DE1076761B - Curved waveguide section or bend - Google Patents

Description

GERMAN

The invention relates to curved waveguide sections or bends used for transmission electromagnetic waves of the Hoi type are suitable.

The H ₀₁ electromagnetic waveform is of particular interest because of its low damping when it is transmitted along the inside of a hollow metal tube at a frequency well above the cutoff value. This property is a result of the absence of a longitudinal flow in the pipe wall. Difficulties arise when such a waveform is transmitted along a straight tubular waveguide and at a frequency of 35,000 megahertz, with attenuations on the order of 14 decibels per 1,600 m in a copper pipe with an inner radius of 1.72 cm ( 3.81 cm outer diameter) can easily be obtained. Changes in the pipe cross-section, which must normally be expected in industrial production, and tolerances in the longitudinal alignment, which can easily be counteracted, are taken into account here. However, in the practical use of such a waveguide as, for example, a long-distance transmission channel, intended curved portions, usually called bends, are inevitable, and it has been found that in such bends other _{waveforms deviating from the H 01} shape tend to cause an increase in losses .

An elbow is already known which has a special dielectric in the area of its curvature Material is filled, its dielectric constant with respect to the arc, which the elbow describes, increases radially inward. The manufacture of such a manifold runs into difficulties, since such a material cannot be produced with the required uniformity.

The aim of the invention is to create a waveguide bend which is suitable for the transmission of the electromagnetic H ₀₁ waveform and in which the losses are reduced in comparison with these previously used waveguides.

The invention eliminates the material difficulties eliminated as the required dielectric properties; especially their variation, result in the manufacture of the manifold according to the invention by itself.

In the case of a curved waveguide section or bend for the transmission of electromagnetic waves, of the type H _olJ in which the dielectric constant increases radially inward, the filling according to the invention consists of a dielectric cellular material, in particular cellular polyethylene or

Curved waveguide section
or elbow

Applicant:

Imperial Chemical Industries Limited,

London,

and Harold Everard Monteagle Barlow,
Banstead, Surrey (UK)

Representative: Dipl.-Ing. A. Bohr, Dipl.-Ing. H. Bohr,
Dipl.-Ing. S. Staeger, Munich 5,

and Dr.-Ing. H. Fincke, Berlin-Lichterfelde, Drakestr. 51, Patent attorneys

Claimed priority:
ao Great Britain from May 17, 1957

Harold Everard Monteagle Barlow,

Banstead, Surrey (UK),

has been named as the inventor

cellular polystyrene, which is introduced into an initially straight tube with a conductive inner wall and such is designed that after bending the tube, the resulting bend in its interior a Has dielectric constant that is greatest in the area of its inner radius and in the area of its Outer radius; is smallest.

In order to minimize losses as much as possible, it is important that the space within the The manifold is mostly filled with air. This requirement is met by a cellular dielectric material, in particular polyethylene or polystyrene, in to a high degree. It is also particularly suitable for filling a waveguide bend because when an initially straight, filled pipe is bent, it compresses in the area of the inner radius of the bend and expands in the area of the outer radius, whereby the dielectric constant at the inner radius is increased and decreased at the outer radius. It has been shown that a close approximation to the required field distribution with reduced losses in the manifold is obtained even then, when the waveguide is bent so much that its radius of curvature is only fifty to Hundreds of times the pipe radius.

909 758/356

In addition, in order to change the surface reactance of the elbow /.n, the inside of a tube can be provided with circumferential grooves or grooves, after which the tube is bent to the required radius of curvature, each groove leading to a coaxial H ₀₁ waveform. At least three circumferential grooves per wavelength of the H ₀₁ circular waveform should be provided in the waveguide in order to effectively distribute the surface reactance over the length of the waveguide. For this purpose, each groove must be filled with a high quality dielectric material so that the width and the spacing of the grooves from one another can be reduced accordingly.

When the waveguide is bent, the groove is widened and in the area of the outer radius of the bend their depth diminishes while the part of each groove. which lies in the area of the inner radius of the bend, gets narrower and deeper.

