EP0064458A1 - High selectivity rectangular waveguide bandpass filter - Google Patents

High selectivity rectangular waveguide bandpass filter Download PDF

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Publication number
EP0064458A1
EP0064458A1 EP82400757A EP82400757A EP0064458A1 EP 0064458 A1 EP0064458 A1 EP 0064458A1 EP 82400757 A EP82400757 A EP 82400757A EP 82400757 A EP82400757 A EP 82400757A EP 0064458 A1 EP0064458 A1 EP 0064458A1
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EP
European Patent Office
Prior art keywords
cavities
filter
guide
band
notch
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Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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EP82400757A
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German (de)
French (fr)
Inventor
Yves Le Nohaic
Marc Sauvage
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Thales SA
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Thomson CSF 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
    • H01P1/207—Hollow waveguide filters
    • H01P1/208—Cascaded cavities; Cascaded resonators inside a hollow waveguide structure
    • 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 present invention relates to band pass filters in rectangular guide, having a high frequency selectivity.
  • the present invention aims to avoid the drawbacks of the prior art without increasing the cost price of the filter.
  • a band pass filter in rectangular guide, with high frequency selectivity comprising a rectangular guide which will said main guide and shunt susceptances placed inside the main guide so as to delimit there n (n integer greater than 0) successive main cavities, is characterized in that it comprises m (m integer greater than 0 and less or equal to n) notch cavities respectively coupled to m of the n main cavities and whose notch effect occurs at the limit of the passband of the bandpass filter.
  • FIG. 1 is a cross-sectional view of a filter according to the invention.
  • This figure shows a rectangular waveguide 1 with its two connection flanges 10, 11.
  • the interior of this guide is divided into four cavities 2, 3, 4, 5, using shunt susceptances formed by rods such that T 1 , T 2 9 T 3 9 T 4 , T 5 ; these rods are arranged in pairs so as to delimit cavities with a length slightly less than where g is the wavelength guided in the guide corresponding to an average operating frequency of 8.1 GHz.
  • Screws with locking nuts 12, 13, 14, 15, 16 are associated with the rods to allow adjustment of the coupling between the cavities, and of the coupling between the cavities 2 and 5 and the filter ports.
  • Other screws with locking nuts, 20, 30, 40, 50, are respectively associated with the cavities 2, 3, 4, 5 into which they penetrate with an adjustable length so as to constitute a means of adjusting these cavities.
  • the filter as just described so far constitutes a conventional bandpass filter with four bandpass cavities; the following description of FIG. 1 will show how it is possible to combine these four cavities with four other cavities 6, 7, 8, 9 each having a role of band-cutting cavity.
  • Figure 1 shows that each of the cavities 2, 3, 4, 5, is pierced with an iris 60, 70, 80, 90 located on the long side of the waveguide opposite to that which is crossed by the adjustment screws 20, 30, 40, 50 and opposite these adjustment screws.
  • These irises constitute a coupling element between respectively the cavities 2, 3, 4, 5, and four band-cutting cavities 6, 7, 8, 9 constituted by sections of waveguides of the same section as the waveguide 1 arranged perpendicular to the long side of the guide d wave 1, having their short sides located in the same plane as the short sides of the waveguide 1 and whose height is substantially less than .
  • These sections of waveguides are welded at one end to the waveguide 1 and are closed at their other end by a metal plate that a screw, 61, 71, 81, 91, associated with a locking nut, cross so as to ensure the adjustment of these cavities.
  • these cavities 6, 7, 8, 9 can be considered as being in series with the band-pass cavities 2, 3, 4, 5; they therefore add their notch function to the band pass function of the cavities of the guide 1, so that the filter according to FIG. 1 is equivalent to a band pass filter associated in series with a band cut filter.
