US2477647A - Antenna - Google Patents

Description

g 1949. s. B. PICKLES ET AL 2,477,647

ANTENNA Filed Jan. 29, 1945 2 Sheets-Sheet l Aug. 2, 1949. s s. PICKLES ET AL 2,477,647

ANTENNA Filed Jan. 29, 1945 2 Sheets-Sheet 2 A 7' TO VF Y Patented Aug. 2, 1949 ANTENNA Sidney l3. Pickles, Jackson Heights, and Anthony Gasaihona,

, ew York, N. Y., assignors tov Federal Telephone and Radio Corporation, New York, N. Y,, a corporation of Delaware Application January 29, 1945, Serial No. 575,079; 1.0 Claims. (Cl. 2.50 33.57)

This invention relates to composite antennas and more particularly to directive antenna systems of the type utilizing directly and parasitically energized antenna arrays.

For temporary or portable use it is often required that antenna-s particularly composite ants s a e f s veral antenna un ts. be d mountably supported in operation. For storage and transportation, however, it is often desired that the parts of the antenna may be separated so as to take up less space than the entire antenna assembly when in use. This is particularly true when the antenna, because of required directional properties, consists of a threeedhnensional array of antenna units which may be quite bulky. At the same time, it is desirable that such antenna structures be made as nearly self supporting as practicable to avoid the necessity of use of supporting guide lines and that the electrical properties of the antenna be of the proper characteristics to give the desired radiation pat-- tern. Moreover, built for assembly at a given site, it is often found that where electrical characteristics are important, the portions separated in the demount-ing operation may not always be properly connected when the antenna is set up for operation.

It is an object of our invention to provide a portable antenna arrangement which may be readily mounted for operation in field use.

It is a still further object of our invention to provide a demountable antenna assembly capable of being taken apart in transportation and storage in which the joints at which the antenna parts are separated are positioned to produce substantially no variation in the electrical characteristics of the system.

It is a, still further object of our invention to provide an antenna u it having the desired characteristics of impedance values and/or being of such self-supporting rigid construction that it may readily be used for obtaining the desired pattern whenever put to use.

According to a feature of our invention, we provide an antenna array consisting of antennas spaced in a common plane and rigidly fastened to relatively rigid transmission conductors at predetermined spaced points in a common plane. Preferably, each of the antennas comprises a pair of arms, and each of the arms consists of two elements s-pacecla small distance apart at the point at which they are fastened with a conductor and joined together at their remote ends. This construction produces a reduced impedance of each of the antennas and at the same time in such demountable antennas.

more rigid construction. The conductors of the transmission line are provided with extensions preferably offset from the plane of the antennas and extending therebeyond a distance dependent upon the antenna impedance. Each pair of ex.- tensions is connected bya short-circuiting plate. These short circuited extensions are of such length as to neutralize the reactive impedance of the antenna array so that a point of pure resistive impedance is produced and the antenna array may be mounted by any desired support.- in means fastened to the short circuiting plates. In order to obtain the desired impedance match.- ing of the structure to a feeder transmission line, the two antennas are preferably spaced apart a half wavelength at the operating frequency and an, impedance transformer is connected; to. the transmission conductors at a point adjacent one of these antennas. Because of the half wave spacing between the antennas, the two antennas will be substantially electrically in parallel across the transmission conductors so that the total. impedance of the array will be half that of a single antenna. The impedance transformer may then serve to reduce the entire impedance of the an. tenn-a array as seen from the transmission line substantially to the value of the impedance of this line.

A. second similarly constructed reflector or reradiation antenna array is provided for mounting directly behind the fed antenna array to produce a unidirectional, effect. This reflector ant nna array is likewise mounted at a zero voltage point so that when the composite antenna is assembled for transmission, the electrical effects will always be the same. For storage and shipment, however, these antenna arrays may be separated when removed from the mounting structure so that they may be nested for store ing in a much smaller space than would be required for the entire composite antenna.

A better understanding of our invention and the objects and features thereof may be had by reference to the accompanying drawing, in which:

Fig. l is an illustration in perspective of the composite antenna assembly as mounted for use; and

Fig. 2 is a circuit diagram of the directly fed antenna array illustrating the electrical properties thereof.

