EP2882033A1 - Résonateur et filtre radiofréquence - Google Patents

Résonateur et filtre radiofréquence Download PDF

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Publication number
EP2882033A1
EP2882033A1 EP13196298.7A EP13196298A EP2882033A1 EP 2882033 A1 EP2882033 A1 EP 2882033A1 EP 13196298 A EP13196298 A EP 13196298A EP 2882033 A1 EP2882033 A1 EP 2882033A1
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EP
European Patent Office
Prior art keywords
coaxial line
conductor
radio
resonator
outermost
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Withdrawn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
EP13196298.7A
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German (de)
English (en)
Inventor
Hakim Aouidad
Eric Rius
Jean-François FAVENNEC
Yann Clavet
Alexandre Manchec
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.)
Centre National de la Recherche Scientifique CNRS
ELLIPTIKA
Univerdite de Bretagne Occidentale
Ecole Nationale dIngenieurs de Brest ENIB
Original Assignee
Centre National de la Recherche Scientifique CNRS
ELLIPTIKA
Univerdite de Bretagne Occidentale
Ecole Nationale dIngenieurs de Brest ENIB
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.)
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Publication date
Application filed by Centre National de la Recherche Scientifique CNRS, ELLIPTIKA, Univerdite de Bretagne Occidentale, Ecole Nationale dIngenieurs de Brest ENIB filed Critical Centre National de la Recherche Scientifique CNRS
Priority to EP13196298.7A priority Critical patent/EP2882033A1/fr
Publication of EP2882033A1 publication Critical patent/EP2882033A1/fr
Withdrawn legal-status Critical Current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
    • 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
    • H01P7/00—Resonators of the waveguide type
    • H01P7/04—Coaxial resonators

