US2660674A - Slotted antenna system - Google Patents

Description

Nov. 24, 1953 G. H. BROWN 2,560,674

SLOTTEID ANTENNA SYSTEM Filed Oct. 14, 1948 2 Sheets-Sheet l \NVENTOR r0 mam/z 60 GEORGE BROWN AT ORNEY Nov. 24, 1953 G. H. BROWN 2,660 674 SLOTTED ANTENNA SYSTEM Filed Oct. 14, 1948 2 Sheets-She'=t 2 OIPLEXER um 24 52 $54 r0 V/SZ/AL/ 2 T0 All/R41 TRAMS'. TIM/K5- U/V/T 70 40 041 r0 wsu/u mus. TRANS.

INJENTCER GEORGE H. BROWN ATTORN EY Patented Nov. 24, 1953 SLOTTED ANTENNA SYSTEM George H. Brown, Princeton, N. J., assignor to Radio Corporation of America, a corporation of Delaware Application October 14, 1948, Serial No. 54,462

26 Claims. 1

The invention relates to high frequency antenna systems and particularly pertains to high frequency antennas providing uniform radiation patterns in the horizontal plane.

Several ultra-high frequency antenna systems for broadcast and other services requiring uniform radiation in the horizontal plane are known to the art. The turnstile antenna, having four horizontal radiating elements emanating from a vertical supporting member in a manner suggestive of its name, has proved to be particularly useful in television broadcasting because its construction is simple, high vertical directivity is easily attained by stacking a number of radiating-element layers, and the required phase-quadrature relations render it feasible to employ simple networks to apply both visual and aural excitation. The terms visual and aural excitation as herein used will be construed to mean radio Waves modulated by signals proportional to picture tones and sound variations desired to be transmitted for entertainment or other purposes. The pylon antenna has proved particularly advantageous for broadcast service especially in frequency modulation applications. The Pylon Antenna described in copending U. S. patent application Serial No. 593,152, filed May 11, 1945, by Woodrow Darling, now U. S. Patent 2,513,007, issued June 27, 1950, basically comprising a vertical cylinder with a slot cut along one side and having a feed line connected across the slot at the center thereof, is also simple in construction and particularly adaptable for stacking a number of such elements in the vertical directions to improve the vertical directivity while maintaining a uniform horizontal radiation pattern. There is a third high frequency broadcasting antenna described in co pending U. S. patent application Serial No.

718,791 filed December 2'7, 1946, by John E. Pauch,

now U. S. Patent 2,568,560, issued September 18, 1951, sometimes known as the prismatic antenna, comprising a plurality of vertical radiator elements arranged in the horizontal plane to form an interrupted geometrical pattern as a prism interrupted at the corners thereof, the interruptions of which when viewed in the vertical direction can be considered as open-ended slots, which slots are fed at the center much in the same manner as that of the pylon antenna to produce a uniform horizontal radiation pattern. This latter type of antenna is fairly simple in construction and may be varied in height to provide a desired vertical directivity while maintaining uniform radiation in the horizontal direction.

The above mentioned antennas have proved entirely unsatisfactory when the frequency of the carrier wave is of the order of 500 megacycles and higher. The radiators conventionally employed with the turnstile antennas then become exceedingly difficult to construct and also the supporting member approaches an appreciable fraction of the operating Wavelength. The pylon antenna has the serious disadvantage that in order to produce a relatively uniform radiation pattern the horizontal cross-section of the antenna must be small, giving rise to a large inductive reactance component which tends to make the interior act as a wave guide, thus establishing a cut-off which is highly undesirable and necessitates complex measures to neutralize the same. Although fairly simple in construction, the barrel-stave antenna is inherently mechanically weak, requiring complex insulating and spacing provisions.

These and other, more complex, antenna systems have been also employed heretofore in radio navigation applications where the inherent disadvantages mentioned in regard to program broadcast services are even more apparent and, in addition, any non-circularity of the radiation patterns which for program broadcast service may be permitted to a certain extent even though undesirable, simply cannot be tolerated for the latter purposes. In order to eliminate the error introduced by non-circularity of the radiation pattern, complex systems have been devised and employed at great expense in efliciency and economy.

Furthermore, the prior art radio navigation systems have usually required complex antenna systems because of the manner in which wave energy is desired to be radiated. For example, the omni-directional range heretofore usually employed utilizes an antenna system having five, closely spaced, individual, loop antennas interconnected and fed with radio frequency energy in the desired manner. Obviously, such a complex arrangement has been employed as a necessity rather than a desirability since the close spacing required of the individual radiators results in an undesirably low radiation resistance and the coupling between radiators results in serious unbalance. Furthermore, the horizontally polarized omni-range exhibits a large 00- tantal error due to the inability to keep the phase displacement factor small with loop antennas; where d is the spac ing between antennas and is the wavelength, both in meters.

