US2635187A - Broad band antenna - Google Patents

Description

INVENTOR ARTHUR DORNE ATTORNEY A DORNE BROAD BAND ANTENNA Filed March 29, 1946 l 1 h I7-H Hi8 lr II April 14, 1953 Patented Apr. 14, 1953 BROAD BAND ANTENNAM Arthur Dome, Freeport, N. assignor to the United States of America as represented by the Secretary of War Application March 29, 1946, Serial No. 657,939

2 Claims. (01. 250-33) This invention relates generally to electrical apparatus and more particularly to antennas.

tern varies substantially as the operating frequency is varied.

In many antenna applications, direction finding systems for example, a shifting antenna pattern is undesirable and may admit confusion in the interpretation of the intelligence presented by the radio frequency apparatus.

It is an object of the present invention to provide an antenna particularly adaptedfor use with radio frequency direction finding systems.

It is also an object to provide an antenna whose response pattern remains substantially constant in shape over a wide range of operating frequencies.

An antenna, which accomplishes the aforesaid objects, consists of a balanced, sleeved, dipole with four auxiliary stub radiators attached to the dipole. A center fed dipole has its central portion enclosed concentrically in a metallic sleeve which has a large circumference with respect with its length. The ends of the dipole, which protrude beyond the ends of the sleeve, are enlarged to approximately the size of the sleeve. At each end of the sleeve, two auxiliary stub radiators are attached to the dipole. These stubs are oriented perpendicularly with respect to the 1ongitudinal axis of the dipole and all four stubs are in the same geometric plane.

Other objects, features and advantages of this invention will suggest themselves to those skilled in the art and will become apparent from the following description of the invention taken in connection with the accompanying drawings in which:

Fig. l is an elevation of an antenna embodying the principles of this invention; and Fig. 2 is an end view of Fig. 1.

Referring now to Fig. 1, a balanced dipole consisting of dipole elements Ill and II has its central portion concentrically enclosed by a. metallic sleeve I2. The outer ends of dipole elements l0 and II are enlarged to approximately the size of sleeve l2. Two auxiliary radiator stubs, I3 and I4, are connected to dipole element l0 perpendicular to the longitudinal axis of dipole element I0, near one end of sleeve I2. Similarly, two auxiliary radiator stubs I5 and [6 are connected to dipole element II. Stubs I3, [4, I5 and I6 are all in the same geometrical plane. This sleeved dipole antenna is center fed and two conductors, I1 and I8 respectively, of a balanced two wire transmission line, are inserted through holes in sleeve I2, and connected to the dipole elements.

Conductor I1 is connected to an end of dipole ele-.

ment I 0 and, similarly, conductor I8 is connected to dipole element I I.

Referring now to Fig. 2, an end view of Fig. 1 is shown and the same reference numbers used in Fig. 1 are again repeated.

Generally, the radiation characteristics of an antenna, when used for transmitting, are similar to the response characteristics of that antenna when used as a receiving antenna. Consequently, for the purpose of explanation, the device of this invention will be considered as a transmitting antenna.

Conductors I1 and I8 apply equal and opposite voltages to dipole elements I0 and II. The enlarged ends of dipole elements I0 and II radiate some energy into space but their principal function is to electrically excite sleeve I2, which contributes most of the radiation from this antenna. Having a large surface area and a large periphery compared to its length, sleeve I2 is closely coupled to space and hence, readily radiates any radio frequency energy induced on it.

If the bidirectional characteristics of this antenna pattern are to be utilized, the antenna should be oriented so that the four stubs I3, I4, I5 and I6 are in a plane which is perpendicular to the desired directions of maximum radiation. The total length of the antenna should be of the order of one-third of a wavelength corresponding to the lower operating frequency. The length of each of stubs I3, I4, 15 and I6 should be about one-tenth of a wavelength corresponding to the abovementioned lowest operating frequency.

It has been found experimentally that the addition of stubs I3, I4, I5 and I6 to the dipole elements, substantially influences the antenna pattern characteristics. These stubs have no pronounced effect other than to control the radiation pattern of the antenna. When these four stubs are used with the antenna, the radiation pattern of the antenna maintains a substantially constant shape as the operating frequency is varied over wide ranges. With conventional antennas, when the operating frequency is varied over Wide ranges, the antenna pattern often changes rapidly in directivity, the magnitude of minor lobes vary, and the main lobe may even split into several secondary lobes.

The principle of operation of these stubs l3, l4, I5 and I6 is not at the present time well understood, however, it has been established experimentally that the use of these stubs does allow an antenna to be used over wider ranges of frequency, before the shape of the antenna pattern becomes distorted.

The antenna herein disclosed has been used with a small section of a parabolic reflector to obtain a broad band, unidirectional antenna for use with direction finding systems.

In this particular application, the antenna operated over a frequency range of approximately 5 to l, and within this frequency range the lobe pattern remained substantially constant in shape and the gain of the antenna was equal to or better than that of a standard dipole in free space.

While there has been here described what is at present considered to be 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 scope of the invention as set forth in the appended claims.

What is claimed is:

1. A broad band directional plane polarized antenna including a center fed exciter dipole having outer ends larger in diameter than the central portion, a tubular conductive sleeve radiator concentrically enclosing the central portion of said dipole, and a plurality of stubs connected to said dipole near the ends of said sleeve radiator, the longitudinal axis of each of said stubs being perpendicular to the longitudinal axis of said dipole whereby the shape of the response pattern of said antenna is directional and remains substantially constant throughout the operating frequency band.

2. A plane polarized antenna with a substantially constant directional radiation pattern over a broad operating frequency band including a pair of center-fed exciter dipole elements havin a total length approximately one-third of a wavelength corresponding to the lowest operating frequency and outer ends of larger diameter than the central portions, a metallic sleeve radiator concentrically enclosing and insulated from the central portions of said dipole elements with the enlarged ends of said dipole elements extending beyond the ends of said sleeve radiator, four identical cylindrical stubs each having a length approximately one-tenth of a wavelength corresponding to the lowest operating frequency, two of said stubs being connected to one of said dipole elements near an end of said sleeve radiator and two of said stubs being. connected to the other of said dipole elements near the other end of said sleeve radiator, each of said four-stubs being oriented perpendicularly with respect to the longitudinal axis of said dipole elements and all of said stubs being in the same geometrical plane, and a two-wire feed line connected to said dipole elements near their centers.

ARTHUR DORNE.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,175,363 Roberts Oct. 10, 1939 2,274,149 Lubcke Feb. 24, 1942 2,287,220 Alford June 23, 1942 2,313,046 Bruce Mar. 9, 1943 2,410,597 Brown et a1. -21--- Nov. 5, 1946 2,411,976 Peterson Dec. 3, 1946 2,419,672 Busignies Apr. 29, 1947

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