EP0285503B1 - Filter with distributed constant elements associating two kinds of coupling arrangements - Google Patents

Filter with distributed constant elements associating two kinds of coupling arrangements Download PDF

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Publication number
EP0285503B1
EP0285503B1 EP88400702A EP88400702A EP0285503B1 EP 0285503 B1 EP0285503 B1 EP 0285503B1 EP 88400702 A EP88400702 A EP 88400702A EP 88400702 A EP88400702 A EP 88400702A EP 0285503 B1 EP0285503 B1 EP 0285503B1
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Prior art keywords
resonators
filter
fact
filter according
earth
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German (de)
French (fr)
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EP0285503A1 (en
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Patrick Giraudeau
Philippe Rousseau
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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
    • H01P1/201—Filters for transverse electromagnetic waves
    • H01P1/203—Strip line filters

Definitions

  • the invention relates mainly to a filter comprising elements with distributed constants using at least two different types of coupling.
  • Such a filter includes resonators.
  • the signal propagates by coupling between the consecutive resonators of the filter.
  • the filters with distributed constants are produced in stripline technology, the resonators being deposited by metallization on one side of a low loss dielectric, the metallization of the second side constituting the ground plane.
  • Comblin type filters present difficulties in achieving and obtaining the desired filtering.
  • the filters according to the present invention include distributed constant resonators.
  • the signal is propagated by coupling between the constituent resonators of the filter.
  • the filters according to the present invention comprise at least two types of coupling between successive resonators.
  • U-shaped resonators also called hairpin resonators
  • the inversion of certain U-shaped resonators compared to the arrangement of a filter of conventional type allows easy connection of a transverse coupler between resonators arranged symmetrically with respect to the center of the filter.
  • Such filters can be used, for example, to make templates or to eliminate frequency side lobes from an electrical signal.
  • filters comprising at least two types of coupling described by the Japanese patent JP-A-60 185 402. These contain an odd number of overlapping U-shaped resonators to achieve a first type of coupling between the outer sides resonators and a second type of coupling between the inner sides of the resonators.
  • the capacitors with variable capacitance are removed in this way, on the one hand, the reduction in capacitive coupling between capacitors is obtained, and on the other hand, facilitating the installation of said capacitors with variable capacity on the filters insofar as these capacitors are more distant from each other.
  • the main object of the invention is a microwave filter as defined by claim 1.
  • the filter of FIG. 1 comprises a plurality of resonators 1 in the shape of the letter U.
  • the resonators are also called hairpin resonators (hairpin in English terminology).
  • Each resonator has two branches of length L arranged symmetrically and orthogonally with respect to a base.
  • the resonators 1 are arranged in staggered rows and in such a way that the branches of the two successive resonators 1 have an electromagnetic coupling.
  • the filters include six 1-U resonators.
  • the first and last 1-U resonators are coupled with connection means 2.
  • connection means 2 comprise a branch of length L parallel to the branches of first and last resonators 1 as well as a metallized orthogonal strip terminated by a metallized hole 3.
  • the electrical connection is made at the metallized hole 3.
  • the filters illustrated in FIG. 1 have the disadvantage that it is extremely difficult to achieve coupling, by means of a capacitor between two resonators 1 in U symmetrical with respect to the transverse axis 16 of the filter.
  • the resonators arranged symmetrically with respect to a transverse axis 16 of the filter comprise bases of the U on the opposite sides of the filter, the metallizations having to join these two bases, for example of the first and of the last resonators or of the second and of the fifth, may interfere with the operation of the filter.
  • the filters illustrated in FIG. 2 include a plurality of straight resonators 10.
  • the straight resonators 10 are arranged parallel to each other.
  • Each straight resonator 10 is connected, by a first of its ends to ground 4, and by a second end to a first frame of a variable capacitor 5.
  • the second frame of the variable capacitor 5 is connected to ground 4.
  • the filter illustrated in FIG. 2 can have parasitic couplings between the capacitors of variable capacitor 5 and the resonator 10 and between the capacitors themselves due to their proximity.
  • the size of the variable capacitors 5 poses problems in terms of the geometric construction of the filter due to their proximity.
  • FIG. 3 we can see a first embodiment of a filter according to the present invention.
  • the filter of FIG. 3 comprises U-shaped resonators 1.
  • the first three U-shaped resonators 1 are arranged in staggered rows.
  • the fourth U-shaped resonator 1 has a base arranged on the same side as the third resonator 1.
  • the fourth resonator 1 as well as the fifth and the sixth are arranged symmetrically relative to the transverse axis 16 of the filter relative to the third, second and first U-shaped resonators 1.
  • the ends of the legs of each U-shaped resonator may be brought to ground (not shown in FIG. 3) .
  • the couplings between the first and second resonators 1, the second and third resonators 1, the fourth and fifth resonators 1 and the fifth and sixth resonators 1 are of the same type, the ends of the branches of U capable of be brought to ground being opposite to the axis 160.
  • the ends of the branches of the resonators likely to be grounded are on the same side of the axis 160.
  • the coupling between the third and the fourth resonators 1 is of a different type from those between the other resonators 1.
  • resonators 1 in U arranged symmetrically with respect to the transverse axis of the filter 16, having the bases on the same side of the filter. These bases are capable of being connected via, for example a capacitor so as to form a filter comprising two zones of high attenuation arranged symmetrically with respect to the central frequency of the filter.
  • the axis 16 is an axis of symmetry of the filter.
  • the barycenter of the filter constitutes the intersection of the axis 16 with a longitudinal axis 160 orthogonal to the axis 16.
  • FIG. 4 a second example of embodiment of a filter according to the present invention can be seen comprising resonators 1 in U.
  • the filter illustrated in FIG. 4 comprises ten resonators.
  • the first seven U-shaped resonators are staggered, as in a conventional filter.
  • the seventh and eighth resonators have arms arranged on the same side.
  • the last three U-shaped resonators, the eighth, the ninth and the tenth are staggered.
  • the filters of FIG. 3 and 4 are given as nonlimiting examples of the arrangements of the U-shaped resonators 1. Other arrangements such as, for example, those comprising several coupling changes do not depart from the scope of the present invention.
  • FIG. 5 a filter of the combline type according to the present invention can be seen.
  • the filters of FIG. 5 comprise a plurality of straight resonators at 10.
  • the straight resonators at 10 are arranged in parallel by one compared to others.
  • the first straight resonator at 10 is connected, by a first of these ends to ground 4 and by a second end to a first frame of a variable capacitor 5.
  • the second frame of the variable capacitor 5 is connected to ground 4.