The above described disadvantages are obviated in an ultra high frequency antenna system according to the invention wherein a simple conductive tubular member capable of being integrally joined to a rigid mechanical supporting element is provided with a plurality of slots which are excited with high frequency energy in a simple and eificient manner effecting capacitive .reactance in the interior of the antenna and providing radio frequency conditions along the conductive member whereby the use of simplified and compact feeder assemblies are practicable even for installations calling for a relatively complex method of excitation.

Accordingly, one of the objects of the invention is found in the design of an efiicient ultrahigh frequency transmitting antenna.

Another object of the invention is to provide an ultra-nigh frequency transmitting antenna capable of uniform radiation in all directions in a horizontal plane about the antenna.

A further object of the invention is to provide an ultra-high frequency transmitting antenna having a circular horizontal radiation pattern together with compression of the radiation in the vertical direction.

Still another object of the invention is to provide an antenna system employing a tubular metal structure and avoiding the cut-off effect of the normal wave guide.

A. still further object of the invention is to provide a multiple-slot antenna capable of radiating energy in response to excitation from a plurality of R. F. sources.

Yet another object of the invention is to provide an efficient ultra high frequency modulation broadcast antenna.

Yet a further object of the invention is to provide an antenna system for omni-directional ranges having low octantal error and a single radiating element providing simplified construction and installation.

It is still another and further object of the invention to provide a practical antenna design which permits a plurality of antenna sections of novel design to be supported by a single conductive supporting member.

These and other objects of the invention will appear as the specification progresses.

The invention will be described in detail with reference to the accompanying drawing forming a part of the specification and in which:

Figure 1 is a diagram illustrating the mode of operation of an antenna system known to the art;

Figure 2 is an illustration of the radiating elements of an antenna system according to the invention;

Figure 3 is an illustration, partly in crosssection and partly in perspective, of the novel method of feeding the radiating elements shown in Figure 2;

Figure 4 is a further illustration of the method of feeding the radiating elements of the type shown in Figure 2;

Figures 5 and 6 are illustrations of feeder harnesses for applying ultra high frequency energy according to the invention to the antenna structure shown. in Figure 2; and

Figures '7 and 8 are illustrations of the method of feeding alternate embodiments of the invention.

In order that the antenna system according to the invention be more readily understandable, reference is first made to the mode of operation of a known antenna system from a discussion of which novel features of the invention will become apparent as the specification progresses. Referring to Fig. 1, there is shown a cross section of a known multiple-slot antenna taken at the center of the slots at which :point radiatingelements H, I2 and I3 are excited at the edges thereof in the conventional manner by means including afeeder assembly l4 comprising a coaxial feed line I6 connected in parallel to distributor feeds I1, 18 and IS. The inner conductors of feeders ll, l8 and I9 are connected to corresponding edges of radiators H, l2 and I3 respectively while the outer conductors are connected to the adjacent radiator immediately across the slots or gaps formed between the radiators as shown in Fig. 1. Applied in this manner, the instantaneous currents flowing in the radiators proceed in the same direction around the assembly as indicated by the solid arrows to -produce a radiant energy field radiating from the assembly with uniform intensity. In this conventional antenna assembly it should be noted that the same instantaneous potential exists across all of the slots and that corresponding edges of the slots exhibit the same instantaneous potential.

Referring to Fig. 2 there is shown an embodiment of an antenna according to the invention which comprises a supporting member 20 and four radiating element members 2I-24, each of which is exactly similar to the others. For pur- 'slots cut into the uppermost end of the structure at the proper loci. It is of course to be understood that a single element or any number of them may be used with the results dependin upon the type of radiation desired. For example, it is anticipated that for FM broadcast services a four-element antenna will be found most desirable for general use, while in radio navigation applications, it will in all probability be found that but one element will be suflicient for most installations and this is particularly anticipated for installations involving mobile or transportable equipment.

Particular reference will be made to only one of the radiating elements as an illustrative example in explanation of the novel features of the invention. Referring still to Fig. 2, it will be seen that a radiating element is constituted by a metallic cylinder 24 having four longitudinal slots 3l-34 cut into the walls thereof. In the preferred embodiments of the invention slots 31-34 are equidistantly spaced around the periphery of cylinder 24; however, it is to be understood that it is within the scope of the invention to employ more or fewer slots, equally or unequally spaced in accordance with the intent of the designer and the problems at hand. For convenience slots 3|34 are referred to hereinafter as north, east, south and west slots, which designations are readily associated with the corresponding cardinal points of the compass and tend to present a clearer understanding of the adaptation of the subject antenna to types of problems for which it was principally designed.

Further in the interest of clarity and convenience the longitudinal edges of each pair of slots which lie diametrically opposite each other or which appear in the same relative position in a traverse about the periphery in a single direction are termed the corresponding edges, and the edges which are immediately opposite each other are termed the opposing edges as against the apposing edges of the same slot. For example, edges 48 and 41 of the section shown in Fig. 3 are apposing edges, as are edges 48 and 49. Edges 41 and 49 which are diametrically opposite each other are corresponding edges, while opposing edges 41 and 48 are immediately opposite each other. With respect to a given edge 46, the edge 47 of the same slot is the apposite edge; the immediately opposing edge 49 is the opposite edge; and the diametrically opposite edge 48 is the corresponding edge.

