EP0430136A1 - Band elimination filter for microwave waveguide - Google Patents

Band elimination filter for microwave waveguide Download PDF

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Publication number
EP0430136A1
EP0430136A1 EP90122545A EP90122545A EP0430136A1 EP 0430136 A1 EP0430136 A1 EP 0430136A1 EP 90122545 A EP90122545 A EP 90122545A EP 90122545 A EP90122545 A EP 90122545A EP 0430136 A1 EP0430136 A1 EP 0430136A1
Authority
EP
European Patent Office
Prior art keywords
short
waveguide
coaxial line
screw
conductor
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.)
Ceased
Application number
EP90122545A
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German (de)
French (fr)
Inventor
Jean-Claude Cruchon
Jean-Denis Schubert
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Alcatel CIT SA
Original Assignee
Alcatel Telspace SA
Alcatel Transmission par Faisceaux Hertziens SA
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Filing date
Publication date
Application filed by Alcatel Telspace SA, Alcatel Transmission par Faisceaux Hertziens SA filed Critical Alcatel Telspace SA
Publication of EP0430136A1 publication Critical patent/EP0430136A1/en
Ceased 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
    • H01P1/207—Hollow waveguide filters
    • H01P1/209—Hollow waveguide filters comprising one or more branching arms or cavities wholly outside the main waveguide

