EP0443481A1 - Tunable microwave filter - Google Patents

Tunable microwave filter Download PDF

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Publication number
EP0443481A1
EP0443481A1 EP91102262A EP91102262A EP0443481A1 EP 0443481 A1 EP0443481 A1 EP 0443481A1 EP 91102262 A EP91102262 A EP 91102262A EP 91102262 A EP91102262 A EP 91102262A EP 0443481 A1 EP0443481 A1 EP 0443481A1
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EP
European Patent Office
Prior art keywords
filter
ferrite
agile
microwave filter
resonator
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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.)
Granted
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EP91102262A
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German (de)
French (fr)
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EP0443481B1 (en
Inventor
Carol Brouzes
Claude Ressencourt
Alain De Place
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Alcatel CIT SA
Alcatel Lucent NV
Original Assignee
Alcatel Telspace SA
Alcatel Transmission par Faisceaux Hertziens SA
Alcatel NV
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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
    • H01P1/207—Hollow waveguide filters
    • H01P1/208—Cascaded cavities; Cascaded resonators inside a hollow waveguide structure
    • H01P1/2084—Cascaded cavities; Cascaded resonators inside a hollow waveguide structure with dielectric 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
    • H01P1/215—Frequency-selective devices, e.g. filters using ferromagnetic material
    • 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

