EP0520919B1 - Filtering device for electromagnetic waves in a waveguide with symmetry around the rotational axis, and inserted pieces of rectangular waveguide - Google Patents

Filtering device for electromagnetic waves in a waveguide with symmetry around the rotational axis, and inserted pieces of rectangular waveguide Download PDF

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Publication number
EP0520919B1
EP0520919B1 EP92460018A EP92460018A EP0520919B1 EP 0520919 B1 EP0520919 B1 EP 0520919B1 EP 92460018 A EP92460018 A EP 92460018A EP 92460018 A EP92460018 A EP 92460018A EP 0520919 B1 EP0520919 B1 EP 0520919B1
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EP
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Prior art keywords
filtering
waveguide
rectangular
sections
circular
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EP92460018A
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German (de)
French (fr)
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EP0520919A1 (en
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Christian Sabatier
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Orange SA
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France Telecom SA
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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
    • H01P1/213—Frequency-selective devices, e.g. filters combining or separating two or more different frequencies
    • H01P1/2131—Frequency-selective devices, e.g. filters combining or separating two or more different frequencies with combining or separating polarisations
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01P—WAVEGUIDES; RESONATORS, LINES, OR OTHER DEVICES OF THE WAVEGUIDE TYPE
    • H01P1/00—Auxiliary devices
    • H01P1/16—Auxiliary devices for mode selection, e.g. mode suppression or mode promotion; for mode conversion
    • H01P1/161—Auxiliary devices for mode selection, e.g. mode suppression or mode promotion; for mode conversion sustaining two independent orthogonal modes, e.g. orthomode transducer
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01P—WAVEGUIDES; RESONATORS, LINES, OR OTHER DEVICES OF THE WAVEGUIDE TYPE
    • H01P1/00—Auxiliary devices
    • H01P1/165—Auxiliary devices for rotating the plane of polarisation
    • H01P1/17—Auxiliary devices for rotating the plane of polarisation for producing a continuously rotating polarisation, e.g. circular polarisation