Definitions

  • the invention relates to a band eliminator filter for microwave waveguides.
  • a microwave transmission system it is often necessary to weaken one frequency band without weakening another neighboring frequency band.
  • the separation of the transmitted and received waves is ensured by a frequency difference and by a crossover of the polarizations, but it is nevertheless necessary to attenuate the transmitted waves arriving on the receiver. , to avoid phenomena of saturation, undesirable beats, etc ...
  • a band eliminator filter consisting of at least one resonant cavity coupled to a waveguide by an iris. To sufficiently attenuate the frequency band to be eliminated, it is conventional to multiply the number of cavities coupled to the guide section. These cavities are separated by an odd number of quarters of the wavelength corresponding to the central frequency of the band to be passed without attenuation.
  • the guide has a rectangular section, the cavities are arranged on at least one of the long sides of the guide, and optionally on both sides, to multiply the number of cavities while minimizing the bulk.
  • this type of band eliminator filter is very bulky and expensive. It is therefore particularly ill-suited for producing stations with low capacity, which must have a low cost, and in which it is desirable to integrate in a single housing the transmission device and the microwave reception device.
  • the object of the invention is to propose a band eliminator filter for waveguides, the production of which is inexpensive and the space requirement of which is small enough to allow its integration into a transmitting / receiving head of a station. at low capacity.
  • the object of the invention is a band eliminator filter comprising at least one resonator consisting of an element with inductive susceptance and a capacitive susceptance element, compact and easy to produce, the first being consisting of a short-circuited coaxial line, and the second consisting of a short conductor plunging into the waveguide, and which extends the central conductor of the line.
  • the inner conductor comprises a metal screw, screwed into the threaded hole; this screw comprising a cylindrical extension having the same axis of symmetry of revolution as the screw but having a smaller diameter.
  • the part of the threaded hole which is not occupied by the screw constitutes an external conductor for the coaxial line, while the extension of the screw constitutes an internal conductor, and that the screw itself constitutes a short circuit to the end of the coaxial line.
  • This embodiment is very simple, since it suffices to modify a conventional brass screw, by removing metal by means of a lathe, to constitute an extension having a length equal to an odd multiple of a quarter of the wavelength corresponding to the center frequency of the band to be eliminated.
  • the short-circuited coaxial line comprises an externally threaded cylindrical sleeve, internally smooth, closed at one end by a conducting plane constituting a short-circuit and carrying a coaxial cylindrical conductor constituting the inner conductor.
  • the socket is screwed into the threaded hole.
  • This embodiment is slightly more complex since such a socket cannot be produced by modifying a screw. On the other hand, it has the advantage of allowing the use of a waveguide section having thinner walls.
  • the two embodiments have the advantage of being much less expensive and much less bulky than conventional filters, for a given number of resonators.
  • FIG. 1 schematically represents a known example of realization of an adjustable capacitive susceptance. It comprises a waveguide 1 in which a metal screw 2 is inserted which is screwed into a threaded hole 5 situated in the plane of symmetry of the section of the guide 1.
  • the screw 2 comprises a slot 3 allowing it to be screwed or the unscrew to adjust the recess, so that the end 6 of the screw slightly protrudes inside the waveguide 1.
  • the value of the susceptance is adjusted by screwing or unscrewing the screw 2, then this ci is immobilized by means of a nut 4 screwed on the screw 2 and tightened against the external surface of the waveguide.
  • a coaxial line short-circuited at one end has, at the other end, an inductive susceptance when the length l of the line is less than a quarter of the wavelength ⁇ or slightly less than an odd multiple of a quarter of the wavelength.
  • FIG. 2 schematically represents a short-circuited coaxial line comprising an inner conductor 7 and an outer conductor 8 each having a cylindrical shape with a circular section.
  • the short circuit is constituted by a metallic plane 9 connecting the conductors 7 and 8 to one end of the line.
  • the susceptance of this line is adjustable by varying the length of the line.
  • the invention consisted in combining these two known means to constitute a resonator eliminating a frequency band.
  • these means cannot be combined in any way, otherwise there is a significant disturbance in the propagation of the frequencies to be passed.
  • Figures 3 and 4 show a first embodiment of the filter according to the invention, comprising a single resonator and a waveguide with rectangular section.
  • a short-circuited coaxial line is constituted by a threaded hole 19 and by a screw 12 which is shown in section in FIG. 4.
  • the hole 19 is drilled in the longest side of the guide 11, in the plane of symmetry of the latter. this.
  • the screw 12 comprises: a slot 13 for screwing it in or out screw in using a screwdriver; a threaded part 14 provided with a thread 15 corresponding to the thread of the hole 19, and a smooth part 17 having a cylindrical shape with circular section having the same axis of symmetry YY 'as the part 14, and extending the latter.
  • Part 17 has a length equal to an odd multiple of a quarter of the wavelength corresponding to the center frequency of the frequency band to be eliminated. In this example, it is exactly one quarter wavelength.
  • Part 17 constitutes the inner conductor of a coaxial line with circular section, and constitutes a bar plunging into the guide 11.
  • the outer conductor of the coaxial line consists of the threaded hole 19, in the part not occupied by the screw 12
  • the length of the unoccupied part of the threaded hole 19 is slightly less than a quarter of a length and has an inductive susceptance.
  • a shoulder 16 constitutes a conducting plane short-circuiting the end of the coaxial line.
  • the length of the external conductor of this line is adjusted by screwing or unscrewing the screw 12. The adjustment is such that the length of the line is slightly less than a quarter of a wavelength, therefore a portion of part 17 exceeds inside the guide 11 and has a capacitive susceptance, the value of which also depends on the position of the screw 12.
  • a nut 18 is screwed onto the screw 12, and is tightened on the external surface of the wave guide, to immobilize screw 12 after it has been adjusted.
  • the guide 11 can be produced in a very conventional manner by extruding an aluminum alloy.
  • the thickness of the wall must be sufficient so that the unoccupied part of the threaded hole 19 can have a length close to a quarter of the wavelength corresponding to the central frequency of the strip to be eliminated.
  • the screw 12 can be produced by machining a conventional screw made of brass, to reduce its diameter over part of its length and form a shoulder 16. It may possibly be covered with a conventional electrolytic deposit, terminated by a layer of gold.
  • the production of the threaded hole 19 and of the screw 12 are therefore very simple compared to the production of the cavities coupled by an iris, which include the conventional filters.
  • the size of the screw 12 is much smaller than the size of a cavity coupled by an iris.
  • Such a filter may include a plurality of identical circulated coaxial lines aligned in a plane of symmetry of the guide, where the electric field is maximum. They are spaced by an odd number of quarters of the wavelength corresponding to the center frequency of the band to be passed.
  • FIG. 5 diagrammatically represents a second embodiment of the filter according to the invention, comprising 5 resonators similar to that described above.
  • Three resonators, comprising screws 21 to 23, are located on a first line and two resonators, comprising two screws 24 and 25, are located on a second line, these two lines being symmetrical with respect to the axis XX 'of symmetry of the waveguide 27.
  • These two lines are located in a plane of symmetry of the waveguide 27, where the electric field vector E is maximum.
  • two successive resonators are spaced by a half wavelength ⁇ 'from the center frequency of a frequency band to be passed.
  • the resonators located on the first line are offset by a quarter of a wavelength relative to the resonators located on the second line.
  • Screw 24 is located midway between screws 21 and 22.
  • Screw 25 is located midway between screws 22 and 23. This arrangement of the resonators provides a transfer function with very low attenuation for the frequencies to be left pass; and an attenuation transfer function proportional to the number of resonators, for the frequencies to be eliminated.
  • the screws 21 to 25 have a diameter of 3 millimeters which is reduced to 0.63 millimeters in the part 17 constituting the inner conductor of the coaxial line.
  • This part 17 has a length of 5.05 millimeters.
  • the coaxial line has a characteristic impedance of 96 ohms.
  • the value of the characteristic impedance of the coaxial line partly determines the value of the coupling between the coaxial line and the waveguide; and determines the overvoltage factor of the resonator, in other words determines the attenuation and the width of the attenuated band.
  • the characteristic impedance of the coaxial line can be between 60 and 100 ⁇
  • FIG. 6 represents the graph G of the attenuation and the graph R of the standing wave rate for the exemplary embodiment represented in FIG. 5, used to eliminate the frequency band BA, from 14 to 14.5 GHz, and to pass the BP frequency band from 10.7 to 12.75 GHz. It appears that the attenuation of the band from 14 to 14.5 GHz is more than 20 dB and that the standing wave rate in the band from 10.7 to 12.75 GHz, expressed in absolute value, is less than 1.15, while the insertion losses are less than 0.2 dB. These figures are to be compared with the performance of a conventional filter made up of five cavities coupled to a waveguide by irises.
  • a conventional filter provides attenuation, of the band to be eliminated, greater than 50 dB, and a standing wave rate, in the passband, of less than 1.05; with insertion losses of less than 0.05 dB.
  • the filter according to the invention therefore has more modest performance, but on the other hand the price of the realization tion is about 3 to 4 times smaller, and the size is much reduced.
  • the invention is not limited to the examples described above. Many variants are within the reach of those skilled in the art, as regards the production of the coaxial line constituting the resonator and as regards its integration into a waveguide of an emission device. microwave reception.
  • FIGs 7 and 8 show a third embodiment of a filter according to the invention.
  • This example comprises a single resonator essentially constituted by a socket 32 screwed into a threaded hole 39 which is drilled in the largest wall of a guide 31 with rectangular section.
  • Figure 8 shows the socket 32 seen in section.
  • the axis of symmetry ZZ 'of the sleeve 32 is located in the plane of symmetry of the guide 31.
  • the outer surface of the sleeve 32 has a thread 35 over its entire length.
  • a slot 34 makes it possible to screw or unscrew the socket 32 in the hole 39.
  • a nut 38 screwed onto the socket 32 makes it possible to immobilize the socket 32 after having adjusted its position to obtain agreement on the central frequency of the frequency band to be eliminated.
  • the socket 32 is hollow. Its interior has a smooth cylindrical surface 36 and it contains a rod 37 having a cylindrical shape whose axis of symmetry of revolution coincides with the axis of symmetry of revolution ZZ 'of the sleeve 32.
  • the diameter of the rod 37 is less than the inside diameter of the socket 32, and its length is equal to an odd number of quarters of the wavelength corresponding to the central frequency of the band to be eliminated. In this example, the length of the rod 37 is equal to a quarter of a wavelength.
  • the length of the rod 37 is greater than the depth of the sleeve 32 so that the rod 37 protrudes at the mouth of the sleeve.
  • the interior of the socket and a free part of the threaded hole 39 constitute the outer conductor of a coaxial line; while the rod 37 constitutes an inner conductor of this line and that the end of the rod 37 constitutes a plunger penetrating into the waveguide 31 to constitute a capacitive susceptance connected to the end of the coaxial line.
  • the bottom 33 of the socket 32 has a flat surface, orthogonal to the axis of symmetry ZZ ', and constitutes a short circuit at the other end of the coaxial line.
  • the length of the socket 32 is less than a quarter of a wavelength so that the socket does not protrude inside the guide 31, and that part of the threaded hole 39 is not occupied by the socket 32 and forms part of the coaxial line.
  • the third embodiment allows the use of a guide section 31 having a wall of thickness less than the length of the coaxial line to be produced, while the first embodiment requires a waveguide having a wall thickness greater than the length of the coaxial line to be produced.
  • FIG. 9 represents a fourth embodiment of a filter according to the invention, comprising a resonator 42 constituted by a socket, analogous to the socket 32 described above described, screwed into a threaded hole 43 which is drilled in the wall of a waveguide 41 with circular section.
  • the conductor 44 of the short-circuited coaxial line has its major axis which passes through the center of the guide and which is parallel to the electric field E of the waves to be eliminated.
  • FIG. 10 represents a fifth embodiment of a filter according to the invention, which is combined with a transition from coaxial cable to waveguide.
  • This transition comprises a waveguide 49, of rectangular section, closed by a metal plate 51; and comprises an antenna 50 immersed in the guide 49.
  • the antenna 50 is connected to the central conductor of a coaxial cable 52 by a coaxial connector 53.
  • the antenna 50 passes through a hole 54 drilled in the wall of the guide 49, on its largest side, and in its plane of symmetry.
  • This transition also constitutes a band eliminator filter thanks to a plurality of resonators constituted by sockets 55 to 57 screwed into threaded holes, 58 to 60. These sockets 55 to 57 are similar to the socket 32 described. previously.
  • the antenna 50 is placed at a distance equal to a quarter of the wavelength ⁇ 'corresponding to the central frequency of the frequency band to be passed, relative to the metal plate 51 closing the waveguide.
  • the nearest resonator, 55 is placed at a distance at least equal to the wavelength ⁇ 'corresponding to the central frequency of the band to be passed, relative to the antenna 50.
  • the other resonators are located at regular intervals, equal to odd multiples of a quarter of the wavelength ⁇ 'corresponding to the center frequency of the band to be passed. For example, the intervals are all equal to a quarter of a wavelength.

