US2778015A - Antenna - Google Patents

Description

LAN J. CHU

' Jan. 15, 1957 ANTENNA 3 Sheets-Sheet 1 Filed May 22, 1953 I INVENTOR. ZAIV .1 0/0 By M ML m ATTORNL'YS' LAN J. CHU

Jan. 15, 1957 ANTENNA Filed May 22, 1953 3 Sheets-Sheet 2 INVENTOR.

' LA/V J. G'HU ATTORZVFYS Jan. 15,1957 LAN J. CIV-IU ANTENNA s Sheets- Sheet 3 Filed May 2 19 N VEN TOR. LAN J. GHU

ATTOR/WEYS' United States Patent ANTENNA Lan J. Chu, Lexington, Mass., assignor to The Gabriel Company, Cleveland, Ohio, a corporation of Ohio Application May 22, 1953, Serial No. 356,808

24 Claims. (Cl. 343-770) The present invention relates to antennas and, more specifically to antenna structures particularly adapted for use in the ultra-high-frequency range.

In some ultra-high-frequency and very-high-frequency antenna transmitting systems, such as, for example; those employed for television transmissions, an omni-directional horizontal radiation pattern and a high-gain vertical radiation pattern are required to provide uniform broadcasting in all directions of azimuth and over a desired field of coverage. It is often the requirement, moreover, that the polarization of the radiated energy be horizontal. Many antennas have been designed for producing such patterns. Some of these antennas are in the form of helical arrays; others, in the form of circular loo'ps; still others employ antennas of various other configurations such as bat wings and the like; and antennas have also been proposed embodying a plurality of a'ri'gularly disposed wave guides or horns, including bi-conical horns. Antennas of this character, however, are quite costly to manufacture, requiring specially designed components. Present-day commercial antennas of this type, moreover, utilize large numbers of cumbersome and expensive insulators which are subject to periodic deterioration under the influence of atmospheric conditions, and they require, also, phaseand impedance-correcting networks and other devices associated with the feed transmission lines that add cost and complexity to the equipment. Not only is it desirable to reduce the cost of manufacture of such antennas, therefore, but it is quite advantageous to eliminate the necessity for the use of insulators and such phaseand impedance-correcting devices.

A very satisfactory antenna that obviates these difficulties is described in a copending application of Howard J. Rowland, Serial No. 251,516, filed October 16, 1951. There are some instances, however, where, in addition to overcoming these difficulties, either an extremely tall antenna structure is required, or a very high degree of circularity in the horizontal radiation pattern is essential, or both.

An object of the present invention is to providea new and improved antenna of this character that is adapted to produce a very high degree of circularity in a horizontally polarized omni-directional radiation pattern in the horizontal plane, and that is constructionally adapted to support itself even when of very tall dimensions.

A further object of the invention is to provide such an antenna that is particularly adapted for use in the ultrahigh-frequency range.

Other and further objects will be explained hereinafter and will be more particularly pointed out in the appended claims.

In summary, the invention relates to an antenna system for transmitting radio-frequency energy of apredet'ermined wavelength comprising a plurality of, preferably five, substantially parallel transmission-line conductors four of which preferably comprise tubular columns of substantially circular cross section symmetrically disposed With respect to the fifth transmission-line conductor-with Patented Jan. 15, 1957 substantially equal spacing between the adjacent tubular column transmission-line conductors. Means is provided, preferably in the form of a coaxial line, for energizing the fifth transmission-line conductor from the inner coaxial-line conductor and the tubular column transmissionline conductors in anti-phase therewith from the outer coaxial-line conductor. Several branch-conductor groups each comprising four appropriately dimensioned branch conductors are disposed in substantially parallel planes normal to the transmission-line conductors and spaced therealong at intervals corresponding substantially to the said predetermined wavelength. The four branch conductors of each group are connected at one of their ends to the fifth transmission-line conductor and at their other ends to substantially co-planar points disposed in the outer surfaces of the respective four tubular column transmission-line conductors to radiate horizontally polarized waves-omnidirectionally with a high degree of circularity in the horizontal pattern. Preferred constructional details and dimensions will be hereinafter pointed out.

The invention will now be described in connection with the accompanying drawings Fig. l of which is a perspective view of a preferred form of the invention, partly cut away to illustrate structural details;

Figs. 2, 3 and 4 are sectional views, upon enlarged scales, taken upon the respective lines 22, 3-3 and 4-4 of Fig. 1, looking in the direction of the arrows;

Fig. 5 is a view similar to Fig. 1, though of enlarged scale, of a modification;

I Fig. 6-is a sectional view, upon still a greater scale, taken upon the line 6-6 of Fig. 5, looking in the direction of the arrows;

Fig. 7 is a perspective of a further modification; and

Figs. 8, 9 and 10 are sectional views, upon slightly different scales, taken upon the respective lines 8-8, 9"9 and 1010 of Fig. 7, looking in the direction of thearrows.

