EP3324482A1 - Dielektrischer resonator - Google Patents

Dielektrischer resonator Download PDF

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Publication number
EP3324482A1
EP3324482A1 EP16199728.3A EP16199728A EP3324482A1 EP 3324482 A1 EP3324482 A1 EP 3324482A1 EP 16199728 A EP16199728 A EP 16199728A EP 3324482 A1 EP3324482 A1 EP 3324482A1
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EP
European Patent Office
Prior art keywords
ring
dielectric
dielectric resonator
electrodes
face
Prior art date
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Withdrawn
Application number
EP16199728.3A
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English (en)
French (fr)
Inventor
Mustafa Safaa Ahmed Bakr
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Technische Universitaet Graz
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Technische Universitaet Graz
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Application filed by Technische Universitaet Graz filed Critical Technische Universitaet Graz
Priority to EP16199728.3A priority Critical patent/EP3324482A1/de
Publication of EP3324482A1 publication Critical patent/EP3324482A1/de
Withdrawn legal-status Critical Current

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01P—WAVEGUIDES; RESONATORS, LINES, OR OTHER DEVICES OF THE WAVEGUIDE TYPE
    • H01P7/00—Resonators of the waveguide type
    • H01P7/10—Dielectric resonators
    • H01P7/105—Multimode resonators