Definitions

  • the invention relates to a radio-frequency resonator, and more specifically to a stepped-impedance coaxial radio-frequency resonator.
  • the invention also relates to a radio-frequency filter comprising a plurality of coupled resonators.
  • radio-frequency designates frequency comprised between 3 kHz and 300 GHz.
  • the invention applies more specifically to frequencies belonging to the UHF (Ultra-High-Frequency) band, i.e. comprised between 300 MHz and 3 GHz, although it can also apply to frequencies belonging to the VHF (Very-High-Frequency) band, i.e. comprised between 30 MHz and 300 MHz, and/or to the SHF (Super-High-Frequency) band, i.e. comprised between 3 GHz and 30 GHz, and/or millimetric band, i.e. comprised between 30 GHz and 300 GHz.
  • UHF Ultra-High-Frequency
  • VHF Very-High-Frequency
  • SHF Super-High-Frequency
  • waveguide (or "volume") resonator and filters At the other end of the spectrum, waveguide (or "volume") resonator and filters have very high quality factors (up to 10.000 or more) and low insertion losses, but they are very bulky.
  • Microstrip, coaxial and dielectric resonators offer intermediate performances. Within the coaxial technology, in particular, one can distinguish between uniform air coaxial resonators, with better electrical properties, and uniform dielectric coaxial resonators, more compact but with lower Q and higher insertion losses.
  • Coaxial stepped impedance resonators constituted by a plurality of coaxial line sections of different characteristic impedance connected in cascade, offer an interesting tradeoff between conflicting electrical and mechanical requirements.
  • the coaxial line sections can be partially or wholly loaded with high-dielectric-constant ceramics for further miniaturization, but again at the expenses of increased losses and reduced Q.
  • Coaxial stepped impedance resonators are described, in particular, by the following papers:
  • Document US 4,292,610 describes a stepped-impedance coaxial resonator having a particularly compact structure.
  • a resonator comprises an outer, hollow conductor 1, an inner conductor 2 coaxially mounted within the outer conductor and having a first end short-circuited to a wall of the outer conductor and a second end spaced from the wall of the outer conductor, and an intermediate hollow conductor 3 coaxially mounted between said inner conductor and said outer conductor.
  • Intermediate conductor 3 has a closed end short-circuited to the second end of the inner conductor, and an open end.
  • Conductors 1, 2 and 3 form three coaxial line sections I, II and III having different geometries and therefore, in general, different characteristic impedances Z 1 , Z 2 and Z 3 .
  • sections II and III are nested with each other.
  • a drawback of this resonator is its lack of design flexibility, as the electrical lengths and the characteristic impedances of the different coaxial line sections are not independent from each other. Moreover, the number of cascaded different coaxial line sections cannot be changed, and the resonator is not easily made tunable.
  • the invention aims at curing, at least in part, some or all the above-mentioned drawbacks of the prior art, and more particularly at providing a new resonator structure achieving a better tradeoff between the conflicting requirements of reduced size and good electrical performances.
  • An object of the present invention is a radio-frequency resonator comprising a plurality of coaxial line sections connected in cascade, each of said coaxial line sections comprising an inner conductor surrounded by an outer conductor of tubular shape, wherein said coaxial line sections are nested within each other, the outer conductor of each said coaxial line section, except an outermost one, serving as the inner conductor of another one of said coaxial line sections, the resonator being characterized in that each conductor of each coaxial line section, except the outer conductor of the outermost coaxial line section, has an open-circuit end and an opposite end which is short-circuited to said outer conductor of said outermost coaxial line section, and in that said conductors of said coaxial line sections - except the outer conductor of said outermost coaxial line section - are arranged head-to-tail, their open-circuit and short-circuited ends being alternatively situated on opposite sides of the resonator.
  • Another object of the invention is a radio-frequency filter comprising a plurality of such radio-frequency resonators mounted adjacent to each other and coupled by openings in the outer conductors of their respective outermost coaxial lines, forming coupling irises.
  • said radio-frequency resonators may be identical to each other.
  • coaxial line should be interpreted broadly, as indicating any transmission line section comprising an elongated conductor ("core”) surrounded - without direct contact - by a tubular conductor ("shielding"), both conductor having constant cross-sections (i.e. being "cylindrical” in the general sense of the term, not limited to circular-base cylinders) and parallel longitudinal axis.
  • This definition includes e.g. "eccentric coaxial lines”, which are not exactly “coaxial” in geometrical terms.
  • the physical structure of a quarter-wave radio-frequency resonator according to the invention is represented on figure 3 .
  • n>1 coaxial line sections are nested within each other (""matryoshka" structure), disposed head-to-tail - i.e. with open-circuit and short-circuit ends on alternate sides of the resonator.
  • the innermost or central conductor C 1 can be either tubular (i.e. hollow) or rod-like (i.e.
  • the outermost conductor C n+1 has a lateral surface and two opposite base surfaces, forming a conductive shell. All the conductors, except the outermost one, have an open-circuit end and an opposite end which is short-circuited to the outermost conductor C n+1 .
  • Conductors are arranged head-to-toe in the sense that their open-circuit and short-circuited ends are alternatively situated on opposite sides of the resonator (on figure 3 , odd-numbered conductors have their left end short-circuited to the left base surface of the outermost conductor, while even-numbered conductors have their right end short-circuited to the right base surface of the outermost conductor).