Definitions

  • the field of the invention is that of filtering in the electromagnetic waveguides. More specifically, the invention relates to a device for filtering waves circulating in waveguides with symmetry of revolution, such as the circular waveguides or the coaxial waveguides used in TE 11 mode.
  • the invention applies in particular to dual-band filtering.
  • An important use of this invention is in fact the production of bi-band and bi-polarization duplexers, especially when the accesses of the duplexers are in the same standard of rectangular guide. This is for example the case of the bands 10.95-12.5 GHz and 14-14.5 GHz in WR 75. In general, the horizontal and vertical polarizations of these duplexers are not identical in the two frequency bands considered.
  • FIG. 1 is a schematic representation of such a duplexer, of known type.
  • the high band 11 for example 14-14.5 GHz
  • low band 12 for example 10.95-12.5 GHz
  • the outlet 13 towards the radiating element is in circular waveguide.
  • the excitation is done by coupling using a slot in the duplexer 14, between the rectangular guide and the circular guide.
  • a slot in the duplexer 14 In order for the wave to propagate towards the radiating element and not towards the high band access II as a rectangular guide, it is necessary to place a rectangular to circular transition 15 and a polarization filter 16 between the access high band 11 and duplexer 14.
  • FIG. 2 shows a metal blade filter 21, and FIG. 3 a filter with metallic wires 31, 32, 33.
  • a 1 degree error in the positioning of this blade 21 or these wires 31, 32, 33 causes a decoupling (transmission of the electromagnetic wave from access 11 to access 12) maximum of 35 dB, which is generally insufficient.
  • the production of these devices therefore requires great precision in the placement and fixing of the blade 21 or of the wires 31, 32, 33 inside the circular guide 22.
  • the manufacture of such filters requires several steps successive and delicate.
  • document DE-A-3 326 829 describes a band-pass filter produced using rectangular cavities coupled together by circular openings also called iris. Filtering is done as a function of frequency, the bandwidth being fixed using the lengths of the different rectangular cavities.
  • This document DE'829 is very far from the invention since it relates to frequency filtering and not to polarization filtering.
  • the main guide described in this document is rectangular and not with symmetry of revolution, since the irises, whether thick or not, cannot behave like portions of circular waveguide.
  • Document GB-582,856 describes a transmitter (or receiver) consisting of a circular waveguide portion closed at one end, a probe fixed to the circular guide portion, and a guide portion rectangular wave, placed in the extension of the circular guide portion, at its unclosed end.
  • This document is also very far from the invention. Indeed, it describes a transmitter (or receiver) and not a filter. Furthermore, the structures of this transmitter are very different from those of the filter of the invention.
  • this transmitter comprises a probe whereas the filter of the invention does not require such an element; the circular guide portion of this transmitter is closed at one of its ends, whereas in the invention it is a circular main guide open at its two ends; the rectangular guide portion of this transmitter is placed in the extension of the circular guide portion, so as to be able to emit or receive waves, while the rectangular guide section of the filter of the invention is inserted in substitution in the guide main circular).
  • Document GB-2 166 297 describes an antenna excitation device operating on two distinct frequency bands, comprising two polarization duplexers. This document is very far from the invention. Indeed, the duplexers described do not include any polarization filtering element.
  • the invention particularly aims to overcome the drawbacks of polarization filters according to the prior art.
  • an objective of the invention is to provide a polarization filtering device for waveguides with symmetry of revolution which is easily achievable, from the mechanical point of view, and in particular a filtering device which does not require the postponement of elements inside the waveguide.
  • Another objective of the invention is to provide such a filtering device providing satisfactory decoupling, of at least 40 to 45 dB.
  • a particular objective of the invention is to provide such a filtering device allowing the total reflection of one polarization, and the total transmission of the other polarization, in a given frequency band.
  • the invention also has the additional objective of providing such a device, making it possible to pass from a linear polarization to a circular polarization.
  • These rectangular waveguide sections introduce an asymmetry into the main waveguide. According to their geometrical characteristics, their number and their spacing, they allow for example to obtain a filter having a coefficient of reflection close to 1 for one of the polarizations, and a reflection coefficient close to 0 for the other polarization, in a given frequency band. For other dimensions, it is also possible that there is no longer any overlap between the filtered band and the bandwidth of the filter.
  • each section is abrupt (that is to say, it consists of a wall substantially perpendicular to the axis of symmetry of the main guide). No particular element of progressive transition, or of adaptation, is necessary between the main waveguide and the filtering sections. These abrupt transitions are of course closed by a metallic conductor on the part of the transition where the two sections of the rectangular and circular guides do not coincide (otherwise, the waves would no longer be guided).
  • said main waveguide element is of the type of circular waveguides or of the type of coaxial waveguides in TE 11 mode.
  • the width of said sections of rectangular waveguides is greater than or equal to the diameter of said main waveguide element.
  • said main waveguide element and said sections of rectangular guides are centered on said axis of symmetry.
  • the device of the invention comprises a set of at least two sections of rectangular waveguide inserted at spaced locations in said main waveguide element.
  • the invention therefore relates in particular to a filtering device, produced by inserting rectangular sections of waveguides introducing asymmetry into a main waveguide with symmetry of revolution.
  • the main waveguide is a circular waveguide.
  • the invention can be easily generalized to other types of waveguides.
  • the main waveguide can also be, for example, a coaxial waveguide in mode T 11 .
  • elements of guides of known type said to be of symmetry of revolution, provided that their symmetry is eliminated, for example by placing a dielectric strip along one of the polarizations.
  • FIG. 4 illustrates, in a schematic perspective representation, a filter element according to the invention.
  • the circular main waveguide is separated into two parts 41 A and 41 B , between which a rectangular waveguide section 42 is inserted.
  • FIGS. 6A and 6B By combining several elements as shown in this FIG. 4, it is possible to produce a precise and effective filter, as illustrated in FIGS. 6A and 6B presented below.
  • the main waveguide 41 A , 41 B is connected to the rectangular section 42 by walls 44 A and 44 B which close the part of the transition on which the sections of the circular and rectangular guides do not coincide.
  • the walls 44 A and 44 B must be steep. In other words, the walls 44 A and 44 B are substantially perpendicular to the axis of symmetry 45 of the main waveguide 41 A , 41 B. No transition element is inserted. These walls 44 A and 44 B are metallic. They cannot of course be completely open (presence of air) or made of a dielectric. Otherwise, the wave could escape and would no longer be guided.
  • the circular guide 41 A is placed in the center of the rectangular guide 42, and the common section 43 of the two waveguides is circular.
  • the height of the rectangular guide 42 is therefore at least equal to the diameter of the circular guide 41 A.
  • all of the sections 41 A , 42, 41 B are centered on the same longitudinal axis, namely the axis of symmetry 45. In other applications, however, provision may be made for these sections are shifted.
  • the geometry of the rectangular guide section (height, width and thickness), as well as the number of sections and the spacing between these sections, depend on the characteristics desired for the filter. These various parameters can for example be determined according to the modal method.
  • the bandwidth can therefore be high (for example of the order of 10%).
  • the invention finds a preferred application in dual-band and bi-polarization duplexers such as that shown schematically in FIG. 1.
  • the polarization filter 16 must completely transmit the one of the polarizations, and reflect the other polarization.
  • the numerical example described below relates to such a filter, for the frequency band 12-13 GHz.
  • the polarization of the wave propagating in the circular guide can be placed along the diagonal of the rectangular guide.
  • the device of the invention can find many other applications, both in the field of filtering and in that of polarization.
  • FIG. 5 therefore presents the dimensions of a filter, the performance of which is illustrated by FIGS. 6A and 6B.
  • This filter consists of four sections of rectangular waveguides 51 A to 51 D , inserted in the circular waveguide 52.
  • the excitations are in TE 11 mode in the circular waveguide 52.
  • this embodiment does not correspond to an optimized filter, but aims to allow the validation of a software calculation, as shown in FIGS. 6A and 6B.
  • FIG. 6A indeed shows the curve 61 A of the reflection coefficient of the filtering device of FIG. 5, when the polarization in TE mode 11 in circular guide is perpendicular to the short side of the rectangular sections 51 A to 51 D.
  • the TE 11 mode is completely transmitted on the 12-13 GHz frequency band, the reflection coefficient being close to 0.
  • the objective of this filter given as an example is to provide a filtering result closest to that theoretically fixed by calculation for a given application, represented by a series 61 A of + signs.
  • the curve 62 A of measured reflection shows that it is possible, with the device of the invention, to conform the filtering characteristics so precise. It can be seen that the curve 62 A is very close to the desired results 61 A.
  • FIG. 6B shows the reflection coefficient of the same device, when the polarization of the TE 11 mode in a circular guide is parallel to the short side of the rectangular sections 51 A to 51 D. TE 11 mode is then fully reflected for the 12-13 GHz frequency band. Indeed, the reflection coefficient close to 1, and the transmission is therefore zero.
  • the invention is of course not limited to the embodiment described above. It is in fact possible, for example, to produce filters using rectangular sections of different geometries. These different sections can then be joined or not, and separated by spaces of fixed or variable sizes.
  • the device of the invention can also be used for filtering a frequency band in a circular guide in TE 11 mode, in the case of a rectilinear polarization.
  • Another application of the device of the invention is also the production of polarizers to transform a linear polarization into circular polarization.
  • a polarizer is a device which makes it possible to pass from a linear polarization to a circular polarization.
  • the linear polarization must be parallel to a diagonal of the rectangular guide.
  • a circular polarization is then obtained, the waves polarized horizontally and vertically not having the same phase speed in the rectangular guide.
  • a complete polarizer can be produced by combining several elements according to the invention or by combining them with other elements already known.

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Description

Le domaine de l'invention est celui du filtrage dans les guides d'ondes électromagnétiques. Plus précisément, l'invention concerne un dispositif de filtrage d'ondes circulant dans des guides d'ondes à symétrie de révolution, tels que les guides d'ondes circulaires ou les guides d'ondes coaxiaux utilisés en mode TE11.The field of the invention is that of filtering in the electromagnetic waveguides. More specifically, the invention relates to a device for filtering waves circulating in waveguides with symmetry of revolution, such as the circular waveguides or the coaxial waveguides used in TE 11 mode.