Among the commercially available self-supporting st-i'uc'tures mass-produced for other fields of endeavor, such as building construction, are tubular columns of circular cross section, as of steel. In accordance with the present invention, four such similar columns are utilized asan antenna structure. In Figs. 1, 2, 3 and 4, vertically arranged spaced tubular columns are shown at 2, 4, 6 and 8 symmetrically disposed with respect to a preferably substantially'parallel centrally disposed transmission-line conductor 10 and with substantially equal spacing S between the adjacent tubular columns. The centers of the columns thus form a square. The tubular columns are connected together at the bottom of the antenna by an end plate 7, as by welding or with the aid of bolts. The tops of the columns 2', 4, 6 and 8 may be electrically connected by conductors 40 and spacer plates 21 that aid in the mechanical support. A platform 57 may be welded or otherwise secured to the top of the antenna for supporting abeacon light, the power cables 1 of which may be carried upward through one of the tubular columns, shown as the column 4; The bottom end plate 7 is provided with an insulation-filled aperture 5 for receiving the centrally disposed transmission-line conductor 10 and its terminal connector 10, and may be secured to the top of a conventional antenna tower 9, as by welding or any other desired means. As will be hereinafter appear, the structural properties of the tubular columns and the associated energizing conductors are such that no bracing or other auxiliary supporting devices are required even if very tall structures are utilized. v

The tubular columns 2, 4, 6 and 8 are all connected by the plate 7 to the outer conductor 12 of a coaxialfee'd transmission line of less diameter and hence of less circumferential transverse surface dimension to serve as equipot'entialtransmission-line conductors energized there-- by. The transmission-line conductor is energized in anti-phase therewith through itsconnection by the terminal connector 10' with the inner conductor 14 of the coaxial-feed transmission line that, in turn, connects with, for example, a television transmitter, such as the transmitter 16 of Fig. 7, located, perhaps, at the base of the tower 9. The antenna structure may be grounded through the tower 9.

Along the transmission- line conductors 2, 4, 6, 8 and 10, several branch-conductor groups are provided each comprising four branch conductors 18, 24, 32 and 34, disposed in substantially parallel planes preferably substantially normal to the transmission-line conductors and spaced therealong vertically at intervals corresponding substantially to the predetermined wavelength with which the antenna is to operate.

The branch conductors 18, 24, 32 and 34 are connected at one of their ends to the centrally disposed transmissionline conductor 10, as at 13, extend, in part, radially outward and then preferably extend at right angles as shown at 22. At their other ends, the branch conductors are connected to preferably co-planar points along the outside surfaces of the respective'tubular column transmission- line conductors 6, 8, 2 and 4 by the preferably horizontally disposed connecting portions 22, as at points 20. Each branch conductor, such as, for example, the branch conductor 18, becomes one element of a further three-element branch transmission line the other two elements of which comprise the side of the tubular column conductor to which it is connected, such as the right-hand side of the tubular column conductor 6, and the side of the adjacent tubular column conductor, such as the left-hand side of the tubular column conductor 4. Current then flows outward along the branch conductor 18 and back in the opposite direction along the right-hand side of the tubular column conductor 6, but in the same direction along the left-hand side of the tubular column conductor 4 as along the conductor 18. The appropriate impedance adjustment for this unbalanced. three-conductor feed may be effected by adjusting the position of the point 20 along the right-hand side of the tubular column conductor 6. For the purposes hereindescribed, it has been found advantageous to locate the point 20 right near the outer edge of the tubular column conductor, as shown. If desired, a stub, not shown, perhaps similar to that later discussedin connection with the embodiment of Fig. 5, may be used at the top of the array for assisting in matching the complete array. The location of the points 20 along one of the side edges of each tubular column may also be adjusted to effect desired phase relationships. The spacing S between the parallel sides of adjacent columns and the spacing from the inner conductor 10, as represented by the length of the upper conductors 40, Fig. 3, may also be varied to effect desired impedance and phase relationships without the necessity for utilizing special lines, networks or other devices.