Referring to Fig. 3 there is shown a cross section of element 24 of Fig. 2 taken on line 3-3. Radio frequency energy is applied to the radiatingelements of the novel antenna in a manner according to the invention as shown in Fig. 3 wherein there is provided a coaxial transmission line 37 which is bifurcated to form lines 38 and 39 of equal length supplying energy in the same phase relationship to the east and west slots at the centers thereof. The center conductors of lines 38 and 39 are connected to opposite edges 42 and 45 of the east and west slots and the outer conductors are connected to opposite edges 43 and 44 of the east and west slots respectively. It will be seen from an inspection of Fig. 3 that the instantaneous currents flowing around the periphery of radiator element 24 from the points just mentioned flow in opposing directions as shown by the solid arrows, that is exactly the opposite of the known antenna shown for comparison in Fig. 1. By means of these connections magnetic fields will be set up in the east and west slots but no field will be set up in the north and south slots. This has been proven by actual test in which it has been found that the radiation in the horizontal plane may be accurately expressed by the Quantity Cos 0, where 0 is the angle measured with the east direction taken as 0 equal to 0. This last expression has been found extremely accurate for any diameter of radiator element lying between and A of the operating wavelength.

For the sizes of structure usually used, the pylon prismatic antennas .previously mentioned exhibit an inductive internal reactance which tends to make the interior of the structure function as a wave guide and establish a cut-off frequency below which the antenna will not function. This effect is highly disadvantageous and is a factor tending to limit the use of the latter antennas. However, because of the novel manner in which the antenna of the invention is fed, the internal reactance is made capacitive in nature. Thus, by means of this heretofore unknown feature an antenna can be produced which not only avoids one of the major objections to the antennas of the prior art but also permits the radiation of highly desirable complex waves as will now be shown.

It should be noted. that when applying radio frequency energy to radiator element l l as shown in Fig. 3 both apposite edges 46, 41, of the south slot are at equal potential and apposite edges 48 and 49 of the north slot are likewise at equal potential though diifering from that of the former. Recognizing this fact, it can be seen that a similar R. F. feed system can be connected to the south and north slots with no interaction occurring between the application of R. F. energy to the east and west slots and the north and south slots. This is shown better in Fig. 4 wherein the element 24 has been figuratively unrolled to present a clear and readily understandable diagram of the method of feed in which the east and west slots are fed by means of the harness assembly previously described with reference to Fig. 3 and the north and south slots are fed by a transmission line assembly exactly similar to that previously described but so connected that interaction of energy between the two sets of slots is avoided.

Referring again to Fig. 2 there is shown a practical embodiment of an antenna according to the invention useful in transmission of television signals wherein four radiator elements 2l-24 are fastened together by means of flanges 26, 27 and 28 to form a unitary structure which is supported on a suitable column 2|] by means of flange 25. As previously stated, it is not at all necessary to employ separate sections, however, and it is contemplated in practice to construct such an antenna and supporting member in the form of a single tubular member having the necessary slots cut into it in the desired loci. The slots are spaced a wavelength apart from center to center in the vertical direction, and it has been found in practice that slots 3!, 32, 33 and. 34 may be anywhere one half wavelength to a full wavelength long. However, it has been found that for the usual coaxial transmission line slot lengths lying between 0.75 and 1.0 wavelength are better and preferably a slot length of 0.85 wavelength is employed. With a slot length of 0.85 wavelength an impedance of approximately 25 ohms is obtained in either direction from the center of the slot at which the energy is applied, which impedance has been found very convenient to use. The slots are energized by transmission lines connected on the inside of the radiator elements by means of coaxial transmission lines as shown in the remaining figures of the drawing. For example, the system as previously described in reference to Fig. 4 can be employed for television broadcasting by utilizing a qu ater-wave phasing loop 5| inserted, in line 37, but which may with equal effect be inserted in either one of the transmission lines 37 or 51 which are in turn connected to a well known diplexer 52 (such as is disclosed in copending U. S. application, Robert Wayne Masters, Serial Number 714,620, filed December 6, 1946, now U. S. Patent 2,570,579, issued October 9, 1951), to which transmission lines 53 and 54 are connected to an aural transmitter and a visual transmitter respectively. The two sets of slots are fed in phase quadrature, thus producing the equivalent radiation of that produced by the turnstile antenna. Referring to the previously established reference angle, the north and south slots radiate according to the law sin 0. and if the north and south slots have R. F. energy applied to them in phase quadrature to that applied to the east and west slots, the resultant field will be cos 6+ sin. 0, which will be immediately recognized as the expression of a perfect circle.

The arrangement of Fig. can be extended to any number of elements stacked in the vertical direction.

