Method for limiting interference between satellite communications systems

• US 20010045494A1
• Filed: 01/05/2001
• Published: 11/29/2001
• Est. Priority Date: 01/07/2000
• Status: Active Grant

• Current Assignee: The Boeing Co.
• Original Assignee: The Boeing Co.
• Inventors: Higgins, Robert P.
• Granted Patent: US 6,511,020 B2
• Time in Patent Office: Days
• US Class Current: 244/158R
• CPC Class Codes: B64G 1/1007 Communications satellites
• CPC Class Codes: B64G 1/1085 Swarms and constellations
• CPC Class Codes: B64G 1/242 Orbits and trajectories
• CPC Class Codes: H04B 7/18513 Transmission in a satellite or space-based system
• CPC Class Codes: H04B 7/195 Non-synchronous stations

Abstract

Boeing achieves satellite diversity by having a large discrimination angle for a MEO constellation of communications satellites to limit interference in the Ku-band with GSO communications systems. Each satellite entering an exclusion zone over a GSO ground station terminates all transmissions to provide EPFD within acceptable limits. The Boeing MEO constellation preferably comprises 20 satellites, 5 in each orbit. The four orbits are inclined at about 57° with respect to the equator. Services include an Integrated Digital Service (IDS) and Backhaul Data Service (BDS) to accommodate the needs of different users.

Claims

1. A method to reduce interference between a GSO satellite and its GSO ground station when operating an NGSO satellite or constellation of satellites orbiting at medium earth orbit (MEO), comprising the step of:

terminating all transmission signals generated on a particular NGSO satellite or eminating from an NGSO ground station in communication with the NGSO satellite when the NGSO satellite is in an exclusion zone defined for a GSO ground station antenna.

2. The method of

claim 1

wherein the exclusion zone is from 15°

North to 15°

South latitude.

3. A satellite communications system implementing the method of

claim 1

.

4. A satellite constellation communication system, comprising:

a plurality of satellites forming a constellation orbiting the Earth in four sets, each set defining an orbital plane, each plane inclined about 57°

relative to the equator, the satellites being at an altitude of medium earth orbit (MEO)of about 20,000 km,

the system providing truly global coverage while substantially minimizing the number of operational satellites required.

5. The system of

claim 4

wherein eash set includes at least one spare satellite.

6. The system of

claim 4

wherein the constellation has the satellites spaced so that at least two operational satellites are in view to a user outside the Tropics at an elevation angle relative to the user at or above 30°

7. The system of

claim 4

further comprising a plurality of gateways, each gateway being stationed at a fixed location on the Earth and functioning as a network distributor for communication signals to and from a user and the constellation, wherein the satellite spacing in the constellation and the gateway locatons have each satellite having visible in a field of view for communication transmission at least two gateways at any location of the satellite in its orbit.

8. A commmunication satellite particularly adapted for use in a MEO satellite constellation and system for full service, global comunication or communication (voice) and data signals, comprising:

(a) a platform;

(b) at least two transceivers on the platform for receiving and transmitting of the signals, each transceiver including Integrated Digital Service (IDS) and Backhaul Data Service (BDS) for transmission, each transceiver also having a feeder link antenna and a tracking control system adapted for pointing and tracking the feeder link antenna at a selected gateway on the Earth,

wherein seamless handoff between gateways occurs because each feeder link antenna has its own, dedicated tracking control system to allow each antenna to point at a different, selected gateway.

9. The satellite of

claim 8

wherein the BDS uses a multi-beam electronically steered phased array antenna.

10. The satellite of

claim 8

wherein the IDS system is substantially as shown in FIG. 13 and 14 and wherein the BDS system is substanially as shown in FIG. 15 and 16.

11. A method for mitigating intra-system interference in a satellite communication system having Integrated Digital Service (IDS) and Backhaul Data Service (3DS) operating at essentially a common frequency, comprising the steps of:

steering independent transmit antennas on separate satellites in a constellation, each antenna casting a footprint on the ground during transmission, so that a user in one footprint receives an IDS signal from a first satellite and a BDS signal from another satellite.

12. In a satellite communication system having a plurality of satellites in a medium earth orbit (MEO) constellation transmitting a signal to a user in a broadcast footprint on the Earth, the method for minimizing interfeence with or emissions to co-frequency competing communication systems, comprising the step of:

transmitting only from the one satellite in the constellation that provides the highest elevation angle for the user while turning off other transmitters on other satellites otherwise capable of transmitting to the same footprint to conserve power consumption of the system.