EP2887449A1 - Filtre à cavité accordable - Google Patents

Filtre à cavité accordable Download PDF

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Publication number
EP2887449A1
EP2887449A1 EP13306741.3A EP13306741A EP2887449A1 EP 2887449 A1 EP2887449 A1 EP 2887449A1 EP 13306741 A EP13306741 A EP 13306741A EP 2887449 A1 EP2887449 A1 EP 2887449A1
Authority
EP
European Patent Office
Prior art keywords
tunable
cavity
filter according
cavity filter
control voltage
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP13306741.3A
Other languages
German (de)
English (en)
Inventor
Wolfgang Templ
Dirk Wiegner
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Alcatel Lucent SAS
Original Assignee
Alcatel Lucent SAS
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Alcatel Lucent SAS filed Critical Alcatel Lucent SAS
Priority to EP13306741.3A priority Critical patent/EP2887449A1/fr
Publication of EP2887449A1 publication Critical patent/EP2887449A1/fr
Withdrawn legal-status Critical Current

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Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01P—WAVEGUIDES; RESONATORS, LINES, OR OTHER DEVICES OF THE WAVEGUIDE TYPE
    • H01P1/00—Auxiliary devices
    • H01P1/20—Frequency-selective devices, e.g. filters
    • H01P1/201—Filters for transverse electromagnetic waves
    • H01P1/205—Comb or interdigital filters; Cascaded coaxial cavities
    • H01P1/2053—Comb or interdigital filters; Cascaded coaxial cavities the coaxial cavity resonators being disposed parall to each other
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01P—WAVEGUIDES; RESONATORS, LINES, OR OTHER DEVICES OF THE WAVEGUIDE TYPE
    • H01P1/00—Auxiliary devices
    • H01P1/20—Frequency-selective devices, e.g. filters
    • H01P1/207—Hollow waveguide filters
    • H01P1/208—Cascaded cavities; Cascaded resonators inside a hollow waveguide structure
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01P—WAVEGUIDES; RESONATORS, LINES, OR OTHER DEVICES OF THE WAVEGUIDE TYPE
    • H01P7/00—Resonators of the waveguide type
    • H01P7/04—Coaxial resonators
    • 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

