US2990545A - Broad-band omnidirectional spherical lens antenna with rotating amplitude modulationpattern - Google Patents

Description

June 1961 D. F. BOWMAN 2,990,545

BROAD-BAND OMNIDIRECTIONAL SPHERICAL LENS ANTENNA WITH ROTATING AMPLITUDE MODULATION PATTERN Filed June 17, 1958 4 Sheets-Sheet 1 D. F. BOWMAN June 27, 1961 ,990,545 BROAD-BAND OMNIDIRECTIONAL SPHERICAL LENS ANTENNA WITH ROTATING AMPLITUDE MODULATION PATTERN Filed June 17, 1958 4 Sheets-Sheet 2 INVENTOR. 1

.am/m A ear/WW Arraz/VEYJ June 27, 1961 BOWMAN 2,990,545

BROAD-BAND OMNIDIRECTIONAL SPHERICAL LENS ANTENNA WITH ROTATING AMPLITUDE MODULATION PATTERN Filed June 17, 1958 4 Sheets-Sheet 3 INVENTOR. j? 10.0 F BOW/144A Arrd/V'fi June 27, 1961 D BOWMAN 2,990,545

BROAD-BAND OMNIDIRE ONAL P ER L LENS ANTENNA 1 WITH ROTATING AMPLITUDE DUL 0N PATTERN Filed June 17, 1958 4 Sheets-Sheet 4 tates P n a 2,990554'5- Y Y BROKE-BAND OMNIDIRECTIONAL SPHERICAL LENS ROTATING AMPLL TUDE MODULATION PATTERN- David F. Bowman, Wayne; Pa, .assignor to I-T-E "Circuit Breaker Company Philadelphia, Pa., a corporation of Pennsylvania.

Filed'June' 17, ,1'958,,Ser. No; 742,646 13 Claims. (Cl; 343-755) invention relates generally to directional transrrritting antenna; and more particularly relates to novel antenna-for transmitting the directional radio pattern for the radio navigational system known as Tacan.

TheTacan system has beendeveloped in recent years, initi'allytor military aircraft; being an abbreviation of tactical air navigation; It operates in the UHF spectrum, being assigned the range 960 me. to 1215 mc. TIhBlOW band'Tacan range'is 960 to'1024 mc.; the high band, 1150 to 12-15 mc. The intermediate band 1024 to 1150 mc. is used for'interrogation'of theTacan station by an aircraft fordistancedeterminations.

The CivihAeronautics Administration is setting up a system of transmitting stations combining Tacan with civilian VHF omnirange or VOR. The latter system is'known as Vortac. One of the new requirements for the Tacantransrnitter antenna is that it be directly adaptable to efficiently transmit" its'patterned signals over any frequencyin either oftheTacanhighor 10W bands. The present invention provides novel antenna systems with broad band characteristics to accomplish this feature.

Another" important- Ci'vil Aeronautics Administration requirement is to have the transmitted Tacan pattern be efiective over an elevation range from the horizonto at least 60" above the-horizon." Such wide elevation cover age has been unattainable with prior antennae. Further; the new Tacan transmitted signals are to be of higher gain than'heretofore, namely, to be six db over that of an isotropic source; The antenna systems ofthe' present invention accomplish these important and desirable objec= tives.

In accordance with my invention, 1 utilize'a: dielectric sphere known as a Luneberg lens, and provide multiple or infinite point sources of the radio waves to be radiated from a circularpathon the sphere. 'I'he-resultis 360 horizontal radio pattern of general toroidal formr 'I' further incorporate therein modulators to shape the toroidal form with fundamental and nine lobed modulations to constitute the characteristic Tacan pattern. Rotation of the modulated point sources at 900 rpm. about the sphere results in the Tacan signal transmission intercepted at 15 and 135 cycles persecond.

It is'accordinglya" primary object of the present invention to provide a novel transmitter antenna incorporating a dielectric sphere with multiple radio point source thereabout to produce a generally toroidal pattern.

Another object ofthepresent invention is to provide a novel Tacan antenna? utilizing a dielectric sphere to transmit a'Tacanrpatternzwith a gain at the to elevation angles of six db over an isotropic source.

