US2945231A - Communication antenna - Google Patents

Description

July 12, 1960 M. w. SCHELDORF COMMUNICATION ANTENNA Original Filed Sept. 15, 1955 2 Sheets-Sheet 1 @JZMW July 12, 1960 M. w SCHELDORF 2,945,231

comumcuxon ANTENNA I Original Filed Sept. 15, 1955 2 Sheets-Sheet 2 um ZOWc'Z MIDDLE THIRD #1957 UPPEK Til/K0 1705 T State Uite v This-invention relates to antennas and more specifical- 1y to a novel construction for the type of antenna employing a rigid self-supporting conducting structuresuch as a mast or tower as a radiating element thereof. This application is a continuation of application Serial No. 534,569, filed September 15, 1955, now abandoned.

In one type of antenna, designed for maximizing radiation normal to the antenna and minimizing radiation in the direction of extensionof the antenna, the signal is fed directly to the radiator, which has a lengthof a substantial number of half wavelengths-radiation from Ealternate half-wavelengths is i suppressed; jthus producing the desired concentration of'radiat-ion perpendicu lar to the antenna and eliminating the lobes'in the radia 'tion pattern in undesired directions whichare produced in the absence of such' suppressiong Radiation suppressors of high efiiciency for such purposesaredescribed' in the co-pendi'ng application offthe same inventor, Serial No. 545,662, filedlNovember 8, 1955, now abandoned, and in U. S. Patent 2,852,774. However, the particular form of suppressor therein illustrated is poorly suited for employment on large radiating elements such as vertical polygonal towers. It is accordinglyan objectof the present invention'to' provide an improved form of radiation suppressor capable of simple and economical construction and mounting for the suppression of radiationfrom particular portionsof radiating elements, particularly where such elements are of large cross-sectional dimensions, such as towers and large-diameter pipes and 'tubes and suppressed-radiation antennas employing such suppressors. 5 Where such a self-supporting vertical radiator is employed, it becomes necessary, 'inorder to maximize the desired horizontal radiation, tois olate the radiating por- 'tion oi the" antenna from the lowermost portionadjaoent theea rth or other support upon which the antenna rests. Well-known manner of accomplishing this is to incorporate-electrically insulating material as a portion 'of the structure, thus isolating theradi-atin'gand' suppoift portions atall frequencies. A simple'r; method, in airftennas designed forparticular fre'quenciies is to incorpothe lower end of the desired'jradiating portion, thus 'isolating the lower'or supportfportion for thefrequen cies which are of importance; "For: this purpose, the present inventionprovidesan improved form of the' radiation "choke described-"in co-pending application Serial No.

5451 6 63, filed November 8,1955, Patent No. 2,896,206

rigidity of. any single individu'almount' in-use Qfitthean tenna will seriously impair its performance. 'Such culties are eliminated: in the present-"snu'cture. by the etn-i p'loyrnent of spacersbetweenthesecomponentspthe spacers being. conductors extending parallel with the radiating. element and acting as radial extensions there of, the entireiassembly of'components' and spacers being strong in alignment with suitable intervening insulators and rigidly held at both ends. to provide a.stable:- and rigid assembly. In addition, in the embodiment of the invention to be illustrated, auxiliary mounts are provided along the length of the assembly of components and spacers, thus: assuring minimum effect of theloo'sening of any single mount on: the-overallstability oftheoriem tation. of the components In addition; the use of the spacers eliminates the necessity ofirrraking' elaborate measurements injtlieassembly of lthe components to the, radiating element andials'o offers thegfurther advantage that th eifective' crossesecti'onal dimensions of. the radiateienieut areinc1'eased,- thus widening thefrequency band of the antenna/' I ii "For more complete understanding of the manner of accomplishment of thesexobjects and advantages of the invention, and also ofiiurther objects' and advantages not-'yetdiseussed, reference is made to an embodiment of the invention illustrated in the attached drawing in which: N V t Figure I'is a schematic diagram of provided with the suppressor features of the present iiiventiong. 'f 'FigUICZ- is a perspective view of atypical antenna constructed' in accordance with the present invention, where- "in'th e mast is of triangular cross-section;

