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Publication numberUS3015821 A
Publication typeGrant
Publication dateJan 2, 1962
Filing dateJul 29, 1957
Priority dateJul 29, 1957
Publication numberUS 3015821 A, US 3015821A, US-A-3015821, US3015821 A, US3015821A
InventorsBogner Richard D
Original AssigneeAvien Inc
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
End fire element array
US 3015821 A
Abstract  available in
Images(3)
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Claims  available in
Description  (OCR text may contain errors)

Jan. 2, 1962 R. D. B OGNER END FIRE ELEMENT ARRAY 3 Sheets-Sheet 1 Filed July 29, 1957 END FIRE RADIATORS FIG.I

FIG. 2

'90 -75 -6O '45 -3O -l5 9 (ANGLE FROM BEAM PEAK IN DEGREES) INVENTOR.

RICHARD D. BOGNER AGENT Jan. 2, 1962 R. D. BOGNER 3,015,821

END FIRE ELEMENT ARRAY Filed July 29 195'? 3 Sheets-Sheet 2 FIG. 3

F I G. 6

FIG. 8

50 5| 52 53 L 5|, 5s 51 53 E mmvrox.

RICHARD 0. BOGNER BY prwmx AGENT Jan. 2, 1962 R. D. BOGNER 3, ,8

END FIRE ELEMENT ARRAY Filed July 29. 195'? 5 Sheets-Sheet 3 INVENTOR.

AGENT vRICHARD D.. BOGNER FIG. 5

L i i United States Patent ()1 3,015,821 END FIRE ELEMENT ARRAY Richard D. Bogner, Bethpage, N.Y., assignor to Avien, Inc., Woodside, N.Y., a corporation of New York Filed July 29, 1957, Ser. No. 674,926 9 Claims. (Cl. 343-453) This application is a continuation in part of my copending application entitled Antenna, Serial No. 631,869, now Patent No. 2,955,287, filed Dec. 31, 1956 and assigned to the assignee of this application. i

This invention relates to directional antennas.

In the design of directional antennas, the general considerations include as a goal the obtaining of high gain, narrow beam width and low side lobes. These desideratums are generally not achievedrin full because of practical considerations of weight, size or mechanical limita-, tions. An antenna design frequently requires compromise of both maximum desired side lobe level and maximum desired beamwidth at the half power level, in a given plane, for an antenna of a given maximum'physical size. In some applications, the designer mayberequired to accept a more moderate gain in order to achieve lower side lobe levels, or compromise all. Characteristics because of size considerations. I g

It .is often required in the design of antennas especially, for example, large rotating antennas, that the diameter of a circle which circumscribes the antenna in a plane normal to the rotation axis be minimized for a given radiationpattern, half power beamwidth and side lobe level in that plane. This plane is often the plane of largest antenna linear dimension and is usually the azimuth plane. Y

An antenna structure is described herein which. requires a smaller circumscribed diameter for a given half power beamwidth and side lobe level, than has previously been considered practical to obtain. t

I have discovered that by properly arranging a number of end fire elements inan array I can achieve an antenna pattern of narrower beamwidth consistent with a given side lobe level, in a smaller antenna diameter than was previously considered practicable. Briefly stated,- the antenna of this invention consists of an integral number of substantially identical end fire radiators arranged in an equally spaced array. The spacing between elements, the length of the elements, the number of elements and other critical dimensions-are so chosen in accordance with the procedure stated more fully hereinafter that for a given circumscribed diameter an antennaof surprisingly high gain, or surprisingly narrow beamwidth for agiven low side lobe level, is obtained in a compact structure. 1 i

There follows hereinafter a mathematical analysis of the antenna-which established a preferred range of con figurations providing optimum performance.

It is a general object of this invention to provide a high gain directional antenna having a narrow half power level beamwidth and low side lobe level in relation to the diameter of a circumscribed circle.

It is another object of this invention to provide a directional antenna of small height and breadth for a given value of antenna gain.

It is still a diiferent object to provide a high gain directional antenna of small weight.-

A further object of this invention is to provide a high gain directional antenna characterized by very low side lobe levels. a

A still different object of this invention is to provid an improved antenna of high performance characteristics susceptible of being embodied in a rigid mechanical structure.

3,015,821 Patented Jan. 2 1962 ice A further object is to provide an antenna capable of being simply and quickly assembled and disassembled by relatively unskilled personnel.