  • the second straight resonator 10 is connected at a first end to a first armature of a variable capacitor 5; the second armature of the variable capacitor 5 is connected to ground 4; the second end of the right resonator 10 is connected to ground 4, etc ...
  • variable capacity capacitors 5 are thus more distant from each other than in a conventional filter type. Thus, the problem of space requirement of the capacitors with variable capacity 5 is solved and the parasitic coupling between these capacitors is reduced.
  • FIG. 6 one can see a filter according to the present invention making it possible to obtain two zones of strong attenuations, for example with respect to the central operating frequency of the filter. These zones of strong attenuations are also called zero of the filter.
  • the filters comprise eight U-shaped resonators 1 arranged symmetrically with respect to the transverse axis 16 of the filter.
  • the bases of the third and sixth resonators 1 in U are connected via a variable capacity capacitor 55.
  • the capacitor 55 makes it possible to adjust the response curve of the filter of FIG. 6.
  • resonators arranged symmetrically with respect to the transverse axis of the filter 16 can be connected via a capacitor 55.
  • each resonator 1 in U is connected to a first armature of a capacitor variable 5.
  • the second armature of the variable capacitor 5 is connected to ground 4.
  • connection of the base of the U-shaped resonators 1 to the first armature of the capacitors with variable capacitance 5 is carried out at an axis of symmetry 15 of said U-shaped resonator 1.
  • the capacitors 5 are shown at outside the U formed by the resonator 1. It is understood that the variable capacitors 5 connected inside the U formed by the resonator 1 do not depart from the scope of the present invention.
  • variable capacity capacitors 5 allows fine adjustment of the filter.
  • the length L of the branches of the resonators 1 in U is less in the case of the device of FIG. 7 than that of the device of FIG. 1 or of FIG. 6.
  • L is less than ⁇ g / 8, ⁇ g being the wavelength guided at the center frequency of the filter.
  • the filters as illustrated in Figure 7 have a smaller footprint. This reduction in size is particularly important for the production of filters for on-board equipment, for example on board aircraft or satellites.
  • FIG. 8 an alternative embodiment of the device in FIG. 7 can be seen.
  • the U-shaped resonators 1 are connected by a transmission line 66, a variable capacity 77 being wired between the middle of this line 66 and the mass 4, the resonators in the case of the figure are respectively the third and the sixth resonators 1 in the form of U.
  • UHF frequency
  • band L the value of the capacity 55 becomes very weak.
  • capacity 77 remains more easily achievable.
  • FIG. 8 an exemplary embodiment has been illustrated in which a direct coupling 20 has been used as the connection means.
  • the direct coupling 20 is a metallization directly connected to the first and last resonators 1 in U.
  • the direct coupling 20 allows to solve the problem of realization of the couplings of the type of FIG. 7. In fact in the case of wide bandwidths the etching of the coupling space is very low ( ⁇ 100 ⁇ m).
  • the location of the branch of the U-shaped resonator to which the direct connection 20 is made is determined by calculation, for example using the specific software developed for determining the elements of the filter.
  • the connection at the end of metallization 20 constituting the direct coupling is made for example by means of a metallized hole 3. It is understood that the direct connection is not limited to the embodiment of FIG. 8 but can be used in all the embodiments of the filter according to the present invention.
  • the filters according to the present invention are produced in triplate technology.
  • An exemplary embodiment of a filter in triplate technology is illustrated in FIG. 9.
  • FIG. 9 corresponds to a detail of embodiment of the filter of FIG. 8 seen in section along the axis AA ⁇ .
  • the U-shaped resonators 1 are placed substantially in a plane included in a low loss dielectric 7. At least two faces of the dielectric are covered by a metallization constituting the ground plane 4.
  • the low loss dielectric 7 forms a rectangular parallelepiped whose six faces are covered by metallizations forming the ground plane 4 of said filter.
  • the vertical connections bear the references 13. They allow, on the one hand to connect the ends of the branches of the resonator 1 in U to the ground plane 4, and on the other hand to connect the variable capacitor 5 at the base of the resonators 1 in U.
  • the metallization of the ground plane 4 includes savings 9 avoiding short-circuiting the bases of the U-shaped resonators with the ground.
  • variable capacitors 5 are shown diagrammatically in FIG. 9.
  • the variable capacitors 5 will be installed for example on the surface of the filter according to the present invention.
  • the filter according to the present invention is enclosed in a hermetic casing, it is possible to allow the adjustment screws of the variable capacity capacitors 5 to protrude.
  • triplate technology is not limited to the embodiment of the filter according to the invention of FIG. 6.
  • the triplate technology can be applied to all the filters according to the present invention.
  • FIG. 12 we can see a symbolic representation of a second coupling between two resonators 1.
  • the coupling is carried out in FIG. 12 between two lines 30 and 31 corresponding, for example, to the coupling between the fourth and the fifth resonators in FIG. 8.
  • Line 30 has an input at point A and a connection to ground 4.
  • Line 31 has an output at point B located on the same side of line 31 as point A, and a connection to ground 4.
  • FIG. 13 we can see an equivalent diagram of a portion of the filter according to the present invention illustrated in FIG. 11 established from the book by Matthaei edition 1980, Microwaves Filters, Impedance Matching Networks and Coupling Structures.
  • a portion corresponding to two coupled branches of the two resonators 1 corresponds to a serial line 21 and two parallel lines 22 (stubs in English terminology) with an electrical angle ⁇ .
  • Line 21 with an electrical angle ⁇ corresponds to the coupling between two resonators.
  • the line 22 with an electrical angle ⁇ corresponds to the branches of the U-shaped resonators 1.
  • computer-aided design software for the realization of the filters. You can for example use CAD software, ESOPE, SUPERCOMPACT or TOUCHSTONE.
  • the translation is carried out by a computer to which the filter which one wishes to obtain is indicated.
  • FIG. 14 one can see an equivalent diagram of a portion of filter according to the present invention corresponding to the representation of FIG. 12.
  • the equivalent diagram of FIG. 14 differs from the equivalent diagram of FIG. 13 by the presence between the points A and B of a series 210 electric angle stub ⁇ .
  • the abscissa axis 47 we have plotted the frequency f.
  • the amplitude A has been plotted.
  • the ordinate axis 41 is for example an axis whose scale is logarithmic.
  • An example of frequency response of the filter according to the present invention bears the reference 43.
  • This filter makes it possible to obtain two zeros centered on the frequencies 44 and 46, for example arranged symmetrically with respect to the central frequency 45 of the filter.
  • the zeros 44 and 46 of the filter will be by example superimposed on frequency side lobes in the electrical signal to be filtered, which would otherwise be very annoying.
  • the curve 43 is substantially vertical. On the greater part centered around the frequency 45 the curve 43 is substantially horizontal.
  • the technology according to the present invention can be used from high radio frequencies. Its effectiveness is particularly very important in the VHF, UHF and L band.
  • the invention applies mainly to the production of filters, in particular microwave filters and to the device using such filters.

