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Publication numberUS3633208 A
Publication typeGrant
Publication dateJan 4, 1972
Filing dateOct 28, 1968
Priority dateOct 28, 1968
Also published asDE1953732A1, DE1953732B2, DE1953732C3
Publication numberUS 3633208 A, US 3633208A, US-A-3633208, US3633208 A, US3633208A
InventorsAjioka James S
Original AssigneeHughes Aircraft Co
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Shaped-beam antenna for earth coverage from a stabilized satellite
US 3633208 A
Abstract
The apparatus of the present invention provides an antenna having a beam shaped for optimum earth coverage from a synchronous satellite. Due to the difference in range and atmospheric attenuation from a synchronous satellite to various points on earth, a conventional beam with maximum gain toward the center of the earth, is inefficient because it has the highest gain where the least gain is required. Since the paths tangential to the earth are longest and since they traverse through more atmosphere, the gain of the disclosed antenna is highest in this region and decreases to a minimum for the path normal to the earth. In addition, the beam pattern of the antenna has "flat portions" at the edge to allow for stabilization errors of the satellite whereby equal effective signal is provided over the entire portion of the earth covered by the antenna beam. The antenna generates a beam pattern that is rotationally symmetrical and has the capability of dual orthogonal polarization.
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Description  (OCR text may contain errors)

1 1 amazes Pn'mary ExaminerEli Lieberman AttomeysJames K. Haskell and Robert H. Himes ABSTRACT: The apparatus of the present invention provides an antenna having a beam shaped for optimum earth coverage from a synchronous satellite. Due to the difference in range and atmospheric attenuation from a synchronous satellite to various points on earth, a conventional beam with maximum gain toward the center of the earth, is inefficient because it has the highest gain where the least gain is required. Since the paths tangential to the earth are longest and since they traverse through more atmosphere, the gain of the disclosed antenna is highest in this region and decreases to a minimum for the path normal to the earth. In addition, the beam pattern of the antenna has flat portions" at the edge to allow for stabilization errors of the satellite whereby equal effective signal is provided over the entire portion of the earth covered by the antenna beam. The antenna generates a beam pattern that is rotationally symmetrical and has the capability of dual orthogonal polarization.

SHAPED-BEAM ANTENNA FOR EARTH COVERAGE FROM A STABILIZED SATELLITE BACKGROUND OF THE INVENTION Contemporary antennas are simple or multimode horns and planar arrays of nominally half-wave elements spaced of the order of half to three-quarters of a wavelength. Simple or multimode horns do not give the proper shaping or are of extremely narrow bandwidth. An array, on the other hand, is extremely complex because of the large number of elements, is quite narrow band and is quite lossy because of complex feed network. Further, if polarization diversity is desired, the complexity is more than doubled.

SUMMARY OF THE INVENTION It is well known that a Lambda function, .I,(u)/u, aperture distribution will give a rotationally symmetrical sector-shaped pattern exactly but would require an infinite aperture. In accordance with the present invention, this aperture distribution is approximated by a horn array wherein a larger center horn provides a distribution approximating the main lobe of the J,(u)/Au function while a ring of smaller horns 180 out of phase with the center horn approximates the distribution of the first minor lobe of the J, (u)/u function. The resulting horn array generates a concave shaped beam with almost perfect rotational symmetry and with minimum absolute gain greater than 18 db. 9.5 from center. When used on a stabilized satellite at synchronous altitude, 95 from center is at the earths edge where one usually experiences the weakest signal. In addition to its use on satellites, the array of the present invention is also useful as the feed for a Cassegrain antenna.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 illustrates the nine-horn array of the invention, in

perspective, without feed system;

FIG. 2 shows a cross section of the nine-horn array of FIG.

FIG. 3 shows a schematic diagram of a feed system for the nine-horn array of FIG. 1;

FIG. 4 illustrates measured patterns of the nine-horn array of FIG. 1 without multimoding;

FIG. 5 illustrates measured patterns of the nine-horn array of FIG. 1 with center horn multimoded; and

FIG. 6 shows the ideal pattern for earth coverage.

