Mobile communication satellite payload

• US 5,422,647 A
• Filed: 05/07/1993
• Issued: 06/06/1995
• Est. Priority Date: 05/07/1993
• Status: Expired due to Term

• Current Assignee: Space Systems/Loral Incorporated (Loral Space and Communications Incorporated)
• Original Assignee: Space Systems/Loral Incorporated (Loral Space and Communications Incorporated)
• Inventors: Hirshfield, Edward, Tsao, Chich-Hsing A.
• Primary Examiner(s): Issing, Gregory C.
• Application Number:
  US08/060,207
• Time in Patent Office: 760 Days
• Field of Search: 342/353, 342/354, 342/371, 342/373
• US Class Current: 342/354
• CPC Class Codes: B64G 1/1007 Communications satellites
• CPC Class Codes: B64G 1/1085 Swarms and constellations
• CPC Class Codes: B64G 1/66 Arrangements or adaptations of apparatus or instruments, not otherwise provided for
• CPC Class Codes: H01Q 1/288 Satellite antennas
• CPC Class Codes: H01Q 21/061 Two dimensional planar arrays
• CPC Class Codes: H01Q 21/064 using horn or slot aerials slotted waveguides arrays H01Q21/005
• CPC Class Codes: H01Q 21/065 Patch antenna array
• 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 7/18571 for satellites; for fixed or mobile stations
• CPC Class Codes: H04B 7/2041 Spot beam multiple access
• CPC Class Codes: Y02D 30/70 in wireless communication networks

Abstract

A communications satellite payload provides for efficient communications between user devices, such as hand held cellular telephones, and terrestrial gateways that may be connected to world-wide public telephone and telegraph (PTTs) networks. The satellite payload simultaneously supports a plurality of independent antenna beams, for example 12 or 16 beams, on both the uplink and downlink for user devices employing full duplex communications. The satellite payload furthermore supports an identical number of full duplex channels between a terrestrial gateway and the satellite. The communications satellite payload is carried by one satellite of a plurality of such satellites in a low earth orbit (LEO) constellation to provide worldwide communications. Downlink beam forming occurs prior to final amplification of transmitted signals, thereby reducing losses within the beam forming equipment. A multi-element phased array of receiving antennas and a multi-element phased array of transmitting antennas is also disclosed, wherein each element of each phased array is utilized for each individual one of a plurality of received or transmitted beams.

Claims

1. A satellite payload for use with a communication system, the payload comprising:

a phased array receiving antenna having n receive elements for receiving RF signals within a first band of frequencies;

first beam forming means having an input coupled to each of said n receive elements for forming m uplink beams from RF signals received by said phased array receiving antenna, wherein n is greater than one, and wherein m is less than n;

ground station communication means, having an input coupled an output of said first beam forming means, for converting said m uplink beams into RF signals within a second band of frequencies and for transmitting RF signals to and for receiving RF signals from a ground station, the transmitted and received RF signals being within said second band of frequencies;

second beam forming means having an input coupled to an output of said ground station communication means for forming m downlink beams from the RF signals received from said ground station, said m downlink beams being formed within a third band of frequencies; and

a phased array transmitting antenna having n transmit elements for transmitting said m downlink beams as RF signals within said third band of frequencies, each of said transmit elements having a power amplifier means associated therewith, each of said power amplifier means having an input coupled to an output of said second beam forming means and an output coupled to one of said transmit elements, wherein each of said n transmit elements transmits RF energy for each of said m downlink beams,

wherein each of said m uplink beams has a corresponding downlink beam that illuminates a same region from which said uplink beam originates, and wherein a power level of said corresponding one of said downlink beams is a function of a power level of said uplink beam.

2. A satellite payload as set forth in claim 1, wherein said first band of frequencies is within an L-band, wherein said second band of frequencies is within a C-band, and wherein said third band of frequencies is within an S-band.

3. A satellite payload as set forth in claim 1, wherein each of said n receive elements has a plurality of receive amplifiers coupled thereto.

4. A satellite payload as set forth in claim 3, wherein an input of each of said receive amplifiers is coupled into free space at one of said receive elements.