Definitions

  • the present invention relates to an agile microwave filter, and in particular to a filter of this type suitable for use, both at transmission and at reception, for the production of frequency-agile radio-relay systems.
  • An agile filter is a filter whose central frequency can be voluntarily moved, in a range of frequencies which can cover a large fraction of an octave, by means of an electric or electronic control.
  • Such filters are, with frequency synthesizers, the essential elements for producing agile radio-relay systems, which are in particular widely used in applications where it is desired to be able to very quickly change the emission frequency of a signal.
  • the most conventional agile filter is the resonant cavity filter, the tuning of which is carried out mechanically under the control of a motor.
  • This type of filter can withstand high powers, but it can no longer be suitable in current applications because its operating time to achieve a frequency change is extremely high, of the order of a minute to fix ideas, while some Projected applications will require a channel switching time much less than a second, and more specifically on the order of a millisecond.
  • they have the other disadvantages of being bulky, rather heavy, and particularly expensive and complex to produce because of the delicate and precise mechanical requirements which are to be implemented.
  • variable capacity diodes or "varactors” which react in a very short time, typically of the order of a microsecond.
  • variable capacity diodes or "varactors”
  • Such filters cannot be envisaged, for radio-relay systems, because of their acceptable power which is much too low (less than 0 dBm), as well as their operating frequency which is, with the components currently known, limited to frequencies below 2 Gigahertz.
  • the document FR-A-2.521.786 describes, with reference to the document FR-A-2.509.537, a bandpass filter with dielectric resonators placed in a waveguide whose dimensions of the cross section are about 2.5 times the transverse dimensions of these resonators.
  • a Yttrium iron garnet tablet is placed on each of these dielectric resonators in order, under the action of adjustable external magnetic fields, to make this filter magnetically tunable.
  • the air gap of the magnetic circuits necessary for the creation of these magnetic fields is then very large, so that the number of amperes turns, and therefore the necessary current consumption, are very high to obtain a satisfactory range of variation.
  • the production of such composite resonators is quite expensive, precisely because of this composite character.
  • document FR-A-2,610,766 of the Applicant describes a power resonator made up at least partially of polycrystalline ferrite, and whose tuning is changed very quickly by the application of an adjustable external magnetic field.
  • the technique presented in this document is based on the use of a resonant coaxial line produced from a cylindrical bar of metallized polycrystalline ferrite.
  • This ferrite resonator is placed in a device capable of creating a variable magnetic field. The latter then varies the magnetic permeability of the ferrite material so as to modify the electrical length of the coaxial line, thereby varying the frequency of this resonator.
  • the no-load overvoltage of the structure described in this document FR-A-2,610,766 is limited by the metallic confinement of the microwave electromagnetic fields of the coaxial cavity, all the more sensitive as the permittivity dielectric of the material reduces the dimensions of the resonant cavity compared to its counterpart filled with air, as well as by the appearance of disturbing parasitic modes which would be consequent to a possible enlargement of the structure, carried out to increase this overvoltage at no load.
  • the invention aims to remedy these various drawbacks. It relates for this purpose to an agile microwave filter whose structure is similar to that of filters with dielectric resonator (s) placed (s) for example in a waveguide operating under the cutoff, but for which the or the dielectric confinement resonators are replaced by similar resonators, but made of ferrite material and not of purely dielectric material, means being moreover provided for applying to this or these ferrite resonators a magnetic field of adjustable intensity, so as to move the center frequency of the filter.
  • this agile microwave filter is composed of a ferrite cylinder 1, of diameter D and height h which, like filters with dielectric resonator (s) of the art known, is placed on the bottom of a portion 2 of section guide rectangular and operating in evanescent mode, that is to say under the cut.
  • the ferrite bar 1 operates in TM01 ⁇ mode, while the guide in evanescent mode 2 is excited in TM11 mode by a coaxial antenna 3 placed at the input of the filter and conventionally passing through a first metal end plate 4.
  • the input microwave signal is conveyed to this antenna 3 by the coaxial cable for supplying the signal 5.
  • the filter output signal is taken from the other end of the guide 2 by the coaxial antenna 6 which likewise crosses the second metal end plate 7, this antenna 6 conventionally extending the cable core output coaxial 8 (in the same way as the antenna 3 extends, for its part, the core of the input coaxial cable 5).
  • Ferrite bar 1 has the property, currently rather misunderstood, of having not only a high magnetic permeability, but also a rather high dielectric permittivity, its relative permittivity being of the order of 15, while that of resonator materials conventional dielectric is of the order of 40. It follows that, contrary to what one might think a priori, the bar 1 achieves here, without it being, like that of document FR-A-2,610,766 , shielded by two concentric metallic layers, a dielectric confinement giving it a resonator function.
  • the resonance frequency of the ferrite rod 1 depends on the product of its dielectric permittivity by its magnetic permeability, so that in fact it will be possible to vary the resonance frequency of the bar 1, and therefore the central frequency of tuning of the filter of FIG. 1 by varying this magnetic permeability which, for ferrite material, is possible by applying to it a polarizing magnetic field of adjustable intensity, like what is described in the document FR-A-2,610,766 cited above.
  • the ferrite bar 1 is also placed in a magnetic field H which is created, coaxially with the bar 1, between the two pole pieces 9, 10 of an electromagnet 11 comprising a soft iron magnetic circuit 12 and an excitation coil 13 traversed by a direct current of adjustable value: by varying the excitation current of the coil 13, the value of the field H is varied, and consequently the resonance frequency of the bar 1, this which moves the center frequency of the filter.
  • the central frequency of the microwave filter according to FIGS. 1 or 2 could be continuously displaced between 14,450 Gigahertz and 15,447 Gigahertz without excessive current consumption in these windings.
  • FIG. 3 shows the production of an agile bandpass filter formed by the association, in the same guide 2, of two ferrite resonators 15 and 16 also operating as resonators with dielectric confinement, this filter being basically similar to conventional band filters with dielectric resonators (see for example FIG. 1 of the document FR-A-2,590,537 cited above) except that the coupled resonators 15, 16 are made of ferrite and that in addition they are subjected, like the resonator 1 according to FIGS. 1 and 2, with the respective adjustable magnetic fields H1 and H2 created by the electromagnets 11 A and 11 B.
  • the windings 13 A and 13 B of these electromagnets 11 A and 11 B are each supplied with excitation current adjustable by a supply and control unit 17.
  • the invention is not limited to the exemplary embodiments which have just been described.
  • the relative dimensions of the resonators and of the guide could be different.
  • Other input and output coupling modes for example produced using iris, could be used, in which case the guide used could not operate in evanescent mode, etc.
  • the circuits electromagnets can, without going outside the scope of the invention, include permanent magnets contributing to the creation of the magnetic field.

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Abstract

Ferrite-tuneable agile microwave filter. <??>It is built as a filter with resonators with dielectric confinement, and therefore comprises an evanescent-mode guide (2) and resonant cylinders (15, 16) placed in this guide. Furthermore, means (11A, 11B, 17) are provided for applying an adjustable magnetic field (H1, H2) to these cylinders (15, 16), which have the feature of being made of ferrite, in order to shift the central frequency of this filter. <IMAGE>

Description

La présente invention se rapporte à un filtre agile hyperfréquence, et en particulier à un filtre de ce type apte à être utilisé, aussi bien à l'émission qu'à la réception, pour la réalisation de faisceaux hertziens agiles en fréquence.The present invention relates to an agile microwave filter, and in particular to a filter of this type suitable for use, both at transmission and at reception, for the production of frequency-agile radio-relay systems.