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Description

L'invention concerne principalement un filtre comportant des éléments à constantes réparties utilisant au moins deux types de couplage différents.The invention relates mainly to a filter comprising elements with distributed constants using at least two different types of coupling.

Il est connu de réaliser des filtres à constantes réparties. Un tel filtre comporte des résonateurs. Le signal se propage par couplage entre les résonateurs consécutifs du filtre. Les filtres à constantes réparties sont réalisés en technologie stripline, les résonateurs étant déposés par métallisation sur une face d'un diélectrique à faible perte, la métallisation de la seconde face constituant le plan de masse.It is known to produce filters with distributed constants. Such a filter includes resonators. The signal propagates by coupling between the consecutive resonators of the filter. The filters with distributed constants are produced in stripline technology, the resonators being deposited by metallization on one side of a low loss dielectric, the metallization of the second side constituting the ground plane.

Il est aussi connu de réaliser des filtres appelés combline comportant des résonateurs droits dont les extrémités, sont connectées, d'une part directement, et d'autre part à travers un condensateur variable, au plan de masse.It is also known to produce filters called combline comprising straight resonators whose ends are connected, on the one hand directly, and on the other hand through a variable capacitor, to the ground plane.

Les filtres de type combline présentent des difficultés de réalisation et d'obtention du filtrage désiré.Comblin type filters present difficulties in achieving and obtaining the desired filtering.

La proximité des condensateurs variables pose des problèmes d'encombrement pour la construction du filtre.The proximity of the variable capacitors poses problems of space for the construction of the filter.

De plus, avant la réalisation de l'invention on croyait que le fait de rajouter des éléments à constantes localisées sur un filtre à constantes réparties en augmentait l'encombrement.In addition, before carrying out the invention, it was believed that adding elements with localized constants on a filter with distributed constants increased the space requirement.

Il est également connu de l'article "Narrow-band stripline or microstrip filters with transmission zeros at real and imaginary frequencies" écrit par Kari T. Jokela publié dans IEEE transactions on microwave theory and techniques, vol MTT-28, No 6, june, 1980 de réaliser des filtres passe-bande comportant de très fortes atténuations aux extrémités de la bande passante. Les filtres décrits dans cet article comportent un nombre pair de résonateurs à constante répartie, des résonateurs placés symétriquement par rapport au centre du filtre étant couplés.It is also known from the article "Narrow-band stripline or microstrip filters with transmission zeros at real and imaginary frequencies" written by Kari T. Jokela published in IEEE transactions on microwave theory and techniques, vol MTT-28, N o 6, june, 1980 to produce bandpass filters with very high attenuations at the ends of the passband. The filters described in this article include an even number of distributed constant resonators, resonators placed symmetrically with respect to the center of the filter being coupled.

Les filtres selon la présente invention comportent des résonateurs à constantes réparties. Le signal se propage par couplage entre les résonateurs constitutifs du filtre. Comme il sera expliqué ci-dessous les filtres selon la présente invention comportent au moins deux types de couplage entre résonateurs successifs.The filters according to the present invention include distributed constant resonators. The signal is propagated by coupling between the constituent resonators of the filter. As will be explained below, the filters according to the present invention comprise at least two types of coupling between successive resonators.

Dans le cas de filtres utilisant des résonateurs en forme de U, appelés aussi résonateurs en épingle à cheveux l'inversion de certains résonateurs en U par rapport à la disposition d'un filtre de type classique permet une connexion facile d'un coupleur transversal entre des résonateurs disposés symétriquement par rapport au centre du filtre. Par exemple pour réaliser un filtre comportant deux zones d'atténuation très importantes symétriques par rapport à la fréquence centrale du filtre. De tels filtres sont utilisables par exemple pour réaliser des gabarits ou pour éliminer des lobes secondaires fréquentiels d'un signal électrique.In the case of filters using U-shaped resonators, also called hairpin resonators, the inversion of certain U-shaped resonators compared to the arrangement of a filter of conventional type allows easy connection of a transverse coupler between resonators arranged symmetrically with respect to the center of the filter. For example, to make a filter comprising two very important attenuation zones which are symmetrical with respect to the central frequency of the filter. Such filters can be used, for example, to make templates or to eliminate frequency side lobes from an electrical signal.

Il existe des filtres comportant au moins deux types de couplage décrits par le brevet japonais JP-A- 60 185 402. Ceux-ci contiennent un nombre impair de résonateurs en forme de U se chevauchant pour réaliser un premier type de couplage entre les côtés extérieurs des résonateurs et un deuxième type de couplage entre les côtés intérieurs des résonateurs.There are filters comprising at least two types of coupling described by the Japanese patent JP-A-60 185 402. These contain an odd number of overlapping U-shaped resonators to achieve a first type of coupling between the outer sides resonators and a second type of coupling between the inner sides of the resonators.

Dans le cas d'utilisation de deux types de couplage d'un filtre de type combline on réalise l'éloignement des condensateurs à capacité variable ainsi, on obtient d'une part la diminution du couplage capacitif entre condensateurs, et d'autre part, on facilite l'implantation desdits condensateurs à capacité variable sur les filtres dans la mesure où ces condensateurs sont plus éloignés les uns des autres.In the case of using two types of coupling of a filter of the combline type, the capacitors with variable capacitance are removed in this way, on the one hand, the reduction in capacitive coupling between capacitors is obtained, and on the other hand, facilitating the installation of said capacitors with variable capacity on the filters insofar as these capacitors are more distant from each other.

L'invention a principalement pour objet un filtre hyperfréquence tel que défini par la revendication 1.The main object of the invention is a microwave filter as defined by claim 1.

L'invention sera mieux comprise au moyen de la description ci-après des figures données comme des exemples non limitatifs parmi lesquels :