DESCRIPTION Referring now to FIGS. 1 and 2 of the drawings, the array of the present invention includes a large conical center horn 10 which is mounted to a disk 12 by means of a standoff support 14 attached to a flange 15 at the neck portion thereof. In accordance with the invention, an integral number of smaller conical horns 16-23 are disposed in alignment with and at equal intervals about the large conical center horn 10. Although a number of horns equal to an exponential of the base two can be used, i.e., 2, 4, 8, l6 it has been found that the use of the eight conical horns l623 is advantageous from the standpoint of relative aperture area and simplicity of the driving apparatus. In order for the smaller conical horns 16-23 to surround the center horn 10 without leaving a gap, the diameter of the respective apertures thereof are made equal to 0.618 times the diameter of the aperture of the center horn 10. Under these circumstances, the ratio of the area of the apertures of the conical horns 16-23 to the area of the aperture of the center horn 10 is 3. In addition, the flare angle of the center horn 10 and peripheral horns 16-23 control the phase front over the respective horn aperture. Larger flare angles produce more convex phase fronts and smaller flare angles less convex phase fronts. In this respect, the peripheral horns 16-23 can be tilted in with respect to the center horn 10 to achieve additional control of the phase over the entire aperture of the array. The disk 12 includes eight equally spaced radial slots adapted to accommodate the neck portions of the conical horns 16-23 thereby enabling the respective flanges thereof to be attached thereto. The center horn 10 may be multimoded in accordance with known techniques or as described in copending application for patent titled Broadband Multimode Horn Antenna by James S. Ajioka, Ser. No. 771,178 filed Oct. 28, 1968 and assigned to the same patentee as is the present case. The specification of this patent is incorporated herein by reference.

Referring to FIG. 3 there is shown a schematic diagram of an apparatus for feeding the nine-horn array of FIG. 1, As previously explained, the nine-horn array of the present invention approximates the main lobe 27 and first minor lobe" 28 of a Lambda function .I,(u)/u as indicated by the characteristic 30, FIG. 3. To achieve this, an input 25 passes through a power divider 26 and connects to the input flange 15 of the center horn 10. The antenna pattern is shaped by the division of power between the center horn l0 and the surrounding smaller horns l623. To achieve the division to approximate the characteristic 30, the power divider 26 splits the power in a manner to direct percent of the input power to the center horn 10. The remaining output from power divider 26 is connected to the shunt arm of a magic tee 32, the series arm of which is terminated. Output arms from the magic tee 32 are, in turn, connected to shunt arms of magic tees 33, 34, the series arms of which are again terminated. The output arms of magic tees 33, 34 are then connected to the shunt input arms of magic tees 35, 36, 37, 38, the series arms of which are terminated. Finally, the output arms of the magic tees 35 36, 37, 38 are connected to the input flanges of the smaller conical horns 16-23. The inputs of the conical horns 16-23 are oriented in a manner such that the polarity of the signal ap pearing at the respective apertures thereof are out of phase from the signal appearing at the aperture of the large conical horn 10. The 180 phase difference is employed because of the opposite polarity of the first minor lobes 28 relative to the main lobe 29 of the characteristic 30. All of the inputs to the conical horn l0 and to the conical horns 16-23 are designed to launch a dominant TE mode which may be multimoded in the case ofhorn 10. In the event that dual orthogonal polarization is desired, an orthogonal mode transducer (not shown) is interposed between each horn 10, 16-23 and the feed network of FIG. 3 and a similar network connected from the orthogonal mode transducers used for the orthogonal mode. Also it is understood that the terminations can be removed from any or all of the magic tees 32-38 for the purpose of providing antenna-pointing error correction information commonly known as monopulse operation. In the case of operation from a stabilized satellite, error correction is not required as there is no movement between the transmitter and receiver other than minor variations resulting from the stabilization.

Referring to FIG. 6 there is shown an ideal pattern 40 for earth coverage versus a conventional pattern 41 for operation from synchronized satellites 42, 43, respectively. The ideal pattern 40 has shoulders 44, 45 which are 3.6 db. up from the center beam intensity whereby maximum signal is directed toward the edge of the earth as seen from the satellite 42 thereby providing a substantially uniform signal over the portion of the earths surface covered. The shoulders 44, 45 of pattern 40 are of the order of one degree in width to allow for minor errors in the orientation of the satellite 42. As contrasted with the ideal pattern 40, the conventional pattern 41 is the weakest at the edge of the earth where maximum signal is needed. Also, a substantial portion of the pattern 41 is wasted as the energy therein never falls on the earth.