Referring to Fig. 5 there is shown a portion of an R. F. feed assembly arranged in the interior of a structure according to Fig. 2, the stack of assume north :slots :only being shown for convenience, it ibein'g understood that 'the remaining slots are fed 'in :similar fashion. A concentric transmission line fill is bifurcated into transmission lines 6! and 562 of equal length to apply R. F. energy in thesame phase to north andsouth slots. Trans- ;mission line [it is again bifurcated to form .secondary transmission lines 63 and $4 of equal length dividing-again into four additional transmission lines 85. $6, 5? and 63 respectively, each heing'three-quarter wavelengths long and 50 ohms impedance. I he outer conductors of transmission lines .65 and-filiare connected tocorrespondfing edges 99, 89 of the lowermost slots of the north stack while the inner conductors are connected to corresponding edges -98 and 88 respectively. The corresponding edges 38 and 180i the two uppermost slotsare connected to the center :conductors of transmission lines 68 and 51 while the corresponding'edges 49 and :9 are connected .to theeuter conductors thereof. In this manner corresponding edges 4%. i8, 852 and 93 are con- :nected in the same phase and in opposition to that of the respective opposite edges 49, 19,89 and 99.

Asimpler feeder assembly-providing equivalent results of that described is shown in Fig. 6 whereinedges ail-and is of the two uppermost slots are connected together by the outer conductor of a imultiple-of wavelengths of transmission line 12, one end of whoseconductor is connected to edge 49 of the uppermostslot. Similarly corresponding edges 88 and 98 of .the lowermost slots are connected together by the outer conductor of a .multiple of wavelengths of transmission line H, one end of whose innerconductor is connected toedge of -95 of the lowermost slot. A solid dielectric transmission line of one and one-half electrical wavelengths and having a physical length of approximately one wavelength is conveniently employed in practice. 'ductorscf transmission lines H and 12 are connected directly to the inner conductors of trans- .mission lines .83 and 64, which lines correspond exactly to the transmission lines .63 and 64 of Fig. 5, the impedance of lines 63 and 64 being 50 ohms at the point or" connection. The outer conductors of lines 63 and .64 are connected to corresponding edges 19 and 39 of the centrally located slots. mitter the .transmission .line assembly is identical to that shown in Fig. 5. The remaining slots being connected in like manner, each stack of slots is fed in the same phase toproduoe an over- .all circular radiation pattern in the horizontal plane and compressed in the vertical direction.

The previously described underlying principles of the invention can be applied .inmany ways to utilize a number of useful antenna systems. For example, a highly improved omni-directional .radio range antenna of extremely simple and convenient construction may be obtained by employing a multiple slotted structure as shown at 24 in Figure 2 and applying R. F. excitation according to the invention to derive the same R. F. field patterns presently developed by means of a relatively complexantenna system.

The prior art omni-directional radio range, or omni-range as it is termed by the artisan, requires five antennas, four being arranged to define a square with a fifth antenna being located at the geometrical center thereof. For vertical polarizationof the fields, dipoles are used, and loop antennas are used to provide horizontal polarization,

the central loop sometimes being arranged above From this point on to the trans- The inner con- 7 the .others because of space limitations but the arrangement remains essentially the same in principle. In either event thecentral antenna is excited with .R. energy .at carrier wave frequency to provide .a reference voltage and the othervantennas are excited by suppressed-carrier .side band waves to produce a rotating R. ,F. field.

The central antenna is pulsed to radiate a carrier frequency waveat some orienting direction, usuallynorth in actualpractice, so that the phase anglebetween the reference field and the rotating .fieldis proportional to the azimuthal angle from the orienting direction.

This is accomplished by means of an antenna according to the .invention wherein the arrangement of Fig. 4 is employed to radiate a rotating magnetic field-the phase angle of which is utilized to determine the direction of an observer with respect to the antenna. This is shown in Fig, 17 whereinone pair of side-bands are applied at A and the remaining side-bands are applied at B, it being recognized that the feed arrangement .is thesame as that for Fig. 4 but drawn in an inverted position. Components producing the carrier .andside bands are not shown nor will they be described in detail since they are quite well .known in the art. It the-diameter of cylinder 24 does not exceed 0.4 wavelength at the operating frequency the pattern resulting from the side bands fed at A can beexpressed as proportional to=cos 0 and that produced by side bands applied at B will be proportional to sin 0. Preferably the length L is made one quarter wavelength or .an

odd multiple of quarter wavelengths long at the operating frequency solely to obtain desirable impedance matching, but it should be understood that this length plays no part in preventing coupling between the feed systems.

