FR2463539A1 - MECHANICAL FILTER STRUCTURE WITH ELECTRICALLY COUPLED CERAMIC RESONATORS AND METHOD OF MANUFACTURING THE STRUCTURE - Google Patents

Abstract

THE INVENTION RELATES TO THE MANUFACTURE OF A STRUCTURE ALLOWING THE MECHANICAL ASSEMBLY AND ELECTRIC COUPLING OF THE RESONATORS OF A CERAMIC FILTER. A SELF-SUPPORTING STRUCTURE, CONSTITUTED BY THE ONLY COUPLING CONDUCTORS AND RESONATORS NECESSARY FOR THE REALIZATION OF A GIVEN FILTERING NETWORK, IS OBTAINED BY CUTTING OR SELECTIVE ATTACK OF A METAL SHEET TO FORM A SET OF 6, 9 METALLIC TAPE THAT WILL CONSTITUTE THE CONDUCTORS OF THE FILTER. THE ASSEMBLY INCLUDES AT LEAST TWO LONGITUDINAL RIBBONS 5, 6 AND TRANSVERSAL RIBBONS 9 CONNECTED ON AT LEAST ONE CENTRAL AXIS BY RIBBONS WITH A PARTICULAR PROFILE WHICH ARE THEN CUT INTO TWO ELEMENTS 7 TO BE STRAIGHTENED VERTICALLY AND WELD EACH ON ONE FACE OF ' A RESONATOR 1, 2. A VERTICAL PROFILING OF THE RIBBONS 5 AND 6, FOR EXAMPLE TRAPEZOIDAL 11, IMPROVES THE RIGIDITY OF THE STRUCTURE. APPLICATION TO THE MANUFACTURE OF LARGE SERIES CERAMIC FILTERS BY CUTTING STRUCTURES IN ACCORDANCE WITH THE INVENTION IN AN ENDLESS TAPE.

Description

The present invention relates to the mechanical structure of filters

  with ceramic resonators, which will be referred to more briefly, by the former

  Pressure "Ceramic filters", in which at least two resonators are coupled by electrical conductors, and a method of manufacturing this structure. The patent of the Federal Republic of Germany (FRG) DE-AS 1796 146 can be consulted regarding the use of ceramic resonators to constitute certain types of filters, in particular narrow-band filters for the medium-frequency circuits of the radio frequency receivers. broadcasting. DE-AS Patent 2,017. 488 (FRG) discloses several embodiments of filter networks with ceramic resonators but, like the first patent cited, makes no reference to the construction

mechanical ceramic filters.

  The patent application P 28 48 844 0 - 35, filed in the FRG Novemore i1'7u, relates to a piezoelectric ceramic filter comprising a plurality of ceramic resonators supported by a base plate of insulating material. The resonators are held along their nodal line in notches of appropriate width of the insulating plate or lead conductors printed on one side of this plate according to

  the required scheme of the filter network.

  The object of the present invention is to provide a structure of

  ceramic filter. much simpler and less expensive manufacturing.

  This object is achieved in that in a structure according to the invention, the coupling conductors of the ceramic resonators are conductive ribbons cut in a metal sheet so as to have end portions which are then straightened by a simple folding operation and electrically and mechanically connected

  said resonators to constitute a self-supporting structure.

  The elements constituting the mechanical structure of a ceramic filter are thus reduced to the absolutely necessary minimum for the electromechanical filtering circuit, ie the coupling conductors and the ceramic resonators. These essential elements are assembled in a self-supporting structure that does not require additional parts

  such as resonator supports, base plates etc ...

  - The invention will be better understood when reading the description

  which will follow, made by way of non-limiting example with reference to the appended figures which represent: FIG. 1: an example of a conventional ceramic filter scheme;

2 463539

  Figure 2: a top view of a structure.conforme the invention for the ceramic filter of Figure 1; Figure 3: a side view of the previous structure; Figures 4 and 5: respective top views of two different structures according to the invention for the series production of filters in accordance with the diagram of Figure 1; FIG. 6: a perspective view of a part of a filter

  ceramic structure according to the invention.