With such an arrangement, moreover, the rectangular wave-transmission loops or frames formed by the outer rims or edges of the transmission lines 2, 4, 6, 8 and the spacers 21, are provided with long sides such as 4, 6, about a wavelength in length, shorter sides 21 less than a half-wavelength in length, and since only essentially the outer rims or edges are effective, an efiective depth or thickness of negligible dimensions. The feed system embodying the exciters, 18, 24, 32, 34, moreover, with the end portions 22 substantially in the plane of the loop or frame, as shown, may be oriented substantially parallel to the shorter sides, formed by the spacers 21 and thus insuring excitation by radio-frequency energy of polarization perpendicular to the plane of the longer sides 4, 6 of the frame.

While the length of the branch conductors 18, 24, 32 and 34 can be made small, consistent with preventing the short-circuiting of the energy that is passed upward along the five- conductor transmission lines 2, 4, 6, 8, 10,

and outward to the outer edges of the tubular column conductors 2, 4, 6 and 8, it can not be made too large without producing sharp lobes in the radiation pattern of the antenna that destroy the circularity of the desired omni-directional radiation pattern. The overall width or diameter of the antenna array on the other hand, must be large enough to support the necessary structure. If the degree of circularity or omnidirectionality of the horizontal field pattern produced by the antenna, defined in terms of the maximum-to-minimum field intensity ratio in the pattern, is to be very great, the length of the branch conductors 18, 24, 32 and 34 should be substantially equal to or less than about the half-wavelength of the radio energy. The spacing S between the parallel side surfaces of the adjacent beam conductors 2, 4, 6 and 8, furthermore, is preferably adjusted to a value considerably less than the length of the branch conductors in order to maintain the omni-directional radiation pattern characteristic. An antenna particularly suited for the ultrahigh frequency range of from about 500 to about 890 megacycles per second, for example, having branch conductors 18, 24, 32, 34 of length about four and one-half inches, columns of radius about four inches and a spacing S between the parallel sides of adjacent columns of about one inch, has been found to produce a remarkable degree of circularity in the omni-directional horizontal pattern. For antennas designed for operation with different predetermined wavelengths in the said 500 to 890 megacycle range, the length of the branch conductors may vary from about three and one-half to about six inches; the diameter of the tubular column conductors, from about three to about six inches; and the spacing S, from about one-half inch to about two inches.

It has been found that the circularity of the omnidirectional pattern is markedly improved over that ohtainable with other types of structural conductors since circular auxiliary current paths form transversely along the circular sides of the tubular column transmissionline conductors along their complete length. This construction also appears to minimize cross-polarization effects since any vertically polarized radiation components that may be set up are interrupted by the horizontal path for current provided by the circular contour around the outer surfaces of the tubular columns.

As an illustration of the unusual effectiveness of the tubular column outer surface circular contour, the beforedescribed antenna was operated at a frequency of about 800 megacycles with maximum variations of less than 0.5 decibel from the mean value in the horizontal pattern.

An array of this character, about ten to twenty wavelengths long, will produce sufficient directivity and gain in the vertical plane for the television purposes before mentioned. A twelve-wavelength array, for example, has been found to produce a half-power vertical principal lobe angle of about 4.2 degrees. A high gain of 11 decibels over a tuned dipole was achieved, with a power gain of 14 and a voltage standing-wave ratio of less than 1.1 to 1.

Not only does the use of the tubular columns and the associated transmission-line system completely obviate the necessity for bracing or other auxiliary supports, as before pointed out, even for great heights, but the necessity for insulators has also become obviated. Except for providing additional structural rigidity, moreover, the spacer elements 21, shown in Figs. 1 and 11, disposed at each wavelength interval along the array, need not be employed insofar as electrical performance is concerned. Bolts or other securing means, if any, may, indeed, be substituted therefor.

This type of antenna may, of course, be utilized'for otherpurposes than providing the best possible omnidirectional pattern, in which event symmetry may not be required and less than or more than four columns may be utilized, The branch conductors 18, 24, etc. may

then extendin other directions than-at right anglesto the of the conductor Though the antenna s cture ef the present invention has been discussed .in connection with its application to ultra-highfrequency transmissions, such as in the television field, furthermore, it. will be understood that the antenna may, if desired, be adapted for use, also, as areceiving structure in which event the before-mentioned transmitter will be replaced by a receiver. The antenna may, also,by appropriate scaling of its dimensions, be applied to frequencies in the very-high-frequency range as well as to frequencies above the ultra-high-frequency range. It is not essential,.moreover, though it is most convenient, to utilize the coaxial type of transmission-line feed, for other types of feed lines may be employed.

While the before-described arrangement of the preferred embodiment of Fig. 1 is particularly adapted for television purposes, furthermore, tubular column structures of elliptical, square, rectangular or other configuration may be utilized as the structural element, though the circular cross section has been found to producethe previously described extremely high degree ofcircularity in the horizontal pattern.

