US2688081A - Antenna system - Google Patents

Description

Aug. 31, 1954 E A, LAPQRT 2,688,081

ANTENNA SYSTEM Filed Nov. 26, 1951 2 Sheets-Sheet l @Q Ar F591/ Aug. 31, 1954 E. A. LAPQRT ANTENNA SYSTEM Filed Nov. 26, 1951 2 Sheets-Sheet 2 @A ma Patented ug. 31, 1954 eric@ ANTENNA SYSTEM Edmund A. Laporta, Glen Ridge, N. J., assignor to Radio Corporation of America, a corporation of Delaware Application November 26, 1951, Serial N o. 258,249

9 Claims.

My present invention relates to an antenna system for radiating a uniform field in all directions toward the horizon and With equal components of Vertical and horizontal polarization.

The use of very high frequency energy for radio communication is desirable because of the great distances covered by comparatively small amounts of energy. However, the use of short Waves for communication is handicapped by phase distortion and echo effects produced by the signal being reiiected from varied reflecting surfaces such as buildings and other structures. Fur.- thermore, in various localities, the distortion is more pronounced for a Wave which is polarized in a vertical direction than for one which is polarized in a horizontal direction. In air to ground communication linearly polarized waves are received differently with different attitudes of the aircraft. These difficulties may be mini-l mized by transmitting signals which are polarized in both horizontal and vertical planes instead of in a single plane only.

An object of my invention is to provide an antenna system which will radiate vertically and horizontally polarized energy at the same time, that is, circularly polarized waves.

Another aim of my invention is to provide an antenna which will radiate both elds uniformly in all directions toward the horizon.

Another purpose of my invention is to provide a novel form of antenna for communication with aircraft.

The above and other objects, aims, and purposes are attained by providing an antenna system having both Vertical and horizontal radiating arrays fed so as to radiate a field which rotates and which has a uniform value in all horizontal directions. The horizontal array consists of a number of turnstiles made of four radiators, each .one-quarter wavelength long. The radiators are supported at one end by a vertical supporting mast, and energizing currents are fed to the radiators at a point near the supported ends. Two of the quarter wavelength antennas therefore comprise a center fed dipole. While one of the dipoles is fed in phase quadrature with respect to its companion dipole, the corresponding elements in each turnstile are cophased. rlhe vertical array consists of a plurality of center fed dipoles placed between the open ends of the corresponding horizontal elements. Adjacent vertical elements are fed in phase quadrature with respect to each other while opposite vertical elements are fed in an anti-phase relationship.

Myfinvention will be better understood from the following description with continual reference to the accompanying drawings. Similar reference numerals refer to similar parts of the drawings in which:

Figure l is a plan view of an antenna constructed in accordance with my invention;

Figure 2 illustrates the side View of one plane of the antenna assembly; and

Figure 3 illustrates diagrammatically a desired form o1"- external feeder system for my invention.

Referring new to Figures l and 2, there is shown a vertical tubular support d to which quarter wavelength horizontal elements 6 and 8 are atetached by means of tie rod I0 and insulators l2. Tie rod i0 passes from the extremity of one radiator 6 to that of the opposite radiator 8 and is insulated therefrom throughout its length. Plugs 2 at the ends of the radiators provide an electrical connection between the tie rod and the radiators, the tie rod forming a concentric transmission line with the inside of the tubular radiators of very nearly one-quarter wavelength. Due to the short circuit at the ends of the radiaf tors, a very high impedance is reected at the central feed points I and J and the effect of the continuous metallic tie rod is eliminated from the feeder circuit. The plugs are preferably threaded to enable the tie rod to be tightened. The result is that the radiators are self Supporting and are rigidly assembled to the vertical supe porting mast. in a similar manner the quarter Wave horizontal elements lil and i6 are mounted on mast il at a point about one-half Wavelength below the upper horizontal elements.

