Satellite communication array transceiver

• US 6,597,730 B1
• Filed: 11/03/1999
• Issued: 07/22/2003
• Est. Priority Date: 11/03/1999
• Status: Expired due to Term

• Current Assignee: Northrop Grumman Systems Corporation (Northrop Grumman Corporation)
• Original Assignee: Northrop Grumman Corporation
• Inventors: Bader, Todd R.
• Primary Examiner(s): Chin, Stephen
• Assistant Examiner(s): Lugo, David B.
• Application Number:
  US09/432,370
• Time in Patent Office: 1,357 Days
• Field of Search: 375/219, 375/140, 375/141, 375/146, 375/147, 375/260, 375/267
• US Class Current: 375/219
• CPC Class Codes: H01Q 1/241 used in mobile communications, e.g. GSM H01Q1/247, H01Q1/248 take precedence
• CPC Class Codes: H01Q 21/08 the units being spaced along or adjacent to a rectilinear path waveguide fed H01Q21/0037
• CPC Class Codes: H01Q 3/26 varying the relative phase or relative amplitude of energisation between two or more active radiating elements; varying the distribution of energy across a radiating aperture H01Q3/12, H01Q3/22, H01Q3/24 take precedence

Abstract

A satellite communications system (10) that employs an array of separate and easily deployable antennas (12) for transmission and reception purposes to accommodate high data rate transmissions. The antennas (12) can be deployed randomly at a communications site and are physically separated. Each antenna (12) transmits and receives the same information. A coded signal is used to identify the transmission from each antenna (12) for calibration purposes to align the bits transmitted by each antenna (12) and provide carrier frequency phase matching. The coded signals are used to compare the phase and timing relationship between each antenna signal and a reference antenna signal when the separate antennas receive all of the coded signals. Correction computations are performed and specialized phase and data alignment systems (24, 32) are employed to delay and adjust the phases of the various transmitted signals relative to the reference antenna (12) to provide the desired alignment. Additionally, phase and timing systems (194) are used to determine and correct the phase and data variations between the data received by the antennas (12) so that they can be combined and processed.

Claims

1. A transceiver for receiving and transmitting signals, said transceiver comprising:

an array of antennas, each of the antennas being randomly positioned relative to each other, each of the antennas identifying a separate channel of the transceiver where one of the channels is a reference channel, each channel receiving and transmitting signals on a common carrier frequency including the same data;

a code generation system, said code generation system generating a unique calibration signal for each channel, each channel transmitting its calibration signal and receiving the calibration signals from all of the channels;

an alignment error system, said alignment error system generating an alignment error signal that identifies an alignment error between the calibration signal transmitted by each channel and the calibration signal transmitted by the reference channel;

a phase error determination system, said phase error determination system determining a phase error signal that is the difference between the phase of the carrier signal transmitted by each channel and the phase of the carrier signal transmitted by the reference channel; and

a correction system, said correction system generating a time correction for each channel that aligns the calibration signal transmitted by each channel with the calibration signal transmitted by the reference channel and generating a phase correction signal that aligns the phase of the carrier signal transmitted by each channel and the phase of the carrier signal transmitted by the reference channel.

2. The transceiver according to claim 1 wherein the correction system includes a delay device in each channel for delaying the calibration signal for that channel relative to the calibration signal for the reference channel.

3. The transceiver according to claim 1 wherein the calibration signal in each channel is phase locked to a data signal for that channel.

4. The transceiver according to claim 1 wherein the alignment error system and the phase error system include a decoder for each channel, each decoder identifying the code for its channel from the codes of all of the channels.

5. The transceiver according to claim 4 further comprising a time difference system, said time difference system being responsive to a frame sync signal from each decoder that identifies a position of the calibration signal in time, said time difference system outputting a delay error for each channel that is representative of the delay necessary to align the calibration signal for each channel with the calibration signal for the reference channel.