Plexiglass, polyvinyl. chloride or similar radio wave transparent sheet material, such as the flat strips 52, Fig. 1, may be inserted within guides 152 and secured, as by screws or other means, to the edges of the spacers 2 1, to close off the space between the parallel sides of the adjacent column transmission-line conductors to the effects of the atmosphere. The beacon power cable 1 is also protected since it is within the tubular column 4.

In the event that it is desired to feed different stacked sections of an antenna of this character, such as the pair of antenna sections A and B' of Fig. 5, it may be desired to carry the feed upward within one of the tubular columns to a central location such as midway between the sections A and B. In this embodiment of the invention, the inner conductor 10 of the lower section A, Fig. 6, is connected to the base plate 7. The outer conductor 12 of the coaxial feed system 12-14 is also connected to the base plate 7 and the inner conductor 14 is extended, as at 114 upward within the tubular column 4. At the junction between the antenna sections A and B, formed by the connecting member 160, the inner conductor extension 114' branches, as at H5, and connects at 116 to the top of the conductor 10px" the lower antenna section A and to the bottom of the conductor 10 or" the upper antenna section B. Proper phasing may be achieved through the movement of the capacitive plunger 182, as by means of the screw 194', in the stub section formed by the portion of the branch 115 to the right of the conductor 114 and an outer sleeve 163 connected with and branching from the tubular conductor 4. Since the tubular conductor 4 is here used for the feed line 114, the beacon power cable 1 may be carried upward through the tubular conductor 6.

Other types of feed systems, as before stated, may also be employed. In Fig. 7, as an example, two similar antenna sections A and B of the character described are somewhat differently excited. Referring to the upper antenna section B, Fig. 8, it will be observedtha't this section is excited in the same way as the antenna of Fig. l. The inner conductor 10 of theupper antenna section B, however, is an enlarged extension of the coaxial feed-line inner conductor 14 that passes upward through, though insulated at 101 from, the conductor 10 of the lower antenna section A. This conductor 10 of the lower antenna section A is insulated at 103 from the conductor 10 of the upper antenna section B. If the branch conductors of the lower antenna section A terminated on the same tubular conductors as the corresponding branch conductors of the upper antenna section B, with this type of feed, then the lower antenna section would radiate currents out of phase with the upper antenna section. This can be" seen by tracing the rent; flowsupward along cenductor .14 and upward along the conductor 10 of the upper antenna section B. The current will then flow from right to left across the branch conductor 18-22 and down the tubular conductor. 6 If the branch conductor 1822 of the lower antenna seetion A were also connected to the tubular conductor. however, current would flow from the conductor 6 back from left-to-right along the branch conductor 18-.-22 of the lower antenna section. This current wouldflow in opposite directions in the branch conductors of the upper and lower antenna sections, which is not desired. connecting the bran-ch conductors 1822 of the lo wer antenna sectionA to the different tubular conductor 4, however, current flows across this branch conductor 18-22 from right-to-left as desired. This is because the current flowing up the inner conductor 14, flows down the inner surface of the lower antenna section conductor 10 since this conductor 10 terminates at the in sulator 103. Current flowingdown the inner surface, however, means current flows up-the outer surface of this conductor 10 and hence it flows into the conductor 10 from the branch conductor 18-22, which is from rightto-left. H p With the'teed system of Figs. 7 to 10, therefore, the branch conductors 18, 24, 32, 34 of the lower antenna section A are connected to the respective tubular column conductors 4,6, 8 and 2, whereas, the corresponding branch conductors of the upper antenna section B connect with the different respective tubular column conductors 6,8,2and4. p

Further modifications will occur to those skilledin the .art andall such are considered to fall within the spiritand scope of the invention as defined in the appended claims. 1

What is claimed is: l

1. An antenna system for transmitting radio-frequency energy of a predetermined wavelength comprising a plurality in excess of two of substantially parallel transmission-line conductors of length at least equal to the said predetermined wavelength, all but one of the transmission-line conductors comprising tubular columns symmetrically disposed with respect to the said one transmission-line conductor, means for energizing the said one transmission-line conductor with radio-frequency energy of the said predetermined wavelength and thesaid othertransmission-line conductors in anti-phase therewith, and a plurality of branch conductors equal in number to one less than the plurality of transmission-line conductors completely disposed within the space between the transmission-line conductors connected at one of their ends to the said one transmission-line conductor and at their other ends to points disposed along the outer surfaces of the respective tubular column transmission-line conductors and each of length not greater than substantially one-half the said predetermined wavelength. M

