EP1858109A1

EP1858109A1 - Dielectric TE dual mode resonator

Info

Publication number: EP1858109A1
Application number: EP06009965A
Authority: EP
Inventors: Michael Dr.-Ing. Höft
Original assignee: Matsushita Electric Industrial Co Ltd
Current assignee: Panasonic Corp
Priority date: 2006-05-15
Filing date: 2006-05-15
Publication date: 2007-11-21

Abstract

The present invention relates to a dielectric dual mode resonator (1) comprising a dielectric core element (2) made of dielectric material having a dielectric constant ε_r of between 20 and 80, and having a cross-shape in a horizontal direction, wherein the dielectric core element (2) is formed with two through-holes (3, 4) lying in a horizontal plane and intersecting each other in substantially right angles.

Description

The present invention relates in general to the field of filters and, in particular, to dielectric filters and dielectric resonators, an example of which are dielectric TE (transverse electric) dual mode resonators for use in communications systems.
A dielectric resonator is the basic unit of a filter. In general, a dielectric resonator is a piece of high dielectric constant material that functions as a miniature microwave resonator because of internal reflections of electromagnetic waves at the high dielectric constant material/air boundary. This results in confinement of energy within, and in the vicinity of, the dielectric material which forms the resonator structure. As the mode of the dielectric resonator, a TE (transverse electric) mode and a TM (transverse magnetic) mode are known.
The shaped piece of high dielectric constant material is commonly known as a puck. Said puck is usually supported by a structure made of low dielectric constant material and is surrounded by a conducting enclosure. At the resonance frequency most of the electromagnetic energy is stored within the dielectric resonator, and the support is provided to ensure that there is no electric contact between the puck and the enclosure. Further, the conducting enclosure acts as a shield to prevent radiation.
In general, dual mode DR (dielectric resonator) filters, realized by using two dielectric resonators to produce a dual mode dielectric filter, are superior to single mode DR filters as they exhibit two resonance frequencies. Thus, dual mode DR filters are important in reducing the size of filters.
At the resonance frequency of a dielectric resonator, the magnetic field energy equals the electric field energy and electromagnetic fields can be transmitted with minimal loss. The resonance frequencies of a dual mode dielectric resonator are controlled by its shape and cross sectional area and by its permittivity constant. Important characteristics of a dielectric resonator are its field pattern, its Q factor, its resonance frequencies and its spurious free bandwidth. It is known that these factors depend on the dielectric material used, the shape of the dielectric resonator, and the resonator mode used. The quality factor Q is an important design parameter in the design of dielectric resonator filters which is determined by losses in a structure. The resonator bandwidth is inversely proportional to Q. A high Q is a desirable property of a dielectric resonator as it infers low insertion losses.
Another factor that is important in the design of ceramic filters is the tuning of the individual resonance frequencies of the dielectric resonators to achieve a desired filter response. Such adjusting means are usually realized by a screw in a direction orthogonal to the refection surface or by a screw between two resonators to adjust the coupling between the resonators.
The publication "DUAL-MODE TE01δ DIELECTRIC RESONATOR", I.C. Hunter et al., 29th European Microwave Conference - Munich 1999, pages 51 to 54, discloses a dielectric resonator consisting of two orthogonal hollow dielectric cylinders. As described on page 51, left column, the dual mode dielectric resonator structure is arranged in a metal housing and supported on an alumina support, and the resonator is made of ceramic, in particular a mixture of calcium titanate and neodymium aluminate.
US 6,650,208 describes a TE dual mode resonator filter having two dual mode resonators which are constructed in a similar manner. Each of the dual mode resonators includes a cross-shaped resonator body made of low loss dielectric material, for example ceramic, with a dielectric constant between 36 and 45. Both resonator bodies are attached with a distance between them on a planar interior surface of the cavity of an enclosure formed from a conductive material, for example metal. One of the dual mode resonators includes an input connector that is adapted to receive RF signals for processing by the filter, and the other dual mode resonator includes an output connector to provide a filter output signal.
US 6,518,857 relates to a multimode dielectric resonator apparatus which is configured such that a TM mode and a TE mode are transformed into multiplex modes. In this apparatus, a dielectric core is configured of a plate-like TM mode dielectric core portion and a TE mode dielectric core portion protruding therefrom in the vertical direction, for example in a spherical shape.
US 5,880,650 discloses a multimode composite resonator, in particular for a microwave filter, which includes a resonant cavity, a dielectric resonator element disposed inside the cavity, a tuning element for each mode and a coupling element for coupling between modes.
WO 2006/026826 relates in general to a multiband filtering apparatus for use in a communications system. In one embodiment, such an apparatus for operating in the TE mode and the TM mode comprises a resonant structure having ceramic body element of cruciform configuration with the top and bottom surfaces of each arm member being beveled. Said body also includes a central void with one or more curved surfaces.
WO 2004/066430 describes a multimode dielectric resonator device having two TE01 modes and two TM01 modes. Two dielectric resonator elements are integrated perpendicular to each to form a cross shape. Further, protrusion portions are provided to upper and lower portions of the cross shaped dielectric core. Therefore, the effective dielectric constant of the portion where the dielectric flux of the even mode of the TE coupling modes passes is made different from that of the portion where the dielectric flux of the odd mode of the TE coupling mode passes. Additionally, a protrusion portion is provided to an intermediate layer portion of the dielectric core. Therefore, the effective dielectric constant of the portion where the dielectric flux of the even mode of the TM coupling modes passes is almost equal to that of the portion where the dielectric flux of the odd mode of the TM coupling mode passes.
