US2567858A - Scalloped plural dipole antenna - Google Patents

Description

Sept. 11, 1951 H. J. RIBLET ET AL SCALLOPED PLURAL DIPOLE ANTENNA Filed July 9, 1945 INVENTORS MAC E. VANVALKENBURG HENRY J RIBLET ATTORNFY a .r w

Patented Sept. 11, 1951 Henry J." Riblet; and Mac Van Valkenburg, '-Cambridge, Mass., assignors, by mesne assignlments, to the United States of America as represented by the Secretary of War Application July 9, 1945, Serial No. 604,026

This invention relates to antennae, and more particularly to a directional type antenna especially adapted for use in high-frequency communication systems. 3

One object of this invention is to provide an antenna which will radiate circularly polarized electromagnetic energy.

Another object of the invention is to provide an antenna with a uniform radiation pattern in the horizontal plane. v

A further object is to provide radiation generally restricted to the horizontal plane.

Another object is to provide an antenna accomplishing the above objects which will be insensitive to frequency changes over a comparatively broad band of frequencies.

Other objects and advantages of the invention will appear more fully herein. 4

In the drawings:

Fig. 1' is a perspective viewof a preferred embodiment of the invention;

feed line have been chosen for reasons of convenience. These dipole units may be constructed in any suitable manner, preferably as fully ex plained in the co-pending application of Henry J. Riblet, Serial No. 532,793, now Patent No.- 2,485,920, filed April 26, 1944.

Fig. 2 shows one' dipole unit 4 in side view Collar line, and make good electrical contact therewith. Y-

Arms 6 to l l inclusive support dipoles consisting of paired radiating elements l3 and I4, l5 and' I6, and I1 and I8.

Adjustable screws or probes I9, 20, and 2| may be threaded or thrust through radiating elements [3, l5 and I1, respectively, to make electrical contact therewith, and extend through aligned apertures in collar l2 and transmission line 5 so that they may be excited by energy from within the line. The following explanation may be advanced regarding the excitation of the dipole radiating elements. If probe I9 is excited by afield within transmission. line 5. it will. excite radiating .:ele-.

Fig. 2 is a side view of one of the dipole units;

9 Claims; (01. eso-33.53)

merit I3. Radiating element M will also be excited, as supporting elements 6 and 7 will act like a two-wire open transmission line open-circuited at one end. The electrical length of supporting elements 6 to H inclusive is such that radiating elements l3 to !8 inclusive are effectually insulated from'the outer surface of enclosed transmission line 5 at the operating frequency' A's explained in the aforementioned application, after suitable adjustment probes I9, 20, and 2| may be cut and soldered or crimped to radiating elements l3, l5, and I1, respectively. Dipole elements l3 toll inclusive, are shaped to extend circularly about the transmission line, and are spaced a small distance from each other. Thus,

dipole unit 4 consists of three dipoles spaced symmetrically at intervals'of about the axis of i the transmission line; e Fig. 3 displaysa face view of Fi 1, and particularly the cylindrical scalloped metallic shells 22 and 23and the'coupling thereto. The diameter a of elements 22 and 23 may be somewhat less than the diameter b between outer faces of the dipoles of unit 4, as shown in Fig. 2. Attached to collar are three pair of metallic supporting elements spaced at 120 intervals about collar [2,

of which only one pair 26 and 21 are shown in Fig. 3 'and'twopair 24 and 25, and 26 and 2'! are shown in the view of Fig. 1, supporting elements 22 and 23 in axial alignment with the collar and the dipole unit 4.

Considering cylindrical shell 22, it has three arcuately shaped recesses, (two of which, 28 and 29, appear in Fig. 3) symmetrically formed and ispaced'at 120 intervals about one boundary of the cylindrical surface. The other boundary of cylindrical element 22 has similar arcuate recess'es or scallops of which 30 and 3| are shown,- each in longitudinal alignment with a recess on the first boundary. Thus recesses 28 and 30 are in alignment, recesses 34 and 29 are in alignment, etc. Scalloped cylindrical element 23 is shaped in the'same way as scalloped cylindrical element 22, with the possible exception of three small projections such as 32 and 33. It has aligned re- 0655881351 and '36 and 39 and 48 which are aligned with recesses 28 and Hand 29 and 3! respectively. Projection 32 is slotted or threaded so that probe'or screw 34 .can be inserted therein and make good electrical contact therewith. An aperture 34 in the collar and an aligned aperture in the transmission line permits th probes (each projection of one boundary of element 23 has one) toreceive energy from the transmission 'linein J the, same manner as. probeslor, screws 1 9, 20, and

2| of Fig. 2. Excitation thus received by element 23 is communicated to supporting elements 21 and 26 of Fig. 3 in a manner similar to that in which supporting elements 6 and 1 of Fig. 2 are excited. That is, supports 21 and 26 act together like a quarter wave length open transmission line short-circuited at the far end and opencircuited at the near end.