A further object of the present invention'is to provide a novel antenna incorporating a dielectric sphere to transmit a generally toroidal 360 radio pattern with eifective signal strength from horizon to at least 60 above the horizon.

Still another object of the present invention is to pro vide -a. novel antenna-system capable of efliciently transmitting a Ta'can-radiov array at any frequency over the: whole UHF Tacan band.

Still a further object of the present invention is to provide a novel Tacan transmitter antenna that is efli-' I 2,990,545 Patented June 27, 1961 1 2 cient; rugged and capable of long-time uninterrupted operation.

The aboveand further objects of the present invention willbecome more apparent from the following description of exemplary embodiments thereof, illustrated in the drawings, in which? FIGURE 1 is a polar representation of anidealized radio Tacan pattern in a single elevation plane.

FIGURE-2 is a polar representation of the antenna radiationpattern in a single azimuth plane as modulated with nine lobes.

FIGURE 3 is a polar representation of the antenna radiationpattern in a single azimuth plane as modulated bythe fundamental frequency.

FIGURE 4 is a polar representation of the composite antenna radiation pattern per FIGURES 2 and 3;

FIGURE 5 is 'a diagrammatic showing of the operation of a Luneberg lens with a single radio point source.

FIGURE 6 is a curve illustrating the relative signal strength of the Luneberg lens beam at angular deviations from the normal direction.

FIGURE 7 is a polar representation of thebeam emit ted from the' lens of FIGURES.

FIGURE 8' is a perspectiveschematie diagram of the multiple or infinite radio point sources for the spherical lens, .in accordance.with my invention.

FIGURE 9 is a perspective illustration: of an. exem plary means for generating theradio point sources in the lensof FIGURE 8.

FIGURE 10 is across-section view through-a spherical antenna arrangement utilizing the signal feed means of FIGURE 9.

FIGURE: 11 is a plan view of the signal feed system of FIGURES 9 and 10 incorporating modulator elements;

FIGURE 12 isan-enlarged cross-sectional view through the line 1.z-'-1-z of FIGURE 11', illustrating an exemplary modulator element.

FIGURE 13 is 'a diagrammatic showingof a. modified spherical lens: antenna in accordance with my invention:

FIGURE' 14 is. a polar representation: in: a single-elevation plane of theradiation pattern of the antennaof FIGURE 13;

FIGURES 15, 16 and 17 are'illustrations of further forms which my antennamay assume inipractice;

FIGURE 18 is a polar representation in-wa singleazimuthal plane of the. radiation pattern of theantenna of FIGUREv l7.

FIGURES-19 and 20 are schematic showings of alternate. radio signal feed positions with respect to the antenna hereof.

FIGURE 21 is plan view of the trigger disc of' the pulse generator. ofithe invention system. per FIGURE 22;

FIGURE 22 is a cross-sectional view vertically'through acompleteiantenna structure in accordance to thepreseut invention.

In FIGURE. 1, I have represented in polar form the new Civil: Aeronautics Administrationrequirements asto theradiated Tacan pattern inan elevation plane. Radial lobes- 31, 31a. are specified to be greater in amplitude than the=carrier level, represented in FIGURE-2 bythe broken uniform circlefil with center c. The troughs 31a are specified to be 21% less in amplitude than the carrier level.

The Tacan pattern also requires a fundamental modulation as represented by FIGURE 3. This may be the essentially circular pattern- 33, having its center c' displaced from reference center c whereby in amplitude the peak of curve 33 is 21% greater and the valley of curve 33 is 21% less than the radius of the reference circle 32.

The Tacan 360 radiation pattern is represented in FIGURE 4 by polar curve 35, in a typical azimuth plane, with point as the origin. Curve 35 is the composite fundamental and nine loge modulation of the basic omnidirectional uniform 360 radio pattern represented by basic circle 32. The pattern 35 is rotated about its origin at c to effect the Tacan system results. The antenna of the present invention produces a rotating spatially modulated Tacan pattern as represented by theFIGURES 1 through 4.