  • la figure 1 est un schéma d'un premier exemple de réalisation de filtre de type connu ;
  • la figure 2 est un second exemple de réalisation de filtre de type connu ;
  • la figure 3 est un premier exemple de réalisation de filtre selon la présente invention ;
  • la figure 4 est un deuxième exemple de réalisation de filtre selon la présente invention ;
  • la figure 5 est un troisième exemple de réalisation de filtre selon la présente invention ;
  • la figure 6 est un quatrième exemple de réalisation de filtre selon la présente invention ;
  • la figure 7 est un cinquième exemple de réalisation de filtre selon la présente invention ;
  • la figure 8 est un sixième exemple de réalisation de filtre selon la présente invention ;
  • la figure 9 est une coupe selon AA' de la figure 8 ;
  • la figure 10 est une courbe montrant la performance du dispositif de la figure 9 ;
  • la figure 11 est une représentation d'un premier couplage utilisé dans le dispositif selon la présente invention ;
  • la figure 12 est un second couplage utilisé dans les filtres selon la présente invention ;
  • la figure 13 est un schéma équivalent du couplage de la figure 11 ;
  • la figure 14 est un schéma équivalent du couplage de la figure 12 ;
  • la figure 15 est une courbe de réponse d'un filtre selon la présente invention.
The invention will be better understood by means of the description below of the figures given as nonlimiting examples among which:
  • FIG. 1 is a diagram of a first exemplary embodiment of a filter of known type;
  • FIG. 2 is a second exemplary embodiment of a filter of known type;
  • Figure 3 is a first embodiment of a filter according to the present invention;
  • Figure 4 is a second embodiment of the filter according to the present invention;
  • FIG. 5 is a third exemplary embodiment of a filter according to the present invention;
  • Figure 6 is a fourth embodiment of a filter according to the present invention;
  • Figure 7 is a fifth embodiment of a filter according to the present invention;
  • FIG. 8 is a sixth exemplary embodiment of a filter according to the present invention;
  • Figure 9 is a section along AA 'of Figure 8;
  • Figure 10 is a curve showing the performance of the device of Figure 9;
  • FIG. 11 is a representation of a first coupling used in the device according to the present invention;
  • Figure 12 is a second coupling used in filters according to the present invention;
  • Figure 13 is an equivalent diagram of the coupling of Figure 11;
  • Figure 14 is an equivalent diagram of the coupling of Figure 12;
  • Figure 15 is a response curve of a filter according to the present invention.

Sur les figures 1 à 15 on a utilisé les mêmes références pour désigner les mêmes éléments.In FIGS. 1 to 15, the same references have been used to designate the same elements.

Sur la figure 1, on peut voir un exemple de réalisation des filtres à constantes réparties de type connu. Le filtre de la figure 1 comporte une pluralité de résonateurs 1 en forme de la lettre U. Les résonateurs sont aussi appelés résonateurs en épingle à cheveux (hairpin en terminologie anglo-saxonne). Chaque résonateur comporte deux branches de longueur L disposées symétriquement et orthogonalement par rapport à une base. Les résonateurs 1 sont disposés en quinconce et de manière à ce que les branches des deux résonateurs 1 successifs présentent un couplage électromagnétique.In FIG. 1, one can see an embodiment of the filters with distributed constants of known type. The filter of FIG. 1 comprises a plurality of resonators 1 in the shape of the letter U. The resonators are also called hairpin resonators (hairpin in English terminology). Each resonator has two branches of length L arranged symmetrically and orthogonally with respect to a base. The resonators 1 are arranged in staggered rows and in such a way that the branches of the two successive resonators 1 have an electromagnetic coupling.

Dans l'exemple illustré les filtres comportent six résonateurs 1 en U. Le premier et dernier résonateurs 1 en U sont couplés avec des moyens de connexion 2.In the example illustrated, the filters include six 1-U resonators. The first and last 1-U resonators are coupled with connection means 2.

Dans l'exemple illustré sur la figure les moyens de connexion 2 comportent une branche de longueur L parallèle aux branches de premier et dernier résonateurs 1 ainsi qu'une bande métallisée orthogonale terminée par un trou métallisé 3.In the example illustrated in the figure, the connection means 2 comprise a branch of length L parallel to the branches of first and last resonators 1 as well as a metallized orthogonal strip terminated by a metallized hole 3.

La connexion électrique est réalisée au niveau du trou métallisé 3.The electrical connection is made at the metallized hole 3.

Les filtres illustrés sur la figure 1 présentent le désavantage qu'il est extrêmement difficile de réaliser le couplage, par l'intermédiaire d'un condensateur entre deux résonateurs 1 en U symétriques par rapport à l'axe tranversal 16 du filtre. En effet, les résonateurs disposés symétriquement par rapport à un axe tranversal 16 du filtre comportent des bases du U des côtés opposés du filtre, les métallisations devant rejoindre ces deux bases, par exemple du premier et du dernier résonateurs ou du second et du cinquième, risqueraient de perturber le fonctionnement du filtre.The filters illustrated in FIG. 1 have the disadvantage that it is extremely difficult to achieve coupling, by means of a capacitor between two resonators 1 in U symmetrical with respect to the transverse axis 16 of the filter. Indeed, the resonators arranged symmetrically with respect to a transverse axis 16 of the filter comprise bases of the U on the opposite sides of the filter, the metallizations having to join these two bases, for example of the first and of the last resonators or of the second and of the fifth, may interfere with the operation of the filter.

Sur la figure 2, on peut voir un filtre de type connu dit combline. Les filtres illustrés sur la figure 2 comporte une pluralité de résonateurs droits 10. Les résonateurs droits 10 sont disposés parallèlement les uns par rapport aux autres. Chaque résonateur droit 10 est relié, par une première de ses extrémités à la masse 4, et par une seconde extrémité à une première armature d'un condensateur variable 5. La seconde armature du condensateur variable 5 est reliée à la masse 4.In Figure 2, we can see a known type filter called combline. The filters illustrated in FIG. 2 include a plurality of straight resonators 10. The straight resonators 10 are arranged parallel to each other. Each straight resonator 10 is connected, by a first of its ends to ground 4, and by a second end to a first frame of a variable capacitor 5. The second frame of the variable capacitor 5 is connected to ground 4.

Le filtre illustré sur la figure 2 peut présenter des couplages parasites entre les capacités de condensateur variable 5 et le résonateur 10 et entre les capacités elles-mêmes du fait de leur proximité. De plus, l'encombrement des condensateurs variables 5 pose des problèmes au niveau de la construction géométrique du filtre du fait de leur proximité.The filter illustrated in FIG. 2 can have parasitic couplings between the capacitors of variable capacitor 5 and the resonator 10 and between the capacitors themselves due to their proximity. In addition, the size of the variable capacitors 5 poses problems in terms of the geometric construction of the filter due to their proximity.