2. An antenna system for transmitting radio-frequency energy of a predetermined wavelength comprising a plurality in excess of two of substantially parallel transmission-line conductors of length at least equal to the said predetermined wavelength, all but one of the transmission-line conductors comprising tubular columns symmetrically disposed with respect to the said one transmission-line conductor, means for energizing the said one transmission-line conductor with radio-frequency energy of the said predetermined wavelength and the said other transmission-line conductors in anti-phase therewith, and a plurality of branch conductors'equal in number to one less than the plurality of transmission-line conductors completely disposed within the space between the transmission-line conductors in a plane substantially normal thereto connected at one of their ends to the said one transmission-line conductor and at their other ends to substantially co-planar points disposed along the' outer surfaces of the respective tubular column transmissionsion-line conductors of length equal to several times the said predetermined wavelength, all but one of the transmission-line conductors comprising tubular columns symmetrically disposed with respect to the said one transmission-line conductor, means for energizing the said one transmission-line conductor with radio-frequency energy j of the said predetermined wavelength and the said other transmission-line conductors in anti-phase therewith, and

several branch-conductor groups each comprising a plurality of branch conductors equal in number to one less than the plurality of transmission-line conductors, the branch-conductor groups being completely disposed within the space between the transmission-line conductors in substantially parallel planes substantially normal to the transmission-line conductors spaced therealong at intervals corresponding substantially to the said predetermined wavelength, the plurality of branch conductors "of each group being connected at one of their ends to the said one transmission-line conductor and at their other ends to substantially coplanar points disposed along the outer surfaces of the respective tubular column transmission-line conductors and each of length not greater than substantially one-half the said predetermined wavelength.

" 4. An antenna system for transmitting radio-frequency energy of a predetermined wavelength comprising five spaced substantially parallel transmission-line conductors of length at least equal to the said predetermined waveing tubular columns of substantially circular cross section symmetrically disposed with respect to the fifth transmission-line conductor with substantially equal spacing between the adjacent tubular column transmissionline conductors, means for energizing the fifth transmission-line conductor with radio-frequency energy of the said predetermined wavelength and the tubular column transmission-line conductors in anti-phase therewith, and

energy of a predetermined wavelength comprising five spaced substantially parallel transmission-line conductors I of length at least equal to the said predetermined Wavelength, four of the transmission-line conductors comprising tubular columns of substantially circular cross section symmetrically disposed with respect to the fifth transmission-line conductor with substantially equal spacing between the adjacent tubular column transmission-linc conductors, means for energizing the fifth transmissionline conductor with radio-frequency energy of the said predetermined wavelength and the tubular column transmission-line conductors in anti-phase therewith, and four branch conductors disposed completely within the space between the transmission line conductors in a plane substantially normal to the transmission-line conductor connected at one of their ends to the fifth transmission line conductor, extending between the adjacent tubular column transmission-line conductors and connected at their other ends to substantially co-planar points disposed along the outer surfaces of the respective four tubular column transmission-line conductors near the outermost I, portions thereof.

6. An antenna system for transmitting radio-frequency energy of a predetermined wavelength comprising five spaced substantially parallel transmission-line conductors "of length at least equal to the said predetermined wavelength, four of the transmission-line conductors comprislength, four of the transmission-line conductors com prising tubular columns of substantially circular cross section symmetrically disposed with respect to the fifth transmission-line conductor with substantially equal spacing between the adjacent tubular column transmissionline conductors, means for energizing the fifth transmission-line conductor with radio-frequency energy of the said predetermined wavelength and the tubular column transmission-line conductors in anti-phase therewith, and four branch conductors disposed completely within the space between the transmission-line conductors in a plane substantially normal to the transmission-line conductors connected at one'of their ends to the fifth transmissionline conductor, extending radially between the adjacent tubular column transmission-line conductors, extending near their other ends at right angles to the said radial extensions and connected at their said other ends to substantially co-planar pointsdisposed along the outer surfaces of the respective four tubular column transmissionline conductors near the outermost portions thereof.

7. An antenna system for transmitting radio frequency energy of a predetermined wavelength comprising five spaced substantially parallel transmission-line conductors of length at least equal to several times a predetermined radio-frequency wavelength, four of the transmissionline conductors comprising tubular columns of substantially circular cross-section symmetrically disposed with respect to the fifth transmission-line conductor with substantially equal spacing between the adjacent tubular column transmission-line conductors, means for energizing the fifth transmission-line conductor with radiofrequency energy of the said predetermined wavelength and the tubular column transmission-line conductors in anti-phase therewith, and several branch-conductor groups each comprising four branch conductors, the branch conductor groups being disposed completely within the space between the transmission-line conductors in substantially parallel planes substantially normal to the transmission-line conductors spaced therealong at intervals corresponding substantially to the said predetermined wavelength, the four branch conductors of each group being connected at one of their ends to the fifth transmission-line conductor, extending radially between the adjacent tubular column transmission-line conductors, extending near their other ends at right angles to the said radial extensions and connected at their said other ends to substantially coplanar points disposed along the outer surfaces of the respective four tubular column transmission-line conductors near the outermost portions thereof and each of length not greater than substantially one-half the predetermined wavelength.