Un filtre agile est un filtre dont la fréquence centrale peut être volontairement déplacée, dans une gamme de fréquences pouvant couvrir une fraction importante d'une octave, au moyen d'une commande électrique ou électronique. De tels filtres sont, avec les synthétiseurs de fréquence, les éléments indispensables à la réalisation des faisceaux hertziens agiles, qui sont en particulier très utilisés dans les applications où l'on désire pouvoir changer très rapidement la fréquence d'émission d'un signal.An agile filter is a filter whose central frequency can be voluntarily moved, in a range of frequencies which can cover a large fraction of an octave, by means of an electric or electronic control. Such filters are, with frequency synthesizers, the essential elements for producing agile radio-relay systems, which are in particular widely used in applications where it is desired to be able to very quickly change the emission frequency of a signal.

Ces filtres agiles doivent non seulement pouvoir changer très rapidement de fréquence centrale, mais encore supporter des niveaux de puissance variables :

  • . employés à l'émission, ils fonctionnent sous forte puissance (en sortie des amplificateurs d'émission) et ont pour rôle d'éviter à l'émetteur de polluer les canaux voisins ;
  • . employés à la réception comme filtres de canal, ils permettent au récepteur de n'amplifier que le signal utile, à l'exclusion de la pollution introduite par les émissions adjacentes ; bien que fonctionnant alors en principe sous faible puissance, ils doivent néanmoins ne pas pouvoir être détériorés ou détruits par ces émissions adjacentes, qui peuvent leur appliquer des signaux perturbateurs de puissance très supérieure à celle des signaux normalement reçus.
These agile filters must not only be able to change the central frequency very quickly, but also withstand varying power levels:
  • . used for transmission, they operate under high power (at the output of the transmission amplifiers) and have the role of preventing the transmitter from polluting neighboring channels;
  • . used at reception as channel filters, they allow the receiver to amplify only the useful signal, excluding the pollution introduced by adjacent emissions; although operating then in principle under low power, they must nevertheless not be able to be damaged or destroyed by these adjacent emissions, which can apply to them disturbing signals of much higher power than the signals normally received.

De nombreux types de filtres agiles hyperfréquence ont été jusqu'à présent soit utilisés, soit décrits dans la littérature.Many types of agile microwave filters have so far been either used or described in the literature.

Le filtre agile le plus classique est le filtre à cavités résonnantes dont l'accord est réalisé mécaniquement sous commande d'un moteur. Ce type de filtre peut supporter des puissances élevées, mais il ne peut plus convenir dans les applications actuelles car son temps de manoeuvre pour réaliser un changement de fréquence est extrêmement élevé, de l'ordre de la minute pour fixer les idées, alors que certaines applications projetées exigeront un temps de commutation de canal très inférieur à la seconde, et plus spécifiquement plutôt de l'ordre de la milliseconde. En outre, ils ont pour autres inconvénients d'être encombrants, plutôt lourds, et particulièrement onéreux et complexes à réaliser en raison des impératifs mécaniques délicats et précis qui sont à mettre en oeuvre.The most conventional agile filter is the resonant cavity filter, the tuning of which is carried out mechanically under the control of a motor. This type of filter can withstand high powers, but it can no longer be suitable in current applications because its operating time to achieve a frequency change is extremely high, of the order of a minute to fix ideas, while some Projected applications will require a channel switching time much less than a second, and more specifically on the order of a millisecond. In addition, they have the other disadvantages of being bulky, rather heavy, and particularly expensive and complex to produce because of the delicate and precise mechanical requirements which are to be implemented.

L'accord de la cavité résonnante peut aussi être apporté par l'utilisation de diodes à capacité variable, ou "varactors", qui réagissent en un temps très bref, typiquement de l'ordre de la microseconde. De tels filtres ne sont malheureusement pas envisageables, pour les faisceaux hertziens, en raison de leur puissance acceptable qui est beaucoup trop faible (inférieure à O dBm), ainsi que leur fréquence de fonctionnement qui est, avec les composants connus actuellement, limitée à des fréquences inférieures à 2 Gigahertz.The tuning of the resonant cavity can also be brought about by the use of variable capacity diodes, or "varactors", which react in a very short time, typically of the order of a microsecond. Unfortunately, such filters cannot be envisaged, for radio-relay systems, because of their acceptable power which is much too low (less than 0 dBm), as well as their operating frequency which is, with the components currently known, limited to frequencies below 2 Gigahertz.