Figure 3' isa cross-sectional view as seen in the directionof the arrows along the line 3-3 of'Figure 2; 1 -Figure 4 is adetailed viewof one of the mounting and insulating support: members on" one legof the triangular mast; and

a ts "rate one or more suitable radiation chokestructuresfiat section I. l The restof the'lower'portion of" last "is isolated from those portions A through I by a choke Figure s i's a detailed view of the antenna sections ales}; one leg of the'mast-illustrated in Fi'gureZL' J 7 Referring to Figure 1, it will ben'oted thatthcre has been shown diagrammatically a mast structure 11, which ina' physical embodiment comprises a self-supporting "structure such as that illustrated in Figure 2. Such struc ture maybe triangularor square, and henceis herein-re- "ferred toasbeing polygonali-n cross-section. "Certain portionsof the antenna are arranged to radiate energy, fancl other portions are arranged to have radiations uppressed "therefrom. At thesection A the antennauaidilength long. The section B is to radiate energy, and are: Wise is one half wavelength long; The next succeeding section C is tenave radiation suppressed therefrom. of the next we sections D and His one qu-arter' length Iong.*-'1"-i1e'-section Dhas 'a' structuretforfradiasea similar 7 -t o one"-ha'if of section B, and adjaceiit to section D is the feed' portion E to which radiant energy "is supplied from a coaxial conductor "12. Immediately below the feed section B tliereiis a radiation section' l one-half wavelength long. The overall length of lie portions D, E and F equal toone wavelength, fBe} ZIow the section F is a section G, from which radiation" suppressed, followed by a radiation section 'H. 1D turn is followed by :a; suppressor section l andgaradia o ditions of; required use. Where, for example-, suppresan antenna array 7 ii -While-- a lparticular -arrangement of "radiation sections-and radiation suppressors. has been-shown in Fig- 1 1 is formed of .three :verticaltubular members or pipes 13,- 14 and 15- supported 'in suitable manner by crossbraces16 extendingbetween the? respective corner support ro'ds. Extending outwardly from each of the rods, such as 13, on a line bisecting the angle between two adjacent braces 16, is the structure or structures comprising the suppressed radiation array schematically shown in Figure- 1. For-convenient reference to the various portions,

the: same lettering A through K has been applied to Figure 2'. 9 -JI'he details of the structures'appearing at each of the I rods 13, 14, and 15 are more readily apparent from an examinationT'of Figures .4-and 5; In Figure 5 a corner rod support member'15 :has been illustrated and carries the various antenna andsuppressor sections and feedelese'ctioneAzis supported 'betweentwo'brackets .18 and 19 These insulating memberssupport a; rod structure 23 comprising 'a rod portion 24 extending between the insulators Hand 22 and joined to two one- quarter wave portions 25 and 26 held in position by a coupling insulator 27. Atthe ends of the rod 24 su'itable connector portions 28 sor sections and those extended ma'st sections which are .identical to those portions A. and B above described in ments A through], followed by a choke section K. The

, provided with a plurality of insulating members 21, 22. v

and .259 connect the rod 24 to. the portions 25. and 26,

. respectively. The details of the; insulator arrangement for, this sectionA are shown more clearly inthe enlarged view of Figure 4. Since it is desired to suppress the gadiation from that-portion of the mast A for a distance of one-half wavelength, the rod 24is substantially onehalf wavelength long. A simple rod of a length 24 is not sufficient to suppress the radiation, and hence the portions 25 and 26 are provided which have a mechanical length slightly less than a quarter wavelength long. Their efiect-ive wavelength relation, however, is substantially that of a quarter wavelength with respect to the rod 24 because'of'the interconnecting portions 28 and 29. Corresponding portions of the suppressor structures on the pipes 13, 14, and 15 are interconnected by rods 30 to form a cageconstruction eflr'ectively enclosing the mast radiator, only a portion of such interconnecting rods 30 being shown for simplicity of illustration.

The next succeeding section B carries an extended-mast surface member comprising a closed loop wire member 31 where the two portions comprising vertical wires 32 and 33 are arranged parallel the same distance apart as .the wire portions 24, 25 and 26 of the preceding suppressor section A. The wires 32 and '33 are connected at .their ends by portions 34 and 35 to form a complete loop.

At the mid-point a conductor 36 is connected to each of the wires 32 and 33 and to the mast member 15 by a clamp 37. From the details of Figure 4 it will-bejnoted that the upper and lower ends of each of the wires 32 and 33 are supported by direct metal contact with fastendetail.

The section D is an extended mast section a quarter wavelengthlong, formed of wire members or rods 41 and 42 connected to a conductor 43 clamped to the mast 15 by a clamp 44. It will be noted that the portion D corresponds to the upper half of the extended mast section 31 of section B. The next portion E, which is a quarter wavelength long, comprises the rods 41 and 42 and a connection 45 to the central conductor of the coaxial line 12. The central conductor of the coaxial line 12 at this point also branches out so as to be connected to the other corner portions E of the other two legs or tubular structural members 13 and 14 of the antenna tower. It will be noted that the bracket 46, which supports the conductive connection 45, is provided with insulator members 47 at its upper side so as to support the conductor 45 in insulated fashion. The bracket46 conductively connects the upper end of the extended mast portion Fto the tubular support member 15.