Sur la figure 3, on peut voir un premier exemple de réalisation d'un filtre selon la présente invention. Le filtre de la figure 3 comporte des résonateurs 1 en forme de U. Les trois premiers résonateurs 1 en forme de U sont disposés en quinconce. Le quatrième résonateur 1 en forme de U a une base disposée du même côté que le troisième résonateur 1. En fait, dans l'exemple de réalisation illustrée sur la figure 3, le quatrième résonateur 1 ainsi que le cinquième et le sixième sont disposés symétriquement par rapport à l'axe transversal 16 du filtre par rapport aux troisième, deuxième et premier résonateurs 1 en U. L'extrémité des branches de chaque résonateur en U est susceptible d'être portée à la masse (non représentée sur la figure 3). Ainsi, les couplages entre le premier et le second résonateurs 1, le second et le troisième résonateurs 1, le quatrième et le cinquième résonateur 1 et le cinquième et le sixième résonateurs 1 sont de même type, les extrémités des branches de U susceptibles d'être portées à la masse étant à l'opposée par rapport à l'axe 160. Par contre, dans le couplage entre le troisième et le quatrième résonateurs 1 les extrémités des branches des résonateurs susceptibles d'être portées à la masse sont du même côté de l'axe 160. Le couplage entre le troisième et le quatrième résonateurs 1 est d'un type différent de ceux entre les autres résonateurs 1.In Figure 3, we can see a first embodiment of a filter according to the present invention. The filter of FIG. 3 comprises U-shaped resonators 1. The first three U-shaped resonators 1 are arranged in staggered rows. The fourth U-shaped resonator 1 has a base arranged on the same side as the third resonator 1. In fact, in the embodiment illustrated in FIG. 3, the fourth resonator 1 as well as the fifth and the sixth are arranged symmetrically relative to the transverse axis 16 of the filter relative to the third, second and first U-shaped resonators 1. The ends of the legs of each U-shaped resonator may be brought to ground (not shown in FIG. 3) . Thus, the couplings between the first and second resonators 1, the second and third resonators 1, the fourth and fifth resonators 1 and the fifth and sixth resonators 1 are of the same type, the ends of the branches of U capable of be brought to ground being opposite to the axis 160. On the other hand, in the coupling between the third and the fourth resonators 1 the ends of the branches of the resonators likely to be grounded are on the same side of the axis 160. The coupling between the third and the fourth resonators 1 is of a different type from those between the other resonators 1.

Le fait de disposer de deux types de couplage différents dans un même filtre utilisant des résonateurs en épingle à cheveux, ayant un nombre de résonateurs 1 pair permet de disposer des résonateurs 1 en U disposés symétriquement par rapport à l'axe transversal du filtre 16, ayant les bases d'un même côté du filtre. Ces bases sont susceptibles d'être reliées par l'intermédiaire, par exemple d'un condensateur de façon à former un filtre comportant deux zones de forte atténuation disposées symétriquement par rapport à la fréquence centrale du filtre.Having two different types of coupling in the same filter using pin resonators hair, having a number of resonators 1 pair makes it possible to have resonators 1 in U arranged symmetrically with respect to the transverse axis of the filter 16, having the bases on the same side of the filter. These bases are capable of being connected via, for example a capacitor so as to form a filter comprising two zones of high attenuation arranged symmetrically with respect to the central frequency of the filter.

L'axe 16 est un axe de symétrie du filtre. Le barycentre du filtre constitue l'intersection de l'axe 16 avec un axe longitudinal 160 orthogonal à l'axe 16.The axis 16 is an axis of symmetry of the filter. The barycenter of the filter constitutes the intersection of the axis 16 with a longitudinal axis 160 orthogonal to the axis 16.

Sur la figure 4, on peut voir un second exemple de réalisation d'un filtre selon la présente invention comportant des résonateurs 1 en U. Le filtre illustré sur la figure 4 comporte dix résonateurs. Les sept premiers résonateurs en U sont disposés en quinconce, comme dans un filtre de type classique. Le septième et le huitième résonateurs comportent des bras disposées du même côté. Les trois derniers résonateurs 1 en U, le huitième, le neuvième et le dixième sont disposés en quinconce.In FIG. 4, a second example of embodiment of a filter according to the present invention can be seen comprising resonators 1 in U. The filter illustrated in FIG. 4 comprises ten resonators. The first seven U-shaped resonators are staggered, as in a conventional filter. The seventh and eighth resonators have arms arranged on the same side. The last three U-shaped resonators, the eighth, the ninth and the tenth are staggered.

Dans l'exemple illustré sur la figure 4 il est facile de connecter électriquement, par exemple par l'intermédiaire d'un condensateur (non représenté) le premier résonateur 1 en U au dixième résonateur 1 en U, le deuxième résonateur 1 en U au neuvième résonateur 1 en U, ou le troisième résonateur 1 en U au huitième résonateur 1 en U.In the example illustrated in FIG. 4, it is easy to connect electrically, for example by means of a capacitor (not shown), the first 1-U resonator to the tenth 1-U resonator, the second 1-U resonator to the ninth 1-in-U resonator, or the third 1-in-U resonator in the eighth 1-in-U resonator.

Les filtres de la figure 3 et 4 sont donnés comme des exemples non limitatifs des dispositions des résonateurs 1 en forme de U. D'autres dispositions comme par exemple celles comportant plusieurs changements de couplage ne sortent pas du cadre de la présente invention.The filters of FIG. 3 and 4 are given as nonlimiting examples of the arrangements of the U-shaped resonators 1. Other arrangements such as, for example, those comprising several coupling changes do not depart from the scope of the present invention.

Sur la figure 5, on peut voir un filtre de type combline selon la présente invention. Les filtres de la figure 5 comportent une pluralité de résonateurs droits à 10. Les résonateurs droits à 10 sont disposés parallèlement les uns par rapport aux autres. Le premier résonateur droit à 10 est relié, par une première de ces extrémités à la masse 4 et par une seconde extrémité à une première armature d'un condensateur variable 5. La seconde armature du condensateur variable 5 est reliée à la masse 4.In FIG. 5, a filter of the combline type according to the present invention can be seen. The filters of FIG. 5 comprise a plurality of straight resonators at 10. The straight resonators at 10 are arranged in parallel by one compared to others. The first straight resonator at 10 is connected, by a first of these ends to ground 4 and by a second end to a first frame of a variable capacitor 5. The second frame of the variable capacitor 5 is connected to ground 4.

Le second résonateur droit 10 est relié à une première extrémité à une première armature d'un condensateur variable 5 ; la seconde armature du condensateur variable 5 est reliée à la masse 4 ; la seconde extrémité du résonateur droit 10 est reliée à la masse 4, etc...The second straight resonator 10 is connected at a first end to a first armature of a variable capacitor 5; the second armature of the variable capacitor 5 is connected to ground 4; the second end of the right resonator 10 is connected to ground 4, etc ...

Les condensateurs à capacité variable 5 sont ainsi plus éloignés les uns des autres que dans un filtre combline de type classique. Ainsi, on résout le problème d'encombrement des condensateurs à capacité variable 5 et on réduit le couplage parasite entre ces condensateurs.The variable capacity capacitors 5 are thus more distant from each other than in a conventional filter type. Thus, the problem of space requirement of the capacitors with variable capacity 5 is solved and the parasitic coupling between these capacitors is reduced.

Sur la figure 6, on peut voir un filtre selon la présente invention permettant d'obtenir deux zones de fortes atténuations, par exemple par rapport à la fréquence centrale de fonctionnement du filtre. Ces zones de fortes atténuations sont aussi appelées zéro du filtre.In FIG. 6, one can see a filter according to the present invention making it possible to obtain two zones of strong attenuations, for example with respect to the central operating frequency of the filter. These zones of strong attenuations are also called zero of the filter.

