Satellite communications system having multiple downlink beams powered by pooled transmitters

• US 4,831,619 A
• Filed: 08/14/1986
• Issued: 05/16/1989
• Est. Priority Date: 08/14/1986
• Status: Expired due to Term

• Current Assignee: Hughes Electronics Corporation (Rtx Corporation)
• Original Assignee: Hughes Aircraft Company (Rtx Corporation)
• Inventors: Rosen, Harold A.
• Primary Examiner(s): Olms, Douglas W.
• Assistant Examiner(s): Marcelo, Melvin
• Application Number:
  US06/896,910
• Time in Patent Office: 1,006 Days
• Field of Search: 455/12, 455/33, 455/13, 455/16, 370/104, 370/75, 343/754, 330/124 R, 330/126
• US Class Current: 370/325
• CPC Class Codes: H01Q 25/00 Antennas or antenna systems providing at least two radiating patterns arrangements for changing or varying the orientation or the shape of the directional pattern H01Q3/00
• CPC Class Codes: H04B 7/2041 Spot beam multiple access
• CPC Class Codes: Y02D 30/70 in wireless communication networks

Abstract

A satellite communications system employs separate subsystems for providing broadcast and point-to-point two-way communications using the same assigned frequency band. The broadcast and point-to-point subsystems employ an integrated satellite antenna system which uses a common reflector (12). The point-to-point subsystem achieves increased communication capacity through the reuse of the assigned frequency band over multiple, contiguous zones (32, 34, 36, 38) covering the area of the earth to be serviced. Small aperture terminals in the zones are serviced by a plurality of high gain downlink fan beams (29) steered in the east-west direction by frequency address. A special beam-forming network (98) provides in conjunction with an array antenna (20) the multiple zone frequency address function. The satellite (10) employs a filter interconnection matrix (90) for connecting earth terminals in different zones in a manner which permits multiple reuse of the entire band of assigned frequencies. A single pool of solid state transmitters allows rain disadvantaged users to be assigned higher than normal power at minimum cost. The intermodulation products of the transmitters are geographically dispersed.

Claims

1. Apparatus for communicatively interconnecting any of a plurality of terminal sites within an area on the earth, comprising:

a satellite positioned above the earth;

means carried by said satellite for respectively receiving from uplink terminal sites in said area a plurality of uplink radio frequency beams each carrying a receive signal;

means carried by said satellite for converting said receive signals into transmit signals each including a plurality of corresponding subsignals destined to be received at downlink terminal sites in said area by changing the frequencies of said receive signals;

a plurality of amplifiers carried by said satellite for collectively amplifying all of said transmit signals such that each of said transmit signals is amplified by all of said amplifiers; and

means carried by said satellite for forming a plurality of downlink radio frequency beams each carrying one of said transmit subsignals destined to be received by one of said downlink terminal sites and primarily covering only a portion of said area, said beam-forming means including -

(1) a first plurality of lines for respectively carrying said transmit signals, and

(2) a second plurality of spaced apart lines intersecting said first plurality of lines at crossover points and extending radially from a reference point so as to diverge from each other, each of said second plurality of lines being coupled with each of said first plurality of lines at said crossover points such that a portion of the energy of each of the transmit signals carried by each of the first plurality of lines is transferred to each of said second plurality of lines, each of said second plurality of lines having an output for outputting all of said transmit signals, each of said outputs being associated with and coupled to one of said amplifiers such that each of said amplifiers amplifies all the transmit signals from an associated one of said amplifiers; and

means carried by said satellite for respectively transmitting said downlink beams to corresponding portions of said area.

2. The apparatus of claim 1, wherein said first plurality of lines extend circumferentially about said reference point and are radially spaced relative to said reference point such that the distance between adjacent crossover points increases with increasing radial distance of the crossover points from said reference point.

3. The apparatus of claim 2, wherein at least certain of the lines in said first plurality of lines are unequally radially spaced apart from each other.

4. The apparatus of claim 2, wherein said first plurality of lines includes a first set of essentially contiguous lines and a second set of essentially contiguous lines spaced apart from said first set thereof.

5. Apparatus for communicatively interconnecting any of a plurality of terminal sites within an area on the earth, comprising:

a satellite positioned above the earth;

means carried by said satellite for respectively receiving from uplink terminal sites in said area a plurality of uplink radio frequency beams each carrying a receive signal;

means carried by said satellite for converting said receive signals into transmit signals each including a plurality of corresponding subsignals destined to be received at downlink terminal sites in said area by changing the frequencies of said receive signals;

a plurality of amplifiers carried by said satellite for collectively amplifying all of said transmit signals such that each of said transmit signals is amplified by all of said amplifiers; and

means carried by said satellite for forming a plurality of downlink radio frequency beams each carrying one of said transmit subsignals destined to be received by one of said downlink terminal sites and primarily covering only a portion of said area, said beam-forming means including -

(1) a first plurality of lines for respectively carrying said transmit signals, and

(2) a second plurality of spaced apart lines intersecting said first plurality of lines at crossover points and extending radially from a reference point so as to diverge from each other, each of said second plurality of lines being coupled with each of said first plurality of lines at said crossover points such that a portion of the energy of each of the transmit signals carried by each of the first plurality of lines is transferred to each of said second plurality of lines, each of said second plurality of lines having an output for outputting all of said transmit signals, each of said outputs being associated with and coupled to one of said amplifiers such that each of said amplifiers amplifies all the transmit signals from an associated one of said amplifiers, said first plurality of lines extending circumferentially about a reference point and being radially spaced relative to said reference point such that the distance between adjacent crossover points increases with increasing radial distance of the crossover points from said reference point; and

means carried by said satellite for respectively transmitting said downlink beams to corresponding portions of said area.

6. The apparatus of claim 5, wherein at least certain of the lines in said first plurality of lines are unequally radially spaced apart from each other.

7. The apparatus of claim 5, wherein said first plurality of lines includes a first set of essentially contiguous lines and a second set of essentially contiguous lines spaced apart from said first set thereof.