  • Figure 2 is a top view of the filter according to the invention; in this figure the band-cutting cavity 9 has been shown in section along a plane XX indicated in FIG. 1.
  • FIG. 2 shows, by comparing with FIG. 1, that the bandpass cavities of the filter are produced by means of the pairs of rods T 1 -T ' 1 , T2-T' 2 , T 3 -T ' 3 , T4- T'4, T 5 -T ' 5 perpendicular to the long side of the guide.
  • Figure 2 also shows that each pair of rods and the screw for adjusting the inter-cavity coupling (12 to 16) are arranged in the same transverse plane of the guide 1. From the ends of the guide towards the center, the rods have their diameter which increases while that the spacing between the two rods of the same pair decreases.
  • FIG. 1 shows, by comparing with FIG. 1, that the bandpass cavities of the filter are produced by means of the pairs of rods T 1 -T ' 1 , T2-T' 2 , T 3 -T ' 3 , T4- T'4, T 5 -T ' 5 perpendicular to the long side of the guide.
  • Figure 2 also shows that each pair
  • the irises such as 90 used for coupling between a band-cutting cavity, such as 9, and a band-pass cavity, have an oblong shape, the major axis of which, not shown, is perpendicular to the edges of the guide 1 .
  • FIG. 3 is an end view, on the side of the flange 10, of the filter already shown in FIGS. 1 and 2.
  • the adjustment screws 12 and 20 Through the opening of the guide 1 appear the adjustment screws 12 and 20 as well as the rods T 1 and T ' l and the stems T 2, T' 2 , T 3 , T ' 3 partially hidden.
  • the band-cutting cavity 6 and the screw with locking nut, 61 allowing the adjustment of this cavity.
  • the flange 10 is a square flange pierced, in the vicinity of its four angles, with threaded holes, 101 to 104, intended to allow the mechanical connection of the filter to the other elements of the assemblies for which it is intended.
  • FIG. 4 is a graph showing, by two curves A and B, the frequency responses of the filter according to FIGS. 1 to 3 (curve A) and of this same filter without the notch qualities 6 to 9 and without the irises of coupling 60, 70, 80, 90 (curve B), that is to say of a conventional band-pass filter.
  • FIG. 4 Also shown in FIG. 4 are the reflection losses due to the filter, as a function of the frequency (curve C).
  • curve C shows that in the flat part of the response curve of the filter according to Figures 1 to 3, the reflection losses are at most of the order of 25 dB, which corresponds to a standing wave ratio (ROS ) of 1.1.
  • ROS standing wave ratio
  • notch cavities 6 and 8 had been tuned on 7.9 GHz while the notch cavities 7 and 9 had been tuned on 8.3 GHz, which explains why both the flank before the rear flank of curve A have much steeper slopes than the corresponding flanks of curve B.
  • one or more notch cavities will be coupled respectively to one or more bandpass cavities of the conventional filter; the choice of the number of notch cavities and their tuning frequency depends on the shape of the flanks to be obtained, it being understood that the tuning frequency will be one of the frequencies relating to the flanks to be obtained.
  • the invention is not limited to the example described.
  • the shunt susceptances formed of rods which separate the band pass cavities, can be replaced by shunt susceptances of the iris or flap type and the number of band cut cavities can be lower.
  • the number of bandpass cavities of the filter some of the band pass cavities are therefore not associated with a band cut cavity.
  • the band-cut cavities can be arranged differently with respect to the guide of the band-pass cavities, for example always perpendicular to one of the long sides of this guide but with the large sides of their cross section making an angle different from 90 ° with the transverse edges of the guide; experience has shown that it is also possible to arrange the band-cut cavities perpendicular to the short sides of the guide of the band-pass cavities.
  • the number and the location of the notch cavities are parameters which make it possible to intervene on the shape of the frequency response of the filter according to the invention.