By means of a transmission .line assembly comprising a coaxial transmission line which is bifurcated to form lines 8| and 82 of equal length which are in turn bifurcated to form equal length lines 83-86 whereby the carrier wave applied to line '80 at C is applied in the same phase to all slots of element 24, the inner conductors of lines '83,.84, and 86 are connected to corresponding edges 48, 46, 42 and 44 respectively, the outer conductors being connected respectively 'to the respective opposite edges 49, 41, 43 and 45 as shown. There will be no interaction between'the feed system since the voltage applied at A will not induce any potential across the north or south slots and hence no signal from A will be transmitted along lines 83 and 84 and potentials at the far ends of lines 85 and 86 will be out of phase so that no signal from A will be transmitted along line 82. By similar analysis it can be seen that there will be no interaction between signals applied at A, B and C. Applying one set of side bands at A, one set at B, and the carrier at C in the manner heretofore employed in omniranges will result in the transmission of two radio waves having a phase difference proportional to the azimuthal angle from a given reference angle at which the carrier is impressed.

For practical considerations, it has been .found preferable in omni-range applcations to employ a slot length between one half and a wavelength long with a radiatordiameterof 0.3 wavelength although it is to be understood that these dimensions are neitherabsolute nor critical.

The fact that the slot length is not too critical for .operation at tolerable efliciencies provides a means-for adding to the versatility of the novel antenna system previously described. It is .con-

templated that in actual practice it will be highly desirable for a radio broadcasting station to provide both FM and television services to the community in which it is located. For economical. and aesthetical reasons a single antenna system such as that shown in Fig. 8 will prove highly advantageous. Here the antenna is excited by a television signal applied near the centers of the slots as previously described with reference to Fig. 4 and further excited at points a bit remote from the centers of the slots by an FM signal of frequency different from that of the television signal. For example, a television signal at 67.25 mc./s. can be applied across the slots of length especially favorable to that service and an FM signal at 97.3 mc./s. applied across the slots at a point approximately one half the distance between the centers and the ends of the slots; the slots being excited substantially as full wave elements for the lower frequency and substantially as one and one-half wave elements for the higher frequency. Obviously the relationship of the frequencies can be inverted while retaining the principle of operation whereby little or no interaction between the signals will take place.

Further interaction is also prevented, especially when there is no harmonic relationship at all between the signal frequencies, by making the feeder assembly for one frequency a quarter wavelength at the other frequency and vice versa as shown in Fig. 8. The exact points of excitation are not critical, however, and moreover a means of providing a desirable impedance match is constituted by moving the points of excitation along the slots.

By use of the arrangement of Fig. 5, or that of Fig. 6, a plurality of elements may be stacked in the vertical direction if desired. Inasmuch as it is expected that the antenna systems described will lend themselves to any and all R. F. installations, it is also contemplated that the interior of the conductive element be protected from the elements by covering the slots with some form of insulating material having a low loss factor and preferably being transparent to provide a means whereby a visual inspection may be made of the interior without removing access covers and so forth. One such material suggested is widely known as Plexiglas, and polyethylene has also been used with excellent results.

While the invention has been described with reference to several express embodiments thereof, it is understood that many obvious modifications will be suggested to those skilled in the art without departing from the spirit and the scopeof the invention.

I claim:

1. An antenna system comprising a radiator element of hollow cylindrical conductive tubing having four longitudinally arranged slots therein and equally spaced about the periphery thereof, a first length of transmission line having one conductor connecting the edges of diametrically opposed slots lying on the same side of a plane passing diametrically through said cylindrical tubing and between the longitudinal edges of said slots and having the other conductor connecting the remaining edges of said slots, a second length of transmission line connecting the edges of the other diametrically opposed slots lying on the same sides of a plane passing diametrically through said cylindrical tubing and between the longitudinal edges of said other slots, and means to apply radio frequency energy in phase quadrature to the midpoints of said first and second I6 lengths of transmission line thereby to produce a rotating radio frequency field about said radiator element.

2. An antenna system comprising a radiator element of hollow cylindrical conductive tubing having four longitudinally arranged slots therein, said slots being organized about a common longitudinal axis of said element to effect pairs of slots in registry, a first length of transmission line having one conductor thereof connecting the edges of a pair of slots lying on the same side of a plane passing through said common axis and between the edges of said slots and having the other conductor thereof connecting the remaining edges of said slots, a second length of transmission line connecting the edges of the other slots in like manner, said transmission lines being connected substantially at the midpoints of said slots, and means to apply radio frequency energy in phase quadrature to the midpoints of said first and second lengths of transmission line thereby to produce a rotating radio frequency field about said radiator element.

3. An antenna system including a conductive surface element having at least two elongated slots arranged in parallel relationship therein, the edges of said slots in a given direction transverse to the longitudinal axis of said slots being designated A, B, C, D in the order named, edges A and B being opposing edges of one slot and edges 0 and D being opposing edges of the other slot, means to apply radio frequency energy to said element, said means comprising radio frequency transmission line structure applying instantaneous in-phase potentials of given polarity simultaneously to edges B and. C and of polarity opposite to said given polarity simultaneously to edges A and D.

4. An antenna system including a tubular conductive member having at least two elongated slots arranged in parallel relationship therein, the edges of said slots in a given direction about the periphery of said member being designated A, B, C, D in the order named, edges A and B being opposing edges of one slot and edges C and D being opposing edges of the other slot, means to apply radio frequency energy to said member, said means comprising radio frequency transmission line structure applying instantaneous inphase potentials of given polarity simultaneously to edges B and C and of polarity opposite to said given polarity simultaneously to edges A and D.