  A ceramic filter structure according to the invention is preferably produced as the interconnection of a set of ceramic filters of the type shown in FIG. 1. In this figure, the individual ceramic resonators are represented by rectangles bearing the numerical references 1 to 4, and the references E, A, G respectively represent the input terminal, the output terminal and the terminal common to the two doors of the filtering tripole obtained by the indicated coupling of the four resonators. It should be noted that the ceramic filter structure according to the invention is not limited to an elementary filter cell of this type, but that it can be used to construct any required filtering network, regardless of its complexity. . FIG. 1 therefore represents a diagram among others, with the aim of providing a reference to the physical embodiments represented by the following figures. Referring now to Figures 2 and 3 which are respectively bottom and side views of a structure according to the invention for the previous elementary filter. They show how the ceramic resonators 1 to 4 are connected by metal ribbons 5, 6, 9 provided with vertical terminations 7. The diagram of the filter is recognizable in FIG. 2 and the self-supporting structure obtained, eliminating any need for an additional piece of metal. frame without utility

  for the functions specific to the filter, appears clearly figure 3.

  The interconnection diagram of FIG. 2 is formed preferably

  by eliminating unnecessary parts of a metal strip by selective metal etching or die cutting. The end portions 7 are preferably folded up 900 and electrically and mechanically connected to the appropriate ceramic resonators, for example by welding. The portions 7 may be vertical only in their upper half, each resonator being maintained above the base plane of the structure between the vertical ends of the end portions 7, as shown in FIG. 3. The shape of these end portions can be seen completely as in Figure 6 and, in referring to this figure, we see that their first half has the normal width of the ribbon at the lower end o is the first fold at an angle less than 900 and s' refines to the narrower base of the upper half o a second fold brings this end of

connection in the vertical plane.

  When a ceramic filter having a structure conforming to

  the invention is placed or mounted on a base plate of a frame of equipment-

  electrically, ceramic resonators can still oscillate freely. A sheet of a suitable metal must of course be used for the formation of conductive ribbons, for example the material sold under the name Vakon 520 S. The sheet of this material may have, for example,

for example, a thickness of 0.1 mm.

  The interconnection diagram preferably comprises two conductive strips 7, 6, parallel to each other, and the ceramic resonators 1 to 4 are arranged one behind the other in a single row. Of course, the manufacture of a ceramic filter structure according to the invention is carried out continuously with many other structures in a much longer metal strip, and the individual filters are then detached by cutting the corresponding segments of this strip.

  that one can practically consider as an endless band.

  The structure of the invention is a mechanical assembly of electrical conductors and ceramic resonators. Transverse connection strips (9) are provided at the points of the circuit which require it for technical reasons and the continuity of the longitudinal strips is generally preserved in the first cutting operation to increase the rigidity of the strip during manufacture. The original continuity of the parallel ribbons 5 and 6 is shown in dashed lines in FIG. 4 which more precisely illustrates the practical embodiment of a filter structure similar to that of FIG. 2. Dashed lines also indicate connections. individual longitudinal

  8 between the end portions 7 of several trans-ribbons

  versaux 9, these connections being still stiffness links along a central axis parallel to the two ribbons 5, 6 and on which the resonators 1 to

  4 are mounted in line between the free ends, straightened vertically

  7 also shows the separating lines along which the endless metal band is divided into corresponding individual filter structures.

2463539.

  to the diagram in Figure 1. The stiffness connections are then removed

  during the same cutting operation.

  A structure in which the physical implantation of the filter elements is different but which still responds to the electrical diagram of FIG. 1 is shown in FIG. 5. More precisely, the latter represents two identical structures formed side by side on the same metal strip. and to detach from one another and the other structures obtained by the continuous manufacturing process, by cutting the strip along the lines 10. In this type of structure also in accordance with the invention, the four ceramic resonators are divided into two

  parallel rows between two metal ribbons of the same direction 5 and 6.

  The structure obtained is therefore shorter but wider than the first.

  Figure 5 shows the second structure as square while the structure of Figure 4 has the shape of a rectangle four times longer than

  large. The surface of the two structures is identical.

  Additional longitudinal connections 8 are still used during manufacture of the structure of FIG. 5 as well as the transverse connections 9 necessary to obtain the required electrical diagram. At the moment of detachment of the individual structures along the lines 10, smaller cuts will also be made, as already mentioned, to eliminate the short circuits that may remain between the terminals of certain resonators. According to the configuration of FIG. 5, the cuts made according to the large lines 10 leave no short circuit but the indicated portions between the small and the

  10 are unnecessary and should also be deleted.