These and other objects, the nature of the present invention, its various features and advantages, will appear more fully upon consideration of the various specific illustrative embodiments shown in the accompanying drawings and of the following detailed description ofthese embodiments.

In the drawings:

FIGURE 1 shows in plan an antenna array of this invention. v

FIGURE 2 is a rectangular plot of a measured typical field strength pattern (in db) propagated by a four equally fed element antenna of this'invention which is four wavelengths in diameter in the plane of the array.

FIGURE 3 is a pictorial representation of a single element of an array of this invention wherein the element utilizes a flat supporting rod and rectangular wire mesh discs. The element is shown energized by a dipole launcher.

FIGURE 4 is a pictorial representation of a portion of an array of this invention utilizing a round support rod and round discs energized by a wave-guide launcher. FIGURE 5 is a general schematic showing in plan of a four element array of this invention employing a di-' pole launched cigar element.

FIGURE 6 shows in plan the projection in a vertical plane of the elements of a fourarray antenna.

FIGURES 7, 8 and 9 show in schematic form, the side, front and plan views respectively of another antenna array.

As employed hereinafter the term degrees refers to electrical degrees. The linear dimensions are stated as relative values throughout, relative either to one wavelength or to 360 electrical degrees (which is equivalent to one wave length) of the operating frequency. A length stated as 2 for example, means either two wave lengths or two (360) equal to 720 electrical degrees.

The structure consists of an n number of substantially identical end fire radiators 2a, 2b, 2c, etc., of length L and end width w, arranged in an equally spaced array and inscribed in a circle 4 of diameter d. The spacing between elements is s, and the distance from the center of the end radiator 2a to the furthest edge of the ground plane 6 is A. Since the width of the resulting radiation beam (FIGURE 2) is an inverse function of both the pro-duct ns, and the square root of the length L, this beam will be narrowest for given d when both L and ns are made as large as possible. The circumscribed circle of diameter d referred to is defined by four points, the outside corners of the end radiators 2a and 2e and the edges of the ground plane. There exists simple plane geometry relationship as shown ni FIGURE 1 which .may be expressed as a mathematical relationship between L, d, w, A, n and s (or between L and the product (n- -l)s for a fixed a, A, and w, the latter two values being small and relatively constant in a practical system), based on simple plane geometry relationships in conjunction with FIG-- URE 1 which relationship is A second and separate relationship can be set up between L and its if the required condition of low side lobes is to be met with the minimum diameter d. In general, it is desirable to maximize ns within the circle consistent with an L just large enough to give the side lobe level required, since L must be larger, in most cases, for a given element factor beamwidth, base length is defined as the distance between center lines of end elements and is- (n1)s for n elements than the base length (n-l)s for a given array factor beamwidth.

I-Equal amplitude feed embodiment For the casein which each of the elements of the array is fed with substantially the same amplitude of signal, side lobe levels of the entire antenna in the order of 22 to 26 dbbelow the beam peak level in the plane of interest can be obtained. For this situation, the required relationship between L and us can be determined from the fact that the shortest value of L giving rise to 2226 db side lobes has been found to occur when the angular displacement of the first element pattern null from the beam peak (6 is between 63% and 84% greater than the displacement of the first array factor null Adding to this the two known facts that (l) for close to optimally designed end fire elements, having 8-l3 db first (maximum) side lobes, 0 lies between 40 and 50 times the reciprocal of the square root of L, and that (2) the array factor null occurs at 180 divided by ns for ns 2 /2, the required range of L in terms of as can be found as follows:

Substituting (3) and (4) in (2) and solving for the maximum and minimum simultaneous extremes of (2) and (3):

1 2 emf S S 0 Equation 5 and the mathematical relationship previously described between L and (nl)s [Eq. 1] allow a mathematicaldetermination of a range of the number of elements, their spacing and length required to make optimum use of the area of the circle of diameter d. The values of w and A, as well as the exact function between the length L of the end fire element and the position of the first end fire element pattern null 0 must be known in any particular case for an exact solution; since it is desirable to have a mini-mum w and A, and since also the range of the optimum relationship between L and 0 is well known as described, however, the structure may in generalbe determined within narrow and defined limits.

Simultaneous solution of Eq. 1 and Eq. 5 over the range of the latter show that this antenna design provides adistinct advantage over conventional techniques in terms of obtainable beamwidth for 2226 db side lobe levels in a given diameter d. This advantage, however, is shown by the solutions to occur only in the range of d between 2 and 12 wavelengths, which requires a range of n between 2 and 16.

