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

• US 5,278,863 A
• Filed: 04/10/1992
• Issued: 01/11/1994
• 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:
  US07/866,910
• Time in Patent Office: 641 Days
• Field of Search: 375/1, 380/34, 455/12.1, 455/17.1, 455/13.2, 455/13.3, 455/13.4
• US Class Current: 375/130
• 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 multi-path fading 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 a first signal using spread spectrum modulation from a first satellite source traveling on a geosynchronous orbit;

substantially simultaneously broadcasting a second signal using spread spectrum modulation, said second signal having substantially the same content and frequency as said first signal from a second satellite source on said geosynchronous orbit, said second satellite source being spaced from said first satellite source a predetermined number of degrees to reduce multi-path fading and to reduce signal attenuation from physical objects in the paths of said first signal and said second signal and

producing an output signal from said first signal and said second signal at a plurality of fixed receivers and a plurality of mobile receivers located at or near the surface of the earth.

2. The method of claim 1 further comprising measuring the signal strengths of said first and said second signals, and selecting the stronger signal from said first and said second signals.

3. The method of claim 1 further comprising combining said first and said second signals to form said output signal.

4. The method of claim 1 wherein said first and said second signals are modulated sufficiently to resist multi-path fading.

5. The method of claim 2 wherein said first and said second signals are modulated sufficiently to resist multi-path fading.

6. The method of claim 3 wherein said first and said second signals are modulated sufficiently to resist multi-path fading.

7. The method of claim 1 or claim 2 or claim 3 or claim 4 or claim 5 or claim 6 wherein said predetermined number of degrees is in the range of about 25 degrees to about 50 degrees.