Cet accord peut aussi être obtenu de manière rapide par l'action d'un champ magnétique polarisant un résonateur à billes YIG (Yttrium Iron Garnet). La tenue en puissance d'un tel résonateur reste cependant beaucoup trop faible, environ du même ordre de grandeur de celle des filtres à varactors précités.This agreement can also be obtained quickly by the action of a magnetic field polarizing a YIG (Yttrium Iron Garnet) ball resonator. The power handling of such a resonator however remains much too low, approximately of the same order of magnitude as that of the above-mentioned varactor filters.

Le document FR-A-2.521.786 décrit, en se référant au document FR-A-2.509.537, un filtre passe-bande à résonateurs diélectriques placés dans un guide d'ondes dont les dimensions de la section transversale sont de l'ordre de 2,5 fois les dimensions transversales de ces résonateurs. Une pastille de grenat de fer Yttrium est placée sur chacun de ces résonateurs diélectriques afin, sous l'action de champs magnétiques extérieurs réglables, de rendre ce filtre accordable magnétiquement. L'entrefer des circuits magnétiques nécessaires à la création de ces champs magnétiques est alors très large, de sorte que le nombre d'ampères tours, et donc la consommation de courant nécessaire, sont très élevés pour obtenir une gamme de variation satisfaisante. Par ailleurs, la réalisation de tels résonateurs composites est assez onéreuse, en raison justement de ce caractère composite.The document FR-A-2.521.786 describes, with reference to the document FR-A-2.509.537, a bandpass filter with dielectric resonators placed in a waveguide whose dimensions of the cross section are about 2.5 times the transverse dimensions of these resonators. A Yttrium iron garnet tablet is placed on each of these dielectric resonators in order, under the action of adjustable external magnetic fields, to make this filter magnetically tunable. The air gap of the magnetic circuits necessary for the creation of these magnetic fields is then very large, so that the number of amperes turns, and therefore the necessary current consumption, are very high to obtain a satisfactory range of variation. Furthermore, the production of such composite resonators is quite expensive, precisely because of this composite character.

Enfin, le document FR-A-2.610.766 de la Demanderesse décrit un résonateur de puissance constitué au moins partiellement de ferrite polycristallin, et dont l'accord est changé très rapidement par l'application d'un champ magnétique extérieur réglable. La technique présentée dans ce document est basée sur l'emploi d'une ligne coaxiale résonnante réalisée à partir d'un barreau cylindrique de ferrite polycristallin métallisé. Ce résonateur à ferrite est placé dans un dispositif apte à créer un champ magnétique variable. Ce dernier fait alors varier la perméabilité magnétique du matériau ferrite de façon à modifier la longueur électrique de la ligne coaxiale, en faisant par là même varier la fréquence de ce résonateur.Finally, document FR-A-2,610,766 of the Applicant describes a power resonator made up at least partially of polycrystalline ferrite, and whose tuning is changed very quickly by the application of an adjustable external magnetic field. The technique presented in this document is based on the use of a resonant coaxial line produced from a cylindrical bar of metallized polycrystalline ferrite. This ferrite resonator is placed in a device capable of creating a variable magnetic field. The latter then varies the magnetic permeability of the ferrite material so as to modify the electrical length of the coaxial line, thereby varying the frequency of this resonator.

Cette dernière technique ne permet toutefois pas d'obtenir les forts coefficients de surtension à vide qui sont indispensables à la réalisation des filtres hyperfréquences à bande très étroite nécessaires aux faisceaux hertziens actuels. En effet, la surtension à vide de la structure décrite dans ce document FR-A-2.610.766 est limitée par le confinement métallique des champs électromagnétiques hyperfréquences de la cavité coaxiale, d'autant plus sensible que la permittivité diélectrique du matériau réduit les dimensions de la cavité résonnante par rapport à son homologue remplie d'air, ainsi que par l'apparition de modes parasites perturbateurs qui seraient conséquents à un éventuel agrandissement de la structure, effectué pour augmenter cette surtension à vide.The latter technique does not, however, make it possible to obtain the high no-load overvoltage coefficients which are essential for the production of very narrow band microwave filters necessary for current radio-relay systems. Indeed, the no-load overvoltage of the structure described in this document FR-A-2,610,766 is limited by the metallic confinement of the microwave electromagnetic fields of the coaxial cavity, all the more sensitive as the permittivity dielectric of the material reduces the dimensions of the resonant cavity compared to its counterpart filled with air, as well as by the appearance of disturbing parasitic modes which would be consequent to a possible enlargement of the structure, carried out to increase this overvoltage at no load.

