US2757371A

US2757371A - Vertically polarized antenna

Info

Publication number: US2757371A
Application number: US214537A
Authority: US
Inventors: Marvel W Scheldorf
Original assignee: Andrew LLC
Current assignee: Commscope Technologies LLC
Priority date: 1951-03-08
Filing date: 1951-03-08
Publication date: 1956-07-31
Anticipated expiration: 1973-07-31

Description

July 31, 1956 M. w. SCHELDORF VERTICALLY POLARIZED ANTENNA Filed March 8, 1951 W a 1 7 M 2,751,311- 1 VERTICALLY POLARIZED ANTENNA Marvel w.- Scheldorf, Palos Heights, nl.,- assignor to Andrew Corporation; a corporation of Illinois Application March 8, 1951, steam. 214,537

sclaims. 01. 343-905) The present invention relates to a vertically polarized antenna, and more particularly to such an antenna adapted for'VHF operation.

In the past it has been common to provide vertical polarization by antennas of the coaxial type. Particularly for mobile communication service it has been customary to stack concentric cylinders over a supporting mast structure. In the past it has been found'that' at times'coaxial antennas did not produce the transmission characteristics desired. It has also been found that the ground plane antenna likewise at times did not produce the desired transmission characteristics.

The coaxial antenna in one form consistsof a vertieal quarter wave-length extension of the inner conductorof the transmission line plus a quarter wave-length cylinder over the outer conductor of that line connected at the upper end and free at the bottom to form what is commonly known as a skirt. I

The ground-plane antenna consisting of a vertical quarter wave-length extension of the inner conductor of the transmission line and a half wave-length diameter ground plane fastened to'the end of the outer conductor of that line in a horizontal plane is not susceptible of modification to employ stacking. A number of attempts have been made to solve the vertically polarized stacking problem. It would seem that the predominant cause for their failure is that they employ the concentric cylinder prin ciple. These cylinders must have'considerable clearance fro'mthe mast for electrical isolation, and hence presentlargewind loading areas. Thisrequires a large mast diameter, which is bulky and consequently the entire assembly is unreasonably bulky. Such an arrangement furthermore'requires feed hnes to be brought up through'the mast" which makes service of the junctions diflicult or'impos sible."

It-has' been found that one of themost annoying difiiculties of both the ground plane antenna and coaxial antennas 'is the tendency to couple power to the mast, with corresponding sensitivity to surrounding objects and height above the-ground. It, therefore, would be desirable to provide an improved antenna structure not subject to certain of these difii'culties.

It is, therefore, an object of the present invention to provide an improved vertically polarized antenna having a substantially circular horizontal pattern.

A further object of the present invention is to provide an improved vertically polarized antenna having a high power gain. p

Still another objeet of the present invention is to provide a'n'improved vertically polarized antenna which has negligible" coupling to the supporting mast. U 7

A still further object of'the present inventionfis to provide animp'roved antenna requiring'a minimumnumber of 'feedpdin'ts; I

Still'anoth'er object of the present invention is to provide a vertically polarized antenna having a minimum wind load.

Other and further objects of the present invention sub- Patented July 31, 1956 sequently will become apparent by reference to the following description'taken in conjunction with theacconipanying drawing wherein:

Figure l is a representation of an'antenna constructed in accordance with the principles of the present invention;

Figure rangement for providing a minimum number of feed points for the radiating elements shown in the antenna of Figure 1;

Figure 3 is a side view of one of the radiating elements; Figure 4 is a diagrammatic top view of the antenna" arrangement illustrated in Figure 1; and

Figures 5 and 6 are graphical representations illustrat ing certain radiation characteristic patterns of 'the antenna. In Figure 1 there is shown a supportingmast l lwhich carries a plurality of radiating elements 12 through 19' arranged in equal numbers on opposite sides of the mast'll' in a stepped or staggered relation. Each of the radiating elements 12 to 19 is a fomed dipolei In the development of this antenna it was found that a single folded dipole radiating element mounted on a' mastwas comparatively free from coupling to the mast, but'did'n'ot in of itself provide 'a circular horizontal radiation pattern. The use of a pair of dipole elements arranged on opposite sides of the mast provided 'anarrangethe various'forms'of coaxial antennas. Froinan arrangement employing two folded dipole elements on a mast therena'tura'lly was developed a folded dipole element array of the stacked variety illustrated in Figure 1.