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Abstract

The filter comprises a waveguide (1) inside which are disposed shunt susceptances, for example of the rod type (T1, T2, T3, T4, T5), so as to define therein successive band-pass cavities (2-5). Band-stop cavities (6-9) outside the guide are coupled to the band-pass cavities via irises (60, 70, 80, 90) drilled in the wall of the guide. Application to the field of microwaves. <IMAGE>

Description

La présente invention se rapporte à des filtres passe-bande en guide rectangulaire, présentant une grande sélectivité en fréquence.The present invention relates to band pass filters in rectangular guide, having a high frequency selectivity.

Pour obtenir une bonne sélectivité en fréquence avec un filtre, il est connu de réaliser ce filtre de manière que sa fonction de filtrage présente des zéros de transmission.To obtain good frequency selectivity with a filter, it is known to make this filter so that its filtering function has transmission zeros.

Pour obtenir une fonction de filtrage présentant des zéros de transmission il est connu d'employer soit des filtres dits elliptiques utilisant des cavités bi-modes, soit des associations en cascade de filtres passe-bande et de filtres coupe-bande. Mais les filtres dits elliptiques utilisant des cavités bi-modes ont des bandes passantes étroites; quant aux associations de filtres passe-bande et coupe-bande, elles ont l'inconvénient de constituer des ensembles mécaniques encombrants.To obtain a filtering function having transmission zeros, it is known to use either so-called elliptical filters using dual-mode cavities, or cascading associations of bandpass filters and bandstop filters. But the so-called elliptical filters using dual-mode cavities have narrow bandwidths; as for the associations of band pass filters and band cutters, they have the disadvantage of constituting bulky mechanical assemblies.

Il est également connu, par le brevet US 3 882 434, d'améliorer la sélectivité en fréquence d'un filtre passe-bande à cavité en réinjectant dans une cavité B du filtre de l'énergie captée sur une cavité A du filtre mais avec une phase différente de celle de l'énergie qui va directement de A à B ; le couplage en dérivation (cross coupling dans la littérature anglo-saxonne) permettant cette réinjection, est réalisé au moyen d'un filtre passe-bande auxiliaire mis en parallèle sur le filtre passe-bande principal, entre les cavités A et B. Une telle réalisation conduit à une courbe de temps de propagation de groupe plate, ce qui n'est pas le but recherché par la présente invention et constitue donc un autre type d'application. De plus dans une telle réalisation le filtre auxiliaire amène deux zéros dans la courbe de transmission du filtre principal qui sont symétriques de la fréquence centrale du filtre auxiliaire ; il n'est donc pas possible de faire, si nécessaire, que tous les zéros aient lieu sur la même fréquence.It is also known, from US Pat. No. 3,882,434, to improve the frequency selectivity of a bandpass filter with cavity by re-injecting into a cavity B of the filter energy captured on a cavity A of the filter but with a phase different from that of the energy which goes directly from A to B; the coupling in derivation (cross coupling in the Anglo-Saxon literature) allowing this reinjection, is carried out by means of an auxiliary band-pass filter placed in parallel on the main band-pass filter, between the cavities A and B. Such a realization leads to a flat group propagation time curve, which is not the aim sought by the present invention and therefore constitutes another type of application. Furthermore in such an embodiment the auxiliary filter brings two zeros in the transmission curve of the main filter which are symmetrical with the central frequency of the auxiliary filter; it is therefore not possible to make, if necessary, that all zeros take place on the same frequency.

La présente invention a pour but d'éviter les inconvénients de l'art antérieur sans pour cela augmenter le prix de revient du filtre.The present invention aims to avoid the drawbacks of the prior art without increasing the cost price of the filter.

Ceci est obtenu en mélangeant, avec des éléments présentant une fonction passe-bande, des éléments présentant une fonction coupe-bande.This is achieved by mixing, with elements having a band pass function, elements having a band cut function.

Selon l'invention un filtre passe-bande en guide rectangulaire, à grande sélectivité en fréquence, comportant un guide rectangulaire qui sera dit guide principal et des susceptances shunt placées à l'intérieur du guide principal de manière à y délimiter n (n entier supérieur à 0) cavités principales successives, est caractérisé en ce qu'il comporte m (m entier supérieur à 0 et inférieur ou égal à n) cavités coupes-bande respectivement couplées à m des n cavités principales et dont l'effet coupe-bande se produit en limite de la bande passante du filtre passe-bande.According to the invention a band pass filter in rectangular guide, with high frequency selectivity, comprising a rectangular guide which will said main guide and shunt susceptances placed inside the main guide so as to delimit there n (n integer greater than 0) successive main cavities, is characterized in that it comprises m (m integer greater than 0 and less or equal to n) notch cavities respectively coupled to m of the n main cavities and whose notch effect occurs at the limit of the passband of the bandpass filter.

La présente invention sera mieux comprise et d'autres caractéristiques apparaîtront à l'aide de la description ci-après et des figures s'y rapportant qui représentent :

  • - les figures 1 à 3, trois vues d'un même filtre selon l'invention
  • - la figure 4 un graphique avec deux courbes relatives au filtre des figures 1 à 3.
The present invention will be better understood and other characteristics will appear with the aid of the description below and of the figures relating thereto which represent:
  • - Figures 1 to 3, three views of the same filter according to the invention
  • - Figure 4 a graph with two curves relating to the filter of Figures 1 to 3.