It was stated in my above referenced copending application that the element spacing was restricted to the range of 160 to 320 electrical degrees. The basis of the lower limit was, and still remains, high mutual coupling and physical size of the elements, which are around 120' degrees'wide. The basis of the upper limit of 320. degrees was creation of high side lobes at large angles off the beam peak due to both the array factor characteristic, and the fact that the element side lobes are usually high. The total pattern is the product of array and element factors. The array factor characteristic states that this factor reaches a maximum value (unity) at other angles in addition to 6:0, the normal to the array, when the spacing s becomes equal to or greater than 360 degrees. A high element side lobe level is especially evident for the case of horizontal polarization (the common radar and scatter propagation case). where the element pattern often has a high level out to the region of 90 degrees off the peak (0:90). In fact, this level often remains high after the first side lobe, and in the order of 16 db below the peak. An improvement of only about 6 db is realized at 90 degrees using a 320 degree element spacing, giving a 16+6=22 db product side lobe at 90 degrees. This side lobe level (22 db) was stated as being the maximum tolerable for the uniform amplitude case. (Even lower side lobe levels are necessary for the tapered amplitude case.) This 320 degree limitation is therefore completely safe and generally necessary.

It has been discovered, however, that if the element pattern does in special cases offer lower second and succeeding side lobe levels, the allowable maximum spacing can be made larger than 320 degrees with low product side lo-bes maintained. As shown previously, the largest possible spacing is the most desirable as regards meeting the objectives of maximum obtainable gain within a given swing circle and of minimum mutual coupling between and among elements.

Two slightly different cases of element pattern are disclosed hereinafter which may allow larger spacing.

in case I, the level of the element pattern never rises higher than 22 db below the peak level anywhere beyond the first side lobe. In this case a secondary (or higher order) array factor unity value can be allowed to occur (by virtue of element spacing equal to or greater than 360 degrees) at any angular position between 0:90 degrees and 6:0 (0 is defined as the angle between the beam peak,.or the array normal where 0:0, and the 22 db level on the side of the first element side lobe furthest from the beam peak.)

In case 11, the second element side lobe does rise above 22 db, but the third and succeeding side lobes are low. Here the array factor unity and the second side lobe peak cannot be allowed to be coincident, but a low product side lobe can still result if a second array factor unity occurs near the null between the first and second element side lobes. Because of the array factor and element factor side lobes are of the same order of angular width in this design, it is improbable that the produut side lobe level will rise above 22 db with the restrictions on element pattern stated for case II.

In both cases, therefore, the same criterion can be imposed to determine maximum allowable spacing: the sec ond array factor unity value cannot in general occur any closer to the beam peak than the angular position of the 22 db level on the side of the first element side lobe nearest the second element side lobe. For practical purposes, the position of the null between the first and second ele-.

1 ment side lobes can be used to replace the 22 db level,

since the angular separation between these 2 positions is extremely small.

It 'must be re-empha-sized before proceeding that this increased angular spacing is only tolerable if the element pattern displays thelow levels beyond the first side lobe described as necessary, simultaneous with the narrow first null-width with respect to length stated originally as a requisite for gain improvement using this technique. In general only the cigar and certain other retarded surface wave type end fire elements have been observed in certain cases to exhibit this combination of characteristics,

Use of spacings in the range 320 degrees to Sill-T 1/1 degrees is therefore restricted to embodiments employing the cigar end fire element in one of its various forms. The angle between the array normal and the second unity value of the array factor is H=arc sin[21r/S](Eq. 6) where s is the element spacing. This angle 0 is degrees at S=21r=360 degrees, and decreases toward 0:0 as S becomes larger. This angle 0 must be equated to the angle 0 referred to previously. It can be found empirically that 0 ==4fl where 0:13 was defined to be the angular position of the element half power level. Therefore, substituting:

where S is the maximum spacing in radians.

I However, t

, vi i -4r degrees as stated previously.