L'invention vise à remédier à ces divers inconvénients. Elle se rapporte à cet effet à un filtre agile hyperfréquence dont la structure est semblable à celle des filtres à résonateur (s) diélectrique(s) placé(s) par exemple dans un guide d'ondes fonctionnant sous la coupure, mais pour lequel le ou les résonateurs à confinement diélectrique sont remplacés par des résonateurs semblables, mais réalisés en matériau ferrite et non pas en matériau purement diélectrique, des moyens étant par ailleurs prévus pour appliquer à ce ou ces résonateurs en ferrite un champ magnétique d'intensité réglable, de manière à déplacer ainsi la fréquence centrale du filtre.The invention aims to remedy these various drawbacks. It relates for this purpose to an agile microwave filter whose structure is similar to that of filters with dielectric resonator (s) placed (s) for example in a waveguide operating under the cutoff, but for which the or the dielectric confinement resonators are replaced by similar resonators, but made of ferrite material and not of purely dielectric material, means being moreover provided for applying to this or these ferrite resonators a magnetic field of adjustable intensity, so as to move the center frequency of the filter.

De toute façon, l'invention sera bien comprise, et ses avantages et autres caractéristiques ressortiront, lors de la description suivante de trois exemples non limitatifs de réalisation, en référence au dessin schématique annexé dans lequel :

  • Figure 1 montre un premier exemple de réalisation de ce filtre agile ;
  • Figure 2 est une variante du filtre de la figure 1 ;
  • Figure 3 est un exemple de réalisation de filtre passe-bande comprenant plusieurs éléments résonnants.
In any case, the invention will be well understood, and its advantages and other characteristics will emerge during the following description of three nonlimiting exemplary embodiments, with reference to the appended schematic drawing in which:
  • Figure 1 shows a first embodiment of this agile filter;
  • Figure 2 is a variant of the filter of Figure 1;
  • Figure 3 is an exemplary embodiment of a bandpass filter comprising several resonant elements.

En se référant à la figure 1, ce filtre agile hyperfréquence est composé d'un cylindre de ferrite 1, de diamètre D et de hauteur h qui, à l'instar des filtres à résonateur(s) diélectrique(s) de l'art connu, est placé sur le fond d'une portion 2 de guide à section rectangulaire et fonctionnant en mode évanescent, c'est à dire sous la coupure.Referring to Figure 1, this agile microwave filter is composed of a ferrite cylinder 1, of diameter D and height h which, like filters with dielectric resonator (s) of the art known, is placed on the bottom of a portion 2 of section guide rectangular and operating in evanescent mode, that is to say under the cut.

Plus précisément, le barreau de ferrite 1 fonctionne en mode TM₀₁δ, tandis que le guide à mode évanescent 2 est excité selon le mode TM₁₁ par une antenne coaxiale 3 placée en entrée du filtre et traversant classiquement une première plaque métallique d'extrémité 4. Le signal hyperfréquence d'entrée est véhiculé jusqu'à cette antenne 3 par le câble coaxial d'amenée du signal 5.More precisely, the ferrite bar 1 operates in TM₀₁ δ mode, while the guide in evanescent mode 2 is excited in TM₁₁ mode by a coaxial antenna 3 placed at the input of the filter and conventionally passing through a first metal end plate 4. The input microwave signal is conveyed to this antenna 3 by the coaxial cable for supplying the signal 5.

De façon totalement symétrique, le signal de sortie du filtre est prélevé à l'autre extrémité du guide 2 par l'antenne coaxiale 6 qui traverse de même la seconde plaque métallique d'extrémité 7, cette antenne 6 prolongeant classiquement l'âme du câble coaxial de sortie 8 (de la même façon que l'antenne 3 prolonge, quant à elle, l'âme du câble coaxial d'entrée 5).Completely symmetrical, the filter output signal is taken from the other end of the guide 2 by the coaxial antenna 6 which likewise crosses the second metal end plate 7, this antenna 6 conventionally extending the cable core output coaxial 8 (in the same way as the antenna 3 extends, for its part, the core of the input coaxial cable 5).