Turnin first to Fig, 1, there is shown generally at l the directly fed antenna array of the composite antenna and at 2 the parasitically fed or reflector array. Antenna array l consists of two dipole antennas 3 and 4 fixedly secured to the conductors and 6 of a transmission line I. Antennas 3 and 4 are preferably spaced apart substantially a half wavelength at the operating frequency and line 1 may be transposed as shown at 8 so that antennas 3 and 4 will be energized cophasally. Antenna 3 may consist of separate arms extending in opposite directions from conductors 5 and 6, each of the arms comprising upper elements 9 and lower elements If! spaced apart a small distance at the juncture with conductors 5 and 6 and joined together at their remote ends by any suitable means such as plates ll. Similarly, antenna l may consist of upper elements l2 and lower elements l3 spaced apart at their juncture with conductors 5 and 6 and joined at their remote ends by means of plates [4. Antennas 3 and 4 are preferably arranged in the same plane. Conductors 5 and 6 have extensions extending beyond the upper end of antenna array l as shown at l5 and beyond the lower end as shown at it. These extensions l5, [6 are made of the desired length at the oper atin frequency and shorted together at their remote ends by means of shorting supporting plates l1 and I8, respectively. When the antennas are made 1.25 wave lengths at the operating frequency, for example, the extensions are made of such length so as to provide an inductive impedance to neutralize the capacitive reactance of the antenna. These extensions l5 and I6 extend away from the plane of antennas 3 and 4 as illustrated. Preferably, they extend a distance inwardly suflicient to provide half of the desired spacing between the fed antenna array I and the parasitic antenna array 2. Since these shorting plates l1 and I8 are substantially at ground potential, they may be used for mounting the antenna without producing any effect on the antenna assembly. An impedance transformer i9 is coupled to conductors 5 and 6 at a point adjacent antenna 4. This impedance transformer is made substantially a quarter of a wavelength long and is arranged for coupling to a feeder line 20. Transformer It serves to reduce the overall impedance of antenna array l substantially to the impedance of feeder line 2t.

Parasitic antenna array 2 consists likewise of two antennas 2i and 22 substantially similar in construction to antenna units 3 and l fastened to separate supporting lines 23, 24 of a second transmission line. Antennas 2! and 22 also comprise separate upper and lower elements 25, 26, 21 and 23 fastened together at their remote ends as indicated at 29 and 3E]. The conductors 23 and 24 are provided with extensions 3| and 32 extending a substantial amount beyond antennas 2! and 22, respectively, and extending away from the plane in which antennas 2| and 22 are arranged. These extensions are short circuited by short circuiting and supporting plates 33, 34. The extensions are made of such a length as to tune the parasitic antenna array to provide maximum front to back ratio. The central portions of conductors 23 and 24 serve only as supports for the parasitic radiators 2 I, 22 and are short circuited at the midpoint by short circuiting bar 35. Thus, the portions of the line provide substantially infinite impedance to energy from radiators 2| and 22. For mounting the composite antenna, plates l7 and 33 are demountably clamped to a supporting structure 36 and plates 58 and 35 to a supporting structure 3'! by clamping means 38. It will be evident that when the composite antenna is demounted for storage, antenna arrays I,

and 2 may be separated for space saving and stacking. However, since the clamping takes place at a voltage neutral point, no change in the electrical properties of the antenna will occur even should the plates thereof be dirty so that good electrical connections are not provided.

For monitoring purposes, a coupling loop 39 provided with a socket 40 may be arranged coupled to the two conductors 23, 24 of the parasitic antenna array as indicated.

The antenna unit is remarkably free from the affects of atmospheric conditions. However, wet snow bridging between conductors 5 and E or 23, 24 may cause some trouble. To avoid this difficulty, a cover of insulating material, not shown, may be fitted over the unit but need not cover the extending radiators 3, 4, 2| and 22.

A better understanding of the electrical properties of the antenna in accordance with our invention may be had by reference to Fig. 2. In Fig. 2, the antenna 3 is shown as having a normal impedance wl and similarly antenna A has the same impedance wl. This impedance is lower than would be obtained with an ordinary single rod dipole. These two antenna units interconnected by line I will present at a junction point H of transformer l9 and transmission line I an impedanc equal to If then transformer l9 has a 5 to 1 impedance transformation ratio, the impedance of the entire antenna array looking in from line 20, at point 42, will have an impedance of This impedance may be so chosen that it is sub stantially equal to the normal impedance of feeder line 20. Thus, an impedance matching of the antenna assembly to the feeder line is readily obtained. The spacing between the antenna arrays I and 2 may be so chosen as to provide the desired directional properties. Where it is desired to have maximum front to back radiation, the spacing should be made substantially about electrical degrees. Accordingly, in the general construction this spacing may be considerably different from the optimum spacing. It should be understood that transmission line sections l5, It may be made to differ from the chosen length by multiples of a half wavelength line and still preserve the desired results. All that is necessary is that these lines be made substantially electrically of such a length as to preserve the desired impedance.