Therefore,

S =360/sin 9: degrees (8) Equation 8 defines the maximum allowable spacing S in degrees as a function of L, the element length in wavelengths. This spacing is 560 degrees for L=4, and 431 degrees for L=2, for example. 7

The increase in range of allowable spacing for this restricted type of element is therefore between [320] degrees and a 360 sin 7 lv ,Z degrees, whereas previously the range was {160] to [-3 degrees-- 3 Based on the foregoing relationships and experimental data, the following limitations have therefore been found critical; for-the case" of substantially-equal amplitudes (or 22-26 db side lobe levels):

1. sh lbe be we .x a m t sj'shall be between l60 and 320 electricaldegrees in'general, and between 160 and 360/ 80 .SlIl

" degi'ees'for elements falling in 'the general classnof (where L ands are in wavelengths). n shall be between 3 and 15 in number. A representative'set of solutions for d=4 (wavelengths),

are found from Eq. 1, 2, 3 and 4 to be:

and %(TLS)2 The values of d, 6 0 A and w chosen above are only representative of choices in the allowable ranges of these parameters, showing that a discrete solution for n, s and L is then possible. Small variations in the relationships between 0 and 0 and 0 and L, required in any case will cause small changes in the values of S and L for a given d and n.

II-Tapered amplitude feed embodiment in the limit. Forany particular side lobe level desired,

L between Vs (ns) and /2 (ns) I I s shall be between 160 and 320 electrical degrees in general, and between 80 and 360 SlIl de rees g for elements falling in the general class of cigars. n between 3 and 18 d between 2k and 15 Suitable end fire radiators include in general helices, dielectric rods such as polyrods and ferrods and cigars,

except for therange of s above 320 degrees, where only cigars have been found suitable.

' .The cigar class of elements as shown illFIGURES- 3," 4 and 5 are preferred for linearly polarized radiation for any spacing. Experimentally, it 'has' been-found that the cigar-type elements alone allow metallic support along their lengths in the'fo'rm of thin rods normal to the prin-- cipal polarization electric vector; eliminating the need forv long cantilevered structures and providing extremely rigid mechanical structures. Further, such an all metallic structure has been found lower in loss than structures in-f volving use of dielectrics. The cigars, therefore, provide a distinct and incontrovertible advantage .both'in gain, weight and mechanical rigidity. r

' A typical structure is shown in FIGURE 4 wherein the cigar elements may consist of a cylindrical rod 29 and mounted thereon a plurality of discs 22. The discs 22 are spaced approximately /s)\' to /2 apart and are approximately Mm to /2k in diameter. When the radiator of length L (L is expressed in wavelengths of operating frequency) is energized by a launcher such as a wave-- guide cavity 24, the electrical length L is measured from the feed 28 to the effective end (the end disc 46). A minor protrusion of rod 20 may be disregarded.

In FIGURE 5 there is shown schematically a similar cigar element array fed by means of a dipole. In this instance the length L is measured from the dipole ele ment 26 to the effective end (disc 48). a

The structure is adapted to extremely simple and rigid mechanical construction. Pedestal 30 which may be of a rotating type supports the antenna by means of arms 32, 34, and 36. Beam 35, in turn, supports the other cigar elements by means of a similar arm arrangement.

The transmission line structure used to feed the elements may consist of a series of bilateral or other parallel splits, a series feed arrangement, or any other which provides the required amplitude, phase, and impedance with adequate decoupling.

The various elements or radiators 2a, 2b etc., shall be fed substantially in phase. The end elements may in certain cases be modified slightly from the other elements to reduce the diameter d, such a small alteration in certain cases not appreciably disturbing the performance.

Septa, chokes, or metal plates may in some cases be placed around or between the bases of the elements to reduce or alter mutual coupling effects.

Typical uses for the antenna include object location, communication, scatter propagation, and object detection.

The array of this invention may be stacked in multiple to provide a battery of such arrays providing a desired pattern in the vertical plane, controlled by the relative pointing, phase or amplitude of the banks.

The ground plane 61 may be solid metal or may be in the form of an expanded wire mesh or screen in order to reduce weight. Likewise as shown in FIGURE 3 the discs may be formed of wire mesh.

FIGURE 3 shows a dipole 62 feeding rectangular discs 63 formed of wire mesh. The support is a flat member 65 rather than a rod.

While I have chosen to show a balanced feed dipole structure in FIGURE 3 fed by balanced input line 64, it is to be understood that a conventional unbalanced feed utilizing a balun may be employed.

It is not intended to imply that Support rod need be of metal: It may be of a dielectric material such as glass fiber impregnated with epoxy resin. The discs may consist of solid metal, or wire mesh, or simple rods, and may be of any shape symmetrical about a plane normal to the plane of interest and containing the axis of the metal rod. The spacing between discs will be between /s)\ and /2)\, and the disc width in the plane of interest also between /s7\ and VA.

