FR2511548A1 - COAXIAL STRUCTURE TAPE FILTER - Google Patents

Abstract

BAND CUT FILTER WITH DIELECTRIC RESONATORS, ALLOWING TO CUT A WIDE BAND OF FREQUENCIES. THIS FILTER IS REALIZED USING A COAXIAL WAVE GUIDE 1 AND DIELECTRIC RESONATORS 2, 3 PIERCED WITH A HOLE; THE INTERNAL CONDUCTOR 10 OF COAXIAL GUIDE 1 PASSES THROUGH THE HOLE OF EACH OF THE RESONATORS. APPLICATION TO THE FIELD OF HYPERFREQUENCES.

Description

COAXIAL STRUCTURE TAPE FILTER

  The present invention relates to a notch filter comprising

  both a coaxial waveguide closed at both ends and N resonators

  dielectrics arranged in the coaxial waveguide.

  Such filters are known in the microwave field.

  In these known filters the resonators are each arranged on one side of the inner conductor of the waveguide, generally the same side for all the resonators, and are secured to the inner wall of the outer conductor, for example by a support fixed to this wall or by a screw for adjusting the position of the resonator, screw which passes through the conductor

external coaxial waveguide.

  These known notch filters have the drawback of not

  not cut a wide band of frequencies.

  The object of the present invention is to remedy this defect by proposing band-stop filters of clearly defined bandwidth.

  greater than the bandwidth of known filters.

  This is achieved by a filter in which the arrangement of the resonators allows efficient coupling to the coaxial waveguide by

  via the TM 11 electric dipole mode.

  According to the invention, a notch filter comprising a coaxial waveguide closed at both ends and N resonators (n positive integer) arranged in the coaxial waveguide, is characterized in that the resonators are pierced, from part of a hole through which passes

  the inner conductor of the coaxial guide.

  The present invention will be better understood and other characteristics

  ticks will appear using the following description and figures

  which represent: FIG. 1 a view of a filter according to the invention, some parts of which have been removed to show the inside,

  FIG. 2 is a sectional view of the filter of FIG.

  FIG. 1 shows a filter with a coaxial structure of which a part of the casing has been removed and another cut to allow to see the

internal elements.

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  The filter according to FIG. 1 is made from a coaxial waveguide, 1, of longitudinal axis, YY, whose inner conductor 10 is

  connected at both ends to the international conductors respectively

  60, 70, two coaxial jacks 6 and 7 The outer conductor 11 of the coaxial guide has at its ends, the section of its inner wall which decreases; thus are constituted two adaptation sections, 12, 13, to adapt the impedance of the guide to that of the coaxial conductors to which it is intended to be connected by its sockets 6 and 7 This external conductor It is in fact made up of two parts symmetrical with respect to the plane of Figure 1; one, 110, of these two parts appears in Figure 1 while the other has, as indicated before, been removed to show the interior

of the filter.

  Two plates, 4, 5, sectional views along a plane which is the plane of Figure 1, are pierced respectively by two holes 40, 60 through which pass the inner conductors of the outlets 6, 7; these two plates

  are screwed at the end of the guide As for sockets 6 and 7 they are, themselves

  same, respectively screwed into the plates 4, 5, thus forming, with these plates and the outer conductor 11 of the guide 1, a closed housing of which

  the internal surfaces are silver.

  Two dielectric resonators 2, 3 of zirconium titanate permittivity 36 bring a band-cut function in the coaxial guide 1 These resonators are in the form of hollow cylinders of outer diameter substantially equal to three times the diameter of their inner hole and the These resonators are arranged in such a way that their longitudinal axis coincides with the longitudinal axis YY of the coaxial waveguide 1, that is to say such that the inner conductor of the guide wave traverses the hole of the resonators Two spacers, 30, made of organic permittivity glass 2, in the form of a cylindrical sleeve, are interposed between the inner conductor 10 of the guide 1 and,

  respectively, the resonators 2 and 3.