It will be readily apparent that while we have disclosed as a particular embodiment of this invention a desirable constructive example, many variations in the details thereof and in the structural assembly may be had without departing from the scope of our invention. It should be distinctly understood that thi specific description is made merely by way of exampl and is not intended as a limitation of our invention as set forth in the objects thereof and in the appended claims.

We claim:

1. A demountable antenna structure, comprising a first pair of conductors forming a twoconductor transmission line, two antennas fastened to the conductors of said first pair in spaced relation, said antennas being substantially in a given plane, said conductors extending substantially a quarter wavelength at the operating freamass? portingstructure.

2. A dernountable antenna structure, comprising a first pair of r-elativelyrigid conductorsforming a two-conductor transmission line, two relatively rigid dipole antennas fastened to the conductors of said first pair in spaced relation, said antennas being substantially in a given plane, said conductors extending beyond said antennas, and having their ends in a plane spaced from said given plane, conductive means fasteningtogether the ends of said conductors, a second pair ofrelatively rigid conductors forming second two-con ductor transmission line, other relatively rigid dipole antennas fastened to the conductors of said second line in spaced relation and substantially in a single plane, the ends of said conductors of the second pair extending substantially a quarter wavelength at said operating frequency beyond said other antennas and having their ends spaced from said single plane, conductive means fastening together the ends of the conductors of said second pair, and means for securing said conductive means together on a supporting structure.

3. A demountable antenna structurecornprising a first pair of conductors forming a tWOaCOn" ductor transmission line, two antennas fastened to the conductors of said first pair spaced apart a half wave length in a given plane, said teen ductors extending beyond said antennas, and having their ends in a plane spaced from said given plane, conductive means fastening together the ends of said conductors, a second pair of corn ductors forming a second two-conductor transmission line, other dipole antennas fastened to the conductors of said second pair spaced apart a half wavelength in a single plane, the ends of said conductors of the second pair extending beyond said other antennas and having their ends spaced from said single plane, conductive means fastening together the ends of the conductors of said second pair, and means for securing said conductive means together on a supportin structure.

4. A demountable antenna structure, comprising a first pair of relatively rigid conductors forming a two-conductor transposed transmission line, two relatively rigid dipole antennas fastened to the conductors of said first pair spaced apart a half Wavelength at the operating frequency substantially in a given plane, said conductors extending beyond said antennas, and having their ends of a plane spaced from said given plane, con ductive means fastening together the ends of said conductors, a second pair of relatively rigid conductors forming a second two-conductor transmission line, other relatively rigid dipole antennas fastened to the conductors of said second pair in spaced relation and substantially in a single plane, the ends of said conductors of the second pair extending beyond said other antennas and having :their ends spaced from said single :plane, conductive means fastening together the ends of the conductors of said second gpair meansfor securing said conductive means together on a supporting structure, .and impedance transformer means coupledto saidfirst transmission line adjacentone of said antennas.

5. Ademountable antenna structure, comprising a'fir-st pair of rigid conductors forming .a twoconductor transmissionline, two rigid dipol an" tennaseach-comprising separate elements extending'from said first pair of conductors, said elements being joined together atitheir remote ends and being spaced apart at their juncture With .the conductors of saidlfirst line, said antennas being spaced apart substantially a half wavelength at the operatin frequency substantiall ina given plane,;said conductors extending beyond said antennas, and-having their ends'in a plane spaced from said given plane, conductive means fasten ing together the ends of said conductors, asecond pair of rigid conductors forming a second two-conductor transmission line, other rigid dipole antennas of similar construction to said dipoles first *named fastened to the conductors of said second line, in spaced relation and substantiallyc-in a single planeythe ends of said iconductors of the second pair extending beyond said other antennas and having their ends spaced from saidsingle plane, conductive means fasten-- ing together the ends of the conductors of said second pair, and means for securing said conductive meanstogether on a supporting structure.

