US2631237A - Antenna - Google Patents

Description

March 10, 1953 w. SICHAK EI'AL ANTENNA Filed May 8, 1948 NVENTORS W/Z L/AM SKI/AK 5/14 VA7ZW MIL 4220 Patented Mar. 10, 1953 UNITED STATES ATENT OFFICE ANTENNA.

Application May 8, 1948, Serial No. 25,916

10 Claims. 1. This invention relates to antennas, and more particularly it relates to. antenna for producing or responding to circularlypolarized waves.

A principal object of the invention is to pro- 1 vide a high-gain omni-directional circularly polarized antenna which is particularly suitable for any system operating atv a very high frequency,

' for example one hundred megacycles or more.

Another object is to provide acircularly polarized antenna comprised of a horizontal loop por- 1 tion for producing horizontally polarized electric T field components and integral vertical radiators for producing vertically polarized components, the horizontal and vertical elements being especially designed to. form a rigid structural assembly'and having special means for producinga predetermined phase shift between the horizontaland vertical electric field components.

Another object is to provide an antenna array consisting of a stacked-up series of antenna units, each unitcomprising a horizontal loop currentelement. and a series of vertical dipoles, the several units being spaced from each. other and provided with intervening metal discs, two for each unit, to control the phase relation between the horizontal and vertical components of the electric fields from each uni A; feature or the invention. rela esto a h sain cra -dir ctional andheir u arlv po ar d antennawhi h comprises a s ries o sim lar su- 1' n rposed; units each: c nsistin of s of rad al-1 :tion elem nts o produ e. a 10 9- c rent with h rizental polarization andeach unit-having a plural tr of. tub elemen or d pol rr n d sy metrically with respect to the vertical axis of the antenna. Each antenna unit is located between a pair of conductive discs which establish a ninety-degree phase difference between the horizontal and vertical. electric field components.

tion between the two field compo ents. here. is

located between each unit a circular conducting plate, the diameters of the plates being chosen so that they act as th equivalent of radial, or annular wave transmission linesfor decreasing the velocity of the horizontal electric field coinponents, but without substantially. delaying, the vertical electric field components.-

A further featurerelates to a circularly polarized antenna comprised of a: series of superposed horizontal units supported from a common central mast which may take the form of a QOraXiaI transmission line. Rigidly and integrally. jastened to the outer conductor of thisline, at spaced intervals longitudinally of the line, are a series of horizontal dipoles arranged'to fprrn a substantially continuous radiationv loop, each horizontal dipole also having rigidly attached .to it a vertical dipole. Also rigidly attached to. said outer conductor are a series of large diam-filler metal plates, each of said. antenna unitsbeill .10-

- cated between a; correspondin pair. of-said plates,

which plates form the equivalentofa wave transmission line for producing a predeterminedphase delay in the horizontal electric field. components from the loops.

A further feature relates to a simplified and ru d h ha a t na or. rcu ar or llip cal polarized waves; The above mentioned and other features, and objects of; this invention; and the manner. or. attaining them will become more, apparent and the invention; itself will be. best understood, by. reierence to the following description.of-anemhodiment of the invention taken in conjunction with the accompanyin drawings, w er in: Fig. l is an elevational view of an antenna array according to the invention. i I

Fig. 2- is a; perspective view of one of -th .horizontal radiation current loop units. I

Fig. 3 is a sectional: view of F l. akenialon the line 3-..-3 thereof, and viewed in the direction of the arrows.

Fig. 4 is another sectional view of liig. 1; teen along the 111134??? thereof, and viewed in; the direction of the arrows.

It has been known heretofore that the combination of a loop antenna: currentv and dipole antenna current in mutually concentric relation,

can bearran ged to produce a circular-Jorelliptical polarization of the radiated waves. 'A circular y polarized wave may be considered as the resultant of a vertically polarized wave imposed on a horizontally polarized wave both waves travelling in the same direction. The circular polarization is obtained when the fields of the two waves are in time quadrature relation with respect to each other. In other words, at any given instant of time, the resultant field intensity vector of the vertically and horizontally polarized waves is constant in magnitude and rotates in the plane of the wave travel at synchronous speed. While, theoretically, the simplest form that such a circularly polarized antenna can take, consists of a simple horizontally disposed circular radiator 01' loop, and a concentric vertical radiator or dipole, it is not always feasible to obtain the desired circular polarization because of the necessity of rigidly supporting the loop and vertical dipole in fixed concentric relation. This problem is particularly difi'lcult where an array of such units are to be supported from a common mast. thermore, when the antenna is to be used at very high frequencies, for example one hundred megacycles or more, the supporting mast must be metallic. ously afiect the phase of the resultant vertically This formof metallic mast may seripolarized radiation. In accordance with the present invention, the above-noted difiiculties are overcome by providing an array of stacked-up units each consisting of horizontal loop sections and vertical dipoles which are rigidly attached to a common central tubular metal mast. In order to insure the required ninety-degree relation between the vertical, and horizontal electric field components from each stacked unit, each unit is provided, with a pair of large diameter metal discs or plates, so that in efiect each unit is located at the central region between the spaced discs. These discs are proportioned in diameter and vertical spacing with respect to the operating frequency of the antenna, so as to produce a ninety-degree delay in the horizontal electric field components, without substantially delaying the cooperating vertical electric field components.