L'invention s'applique en particulier au filtrage bi-bandes. Une utilisation importante de cette invention est en effet la réalisation de duplexeurs bi-bandes et bi-polarisations, notamment lorsque les accès des duplexeurs sont dans le même standard de guide rectangulaire. C'est par exemple le cas des bandes 10,95-12,5 GHz et 14-14,5 GHz en WR 75. En règle générale, les polarisations horizontales et verticales de ces duplexeurs ne sont pas identiques dans les deux bandes de fréquence considérées.The invention applies in particular to dual-band filtering. An important use of this invention is in fact the production of bi-band and bi-polarization duplexers, especially when the accesses of the duplexers are in the same standard of rectangular guide. This is for example the case of the bands 10.95-12.5 GHz and 14-14.5 GHz in WR 75. In general, the horizontal and vertical polarizations of these duplexers are not identical in the two frequency bands considered.

La figure 1 est la représentation schématique d'un tel duplexeur, de type connu. Les accès bande haute 11 (par exemple 14-14,5 GHz) et bande basse 12 (par exemple 10,95-12,5 GHz) sont en guides d'ondes rectangulaires. La sortie 13 vers l'élément rayonnant est en guide d'ondes circulaire.Figure 1 is a schematic representation of such a duplexer, of known type. The high band 11 (for example 14-14.5 GHz) and low band 12 (for example 10.95-12.5 GHz) accesses are in rectangular waveguides. The outlet 13 towards the radiating element is in circular waveguide.

Pour la bande basse 12, l'excitation se fait par couplage à l'aide d'une fente dans le duplexeur 14, entre le guide rectangulaire et le guide circulaire. Pour qu'il y ait propagation de l'onde vers l'élément rayonnant et non vers l'accès bande haute Il en guide rectangulaire, il est nécessaire de placer une transition rectangulaire à circulaire 15 et un filtre de polarisation 16 entre l'accès bande haute 11 et le duplexeur 14.For the low band 12, the excitation is done by coupling using a slot in the duplexer 14, between the rectangular guide and the circular guide. In order for the wave to propagate towards the radiating element and not towards the high band access II as a rectangular guide, it is necessary to place a rectangular to circular transition 15 and a polarization filter 16 between the access high band 11 and duplexer 14.

On connaît déjà plusieurs types de filtres de polarisation, tels que ceux représentés en figures 2 et 3. La figure 2 présente un filtre à lame métallique 21, et la figure 3 un filtre à fils métalliques 31, 32, 33. Ces éléments métalliques 21 ou 31, 32 et 33, sélectivement placés dans le guide d'ondes 22, permettent d'éliminer une polarisation donc une bande de fréquence donnée.Several types of polarization filters are already known, such as those represented in FIGS. 2 and 3. FIG. 2 shows a metal blade filter 21, and FIG. 3 a filter with metallic wires 31, 32, 33. These metallic elements 21 or 31, 32 and 33, selectively placed in the waveguide 22, make it possible to eliminate a polarization, therefore a given frequency band.

Une erreur de 1 degré dans le positionnement de cette lame 21 ou de ces fils 31, 32, 33 entraîne un découplage (transmission de l'onde électromagnétique de l'accès 11 à l'accès 12) maximum de 35 dB, ce qui est en règle générale insuffisant. Mécaniquement, la réalisation de ces dispositifs demande donc une grande précision dans le placement et la fixation de la lame 21 ou des fils 31, 32, 33 à l'intérieur du guide circulaire 22. Par ailleurs, la fabrication de tels filtres nécessitent plusieurs étapes successives et délicates.A 1 degree error in the positioning of this blade 21 or these wires 31, 32, 33 causes a decoupling (transmission of the electromagnetic wave from access 11 to access 12) maximum of 35 dB, which is generally insufficient. Mechanically, the production of these devices therefore requires great precision in the placement and fixing of the blade 21 or of the wires 31, 32, 33 inside the circular guide 22. Furthermore, the manufacture of such filters requires several steps successive and delicate.

On connaît également, dans l'état de la technique, d'autres types de filtre d'ondes électromagnétiques. Toutefois, ces autres types de filtres n'assurent pas, contrairement au filtre de l'invention, un filtrage de polarisation d'ondes électromagnétiques circulant dans un élément de guide d'ondes principal à symétrie de révolution.Other types of electromagnetic wave filter are also known in the state of the art. However, unlike the filter of the invention, these other types of filters do not provide polarization filtering of electromagnetic waves circulating in a main waveguide element with symmetry of revolution.

Ainsi, le document DE-A-3 326 829 décrit un filtre passe-bande réalisé à l'aide de cavités rectangulaires couplées entre elles par des ouvertures circulaires appelées aussi iris. Le filtrage se fait en fonction de la fréquence, la bande-passante étant fixée à l'aide des longueurs des différentes cavités rectangulaires. Ce document DE'829 est très éloigné de l'invention puisqu'il concerne un filtrage de fréquence et non pas un filtrage de polarisation. Par ailleurs, le guide principal décrit dans ce document est rectangulaire et non pas à symétrie de révolution, puisque les iris, qu'ils soient épais ou non, ne peuvent pas se comporter comme des portions de guide d'ondes circulaires.Thus, document DE-A-3 326 829 describes a band-pass filter produced using rectangular cavities coupled together by circular openings also called iris. Filtering is done as a function of frequency, the bandwidth being fixed using the lengths of the different rectangular cavities. This document DE'829 is very far from the invention since it relates to frequency filtering and not to polarization filtering. Furthermore, the main guide described in this document is rectangular and not with symmetry of revolution, since the irises, whether thick or not, cannot behave like portions of circular waveguide.

Le document "Microwave filters, impedance-matching networks and coupling structures" (Matthaei et al.) décrit un filtre basé sur l'association de tronçons de guide d'ondes ayant tous la même fréquence de coupure (homogène) et la même longueur (égale à une demi-longueur d'ondes). Ce document est également très éloigné de l'invention. En effet, le filtre de l'invention n'est pas un cas particulier du filtre décrit dans ce document, et ce document ne divulgue ni ne suggère en aucun cas les caractéristiques de l'invention.The document "Microwave filters, impedance-matching networks and coupling structures" (Matthaei et al.) Describes a filter based on the association of waveguide sections all having the same (homogeneous) cutoff frequency and the same length ( equal to half a wavelength). This document is also very far from the invention. Indeed, the filter of the invention is not a particular case of the filter described in this document, and this document does not disclose or in any way suggest the characteristics of the invention.