5. An antenna system including a tubular conductive member having at least a pair of slots therein spaced about the periphery thereof, with the edges of said slots defining parallel planes passing centrally through said member, means to apply radio frequency energy to said member, said means including equal lengths of transmission line connected in parallel at the ends thereof, said lengths of transmission line being connected at the other ends thereof individually to said conductive member at the edges of said slots, conductors of said lengths of transmission line having ends connected together being connected individually at the opposite ends to the edges of said slots which are in the same one of said planes, thereby to produce a capacitive reactance component at the point of connection of said conductive member to said lengths of transmission line.

6. An antenna system including a tubular conductive member having at least a pair of slots therein spaced about the periphery thereof, with the edges of said slots defining substantially parallel planes passing through, said member, means to apply radio-frequency energy to said member, said means including equal lengths of transmission line connected in parallel at the ends thereof, said lengths of transmission line being connected at the other ends thereof individually to said conductive member at the edges of said slots, conductors of said lengths of transmission line having ends connected together being connected individually at the opposite ends to the edges of said slots which are in the same one of said planes.

'7. Anantenna system including a tubular conductive member having at least a pair of slots therein spaced about the periphery thereof, with the edges of. said slots defining substantially parallel planes passing throughsaid member, means to, apply radio-frequency energy to said member, said means including, a lengthof coaxialtrans mission line havingcenter and sheath, conductors, the endsof said conductors being connected at the opposite ends thereof to theuedgesof said slots which are in. the same one of; said planes, and meansto couple utilization apparatus at the midpoint of said. length of coaxial transmission line.

8; An antenna system, including a conductive surface element having atleast four elongated slots arranged in. parallel, relationship therein, the edges of said slotsina given direction, transverse tothe longitudinal axis of the slots being designated 'A, a, B, b, C; c, D, d in the order named, edges A and a being apposing edges of one slot and edges B and I) being apposing edges ofv another slot, means to apply radio-frequency energy tosaid element, said means. comprising radio-frequency transmission. line structure applying instantaneous in-phase potentials ofgiven polarity. simultaneously to edges A and. c and. of. polarity. opposite to said given polarity simultaneously. to edges a and C, whereby substantial zero potential exists across edges Band D and across edges D; and cl.

9. An antenna system including a conductive tubular member having a plurality of pairs of complementary slots arrangedabout the periphery thereof in substantially. parallel relationship therein, the edges of. the complementary slots defining non-intersecting substantially. plane surfaces passing through said member, means to apply radio-f-requency energy across eachof said slots to render the edges of complementary slots lying in one of said planes of: oneinstantaneous polarity and the edges of said complementary slots lying in the other of said. planes. of in,- stantaneous polarity-opposite to saidone polarity whereby instantaneous currents induced by complementary slotsfiow in opposingdirections about the periphery of said. conductive tubular. member.

10. An antenna system including a. tubular conductive radiator structure having an. even number of slots arranged longitudinally, therein, slots located substantially on opposite sides of said structure complementing each other, the longitudinal edges of, said complementary slots defining substantially parallel plane surfaces passing through said structure, and means to apply radio-frequency wave energy across said complementary slots, both of the edges of each pair of complementary slots lying in the same one of said plane surfaces-being energized in the same phase relationship.

11. An antenna system including a, radiator section comprising a hollow cylindrical member having four elongated slots substantially longitudinall arranged and equally spaced about the periphery thereof, opposing ones of said slots being coupled in pairs, the longitudinal edges of each of said pairs of slots defining a pair of substantially parallel plane surfaces passing through said member, means to apply radio-frequency energy in the same phase to each of said slots in each of said coupled pairs of slots with the edges of said pairs of slots lying in the same one of said surfaces having the same instantaneous polarity, and means to apply radio frequency energy to said coupled pairs of slots in phase quadrature to radiate a radio frequency wave having a circular horizontal pattern.

12. An antenna system including a stack of radiator sections each comprising a hollow cylindrical member having four elongated slots substantially longitudinally arranged and equally spaced about the periphery thereof, opposingones of said slots being coupled in pairs, the longitudinal edges of each of said pairs of slots defining a pair of substantially parallel plane surfaces passing through said member, means to apply radio-frequency energy in the same phase to each of said slots in each of said coupled pairs of slots of each stack of slots with the edges of said pairs of slots lying in the same one of said surfaces having the same instantaneous polarity, and means to apply radio-frequency energy to said coupled pairs of stacked slots in phase quadrature to radiate a radio-frequency wave having a circular horizontal pattern and a directive vertical pattern.

