US2416675A - Horn antenna system - Google Patents

Description

Mmh4,1947. .icack'ngp i 2,416,675

i HORN ANTENNA SYSTEM Ac. BECK WVEVTORS-H r FR//s 4 Arron/v5? March 4,1947. Aye, BECK'ETAL 2,416,675 'I HORN ANTENNA.y SYSTEM Filedl Nov. 2e, 19211` s .sheets-sheet 2 ATTORNEY Maich 4, 1947. A. c. BECK Em. 2,416,675

` Holm 'ANTENNA SYSTEM maur/c uw f DIRECT/01ML CHMCTI'RISTK Il PLNE a' LONG! TUD/NAL AXIS 'f' ELECTRIC PLANL ATTORNEY Patented Mar. 4, 1947 .www

A'hl-{()RN ANTENNA SYSTEM Alfred C. Beck, Red Bank, andy Harald T. Frlls, Rumson, N. J., asslgnors to Bell Telephone Laboratories, Incorporated, New York, N. Y., a

corporation of New York Application `November 26, 1941, Serial No. 420,454

This invention relates to antenna systems and more particularly to ultra-short wave and microwave horn antenna systems.

As is known, horn antennas for projecting or collecting radio energy in a fixed unidirection coinciding with the longitudinal horn axis, and horn antennas associated with deflectors for securing omnidirectional or non-directional `radio action in a plane perpendicular to the longitu-n dinal axis, have been suggested for use in the ultra-short wave (below meter wave-length) and the microwave (below 1 meter) elds. For example, United States Patents 2.206,923 and 2,369,808, both granted to G. C. Southworth, and British Patents 534,066 and 534,067, W. L. Barrow, both complete accepted February 26, 1941, disclose horn antennas and horn antennas asso' ciated with deiiectors. In most of the horn antenna systems heretofore proposed for propagating energy unidirectionally, the wave front is not at since the diverging wave paths extending from the horn throatl aperture to the horn mouth aperture, are unequal in length whereby the wave components in the plane of the mouth aperture are toA some extent in phase disagreement. It now appears desirable to secure phase agreement among the wave components propagated in the same direction and to improvev greatly the. operation of unidirectional horn antennas. Moreover, it is now desirable to project or collect radiant energy, unidirectionally in a plane perpendicular to the longitudinal horn axis, and to control accurately the unidirectional action of horn antennas especially horn antennas having relatively large dimensions. 4

It is one object of this invention to project and collect, in a horn antenna. system, only in-phase vx-.ve components in a given single direction.`

It is another object of this invention to steer or control the direction of maximum radiant action of a large antenna in a simple manner utilizing a minimum of equipment. l l

It is still another object of this invention to deflect or direct all the wave energy emitted by a horn antenna along a single path, substantially, included in a plane perpendicularly related to the longitudinal horn axis.

It is a further object of this invention to project or collect radio waves unidirectionally in ya- 'horizontal plane utilizing a vertical horn antenna and relatively simple supporting structure.`

It is still another object of this'invention tol project or collect, in a'slngle'point `direction included in a horizontal plane. either horizontally 14- Claims. (Cl. Z50-11) or vertically polarized waves utilizing the same vertical horn antenna. v

According to one embodiment of the invention a. plane or paraboloidal unipoint, directional deector is attached to one mouth aperture edge of a large vertical horn antennahavlng a'square transverse cross section, for projecting or collect-k ing energy in a single direction in a horizontal plane. The paraboloidal deiiector has a circular' contour in the wave 'front plane and a parabolic contour in the wave propagation plane. the wave front plane being perpendicular to the wave direction and the propagation plane being perpendicular to the wave front plane and including the wave direction. The horn sides or walls adjacent the defiector are in effect continued to the de` ilector and the extended side portions function as shields to confine the radiation or collection to the given horizontal unipoint direction, the

defiector aperture facing, of course, the desired horizontal direction of action. The hom may-'ber self-supporting or it may be mounted in a cribi or cradle having a pivot, or point support'g-thehorn being held in a vertical position by` means of four guy cables attached to the cornersoffthe mouth aperture. PreferablyturnbuclclesiaeprolI vided in the guy cables for the purpose fpermit' ting tilting oi the horn in the vertical plane vand' slight twisting or rotation about, .the vertical or longitudinal horn axis. The hornis connectedto a horizontal wave guideline through a straightv throat section or twisted throat,v section, dev pendent upon the plane of wave polarization desired and the direction of extension of the -line relative to the front side of the horn.

