EP0078486A1 - Temperature-stabilized microwave filter - Google Patents

Temperature-stabilized microwave filter Download PDF

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Publication number
EP0078486A1
EP0078486A1 EP82109872A EP82109872A EP0078486A1 EP 0078486 A1 EP0078486 A1 EP 0078486A1 EP 82109872 A EP82109872 A EP 82109872A EP 82109872 A EP82109872 A EP 82109872A EP 0078486 A1 EP0078486 A1 EP 0078486A1
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EP
European Patent Office
Prior art keywords
filter
rods
bores
locking screws
tuning
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP82109872A
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German (de)
French (fr)
Inventor
Jean-Pierre Boujet
Gérard Gaille
Charles Jousselin
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Alcatel Lucent SAS
Original Assignee
Alcatel CIT SA
Alcatel SA
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Publication date
Application filed by Alcatel CIT SA, Alcatel SA filed Critical Alcatel CIT SA
Publication of EP0078486A1 publication Critical patent/EP0078486A1/en
Withdrawn legal-status Critical Current

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01P—WAVEGUIDES; RESONATORS, LINES, OR OTHER DEVICES OF THE WAVEGUIDE TYPE
    • H01P1/00—Auxiliary devices
    • H01P1/20—Frequency-selective devices, e.g. filters
    • H01P1/207—Hollow waveguide filters
    • H01P1/208—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