All above mentioned prior art resonators filters have common drawbacks. First: the known resonator filters are relatively heavy and bulky, in particular for mobile communications systems. Second: the design and construction of the prior art filters is complex and manufacturing of these filters is relatively expensive. Third: it is difficult to adapt the prior art filters for use with different frequencies. Fourth: tuning of the prior art filters is difficult and complex.
It is an object of the present invention to provide a dielectric dual mode resonator, and in particular a dielectric TE (transverse electric) dual mode resonator, which is adapted to overcome the above mentioned drawbacks.
This object is achieved by a dielectric dual mode resonator as defined in claim 1. Preferred embodiments of the dielectric dual mode resonator are set out in the dependent claims.
In general, the present invention provides a novel dielectric dual mode resonator, and in particular a dielectric TE dual mode resonator, having a simple and compact design as well as excellent tuning capabilities. Further, the dielectric dual mode resonator according to the present invention is easy to produce and allows matching to different desired frequencies in a simple manner.
The dielectric dual mode resonator comprises a dielectric core element made of ceramic or other dielectric material having a dielectric constant ε_r of between 20 and 80, preferably of between 35 and 45, and most preferred of about 42, and has a cross-shaped or cross-like configuration in horizontal direction. In other words, the core element is formed by two integrated parallelepiped dielectric elements which intersect in right angles. Further, the horizontal cross-shaped top and bottom surfaces of the core element are substantially planar, and the rectangular vertical side wall areas of the cross-shaped core element are also substantially planar.
The cross-shaped dielectric core element is formed with at least one through-hole. In a preferred embodiment, the dielectric core element is formed with two through-holes having a round or oval cross-section, although other cross-sectional configurations are also possible.
The two through-holes lie in the same horizontal plane and intersect each other in the middle of the dielectric core element to form a cross-shaped structure arranged with an angle relative to the cross-shape of the dielectric core element. Alternatively, the two through holes lie in horizontal planes which are different from each other. It is also possible that the through-holes lie in planes which are inclined with an angle relative to a horizontal plane. Preferably, the angle between the through-holes, when view from above in vertical direction, is between 80° and 100°, most preferred, the angle is 90°. The angle between the cross-shaped arrangement of the two through-holes and the cross-shaped arrangement of the core element, when view from above in vertical direction, is between 30° and 60°, most preferred this angle is about 45°.
In a preferred non-limiting embodiment, the height of the dielectric core element is between about 20 mm and 25mm, most preferred between about 22mm and 23mm, and the overall width of the dielectric core element is between about 20 mm and 30mm, most preferred between about 24mm and 28mm, wherein the arm members of the cross having a width of about 10 mm.
The through-holes are arranged in a plane substantially parallel and between the horizontal top and bottom surfaces of the cross-shaped dielectric core element. Preferably the plane of the through-holes is centered between the top and bottom surfaces of the core element. Further, the through-holes have a diameter of between 4 mm and 14 mm, preferably of 8 mm, to form an inner cavity having a volume of about 40 mm³, for example. However, as an important feature of the present invention, different diameters of said through-holes could be used to adjust frequency and coupling of the dielectric dual mode resonator of the present invention. Further, different cross-sections (round, oval, or other) of the through-holes may be used for the same purpose. It is noted that the two through-holes may have different cross-sections and diameters.
The dielectric core element is arranged in a cubical enclosure made of conductive material. In a preferred embodiment, said enclosure having a height and a width of about 40 mm.
Further, the dielectric core element is attached to the interior bottom surface of the conductive enclosure by means of an annular support element. The support element has a dielectric constant ε_r of between 8 and 12, and preferably of about 10. Further, the inner diameter of the support element is about 10 mm, the outer diameter of the support element is about 15 mm, and the height of the support element is about 10 mm.
For tuning the dielectric dual mode resonator, several conductive tuning elements are provided within the enclosure. These tuning elements could by screws, for example M4 screws, with adjustable lengths. Preferably, two tuning screws are provided, wherein the length of the screw for adjusting the first mode is about between 10 mm and 25 mm, and the length of the second screw for adjusting the second mode is between about 10 mm and 25 mm. Additionally, it is preferred that the position of the screws relative to the dielectric core element (i.e. also the distance between the screws and the core element) is also adjustable.
Inter-resonator-coupling of two or more dielectric dual mode resonators is also possible. To achieve such coupling, the enclosures of for example two or more dielectric dual mode resonators are connected, wherein an open aperture having an adjustable width is provided between the housings of adjacent arranged enclosures. Within said aperture, a length adjustable conductive screw is provided.
The invention will in the following be described in connection with the embodiments shown in the drawings, in which