The vertical radiators I8 and 2t comprise a center-fed dipole which is connected to the supfv porting mast by elements 22 and 2d. Elements 22 and 2d are electrically bonded to mast i at a point about one-quarter wavelength below the upper horizontal radiators. Due to the short circuit at their inner ends, these elements form a balanced quarter-wave insulating transformer which supports and feeds the vertical radiators. Similarly, vertical radiators 25 and 28 comprise a second center fed dipole, supported by elements 30 and 32. Feed lines 3d and 36 interconnect elements 6 and 3 and elements 8 and 22 respectively, while feed lines S8 and llt interconnect elements 32 and IS and elements 2G. and lffl respectively.- This is but one way of interconnecting the horizontal and vertical array, A second method will be disclosed in the following description of the external feeder system which supplies excitation currents to the antenna at points A and B.

What has been described in the above paragraph is but one plane of my antenna system. This plane may lie, for instance, in an east-west direction. A second similar set, or group, of vertical and horizontal elements mounted on mast 4 are arranged in a plane perpendicular to the above described arrangement, or in a north-south direction. This is more clearly shown in Figure l. The complete antenna consists of two pairs of coplanar quarterwave radiators arranged in the manner of cruciforms, one of said pairs being perpendicular to the other, and the said arrays disposed one above the other in parallel planes, and two vertical arrays, each array consisting of a part of coplanar vertical dipoles arranged between the ends of the horizontal turnstiles, one pair of vertical dipoles lying in a plane perpendicular to the other pair of vertical dipoles, with means for interconnecting selected pairs of horizontal and vertical radiators.

One form of feeder system, and a method of developing the balanced 2-phase excitation required for field rotation based on the use of concentric cables is shown in Figure 3. The feeder system comprises two pairs of feed lines and three transmission line loops 44, 4E, and 48. The feed lines to the N-S radiators are fed by transmission line loop 44 of any convenient length. To a selected point on the loop 44 is connected one end of loop 48. The point of connection on loop 44 is so chosen that the differential lengths of the conductors of loop 44 from the selected point to the feed lines of the N-S radiators is a half wavelength. Thus the excitation currents at points A and -A in Figure 3, which are fed to the corresponding points A and -A on elements 3E! and 32 in Figure 2, are in phase opposition. This is also true of the currents at points B and -B which are fed to the elements 22 and 24 in Figure 2. The feed lines to the E-W radiators are fed by loop 46. The other end of loop 48 is connected to a selected point on loop 46 such that the differential distance from the selected point to the E-W feed lines is one-half wavelength. This differential distance results in antiphase currents at points A 'and -A and at B and -B. In order to provide a rotating eld it is necessary that the currents fed to the E-W radiators be in phase quadrature with the currents fed to the N-S radiators. This phase quadrature relationship, or 90 degree phase dierence results in the currents in the E-W radiators building up in amplitude while the currents in the N-W radiators are decreasing in amplitude. The net result is a rotating eld. To bring about the required phase quadrature relationship, loops 44 and 4B are fed by loop 48 which in turn is fed by any suitable generator, not shown, through a transmission line 5U. Transmission line 50 is connected to loop 48 at a point so selected that the differential distance from the selected point to loops 44 and 46 is one-quarter wavelength. This differential distance supplies the required 90 degree phase shift. Suitable matching stubs, shown in Figure 3, are provided to take care of any impedance unbalance in the feeder circuit.

Referring again to Figure 2, it is to be noted that the upper interconnecting lines or feeders 34 and 3S run directly to the left and right horizontal radiators, respectively. In the case of the lower horizontal radiators, the feeders 38 and 48 are transposed in order to cophase the currents in the lower horizontal radiators with those in the upper radiators. The current directions at a particular instant are noted by arrows. One fea- 4 ture of my invention is evidenced by this arrangment which makes the electrical distance from point E to the end of its vertical radiator the same as from point E to the end of its attached horizontal radiator, and the power division between the two systems can be adjusted by the location of the tapping points G-G and H-H. Thus both horizontal and vertical radiators are center fed. If in practice the power division requires equalizing due to slight imperfections in symmetry, a further adjustment can be made by moving the tapping point on the horizontal radiators from the exact center of the radiators outwardly to the points I and J, the location of which would be determined experimentally. Fields radiated from all the feeders are balanced and will cancel in outer space.