Definitions

  • the present invention relates to temperature stabilized microwave filters. It relates more particularly to filters with resonant cavities in which tuning rods carry out the final electrical adjustment of the cavities and the temperature stabilization of the filter, that is to say the maintenance of the electrical response of the filter in a wide range of temperature.
  • each resonant cavity is obtained by means of a tuning screw, metallic or preferably dielectric, inserted through a wall of the cavity and opening more or less inside the cavity to obtain the agreement of the cavity on a desired frequency.
  • tuning screw metallic or preferably dielectric
  • Filters commonly made of brass or aluminum and tuned as defined above, however, drift in frequency when the metal that constitutes them expands or contracts according to variations in ambient temperature. This drift in the tuning frequency of each cavity is caused by mechanical variations in the length of the cavity and the long side of the cross section of the cavity which cause, during a rise in temperature, an increase in the volume of the cavity giving rise to a lowering of its tuning frequency.
  • the adjustment of the tuning frequency of the cavities and the compensation of the drift tuning of the cavities and the bandwidth of the resulting filter, as a function of temperature are obtained by using tuning screws whose rods are made of temperature stable material and of which only the threaded heads are screwed into the body of the filter forming, for each screw, at the level of each of the cavities, a tubular support delimiting a conduit of length greater than the wall of each of the cavities with which the rod which opens into the cavity is without contact.
  • the rod consisted of a quartz cylinder glued into a threaded head of material known under the name Invar. The judicious choice of the diameter of the quartz rod, its length and its anchoring point allows very good compensation for frequency drifts in temperature to be obtained.
  • the present invention aims, while implementing the basic idea of the embodiment cited above, that is to say by moving the fixing point of the tuning screw of the cavity concerned, to allow a clearly simplified embodiment of the resulting filter.
  • the filter according to the invention obtained by mechanical machining, has a reduced cost price.
  • the present invention relates to a microwave filter comprising resonant cavities machined in the body of the filter, coupled together and each tuned by means of a tuning rod made of temperature stable material, a first end of which opens into the cavity concerned, without contact with its walls, and is held there positioned by means of fixing its second end in the filter body, said filter body having bores opening out on one of its faces and into the respective cavities, characterized in that that said fixing means comprise the end portion of each of the bores, opposite said cavities, the diameter of which is substantially equal to the diameter d of said tuning rods and means for locking at constant pressure the second end of each of said rods in the terminal portion of the bore which receives it.
  • a longitudinal slot cuts, over their height and substantially along their median axis, said end portions of said bores.
  • said locking means comprise locking screws inserted, transversely and on either side of each of said tuning rods and at the end portions of said bores receiving said tuning rods, in the filter body having , in pairs, in pairs, free play holes for the rods of the locking screws on one side of said slot and anchoring holes for the rods of said locking screws on the other side of said slot.
  • said locking screws and the end portions of said bores are dimensioned so that the ratio of the length L of the rod portion for each locking screw, comprised between its head and its anchoring point, to the diameter d of the portions end of the bores is substantially equal to the ratio between the coefficient of linear expansion of the material constituting the filter body and the difference between this coefficient and the coefficient of linear expansion of said locking screws, the material of the locking screws being chosen such that its coefficient linear expansion is less than the coefficient of linear expansion of the material constituting said filter body.
  • the microwave filter is produced in two parts 1 and 2 assembled to each other along the median longitudinal plane of the filter and defining together the filter body.
  • Each of these parts 1 and 2 comprises a row of cells 3 or 4 machined in the faces to be assembled, which define in the resulting filter a plurality of resonant cavities such as 5 coupled together and to the terminal half-cavities by irises of coupling such as 6.
  • These coupling irises, here rectangular, are defined by the partitions such as 7 and 8 separating the cells in one and the other of the rows and positioned two by two opposite in the resulting filter.
  • the two parts 1 and 2 of the filter are made of material which is easy to machine, for example aluminum. They are assembled to each other by means of screws and / or centering rods mounted in pairs of passages such as 9 formed in the body of the filter on either side of the resonant cavities.
  • each of the resonant cavities such as 5 is tuned by means of a cylindrical tuning rod 10 made of temperature stable material, for example quartz.
  • a cylindrical tuning rod 10 made of temperature stable material, for example quartz.
  • One end of this rod 10 opens into the interior of the cavity and is held there suitably positioned by holding the rod 10 in the body 1-2 of the filter, at the opposite end of this rod.
  • the diameter of the tuning rods and the position of the fixing point of each of them are determined relative to the center of the cavity to obtain the desired compensation for the frequency drift of the filter as a function of the temperature, the variations in the dimensions of the cavities (length and width) with temperature being compensated for by the displacement of the rods, of practically invariable dimensions, but fixed at a distance from the respective cavities in the body of the filter, inside the cavities.
  • the two parts 1 and 2 each comprise, for the insertion of each of the tuning rods in the respective cavities, a series of semi-circular grooves such as 11 or 12 machined in the faces to be assembled from these parts and opening out respectively in the cells 3 or 4.
  • These grooves 11 and 12 are two by two facing one another in the resulting filter and define therein a series of bores 13 opening into the respective resonant cavities 5.
  • the terminal portion of each of the bores, opposite to each of the cavities is of diameter substantially equal to the diameter d of the rods, the bores being on the rest of their length of diameter greater than that of the rods with which they are each without contact on these portions.
  • the terminal portions of the bores define in the body 1-2 of the filter the zone for holding the tuning rods.
  • Each of the rods is then kept blocked individually in the terminal portion of the bore which receives it by means of two locking screws 15 inserted transversely to the rod 10 considered, on either side of them.
  • each of the two parts 1 and 2 of the filter body has, on either side of each of its grooves 11 or 12 and in the vicinity of the longitudinal edge on which the grooves open, two holes 17 or 18 transverse to the grooves for the passage of the rods of the two locking screws concerned 15.
  • the holes 18 have a diameter greater than that of the rods of locking screws received, the rods of locking screws are free in these holes while the locking screw heads will abut against the external face of this part 2.
  • the holes 17 are tapped and correspond to the rods of the locking screws, threaded at least on their ends; the locking screw rods will be anchored in these threaded holes 17.
  • the inner face of one of the parts 1 and 2 of the filter has, moreover, over its length and slightly projecting over the height of the resulting bore portions 13 of diameter substantially equal to that of the rods 10, a recess or a notch clearance 20 which defines, in the filter, a longitudinal clearance slot 21 at least over the height of the rod holding zone while the faces of the two parts 1 and 2 also bear strictly on one another.
  • slot 21 can be obtained, in a variant not illustrated, by means of two recesses formed, on the internal face of one and the other of the parts 1 and 2 respectively.
  • the part 2 of the filter in which the holes for the locking screws 15 are wide to leave the rods of these locking screws free has, moreover, a longitudinal groove 22 on its outer face, limiting in height the rod holding area 10 in the body 1-2 of the filter.
  • This part 2 also has a series of transverse slots 23 separating from each other, on this part 2, the pairs of locking screws 15 assigned to the maintenance of the different tuning rods 10, by dividing it, over at least the height of the holding zone, in individual supports for said tuning rods 10; in the illustrated embodiment, these slots 23 intersect the longitudinal groove 22 and therefore extend beyond the height of the zone for holding the tuning rods 10.
  • the clearance slot 21, the series of transverse slots 23 and the longitudinal groove 22 in the part 2 of the filter body make the tightening of the different tuning rods 10 in the filter body practically independent of each other; in particular the blocking pressure of the rods in their respective bores is controllable for each rod individually and can be made constant from one rod to another.
  • FIGS. 5 and 6 which are two sectional views of the filter, respectively in the longitudinal zone for holding the tuning rods and in an intermediate zone between this holding zone and the cavity zone, it can clearly be seen that the rods d 'chord 10 are kept tight between the two parts 1 and 2 in the bore portions at their diameter, by means of pairs of locking screws 15, while the same chord rods 10 are without contact with the bores 13, outside this holding zone.
  • the parts 1 and 2 are, in particular at the level of the zone for holding the tuning rods in the resulting bores, of reduced thickness compared to the zone in which the cells are formed. 3 and 4.
  • the filter thus has the general shape of a rectangular parallelepiped, including the row of resonant cavities 5 and receiving the screws and / or centering rods referenced 19 ensuring the assembly of its parts 1 and 2, which is surmounted by a median longitudinal support of significantly less thickness, in the example illustrated, substantially in a report 3, in which are secured, offset from the cavities, the fixings by tightening or blocking of their tuning rods.
  • This structure is easy to obtain and comes entirely from mechanical machining.
  • the locking screws 15 and the end portions of the bores 13, or the tuning rods 10, are dimensioned, so that the ratio of the length L of the portion of each of the locking screws between its head and the point d anchoring in part 1 of the filter to the diameter d of the bores in the holding zone or diameter of the tuning rods is substantially equal to the value of the ratio between the coefficient of linear expansion of the material constituting the body of the filter and the difference between this coefficient and the coefficient of linear expansion of the material of the rods of the locking screws.
  • the material constituting the locking screws is chosen so that its coefficient of linear expansion is lower than that of the material constituting the filter body.
  • the length L of the relevant portion of the rods of the locking screws defines the thickness of the part 2, including the width of the slot 21, at this holding zone.
  • the aforementioned length L will be chosen of approximately 12.5 mm for bores or tuning rods having a diameter substantially of 4 mm.

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Abstract

Selon l'invention, les cavités résonnantes (5) du filtre sont accordées chacune au moyen d'une tige d'accord (10) en matériau stable en température dont une extrémité débouche dans la cavité concernée, sans contact avec ses parois, et dont la seconde extrémité est bloquée, à distance de la cavité dans le corps (1-2) du filtre présentant en correspondance, au niveau de cette seconde extrémité, un alésage (13) sensiblement de même diamètre que la tige d'accord. Le blocage est assuré par une paire de vis (15) dont les tiges sont libres dans le corps du filtre d'un côté d'une fente longitudinale (21) coupant l'alésage et sont ancrées dans le corps du filtre de l'autre côté de la fente.According to the invention, the resonant cavities (5) of the filter are each tuned by means of a tuning rod (10) of temperature stable material, one end of which opens into the cavity concerned, without contact with its walls, and whose the second end is blocked, at a distance from the cavity in the body (1-2) of the filter having in correspondence, at this second end, a bore (13) substantially of the same diameter as the tuning rod. The blocking is ensured by a pair of screws (15) whose stems are free in the body of the filter on one side of a longitudinal slot (21) cutting the bore and are anchored in the body of the filter on the other side of the slot.

