EP0114140B1 - Tunable microwave filter with tm010 mode dielectric resonators - Google Patents

Tunable microwave filter with tm010 mode dielectric resonators Download PDF

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Publication number
EP0114140B1
EP0114140B1 EP84400077A EP84400077A EP0114140B1 EP 0114140 B1 EP0114140 B1 EP 0114140B1 EP 84400077 A EP84400077 A EP 84400077A EP 84400077 A EP84400077 A EP 84400077A EP 0114140 B1 EP0114140 B1 EP 0114140B1
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Prior art keywords
resonators
filter
base
dielectric
guide
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German (de)
French (fr)
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EP0114140A1 (en
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Jean-Luc Etienne
Jean-Claude Cruchon
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Alcatel Thomson Faisceaux Hertziens SA
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Alcatel Thomson Faisceaux Hertziens SA
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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
    • H01P7/10—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
    • H01P1/219—Evanescent mode filters

Definitions

  • the invention relates to the field of tunable microwave filters, and more particularly relates to a filter of this type with dielectric resonators, in which the resonators resonate according to the TM010 mode.
  • Tunable microwave filters with dielectric resonators developed up to now, however, have a certain number of drawbacks.
  • parasitic modes in these filters which can disturb their frequency responses.
  • tuning systems are provided for varying the tuning frequency of the resonators.
  • These systems generally comprise, associated with the resonators themselves, adjustable sinking dielectric rods. These elements allow tuning but they can degrade the overvoltage coefficient obtained when the resonator is alone.
  • these filters have always used selected modes TE018 or TM018 which have good no-load overvoltage coefficients. However, as indicated above these coefficients decrease in the complete system, with its means of agreement. Contrary to the generally accepted idea, these modes are not the only ones that can be implemented in dielectric resonators to produce filters with acceptable characteristics.
  • the subject of the invention is in fact a tunable microwave filter, with dielectric resonators operating according to the TM010 resonance mode.
  • a document of known art FR-A-1 496 177 describes a high frequency filter comprising a tube constituted by a conductive part at least at its inner surface part, and by several rods which are constituted by at least one conductive part to their surface parts and which have an electrical length equal to an integer multiple of a quarter wavelength chosen from the cut-off frequency band of the tube and which are arranged in the tube along the axis of that -this by cutting the axis.
  • the invention relates to a tunable microwave filter, with cylindrical resonators comprising a metal housing associated with a base also metallic forming a waveguide said under the cut-off and a series of cylindrical resonators arranged inside the housing, input and output coupling with the extreme resonators, these resonators having one of their ends in contact with the metal base, their other ends being at an adjustable distance from a ground plane formed by the bottom of the housing for achieve frequency tuning, characterized in that these resonators are dielectric resonators resonating according to the TM010 mode, in that the ends of these dielectric resonators in contact with the base are movable by sliding in first fixing holes provided for this effect in the base, and in that screws with adjustable penetration are arranged in second fixing holes provided in the base, in alternating with the first holes, to adjust the coupling between resonators.
  • the sub-assemblies which fit into a specific microwave material must be at low cost while retaining high performance.
  • the dielectric resonators in TM010 mode integrated to perform a filtering function, make it possible to obtain a gain compared to filters in evanescent, coaxial guided structure (comb filter or cross-digital filter), and compared to filters with dielectric resonators in TE01 ⁇ and TMOL X modes.
  • dielectric resonators in TM010 0 mode can be used in a very simple manner and associated with various but always simple tuning means which do not introduce disturbance in the resonance mode. In addition, there is no need for supports for the dielectric resonators.
  • FIG. 1 shows an embodiment of the microwave filter according to the invention in longitudinal section, this filter having a bandpass function.
  • This filter consists of three coupled dielectric resonators, 1, 2, 3, of cylindrical shape, the first and the last of these resonators being coupled to input 4 and output 5 means respectively.
  • these resonators are in contact with a metal base 6 to which they are fixed.
  • holes are provided in the base, the dielectric resonators being provided to slide in these holes.