Le barreau de ferrite 1 a la propriété, actuellement plutôt méconnue à tort, d'avoir non seulement une forte perméabilité magnétique, mais encore une permittivité diélectrique plutôt élevée, sa permittivité relative étant de l'ordre de 15, alors que celle des matériaux résonateurs diélectriques classiques est de l'ordre de 40. Il en résulte que, contrairement à ce que l'on pourrait penser à priori, le barreau 1 réalise ici, sans qu'il soit, comme celui du document FR-A-2.610.766, blindé par deux couches métalliques concentriques, un confinement diélectrique lui conférant une fonction de résonateur.Ferrite bar 1 has the property, currently rather misunderstood, of having not only a high magnetic permeability, but also a rather high dielectric permittivity, its relative permittivity being of the order of 15, while that of resonator materials conventional dielectric is of the order of 40. It follows that, contrary to what one might think a priori, the bar 1 achieves here, without it being, like that of document FR-A-2,610,766 , shielded by two concentric metallic layers, a dielectric confinement giving it a resonator function.

En réalité cependant, la fréquence de résonance du barreau de ferrite 1 dépend du produit de sa permittivité diélectrique par sa perméabilité magnétique, de sorte qu'en fait, il va être possible de faire varier la fréquence de résonance du barreau 1, et donc la fréquence centrale d'accord du filtre de la figure 1 en faisant varier cette perméabilité magnétique ce qui, pour du matériau ferrite, est possible en lui appliquant un champ magnétique polarisant d'intensité réglable, à l'instar de ce qui est décrit dans le document FR-A-2.610.766 précité.In reality, however, the resonance frequency of the ferrite rod 1 depends on the product of its dielectric permittivity by its magnetic permeability, so that in fact it will be possible to vary the resonance frequency of the bar 1, and therefore the central frequency of tuning of the filter of FIG. 1 by varying this magnetic permeability which, for ferrite material, is possible by applying to it a polarizing magnetic field of adjustable intensity, like what is described in the document FR-A-2,610,766 cited above.

Dans ce but, le barreau de ferrite 1 est en outre placé dans un champ magnétique H qui est créé, coaxialement au barreau 1, entre les deux pièces polaires 9, 10 d'un électro-aimant 11 comportant un circuit magnétique en fer doux 12 et une bobine d'excitation 13 parcourue par un courant continu de valeur réglable : en faisant varier le courant d'excitation de la bobine 13, on fait varier la valeur du champ H, et par suite la fréquence de résonance du barreau 1, ce qui déplace la fréquence centrale du filtre.For this purpose, the ferrite bar 1 is also placed in a magnetic field H which is created, coaxially with the bar 1, between the two pole pieces 9, 10 of an electromagnet 11 comprising a soft iron magnetic circuit 12 and an excitation coil 13 traversed by a direct current of adjustable value: by varying the excitation current of the coil 13, the value of the field H is varied, and consequently the resonance frequency of the bar 1, this which moves the center frequency of the filter.

A noter que la propriété de conduction magnétique du barreau 1, combinée avec sa hauteur h non négligeable, entraîne pour le circuit magnétique 12, un entrefer assez restreint, ce qui permet de faire varier ce champ H, et donc de déplacer la fréquence centrale du filtre dans de bonnes proportions sans nécessiter, pour les bobinages 13, une consommation de courant excessive.Note that the magnetic conduction property of the rod 1, combined with its non-negligible height h, results in a fairly small air gap for the magnetic circuit 12, which makes it possible to vary this field H, and therefore to shift the central frequency of the filter in good proportions without requiring, for the windings 13, excessive current consumption.

A titre d'exemple, il a été utilisé pour la réalisation d'un tel filtre agile hyperfréquence, un matériau ferrite polycristallin de type grenat dont la largeur de raie effective est très faible, afin d'avoir un coefficient de surtension important (supérieur à 2000).For example, it was used for the production of such an agile microwave filter, a polycrystalline ferrite material of garnet type whose effective line width is very small, in order to have a high overvoltage coefficient (greater than 2000).