La figure 1 est une vue en coupe transversale d'un filtre selon l'invention. Cette figure montre un guide d'onde rectangulaire 1 avec ses deux brides de raccordement 10, 11. L'intérieur de ce guide est divisé en quatre cavités 2, 3, 4, 5, à l'aide de susceptances shunts formées de tiges telles que T1, T29 T39 T4, T5; ces tiges sont disposées par paires de manière à délimiter des cavités d'une longueur légèrement inférieure à

Figure imgb0001
où g est la longueur d'onde guidée dans le guide correspondant à une fréquence moyenne de fonctionnement de 8,1 GHz. Des vis avec écrous de blocage 12, 13, 14, 15, 16 sont associées aux tiges afin de permettre le réglage du couplage entre les cavités, et du couplage entre les cavités 2 et 5 et les accès du filtre.D'autres vis avec écrous de blocage, 20, 30, 40, 50, sont respectivement associées aux cavités 2, 3, 4, 5 dans lesquelles elles pénètrent d'une longueur réglage de manière à constituer un moyen de réglage de ces cavités.Figure 1 is a cross-sectional view of a filter according to the invention. This figure shows a rectangular waveguide 1 with its two connection flanges 10, 11. The interior of this guide is divided into four cavities 2, 3, 4, 5, using shunt susceptances formed by rods such that T 1 , T 2 9 T 3 9 T 4 , T 5 ; these rods are arranged in pairs so as to delimit cavities with a length slightly less than
Figure imgb0001
 where g is the wavelength guided in the guide corresponding to an average operating frequency of 8.1 GHz. Screws with locking nuts 12, 13, 14, 15, 16 are associated with the rods to allow adjustment of the coupling between the cavities, and of the coupling between the cavities 2 and 5 and the filter ports. Other screws with locking nuts, 20, 30, 40, 50, are respectively associated with the cavities 2, 3, 4, 5 into which they penetrate with an adjustable length so as to constitute a means of adjusting these cavities.

Le filtre tel qu'il vient d'être décrit jusqu'ici constitue un filtre passe-bande classique à quatre cavités passe-bande; la suite de la description de la figure 1 va montrer comment il est possible d'associer à ces quatre cavités quatre autres cavités 6, 7, 8, 9 ayant chacune un rôle de cavité coupe-bande.The filter as just described so far constitutes a conventional bandpass filter with four bandpass cavities; the following description of FIG. 1 will show how it is possible to combine these four cavities with four other cavities 6, 7, 8, 9 each having a role of band-cutting cavity.

La figure 1 montre que chacune des cavités 2, 3, 4, 5, est percée d'un iris 60, 70, 80, 90 situé sur le grand côté du guide d'onde opposé à celui qui est traversé par les vis de réglage 20, 30, 40, 50 et en face de ces vis de réglage. Ces iris constituent un élément de couplage entre respectivement les cavités 2, 3, 4, 5, et quatre cavités coupe-bande 6, 7, 8, 9 constituées par des tronçons de guides d'onde de même section que le guide d'onde 1 disposé perpendiculairement au grand côté du guide d'onde 1, ayant leurs petits côtés situés dans le même plan que les petits côtés du guide d'onde 1 et dont la hauteur est sensiblement inférieure à

Figure imgb0002
. Ces tronçons de guides d'onde sont soudés à l'une de leur extrémité sur le guide d'onde 1 et sont fermés à leur autre extrémité par une plaque métallique qu'une vis, 61, 71, 81, 91, associée à un écrou de blocage, traverse de manière d'assurer le réglage de ces cavités.Figure 1 shows that each of the cavities 2, 3, 4, 5, is pierced with an iris 60, 70, 80, 90 located on the long side of the waveguide opposite to that which is crossed by the adjustment screws 20, 30, 40, 50 and opposite these adjustment screws. These irises constitute a coupling element between respectively the cavities 2, 3, 4, 5, and four band-cutting cavities 6, 7, 8, 9 constituted by sections of waveguides of the same section as the waveguide 1 arranged perpendicular to the long side of the guide d wave 1, having their short sides located in the same plane as the short sides of the waveguide 1 and whose height is substantially less than
Figure imgb0002
 . These sections of waveguides are welded at one end to the waveguide 1 and are closed at their other end by a metal plate that a screw, 61, 71, 81, 91, associated with a locking nut, cross so as to ensure the adjustment of these cavities.

