Mobile satellite communication system utilizing polarization diversity combining

• US 6,526,278 B1
• Filed: 03/03/2000
• Issued: 02/25/2003
• Est. Priority Date: 03/03/2000
• Status: Expired due to Fees

• Current Assignee: Google Technology Holdings LLC (Alphabet Inc.)
• Original Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Inventors: Monsen, Peter, Startup, James William, Kleiner, Norbert, Hanson, Duke Edward, Peters, Robert Anthony, Emmons, Thomas Peter Jr.
• Primary Examiner(s): Le, Thanh Cong
• Assistant Examiner(s): LE, LANA N
• Application Number:
  US09/517,975
• Time in Patent Office: 1,089 Days
• Field of Search: 455/296, 455/303, 455/305, 455/306, 455/427, 455/456, 455/429, 342/361, 342/362, 342/359, 342/363, 342/365, 342/366, 342/371-374
• US Class Current: 455/427
• CPC Class Codes: H04B 7/10 Polarisation diversity; Directional diversity
• CPC Class Codes: H04B 7/18534 for enhancing link reliablility, e.g. satellites diversity
• CPC Class Codes: Y02D 30/70 in wireless communication networks

Abstract

The present invention utilizes a dual polarization reception system (200) that utilizes the energy available in orthogonal polarizations to effectively increase link margin, thereby allowing for adequate signal quality reception in difficult environments. A co-polarized and a cross-polarized signal are separately downconverted and demultiplexed. The signals from each demultiplexed output are then sampled and weighted. The weighted samples for each polarity are combined in soft decision combining/decoding circuitry (255, 360), and this circuitry determines the most likely state of a received symbol'"'"'s transmitted value.

Claims

1. A mobile satellite communications system comprising:

at least one subscriber unit (SU) comprising means for transmitting a first co-polarized signal comprising substantially a single polarization;

at least one satellite comprising means for receiving said first co-polarized signal transmitted from said at least one SU and means for receiving a first cross-polarized signal; and

decision means for separately assigning weighted factors to samples and decoding to determine a most likely state of a received symbol'"'"'s transmitted value.

2. The mobile satellite communications system as claimed in claim 1, wherein said at least one satellite further comprises means for transmitting a second co-polarized signal comprising substantially a single polarization.

3. The mobile satellite communications system as claimed in claim 2, wherein said at least one SU further comprises means for receiving said second co-polarized signal transmitted from said at least one satellite and means for receiving a second cross-polarized signal.

4. The mobile satellite communications system as claimed in claim 3, wherein said at least one SU further comprises:

a dual-polarization antenna; and

a hybrid coupler coupled to said dual-polarization antenna for establishing a received co-polarized signal and a received cross-polarized signal.

5. The mobile satellite communications system as claimed in claim 4, wherein said at least one SU further comprises means for processing said received co-polarized signal and said received cross-polarized signal.

6. The mobile satellite communications system as claimed in claim 5, wherein said means for processing said received co-polarized signal and said received cross-polarized signal further comprises;

a first downconverter coupled to a first output of said hybrid coupler for downconverting said received co-polarized signal;

a second downconverter coupled to a second output of said hybrid coupler for downconverting said received cross-polarized signal;

a first analog-to-digital (A/D) converter coupled to said first downconverter for creating a first set of sampled signals from a downconverted received co-polarized signal;

a second analog-to-digital (A/D) converter coupled to said second downconverter for creating a second set of sampled signals from a downconverted received cross-polarized signal;

a first demultiplexer coupled to said first A/D converter for demultiplexing a first desired user signal from said first set of sampled signals;

a second demultiplexer coupled to said second A/D converter for demultiplexing a second desired user signal from said second set of sampled signals; and

said decision means coupled to said first demultiplexer and said second demultiplexer, said decision means assigning weighting factors to samples of said first desired user signal and to samples of said second desired user signal and combining said weighted samples.

7. The mobile satellite communications system as claimed in claim 6, wherein said decision means further comprises:

a residual carrier recovery circuit coupled to said first demultiplexer, said residual carrier recovery circuit comprising means for individually tracking residual carrier phase for said received co-polarized signal and said received cross-polarized signal;

a symbol timing circuit coupled to said residual carrier recovery circuit, said symbol timing circuit comprising means for determining timing information from said first desired user signal and said second desired user signal;

a first soft decision computing circuit coupled to said residual carrier recovery circuit and said symbol timing circuit, said first soft decision computing circuit comprising means for capturing samples of said first desired user signal at optimum times within a symbol period;

a second soft decision computing circuit coupled to said residual carrier recovery circuit and said symbol timing circuit, said second soft decision computing circuit comprising means for capturing samples of said second desired user signal at optimum times within said symbol period; and

a soft decision combining/decoding circuit coupled to said first soft decision computing circuit and said second soft decision computing circuit, said soft decision combining/decoding circuit comprising means for weighting, combining, and decoding samples to determine most likely states of transmitted symbols using the states of the received samples for said received co-polarized signal and said received cross-polarized signal.

8. The mobile satellite communications system as claimed in claim 6, wherein said first demultiplexer and said second demultiplexer comprise a plurality of channel filters and decode frequency division multiple access (FDMA) signals.

9. The mobile satellite communications system as claimed in claim 6, wherein said first demultiplexer and said second demultiplexer comprise a plurality of despreading functions and decode code division multiple access (CDMA) signals.