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Abstract

The invention relates to a filter for eliminating a frequency band, whilst allowing through another frequency band with a minimum of disturbance. An embodiment comprises: … …  - a waveguide (11); …  - at least one short-circuited coaxial line comprising an inner conductor (17) and an outer conductor (19), the inner conductor (17) being a conducting rod prolonging a screw (12), and the outer conductor being a threaded hole (19) which is drilled in the wall of the waveguide (11). The screw (12) constitutes an adjustable short-circuit. … …<??>The short-circuited coaxial line has a length slightly less than a quarter of the wavelength corresponding to the central frequency of the band to be eliminated, so as to constitute an inductive susceptance. The end of the inner conductor (17) juts out slightly into the waveguide (11), in order to constitute a capacitive susceptance which is connected to the end of the coaxial line in order to constitute a resonator tuned to the central frequency of the band to be eliminated. …<??>Application to the construction of terrestrial transmission-reception stations. …<IMAGE>…

Description

L'invention concerne un filtre éliminateur de bande pour guide d'ondes hyperfréquences. Dans un système de transmission par micro-ondes, il est souvent nécessaire d'affaiblir une bande de fréquences sans affaiblir une autre bande de fréquences voisine. Par exemple, dans une tête d'émission-réception, la séparation des ondes émises et des ondes reçues est assurée par un écart de fréquence et par un croisement des polarisations, mais il est néanmoins nécessaire d'atténuer les ondes émises arrivant sur le récepteur, pour éviter des phénomènes de saturation, de battements indésirables, etc...The invention relates to a band eliminator filter for microwave waveguides. In a microwave transmission system, it is often necessary to weaken one frequency band without weakening another neighboring frequency band. For example, in a transmission-reception head, the separation of the transmitted and received waves is ensured by a frequency difference and by a crossover of the polarizations, but it is nevertheless necessary to attenuate the transmitted waves arriving on the receiver. , to avoid phenomena of saturation, undesirable beats, etc ...

Il est connu de réaliser un filtre éliminateur de bande constitué d'au moins une cavité résonnante couplée à un guide d'ondes par un iris. Pour atténuer suffisamment la bande de fréquences à éliminer, il est classique de multiplier le nombre de cavités couplées au tronçon de guide. Ces cavités sont séparées d'un nombre impair de quarts de la longueur d'onde correspondant à la fréquence centrale de la bande à laisser passer sans atténuation. Lorsque le guide a une section rectangulaire, les cavités sont disposées sur au moins l'un des grands côtés du guide, et éventuellemnt sur les deux côtés, pour multiplier le nombre de cavités en minimisant l'encombrement. Cependant ce type de filtre éliminateur de bande est très encombrant, et coûteux. Il est donc particulièrement mal adapté pour réaliser des stations à faible capacité, devant avoir un faible coût, et dans lesquelles il est souhaitable d'intégrer en un seul boîtier le dispositif d'émission et le dispositif de réception hyperfréquences.It is known to produce a band eliminator filter consisting of at least one resonant cavity coupled to a waveguide by an iris. To sufficiently attenuate the frequency band to be eliminated, it is conventional to multiply the number of cavities coupled to the guide section. These cavities are separated by an odd number of quarters of the wavelength corresponding to the central frequency of the band to be passed without attenuation. When the guide has a rectangular section, the cavities are arranged on at least one of the long sides of the guide, and optionally on both sides, to multiply the number of cavities while minimizing the bulk. However, this type of band eliminator filter is very bulky and expensive. It is therefore particularly ill-suited for producing stations with low capacity, which must have a low cost, and in which it is desirable to integrate in a single housing the transmission device and the microwave reception device.

Le but de l'invention est de proposer un filtre éliminateur de bande pour guide d'ondes, dont la réalisation soit peu coûteuse et dont l'encombrement soit suffisamment faible pour permettre son intégration dans une tête d'émission-réception d'une station à faible capacité. L'objet de l'invention est un filtre éliminateur de bande comportant au moins un résonateur constitué d'un élément à susceptance inductive et d'un élément à susceptance capacitive, peu encombrants et faciles à réaliser, le premier étant constitué d'une ligne coaxiale court-circuitée, et le second étant constitué d'un conducteur de faible longueur plongeant dans le guide d'ondes, et qui prolonge le conducteur central de la ligne.The object of the invention is to propose a band eliminator filter for waveguides, the production of which is inexpensive and the space requirement of which is small enough to allow its integration into a transmitting / receiving head of a station. at low capacity. The object of the invention is a band eliminator filter comprising at least one resonator consisting of an element with inductive susceptance and a capacitive susceptance element, compact and easy to produce, the first being consisting of a short-circuited coaxial line, and the second consisting of a short conductor plunging into the waveguide, and which extends the central conductor of the line.

Selon l'invention, un filtre éliminateur de bande pour guide d'ondes hyperfréquences, comportant :

  • un guide d'ondes;
  • au moins une ligne coaxiale court-circuitée comportant un conducteur intérieur et un conducteur extérieur coaxiaux; le conducteur intérieur ayant une longueur égale à un multiple impair du quart de la longueur d'onde correspondant à la fréquence centrale d'une bande de fréquences à éliminer, et plongeant dans le tronçon de guide d'ondes pour être couplé au champ électrique; et le conducteur extérieur ayant une longueur inférieure au dit multiple; est caractérisé en ce que le conducteur extérieur est constitué, au moins en partie, par un trou cylindrique fileté percé dans une paroi du guide d'ondes, et dont la longueur électrique est ajustable par un court-circuit vissable dans ledit troi fileté.
According to the invention, a band eliminator filter for microwave waveguides, comprising:
  • a waveguide;
  • at least one short-circuited coaxial line comprising an inner conductor and an outer coaxial conductor; the inner conductor having a length equal to an odd multiple of a quarter of the wavelength corresponding to the central frequency of a frequency band to be eliminated, and plunging into the waveguide section to be coupled to the electric field; and the outer conductor having a length less than said multiple; is characterized in that the external conductor is constituted, at least in part, by a threaded cylindrical hole drilled in a wall of the waveguide, and the electrical length of which is adjustable by a short circuit screwable in said threaded hole.

