US 3623115 A
Description (OCR text may contain errors)
United States Patet  Inventors Erich Schuttloffel Backnang; Hans-Dieter Kuhne, Allmersbach, both of Germany  Appl. No. 877,630  Filed Nov. 18, 1969  Patented Nov. 23, 1971  Assignee Teleiunken Patentverwertungsgesellschaft m.b.H 2!! 999990 NE!!!  Priority Dec. 7, 1968  Germany  P1813406.0
 DIRECTIONAL ANTENNA 6 Claims, 3 Drawing Figs.
 U.S. Cl 343/781, 343/786, 343/840, 333/34  Int.Cl HOIq 13/02, HOlq 19/14  Field of Search 333/98; 29/600; 343/781, 786, 840, 772
 References Cited UNITED STATES PATENTS 2,814,038 11/1957 Miller 343/762X M Ma 2,956,248 11/1960 Strand 333/98 X 3,140,491 7/1964 Ashbaugh et a1. 343/840 X 3,444,487 5/1969 Krank et a1. 333/95 OTH ER REFERENCES Primary ExaminerHerman Karl Saalbach Assistant Examiner-Marvin Nussbaum Allorney-Spencer & Kaye ABSTRACT: A feeder waveguide for a parabolic antenna formed from a seamless aluminum tube having an elliptical cross section and walls of continuously varying thickness. The wall thickness of the waveguide is smallest along the axes ofits elliptical cross section, and is greatest at points lying between the major and minor axes of the elliptical cross section. The waveguide has a horn formed in one ofits ends and a connecting flange formed in the other ofits ends.
DIRECTIONAL ANTENNA BACKGROUND OF THE INVENTION The present invention relates to parabolic antennas and particularly to feeder elements therefor.
It has been known for some time to use parabolic antennas for the transmission and reception of microwave signals, e.g. UHF television broadcasts. These antennas are of a small diameter, such as 60 centimeters. Directional antennas of the parabolic type are made up of a special radiator, such as a horn, a parabolic mirror which is illuminated by or illuminates, the radiator, and as associated feeder waveguide. These known arrangements are very complicated and expensive, primarily with regard to the special driven radiator.
The publication Nachrichtentechnik" Volume l3, No. 6, (1963), page U 51, FIG. I, discloses a directional antenna having a bent over waveguide whose open end serves as the radiator for a parabolic reflector. Such a feeder waveguide may be constructed either from a plurality of sections which are connected together by means of flanges, or in one piece by known galvanoplastic methods. Both of these fabrication methods require considerable expenditures. In addition, the illumination of the parabolic mirror by the open end of the waveguide is unsatisfactory, since it does not fully produce the desired directional effect.
A paper entitled A microwave energy transmission line with low damping which can be reeled onto a drum which appeared in 'the publication Neue Technische Zeitung, Number 10, 1965, pages 607 to 615, discloses a flexible waveguide which has an elliptical inner cross section. The waveguide is made flexible by being constructed from a corrugated tube.
SUMMARY OF THE INVENTION It is an object of the present invention to provide a directional antenna which is suitable for low-cost mass production, while still meeting the desired operating standards.
The directional antenna of the present invention is based on the known types of parabolic antennas, but is provided with an improved feeder waveguide. This feeder waveguide is constructed from a seamless aluminum tube having an elliptical inner cross section. The wall thickness of the waveguide continuously varies from a minimum along the axes of the elliptical inner cross section to a maximum at points lying between the major and minor axes of the elliptical cross section. The waveguide of the present invention is also provided with a horn, or other driven element, at its open end, in the manner ofthe previously known embodiments.
BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a side elevation view of a directional antenna according to the present invention.
FIG. 2 is a cross-sectional view taken generally along the lines 22 of FIG. 1, showing the varying wall thickness of the waveguide.
FIG. 3 shows a measured pattern.
DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a directional antenna having a parabolic mirror or reflector l. The reflector 1 has a relatively wide rim portion 13 which is attached in a suitable manner, such as by welding or with screw fasteners, to mounting members 11b and 14b. Mounting member 11b is rotatably attached to another mounting member, such as a clamp 11a, by means of a bearing pin 8. Mounting member 14b is moveably attached to another mounting member, such as a clamp 14a, by means ofa bearing pin arrangement 7 which slides in a slot 9. Clamps 11a and 14a are clamped to a suitable support, such as mast 5. The antenna could also be mounted on a frame, or other suitable support. This mounting permits the reflector l to be aimed in a certain direction. The pin connections permit the reflector l to be adjusted with respect to the horizontal plane, and the clamps 11a and 14a permit the reflector I to be adjusted with respect to the vertical plane.
Although the description below relates to an antenna used for transmitting, it is to be understood that the same antenna may be used for receiving without modification.
