Antenna system for controlling and redirecting communications beams

• US 5,734,345 A
• Filed: 04/23/1996
• Issued: 03/31/1998
• Est. Priority Date: 04/23/1996
• Status: Expired due to Term

• Current Assignee: Northrop Grumman Systems Corporation (Northrop Grumman Corporation)
• Original Assignee: TRW Limited (Zeppelin - Stiftung der Stadt Friedrichshafen)
• Inventors: Ho, Antony Y., Melnick, Martin, Chen, Chun-Hong Harry
• Primary Examiner(s): Sotomayor, John B.
• Application Number:
  US08/636,366
• Time in Patent Office: 707 Days
• Field of Search: 342/74, 342/75, 342/78, 342/81, 342/367, 342/373, 342/374, 342/371
• US Class Current: 342/74
• CPC Class Codes: H01Q 21/22 Antenna units of the array energised non-uniformly in amplitude or phase, e.g. tapered array or binomial array
• CPC Class Codes: H01Q 3/2694 using also variable phase-shifters H01Q3/2688 takes precedence
• CPC Class Codes: H01Q 3/40 with phasing matrix
• CPC Class Codes: H04B 7/2041 Spot beam multiple access

Abstract

An antenna system 10 for a communications satellite which transmits and receives communications from ground based devices. The system includes an antenna array 16 containing a plurality of feed elements 18 which cooperate to receive or transmit coverage beams arranged in a circular layout at a coverage area in a far-field region proximate the surface of the earth. The feed elements 18 are arranged in a non-circular layout within the antenna array 16. This system further includes a beam forming network 14 for mapping coverage beam signals onto feed signals which drive the antenna array 16. The beam forming network 14 includes a beam forming matrix 28 and a beam connecting network 30. The beam connecting network 30 separates each coverage beam signal into a plurality of component signals weighted to have differing amplitudes from one another. The component signals are delivered to the beam forming matrix 28 which in turn produces corresponding feed signals to drive the antenna array 16 in such a manner as to form feed beams which cooperate to define the coverage beams at the far-field region. The beam connecting network 30 weights the component signals unevenly in order to shift corresponding resultant coverage beams inward or outward until aligned within the coverage area in a circular layout along concentric circles.

Claims

1. An antenna system for receiving or transmitting communications signals between a communications satellite and earth based unit located within a coverage area of said system, said system defining a plurality of coverage beams forming said coverage area in a far field region, said system comprising:

an antenna array containing a plurality of feed elements which cooperate to receive or transmit coverage beams arranged in a circular layout in a coverage area in a far field region, said feed elements being arranged in a non-circular layout; and

a beam forming network containing a plurality of beam ports and feed ports, said feed ports conveying feed signals related to said coverage beams, said feed ports conveying said feed signals between said beam forming network and said feed elements, said beam ports conveying coverage signals between said beam forming network and the communications satellite, each of said coverage signals uniquely corresponding to one of said coverage beams, said beam forming network defining a weighted mapping relation between said feed signals and said coverage signals such that said feed elements arranged in said non-circular layout cooperate to receive or transmit coverage beams arranged in a circular layout in said coverage area.

2. The system of claim 1, wherein said beam forming network divides said coverage signals into component signals and groups said component signals into clusters, each cluster containing component signals from at least two coverage signals, said beam forming network formed each cluster of signal components into a corresponding singlet signal, said beam forming network outputting said feed signals based on said singlet signals, said feed elements transmitting said feed beams based on said feed signals.

3. The system of claim 1, wherein said non-circular array of feed elements receives incoming coverage beams from said coverage area arranged in said circular layout, said feed elements outputting feed signals corresponding to said incoming coverage beams, said beam forming network transforming said feed signals into said component signals and combining predetermined component signals, based on a predefined weighted mapping scheme, to form said coverage signals, each coverage signal corresponding to one of said coverage beams.

4. The system of claim 1 wherein said beam forming network includes a beam connecting network for converting said coverage signals into singlet signals, each singlet beam signal containing components from a predetermined number of coverage signals, said beam connecting network varying an amplitude of said components to redirect said coverage beams into said circular layout at said coverage area said beam forming network converting said singlet signals to said feed signals.

5. The system of claim 1, wherein each coverage signal and associated coverage beam has a unique frequency, said beam forming network including a beam connecting network for dividing each coverage signal into multiple signal components having a predetermined common frequency and different amplitudes, said predetermined amplitudes being set to direct said feed elements arranged in said non-circular layout to cooperate to transmit said coverage beams in said circular layout.