Selon un premier mode de réalisation du filtre selon l'invention, le conducteur intérieur comporte une vis en métal, vissée dans le trou fileté; cette vis comportant un prolongement cylindrique ayant le même axe de symétrie de révolution que la vis mais ayant un diamètre plus petit. La partie du trou fileté qui n'est pas occupée par la vis constitue un conducteur extérieur pour la ligne coaxiale, alors que le prolongement de la vis constitue un conducteur intérieur, et que la vis elle-même constitue un cour-circuit à l'extrémité de la ligne coaxiale.According to a first embodiment of the filter according to the invention, the inner conductor comprises a metal screw, screwed into the threaded hole; this screw comprising a cylindrical extension having the same axis of symmetry of revolution as the screw but having a smaller diameter. The part of the threaded hole which is not occupied by the screw constitutes an external conductor for the coaxial line, while the extension of the screw constitutes an internal conductor, and that the screw itself constitutes a short circuit to the end of the coaxial line.

Ce mode de réalisation est très simple, car il suffit de modifier une vis classique en laiton, en enlevant du métal au moyen d'un tour, pour constituer un prolongement ayant une longueur égale à un multiple impair du quart de la longueur d'onde correspondant à la fréquence centrale de la bande à éliminer.This embodiment is very simple, since it suffices to modify a conventional brass screw, by removing metal by means of a lathe, to constitute an extension having a length equal to an odd multiple of a quarter of the wavelength corresponding to the center frequency of the band to be eliminated.

Selon un autre mode de réalisation, la ligne coaxiale court-circuitée comporte d'une douille cylindrique filetée extérieurement, lisse intérieurement, obturée à une extrémité par un plan conducteur constituant un court-circuit et portant un conducteur cylindrique coaxial constituant le conducteur intérieur. La douille est vissée dans le trou fileté.According to another embodiment, the short-circuited coaxial line comprises an externally threaded cylindrical sleeve, internally smooth, closed at one end by a conducting plane constituting a short-circuit and carrying a coaxial cylindrical conductor constituting the inner conductor. The socket is screwed into the threaded hole.

Ce mode de réalisation est légèrement plus complexe car une telle douille ne peut être fabriquée en modifiant une vis. Par contre, il a l'avantage de permettre l'utilisation d'un tronçon de guide d'ondes ayant des parois plus minces.This embodiment is slightly more complex since such a socket cannot be produced by modifying a screw. On the other hand, it has the advantage of allowing the use of a waveguide section having thinner walls.

Les deux modes de réalisation présentent l'avantage d'être bien moins coûteux et bien moins encombrants que les filtres classiques, pour un nombre de résonateurs donné.The two embodiments have the advantage of being much less expensive and much less bulky than conventional filters, for a given number of resonators.

L'invention sera mieux comprise et d'autres caractéristiques apparaîtront à l'aide de la description ci-dessous et des figures l'accompagnant :

  • les figures 1 et 2 illustrent le fonctionnement du filtre selon l'invention;
  • les figures 3 et 4 représentent schématiquement un premier exemple de réalisation du filtre selon l'invention;
  • la figure 5 représente schématiquement un deuxième exemple de réalisation comportant plusieurs étages de filtrage;
  • la figure 6 représente le graphe de l'atténuation et le graphe du taux d'ondes stationnaires, pour le deuxième exemple de réalisation du filtre selon l'invention;
  • les figures 7 et 8 représentent un troisième exemple de réalisation;
  • la figure 9 représente schématiquement un quatrième exemple de réalisation pour un guide d'ondes à section circulaire;
  • la figure 10 représente un cinquième exemple de réalisation du filtre selon l'invention, combiné avec une transition câble coaxial-guide d'ondes;
The invention will be better understood and other characteristics will appear with the aid of the description below and the accompanying figures:
  • Figures 1 and 2 illustrate the operation of the filter according to the invention;
  • Figures 3 and 4 schematically show a first embodiment of the filter according to the invention;
  • FIG. 5 schematically represents a second exemplary embodiment comprising several filtering stages;
  • FIG. 6 represents the attenuation graph and the standing wave rate graph, for the second embodiment of the filter according to the invention;
  • Figures 7 and 8 show a third embodiment;
  • FIG. 9 schematically represents a fourth exemplary embodiment for a waveguide of circular section;
  • FIG. 10 shows a fifth embodiment of the filter according to the invention, combined with a transition from coaxial cable to waveguide;

Il est connu qu'un barreau métallique faiblement enfoncé dans un guide d'ondes présente une susceptance capacitive qui croît avec l'enfoncement, devient infinie, et change de signe pour un enfoncement voisin du quart de la longueur d'onde. Au-delà de cette valeur, la susceptance est inductive et décroît jusqu'à ce que le barreau touche la paroi du guide d'onde qui est opposée à la paroi dans laquelle le barreau est enfoncé.
La figure 1 représente schématiquement un exemple connu de réalisation d'une susceptance capacitive réglable. Il comporte un guide d'ondes 1 dans lequel est enfoncé une vis métallique 2 qui est vissée dans un trou fileté 5 situé dans le plan de symétrie du tronçon du guide 1. La vis 2 comporte une fente 3 permettant de la visser ou de la dévisser pour ajuster l'enfoncement, de telle sorte que l'extrémité 6 de la vis dépasse légèrement à l'intérieur du guide d'ondes 1. La valeur de la susceptance est réglée en vissant ou en dévissant la vis 2, puis celle-ci est immobilisée au moyen d'un écrou 4 vissé sur la vis 2 et serré contre la surface externe du guide d'ondes.It is known that a metal bar weakly inserted in a waveguide has a capacitive susceptance which increases with the depression, becomes infinite, and changes sign for a depression close to a quarter of the wavelength. Above this value, the susceptance is inductive and decreases until the bar touches the wall of the waveguide which is opposite to the wall in which the bar is inserted.
FIG. 1 schematically represents a known example of realization of an adjustable capacitive susceptance. It comprises a waveguide 1 in which a metal screw 2 is inserted which is screwed into a threaded hole 5 situated in the plane of symmetry of the section of the guide 1. The screw 2 comprises a slot 3 allowing it to be screwed or the unscrew to adjust the recess, so that the end 6 of the screw slightly protrudes inside the waveguide 1. The value of the susceptance is adjusted by screwing or unscrewing the screw 2, then this ci is immobilized by means of a nut 4 screwed on the screw 2 and tightened against the external surface of the waveguide.

Par ailleurs, il est connu qu'une ligne coaxiale court-circuitée à une extrémité présente, à l'autre extrémité, une susceptance inductive lorsque la longueur l de la ligne est inférieure au quart de la longueur d'onde λ ou légèrement inférieure à un multiple impair du quart de la longueur d'onde.Furthermore, it is known that a coaxial line short-circuited at one end has, at the other end, an inductive susceptance when the length l of the line is less than a quarter of the wavelength λ or slightly less than an odd multiple of a quarter of the wavelength.