  Figure 2 is a sectional view taken along a sectional plane perpendicular to XX to the plane of Figure 1; this section plane is perpendicular to the longitudinal axis YY of the coaxial waveguide 1 and passes through the resonator 2 FIG. 2 shows four concentric elements: in the center the inner conductor 10 of the coaxial guide,

  the spacer 20 of internal diameter substantially equal to the diameter

  the internal conductor 10, the resonator 2 whose diameter of the hole is substantially equal to the outside diameter of the spacer, and the outer conductor 11 of the coaxial guide 1 with its two parts, 110 and 111; this external conductor has, at least outside the adaptation sections 12 and 13 (see FIG. 1), an inside diameter which is clearly greater than the outside diameter of the

  resonator 2 and therefore also resonator 3 (see Figure 1).

  As they have been described and shown the resonators 2 and 3 are not in contact with the outer conductor 11 of the coaxial guide 1 and a low permittivity material (spacers 20 and 30) is interposed between each of them and the driver internal 10 of the guide; this arrangement is intended to minimize Joule losses in the filter, it being understood that it is possible to produce filaments according to the invention where the

  resonators would be in contact with one or both of the

coaxial guide.

  Figure 2 has also been shown in phantom

  broken with an arrow, the magnetic field lines, H, which correspond to

  TM011 propagate in the coaxial guide and provide coupling between the guide and the resonators when they are at their

resonance frequency.

  In the filter which has just been described, as indeed in the case of conventional notch filters, the distance between the resonators is of the order of 3 X g λ g is the wavelength, in the guide of wave, corresponding to the average frequency of the band cut by the filter and o X g is equal to the length (base> X, in free space, corresponding to the average frequency of the band cut by the filter, when the guide

  is a coaxial guide as is the case for the described filter.

  As an indication, the filter which has been described with reference to FIGS. 1 and 2 has an overall length of approximately 15.5 cm. This filter, as conceived, makes it possible to obtain a decay of 56 decibels in a band of

  400 M Hz centered on a frequency of 3 850 M Hz.

  It should be noted that the bandwidth of the notch filter according to FIGS. 1 and 2 can be modified by changing the coupling between the resonators and the coaxial waveguide; this change can be obtained by a modification of the diameter of the inner hole of the resonators: the closer this diameter is to that of the inner conductor of the waveguide

  coaxial and the width of the cut tape is important.

  The present invention is not limited to the example described or to the variants suggested above. Thus, the filter may comprise only one resonator or may comprise three or even more; in the latter case two consecutive resonators will be spaced apart by about 3 x 20, being, as indicated above, the wavelength, in the free space, corresponding to the average frequency of the band cut by the filter. , Interposed between the resonators 2, 3 and the inner conductor 10 (see FIGS. 1 and 2) may, for example, be replaced by spacers arranged between the resonators and the

  external conductor 11 of the coaxial guide.

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Claims (5)

REVEN l DICATIONS   1 Notch filter with a coaxial waveguide (1) closed at both ends and N resonators (n positive integer) (2, 3)   disposed in the coaxial waveguide, characterized in that the resonances   2, 3) are pierced, from one side, through a hole through which the inner conductor (10) of the coaxial guide passes. 2 filter according to claim 1, characterized in that it comprises isolation means (20, 30) for electrically isolating the resonators   internal (10) and external (II) conductors of the coaxial waveguide.   3 Filter according to claim 2, characterized in that the insulation means are spacers of low permittivity dielectric material, interposed between each resonator (2, 3) and the driver   internal (10) of the coaxial waveguide (1).   4 Filter according to claim 1, characterized in that, the inner conductor of the coaxial guide being a cylinder of diameter d and the resonators of the tubular resonators of internal diameter D (with D> d), a dielectric tubular spacer of low permittivity separates   each resonator of the inner conductor of the coaxial guide, this spacer   having substantially equal inner and outer diameters   at d and D. Filter according to Claim 1, where N is at least 2, characterized in that the distance between two consecutive resonators (2, 3) is of the order of 3, where is the wavelength, corresponding to the   average frequency of the band cut by the filter.