Radio frequency filter according to any of claims 1 to 6, characterised in that the inner conductor end portions (5c) to be coupled are arranged in such a way that the central axes thereof are offset from one another.
9. Radio frequency filter according to any of claims 1 to 8, characterised in that the outer conductor (1), the inner conductor coupling device (15) and the inner conductor end portions (5c) have different diameters, different cross-sectional shapes and/or different designs, in particular are pin-shaped, fork-shaped or pot-shaped and/or have or comprise different outer and/or inner diameters, gradations and/or projections or have at least portions in the longitudinal direction having conically modified outer or inner surfaces.
10. Radio frequency filter according to any of claims 1 to 9, characterised in that

    a) the inner conductor coupling device (15), in particular in the form of an inner conductor coupling element (115), has a square shape, a rectangular shape, an n-polygonal shape and/or cross-sectional shape having concave curved portions, and/or

    b) the inner or outer surface portions (15c) facing the relevant inner conductor end portions (5c) have surfaces which extend straight or are at an angle to one another or are provided with curved surface portions, and/or

    c) the surface portions (15b) facing away from the inner conductor end portions (5c) in the direction of the outer conductor (1) comprise straight or optionally angled surface portions or curved surface portions.
11. Radio frequency filter according to any of claims 1 to 10, characterised in that the at least one branch line (7) is galvanically connected, at the end thereof opposite the inner conductor coupling device (15), to the outer conductor (1).
12. Radio frequency filter according to any of claims 1 to 10, characterised in that the at least one branch line (7) is capacitively coupled, at the end thereof opposite the inner conductor coupling device (15), to the outer conductor (1).
13. Radio frequency filter according to claim 12, characterised in that the branch line (7) has a branch line portion, coupling portion or base portion (7a) which is preferably arranged in an outer conductor recess (1') using a dielectric made of air or solid material.
14. Radio frequency filter according to any of claims 1 to 13, characterised in that the inner conductor end portions (5c) having the inner conductor coupling device (15) are held using a solid dielectric (23) and/or the inner conductor portions (5b) having the outer conductor inner surface (la) are held using a solid dielectric.
15. Radio frequency filter according to any of claims 1 to 14, characterised in that the inner conductor coupling device (15) is mechanically held via the branch line (7) which is galvanically connected to the outer conductor or via the branch line (7) which is capacitively coupled to the outer conductor (1) using a dielectric (23a).
16. Radio frequency filter according to any of claims 1 to 15, characterised in that a plurality of pairs of inner conductor portions (5a) that are coupled to one another are connected in series, and in that, for each coupled pair of inner conductor portions (5a), an additional blocking pole can be generated below the pass band using an associated inner conductor coupling device (15) in each case.
17. Radio frequency filter according to any of claims 1 to 16, characterised in that in the case of a plurality of pairs of inner conductor portions (5a) coupled in series, the inner conductor coupling devices (15) are designed identically or differently.
18. Radio frequency filter according to any of claims 1 to 17, characterised in that the branch line (7) is provided or extends in the inner conductor space (21) or in a branch line channel (9) extending transversely therefrom, the branch line channel (9) being provided in the material of the outer conductor housing (10) or in the material of an outer conductor cover (la).
19. Radio frequency filter according to any of claims 1 to 18, characterised in that the inner conductor end portions (5c) have the same shape or a different shape and are in particular designed to be interlocking.

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