Frequency sharing for satellite communication system

• US 5,822,680 A
• Filed: 11/07/1996
• Issued: 10/13/1998
• Est. Priority Date: 11/07/1996
• Status: Expired due to Term

• Current Assignee: Rateze Remote Mgmt. L.L.C. (Intellectual Ventures LLC)
• Original Assignee: Teledesic, LLC (Michael J. Larson, MBA)
• Inventors: Patterson, David P., Sturza, Mark Alan, Stuart, James R.
• Primary Examiner(s): Vo, Nguyen
• Assistant Examiner(s): ARMSTRONG, DARNELL R
• Application Number:
  US08/744,337
• Time in Patent Office: 705 Days
• Field of Search: 455/3.2, 455/12.1, 455/13.1, 455/13.2, 455/13.3, 455/63, 455/278.1, 455/296, 455/427, 455/429, 455/430, 455/431, 455/447, 455/562, 342/75, 342/352, 342/356, 342/359, 370/316, 370/317
• US Class Current: 455/12.1
• CPC Class Codes: H04B 7/18513 Transmission in a satellite or space-based system
• CPC Class Codes: H04B 7/195 Non-synchronous stations

Abstract

A communication system and methods for sharing a common communication frequency, without interfering with a second communication system which has a plurality of satellites operating in geostationary orbits (GO) and ground stations (GS) which communicate with the satellites (GEO) on the common communication frequency, is disclosed. Conventional geostationary satellites broadcast in C and K_u bands. Ground stations (GS) which receive these signals must have their antennas pointed toward the plane of the Equator (EQ). Satellites (10) which occupy inclined orbits (LO) and communicate with terrestrial terminals (12) propagate beams of energy that do not intersect the plane of the Earth'"'"'s Equator. Terrestrial terminals (12) in the northern hemisphere communicate with a satellite (10) only when the sub-satellite point of the satellite (10) is at a latitude more northerly than the terrestrial terminal (12). Terrestrial terminals (12) in the southern hemisphere communicate with a satellite (10) only when the sub-satellite point of the satellite (10) is at a latitude more southerly than the terrestrial terminal (12). The spatial isolation of signals achieved by this novel pointing method insures that both the geostationary and inclined orbit satellite systems do not interfere with each other.

Claims

1. A communication system for sharing, without interfering with a second communication system, a common communication frequency, said second communication system having a plurality of satellites (GEO) operating in Equatorial orbital planes (GO) and ground stations (GS) which communicate with said plurality of satellites (GEO) in said Equatorial orbit planes (GO) on said common communication frequency;

said communication system comprising;

a satellite (10) operating in an inclined orbit;

a terrestrial terminal (12);

said terrestrial terminal (12) having an antenna which transmits and receives a beam of radiant energy (14) for communicating with said satellite (10);

said beam of radiant energy (14) having a frequency common with said second communication system; and

said terrestrial terminal (12) communicating with said satellite (10) only when said beam of radiant energy (14) does not intersect said Equatorial orbital planes (GO).

2. The system as claimed in claim 1 in which said satellite (10) operates in an inclined orbit at an altitude less than that of an inclined geosynchronous orbit.

3. The system as claimed in claim 1 in which said satellite (10) operates in an inclined geosynchronous orbit.

4. The system as claimed in claim 1 in which said satellite (10) operates in an inclined eccentric orbit, said inclined eccentric orbit having an apogee greater than that of an inclined geosynchronous orbit.

5. A communication system for sharing, without interfering with a second communication system, a common communication frequency, said second communication system having a plurality of satellites (GEO) operating in Equatorial orbital planes (GO) and ground stations (GS) which communicate with said plurality of satellites (GEO) in said Equatorial orbit planes (GO) on said common communication frequency;

said communication system comprising;

a constellation of satellites (10) operating in a plurality of inclined orbits;

each one of said satellites (10) having a sub-satellite point on Earth (E);

a plurality of terrestrial terminals (12) located at latitudes in Earth'"'"'s northern and southern hemisphere substantially above and below the Equator;

each one of said plurality of terrestrial terminals (12) having an antenna for communicating with one of said plurality of satellites (10);

said communication carried out on a frequency common with said second communication system;

each of said terrestrial terminals (12) in said northern hemisphere communicating with one of said satellites (10) only when said sub-satellite point of said satellite (10) is also in said northern hemisphere at a latitude more northerly than that of said terrestrial terminal (12); and

each of said terrestrial terminals (12) in said southern hemisphere communicating with one of said satellites (10) only when said sub-satellite point of said satellite (10) is also in said southern hemisphere at a latitude more southerly than that of said terrestrial terminal (12).

