NL2020698B1 - A resonator apparatus - Google Patents

A resonator apparatus Download PDF

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Publication number
NL2020698B1
NL2020698B1 NL2020698A NL2020698A NL2020698B1 NL 2020698 B1 NL2020698 B1 NL 2020698B1 NL 2020698 A NL2020698 A NL 2020698A NL 2020698 A NL2020698 A NL 2020698A NL 2020698 B1 NL2020698 B1 NL 2020698B1
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NL
Netherlands
Prior art keywords
cavity
housing part
cavity resonator
mode
operational state
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NL2020698A
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Dutch (nl)
Inventor
Riedinger Ralf
Hofer Joachim
Alexander Steele Gary
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Univ Vienna
Univ Delft Tech
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Priority to NL2020698A priority Critical patent/NL2020698B1/en
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Publication of NL2020698B1 publication Critical patent/NL2020698B1/en

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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
    • H01P7/06—Cavity resonators
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01P—WAVEGUIDES; RESONATORS, LINES, OR OTHER DEVICES OF THE WAVEGUIDE TYPE
    • H01P1/00—Auxiliary devices
    • H01P1/16—Auxiliary devices for mode selection, e.g. mode suppression or mode promotion; for mode conversion
    • H01P1/162—Auxiliary devices for mode selection, e.g. mode suppression or mode promotion; for mode conversion absorbing spurious or unwanted modes of propagation

Abstract

A cavity resonator comprising a cavity comprising a first housing part that comprises at least a part of a hollow cylindrical shape with an average inner diameter R; and one open end of the hollow cylindrical shape; a second housing part that comprises at least a part of a plate with an average diameter r fitting to the one open end of the hollow cylindrical shape; wherein r is smaller than R; wherein the first housing part and the second housing part are movable from each other configured to change a volume of the cavity and a resonance frequency of a resonance mode in the cavity in an operational state of the cavity resonator; first coupling means connected to the first housing part or the second housing part for generating an electromagnetic field in the cavity and exciting the resonance mode in the operational state of the cavity resonator; wherein the resonance mode is a TEOnm or TMOnm mode with n; m; Z 1; second means connected to the first housing part or the second housing part for extracting the electromagnetic field in the cavity in the operational state of the cavity resonator