10. The mobile satellite communications system as claimed in claim 6, wherein said first demultiplexer and said second demultiplexer comprise a plurality of timing and switching functions and decode time division multiple access (TDMA) signals.

11. The mobile satellite communications system as claimed in claim 5, wherein said means for processing said received co-polarized signal and said received cross-polarized signal further comprises:

a first analog-to-digital (A/D) converter, coupled to output of first said downconverter, comprising means for creating a first set of sampled signals from said received co-polarized signal;

a second analog-to-digital (A/D) converter, coupled to output of second said downconverter, comprising means for creating a second set of sampled signals from said received cross-polarized signal;

a first demultiplexer coupled to said first A/D converter, said first demultiplexer comprising means for demultiplexing a first desired user signal from said first set of sampled signals;

a second demultiplexer coupled to said second A/D converter, said second demultiplexer comprising means for demultiplexing a second desired user signal from said second set of sampled signals; and

a decision means coupled to said first demultiplexer and said second demultiplexer, said decision means comprising means for separately assigning weighting factors to samples of said first desired user signal and samples of said second desired user signal, combining said weighted samples, and decoding to determine the most likely state of a received symbol'"'"'s transmitted value.

12. The mobile satellite communications system as claimed in claim 1, wherein said at least one satellite further comprises a phased array antenna having a first set of elements for receiving said first co-polarized signal and having a second set of elements for receiving said first cross-polarized signal.

13. The mobile satellite communications system as claimed in claim 1, wherein said at least one satellite further comprises:

a phased array antenna having a plurality of dual-polarization antenna elements; and

a plurality of hybrid couplers coupled to said plurality of dual-polarization antenna elements, said plurality of hybrid couplers establishing a plurality of received co-polarized signals and a plurality of received cross-polarized signals.

14. The mobile satellite communications system as claimed in claim 13, wherein said at least one satellite further comprises:

a plurality of first downconverters, coupled to first outputs of said plurality of hybrid couplers, for downconverting said plurality of received co-polarized signals;

a plurality of second downconverters, coupled to second outputs of said plurality of hybrid couplers, for downconverting said plurality of received cross-polarized signals;

a plurality of first A/D converters, coupled to said plurality of first downconverters, for creating first sets of sampled signals from downconverted received co-polarized signals;

a plurality of second A/D converters, coupled to said plurality of second downconverters, for creating second sets of sampled signals from downconverted received cross-polarized signals;

a plurality of first demultiplexers, coupled to said plurality of first A/D converters, for demultiplexing first desired user signals from said first sets of sampled signals;

a plurality of second demultiplexers, coupled to said plurality of second A/D converters, for demultiplexing second desired user signals from said second sets of sampled signals; and

a plurality of decision means coupled to said plurality of first demultiplexers and said plurality of second demultiplexers, said plurality of decision means separately assigning weighting factors to samples of said first desired user signals and samples of said second desired user signals, combining said weighted samples, and decoding to determining the most likely state of a received symbol'"'"'s transmitted value.

15. The mobile satellite communications system as claimed in claim 1, wherein said at least one satellite further comprises:

a phased array antenna having a plurality of dual-polarization antenna elements that establish a plurality of received co-polarized signals and a plurality of received cross-polarized signals.

16. The mobile satellite communications system as claimed in claim 1, wherein said at least one SU further comprises:

a phased array antenna having a plurality of dual-polarization antenna elements; and

a plurality of hybrid couplers coupled to said plurality of dual-polarization antenna elements, said plurality of hybrid couplers establishing a plurality of received co-polarized signals and a plurality of received cross-polarized signals.

17. The mobile satellite communications system as claimed in claim 1, wherein said at least one satellite further comprises means for establishing M single polarization reception paths and N dual polarization reception paths, where M and N are non-zero integers.

18. A dual-polarization reception satellite comprising:

a phased array antenna having a plurality of dual-polarization antenna elements;

a plurality of hybrid couplers coupled to said plurality of dual-polarization antenna elements, said plurality of hybrid couplers comprising means for establishing a plurality of received co-polarized signals and a plurality of received cross-polarized signals; and

a plurality of decision means for separately assigning weighting factors and for decoding to determine a most likely state of a received symbol'"'"'s transmitted value.

19. The dual-polarization reception satellite as claimed in claim 18, wherein said dual-polarization reception satellite further comprises:

a plurality of first downconverters, coupled to first outputs of said plurality of hybrid couplers, for downconverting said plurality of received co-polarized signals;

a plurality of second downconverters, coupled to second outputs of said plurality of hybrid couplers, for downconverting said plurality of received cross-polarized signals;

a plurality of first A/D converters, coupled to said plurality of first downconverters, for creating first sets of sampled signals from downconverted received co-polarized signals;

a plurality of second A/D converters, coupled to said plurality of second downconverters, for creating second sets of sampled signals from downconverted received cross-polarized signals;

a plurality of first demultiplexers, coupled to said plurality of first A/D converters, for demultiplexing first desired user signals from said first sets of sampled signals;

a plurality of second demultiplexers, coupled to said plurality of second A/D converters, for demultiplexing second desired user signals from said second sets of sampled signals; and

said plurality of decision means coupled to said plurality of first demultiplexers and to said plurality of second demultiplexers, said plurality of decision means separately assigning the weighting factors to samples of said first desired user signals samples of said second desired user signals and for combining said weighted samples.