FIGURE 5 illustrates the action of a Luneberg lens 40 on a single radio point source P. The Luneberg lens, as known in the art per se, is a sphere of dielectric material in which the dielectric constant varies gradually with the radius from center c. It is densest, namely of the value 2.0 at the center, to least dense at the surface, namely with a value of 1.0. In such a sphere 40, the index of refraction n of the radio waves 41 passing therethrough varies with the normalized radius r according to the formula n= /2r At the microwave frequencies utilized in Tacan transmission, namely, of the order of 1,000 megacycles, the lens 40 produces a uniform emergent radio beam 42. Thus, any circular aperture at or near the lens, represented at A, along beam 42 will have a radio pattern of uniform phase and uniform amplitude.

FIGURE 6 represents the relative amplitude or signal strength 2 of a beam such as 42, when measured at angular deviations a with respect to the beam (42) axis (fairly remotely from lens 40). It is noted, as FIGURE 6 curve 43 shows for a horizontal beam ('42), in that there is an elevation signal variation from the peak value ofe at 44 on the beam axis 45. The main lobe of curve 43 in effect reaches the zero level at points indicated at 46, 46

which, depending upon the sphere diameter and other factors may occur, for example, at +6, +8", etc.

It is also to be noted that minor lobes 47-.-.47, 48-48 and 49-49 are also represented in curve 43'for greater elevation deviation from a horizontal beam (42). FIGURE 7 shows a polar curve 50 in elevation for a horizontal beam (42) from a spherical lens (40). The

main lobe 51 extends uniformly above (52) and below (53) the beam axis 54. The minor lobes 55, 56 and 57 correspond to those indicatedat 47, 48, 49 in FIGURE 6. The relative signal strength 2 is determined by the intersection of curve 50 with the elevation line 58 at a degrees from a vehicle V such as an aircraft.

An important feature of my invention is to utilize a radio microwave lens such as a Luneberg sphere and apply simultaneously thereto an infinite numberof radio point sources along a circular region thereof. FIGURE 8 diagrammatically represents the'lens 60 with the multiple or infinite radio point sources, P, P along the equatorial circle 61. The lens center is 'at 'c, and its zenith at line 62.

The 360 array 61 of point sources, P, P produces a toroidal pattern of an otherwise linear beam (42) due to a single point source noted above in connection with FIGURE 5. For uniformly phased and equal amplitude radio point sources, P, P along circle 61, there results a symmetrical toroid pattern having a common vertical polar configuration along any elevation plane. Means are provided by my present invention to compositely modulate and rotate such uniform toroid patterns to effectuate the requisite Tacan specifications described in connection with FIGURES 1 through 4 hereinabove.

FIGURE 9 is a perspective illustration of a unifor-m continuous or infinite point source feed or line for the microwave lens hereof. This feed or line system comprises two spaced metal discs 62, 63 fed by a center coaxial transmission line 64. A uniform axial radio source is projected by the transmission discs 62, 63 as indicated by radial lines 65, 65. Rotation of the disc array 62, 63 as indicated by arrow a effects a direct spacial rotation of the source pattern 65. 1

, FIGURE 10 is a cross-sectional view through a simplified version of the invention Tacan antenna. 'The dielectric sphere 70 is of the Luneberg type with radial dielectric constant change, as described in connection with lens 40 of FIGURE 5. Two discs 71, 72 are arranged horizontally along the diameter of sphere 70. A coaxial transmission line with outer conductor 73 and inner conductor 74 couples to the opposed discs 71, 72 to feed a source of radio signals s to discs 71, 72.

The signals from source .9 are indicated as moving to the discs 71, 72 by arrow b, and then to radiate across the discs to their perimeters as indicated by arrows d, d as in the manner of FIGURE 9. The perimeter region of each disc 71, 72 preferably, though not necessarily, extends beyond the surface of lens 70. A horn reflector band 75 surrounds the periphery of discs 71, 72 to reflect the incident radio signal waves back to the lens 70 along the sphere. This reflection by band 75 effects the infinite radio point sources along a circular path of sphere 70 in the manner of FIGURE 8.