La figure 2 représente schématiquement une ligne coaxiale court-circuitée comportant un conducteur intérieur 7 et un conducteur extérieur 8 ayant chacun une forme cylindrique à section circulaire. Le court-circuit est constitué par un plan métallique 9 reliant les conducteurs 7 et 8 à une extrémité de la ligne. La susceptance de cette ligne est réglable en faisant varier la longueur de la ligne.FIG. 2 schematically represents a short-circuited coaxial line comprising an inner conductor 7 and an outer conductor 8 each having a cylindrical shape with a circular section. The short circuit is constituted by a metallic plane 9 connecting the conductors 7 and 8 to one end of the line. The susceptance of this line is adjustable by varying the length of the line.

L'invention a consisté à combiner ces deux moyens connus pour constituer un résonateur éliminant une bande de fréquences. Mais ces moyens ne peuvent pas être combinés n'importe comment, sous peine de causer une pertubation importante de la propagation des fréquences à laisser passer.The invention consisted in combining these two known means to constitute a resonator eliminating a frequency band. However, these means cannot be combined in any way, otherwise there is a significant disturbance in the propagation of the frequencies to be passed.

Les figures 3 et 4 représentent un premier exemple de réalisation du filtre selon l'invention, comportant un seul résonateur et un guide d'ondes à section rectangulaire. Une ligne coaxiale court-circuitée est constituée par un trou fileté 19 et par une vis 12 qui est représentée en coupe sur la figure 4. Le trou 19 est percé dans le plus grand côté du guide 11, dans le plan de symétrie de celui-ci.Figures 3 and 4 show a first embodiment of the filter according to the invention, comprising a single resonator and a waveguide with rectangular section. A short-circuited coaxial line is constituted by a threaded hole 19 and by a screw 12 which is shown in section in FIG. 4. The hole 19 is drilled in the longest side of the guide 11, in the plane of symmetry of the latter. this.

La vis 12 comporte : une fente 13 pour la visser ou la dé visser au moyen d'un tournevis; une partie filetée 14 munie d'un filetage 15 correspondant au filetage du trou 19, et une partie lisse 17 ayant une forme cylindrique à section circulaire ayant le même axe de symétrie YY' que la partie 14, et prolongeant cette dernière. La partie 17 a une longueur égale à un multiple impair du quart de la longueur d'onde correspondant à la fréquence centrale de la bande de fréquences à éliminer. Dans cet exemple, elle est égale exactement à un quart de longueur d'onde. La partie 17 constitue le conducteur intérieur d'une ligne coaxiale à section circulaire, et constitue un barreau plongeant dans le guide 11. Le conducteur extérieur de la ligne coaxiale est constitué par le trou fileté 19, dans la partie non occupée par la vis 12. La longueur de la partie non occupée du trou fileté 19 est légèrement inférieure à un quart de longueur et présente une susceptance inductive. A la jonction de parties 14 et 17, un épaulement 16 constitue un plan conducteur court-circuitant l'extrémité de la ligne coaxiale. La longueur du conducteur extérieur de cette ligne est réglée en vissant ou en dévissant la vis 12. Le réglage est tel que la longueur de la ligne est légèrement inférieure à un quart de longueur d'onde, par conséquent une portion de la partie 17 dépasse à l'intérieur du guide 11 et présente une susceptance capacitive dont la valeur dépend aussi de la position de la vis 12. Un écrou 18 est vissé sur la vis 12, et est serré sur la surface externe du guide d'ondes, pour immobiliser la vis 12 après qu'elle ait été réglée.The screw 12 comprises: a slot 13 for screwing it in or out screw in using a screwdriver; a threaded part 14 provided with a thread 15 corresponding to the thread of the hole 19, and a smooth part 17 having a cylindrical shape with circular section having the same axis of symmetry YY 'as the part 14, and extending the latter. Part 17 has a length equal to an odd multiple of a quarter of the wavelength corresponding to the center frequency of the frequency band to be eliminated. In this example, it is exactly one quarter wavelength. Part 17 constitutes the inner conductor of a coaxial line with circular section, and constitutes a bar plunging into the guide 11. The outer conductor of the coaxial line consists of the threaded hole 19, in the part not occupied by the screw 12 The length of the unoccupied part of the threaded hole 19 is slightly less than a quarter of a length and has an inductive susceptance. At the junction of parts 14 and 17, a shoulder 16 constitutes a conducting plane short-circuiting the end of the coaxial line. The length of the external conductor of this line is adjusted by screwing or unscrewing the screw 12. The adjustment is such that the length of the line is slightly less than a quarter of a wavelength, therefore a portion of part 17 exceeds inside the guide 11 and has a capacitive susceptance, the value of which also depends on the position of the screw 12. A nut 18 is screwed onto the screw 12, and is tightened on the external surface of the wave guide, to immobilize screw 12 after it has been adjusted.

Il est à remarquer que l'extrémité de la partie 17 plonge dans le guide 11 à l'endroit où le champ électrique E est maximal. Son dépassement dans le guide est faible, ce qui évite de perturber beaucoup la propagation des ondes dans le guide 11.It should be noted that the end of the part 17 plunges into the guide 11 at the point where the electric field E is maximum. Its protrusion in the guide is low, which avoids greatly disturbing the propagation of the waves in the guide 11.

Le guide 11 peut être réalisé de manière très classique par extrusion d'un alliage d'aluminium. L'épaisseur de la paroi doit être suffisante pour que la partie non occupée du trou fileté 19 puisse avoir une longueur voisine du quart de la longueur d'onde correspondant à la fréquence centrale de la bande à éliminer.The guide 11 can be produced in a very conventional manner by extruding an aluminum alloy. The thickness of the wall must be sufficient so that the unoccupied part of the threaded hole 19 can have a length close to a quarter of the wavelength corresponding to the central frequency of the strip to be eliminated.

La vis 12 peut être réalisée en usinant une vis classique en laiton, pour réduire son diamètre sur une partie de sa longueur et constituer un épaulement 16. Elle peut éventuellement être recouverte d'un dépot électrolytique classique, terminé par une couche d'or. La réalisation du trou fileté 19 et de la vis 12 sont donc d'une très grande simplicité par rapport à la réalisation des cavités couplées par un iris, que comportent les filtres classiques D'autre part, l'encombrement de la vis 12 est beaucoup plus faible que l'encombrement d'une cavité couplée par un iris.The screw 12 can be produced by machining a conventional screw made of brass, to reduce its diameter over part of its length and form a shoulder 16. It may possibly be covered with a conventional electrolytic deposit, terminated by a layer of gold. The production of the threaded hole 19 and of the screw 12 are therefore very simple compared to the production of the cavities coupled by an iris, which include the conventional filters. On the other hand, the size of the screw 12 is much smaller than the size of a cavity coupled by an iris.

Il est envisageable de juxtaposer plusieurs filtres tel que celui représenté sur la figure 3, pour constituer un filtre procurant une plus grande atténuation de la bande de fréquences à éliminer. Un tel filtre peut comporter une pluralité de lignes coaxiales circuitées, identiques, alignées dans un plan de symétrie du guide, où le champ électrique est maximal. Elles sont espacées d'un nombre impair de quarts de la longueur d'onde correspondant à la fréquence centrale de la bande à laisser passer.It is possible to juxtapose several filters such as that shown in FIG. 3, to constitute a filter providing greater attenuation of the frequency band to be eliminated. Such a filter may include a plurality of identical circulated coaxial lines aligned in a plane of symmetry of the guide, where the electric field is maximum. They are spaced by an odd number of quarters of the wavelength corresponding to the center frequency of the band to be passed.

