DE898339C - High frequency filter in connection with a high frequency waveguide - Google Patents

Description

The invention relates to microwave transmission equipment and, more particularly, to a filter and Means for looping the filter into a transmission system by means of appropriate coupling devices.

In addition to the transmission of microwave energy over radio links, koaxjale There is another very broadband transmission option for cables and hollow waveguides Microwave energy through the so-called surface waveguide, this is a metallic wire with a dielectric surface layer. By The dielectric covering of the wire will expand the electromagnetic field around it the wire is very limited and concentrated tightly around the wire. For example, has an ordinary No. 12 enamelled copper wire has an electromagnetic field concentration that is within a radius of 75 to 100 mm around the wire and taking all of the high frequency energy propagates in this field. This surface wave guide has very small losses and is practically free from electrical and other interference as long as the concentrated electrical Field around the conductor is not disturbed.

It is an object of the invention to provide a filter for the passage of certain microwave frequencies and the specification of a coupling arrangement for the filter in microwave transmission lines.

Embodiments of the invention Filters are described in more detail with reference to the drawings.

Fig. Ι is a side view of an inventive Filters;

Fig. 2 shows a longitudinal sectional view of the same type of filter with a surface waveguide is coupled;

Fig. 3 is a longitudinal sectional view of the filter connected to a coaxial line, and

Figure 4 is a longitudinal sectional view of another filter coupled to a coaxial line is.

! ■ 5 Fig. 1 shows a filter which consists of a conductor ι whose diameter can be the same as the diameter of the surface waveguide to which the filter is coupled, although the conductor can also have any other size, depending on the filter design and the Coupling into the transmission system. The conductor ι is provided with reinforced parts that can have the shape of disks that are applied to the conductor ι at intervals. A. The basic filter part consists of a number of such disks. The disks can be circular, elliptical, rectangular, triangular or any other shape as long as they do not cause disturbance in the wave propagation. The conductor 1 can also have a cross-section other than round, namely a cross-section which is approximately the same as the cross-section of the disks applied to it. The distance d between the panes has a direct influence on the frequency band allowed through by the filter. The upper limit wavelength of the filter can be given by the formula

0 = d / 2
and the lower cutoff wavelength by the formula

u = d

being represented. A narrow bandpass filter can be achieved by using two such filters in Daisy chain can be constructed with one of the filters as a high pass filter and the other as a a low-pass filter is constructed.

The above equations apply in the event that no radiation occurs. Too great a thickness W in relation to the distance d would cause undesirable energy radiation. The thickness W should therefore be kept small. The ratio of the cross-sectional dimensions or the diameter D to the diameter of the conductor 1 influences the steepness and attenuation of the filter.

The difference between the radius of the washers and the radius of the conductor should not be greater than be a quarter wavelength of the upper limit wavelength.

The filter shown in Fig. 1 is not dielectric Covering, however, it can be covered with enamel, glass, polystyrene, polyethylene, etc. when the electromagnetic field is concentrated along the filter tightly around the filter parts shall be. The filter shown in FIG. 2 shows such a dielectric covering 3. The filter shown in FIG The filter structure shown has end plates, dis reduce interference in microwave propagation in either direction through the filter. The end parts consist of a number of disks 4, the diameter of which is continuous, except for an end disk 5 of the filter, the diameter of which is only slightly larger than the diameter of the Conductor 1. The conductor 1 is coupled to a surface waveguide 6 or behind the end plate 5 j itself forms part of the conductor 6. The conductor 1 and the disks of the filter are provided with an insulating layer 3, the thickness of which corresponds to the insulation on the surface waveguide 6! These However, insulation coverage of the filter can be thicker or thinner, depending on which one Diameter the electromagnetic field around the filter! Should be concentrated and which Filter effect is to be achieved.