The reflector 75 is trough-shaped with a cross-section corresponding to a horn radiator. Horn reflector band 75 has a central flat region 76 constituting the reflector section opposite the signal emergent region of discs 71, 72, and two angular regions 77, 78 constituting the horn walls. Properly matched construction will produce substantially total transmission into the lens as indicated by arrow e with negligible reflection back into the narrowly spaced discs 71, 72 and with negligible undesired transmission, for example as shown by arrow 1. An efficient radio transmission system, with low VSWR is thus offected, providing the continuous point source band about lens 70. A Tacan type toroidal pattern results. A series of beam modulator elements 80 are provided along the transmission discs 71, 72. Elements 80 modulate the otherwise azimuthally uniform toroidal beam emanating from lens 70 with the multiple lobes in accordance with FIGURE 4. An exemplary modulator element 80 is a bolt 80 mounted between discs 71, 72 in the radial path of a portion of the radio waves therebetween.

FIGURE 11 is a plan view of the disc assembly 71, 72, showing the top disc 71 and the multiple lobe modulator elements 80, 80. Nine elements 80 produce nine uniform lobes (31). The desired amplitude of the lobes is determined by suitable radial spacing of the elements 80 on discs 71, 72, their diameter, and their metal composition, as will now be understood by those skilled in the art. A tenth modulator bolt 81 is located closer radially to center 0 of discs 71, 72 and constitutes the fundamental modulator for the lower frequency, corresponding to curve 33 of FIGURES 3 and 4.

FIGURE 12 illustrates an enlarged cross-section of modulator bolt 80 having nut 82 set between discs'71, 72.

For maximum utilization of the emitted signal strength, and also to better meet the six db gain requirement, the radio transmission discs are moved below the equatorial area of the spherical lens.

FIGURE 13 illustrates lens 85 with transmission discs 86, 87 set below the equatorial diameter88. The n'm reflector 89 surmounts the projecting periphery of discs 86, 87. The coaxial signal s feed line 90 suitably couples with discs 86, 87. It is noted that for Tacan operation, the modulator transmission disc combination is rotated about its zenith axis, along 1;. The lens 85 and reflector 89 are preferably stationary. The-reflector 89 is advantageously supported on lens 85.

FIGURE 1 14 illustrates in polar formrthei-upward-tilt efiectedt-by the lowering of transmission discs 86:37: The. below :horizon area 92' of curve 91yis: reducedas compared: toyarea 53 of FIGURE-7. Furthemthe: 5*"; elevation: line-intersection point, 94' :is. increased 1 in gain to: better meet. the requisitesix db. The curve 91 peak is.:shiftedz-close.- to the 5 li'ne. 94-, .though not-:necessaiily on it. a r FIGURES. 15 and 16 showalternate; forrnmfor: the lowering of the transmission. circumference to: elfect the upward. beam tiltas perFIGURES 1-3, 14. The lens 1000f FIGURE 15 has two spaced conical metal members 101', 102, with a central coaxial feed line 103. The reflector band 104 for lens 100 is shown asfl'at. This permits the cone peripheries to remain: interior of sphere 100. In sphere 105 of FIGURE 16, the two conical metal: members 106, '107'havea common apex-position, as at center c. They are fed by line108. A trough horn-type reflector band109 is used' therefor.

Another important feature of the invention antenna is to'be effective to the 60 elevation line per FIGURE 1. This requires a smoothing in of the lobes 95, 95of FIGURE 14 polar curve and of the nullsbetween lobes as indicated in FIGURE 18 at shaded area 120. Thus," signals are radiated about the 360 toroidpattern tothe 60 altitude with minimumcosecant 121' magnitudes maintained.

In FIGURE 17 is shown one form of the antenna 'hereof which smooths in the lobes 95. This antenna comprises a lens 1100f the Luneberg type with selected areas ofdifferent dielectn'c configuration. The modulator transmission plate array shown is with spaced cones 111, 112; and horn rim reflector 113. In the upper section of lens 110;is a conical or other suitably shaped region 114 of greater dielectric constant material than that generally present in a Luneberg lens. In the lower lens section, thereis a conical region 115 of material having a generally lower dielectric constant than present for a Luneberg lens.

