US2908003A - Search antenna - Google Patents

Description

E. L. BOCK SEARCH ANTENNA Oct. 6, 1959 2 Sheets-Sheet 1 Filed June 6, 1957 INVENTOR. EBA/57' L. 506

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E. L. BOCK SEARCH ANTENNA Oct; 6, 1959 2\ Sheets-Sheet 2 M mw Filed June 6, 1957 United States Patent SEARCH ANTENNA Ernst L. Bock, Sepulveda, Califl, assignor to the United States of America as represented by the Secretary of the Air Force Application June 6, 1957, Serial No. 664,145

2 Claims. (Cl. 343-780) This invention relates to a pillbox type radiating antenna having smooth elevation plane patterns in horizontal polarization and which utilizes one of the metallic walls of the pillbox line source as an image plane.

One object of the invention is to provide a radiating antenna which permits an economical utilization of space and provides elevation plane patterns in horizontal polarization that have essentially no ripples and which follow closely the relation where the elevation angle =15 to 70 and the constant normalizing factor 11/; is chosen between 15 and 25 degrees depending upon the particular application.

This and other objects are accomplished by providing a semicircular element adjacent the aperture of the pillbox to rotate the effective radiating aperture of the pillbox through 180 degrees and to orient it in a plane perpendicular to an image plane formed by one of the metallic sides of the pillbox.

The use of an image plane effectively increases the pattern gain in the elevation plane by about 3 decibels by reducing the half-power beam width to half that obtained from the physical height of the radiating aperture in the absence of the image plane.

In the drawing:

Fig. 1 is a side view of the antenna of the invention showing the location of the semicylindrical elements.

Fig. 2 is a view in perspective of the antenna of the invention.

Fig. 3 is a plot of the vertical pattern for Equation 1 for #1 equal to 15 and 15 70.

Referring now to Fig. 1 reference numeral refers to an antenna having a first radiating section 11 and a secand radiating section 12. Each of said sections have pillbox type radiating elements 13 which have parabolically shaped reflecting surfaces 14, two parallel side walls 15 and 16 and radiating apertures 17. Semicylindrical elements 18 are located between said pillboxes adjacent said apertures with the concave portion of said cylindrical elements facing the apertures 17. These cylindrical elements effectively rotate the radiating apertures through 180 degrees and orient it in a plane perpendicular to side wall 16. Each of the side walls 16 then acts as an image plane to modify the radiation pattern and cause it to conform substantially to the relation recited in the Equation 1. Energy is fed to the pillbox radiating elements by means of wave guides 19. Wave shaping elements 20 which consist of a relatively short section of metal shaped as an inclined plane are located on walls 16 adjacent the effective radiating aperture to more closely produce the desired shape. The exact size and 2,908,003 Patented Oct. 6, 1959 position of the wave shaping elements are determined empirically. While two antenna sections are illustrated, it is to be understood that one could be used alone, if desired. There is thus provided a radiating antenna which requires less space and which provides elevation plane patterns in horizontal polarization that are substantially smooth.

While one embodiment of the invention has been described in some detail, it is to be understood that numerous changes may be made without departing from the general principles and scope of the invention.

I claim:

1. An antenna, comprising: 'a pillbox type radiating element having a parabolic reflecting surface and a pair. of parallel plate members, with substantially the same dimensions, closing the parabolic shaped end portions of said reflecting surface and forming therewith a chamber having an elongated rectangular shaped radiating aperture, means for feeding electro-magnetic energy to said radiating element, a semi-cylindrical element, having a semi-circular cross section and further having a length equal to the length of said aperture, located adjacent said aperture with its axis adjacent and parallel to the free edge of one of said plate members, one edge of said semi-cylindrical member being attached to the edge of the other of said plate members, the other edge of said semi-cylindrical member being located in the plane of said aperture and spaced a distance from said one plate member equal to the width of said aperture and radiation pattern shaping means located on the external surface of said plate member along the edge adjacent said aperture.

2. An antenna having a first and second radiating section, each of said sections having a pillbox type radiating element with a parabolic reflecting surface and a pair of parallel plate members with substantially the same dimensions, closing the parabolic shaped end portions of said reflecting surface and forming therewith a chamber having an elongated rectangular shaped radiating aperture, means for feeding electro-magnetic energy to said radiating element, a semi-cylindrical element having a semicircular cross section and further having a length equal to the length of said aperture, located adjacent said aperture with its axis adjacent and parallel to the free edge of one of said plate members, one edge of said semicylindrical member being attached in the edge of the other of said plate members, the other edge of said semicylindrical member being located in the plane of said aperture and spaced a distance from said one plate mem-/ ber equal to the width of said aperture and radiation pattern shaping means located on the external surface of said one plate member along the edge adjacent said aperture, the semi-cylindrical elements of said first and second radiating sections being located back to back with their convex portions adjacent each other.

References Cited in the file of this patent UNITED STATES PATENTS 2,566,900 McArthur Sept, 4, 1951. 2,594,871 Chu Apr. 29, 1952 2,597,391 Sichak May 20, 1952, 2,617,032 Allison Nov. 4, 1952 2,625,679 Iams Jan. 13, 1953 2,767,396 Cutler Oct. 16, 1956 2,824,305 Ohlemacher Feb. 18, 1958 FOREIGN PATENTS 4 Great Britain May 5, 1954

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