A feeder waveguide 2 has a horn 3 at its open end, as shown in FIG. I. The horn 3 could, of course, also be attached to the waveguide 2 by suitable means. Although a horn has been shown, other suitable driven elements could be used. The aperture 4 of the horn 3 determines the field of illumination of the parabolic reflector l. The feeder waveguide 2 is rigidly connected to the rim of the parabolic reflector l by the portion 10 of the mounting member 11b. The parabolic reflector l, feeder waveguide 2 and the various mounting elements form a structural unit with each other which can be easily installed and which can be electrically connected to a suitable system by means of the connecting flange 12 at the lower end of waveguide 2. Flange 12 may be of any well known, suitable type.
In an alternate embodiment, the. rim 13 of the parabolic reflector 1 can be provided with a suitable passage through which the bent over end of the feeder waveguide is passed. This is shown in FIG. 1 by the dotted lines.
FIG. 2 shows a cross section throughthe feeder waveguide 2. This waveguide is constructed from a seamless aluminum tube, which is formed as by drawing, and which has a continuously varying wall thickness along its cross-sectional profile. The walls of the waveguide 2 are the thinnest at the points indicated as 15 and 16, which are along the minor and major axes A and B, respectively, of its cross section 6. Between these minimum values, the wall thickness continuously increasesto maximum values, at 17 and 18, which lie between the major and minor axes. The inner surface of the waveguide 2 is thus seen to form an effective inner cross section 6 which has the approximate shape of an ellipse. This configuration of the feeder waveguide results in very little deformation of the inner cross section when the waveguide is bent or twisted. However, the waveguide simultaneously exhibits sufficient mechanical stability to perform its function.
The parabolic reflector l is preferably an axially symmetrical paraboloid reflector having a circular aperture. The parabolic reflector 1 may be constructed. from a light metal or metal-laminated synthetic. These types of construction permit low-cost mass production.
In order to produce the desired directional characteristic of the antenna, i.e. an axially symmetrical radiation pattern, the aperture 4 of the waveguide 2 and the aperture of the parabolic reflector I may be suitably selected. A circular aperture of that parabolic reflector l is preferable, with a ratio f/D from 0.4 to 0.25;fbeing the focal length and D the diameter of the reflector l.
The feeder waveguide 2 may be cut ofl' at the desired length from a straight waveguide train manufactured by the foot or meter. The section cut off is then easily bent into the desired shape, and one end is expanded in a known manner by means of a special tool to form the horn. Due to the easy flexibility of the aluminum waveguide, this is possible with very simple means. Moreover, the individual components may be prefabricated and combined into a structural unit so that an easily produceable and installable directional antenna results which has a great variety of uses. For a particular embodiment of the invention intended to transmit or receive waves in the frequency band of 6 GHz. the aluminum feeder waveguide has the following dimensions:
major diameter B 42 mm.
minor diameter A 24 mm.
thickness of the guide near the diameter B 2.0 mm.
thickness of the guide near the diameter A 3.0 mm.
the thickness of the guide between the diameters A,B 5.5 mm.
The horn 3 is widened in such a manner that the aperture 4 is approximately a circle having a diameter of 36 mm. The transition from the guide to the aperture 4 is a cone including an angle of 8. The end part of the cone was formed as a cylinder for about mm. A dielectric housing was mounted on this cylinder.
The parabolic mirror has a diameter D of 1,750 mm. and the focus length 437.5 mm. The ratio f/D is 0.25.
F l0. 3 shows the measured pattern of an embodiment of the invention. The frequency was 6.15 GHz. The polarization was horizontal.
It will be understood that the above description of the present invention is susceptible to various modifications, changes and adaptations, and the same are intended to be comprehended within the meaning and range of equivalents of the appended claims.
1. A directional antenna comprising, in combination:
a. a parabolic reflector having a circular aperture with a diameter D and defining a focal length f, the ratio f/D being between 0.4 and 0.25;
b. a feeder waveguide formed from a seamless tube constructed of aluminum and having an elliptical inner cross section and walls of continuously varying thickness, said wall thickness being least along the major and minor axes of the elliptical cross section and greatest at points lying between the major and minor axes of the elliptical cross section; and
c. horn means formed integrally in one end of said waveguide for illuminating said parabolic reflector.
2. A directional antenna as defined in claim 1 wherein the other end of said waveguide is constituted by a connecting flange means for permitting the waveguide to be connected to a suitable system, and wherein said reflector and said waveguide are combined into a structural unit.
3. A directional antenna as defined in claim 2 further including mounting means for adjustably mounting said reflector and said waveguide, said reflector and said waveguide being combined into a structural unit with said mounting means 4. A directional antenna as defined in claim 3 wherein said reflector is constructed of a light material.
5. A directional antenna as defined in claim 4 wherein said mounting means has means for mounting said waveguide attached near to the periphery of said parabolic reflector.
6. A directional antenna as defined in claim 4 wherein said parabolic reflector has passage means in its periphery in which said waveguide is held.