Le document GB-582 856 décrit un émetteur (ou récepteur) constitué d'une portion de guide d'ondes circulaire fermée à une extrémité, d'une sonde fixée sur la portion de guide circulaire, et d'une portion de guide d'ondes rectangulaire, placé dans le prolongement de la portion de guide circulaire, à son extrémité non fermée. Ce document est lui aussi très éloigné de l'invention. En effet, il décrit un émetteur (ou récepteur) et non pas un filtre. Par ailleurs, les structures de cet émetteur sont très différentes de celles du filtre de l'invention. Notamment, cet émetteur comprend une sonde alors que le filtre de l'invention ne nécessite pas un tel élément ; la portion de guide circulaire de cet émetteur est fermée à une de ses extrémités, alors que dans l'invention il s'agit d'un guide principal circulaire ouvert à ses deux extrémités ; la portion de guide rectangulaire de cet émetteur est placé dans le prolongement de la portion de guide circulaire, de façon à pouvoir émettre ou recevoir des ondes, alors que le tronçon de guide rectangulaire du filtre de l'invention est inséré en substitution dans le guide principal circulaire).Document GB-582,856 describes a transmitter (or receiver) consisting of a circular waveguide portion closed at one end, a probe fixed to the circular guide portion, and a guide portion rectangular wave, placed in the extension of the circular guide portion, at its unclosed end. This document is also very far from the invention. Indeed, it describes a transmitter (or receiver) and not a filter. Furthermore, the structures of this transmitter are very different from those of the filter of the invention. In particular, this transmitter comprises a probe whereas the filter of the invention does not require such an element; the circular guide portion of this transmitter is closed at one of its ends, whereas in the invention it is a circular main guide open at its two ends; the rectangular guide portion of this transmitter is placed in the extension of the circular guide portion, so as to be able to emit or receive waves, while the rectangular guide section of the filter of the invention is inserted in substitution in the guide main circular).

Le document GB-2 166 297 décrit un dispositif d'excitation d'antenne fonctionnant sur deux bandes de fréquence distincte, comprenant deux duplexeurs de polarisation. Ce document est très éloigné de l'invention. En effet, les duplexeurs décrits ne comprennent aucun élément de filtrage de polarisation.Document GB-2 166 297 describes an antenna excitation device operating on two distinct frequency bands, comprising two polarization duplexers. This document is very far from the invention. Indeed, the duplexers described do not include any polarization filtering element.

L'invention a notamment pour objectif de pallier les inconvénients des filtres de polarisation selon l'art antérieur.The invention particularly aims to overcome the drawbacks of polarization filters according to the prior art.

Plus précisément, un objectif de l'invention est de fournir un dispositif de filtrage de polarisation pour guides d'ondes à symétrie de révolution qui soit aisément réalisable, du point de vue mécanique, et notamment un dispositif de filtrage ne nécessitant pas le report d'éléments à l'intérieur du guide d'ondes.More specifically, an objective of the invention is to provide a polarization filtering device for waveguides with symmetry of revolution which is easily achievable, from the mechanical point of view, and in particular a filtering device which does not require the postponement of elements inside the waveguide.

Un autre objectif de l'invention est de fournir un tel dispositif de filtrage fournissant un découplage satisfaisant, d'au moins 40 à 45 dB.Another objective of the invention is to provide such a filtering device providing satisfactory decoupling, of at least 40 to 45 dB.

Un objectif particulier de l'invention est de fournir un tel dispositif de filtrage permettant la réflexion totale d'une polarisation, et la transmission totale de l'autre polarisation, dans une bande de fréquence donnée.A particular objective of the invention is to provide such a filtering device allowing the total reflection of one polarization, and the total transmission of the other polarization, in a given frequency band.

L'invention a également pour objectif complémentaire de fournir un tel dispositif, permettant de passer d'une polarisation linéaire à une polarisation circulaire.The invention also has the additional objective of providing such a device, making it possible to pass from a linear polarization to a circular polarization.

Ces objectifs, ainsi que d'autres qui apparaîtront par la suite, sont atteints selon l'invention à l'aide d'un dispositif de filtrage de polarisation selon la revendication 1.These objectives, as well as others which will appear subsequently, are achieved according to the invention using a polarization filtering device according to claim 1.

Ces tronçons de guide d'ondes rectangulaires introduisent une dissymétrie dans le guide d'ondes principal. Selon leurs caractéristiques géométriques, leur nombre et leur espacement, ils permettent par exemple d'obtenir un filtre ayant un coefficient de réflexion proche de 1 pour l'une des polarisations, et un coefficient de réflexion voisin de 0 pour l'autre polarisation, dans une bande de fréquence donnée. Pour d'autres dimensions, il est également possible qu'il n'y ait plus de recoupement entre la bande filtrée et la bande passante du filtre.These rectangular waveguide sections introduce an asymmetry into the main waveguide. According to their geometrical characteristics, their number and their spacing, they allow for example to obtain a filter having a coefficient of reflection close to 1 for one of the polarizations, and a reflection coefficient close to 0 for the other polarization, in a given frequency band. For other dimensions, it is also possible that there is no longer any overlap between the filtered band and the bandwidth of the filter.

La transition entre chaque tronçon est abrupte (c'est-à-dire qu'elle est consitutée d'une paroi sensiblement perpendiculaire à l'axe de symétrie du guide principal). Aucun élément particulier de transition progressive, ou d'adaptation, n'est nécessaire entre le guide d'ondes principal et les tronçons de filtrage. Ces transitions abruptes sont bien sûr fermées par un conducteur métallique sur la partie de la transition où les deux sections des guides rectangulaire et circulaire ne coïncident pas (dans le cas contraire, les ondes ne seraient plus guidées).The transition between each section is abrupt (that is to say, it consists of a wall substantially perpendicular to the axis of symmetry of the main guide). No particular element of progressive transition, or of adaptation, is necessary between the main waveguide and the filtering sections. These abrupt transitions are of course closed by a metallic conductor on the part of the transition where the two sections of the rectangular and circular guides do not coincide (otherwise, the waves would no longer be guided).