6. The system of claim 1, wherein said beam forming network includes a beam forming matrix for subsignals components of said coverage signal phase shifted with respect to one another.

7. The system of claim 1, wherein said beam forming network includes a beam forming matrix and a beam connecting network, said beam connecting network dividing said coverage signal into weighted component signals of differing amplitude and collecting sub-sets of said component signals to produce singlet signals therefrom, said beam forming matrix converting said singlet signals to said feed signals.

8. The system of claim 1, wherein said feed elements define feed beams which cooperate to define singlet beams, each singlet beam containing components of multiple coverage beams, said feed elements defining said singlet beams in a non-circular layout, wherein singlet beams having components from a single coverage beam are clustered adjacent one another in a singlet cluster and interact to define a corresponding coverage beam, said corresponding coverage beam having a center shifted from a center of said singlet cluster.

9. The system of claim 1, wherein said feed elements are arranged in a hexagonal layout, each feed element defining a feed beam, said feed beams cooperating to define singlet beams arranged in a hexagonal layout, said singlet beams cooperating to define said coverage beams in a circular layout.

10. The system of claim 1, wherein said beam forming network defines said weighted mapping relation by dividing each coverage signal into multiple components signals differing in at least one of amplitude and phase with respect to one another.

11. A method for defining and redirecting a plurality of coverage beams received by or transmitted from a communications satellite, said coverage beams being arranged in a circular layout at a coverage area in a far field region, said method comprising the steps of:

defining a one to one relation between a plurality of coverage signals and a unique corresponding plurality of coverage beams arranged in a circular layout;

conveying feed signals to or from an antenna array having a plurality of feed elements arranged in a non-circular layout, said feed elements operating in connection with said plurality of coverage beams arranged in said circular layout;

defining a mapping relation between said feed signals and a plurality of component signals, wherein said component signals are arranged in clusters, each of said clusters corresponding to a unique coverage signal;

defining a mapping relation between each cluster of component signals and a corresponding unique coverage signal; and

setting at least one of amplitudes and phases of said component signals in a cluster unevenly with respect to one another to align said coverage beams in said circular layout at said coverage area.

12. The method of claim 11, further comprising the steps of:

dividing said coverage signals into said component signals and grouping said component signals into clusters to form singlet signals, each of said singlet signals containing component signals from at least two coverage signals; and

outputting said feed signals based on said singlet signals.

13. The method of claim 11, further comprising the steps of:

receiving a first incoming coverage beam from said coverage area arranged in said circular layout;

outputting feed signals corresponding to said first incoming coverage signal;

transforming said feed signals into a first cluster component signals; and

combining said first cluster of component signals, based on a predefined weighted mapping scheme, to form a corresponding unique first outgoing coverage signal, such first outgoing coverage signal corresponding to said first incoming coverage beam.

14. The method of claim 11, further comprising the steps of converting a first incoming coverage signal into a first set of singlet signals, each singlet signal of said first set containing at least one component signal from said first incoming coverage signal;

setting an amplitude of at least one of said component signals greater than that of the remaining component signals; and

converting said singlet signals to said feed signals.

15. The method of claim 11, further comprising the steps of:

assigning a unique frequency to each coverage signal and associated coverage beam;

dividing each coverage signal into multiple component signals having a predetermined common frequency and predetermined different amplitudes; and

setting said predetermined different amplitudes to direct said feed elements arranged in said non-circular layout to cooperate to transmit said coverage beams in said circular layout.

16. The method of claim 11, further comprising the step of outputting sub-signals of said coverage signal phase shifted with respect to one another.

17. The method of claim 11, further comprising the steps of:

dividing said coverage signal into weighted component signals of differing amplitude;

collecting sub-sets of said component signals to produce singlet signals therefrom; and

converting said singlet signals to said feed signals.

18. The method of claim 11, further comprising the step of defining feed beams which cooperate to define singlet beams, each singlet beam containing components of multiple coverage beams, said singlet beams being defined in a non-circular layout, wherein singlet beams having components from a single coverage beam are clustered adjacent one another in a singlet cluster, singlet beams within said singlet cluster interacting to define a corresponding coverage beam, said corresponding coverage beam having a center redirected from a center of said singlet cluster.

19. The method of claim 11, further comprising the step of arranging said feed elements in a hexagonal layout, each feed element defining a feed beam, said feed beams cooperating to define singlet beams arranged in a hexagonal layout, said singlet beams cooperating to define said coverage beams in a circular layout.

20. The method of claim 11, wherein said setting step includes setting said amplitudes and phases of said component signals in each cluster unevenly with respect to one another.