US2449562A - Antenna - Google Patents

Description

A. S. MEIER Sept. 21, 1948,

ANTENNA 3 Sheets-Shegt 1 Filed Oct. 3, 1944 F/Gl Sept; 21-, 1948. v A. s. MEIER 2,449,562

ANTENNA Filed 001:. 3, 1944 l 3 Sheets-Sheet 2 2 23 25 INVENTOR.

K7 TTOR/VEY Patented Sept. 21, 1948 ANTENNA Allen S. Meier, Xenia, Ohio, assignor to the United States of America as represented by the Secretary of War Application October 3, 1944, Serial No. 557,038

(Granted under the act of March 3, 1883, as amended April 30, 1928; 3'70 0. G. 757) 2 Claims.

The invention described herein may be manufactured and used by or for the Government for governmental purposes, without the payment to me of any royalty thereon. v

This invention relates to antennas and more particularly to an antenna arrangement having broad band characteristics. I

Antennas that areto be mounted upon airborne craft are designed to have favorable aerodynamic qualities. For this reason, stub. whip and loop antennas that have had good transmission characteristics, haveenjoyed widespread acceptance and use. Antennas of these types have been characterized by limitations in the bandwidths of the signals that they will transmit with optimum performance. ..In the past, the usual method of adapting an antenna to the radiation of electrical signals of broad bandwidths was to increase .thev lateral dimensions of the antenna, since the bandwidth is a function of the ratio of the length of the antenna to its breadth. Where broad band signals are to be transmitted, antennas that have been available heretofore have been hollow sheet metal bodies of closed cylindrical, spherical, conical, and waisted shapes that are not aerodynamically sound because of their very large air drag, and that are too conspicuous for tactical purposes at low frequencies. The characteristics of these antennas are such that for the transmission of bands of some widths that are becoming increasingly important in some phases of radio work, these hollow antennas would of necessity be prohibitively large.

Heretofore, little attention has been paid to the physical contour of the surface area in the immediate vicinity of the base of an antenna mounted thereon other than to specify that it should be a flat ground plane.

The objects of the present invention include the provision of antenna and fuselage associated constructions that take advantage of physical relations between small-diameter antennas of conventionally acceptable lengths and dimensions, and the contours of surface areas in the immediate vicinity of the bases of antennas that are mounted thereon, that have been neglected or ignored heretofore; in antenna and mounting assemblies that have markedly improved electrical characteristics in the width of the signal band that the antenna will conduct or transduce without retuning; in the provision of antenna mountings and antenna combinations wherein the antennas haverelatively small lateral dimensions and that provide tactically inconspicuous antenna assemblies that are suitable for the transmissions of abroad band of frequencies; and in the provision of both permanently mounted and retractable improved forms of broad band antennas that are aerodynamically sound.

With the above and other objects in view that will be apparent to those who are informed in the field of radio antennas, suitable illustrative embodiments of broad band antennas and the mountings therefor that embody the present invention are illustrated in the accompanying drawings, wherein:

Fig. 1 is a fragmentary side elevation of an improved antenna and a curved mounting surface assembly which embodies the present invention;

Fig. 2 is an enlarged fragmentary axial section of the assembly that is shown in Fig. 1;

Fig. 3 is a fragmentary side elevation of a modified antenna and a curved mounting surfaceassembly that is retractable toward the interior of an aircraft or the like on which it may be mounted;

Fig. 4 is a fragmentary axial section of the assembly that is shown in Fig. 3;

Fig. 5 is a diagram showing approximately the radiation pattern, projected upon a vertical plane, of a Whip antenna mounted upon a flat ground plane;

Fig. 6 is a diagram showing approximately the radiation pattern, projected upon a vertical plane, of a whip antenna mounted upon a curved plane in conformity with the present invention; and

' Fig. 7 is a graphical presentation of approximately the resistance and reactance with frequency curves of an antenna mounted upon a flat ground plane in comparison with the same antenna mounted upon a curved ground plane to embody the present invention. 1

The first form of antenna and antenna mounting assembly that is shown in Figs. 1 and 2 of the accompanying drawings, is illustrative of a usual form of antenna mounted upon a conducting surface having a sufflciently curved contour to impart broad band characteristics to the antenna.

The improved form of antenna assembly that is shown in these figures of the drawing comprises an antenna l of the whip type and of a desired length. The improved antenna I has a thrust assuming portion, such as a flange 2 or the like, spaced upwardly from the lower end thereof. The antenna flange 2 rests upon the upper face of a centrally tapped outwardly frusto-conical socket 3 that seats within a correspondingly shaped apex].-

3 ture that is disposed centrally of a preferably circular dielectric mount 4. The mount 4 is secured to a conducting surface 5 of a desired curved contour, such as cylindrical, oval, round or other desired shape in any desired manner, as by bolts 6 and nuts 1, or the like. The surface 5 may be a special mounting for the antenna I, the skin of an aeroplane at the oval or cylindrical part thereof, or other suitable support. The socket 3 is firmly secured within the aperture in the dielectric mount 4 in any suitable manner, as by the use of a nut 8 that turns upon-the threaded lower end of the socket 3. A washer l8, beneath the nut 8, extends radially to overlie an adjacent area on the lower face of the mount 4.