The result of the denser dielectric region 114 and lighter dielectric region 115 in sphere 110 is to change the minor lobed polarpattern, see 95, 95 in FIGURE 14, to a. smoothed-in area indicated. irregularly as 1211- in FIGURE 18. This causes a continuous cosecant-121 relation as desired. Only the upper section of curve 122 is shown in FIGURE 18. The lower minor lobe polar portion is not significant in the Tacan display.

Other methods and arrangements may be used to effect the smoothing of lobes 95 (FIGURE 14) into toroidal area. 120 (FIGURE. 18). For example, the horn sect-iomofreflector (89 of FIGURE 13) may have its upper portion tilted at an angle away from sphere (85) to tilt or modify the phase front of the energyemerging from the horn reflector. Alternatively, the shape of either the upper. or. the'lower section of the sphere (as at 85) and the dielectric constant within this section may .be progressively. altered to effect such smoothing in (120') of the lobes (95).

While I have above illustrated the invention with the multiple radio point sources at or reasonably close to thesurface of the microwave lens, these may be different if the dielectric constant is varied within the lens in the proper manner as well known in the art.

FIGURE 19-illustrates these point sources represented by P remote from lens 125. The resultant beam at aperture'A' is uniform as required. Also, the radio point sources, represented by P" in FIGURE 20 may be well' within-. the lens 126. The resultant beam at apertureA is:uniform;.

A physical assembly of a Tacan antenna in accordance with mypinventionlhereof is illustrated in vertical cross section in FIGURE 22. The lens 130 comprises .two hemispheresw131, 132 of dielectric material. The practical-radial variation of the dielectric constant of hemie.

' mission discs 140, 141 has no electrical function.

spheres-131; 132; in' the. .Lunebergylens' manner already described-,is understoodlby those skilled in the art and is notfdetailed. v

The upper hemisphere 131 has its center c spaced above thecenter c of: the lowerione 13-2. Open regions 13 3, 134 are formed between hemispheres 131, 132 to containithe rotatingrmodul'ator. transmission discs. The hemispheres 1 31",? 132- are suitably fastened together by hardware 135,436. The assembly is-supported in a di-. electric support cone 1371 on frame 1'38 mounted on base 139.

The rotatable spaced transmission metal discs..1'40, have a firm. foam dielectric layer 142. therebetween for composite support. The discs 140, 141' are signal fed by. andfsecured with coaxial transmission line. 143, 144. Innerconductor 143- is' connected to upper disc by": screw 145 and transformer sleeve- 146. The outer conductor 144-connects by bracket 147 to lower plate 141 Outer conductor 144 is: rotatably supported by roller bearings 148; 149.

The coaxialline 143; 144iextends through hollow shaft motor 150. The-outer line-144 has a reduced diameter section- 144 that is rotated by motor 150 and rotates discs 140, 14 1 at 900 rpm. Discs 140, 141 have slab modulator elements 151', 151' to perform the results of bOlts SO of the other modifications described above. The ringreflector 152 is flat as in FIGURE. 15. A motor speed regulator is preferably employed to stabilize the rotation at requisite uniform speed. A sine wave generator 152, a pulse generator 153 and rotary electrical line coupler 154 are'mounted beneath motor 150; The pulse generator 153 uses a disc 155 having elements 156 to effect the Tacan signal triggering.

The foam dielectric between the rotating radio trans"- Its dielectric constant is thus kept low, such as 1.05 A firm' foamlayer of styrene is suitable. The pulse generator- 153and the sine generator 152 are connected to the Tacan electrical and electronic equipment (not shown), in the usual manner. The pulse generator 153 comprises a disc 155 of dielectric material with nine metallic members 156 spaced near its periphery 40 apart.

FIGURE 21 shows this arrangement. Disc 155 is secured to therotating central transmission line at hub 157. The rotating trigger members 156 coact with the stationary yoke-158" toeffect the identifying timed pulses for the-distance measurement determinations ofthe mov ing vehicle. The fundamental frequency triggering is per.- formed by passage of member 159.