  To improve the mechanical stability of the self-supporting structure

  according to the invention, the two outer conductors 5 and 6 can be bent in the vertical plane so as to have a sinuous profile between two levels of this plane, as indicated in the perspective view of FIG. The profile shown is more precisely comprised of trapezoidal sections 11 extending above the base plane of the longitudinal ribbons 5. 6 and transverse ribbons 9; it must be emphasized, however, that the invention is not limited to the use of a

  such profile and that striated or corrugated shapes are also valid -

  75. to increase the rigidity of the ribbons.

  In all cases, we obtain a very simple self-supporting structure and very easy manufacturing which consists only of the conductors and resonators necessary for the electrical function of the filter. The manufacture is summed up in fact with the already indicated operations of cutting a virtually endless metal strip according to a succession of interconnection diagrams by metal strips, each appropriate to a chosen physical configuration of the coupling conductors of a filter, of folding to the press of the end parts attached to certain ribbons, deformation of the longitudinal ribbons to give them a sinuous or wavy longitudinal profile; fastening each resonator between a respective pair of terminal portions above the base plane of said ribbons so as to mechanically hold and electrically couple said resonators, and cut-press superfluous connections connecting the individual filters to the strips; as well as some

  internal conductors of each filter.

  The pattern of conductive ribbons is preferably achieved by selectively etching unnecessary portions of the metal strip or by cutting these portions by means of a punching machine, wherein interconnected patterns of a plurality of filters are formed in series in the same manner. tape, as already indicated. After their folding, it is better for the end parts to be tinned to increase their weldability on the

  electrodes of ceramic resonators.

  It is obvious that the previous description was made

  as a non-limitative example and that other variants could be

  be considered without departing from the scope of the invention.

6 2463539

Claims (8)

  1. Ceramic filter structure comprising at least two   ceramic resonators coupled by electrical conductors, characterized   derided by the fact that said conductors are metal ribbons   (5,6,8,9), cut from a sheet of metal according to a schemad'intercon-   an appropriate connection in which certain segments (8, 9) of said ribbons have a shaped or profiled end portion (7) which is electrically and mechanically connected to a corresponding electrode of one of the ceramic resonators, so that the set of conductive ribbons   and resonators constitutes a self-supporting structure.   Ceramic filter structure according to claim 1,   characterized by the fact that it comprises two parallel conducting ribbons   to each other and, if necessary, interrupted or connected to each other on the other side (1 i 4) being arranged on one or several rows between said ribbons parallel.   3. ceramic filter structure according to claim 1 or 2, characterized in that said end portions of the conductive strips are lateral cuts perpendicular to the transverse tapes which connect them to a longitudinal strip, or to two parallel tapes, and folded orthogonally in terms of said ribbons   so that the ceramic resonators are mounted above said plane.   4. Ceramic filter structure according to any one   Claims 1 to 3, characterized in that said ribbons   parallel longitudinal lines are bent several times in the vertical plane so as to present a sinuous or corrugated longitudinal profile between   two horizontal lines of said vertical plane.   5. Method of manufacturing ceramic filter structures   according to any of claims 1 to 4, characterized by   the fact that it comprises the cutting operations of a virtually endless metal band, according to a succession of interconnected grids, each composed of narrow segments of the strip, the continuous assembly of which constitutes the conductive ribbon diagram required for a given ceramic filter folding, in the vertical plane, the short metal segments constituting said end portions (7), for forming the elongated segments constituting said longitudinal strips in a sinuous or corrugated profile in the vertical plane, for inserting said ceramic resonators (1 to 4) between said vertical end portions (7) with formation of joints ensuring good mechanical rigidity and good electrical contacts, and cutting of the individual filter structures by breaking the junctions between said successive grids and stiffness segments not included in the diagram of conductive ribbons of each filter. 6. Manufacturing method according to claim 5, characterized in that said pattern of conductive ribbons is obtained by selective attack of the parts of the strip located outside of said   segments necessary to said scheme and said stiffness segments.   7. Manufacturing process according to claim 5, characterized in that said pattern of conductive ribbons is cut   to the press in said metal strip.   8. Manufacturing process according to any one of   claims 5 to 7, characterized in that said parts   Terminals are tinned after being folded.