Instead of providing circumferential grooves or grooves on the inside of the pipe, this can Tube can be made from a number of metal rings placed inside a rubber tube and separated from each other by thin flexible metal spacers that are slightly compressed can be and form the bottom of the groove.

Figures 1 and 2, and 3 and 4 of the accompanying drawings show two methods of manufacture a curved waveguide section or bend, where the dielectric constant of the dielectric material in the manifold is over the. cross-section of the waveguide has been appropriately changed.

According to FIGS. 1 and 2, a copper pipe 1 with a length substantially equal to that of the bend, to be made with cellular polystyrene 3 filled and then (Fig. 2) bent to the required radius of curvature. During the When bending, the cellular polystyrene is stretched in the area of the outer radius of the bend and in the area of the inner radius compressed.

According to FIGS. 3 and 4, a copper tube 5 with a length essentially equal to that of the herzu- • providing manifold with a number of thin discs 7 made of cellular polystyrene, which in the same Are spaced from each other. After that, the pipe becomes the required radius of curvature bent, the disks during bending in the area of the outer radius of the bend a larger Distance and get a smaller distance from each other in the area of the inner radius.

Fig. 5 shows a section through a semiconductor section or bend showing the surface reactance automatically changed around the periphery when the pipe becomes necessary Radius of curvature is bent. The waveguide consists of a number of equidistantly spaced arranged rings 9, which are located inside a rubber tube 11 that holds the rings in place. Each ring is separated from the adjacent one by a spacer 13 made of spring metal, with between two metal rings each have a dielectric loading ring 15 with a high dielectric constant is inserted. In addition, the waveguide contains a filling made of a dielectric cellular material, this is not shown for the sake of clarity. Will the pipe made this way bent to the required radius of curvature, the distance between two adjacent ones increases Rings in the area of the outer radius of the elbow, while it is in the area of the inner radius decreased. Therefore, the section in the area of the outer radius of the bend is more capacitive than in the Area of the inner radius of the elbow. The solid dielectric material in the groove should preferably be have a low loss relative dielectric constant of about 8 and may be made of polyethylene exist, which is mixed with titanium dioxide.

Claims (5)

PATENT REQUIREMENTS: 1. Curved waveguide section or bend for the transmission of electromagnetic waves of the type H ₀₁ , in which the dielectric constant increases radially inward, characterized by a filling consisting of a dielectric cellular material, in particular cellular polyethylene or cellular polystyrene, which is initially straight tube with conductive inner wall is introduced and designed such that after bending the tube, the elbow created thereby has a dielectric constant in its interior which is greatest in the area of its inner radius and smallest in the area of its outer radius. 2. Arrangement according to claim 1, characterized in that the dielectric material in Form of disks is introduced into the tube, each of these disks extending over the cross section of the tube extends away and is spaced from the adjacent disc. 3. Arrangement according to claim 1 or 2, characterized in that the surface reactance of the Tube changes around its periphery and in the area of the outer radius of the bend the capacity is greater than in the area of the inner radius of the bend. 4. Arrangement according to claim 3, characterized in that the wall of the tube circumferential grooves has, of which at least three are provided per wavelength of the transmitted electromagnetic waves, and that each groove is filled with a dielectric material of high dielectric constant in such a way that that due to the widening of the grooves occurring as a result of the bend in the area of the outer radius and the narrowing of the groove in the area of the inner radius of the bend is the surface reactance is changed. 5. Arrangement according to claim 4, characterized in that the grooves by metal rings be formed with spacers in between from spring material and between two Metal rings a dielectric loading ring with a high dielectric constant is inserted in such a way that that due to the increase in distance occurring as a result of the bend in the area of the outer radius and the reduction in distance in the region of the inner radius of the bend is the surface reactance is changed. Considered publications:
U.S. Patent No. 2,129,712. 1 sheet of drawings © 909 758/356 2.60