Definitions

  • the present invention relates to a tunable cavity filter.
  • Radio transmitter carrier frequencies in 4G and 5G wireless systems vary between 700 MHz and 4 GHz.
  • cavity filters are used especially in case of high transmission power.
  • the geometrical dimensions of the filter are defined by physical characteristics. The geometrical dimensions are often tuned in a complex process to meet the required performance.
  • Cavity filters may be tuned to the required frequency by mechanical adjustment, e.g. by turning a screw, in order to change the characteristic capacitances. This may be done once during or at the end of the manufacturing process. The adjustment is elaborative and is often not correctable or adjustable later on in the field.
  • Using servo/step motor drives to move tuning screws and thus to change the capacitances of the cavity is more flexible but at the cost of higher system complexity, cost and failure probability.
  • Using the piezo-electrical effect by means of a piezoelectric drive suffers from the small deflection of the piezoelectric drive, thus providing only a small tuning range.
  • a tunable cavity filter comprises a housing which is made of metal forming a cavity. Inside the cavity, a tunable element is attached to one side of the cavity. "Attached" is to be understood in that the tuning element is directly glued, screwed or otherwise mechanically attached to the inner surface of one side of the cavity.
  • the tunable element is expandable or compressible using a control voltage, thus, if a control voltage is applied, the tunable element expands or compresses itself.
  • the proposed cavity filter is advantageous, because such a structure can be manufactured more easily than other filters known in the prior art. Due to the low mechanical complexity, the manufacturing costs are kept low.
  • the cavity filter is easily tunable, only by applying a control voltage and has a comparably large tuning range. Complex tuning processes as last step of the manufacturing process or during use for fine-tuning of the filter are omitted. In contrast, the filter specification can be adapted and tuned easily by applying the control voltage.
  • the tunable cavity filter further comprises a control input for receiving the control voltage.
  • the control voltage is permanently applied to the control input. There is no or only few current dissipation through the tunable element when the tuning element does not change its geometry, though the power dissipation is negligible. Only when the control voltage is changed and the geometry of the tuning element changes, the power dissipation is non-negligible.
  • the control voltage is only applied to the control input during the tuning process and afterwards, the control voltage is switched off.
  • the control input is electrically connected to the tunable element and is for applying the control voltage to the tunable element. In one embodiment, the control voltage is a DC voltage.
  • the tunable cavity filter further comprises a resonator within the cavity.
  • the resonator is defined by an axial rod attached to one side of the cavity and extending into the cavity.
  • the axial rod is made of metal or is metalized.
  • the frequency of the cavity filter is amongst others defined by the distance between the end of the axial rod and the tunable element. This is advantageous as this distance is easily adjustable by expanding and compressing the tunable element.
  • a metallization layer is attached to the inner side of the tunable element.
  • the tunable element is covered by a metallization.
  • Inner side of the tunable element means the side which is not in direct contact with the cavity.
  • the inner side of the tunable element is the side which is closest to the axial rod.
  • Metalizing the top of the tunable element has the advantage that a cavity is built which has a variable size by moving the metallization layer up and down by expanding and compressing the tunable element.
  • the metallization layer on the inner side of the tunable element and the side walls of the cavity are arranged without space between them such that the edges of the metallization layer and the side walls of the cavity are electrically connected.
  • an isolation layer is included between the metallization layer and the inner side of the tunable element. Thus, the metallization layer and the tunable element are not electrically connected. In one embodiment, isolation layers are included between the cavity and the tunable element. Thus the tunable element and the cavity are not electrically connected.
  • the tunable element of the tunable cavity filter is expanded when a suitably polarized control voltage is attached.
  • the tunable element of the tunable cavity filter is compressed when the polarity of the control voltage is reversed.
  • the degree of expansion and the degree of compression corresponds to the absolute value of the applied control voltage and to the sign of the applied control voltage.
  • the tunable element when applying a voltage above a certain threshold, the tunable element is expanded to the maximum value and when applying a voltage below this certain threshold, the tunable element is not expanded at all.
  • the expansion is performed stepwise.
  • the tunable element is an ionic electroactive polymer.
  • Ionic electroactive polymers are for example ionic gels, ionic polymer-metal composites, stimuli-responsive gels or the like. Ionic electroactive polymers have the advantage that only a low voltage, e.g. a few volts are necessary to control them.
  • the tunable element is made of a dielectric electroactive polymer.
  • Dielectric electroactive polymers are for example ferroelectric polymers, electrostrictive graft polymers, liquid crystalline polymers or the like. Dielectric electroactive polymers are controlled by a voltage which is applied and almost no current is needed.
  • One group of dielectric electroactive polymers are dielectric elastomers, which provide a large strain and are thus dedicated for the use in a cavity filter as tuning element. A large tuning range of the cavity filter is realized with such dielectric elastomers.