8. An antenna system for transmitting radio-frequency energy of a predetermined wavelength comprising five spaced substantially parallel transmission-line conductors of length at least equal to several times a predetermined radio-frequency wavelength, four of the transmissionline conductors comprising tubular columns of subs-tantiaily circular cross-section symmetrically disposed with respect to the fifth transmission-line conductor with substantially equal spacing between the adjacent tubular column transmission-line conductors, means for energizing the fifth transmission-line conductor with radio-frequency energy of the said predetermined wavelength and the tubular column transmission-line conductors in antiphase therewith, and several branch-conductor groups each com-prising four branch conductors, the branch-conductor groups being disposed completely within the space between the transmission-line conductors in substantially parallel planes substantially normal to the transmission- -line conductors spaced therealong at intervals corresponding substantially to the said predetermined wavelength, conductive supporting plates connected between adjacent tubular column transmission-line conductors substantially mid-way between successive groups of branehconductors, the four branch conductors of each group being connected at one of their ends to the fifth transmission-line conductor, extending radially between the adjacent tubular column transmission-line conductors, extending near their other ends at right angles to the said radial extensions and connected at their said other ends to substantially coplanar points disposed along the outer surfaces of the respective four tubular column transmissionaline conductors near the outermost portions thereof and each of length not greater than substantially one-half the predetermined wavelength.

9. An antenna as claimed in claim 8 and provided with means disposed at each end of the antenna for connecting together the corresponding ends of the four tubular column transmission-line conductors in order to provide for mounting the antenna at one end and for supporting a beacon light at the other end, the connecting means at the said one end being provided with an aperture for receiving the fifth transmission-line conductor, and electrical cables for the beacon light supported Within one of the tubular column transmission-line conductors.

10'; An antenna system for transmitting radio-frequency energy in the band extending from substantially 500 mega'cycles to substantially 890 megacycles comprising five substantially parallel transmission-line conductors of length at least equal to substantially ten to twenty wavelengths of the energy, four of the transmission-line conductors comprising tubular columns of substantially circular cross-section substantially three to six inches in outerdiameter symmetrically disposed with respect to the fifth transmission-line conductor with substantially equal spacing between the adjacent tubular columns of from substantially one-half inch to approximately two inches, means for energizing the fifth transmission-line conductor with the radio-frequency energy and the tubular column transmission-line conductors in anti-phase therewith, and from substantially ten to twenty branchconductor groups each comprising four branch conductors, the branch-conductor groups being disposed completely Within the space between the transmission-line conductors in substantially parallel planes substantially normal to the transmission-line conductors spaced therealong at intervals of substantially the said wavelength, thefour branch conductors of each group being connected at one of their ends to the fifth transmission-line conductor and at their other ends to substantially co-planar points disposed along the outer surfaces of the respective four tubular column transrnissiondihe conductors and each of length of from approximately three and onehalf 'to' substantially six inches.

1'1. An antenna system for transmitting or receiving radio-frequency energy of a predetermined wavelength comprising a plurality of tubular column transmissionline conductors of length substantially equal to or greater than the predetermined wavelength parallel and substantially symmetrically disposed with respect to a centrally disposed transmission-line conductor, means whereby the centrally disposed transmission-line conductor may be energized with radio-frequency energy of the predetermined wavelength and the plurality of transmission-line conductors in anti-phase therewith, and a plurality of branch conductors equal in number to the plurality of transmission-line conductors completely disposed within thespace between the transmission-line conductors respectivelyconnected to the centrally disposed conductor and points disposed along the outer surfaces of the respective plurality of transmission-line conductors and each of length not greater than substantially one h'alt' the predetermined wavelength.

12. An antenna system for transmitting radio-frequency energy of a-predetermined wavelength comprising. a plurality of substantially parallel transmission-line conductor means of length at least equal tothe said predetermined wavelength, all but one of the transmissionline conductors means comprising tubular columns symmetrically surrounding the said one transmission-line conductor mean's,,me'ans for energizing the saidonetran'smission-line conductor means with radio-frequency energy of the said predetermined wavelength and the. tubular column transmission-line conductor means in antiphase therewith, and a plurality of branch conductors equal in number to the number of tubular column transmission-line conductor means completely disposed with in the space between the transmission-line conductor means connected at one of their end'sto the said one transmissionline conductor means and at their other ends to points disposed along the outside surfaces of the respective tubular column transmission-line conductor means and each of length not greater than substantially onehalf the said predetermined wavelength.

