US2303611A - Television broadcast antenna - Google Patents

Description

Dec. 1, 1942. P. s. CARTER 2,303,611

TELEVISION BROADCAST A EN v Filed Aug.- 23, 1941 3 Sheets-Sheet 1 pkigamgfmgni ATTORNEY Dec. 1,1942. P. s. CARTER 'TELEVISION BROADCAST ANTENNA 3 Sheets-Sheet 2 VENTOR I [alga .W

Filed Aug. 23, 1941' m 6m m Dec. 1, 1942. s, CARTER 2,303,611

TELEVISION, BROADCAST ANTENNA Filed Aug. 25, 1941 3 Sheets-Sheet 3 INVENTOR ATTORNEY Patented Dec. 1, 1942 TELEVISION BROADCAST ANTENNA Philip S. Carter, Rocky Point, N. Y., assignor to Radio- Corporation of America, a corporation of Delaware Application August 23, 1941, Serial No. 408,012

12' Claims.

The present invention relates to antennas and, more particularly to wide band broadcast antennas for radiating horizontally polarized waves.

An object of the present invention is the provision of an antenna for the radiation of horizontally polarized waves without discrimination over a wide frequency band.

A further object of the present invention is the provision of a radiator, as aforesaid, which has low directivity in the horizontal plane.

Still another object is the provision of an antenna for horizontally polarized radiation which is so arranged around a conductive vertical supporting structure that induced currents around said structure aid in producing a uniform radiation pattern.

A further object of the invention is the provision of an antenna according to the foregoing objects which is suitable for operation over a wide frequency band.

Still a further object is the provision of an antenna according to the foregoing objects which may be used as an element of a vertical antenna array to improve directivity in the vertical plane.

The foregoing objects, and others which may appear from the following detailed description, are attained in accordance with the present invention by the provision of four horizontal dipole radiators equally spaced about a conductive cylinder or supporting column having a periphery of the order of four wavelengths, the opposite ones of said dipoles being energized in phase and adjacent ones in phase quadrature.

The present invention will be more fully understood by reference to the following detailed description which is accompanied by drawings in which Figures 1 and 2 illustrate the radiation pattern in the horizontal plane by an antenna array comprising four dipole radiators arranged around a conductive mast having a periphery of about four wavelengths and energized in diiferent phase relationships. Figure 3 illustrates the horizontal radiation pattern of an antenna array arranged as in Figures 1 and 2 but in which the antenna elements are energized in accordance with the principles of the present invention. Figure 4 is a plan view of an antenna constructed according to the principles of the present invention in which the vertical planes for the radiation patterns in Figures 5, 6 and 7 are indicated. Figures 5, 6 and 7 show the radiation patterns in several vertical planes passing through the center of the antenna shown in Figure 4. Figure 8 layers of radiating units fed in phase with each other whereby high angle radiation is reduced.

Referring, now, to Figure 1 there is shovm a conducting spire, cylinders or supporting column 5!! having a periphery length of the order of four wavelengths. Arranged around the conducting spire l B in a single horizontal plane are four horizontal dipoles ii, l2, l3 and I4 fed cophasally, The arrows in Figure 1 represent the instantaneous directions of the currents in the dipoles and all point in the same direction of rotation, i. e. counter-clockwise. These arrows define the term cophasally for the purpose of the present consideration. Throughout the present specification and in the claims forming a part thereof, by the term in phase is meant that condition wherein the instantaneous currents in the horizontal dipoles surrounding a cylinder are in the same direction of rotation, for example, clockwise. When the currents in any. two dipoles are in phase opposition arrows representing their instantaneous directions will point in opposite directions of rotation, i. e., one arrow clockwise and the second counter-clockwise. This must be distinguished from the practice in the prior art, when considering two parallel dipoles by themselves, where rotation is not involved, wherein dipoles carrying current in opposite instantaneous directions are considered as being fed in phase opposition. This, however, is in the same direction of rotation around the center point and indicates cophasal feed in accordance with the definitions here intended. This viewpoint has been chosen in connection with circular arrays in order to avoid serious confusion. The energy source and the transmission lines are not shown but may follow practice at present known in the art.

Curve IS in Figure 1 illustrates the radiation pattern obtained by dipoles ll, [2, l3 and M in the absence of the conducting cylinder H1. With the conducting cylinder H] in place a radiation pattern as indicated by the solid line I6 is obtained. It will be noted that whether cylinder I0 is present or absent there is a very large variation in the horizontal plane with a change in direction angle. Since the object in the broadcast antenna system is usually to produce equal radiation in all horizontal directions it will be seen that the antenna array shown in Figure l is not particularly suitable for broadcast radiation. Although the addition of four more dipoles to the array of four, making an eight unit array, would greatly diminish the variation in field strength with direction, it is often impossible to use more than shows in elevation a vertical array using two four units. This is particularly true in the case of antennas arranged around the periphery of a tower which has been constructed previously with other objects in mind.

The pattern shown in Figure 1 is strictly true only for an antenna array about a conducting cylinder but there is little difference in the result if a hexagon, a square or some other shape of about the same periphery is substituted for the cylinder.