  • holes can be lined with a small thickness of dielectric, for example polytetrafluoroethylene (teflon, under its trade name) from 2 to 7/100 e mm thick to avoid deterioration of the surface conditions during the sliding of the resonator.
  • dielectric for example polytetrafluoroethylene (teflon, under its trade name) from 2 to 7/100 e mm thick to avoid deterioration of the surface conditions during the sliding of the resonator.
  • a cover 7 forms, with the fixing base 6, a housing constituting a metal shielding enclosure forming a guide, the section of which can be any, for example rectangular, circular or reentrant.
  • the part of the resonator external to the guide can be coated with a coating of the glue or silver paint type.
  • the bottom of the housing is at a relatively small distance x from the ends of the resonators 1, 2 and 3, this distance being adjustable by driving the dielectric resonators 1, 2 and 3 inside the guide. The resonators can be blocked when the tuning frequency is obtained.
  • the dimensions of the housing are such that the guide thus formed has a cutoff frequency greater than the frequency at which the filter is used.
  • the guide which does not allow guided propagation, is said to be "under the cut".
  • the filtering function of this filter is obtained by locating the electromagnetic field in and near the dielectric resonators in the TM010 mode.
  • the coupling between successive resonators, which determines the passband of the filter, is obtained by an adequate distance of two successive resonators in the guide, and this coupling can be adjusted by metal screws, such as 8, for the adjustment of the susceptance of coupling between adjacent resonators.
  • the guide enters and exits through coaxial sockets, the external cylindrical end being fixed to the fixing base, and the internal conductor passing through this fixing base to form inside the guide an adjustable loop coupled on the magnetic field of each extreme resonator.
  • the tuning of this filter to the minimum frequency of the tuning frequency adjustment band takes place when the resonators are in contact with the bottom of the case.
  • Figure 2 is a cross-sectional representation of the microwave filter shown in Figure 1 at the dielectric resonator 1.
  • the field lines have been shown in this figure.
  • the electric field is located in and near the dielectric resonators, the magnetic field lines, orthogonal to the electric field lines forming circles whose centers are on the axis of the resonator, inside and outside the resonator.
  • the accesses 4 and 5 are made by coaxial sockets.
  • the coupling between these coaxial sockets and the resonators of the ends can also be achieved by antennas. Adjusting metal screws 8 make it possible to adjust the coupling between adjacent resonators.
  • the microwave resonators consist of zirconium titanate ZrTi0 4 to which tin Sn is added, in order to improve the temperature coefficient.
  • the first spurious response is rejected around 3.4 to 3.7 GHz.
  • the frequency tuning is obtained by varying the effective length of the resonator inside the guide and this frequency can vary between 2 and 2.5 GHz for example.
  • This structure also makes it possible to produce notch filters. In this case the coupling of the resonators with an electric line provided inside the guide, longitudinally, is carried out by the ends of the resonators.
  • the input and output couplings can be carried out by guide, the ends of the guide forming the enclosure of the filter being open to make the connection.
  • the input and output can be coupled differently, one by guide, the other by coaxial socket.
  • the shape of the guide can be any, line guide, U-shaped guide or guide having the shape of a crown.
  • the arrangement in U allows for example to provide retro-couplings between nonadjacent resonators to modulate the response of the filter. It is also possible to associate several filters, for example in parallel, coupled to a common access as a guide for producing a diplexer or a multiplexer.
  • the main advantage of the microwave filter according to the invention is the simplicity of its structure.
  • due to the mode itself there is no parasitic mode close to the response of the filter.

Abstract

A filter comprising a metal case having a metal base and a lid forming a guide of any section but under cut-off, that is to say which does not allow guided propagation. Cylindrical dielectric resonators are in contact with the metal securing base and the resonators resonate then in the TM010 mode. For frequency tuning of the filter, the distance between the bottom of the lid and the ends of the dielectric resonators supported by the base is variable. The invention applies more especially to tuneable band-pass filters.

Description

L'invention se rapporte au domaine des filtres hyperfréquences accordables, et a plus particulièrement pour objet un filtre de ce type à résonateurs diélectriques, dans lequel les résonateurs résonnent suivant le mode TM010.The invention relates to the field of tunable microwave filters, and more particularly relates to a filter of this type with dielectric resonators, in which the resonators resonate according to the TM010 mode.