13. An antenna system including a hollow conductive tubular member having at least two slots arranged therein, opposing edges of said slots defining a pair of substantially parallel plane surfaces passing through said member, means to apply radio frequency energy across the apposing edges of one of said slots, and means. interconnecting the opposing edges of said slots to apply said radio frequency energy to the other of said slots with the edges of said slots lying in the same one of said defined planes being excited in the same instantaneous polarity.

14. An antenna system comprising a tubular conductive supporting member having two complementary pairs of elongated slots arranged longitudinally therein, the slotsof each of said pairs being in substantially exact alignment across the interior of said tubular supporting member, each pair of said slots being coupled by radio frequency transmission lines. to apply radio frequency energy thereto with a longitudinal edge of one slot of each pair of slots at the same instantaneous polarity as the opposing longitudinal edge of theother slot of said pair of slots, thereby to cause instantaneous radio frequency currents to, flow in opposing directions about the periphery of said member, means to apply radio frequency energy to radio frequency, transmission lines coupling one pair of slots, means to apply additional radio frequency energy in phase quadrature to the first named, energy to radio frequency, transmission lines coupling the other pair of slots to produce rotating vector radiation of uniform intensity in the plane transverse to the longitudinal axis of said member meanS to apply further radio. frequency energy to radio frequency transmission lines. coupling both, of said pairs of slotstoproduce a pulse, of radiated energy of uniform intensity. in saidv plane, whereby. the direction of radiation with respect to said member is proportional to the phase angle between said rotating vector radiation and. said pulsed radiation with respect to the angle of said rotating vector radiation at which said pulse is emitted.

15. An antenna system comprising a tubular conductive supporting member having two complementary pairs of elongated slots arranged longitudinally therein, the slots of each of said pairs being in substantially exact alignment across the interior of said tubular supporting member, each pair of said slots being coupled by radio frequency transmission lines to apply radio frequency energy thereto with a longitudinal edge of one slot of each pair of slots at the same instantaneous polarity as the opposing longitudinal edge of the other slot of said pair of slots, thereby to cause instantaneous radio frequency currents to flow in opposing directions about the periphery of said member, means to apply radio frequency energy corresponding to a first pair of sidebands of a modulated radio frequency carrier wave to radio frequency transmission lines coupling one pair of slots, means to apply additional radio frequency energy corresponding to a second pair of sidebands of said modulated carrier wave to radio frequency transmission lines coupling the other pair of slots, and means to apply radio frequency energy corresponding to said carrier wave to radio frequency transmission lines coupling both of said pairs of slots.

16. An antenna system comprising a tubular conductive member having at least a pair of elongated slots arranged in the walls thereof, the midpoints of the corresponding edges of said slots being substantially diametrically opposed, and means to couple a source of radio frequency energy across the edges of both slots of said pair of slots, one edge of one of the slots of said pair and the edge of the other slot opposing the one edge of said one slot being excited in the same instantaneous polarity and phase, and the remaining edges of the slots being simultaneously excited in the opposite instantaneous polarity and phase.

17. An antenna system comprising a tubular conductive member having at least a pair of elongated slots arranged in the walls thereof, the midpoints of the corresponding edges of said slots being substantially diametrically opposed, and

means to couple the conductors of a transmission line across the edges of both slots of said pair of slots, one conductor of said transmission line being coupled to one edge of one of the slots of said pair, another conductor of said transmission line being coupled to the other edge of said one slot and to the edge of the other slot corresponding to the one edge of said one slot, and the remaining edge of the other slot being coupled to said one conductor of said transmission line.

18. An antenna system comprising a hollow conductive member having at least a pair of elongated slots arranged in the walls thereof with the longitudinal edges thereof substantially parallel to each other and the longitudinal axis of said hollow conductive member, the corresponding edges of said slots appearing in the same relative position in a traverse about the periphery of said member in a single direction, means to apply radio frequency energy across apposing edges of said slots, and means to couple the non-corresponding edges of both slots of said pair of slots together.

19. An antenna system comprising a tubular conductive member having at least a pair of elongated slots arranged in the walls thereof with the longitudinal axes thereof substantially parallel to each other and the longitudinal axis of said tubular conductive member, the corresponding edges of said slots being substantially diametrically opposed, and means to couple the conductors of a transmission line across the edges of both slots of said pair of slots, one conductor of said transmission line being coupled to one edge of one of the slots of said pair, another conduetor of said transmission line being coupled to the other edge of said one slot and to the edge of the other slot corresponding to the one edge of said one slot, and the remaining edge of the other slot being coupled to said one conductor of said transmission line.

20. An antenna system comprising a tubular conductive member having at least a pair of elongated slots arranged in the walls therewith with the longitudinal axes thereof substantiall parallel to the longitudinal axis of said tubular conductive member, the corresponding edges of said slots being substantially diametrically opposed, means to apply radio frequency energy across apposing edges of both slots of said pair of slots, a first conductor connecting one edge of one of the slots with the opposing edge of the other slot of said pair, a second conductor connecting the other edge of said one slot to the other edge of the other slot.