The basic microwave signal to be modulated and broadcasted by the antenna system thereof is fed by a coaxial transmission line into the input of rotary coupler 154. The radio signal, at the selected Tacan broadcast frequency, is thus fed to internal'rotating coaxial cable 143,- 144 through the coupler 154. Suitable matching transformations are maintained to the coupler 154,. through the motor with the line 143, 144, and on to the rotating discs. The discs rotate unhindered. in. the clearspace set thereabout within lens 130..

The antenna systemof my invetnion is not frequency sensitive over the Tacan microwave band, and accordingly one basic construction can be used for all Tacan andf Vortac installations, regardless of the frequency selected to transmit. The radial distance of'the modulatorele ments may be shifted in some cases, before installation, for some selected frequency region. Pre-drilled' series of openings for this purpose may be provided.

In a physical embodiment of the invention antenna, a Luneberg-type sphere 'wasused, 18" in'diameter. The rotatable radio transmission discs were located below the sphere center and-coaxial with its zenith, being 26" 'in di-- ameter to 1 project .beyond the sphere. spacedi interiorly.

A horn-sectioned reflector ring surrounded the. project ing, periphery; of the transmission discs, with an outer These discs were circumference of 27". Thus, the outer horn rim was V2" from the disc periphery. The reflector base opening was about 4" across, and supported on the sphere. The modulator bolt elements were mounted at a radius of 8 /2" from the center of the discs; with the fundamental modulator at 2 radius.

While I have described my invention in connection with several exemplary embodiments, modifications and variations thereof may be made Without departing from the broader spirit and scope of the invention, as described in the following claims.

I claim:

1. A transmitter antenna comprising a radio wave lens extending for 360 about its zenith, a radio transmission structure rotatable with respect to said lens for applying impressed signal energyabout a 360 segment of said lens, said structure including a pair of opposed metallic plates supported within the lens, and motor means for continuously rotating said transmission structure, said metallic plates being supported horizontally within the lens at a position below the equatorial plane of the lens to eflectuate an upwards tilt of the radiated radio pattern.

2. A transmitter antenna of the character described comprising a microwave lens composed of a generally spherical body of dielectric material having its dielectric constant vary substantially inversely with its radial extent from a central value of 2 to a peripheral value of 1, a radio transmission structure rotatably supported within the lens symmetrically about its zenith diameter to radiate radio energy along a horizontal 360 spherical segment, a reflector rim arranged about said segment to reflect the 360 beam energy through the lens and produce a generally toroidal radiation pattern about the sphere zenith, modulator elements mounted with said structure to amplitude modulate the radiated pattern, a coaxial transmission line coupled to said structure and rotatably supported insaid spherical body along its zenith diameter, an electrical coupler for the coaxial line, and motor means connected to said coaxial line to continuously rotate said line and structure to produce a rotating amplitude space modulated toroidal radiation pattern.

3. A transmitter antenna as claimed in claim 2, in which the region of said dielectric spherical body about the rotatable structure is hollow.

4. A transmitter antenna as claimed in claim 2, in which the upper hemispherical portion of said body is spaced from the lower hemispherical portion thereof.

5. A transmitter antenna as claimed in claim 4, in which the said radio transmission structure is centered below the center of the lower hemispherical portion.

6. A transmitter antenna as claimed in claim 2, in which the upper portion of the dielectric body is deformed from the spherical form to emphasize the radiated pattern strength at the upper altitude angles.

7. A transmitter antenna as claimed in claim 2, in which the upper hemispherical portion of the dielectric body contains a region of dielectric material substantially greater than that of the body material surrounding it to emphasize the radiated pattern strength at the upper altitude angles.

8. A transmitter antenna comprising a microwave lens composed of a generally spherical body of dielectric material, a radio transmission structure rotatably supported within the lens symmetrically about its zenith diameter to radiate radio signal energy along a horizontal 360 spherical segment, a reflector arranged about said segment to reflect the 360 signal energy through the lens and produce a generally toroidal radiation pattern about the lens zenith, modulator elements mounted with said structure to amplitude modulate the 360 radiated pattern, transmission line means coupling signal energy to said interior structure, and motor means for rotating'said'structure and elements to produce a rotating amplitude space modulated toroidal radiation pattern.