Du point de vue électrique, ces cavités 6, 7, 8, 9 peuvent être considérées comme étant en série avec les cavités passe-bande 2, 3, 4, 5; elles ajoutent donc leur fonction coupe-bande à la fonction passe-bande des cavités du guide 1, si bien que le filtre selon la figure 1 est équivalent à un filtre passe-bande associé en série à un filtre coupe-bande.From the electrical point of view, these cavities 6, 7, 8, 9 can be considered as being in series with the band-pass cavities 2, 3, 4, 5; they therefore add their notch function to the band pass function of the cavities of the guide 1, so that the filter according to FIG. 1 is equivalent to a band pass filter associated in series with a band cut filter.

La figure 2 est une vue de dessus du filtre selon l'invention; sur cette figure la cavité coupe-bande 9 a été représentée en coupe selon un plan XX indiqué sur la figure 1.Figure 2 is a top view of the filter according to the invention; in this figure the band-cutting cavity 9 has been shown in section along a plane XX indicated in FIG. 1.

La figure 2 montre, en comparant avec la figure 1, que les cavités passe-bande du filtre sont réalisées au moyen des paires de tiges T1-T'1, T2-T'2,T3-T'3, T4-T'4, T5-T'5 perpendiculaires au grand côté du guide. La figure 2 montre également que chaque paire de tiges et la vis pour le réglage du couplage intercavité (12 à 16) sont disposées dans un même plan transversal du guide 1. Des extrémités du guide vers le centre les tiges ont leur diamètre qui augmente tandis que l'écartement entre les deux tiges d'une même paire diminue. Sur la figure 2 apparaît également que les iris tels que 90, servant au couplage entre une cavité coupe-bande, telle que 9, et une cavité passe-bande, ont une forme oblongue dont le grand axe non représenté esfperpendiculaire aux arêtes du guide 1.FIG. 2 shows, by comparing with FIG. 1, that the bandpass cavities of the filter are produced by means of the pairs of rods T 1 -T ' 1 , T2-T' 2 , T 3 -T ' 3 , T4- T'4, T 5 -T ' 5 perpendicular to the long side of the guide. Figure 2 also shows that each pair of rods and the screw for adjusting the inter-cavity coupling (12 to 16) are arranged in the same transverse plane of the guide 1. From the ends of the guide towards the center, the rods have their diameter which increases while that the spacing between the two rods of the same pair decreases. In FIG. 2, it also appears that the irises such as 90, used for coupling between a band-cutting cavity, such as 9, and a band-pass cavity, have an oblong shape, the major axis of which, not shown, is perpendicular to the edges of the guide 1 .

La figure 3 est une vue en bout, du côté de la bride 10, du filtre déjà représenté sur les figures 1 et 2. A travers l'ouverture du guide 1 apparaissent les vis de réglage 12 et 20 ainsi que les tiges T1 et T'l et les tiges T 2, T'2, T3, T'3 partiellement cachées. Sur cette figure apparaissent également la cavité coupe-bande 6 et la vis avec écrou de blocage, 61, permettant le réglage de cette cavité. Comme le montre la figure 3, la bride 10 est une bride carrée percée, au voisinage de ses quatre angles, de trous filetés, 101 à 104, destinés à permettre le raccordement mécanique du filtre aux autres éléments des montages auquel il est destiné.FIG. 3 is an end view, on the side of the flange 10, of the filter already shown in FIGS. 1 and 2. Through the opening of the guide 1 appear the adjustment screws 12 and 20 as well as the rods T 1 and T ' l and the stems T 2, T' 2 , T 3 , T ' 3 partially hidden. In this figure also appear the band-cutting cavity 6 and the screw with locking nut, 61, allowing the adjustment of this cavity. As shown in FIG. 3, the flange 10 is a square flange pierced, in the vicinity of its four angles, with threaded holes, 101 to 104, intended to allow the mechanical connection of the filter to the other elements of the assemblies for which it is intended.

