Composite multi-beam and shaped beam antenna system

• US 5,576,721 A
• Filed: 11/21/1994
• Issued: 11/19/1996
• Est. Priority Date: 03/31/1993
• Status: Expired due to Fees

• Current Assignee: Space Systems/Loral Incorporated (Loral Space and Communications Incorporated)
• Original Assignee: Space Systems/Loral Incorporated (Loral Space and Communications Incorporated)
• Inventors: Hwang, Yeongming, Jakstys, Vito J.
• Primary Examiner(s): Hajec, Donald T.
• Assistant Examiner(s): Ho, Tan
• Application Number:
  US08/342,653
• Time in Patent Office: 729 Days
• Field of Search: 343/753, 343/754, 343/755, 343/756, 343/781 R, 343/781 P, 343/781 CA, 343/786, 343/909, 343/840, 342/373, 342/374
• US Class Current: 343/753
• CPC Class Codes: H01Q 15/0013 said selective devices working as frequency-selective reflecting surfaces, e.g. FSS, dichroic plates, surfaces being partly transmissive and reflective
• CPC Class Codes: H01Q 25/007 using two or more primary active elements in the focal region of a focusing device for operation on different wavebands H01Q5/22

Abstract

A composite antenna for use in satellite communication provides both the functions of multiple beams and a shaped beam radiated from a single radiating aperture. The radiating aperture may employ a mirror or a lens. Transmitted radiation from an array of radiators is coupled via a subreflector to the main reflector or lens which constitutes the radiating aperture of the antenna system. During reception of radiant-energy signals, signals received by the main reflector or lens are coupled via a separate subreflector to a separate array of receiving radiators operated at a frequency band different from that of the transmit array. The two subreflectors are combined into a single subreflector assembly employing a metallic concave reflector covered by a layer or coating of frequency selective optical material which allows for propagation of radiation at one frequency to the metal reflector while reflecting radiation in the other frequency band from a surface of the coating. Separate beamformers are employed for receiving and transmitting radiant-energy signals, the beamformers combining signals of clusters of radiators to provide for multiple beams wherein each of a plurality of the beams is formed by a cluster of radiators. Additional connection is provided via diplexers to the beamformers to select radiators to be employed for generation of shaped beams for both reception and transmission. The reflecting surfaces have diameters much larger than the diameters of the radiators to provide for individual beams from each of the radiators.

Claims

1. An antenna system comprising:

collimating means having a least one optical element;

a plurality of radiators arranged in at least one array, said one array of radiators illuminating said one optical element with radiation, said collimating means serving to form multiple beams of radiation from multiple ones of said radiators for illuminating a subject with said beams;

wherein said one optical element has a cross-sectional dimension which is much larger than cross-sectional dimensions of individual ones of said radiators for forming the beams of radiation from respective ones of said radiators, individual ones of the beams illuminating contiguous regions of the subject;

the subject has an irregular configuration with undulations, and individual ones of said radiators are positioned in said one array in a two-dimensional arrangement which conforms to the undulations in the configuration of the subject;

sizes of radiating apertures of said radiators differ wherein radiators of smaller radiating aperture are employed to illuminate a portion of the subject having a boundary with complex undulation while radiators of larger radiating aperture are employed to illuminate a portion of the subject having a boundary with gradual undulation;

cross-sectional dimensions of said radiators of smaller radiating aperture are less than a wavelength of the radiation, and cross-sectional dimensions of said radiators of larger radiating aperture are greater than a plurality of wavelengths of the radiation;

said system further comprises beam-forming means coupled to said radiators and having a network for energizing clusters of said radiators to provide multiple beams of radiation, there being a separate beam from each of said clusters, at least one of said beams from one of said clusters having an irregular two-dimensional footprint; and

energizing means connecting with said network for energizing all of said clusters of radiators simultaneously to provide a shaped-beam illumination of said subject.

2. A system according to claim 1 wherein said energizing means includes filter means interconnecting said energizing means with said beam-forming means for allowing operation of said beam-forming means to produce said multiple beams at a first radiation frequency and operation of said energizing means to produce said shaped beam at a second radiation frequency different from said first frequency.

3. A system according to claim 2 wherein said network includes a plurality of dual mode converters for joining said radiators to provide said clusters.

4. A system according to claim 2 further comprising meanderline polarizing means disposed at said one array of radiators for converting linear polarization of said radiators to circularly polarized radiation during transmission of radiation from said radiators, and for converting circular polarization to linear polarization during reception of radiation at said radiators.

5. A system according to claim 4 wherein said polarizing means comprises a plurality of meanderline polarizers located at respective ones of said radiators.

6. A system according to claim 4 wherein said polarizing means comprises a common meanderline polarizer assembly extending across all of said radiators.

7. A system according to claim 6 wherein each of said radiators is configured as a horn, each horn facing said common meanderline polarizer.

8. A system according to claim 1 wherein each of said radiators is a horn having a square shaped radiating aperture, corresponding sides of the horns being parallel to provide for continuous illumination of at least a portion of the subject.