Figure 2 shows in dotted line 25 the horizontal pattern for the same array as in Figure 1 when the dipole units are fed in successive quarter phase relation proceeding around the array and solid line 26 indicates the pattern when the conducting cylinder !8 is inserted. The arrow heads on dipoles I! and I3 indicate that at a given instant these two dipoles are carrying maximum high frequency current with respect to dipoles l2 and M, which are at that instant carrying zero current, as indicated by the circles at their midpoints. It will be noted that the directivity patterns in Figure 2 are very little, if any, improvement over the pattern shown in Figure 1. However, when, in accordance with the principles of the present invention the antenna is so energized that diametrically opposite dipoles are fed cophasally and the two pairs in quarter phase relation to each other, a directivity pattern such as shown in Figure 3 is obtained. The dotted line 35 indicates the directivity pattern in the absence of the conducting cylinder in and it will be noted this pattern has a considerable variation in the horizontal plane. However, in the presence of the conducting cylinder the directivity pattern indicated by line 36 is obtained. The scale for the dotted line curve 35 is twice that of the solid line 36 as indicated by the double reference scale for the field strength. It will be noted that the sharp dips in the radiation pattern have been eliminated and that although the pattern does depart somewhat from a perfect circle the radiation is reasonably constant in all horizontal directions.

Figures 5, 6 and 7 show the vertical patterns in 3 different planes as indicated by lines 5, 5, 6, 6 and I in Figure 4 for a single layer antenna constructed in accordance with the invention. In Figure 5 the dotted line 45 indicates the vertical directivity pattern in the absence of the conducting cylinder l0 and the solid line 45 with degrees to the vertical is quite high. The high angle radiation may be reduced in accordance with another aspect of the present invention shown in Figure 8 and which will be described more fully hereafter with reference to that figure.

Figure 6 illustrates the vertical directivity pattern in a plane through a pair of dipoles in quadrature phase relationship with respect to the dipoles considered in Figure 5, that is, through planes 6, 6 of Figure 4.

Figure 7 indicates the pattern in a vertical plane at an angle half-way between the first two, that is, along line I, I of Figure 4, and is believed to be self-explanatory.

In Figure 8 I have indicated how the comparatively large radiation at angles in the vicinity of 30 degrees to the vertical may be reduced by using two layers of units fed in phase with each other and separated by a spacing of approximately .58 wavelength. At this spacing the radiation in the direction of 30 degrees to the vertical is zero and at all angles in the vicinity of this angle it will be quite small.

The mathematical theory of the operation of the antenna, according to the present invention, is quite involved and will not be given here since it is believed that the invention will be clearly understood from the analysis and diagrams given. However, it may be said that in determining the field distribution the primary field from the dipole or dipoles must be first considered as broken up into an infinite number of cylindrical waves. The field of the primary waves causes peripheral currents to flow in the conducting cylinder l0. These currents in the cylinder set up a system of secondary waves whose amplitudes are just sumcient to result in zero tangential component of electric forces along the surface of the cylinder.

While I have particularly shown and described several embodiments of my invention, it is to be clearly understood that my invention is not limited thereto but that modifications may be made within the scope of the invention.

I claim:

1. A high frequency radiator system including a plurality of pairs of horizontal dipole radiators arranged in diametrally opposed pairs around a conductive supporting column, the dipoles of each pair being energized by high frequency energy in an in-phase relationship and adjacent dipoles being energized in a phase quadrature relationship.

2. A high frequency radiator system including a plurality of pairs of horizontal dipole radiators arranged in diametrally opposed pairs around a conductive supporting column having a circumference of the order of four wavelengths at the operating frequency, the dipoles of each pair being energized by high frequency in an in-phase relationship and adjacent dipoles being energized in a phase quadrature relationship.

3. A high frequency radiator system including four horizontal dipole radiators arranged in diametrally opposed pairs around a conductive supporting column, the dipoles of each pair being energized by high frequency energy in an inphase relationship and adjacent dipoles being energized in a phase quadrature relationship. 4. A high frequency radiator system including four horizontal dipole radiators arranged in diametrally opposed pairs around a conductive supporting column having a circumference of the order of four wavelengths at the operating frequency, the dipoles of each pair being energized by high frequency in an in-phase relationship and adjacent dipoles being energized in a phase quadrature relationship.

5. An antenna comprising a plurality of radiator systems according to claim 1, said radiator systems being arranged along a common vertical axis, the spacing between adjacent systems being such that the radiation from said antenna at angles in the vicinity of 30 degrees to the vertical is a minimum.

6. An antenna comprising a plurality of radiator systems, according to claim 2, said radiator systems being arranged along a common vertical axis, the spacing between adjacent systems being such that the radiation from said antenna at angles in the vicinity of 30 degrees to the vertical 1s a minimum.

'7. An antenna comprising a plurality of radiator systems, according to claim 3, said radiator systems being arranged along a common vertical axis, the spacing between adjacent systems being such that the radiation from said antenna at angles in the vicinity of 30 degrees to the vertical is a minimum.

8. An antenna comprising a plurality of radiator systems, according to claim 4, said radiator systems being arranged along a common vertical axis, the spacing between adjacent systems being such that the radiation from said antenna at angles in the vicinity of 30 degrees to the vertical is a minimum.

9. An antenna comprising a plurality of radiator systems, according to claim 1, said radiator systems being arranged along a common vertical axis, the spacing between adjacent systems being of the order of .58 of the operating Wavelength.

10. An antenna comprising a plurality of radiator systems, according to claim 2, said radiator systems being arranged along a common vertical axis, the spacing between adjacent systems being of the order of .580f the operating wavelength.

11. An antenna comprising a plurality of radiator systems, according to claim 3, said radiator systems being arranged along a common vertical axis, the spacing between adjacent systems being of the order of .58 of the operating wavelength.

12. An antenna comprising a plurality of radiator systems, according to claim 4, said radiator systems being arranged along a common vertical axis, the spacing between adjacent systems being of the order of .58 of the operating wavelength.

PHILIP S. CARTER.

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