Le filtre qui vient d'être décrit à l'aide des figures 1 à 3 est un filtre destiné à fonctionner avec une fréquence centrale de 8,1 GHz; ce filtre présente une bande passante méplat de 300 MHz et des pertes à 8,1 GHz de 0,25 dB. Les principales dimensions mécaniques de ce filtre sont les suivantes :

  • - longeur totale du filtre 140 mm
  • - largeur intérieure des grands côtés du guide et des grands côtés des cavités coupe-bande : 28,5 mm
  • - largeur intérieure des petits côtés du guide et des petits-côtés des cavités coupe-bande : 12,5 mm
  • - intervalle séparant les vis de réglage des cavités passe-bande 20, 30, 40, 50 : 28 mm
  • - hauteur intérieure des cavités coupe-bande : 20 mm.
The filter which has just been described with the aid of FIGS. 1 to 3 is a filter intended to operate with a central frequency of 8.1 GHz; this filter has a flat bandwidth of 300 MHz and losses at 8.1 GHz of 0.25 dB. The main mechanical dimensions of this filter are as follows:
  • - total length of the filter 140 mm
  • - internal width of the long sides of the guide and the long sides of the notch cavities: 28.5 mm
  • - internal width of the short sides of the guide and the short sides of the notch cavities: 12.5 mm
  • - interval between the adjustment screws of the band pass cavities 20, 30, 40, 50: 28 mm
  • - inner height of the notch cavities: 20 mm.

La figure 4 est un graphique montrant, par deux courbes A et B, les réponses en fréquence du filtre selon les figures 1 à 3 (courbe A) et de ce même filtre sans les qualités coupe-bande 6 à 9 et sans les iris de couplage 60, 70, 80, 90 (courbe B) c'est-à-dire d'un filtre passe-bande de type classique.FIG. 4 is a graph showing, by two curves A and B, the frequency responses of the filter according to FIGS. 1 to 3 (curve A) and of this same filter without the notch qualities 6 to 9 and without the irises of coupling 60, 70, 80, 90 (curve B), that is to say of a conventional band-pass filter.

La comparaison des courbes A et B de la figure 4 montre que la réponse du filtre selon les figures 1 à 3 est beaucoup plus sélective en fréquence que celle du filtre passe-bande classique correspondant : chute de 0 à -47 dB sur environ 120 MHz alors que la même chute se fait sur environ 270 MHz avec le filtre classique.The comparison of curves A and B in FIG. 4 shows that the response of the filter according to FIGS. 1 to 3 is much more selective in frequency than that of the corresponding conventional bandpass filter: drop from 0 to -47 dB over approximately 120 MHz whereas the same fall is made on approximately 270 MHz with the conventional filter.

Sur la figure 4 ont également été représentées les pertes par réflexion dues au filtre, en fonction de la fréquence (courbe C). Cette courbe montre que dans la partie du méplat de la courbe de réponse du filtre selon les figures 1 à 3, les pertes par réflexion sont au maximum de l'ordre de 25 dB, ce qui correspond à un rapport d'onde stationnaire (ROS) de 1,1.Also shown in FIG. 4 are the reflection losses due to the filter, as a function of the frequency (curve C). This curve shows that in the flat part of the response curve of the filter according to Figures 1 to 3, the reflection losses are at most of the order of 25 dB, which corresponds to a standing wave ratio (ROS ) of 1.1.

Il est à noter par ailleurs que les cavités coupe-bande 6 et 8 avaient été accordées sur 7,9 GHz tandis que les cavités coupe-bande 7 et 9 avaient été accordées sur 8,3 GHz, ce qui explique qu'aussi bien le flanc avant que le flanc arrière de la courbe A ont des pentes beaucoup plus raides que les flancs correspondants de la courbe B. Pour certaines applications il peut être intéressant d'avoir un flanc à pente raide (comme dans la courbe A) et l'autre flanc avec une pente moins raide (comme dans la courbe B); dans le cas du filtre décrit et pour, par exemple, n'avoir que le flanc avant à pente raide, il suffit alors d'accorder les quatre filtres coupe-bande sur 7,9 GHz.It should also be noted that the notch cavities 6 and 8 had been tuned on 7.9 GHz while the notch cavities 7 and 9 had been tuned on 8.3 GHz, which explains why both the flank before the rear flank of curve A have much steeper slopes than the corresponding flanks of curve B. For some applications it may be interesting to have one side with a steep slope (as in curve A) and the other side with a less steep slope (as in curve B); in the case of the filter described and for, for example, having only the steep slope front flank, it then suffices to tune the four notch filters on 7.9 GHz.