Figure 1 diagrammatically shows a three-dimensional view of the general structure of the dielectric dual mode resonator according to the present invention;
Figure 2 shows a diagrammatic side view of the dielectric dual mode resonator of Figure 1;
Figure 3 shows a diagrammatic top view of the dielectric dual mode resonator of Figures 1 and 2;
Figure 4 diagrammatically shows a three-dimensional view of the general structure of the dielectric dual mode resonator according to the present invention having adjustment screws for tuning the frequencies of the resonator;
Figure 5 shows a diagrammatic top view of the dielectric dual mode resonator of Figure 4;
Figure 6 diagrammatically shows a three-dimensional view of the general structure of the dielectric dual mode resonator according to the present invention having adjustment screws for tuning the coupling factor of the resonator;
Figure 7 shows a diagrammatic top view of the dielectric dual mode resonator of Figure 6;
Figure 8 diagrammatically shows a three-dimensional view of the general structure of two adjacent arranged dielectric dual mode resonators according to the present invention having an adjustment screw for tuning the coupling factor between said two resonators;
Figure 9 shows a diagrammatic top view of the dielectric dual mode resonators of Figure 8;
Figure 10 diagrammatically shows a three-dimensional view of the general structure of a six pole dielectric dual mode resonator according to the present invention having a plurality of adjustment screws for tuning the coupling factors and the frequencies of the individual resonators, as well as the coupling of the input and output;
Figure 11 shows a diagrammatic top view of the dielectric dual mode resonators of Figure 10;
Figure 12 diagrammatically shows a three-dimensional view of the general structure of a six pole dielectric dual mode resonator according to the present invention having a plurality of adjustment screws for tuning the coupling factors, the frequencies of the individual resonators, the coupling of the input and output, and having an input resonator and an output resonator used as combline resonators;
Figure 13 shows a diagrammatic top view of the dielectric dual mode resonators of Figure 12;
Figure 14 shows a schematic view of the resonator of the present invention used for cross-coupling;
Figure 15 shows the node diagram of the structure of Figure 14; and
Figure 16 shows a diagram of the frequency response of the resonator of Figure 14.