L'évolution des travaux récents dans le domaine des matériaux diélectriques a conduit à l'utilisation de tels matériaux pour la réalisation de resonateurs diélectriques, ayant une constante diélectrique suffisamment élevée, avec des coefficients de température acceptables. La plupart des filtres réalisés avec ces résonateurs diélectriques mettent en oeuvre des résonateurs de forme cylindrique plutôt que parallélipipédique ou sphérique qui présentent un meilleur coefficient de surtension, sont plus facilement usinables et ont un domaine d'utilisation vers les fréquences "basses" de la gamme hyperfréquence (inférieures à 10 GHz).The evolution of recent work in the field of dielectric materials has led to the use of such materials for the production of dielectric resonators, having a sufficiently high dielectric constant, with acceptable temperature coefficients. Most filters made with these dielectric resonators use resonators of cylindrical rather than parallelepipedic or spherical shape which have a better overvoltage coefficient, are more easily machinable and have a field of use towards the "low" frequencies of the range. microwave (below 10 GHz).

Cette technique a conduit à des améliorations notables des filtres hyperfréquences tant du point de vue de leurs dimensions que du point de vue de leurs performances et de leurs prix de revient. En effet, si l'on compare les filtres à résonateurs diélectriques aux différents types de filtres utilisés antérieurement à tige, à iris, ou en mode évanescent, on remarque que:

  • - le coefficient de surtension des filtres à résonateurs diélectriques est légèrement inférieur à celui des filtres à tige ou à iris et très largement supérieur à celui des filtres en mode evanescent;
  • - les filtres à resonateurs diélectriques ont un encombrement et un poids plus faibles;
  • - le coût des filtres à résonateurs diélectriques est sensiblement égal à celui des filtres en mode évanescent et très inférieur à ceux des filtres des deux autres types.
This technique has led to significant improvements in microwave filters both from the point of view of their dimensions and from the point of view of their performance and their cost prices. Indeed, if we compare the filters with dielectric resonators to the different types of filters previously used with rod, iris, or in evanescent mode, we notice that:
  • - the overvoltage coefficient of filters with dielectric resonators is slightly lower than that of rod or iris filters and very much higher than that of filters in evanescent mode;
  • - filters with dielectric resonators have a smaller footprint and weight;
  • - The cost of filters with dielectric resonators is substantially equal to that of filters in evanescent mode and much lower than those of filters of the other two types.

Les filtres hyperfréquences accordables à résonateurs diélectriques développés jusqu'à maintenant présentent cependant un certain nombre d'inconvénients tout d'abord il existe dans ces filtres des modes parasites qui peuvent perturber leurs réponses en fréquence. De plus, il est difficile d'obtenir une largeur de bande variable dans de grandes proportions avec un filtre de gabarit donné. Enfin pour obtenir l'accordabilité du filtre dans une grande largeur de bande, des systèmes d'accord sont prévus pour faire varier la fréquence d'accord des résonateurs. Ces systèmes comportent généralement, associées aux résonateurs proprement dits, des tiges de diélectrique d'enfoncement réglable. Ces éléments permettent l'accord mais ils peuvent dégrader le coefficient de surtension obtenu lorsque le résonateur est seul. De plus ils posent des problèmes d'usinage et de réglage. Jusqu'à présent ces filtres utilisaient toujours des modes sélectionnés TE018 ou TM018 qui présentent de bons coefficients de surtension à vide. Cependant, comme indiqué ci-dessus ces coefficients diminuent dans le système complet, avec ses moyens d'accord. Contrairement à l'idée généralement admise, ces modes ne sont pas les seuls à pouvoir être mis en oeuvre dans des résonateurs diélectriques pour réaliser des filtres de caractéristiques acceptables.Tunable microwave filters with dielectric resonators developed up to now, however, have a certain number of drawbacks. First of all, there are parasitic modes in these filters which can disturb their frequency responses. In addition, it is difficult to obtain a variable bandwidth in large proportions with a given template filter. Finally, to obtain the tunability of the filter over a large bandwidth, tuning systems are provided for varying the tuning frequency of the resonators. These systems generally comprise, associated with the resonators themselves, adjustable sinking dielectric rods. These elements allow tuning but they can degrade the overvoltage coefficient obtained when the resonator is alone. In addition, they pose machining and adjustment problems. Until now, these filters have always used selected modes TE018 or TM018 which have good no-load overvoltage coefficients. However, as indicated above these coefficients decrease in the complete system, with its means of agreement. Contrary to the generally accepted idea, these modes are not the only ones that can be implemented in dielectric resonators to produce filters with acceptable characteristics.

