EP1885017A1 - Abstimmbares Bandpass-Filter - Google Patents

Abstimmbares Bandpass-Filter Download PDF

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Publication number
EP1885017A1
EP1885017A1 EP06015382A EP06015382A EP1885017A1 EP 1885017 A1 EP1885017 A1 EP 1885017A1 EP 06015382 A EP06015382 A EP 06015382A EP 06015382 A EP06015382 A EP 06015382A EP 1885017 A1 EP1885017 A1 EP 1885017A1
Authority
EP
European Patent Office
Prior art keywords
cam
coupling
tuning
bandpass filter
track
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Withdrawn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
EP06015382A
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English (en)
French (fr)
Inventor
Olaf Bartz
Michael Höft
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.)
Panasonic Corp
Original Assignee
Matsushita Electric Industrial Co Ltd
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 Matsushita Electric Industrial Co Ltd filed Critical Matsushita Electric Industrial Co Ltd
Priority to EP06015382A priority Critical patent/EP1885017A1/de
Publication of EP1885017A1 publication Critical patent/EP1885017A1/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Withdrawn legal-status Critical Current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
    • H01P7/04—Coaxial resonators
    • 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

Definitions

  • the present invention relates to tunable bandpass filters comprising a plurality of resonator cavities arranged serially along a first direction, each resonator cavity being equipped with a movable frequency tuning element extending in the cavity, and a control mechanism having a movable control element, wherein the tuning elements and the control element are arranged such that an adjusting movement of the movable control element causes the tuning elements to be simultaneously displaced within the resonator cavities in dependence of the adjusting movement of the control element in order to adjust the centre frequencies of the resonator cavities.
  • Such tunable bandpass filter is for example known from US 2005/0212623 .
  • a dielectric tuning element is located, which is guided for linear movement along the inner surface of the lid of the cavity resonator.
  • the tuning element is connected to a control element located at the outer surface of the lid wall by a pin extending through an elongated slot in the lid wall.
  • the control element is formed by a rod extending along the series of resonator cavities in a first direction. This rod carries a dielectric tuning element in each of the resonator cavities in the series of resonators, and by displacement of the rod along the first direction, a simultaneous displacement of the dielectric tuning element in the resonator cavities may be performed to allow a desired adjustment of the centre frequencies.
  • US 2006/0038640 A1 describes a cavity resonator (also for use in multiple resonator assemblies such as combline resonators) having an inner conductor with a movable end cap.
  • the end cap is mounted on a central rod and is separated from the inner surface of the lid by a dielectric disc. The distance between lid surface and the end cap determines the capacitance of the capacitor formed by lid surface, dielectric disc and end cap. This capacitance in turn influences the resonator frequency.
  • an electromagnet is provided which drives the rod carrying the end cap against a biasing force to a desired position.
  • SDR Software-defined radio
  • analogue radio systems are being replaced by digital radio system for various radio applications in military, civilian and commercial spaces.
  • programmable hardware modules are increasingly being used in digital radio systems.
  • the aims of SDR are to define radio functions by software, and to configure a common hardware platform for a specific air interface by downloading software during operation or as part of the production cycle.
  • tunable bandpass filters are needed. These filters have to be multi-standard filters and must be tunable over wide range.
  • a tunable bandpass filter comprising a plurality of resonator cavities arranged serially along a first direction, each resonator cavity being equipped with a movable frequency tuning element extending into the cavity, and a control mechanism having a movable control element, wherein the tuning elements and the control element are arranged such that an adjusting movement of the movable control element causes the tuning elements to be simultaneously displaced within the resonator cavities in dependence of the adjusting movement of the control element in order to adjust the centre frequencies of the resonator cavities, characterised in that each frequency tuning element comprises a cam follower which is projecting from a wall of the respective resonator cavity to the outside and which is guided for shifting movement therein to allow to adjust the position of frequency tuning element by sliding the cam follower further inside or outside with respect to the resonator cavity wall; the control element comprises a cam shaft extending in the first direction and having a plurality of cam sections along its length, each cam section comprising a cam track in the form of