The dipole elements are arranged about collar I2 so that each dipole is placed symmetrically at the space opening formed by the arcuate recesses in the cylindrical elements. Thus dipole arms 13 and i4 reaching substantially 120" about collar l2 are centered at the arc of recess 3|. Elements l5 and I6 are likewise centered in the arcuate recesses 30 and 35 of elements 22 and 23, etc.

In dimensions one preferred embodiment of the invention has diameter a of scalloped cylindrical elements 22 and 23 approximately onehalf wavelength, and the scallops or cut-out portions extend circumferentially about one-half wave length. The arcuate shape of the scallops is not critical, but will afiect the impedance presented to the probes or screws, such as 34. Also, in this embodiment the large longitudinal dimension c of the cylindrical scalloped elements is a little less than one-half wave-length, or about of a wavelength. The scallops are circularly formed with a diameter of a little less than a half wave length, and in between the deepest cut-out portions of each shell the longitudinal dimensions d is a little less than one-quarter wavelength. These dimensions are not critical, nor is the shape of the scalloped portions. However, if dimension d is made too small or too large, the resulting impedance presented by the shells is such that the desired circular polarization will be difficult if not impossible of achievement. In that event elliptical polarization will result. Three dipole units are used with two scalloped cylindrical elements such as 22 and 23.

It will appear from the description above that the cylindrical shells 22, 23, in effect constitute three dipoles mounted parallel to the axis of the cylinder at equal distance from the axis and spaced 120 apart about the axis. This follows since the three longer longitudinal dimensions of each scalloped cylinder are aligned with the three longer longitudinal dimensions of the other scalloped cylinder. These three sets of dipoles are fed in the same manner as the three sets of curved dipoles and hence each set is excited and radiates as a dipole.

Circular polarization requires space quadrature, phase quadrature, and equality of components of the electric vector in a plane normal to the direction or propagation of energy. Assuming the axis of the structure to be vertical, so that the horizontal plane is perpendicular thereto, it is apparent that currents on the dipoles will produce generally horizontally polarized radiation in space. Currents on the scalloped cylindrical elements generally are in a direction parallel to the axis of the elements, and therefore will produce generally vertically polarized radiation. Thus, space quadrature is effected.

As shown in Fig. 1, two dipole units, 31 and 38 may be utilized with dipole unit I and scalloped cylindrical elements 22 and 23 to form a complete antenna. Elements 22 and 23 are mounted by supporting elements on the same collar as dipole unit 4, as explained. Adjustment of the depth of insertion of the screws or probes will alter the phasing, and it is thus-possible to obtain phase quadrature, as well as substantial equality of the intensity of radiation from the dipole units and the scalloped cylindrical elements. Thus, circular polarization results, as space quadrature already exists. If the adjustments are not correctly made, then elliptical polarization will result.

A test of the polarization ratios exhibited by an antenna built according to this invention along different angles in the previously defined horizontal plane, show an excellent uniformity of circular polarization. Tests of signal strength from the antenna in a plane vertical to its axis show that stron signals are confined to within 15 to 20 from the horizontal or azimuthal plane. Signal strength in the horizontal plane is uniform to a high degree for different angles of azimuth.

Tests show that the antenna exhibits broad band characteristics having band widths of 6% to 7% between half energy points and a nearly flat response extending over more than half of the band width.

The broad banding is characteristic of a thickening of the radiating dipoles of the dipole units and is also a result of the scalloping of the scalloped cylindrical elements.

Of course, any number of dipoles other than three could be arranged circumferentially as described, and a like number of scallops cut from the cylindrical elements. More than one pair of scalloped elements could be employed axially spaced along the transmission line.

It will be apparent to those skilled in the art that many variations of the invention may be made, and therefore it is not desired to restrict the scope of the claims to the precise embodiment here disclosed.