L'invention a en effet pour objet un filtre hyperfréquence accordable, à résonateurs diélectriques fonctionnant suivant le mode de résonance TM010.The subject of the invention is in fact a tunable microwave filter, with dielectric resonators operating according to the TM010 resonance mode.

Un document de l'art connu FR-A-1 496 177 décrit un filtre à hautes fréquences comprenant un tube constitué par une partie conductrice au moins à sa partie de surface intérieure, et par plusieurs tiges qui sont constituées par une partie conductrice au moins à leurs parties de surface et qui possèdent une longueur électrique égale à un multiple entier d'un quart de longueur d'onde choisie dans la bande de fréquences de coupure du tube et qui sont disposées dans le tube le long de l'axe de celui-ci en coupant l'axe.A document of known art FR-A-1 496 177 describes a high frequency filter comprising a tube constituted by a conductive part at least at its inner surface part, and by several rods which are constituted by at least one conductive part to their surface parts and which have an electrical length equal to an integer multiple of a quarter wavelength chosen from the cut-off frequency band of the tube and which are arranged in the tube along the axis of that -this by cutting the axis.

Un article de l'art connu intitulé "Bandpass filters using TM010 dielectric rod resonators" de Y. KOBAYASHI et al. paru dans IEEE MTT-S International Microwave Symposium digest (Ottawa, 27 - 29 Juin 1978, pages 233 - 235) décrit des filtres passe-bande hyperfréquences utilisant des résonateurs en forme de barreau de type diélectriques, résonnant suivant le mode TM010. Cet article décrit des filtres dans lesquels les résonateurs λ/2 ou n ')../2 sont fixes et bloqués entre deux plans de masse.An article in the known art entitled "Bandpass filters using TM010 dielectric rod resonators" by Y. KOBAYASHI et al. published in IEEE MTT-S International Microwave Symposium digest (Ottawa, June 27 - 29, 1978, pages 233 - 235) describes microwave bandpass filters using bar-type resonators of the dielectric type, resonating according to the TM010 mode. This article describes filters in which the resonators λ / 2 or n ') ../ 2 are fixed and locked between two ground planes.

Par contre l'invention concerne un filtre hyperfréquence accordable, à résonateurs cylindriques comportant un boîtier métallique associé à un socle également métallique formant un guide d'ondes dit sous la coupure et une suite de résonateurs cylindriques disposés à l'intérieur du boîtier, des moyens de couplage d'entrée et de sortie avec les résonateurs extrêmes, ces résonateurs ayant l'une de leurs extrémités en contact avec le socle métallique, leurs autres extrémités étant à une distance réglable d'un plan de masse formé par le fond du boîtier pour réaliser l'accord de fréquence, caractérisé en ce que ces résonateurs sont des résonateurs diélectriques résonnant suivant le mode TM010, en ce que les extrémités de ces résonateurs diélectriques en contact avec le socle sont déplaçables par coulissement dans de premiers trous de fixation prévus à cet effet dans le socle, et en ce que des vis à pénétration réglable sont disposées dans de seconds trous de fixation prévus dans le socle, en alternance avec les premiers trous, pour l'ajustement du couplage entre résonateurs.On the other hand, the invention relates to a tunable microwave filter, with cylindrical resonators comprising a metal housing associated with a base also metallic forming a waveguide said under the cut-off and a series of cylindrical resonators arranged inside the housing, input and output coupling with the extreme resonators, these resonators having one of their ends in contact with the metal base, their other ends being at an adjustable distance from a ground plane formed by the bottom of the housing for achieve frequency tuning, characterized in that these resonators are dielectric resonators resonating according to the TM010 mode, in that the ends of these dielectric resonators in contact with the base are movable by sliding in first fixing holes provided for this effect in the base, and in that screws with adjustable penetration are arranged in second fixing holes provided in the base, in alternating with the first holes, to adjust the coupling between resonators.