The invention will be more fully understood' from the following specification taken in con junction with the drawing on which like reference characters denote elements of similar function and on which:

Fig. 1 illustrates a horn-deflector antenna-system constructed in accordance with the inven-y tion; Figs. 2, 3 and 4 are respectively side, front and top cross sectional diagrammatic views used in explaining the operation of the system of Fig. 1: Figs. 5 and 6 illustrate, respectively, a twisted horn throat section and a planel reflector which may be substituted in the system'of Fig. 1 for the straightf throat section and paraboloidal reflector.' and Figs. 7 and 8 are directive diagrams for 'the system of Fig. 1 modified to include the plane reector of Fig. 6.

Referring to Fig, 1, reference numeral l desig nates a vertical horn antenna' comprising ve horn sections 2 and having a'front wall 3, back vanized zinc.

wall 4, side walls 5, a transverse graduated cross sectional area 6, a longitudinal axis 1, a mouth aperture 8, a throat aperture 9 and an optimum ratio of horn length to horn mouth aperture area, the length being measured along the axis 'l between the mouth aperture 8 and the throat aperture 9. The horn proper .isian inverted square pyramidal lstructure having avirtual y apex III. The throat aperture 9 is connected through cou'- pling sections II and I2 to a wave guide I3 and a translation device I4 which may be a transmitter or receiver. As is shown on the drawing, the cross sectional area of the section I2 is rectangular whereas the cross sectional area of section I I changes uniformly from rectangular to square. As used herein, the term rectangular denotes a rectangular configuration other than square, and the generic term "quadrangular signifies rectangular or square.

Reference numeral I5 designates a paraboloidal dei-lector attached to the back edge I6 of the horn mouth aperture 8 and to the extended wall portions or shields Il, the deector being positioned, as is explained in more detail below, so

as to face both the throat aperture 9 and the wall opening I3 formed in the plane of the front wall 3 by the front edges I9 of the shields I'I, the front edge of-the deflector I5, and the top edge 2li of the front wall 3. Thehorn I and deflector I5 are preferably of light weight construction as, for example, wood, the inside surfaces being lined with copper-coated paper or gal- The opening I8 may, if desired, be equipped with a plywood cover 2I for weather protection. The horn sections 2 and throat sections II and I2, are preferably detachable so that they may be nested for the purpose of facilitating transportation.

The lower portion of horn I is symmetrically included within the metallic or wooden cradle structure 22 whichis mounted on the pivot or point support 23 and ground plate 24. The corners 25 of the mouth aperture 8 are each connected to the ground 26 by a separate guy cable 21. Each guy cable includes a turnbuckle 28 which permits a certain amount of movement or twisting of the horn I about its longitudinal axis 'l and substantial rotation or tilting about the pivot support 23 in the plane of the wave direction 29 and the axis 1, whereby the effective direction of radio action of the system may be steered or aligned with a desired path of propagation.

Referring to Figs. 1, 2, 3 and 4, the defiector I5 has, in the moving vertical plane 30 of the wave front, a circular contour represented by the curved lines or arcs BB', CC', DD' RR', Fig. 3, with centres on a line 3i', Fig. 2, passing through point A. Point A is located at the virtual apex II) of the horn. In the vertical plane 32 of wave propagation, the deflector has a parabolic contour BJR, Fig. 2, thev focus of the parabolic curve being also at A. In Fig. 2, the plane 30 is perpendicular to the paper and includes points S and C and the plane 32 includes the paper and points A, B, R, S, and C. In Iother words, the defiector I5 is a paraboloid nf revolution and resembles a portion ofan automobile headlight reflector. As shown by Fig-3, a longitudinal cross section of the horn and attached deector, taken in the plane 39 of the wave front. is sectorial. The parabolic curve or contour is expressed by the following equation for polar coordinates '1-I-sin a 4 where edge AB.

As illustrated by Fig. 2, the diverse bent paths ABC, ABE, AFG ARS included in the plane of propagation 32 and extending from the virtual apex I0 via the deflector I5 to the plane 30 of the desired wave front, have by virtue of the position and shape of the deflector I5, equal lengths. In any of the planes ABB', ADD', etc., Figs. 3 and 4, which planes are in quadrature `to plane 32, the diverse paths as, for example, AV

and AW, are equal and the right-angle extensions VV' and WW of these paths to the desired wave front 30 are also equal.