Description

Field of the invention
The present invention relates to a resonator apparatus, in particular a cavity resonator apparatus.
Background art
A major challenge in the field of microwave sources is reducing the noise in the generated signal. In particular, in comparison to lasers, which can act a frequency standards where the phase fluctuations can be limited by fundamental physics (shot noise), the current state-of-the-art of commercial microwave generators is several orders of magnitude from reaching these fundamental limits: frequency noise in microwave sources is currently dominated by technical limitations of the oscillators and electronics used in the sources.
There is therefore a need to improve the phase noise performance of microwave sources.
Summary of the invention
According to a first aspect, the invention provides a cavity resonator comprising: a cavity comprising a first housing part that comprises at least a part of a hollow cylindrical shape with an average inner diameter R, and one open end of the hollow cylindrical shape; a second housing part that comprises at least a part of a plate with an average diameter r fitting to the one open end of the hollow cylindrical shape; wherein r is smaller than R; wherein the first housing part and the second housing part are movable from each other configured to change a volume of the cavity and a resonance frequency of a resonance mode in the cavity in an operational state of the cavity resonator; first coupling means connected to the first housing part or the second housing part for generating an electromagnetic field in the cavity and exciting the resonance mode in the operational state of the cavity resonator, wherein the resonance mode is a TEOnm or TMOnin mode with n, m, > 1; second means connected to the first housing part or the second housing part for extracting the electromagnetic field in the cavity in the operational state of the cavity resonator.
Advantageously, the cavity resonator allows resonance frequency tuning while maintaining a high quality factor of the cavity resonator.
According to another aspect, the invention provides a method for operating a cavity resonator, comprising: setting a first housing part and a second housing part of a cavity of the cavity resonator in a position obtaining a volume of the cavity and a resonance frequency of a resonance mode in the cavity in an operational state of the cavity resonator, wherein the first part comprises at least a part of a hollow cylindrical shape with an average inner diameter R, and one open end of the hollow cylindrical shape; the second housing part comprises at least a part of a plate with an average diameter r fitting to the one open end of the hollow cylindrical shape; wherein r is smaller than R; wherein the first housing part and the second housing part are movable from each other; generating an electromagnetic field in the cavity and exciting the resonance mode in the operational state of the cavity resonator by first coupling means connected to the first housing part or the second housing part; extracting the electromagnetic field in the cavity in the operational state of the cavity resonator by second means connected to the first housing part or the second housing part; wherein the resonance mode is a TEOnm or TMOnin mode with n, m, > 1.
Further advantageous embodiments are disclosed in the attached claims.
Short description of drawings
Embodiments of the present disclosure will be described hereinafter, by way of example only, with reference to the accompanying drawings which are schematic in nature and therefore not necessarily drawn to scale. Furthermore, like reference signs in the drawings relate to like elements.
Fig. 1 schematically shows a cavity resonator according to an embodiment of the present disclosure.
Fig. 2 schematically shows a test design of a cavity resonator for room temperature.
Fig. 3 schematically shows a model geometry for numeric simulation.
Fig. 4 schematically shows a simulated TEO 11 mode.
Fig. 5 schematically shows a simulated TE011 mode with coupling in and out of the cavity.
Fig. 6 shows a S21 power spectrum of Fig. 5.
Fig. 7 schematically shows a simulated TE011, TE012, TE021, TE044 mode.
Description of embodiments
Figure 1 schematically shows a cavity resonator according to an embodiment of the present invention. The cavity resonator comprises a cavity 110 that comprises a first housing part 120 that is a housing with an opening 122, and a second housing part 130 that is a lid fit to the opening 122. The first housing part 120 comprises at least a part of a hollow cylindrical shape with an average inner diameter R, and one open end (122) of the hollow cylindrical shape. The second housing part (130) comprises at least a part of a plate with an average diameter r fitting to the one open end of the hollow cylindrical shape. The housing 120 and the lid 130 are movable from each other by a moving mechanism e.g. piezo materials, screws, etc. such that a volume of the cavity 110 can be changed. Subsequently a resonance frequency of a resonance mode in the cavity 110 can be tuned in an operational state of the cavity resonator. The cavity 110 is provided with a gap 140 with a gap area between the housing 120 and the lid 130;