6. The system as claimed in claim 5 in which said constellation of satellites (10) operate in a plurality of inclined orbits, each of which said plurality of inclined orbits has an altitude less than that of an inclined geosynchronous orbit.

7. The system as claimed in claim 5 in which said constellation of satellites (10) operate in a plurality of inclined geosynchronous orbits.

8. The system as claimed in claim 5 in which said constellation of satellites (10) operate in a plurality of inclined eccentric orbits, each of which said plurality of inclined eccentric orbits has an apogee greater than that of an inclined geosynchronous orbit.

9. The system as claimed in claim 5 in which said constellation of satellites (10) operate in a plurality of inclined orbits, at least one of which orbits has an altitude less than that of an inclined geosynchronous orbit, at least one of which orbits has an apogee greater than that of an inclined geosynchronous orbit and at least one of which orbits is an inclined geosynchronous orbit.

10. Communication apparatus for sharing, without interfering with a second communication apparatus, a common communication frequency, said second communication apparatus having a plurality of satellites (GEO) operating in Equatorial orbital planes (GO) and ground stations (GS) which communicate with said plurality of satellites (GEO) in said Equatorial orbit planes (GO) on said common communication frequency;

said communication apparatus comprising;

a constellation of satellites (10) operating in a plurality of inclined orbits;

a plurality of terrestrial terminals (12) located at latitudes in Earth'"'"'s northern and southern hemisphere substantially above and below the Equator;

each one of said plurality of terrestrial terminals (12) having an antenna for communicating with one of said plurality of satellites (10);

said communication carried out on a frequency common with said second communication system;

each of said terrestrial terminals (12) in said northern hemisphere communicating with one of said satellites (10) only when a sub-satellite point of said satellite (10) is also in said northern hemisphere at a latitude more northerly than that of said terrestrial terminal (12);

each of said terrestrial terminals (12) in said southern hemisphere communicating with one of said satellites (10) only when a sub-satellite point of said satellite (10) is also in said southern hemisphere at a latitude more southerly than that of said terrestrial terminal (12);

said plurality of inclined orbits including at least one orbit which has an altitude less than that of an inclined geosynchronous orbit, at least one orbit which has an apogee greater than that of an inclined geosynchronous orbit and at least one orbit which is an inclined geosynchronous orbit.

11. A method for sharing a common communication frequency by a communication system, without interference with a second communication system, said second communication system having a plurality of satellites (GEO) operating in Equatorial orbital planes (GO) and ground stations (GS) which communicate with said plurality of satellites (GEO) in said Equatorial planes (GO) on said common communication frequency;

said method comprising the steps of;

operating a satellite (10) in an inclined orbit;

communicating with said satellite (10) by transmitting and receiving a beam of radiant energy (14) from a terrestrial terminal (12);

said beam of radiant energy (14) having a frequency common with said second communication system; and

communicating with said satellite (10) from said terrestrial terminal (12) only when said beam of radiant energy (14) does not intersect said Equatorial orbital planes (GEO).

12. The method as claimed in claim 11 in which said step of operating a satellite (10) in an inclined orbit includes the step of operating a satellite (10) in an orbit which has an altitude less than that of a geosynchronous orbit.

13. The method as claimed in claim 11 in which said step of operating a satellite (10) in an inclined orbit includes the step of operating a satellite (10) in an inclined geosynchronous orbit.

14. The system as claimed in claim 11 in which said step of operating a satellite (10) in an inclined orbit includes the step of operating a satellite (10) in an inclined eccentric orbit, said inclined eccentric orbit having an apogee greater than that of an inclined geosynchronous orbit.