FIGURE 6 shows in plan the projection in a vertical plane of the elements of a four array antenna.

A typical antenna consisting of four arrays, 40, 41, 42, and 43 is shown in FIGURE 6. The number of elements in all arrays need not be identical but may be varied to shape the resulting pattern. In general, the beamwidth of each array should be approximately the same.

There is shown in FIGURES 7, 8, and 9 respectively, in schematic form, the side, front, and plan view of an antenna array in which the radiating elements .50 and 52 are tilted with respect to elements 51 and 53. In embodiments employing tilted elements it is important that the measurements of element length and spacing be that of the projection of the element onto the plane common to the elements.

What I claim is:

1. A high gain antenna for transmission of energy of wavelength x comprising a plurality of retarded surface wave end fire elements, each of said elements being composed of a plurality of discrete metallic members, each said member being greater than M4 and less than M2 in major dimension, each said member being symmetrical about a plane containing an axis common to said members, said members being spaced between M8 and M2 apart along said axis, said axis being aligned in the direction of propagation of said element to form an elongated radiator fitting within a circumscribing cylinder coaxial withsaid axis, said cylinder having a diameter which is greater than M4 and less than M2, said elements being arranged so that their projections onto a common plane are parallel; a launcher arranged symmetrically about said axis for propagation of energy along said axis and means for feeding said launchers in common phase, said elements being spaced at least electrical degrees apart 3. The antenna of claim 1 wherein said elements are.

equally spaced.

4. The antenna of claim 1 wherein said discrete metallic members are uniformly spaced along said common axis.

5'. A high gain antenna for transmission of energy of wavelength x, comprising a plurality of retarded surface wave end fire elements, each of said elements being composed of a plurality of discrete metallic members, each said member being greater than M4 and less than M2 in major dimension, each said memberbeing symmetrical about a plane containing an axis common to said members, said members being spaced between M8 and M2 apart along said axis, said axis being aligned in the direction of propagation of said element to form an elongated radiator fitting within a circumscribing cylinder coaxial with said axis, said cylinder having a diameter which is greater than M4 and less than M2, said elements being arranged so that their projections onto a common plane are parallel; a launcher arranged symmetrically about said axis for propagation of energy along said axis and means for feeding said launchers in common phase; said elements being spaced between I to 1966 electrical d g sin VI sin References Cited in the file-of this patent UNITED STATES PATENTS 2,419,205 Feldman Apr. 22, 1947 2,556,046 Simpson June 5, 1951 2,588,610 Boothroyd et al Mar. 11, 1952 2,663,797 Koch Dec. 22, 1953 2,684,725 Kock July 27, 1954 2,820,221 Broussaud Jan. 14, 1958 FOREIGN PATENTS T8447 Germany Aug. 2, 1956 VIIIa/21a 732,827

Great Britain June 29, 1955 OTHER REFERENCES Kock and Harvey: A Photographic'Method for Displaying Sound Wave and Microwave Patterns, Wireless Engineer, August 1951, pages 564 to 587 (page 581' relied on).

Patent Citations
Cited PatentFiling datePublication dateApplicantTitle
US2419205 *Nov 4, 1942Apr 22, 1947Bell Telephone Labor IncDirective antenna system
US2556046 *Mar 28, 1946Jun 5, 1951Philco CorpDirectional antenna system
US2588610 *Jun 7, 1946Mar 11, 1952Philco CorpDirectional antenna system
US2663797 *May 5, 1949Dec 22, 1953Bell Telephone Labor IncDirective antenna
US2684725 *May 5, 1949Jul 27, 1954Bell Telephone Labor IncCompressional wave guide system
US2820221 *Sep 13, 1955Jan 14, 1958CsfDirectional aerials
*DE8447C Title not available
GB732827A * Title not available
Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US4514734 *Feb 23, 1983Apr 30, 1985Grumman Aerospace CorporationArray antenna system with low coupling elements
WO2014009697A1 *Jul 3, 2013Jan 16, 2014Antrum LtdAntennas
Classifications
U.S. Classification343/753, 343/817
International ClassificationH01Q19/18, H01Q21/06, H01Q19/10
Cooperative ClassificationH01Q21/06, H01Q19/18
European ClassificationH01Q19/18, H01Q21/06