Communication system utilizing a constellation of satellites and method therefor

• US 6,745,006 B2
• Filed: 01/29/2001
• Issued: 06/01/2004
• Est. Priority Date: 01/29/2001
• Status: Expired due to Fees

• Current Assignee: CDC Propriete Intellectuelle
• Original Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Inventors: Shaneyfelt, James T.
• Primary Examiner(s): Maung, Nay
• Assistant Examiner(s): LELE, TANMAY S
• Application Number:
  US09/772,152
• Publication Number:
  US 20020102939A1
• Time in Patent Office: 1,219 Days
• Field of Search: 455/12.1, 455/13.1, 455/13.2, 455/13.3, 455/427, 455/428, 455/429, 455/430, 370/315, 370/316, 370/326
• US Class Current: 455/13.1
• CPC Class Codes: H04B 7/18521 Systems of inter linked satellites, i.e. inter satellite service for optical links between satellites H04B10/118
• CPC Class Codes: H04B 7/19 Earth-synchronous stations

Abstract

A communication system (20) utilizing a constellation (22) of satellites (24) is presented. A source ground station (52) transmits an uplink signal (34) containing source payload data (32) to a primary satellite (26) located in an orbit (70) about the Earth (56). The primary satellite (26) conveys the source payload data (32) to a secondary satellite (28) located proximate the primary satellite (26) in the orbit (70), where the source payload data (32) is baseband processed to produce destination payload data (42), which is then conveyed back to the primary satellite (26). The primary satellite (26) transmits a downlink signal (50) containing the destination payload data (42) to a destination ground station (54). The primary satellite (26) and secondary satellites are configured to expend majorities of their energy budgets in downlink transmissions and payload data processing, respectively.

Claims

1. A communication system utilizing a constellation of satellites to transmit messages between a source ground station configured to transmit an uplink signal containing source payload data and a plurality of destination ground stations configured to receive a multiplicity of downlink signals, said communication system comprising:

a primary satellite comprising an uplink receiver and a downlink transmitter, wherein the primary satellite is configured to receive said source payload via said uplink signal at said unlink receiver, and to transmit one of said multiplicity of downlink signals to one of said plurality of destination ground said downlink transmitter and

a secondary satellite comprising;

a demodulator configured to demodulate a source intermediate-frequency signal containing said source payload data into said source baseband signal containing said source payload data;

a processor configured to process said source baseband signal to produce a destination baseband signal containing destination payload data in response to said source payload data;

a modulator configured to modulate said destination baseband signal into a destination intermediate-frequency signal containing said destination payload data; and

an intersatellite transmitter configured to provide the destination intermediate-frequency signal to said primary satellite.

2. A communication system as claimed in claim 1 wherein:

said primary satellite is configured to expend a majority of a primary-satellite energy budget in transmitting said multiplicity of downlink signals during a lifetime of said constellation of satellites; and

said secondary satellite is configured to expend a majority of a secondary-satellite energy budget in baseband processing payload data to be contained in a plurality of said multiplicity of said downlink signals during a lifetime of said constellation of satellites.

3. A communication system as claimed in claim 1 wherein:

said primary satellite is located at first position in an orbit about the Earth, and said secondary satellite is located at a second position in said orbit.

4. A communication system as claimed in claim 3 wherein said orbit is a geosynchronous orbit.

5. A communication system as claimed in claim 1 wherein said secondary satellite additionally comprises an intersatellite receiver configured to receive said source intermediate-frequency signal from said primary satellite.

6. A communication system as claimed in claim 1 wherein said secondary satellite additionally comprises:

an uplink receiver configured to receive said uplink signal from said source ground station; and

a down-converter configured to convert said uplink signal into said source intermediate-frequency signal.