9. A system according to claim 8 wherein a ratio of diameter of horn cross section to diameter of said one optical element provides a divergence to a beam from one of said horns which overlaps partially a region of the subject illuminated by an adjacent one of said horns in said one array of radiators.

10. A system according to claim 9 wherein said network includes a plurality of dual mode converters for joining said horns to provide said clusters, and a horn at a boundary of two neighboring clusters is energized via a shared feed of electromagnetic power to radiate into the beams of both of said two neighboring clusters.

11. A system according to claim 10 wherein said network includes coupling means for joining said dual mode converters in branches of said network, said system further comprising multiplexing means for energizing said branches via time division multiplexing.

12. A system according to claim 11 wherein said coupling means comprises a power combiner for reception of radiant signals by said antenna system.

13. A system according to claim 11 wherein said coupling means comprises a power divider for transmission of radiant signals by said antenna system.

14. A system according to claim 1 wherein said network includes a plurality of coupling means for joining said radiators in branches of said network to provide said clusters, said system further comprising multiplexing means for energizing said branches via time division multiplexing.

15. A system according to claim 14 wherein said coupling means are dual mode converters.

16. A system according to claim 1 wherein said network includes a plurality of coupling means for joining said radiators in branches of said network to provide said clusters, said energizing means includes filter means interconnecting said energizing means with said branches for allowing operation of said beam-forming means to produce said multiple beams at a first radiation frequency and operation of said energizing means to produce said shaped beam at a second radiation frequency different from said first frequency, said energizing means further comprising multiplexing means for energizing said branches via frequency division multiplexing.

17. A system according to claim 1 further comprising:

a second array of radiators, and a second beam-forming means connected to the radiators of said second array of radiators;

wherein said collimating means comprises a second optical element having a larger diameter than said one optical element, said one optical element serving as a subreflector for illuminating said second optical element during transmission of electromagnetic power; and

said subreflector comprises two reflecting surfaces of which one reflecting surface is operative to reflect radiation of said one array and a second reflecting surface is operative to reflect radiation of said second array.

18. A system according to claim 17 wherein said second optical element is a main reflector, and said antenna is constructed in the form of a Gregorian antenna.

19. A system according to claim 17 wherein said second optical element is a lens.

20. A system according to claim 17 wherein said one array is operative at a relatively high frequency band and said second array is operative at a relatively low frequency band, said second reflecting surface is configured as a layer of frequency selective optical material disposed on said first reflecting surface wherein said layer is transparent to radiation at said high frequency band and reflective to radiation at said low frequency band, radiation at said high frequency band propagating through said layer to reflect from said first reflecting surface.

21. A system according to claim 20 wherein said one array of radiators is operative simultaneously with said second array of radiators, said one array serving to receive radiant energy signals concurrently with a transmission of radiant energy signals from said second array.

22. A system according to claim 1 wherein at least a plurality of said radiators differ in cross-sectional dimensions from the cross-sectional dimensions of other ones of said radiators, individual ones of said radiators having smaller cross-sectional dimensions are located in positions in said one array corresponding to complex undulations of the subject, and individual ones of said radiators having larger cross-sectional dimensions are located in positions in said one array corresponding to portions of the subject having relatively little undulation, a two-dimensional footprint of a beam of one of said radiators of larger cross-sectional dimensions being larger than a two-dimensional footprint of a beam of one of said radiators of smaller cross-sectional dimensions.

23. A method for adapting an antenna system to provide a shaped-beam illumination of a subject, the subject having an irregular configuration with undulations;

wherein the antenna system comprises;

collimating means having a least one optical element;

a plurality of radiators arranged in at least one array, said one array of radiators illuminating said one optical element with radiation, said collimating means serving to form multiple beams of radiation from multiple ones of said radiators for illuminating the subject with said beams, wherein said one optical element has a cross-sectional dimension which is much larger than cross-sectional dimensions of individual ones of said radiators for forming the beams of radiation from respective ones of said radiators, individual ones of the beams illuminating contiguous regions of the subject; and

beam-forming means coupled to said radiators and having a network for energizing clusters of said radiators to provide multiple beams of radiation;

wherein the method comprises steps of;

sizing the radiating apertures of respective ones of said radiators to provide radiators of smaller radiating aperture for illuminating a portion of the subject having a boundary with complex undulation, and to provide radiators of larger radiating aperture for illuminating a portion of the subject having a boundary with gradual undulation, wherein, in said sizing step, cross-sectional dimensions of said radiators of smaller radiating aperture are less than a wavelength of the radiation, and cross-sectional dimensions of said radiators of larger radiating aperture are greater than a plurality of wavelengths of the radiation;

arranging said radiators to provide that individual ones of said radiators are positioned in said one array in a two-dimensional arrangement which conforms to the undulations in the configuration of the subject; and

energizing a plurality of said clusters of radiators simultaneously via said network to provide a shaped-beam illumination of said subject, there being a separate cluster beam from each of said clusters, at least one of said cluster beams from one of said clusters having an irregular two-dimensional footprint to conform to an an undulation in the configuration of the subject.