Dans l'exemple illustré sur la figure 6 les filtres comportent huit résonateurs 1 en forme de U disposés symétriquement par rapport à l'axe transversal 16 du filtre. Les bases du troisième et du sixième résonateurs 1 en U sont reliées par l'intermédiaire d'un condensateur à capacité variable 55. Le condensateur 55 permet d'ajuster la courbe de réponse du filtre de la figure 6.In the example illustrated in FIG. 6, the filters comprise eight U-shaped resonators 1 arranged symmetrically with respect to the transverse axis 16 of the filter. The bases of the third and sixth resonators 1 in U are connected via a variable capacity capacitor 55. The capacitor 55 makes it possible to adjust the response curve of the filter of FIG. 6.

Il est bien entendu que d'autres résonateurs, disposés symétriquement par rapport à l'axe transversal du filtre 16 peuvent être reliés par l'intermédiaire d'un condensateur 55. Par exemple il est possible de relier le second et le septième résonateurs 1 en forme de U.It is understood that other resonators, arranged symmetrically with respect to the transverse axis of the filter 16 can be connected via a capacitor 55. For example, it is possible to connect the second and the seventh resonators 1 at U shape.

Sur la figure 7, on peut voir une variante de réalisation du filtre de la figure 6. La base de chaque résonateur 1 en U est connectée à une première armature d'un condensateur variable 5. La seconde armature du condensateur variable 5 est connectée à la masse 4.In Figure 7, we can see an alternative embodiment of the filter of Figure 6. The base of each resonator 1 in U is connected to a first armature of a capacitor variable 5. The second armature of the variable capacitor 5 is connected to ground 4.

Avantageusement, la connexion de la base des résonateurs 1 en U à la première armature des condensateurs à capacité variable 5 est effectuée au niveau d'un axe de symétrie 15 dudit résonateur 1 en U. Sur la figure 7, les condensateurs 5 sont représentés à l'extérieur des U formés par le résonateur 1. Il est bien entendu que les condensateurs variables 5 connectés à l'intérieur des U formés par le résonateur 1 ne sortent pas du cadre de la présente invention.Advantageously, the connection of the base of the U-shaped resonators 1 to the first armature of the capacitors with variable capacitance 5 is carried out at an axis of symmetry 15 of said U-shaped resonator 1. In FIG. 7, the capacitors 5 are shown at outside the U formed by the resonator 1. It is understood that the variable capacitors 5 connected inside the U formed by the resonator 1 do not depart from the scope of the present invention.

La présence de condensateurs à capacité variable 5 permet un ajustage fin du filtre.The presence of variable capacity capacitors 5 allows fine adjustment of the filter.

De plus, la longueur L des branches des résonateurs 1 en U est inférieure dans le cas du dispositif de la figure 7 à celle du dispositif de la figure 1 ou de la figure 6. L est inférieur à λg/8, λg étant la longueur d'onde guidée à la fréquence centrale du filtre. Ainsi, les filtres tels qu'illustrés sur la figure 7 présentent un encombrement moindre. Cette diminution d'encombrement est particulièrement importante pour la réalisation des filtres des équipements embarqués, par exemple à bord d'avions ou de satellites.In addition, the length L of the branches of the resonators 1 in U is less in the case of the device of FIG. 7 than that of the device of FIG. 1 or of FIG. 6. L is less than λ g / 8, λ g being the wavelength guided at the center frequency of the filter. Thus, the filters as illustrated in Figure 7 have a smaller footprint. This reduction in size is particularly important for the production of filters for on-board equipment, for example on board aircraft or satellites.

Sur la figure 8, on peut voir une variante de réalisation du dispositif de la figure 7. Les résonateurs 1 en forme de U sont reliés par une ligne de transmission 66, une capacité variable 77 étant câblée entre le milieu de cette ligne 66 et la masse 4, les résonateurs dans le cas de la figure sont respectivement le troisième et le sixième résonateurs 1 en forme de U. Lorsque l'on monte en fréquence (UHF, bande L, . . .), la valeur de la capacité 55 devient très faible. Par contre, la valeur de la capacité 77 reste plus facilement réalisable.In FIG. 8, an alternative embodiment of the device in FIG. 7 can be seen. The U-shaped resonators 1 are connected by a transmission line 66, a variable capacity 77 being wired between the middle of this line 66 and the mass 4, the resonators in the case of the figure are respectively the third and the sixth resonators 1 in the form of U. When one goes up in frequency (UHF, band L,...), the value of the capacity 55 becomes very weak. On the other hand, the value of capacity 77 remains more easily achievable.

Sur la figure 8, on a illustré un exemple de réalisation dans lequel on a utilisé comme moyen de connexion un couplage direct 20. Le couplage direct 20 est une métallisation directement connectée sur le premier et dernier résonateurs 1 en U. Le couplage direct 20 permet de résoudre le problème de réalisation des couplages du type de la figure 7. En effet dans le cas de larges bandes passantes la gravure de l'espace de couplage est très faible (<100 µm). L'endroit de la branche du résonateur en U à laquelle on effectue la connexion directe 20 est déterminé par le calcul par exemple en utilisant le logiciel spécifique développé pour la détermination des éléments du filtre. La connexion en bout de métallisation 20 constituant le couplage direct est réalisée par exemple par l'intermédiaire d'un trou métallisé 3. Il est bien entendu que la connexion directe n'est pas limitée à l'exemple de réalisation de la figure 8 mais peut être utilisée dans tous les exemples de réalisation du filtre selon la présente invention.In FIG. 8, an exemplary embodiment has been illustrated in which a direct coupling 20 has been used as the connection means. The direct coupling 20 is a metallization directly connected to the first and last resonators 1 in U. The direct coupling 20 allows to solve the problem of realization of the couplings of the type of FIG. 7. In fact in the case of wide bandwidths the etching of the coupling space is very low (<100 μm). The location of the branch of the U-shaped resonator to which the direct connection 20 is made is determined by calculation, for example using the specific software developed for determining the elements of the filter. The connection at the end of metallization 20 constituting the direct coupling is made for example by means of a metallized hole 3. It is understood that the direct connection is not limited to the embodiment of FIG. 8 but can be used in all the embodiments of the filter according to the present invention.