A second and preferred method of producing the required transformation is to produce half of the transformation in the upper part of the antenna array and half of the transformation in the lower part of the array. To do this, the feeders shown in Figure 2 interconnect the vertical radiators to which they are attached and the horizontal radiators which lie in the plane normal to the plane of Figure 2. By this method an electrical and mechanical symmetry is retained without compromise. This method, in addition to assuring symmetry, eliminates the end-couplings between the capacitances of the ends of the horizontal and adjacent radiators. This results from the fact that the potential on a vertical radiator is maximum at an instant when the potential on the adjacent horizontal radiator passes through zero.

There have been shown what are now thought to be the preferred constructions of this invention. It will be clear to those skilled in the art that changes may be made without departing from the spirit of my invention.

Having thus described my invention, what I claim as new and desire to secure by Letters Patent is:

1. An antenna system comprising a plurality of horizontal turnstile arrays mounted at their centers on a supporting mast, arrays of center-fed vertical dipoles supported at their centers on said mast, said dipoles having their ends arranged adjacent to but spaced from the ends of said turnstile arrays, feed lines interconnecting selected elements of said horizontal and vertical arrays, and means for supplying balanced two phased excitation currents to said feed lines.

2. An antenna system comprising a pair of horizontal turnstile arrays mounted at their centers on a supporting mast, a plurality of balanced quarter wave insulating transformers conductively connected to said mast at a point intermediate said turnstile arrays, a plurality of center-fed vertical dipoles supported on said mast by said transformers, said dipoles having their ends placed between but spaced from the corresponding ends of said horizontal arrays, feed lines interconnecting elements of said horizontal arrays and said transformers, and means for supplying balanced two phased excitation currents to said transformers.

3. An antenna system comprising two horizontal arrays, each array including a plurality of quarter wave horizontal radiators arranged in a cruciform shape, said horizontal radiators being mounted at their centers on a vertical mast and spaced from each other a distance of one half wavelength of the operating frequency of the said system, a plurality of rbalanced quarter Wave insulating transformers conductively connected to said mast at a point intermediate said horizontal arrays, a plurality of center-fed Vertical dipoles supported on said mast by said transformers, said dipoles having their ends placed between but spaced from the ends of corresponding elements of said horizontal arrays, a pair of feed lines extending from each of said transformers, said feed lines interconnecting selected elements of said horizontal arrays with said transformers, and means for supplying balanced two phase currents to said transformers.

4. An antenna system in accordance with claim 3 characterized in that means associated with said system supplying balanced two phase currents thereto feed opposite vertical dipoles in an antiphased relationship and feed adjacent verti- Acal dipoles in a phase quadrature relationship whereby a vertically polarized rotating field is radiated.

5. An antenna system in accordance with claim 3 characterized in that means associated with said system supplying balanced two phased currents thereto feed corresponding quarter wave horizontal radiators in each array in a cophased relationship and feed adjacent horizontal radiators of each array in a phase quadrature relationship whereby a horizontally polarized rotating iield is radiated.

6. An antenna system comprising a vertical supporting mast, a rst pair of crossed horizontal dipole radiators mounted at their centers on said mast, a second pair of horizontal dipole radiators mounted at their centers at a point on said mast spaced a distance of one half wavelength cf the working frequency of said system from said first pair of radiators, four quarterwave balanced transformers conductively connected to said mast at a point intermediate said pairs of horizontal dipoles, four center-fed vertical dipoles supported and fed by said transformers, said vertical dipoles having their ends positioned between but spaced from corresponding ends of said horizontal radiators, means associated with said transformers feeding balanced two phase excitation currents to said transformers whereby currents in opposite vertical radiators are in an antphase relationship while currents in adjacent vertical radiators are in a phase quadrature relationship so that a rotating vertically polarized eld is radiated, a pair of feed lines extending from each of said transformers, one of said feed lines being connected to an upper horizontal radiator which is coplanar with a corresponding transformer and the other of said feed lines being connected to a lower horizontal radiator which is coplanar with said corresponding transformer whereby the current in corresponding horizontal radiators of said crossed pairs are cophased while currents in adjacent radiators of each crossed pair are in a phase quadrature relationship so that. a rotating horizontally polarized eld is radiated, said vertically polarized field and said horizontally polarized field being of equal intensity and producing a circularly polarized radiated field.