  • the tunable element keeps its expansion state when the control voltage is switched off.
  • a control voltage needs to be applied to the tuning element in order to tune the tuning element.
  • the control voltage is switched off and no further power needs to be applied.
  • power is saved and after tuning the cavity filter does not consume any power.
  • the cavity includes an input port and an output port at a first side of the cavity.
  • the resonator defining element is attached to this first side of the cavity and the tunable element is attached to a second side of the cavity which is the side opposite to the first side of the cavity.
  • further metalized tunable elements are attached to further sides of the cavity.
  • Such tunable elements are attached to the side walls of the cavity. This has the advantage that more degrees of freedom are available to fine tune the cavity filter.
  • a duplex filter for a reception path and for a transmission path is made of at least one tunable cavity filter in the transmission path and at least one tunable cavity filter in the reception path.
  • two or more tunable cavity filters are coupled such that they form a multi-pole filter. In one embodiment, two tunable cavity filters are coupled such that they form a dipole filter.
  • a transceiver device for mobile communication which comprises at least one tunable cavity filter.
  • Fig. 1 depicts a cavity filter as known in the art.
  • the cavity filter comprises a cavity 1, which is metalized.
  • Two RF input/output connectors 2, 3 are located in the upper side of the cavity 1.
  • a resonator defining element 4 (“resonator") is attached to the upper side of the cavity 1 inside the cavity 1.
  • the resonator 4 is attached in the center of one side of the cavity as shown in Fig. 1 . In one embodiment, the resonator is attached beside the center of one side of the cavity.
  • the resonator 4 includes a tuning element 5 which is movable and expands the resonator 4 by a length depending on movement of the tuning element 5.
  • a tuning screw 6 is provided to move the tuning element 5.
  • the resonant frequency is depending, amongst others, on the free space distance d between the tuning element 5 and the below boundary of the cavity 1.
  • Fig.2 and Fig. 3 show a cavity filter according to the invention.
  • the cavity filter comprises a cavity 1, which is metalized.
  • Two RF input/output connectors 2, 3 are located in the upper side of the cavity 1.
  • a resonator defining element 4 ("resonator") is attached to the upper side of the cavity 1 inside the cavity 1.
  • a tunable element 7 is included in the cavity 1 and is attached on the lower side of the cavity 1.
  • the tunable element 7 is attached by gluing, screwing or otherwise mechanically attaching it to the surface of the lower side of the cavity 1.
  • a metallization layer 8 is attached on top of the tuning element.
  • the metallization layer 8 is electrically connected to the cavity walls.
  • an isolation layer is included between the tunable element 7 and the metallization layer 8.
  • an inner cavity is built which is completely metalized providing a filter cavity.
  • no metallization layer 8 is attached.
  • the filter frequency is then influenced by the thickness of the tunable element 7, the geometry of the assembly, and the dielectric constant of the tunable element 7. This means, the space between the resonator 4 and the opposing wall of the cavity 1 is partially filled with the tunable element 7 and with air or a gas within the cavity 1.
  • the ratio between the space filled with the tunable element 7 and the space filled with air or gas between the resonator 4 and the opposing wall of the cavity 1 as well as the geometry of the assembly determines the filter frequency.
  • a further parameter influencing the filter frequency is the difference between the dielectric constant of the tunable element 7 and the dielectric constant of the material in the cavity, i.e. air.
  • a control input 9 is provided for receiving a control voltage 10 and for applying the control voltage 10 to the tunable element 7.
  • the control input 9 is connected to the tunable element 7 by means of highly conductive adhesive.
  • a part of a side wall or the bottom wall is used as a control input 9.
  • the tunable element expands or compresses its size and thus, the upper edge of the tunable element 7 moves up and down.
  • the distance d between the resonator and the metallization layer 8 increases or decreases in dependence of the applied control voltage 10.
  • This distance d influences as a main factor the resonant frequency of the cavity 1 and thus, tuning of the cavity filter is made by applying a corresponding control voltage 10.
  • no metallization layer 8 is provided on top of the tunable element 7, the distance between the resonator 4 and the upper edge of the tunable element 7 increases or decreases in dependence of the applied control voltage 10. This distance is a main factor defining the resonant frequency of the cavity.
  • the ratio between the part below the resonator 4 which is filled with air and the part which is filled with a material with a higher dielectric constant than air, namely the tunable element 7, which has a dielectric constant depending on its material is changing and influences significantly the resonant frequency.
  • the characteristic of the dielectric constant between the resonator 4 and the opposing wall follows a step function, which influences the resonant frequency significantly.
  • the resonant frequency is tuned.
  • Fig. 2 depicts a state of the embodiment when a control voltage 10 is applied such that the tunable element 7 is compressed.
  • Fig. 3 depicts a state of the embodiment when a control voltage 10 is applied such that the tunable element 7 is expanded.
  • DSP digital signal processor
  • ASIC application specific integrated circuit
  • FPGA field programmable gate array
  • ROM read only memory
  • RAM random access memory