Avantageusement, les filtres selon la présente invention sont réalisés en technologie triplaque. Un exemple de réalisation d'un filtre en technologie triplaque est illustré sur la figure 9. La figure 9 correspond à un détail de réalisation du filtre de la figure 8 vu en coupe selon l'axe AAʹ. En technologie triplaque les résonateurs 1 en forme de U sont placés sensiblement dans un plan inclus dans un diélectrique 7 à faible perte. Au moins deux faces du diélectrique sont recouvertes par une métallisation constituant le plan de masse 4. Avantageusement le diélectrique 7 à faible perte forme un parallélépipède rectangle dont les six faces sont recouvertes par des métallisations formant le plan de masse 4 dudit filtre. Les connexions verticales portent les références 13. Elles permettent, d'une part de connecter les extrémités des branches du résonateur 1 en U au plan de masse 4, et d'autre part de connecter le condensateur à capacité variable 5 à la base des résonateurs 1 en U.Advantageously, the filters according to the present invention are produced in triplate technology. An exemplary embodiment of a filter in triplate technology is illustrated in FIG. 9. FIG. 9 corresponds to a detail of embodiment of the filter of FIG. 8 seen in section along the axis AAʹ. In triplate technology, the U-shaped resonators 1 are placed substantially in a plane included in a low loss dielectric 7. At least two faces of the dielectric are covered by a metallization constituting the ground plane 4. Advantageously the low loss dielectric 7 forms a rectangular parallelepiped whose six faces are covered by metallizations forming the ground plane 4 of said filter. The vertical connections bear the references 13. They allow, on the one hand to connect the ends of the branches of the resonator 1 in U to the ground plane 4, and on the other hand to connect the variable capacitor 5 at the base of the resonators 1 in U.

Dans l'exemple illustré sur la figure 9 la métallisation du plan de masse 4 comporte des épargnes 9 évitant de court-circuiter les bases des résonateurs en U avec la masse.In the example illustrated in FIG. 9, the metallization of the ground plane 4 includes savings 9 avoiding short-circuiting the bases of the U-shaped resonators with the ground.

Les condensateurs à capacité variable 5 sont représentés schématiquement sur la figure 9. Dans un exemple réel les condensateurs à capacité variable 5 seront implantés par exemple à la surface du filtre selon la présente invention. Dans le cas où le filtre selon la présente invention est enfermé dans un boîtier hermétique il est possible de laisser dépasser les vis de réglage des condensateurs à capacité variable 5.The variable capacitors 5 are shown diagrammatically in FIG. 9. In a real example the variable capacitors 5 will be installed for example on the surface of the filter according to the present invention. In the case where the filter according to the present invention is enclosed in a hermetic casing, it is possible to allow the adjustment screws of the variable capacity capacitors 5 to protrude.

La réalisation en technologie triplaque n'est pas limitée à l'exemple de réalisation du filtre selon l'invention de la figure 6. La technologie triplaque peut s'appliquer à tous les filtres selon la présente invention.The realization in triplate technology is not limited to the embodiment of the filter according to the invention of FIG. 6. The triplate technology can be applied to all the filters according to the present invention.

Sur la figure 10, on peut voir la courbe de réponse de deux filtres identiques l'un réalisé en technologie microstrip, l'autre réalisé en technologie triplaque. La courbe 24 correspond à la technologie triplaque. La courbe 23 correspond à la technologie microstrip. Le bruit généré est plus faible en technologie triplaque, le gain étant de l'ordre de 10 dB. La réduction de traînage est particulièrement importante dans les applications nécessitant une bonne rejection des signaux parasites.In FIG. 10, we can see the response curve of two identical filters, one made in microstrip technology, the other made in triplate technology. Curve 24 corresponds to the triple plate technology. Curve 23 corresponds to microstrip technology. The noise generated is lower in triplate technology, the gain being of the order of 10 dB. Drag reduction is particularly important in applications requiring good rejection of spurious signals.

Sur la figure 11, on peut voir une représentation symbolique d'un premier couplage entre deux résonateurs 1. Le couplage est effectué sur la figure 11 entre deux lignes 30 et 31 d'impédance Z0 et dont la longueur est égale à l'angle électrique ϑ. La ligne 30 comporte une entrée au point A et une connexion à la masse 4. La ligne 31 comporte une sortie en un point B opposé au point A et une connexion à la masse 4.In Figure 11, we can see a symbolic representation of a first coupling between two resonators 1. The coupling is carried out in Figure 11 between two lines 30 and 31 of impedance Z0 and whose length is equal to the electrical angle ϑ. Line 30 has an input at point A and a connection to ground 4. Line 31 has an output at point B opposite point A and a connection to ground 4.

Sur la figure 12, on peut voir une représentation symbolique d'un second couplage entre deux résonateurs 1. Le couplage est effectué sur la figure 12 entre deux lignes 30 et 31 correspondant par exemple au couplage entre le quatrième et le cinquième résonateurs de la figure 8. La ligne 30 comporte une entrée au point A et une connexion à la masse 4. La ligne 31 comporte une sortie en un point B situé du même côté de la ligne 31 que le point A, et une connexion à la masse 4.In FIG. 12, we can see a symbolic representation of a second coupling between two resonators 1. The coupling is carried out in FIG. 12 between two lines 30 and 31 corresponding, for example, to the coupling between the fourth and the fifth resonators in FIG. 8. Line 30 has an input at point A and a connection to ground 4. Line 31 has an output at point B located on the same side of line 31 as point A, and a connection to ground 4.

Sur la figure 13, on peut voir un schéma équivalent d'une portion du filtre selon la présente invention illustré sur la figure 11 établie d'après le livre de Matthaei édition 1980, Microwaves Filters, Impedance Matching Networks and Coupling Structures. Une portion correspondant à deux branches couplées des deux résonateurs 1 (la capacité 5 n'est pas dans le schéma équivalent) correspond à une ligne série 21 et deux lignes parallèles 22 (stubs en terminologie anglo-saxonne) d'angle électrique ϑ. La ligne 21 d'angle électrique ϑ correspond au couplage entre deux résonateurs. La ligne 22 d'angle électrique ϑ correspond aux branches des résonateurs 1 en forme de U. Avantageusement, on traduit le filtre que l'on veut obtenir en son schéma équivalent en utilisant les critères donnés dans l'ouvrage de Matthaei. Ainsi il est possible d'utiliser un logiciel de conception assisté par ordinateur pour la réalisation des filtres. On peut par exemple utiliser le logiciel de CAO, ESOPE, SUPERCOMPACT ou TOUCHSTONE.In FIG. 13, we can see an equivalent diagram of a portion of the filter according to the present invention illustrated in FIG. 11 established from the book by Matthaei edition 1980, Microwaves Filters, Impedance Matching Networks and Coupling Structures. A portion corresponding to two coupled branches of the two resonators 1 (the capacitor 5 is not in the equivalent diagram) corresponds to a serial line 21 and two parallel lines 22 (stubs in English terminology) with an electrical angle ϑ. Line 21 with an electrical angle ϑ corresponds to the coupling between two resonators. The line 22 with an electrical angle ϑ corresponds to the branches of the U-shaped resonators 1. Advantageously, we translate the filter that we want to obtain in its equivalent scheme using the criteria given in Matthaei's work. Thus it is possible to use computer-aided design software for the realization of the filters. You can for example use CAD software, ESOPE, SUPERCOMPACT or TOUCHSTONE.