In the operation of the nine-horn array of FIG. 1, the ideal pattern 40 is approximated by using a flare angle of the order of 10 for the center horn l0 and for the peripheral horns 17-23 and by adjusting the power divider 26 to deliver 95 percent of the input power to the center horn 10 whereby the remaining 5 percent of the input power is divided between the surrounding horns 16-23 by the magic tees 32-38. A domi- 1 proximates that ofvthe ideal pattern 40, FIG. 6. The

nominally 180 nant TE mode is launched in each of the horns 16-23 and in the center horn 10. Under these circumstances, the nine-horn array of FIG. 1 generates a beam having the H-plane pattern 50, the E-plane pattern 52 and the diagonal plane pattern 54 shown in FIG. 4. As shown in the drawing, the patterns 50, 52, 54, in addition to having rotational symmetry and polarization purity, have a shoulder-to-shoulder.width of 19 which apside lobes in the patterns 50, 52, 54 may be minimized in the manner described in the aforementioned application. titled, -Broadband Multimode Horn Antenna by multimoding the center horn 10. With the center horn l multimoded in this manner, the nine-horn array of FIG. 1 generates a beam having the H-plane pattern 56, the E-plane pattern 58 and the diagonal plane pattern 60 shown in FIG. wherein the size of the side lobes apparent in ,the corresponding patterns 50, 52, 54 are substantially reduced. As before, the shoulder width of the patterns 56, 58, 60, are each 19 which approximates that of the ideal pattern 40 for earth coverage from a synchronous satellite. in other applications such as the feed for a Cassegrain antenna, other power splits by the power divider 26 may be required and larger flare angles used depending on size of reflector and frequency.

What is claimed is:

1. An antenna system comprising a conductive center horn of predetermined size, said center horn having an input at one extremity and an aperture at the remaining extremity thereof; a plurality of'no lessthan four and an integral power of two peripheral'horns, eachhaving an input at one extremity and an aperture at the remaining extremity thereof, each being symmetrical abouta longitudinal axis andeachbeing ofa uniform size smaller than said predetermined size, said plurality of I horns being disposed at uniform intervals about and at the same point along said center horn and aligned in the same direction as said center horn; means coupled to said input at said one extremity of said center horn for launching a first signal of predetermined frequency, phase, and power from said center horn; and means coupled to said respective inputs of said plurality of horns for simultaneously launching a second signal therefrom, said secondsignal having a frequency equal to said predetermined frequency, a power that is only a fraction of said predetermined power and a phasethat is relative to said predetermined phase.

2. The antenna system as defined in claim 1 wherein the total area of said apertures of said plurality of horns is substantially three times the area ofsaid aperture ofsaid center horn.

3. The antenna system as defined in claim 1 wherein said aperture of said center horn and said apertures of said plurality of horns are in a common plane.

4. The antenna system as defined in claim 1 additionally including means disposed in said center horn for multimoding said center horn.

5. An antenna system for generating a predetermined antenna pattern in response to an applied signal, said system comprising a conductive conical center horn of predetermined size, said conical center horn having an input at one extremity and an aperture at the remaining extremity thereof; eight conductive conical peripheral horns, each having an input atone extremity and an aperture at the remaining extremity thereof and each being of a uniformsize smaller than said predetermined size, said eight peripheral horns being disposed at uniform intervals about said center horn; and means coupled to said input of said conical center horn and to said respective inputs of said eight conical peripheral horns and responsive to said applied signal for launching a major portion of the power ofsaid signal from said conical centerhorn asawave ina TE dominant mode with a predetermined phase and for launching the remaining portion of the power of said signal equally from said eight peripheral horns as respective waves in TE dominant modes with a phase nominally 180 relative to said predetermined phase.

6. The antenna systemas defined in claim 5 wherein the respective diameters of said eight peripheral conical horns equal 0.618 times the dlametero said aperture ofsaid conical center horn.

7. The antenna system as defined in claim 5 additionally including means in said conical center horn for multimoding said conical center horn.