The gap area is defined as the smallest gap area spanned between the first part and the second part. In Fig. 1 this smallest gap area has a ring shape.
The cavity resonator further comprises first means 150 that are a connector for connecting to a coax cable. The connector 150 is for generating an electric field in the cavity 110 in the operational state of the cavity resonator.
The cavity resonator further comprises second means 160 that are a connector for connecting to a coax cable. The connector 160 is for extracting an electric field in the cavity 110 in the operational state of the cavity resonator.
The housing 120 and the lid 130 of can be both physically and electrically separated such that no electric current can flow between the two parts. This situation can be for any electromagnetic resonance mode in the cavity 110.
A quality factor of a cavity comprising two parts with a gap in between can be expressed in:
1/Qtot — 1/Qohmic + 1/Qgap wherein Qtot is the total quality factor of the cavity, Qohmic is the quality factor due to the ohmic part of the cavity effected by the material of the cavity, and Qgap is the quality factor due to the radiative losses though the gap.
For a cavity working at room temperature, Qgap » Qohmic, thus Qtot is dominated by Qohmic. For a cavity working at cryogenic temperature, for example below 4K, Qohmic » Qgap, thus Qiot is dominated by Qgap.
A high quality factor of the resonance in the cavity 110 can be achieved due to that for the desired resonance mode in the cavity 110 in the operational state of the cavity resonator, the electric field norm is largely decreased in the gap 140 between the two movable parts. In other words, n(E x H) is largely decreased, where n is a vector pointing out of the cavity, E is the electric field vector, and H is the magnetic field vector, S = E x H is the Poynting vector.
At the resonance frequency in the operational state of the cavity resonator, a geometrical symmetry of the lid 130 is configured to match to a geometrical symmetry of the resonance mode. In this way, a minimal surface current or in other words a vanishing B field is obtained at the gap area so Qgap is increased, thus Qtoi is also increased.
Advantageously, when the second part 130 is moved at such a position with respect to the first part 120 that a resonance mode TEOnin or TMOnm with n, m > 1 is achieved in the cavity resonator in its operational state, a minimal surface current or in other words a vanishing B field is obtained at the gap area between the first part 120 and the second part 130 so Qgap is increased, thus Qtot is also increased.
More advantageously, because the surface current is low at the gap, the ratio r/R can be quite low, for example r/R>0.6 or >0.8. This makes manufacturing especially small cavities easier because a small gap requires more precise engineering.
Figure 2 schematically shows a test design for room temperature testing. The lid 130 can be moved with respect to the housing 120 via a screw.
Figure 3 schematically shows a model geometry for numeric simulation. We investigate the electromagnetic losses that the gap 140 between the cavity walls or housing 120 and the lid 130 will cause. The corresponding COMSOL model (CylCav Q.mph) assumes a perfect conductor for the cavity material, i.e. all the losses are due to scattering out of the cavity 110
According to an embodiment of the present invention, the cavity resonator comprises third means 370 for removing a degeneracy of at least two electromagnetic modes generated in the cavity 110 in an operational state of the cavity resonator. In fig. 3, the third means are a stepped part located at one end of a cylindrical housing 120 of the cavity 110 opposite to the lid 120. The stepped part 370 is radially symmetric. The stepped part 370 is for removing a degeneracy of the TE011 and the TM111 mode.
Figure 4 schematically shows a simulated TE011 mode (4.3568 GHz) in a cavity of 6cm radius, 5cm height, 1cm step height, and 1mm gap. The electric field norm (V/m) is plotted in a simulated cross-section of the cavity with a stepped part 470. We find that the TEO 11 mode retains a high quality factor Q even for rather large gaps 140 (>lmm) between the cavity walls or housing 120 and the lid 130. Optionally, the Q is independent of the axial lid position.
Figure 5 is similar to Figure 4 wherein we model coupling in and out of the cavity. We use small loop at the end of coax cables and sticking them in the cavity (the orientation of the loops has to be such that there is a good overlap between the fields from the loop and the cavity mode).