Description

La présente invention porte sur les filtres hyperfréquences stabilisés en température. Elle concerne plus particulièrement les filtres à cavités résonnantes dans lesquelles des tiges d'accord réalisent le réglage électrique final des cavités et la stabilisation en température du filtre, c'est-à-dire le maintien de la réponse électrique du filtre dans une grande gamme de température.The present invention relates to temperature stabilized microwave filters. It relates more particularly to filters with resonant cavities in which tuning rods carry out the final electrical adjustment of the cavities and the temperature stabilization of the filter, that is to say the maintenance of the electrical response of the filter in a wide range of temperature.

Il est connu de constituer un filtre hyperfréquence à l'aide de cavités résonnantes couplées entre elles ; dans chaque cavité la fréquence de résonnance est déterminée par les dimensions de la cavité.It is known to constitute a microwave filter using resonant cavities coupled together; in each cavity the resonant frequency is determined by the dimensions of the cavity.

Le réglage précis de la longueur électrique de chaque cavité résonnante est obtenu au moyen d'une vis d'accord, métallique ou de préférence diélectrique, insérée à travers une paroi de la cavité et débouchant plus ou moins à l'intérieur de la cavité pour obtenir l'accord de la cavité sur une fréquence voulue. Ces vis évitent un usinage précis de la cavité et une mise au point finale de leurs dimensions, qui sont des opérations incompatibles avec des fabrications en série, en assurant donc le réglage final de la fréquence de résonnance des cavités.The precise adjustment of the electrical length of each resonant cavity is obtained by means of a tuning screw, metallic or preferably dielectric, inserted through a wall of the cavity and opening more or less inside the cavity to obtain the agreement of the cavity on a desired frequency. These screws avoid precise machining of the cavity and a final adjustment of their dimensions, which are operations incompatible with mass production, thus ensuring the final adjustment of the resonance frequency of the cavities.

Les filtres, réalisés de manière courante en laiton ou en aluminium et accordés ainsi qu'il a été défini ci-avant, dérivent cependant en fréquence lorsque le métal qui les constitue se dilate ou se contracte suivant les variations de température ambiante. Cette dérive de la fréquence d'accord de chaque cavité est provoquée par les variations mécaniques de la longueur de la cavité et du grand côté de la section transversale de la cavité qui entrainent, lors d'une élévation de température, une augmentation du volume de la cavité donnant lieu à un abaissement de sa fréquence d'accord.Filters, commonly made of brass or aluminum and tuned as defined above, however, drift in frequency when the metal that constitutes them expands or contracts according to variations in ambient temperature. This drift in the tuning frequency of each cavity is caused by mechanical variations in the length of the cavity and the long side of the cross section of the cavity which cause, during a rise in temperature, an increase in the volume of the cavity giving rise to a lowering of its tuning frequency.

Pour compenser cette dérive d'accord en fonction de la température, il est connu d'utiliser des vis d'accord en matériau pratiquement stable en température fixées sur le corps du filtre de manière à ce qu'elles sortent des cavités lorsque le corps du filtre se dilate : lorsque la tige d'accord sort de la cavité, la fréquence d'accord de celle-ci remonte.To compensate for this tuning drift as a function of the temperature, it is known to use tuning screws of material practically stable in temperature fixed on the filter body so that they come out of the cavities when the body of the filter expands: when the tuning rod leaves the cavity, the tuning frequency of the latter rises.

Ainsi, selon le document du brevet FR-A-2 326 077, le réglage de la fréquence d'accord des cavités et la compensation de la dérive d'accord des cavités et de la bande passante du filtre résultant, en fonction de la température, sont obtenus en utilisant des vis d'accord dont les tiges sont en matériau stable en température et dont seules les têtes filetées sont vissées dans le corps du filtre formant, pour chaque vis, au niveau de chacune des cavités, un support tubulaire délimitant un conduit de longueur supérieure à la paroi de chacune des cavités avec laquelle la tige qui débouche dans la cavité est sans contact. Ainsi, par exemple, la tige était constituée d'un cylindre de quartz collé dans une tête filetée en matériau connu sous la dénomination Invar. Le choix judicieux du diamètre de la tige de quartz, de sa longueur et de son point d'ancrage permettent d'obtenir une très bonne compensation des dérives de fréquence en température.Thus, according to patent document FR-A-2 326 077, the adjustment of the tuning frequency of the cavities and the compensation of the drift tuning of the cavities and the bandwidth of the resulting filter, as a function of temperature, are obtained by using tuning screws whose rods are made of temperature stable material and of which only the threaded heads are screwed into the body of the filter forming, for each screw, at the level of each of the cavities, a tubular support delimiting a conduit of length greater than the wall of each of the cavities with which the rod which opens into the cavity is without contact. Thus, for example, the rod consisted of a quartz cylinder glued into a threaded head of material known under the name Invar. The judicious choice of the diameter of the quartz rod, its length and its anchoring point allows very good compensation for frequency drifts in temperature to be obtained.

Si le fonctionnement des filtres ainsi obtenus est satisfaisant, il n'en demeure pas moins que son prix de revient est élevé et que la concordance entre le filetage de la tête de vis et le taraudage dans le corps du filtre demeure difficile à obtenir sans jeu et met en cause une réalisation industrielle à grande échelle de tels filtres.If the functioning of the filters thus obtained is satisfactory, the fact remains that its cost price is high and that the agreement between the thread of the screw head and the tapping in the body of the filter remains difficult to obtain without play. and calls into question a large-scale industrial production of such filters.