13. A pair of similar antenna sections, one stacked upon the other, for transmitting radio-frequency energy of a predetermined Wavelength, each section comprising a plurality of substantially parallel transmission line conductor means of length at least equal to the said predetermined wavelength, all but one of the transmissionline conductor means comprising tubular columns symmetrically surrounding the said one transmission-line conductor means, and a plurality of branch. conductors equal in number to the number of tubular column transmission-line conductor means completely disposed within the space between the transmission-line conductor means connected at one of their ends to the said one transmission-line conductor means and at their other ends to points disposed along the outside surfaces of the respective tubular column transmission-line conductor means and each of length not greater than substantially one-half the saidpredetermined wavelength, and means carried upward within one of the lower antenna section tubular column transmission-line conductors for energizing the said one transmission-line conductor of both the antenna sections'with radio-frequency energy of the said predetermined wavelength.-

14. A pair of similar antenna sections, one stacked upon the. other, for transmitting radio-frequency energy of a predetermined wavelength, each section comprising a plurality of substantially parallel transmission-line conductors of length at least equal to the said predetermined wavelength,- one of the transmission-line conductors being symmetrically disposed with respect to the other transmission-line conductors, the said one transmission-line conductor of the lower antenna section being the outer conductor of a coaxial line the inner conductor of which extends upward beyond the lower antenna section to form the said one transmission-line conductor of the upper antenna section means for supplying radio-frequency energy to the said coaxial line, means for connecting the lower ends of the lower antenna section other transmission-line conductors to the said one transmission-line conductor thereof, means for connecting the upper ends of the upper. antennasection other transmission-line conductors to, the upper end of the said one transmissionline conductor thereof, each antenna section having one or more pluralities of branch conductors equal in number to one less than the plurality of transmission-line conductors disposed within the space between the transmission-line conductors in a plane or planes substantially normal thereto connected at one of their ends to the said one transmission-line conductor and at their other ends to the respective other transmission-line conductors and each of length not greater than substantially one-half the said predetermined wavelength, the branch conductors of one antenna section being connected at their said other ends to different other transmission-line conductors of the said one antenna section than the corresponding branch conductor of the other antenna section.

15. A pair of similar antenna sections, one stacked upon the other, for transmitting radio-frequency energy of a predetermined wavelength, each section comprising a plurality of substantially parallel transmission-line conductors of length at least equal to the saidpredetermined wavelength, one of the transmission-line conductors being symmetrically disposed with respect to the other transmission-line conductors, the said other transmission-line conductors comprising tubular columns, the said one transmission-line conductor of the lower antenna section being the outer conductor of a coaxial line the inner conductor of which extends upward beyond the lower antenna section to form the said one transmission-line conductor of the upper antenna section, means for supplying radio-frequency energy to the said coaxial line, means for connecting the lower ends of the lower antenna section other transmission-line conductors to the said one transmission-line conductor thereof, means for connecting the upper ends of the upper antenna section other transmission-line conductors to the upper end of the said one transmission-line conductor thereof, each antenna section having one or more pluralities of branch conductors equal in number to one less than the plurality of transmission-line conductors disposed within the space between the transmission-line conductors in a plane or planes substantially normal thereto connected at one of their ends to the said one transmission-line conductor, extending at first radially and then at substantially right angles thereto and connected at their other ends to the respective other transmission-line conductors and each of length not greater than substantially one-half the said predetermined wavelength, the right-angular extensions of the corresponding branch conductors of each antenna section extending in opposite directions in order that the branch conductors of one antenna section may be connected at their said other ends to different other transmission-line conductors of the said one antenna section than the corresponding branch conductors of the other antenna section.

16. An antenna system for transmitting radio-frequency energy of a predetermined wavelength comprising a plurality in excess of two of substantially parallel longitudinally extending transmission-line conductors of length at least equal to the said predetermined wavelength, all but one of the transmission-line conductors comprising tubular columns of greater transverse surface dimension than the said one transmission-line conductor and being symmetrically disposed with respect to the said one transmission-line conductor in order to define between them longitudinally extending openings of transverse dimensions small with respect to the said transverse surface dimension, means for energizing the said one transmissionline conductor with radio-frequency energy of the said predetermined wavelength and the said other transmission-line conductors in anti-phase therewith, and a plurality of branch conductors equal in number to one less than the plurality of transmission-line conductors disposed within the said openings and connected at one of their ends to the said one transmission-line conductor and at their other ends to the respective other transmission-line conductors in order to provide radio-frequency excitation at the said openings.