Dans un mode de réalisation préférentiel, ledit élément de guide d'ondes principal est du type des guides d'ondes circulaires ou du type des guides d'ondes coaxiaux en mode TE11.In a preferred embodiment, said main waveguide element is of the type of circular waveguides or of the type of coaxial waveguides in TE 11 mode.

De façon préférentielle, la largeur desdits tronçons de guides d'ondes rectangulaires est supérieure ou égale au diamètre dudit élément de guide d'ondes principal.Preferably, the width of said sections of rectangular waveguides is greater than or equal to the diameter of said main waveguide element.

Dans un mode de réalisation avantageux de l'invention, ledit élément de guide d'ondes principal et lesdits tronçons de guides rectangulaires sont centrés sur ledit axe de symétrie.In an advantageous embodiment of the invention, said main waveguide element and said sections of rectangular guides are centered on said axis of symmetry.

Avantageusement, le dispositif de l'invention comprend un jeu d'au moins deux tronçons de guide d'ondes rectangulaires insérés en des emplacements espacés dans ledit élément de guide d'ondes principal.Advantageously, the device of the invention comprises a set of at least two sections of rectangular waveguide inserted at spaced locations in said main waveguide element.

Il apparaît en effet que la qualité du filtrage est fonction du nombre de tronçons rectangulaires mis en oeuvre. On notera par ailleurs qu'il est tout à fait envisageable d'utiliser des tronçons rectangulaires selon l'invention en combinaison avec d'autres éléments de types connus, tels que les filtres à plaque ou fils métalliques.It appears that the quality of the filtering is a function of the number of rectangular sections used. Note also that it is entirely possible to use rectangular sections according to the invention in combination with other elements of known types, such as plate filters or metal wires.

Le dispositif de l'invention peut notamment être utilisé pour l'une au moins des applications suivantes :

  • filtrage d'une bande de fréquence dans un élément de guide d'ondes circulaire en mode TE11 ;
  • filtrage d'une polarisation horizontale ou verticale dans un élément de guide d'ondes circulaire en mode TE11.
L'invention concerne également les duplexeurs mettant en oeuvre un dispositif de filtrage tel que décrit ci-dessus.The device of the invention can in particular be used for at least one of the following applications:
  • filtering of a frequency band in a circular waveguide element in TE 11 mode;
  • filtering of a horizontal or vertical polarization in a circular waveguide element in TE 11 mode.
The invention also relates to the duplexers implementing a filtering device as described above.

D'autres caractéristiques et avantages de l'invention apparaîtront à la lecture suivante d'un mode de réalisation préférentiel de l'invention, donné à titre illustratif et des dessins annexés, dans lesquels :

  • la figure 1 est la représentation schématique d'un duplexeur pouvant mettre en oeuvre un dispositif de filtrage selon l'invention ;
  • les figures 2 et 3 représentent deux types de filtres de polarisation de types connus, respectivement à lame métallique et à fils métalliques reportés à l'intérieur du guide d'ondes, déjà décrits en préambule ;
  • la figure 4 est une représentation schématique d'un élément de filtrage selon l'invention, à tronçon rectangulaire inséré en substitution dans un guide d'ondes principal circulaire ;
  • la figure 5 présente les dimensions du dispositif de filtrage décrit à titre préférentiel, comprenant quatre éléments de filtrage tels que représentés en figure 4;
  • les figures 6A et 6B illustrent les coefficients de réflexion du dispositif de la figure 5 lorsque les polarisations du mode T11 en guide circulaire sont respectivement parallèle et perpendiculaire au petit côté des tronçons de guide rectangulaire.
Other characteristics and advantages of the invention will appear on the following reading of a preferred embodiment of the invention, given by way of illustration and of the appended drawings, in which:
  • Figure 1 is a schematic representation of a duplexer that can implement a filtering device according to the invention;
  • FIGS. 2 and 3 represent two types of polarization filters of known types, respectively with a metal blade and with metallic wires transferred inside the waveguide, already described in the preamble;
  • Figure 4 is a schematic representation of a filter element according to the invention, rectangular section inserted in substitution in a circular main waveguide;
  • Figure 5 shows the dimensions of the filtering device described as preferential, comprising four filter elements as shown in FIG. 4;
  • FIGS. 6A and 6B illustrate the reflection coefficients of the device of FIG. 5 when the polarizations of mode T 11 in circular guide are respectively parallel and perpendicular to the short side of the sections of rectangular guide.

L'invention concerne donc notamment un dispositif de filtrage, réalisé par insertion de tronçons rectangulaires de guides d'ondes introduisant une dissymétrie dans un guide d'ondes principal à symétrie de révolution.The invention therefore relates in particular to a filtering device, produced by inserting rectangular sections of waveguides introducing asymmetry into a main waveguide with symmetry of revolution.

Dans le mode de réalisation décrit ci-dessous en détail, le guide d'ondes principal est un guide d'ondes circulaire.In the embodiment described below in detail, the main waveguide is a circular waveguide.

Il est clair toutefois que l'invention peut être aisément généralisée à d'autres types de guides d'ondes. Ainsi, le guide d'ondes principal peut également être, par exemple, un guide d'ondes coaxial en mode T11. On peut également utiliser conjointement avec des éléments de filtrage rectangulaires selon l'invention des éléments de guides de type connu, dits à symétrie de révolution, à condition de supprimer leur symétrie, en plaçant par exemple une lame diélectrique suivant l'une des polarisations.It is clear, however, that the invention can be easily generalized to other types of waveguides. Thus, the main waveguide can also be, for example, a coaxial waveguide in mode T 11 . It is also possible to use, in conjunction with rectangular filtering elements according to the invention, elements of guides of known type, said to be of symmetry of revolution, provided that their symmetry is eliminated, for example by placing a dielectric strip along one of the polarizations.

La figure 4 illustre, selon une représentation schématique en perspective, un élément de filtrage selon l'invention. Le guide d'ondes principal circulaire est séparé en deux parties 41A et 41B, entre lesquels un tronçon de guide d'ondes rectangulaire 42 est inséré.Figure 4 illustrates, in a schematic perspective representation, a filter element according to the invention. The circular main waveguide is separated into two parts 41 A and 41 B , between which a rectangular waveguide section 42 is inserted.