La présente invention a pour but, tout en mettant en oeuvre l'tidée fondamentale de la réalisation citée ci-avant, c'est-à-dire en déportant le point de fixation de la vis d'accord de la cavité concernée, de permettre une réalisation nettement simplifiée du filtre résultant. Le filtre selon l'invention, obtenu d'usinage mécanique, est de prix de revient réduit.The present invention aims, while implementing the basic idea of the embodiment cited above, that is to say by moving the fixing point of the tuning screw of the cavity concerned, to allow a clearly simplified embodiment of the resulting filter. The filter according to the invention, obtained by mechanical machining, has a reduced cost price.

La présente invention a pour objet un filtre hyperfréquence comportant des cavités résonnantes usinées dans le corps du filtre, couplées entre elles et chacune accordée au moyen d'une tige d'accord en matériau stable en température dont une première extrémité débouche dans la cavité concernée, sans contact avec ses parois, et y est maintenue positionnée par des moyens de fixation de sa seconde extrémité dans le corps du filtre, ledit corps du filtre présentant des alésages débouchant sur l'une de ses faces et dans les cavités respectives, caractérisé en ce que lesdits moyens de fixation comportent la portion terminale de chacun des alésages, à l'opposé desdites cavités, dont le diamètre est sensiblement égal au diamètre d desdites tiges d'accord et des moyens de blocage à pression constante de la seconde extrémité de chacune desdites tiges dans la portion terminale de l'alésage qui la reçoit.The present invention relates to a microwave filter comprising resonant cavities machined in the body of the filter, coupled together and each tuned by means of a tuning rod made of temperature stable material, a first end of which opens into the cavity concerned, without contact with its walls, and is held there positioned by means of fixing its second end in the filter body, said filter body having bores opening out on one of its faces and into the respective cavities, characterized in that that said fixing means comprise the end portion of each of the bores, opposite said cavities, the diameter of which is substantially equal to the diameter d of said tuning rods and means for locking at constant pressure the second end of each of said rods in the terminal portion of the bore which receives it.

Avantageusement, une fente longitudinale coupe, sur leur hauteur et sensiblement selon leur axe médian, lesdites portions terminales desdits alésages.Advantageously, a longitudinal slot cuts, over their height and substantially along their median axis, said end portions of said bores.

De préférence, lesdits moyens de blocage comportent des vis de blocage insérées, transversalement et de part et d'autre de chacune desdites tiges d'accord et au niveau des portions terminales desdits alésages recevant lesdites tiges d'accord, dans le corps du filtre présentant, en correspondance deux à deux, des perçages à libre jeu pour les tiges des vis de blocage d'un côté de ladite fente et des perçages d'ancrage pour les tiges desdites vis de blocage de l'autre côté de ladite fente.Preferably, said locking means comprise locking screws inserted, transversely and on either side of each of said tuning rods and at the end portions of said bores receiving said tuning rods, in the filter body having , in pairs, in pairs, free play holes for the rods of the locking screws on one side of said slot and anchoring holes for the rods of said locking screws on the other side of said slot.

Avantageusement, lesdites vis de blocage et les portions terminales desdits alésages sont dimensionnées de manière que le rapport de la longueur L de la portion de tige pour chaque vis de blocage, comprise entre sa tête et son point d'ancrage, au diamètre d des portions terminales des alésages soit sensiblement égal au rapport entre le coefficient de dilatation linéaire du matériau constituant le corps du filtre et la différence entre ce coefficient et le coefficient de dilatation linéaire desdites vis de blocage, le matériau des vis de blocage étant choisi tel que son coefficient de dilatation linéaire soit inférieur au coefficient de dilatation linéaire du matériau constituant ledit corps du filtre.Advantageously, said locking screws and the end portions of said bores are dimensioned so that the ratio of the length L of the rod portion for each locking screw, comprised between its head and its anchoring point, to the diameter d of the portions end of the bores is substantially equal to the ratio between the coefficient of linear expansion of the material constituting the filter body and the difference between this coefficient and the coefficient of linear expansion of said locking screws, the material of the locking screws being chosen such that its coefficient linear expansion is less than the coefficient of linear expansion of the material constituting said filter body.

L'invention sera décrite ci-après plus en détail en regard d'un exemple de réalisation illustré dans le dessin ci-annexé. Dans ce dessin :

  • - la figure 1 illustre en perspective un filtre hyperfréquence selon l'invention,
  • - les figures 2 et 3 sont des vues de face illustrant les deux parties constitutives du filtre, selon la figure 1.
  • - la figure 4 est une vue de côté dudit filtre,
  • - les figures 5 et 6 sont deux vues en coupe, selon les lignes V-V et VI-VI de la figure 4, dudit filtre.
The invention will be described below in more detail with reference to an exemplary embodiment illustrated in the accompanying drawing. In this drawing:
  • FIG. 1 illustrates in perspective a microwave filter according to the invention,
  • - Figures 2 and 3 are front views illustrating the two constituent parts of the filter, according to Figure 1 .
  • FIG. 4 is a side view of said filter,
  • - Figures 5 and 6 are two sectional views, along the lines VV and VI-VI of Figure 4, of said filter.

En regard de la figure 1 ou des figures 2 et 3, on voit que le filtre hyperfréquence est réalisé en deux parties 1 et 2 assemblées l'une à l'autre selon le plan longitudinal médian du filtre et définissant ensemble le corps du filtre. Chacune de ces parties 1 et 2 comporte une rangée d'alvéoles 3 ou 4 usinés dans les faces à assembler, qui définissent dans le filtre résultant une pluralité de cavités résonnantes telles que 5 couplées entre elles et aux demi-cavités terminales par des iris de couplage tels que 6. Ces iris de couplage, ici rectangulaires, sont définis par les cloisons telles que 7 et 8 séparant les alvéoles dans l'une et l'autre des rangées et positionnées deux à deux en regard dans le filtre résultant.With reference to FIG. 1 or to FIGS. 2 and 3, it can be seen that the microwave filter is produced in two parts 1 and 2 assembled to each other along the median longitudinal plane of the filter and defining together the filter body. Each of these parts 1 and 2 comprises a row of cells 3 or 4 machined in the faces to be assembled, which define in the resulting filter a plurality of resonant cavities such as 5 coupled together and to the terminal half-cavities by irises of coupling such as 6. These coupling irises, here rectangular, are defined by the partitions such as 7 and 8 separating the cells in one and the other of the rows and positioned two by two opposite in the resulting filter.