9. A transmitter antenna comprising a microwave lens within the lens symmetrically about its zenith diameter.

composed of a generally spherical body of dielectric material, a radio transmission structure rotatablysupported within the lens symmetrically about its zenith diameter to radiate radio signal energy along a horizontal 360 spherical segment, a reflector arranged about said segment to reflect the 360 signal energy through the lens and produce a generally toroidal radiation pattern about the lens zenith, modulator elements mounted with said structure to amplitude modulate the 360 radiated pattern, transmission line means coupling signal energyto said interior structure, and motor means forrotating said structure and elements to produce a rotating amplitude space modulated toroidal radiation pattern, in which the radio transmission structure includes a pair of opposed metallic plates providing a 360 signal radial transmission line.

10. A transmitter antenna comprising a microwave lens composed of a generally spherical body of dielectric material, a radio transmission structure rotatably supported within the lens symmetrically about its zenith diameter to radiate radio signal energy along a horizontal 360 spherical segment, a reflector arranged about said segment to reflect the 360 signal energy through the lens and produce a generally toroidal radiation pattern about the lens zenith, modulator elements mounted with said structure to amplitude modulate the 360 radiated pat-tern, transmission line means coupling signal energy to said interior structure, and motor means for rotating said structure and elements to produce a rotating amplitude space modulated toroidal radiation pattern, in which the radio transmission structure includes a pair of opposed metallic plates providing a 360 signal radial transmission line; with said reflector arranged adjacent the lens surface and opposite the peripheral region of said plates and directed to effect the said reflection of the radially radiated structure signal energy into the lens.

11. A transmitter antenna comprising a microwave lens composed of a generally spherical body of dielectric material, a radio transmission structure rotatably supported within the lens symmetrically about its zenith diameter to radiate radio signal energy along a horizontal 360 spherical segment, a reflector arranged about said segment to reflect the 360 signal energy through the lens and produce a generally toroidal radiation pattern about the lens zenith, modulator elements mounted with said structure to amplitude modulate the 360 radiated pattern, transmission line means coupling signal energy to said interior structure, and motor means for rotating said structure and elements to produce a rotating amplitude space modulated toroidal radiation pattern, in which said reflector is arranged adjacent the lens surface and opposite the peripheral region of said structure and directed to effect the said reflection of the radially radiated structure signal energy into the lens.

12. A transmitter antenna comprising a microwave lens composed of a generally spherical body of dielectric material, a radio transmission structure rotatably supported within the lens symmetrically about its zenith diameter to radiate radio signal energy along a horizontal 360 spherical segment, a reflector arranged about said segment to reflect the 360 signal energy through the lens and produce a generally toroidal radiation pattern about the lens zenith, modulator elements mounted with said structure to amplitude modulate the 360 radiated pattern, transmission line means coupling signal energy to said interior structure, and motor means for rotating said structure and elements to produce a rotating amplitude space modulated toroidal radiation pattern, in which said transmission line means includes a coaxial line mechanically and electrically coupled to said structure and connected with said motor means.

13. A transmitter antenna comprising a microwave lens composed of a generally spherical body of dielectric material, a radio transmission structure rotatably supported to radiate radio signal energy along a horizontal 360 9 spherical segment, a reflector arranged about said segment to reflect the 360 signal energy through the lens and produce a generally toroidal radiation pattern about the lens zenith, modulator elements mounted with said structure to amplitude modulate the 360 radiated pattern, transmission line means coupling signal energy to said interior structure, and motor means for rotating said structure and elements to produce a rotating amplitude space modulated toroidal radiation pattern, in which the radio transmission structure includes a pair of opposed metallic plates providing a 360 signal radial transmission line, with said reflector arranged adjacent the lens surface and opposite the peripheral region of said plates and directed to efiect the said reflection of the radially radiated structure signal energy into the lens, in which said transmission line means includes a coaxial line mechanically and electrically coupled to said structure and connected with said motor means said coaxial line extending along the zenith diameter of the lens.

References Cited in the file of this patent UNITED STATES PATENTS

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