US2512137A - Antenna - Google Patents

Description

J 1950 L. BUCHWALTER El'AL 2,512,137

ANTENNA Filed June 16, 1944 INVENTOR. LOU/SE BUCHWALTER BYGEORGE G HARVEY Q/Au Patented June 20, 1950 ANTENNA Louise Buchwalter, Hallsville, Ohio, and George G. Harvey, Boston, Mass, assignors, by mesne assignments, to the United States of America as represented by the Secretary ofWar Application June 16, 1944, Serial No. 540,570

1 This invention relates to an antenna and more particularly to an antenna suitable for use with a high frequency radio communication system.

The principal object of the invention is to provide an antenna capable of radiating electromagnetic wave energy polarized in such a manner as to be receivable in equal strength by either a vertically or horizontally polarized receiving antenna. Another object contemplates an antenna having a radiation pattern that is approximately circular in a horizontal plane passing through the antenna (uniform in azimuth) and that has a substantial range in the vertical aspect.

The present antenna comprises an integral metallic radiating element adapted to be mounted directly upon as associated feeder transmission line. The element'consists of a plurality of dipoles, the number being three in the illustrated embodiment, with the axis of each dipole being inclined generally at an angle of 45 with the horizontal. This latter feature provides the desired polarization characteristic. Dipole supporting members extend radially from the associated feeder transmission line, and the dipoles mounted at the ends thereof may be axially curved in such a manner that their projections on a horizontal plane substantially define a circle. The dipoles are excited in phase by means of adjustable probes, each of which extends from a suitable point on a dipole radially to the region of wave propagation within the feeder transmission line.

The antenna element described generally above may be used singly as an antenna, or a plurality of such elements may be arranged on a feeder transmission line to consitute a linear antenna array.

In the drawing, Fig. 1 is a side elevational view of the present antenna mounted on a transmission line; Fig. 2 is a sectional view on the line 2 2 of Fig. 1; and Fig. 3 illustrates a modification of the invention.

Referring now to the drawings, and particularly to Figs. 1 and 2, a coaxial cable 5 having solid central conductor 6 and spaced outer conductor I is suitably disposed in a vertical position. Although a coaxial cable is here shown and described, it is to be understood that the present antenna may be applied with equal facility to a wave guide type transmission line, if desired, care being taken in that case to provide proper excitation of the guide to insure propagation in the appropriate mode. Bigidly mounted on outer cable conductor I is a metallic antenna element generally designated by ID. Element [0 com- 7 Claims. (01. 250-33) prises a central supporting collar I I, which is secured to outer conductor I in any suitable manner as by a soldered connection. Collar H carries a plurality of pairs of dipole supporting arms,

each arm being the order of a quarter wave in length, the two arms of each pair extending in spaced parallel relation as shown in Fig. 2; one arm of each pair of arms being formed of dielectric material and supporting the probe fed dipole section and the other arm of each pair of arms being formed of electrically conductive material. The pairs of arms extend radially away from collar I l and lie generally in a plane normal to the axis of coaxial cable 5. Three pairs of arms are shown in the drawing, the'individual arms being respectively numbered I2, l3, l4, IE, IS and I1. Referring now to the pair comprising spaced arms !2 and I3, the arms carry at their outer ends dipole sections I8 andlS, respectively, the arm l8 being provided with a projection 20 extending substantially across the space between arms l2 and t3. As will be understood, sections [8 and I9 constitute one dipole. Similarly, arms l4 and I5 have dipole sections 2| and 22, respectively, the section 2| having projection 23, and arms l6 and I1 have sections 24 and 25 and a corresponding projection 26. Thus, the antenna element described comprises three dipoles uniformly spaced around a feeder transmission line.

The dipole comprising sections I8 and I9 is excited by means of a probe 30, which is threaded through projection 20. Probe 3B is disposed radially of the antenna element between arms l2 and I3 and extends into the region of propagation within coaxial cable 5 through suitably aligned apertures 3I and 32 in collar II and outer cable conductor I, respectively. Probes 33 and Mare similarly provided for excitation of each of the other two dipoles. The probes are adapted to be adjusted radially for the type of coupling de-- sired, direct coupling to center conductor 6 being illustrated herein. In general, the probes will be so adjusted that the dipoles will be excited in phase. After suitable adjustment of the probes, the head ends thereof may be cut off and solder applied to the respective projections to provide a good electrical connection and to prevent subsequent displacement of the probes.