Figure 6 shows the transmitted signal S21 in dB versus applied frequency in GHz with a resonance (TE011 mode) at 4.3568 GHz.
For Figs. 4-6 the simulated cavity has the dimension of 6cm radius, 5cm height, 1cm step, 1mm gap.
Figures 7a-d schematically show a simulated TE011, TE012, TE021, TE044 mode in a right half of the cavity with a radius of 6cm, height of 5cm. The cavity geometry and the modes are symmetric with respect to the vertical axis (i.e. left vertical line of the figures). The scale bar shows the normalized electric field in V/m. Figures 7ad respectively show a mode of 4.2746 GHz, 6.7257 GHz, 6.3334 GHz, 6.002GHz. As shown in Figures. 4, 5 and 7a-d, the surface current is low at the gap for these inodes so Qgap is increased, thus Qtot is also increased.
In an embodiment, the hollow cylindrical shape of the cavity resonator comprises a radius between 1cm and 20cm, a height between 1cm and 20 cm, in particular between 3cm and 20cm, the stepped part comprises a step height between 0.1cm and 2cm.
In an embodiment, the cavity resonator comprises a tunable microwave cavity that improves the phase noise performance of microwave sources by several orders of magnitude, potentially reaching the theoretical quantum shot noise limit. This will enable new applications of microwave sources, from quantum experiments, to atomic clocks, to commercial communication and radar applications.
The design is based on a 3-dimensional cylindrical microwave cavity with a special design such that the mode used has no currents flowing on the surface of the metal walls of the cavity. Doing so, it is possible to make one of these walls movable, allowing one to tune the frequency of the cavity by at least a factor of two, while maintaining the extremely narrow linewidth (5 kHz) of the cavity filter.
At least part of the cavity resonator is made of, copper or/and high conductivity copper or/and using superconducting metals to increase the Qoiunic. At cryogenic temperatures superconducting metals are preferred. Operation with quality factors of up to one million (5 kHz linewidth) should be possible with high conductivity copper at 2 Kelvin using a commercially available cryogenic cooler. Using superconductors such as Niobium with careful surface treatment, it should be possible to achieve quality factors on the order of 10Λ11 (linewidth 50 mHz).
For comparison, the current state-of-the-art oscillators based on YIG resonators in commercial generators have resonance linewidth on the order of a few MHz, three orders of magnitude larger than our copper cavities, and 8 orders of magnitude larger than we expect for superconducting cavities. By lowering the linewidth of the oscillator used to generate microwave signals by up to 8 orders of magnitude, we expect dramatic and disruptive improvements of phase performance of microwave sources.
The present invention can be used in at least two ways to reduce the phase noise of microwave generators: in the first technique, the cavity can be used as a tunable filter that be used to remove the unwanted sideband phase-noise of existing commercial generators, and could be brought quickly onto the market.
As a second product, this microwave cavity can be integrated as the reference oscillator used inside of the microwave source, enabling a direct end-product microwave source with extremely high frequency purity.
The present invention has been described above with reference to a number of exemplary embodiments as shown in the drawings. Modifications and alternative implementations of some parts or elements are possible, and are included in the scope of protection as defined in the appended claims.
In the foregoing description of the figures, the invention has been described with reference to specific embodiments thereof. It will, however, be evident that various modifications and changes may be made thereto without departing from the scope of the invention as summarized in the attached claims.
In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiments disclosed, but that the invention will include all embodiments falling within the scope of the appended claims.
In particular, combinations of specific features of various aspects of the invention may be made. An aspect of the invention may be further advantageously enhanced by 5 adding a feature that was described in relation to another aspect of the invention.
It is to be understood that the invention is limited by the annexed claims and its technical equivalents only. In this document and in its claims, the verb to comprise and its conjugations are used in their non-limiting sense to mean that items following the word are included, without excluding items not specifically mentioned. In addition, 10 reference to an element by the indefinite article a or an does not exclude the possibility that more than one of the element is present, unless the context clearly requires that there be one and only one of the elements. The indefinite article a or an thus usually means at least one.