L'invention sera mieux comprise et d'autres caractéristiques apparaîtront à l'aide de la description qui suit en référence aux figures annexées.

  • - la figure 1 est le schéma d'une coupe longitudinale d'un mode de réalisation du filtre hyperfréquence suivant l'invention.
  • - la figure 2 est le schéma d'une coupe transversale du filtre représenté sur la figure 1, au niveau d'un résonateur diélectrique.
The invention will be better understood and other characteristics will appear from the following description with reference to the appended figures.
  • - Figure 1 is a diagram of a longitudinal section of an embodiment of the microwave filter according to the invention.
  • - Figure 2 is a diagram of a cross section of the filter shown in Figure 1, at a dielectric resonator.

Les sous-ensembles qui rentrent dans un matériel hyperfréquence déterminé se doivent d'être a faible prix de revient tout en conservant des performances élevées. Les résonateurs diélectriques en mode TM010, intégrés pour réaliser une fonction de filtrage, permettent d'obtenir un gain par rapport aux filtres en structure guidée évanescente, coaxiale (filtre en peigne ou filtre inter-digité), et par rapport aux filtres à résonateurs diélectriques dans les modes TE01λ et TMOL X. Le coefficient de surtension à vide d'un résonateur diélectrique en mode TM010, varie de Q = 5000 à 2 GHz à Q = 2800 à 6 GHz; ces valeurs sont suffisantes pour réaliser des filtres à bande large ou à bande étroite, ou des filtres sélectifs à fréquence d'accord variable, ayant des couplages aux accès du type coaxial-coaxial, guide-guide, ou guide-coaxial, à condition que les moyens d'accord qui y sont associés ne détériorent pas ces coefficients. Or des résonateurs diélectriques en mode TM010 0 peuvent être utilisés d'une manière très simple et associés à des moyens d'accord divers mais toujours simples qui n'introduisent pas de perturbation dans le mode de résonance. De plus, il n'y a pas besoin de supports pour les résonateurs diélectriques.The sub-assemblies which fit into a specific microwave material must be at low cost while retaining high performance. The dielectric resonators in TM010 mode, integrated to perform a filtering function, make it possible to obtain a gain compared to filters in evanescent, coaxial guided structure (comb filter or cross-digital filter), and compared to filters with dielectric resonators in TE01λ and TMOL X modes. The no-load overvoltage coefficient of a dielectric resonator in TM010 mode varies from Q = 5000 to 2 GHz to Q = 2800 to 6 GHz; these values are sufficient to produce broadband or narrowband filters, or selective filters with variable tuning frequency, having couplings of the coaxial-coaxial, guide-guide, or guide-coaxial type, provided that the means of agreement which are associated therewith do not deteriorate these coefficients. However, dielectric resonators in TM010 0 mode can be used in a very simple manner and associated with various but always simple tuning means which do not introduce disturbance in the resonance mode. In addition, there is no need for supports for the dielectric resonators.

La figure 1 représente un mode de réalisation du filtre hyperfréquence suivant l'invention en coupe longitudinale, ce filtre ayant une fonction passe-bande. Ce filtre est constitué de trois résonateurs diélectriques couplés, 1, 2, 3, de forme cylindrique, le premier et le dernier de ces résonateurs étant couplés à des moyens respectivement d'entrée 4, et de sortie 5. Pour fonctionner suivant un mode de résonance TM010, ces résonateurs sont au contact d'un socle métallique 6 auquel ils sont fixés. Dans ce mode de réalisation, des trous sont prévus dans le socle, les résonateurs diélectriques étant prévus pour coulisser dans ces trous. Ces trous peuvent être chemisés par une faible épaisseur de diélectrique, par exemple du polytétrafluoréthylène (téflon, sous son nom commercial) de 2 à 7/100e mm d'épaisseur pour éviter la détérioration des états de surface lors du coulissement du résonateur.FIG. 1 shows an embodiment of the microwave filter according to the invention in longitudinal section, this filter having a bandpass function. This filter consists of three coupled dielectric resonators, 1, 2, 3, of cylindrical shape, the first and the last of these resonators being coupled to input 4 and output 5 means respectively. To operate according to a mode of resonance TM010, these resonators are in contact with a metal base 6 to which they are fixed. In this embodiment, holes are provided in the base, the dielectric resonators being provided to slide in these holes. These holes can be lined with a small thickness of dielectric, for example polytetrafluoroethylene (teflon, under its trade name) from 2 to 7/100 e mm thick to avoid deterioration of the surface conditions during the sliding of the resonator.