In operation, Fig. 1, assuming the system is used for transmission, energy from the transmitter I4 is supplied by the rectangular wave guide I3 to the horn I and the wave components are propagated along the diverging paths within the horn I. After passing through the mouth aperture 8 the waves impinge upon deector I5 and thence are directed or deflected through the wall opening I8 in a substantially horizontal direction 29. Since the lengths of the diverse'paths in the plane 32 extending from the throat aperture 94 to the desired wave front 30 are substan` tially equal, the wave components or `waveletsin the. vertical wave front plane 30 are in phase vand combine to produce a maximum eect in the cal reasons at some sacrifice in operating eifectiveness. The predominating wave propagated inside the wave guide I3 and supplied to the horn I is, as is well-known, polarizedin a direction coinciding with the short transverse dimension as shown by arrows 33, Fig. 1. Hence, with the wave guide connected so as to extend in a frontto-back line direction relative to the horn, as

shown in Fig. 1, the wave impinging upon de-A ector I5 is, immediately before intercepting the deiector, polarized horizontally in the vertical plane of propagation 32' and after reflection is vertically polarized in said plane as shown by arrow 34 in Fig. 1.

Referring to Fig. 5, numeral I2' designates atwisted throat section which `may be used in place of the straight throat section I2 included in th'e system of Fig. 1 for rendering the polarization of the emitted wave horizontal. To make the conversion, section Il shown in Fig. 1 is rotated as shown in Fig. 5, and the twisted throat section I2' is then fitted between horn section II and the wave guide I3. In operation,

the twisted throat functions to rotate the polarization plane of the wavelets propagated within the horn 90. the wave after passing through the twisted throat section vbeing horizontally polarized in a vertical plane perpendicularlyrelated tothe vertical propagation plane 82.

As a result, the polarization of the wave is reversed or changed 180 by deflector I5 but, as emitted through the aperture I8 in wave propagation direction 29, the wave is horizontally polarized, Thus, the same horn antenna system may be employed for' emitting or receiving either vertically polarized or horizontally polarized waves in a given propagation direction. As analternative, the line I3 may extend in a side-to-side.

line direction, that is. in a direction making a right angle to the direction shown in Fig. 1, the

section` II being oriented as shown vin Fig. 5. With this modificationthe straight section I2 is employed to `produce horizontally polarized waves and the twisted section I2' to produce vertically polarized waves.

than the paraboloidal assembly. In operation,

, 'l2 (Fig. 7) and curves 80, 8i and 82 (Fig. `8)

represent, respectively, the directiveV` characteristics of a vertical horn not equipped with a deflector assembly, a horn antenna having a plane reflector I5" but not shield members I 'l', and a horn antenna equipped with a plane deflector Vand shield members, as illustrated by Fig. 6.

Fig. 'l represents the magnetic plane directive characteristic and Fig. 8 represents the electric plane characteristic.A As may be' seen by com paring curves land 1I, and 80 and 8l, the open deflector I5' functions to change the direction of maximum radio action 90. Also as may be seen by comparingcurves 1I and 12, and curves 8i and 82, the shield members I'I increase thev sharpness of the directional effect and prevent or eliminate the minor lbes as, for example, lobe 83.

Although the invention has been explained in connection with certain embodiments, it is to be understood that it is not to be limited to the ap-` paratus illustrated, inasmuch as other equip-- ment and apparatus may. be satisfactorily em-I ployed in practicing the invention.

What'is claimed is:

-1. A quadrangular horn antenna having me'- tallic walls each-of varying width and an aperture in one wall at its wide end, said horn antenna having a sectorial cross section. in the plane of said aperture.

y 2. A dielectric channelforconveying electrof magnetic waves, said channel having metallic walls and an aperture facing in a direction perpendicular to its longitudinal axis, substantially,

said channel having in a plane perpendicular to said direction and including vits longitudinal axis a cross-sectional area bounded by two angularly related lines and a curvate line connecting said lines 'at their widest separation.