Les deux parties 1 et 2 du filtre sont en matériau aisé à usiner, par exemple en aluminium. Elles sont assemblées l'une à l'autre au moyen de vis et/ou tiges de centrage montées dans des paires de passages tels que 9 formés dans le corps du filtre de part et d'autre des cavités résonnantes.The two parts 1 and 2 of the filter are made of material which is easy to machine, for example aluminum. They are assembled to each other by means of screws and / or centering rods mounted in pairs of passages such as 9 formed in the body of the filter on either side of the resonant cavities.

Ainsi que visible également dans la figure 4, chacune des cavités résonnantes telles que 5 est accordée au moyen d'une tige cylindrique d'accord 10 en matériau stable en température par exemple en quartz. Une extrémité de cette tige 10 débouche à l'intérieur de la cavité et y est maintenue convenablement positionnée par maintien de la tige 10 dans le corps 1-2 du filtre, au niveau de l'extrémité opposée de cette tige. Bien entendu, on détermine le diamètre des tiges d'accord et la position du point de fixation de chacune d'elles par rapport au centre de la cavité pour obtenir la compensation désirée de la dérive en fréquence du filtre en fonction de la température, les variations des dimensions des cavités (longueur et largeur) avec la température étant compensées par le déplacement des tiges, de dimensions pratiquement invariables, mais fixées à distance des cavités respectives dans le corps du filtre, à l'intérieur des cavités.As also visible in FIG. 4, each of the resonant cavities such as 5 is tuned by means of a cylindrical tuning rod 10 made of temperature stable material, for example quartz. One end of this rod 10 opens into the interior of the cavity and is held there suitably positioned by holding the rod 10 in the body 1-2 of the filter, at the opposite end of this rod. Of course, the diameter of the tuning rods and the position of the fixing point of each of them are determined relative to the center of the cavity to obtain the desired compensation for the frequency drift of the filter as a function of the temperature, the variations in the dimensions of the cavities (length and width) with temperature being compensated for by the displacement of the rods, of practically invariable dimensions, but fixed at a distance from the respective cavities in the body of the filter, inside the cavities.

Les deux parties 1 et 2 comportent chacune, pour l'insertion de chacune des tiges d'accord dans les cavités respectives, une série de rainures semi-circulaire telles que 11 ou 12 usinées dans les faces à assembler de ces parties et débouchant respectivement dans les alvéoles 3 ou 4. Ces rainures 11 et 12 sont deux à deux en regard dans le filtre résultant et y définissent une série d'alésages 13 débouchant dans les cavités résonnantes respectives 5. Pour le maintien de chacune des tiges, la portion terminale de chacun des alésages, à l'opposé de chacune des cavités, est de diamètre sensiblement égal au diamètre d des tiges, les alésages étant sur le reste de leur longueur de diamètre supérieur à celui des tiges avec lesquelles ils sont chacun sans contact sur ces portions. Les portions terminales des alésages, de diamètre sensiblement égal à d, définissent dans le corps 1-2 du filtre la zone de maintien des tiges d'accord. Chacune des tiges est alors maintenue bloquée individuellement dans la portion terminale de l'alésage qui la reçoit au moyen de deux vis de blocage 15 insérées transversalement à la tige 10 considérée, de part et d'autre d'elles.The two parts 1 and 2 each comprise, for the insertion of each of the tuning rods in the respective cavities, a series of semi-circular grooves such as 11 or 12 machined in the faces to be assembled from these parts and opening out respectively in the cells 3 or 4. These grooves 11 and 12 are two by two facing one another in the resulting filter and define therein a series of bores 13 opening into the respective resonant cavities 5. For the maintenance of each of the rods, the terminal portion of each of the bores, opposite to each of the cavities is of diameter substantially equal to the diameter d of the rods, the bores being on the rest of their length of diameter greater than that of the rods with which they are each without contact on these portions. The terminal portions of the bores, of diameter substantially equal to d, define in the body 1-2 of the filter the zone for holding the tuning rods. Each of the rods is then kept blocked individually in the terminal portion of the bore which receives it by means of two locking screws 15 inserted transversely to the rod 10 considered, on either side of them.

A cet effet, chacune des deux parties 1 et 2 du corps du filtre présente, de part et d'autre de chacune de ses rainures 11 ou 12 et au voisinage du bord longitudinal sur lequel débouchent les rainures, deux perçages 17 ou 18 transversaux aux rainures pour le passage des tiges des deux vis de blocage concernées 15. Dans l'une des deux parties du corps du filtre, ici la partie 2, les perçages 18 sont de diamètre supérieur à celui des tiges de vis de blocage reçues, les tiges de vis de blocage sont libres dans ces perçages tandis que les têtes de vis de blocage viendront en butée contre la face externe de cette partie 2. Dans l'autre partie 1, les perçages 17 sont taraudés et correspondent aux tiges des vis de blocage, filetées au moins sur leurs extrémités ; les tiges de vis de blocage viendront s'ancrer dans ces perçages taraudés 17.To this end, each of the two parts 1 and 2 of the filter body has, on either side of each of its grooves 11 or 12 and in the vicinity of the longitudinal edge on which the grooves open, two holes 17 or 18 transverse to the grooves for the passage of the rods of the two locking screws concerned 15. In one of the two parts of the filter body, here part 2, the holes 18 have a diameter greater than that of the rods of locking screws received, the rods of locking screws are free in these holes while the locking screw heads will abut against the external face of this part 2. In the other part 1, the holes 17 are tapped and correspond to the rods of the locking screws, threaded at least on their ends; the locking screw rods will be anchored in these threaded holes 17.