Below the extended mast surface member J there is located a choke 50 formed of a wire 51 one-half wavelength long connected by bridging portions 52 and 53 to quarter wavelength portions 54 and 55 held in position by a coupling insulator 56. The mid-point of the half-wavelength wire 51is conductively connected by a connector 57 attached toa clamp 58 surrounding the tubular member 15. It will be noted that-the configuration of the wires 51 through 55 has the general appearance of a folded dipole member. This member, because of the mid-point connection to the tower, serves as a choke to preclude the passage of any radiating currents below the extended mast section I, thus isolating the active portion of the antenna from the support portion.

;It will be noted that the vertically aligned interspersed elongated conductors and insulators form unitary assemblies of a length of a'plurality of wavelengths running parallel with the conducting radiating element, the various conductors having differing electrical connections to provide them with difiering effects upon radiation. All of such assemblies are substantially identical and are at substantially identical heights on the tower which in this case, constitutes the radiating conducting element.

Although a single embodiment of the invention has herein been illustrated and described, the application of the teachings of the invention to structures completely wavelength intervals along each vertical member, the reing clamps 37 and 38 of a bracket l 9' so that the wires 1 32 and 33 are conductively connected radially to the radiating element at intervals of at, most "one-quarter wavelength to constitute these wires electrically mere en- .largementsjof the radiating element, Connecting wire 35 at the bottom of the structure B is supported by an assembly in which the insulator portions and the clamps are inverted with respect'to the assembly at the top so to support in insulated fashion the next succeeding suppressor section C.

.i For convenience in understanding the invention, similar reference characters have been applied to those suppresmaining alternate half wavelength comprising radiating portions, each suppressor comprising a shield conductor spaced parallelto saidfvertical member and insulated therefrom, said shield conductor being-connected to two .one-quarter .wavelength shield conductors spaced parallel thereto, a choke isolating the remainder of said vertical member from those radiating and non-radiating portions, and a feed point intermediate saidnon-radiating portions.

2. An antenna comprising a supporting mast having a polygonal cross-section with a vertical conductive member at each corner of the polygon, said vertical members being interconnected at intervals by braces, a plurality. of half wavelength radiation suppressors located at alternate half wavelength intervals along each vertical member, the remaining alternate half wavelength inter- .vals comprising'radiating portions, each suppressor comprising a shieldconductor spaced parallel to said vertical member and insulatedtherefrom, said shield con- M) An Sillh antennanofnclaiml having :lth'e' radiating portions extended radially to the outer shield conductors of said suppressors.

4. The antenna of claim 3 wherein each radiating portion is provided with two parallel conductors connected at their ends and at the midpoints to said vertical mem-,

her, said conductors being aligned vertically with the shield conductors of adjacent suppressors.

5. An antenna radiation suppressor adapted to shield a half wavelength of an antenna conductor comprising a half wavelength shield conductor arranged parallel to said antenna conductor, a pair of one-quarter Wavelength shield conductors extending conductively from the ends of said half wavelength shield conductor toward the center thereof parallel thereto in the plane of said shield conductor and said antenna conductor, the adjacent ends of said quarter wavelength shield conductors producing a high impedance point at the center of said half wavelength shield conductor.

6. The antenna of claim 2 wherein said choke comprises a half wavelength conductor arranged parallel to said antenna conductor and connected at its midpoint to said antenna conductor, and a pair of one-quarter wavelength conductors extending from the ends of said half wavelength conductor toward the center thereof parallel thereto in the plane of said conductor and said antenna conductor.

7. An antenna comprising a polygonal conducting tower of a height of at least a plurality of wavelengths of a signal frequency, each corner having aifixed thereto and outwardly spaced therefrom vertically aligned interspersed elongated conductors and insulators forming a unitary linear assembly of a length of a plurality of wavelengths running parallel with the tower, the various conductors having differing electrical connections to provide them with differing efiects uponrradiation, all of such assemblies being substantially identical and being ments ofthe radiating =element and others of man a;

ductors ha ingaportions; thereof of at least one quarterj wavelength free ofradial connection tothe rigid element to" alter the radiation gpattern of thecelement.