In the following detailed description, reference is made to the accompanying drawings that form part of it, and in which is shown by way of illustration specific embodiments of the present invention. Embodiments of the present invention provide improvements in dielectric dual mode resonators which are used in, for example, cavity filters for wireless telecommunications networks.
Reference is now made to Figures 1 to 3 which show a preferred embodiment of a dielectric dual mode resonator, indicated generally at 1. The dielectric dual mode resonator 1 comprises a dielectric core element 2 made of ceramic or other dielectric material having a dielectric constant ε_r of between 35 and 45, and most preferred of about 42. The core element 2 has a cross-shaped configuration in horizontal direction when viewed from above. The horizontal cross-shaped top and bottom surfaces of the core element 2 are substantially planar, and the rectangular vertical side wall areas of the cross-shaped core element are also substantially planar.
The cross-shaped dielectric core element 2 is formed with two through- holes 3, 4 having a round or oval cross-section, although other cross-sectional configurations are also possible.
The two through- holes 3, 4 lie in the same horizontal plane, as shown in Figure 2, and intersect each other in the middle of the dielectric core element 2 to form a cross when viewed from above, as shown in Figure 3. The angle between the through-holes, when viewed from above, is about 90°. The angle between the cross-shaped arrangement of the two through-holes and the cross-shaped arrangement of the core element, when viewed from above in Figure 3, is about 45°.
It is also possible that the through-holes have different diameters or different cross-sections to adjust frequency and coupling of the dielectric dual mode resonator. Further, each of the through-holes may be composed of several sections having different diameters and/or cross-sections to adjust frequency and coupling of the dielectric dual mode resonator. In another configuration, each of the through-holes is composed of two sections having different diameters and/or cross-sections to adjust frequency and coupling of the dielectric dual mode resonator.
The height of the dielectric core element in vertical direction (see Figure 2) is between about 22mm and 23mm, and the overall width of the dielectric core element in horizontal direction (see Figure 2) is between about 24mm and 28mm, wherein the arm members 5 of the cross having a width of about 10 mm.
The through-holes are arranged in a plane substantially parallel and between the horizontal top and bottom surfaces 6, 7 of the cross-shaped dielectric core element 2. Preferably, the plane of the through-holes is centered between the top and bottom surfaces of the core element, and the diameter of the through-holes is preferably about 8 mm. However, different diameters of said through-holes can be used, and the two through-holes may have different cross-sections and diameters.
The dielectric core element 2 is arranged in a cubical enclosure 8 which is made of conductive material and has a height and a width of about 40 mm.
The dielectric core element 2 is attached to the interior bottom surface 9 of the conductive enclosure 8 by means of an annular support element 10. The support element has a dielectric constant ε_r of between 8 and 12, and preferably of about 10. The inner diameter of the support element 10 is about 10 mm, the outer diameter of the support element 10 is about 15 mm, and the height of the support element is about 10 mm.
Figures 4 and 5 show a dielectric dual mode resonator 100 which is identical to that of Figures 1 to 3, except for frequency tuning elements 11, 12. Thus, a description and reference numbers of the components shown in Figures 1 to 3 are omitted. As depicted in Figures 4 and 5, two frequency tuning elements 11, 12 in form of length adjustable metal screws are attached to the upper plate 13 (cover lid) of the enclosure 2 and are arranged near the corners of the enclosure opposite to the outer surfaces of the core element 2. In other embodiments (not shown), the frequency tuning elements may comprise a metal part that can be bent toward or away from the core element.
In the preferred embodiment of Figures 4 and 5, the tuning elements 11, 12 are screws, for example M4 screws, wherein the length of one screw for adjusting the first mode is about between 10 mm and 25 mm, and the length of the second screw for adjusting the second mode is between about 10 mm and 25 mm. Additionally, it is preferred that the position of the screws relative to the dielectric core element (i.e. also the distance between the screws and the core element) is also adjustable.
Figures 6 and 7 show another dielectric dual mode resonator 200 which is identical to that of Figures 1 to 5, except for mode tuning elements 14, 15. Thus, a description and reference numbers of the components shown in Figures 1 to 3 are omitted. As depicted in Figures 6 and 7, two mode tuning elements 14, 15 in form of length adjustable metal screws are attached to the upper plate 13 (cover lid) of the enclosure and are arranged in the space between the arms of the core element. Also in this case, the mode tuning elements may comprise a metal part that can be bent toward or away from the core element.
In the preferred embodiment of Figures 6 and 7, the mode tuning elements 14, 15 are screws, for example M4 screws, wherein the length of the screws is about between 10 mm and 25 mm. Additionally, it is preferred that the position of the screws relative to the dielectric core element (i.e. also the distance between the screws and the core element) is also adjustable.
It is important to note that the frequency tuning elements 11, 12 as well as the mode tuning elements 14, 15 are provided in the dual mode resonator. Just for clarity, the frequency tuning elements 11, 12 and the mode tuning elements 14, 15 are depicted in separate drawings. It is also obvious for a person skilled in the art that the frequency tuning elements 11, 12 and the mode tuning elements 14, 15 may have different shapes or may consist of a plurality of different parts which extend in horizontal or vertical direction behind or above the core element.