Definitions

  • the present invention relates to a dielectric resonator comprising a metallic casing, a dielectric partly filling said metallic casing, and at least two electrodes insulatedly penetrating the metallic casing.
  • the invention further relates to a higher order microwave filter comprising such dielectric resonators.
  • Dielectric resonators have been widely used in the microwave range of electromagnetic waves, e.g. as filters in mobile communication and space applications. Such resonators are of relatively small size, a fraction of comparable (metal) cavity resonators, and thermally and mechanically stable and have a high quality factor ("Q-factor"). Further size reduction can be achieved by exploiting multi-mode degenerate resonances in a dielectric resonator, i.e. orthogonal modes which share the same resonant frequency. Such modes can be TM modes, i.e. modes the magnetic field component of which is orthogonal to the direction of wave propagation, or TE modes, i.e. modes the electric field component of which is orthogonal to the direction of wave propagation. TM or TE mode waves can only propagate at wave frequencies above a certain cut-off frequency. In dual-mode resonator filters the fundamental resonant modes, e.g., the TM 11 or TE 11 modes, are often utilized.
  • TM modes i.
  • dielectric filters are made of a dielectric disc, also referred to as a rod or a puck, suspended in a metallic enclosure with necessary mounting fixtures, electrodes for input/output coupling and tuning elements for tuning the resonant frequency. All these auxiliary means introduce additional weight, size and complexity.
  • a dielectric disc also referred to as a rod or a puck
  • All these auxiliary means introduce additional weight, size and complexity.
  • L. Pelliccia et al. "Ultra-compact Pseudoelliptic Waveguide Filters Using TM Dual-Mode Dielectric Resonators", Microwave Conference Proceedings (APMC), 2011 Asia-Pacific , explicate examples for such dielectric resonators and filters.
  • a single-mode dielectric resonator which is made from a single ceramic block with substantially two parts, an outer cup-shaped part with a central inner rod part extending from its bottom.
  • the top of the resonator is covered with a metallic lid and the outer surface of the cup-shaped part is silver plated. Manufacturing such a complex structure is rather difficult and the cavity between inner rod part and outer cup-shaped part is space-consuming, resulting in a resonator having a diameter of 26 mm and a height of 15 mm.
  • this object is achieved with a dielectric resonator of the type mentioned above, wherein the dielectric is integrally and coaxially formed of a disc, a first and a second ring, wherein said disc has a first and a second end face, the first ring axially extending from said first end face and the second ring axially extending from said second end face, wherein said disc and rings have flush circumferential faces together forming a cylindrical mantle surface, wherein the casing is formed by a metallisation of said mantle surface and by a first and a second metallic lid, the first lid spanning said first ring and forming a first cavity inside the first ring and the second lid spanning said second ring and forming a second cavity inside the second ring, and wherein said electrodes reach into at least one of said first and second cavities.
  • the dielectric is a single, i.e. a monoblock, dielectric having the shape of an "H" when seen in a longitudinal section. Such a structure is easy to manufacture.
  • the resonator can be used in dual-mode as well as in higher-order mode, e.g., in triple-mode, and is particularly small for the intended microwave applications: It is about one third the size of conventional dielectric resonators and at least 40% smaller than the above-mentioned single-mode cup-and-rod structure proposed by X. Wang et al. However, despite the small size, the present resonator achieves a remarkably high unloaded Q-factor.
  • each of said first and second rings extends over about one forth of the dielectric in axial direction. This leaves space for the necessary cavities without the need for an extra metal enclosure. It is further preferred that each of said first and second rings has a ratio of inner to outer diameter of about five sixths. Such structure and dimensions lead to particularly advantageous characteristics of the resonator in terms of Q-factor, fundamental resonant mode frequency and spurious window, i.e. the ratio between the fundamental and the first higher-order mode.
  • said metallisation is a silver plating.
  • Such a plating can be kept particularly thin exploiting the excellent electric conductivity of silver.
  • the silver plating adds minimum size and weight to the resonator.
  • any dielectric can be used. However, for achieving a small overall size, it is preferred that the dielectric is a ceramic. Suitable ceramics have high dielectric constants and allow for a small overall form factor.
  • said first end face has a central cylindrical recess for at least partially receiving a tuning element penetrating the first metallic lid.
  • each electrode radially penetrates said second ring next to said second end face.
  • the radial directions of penetration of said electrodes form an acute or an obtuse angle with each other.
  • further coupling elements like screws or through-holes at 45 degrees, can be omitted.
  • said angle is preferably between 35 and 75 degrees or between 105 and 145 degrees, particularly preferably about 53 degrees or about 125 degrees.
  • the invention creates a higher order microwave filter comprising a first and a second dielectric resonator of the above type wherein one of the electrodes of the first dielectric resonator directly connects to one of the electrodes of the second dielectric resonator.
  • inter-resonator coupling the coupling of the resonators
  • more than two resonators can be connected in this way in series. Relating to further advantages and particular embodiments of the filter, it is referred to the above statements on the resonator.
  • the electrodes 4, 5 penetrate the metallic casing 2 while being insulated therefrom.
  • Said dielectric 3 is integrally and coaxially formed of a disc 6 and a first and second ring 7, 8, each of which elements 6, 7, 8 being symmetric around a common central axis 9.
  • the disc 6 has a first and a second end face 10, 11.
  • the end faces 10, 11 are plane and parallel; they could alternatively be, e.g., convex or concave and/or non-parallel.
  • the first ring 7 axially extends in the direction of the axis 9 from said first end face 10 and the second ring 11 axially extends from said second end face 11.
  • the disc 6 and the rings 7, 8 have flush circumferential faces which together form a cylindrical mantle surface 12.