La face intérieure de l'une des parties 1 et 2 du filtre présente, en outre, sur sa longueur et débordant légèrement sur la hauteur des portions d'alésages résultants 13 de diamètre sensiblement égal à celui des tiges 10, un décrochement ou une encoche de dégagement 20 qui définit, dans le filtre, une fente longitudinale de dégagement 21 au moins sur la hauteur de la zone de maintien des tiges alors que les faces des deux parties 1 et 2 portent par ailleurs rigoureusement l'une sur l'autre.The inner face of one of the parts 1 and 2 of the filter has, moreover, over its length and slightly projecting over the height of the resulting bore portions 13 of diameter substantially equal to that of the rods 10, a recess or a notch clearance 20 which defines, in the filter, a longitudinal clearance slot 21 at least over the height of the rod holding zone while the faces of the two parts 1 and 2 also bear strictly on one another.

Bien entendu la fente 21 peut être obtenue, en variante non illustrée, au moyen de deux décrochements formés, sur la face interne de l'une et l'autre des parties 1 et 2 respectivement.Of course the slot 21 can be obtained, in a variant not illustrated, by means of two recesses formed, on the internal face of one and the other of the parts 1 and 2 respectively.

Dans ce filtre, les deux vis de blocage de part et d'autre de chacune des tiges d'accord viennent alors assurer le serrage de l'une et l'autre des parties 1 et 2 sur la tige d'accord 10 concernée convenablement plongée dans la cavité. La pratique montre que la ligne d'ancrage de chacune des tiges d'accord 10 se situe à l'intersection de chacunne de ces tiges avec le plan défini par les axes des vis de blocage 15 qui lui sont associéesIn this filter, the two locking screws on either side of each of the tuning rods then ensure the tightening of one and the other of parts 1 and 2 on the tuning rod 10 concerned. completely immersed in the cavity. Practice shows that the anchoring line of each of the tuning rods 10 is located at the intersection of each of these rods with the plane defined by the axes of the locking screws 15 associated therewith.

Ainsi que visible dans la figure 1, la partie 2 du filtre dans laquelle les perçages pour les vis de blocage 15 sont larges pour laisser libres les tiges de ces vis de blocage présente, en outre, une rainure longitudinale 22 sur sa face extérieure, limitant en hauteur la zone de maintien des tiges 10 dans le corps 1-2 du filtre. Cette partie 2 présente aussi une série de fentes transversales 23 séparant les unes des autres, sur cette partie 2, les paires de vis de blocage 15 affectées au maintien des différentes tiges d'accord 10, en la divisant, sur au moins la hauteur de la zone de maintien, en supports individuels pour lesdites tiges d'accord 10 ; dans la réalisation illustrée, ces fentes 23 coupent la rainure longitudinale 22 et débordent donc sur la hauteur de la zone de maintien des tiges d'accord 10. La fente de dégagement 21, la série de fentes transversales 23 et la rainure longitudinale 22 dans la partie 2 du corps du filtre rendent les serrages des différentes tiges d'accord 10 dans le corps du filtre'pratiquement indépendants les uns des autres ; en particulier la pression de blocage des tiges dans leurs alésages respectifs est contrôlable pour chaque tige individuellement et peut être rendue constante d'une tige à l'autre.As can be seen in FIG. 1, the part 2 of the filter in which the holes for the locking screws 15 are wide to leave the rods of these locking screws free has, moreover, a longitudinal groove 22 on its outer face, limiting in height the rod holding area 10 in the body 1-2 of the filter. This part 2 also has a series of transverse slots 23 separating from each other, on this part 2, the pairs of locking screws 15 assigned to the maintenance of the different tuning rods 10, by dividing it, over at least the height of the holding zone, in individual supports for said tuning rods 10; in the illustrated embodiment, these slots 23 intersect the longitudinal groove 22 and therefore extend beyond the height of the zone for holding the tuning rods 10. The clearance slot 21, the series of transverse slots 23 and the longitudinal groove 22 in the part 2 of the filter body make the tightening of the different tuning rods 10 in the filter body practically independent of each other; in particular the blocking pressure of the rods in their respective bores is controllable for each rod individually and can be made constant from one rod to another.

Dans les figures 5 et 6 qui sont deux vues en coupe du filtre, respectivement dans la zone longitudinale de maintien des tiges d'accord et dans une zone intermédiaire entre cette zone de maintien et la zone des cavités, on voit nettement que les tiges d'accord 10 sont maintenues serrées entre les deux parties 1 et 2 dans les portions d'alésages à leur diamètre, au moyen des paires de vis de blocage 15, tandis que les mêmes tiges d'accord 10 sont sans contact avec les alésages 13, en dehors de cette zone de maintien.In FIGS. 5 and 6 which are two sectional views of the filter, respectively in the longitudinal zone for holding the tuning rods and in an intermediate zone between this holding zone and the cavity zone, it can clearly be seen that the rods d 'chord 10 are kept tight between the two parts 1 and 2 in the bore portions at their diameter, by means of pairs of locking screws 15, while the same chord rods 10 are without contact with the bores 13, outside this holding zone.