  • the cam segments provided on the cam shaft each provide a cam track showing a conical spiral for at least part of its length.
  • conical spiral in the sense of the present invention a function with varying radial distance from the central axis is meant which also proceeds in axial direction with each revolution; for example, the cam track may first, with each revolution around the central axis, increase its radial distance to the central axis, while at the same time proceeding in axial direction, wherein the slope of the conical spiral in axial direction is such that the axial advancement per revolution equals the width of the cam track in axial direction.
  • the term "conical spiral” as used in the present application is not limited to three-dimensional spirals with strictly linear growth along the axial direction. Furthermore, it is not excluded that after a conical spiral portion with increasing radial distance with respect to the central axis that there may be a further portion in which the cam track returns to lower radial distances with respect to the central axis of the cam shaft again.
  • each frequency tuning element is in sliding contact with the cam track surface of the associated cam segment on the cam shaft.
  • This sliding contact may be maintained either by gravitational force, in which case the elongated tuning elements must be positioned vertically and located in the bottom wall of the resonator cavities, or preferably by a biasing force, for example provided by a spring which urges the tuning element to its maximally extended position to the outside of the resonator cavity.
  • Each frequency tuning element may be moved to vary the position of the frequency tuning element with respect to the cavity and thus to vary the centre resonance frequency of the resonator.
  • the positioning of each frequency tuning element is determined by the cam track surface against which its cam follower abuts, i.e. by the radial distance of the conical spiral from the central axis.
  • a predetermined contour of the cam track of each cam segment determines the pattern in which the frequency tuning elements are displaced when the cam shaft is rotated by the drive for a given angle.
  • the cavity resonators have coupling openings between adjacent cavity resonators and have movable coupling tuning elements extending into the coupling openings.
  • the coupling tuning elements are displaceable in the same manner as the frequency tuning elements.
  • there are associated cam segments for the coupling tuning elements and associated cam segments and the coupling tuning elements have cam followers arranged such that the cam followers are in sliding contact with the associated cam segments on the cam shaft so that the rotation of the cam shaft determines, in addition to the positioning of the frequency tuning elements, the positioning of the coupling tuning elements.
  • FIG 1 a cross-sectional view of a single cavity 2 resonator is shown.
  • a frequency tuning element 10 in this case a dielectric ceramic body, extends in the resonator cavity 2 and is carried by a cam follower 12 which projects to the outside of the cavity.
  • the cam followers 12 is guided for linear movement further into and out of the resonator cavity.
  • the cam follower 12 is biased by a spring 16 to a maximally extended position (only in this Figure such bias spring is shown, whereas is has been omitted in the remaining Figures to simplify the graphical illustration).
  • This control element 20 comprises a shaft which is provided with cam sections 22 along its length (in this view of a single resonator only one cam section 22 is shown which is associated with the frequency tuning element and the cam follower of this resonator).
  • the cam section 22 has winding cam track which follows a path of a conical spiral, i.e. its radial distance to the longitudinal axis of the shaft is increasing over at least part of its length.
  • the shaft is mounted in such a manner that it, upon rotation, advances in its longitudinal direction at a rate that corresponds to the slope of the conical spiral of the cam track. In this manner the cam follower 12 may follow the conically spiraling cam track when the shaft is rotating.
  • the shaft may, for example be provided with an outer thread (not shown) at a certain portion which is engaging an inner thread of sleeve which is relatively fixed with respect to the filter.
  • an outer thread not shown
  • the shaft advances upon rotation in the desired manner.
  • frequency tuning elements 10 extend in the resonator cavities 2 and are carried by cam followers 12 which project to the outside of the cavities.
  • the cam segments 22 of the shaft are shaped in a predetermined manner such that by rotation of the shaft 20 the individual cam followers 12 and frequency tuning elements 10 are displaced in a predetermined manner given by the conical spiral shape of the cam segments.
  • a drive 24 for example a step motor, is provided for controlled rotation of the shaft 20 .
  • coupling tuning elements 30 which extend into openings between adjacent resonator cavities 2.
  • the coupling tuning elements 30 are mounted and guided in a similar manner as the frequency tuning elements.