Les dimensions du cylindre résonnant 1 étaient les suivantes :

  • . diamètre D : 5,8 mm
  • . hauteur h : 4,2 mm

avec les dimensions internes suivantes pour le guidage rectangulaire 1 à mode évanescent :
  • . petit côté : 4,9 mm
  • . grand côté : 10,7 mm
The dimensions of the resonant cylinder 1 were as follows:
  • . diameter D: 5.8 mm
  • . height h: 4.2 mm

with the following internal dimensions for rectangular guide 1 in evanescent mode:
  • . short side: 4.9 mm
  • . long side: 10.7 mm

Au lieu de poser le cylindre de ferrite 1 sur le fond du guide 2, il est aussi possible de le poser, comme le montre la figure 2, sur une mince pastille 14 de matériau diélectrique à faible permittivité, elle-même posée sur le fond du guide 2, ce qui permet, dans certains cas, d'éviter des perturbations.Instead of placing the ferrite cylinder 1 on the bottom of the guide 2, it is also possible to place it, as 2 shows it on a thin patch 14 of dielectric material with low permittivity, itself placed on the bottom of the guide 2, which makes it possible, in certain cases, to avoid disturbances.

En jouant sur l'excitation des bobinages 13, la fréquence centrale du filtre hyperfréquence selon les figures 1 ou 2 a pu être déplacée continûment entre 14,450 Gigahertz et 15,447 Gigahertz sans consommation excessive de courant dans ces bobinages.By playing on the excitation of the windings 13, the central frequency of the microwave filter according to FIGS. 1 or 2 could be continuously displaced between 14,450 Gigahertz and 15,447 Gigahertz without excessive current consumption in these windings.

Enfin, la figure 3 montre la réalisation d'un filtre agile passe-bande formé par l'association, dans un même guide 2, de deux résonateurs ferrite 15 et 16 fonctionnant eux-aussi en résonateurs à confinement diélectrique, ce filtre étant basiquement semblable aux filtres de bande classiques à résonateurs diélectriques (voir par exemple la figure 1 du document FR-A-2.590.537 précité) à cette différence près que les résonateurs couplés 15, 16 sont constitués en ferrite et qu'en outre ils sont soumis, à l'instar du résonateur 1 selon les figures 1 et 2, aux champs magnétiques réglables respectifs H₁ et H₂ créés par les électro-aimants 11A et 11B.Finally, FIG. 3 shows the production of an agile bandpass filter formed by the association, in the same guide 2, of two ferrite resonators 15 and 16 also operating as resonators with dielectric confinement, this filter being basically similar to conventional band filters with dielectric resonators (see for example FIG. 1 of the document FR-A-2,590,537 cited above) except that the coupled resonators 15, 16 are made of ferrite and that in addition they are subjected, like the resonator 1 according to FIGS. 1 and 2, with the respective adjustable magnetic fields H₁ and H₂ created by the electromagnets 11 A and 11 B.

Comme indiqué schématiquement au dessin, les bobinages 13A et 13B de ces électro-aimants 11A et 11B sont alimentés chacun en courant d'excitation réglable par une unité d'alimentation et de commande 17.As shown diagrammatically in the drawing, the windings 13 A and 13 B of these electromagnets 11 A and 11 B are each supplied with excitation current adjustable by a supply and control unit 17.

Comme il va de soi, l'invention n'est pas limitée aux exemples de réalisation qui viennent d'être décrits. C'est ainsi par exemple que les dimensions relatives des résonateurs et du guide pourraient être autres. D'autres modes de couplage d'entrée et de sortie, par exemple réalisés à l'aide d'iris, pourraient être utilisés, auquel cas le guide utilisé pourrait ne pas fonctionner en mode évanescent, etc...Bien entendu, les circuits magnétiques des électroaimants pourront, sans sortir du cadre de l'invention, comporter des aimants permanents contribuant à la création du champ magnétique.It goes without saying that the invention is not limited to the exemplary embodiments which have just been described. Thus, for example, the relative dimensions of the resonators and of the guide could be different. Other input and output coupling modes, for example produced using iris, could be used, in which case the guide used could not operate in evanescent mode, etc. Of course, the circuits electromagnets can, without going outside the scope of the invention, include permanent magnets contributing to the creation of the magnetic field.