En associant plusieurs éléments tels que représentés sur cette figure 4, il est possible de réaliser un filtre précis et efficace, ainsi que l'illustrent les figures 6A et 6B présentées plus loin.By combining several elements as shown in this FIG. 4, it is possible to produce a precise and effective filter, as illustrated in FIGS. 6A and 6B presented below.

Le guide d'ondes principal 41A, 41B est connecté au tronçon rectangulaire 42 par des parois 44A et 44B qui ferment la partie de la transition sur laquelle les sections des guides circulaire et rectangulaire ne coïncident pas.The main waveguide 41 A , 41 B is connected to the rectangular section 42 by walls 44 A and 44 B which close the part of the transition on which the sections of the circular and rectangular guides do not coincide.

Selon l'invention, les parois 44A et 44B doivent être abruptes. En d'autres termes, les parois 44A et 44B sont sensiblement perpendiculaires à l'axe de symétrie 45 du guide d'ondes principal 41A, 41B. Aucun élément de transition n'est inséré. Ces parois 44A et 44B sont métalliques. Elles ne peuvent bien sûr pas être complètement ouvertes (présence d'air) ni constituées d'un diélectrique. Sinon, l'onde pourrait s'échapper et ne serait plus guidée.According to the invention, the walls 44 A and 44 B must be steep. In other words, the walls 44 A and 44 B are substantially perpendicular to the axis of symmetry 45 of the main waveguide 41 A , 41 B. No transition element is inserted. These walls 44 A and 44 B are metallic. They cannot of course be completely open (presence of air) or made of a dielectric. Otherwise, the wave could escape and would no longer be guided.

On constate donc que l'usinage d'un tel filtre est très simplifié, par rapport aux filtres représentés en figures 2 et 3. En effet, il n'y a aucun élément à placer à l'intérieur du guide circulaire ni aucune transition particulière à définir. Il suffit de fixer les uns aux autres les différents tronçons ou bien de réaliser le filtre en deux demi-coquilles.It can therefore be seen that the machining of such a filter is very simplified, compared to the filters shown in Figures 2 and 3. Indeed, there is no element to place inside the circular guide nor any particular transition to define. It is enough to fix the different sections to each other or else to make the filter in two half-shells.

Avantageusement, le guide circulaire 41A est placé au centre du guide rectangulaire 42, et la section commune 43 aux deux guides d'ondes est circulaire. Dans ce cas, la hauteur du guide rectangulaire 42 est donc au moins égale au diamètre du guide circulaire 41A.Advantageously, the circular guide 41 A is placed in the center of the rectangular guide 42, and the common section 43 of the two waveguides is circular. In this case, the height of the rectangular guide 42 is therefore at least equal to the diameter of the circular guide 41 A.

Dans le mode de réalisation décrit, l'ensemble des tronçons 41A, 42, 41B sont centrés sur un même axe longitudinal, à savoir l'axe de symétrie 45. Dans d'autres applications, toutefois, on peut prévoir que ces tronçons soient décalés.In the embodiment described, all of the sections 41 A , 42, 41 B are centered on the same longitudinal axis, namely the axis of symmetry 45. In other applications, however, provision may be made for these sections are shifted.

La géométrie du tronçon de guide rectangulaire (hauteur, largeur et épaisseur), de même que le nombre de tronçons et l'espacement entre ces tronçons, sont fonction des caractéristiques voulues pour le filtre. Ces différents paramètres peuvent par exemple être déterminés selon la méthode modale.The geometry of the rectangular guide section (height, width and thickness), as well as the number of sections and the spacing between these sections, depend on the characteristics desired for the filter. These various parameters can for example be determined according to the modal method.

Il n'y a aucune limitation sur les dimensions des côtés du guide rectangulaire, tant que celles-ci sont supérieures au diamètre du guide d'ondes circulaire. La bande passante peut donc être élevée (par exemple de l'ordre de 10 %).There is no limitation on the dimensions of the sides of the rectangular guide, as long as these are greater than the diameter of the circular waveguide. The bandwidth can therefore be high (for example of the order of 10%).

Ainsi qu'on l'a déjà mentionné, l'invention trouve une application privilégiée dans les duplexeurs bi-bandes et bi-polarisations tels que celui représenté schématiquement en figure 1. Dans ce cas, le filtre de polarisation 16 doit transmettre totalement l'une des polarisations, et réfléchir l'autre polarisation. L'exemple chiffré décrit ci-dessous concerne un tel filtre, pour la bande de fréquence 12-13 GHz.As already mentioned, the invention finds a preferred application in dual-band and bi-polarization duplexers such as that shown schematically in FIG. 1. In this case, the polarization filter 16 must completely transmit the one of the polarizations, and reflect the other polarization. The numerical example described below relates to such a filter, for the frequency band 12-13 GHz.

Les dimensions du guide rectangulaire étant plus grandes que le diamètre du guide circulaire, la polarisation de l'onde se propageant dans le guide circulaire peut être placée suivant la diagonale du guide rectangulaire.The dimensions of the rectangular guide being larger than the diameter of the circular guide, the polarization of the wave propagating in the circular guide can be placed along the diagonal of the rectangular guide.

La bande passante étant élevée, il est nécessaire de connecter un guide circulaire en sortie (13) du polariseur.The bandwidth being high, it is necessary to connect a circular guide at the output (13) of the polarizer.

Il est clair par ailleurs que le dispositif de l'invention peut trouver de nombreuses autres applications, tant dans le domaine du filtrage que dans celui de la polarisation.It is also clear that the device of the invention can find many other applications, both in the field of filtering and in that of polarization.

La figure 5 présente donc les cotes d'un filtre, dont les performances sont illustrées par les figures 6A et 6B. Ce filtre est constitué de quatre tronçons de guides d'ondes rectangulaires 51A à 51D, insérés dans le guide d'ondes circulaire 52.FIG. 5 therefore presents the dimensions of a filter, the performance of which is illustrated by FIGS. 6A and 6B. This filter consists of four sections of rectangular waveguides 51 A to 51 D , inserted in the circular waveguide 52.