La figure 5 représente schématiquement un deuxième exemple de réalisation du filtre selon l'invention, comportant 5 résonateurs analogues à celui décrit précédemment. Trois résonateurs, comportant des vis 21 à 23, sont situés sur une première ligne et deux résonateurs, comportant deux vis 24 et 25, sont situés sur une seconde ligne, ces deux lignes étant symétriques par rapport à l'axe XX' de symétrie du guide d'ondes 27. Ces deux lignes sont situées dans un plan de symétrie du guide d'ondes 27, où le vecteur champ électrique E est maximal.FIG. 5 diagrammatically represents a second embodiment of the filter according to the invention, comprising 5 resonators similar to that described above. Three resonators, comprising screws 21 to 23, are located on a first line and two resonators, comprising two screws 24 and 25, are located on a second line, these two lines being symmetrical with respect to the axis XX 'of symmetry of the waveguide 27. These two lines are located in a plane of symmetry of the waveguide 27, where the electric field vector E is maximum.

Sur la première ligne, de même que sur la seconde ligne, deux résonateurs successifs sont espacés d'une demi-longueur d'onde λ'de la fréquence centrale d'une bande de fréquences à laisser passer. Les résonateurs situés sur la première ligne sont décalés d'un quart de longueur d'onde par rapport aux résonateurs situés sur la seconde ligne. La vis 24 est située à mi- distance entre les vis 21 et 22. La vis 25 est située à mi- distance entre les vis 22 et 23. Cette disposition des résonateurs fournit une fonction de transfert à très faible atténuation pour les fréquences à laisser passer; et une fonction de transfert à atténuation proportionnelle au nombre de résonateurs, pour les fréquences à éliminer. Dans cet exemple, les vis 21 à 25 ont un diamètre de 3 millimètres qui est réduit à 0,63 millimètres dans la partie 17 constituant le conducteur intérieur de la ligne coaxiale. Cette partie 17 a une longueur de 5,05 millimètres. Avec de telles dimensions, la ligne coaxiale a une impédance caractéristique de 96 ohms. La valeur de l'impédance caractéristique de la ligne coaxiale détermine en partie la valeur du couplage entre la ligne coaxiale et le guide d'ondes; et détermine le facteur de surtension du résonateur, autrement dit détermine l'atténuation et la largeur de la bande atténuée. L'impédance caractéristique de la ligne coaxiale est donnée par la formule :
Zc = 138. log b a

Figure imgb0001
On the first line, as on the second line, two successive resonators are spaced by a half wavelength λ 'from the center frequency of a frequency band to be passed. The resonators located on the first line are offset by a quarter of a wavelength relative to the resonators located on the second line. Screw 24 is located midway between screws 21 and 22. Screw 25 is located midway between screws 22 and 23. This arrangement of the resonators provides a transfer function with very low attenuation for the frequencies to be left pass; and an attenuation transfer function proportional to the number of resonators, for the frequencies to be eliminated. In this example, the screws 21 to 25 have a diameter of 3 millimeters which is reduced to 0.63 millimeters in the part 17 constituting the inner conductor of the coaxial line. This part 17 has a length of 5.05 millimeters. With such dimensions, the coaxial line has a characteristic impedance of 96 ohms. The value of the characteristic impedance of the coaxial line partly determines the value of the coupling between the coaxial line and the waveguide; and determines the overvoltage factor of the resonator, in other words determines the attenuation and the width of the attenuated band. The characteristic impedance of the coaxial line is given by the formula:
Zc = 138. log b at
Figure imgb0001

où b est le diamètre interne du conducteur extérieur de la ligne coaxiale et où a est le diamètre du conducteur intérieur. Pour obtenir un couplage plus fort ou un coéfficient de surtension maximal, l'impédance caractérisque de la ligne coaxiale peut être comprise entre 60 et 100 Ωwhere b is the internal diameter of the outer conductor of the coaxial line and where a is the diameter of the inner conductor. To obtain a stronger coupling or a maximum overvoltage coefficient, the characteristic impedance of the coaxial line can be between 60 and 100 Ω

La figure 6 représente le graphe G de l'atténuation et le graphe R du taux d'ondes stationnaires pour l'exemple de réalisation représenté sur la figure 5, utilisé pour éliminer la bande de fréquences BA, de 14 à 14,5 GHz, et pour laisser passer la bande de fréquences BP de 10,7 à 12,75 GHz. Il apparaît que l'atténuation de la bande de 14 à 14,5 GHz est supérieure à 20 dB et que le taux d'ondes stationnaires dans la bande de 10,7 à 12,75 Ghz, exprimé en valeur absolue, est inférieur à 1,15, alors que les pertes d'insertion sont inférieures à 0,2 dB. Ces chiffres sont à comparer aux performances d'un filtre classique constitué de cinq cavités couplées à un guide d'ondes par des iris. Un filtre classique procure une atténuation, de la bande à éliminer, supérieure à 50 dB, et un taux d'ondes stationnaires, dans la bande passante, inférieur à 1,05; avec des pertes d'insertion inférieures à 0,05 dB. Pour un même nombre de résonateurs, le filtre selon l'invention a donc des performances plus modestes, mais par contre le prix de la réalisa tion est environ 3 à 4 fois plus petit, et l'encombrement est beaucoup diminué.FIG. 6 represents the graph G of the attenuation and the graph R of the standing wave rate for the exemplary embodiment represented in FIG. 5, used to eliminate the frequency band BA, from 14 to 14.5 GHz, and to pass the BP frequency band from 10.7 to 12.75 GHz. It appears that the attenuation of the band from 14 to 14.5 GHz is more than 20 dB and that the standing wave rate in the band from 10.7 to 12.75 GHz, expressed in absolute value, is less than 1.15, while the insertion losses are less than 0.2 dB. These figures are to be compared with the performance of a conventional filter made up of five cavities coupled to a waveguide by irises. A conventional filter provides attenuation, of the band to be eliminated, greater than 50 dB, and a standing wave rate, in the passband, of less than 1.05; with insertion losses of less than 0.05 dB. For the same number of resonators, the filter according to the invention therefore has more modest performance, but on the other hand the price of the realization tion is about 3 to 4 times smaller, and the size is much reduced.

L'invention ne se limite pas aux exemples décrits ci-dessus. De nombreuses variantes sont à la portée de l'homme de l'art, en ce qui concerne la réalisation de la ligne coaxiale constituant le résonateur et en ce qui concerne son intégration à un guide d'ondes d'un dispositif d'émission-réception par micro-ondes.The invention is not limited to the examples described above. Many variants are within the reach of those skilled in the art, as regards the production of the coaxial line constituting the resonator and as regards its integration into a waveguide of an emission device. microwave reception.