As an alternative construction, the dipole supports and feeder lines may take the form of lengths of coaxial cable. As shown in Fig. 3, a length of cable 35 has central conductor 36 coupled to main central conductor 6, and outer conductor 31 fixed to central supporting collar 38. Dipole sections 39 and 40 are carried at the ends of conductors 3S and 31, respectively, the latter being cut away at its end to provide suitable clearance for section 39. This construction provides improved uniformity in azimuth pattern due to the fact that there is substantially no radiation from the dipole feeder lines. It will readily be seen that dipole sections 39, 4!! correspond to dipole sections l8, l9 illustrated in Fig. 2, and-that the coaxial cable 35 corresponds to elements l2, I3, 39 illustrated therein.

Referring back to Fig. 1, it will be seen that the. I axes of the respective dipoles lie in planes disposed at angles of 45 with the horizontal, the' angle from the horizontal being measured in the l l or vertically polarized receiving antenna in any same direction for each dipole, in this instance, clockwise. Also, the dipoles ma have a curved configuration so that their projectiornas shownin Fig. 2, on a horizontal plane defines a circle.

azimuth characteristic. It also reduces the size ofthe antenna element and permits accommodation of a tubular housing for sealing the device in aweatherproof or pressureproof manner.

Electromagnetic energy radiated from an antenna of this character will have a polarization disposed generally at 45 to the horizontal. Consequently a receiving antenna will receive substantially equal energy whether polarized horizontally or vertically. It has been found that in azimuth the signal strength from such an antenna has a maximum variation of less than 1.4 to 1 with the receiving antenna either horizontally or vertically polarized, the tests in this instance having been made in the it centimeter wavelength band. In general, the present antenna is adapted for use at wave lengths the order of centimeters.

The actual physical dimensions of an antenna element of this character will, of course, depend on the wave length used, the dimensions followed being merely a matter of design in accordance with practice well known in the art.

Having thus described the invention, what is claimed as new and desired to be secured by Letters Patent is:

. 1. An integral metallic antenna construction for use with a transmission line, said construction comprising an inner supporting collar supported externally of said transmission line, a plurality of paired arms extending outwardly from said collar, a section of dipole carried at the end of each arm with a pair Of arms supporting a dipole, an exciting probe carried by the end of one section of each dipole, said probe extending inwardly and into the region of propagation within said transmission line through aligned apertures in said collar and in said transmission line, said dipoles each lying generally in a plane disposed at an angle of 45 with the axis of said transmission line whereby radiations therefrom are so polarized as to be receivable in substantially equal strength by either a horizontally or vertically polarized receiving antenna.

2. The antenna construction defined in claim 1 in which there are three of said dipoles uniformly spaced around said transmission line.

3. An antenna construction adapted for use with a coaxial cable, said construction comprising a cable, a plurality of dipoles symmetrically disposed about said cable, means for supporting and exciting each of said dipoles, each Of said means comprising a length of coaxial line having the axis of said cable and being so curved that their projection on to the plane of said circle defines acircular arc whereby radiations therei from are so polarized as to be receivable in substantially equal strength by either a horizontally direction inthe horizontal plane.

4. An antenna for operation with waves of any polarization and with an omnidirectional pattern in a given plane comprising a support element and a plurality of dipoles arranged with their centers lying in a circle about said element and with their axes at an angle of 45 with respect to the plane of said circle, each of said dipoles being so curvedthat the projection of all of them onto the plane of said circle defines said circle.

arranged with their centers lying on a circle and with their axes at an angle of 45 with respect to the plane of said circle, each of said dipolesbeing so curved that the projection of all of them on to the plane of said circle defines said circle.

7; An antenna for operation with waves of any polarization and with an omidirectional pattern in a given plane comprising a plurality of dipoles arranged with their centers lying on a circle parallel to said plane, the axes of each of saiddipoles being at an angle of 45 with respect to the plane of said circle, each of said dipoles being curved to follow helical paths coaxial with respect to a line perpendicular to the plane of said circle and passing through the center of said circle, said dipoles.

extending circumferentially and longitudinally in the same direction.

LOUISE BUCHWALTER. GEORGE G. HARVEY.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,199,635 Koch May 7, 1940 2,236,393 Beck et a1. Mar. 25, 1941 2,239,724 Lindenblad Apr. 29, 1941- 2,247,739 Werndl July 1, 1941 2,252,062 Chireix Aug. 12, 1941 2,258,953 Higgins Oct. 14, 1941 2,272,839 Hammond Feb. 10, 1942

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