Le guide d'ondes circulaire a un diamètre : c = 17,5 mm ;The circular waveguide has a diameter: c = 17.5 mm;

Les tronçons rectangulaires ont les dimensions suivantes :

  • largeur : a = 28,5 mm ;
  • hauteur : b = 21,26 mm ;
  • longueur : d = 10 mm.
The rectangular sections have the following dimensions:
  • width: a = 28.5 mm;
  • height: b = 21.26 mm;
  • length: d = 10 mm.

L'espacement entre deux tronçons rectangulaires est : e = 15,8 mm.The spacing between two rectangular sections is: e = 15.8 mm.

Les excitations se font en mode TE11 dans le guide d'ondes circulaire 52.The excitations are in TE 11 mode in the circular waveguide 52.

Il est à noter que ce mode de réalisation ne correspond pas à un filtre optimisé, mais vise à permettre la validation d'un calcul logiciel, ainsi que le présentent les figures 6A et 6B.It should be noted that this embodiment does not correspond to an optimized filter, but aims to allow the validation of a software calculation, as shown in FIGS. 6A and 6B.

La figure 6A montre en effet la courbe 61A du coefficient de réflexion du dispositif de filtrage de la figure 5, lorsque la polarisation en mode TE11 en guide circulaire est perpendiculaire au petit côté des tronçons 51A à 51D rectangulaires.FIG. 6A indeed shows the curve 61 A of the reflection coefficient of the filtering device of FIG. 5, when the polarization in TE mode 11 in circular guide is perpendicular to the short side of the rectangular sections 51 A to 51 D.

Dans ce cas, le mode TE11 est complètement transmis sur la bande de fréquence 12-13 GHz, le coefficient de réflexion étant voisin de 0.In this case, the TE 11 mode is completely transmitted on the 12-13 GHz frequency band, the reflection coefficient being close to 0.

L'objectif de ce filtre donné à titre d'exemple est de fournir un résultat de filtrage le plus proche de celui fixé théoriquement par calcul pour une application donnée, représenté par une série 61A de signes +.The objective of this filter given as an example is to provide a filtering result closest to that theoretically fixed by calculation for a given application, represented by a series 61 A of + signs.

La courbe 62A de réflexion mesurée montre qu'il est possible, avec le dispositif de l'invention, de conformer les caractéristiques de filtrage de façon précise. On constate en effet que la courbe 62A est très proche des résultats souhaités 61A.The curve 62 A of measured reflection shows that it is possible, with the device of the invention, to conform the filtering characteristics so precise. It can be seen that the curve 62 A is very close to the desired results 61 A.

La figure 6B présente le coefficient de réflexion du même dispositif, lorsque la polarisation du mode TE11 en guide circulaire est parallèle au petit côté des tronçons 51A à 51D rectangulaires. Le mode TE11 est alors réfléchi totalement pour la bande de fréquence 12-13 GHz. En effet, le coefficient de réflexion proche de 1, et la transmission est donc nulle.FIG. 6B shows the reflection coefficient of the same device, when the polarization of the TE 11 mode in a circular guide is parallel to the short side of the rectangular sections 51 A to 51 D. TE 11 mode is then fully reflected for the 12-13 GHz frequency band. Indeed, the reflection coefficient close to 1, and the transmission is therefore zero.

A nouveau, on constate que la courbe 62B mesurée suit de très près les caractéristiques voulues calculées 61B.Again, it can be seen that the curve 62 B measured follows very closely the desired characteristics calculated 61 B.

Avec ce dispositif de filtrage, des découplages de l'ordre 40 à 45 dB sont obtenus, ce qui correspond aux valeurs obtenues avec les filtres classiques à fils ou à lames, lorsque ces éléments sont bien placés. L'invention permet donc de réaliser des filtres au moins aussi efficaces que ceux de types connus, de façon beaucoup plus facile, du point de vue de la fabrication.With this filtering device, decouplings of the order of 40 to 45 dB are obtained, which corresponds to the values obtained with conventional filters with wires or blades, when these elements are well placed. The invention therefore makes it possible to produce filters at least as effective as those of known types, in a much easier way, from the manufacturing point of view.

Les caractéristiques géométriques de ce filtre ont été déterminées selon la méthode modale. D'autres modes de calculs peuvent également être envisagés. Avantageusement, la mise au point expérimentale d'un filtre selon l'invention se fait à l'aide d'un logiciel d'optimisation, mettant en oeuvre par exemple cette méthode modale.The geometrical characteristics of this filter were determined according to the modal method. Other calculation methods can also be envisaged. Advantageously, the experimental development of a filter according to the invention is done using optimization software, using for example this modal method.

L'invention n'est bien sûr pas limitée au mode de réalisation décrit ci-dessus. On peut en effet réaliser par exemple des filtres mettant en oeuvre des tronçons rectangulaires de géométries différentes. Ces différents tronçons peuvent alors être accolés ou non, et séparés par des espaces de tailles fixes ou variables.The invention is of course not limited to the embodiment described above. It is in fact possible, for example, to produce filters using rectangular sections of different geometries. These different sections can then be joined or not, and separated by spaces of fixed or variable sizes.

Il est également possible d'utiliser conjointement des tronçons rectangulaires selon l'invention et des dispositifs de filtrage classiques, par exemple à lame ou fils métalliques.It is also possible to jointly use rectangular sections according to the invention and conventional filtering devices, for example with metal blades or wires.

Outre le filtrage d'une polarisation (horizontale ou verticale) dans un guide circulaire en mode TE11, dans le cas où coexiste les deux polarisations linéaires, le dispositif de l'invention peut également être utilisé pour le filtrage d'une bande de fréquence dans un guide circulaire en mode TE11, dans le cas d'une polarisation rectiligne.In addition to filtering a polarization (horizontal or vertical) in a circular guide in TE 11 mode, in the case where the two linear polarizations coexist, the device of the invention can also be used for filtering a frequency band in a circular guide in TE 11 mode, in the case of a rectilinear polarization.

Une autre application du dispositif de l'invention est également la réalisation de polariseurs pour transformer une polarisation linéaire en polarisation circulaire.Another application of the device of the invention is also the production of polarizers to transform a linear polarization into circular polarization.