Claims (4)

Filtre agile hyperfréquence, caractérisé en ce qu'il comporte au moins un résonateur (1, 15, 16) à confinement diélectrique constitué en matériau ferrite et placé dans un guide d'ondes (2), et en ce que, dans le but de déplacer la fréquence centrale de ce filtre, des moyens (11, 11A, 11B 17) sont prévus pour appliquer, à chacun de ces résonateurs en ferrite (1, 15, 16), un champ magnétique (H, H1, H2) d'intensité réglable.Agile microwave filter, characterized in that it comprises at least one dielectric confinement resonator (1, 15, 16) made of ferrite material and placed in a waveguide (2), and in that, for the purpose of move the central frequency of this filter, means (11, 11A, 11B 17) are provided for applying, to each of these ferrite resonators (1, 15, 16), a magnetic field (H, H1, H2) of adjustable intensity. Filtre agile hyperfréquence selon la revendication 1, caractérisé en ce que ce guide d'ondes (2) est un guide fonctionnant en mode évanescent.Agile microwave filter according to claim 1, characterized in that this waveguide (2) is a guide operating in evanescent mode. Filtre agile hyperfréquence selon la revendication 1 ou la revendication 2, caractérisé en ce que le résonateur en ferrite (1, 15, 16) est posé sur le fond du guide d'ondes (2).Agile microwave filter according to claim 1 or claim 2, characterized in that the ferrite resonator (1, 15, 16) is placed on the bottom of the waveguide (2). Filtre agile hyperfréquence selon la revendication 1 ou la revendication 2, caractérisé en ce que le résonateur en ferrite (1) est posé sur une mince pastille diélectrique (14, elle-même posée sur le fond du guide d'ondes (2).Agile microwave filter according to claim 1 or claim 2, characterized in that the ferrite resonator (1) is placed on a thin dielectric pad (14, itself placed on the bottom of the waveguide (2).
EP91102262A 1990-02-23 1991-02-18 Tunable microwave filter Expired - Lifetime EP0443481B1 (en)

Applications Claiming Priority (2)

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FR9002280 1990-02-23
FR9002280A FR2658954B1 (en) 1990-02-23 1990-02-23 AGILE MICROWAVE FILTER.

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EP0443481A1 true EP0443481A1 (en) 1991-08-28
EP0443481B1 EP0443481B1 (en) 1995-06-21

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JP (1) JPH0537202A (en)
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ES (1) ES2074180T3 (en)
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FR2694452A1 (en) * 1992-07-30 1994-02-04 Alcatel Telspace Adjustable narrow passband filter with quick response for microwave communications - has coupler of dimensions for evanescent mode with cylindrical polycrystalline ferrite resonator in adjustable magnetic field

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US5440278A (en) * 1994-03-25 1995-08-08 Bartholomew; Darin Ferrite system for modulating, phase shifting, or attenuating radio frequency energy
ES2148042B1 (en) 1997-07-30 2001-05-01 Mecanismos Aux Es Ind S L IMPROVEMENTS IN THE TAPE MACHINES.
US5959512A (en) * 1997-09-19 1999-09-28 Raytheon Company Electronically tuned voltage controlled evanescent mode waveguide filter
US6127907A (en) * 1997-11-07 2000-10-03 Nec Corporation High frequency filter and frequency characteristics regulation method therefor
US8149073B2 (en) * 2007-08-03 2012-04-03 Murata Manufacturing Co., Ltd. Band-pass filter and method for making photonic crystal for the band-pass filter
EP2886524A1 (en) * 2013-12-18 2015-06-24 Skyworks Solutions, Inc. Tunable resonators using high dielectric constant ferrite rods
CN114361754B (en) * 2022-01-10 2022-10-14 电子科技大学 X-waveband magnetic control frequency-adjustable directional coupler
CN115792752B (en) * 2022-10-14 2026-02-03 西南应用磁学研究所(中国电子科技集团公司第九研究所) Single-crystal harmonic oscillator ferromagnetic resonance line width rapid screening device and screening method for magnetic tuning filter

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Also Published As

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JPH0537202A (en) 1993-02-12
DE69110494T2 (en) 1995-11-09
US5184097A (en) 1993-02-02
FR2658954B1 (en) 1992-10-02
CA2036829A1 (en) 1991-08-24
DE69110494D1 (en) 1995-07-27
ES2074180T3 (en) 1995-09-01
CA2036829C (en) 1994-09-20
IL97205A (en) 1994-01-25
FR2658954A1 (en) 1991-08-30
EP0443481B1 (en) 1995-06-21
IL97205A0 (en) 1992-05-25

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