US2963704A

US2963704A - Antenna

Info

Publication number: US2963704A
Application number: US483022A
Authority: US
Inventors: Yates Lester Raymond; Jr Charles Mervyn Dorsey; Weldon Finley Houston
Original assignee: Bendix Corp
Current assignee: Bendix Corp
Priority date: 1955-01-20
Filing date: 1955-01-20
Publication date: 1960-12-06
Anticipated expiration: 1977-12-06
Also published as: ES226158A1; DE1084331B

Description

Dec. 6, 1960 R. YATES ETAL 2,963,704

ANTENNA Filed Jan. 20, 1955 LESTER R. YATES CHARLES MERVYN DORSEY, JR. FINLEY H. WELDON INVEN TOR.

7 ATTOR S United States Patent O ANTENNA Lester Raymond Yates, Charles Mervyn Dorsey, Jr., and Finley Houston Weldon, Baltimore, Md., assignors to The Bendix Corporation, a corporation of Delaware Filed Jan. 20, 1955, Ser- No. 483,022 1 Claim. (Cl. 343895) This invention relates to radio antennas and more particularly to an antenna especially adapted to airborne installations.

Antennas for such service are subject to conflicting requirements. In modern high speed aircraft, protruding members must be kept to a minimum length and be adaptable to an air-foil shape in order to minimize drag. On the other hand, the strength of the radiated field increases with antenna length and reduction in length is in many cases not compatible with field strength requirements.

Furthermore, such antennas intended for use in communications must be able to function effectively over a wide range of frequencies. The antenna impedance must remain matched over this range of frequencies to maintain a low standing wave voltage ratio.

Lightning also is a problem and it is desirable that provision be made for a direct path to ground for direct current without impairing the operating qualities of the antenna and with a minimum of added expense.

It is an object of this invention to provide an antenna having a length which is of small fraction of the operating wave length and capable of functioning efficiently over a wide band of frequencies, exhibiting a low standing wave voltage ratio over the whole range.

It is a further object of the invention to provide such an antenna which is easy and inexpensive to build.

It is another object of the invention to provide an antenna having a base loading circuit so arranged that it includes a direct path to ground for direct current flowing in the antenna, thus constituting an effective protective device against lightning without the addition of additional structure for that purpose.

It is an additional object of the invention to provide a vertically polarized antenna capable of being given a swept-back form for aerodynamical reasons without introducing any appreciable pickup of the horizontal signal component.

The above and other objects and advantages of the invention are realized by an antenna comprising a thin ribbon of conductive material wound in the form of a spiral about a form having a flattened helical cross-section. The antenna is overcoupled to a base mounted antiresonant circuit.

The invention will be further explained with reference to the accompanying drawing, in which:

Fig. 1 is a view in elevation of an antenna embodying the invention;

Fig. 2 is a plan view of the form of anti-resonant circuit utilized in the embodiment of Fig. 1;

Fig. 3 is a cross-section view of the antenna of Fig. 1, taken along the line 33; and

Fig. 4 is a schematic diagram of the antenna and base loading circuit of Fig. 1.

Referring now to the drawing, there is shown in Fig. 1 a mast shaped form mounted on a base plate 11 which may be a portion of the skin of an aircraft. The form 10 may be made of any suitable dielectric material having the necessary strength, such as Bakelite or any of various available moldable plastic compositions. The cross-sectional shape of the mast is that of a flattened oval as shown in Fig. 3, and the mast may be raked 7 back from the vertical as shown in Fig. 1, to provide good aerodynamical characteristics.

Wound around the mast in the form of a helix is a thin ribbon conductor 12. The ends of the ribbon are secured to the form as indicated at 13 and 14 by any desired conventional fastener, such as a screw. The helical conductor is the radiating element of the antenna.

The antenna is completed by an anti-resonant circuit, mounted on the base 11, to which the helical element 12 is overcoupled. The anti-resonant circuit is preferably composed of a hair-pin type inductor 15, illustrated in Figs. 1 and 2, having its ends slotted, as at 16, and having a fixed capacitor 17 conductively secured between its ends. The lower end of the radiating element 12 is connected to an intermediate point of the inductor 15 by a conductor 18. The antenna is fed by means of a coaxial transmission line 20, the outer conductor of which is connected to the base plate 11 which acts as ground and the inner conductor of which is connected to an intermediate point of the inductor 15 by means of a conductor 19. The slots 16 in the ends of the inductor pro vide for its adjustment by movement of the capacitor therealong.

In the operation of the antenna the distributed loading of the flattened helix brings it to resonance at the middle of the frequency range to which the ant=i-resonant circuit is tuned. The latter circuit transforms and parallel compensates the impedance of the radiating element to produce a low standing wave ratio.

In an embodiment of the invention constructed for use in the frequency range extending from 118 to 132 me. the mast was fourteen inches long, three and a half inches wide, and one half inch thick at its thickest point. The radiating element was a ribbon of copper one half inch wide connected by the anti-resonant circuit to a fifty ohm transmission line. With this construction the standing wave ratio did not exceed 1.8 at any point within the range. The horizontal component of the signal was negligible.

The mast and radiating element may be covered with a coating of dielectric material if desired, or an aerodynamically shaped housing of similar material may be placed over it.

It should be noted that lightning protection is built into the construction by virtue of the direct conductive path from the radiating element 12 through the upper end of the coil 15 as shown in Fig. 4 and thence to ground 11.

What is claimed is:

An antenna comprising an elongated form of dielectric material having a cross-section shaped in the form of a flattened oval, a conductive ribbon wound upon said form in a helix, means for mounting said form with a base end adjacent a ground plane and projecting from said ground plane with one end of said ribbon adjacent and the other end remote from said ground plane, a U- shaped inductor at said base end having opposed slots in the free ends of said U-shape and a connection to said ground plane from a point on one side of said U-shape, a capacitor of magnitude to resonate said inductor at signal frequency selectively positioned in said slots, a two conductor transmission line having one conductor connected to said ground plane, and the other conductor connected to said inductor, and a direct connection between said inductor and said one end of said ribbon, said connections to said inductor being at spaced points remote from the terminals of said capacitor.

References Cited in the file of this patent UNITED STATES PATENTS 2,081,274 Hahnemann May 25, 1937 2,575,377 Wohl Nov. 13, 1945 2,652,492 Shanklin Sept. 15, 1953