Smaller aperture antenna for multiple spot beam satellites

• US 20060121848A1
• Filed: 01/18/2006
• Published: 06/08/2006
• Est. Priority Date: 07/14/2000
• Status: Abandoned Application

• Current Assignee: COMSAT Corporation (Reorganized ISA SA)
• Original Assignee: COMSAT Corporation (Reorganized ISA SA)
• Inventors: Zaghloul, Amir I., Williams, Albert E., Killic, Ozlem
• Application Number:
  US11/333,333
• Publication Number:
  US 20060121848A1
• Time in Patent Office: Days
• US Class Current: 455/12.100
• CPC Class Codes: H04B 7/18528 Satellite systems for providing two-way communications service to a network of fixed stations, i.e. fixed satellite service or very small aperture terminal [VSAT] system
• CPC Class Codes: H04B 7/2041 Spot beam multiple access

Abstract

This disclosure describes a method to generate large numbers of spot beams for multiple-beam satellite systems using smaller apertures. This is done by dividing the basic spot beam that has 3 to 4 dB of gain drop within the beam into a number of smaller 1-dB sub-beams. This has the effect of reducing the required peak gain for the antenna by 2-3 dB, thus reducing its size by as much as 50%. The frequency band allocated to the basic beam will be divided among the sub-beams. However, the frequency re-use among the basic beams can be maintained. Frequency allocations have to be coordinated among all beams. This concept is especially applicable to phased arrays using digital beam formers. The DBF complexity is a function of the number of array elements, and is less dependent on the number of beams. Reducing the array size, and consequently reducing the number of elements helps in reducing the complexity, power and mass of the DBF.

Claims

1. A method of communicating via satellite in a system comprising a satellite having a first type antenna capable of transmission of communication signals to a region on the earth'"'"'s surface and a plurality of earth stations disposed in said region, each earth station having a second type antenna capable of reception of said signals, said method comprising;

transmitting from said first type antenna multiple sub-beams within bandwidth allocated to a basic spot beam to said plurality of antennas in said region.

2. A method as claimed in 1, where said sub-beams are transmitted within the frequency range of said basic spot beam.

3. A method as claimed in 1, where said sub-beams are transmitted in a plurality to form a cluster, where said cluster has the same coverage area in said region as said basic spot beams.

4. A method as claimed in 1, where said sub-beams are transmitted by use of a phased array antenna.

5. A method as claimed in 1, wherein said sub-beams require less peak gain than said basic spot beam.

6. A method as claimed in 3, where said clusters are transmitted so as to form a coverage area, said coverage area is a contiguous area defined by a matrix, where each facet of said matrix has interlocking borders, said borders defined as the contours of said spot beams.

7. A method as claimed in 4, wherein said transmission originates from a low or medium earth orbiting system.

8. A method as claimed in 1, wherein said basic beam has 3 or more dB of gain drop.

9. A method as claimed in 1, wherein said sub-beam has less than 1 dB of gain drop.

10. A method as claimed in 1, wherein said sub-beams number 4 or more.

11. A communications system comprising a satellite having a first type antenna capable of transmission of communication signals to a region on the earth'"'"'s surface and a plurality of earth stations disposed in said region, each earth station having a second type antenna capable of reception of said signals;

a phased array antenna;

a digital beam former that produces multiple sub-beams within the parameters of a basic spot beam; and

an aperture sized to produce sub-beams with a gain drop of less than 3 dB.

12. An system as claimed in 11, where said antenna and digital beam former are installed on a satellite.

13. An system as claimed in 12, where said satellite is in low or medium Earth orbit.

14. A satellite antenna comprising;

a phased array antenna;

a digital beam former operatively connected to said phased array and adapted to produce multiple sub-beams, each said sub-beam having a gain that at its peak is approximately equal to an edge gain.