Un couvercle 7 forme avec le socle de fixation 6 un boîtier constituant une enceinte métallique de blindage formant guide dont la section peut être quelconque, par exemple rectangulaire, circulaire ou réentrante. Pour réduire autant que possible les fuites hyperfréquences, la partie du résonateur extérieure au guide peut être enduite d'un revêtement du type colle ou peinture à l'argent. Le fond du boîtier est à une distance x relativement faible des extrémités des résonateurs 1, 2 et 3, cette distance étant réglable par enfoncement des résonateurs diélectriques 1, 2 et 3 à l'intérieur du guide. Les résonateurs peuvent être bloqués lorsque la fréquence d'accord est obtenue. Les dimensions du boîtier sont telles que le guide ainsi formé a une fréquence de coupure supérieure à la fréquence à laquelle le filtre est utilisé. Ainsi, dans les conditions d'utilisation, le guide, qui ne permet pas de propagation guidée, est dit "sous la coupure". La fonction de filtrage de ce filtre est obtenue par la localisation du champ électromagnétique dans et à proximité des resonateurs diélectriques dans le mode TM010. Le couplage entre résonateurs successifs, qui détermine la bande passante du filtre, est obtenu par un éloignement adéquat de deux résonateurs successifs dans le guide, et ce couplage peut être ajusté par des vis métalliques, telles que 8, pour le réglage de la susceptance de couplage entre résonateurs adjacents. L'entrée et la sortie dans le guide sont réalisées par des prises coaxiales, l'embout cylindrique extérieur étant fixé au socle de fixation, et le conducteur intérieur traversant ce socle de fixation pour former à l'intérieur du guide une boucle réglable couplée sur le champ magnétique de chaque résonateur extrême. L'accord de ce filtre à la fréquence minimum de la bande de réglage de fréquence d'accord a lieu lorsque les resonateurs sont en contact avec le fond du boîtier.A cover 7 forms, with the fixing base 6, a housing constituting a metal shielding enclosure forming a guide, the section of which can be any, for example rectangular, circular or reentrant. To reduce microwave leakage as much as possible, the part of the resonator external to the guide can be coated with a coating of the glue or silver paint type. The bottom of the housing is at a relatively small distance x from the ends of the resonators 1, 2 and 3, this distance being adjustable by driving the dielectric resonators 1, 2 and 3 inside the guide. The resonators can be blocked when the tuning frequency is obtained. The dimensions of the housing are such that the guide thus formed has a cutoff frequency greater than the frequency at which the filter is used. Thus, in the conditions of use, the guide, which does not allow guided propagation, is said to be "under the cut". The filtering function of this filter is obtained by locating the electromagnetic field in and near the dielectric resonators in the TM010 mode. The coupling between successive resonators, which determines the passband of the filter, is obtained by an adequate distance of two successive resonators in the guide, and this coupling can be adjusted by metal screws, such as 8, for the adjustment of the susceptance of coupling between adjacent resonators. The guide enters and exits through coaxial sockets, the external cylindrical end being fixed to the fixing base, and the internal conductor passing through this fixing base to form inside the guide an adjustable loop coupled on the magnetic field of each extreme resonator. The tuning of this filter to the minimum frequency of the tuning frequency adjustment band takes place when the resonators are in contact with the bottom of the case.

La figure 2 est une représentation en coupe transversale du filtre hyperfréquence représenté sur la figure 1 au niveau du résonateur diélectrique 1. Les lignes de champ ont été représentées sur cette figure. Comme indiqué ci-dessus, le champ électrique est localisé dans et à proximité des résonateurs diélectriques, les lignes de champ magnétiques, orthogonales aux lignes de champ électrique formant des cercles dont les centres sont sur l'axe du résonateur, à l'intérieur et à l'extérieur du résonateur.Figure 2 is a cross-sectional representation of the microwave filter shown in Figure 1 at the dielectric resonator 1. The field lines have been shown in this figure. As indicated above, the electric field is located in and near the dielectric resonators, the magnetic field lines, orthogonal to the electric field lines forming circles whose centers are on the axis of the resonator, inside and outside the resonator.