17. An antenna system for transmitting radio-frequency energy of a predetermined wavelength comprising a plurality in excess of two of substantially parallel longitudinally extending transmission-line conductors of length at least equal to the said predetermined wavelength, all but one of the transmission-line conductors comprising tubular columns of greater transverse surface dimension than the said one transmission-line conductor and being symmetrically disposed with respect to the said one transmission-line conductor in order to define between them longitudinally extending openings of transverse dimensions small with respect to the said transverse surface dimension, means for energizing the said one transmission-line conductor with radio-frequency energy of the said predetermined wavelength and the said other transmission-line conductors in anti-phase therewith, and a plurality of brance conductors equal in number to one less than the plurality of transmission-line conductors completely disposed within the said openings and connected at one of their ends'to the said one transmissionline conductor and at their other ends to the respective other transmission-line conductors in order to provide radio-frequency excitation at the said openings.

18. An antenna system as claimed in claim 16 and in which the length of each branch conductor is not greater than substantially one-half the said predetermined wavelength.

19. An antenna system as claimed in claim 16 and in which each branch conductor comprises a first portion extending from the said one transmission-line conductor outward along one of the said openings and a second portion extending at right angles to the first portion and terminating upon one of the conductors of the said other transmission-line conductors.

20. An antenna system for transmitting radio-frequency energy of a predetermined wavelength comprising a plurality of substantially parallel longitudinally extending tubular substantially circular cross-section transmissionline conductors of length at least equal to the said predetermined wavelength, all but one of the transmissionline conductors being of substantially the same diameter greater than the diameter of the said one transmissionline conductor and being symmetrically disposed with respect to the said one transmission-line conductor in order to define between them a plurality of narrow longitudinally extending openings, means for energizing the said one transmission-line conductor with radio-frequency energy of the said predetermined wavelength and the said other transmission-lineconductors in anti-phase therewith, and a plurality of branch conductors equal in number to the number of the said other transmission-line conductors disposed in a plane substantially normal thereto connected at one of their ends to the said one transmission-line condoctor and at their other ends to the respective other transmission-line conductors in order to provide radiofrequency excitation at the said openings.

21. An antenna system for transmitting radio-frequency energy of a predetermined wavelength comprising five substantially parallel longitudinally extending tubular substantially circular cross-section transmissionline conductors of length at least equal to several times a predetermined radio-frequency wavelength, four of the transmission-line conductors being of substantially the same diameter greater than the diameter of the fifth transmission-line conductor and being symmetrically disposed with respect to the fifth transmission-line conductor in order to define between adjacent conductors of the four transmission-line conductors substantially equal narrow longitudinally extending openings, means for energizing the fifth transmission-line conductor with radio-frequency energy of the said predetermined wavelength and the four transmission-line conductors in anti-phase therewith, several branch-conductor groups each comprising four branch conductors, the branch-conductor groups being disposed in substantiallyparallel planes substantially normal to the transmission-line conductors spaced therealong at intervals corresponding substantially to the said predetermined wavelength, the four branch conductors of each group being connected at one of their ends to the fifth transmission-line conductor and at their other ends to the respective conductors of the four transmission-line conductors and each of length not greater than approximately one-half the predetermined wavelength in order to provide radio-frequency excitation at the said openings.

22. An antenna system as claimed in claim 21 and in which each branch conductor comprises a first portion extending from the said fifth transmission-line conductor outward along one of the said openings and a second portion extending at right angles to the first portion and 13 terminating upon one of the four transmission-line conductors.

23. An antenna system as claimed in claim 21 and in which the said transverse dimension of each of the openings is less than one-half the said predetermined Wavelength and connecting elements are provided connecting the four transmission-line conductors together at points substantially mid-way between successive branch-conductor groups in order to sub-divide each of the said openings longitudinally into a plurality of co-planar radiating wave-transmission-loop frames of longitudinal dimension corresponding substantially to the said predetermined wavelength and of transverse dimension cor- 14 responding to less than one-half the said predetermined wavelength.

24. An antenna system as claimed in claim 23 and in which each branch conductor comprises a first portion extending from the said fifth transmission-line conductor outward along one of the said openings and a second portion extending at right angles to the first portion substantially parallel to the connecting elements and terminating upon one of the four transmission-line conductors 10 to excite the corresponding wave-transmission-loop frame.

References Cited in the file of this patent UNITED STATES PATENTS 2,521,550 Smith Sept. 5, 1950

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