1 0. antennacompris -ing ,an elongated rigid conducting element having an active portion adapted toradi ate signals f algivcn frequency. and a t-supportportion,"

and means for electricallyjisolating the support portion from the active portion for signals of such frequency i n eluding a radiation choke comprising at least three conductive members disposed symmetrically about the element and parallel therewith and each having a substantially half-wavelength portion spaced from and parallel with the element and substantially quarter-wavelength portions spaced from and parallel with the half-wavelength portion and having their outer ends conductively connected to the ends of the half-wavelength portion and the inner ends mutually insulated, the longitudinal center ofthe half-wavelength portion being conductively connected to the element.

11. An antenna adapted to radiate signals of a given frequency comprising an elongated rigid conducting element of a length of a plurality of wavelengths having on alternate half-wavelength portions thereof radiation suppr'essors each comprising at least three conductive members disposed symmetrically about the element and paralj lel therewith and insulated therefrom and each having a substantially half-wavelength portion outwardly spaced from and parallel with the element and substantially quarter-wavelength portions outwardly spaced from and parallel with the half-wavelength portion and having their outer ends conductively connected to the ends of the halfwavelength portion and their inner ends mutually insulated. a

12. An antenna adapted to radiate signals of a given frequency comprising an elongated rigid conducting eleat substantially identical heights on the tower, and means for feeding a signalwto be radiated to at least a portion of the tower.

.8. An antenna comprising a polygonal conducting tower of a height of a plurality of wavelengths of the signal frequency, said tower being formed of polygonally arranged conducting poles interconnected by conducting cross-braces, each pole having afiixed thereto and outwardly spaced therefrom vertically aligned interspersed elongated conductors and insulators forming a unitary linear assembly of a length of a plurality of wavelengths.

running parallel with the pole, the various conductors having differing electrical connections to the tower to provide them with diifering effects upon radiatiomall of such assemblies being substantially identical and being at substantially identical heights on the tower, and means for feeding a signal to be radiated to at least a portion of the tower.

9. An antenna comprising an elongated rigid conducting element of a length of a plurality of wavelengths having mounted thereon, and spaced therefrom, aligned alternated elongated conductors and insulators forming at least three substantially identical unitary linear assemblies of a length of at least a plurality of wavelengths running parallel with the rigid element and dispersed symmetrically therearound, some of said conductors having all portions thereof conductively connected radiall; to the radiating element atintervals of at most one-quarter wavelength to constitute electrically mere enlargement of a length of a plurality of wavelengths having on longitudinally spaced portions thereof radial extensions comprising at least'three conductive members of onehalf wavelength disposed symmetrically about the ele ment and parallel therewith and conductively connected to the element at their ends and their longitudinal midpoint, and a radiation suppressor conductor insulatedly supported by and between said radial extensions to suppress radiation from the corresponding portion of the element.

13. An antenna structure comprising an elongated con- ;ducting rigid radiating support and a plurality of folded conducting elements in mutually spaced relation along at leastla portionof the length of the radiating member and radially spaced therefrom,;thefolded elements each being conductors having an inner linear portion and an outer linear portion parallel to the inner portion, said portions being conductively'connected attheir ends and one of saidportions including a central insulator, and conducting spacer and support members insulatedly supporting thejelements', each spacer member having inner and outer linear portions aligned with the corresponding portions of the folded elements and having their ends insulatedly joined-to adjacent ends-of the corresponding portions of said folded elements, the inner and outer portions of each of the spacer members being conductively connected 'to each other and to the radiating support at intervals of at most one half the length of the parallel portions of the adjacent folded elements, the folded elements being held in said positions by the spacers, and the spacers being held in said positions by their conductive connections, so that the spacer members constitute part of the radiating support at the frequency, at which the adjacent folded members are of a half-wavelength.

14. A suppressed-radiation antenna comprising an elongated radiating conductor having therearound a plurality of longitudinally spaced radiation suppressors formin'gf" alternated radiating "and suppressed-radiation' segfn'en't's -;-'each electrically snbstantial ly a half-wavelength long; at least portions 'of thej--radiating segments of'the' conductor between the suppressorsfbeingof gTeater'Cross seetional dimension than the segments within the supp'r'essorsp 'QISf-The 'antenna of claim '14 wherein the cross-sectional dimension of said radiating segments is substan tially-equal to that of the suppressors.

16. The antenna of claim 14 wherein there are provided insulators connectingnds of the'po'rtions-of greater oross-seetionalfdimensionfand adjacent ends of the sup-'- presso'rs, each suppressor heing maintairiedin position by the insulators at eachend;

" RefereneesCited inth e file patent a 147,319 7 Sweden -;..'.L ..M. Oct. 19, 1954

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