Dans ce mode de réalisation les accès 4 et 5 se font par prises coaxiales. Le couplage entre ces prises coaxiales et les résonateurs des extrémités peut également être réalisé par des antennes. Des vis métalliques de réglage 8 permettent d'ajuster le couplage entre résonateurs adjacents.In this embodiment, the accesses 4 and 5 are made by coaxial sockets. The coupling between these coaxial sockets and the resonators of the ends can also be achieved by antennas. Adjusting metal screws 8 make it possible to adjust the coupling between adjacent resonators.

Dans un mode de réalisation du filtre suivant l'invention, les résonateurs hyperfréquences sont constitués de titanate de zirconium ZrTi04 auquel on ajoute de l'étain Sn, afin d'améliorer le coefficient de température. Le guide est un guide de section carrée, de L = 38 mm de côté; le diamètre des résonateurs diélectriques a été choisi égal à D = 9,9 mm; la permittivité du matériau Er est égale à 36, et la fréquence la plus basse obtenue est de l'ordre de 2 GHz. Dans ce mode de réalisation, la première réponse parasite est rejetée autour de 3,4 à 3,7 GHz. Comme indiqué l'accord en fréquence est obtenu par variation de la longueur effective du résonateur à l'intérieur du guide et cette fréquence peut varier entre 2 et 2,5 GHz par exemple.In one embodiment of the filter according to the invention, the microwave resonators consist of zirconium titanate ZrTi0 4 to which tin Sn is added, in order to improve the temperature coefficient. The guide is a square section guide, L = 38 mm on the side; the diameter of the dielectric resonators was chosen equal to D = 9.9 mm; the permittivity of the material Er is equal to 36, and the lowest frequency obtained is of the order of 2 GHz. In this embodiment, the first spurious response is rejected around 3.4 to 3.7 GHz. As indicated, the frequency tuning is obtained by varying the effective length of the resonator inside the guide and this frequency can vary between 2 and 2.5 GHz for example.

Cette structure permet de réaliser tous les types de filtres les filtres passe bande, à bande B étroite, par exemple B = 10 MHz à 2 GHz de fréquence centrale, aussi bien que les filtres passe bande à bande large, par exemple B = 200 MHz à 2 GHz, la largeur de bande étant déterminée comme indiqué ci-dessus par les conditions de couplage entre résonateurs adjacents. Cette structure permet également de réaliser des filtres coupe-bande. Dans ce cas le couplage des résonateurs avec une ligne électrique prévue à l'intérieur du guide, longitudinalement, est réalisé par les extrémités des résonateurs.This structure makes it possible to produce all types of filters, band pass filters, narrow B band filters, for example B = 10 MHz to 2 GHz of central frequency, as well as filters broadband bandpass, for example B = 200 MHz to 2 GHz, the bandwidth being determined as indicated above by the coupling conditions between adjacent resonators. This structure also makes it possible to produce notch filters. In this case the coupling of the resonators with an electric line provided inside the guide, longitudinally, is carried out by the ends of the resonators.

De plus, les couplages d'entrée et de sortie peuvent s'effectuer par guide, les extrémités du guide formant l'enceinte du filtre étant ouvertes pour réaliser la connection. L'entrée et la sortie peuvent être couplées différemment, l'une par guide, l'autre par prise coaxiale.In addition, the input and output couplings can be carried out by guide, the ends of the guide forming the enclosure of the filter being open to make the connection. The input and output can be coupled differently, one by guide, the other by coaxial socket.

La forme du guide peut être quelconque, guide en ligne, guide en U ou guide ayant la forme d'une couronne. La disposition en U permet par exemple de prévoir des rétro-couplages entre résonateurs non adjacents pour moduler la réponse du filtre. Il est également possible d'associer plusieurs filtres, par exemple en parallèle, couplés à un accès commun en guide pour réaliser un diplexeur ou un multiplexeur.The shape of the guide can be any, line guide, U-shaped guide or guide having the shape of a crown. The arrangement in U allows for example to provide retro-couplings between nonadjacent resonators to modulate the response of the filter. It is also possible to associate several filters, for example in parallel, coupled to a common access as a guide for producing a diplexer or a multiplexer.