Claims (15)

ConclusiesConclusions 1. Een holteresonator omvattende:A cavity resonator comprising: een holte omvattende een eerste behuizingsdeel (120) dat ten minste een deel van een holle cilindrische vorm met een gemiddelde binnendiameter R, en een open uiteinde (122) van de holle cilindrische vorm omvat;a cavity comprising a first housing portion (120) comprising at least a portion of a hollow cylindrical shape with an average inner diameter R, and an open end (122) of the hollow cylindrical shape; een tweede behuizingsdeel (130) dat ten minste een deel van een plaat omvat met een gemiddelde diameter r passend bij het ene open uiteinde van de holle cilindrische vorm;a second housing part (130) comprising at least a part of a plate with an average diameter r corresponding to the one open end of the hollow cylindrical shape; waarbij r kleiner is dan R;wherein r is less than R; waarbij het eerste behuizingsdeel en het tweede behuizingsdeel van elkaar beweegbaar zijn geconfigureerd om een volume van de holte en een resonantiefrequentie van een resonantiemodus in de holte te veranderen in een operationele toestand van de holteresonator;wherein the first housing part and the second housing part are movably configured from each other to change a volume of the cavity and a resonance frequency of a resonance mode in the cavity to an operational state of the cavity resonator; een eerste koppelingsmiddel (150) verbonden met het eerste behuizingsdeel of het tweede behuizingsdeel voor het genereren van een elektromagnetisch veld in de holte en het exciteren van de resonantiemodus in de operationele toestand van de holteresonator, waarbij de resonantiemodus een TEOmn- of TMOnm-modus is met n, m, > 1;a first coupling means (150) connected to the first housing part or the second housing part for generating an electromagnetic field in the cavity and exciting the resonance mode in the operational state of the cavity resonator, the resonance mode being a TEOmn or TMOnm mode with n, m,> 1; een tweede middel (160) verbonden met het eerste behuizingsdeel of het tweede behuizingsdeel voor het extraheren van het elektromagnetische veld in de holte in de operationele toestand van de holteresonator;a second means (160) connected to the first housing part or the second housing part for extracting the electromagnetic field in the cavity in the operational state of the cavity resonator; 2. De holteresonator volgens conclusie 1, waarbij r/R > 0.6.The cavity resonator according to claim 1, wherein r / R> 0.6. 3. De holteresonator volgens één van de conclusies 1 - 2, verder omvattende een derde middel (370) voor het verwijderen van een degeneratie van ten minste twee resonantiemodi gegenereerd in de holte in een operationele toestand van de holteresonator.The cavity resonator according to any of claims 1 to 2, further comprising a third means (370) for removing a degeneration of at least two resonance modes generated in the cavity in an operational state of the cavity resonator. 4. De holteresonator volgens conclusie 3, waarbij het derde middel een getrapt deel of / en een gegroefd deel van een binnenoppervlak van de holte of een koppelingsgat omvat.The cavity resonator according to claim 3, wherein the third means comprises a stepped portion or / and a grooved portion of an inner surface of the cavity or a coupling hole. 5. De holteresonator volgens conclusie 4, waarbij het getrapte deel of / en het gegroefde deel zich bevindt op een deel van het eerste behuizingsdeel tegenover het tweede behuizingsdeel.The cavity resonator according to claim 4, wherein the stepped part or / and the grooved part is located on a part of the first housing part opposite the second housing part. 6. De holteresonator volgens conclusie 5, waarbij het getrapte deel of / en het gegroefde deel radiaal symmetrisch is.The cavity resonator according to claim 5, wherein the stepped part or / and the grooved part is radially symmetrical. 7. De holteresonator volgens één van de conclusies 5-6, waarbij de holle cilindrische vorm een straal omvat tussen 1 cm en 20 cm, een hoogte tussen 1 cm en 20 cm, waarbij het getrapte deel een staphoogte tussen 0,1 cm en 2 cm omvat.The cavity resonator according to any of claims 5-6, wherein the hollow cylindrical shape comprises a radius between 1 cm and 20 cm, a height between 1 cm and 20 cm, wherein the stepped part has a step height between 0.1 cm and 2 cm. 8. De holteresonator volgens één van de conclusies 3-7, waarbij de ten minste twee elektromagnetische modi de TE011-modus en de TM111-modus omvatten.The cavity resonator according to any of claims 3-7, wherein the at least two electromagnetic modes comprise the TE011 mode and the TM111 mode. 9. De holteresonator volgens één van de conclusies 1 - 8, waarbij de resonantiefrequentie tussen 100 MHz en 200 GHz is met een kwaliteitsfactor tussen 103 en 1012.The cavity resonator according to any of claims 1 to 8, wherein the resonance frequency is between 100 MHz and 200 GHz with a quality factor between 10 3 and 10 12 . 