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  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Control Of Motors That Do Not Use Commutators (AREA)
EP13306741.3A 2013-12-17 2013-12-17 Filtre à cavité accordable Withdrawn EP2887449A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
EP13306741.3A EP2887449A1 (fr) 2013-12-17 2013-12-17 Filtre à cavité accordable

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
EP13306741.3A EP2887449A1 (fr) 2013-12-17 2013-12-17 Filtre à cavité accordable

Publications (1)

Publication Number Publication Date
EP2887449A1 true EP2887449A1 (fr) 2015-06-24

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Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2017023439A1 (fr) * 2015-07-31 2017-02-09 Qualcomm Incorporated Résonateur à cavité accordable
CN109274348A (zh) * 2018-08-06 2019-01-25 东南大学 一种非对称耦合声波导滤波器
WO2021049666A1 (fr) * 2019-09-13 2021-03-18 正毅 千葉 Filtre à haute fréquence
US11139544B2 (en) 2019-09-06 2021-10-05 Nokia Technologies Oy Electrically tunable radio-frequency components and circuits
US11264720B2 (en) 2019-10-28 2022-03-01 Nokia Technologies Oy Tunable radio-frequency device having electrochromic and electro-active materials

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3471811A (en) * 1967-05-05 1969-10-07 Litton Precision Prod Inc Tunable microwave cavity using a piezoelectric device
US20040212457A1 (en) * 1999-03-16 2004-10-28 Eden Richard C High temperature superconducting tunable filter
US20100007442A1 (en) * 2006-04-27 2010-01-14 Powerwave Comtek Oy Tuning element and tunable resonator
US20100127953A1 (en) * 2008-11-25 2010-05-27 Sony Ericsson Mobile Communications Ab Antenna, antenna arrangement and radio communication apparatus
EP2555322A2 (fr) * 2011-07-30 2013-02-06 Diehl BGT Defence GmbH & Co.KG Antenne avec polymère électroactif
US8598969B1 (en) * 2011-04-15 2013-12-03 Rockwell Collins, Inc. PCB-based tuners for RF cavity filters

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3471811A (en) * 1967-05-05 1969-10-07 Litton Precision Prod Inc Tunable microwave cavity using a piezoelectric device
US20040212457A1 (en) * 1999-03-16 2004-10-28 Eden Richard C High temperature superconducting tunable filter
US20100007442A1 (en) * 2006-04-27 2010-01-14 Powerwave Comtek Oy Tuning element and tunable resonator
US20100127953A1 (en) * 2008-11-25 2010-05-27 Sony Ericsson Mobile Communications Ab Antenna, antenna arrangement and radio communication apparatus
US8598969B1 (en) * 2011-04-15 2013-12-03 Rockwell Collins, Inc. PCB-based tuners for RF cavity filters
EP2555322A2 (fr) * 2011-07-30 2013-02-06 Diehl BGT Defence GmbH & Co.KG Antenne avec polymère électroactif

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
DUBOIS P ET AL: "Voltage Control of the Resonance Frequency of Dielectric Electroactive Polymer (DEAP) Membranes", JOURNAL OF MICROELECTROMECHANICAL SYSTEMS, IEEE SERVICE CENTER, US, vol. 17, no. 5, 1 October 2008 (2008-10-01), pages 1072 - 1081, XP011231987, ISSN: 1057-7157, DOI: 10.1109/JMEMS.2008.927741 *

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2017023439A1 (fr) * 2015-07-31 2017-02-09 Qualcomm Incorporated Résonateur à cavité accordable
CN109274348A (zh) * 2018-08-06 2019-01-25 东南大学 一种非对称耦合声波导滤波器
US11139544B2 (en) 2019-09-06 2021-10-05 Nokia Technologies Oy Electrically tunable radio-frequency components and circuits
WO2021049666A1 (fr) * 2019-09-13 2021-03-18 正毅 千葉 Filtre à haute fréquence
CN114365347A (zh) * 2019-09-13 2022-04-15 千叶正毅 高频滤波器
US11894592B2 (en) 2019-09-13 2024-02-06 Selki Chiba High frequency filter
US11264720B2 (en) 2019-10-28 2022-03-01 Nokia Technologies Oy Tunable radio-frequency device having electrochromic and electro-active materials

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