Avantageusement, la traduction est effectuée par un calculateur auquel on indique le filtre que l'on veut obtenir.Advantageously, the translation is carried out by a computer to which the filter which one wishes to obtain is indicated.

Sur la figure 14, on peut voir un schéma équivalent d'une portion de filtre selon la présente invention correspondant à la représentation de la figure 12. Le schéma équivalent de la figure 14 diffère du schéma équivalent de la figure 13 par la présence entre les points A et B d'un stub série 210 d'angle électrique ϑ.In FIG. 14, one can see an equivalent diagram of a portion of filter according to the present invention corresponding to the representation of FIG. 12. The equivalent diagram of FIG. 14 differs from the equivalent diagram of FIG. 13 by the presence between the points A and B of a series 210 electric angle stub ϑ.

Sur la figure 15, on peut voir la réponse en fréquence d'un exemple de réalisation du filtre selon la présente invention.In FIG. 15, one can see the frequency response of an exemplary embodiment of the filter according to the present invention.

Sur l'axe des abscisses 47 on a porté la fréquence f. Sur l'axe des ordonnées 41 on a porté l'amplitude A. L'axe des ordonnées 41 est par exemple un axe dont l'échelle est logarithmique.On the abscissa axis 47 we have plotted the frequency f. On the ordinate axis 41, the amplitude A has been plotted. The ordinate axis 41 is for example an axis whose scale is logarithmic.

Un exemple de réponse en fréquence du filtre selon la présente invention porte la référence 43. Ce filtre permet d'obtenir deux zéros centrés sur les fréquences 44 et 46, par exemple disposées symétriquement par rapport à la fréquence centrale 45 du filtre. Les zéros 44 et 46 du filtre seront par exemple superposés à des lobes secondaires fréquentiels dans le signal électrique à filtrer, qui autrement seraient très gênants.An example of frequency response of the filter according to the present invention bears the reference 43. This filter makes it possible to obtain two zeros centered on the frequencies 44 and 46, for example arranged symmetrically with respect to the central frequency 45 of the filter. The zeros 44 and 46 of the filter will be by example superimposed on frequency side lobes in the electrical signal to be filtered, which would otherwise be very annoying.

Avantageusement, pour obtenir un filtre de gabarit à partir du point 44 et avant le point 46 la courbe 43 est sensiblement verticale. Sur la plus grande partie centrée autour de la fréquence 45 la courbe 43 est sensiblement horizontale.Advantageously, to obtain a template filter from point 44 and before point 46 the curve 43 is substantially vertical. On the greater part centered around the frequency 45 the curve 43 is substantially horizontal.

La technologie selon la présente invention est utilisable à partir des hautes fréquences radioélectriques. Son efficacité est notamment très importante dans les bandes VHF, UHF et en bande L.The technology according to the present invention can be used from high radio frequencies. Its effectiveness is particularly very important in the VHF, UHF and L band.

L'invention s'applique principalement à la réalisation des filtres, notamment des filtres hyperfréquences et au dispositif utilisant de tels filtres.The invention applies mainly to the production of filters, in particular microwave filters and to the device using such filters.

Claims (10)

  1. A radio-frequency filter having a longitudinal axis (160) comprising a plurality of resonators (1, 10), each resonator comprising at least one extremity carried to earth (4), two successive resonators (1, 10) having an electromagnetic coupling zone, the first and last resonators (1, 10) being connected to connection means (2, 20) of the filter, said filter comprising an even number of resonators (1, 10), the resonators not overlapping, characterised by the fact that said filter comprises at least one coupling zone between successive resonators (1, 10), the extremities carried to earth (4) of which are on the same side of the longitudinal axis (160) and at least one coupling zone between successive resonators (1, 10), the extremities carried to earth (4) of which are on either side of the longitudinal axis (160).
  2. A radio-frequency filter according to Claim 1, characterised by the fact that the resonators (1) are U-shaped.
  3. A filter according to Claims 1 or 2, characterised by the fact that it comprises an axis of transverse symmetry (16).
  4. A filter according to Claim 1, characterised by the fact that the resonators (10) are straight resonators connected at one of their extremities to a variable capacitor.
  5. A filter according to Claim 1, 2 or 3, characterised by the fact that two U-shaped resonators (1) disposed symmetrically relative to the axis of transverse symmetry (16) of the filter are electrically connected through the intermediary of a variable capacitor (55).
  6. A filter according to Claim 5, characterised by the fact that two U-shaped resonators (1) disposed symmetrically in relation to the axis of transverse symmetry (16) of the filter are directly connected electrically, through the intermediary of the variable capacitor (55), the bases of all the U-shaped resonators (1) being connected to first armatures of the capacitors (5), the second armatures of which are connected to earth (4).
  7. A filter according to Claim 1, 2 or 3, characterised by the fact that two U-shaped resonators (1) disposed symmetrically relative to the axis of transverse symmetry (16) of the filter are electrically connected through the intermediary of a transmission line (66), an adjustable capacitor (77) being wired between the centre of this line and earth (4).
  8. A filter according to any one of the preceding claims, characterised by the fact that the U-shaped resonators (1) are placed substantially on a plane included in a low-loss dielectric (7), at least two faces of the dielectric (7) being covered by a metallisation constituting the earth plane (4) of the filter.
  9. A filter according to Claim 8, characterised by the fact that the low-loss dielectric (7) forms a rectangular parallelepiped, the six faces of which are covered with metallisations forming the earth (4) of said filter.
  10. A filter according to Claim 1, 2, 3, 5, 6, 7, 8 or 9, characterised by the fact that the extrimities of the U-shaped resonators (1) are electrically connected to earth.
EP88400702A 1987-03-31 1988-03-23 Filter with distributed constant elements associating two kinds of coupling arrangements Expired - Lifetime EP0285503B1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FR8704486A FR2613557A1 (en) 1987-03-31 1987-03-31 FILTER COMPRISING CONSTANT DISTRIBUTED ELEMENTS ASSOCIATING TWO TYPES OF COUPLING
FR8704486 1987-03-31

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EP0285503A1 EP0285503A1 (en) 1988-10-05
EP0285503B1 true EP0285503B1 (en) 1993-01-07

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EP88400702A Expired - Lifetime EP0285503B1 (en) 1987-03-31 1988-03-23 Filter with distributed constant elements associating two kinds of coupling arrangements

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US (1) US4992759A (en)
EP (1) EP0285503B1 (en)
JP (1) JPS63258101A (en)
DE (1) DE3877235T2 (en)
FR (1) FR2613557A1 (en)

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Also Published As

Publication number Publication date
EP0285503A1 (en) 1988-10-05
JPS63258101A (en) 1988-10-25
DE3877235D1 (en) 1993-02-18
US4992759A (en) 1991-02-12
FR2613557A1 (en) 1988-10-07
DE3877235T2 (en) 1993-05-06

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