10. De holteresonator volgens één van de conclusies 1-9, waarbij ten minste een deel van de holte is gegloeid.The cavity resonator according to any of claims 1-9, wherein at least a portion of the cavity is annealed. 11. De holteresonator volgens één van de conclusies 1-10, waarbij ten minste een deel van de holte koper of supergeleidend metaal, bijvoorbeeld Niobium, omvat.The cavity resonator according to any of claims 1-10, wherein at least a portion of the cavity comprises copper or superconducting metal, for example Niobium. 12. De holteresonator volgens één van de conclusies 1-11, waarbij de holteresonator voor cryogeen gebruik is.The cavity resonator according to any of claims 1 to 11, wherein the cavity resonator is for cryogenic use. 13. De holteresonator volgens één van de conclusies 1 - 12, waarbij het eerste of / en tweede middel coaxkabels zijn of / en connectoren zijn voor het verbinden met coaxkabels.The cavity resonator according to any one of claims 1 to 12, wherein the first or / and second means are coaxial cables or / and are connectors for connecting to coaxial cables. 14. Een microgolfbron omvattende een holteresonator volgens één van de conclusies 1 13 als een referentieoscillator.A microwave source comprising a cavity resonator as claimed in any one of claims 13 as a reference oscillator. 15. Werkwijze voor het bedrijven van een holteresonator volgens één van de conclusies 1-13, omvattende:A method of operating a cavity resonator according to any of claims 1-13, comprising: het plaatsen van een eerste behuizingsdeel en een tweede behuizingsdeel van een holte van de holteresonator in een positie die een volume van de holte en een resonantiefrequentie van een resonantiemodus in de holte verkrijgt in een operationele toestand van de holteresonator, waarbij het eerste deel ten minste een deel van een holle cilindrische vorm met een gemiddelde binnendiameter R, en een open einde (122) van de holle cilindrische vorm omvat;placing a first housing part and a second housing part of a cavity of the cavity resonator in a position that obtains a volume of the cavity and a resonance frequency of a resonance mode in the cavity in an operational state of the cavity resonator, the first part having at least one comprises part of a hollow cylindrical shape with an average inner diameter R, and an open end (122) of the hollow cylindrical shape; het tweede behuizingsdeel (130) ten minste een deel van een plaat omvat met een gemiddelde diameter r passend bij het ene open uiteinde van de holle cilindrische vorm;the second housing part (130) comprises at least a part of a plate with an average diameter r corresponding to the one open end of the hollow cylindrical shape; waarbij r kleiner is dan R;wherein r is less than R; waarbij het eerste behuizingsdeel en het tweede behuizingsdeel van elkaar beweegbaar zijn;wherein the first housing part and the second housing part are movable from each other; het genereren van een elektromagnetisch veld in de holte en het exciteren van de resonantiemodus in de operationele toestand van de holteresonator door een eerste koppelingsmiddel verbonden met het eerste behuizingsdeel of het tweede behuizingsdeel;generating an electromagnetic field in the cavity and exciting the resonance mode in the operational state of the cavity resonator by a first coupling means connected to the first housing part or the second housing part; het extraheren van het elektromagnetische veld in de holte in de operationele toestand van de holteresonator door een tweede middel verbonden met het eerste behuizingsdeel of het tweede behuizingsdeel;extracting the electromagnetic field in the cavity in the operational state of the cavity resonator by a second means connected to the first housing part or the second housing part; waarbij de resonantiemodus een TEOnm- of TMOnm-modus is met n, m, > 1.wherein the resonance mode is a TEOnm or TMOnm mode with n, m,> 1.
NL2020698A 2018-03-30 2018-03-30 A resonator apparatus NL2020698B1 (en)

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Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2000216602A (en) * 1999-01-26 2000-08-04 Nec Eng Ltd Band pass filter
US20110298566A1 (en) * 2010-06-02 2011-12-08 Bahram Yassini Te011 cavity filter assembly and method
US20180017704A1 (en) * 2015-02-26 2018-01-18 The Regents Of The University Of California Gravitational radiation communication system

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2000216602A (en) * 1999-01-26 2000-08-04 Nec Eng Ltd Band pass filter
US20110298566A1 (en) * 2010-06-02 2011-12-08 Bahram Yassini Te011 cavity filter assembly and method
US20180017704A1 (en) * 2015-02-26 2018-01-18 The Regents Of The University Of California Gravitational radiation communication system

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