3. .In combination, a metallic horn antenna having a longitudinal axis and a cuadrangular mouth aperture for propagating in a direction aligned with said axis waves having a concavoconvex or curved wave front, said horn comprising four angularly related walls each having a metallic inner surface, a concave metallic deilector attached to' one edgeof said horn aperture and a separate plane metallic shieldattacl'ied to each` aperture edge radjacent said first-mentioned edge, whereby the waves are propagated in a single direction substantially perpendicular to said axis and the curved wave front is changed to a'plane wavefront.-

4. A quadrangular metallic horn antenna hav-. ing a throat aperture and a side aperture in lits front wall, a metallic paraboloidal deilector facing said apertures and having a finite focus located on the longitudinal axis of said horn. whereby the lengths of the wave paths extending from the horn throat aperture to said side aperture via said de ector are substantially y equal.

5. In combination, a vertical horn-shaped di" electric channel for conveying transverse electric microwaves, a metallic paraboloidal reflector attached thereto and facing the mouth aperture of said horn, the focal axis of said reflector being in a horizontal plane, the horn being included between the reflector surface and the reector focus, said horn having its longitudinal axis superimposed on 'a linearv path extending between said focus and said surface, the length of the horn along said longitudinal axis being shorter than said path, whereby unidirectional action in the horizontal lplane is secured.

6. A horny antenna system lined with conductive material and having ak rectangular cross section, one side of said horn being extended be'- yond and at an angle to the plane of the horn mouth aperture and the twoA sides adjacent said first, mentioned 'side being extended so as to touch the extended rst side, whereby an aperture is formed in the plane of the remaining side.

7. In combinationfa metallic horn antenna havingits longitudinal axis aligned with a given direction, said horn having a throat aperture and a rectangular mouth aperture, a metallic deilector attached to said horn along one edge of the mouth aperture for confining the travel of waves projected or collected by said horn to a single direction, substantially, said deilector being included in aplane perpendicularly related to said given direction, and a device for generating or receiving radio waves connected to the throat aperture.

8. In combination with an antenna system comprising a horn and a deflector for project-` ing or collecting a maximum amount of radio energy in substantially one point direction. perpendicular to the longitudinal axis of said horn. means comprising a point supporting structure for mechanically steering the direction of maxi imum action of said system in a plane containing said horn axis and in a plane perpendicular tosaid axis. .v s l 9. A vertical horn antenna system yhaving an aperture facing in a point direction included in a horizontal plane and-.means for adjusting or steering the directive characteristic of said horn comprising a point supporting structure for said horn antenna and adjustable guy wires extendandere ing from diilerent upper portions oi said horn .to the earth. 1

10. In combination, a metallic horn antenna having a square mouth aperture and its longitudinal axisA perpendicularlyl aligned with the desired direction oi' radio action, a metallic deiiector facing the mouth aperture of said horn, said deiiector having a circular contour in the plane of said axis and a parabolic contour in the plane of said direction and having its focus on said longitudinal axis.

11. An antenna system ior projecting or coln lectlng wave components in a given direction,

' the system comprising a rectangular horn having` a. side aperture in its front wall 'and a throat aperture, a paraboloidal reflector facing said side aperture and said throat aperture, 'the reflector focus being located on the longitudinal `horn axis and the distance between the focus and 'the reector being greater'than the length of the horn as measured along s'aid longitudinal axis, the focal axis o! said reflector being perpendicular to said longitudinal axis and aligned with said direction, whereby all of the wave paths extending from the throat aperture via 20 Number said reflector to a plane perpendicular to said direction have equal lengths and the in-phase wave components emitted or collected by said system are included inaplane.

12. In combination, a vertical horn antenna having a square mouth,y a unidirectional deflector attached to one edge of said mouth fo` confining the wave propagation to a single direction, substantially, in a horizontal plane, a

transmitter connected to a rectangular wave guide, a wave guide member having at. one end a square cross section and at'the other end a rectangular cross section .and connecting said wave guide to the horn throat.

18. A combination in accordance with claim 12, the wave guide member being linear along its longitudinal axis.

14. A combination in accordance with claim 12. the wave guide member being twisted 90 degrees about its longitudinal axis.

ALFRED c. BECK. `HARALD T. Fans.

REFERENCES crrEn The following references are oi record ln the ille of this patent:

UNITED STATES PATENTS OTHER REFERENCES Proceedings of the I. R. E., v01. 28,` No'. 3, Marchv 1940 (pages 13D-131).

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