What is claimed is:

1. A component of an antenna adapted to be electrically coupled to an enclosed transmission line, comprising two cylindrical metallic shells, each having a plurality of substantially symmetrical scallops formed of arcuate recesses equally spaced around the axis of the shell along one edge thereof, and each having a like number of substantially similar scallops along the other edge of the shell in axial alignment with the scallops along said one edge, a supporting metallic element in electrical contact with each protruding portion of the scallops of said one edge of each shell, said metallic elements supporting said shells in axial alignment with said protruding portions of said one edge of one of said shells near to and in axial alignment with said one edge of the other of said shells, said supporting elements of said one shell being in electrical contact with the outer surface of said transmission line, and a plurality of probes each being in electrical contact with said other shell in the neighborhood where one of said protruding portions is in electrical contact with said supporting element, said probes extending inwardly and being adapted to receive energy from said transmission line through suitably aligned apertures therein, whereby said shells are electrically coupled to said transmission line.

2. The combination of claim 1, further com prising a plurality of dipoles equal in number to the number of scallops along one of said edges, supporting means for said dipoles, said dipoles being shaped and supported to extend circumferentially in axial alignment with said shells, each dipole extending substantially between the arcuately shaped recess of said one edge of one shell and the arcuately shaped recess of said one edge of the other shell, and means for electrically coupling said dipoles to said transmission line.

3. An antenna component comprising a pair of aligned cylindrical metallic shells each having a plurality of symmetrical scallops formed of arcuate recesses equally spaced around the axis of each said shell along one edge thereof, and. a like number of similar scallops along the other edge of each said shell in axial alignment with the scallops alon said one edge, the scallops in each edge of each said shell being aligned with those in the other edges of said shells, each of said shells being substantially an odd number of quarter wave lengths long at the operating frequency and said recesses having an axial dimension of an odd number of quarter wave lengths.

4. An antenna for producing circularly polarized Waves comprising a pair of aligned cylindrical metallic shells having a plurality of symmetrical scallops formed of recesses equally spaced around the axis of said shells along both edges of both said shells, said scallops being axially aligned, and means arranged between said shells for producing radiation polarized in the plane transverse to the axis of said cylinder, said radiation producing means having an omnidirectional radiation pattern in said transverse plane.

5. An antenna for producing circularly polarized Waves comprising a first plurality of dipoles arranged parallel to the axis of a cylinder on the surface of said cylinder and a second plurality of dipoles arranged in a plane perpendicular to the axis of said cylinder and between the poles of said first-mentioned dipoles, said second-mentioned dipoles being arranged with their centers on a circle concentric with said cylinder and being perpendicular to the radii of said circle.

6. An antenna fOr producing circularly polarized waves comprising a first plurality of dipoles arranged on the surface of a'cylinder parallel to and equally spaced around the axis of said cylinder, the centers of said first-mentioned dipoles being in a plane perpendicular to the axis of said cylinder, and a second plurality of dipoles arranged in said plane and equally spaced between the centers of said first-mentioned dipoles, said second-mentioned dipoles being curved and being arranged in a circle concentric with said cylinder.

'7. An antenna for producing circularly polarized waves comprising a pair of aligned cylindrical metallic shells having a plurality of symmetrical scallops formed of recesses equally spaced around the axis of said shells along both edges of both said shells, said scallops being axially aligned, and a plurality of dipoles arranged in a plane perpendicular to the axis of and between said cylindrical shells, said dipoles being curved and being arranged in a circle concentric with the axis of said shells, the center of each said dipole being arranged symmetrically with respect to a pair of aligned scallops.

8. An antenna for producing circularly polarized waves comprising a pair of aligned cylindrical metallic shells having a plurality of symmetrical scallops formed of recesses equally spaced around the axis of said shells along both edges of both said shells and three sets of dipoles each arranged in a plane perpendicular to the axis of said cylinder, one of said sets of dipoles being arranged between said shells and the other two of said sets of dipoles being arranged adjacent to one of the ends of said shells, the dipoles in each of said sets being curved and being arranged to form a circle concentric with said cylinder.

9. An antenna according to claim 8 further comprising a coaxial transmission line arranged concentrically inside said cylindrical shells, means coupling said transmission line to said dipoles for energization of said dipoles, and means coupling said transmission line to the portion between the scallops of one of said shells at the end adjacent the other of said shells for energization of said shells.

HENRY J. RIBLET. MAC E. VAN VALKENBURG.

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

UNITED STATES PATENTS Number Name Date 1,909,615 Gothe May 6, 1933 3 Au ug. 7 1 34;

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