  • the outer ends of the coupling tuning elements 30 are likewise formed as cam followers 32 arranged to be in sliding contact with cam segments 23 of the control element 20.
  • the positioning of the coupling tuning elements 30 may be varied in a predetermined way together with the adjustment of the centre frequencies of the resonators by the frequency tuning elements 20.
  • FIGS 3 to 5 show an embodiment of a filter comprising four coupled cavity resonators 2.
  • Each cavity resonator comprises a frequency tuning element 10 carried by a cam follower 12 which rides on the cam track of an associated cam section 22 on a shaft 20.
  • coupling tuning elements 30 with cam followers 32 are adjusted by their associated cam segments 23.
  • There is a further shaft 21 which is provided with one cam segment 23 which controls the positioning of an associated coupling tuning element.
  • the shafts 20 and 21 may in principle be rotated independently. However, it is also possible to provide a single drive (not shown) and to provide transmissions to the three shafts 20, 21.
  • FIGS 6 and 7 An alternative arrangement is shown in Figures 6 and 7 which in many aspects is similar to the filter of Figures 3 to 5, but comprises two additional shafts 21' which carry cam segments 23 which are associated with the coupling tuning elements 30 which determine the coupling of the resonators 2 which are associated with one shaft 20.
  • this arrangement it is possible to adjust the coupling tuning elements completely independent of the frequency tuning elements since the shafts 21, 21' may be rotated independently of the shafts 20.
  • Fig. 8 shows how the centre frequency of a single resonator of the type as shown in Fig. 1 is varying when the depth at which the frequency tuning element is intruding into the cavity is varied, this depth being designated as tf.
  • the variation of the centre frequency of the resonator is shown for three different cavity dimension, namely three different heights of the cavity hc.
  • Fig. 9 the behaviour of an exemplary bandpass filter comprising five resonators is shown.
  • the return loss S11 is shown in dashed lines and the transmission S21 in full lines.
  • the bandpass filter has a centre frequency of about 1400 MHz.
  • the centre frequencies of the resonators are increased such that the centre frequency of the filter is about 2000 MHz.
  • the centre frequency of the filter is adjusted to 2600 MHz. This increase of the centre frequency is achieved by moving the frequency tuning elements to lower intrusion lengths into the cavities, i.e.
  • the bandwidth of the filter is increasing with increasing centre frequencies. More precisely, the bandwidth of the filter is proportional to the centre frequency.
  • Fig. 12 shows that a variation of the centre frequency also leads to a variation in the coupling of resonators.
  • Fig. 13 shows the coupling factor k (in units of 10 -3 ) of adjacent first and second cavity resonators as a function of the coupling tuning element adjustment length tk (intrusion length), for three different values of the intruding length tf of the frequency tuning elements into the resonators cavities.
  • tk introduction length
  • a coupling between the first and second resonator of an exemplary filter is shown as decreasing with increasing centre frequency.
  • This decreasing coupling may be achieved by displacing the coupling elements in a manner so that the coupling reduction as shown in Fig. 10 is achieved.
  • the shape of the cam segments 23 effective for the cam followers 32 of the coupling tuning elements 30 may be chosen in relation to the cam sections 22 effective for the cam followers 12 of the frequency tuning elements 10 such that the bandwidth is maintained constant when the centre frequency of the band pass is adjusted.
  • a further schematical view of a single resonator which may be used in a filter according to the invention is shown.
  • This resonator is shown to be equipped with a tuning screw 40.
  • This tuning screw 40 may be useful in addition to the possible adjustment by way of the frequency tuning elements in order to allow to compensate for manufacturing tolerances in large scale production of filters.
  • the tuning may be performed using the cam surface, cam followers and tuning elements.
  • the cam follower does not extend into the resonator cavity but only up to a flexible wall portion of the resonator cavity.
  • the flexible wall portion which forms the frequency tuning element By moving the flexible wall portion which forms the frequency tuning element, the centre frequency of the resonator is varied.
  • the cam follower abuts against a cam segment on a shaft, and the position of the cam follower 12 may be adjusted by rotating the spiralling cam track of the cam segment so that a desired adjustment is achieved.
  • frequency and coupling tuning utilising the spiral cam track on a rotatable shaft have been described. It is evident that other tuning elements may be controlled and adjusted in the same manner for, example cross-coupling tuning element, tuning elements for coupling electromagnetic energy to the filter (input) or for extracting electromagnetic energy from the filter (output), etc.. It is noted that in general the input and output side of the filter is interchangeable depending on the intended operation.