D'une manière générale, lorsque l'une au moins des pentes de la réponse en fréquence d'un filtre passe-bande à cavités, classique devra être rendue plus raide, une ou plusieurs cavités coupe-bande seront couplées respectivement à une ou plusieurs cavités passe-bande du filtre classique; le choix du nombre de cavités coupe-bande et de leur fréquence d'accord est fonction de l'allure des flancs à obtenir, étant entendu que la fréquence d'accord sera une des fréquences relatives aux flancs à obtenir.In general, when at least one of the slopes of the frequency response of a conventional bandpass filter with cavities will have to be made stiffer, one or more notch cavities will be coupled respectively to one or more bandpass cavities of the conventional filter; the choice of the number of notch cavities and their tuning frequency depends on the shape of the flanks to be obtained, it being understood that the tuning frequency will be one of the frequencies relating to the flanks to be obtained.

L'invention n'est pas limitée à l'exemple décrit. C'est ainsi, par exemple, que les susceptances shunts, formées de tiges qui séparent les cavités passe-bande, peuvent être remplacées par des susceptances shunts du type à iris ou à volets et que le nombre des cavités coupe-bande peut être inférieur au nombre des cavités passe-bande du filtre ; certaines des cavités passe-bande ne sont, alors, pas associées à une cavité coupe-bande. De même les cavités coupe-bande peuvent être disposées différemment par rapport au guide des cavités passe-bande, par exemple toujours perpendiculairement à l'un des grands côtés de ce guide mais avec les grands .côtés de leur section transversale faisant un angle différent de 90° avec les arêtes transversales du guide; l'expérience a montré qu'il est également possible de disposer les cavités coupe-bande perpendiculairement aux petits côtés du guide des cavités passe-bande. Le nombre et l'emplacement des cavités coupe-bande sont des paramètres qui permettent d'intervenir sur la forme de la réponse en fréquence du filtre selon l'invention.The invention is not limited to the example described. Thus, for example, the shunt susceptances, formed of rods which separate the band pass cavities, can be replaced by shunt susceptances of the iris or flap type and the number of band cut cavities can be lower. the number of bandpass cavities of the filter; some of the band pass cavities are therefore not associated with a band cut cavity. Likewise the band-cut cavities can be arranged differently with respect to the guide of the band-pass cavities, for example always perpendicular to one of the long sides of this guide but with the large sides of their cross section making an angle different from 90 ° with the transverse edges of the guide; experience has shown that it is also possible to arrange the band-cut cavities perpendicular to the short sides of the guide of the band-pass cavities. The number and the location of the notch cavities are parameters which make it possible to intervene on the shape of the frequency response of the filter according to the invention.

Claims (4)