Les figure 7 et 8 représentent un troisième exemple de réalisation d'un filtre selon l'invention. Cet exemple comporte un seul résonateur constitué essentiellement par une douille 32 vissée dans un trou fileté 39 qui est percé dans la plus grande paroi d'un guide 31 à section rectangulaire. La figure 8 représente la douille 32 vue en coupe. L'axe de symétrie ZZ' de la douille 32 est situé dans le plan de symétrie du guide 31. La surface extérieure de la douille 32 comporte un filetage 35 sur toute sa longueur. A l'extrémité, de la douille 32, située à l'extérieur du guide 31, une fente 34 permet de visser ou de dévisser la douille 32 dans le trou 39. Un écrou 38 vissé sur la douille 32, permet d'immobiliser la douille 32 après avoir réglé sa position pour obtenir l'accord sur la fréquence centrale de la bande de fréquences à éliminer.Figures 7 and 8 show a third embodiment of a filter according to the invention. This example comprises a single resonator essentially constituted by a socket 32 screwed into a threaded hole 39 which is drilled in the largest wall of a guide 31 with rectangular section. Figure 8 shows the socket 32 seen in section. The axis of symmetry ZZ 'of the sleeve 32 is located in the plane of symmetry of the guide 31. The outer surface of the sleeve 32 has a thread 35 over its entire length. At the end of the socket 32, located outside the guide 31, a slot 34 makes it possible to screw or unscrew the socket 32 in the hole 39. A nut 38 screwed onto the socket 32 makes it possible to immobilize the socket 32 after having adjusted its position to obtain agreement on the central frequency of the frequency band to be eliminated.

La douille 32 est creuse. Son intérieur a une surface cylindrique lisse 36 et il contient une tige 37 ayant une forme cylindrique dont l'axe de symétrie de révolution est confondu avec l'axe de symétrie de révolution ZZ' de la douille 32. Le diamètre de la tige 37 est inférieur au diamètre intérieur de la douille 32, et sa longueur est égale à un nombre impair de quarts de la longueur d'onde correspondant à la fréquence centrale de la bande à éliminer. Dans cet exemple, la longueur de la tige 37 est égale à un quart de longueur d'onde. La longueur de la tige 37 est supérieure à la profondeur de la douille 32 de telle sorte que la tige 37 dépasse à l'embouchure de la douille.The socket 32 is hollow. Its interior has a smooth cylindrical surface 36 and it contains a rod 37 having a cylindrical shape whose axis of symmetry of revolution coincides with the axis of symmetry of revolution ZZ 'of the sleeve 32. The diameter of the rod 37 is less than the inside diameter of the socket 32, and its length is equal to an odd number of quarters of the wavelength corresponding to the central frequency of the band to be eliminated. In this example, the length of the rod 37 is equal to a quarter of a wavelength. The length of the rod 37 is greater than the depth of the sleeve 32 so that the rod 37 protrudes at the mouth of the sleeve.

Lorsque la douille 32 est mise en place dans le trou fileté 39, l'intérieur de la douille et une partie libre du trou fileté 39 constituent le conducteur extérieur d'une ligne coaxiale; alors que la tige 37 constitue un conducteur intérieur de cette ligne et que l'extrémité de la tige 37 constitue un plongeur pénétrant dans le guide d'ondes 31 pour constituer une susceptance capacitive reliée à l'extrémité de la ligne coaxiale. Le fond 33 de la douille 32 a une surface plane, orthogonale à l'axe de symétrie ZZ', et constitue un court-circuit à l'autre extrémité de ligne coaxiale. La longueur de la douille 32 est inférieure à un quart de longueur d'onde de telle sorte que la douille ne dépasse pas à l'intérieur du guide 31, et qu'une partie du trou fileté 39 n'est pas occupée par la douille 32 et constitue une partie de la ligne coaxiale.When the socket 32 is placed in the threaded hole 39, the interior of the socket and a free part of the threaded hole 39 constitute the outer conductor of a coaxial line; while the rod 37 constitutes an inner conductor of this line and that the end of the rod 37 constitutes a plunger penetrating into the waveguide 31 to constitute a capacitive susceptance connected to the end of the coaxial line. The bottom 33 of the socket 32 has a flat surface, orthogonal to the axis of symmetry ZZ ', and constitutes a short circuit at the other end of the coaxial line. The length of the socket 32 is less than a quarter of a wavelength so that the socket does not protrude inside the guide 31, and that part of the threaded hole 39 is not occupied by the socket 32 and forms part of the coaxial line.

Comme il apparaît en comparant les figures 3 et 7, le troisième exemple de réalisation permet d'utiliser un tronçon de guide 31 ayant une paroi d'épaisseur inférieure à la longueur de la ligne coaxiale à réaliser, alors que le premier exemple de réalisation nécessite un guide d'ondes ayant une épaisseur de paroi supérieure à la longueur de la ligne coaxiale à réaliser.As it appears by comparing Figures 3 and 7, the third embodiment allows the use of a guide section 31 having a wall of thickness less than the length of the coaxial line to be produced, while the first embodiment requires a waveguide having a wall thickness greater than the length of the coaxial line to be produced.

La figure 9 représente un quatrième exemple de réalisation d'un filtre selon l'invention, comportant un résonateur 42 constitué par une douille, analogue à la douille 32 décrite décrite précédemment, vissée dans un trou fileté 43 qui est percé dans la paroi d'un guide d'ondes 41 à section circulaire. Le conducteur 44 de la ligne coaxiale court-circuitée a son grand axe qui passe par le centre du guide et qui est parallèle au champ électrique E des ondes à éliminer.FIG. 9 represents a fourth embodiment of a filter according to the invention, comprising a resonator 42 constituted by a socket, analogous to the socket 32 described above described, screwed into a threaded hole 43 which is drilled in the wall of a waveguide 41 with circular section. The conductor 44 of the short-circuited coaxial line has its major axis which passes through the center of the guide and which is parallel to the electric field E of the waves to be eliminated.