Un polariseur est un dispositif qui permet de passer d'une polarisation linéaire à une polarisation circulaire. Dans le cas de l'invention, la polarisation linéaire doit être parallèle à une diagonale du guide rectangulaire. En sortie, on obtient alors une polarisation circulaire, les ondes polarisées horizontalement et verticalement n'ayant pas la même vitesse de phase dans le guide rectangulaire. Un polariseur complet peut être réalisé en associant plusieurs éléments selon l'invention ou bien en les associant avec d'autres éléments déjà connus.A polarizer is a device which makes it possible to pass from a linear polarization to a circular polarization. In the case of the invention, the linear polarization must be parallel to a diagonal of the rectangular guide. At the output, a circular polarization is then obtained, the waves polarized horizontally and vertically not having the same phase speed in the rectangular guide. A complete polarizer can be produced by combining several elements according to the invention or by combining them with other elements already known.

Claims (7)

  1. Device for polarization filtering of electro-magnetic waves propagating in a rotationally symmetric main waveguide element (41A, 41B; 52) extending along an axis of symmetry (45),
    characterized in that it comprises at least one rectangular filtering waveguide section (42; 51A to 51D) inserted in substitution into the said main waveguide element (41A, 41B; 52),
    each transition (44A, 44B) between the said main waveguide element (41A, 41B; 52) and each of the said filtering sections (42; 51A to 51D) being constituted by a metal wall which is substantially perpendicular to the said axis of symmetry (45),
    the number and the geometrical and/or dimensional characteristics of the said rectangular waveguide sections (42; 51A to 51D) being chosen so as to constitute a filter with a predetermined filtering profile.
  2. Device according to Claim 1, characterized in that the said main waveguide element (41A, 41B; 52) is of the circular waveguide type or of the TE11 mode coaxial waveguide type.
  3. Device according to either one of Claims 1 and 2, characterized in that the width of the said rectangular waveguide sections (42; 51A to 51D) is greater than or equal to the diameter of the said main waveguide element (41A, 41B; 52).
  4. Device according to any one of Claims 1 to 3, characterized in that the said main waveguide element (41A, 41B; 52) and the said rectangular guide sections (42; 51A to 51D) are centred on the said axis of symmetry (45).
  5. Device according to any one of Claims 1 to 4, characterized in that it comprises a set of at least two rectangular waveguide sections (42; 51A to 51D) inserted at locations spaced out in the said main waveguide element (41A, 41D; 52).
  6. Use of a filtering device according to any one of Claims 1 to 5 for at least one of the following applications:
    - filtering of a frequency band in a TE11 mode circular waveguide element;
    - filtering of a horizontal or vertical polarization in a TE11 mode circular waveguide element.
  7. Dual-band duplexer, characterized in that it comprises at least one filtering device (16) according to any one of Claims 1 to 5.
EP92460018A 1991-06-26 1992-06-24 Filtering device for electromagnetic waves in a waveguide with symmetry around the rotational axis, and inserted pieces of rectangular waveguide Expired - Lifetime EP0520919B1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FR9108137 1991-06-26
FR9108137A FR2678434B1 (en) 1991-06-26 1991-06-26 DEVICE FOR FILTERING ELECTROMAGNETIC WAVES CIRCULATING IN A WAVEGUIDE OF A FIRST TYPE WITH REVOLUTION SYMMETRY, WITH SECONDS OF WAVEGUIDES OF A SECOND TYPE INSERTED.

Publications (2)

Publication Number Publication Date
EP0520919A1 EP0520919A1 (en) 1992-12-30
EP0520919B1 true EP0520919B1 (en) 1996-06-12

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US (1) US5309128A (en)
EP (1) EP0520919B1 (en)
JP (1) JPH05235605A (en)
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Publication number Priority date Publication date Assignee Title
FR2853143A1 (en) * 2003-03-31 2004-10-01 Thomson Licensing Sa FLOATING MICROWAVE FILTER WITH WAVEGUIDE STRUCTURE
CN115377638B (en) * 2022-06-23 2023-03-14 湖南大学 High-power microwave coaxial TEM-circular waveguide TE 11 Mode converter

Family Cites Families (12)

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Publication number Priority date Publication date Assignee Title
GB582856A (en) * 1944-07-05 1946-11-29 John Betteley Birks Improvements in or relating to electromagnetic radiators or receivers
US2719274A (en) * 1951-07-09 1955-09-27 Gen Precision Lab Inc Microwave switches
DE3326829A1 (en) * 1983-07-26 1985-02-14 Licentia Patent-Verwaltungs-Gmbh, 6000 Frankfurt Method for producing a multi-circle microwave bandpass filter, especially for the millimetric waveband
DE3439414A1 (en) * 1984-10-27 1986-04-30 kabelmetal electro GmbH, 3000 Hannover ANTENNA EXTENSION FOR AT LEAST TWO DIFFERENT FREQUENCY BANDS
US4725795A (en) * 1985-08-19 1988-02-16 Hughes Aircraft Co. Corrugated ridge waveguide phase shifting structure
JPS6248101A (en) * 1985-08-27 1987-03-02 Alps Electric Co Ltd Waveguide filter
US4920351A (en) * 1986-03-24 1990-04-24 Computer Science Inovations, Inc. Diplexer for orthogonally polarized transmit/receive signalling on common frequency
DE3613474C2 (en) * 1986-04-22 1995-02-23 Deutsche Aerospace Waveguide polarization converter
US4780694A (en) * 1987-11-23 1988-10-25 Hughes Aircraft Company Directional filter system
CA1251835A (en) * 1988-04-05 1989-03-28 Wai-Cheung Tang Dielectric image-resonator multiplexer
US4906951A (en) * 1989-02-15 1990-03-06 United States Department Of Energy Birefringent corrugated waveguide
US5184098A (en) * 1992-02-10 1993-02-02 Hughes Aircraft Company Switchable dual mode directional filter system

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DE69211428T2 (en) 1997-02-13
FR2678434B1 (en) 1994-02-04
EP0520919A1 (en) 1992-12-30
FR2678434A1 (en) 1992-12-31
DE69211428D1 (en) 1996-07-18
US5309128A (en) 1994-05-03
JPH05235605A (en) 1993-09-10

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