8. An antenna system for generating a predetermined antenna pattern in response to an applied signal, said system comprising a conductive conical center horn of predetermined size, said conical center horn having an input atone extremity tees having a shunt input arm and first and second output arms, said first and second output arms of said first, second,

third and fourth magic tees being connected, respectively,to

said inputs'of said eight conical peripheral horns to launch signals of predetermined polarity therein, said first and second output arms of said fifth and sixth magic tees being connected to said shunt arms ofsaid first, second, third, and fourth magic tees, and said first and second output arms of said seventh magic tee connected to said shunt arms of said fifth and sixth magic tees; and means including a power divider responsive to said signal and having outputs connected to said input of said conical center horn and said shunt arm of said seventh magic tee for directing a major portion of the power of said signal to said center horn and the remaining portion of the power of said signal to said shunt arm of said seventh magic tee.

9. The antenna system as defined in claim 8 wherein said power divider directs percent of the power of said signal to said center horn and the remaining 5 percent thereof to said shunt arm of said seventh magic tee.

Patent Citations
Cited PatentFiling datePublication dateApplicantTitle
US3295134 *Nov 12, 1965Dec 27, 1966Sanders Associates IncAntenna system for radiating directional patterns
US3482251 *May 19, 1967Dec 2, 1969Philco Ford CorpTransceive and tracking antenna horn array
Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US4090203 *Sep 29, 1975May 16, 1978Trw Inc.Low sidelobe antenna system employing plural spaced feeds with amplitude control
US4364052 *Oct 29, 1980Dec 14, 1982Bell Telephone Laboratories, IncorporatedAntenna arrangements for suppressing selected sidelobes
US4376940 *Oct 29, 1980Mar 15, 1983Bell Telephone Laboratories, IncorporatedAntenna arrangements for suppressing selected sidelobes
US4516130 *Mar 9, 1982May 7, 1985At&T Bell LaboratoriesAntenna arrangements using focal plane filtering for reducing sidelobes
US4586051 *Feb 28, 1983Apr 29, 1986Agence Spatiale EuropeenneReflector distortion compensation system for multiple-beam wave satellite antennas
US4757324 *Apr 23, 1987Jul 12, 1988Rca CorporationAntenna array with hexagonal horns
US4967077 *May 9, 1989Oct 30, 1990The United States Of America As Represented By The Secretary Of The Air ForceMultiple aperture arrays for optical and radio frequency signals
US4972199 *Mar 30, 1989Nov 20, 1990Hughes Aircraft CompanyLow cross-polarization radiator of circularly polarized radiation
US5113197 *Dec 28, 1989May 12, 1992Space Systems/Loral, Inc.Conformal aperture feed array for a multiple beam antenna
US5812096 *Sep 26, 1997Sep 22, 1998Hughes Electronics CorporationMultiple-satellite receive antenna with siamese feedhorn
US5859620 *Nov 27, 1996Jan 12, 1999Hughes Electronics CorporationMultiband feedhorn mount assembly for ground satellite receiving antenna
US5874923 *Jul 20, 1995Feb 23, 1999Trulstech Innovation HandelsbolagFeeder horn, intended particularly for two-way satellite communications equipment
US6388635 *Nov 11, 1999May 14, 2002C2Sat Communications AbFeeder horn, intended especially for two-way satellite communication
US6424312Dec 7, 2000Jul 23, 2002AlcatelRadiating source for a transmit and receive antenna intended to be installed on board a satellite
US8421700 *Feb 4, 2012Apr 16, 2013Ubiquiti Networks, Inc.Antenna system and method
US20120133564 *Feb 4, 2012May 31, 2012Ubiquiti Networks Inc.Antenna system and method
EP1107359A1 *Dec 7, 2000Jun 13, 2001Alcatel Alsthom Compagnie Generale D'electriciteRadiating source for an antenna to be installed in a satellite
EP1124283A2 *Feb 6, 2001Aug 16, 2001The Boeing CompanyBeam forming network having a cell reuse pattern and method for implementing same
Classifications
U.S. Classification343/778, 343/786, 342/368
International ClassificationH01Q19/10, H01Q19/17, H01Q21/29, H01Q21/00
Cooperative ClassificationH01Q19/17
European ClassificationH01Q19/17