Figures 8 and 9 show another embodiment of an dielectric dual mode resonator 300 according to the present invention. This embodiment of a 6 pole resonator is realized by two adjacent arranged resonators 300-1 and 300-2 as shown in the previous Figures 1 to 7. As can be seen from Figures 8 and 9, the side walls of two adjacent arranged resonators 300-1 and 300-2 are coupled with each other, wherein corresponding portions of the interconnected side walls are removed to form a rectangular opening 16 between the adjacent resonators 300-1 and 300-2. Preferably, said opening 16 extends in the same direction as the core elements, i.e. from the bottom surface, where the core elements are mounted, to the upper plate of the enclosures. Thus, said opening 16 has the same height as the enclosures and a width of between 15 mm and 30 mm. The remaining wall section between the adjacent enclosures has a thickness of about 4 mm.
Further, as shown in Figures 8 and 9, a tuning element 20 is attached to the upper plate 13 and extends vertically in downward direction within the opening, i.e. from the upper plate towards the bottom surface 9. Preferably, said tuning element 20, which is for inter-resonator coupling, is arranged in the center of the opening as shown in Figure 9. However, the position of the tuning element can be varied. Preferably, the tuning element 20 is a metal screw having a diameter of about 4 mm and a length of between about 10 mm and 35 mm. It is obvious, that the length and position of said tuning element 20 can be varied to adjust inter-resonator coupling.
Figures 10 and 11 show an additional embodiment of a dielectric dual mode resonator 400 according to the present invention. This embodiment of a 6 pole resonator is realized by three adjacent arranged resonators 400-1, 400-2 and 400-3, which are similar to the resonators as shown in the previous Figures 1 to 7. As can be seen from these Figures, the side walls of the adjacent arranged resonators 400-1, 400-2 and 400-3 are coupled with each other, wherein corresponding portions of the interconnected side walls are removed to form rectangular openings 16-1 and 16-2 between the adjacent resonators 400-1, 400-2 and 400-3. Preferably, said openings 16-1 and 16-2 extend in the same direction as the core elements, i.e. from the bottom surface 9, where the core elements 2 are mounted, to the upper plate 13 of the enclosures. Thus, said openings 16-1 and 16-2 have the same height as the enclosures and a width of between 15 mm and 30 mm. The remaining wall sections between the adjacent enclosures have a thickness of about 4 mm.
As further shown in Figures 10 and 11, a plurality of tuning elements for frequency tuning, mode tuning and inter-resonator coupling is provided. These tuning elements have already been described with reference to the previous Figures.
Additionally, the resonator arrangement of Figures 10 and 11 is provided with input and output connectors 21, 22 for receiving radio frequency (RF) signals for processing by the resonator arrangement and for providing an output signal from the resonator arrangement. The input/ output connectors 21, 22 are connected to capacitive probes 23, 24 which extend in vertical direction within the enclosures of the left and right resonators 400-1 and 400-2. These capacitive probes 23, 24 interact with length adjustable tuning elements 25, 26 which are similar to the other tuning elements and are arranged near and opposite to the capacitive probes 23, 24 for adjusting input/output coupling of the resonator arrangement. By varying the dimensions and distance of the capacitive probes 23, 24, rough adjustment of input/output coupling is achieved. By varying the length of the tuning elements 25, 26, fine adjustment of input/output coupling is achieved. An electric contact between the probes 23, 24 and the respective tuning elements 25, 26 is also possible, leading to a kind of inductive coupling loop. Similar inductive coupling could be achieved by a proper shaped wire or belt, which is connected between the inner conductors of the connectors 21, 22 and respective resonator housing. Further modification would be a proper shaped capacitive coupling wire or belt, i.e. a wire or belt connected to the inner conductors of the connectors 21, 22, but having no connection to the resonator housing.
Figures 12 and 13 show another example of a dielectric dual mode resonator 500 according to the present invention. This embodiment of a 6 pole resonator is realized by two adjacent arranged resonators 500-1 and 500-2, which are similar to the resonators as shown in the previous Figures. Additionally, an input resonator 500-3 and an output resonator 500-4 (combline resonators) are provided which are coupled to resonators 500-1, 500-2 via openings 25-1, 25-2, respective wall sections 26-1, 26-1, and inter-resonator tuning elements 28-1, 28-2. The frequency tuning elements and mode tuning elements are similar to that of the previous embodiments. Further, the input and output connectors 21, 22 and the capacitive probes 23, 24 are similar to that of Figures 10 and 11. Preferably, the inner conductors 27-1, 27-2 of the input and output combline resonators 500-3 and 500-4 are attached to the bottom of the input/output resonators, since in such a way the resonances could be tuned by screws 30, 31 which are placed at the top of the housing similar to all other tuning elements.
Figure 14 shows in general the concept of cross-coupling. The components of such a resonator arrangement are identical or at least similar to those of the previous embodiments.
Figure 15 shows the respective node diagram for the embodiment of Figure 14, and Figure 16 depicts a diagram of the frequency response of the resonator of Figure 14.
The above specific embodiments relate in general to dielectric dual mode resonators, i.e. TE dual mode resonators and TM dual mode resonators. However, it should be understood that all above embodiments are preferably realized in the area of dielectric TE dual mode resonators.