'6. Aidemountable antenna structure-comprising afirstnpair of rigid conductors forming a'twoconductortransmission line, two rigid dipole antennas each comprising separate elements extending from said firstpair of conductors, said elements bein joined together at their remote ends and being. spaced apart at their juncture with the conductors of said first line, said antennas being spaced apart substantially a half wavelength at the'operating frequency substantially in a given rplane, said conductors extending beyond said antennas, and having their ends in a plane spaced from said given plane, conductive means fastening together the ends of said conductors, asecond pair of rigid conductors formin a second twoconductor'transmission line, other rigid dipole antennas of similar construction to said dipoles first named-fastened:totheconductors of said second line, in spaced relation and substantially in a single plane, the ends of said conductors of the second pair extending beyond said other antennas and having their ends spaced from said single plane, conductive means fastening together the ends of the conductors of said second pair, means for securing said conductive means together on a supporting structure, impedance transformer means coupled to said first transmission line adjacent one of said fed antennas, and a coupling loop mounted in coupling relation with said second transmission line.

7. A demountable antenna structure, comprising a first pair of relatively rigid conductors, forming a two-conductor transposed transmission line, two relatively rigid dipole antennas each dipole comprising two arms each arm comprising two elements, said elements being fastened to the conductors of said first line at spaced points thereon, the remote ends of the dipole elements being rigidly fastened together, said antennas bein spaced apart a half wavelength at the operating frequency substantially in a given plane, said conductors extending beyond said antennas, and having their ends in a plane spaced from said given plane, conductive means fastening together the ends of said conductors, a second pair of relatively rigid conductors forming a second two-conductor transmission line, other relatively rigid dipole antennas fastened to the conductors of said second pair in spaced relation and substantially in a single plane, the ends of said conductors of the second pair extending beyond said other antennas and having their ends spaced from said single plane, conductive means fastening together the ends of the conductors of said second pair, means for securing said conductive means together on a supporting structure, and impedance transformer mean coupled to said first transmission line adjacent one of said antennas.

8. An antenna array operating at a predetermined frequency comprising a length of two conductor transmission line having ends, dipole antennas, each of said poles of said dipole antennas comprising antenna elements, the poles of each of said dipole antennas extending in opposite directions in a given plane from said conductors and joined thereto, said elements of each of said poles being conductively joined together at their remote ends and being joined to said conductors at predetermined points thereon spaced small distances apart, said dipole antennas being in the given plane and spaced substantially a half wavelength apart along said transmission line at the operating frequency, the conductors of said transmission line being transposed to feed the dipole antennas cophasally, reactance neutralizing means comprising extensions of said conductors, said extensions having a predetermined length at the operating frequency and being in a plane spaced from said given plane, means electrically connecting said extensions together, said conneoting means comprising support means for said antenna array at substantially a minimum impedance point of said array.

9. A device as set forth in claim 8, further comprising a feeder transmission line, mean for matching the impedance of said feeder to said two conductor transmission line comprising an impedance transformer coupled toa point on said two conductor transmission line where the impedance is substantially equal to the parallel impedance of said antennas.

10. An antenna array for operating at a predetermined frequency comprising a length of relatively rigid two-conductor transmission line having ends, a plurality of rigid dipole antennas fastened to said conductors at pre-determined spaced points along the length thereof, each pole of said dipole antennas including two-conducting elements fastened to one of said conductors of said rigid transmission line at spaced points, said two-conducting elements being connected at their remote ends, reactance neutralizing means comprising relatively rigid two-conductor extensions of said line at said ends, said two-conductor extensions being substantially one-quarter Wave length at the operating frequency, rigid connecting means electrically connecting the ends of said conductor extensions, said connecting means comprising support means for said antenna array at substantially a minimum impedance point of said array, and an impedance transformer electrically coupled to said transmission line at a point substantially at the connection of one of said antennas thereto, the spacing of said antennas along said conductors of said transmission line and the position of connection of said impedance transformer to said line being selected such that the effective impedance presented to said impedance transformer is substantially equal to the parallel impedance of said antennas.

SIDNEY B. PICKLES. ANTHONY M. CASABONA.

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

UNITED STATES PATENTS Number Name Date 1,927,393 Darbord Sept. 19, 1933 2,086,976 Brown July 13, 1937 2,183,784 Carter Dec. 19, 1939 2,187,014 Buschbeck et al. Jan. 16, 1940 2,287,220 Alford June 23, 1942 2,298,449 Bailey Oct. 13, 1942 2,338,564 Aram Jan. 4, 1944 2,341,558 Kandoian Feb. 15, 1944 2,352,977 Scheldorf July 4, 1944 FOREIGN PATENTS Number Country Date 416,296 Great Britain Sept. 13, 1934

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