In order such as'shown' in Figure 1, thereis arrangement diagrammatically represented in Figure 2.

to any" appreciable extent;

junetion of each pair. the dipoles line 21 at its upper extremity is'connected to thedipole element 12.

dipoleelement 16 (.932 being the relative velocity of propagation in transmission line 21). From thatjunction to the junctionco'nnected tothe dipole'element 13"the" distance is 1.068 half wave-length. The distance from the'jun'ction to element 13 to the dipole element 17 again is .932 half wave-length. A similar junction vertical transmission line'22 interconnects the

dipole elements

14, 15,

18 and 19. The two

vertical junction transniission'lines

21 and 22 are interconnected by a spiral junction trans mission hne 23 arranged on the other side of the mast.

The center or the spiral section 23 is connected to the" main feed'transm'ission line' 24"which is on the'same side of the mast. In one embodiment the two vertical junc-' tion transmission lines, such as the transmission-lines 21 and 2.2,had an impedance value of 51.5 ohms. The's'pifal junction transmission line had an impedance'value of' 63.8 ohms which was joined to the main feed transmission line having an impedance of 5 1.5 ohms. Thus at each T junction there is a'o'ne to two'impedance'transformer so that standing wave ratios in the feed transmission lines arethe same as for the linesbeing fed. The arrangement illustrated in Figure 2 has the advantage of keeping the main feed transmission line and spiral junctiontransmission line away from the elements thereby to preve'ntu'ribalances and'disturbances iiithe radiation pattern.- 7 Such" an arrangement furthermore has certain physical advantages in that there is no obstruction to the end seal units, which support the dipole elements, and the junction with 2 is a diagrammatic representation of an ark ment produc'ingthe desired circular horizontal p'atternj without many of the disadvantages encountered in other types of antennas, such as the 'grou'nd'plane antenna" and to supply energy toastacke'darrangement,

employed aharness At a distance 's'uchas' .932 half I wave-length there is provided a junction which is connected tothe' 3 the main feed transmission line is at a position where the line is easily brought down the rnast.

Figure 3 illustrates one of the dipole radiating elements which is formed of a plurality of rods or

tubes

26, 27 and 28. The rod 27 is connected to the rod 26 at one end by a strap or bar 29. The other rod 28 is connected to the rod 26 by a strap or bar 31. One of the rods such as the rod 27 at its other end is connected to a conductive member 32 which engages a stud 33 arranged coaxially in an insulator 34. The insulator 34 is partially surrounded by a shield 35 connected to one end of the dipole rod 28.

If the elements shown in Figure 3 when mounted on a mast 11 such as shown in Figure l, were viewed from the top of the trust, the arrangement would be similar to that shown in Figure 4. In that figure the top of the mast 11 is shown as being a large circle. Tangent to the mast are a plurality of'shields and insulating members 35 carrying at their outer extremities the dipole elements which include the

rods

26 and 27. The dipole elements are connected through the conductive studs 33 to the harness arrangement shown in Figure 2. This is diagrammatically represented in Figure 4 by the application of the reference character 21 to the line element extending between four dipole supporting assemblies.

In Figure 5 there is shown a horizontal radiation pattern which is representative of patterns obtained over a band of frequencies from 148 to 162 megacycles. In the center of this diagram there is represented by a cross hatched circle the support mast 11 which carries the vertical feed line 24 and has radiating .dipole elements arranged on opposite sides of the mast 11.

Figure 6 shows the radiation pattern of the antenna in the plane of the feed line.

The resultant antenna structure is one in which there is no substantial coupling to the mast. This is true in the stacked or array arrangement shown in Figure 1, and in the arrangement employing only two radiating elements mounted on opposite sides of the support mast. The central support structure, however, has one other advantage. It provides a vertical polarized antenna which readily permits mounting a beacon or another antenna above it. Likewise a lightning rod may be added to the top of the antenna support without disturbing the operation of the antenna.