1. Filtre passe-bande en guide rectangulaire, à grande sélectivité en fréquence, comportant un guide rectangulaire (1) qui sera dit guide principal et des susceptances shunt (T1, T'1...T5,T'5) placées à l'intérieur du guide principal de manière à y délimiter n (n entier supérieur à 0) cavités principales (2-5) successives, caractérisé en ce qu'il comporte m (m entier supérieur à 0 et inférieur ou égal à n) cavités coupe-bande (6-9) respectivement couplées à m des n cavités principales et dont l'effet coupe-bande se produit en limite de la bande passante du filtre passe-bande.1. Band pass filter in rectangular guide, with high frequency selectivity, comprising a rectangular guide (1) which will be called the main guide and shunt susceptances (T 1 , T ' 1 ... T 5 , T' 5 ) placed inside the main guide so as to delimit there n (n integer greater than 0) successive main cavities (2-5), characterized in that it comprises m (m integer greater than 0 and less than or equal to n) notch cavities (6-9) respectively coupled to m of the n main cavities and whose notch effect occurs at the limit of the pass band of the band pass filter. 2. Filtre passe-bande selon la revendication 1, caractérisé en ce que les cavités coupe-bande (6-9) sont formées par des tronçons de guide rectangulaire, fermés à leurs deux extrémités par une plaque métallique, la plaque métallique de leur première extrémité étant une des parois du guide principale et étant percée d'un iris (60, 70, 80. 90).2. band pass filter according to claim 1, characterized in that the band cut cavities (6-9) are formed by sections of rectangular guide, closed at their two ends by a metal plate, the metal plate of their first end being one of the walls of the main guide and being pierced with an iris (60, 70, 80. 90). 3. Filtre passe-bande selon la revendication 2, caractérisé en ce que les tronçons ont même section transversale que le guide principal, et ont leurs petits côtés respectivement situés dans les mêmes plans que les petits côtés du guide principal.3. Bandpass filter according to claim 2, characterized in that the sections have the same cross section as the main guide, and have their short sides respectively located in the same planes as the short sides of the main guide. 4. Filtre passe-bande selon l'une quelconque des revendications précédentes, caractérisé en ce que k des m cavités coupe-bande ont leur fréquence d'accord comprise dans les fréquences du flanc avant de la réponse en fréquence du filtre et p des m cavités coupe-bande ont leur fréquence d'accord comprise dans les fréquences du flanc arrière de la réponse en fréquence du filtre (avec k et p entiers positifs ou nuls et k + p = m).4. Bandpass filter according to any one of the preceding claims, characterized in that k of the notch cavities have their tuning frequency included in the frequencies of the front edge of the frequency response of the filter and p of the m Notch cavities have their tuning frequency included in the frequencies of the trailing edge of the frequency response of the filter (with k and p positive or zero integers and k + p = m).
EP82400757A 1981-05-08 1982-04-27 High selectivity rectangular waveguide bandpass filter Withdrawn EP0064458A1 (en)

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FR8109225A FR2505557A1 (en) 1981-05-08 1981-05-08 RECTANGULAR GUITAR PASS FILTER HAVING HIGH FREQUENCY SELECTIVITY
FR8109225 1981-05-08

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Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1994005056A1 (en) * 1992-08-15 1994-03-03 Filtronic Comtek Plc Microwave filter
WO2000026985A1 (en) * 1998-11-02 2000-05-11 Jury Vyacheslavovich Kislyakov Microwave filter
EP1250758A1 (en) * 2000-01-26 2002-10-23 Acoustic Technologies, Inc. Band pass filter with improved group delay
CN110767969A (en) * 2018-07-27 2020-02-07 中兴通讯股份有限公司 Cavity filter

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS59226501A (en) * 1983-06-08 1984-12-19 Nippon Hoso Kyokai <Nhk> Microwave filter

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US3882434A (en) * 1973-08-01 1975-05-06 Microwave Dev Lab Phase equalized filter
FR2431774A1 (en) * 1978-07-19 1980-02-15 Communications Satellite Corp MICROWAVE FILTERS WITH NARROW ELLIPTICAL BAND OF ODD ORDER

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US3882434A (en) * 1973-08-01 1975-05-06 Microwave Dev Lab Phase equalized filter
FR2431774A1 (en) * 1978-07-19 1980-02-15 Communications Satellite Corp MICROWAVE FILTERS WITH NARROW ELLIPTICAL BAND OF ODD ORDER

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* Cited by examiner, † Cited by third party
Title
IEEE TRANSACTIONS ON M.T.T., vol. 22, no. 1, janvier 1974, pages 1-5, New York, US *

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1994005056A1 (en) * 1992-08-15 1994-03-03 Filtronic Comtek Plc Microwave filter
WO2000026985A1 (en) * 1998-11-02 2000-05-11 Jury Vyacheslavovich Kislyakov Microwave filter
EP1250758A1 (en) * 2000-01-26 2002-10-23 Acoustic Technologies, Inc. Band pass filter with improved group delay
EP1250758A4 (en) * 2000-01-26 2004-12-15 Acoustic Tech Inc Band pass filter with improved group delay
CN110767969A (en) * 2018-07-27 2020-02-07 中兴通讯股份有限公司 Cavity filter

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JPS57194602A (en) 1982-11-30

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