La figure 10 représente un cinquième exemple de réalisation d'un filtre selon l'invention, qui est combiné à une transition câble coaxial-guide d'ondes. Cette transition comporte un guide d'ondes 49, à section rectangulaire, obturé par une plaque métallique 51; et comporte une antenne 50 plongeant dans le guide 49. L'antenne 50 est reliée au conducteur central d'un câble coaxial 52 par un connecteur coaxial 53. L'antenne 50 passe par un trou 54 percé dans la paroi du guide 49, sur son plus grand côté, et dans son plan de symétrie. Cette transition constitue aussi un filtre éliminateur de bande grâce à une pluralité de résonateurs constituées par des douilles 55 à 57 vissées dans des trous filetés, 58 à 60. Ces douilles 55 à 57 sont analogues à la douille 32 décrite précédemment. L'antenne 50 est placée à une distance égale à un quart de la longueur d'onde λ' correspondant à la fréquence centrale de la bande de fréquences à laisser passer, par rapport à la plaque métallique 51 obturant le guide d'ondes. Le résonnateur le plus proche, 55, est placé à une distance au moins égale à la longueur d'onde λ' correspondant à la fréquence centrale de la bande à laisser passer, par rapport à l'antenne 50. Les autres résonateurs sont situés à intervalles réguliers, égaux à des multiples impairs du quart de la longueur d'onde λ' correspondant à la fréquence centrale de la bande à laisser passer. Par exemple, les intervalles sont tous égaux à un quart de longueur d'onde.FIG. 10 represents a fifth embodiment of a filter according to the invention, which is combined with a transition from coaxial cable to waveguide. This transition comprises a waveguide 49, of rectangular section, closed by a metal plate 51; and comprises an antenna 50 immersed in the guide 49. The antenna 50 is connected to the central conductor of a coaxial cable 52 by a coaxial connector 53. The antenna 50 passes through a hole 54 drilled in the wall of the guide 49, on its largest side, and in its plane of symmetry. This transition also constitutes a band eliminator filter thanks to a plurality of resonators constituted by sockets 55 to 57 screwed into threaded holes, 58 to 60. These sockets 55 to 57 are similar to the socket 32 described. previously. The antenna 50 is placed at a distance equal to a quarter of the wavelength λ 'corresponding to the central frequency of the frequency band to be passed, relative to the metal plate 51 closing the waveguide. The nearest resonator, 55, is placed at a distance at least equal to the wavelength λ 'corresponding to the central frequency of the band to be passed, relative to the antenna 50. The other resonators are located at regular intervals, equal to odd multiples of a quarter of the wavelength λ 'corresponding to the center frequency of the band to be passed. For example, the intervals are all equal to a quarter of a wavelength.

Claims (5)

Filtre éliminateur de bande pour guide d'ondes hyperfréquences, comportant : - un guide d'ondes (11); - au moins une ligne coaxiale court-circuitée comportant un conducteur intérieur (17) et un conducteur extérieur (19) coaxiaux; le conducteur intérieur (17) ayant une longueur égale à un multiple impair du quart de la longueur d'onde correspondant à la fréquence centrale d'une bande de fréquences à éliminer, et plongeant dans le guide d'ondes (11) pour être couplé au champ électrique (E); et le conducteur extérieur (19) ayant une longueur inférieure au dit multiple;
caractérisé en ce que le conducteur extérieur est constitué, au moins en partie, par un trou cylindrique fileté (19) percé dans une paroi du guide d'ondes (11), et dont la longueur électrique est ajustable par un court-circuit (16; 33) vissable dans ledit trou fileté.Band eliminator filter for microwave waveguides, comprising: - a waveguide (11); - at least one short-circuited coaxial line comprising an inner conductor (17) and an outer conductor (19) coaxial; the inner conductor (17) having a length equal to an odd multiple of a quarter of the wavelength corresponding to the center frequency of a frequency band to be eliminated, and plunging into the waveguide (11) to be coupled to the electric field (E); and the outer conductor (19) having a length less than said multiple;
characterized in that the external conductor is constituted, at least in part, by a threaded cylindrical hole (19) drilled in a wall of the waveguide (11), the electrical length of which is adjustable by a short circuit (16 ; 33) screwable into said threaded hole. Filtre selon la revendication 1, caractérisé en ce que le conducteur intérieur de la ligne coaxiale court-circuitée comporte une vis (12) en métal, vissée dans le trou fileté (19) et comportant un prolongement cylindrique (17) ayant le même axe de symétrie de révolution que la vis (12) mais de diamètre plus réduit; la vis (12) constituant un court-circuit à l'extrémité de la ligne coaxiale.Filter according to claim 1, characterized in that the inner conductor of the short-circuited coaxial line comprises a metal screw (12), screwed into the threaded hole (19) and comprising a cylindrical extension (17) having the same axis of symmetry of revolution than the screw (12) but of smaller diameter; the screw (12) constituting a short circuit at the end of the coaxial line. Filtre selon la revendication 1, caractérisé en ce que la ligne coaxiale court-circuitée comporte une douille cylindrique (32) filetée extérieurement, lisse intérieurement, obturée à une extrémité par un plan conducteur (33) constituant un court-circuit pour la ligne coaxiale; ce plan conducteur (33) portant un conducteur cylindrique coaxial (37) constituant le conducteur intérieur; cette douille étant vissée dans le trou fileté (39).Filter according to claim 1, characterized in that the short-circuited coaxial line comprises a cylindrical sleeve (32) externally threaded, internally smooth, closed at one end by a conducting plane (33) constituting a short-circuit for the coaxial line; this conductive plane (33) carrying a coaxial cylindrical conductor (37) constituting the inner conductor; this socket being screwed into the threaded hole (39). Filtre selon la revendication 1, caractérisé en ce qu'il comporte une pluralité de lignes coaxiales court-circuitées (55 à 57), identiques, alignées et espacées d'un nombre impair de quarts de la longueur d'onde correspondant à la fréquence centrale d'une bande de fréquences à laisser passer.Filter according to claim 1, characterized in that it comprises a plurality of short-circuited coaxial lines (55 to 57), identical, aligned and spaced by an odd number of quarters of the wavelength corresponding to the central frequency of a frequency band to pass. Filtre selon la revendication 1, caractérisé en ce qu'il comporte en outre une pluralité de premières lignes coaxiales court-circuitées (21 à 23), identiques, alignées et espacées d'un nombre impair de demi-longueurs d'onde correspondant à la fréquence centrale d'une bande de fréquences à laisser passer; et une pluralité de secondes lignes coaxiales court-circuitées (24 à 25), identiques, alignées et espacées d'un nombre impair de demi-longueurs d'onde correspondant à la fréquence centrale d'une bande de fréquences à laisser passer; les premières et les secondes lignes coaxiales étant disposées de part et d'autre de l'axe de symétrie (XX') du guide d'ondes (27).Filter according to claim 1, characterized in that it further comprises a plurality of first short-circuited coaxial lines (21 to 23), identical, aligned and spaced by an odd number of half-wavelengths corresponding to the central frequency of a frequency band at Give Way; and a plurality of second short-circuited coaxial lines (24 to 25), identical, aligned and spaced by an odd number of half-wavelengths corresponding to the center frequency of a frequency band to be passed; the first and second coaxial lines being arranged on either side of the axis of symmetry (XX ') of the waveguide (27).
EP90122545A 1989-11-30 1990-11-26 Band elimination filter for microwave waveguide Ceased EP0430136A1 (en)

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FR8915805A FR2655199B1 (en) 1989-11-30 1989-11-30 BAND ELIMINATOR FILTER FOR MICROWAVE WAVEGUIDE.

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IL96466A (en) 1994-01-25
FR2655199B1 (en) 1992-10-02
JPH03195102A (en) 1991-08-26
FR2655199A1 (en) 1991-05-31
US5105174A (en) 1992-04-14
CA2031076A1 (en) 1991-05-31
TR24998A (en) 1992-09-01

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