Radio frequency broadcasting systems and methods using two low-cost geosynchronous satellites

• US 5,319,673 A
• Filed: 04/16/1993
• Issued: 06/07/1994
• Est. Priority Date: 04/10/1992
• Status: Expired due to Term

• Current Assignee: Sirius XM Radio Inc. (Liberty Media Corporation)
• Original Assignee: CD Radio, Inc. (Liberty Media Corporation)
• Inventors: Briskman, Robert D.
• Primary Examiner(s): CANGIALOSI, SALVATORE A
• Application Number:
  US08/048,663
• Time in Patent Office: 417 Days
• Field of Search: 375/1, 342/352, 342/357, 342/359, 455/12.1, 455/13.1, 370/75, 370/109, 370/50
• US Class Current: 455/13.1
• CPC Class Codes: H04B 7/185 Space-based or airborne stations; Stations for satellite systemsH04B7/204 takes precedence
• CPC Class Codes: H04H 40/90 specially adapted for satellite broadcast receiving

Abstract

High quality audio broadcasts at radio frequencies to mobile receivers at or near the earth'"'"'s surface are provided by substantially simultaneous transmission of the same signal from two geosynchronous, spatially-separated satellites on the geosynchronous orbit which virtually eliminates multipath fading and foliage attenuation and thereby permits the use of a low-cost space segment.

Claims

1. A method for reducing satellite-based transmitter power in a radio broadcasting system adapted to broadcast radio signals having frequencies in the range of about 300 MHz to about 3,000 MHz comprising:

broadcasting on a first path a first broadcast signal that includes audio program information from a first satellite source traveling on a substantially geosynchronous orbit;

substantially simultaneously broadcasting on a second path a second broadcast signal having substantially the same content and frequency as said first broadcast signal from a second satellite source on said substantially geosynchronous orbit, said second satellite source and said second path being spaced from said first satellite source and said first path a predetermined number of degrees to reduce the power needed to transmit said first and said second signals to a receiver at or near the earth'"'"'s surface; and

assembling and producing said broadcast signal as an output signal from said first broadcast signal and said second broadcast signal at a plurality of fixed receivers having at least one channel to receive said first broadcast signal and at least one channel to receive said second broadcast signal and a plurality of mobile receivers having at least one channel to receive said first broadcast signal and at least one channel to receive said second broadcast signal located at or near the earth'"'"'s surface.

6. The system of claim 1 or claim 2 further comprising a UHF radio receiver that comprises means for measuring the signal strengths of said first and said second signals, and means for forming and outputting an output signal from said first and said second signals.

9. The method of claim 1 or claim 2 or claim 3 or claim 4 wherein said predetermined number of degrees is in the range of about 25 degrees to about 50 degrees.

10. The method of claim 1 or claim 2 or claim 3 further comprising broadcasting said first signal and said second signal at polarizations where the frequency of said first signal is substantially the same as the frequency of said second signal.

11. The system of claim 1 or claim 2 or claim 3 wherein said broadcasting means are adapted to broadcast said first signal and said second signal at opposite polarizations where the frequency of said first signal is substantially the same as the frequency of said second signal.

12. The method of claim 1 or claim 2 or claim 3 or claim 4 wherein said first satellite source comprises at least two separate satellites to provide additional broadcast signal paths.

13. The method of claim 1 or claim 2 or claim 3 or claim 4 wherein said second satellite source comprises at least two separate satellites to provide additional broadcast signal paths.

14. The method of claim 1, or claim 2 or claim 3 or claim 4 wherein said predetermined number of degrees is in the range of about 25 degrees to about 50 degrees.

15. The method of claim 1 or claim 2 or claim 3 or claim 11 further comprising broadcasting said first broadcast signal and said second broadcast signal at opposite polarizations, and where the frequency of said first broadcast signal is substantially the same as the frequency of said second broadcast signal.

16. The method of claim 1 or claim 2 or claim 3 or claim 11 wherein said first broadcast signal and said second broadcast signal are at opposite polarization and where the frequency of said first signal is different from the frequency of said second broadcast signal.

23. The method of claim 1 or claim 2 or claim 3 or claim 4 wherein said assembling step comprises selection of said first broadcast signal or said second broadcast signal for output from at least one of said receivers.

24. The method of claim 1 or claim 2 or claim 3 or claim 4 wherein said assembling step comprises combining said first broadcast signal and said second broadcast signal to produce said output signal at at least one of said receivers.

25. The method of claim 1 or claim 2 or claim 3 or claim 4 wherein said predetermined number of degrees is sufficient to position substantially all of said receivers substantially within line-of-eight of said first satellite source and said second satellite source.

27. The method of claim 1 or claim 2 or claim 3 or claim 4 further comprising utilizing spread spectrum modulation in said broadcasting.