5. A satellite payload as set forth in claim 1, wherein an output of each of said power amplifiers is coupled into free space at one of said transmit elements.

6. A satellite communication system, comprising:

a plurality of terrestrial-based user terminals for transceiving in first and second frequency bands at least voice communications using a Code Division Multiple Access (CDMA) technique;

at least one terrestrial-based ground station for transceiving in a third frequency band at least voice communications using the CDMA technique; and

at least one satellite repeater for relaying at least voice communications between said plurality of user terminals and said at least one ground station, said at least one satellite repeater having a communications payload comprised of;

a phased array receiving antenna having n receive elements for receiving RF signals from user terminals within the first band of frequencies;

first beam forming means having an input coupled to each of said n receive elements for forming m uplink beams from RF signals received by said phased array receiving antenna, wherein n is greater than one, and wherein m is less than n;

ground station communication means, having an input coupled an output of said first beam forming means, for converting said m uplink beams into RF signals within said third band of frequencies and for transmitting RF signals to and for receiving RF signals from said at least one ground station, the transmitted and received RF signals being within said third band of frequencies;

second beam forming means having an input coupled to an output of said ground station communication means for forming m downlink beams from the RF signals received from said ground station, said m downlink beams being formed within said second band of frequencies; and

a phased array transmitting antenna having n transmit elements for transmitting said m downlink beams to user terminals as RF signals within said second band of frequencies, each of said transmit elements having a power amplifier means associated therewith, each of said power amplifier means having an input coupled to an output of said second beam forming means and an output coupled into free space via one of said transmit elements,

wherein each of said n transmit elements transmits RF energy for each of said m downlink beams,

wherein each of said m uplink beams has a corresponding downlink beam that illuminates a same terrestrial region from which said uplink beam originates, and

wherein a power level of said corresponding one of said downlink beams is a function of user demand for said uplink beam.

7. A satellite payload for use with a communication system, the payload comprising:

a phased array receiving antenna having n receive elements for receiving m uplink beams comprised of RF signals within a first band of frequencies, wherein n is greater than one, and wherein m is less than n;

n power dividers each having an input coupled to an output of one of said n receive elements and m outputs;

m uplink beam forming means each having m inputs and one output, individual ones of said m inputs being coupled to one of said m outputs of each of said n power dividers;

m first frequency conversion means each of which has an input coupled to said output of one of said m beam forming means, each of said m first frequency conversion means having an output for providing an RF signal within a second band of frequencies;

means for combining said outputs of said m frequency conversion means and for transmitting an m-channel RF signal to a ground station, the transmitted RF signal being within said second band of frequencies;

means for receiving an m-channel RF signal from the ground station, the received RF signal being within said second band of frequencies;

m second frequency conversion means each of which has an input coupled to an output of said ground station receiving means, each of said m second frequency conversion means being responsive to one channel of the received m-channel RF signal and having an output for providing an RF signal within a third band of frequencies;

m downlink beam forming means each having an input coupled to an output of one of said m second frequency conversion means;

n power combiners each having m inputs for coupling to an output of said m downlink beam forming means and an output; and

a phased array transmitting antenna having n transmitter elements for transmitting m beams comprised of RF signals within said third band of frequencies, each of said n transmitter elements being coupled to an output of one of said n power combiners, wherein each of said n transmitter elements transmits RF energy for each of said m downlink beams,

wherein each of said n uplink beams has a corresponding downlink beam that illuminates a same region from which said uplink beam originates, and wherein a power level of said corresponding one of said downlink beams is a function of a power level of said uplink beam.

8. A satellite payload as set forth in claim 7, wherein said first band of frequencies is within an L-band, wherein said second band of frequencies is within a C-band, and wherein said third band of frequencies is within an S-band.

9. A satellite payload as set forth in claim 7, wherein each of said n receive elements has at least one receive amplifier coupled thereto, and wherein an input of each of said receive amplifiers is coupled into free space at one of said receive elements.

10. A satellite payload as set forth in claim 7, wherein each of said n transmitter elements has at least one transmit amplifier coupled thereto, and wherein an output of each of said transmit amplifiers is coupled into free space at one of said transmitter elements.