The antenna I is seated firmly within the bore of the socket 3 in any suitable manner and prefer ably by a flanged screw 9 that turns up :into the tapped and threaded lower end of the antenna l. A shoulder on the screw 3 extends radially to overlie the lower end of the socket 3. Tightening the screw 9 upon the socket Bdraws the antenna flange 2 tightly against the upper end of the socket 3. The screw 9 preferably continues downwardly to provide a central contact 13 for a connection fitting that is accessible from within an aircraft. An outer contact H is spaced from the inner contact ID with an insulating material 52 interposed therebetween to complete a coaxial con nector for the antenna l. Screws 13 extend thru apertures adjacent the periphery of a connector housing aperture that preferably is countersunk in the bottom of a cylindrical hollow case It, and thread into a strengthening plate l5. The case 14 is secured to the under side of the curved mounting surface 5, by the nuts I.

A modified antennaassembly that also is applied to a surface of electrical conducting material of a desired degree of curvature, is shown in Figs.3 and 4 of the drawings.

In this improved antenna and mounting assembly, an antenna l8 preferably has a frustoconical lower portion I9 that is drawn tightly into a mating aperture in a substantially cylindrical dielectriomount by suitable means such as by 1 a nut 2| or the like,'with or without a washer ll interposedtherebetween. A screw 22 threads into the lower end of the antenna and terminates downwardly in an axially split central contact 23 for the connection of a coaxial fitting thereto. An insulating material 24 is disposed between the central contact 23 and an outer contact 25 part of the coaxial connector. The coaxial connector outer contact 25 continues upwardly-with its upper end spot welded or otherwise secured to or continuous with a radially outwardly extending flange 26. A plurality of screws 21 extend thru a disk 29, the flange 26 and thread into the dielectric mount 20 to secure these parts of the assembly together. The open upper rim of a cylindrical hollow case 28 is secured to an axially extending flange on the disc 29 by screws 30 or the like. A strengthening collar 4| is preferably welded to the case 28 around the aperture within which the outer contact 25 is disposed.

The antenna assembly that is shown in Figs. 3 and 4 of the drawing preferably is made to be retractable to within the inside of the plane fuselage or other curved mounting in a suitable manner. The cylindrical dielectric mount 20 preferably is provided with diametrically projecting pins 3l that enter bayonet slots 32 in a hollow cylindrical sleeve 33. The sleeve 33 is secured in any suitable manner to the curved surface 5 as by bolts 34 and nuts 35 that extend thru rings 36 and 3'! or the like, one of which is welded or otherwise secured alon its radially inner edge to the radially outer surface of the sleeve 33.

The pins 3| are maintained yieldingly seated within the lowermost parts of the slots .32 by suitable means, such as by a wave spring 38 that is interposed between wear rings 39 and 40 that are disposed upon the axial opposite sides of the wave spring 38 to bear against the lower edge of the sleeve 33 and the upper face of disc 2-3, respectively. The resilience of the spring 38 provides a secure electrical ground connection and also holds the assembly firmly together.

In the installation or removal of the mount 20 within the sleeve 33, the yielding resistance of the spring 38 is overcome before the pins 3| may be seated in or removed from, the lowermost parts of the slots 32. Gaskets, not shown, serve to seal the various junctions of the parts of the antenna and mounts that are disclosed herein wherever needed, for minimizing the undesirable entrance of water, dust, wind and the like, into the interior of the ship or other craft upon which the antenna assemblies may be installed.

The described antennas are illustrative of aerodynamically sound, small diameter antennas that have been adapted for broad band work by having the present invention embodied thereinto. It has been determined experimentally that an antenna of small diameter and of commonly available or of conventional design that is built in combination with a curved surface in such -a manner as to embody the present invention is thereby adapted for the conducting of electrical impulses of band widths that Were outside of the range of the same antennas on their usual flat ground plane mounting. A whip antenna that embodies the present invention has an improved radiation pattern and its bandwidth is materially greater than the bandwidth that is obtained from the same antenna when used on a flat ground plane, the bandwidths being compared at the same radiation resistance level, such as the fifty ohm level, for example.

"Comparable radiation patterns projected ona flat vertical plane of a whip antenna are shown in Figs. 5 and 6 of the accompanying drawings. The pattern that is shown in Fig. 5 is that of a whip antenna mounted upon a fiat ground plane. The pattern provides good contact with neighboring planes both laterally and above the point at which the antenna is fed but provides little or no contact with neighboring planes laterally and below the point at which the antennais fed.