  • each of the first and second rings 7, 8 extends over about one forth of the dielectric 3 in the direction of the axis 9, i.e., the height H 1 of the disc 6 is about twice the height H 2 , H 3 of each of the rings 7, 8. Since the disc 6 and said first and second rings 7, 9 share the common mantle surface 12, they have a common outer diameter D 1 .
  • the inner diameter D 2 and/or height H 2 of the first ring 7 could also be smaller or larger than the inner diameter D 3 and/or height H 3 of the second ring 8, respectively.
  • the dielectric 3 can be made of any suitable dielectric material, e.g., a polymer. However, dielectrics 3 with high (relative) dielectric constants are preferred. In the example shown in Figs. 1a and 1b , the dielectric 3 is a ceramic.
  • the metallic casing 2 is formed by a metallisation 13 of the mantle surface 12 and by a first and a second metallic lid 14, 15.
  • the first lid 14 spans the first ring 7 and forms a first cavity 16 inside the first ring 7.
  • the second lid 15 spans the second ring 8 and forms a second cavity 17 inside the second ring 8.
  • the metallisation 13 of the mantle surface 12 can be of any electrically conductive material; in the present example, the metallisation is a silver plating.
  • the first and second metallic lids 14, 15 can be manufactured of any electrically conductive material, e.g., of copper or aluminium.
  • the electrodes 4, 5 reach into at least one of said first and second cavities 16, 17.
  • each electrode 4, 5 radially penetrates the second ring 8 in a respective direction of penetration R 1 , R 2 and next to the second end face 11.
  • both electrodes reach into the same cavity (here: the second cavity 17).
  • one electrode 4 protrudes into the second cavity 17 by a length p 1 while the other electrode 5 (the right electrode in Fig. 1b ) protrudes into the second cavity 17 by a length p 2 ;
  • the two lengths p 1 , p 2 may be identical in specific cases, however, generally they differ from one another.
  • the "first" and “second" cavities 16, 17 are interchangeable, e.g., by turning the resonator 1 upside down or to another orientation.
  • One of the electrodes 4, 5 could alternatively reach into the first cavity 16 and the other into the second cavity 17.
  • the electrodes 4, 5 could be spaced from the first and/or second end faces 10, 11, and/or could penetrate the ring(s) 7, 8 aslant.
  • the electrodes 4, 5 could insulatedly penetrate the first and/or second metallic lids 14, 15 instead of the rings 7, 8.
  • said directions of penetration R 1 , R 2 could be orthogonal to each other.
  • coupling elements e.g., a hole or slot or a screw positioned vertically or horizontally, may be provided at 45 degrees vis-à-vis the orthogonal polarized fields of the two degenerate modes to introduce proper field perturbation for achieving inner-coupling between said modes.
  • said inner-coupling between the orthogonal degenerate T 11 -modes is achieved by introducing an acute or obtuse angle ⁇ between the radial directions of penetration R 1 , R 2 of the electrodes 4, 5.
  • the angle ⁇ may be between 35 degrees and 75 degrees in the acute case or between 105 degrees and 145 degrees in the obtuse case.
  • the angle ⁇ is about 53 degrees (acute case) or about 125 degrees (obtuse case).
  • the electrodes 4, 5 may be inner conductors of coaxial probes 18, 19, the respective outer shields 20, 21 of which may be connected to the metallic casing 2 (here: the metallisation 13), e.g., by circumferential soldering joints 22. Between inner conductors (electrodes) 4, 5 and outer shields 20, 21 of the coaxial probes 18, 19 there are respective dielectric insulators 23, 24.
  • the insulators 23, 24 may be used to ensure insulation of the electrodes 4, 5 vis-à-vis the metallic casing 2 when they penetrate the casing 2.
  • Fig. 2 differs from the example of Fig. 1a in that the end face 10 of the disc 6 has a central cylindrical recess 25 interacting with a tuning element 26 which penetrates the first metallic lid 14 and is movably supported in the latter.
  • the tuning element 26 is movable in both directions of the axis 9 to be at least partially received by the recess 25.
  • the tuning element 26 comprises a screw 27 and a head 28.
  • the head 28 has an axial height h 1 and a diameter d 1 while the recess 25 has an axial depth h 2 and a diameter d 2 exceeding the diameter d 1 of the head 28 for at least partially receiving it; the screw 27 has a diameter d 3 generally smaller than the diameter d 1 of the head 28.
  • the resonator 1 may be manufactured using a ceramic dielectric 3 with a relative dielectric constant of 45 and a loss tangent of 4 ⁇ 10 -5 and silver paint with a thickness of 20 ⁇ m and an electrical conductivity of 2 ⁇ 10 7 S/m as metallisation 13.
  • the thickness of the metallisation 13 depends on the skin depth of the microwave, as known in the art.
  • the unloaded dielectric resonator 1 exhibits an unloaded fundamental resonant frequency of 1.96 GHz for the fundamental resonant mode (here: two orthogonal TE 11 modes) with an unloaded Q-factor of about 3400.
  • the ratio between the fundamental resonant mode and the first higher-order mode (also called: "spurious window" ratio) is 1.392.
  • the first higher-order mode is a TM 01 mode at 2.73 GHz with an unloaded Q-factor of about 3970, followed by two TE 21 modes at 2.78 GHz with an unloaded Q-factor of about 2980, which can be used for multi-mode operation, e.g., said two TE 11 modes and said TM 01 mode for triple mode operation.
  • the dielectric resonator 1 can, inter alia, be used as a filter, e.g., a second order filter, in mobile communications or satellite applications in the microwave range.
  • a filter e.g., a second order filter
  • the resonant frequency is modified.
  • the centre frequency of the fundamental resonant frequency of the resonator 1 can thus be tuned between 1.77 GHz and 1.83 GHz.
  • the centre frequency in the tuneable configuration is lower than the unloaded fundamental resonant frequency of the resonator 1 as the latter was determined without recess 25 and tuning element 26.
  • the bandwidth of the resonator 1 used as a filter can be tuned, in the present example from 9 MHz to 100 MHz.
  • two or more resonators 1 can be used for assembling a higher order microwave filter 29 by connecting them in series.
  • a forth order dual-mode band-pass filter is assembled using a first dielectric resonator 1' and a second dielectric resonator 1" of the type illustrated above.
  • the electrodes 4, 5 here: the right electrode 5
  • the left electrode 4 of the second dielectric resonator 1
  • This example shows a specifically simple way of directly connecting the electrodes 4, 5 of the dielectric resonators 1', 1":
  • the electrodes 4, 5 are here formed by two ends of an inner conductor of a single coaxial probe 19 spanning the distance between the first and second resonators 1', 1".
  • the outer shield 21 of said probe 19 is connected to the metallisations 13 of both resonators 1', 1".
  • other connection types known in the art can alternatively be employed.