Claims

Dielectric dual mode resonator (1; 200; 300; 400; 500) comprising a dielectric core element (2) made of dielectric material having a dielectric constant ε_r of between 20 and 80, and having a cross-shape in a horizontal direction, wherein the dielectric core element (2) is formed with two through-holes (3, 4) lying in a horizontal plane and intersecting each other in substantially right angles.
Dielectric dual mode resonator according to claim 1, wherein the cross-shaped top and bottom surfaces (6, 7) of the core element are substantially planar in said horizontal direction, and the rectangular vertical side wall areas of the cross-shaped core element are substantially planar.
Dielectric dual mode resonator according to one of claims 1 and 2, wherein the through-holes (3, 4) having a round or oval cross-section.
Dielectric dual mode resonator according to one of claims 1 to 3, wherein the through-holes (3, 4) are arranged in a plane parallel and between the horizontal top and bottom surfaces (6, 7) of the dielectric core element (2).
Dielectric dual mode resonator according to one of claims 1 to 4, wherein the plane of the through-holes is centered between the top and bottom surfaces of the core element.
Dielectric dual mode resonator according to one of claims 1 to 5, wherein the two through-holes are formed in the same horizontal plane and intersect each other in the middle of the dielectric core element to form a cross-shaped configuration.
Dielectric dual mode resonator according to claim 6, wherein the cross-shaped configuration of the through-holes being arranged with an angle relative to the cross-shape of the dielectric core element.
Dielectric dual mode resonator according to claim 7, wherein said angle between the cross-shaped configuration of the through-holes and the cross-shape of the dielectric core element is between 30° and 60°.
Dielectric dual mode resonator according to claim 8, wherein said angle between the cross-shaped configuration of the through-holes and the cross-shape of the dielectric core element is about 45°.
Dielectric dual mode resonator according to one of claims 1 to 9, wherein said through-holes having different diameters to adjust frequency and coupling of the dielectric dual mode resonator.
Dielectric dual mode resonator according to one of claims 1 to 9, wherein said through-holes having different cross-sections to adjust frequency and coupling of the dielectric dual mode resonator.
Dielectric dual mode resonator according to one of claims 1 to 9, wherein each of said through-holes is composed of several sections having different diameters and/or cross-sections to adjust frequency and coupling of the dielectric dual mode resonator.
Dielectric dual mode resonator according to one of claims 1 to 9, wherein each of said through-holes is composed of two sections having different diameters and/or cross-sections to adjust frequency and coupling of the dielectric dual mode resonator.
Dielectric dual mode resonator according to one of claims 1 to 13, wherein the height of the dielectric core element in vertical direction is between about 22 mm and about 24 mm, and the overall width of the dielectric core element in horizontal is between about 24 mm about 28 mm, wherein the arm members of the cross having a width of about 10 mm in horizontal direction.
Dielectric dual mode resonator according to one of claims 1 to 14, wherein the through-holes have a diameter of between about 4 mm and about 12 mm, preferably between about 6 mm and about 8 mm.
Dielectric dual mode resonator according to one of claims 1 to 15, wherein the through-holes are dimensioned to form an inner cavity having a volume of about 40 mm³.
Dielectric dual mode resonator according to one of claims 1 to 16, wherein the dielectric core element is arranged in a cubical enclosure (8) made of conductive material.
Dielectric dual mode resonator according to claim 17, wherein said enclosure (8) having a height and a width of about 40 mm.
Dielectric dual mode resonator according to one of claims 17 and 18, wherein the dielectric core element is attached to the interior bottom surface of the conductive enclosure by means of an annular support element (10).
Dielectric dual mode resonator according to claim 19, wherein the support element (10) having a dielectric constant ε_r of between 8 and 12, and preferably of about 10.
Dielectric dual mode resonator according to one of claims 19 and 20, wherein the inner diameter of the support element (10) is about 10 mm, the outer diameter of the support element is about 15 mm, and the height of the support element is about 10 mm.
Dielectric dual mode resonator according to one of claims 1 to 21, wherein the dielectric dual mode resonator is a dielectric TE dual mode resonator.