.Thus there is shown in Fig. 1, a high-gain circularly polarized antenna comprising three stacked-up units I, 2, 3. Since these units are preferably structurally identical, only the con- .struction of unit I will be described herein. QEach unit comprises a horizontal loop radiating r section, one of which is shown in perspective in Fig. 2. It may comprise, for example, a central metallic hub 4 having rigidly and integrally fastened thereto a series of horizontal dipole elements 5a5b. 6a-6b, 1a1b. If desired, the elements 5a to lb can be cast as an integral unit with the hub portion 4 and with their respective radial supporting spokes sa- -tlb, err-9b, Itch-19b and preferably so that the elements 5a to 'lb'form a substantially complete circle except for the gaps ll, l2, l3, l4, l5, 6. The element 5a, 6a and 1a have threaded therethrough respective bolts l1,

l8, I 9, which extend radially inward to a common central point within the hub 4. The hub 4 is provided with cut-out sections 20, 2|, 22, through which the respective bolts pass so as to be out of direct contact with the said hub 4.. The bolts l1, l8, I9, serve as excitation connectors for connecting the respective dipole elements to a common central feed conductor 23 which passes concentrically with respect to the hub 4.

Each of the horizontal dipole elements has integrally attached thereto and extending perpendicular therefrom a pair of vertical dipole elements 240-2), 25a,25b, 26a26b, 2'|a21b,

Fur-

28a-28b, 29a, 2911. These vertical dipole elements can be mounted in any desired positions around the center of the antenna system, providing they are symmetrically located and equally spaced around the antenna axis. Preferably, each of the dipole elements has a length equal to one-half wavelength of the mean operating frequency of the antenna.

Each of the foregoing described units is attached by suitable fastening bolts (not shown) to a central hollow metal mast or pedestal 29 of substantially the same external diameter as the internal diameter of hub 4. The member 29 may form the outer conductor or pipe of a coaxial wave transmission line, the center conductor 23 of which extends upwardly through the units I, 2 and 3, and can either be conductively connected to the respective bolts l1, I'B, l9, of

- therefore, each pair of discs is equally spaced above and below the corresponding l-oop elements 5a to 1b of each unit. The vertical spacing between successive discs on member 29 and their spacing with respect to the associated antenna unit and the disc diameter, will be determined by the operating frequency of the antenna. Thus each pair of discs'acts as the equivalent of a radial wave transmission line of the wave guide type for the radiation from the antennaunit located therebetween. In accordance with wellknown theory of wave transmission through wave guides, the horizontal component of the electric field from each antenna unit is equivalent to the case of transmission of the fundamental TE mode of vibration through an equivalent rectangular wave guide having a width equal to the spacing between the pairs of discs. Consequently, the diameters of the discs and the spac-- ings between each pair of discs can be chosen so that the vertical electric field component and the horizontal electric field component from each of the units l, 2, 3, are at ninety-degree phase difference. By suitable adjustment of the relative impedances of the horizontal antenna loops and the associated vertical dipoles, they can be excited with equal magnitude currents, so that the resultant radiation from each unit has a circular polarization. In other words, each'pair of conductor discs decreases the velocity of the horizontal component of the electric field as it travels outwardly from the associated antenna unit but without substantially increasing the velocity of the vertical component of the electric field. In order to make sure that the excitation currents in the vertical dipole elements and the horizontal loop element of each unit are equal, the several dipole elements are chosen of suitable length and cross-section andrespective spacings around the associated horizontal, loopelement, as is wellknown in the art.

While one particular form of. horizontal loop element is shown for each of the antenna units, it will be understood that any other well-known form may be employed for producing the hori-- zontal loop current, such for example as disclosed in application Serial Number 574,879, filed Januagate-ps7 cry a, 1945. Furthermore, while the drawing shows an antenna consisting 'ofan array ortnree units, it will be "understood that a greater or less number of units may be employed. Likewise,

while each horizontal loop unitis shown as conor sucn'sets maybe employed, roviding the necessary substantially complete circular loo current is setup. Preferably; although not necessarily, each of the antenna units is surrounded by a cylindrical member 39 of a material which is transparent to the electric; and

*c'lucing'horizontal current loops comprising "a series of horizontal di ole elements, and "means connecting-the central conductor and the pipe conductor or said transmission line respectively to the elements of said horizontal dipoles.

'5. An antenna system-tor circularly polarized energy, comprising a-series of antenna units each composed of a'plurality iof radiant-acting membersforming a substantiallysymmetrical closed magnetic fields of the associated antenna" ole;

ments jiln other words, the members 39 act ;as weather. housings for the various antenna elements without having any effect on the electric and magnetic fields of the associated antenna unit.

of our invention in connection with specific'rapparatus, it is to be clearly understood that this description is made only by way of example and not as a limitation to the scope of our invention.