1. 1n an antenna system, the combination of a rst group of radiators comprising a first horizontal dipole mounted at its center on a Vertical supporting mast, a second horizontal dipole radiator mounted at its center on said mast and spaced from said first horizontal dipole a distance of one-half wavelength at the operating frequency, a pair of center-fed Vertical dipoles spaced one half Wavelength apart and having their ends respectively positioned:` betweeni-but'f spaced from the ends of said firstand second horizontal radiators whereby said horizontal disupporting and feeding excitation currents to said vertical dipoles, means conductively con-` necting said transformers to said supporting mast at points intermediate said horizontal dipoles,

means associated with said system feeding excieV tation currents to said transformers wherebythe currents in one of said vertical dipoles is in an antiphase relationship with the currentsin the other of said vertical dipoles, a. second group of radiators comprising a first horizontal dipole mounted at its center on said supporting mastr so as to be coplanarv with but perpendicular tov said first horizontal dipole of said rst group, a second horizontal dipole mounted at its center on said supporting mast so as to be coplanar with but perpendicular to said second horizontal dipole of said first group, a pair of center-fed vertical dipoles spaced one half wavelength apart and positioned between said horizontal radiators in a plane perpendicular to the Vertical dipoles of said first group, a pair of quarterwave insulating transformers supporting said vertical dipoles of `said second group, means conductively connecting said transformers to said mast whereby said transformers are coplanar with but perpendicular to the transformers of said rst group, means associated with said system feeding excitation currents to said transformers of said second group whereby the currents in one of said Vertical dipoles of said second group are in an antiphase relationship with the currents in the other of said vertical dipoles of said second group and whereby the currents in said vertical dipoles of said second group are in phase quadrature with the currents in said vertical dipoles of said rst group, feed lines interconnecting said transformer-s of said first group with said horizontal dipoles of said second group, and feed lines interconnecting said transformers of said second group with said horizontal dipoles of said first i group whereby the currents in the horizontal elements of each group are cophased while the currents in the horizontal elements of said rst group are in a phase quadrature relationship with the horizontal elements of said second group.

8. An antenna system including a vertical conductive mast, a pair of dipoles supported at one end on said mast in nonconductive relationship thereto and extending outwardly therefrom for a distance of substantially a quarter of the operating wavelength of said system, a second pair of dipoles supported on said mast in nonconductive relationship thereto and extending outwardly therefrom for a distance substantially a quarter of said operating wavelength, said first pair of dipoles being above said second pair a distance approximately equal to a half of said operating wavelength, four center-fed vertical dipoles arranged so that the ends of each Vertical dipole are adjacent to but spaced from corresponding ends of said rst pair and said second pair of horizontal dipoles, pairs of elements conductively connected to said mast whereby said pairs of elements form quarter wave transformers to feed and support said vertical dipoles, feed lines interconnecting each of said transformers with a corresponding dipole of said horizontal pairs and means associated with said system for feeding balanced two phased excitationvcurrents to said transformers. l

9. An antenna system comprising in combination a vertical conductive mast, a first pair of crossed dipole radiators supported at their midpoints on said mast and insulated therefrom, a second pair of crossed dipole radiators nonconductively supported on said mast at a distance approximately equal to a half of the operating wavelength of said systems, tie rods passing through each of said dipoles and insulated therefrom throughout their lengths, means electrical- 1y connecting the ends of said tie rods to the ends of said dipoles whereby said dipoles are rigidly supported to said mast, means associated with said system feeding said first and said second pair of crossed dipoles with radio frequency energy in a phase quadrature relationship where- References Cited in the le of this patent UNITED STATES PATENTS Number Name Date 2,465,379 Kondoian Mar. 29, 1949 2,516,706 Laport July 25, 1950 2,539,433 Kandoian Jan. 30, 1951

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