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  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Control Of Motors That Do Not Use Commutators (AREA)
EP06015382A 2006-07-24 2006-07-24 Abstimmbares Bandpass-Filter Withdrawn EP1885017A1 (de)

Priority Applications (1)

Application Number Priority Date Filing Date Title
EP06015382A EP1885017A1 (de) 2006-07-24 2006-07-24 Abstimmbares Bandpass-Filter

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
EP06015382A EP1885017A1 (de) 2006-07-24 2006-07-24 Abstimmbares Bandpass-Filter

Publications (1)

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EP1885017A1 true EP1885017A1 (de) 2008-02-06

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EP06015382A Withdrawn EP1885017A1 (de) 2006-07-24 2006-07-24 Abstimmbares Bandpass-Filter

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Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN102460826A (zh) * 2009-06-22 2012-05-16 Ace技术株式会社 可调谐频率的滤波器
US20120169435A1 (en) * 2011-01-04 2012-07-05 Noriaki Kaneda Microwave and millimeter-wave compact tunable cavity filter
KR101387646B1 (ko) * 2012-09-26 2014-04-23 주식회사 케이엠더블유 무선 주파수 가변 필터 튜닝 장치
EP3553878A4 (de) * 2016-12-30 2019-10-16 Huawei Technologies Co., Ltd. Abstimmbarer filter und abstimmbare filtrierungsvorrichtung
EP3621144A1 (de) * 2018-09-07 2020-03-11 Nokia Solutions and Networks Oy Koaxialer resonator und verfahren zum betrieb eines koaxialen resonators

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3516030A (en) * 1967-09-19 1970-06-02 Joseph S Brumbelow Dual cavity bandpass filter
DE19602815A1 (de) * 1995-01-27 1996-08-08 Israel State Mikrowellenbandpaßfiltervorrichtung mit Kreuzkopplung
EP1258941A2 (de) * 2001-05-18 2002-11-20 Comtech S.r.l. Mimimumordnungsfilter mit gekoppelten Topfkreisen für UHF-Fernsehübertragung
US20050212623A1 (en) * 2003-03-18 2005-09-29 Filtronic Comtek Oy Resonator filter
WO2006012055A2 (en) * 2004-06-25 2006-02-02 Microwave Circuits, Inc. Ceramic loaded temperature compensating tunable cavity filter

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3516030A (en) * 1967-09-19 1970-06-02 Joseph S Brumbelow Dual cavity bandpass filter
DE19602815A1 (de) * 1995-01-27 1996-08-08 Israel State Mikrowellenbandpaßfiltervorrichtung mit Kreuzkopplung
EP1258941A2 (de) * 2001-05-18 2002-11-20 Comtech S.r.l. Mimimumordnungsfilter mit gekoppelten Topfkreisen für UHF-Fernsehübertragung
US20050212623A1 (en) * 2003-03-18 2005-09-29 Filtronic Comtek Oy Resonator filter
WO2006012055A2 (en) * 2004-06-25 2006-02-02 Microwave Circuits, Inc. Ceramic loaded temperature compensating tunable cavity filter

Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN102460826A (zh) * 2009-06-22 2012-05-16 Ace技术株式会社 可调谐频率的滤波器
CN102460826B (zh) * 2009-06-22 2015-11-25 Ace技术株式会社 可调谐频率的滤波器
US20120169435A1 (en) * 2011-01-04 2012-07-05 Noriaki Kaneda Microwave and millimeter-wave compact tunable cavity filter
US9083071B2 (en) * 2011-01-04 2015-07-14 Alcatel Lucent Microwave and millimeter-wave compact tunable cavity filter
KR101387646B1 (ko) * 2012-09-26 2014-04-23 주식회사 케이엠더블유 무선 주파수 가변 필터 튜닝 장치
EP3553878A4 (de) * 2016-12-30 2019-10-16 Huawei Technologies Co., Ltd. Abstimmbarer filter und abstimmbare filtrierungsvorrichtung
US10873118B2 (en) 2016-12-30 2020-12-22 Huawei Technologies Co., Ltd. Tunable filter and tunable filtering device
EP3621144A1 (de) * 2018-09-07 2020-03-11 Nokia Solutions and Networks Oy Koaxialer resonator und verfahren zum betrieb eines koaxialen resonators

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