  • conductors C 1 and C 2 form a first coaxial line section having C 1 as the inner conductor (or “core”) and C 2 as the outer conductor (or “shielding”); similarly, C 2 and C 3 form a second coaxial line section having C 2 as its core and C 3 as its shielding, and so on. Every conductor is then simultaneously the core of a coaxial line section and the shielding of another coaxial line section - except the central conductor, which is only a core, and the outermost conductor, which is only a shielding.
  • Z SC is the impedance of the short-circuit termination.
  • TEM modes can be excited inside the resonator by different means known in the art.
  • a rod (not represented here, but see CR 1 , CR 2 on figure 10 ) can extend transversally to the axis of the coaxial line sections, having a "distal" end connected to the outside of the resonator through an opening in the lateral surface of the outermost conductor, and a "proximal" end contacting - or being spaced from - another conductor.
  • the distal end can be connected to the core of a RF feeding coaxial cable, the shielding of which is connected to the outermost conductor.
  • TEM modes can be also excited e.g. by an iris, or by a "current loop” obtained by forming a loop with the core of the RF feeding coaxial cable, whose distal end contacts the outermost conductor.
  • L be the physical length of all the coaxial line sections, ⁇ ri its relative dielectric constant of the i-th section, d i and D i the diameters of the conductors forming its core and shielding, respectively (it will be noted that the i-th conductor, with i>1, has an inner diameter equal to D i-1 and an outer diameter equal to d i ; if the thickness of the conductor is negligible, D i-1 ⁇ d i ; this approximation was used when discussing figure 3 ).
  • Figure 6A illustrates, the relationship between ⁇ 0 and M expressed by equation (9).
  • Figures 6B illustrates the relation between the ratio F S1 /F 0 and characteristic impedance contrast M.
  • Figures 6D illustrates the unloaded quality factor Q as a function of M.
  • a uniform quarter-wave, air-filled coaxial resonator having the same resonant frequency F 0 would have a length of 341 mm. The invention allows then a length reduction of a factor 11.14.
  • Both the two- and the three-section resonators have a substantially higher quality factor than the uniform dielectric resonator, and only a slightly greater length. From a different point of view, they are much shorter than the uniform air-filled resonator, at the expense of a moderate reduction of the quality factor.
  • Figure 9 shows the electrical scheme of a second-order band-pass filter comprising a parallel connection of two identical 2-section resonators R1 and R2 between admittance inverters.
  • K 01 and K 23 are the external coupling and K 12 the coupling between the resonators.
  • the values of these parameters are determined by a conventional Chebyshev synthesis.
  • Figure 10 illustrates a possible and non limitative, physical implementation of the filter of figure 9 .
  • the outermost conductors C 3 1 , C 3 2 of both resonators are constituted by a common aluminum casing AC, partitioned by an internal wall SW which does not extend on the whole length of the resonators so as to form, with the back wall of the casing, a coupling iris Cl.
  • Two tuning screws TS 1 , TS 2 are provided to adjust the coupling strength, and therefore the coupling K 12 .
  • the intermediate conductors C 2 1 , C 2 2 of both resonators are constituted by respective aluminum tubes fixed to the face wall of the aluminum casing (not shown, to make the inner structure of the filter visible) and not contacting the back wall; their central conductors C 1 1 , C 1 2 are constituted by brass rods fixed to the back wall of the casing and not contacting the face wall.
  • Two excitations rods ER 1 and ER 2 extend transversally; their proximal ends contact the intermediate conductors C 2 1 , C 2 2 while their distal ends exit the resonator through respective openings in the aluminum casing.
  • the distal ends of the excitation rods are connected - trough conventional connectors - to the cores of two coaxial cables, whose shielding are connected to the aluminum casing and to the ground thorough respective conducting chocks (visible on the sides of the casing).
  • the dimensions of the different elements are:
  • a smaller size (e.g. a reduction of the longitudinal dimension from 43 to 25 mm) could be achieved using more sophisticated manufacturing techniques, such as electroforming.
  • Figures 11A and 11 B show the frequency dependence of the scattering parameters S 11 and S 12 , obtained from simulation and from measurement.
  • Figure 11A is a narrow-band representation
  • Figure 12 shows the electrical scheme of a 6 th order filter comprising six identical two-section resonators, with coupling constants K 12 , K 23 , K 34 , K 45 , K 56 and K 67 .
  • the K 16 coupling is important as it allows introducing two transmission zeros near the pass band.
  • Figures 13A and 13B are, respectively, narrow-band and large-band representations of the frequency dependence of scattering parameters S 11 and S 12 .
  • Figure 13A also shows (thick line and dotted line) the required filter specification.
  • Resonators according to the invention and therefore filters built from them, can be made tunable in several ways, two of which are illustrated on figures 14A and 14B .
  • an electrical motor EM is used to move the central conductor C 1 in an axial direction, thus changing the length of the portion of it which is contained within the resonator. This changes the physical - and electrical - length of the first coaxial line section, and therefore the resonance frequency. This allows broad, but slow, tunability.
  • Figure 14B shows an alternative embodiment, wherein a variable capacitor (implemented e.g. by a varactor diode) is connected between the central conductor C 1 (or an intermediate conductor, such as C 2 ) and the ground. This allow faster tuning, but in a narrower range, and reduces the quality factor. It is clear that different tuning mechanisms (e.g. those of figures 14A and 14B ) can be combined in a same device.
  • Figure 15 shows the frequency dependence of the scattering parameters S 11 and S 12 of a tunable filter, for 5 different values P1 - P5 of the central frequency, spanning the 435 MHz - 1.63 GHz range.