Enfin l'exemple de réalisation donné, ayant une fréquence centrale de l'ordre de 2 GHz n'est nullement limitatif et il est possible de réaliser des filtres ayant des fréquences centrales plus élevées, par exemple 7 GHz. Les limites sont fixées par la décroissance du facteur de qualité en fonction de l'augmentation de la fréquence.Finally, the example of embodiment given, having a central frequency of the order of 2 GHz, is in no way limiting and it is possible to produce filters having higher central frequencies, for example 7 GHz. The limits are set by the decrease in the quality factor as a function of the increase in frequency.

Comme indiqué ci-dessus, l'avantage principal du filtre hyperfréquence suivant l'invention est la simplicité de sa structure. De plus, comme indiqué ci-dessus, du fait du mode lui-même, il n'y a pas de mode parasite proche de la réponse du filtre.As indicated above, the main advantage of the microwave filter according to the invention is the simplicity of its structure. In addition, as indicated above, due to the mode itself, there is no parasitic mode close to the response of the filter.

Claims (6)

1. A tuneable ultrahigh frequency filter with cylindrical resonators, which comprises a metal case (7) associated with abase (6) equally made of metal, and forming a waveguide, referred to as "below cut-off", and a succession of cylindrical resonators (1, 2, 3) disposed inside the case; input (4) and output (5) coupling means for the endmost resonators, wherein these resonators (1, 2, 3) have ane of their ends contacting the metal base (6) while their other ends are in an adjustable distance x to the mass plane formed by the bottom of the case in order to perform the frequency tuning, characterized in that the resonators are dielectric resonators (1, 2, 3) resonating in the TM010 mode, that the ends of these dielectric resonators (1, 2, 3) in contact with the base (6) are movable by sliding within first filing holes provided to this effect in the base; and that adjustable penetration screws (6) are disposed within second fixing holes provided in the base, alternating with the first holes, and used for adjusting the coupling between the resonators.
2. A filter according to claim 1, characterized in that the part of the resonator external to the guide may be covered with a coating of the silver paint or bonding agent type, in order to reduce the ultrahigh frequency leaks.
3. A filter according to any one of the preceding claims, characterized in that the dielectric resonators are formed from zirconium titanate ZrTi04 to which tin Sn is added, so as to improve the temperature coefficient.
4. A filter according to any one of the preceding claims, characterized in that the first holes are lined with a thin dielectric layer so as to avoid damage to the surface during sliding of the resonators (1, 2, 3).
5. A filter according to any one of the preceding claims, characterized in that the coupling means of the endmost resonators are constituted of wire coupling loops (9) of adjustable length.
6. A filter according to any one of the preceding claims, characterized in that it comprises an electrical line within the guide disposed longitudinally, which is coupled to the ends of the resonators so as to realize a rejection filter.
EP84400077A 1983-01-19 1984-01-13 Tunable microwave filter with tm010 mode dielectric resonators Expired EP0114140B1 (en)

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AT84400077T ATE41271T1 (en) 1983-01-19 1984-01-13 TUNABLE MICROWAVE FILTER WITH DIELECTRIC RESONATORS IN TM010 MODE.

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FR8300755 1983-01-19
FR8300755A FR2539565A1 (en) 1983-01-19 1983-01-19 TUNABLE HYPERFREQUENCY FILTER WITH DIELECTRIC RESONATORS IN TM010 MODE

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EP0114140A1 EP0114140A1 (en) 1984-07-25
EP0114140B1 true EP0114140B1 (en) 1989-03-08

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EP (1) EP0114140B1 (en)
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FR2539565B1 (en) 1985-04-05
EP0114140A1 (en) 1984-07-25
DE3477104D1 (en) 1989-04-13
FR2539565A1 (en) 1984-07-20
ATE41271T1 (en) 1989-03-15
US4578655A (en) 1986-03-25
CA1207853A (en) 1986-07-15

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