On notera aussi, en regard des figures, que les parties 1 et 2 sont, notamment au niveau de la zone de maintien des tiges d'accord dans les alésages résultants, d'épaisseur réduite par rapport à la zone dans laquelle sont formés les alvéoles 3 et 4. Le filtre présente ainsi la forme générale d'un parallépipède rectangle, incluant la rangée de cavités résonnantes 5 et recevant les vis et/ou tiges de centrage référencées 19 assurant l'assemblage de ses parties 1 et 2, qui est surmonté d'un support longitudinal médian d'épaisseur nettement moindre, dans l'exemple illustré, sensiblement dans un rapport 3, dans lequel sont assurées, déportées des cavités, les fixations par serrage ou blocage de leurs tiges d'accord. Cette structure est aisée à obtenir et est issue en totalité directement d'usinage mécanique.It will also be noted, with regard to the figures, that the parts 1 and 2 are, in particular at the level of the zone for holding the tuning rods in the resulting bores, of reduced thickness compared to the zone in which the cells are formed. 3 and 4. The filter thus has the general shape of a rectangular parallelepiped, including the row of resonant cavities 5 and receiving the screws and / or centering rods referenced 19 ensuring the assembly of its parts 1 and 2, which is surmounted by a median longitudinal support of significantly less thickness, in the example illustrated, substantially in a report 3, in which are secured, offset from the cavities, the fixings by tightening or blocking of their tuning rods. This structure is easy to obtain and comes entirely from mechanical machining.

Les vis de blocage 15 et les portions terminales des alésages 13, ou les tiges d'accord 10, sont dimensionnées, de sorte que le rapport de la longueur L de la portion de chacune des vis de blocage comprise entre sa tête et le point d'ancrage dans la partie 1 du filtre au diamètre d des alésages dans la zone de maintien ou diamètre des tiges d'accord soit sensiblement égal à la valeur du rapport entre le coefficient de dilatation linéaire du matériau constituant le corps du filtre et la différence entre ce coefficient et le coefficient de dilatation linéaire du matériau des tiges des vis de blocage. Le matériau constituant les vis de blocage est choisi de manière à ce que son coefficient de dilatation linéaire soit inférieur à celui du matériau constituant le corps du filtre. Ainsi qu'il apparaît en regard de la figure 4, dans laquelle les tiges des vis de blocage 15 sont ancrées directement sur la face interne de la partie 1 alors que leurs têtes respectives sont en butée contre la face externe de la partie 2 du filtre, la longueur L de la portion concernée des tiges des vis de blocage définit l'épaisseur de la partie 2, en y incluant la largeur de la fente 21, au niveau de cette zone de maintien.The locking screws 15 and the end portions of the bores 13, or the tuning rods 10, are dimensioned, so that the ratio of the length L of the portion of each of the locking screws between its head and the point d anchoring in part 1 of the filter to the diameter d of the bores in the holding zone or diameter of the tuning rods is substantially equal to the value of the ratio between the coefficient of linear expansion of the material constituting the body of the filter and the difference between this coefficient and the coefficient of linear expansion of the material of the rods of the locking screws. The material constituting the locking screws is chosen so that its coefficient of linear expansion is lower than that of the material constituting the filter body. As it appears with reference to FIG. 4, in which the rods of the locking screws 15 are anchored directly on the internal face of part 1 while their respective heads are in abutment against the external face of part 2 of the filter , the length L of the relevant portion of the rods of the locking screws defines the thickness of the part 2, including the width of the slot 21, at this holding zone.

A titre d'exemple, dans le filtre dont le corps 1-2 est en aluminium, dont les tiges d'accord 10 en quartz sont maintenues par des vis de blocage 15 en acier, dont les coefficients de dilatation linéaire de l'aluminium et de l'acier sont respectivement de 22.10 et 15.10" , on choisira la longueur L précitée de 12,5 mm environ pour des alésages ou des tiges d'accord ayant un diamètre sensiblement de 4 mm.For example, in the filter whose body 1-2 is made of aluminum, whose tuning rods 10 made of quartz are held by locking screws 15 made of steel, whose coefficients of linear expansion of aluminum and of steel are 22.10 and 15.10 "respectively, the aforementioned length L will be chosen of approximately 12.5 mm for bores or tuning rods having a diameter substantially of 4 mm.

Dans ces conditions, lors de variations de température ambiante, la variation de la longueur L des portions concernées'des vis de blocage qui lient relativement les deux faces internes des parties 1 et 2 contre la tige d'accord maintient, pratiquement constant le diamètre des alésages dans lesquels sont bloquées les tiges d'accord, ceci quelles que soient les contraintes thermiques subies par le corps du filtre. On obtient ainsi, dans différentes conditions de température, un maintien à pression constante des tiges d'accord dans le corps du filtre évitant leur éclatement ou leur non-serrage selon les variations de température.Under these conditions, during variations in ambient temperature, the variation in the length L of the portions concerned of the locking screws which relatively connect the two internal faces of the parts 1 and 2 against the tuning rod maintains, practically constant, the diameter of the ale wise in which the tuning rods are blocked, this whatever the thermal stresses undergone by the filter body. There is thus obtained, under different temperature conditions, maintaining at constant pressure the tuning rods in the body of the filter avoiding their bursting or non-tightening according to temperature variations.

Claims (5)