2. A method for reducing satellite-based transmitter power in a radio broadcasting system adapted to broadcast radio signals having frequencies in the range of about 300 MHz to about 3,000 MHz comprising:

broadcasting on a first path a first broadcast signal that includes audio program information from a first satellite source traveling on a substantially geosynchronous orbit;

substantially simultaneously broadcasting on a second path a second broadcast signal with substantially identical content from a second satellite source on said substantially geosynchronous orbit, said second satellite source and said second path being spaced from said first satellite source and said first path a predetermined number of degrees to reduce the power needed to transit said first and said second broadcast signal to the earth'"'"'s surface, said second broadcast signal having a frequency different from the frequency of said first broadcast signal; and

assembling and producing said broadcast signal as an output signal from said first and said second broadcast signals at a plurality of fixed receivers having at least one channel to receive said first broadcast signal and at least one channel to receive said second broadcast signal and a plurality of mobile receivers having at least one channel to receive said first broadcast signal and at least one channel to receive said second broadcast signal located at or near the surface of the earth.

3. A method for improving signal reception in a radio system comprising:

broadcasting on a first path of first broadcast signal that includes audio program information having a frequency in the range of about 300 MHz to about 3,000 MHz from a first satellite source traveling on a substantially geosynchronous orbit;

substantially simultaneously broadcasting on a second path a second broadcast signal with identical content having substantially the same frequency as said first broadcast signal or having a frequency different from the frequency of said first broadcast signal from a second satellite source on said substantially geosynchronous orbit, said second satellite source and said second path being spaced from said first satellite source and said first path a predetermined number of degrees to improve reception of said first and said second broadcast signals at a plurality of fixed receiver and a plurality of mobile receivers located at or near the earth'"'"'s surface; and

assembling and producing said broadcast signal as an output signal from said first broadcast signal and said second broadcast signal at said plurality of fixed receivers having at least one channel to receive said first broadcast signal and at least one channel to receive said second broadcast signal and said plurality of mobile receivers having at least one channel to receive said first broadcast signal and at least one channel to receive said second broadcast signal.

7. The system claim 3 wherein said first satellite source comprises at least two separate satellites.

8. The system claim 3 or claim 5 wherein said second satellite source comprises at least two separate satellites.

4. A method for reducing foliage attenuation and signal outage from radio path blockage in a radio broadcasting system adapted to broadcast signals having frequencies in the range of about 300 MHz to about 3,000 MHZ comprising:

broadcasting on a first path a first broadcast signal that includes audio program information having a frequency in said range from a first satellite source traveling on a substantially geosynchronous orbit;

substantially simultaneously broadcasting on a second path a second broadcast signal with identical content having substantially the same frequency as said first broadcast signal or having a frequency different from the frequency of said first broadcast signal from a second satellite source on said geosynchronous orbit, said second satellite source and said second path being spaced from said first satellite source and said first path a predetermined number of degrees to minimize foliage attenuation or radio path blockage; and

assembling and producing said broadcast signal as an output signal from said first broadcast signal and said second broadcast signal at a plurality of fixed receivers having at least one channel to receive said first broadcast signal and at least one channel to receive said second broadcast signal and a plurality of mobile receivers having at least one channel to receive said first broadcast signal and at least one channel to receive said second broadcast signal located at or near the surface of the earth.

5. A UHF radio system adapted to broadcast signals having frequencies in a range of about 300 MHz to about 3,000 MHz comprising:

a broadcasting source for broadcasting on a first path a first broadcast signal that includes audio program information on a first satellite source traveling in a substantially geosynchronous orbit;

a broadcasting source for broadcasting on a second path a second broadcast signal from a second satellite source traveling in said substantially geosynchronous orbit, said second satellite source and said second path being spaced from said first satellite source and said first path a predetermined number of degrees to minimize outage and fading of said first and said second broadcast signals; and

a plurality of fixed receivers and a plurality of mobile receivers for receiving said first and said second broadcast signals, each of said fixed and said mobile receivers being located at or near the surface of the earth, each of said receivers being adapted to produce said broadcast signal as an output signal from said first and said second broadcast signals, each of said receivers including at least one channel to receive said first broadcast signal and at least one channel to receive said second broadcast signal.

17. The system of claim 5 further comprising, in each of said receivers, means for measuring the strengths of broadcast signals from said first and second satellite sources, and means for selecting the stronger broadcast signal from said first and said second signals for output.

18. The system of claim 5 wherein said receiver includes means for combining said first and said second broadcast signals.

19. The system of claim 5 or claim 17 or claim 18 further comprising means for modulating said first and said second broadcast signals to reduce multipath fading.

20. The system of claim 5 or claim 17 or claim 18 or claim 19 wherein said second satellite source is adapted to produce a second broadcast signal having a frequency different from the frequency of said first broadcast signal.

21. The system of claim 5 or claim 17 or claim 18 or claim 19 further comprising a UHF radio receiver that comprises means for measuring the signal strengths of said first and said second broadcast signals and means for forming and outputting the broadcast source from said first and said second broadcast signals.

22. The system of claim 5 or claim 17 or claim 18 or claim 19 wherein said second satellite source is adapted to produce a second broadcast signal having a polarization opposite from the polarization of said first broadcast signal.

26. The system of claim 5 or claim 17 or claim 18 or claim 19 wherein said first satellite source and said second satellite source are spaced apart a distance sufficient to position substantially all of said receivers substantially within line-of-sight of said first and said second satellite sources.

28. The system of claim 5 wherein said broadcasting source utilizes spread spectrum modulation.