US2648002A - Dielectric antenna - Google Patents

Description

Aug. 4, 1953 J. E. EATON 2,648,002 DIELECTRIC ANTENNA Filed Nov. 19, 1945 INVENTOR JAMES E. EATON QI LW ATTORNEY Patented Aug. 4, 1953 Jaines E- name, Canr'brid e, Mesa, assignor, "bi

mesne assignments, to the states America as represented by the Secretary of the Navy Applicants November 19, 1945, seriaiNa. 6295671 '5 Claims. (01. zso saesi invention relates to a radio microwave radiation antenna, and more particularly to a dieleetric rod a'ntefn-iahavir'ig 'theaxis of the feed section thereof offset from the axis of the dielectric rod of the antenna.

object of this invention is to provide a radar antenna which may be mounted directly to a metal surface without destroying the desired characteristics of the radiation pattern produced bythe antenna. I

Another object of this invention is to provide an end-fife antenna foi' radio microwave radiation of novel design which may be mounted directly upon a metal surface, the design being such as to reduce to a 'ininirnumfthe losses due to side lobes normally developed by such ante nnas.

A pa'rt'ic'iilar object of this inven'tion is to prov i'de an end-fire antenna of the dielectric rod type vv-nichmaybe'mouhtea directly upon a metal surface in which the losses due to side lobes are reduced to a minimum.

A more partieu'lar object or this invention is to provide an end-fire radar antenna of the dielectric rod type having the axis of the feed section thereof displaced from the longitudinal axis of the rod section.

A still more particular object of this invention is to provide an end-fire radar antenna of the taper rod type having the exciting probe thereof displaced from the horizontal axis of the tapered section of the rod.

Further objects and advantages of this invention, as well as its construction, arrangement, and operation, will be apparent from the following description and claims in connection with the accompanying drawing, in which the figure is a perspective view of an antenna constructed in accordance with the principles of this invention.

End-fire radio microwave antennas of the dielectric rod type have heretofore been discovered and are well known in the art. Such antennas,

however, have been subject to various disadvantages in particular installations. Such antennas heretofore known in the art have proven unsatisfactory when mounted directly upon a metallic surface such as the wing of an aircraft in that the energy in the main lobe was forced into side lobes, with a resultant loss of antenna gain. This invention provides a novel end-fire antenna in which these undesirable effects are reduced to a minimum.

Referring to the drawing, there is shown a radar antenna constructed according to the principles of the invention having a feeding portion '2"] a "tapered radiating portion ii. '1 metallie surface 23, such as the wing or an an craft, provides a means for mounting the auteam. amehna is 'fdrrne'ddf asolid dielectriaterial such as, for example, polystyrene. An exciting probe 2 is disposed in the feeding section 2 l at rightan'g'le's to theplane which in cludes-the longitudihal axi's trumd g section and the longitudinal-axis of the adia ihgsectibn. exciting probe illu rated as shewaas being the center conductor of aeoax i'al line-2 5, though any-proper means for exciting thepmtemay be used. It is to be noted that ieed' s'ebfztiori 2| "has the lower portion thereof cut away so as to pro:- vitle a step, the height of the cuteout stop being represented by the letter h; and "that exciting probe is oriented parallel to inetal surface "23 on which the antenna is mounted.

The following explanation of the'op'eration of the device --isfbelie ved to be acr'iurate, although another .edu-a-lly plausible emanation may also be true. In operation, exciting-probe '24 sets a fieldin feeding-section a l, which act's asa'wave guide to carry energy into tapered section 22. Because of the ofiset relationship of the exciting probe to the longitudinal axis of the tapered section, the concentration of the fields developed in the tapered section is greatest in the upper region thereof. While some energy difiuses into the lower region of the tapered section, this may be reduced to a minimum by properly adjusting the height h of the step and consequently the displacement of the exciting probe from the axis of the tapered section. In this manner, the side lobes of the antenna pattern can be kept at a minimum value without increasing the beam width in the horizontal plane, and direct mounting of the antenna upon a metal surface is made feasible. In addition to operating satisfactorily when mounted directly upon a plane flat surface as shown in the figure, it has been discovered that the antenna performs equally well when mounted on the fore and aft edge of a metal airfoil since the presence of the side of the airfoil also fails to cause the pattern of radiation developed by the antenna to deteriorate.

While a particular embodiment of this invention has been disclosed and described, it is to be understood that various modifications and changes may be made in this invention without departing from the spirit and scope thereof asv set forth in the appended claims.

What is claimed is:

1. An end-fire radar antenna of the dielectric rod type comprising a solid dielectric member having a tapered portion and a rectangular feeding portion, said feeding portion having an exciting probe inserted therein, the longitudinal axis of said feeding portion being oflset from and coplanar with the longitudinal axis of said tapered portion and the axis of said exciting probe being perpendicular to the plane which includes both the longitudinal axis of said feeding portion and the longitudinal axis of said tapered portion.

2. A radar antenna comprising in combination, a metallic mounting surface, a. tapered solid dielectric radiating section longitudinally disposed on said surface, and a rectangular dielectric feeding section attached to the larger end of said tapered dielectric radiating section, said rectangular feeding portion having equal width but smaller in cross section than said radiating section and so disposed with respect to said tapered section that the longitudinal axis of said feeding section is offset from the longitudinal axis of said radiating section to establish a spaced relationship between said metallic surface and said feeding section.

3. A radar antenna comprising, a solid dielectric rod formed into a feed portion and a radiating portion, said radiating portion being uniform in height and decreasing in width as it extends away from said feed portion, said feed portion being of uniform cross section equal in width to the large end of said radiating portion but of reduced height at one surface thereof whereby the longitudinal axis of said feed portion is offset from the longitudinal axis of said radiating portion.

4. An end fire radar antenna comprising, a solid dielectric rod formed into a feed portion and a radiating portion, said radiating portion being uniform in height and decreasing in width as it extends away from said feed portion, said feed portion being of uniform cross section equal in width to the large end of said radiating portion but of reduced height at one surface thereof, said feed portion being thereby offset from said radiating portion whereby the longitudinal axis of said feed portion is offset from the longitudinal axis of said radiating portion, and an exciting probe disposed within said feed portion and having its longitudinal axis perpendicular to the longitudinal axis of said feed portion.

5. An end fire radar antenna comprising, a metallic mounting surface, a solid dielectric rod formed into a feed portion and a radiating portion, said radiating portion being uniform in height and decreasing in width as it extends away from said feed portion, means for attaching said radiating portion to said mounting surface, said feed portion being of uniform cross section equal in width to the large end of said radiating portion but of reduced height abutting said mounting, said feed portion being thereby offset from said mounting surface whereby the longitudinal axis of said feed portion is offset from the longituditudinal axis of said radiating portion, and an exciting probe disposed within said feed portion and having its longitudinal axis perpendicular to the longitudinal axis of said feed portion, whereby said feed portion when excited by said probe acts as a wave guide to carry energy into said radiating portion with a field concentration greater than in the region of said radiating portion remote from said mounting surface.

JAMES E. EATON.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,161,292 Hahnemann June 6, 1939 2,369,808 Southworth Feb. 20, 1945 2,398,095 Katzin Apr, 9, 1946 2,405,242 Southworth Aug. 6, 1946 2,415,089 Feldman Feb. 4, 1947 2,419,205 Feldman Apr. 22, 1947 2,425,336 Mueller Aug. 12, 1947 2,460,401 Southworth Feb. 1, 1949 2,473,446 Riblet June 14, 1949

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