15. A method for sharing a common communication frequency by a communication system, without interference with a second communication system, said second communication system having a plurality of satellites (GEO) operating in Equatorial orbital planes (GO) and ground stations (GS) which communicate with said plurality of satellites (GEO) in said Equatorial planes (GO) on said common communication frequency;

said method comprising the steps of;

operating a constellation of satellites (10) in a plurality of inclined orbits;

each one of said satellites (10) having a sub-satellite point on Earth (E);

locating a plurality of terrestrial terminals (12) at latitudes in Earth'"'"'s northern and southern hemisphere substantially above and below the Equator;

each one of said plurality of terrestrial terminals (12) having an antenna for communicating with at least one of said satellites (10);

said communicating carried out on a frequency common with said second communication system;

communicating with at least one of said satellites (10) from one of said plurality of terrestrial terminals (12) in said northern hemisphere only when said sub-satellite point of said satellite (10) is also in said northern hemisphere at a latitude more northerly than that of said terrestrial terminal (12); and

communicating with one of said satellites (10) from one of said plurality of terrestrial terminals (12) in said southern hemisphere only when said sub-satellite point of said satellite (10) is also in said southern hemisphere at a latitude more southerly than that of said terrestrial terminal (12).

16. The method as claimed in claim 15, in which said step of operating a constellation of satellites (10) in a plurality of inclined orbits includes the step of operating a constellation of satellites (10) in a plurality of inclined orbits, at least one of said orbits having an altitude less than that of an inclined geosynchronous orbit.

17. The method as claimed in claim 15 in which said step of operating a constellation of satellites (10) in a plurality of inclined orbits includes the step of operating a constellation of satellites (10) in a plurality of inclined orbits, at least one of said orbits being a geosynchronous orbit.

18. The method as claimed in claim 15 in which said step of operating a constellation of satellites (10) in a plurality of inclined orbits includes the step of operating a constellation of satellites (10) in a plurality of inclined eccentric orbits at least one of said orbits having an apogee greater than that of an inclined geosynchronous orbit.

19. The method as claimed in claim 15 in which said step of operating a constellation of satellites (10) in a plurality of inclined orbits includes the step of operating a constellation of satellites (10) in a plurality of inclined orbits, at least one of which said orbits has an altitude less than that of a geosynchronous inclined orbit, at least one of which said orbits has an apogee greater than that of an inclined geosynchronous orbit and at least one of which said orbits is an inclined geosynchronous orbit.

20. A method for sharing a common communication frequency by a communication system, without interfering with a second communication system, said second communication system having a plurality of satellites (GEO) operating in Equatorial orbital planes (GO) and ground stations (GS) which communicate with said plurality of satellites (GEO) in said Equatorial planes (GO) on said common communication frequency;

said method comprising the steps of;

operating a constellation of satellites (10) in a plurality of inclined orbits;

said satellites (10) employing a plurality of Earth-fixed cells (26) in an Earth-fixed grid (20);

each one of said satellites (10) having a sub-satellite point on Earth (E);

locating a plurality of terrestrial terminals (12) at latitudes in Earth'"'"'s northern and southern hemisphere substantially above and below the Equator;

each one of said plurality of terrestrial terminals (12) having an antenna for communicating with at least one of said plurality of satellites (10);

said communicating carried out on a frequency common with said second communication system;

assigning said satellites (10) to communicate with at least one of said terrestrial terminals (12) in an Earth-fixed Cell (26) only when said Earth-fixed cell (26) and said sub-satellite point of said satellite (10) are in said northern hemisphere, and all points within a footprint of said Earth-fixed cell (26) are at a latitude more southerly than that of said sub-satellite point;

assigning said satellites (10) to communicate with at least one of said terrestrial terminals (12) in an Earth-fixed cell (26) only when said Earth-fixed cell (26) and said sub-satellite point of said satellite (10) are in said southern hemisphere, and all point a footprint of said Earth-fixed cell (26) are at a latitude more northerly than that of said sub-satellite point.