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EP16199728.3A 2016-11-21 2016-11-21 Dielektrischer resonator Withdrawn EP3324482A1 (de)

Priority Applications (1)

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EP16199728.3A EP3324482A1 (de) 2016-11-21 2016-11-21 Dielektrischer resonator

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Application Number Priority Date Filing Date Title
EP16199728.3A EP3324482A1 (de) 2016-11-21 2016-11-21 Dielektrischer resonator

Publications (1)

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EP3324482A1 true EP3324482A1 (de) 2018-05-23

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Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4661790A (en) * 1983-12-19 1987-04-28 Motorola, Inc. Radio frequency filter having a temperature compensated ceramic resonator
US4706052A (en) * 1984-12-10 1987-11-10 Murata Manufacturing Co., Ltd. Dielectric resonator
US5200721A (en) * 1991-08-02 1993-04-06 Com Dev Ltd. Dual-mode filters using dielectric resonators with apertures
EP0856903A2 (de) * 1997-02-03 1998-08-05 Murata Manufacturing Co., Ltd. Dielektrischer Multimoden-Resonator und Eigenschafteinstellungsverfahren dafür
WO2002009228A1 (en) * 2000-07-20 2002-01-31 Telecom Italia Lab S.P.A. Dielectric loaded cavity for high frequency filters

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4661790A (en) * 1983-12-19 1987-04-28 Motorola, Inc. Radio frequency filter having a temperature compensated ceramic resonator
US4706052A (en) * 1984-12-10 1987-11-10 Murata Manufacturing Co., Ltd. Dielectric resonator
US5200721A (en) * 1991-08-02 1993-04-06 Com Dev Ltd. Dual-mode filters using dielectric resonators with apertures
EP0856903A2 (de) * 1997-02-03 1998-08-05 Murata Manufacturing Co., Ltd. Dielektrischer Multimoden-Resonator und Eigenschafteinstellungsverfahren dafür
WO2002009228A1 (en) * 2000-07-20 2002-01-31 Telecom Italia Lab S.P.A. Dielectric loaded cavity for high frequency filters

Non-Patent Citations (4)

* Cited by examiner, † Cited by third party
Title
I.C. HUNTER ET AL.: "Dual-Mode Filters With Conductor-Loaded Dielectric Resonators", IEEE TRANSACTIONS ON MICROWAVE THEORY AND TECHNIQUES, vol. 47, December 1999 (1999-12-01), XP011037815
L. PELLICCIA ET AL.: "Ultra-compact Pseudoelliptic Waveguide Filters Using TM Dual-Mode Dielectric Resonators", MICROWAVE CONFERENCE PROCEEDINGS (APMC, 2011
M.S. BAKR ET AL.: "A Novel Dielectric-Loaded Dual-Mode Cavity for Cellular Base Station Applications", EUROPEAN MICROWAVE CONFERENCE, 2016
X. WANG ET AL.: "A TM Mode Monoblock Dielectric Filter", IEEE TRANSACTION ON MICROWAVE THEORY AND TECHNIQUES, vol. 62, February 2014 (2014-02-01), XP011538915, DOI: doi:10.1109/TMTT.2013.2294854

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