1/ Filtre hyperfréquence comportant une série de cavités résonnantes (5) usinées dans le corps (1, 2) du filtre, couplées entre elles et chacune accordée au moyen d'une tige d'accord (10) en matériau stable en température dont une première extrémité débouche dans la cavité concernée, sans contact avec ses parois, et y est maintenue positionnée par des moyens de fixation de sa seconde extrémité dans le corps du filtre, ledit corps du filtre présentant des alésages (13) débouchant sur l'une de ses faces et dans les cavités respectives, caractérisé en ce que lesdits moyens de fixation comportent la portion terminale de chacun des alésages (13), à l'opposé desdites cavités (5), dont le diamètre est sensiblement égal au diamètre d desdites tiges d'accord et des moyens de blocage (15) à pression constante de la seconde extrémité de chacune desdites tiges (10) dans la portion terminale de l'alésage qui la reçoit.1 / Microwave filter comprising a series of resonant cavities (5) machined in the body (1, 2) of the filter, coupled together and each tuned by means of a tuning rod (10) of temperature stable material, one of which first end opens into the cavity concerned, without contact with its walls, and is held there positioned by means of fixing its second end in the filter body, said filter body having bores (13) opening onto one of its faces and in the respective cavities, characterized in that the said fixing means comprise the end portion of each of the bores (13), opposite the said cavities (5), the diameter of which is substantially equal to the diameter d of the said rods agreement and blocking means (15) at constant pressure of the second end of each of said rods (10) in the end portion of the bore which receives it. 2/ Filtre hyperfréquence selon la revendication 1, caractérisé en ce qu'il comporte une fente (21) parallèle à l'axe de la série de cavités et coupant sur leur hauteur et sensiblement selon leur axe médian lesdites portions terminales desdits alésages (13).2 / microwave filter according to claim 1, characterized in that it comprises a slot (21) parallel to the axis of the series of cavities and cutting along their height and substantially along their median axis said end portions of said bores (13) . 3/ Filtre hyperfréquence selon la revendication 2, caractérisé par le fait que lesdits moyens de blocage (15) comportent des vis de blocage insérées, transversalement et de part et d'autre de chacune desdites tiges d'accord (10) et au niveau des portions terminales desdits alésages (13) recevant lesdites tiges d'accord, dans le corps (1-2) du filtre présentant, en correspondance deux à deux, des perçages (18) à libre jeu pour les tiges des vis de blocage d'un côté de ladite fente (21) et des perçages (17) d'ancrage pour les tiges desdites vis de blocage de l'autre côté de ladite fente (21).3 / microwave filter according to claim 2, characterized in that said blocking means (15) comprise blocking screws inserted, transversely and on either side of each of said tuning rods (10) and at the level of end portions of said bores (13) receiving said tuning rods, in the body (1-2) of the filter having, in correspondence two by two, free play holes (18) for the rods of the locking screws of a side of said slot (21) and anchor holes (17) for the rods of said locking screws on the other side of said slot (21). 4/ Filtre hyperfréquence selon la revendication 3, caractérisé par le fait que lesdites vis de blocage (15) et les portions terminales desdits alésages (13) sont dimensionnées de manière que le rapport de la longueur L de la portion de tige pour chaque vis de blocage, comprise entre sa tête et son point d'ancrage, au diamètre d des portions terminales des alésages (13) soit sensiblement égal au rapport entre le coefficient de dilatation thermique linéaire du matériau constituant le corps du filtre et la différence entre ce coefficient et le coefficient de dilatation linéaire desdites vis de blocage, le matériau des vis de blocage étant choisi tel que son coefficient de dilatation linéaire soit inférieur au coefficient de dilatation linéaire du matériau constituant ledit corps du filtre.4 / microwave filter according to claim 3, characterized in that said locking screws (15) and the end portions of said bores (13) are dimensioned so that the ratio of the length L of the rod portion for each screw blocking, between its head and its anchoring point, at the diameter d of the terminal portions of the bores (13) is substantially equal to the ratio between the coefficient of linear thermal expansion of the material constituting the filter body and the difference between this coefficient and the coefficient of expansion linear of said locking screws, the material of the locking screws being chosen such that its coefficient of linear expansion is less than the coefficient of linear expansion of the material constituting said filter body. 5/ Filtre hyperfréquence selon la revendication 4, caractérisé par le fait que le corps (1-2) du filtre présente une série de fentes transversales (23) séparant les unes des autres, du côté de la fente (21) où les perçages (18) pour les tiges des vis de blocage sont à libre jeu, les portions terminales desdits alésages 13.5 / microwave filter according to claim 4, characterized in that the body (1-2) of the filter has a series of transverse slots (23) separating from each other, on the side of the slot (21) where the bores ( 18) for the rods of the locking screws are free play, the end portions of said bores 13.
EP82109872A 1981-10-29 1982-10-26 Temperature-stabilized microwave filter Withdrawn EP0078486A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FR8120296 1981-10-29
FR8120296A FR2515879B1 (en) 1981-10-29 1981-10-29 TEMPERATURE-STABILIZED MICROWAVE FILTER

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Citations (5)

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US2103515A (en) * 1935-08-31 1937-12-28 Rca Corp Low power factor line resonator
US2934740A (en) * 1957-09-10 1960-04-26 Armstrong Cork Co Shorting strap
US3449698A (en) * 1967-03-24 1969-06-10 Hughes Aircraft Co Reactive waveguide post
DE1766372A1 (en) * 1968-05-10 1971-07-01 Telefunken Patent Arrangement for synchronism correction of a backlash-free, jointly tunable, multi-circuit waveguide or coaxial filter
DE2213185A1 (en) * 1972-03-17 1973-09-27 Siemens Ag Adjustable travelling-wave tube - with polyamide in gap between electron collector and cooling jacket

Family Cites Families (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3528042A (en) * 1967-09-22 1970-09-08 Motorola Inc Temperature compensated waveguide cavity
FR2326077A1 (en) * 1975-09-25 1977-04-22 Cit Alcatel Temp. stabilised RF filter - has coupled resonant cavities each with tuning screw in holder outside cavity wall

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2103515A (en) * 1935-08-31 1937-12-28 Rca Corp Low power factor line resonator
US2934740A (en) * 1957-09-10 1960-04-26 Armstrong Cork Co Shorting strap
US3449698A (en) * 1967-03-24 1969-06-10 Hughes Aircraft Co Reactive waveguide post
DE1766372A1 (en) * 1968-05-10 1971-07-01 Telefunken Patent Arrangement for synchronism correction of a backlash-free, jointly tunable, multi-circuit waveguide or coaxial filter
DE2213185A1 (en) * 1972-03-17 1973-09-27 Siemens Ag Adjustable travelling-wave tube - with polyamide in gap between electron collector and cooling jacket

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US4465989A (en) 1984-08-14
FR2515879B1 (en) 1985-05-31
FR2515879A1 (en) 1983-05-06

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