7. A communication system as claimed in claim 1 wherein said primary satellite comprises:

an intersatellite receiver configured to receive a destination intermediate-frequency signal containing said destination payload data from said secondary satellite;

an up-converter configured to convert said destination intermediate-frequency signal into said one downlink signal; and

a downlink transmitter configured to transmit said one downlink signal to said one destination ground station.

8. A communication system as claimed in claim 7 wherein said primary satellite additionally comprises:

an uplink receiver configured to receive said uplink signal from said source ground station;

a down-converter configured to convert said uplink signal into a source intermediate-frequency signal containing said source payload data; and

an intersatellite transmitter configured to transmit said source intermediate-frequency signal to said secondary satellite.

9. A communication system as claimed in claim 1 wherein an intersatellite transmitter in a first one of said primary and secondary satellites and an intersatellite receiver in a second one of said primary and secondary satellites together comprise a free-space optical transmission link configured to convey said payload data.

10. A method of communication utilizing a constellation of satellites comprising a primary satellite having an unlink receiver and a downlink transmitter and a secondary satellite having a processor for processing inter-satellite transmissions, said method comprising the steps of:

a) conveying an uplink signal containing source payload data from a source ground station to the primary satellite;

b) providing the source payload data to the secondary satellite in a source baseband

c) processing said source baseband signal in said processor to produce a destination baseband signal containing destination payload data;

d) transferring the destination baseband signal from the secondary satellite to the primary satellite; and

e) conveying a downlink signal containing said destination payload data from said primary satellite to a destination ground station.

11. A method as claimed in claim 10 additionally comprising:

converting said uplink signal into a source intermediate-frequency signal containing said source payload data prior to said providing step b).

12. A method as claimed in claim 10 wherein said providing activity b) comprises:

e) converting said uplink signal into a first intermediate-frequency signal containing said source payload data; and

f) conveying, when said conveying activity a) conveys said uplink signal to said primary satellite, said first intermediate-frequency signal from said primary satellite to said secondary satellite.

13. A method as claimed in claim 10 wherein:

said providing activity b) and said transferring activity d) convey said first and second intermediate-frequency signals between said primary and secondary satellites utilizing lasers.

14. A communication method as claimed in claim 10 wherein said conveying activity e) comprises:

transmitting said downlink signal from said primary satellite; and

receiving said downlink signal at said destination ground station.

15. A point-to-point communication system utilizing a constellation of satellites, said communication system comprising:

a source ground station configured to transmit an uplink signal containing source payload data;

a primary satellite located at a first position in an orbit about the Earth, said primary satellite expending greater than fifty percent of its energy in transmitting a multiplicity of downlink signals containing destination payload data during a lifetime of said constellation, and said primary satellite comprising;

an uplink receiver configured to receive said uplink signal from said source ground station;

an up-converter configured to convert said uplink signal into a source intermediate-frequency signal containing said source payload data;

an intersatellite transmitter configured to transmit said source intermediate-frequency signal;

an intersatellite receiver configured to receive a destination intermediate-frequency signal containing said destination payload data;

a down-converter configured to convert said destination intermediate frequency signal into one of said multiplicity of downlink signals, said one downlink signal containing said destination payload data; and

a downlink transmitter configured to transmit said one downlink signal;

a secondary satellite located at a second position in

said orbit said secondary satellite expending greater than fifty percent of its energy in producing said destination payload data for each of said multiplicity of said downlink signals during said lifetime of said constellation, and said secondary satellite comprising;

an intersatellite receiver configured to receive said source intermediate-frequency signal from said primary satellite;

a demodulator configured to demodulate said source intermediate-frequency signal into a source baseband signal containing said source payload data;

a processor configured to process said source baseband signal to produce a destination baseband signal containing said destination payload data for said one downlink signal in response to said source payload data;

a modulator configured to modulate said destination baseband signal into said destination intermediate-frequency signal; and

an intersatellite transmitter configured to transmit said destination intermediate-frequency signal so said primary satellite; and

a destination ground station configured to receive said one downlink signal from said primary satellite.