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  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Control Of Motors That Do Not Use Commutators (AREA)
EP13196298.7A 2013-12-09 2013-12-09 Résonateur et filtre radiofréquence Withdrawn EP2882033A1 (fr)

Priority Applications (1)

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EP13196298.7A EP2882033A1 (fr) 2013-12-09 2013-12-09 Résonateur et filtre radiofréquence

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Application Number Priority Date Filing Date Title
EP13196298.7A EP2882033A1 (fr) 2013-12-09 2013-12-09 Résonateur et filtre radiofréquence

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EP2882033A1 true EP2882033A1 (fr) 2015-06-10

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP3525281A4 (fr) * 2016-10-25 2019-10-23 Huawei Technologies Co., Ltd. Combineur et dispositif d'antenne

Citations (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2181901A (en) * 1937-01-04 1939-12-05 Rca Corp Resonant line
US2851666A (en) * 1952-06-20 1958-09-09 Patelhold Patentverwertung Microwave filter with a variable band pass range
GB891444A (en) * 1959-06-30 1962-03-14 Siemens Ag Improvements in or relating to electro-magnetic resonators
US3448412A (en) * 1967-04-21 1969-06-03 Us Navy Miniaturized tunable resonator comprising intermeshing concentric tubular members
US4059815A (en) 1975-07-31 1977-11-22 Matsushita Electric Industrial Co., Limited Coaxial cavity resonator
US4292610A (en) 1979-01-26 1981-09-29 Matsushita Electric Industrial Co., Ltd. Temperature compensated coaxial resonator having inner, outer and intermediate conductors
US5691675A (en) * 1994-03-31 1997-11-25 Nihon Dengyo Kosaku Co., Ltd. Resonator with external conductor as resonance inductance element and multiple resonator filter
WO2009108540A1 (fr) * 2008-02-29 2009-09-03 Applied Materials, Inc. Résonateurs coaxiaux repliés

Patent Citations (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2181901A (en) * 1937-01-04 1939-12-05 Rca Corp Resonant line
US2851666A (en) * 1952-06-20 1958-09-09 Patelhold Patentverwertung Microwave filter with a variable band pass range
GB891444A (en) * 1959-06-30 1962-03-14 Siemens Ag Improvements in or relating to electro-magnetic resonators
US3448412A (en) * 1967-04-21 1969-06-03 Us Navy Miniaturized tunable resonator comprising intermeshing concentric tubular members
US4059815A (en) 1975-07-31 1977-11-22 Matsushita Electric Industrial Co., Limited Coaxial cavity resonator
US4292610A (en) 1979-01-26 1981-09-29 Matsushita Electric Industrial Co., Ltd. Temperature compensated coaxial resonator having inner, outer and intermediate conductors
US5691675A (en) * 1994-03-31 1997-11-25 Nihon Dengyo Kosaku Co., Ltd. Resonator with external conductor as resonance inductance element and multiple resonator filter
WO2009108540A1 (fr) * 2008-02-29 2009-09-03 Applied Materials, Inc. Résonateurs coaxiaux repliés

Non-Patent Citations (3)

* Cited by examiner, † Cited by third party
Title
M. MAKIMOTO; S. YAMASHITA: "Compact Bandpass Filters Using Stepped Impedance Resonator", PROCEEDINGS OF THE IEEE, vol. 67, no. 1, January 1979 (1979-01-01)
S. YAMASHITA; M. MAKIMOTO: "Miniaturized Coaxial Resonator Partially Loaded with High-Dielectric-Constant Microwave Ceramics", IEEE TRANSACTIONS ON MICROWAVE THEORY AND TECHNIQUES, vol. MTT-31, no. 9, September 1983 (1983-09-01)
S. YAMASHITA; M. MAKIMOTO: "The Q-Factor of Coaxial Resonators Partially Loaded with High Dielectric Constant Microwave Ceramics", IEEE TRANSACTIONS ON MICROWAVE THEORY AND TECHNIQUES, vol. MTT-31, no. 6, June 1983 (1983-06-01)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP3525281A4 (fr) * 2016-10-25 2019-10-23 Huawei Technologies Co., Ltd. Combineur et dispositif d'antenne
US10938080B2 (en) 2016-10-25 2021-03-02 Huawei Technologies Co., Ltd. Combiner and antenna apparatus

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