What is claimed is:

1. An antenna for producing substantially circularly polarized waves, comprising a plurality of coplanar antenna elements to set up electric waves polarized in said plane, other antenna elements perpendicular to and cooperating with said first antenna elements to set up electric waves polarized in a plane perpendicular to said given plane, and a pair of metal plates mid-way between which said elements are all located mounted parallel to said plane to provide essentially an effective wave guide section, and ex tending about said antenna elements foria dis tance relative to the operating wave length to produce a time quadrature phase relation between the electric fields of the waves from said elements.

2. A substantially circularly polarized antenna comprising a series of horizontal radiating elements forming an interrupted loop antenna, a conductive supporting pedestal for said antenna and substantially coaxial therewith, at leastone vertically-extending antenna element being supported on said loop antenna, and a pair of metal discs mounted parallel to the plane of said loop antenna, mid-way between which the antenna is located mounted parallel to said'plane to provide essentially an efiective wav-ef guide section, and extending about said antenna elements for a distance relative to the operating wave: length to produce a time quadrature phase relation between the electric fields fromlsaid loop and itsassociated vertical antenna element; v

3. An antenna system according to claim 2, in which said pedestal constitutes the outer conductor of a coaxial wave transmission line and said antenna and said discs are rigidly supported from said-conductor and located symmetrically therearound.

4. A composite antenna comprising a plurality of spaced antenna units each unit including horizontal antenna elements, said elements being positioned to form substantially a closed loop, a plurality of vertical dipole elementsconnected respectively to said units and symmetrically located around the loop axis, a pair of spaced metal discs mid-way between which said antenna units and said dipole elements are mounted, a coaxial wave transmission line having an outer pipe conductor, means to support all said units from said pipe conductor, said means for pro- While we have described above the principles,

radiation loop in a horizontallpl'ane, a. single conductive mast along which-all saidunits are structurally .fastened in spaced relation, a plurality of vertical radiator stubs respectively, attached to the saidradiant-acting "members of each unit, each unit being located mid-way between a pair of metal discs whose spacing and diameter have predetermined dimensions with respect to the mean operating frequency of the antenna to produce a predetermined time delay in the waves from said radiant acting members with respect to the waves from said stub elements.

6. An antenna system according to claim 5, in which said discs are spaced apart a predetermined distance and their diameter is related to the mean operating frequency of the antenna to delay the waves from said radiant-acting members substantially ninety degrees but without substantially delaying the waves from said stub elements.

7. An antenna for circularly polarized waves, comprising a plurality of horizontal dipole elements aligned along a common vertical axis, a plurality of vertical dipole elements carried by said horizontal elements, and a pair of spaced metal discs concentric with said horizontal dipole elements positioned an equal distance on opposite sides of said horizontal elements substantially parallel with said horizontal dipole elements and forming an annular-shaped wave guide whose dimensions are related to the mean operating frequency of the antenna for producing a time phase quadrature relation between the electric fields from the horizontal and vertical dipole elements.

8. An antenna for circularly polarized waves, comprising a central conductive supporting mast, a plurality of circular metal discs concentrically attached to said mast at spaced intervals therealong, an antenna unit located mid-way between each spaced pair of discs each unit comprising a series of antenna elements surrounding said mast in a horizontal plane and a series of antenna elements surrounding said mast and parallel to said mast, said discs being spaced apart and each having a diameterrelated to the mean operating frequency of the antenna to cause the electric fields of the waves from said horizontal and vertical elements to'be in time phase quadrature relation as they emerge from the region between the associated discs.

9. An antenna according to claim 8, in which a cylindrical housing is located between each successive pair of discs said housing including the corresponding antenna unit between said discs and being transparent to the radiations from said antenna units.

10.. An omni-directional circularly polarized antenna, comprising a plurality of antenna elements forming a circular configuration in a horizontal plane, a plurality of vertical dipoles supported by said elements symmetrically around the common vertical axis of said elements, a pair of metal members defining a radial wave guide mid-way between which said elements and dipoles are located ,for (mini-directional wave v transmission the dimensions of said wave guide 7 REFERENCES crrEn The following references are of record in the file of this patent:

UNITED STATES PATENTS Number I Name Date 2 2,289,856 Alford July 14, 1942 Number r 2,310,853

Nmriber .Na,me V..Date

Lindenblad Feb. 9, 1943 Carter Dec. 10, 1946 v Tiley' .2... Dec; 24, 1946 Marohand Sept. 2', 1947 Wheeler Mar. 30, 1928 Woodward June 29, 19 18 Gilbert Aug. 30,1949 Riblet Oct. 25, 1949 Jarvis Dec. 5; 1950 FOREIGN PATENTS Country Date Great Britain Nov.'29 1946

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