In Fig. 3, a filter provided with tapered parts is coupled to a hollow conductor 7 shown, which is the wall of a hollow waveguide or the outer conductor of a coaxial line. The end part 8 of the hollow conductor is preferably bent up in a funnel shape, and the end parts of the filter are funnel-shaped in this Part arranged. The end filter part 5 is closely adjacent to the inner end of the funnel-shaped Part 8, so that the taper angle of the end parts corresponds approximately to the opening angle of the funnel 8. Where the hollow conductor 7 has a center conductor 9, as in the case of a coaxial line, there is insulation tapers from the periphery of the end disk 5 to the surface of the conductor 9, as shown by the body 10 is. The disks preferably have the same contour shape as the cross section of the waveguide or the coaxial line.

In FIG. 4, the filter is located between a microwave transmission line in the manner of a coaxial line, which consists of an outer conductor 11 and an inner conductor 12. The outer conductor 11 is bent up in a funnel shape at 13. The hollow conductor 11 contains a solid dielectric 14 which extends outwardly beyond the funnel-shaped part 13 with a constant external diameter. In this embodiment the filter has a tapered end portion 15 which has a maximum diameter D which corresponds to the diameter of the other parts 16 of the filter. The end part 15 is tapered from its maximum diameter to the surface of the conductor 12 along the same distance as the funnel part 13, so that the taper angle practically corresponds to the opening angle of the funnel.

In both of the exemplary embodiments shown in FIGS. 3 and 4, the tapered end part of the filter is located lao inside the funnel-shaped end of the outer conductor. This arrangement causes a trouble-free Transfer of energy from one mode of energy transport to the other. In Fig. 4 is the thickness of the dielectric body in the conductor 11 along the part 15 in the direction .auf the filter gradually

reduced to the thickness of the dielectric layer with which the filter is coated. These gradual change in the dielectric also helps reduce disturbances in wave propagation at.

Changes in the exemplary embodiments are of course possible without further ado. To the For example, the disks can have a wide variety of shapes, as long as the cross-section de γιο same is symmetrical. The discs can also be manufactured separately and attached to the conductor or the conductors and washers can be made in one piece.

Claims (11)

Patent claims: i. High frequency filter in connection with a high frequency waveguide, marked by a single conductor and a number of reinforced conductor parts that extend in a radial direction Direction away from the conductor and equal, mutual distance from each other exhibit. 2. Filter according to claim 1, characterized in that the reinforced parts with a dielectric layer 'are covered. 3. Filter according to claim 1, characterized in that the conductor and the reinforced Parts of the same are covered with a dielectric layer. 4. Filter according to claim 1, characterized in that the end parts of the filter in the outer Perimeter are stepped, with the outermost end portion in the outer perimeter only slightly is larger than the diameter of the conductor. 5. Filter according to claim 4, characterized in that the conductor and the reinforced Parts are covered with a dielectric layer and that the dielectric layer is dated The circumference of the last reinforced part is tapered to the surface of the conductor. 6. Filter according to claim 1, characterized in that the last reinforced on both sides Part (end part) of the filter of a diameter practically equal to the diameter of the Middle part is tapered down to the diameter of the conductor. 7. Filter according to claim 1, characterized in that a hollow waveguide with a End of the filter is coupled> and that the end portion of the filter is at least partially inside of the end portion of the hollow waveguide. 8. Filter according to claim 1, characterized in that a hollow waveguide with a The end of the filter is coupled so that the hollow waveguide has a funnel-shaped bent up Has end part and that the end part of the filter at least partially within said funnel-shaped part is arranged. 9. Filter according to claim 8, characterized in that the end part of the filter has a Has a diameter that is smaller than the diameter of the waveguide. 10. Filter according to claim 8, characterized in that 'adjacent to the end portion on both sides reinforced parts have a progressively smaller diameter towards the end part. 11. Filter according to claim 8, characterized in that that the hollow conductor contains a body of dielectric material, which is at least also extends over the funnel-shaped part of the hollow conductor, and that the end part ■ the filter is embedded in this dielectric body. Referred publications:
German patent specification No. 600on. 1 sheet of drawings © 5606 11.