US2473446A - Antenna - Google Patents

Description

H. J. RlBLET June R4,, 1949.

ANTENNA Filed Nov. 6, 1945 ///w ML INVENTOR. HENRY .1. RI BLET OyAx/m' 2 442.

ATTORNEY Patented June 14, 1949 UNITED STATES PATENT OFFICE 2,473,446 ANTENNA Henry}; Riblet, Cambridge, Mass, assignor, by inesne assignments, to the United States of America as represented by the Secretary of War Application November 6, 1945, Serial No. 627,041

Claims.

This mv'mimi relates to antennasfor cominuniation systems and more particularly to antennas for radiating waves of electromagnetic In certain radio object locating systems, itis desirable to have a compact and light-weight antenna and a particularly useful antenna is of the probe type comprising generally an elongated cone-shaped member made'of a dielectric material such as polystyrene, sometimes referred to as a "polyrod antenna. The base of the dielectric member is usually a short section of circular wave guide excited by a probe in such a manner to propagate energy toward theapex of the eerie. Such polyrod antennas always have their radiation patterns describing a figure of revolution with their peak signal in the direction of the axis of the antenna, that is, their axis of directivity substantially coincides with the axis of the dielectric cone-shaped member. H

In order to obtain a conical scan in space, it has heretofore been necessary to incline the antenna relative, for example, to a horizontal support, and then to rotate the member about an axis perpendicular to the horizontal support so that the member itself describes a cone. To achieve such conical scanning, special supporting and rotating joints have heretofore been necessary. It has now been found that conical scanning may be achieved without the aforesaid disadvantages simply by rotating the dielectric member about its axis and by providing means to produce a radiation pattern whose peak signal is angularly displaced about the axis of the antenna.

Accordingly, it is an object of the invention to provide an antenna of the kind described with means for angularly displacing the axis of directivity of the radiation pattern produced thereby without angularly displacing the antenna itself.

Another object of the invention is to provide an antenna having a dielectric probe-like member, wich may be in the shape of an elongated cone, with a metal shield partially covering its surface resulting in displacing the axis of symmetry of the radiation pattern produced by the antenna.

For a better understanding of the invention together with other and further objects thereof,

reference is had to" the following description, taken in connection with the accompanying drawing. I

In the drawing: 1

Fig. 1 is a front elevationview of the antenna accordingto the present invention; and h Fig. 2 is a partial longitudinal side view of the antenna of Fig. 1. H I

In the drawing, the antenna comprises a probelike member H inadeof any suitable dielectric material such as polystyrene. Member II as shown is preferably in theshape of an elongated cone having a' substantially cylindrical base por5- tion 12 and a pointed or rounded apex I 3. Mounted on and insubstantial alignment with the base portion [2 is a metallic sleeve or sheath l4, preferably of substantially hollow cylindrical shape and of substantially equal diameter to the base portion I 2. The sheath I4 thus comprises a substantially circular short section of a wave guide transmission line. Energy from a source (not shown) is carried to wave guide or sheath l4 in any suitable manner such as by a section of coaxial line I5 connected to sheath l4 and including a probe or central conductor 46 for exciting energy within wave guide I4. The energy propagated within wave guide 14 is thereby adapted to excite member H and, as thus far described, member II is adapted to radiate energy in a radiation pattern I! Whose axis of symmetry or axis of directivity A is substantially coincidental with the longitudinal axis of member ll.

Partially covering the outer surface of memher i l is a metallic shield or sheet l8. Shield I8 preferably extends substantially the length of member II and is shaped to conform and lie in close contact with the surface of member ll. As shown, member I 8 is broader in width at the base portion l2 and gradually narrows or tapers toward apex 13. Preferably, shield l8 covers not more than half of the surface of member H and preferably along one side thereof. Shield I8 is effective to displace the radiation emitted from member II in a direction away from member l8. Thus, the axis of directivity or the axis of symmetry of the beam pattern I! is angularly displaced from the axis of member II as indicated as H in Fig. 2.

If desired, member H may be rotated about its axis whereby the displaced beam pattern IT or more correctly its axis of directivity substantially describes a cone whereby conical scanning may be achieved.

While there has been described what is at present considered the preferred embodiment of the invention, it will be obvious to those skilled in the art that various changes and modifications may be made therein without departing from the invention.

What is claimed is:

1. An antenna for communication systems comprising a dielectric solid of revolution substantially in the shape of an elongated cone having a cylindrical base portion, exciting means coupled to said base portion to cause said dielectric solid to radiate energy, said energy forming a pattern which normally has its axis of directivity substantially coinciding with the axis of said solid of revolution, a metallic sheet member mounted on said dielectric member and curved to conform to the shape of said dielectric member, said sheet member being so shaped as ,to be included between two angularly displaced planes which in-' tersect along the axis of revolution of said dielectric member, said sheet member covering substantially all of the surface of said dielectric member within one of the angles of intersection of said two planes, said sheet member being effective to angularly displace the axis of directivity of said radiation pattern in a direction away from said sheet member.

2. An antenna for communication systems comprising a dielectric solid of revolution substantially in the shape of an elongated cone having a cylindrical base portion, a hollow cylindrical metallic sheath mounted on and in aligning means, said probe exciting said dielectric member to cause it to radiate energy, said radiated energy forming a pattern normally having its axis of directivity substantially coinciding with the axis of said solid of revolution, a metallic sheet member curved to conform with the surface of said dielectric member, said sheet member being so shaped and so mounted on the surface of said dielectric member as to be included between two angularly displaced planes which intersect along the axis of revolution of said dielectric member with said sheet member covering substantially all of the area included within one of the angles of intersection of said two planes, said sheet member being eiTective to angularly displace the axis of directivity of said radiation pattern in a direction away from said sheet member.

3. An antenna as claimed in claim 1 wherein the area covered by said sheet member is generally not more than half the surface area of said dielectric member.

- 4. An antenna as claimed in claim 1 wherein said antenna is adapted to be rotated about the axis of revolution of said dielectric member whereby the axis of directivity of said displaced radiation pattern substantially describes a cone in space. a

5. An antenna as claimed in claim 2 wherein said antenna is adapted to be rotated about the axis of revolution of said dielectric member and wherein the area covered by said sheet member is generally not more than half the surface area of said dielectric member whereby the axis of directivity of said displaced radiation pattern substantially describes a cone in space.

HENRY J. RIBLET.

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

UNITED STATES PATENTS Number Name Date 2,129,711 Southworth Sept.13, 1938 2,206,923 Southworth July 9, 1940 2,304,540 Cassen Dec. 8, 1942 2,415,089 Feldman Feb. 4, 1947 2,419,205 Feldman Apr. 22, 1947 2.425.336 Mueller Aug. 12, 1947

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