While at the present time no completely satisfactory explanation for the isolation of the antenna has been developed,it may be assumed that the fact that heavy standing waves of transmission line current in the folded ends of the elements, oppose one another, the mast current is consequently low. The specific structure described, does not require a return path for transmission line currents, such as are found necessary in all other arrangements. The radiation currents in the elements are additive at the folded ends but the magnitudes relatively approach zero, so there would be little coupling from this portion of the element.

While for the purpose of illustrating and describing the present invention a certain preferred embodiment has been shown in the drawing, it is to be understood that the invention is not to be limited thereby, since such variations in the physical embodiment are contemplated as may be commensurate with the spirit and scope of the invention set forth in the accompanying claims.

I claim as "my invention:

1. A multi-element antenna comprising a mast supportingan even number of folded dipole elements intwo vertical planes, said elements being located on opposite sides of said mast in staggered relation to each other and in close proximity to said mast, and a coaxial transmission line extending upwardly along said mast, a plurality of vertical transmission lines extending along said mast and each being connected to one half of said dipole elements,

4 and a sinuous transmission line extending between said vertical transmission lines and said first transmission line.

2. A multi-element antenna comprising a mast supporting an even number of folded dipole elements in two vertical planes, said elements being located on opposite sides of said mast in staggered linear relation to each other and in close proximity to said mast, and a coaxial transmission line extending upward along and behind said mast, a plurality of vertical transmission lines extending along the front of said mast, each of said vertical transmission lines being connected to certain dipole elements on opposite sides of said mast, each of said verticaltransmission lines havin'g junctions for pairs of said dipole elements at half wave length distance, and a sinuous coaxial transmission line extending between said vertical transmission lines and said first transmission line.

3. A multi-element antenna comprising a mast supporting an even number of folded dipole elements, said elements being located on opposite sides of said mast in staggered linear relation to each other, a coaxial transmission line extending upwardly along said mast, a plurality of coaxial vertical transmission lines extending along said mast and each being connected to one-half of said 'dipol'e elements, each of said dipole elements having one endconnected to the inner conductor of said coaxial tra'nsmis-:

sio'n line and the other end connected to the outer conductor of said coaxial transmission line, and 'a sinuous transmission line extending between said vertical transmission lines and said firs t transmission line.

4. A multi-element antenna comprising a mast supporting aneven number of dipole elements in two vertical planes, said elements being located on opposite sides of said mast in staggered relation to each other and in close proximity to said mast, each dipole having *one element thereof connected to ground, and a coaxial transmission line extending u'pwardlyalong said mast, a plurality of vertical transmission lines "extending along said mast and each being connected to one-half of said dipole elements, and a sinuous transmission line extending between said vertical transmission lines and 'said first transmission line, said first coaxial transmission line and said plurality of vertical transmission lines 'having like impedance characteristic values.

5. A multi-element antenna comprising a vertical mast supporting an even number-of dipole elements in two vettical planes located on opposite sides of said mast, said"'elements being arranged in staggered linear relation to'each other and in close proximity to said mast, each dipole element having oneelement thereof connected to ground,

and 'a coaxial transmission liue extending along and behind said mast, "aplura'lity of vertical transmission lines extending along the front of said mast, each of said vertical transmission lines being connected to certain 'dipole elements on opposite sides of said mast, said first coaxial transmission line and said plurality of vertical transmission lines having like characteristic impedance values, each of said vertical transmission lines having junctions for pairs of said dipole'elements at -'half wave length distance, and a sinuous coaxial transmission line extending between said vertical transmission 'lines and said first transmission line.

References Cited in the file of this patent UNITED STATES PATENTS 2,080,577 Ponte May 18, 1 937 12,160,053 Barbour Ma 30, 1939 2,199,635 Koch May 7, 1940 2,217,321 Runge et al Oct.f8, 1940 2,234,744 Thomas Mar. 11, 1941 2,286,179 Lindenblad June 9, 1 942 2,512,,5 1-1 Weighton June 20, 1950