The pattern that is shown in Fig. 6 is that of the same whip antenna mounted upon a curved ground plane to embody the present invention. The pattern providesgood contact-with neighborin planes laterally and both above and below the point of contact at which :the antenna 'is fed.

It will thus be-seen that the present invention materially enlarges the antenna radiation pattern to include the lateral zone below an aeroplane that is provided therewith, which 'heretofore has been a common blind spot in interplane communications.

The curves that are shown'in Fig. 7 of the accompanying drawings illustrate the approximate increases in band width at a given resistance level of an antenna mounted upon a curved ground surface to embody the present invention, as compared with the same antenna mounted upon a flat ground plane. The resistance-frequency curve is shown to the left of Fig. 7 and the reactance-frequency curve is shown to the right of Fig. 7. It has been determined experimentally that an antenna that is mounted upon a curved surface to embody the present invention has a materially broader bandwidth at the same level than the same antenna mounted upon a flat ground plane.

This result finds its explanation in viewing the present invention as a center-fed di-pole an tenna. Viewed in this manner the antenna 1 provides one pole of the di-pole and the curved conducting surface 5, that joins the antenna 1 at its base and at the feeding point for both poles, provides the other and laterally expanded pole for the di-pole antenna. With this view of the present invention in mind the matter of accounting for the functional advantages of the present invention will be more apparent.

In conformity with the accepted theory of Marconi antennas the current is zero at the extreme end of the antenna and is at a maximum at the point at which power is fed into the antenna. An antenna assembly that embodies the present invention is not used alone but is used with an expanded counterpoise in the form of the curved antenna supporting conducting surface 5.

With the maximum current fed into the antenna system at the junction of the antenna l and its counterpoise or expanded image 5. it is logical to assume that the electrical fields that are roughly axial to the antenna 1 continue in a laterally expanded form about the counterpoise 5. By the same reasoning, it is logical to assume that the magnetic fields that are normal to the electrical fields thruout are similarly expanded about the counterpoise 5. The deduction properly follows that the type and characteristics of the signals that emanate from an antenna assembly that embodies the present invention have a. form that differs from those that emanate from an antenna I on its usual fiat mounting surface. This theoretical deduction has been substantiated in fact in that conventionally accessible antennas when mounted in conformity with the present invention have been found to have a materially increased bandwidth in performance, as compared with the same antennas on conventional mountings.

It is to be understood that the type of antenna and the mounting therefor that have been disclosed and illustrated herein have been submitted for the purposes of illustrating and explaining the present invention and that other forms of slender antennas and curved mountings therefor may be substituted for the particu lar constructions that have been chosen for this explanation without departing from the present invention as defined by the appended claims.

What I claim is:

1. An antenna and mounting assembly, comprising in combination an antenna having a radially projecting flange spaced from the input end thereof, a socket into the bore of which said antenna is removably disposed with the antenna flange engaging one end thereof and having a frusto-conical outer surface, a dielectric mount that is apertured to receive and provide a mating seat for said socket, means for drawing said socket securely into the aperture in said mount, means engaging said socket for drawing the antenna flange tightly against the end of said socket that is contacted thereby and which means continues to provide an antenna contact, electrical conducting means upon which said mount is secured, and a case in electrical connection with the electrical connecting means and continuing to provide a contact therefor.

2. An antenna and mounting therefor, comprising in combination an antenna having a tapered lower end, a dielectric mount apertured to receive and substantially mate with the tapered lower end of said antenna, means for drawing the tapered end of said antenna snugly into the mating aperture in said mount, an antenna contact electrically connected to said antenna, a pair of pins extending laterally from said mount, a sleeve for receiving said antenna mount and slotted to receive and releasably secure the pins from said mount, spring means yieldingly securing the mount pins in the sleeve slots, and a ground contact insulated from said antenna contact.

ALLEN S. MEIER.

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

UNITED STATES PATENTS Number Name Date 1,305,104 Hewitt May 27, 1919 2,170,849 Berndt Aug. 29, 1939 2,184,729 Bailey Dec. 26, 1939 2,235,139 Bruce Mar. 18, 1941 2,239,724 Lindenblad Apr. 29, 1941 2,258,953 Higgins Oct. 14, 1941 2,266,139 Zukerman Dec. 16, 1941 2,267,951 Roosenstein Dec. 30, 1941 2,313,046 Bruce Mar. 9, 1943 2,354,314 Harsted July 25, 1944 2,368,663 Kandoian Feb. 6, 1945 2,404,093 Van B. Roberts July 16, 1946 FOREIGN PATENTS Number Country Date 813,957 France Mar. 8, 1937 OTHER REFERENCES Biconical Electromagnetic Horns, Proceedings of the IRE, December 1939, pp. 769-700.

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