21. An antenna system comprising a tubular conductive member having at least a pair of elongated slots arranged in the walls therewith with the longitudinal axes thereof substantially parallel to the longitudinal axis of said tubular conductive member, the corresponding edges of said slots being substantially diametrically opposed, and means to couple the conductors of a transmission line across the edges of both slots of said pair of slots, one conductor of said transmission line being coupled to one edge of one of the slots of said pair, another conductor of said transmission line being coupled to the other edge of said one slot and to the edge of the other slot corresponding to the one edge of said one slot, and the remaining edge of the other slot being coupled to said one conductor of said transmission line,

22. An antenna system comprising a tubular conductor having two pairs of elongated slots arranged therein longitudinally of the axis of said tubular conductor, the corresponding edges of each pair of slots being diametrically opposite, means to apply radio frequency energy across apposing edges of each of the slots of one of said pairs of slots with opposing edges of the slots of each of said pair being excited the same instantaneous polarity thereby to cause instantaneous radio frequency currents to flow in opposing directions about said conductor and to produce substantially zero potential corresponding to said radio frequency energy across the remaining slots, and means to apply additional radio frequency energy across apposing edges of the other pair of slots in the same polarity and phase relationship as in said one pair of slots thereby to cause instantaneous radio frequency currents corresponding to said additional radio frequency energy to flow in opposing directions about the periphery of said conductor and to produce substantially zero potential across the first of said slots.

23. An antenna system comprising a tubular conductor having two pairs of elongated slots arranged therein longitudinally of the axis of said tubular conductor, the corresponding edges 15 ofv eachpair of slots; being substantiallydiametrrically opposed;.means to apply radiofrequency energy across two apposing edges. of slots with opposing edges of said two slots excited in. the.

same instantaneous polarity thereby to cause instantaneous radio frequency currents; to: fiowin opposing directions about saidconductor and.

to produce substantially zero potential corresponding to said radio frequency-energy across. theremaining slots, and" means to apply addi. tionalradio. frequency energy in phase quadrature with said first namedenergy acrossapposing edges of the other pair of. slots in the: same. polarity and phase. relationship as: in: the-first. named slots thereby to cause. instantaneous radio frequency currents. corresponding; to said additional radio frequency energy to flow in opposing directions about the. periphery of, said conductor and to produce substantially zero potential across the first of said slots, wherebysaid instantaneous radio frequency currents are combined to produce omni-directional radiation aboutsaid conductor;

24'. An. antenna. system comprising a tubularconductor having two pairs ofslots arranged therein longitudinally of'the longitudinal axis of said conductor, the corresponding edges of each pair of slotsbeing substantially diametrically opposed, means to apply radio frequency energy across apposing edges ofone pair of slots, opposing edges of said one pair of slots being excited in the same instantaneous polarity, thereby to cause instantaneousradi'o frequency currents to flow in opposing directions about said conductors and to produce substantially Zero; potential corresponding to saidzradio. frequency energy across theremaining slots, means to apply additional radio frequency energy in phase quadrature to said first named energy across apposing edges of the other pair of slots in the same instantaneous polarity and phase relationship as. for said one pair of slots thereby to cause instantaneous radio frequency currents corresponding to said additional radio frequency energy to flow in opposing direotions about the periphery ofsaid con.- ductor and to produce substantially zero potential across the first named slots to produce. rotating vector radiation of uniform intensity in. the plane normal to the longitudinal. axis. of said conductor.

25. An antenna system comprisin a tubular conductive member. having a plurality of 'pairs of i6 longitudinal complementary slots. arranged about the: periphery thereof, opposing edges. of each pair of complementary slots defining. a pair of non-intersecting planes passing through said member, the planes-of one pair of complementary slots intersecting similar planesv of other pairsof complementary slots within said member, andmeansto apply the. same radio-frequen-- cy energy across both complementary slotsof said one pair. with the edges. comprising thenonintersecting planes? excited in the same instantaneous'polarity thereby tdproduce substantially zero. potential difference across apposingedges. of the, remaining pairs of slots due tocurrents. induced around said member by said. applicationof radio frequency energy; to said one pair of slots.

26..An antenna. system= comprising a conductive tubular member: having a plurality of pairs of longitudinal slots arranged about the periphery thereof, the slots of eachpair being located on substantially oppositesides. of said member, means to apply radio frequency energy across. apposing edges of one slot. of: one pair of slots. to induce instantaneous currents in one direction about the periphery of said member, and means to apply the'same radio frequency energy across. apposing, edges of the'other slot. of said onepair of slots with opposite instantaneous polarity about the periphery" thereby to induce instantaneous currents in. the opposite: directionabout the. periphery of said-member.-

GEORGELH. BROWN.

References Gited in the file. of. this patent UNITED STATES PATENTS OTHER- REFERENCES.

Electronics, Jordan and Miller; February 1947-, pages 9'0'to 93;

Radio, July 1946; pages-14 and 15.

F. M. & Television, September 1946; pages45 to Electronics; September 1948'; pages 103- to 107.

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