6. The transceiver according to claim 4 wherein each decoder generates in-phase and quadrature-phase signals of the carrier signal transmitted by each channel, and wherein the phase error system includes a plurality of multipliers, wherein a pair of multipliers multiply the in-phase and quadrature-phase signals for each channel and the reference channel.

7. The transceiver according to claim 6 wherein the phase error system further includes a plurality of summers, each summer generating a difference signal between the multiplied in-phase and quadrature-phase signals for each channel and the reference channel, said phase error system further comprising a plurality of accumulators, wherein each accumulator receives a difference signal from a summer and generates the phase error signal.

8. The transceiver according to claim 1 further comprising a receiver combining system that determines a bit timing difference and a phase difference between the signals received by the reference channel and the signals received by the other channels, said combining system providing a bit time aligning signal and a phase correction signal for each channel.

9. The transceiver according to claim 8 wherein each channel includes a delay device and a digital receiver, said delay device receiving the time aligning signal to delay the received signals a predetermined amount and said digital receiver receiving the phase correction signal to phase align the received signals.

10. The transceiver according to claim 8 further comprising a phase accumulator, said phase accumulator being responsive to the phase difference from the combining system and a round trip time signal indicative of a round trip time between the transceiver and a satellite, said accumulator outputting a phase signal to the correction system.

11. The transceiver according to claim 8 wherein the receiver combining system includes a digital combiner that combines the aligned signals received by each channel to a single digital output signal.

12. A satellite communications systems for transmitting signals between Earth based communications sites, one of the communication sites including a transceiver comprising:

an array of antennas, each of the antennas identifying a separate channel of the transceiver where one of the channels is a reference channel, each channel receiving and transmitting signals on a common carrier signal and including the same data signal;

a code generation system, said code generation system generating a unique calibration signal for each channel, each channel transmitting its calibration signal and receiving the calibration signals from all of the other channels, said calibration signal being phase locked to the data signal;

an alignment error system, said alignment error system generating an alignment error signal that identifies an alignment error between the calibration signal and the data signal transmitted by each channel and the calibration signal and the data signal transmitted by the reference channel;

a phase error determination system, said phase error determination system determining a phase error signal that is a difference between the phase of the carrier signal transmitted by each channel and the phase of the carrier signal transmitted by the reference channel;

a correction system including a plurality of delay devices, said correction system generating a time correction for each channel that is applied to a delay device in that channel to align the calibration signal and the data signal transmitted by each channel with the calibration signal and the data signal transmitted by the reference channel, said correction system further generating a phase correction signal that aligns the phase of the carrier signal transmitted by each channel and the phase of the carrier signal transmitted by the reference channel; and

a receiver combining system, said receiver combining system determining a bit timing difference and a phase difference between data signals received by the reference channel and data signals received by the other channels, said combining system providing a time aligning signal and a phase correction signal for each channel to align the data signals in time and in phase.

13. The transceiver according to claim 12 wherein the alignment error system and the phase error system include a decoder for each channel, each decoder identifying the code for its channel from the codes of all of the channels.

14. The transceiver according to claim 13 further comprising a time difference system, said time difference system being responsive to a frame sync signal from each decoder that identifies a position of the calibration signal in time, said time difference system outputting a delay error for each channel that is representative of the delay necessary to align the calibration signal for each channel with the calibration signal for the reference channel.

15. The transceiver according to claim 13 wherein each decoder generates in-phase and quadrature-phase signals of the carrier signal transmitted by each channel and wherein the phase error system includes a plurality of multipliers, wherein a pair of multipliers multiply the in-phase and quadrature-phase signals for each channel and the reference channel.

16. The transceiver according to claim 15 wherein the phase error system further includes a plurality of summers, each summer generating a difference signal between the multiplied in-phase and quadrature-phase signals for each channel and the reference channel, said phase error system further comprising a plurality of accumulators, wherein each accumulator receives a difference signal from a summer and generates the phase error signal.

17. The transceiver according to claim 12 wherein each channel includes a delay device and a digital receiver, said delay device receiving the time aligning signal to delay the received signals a predetermined amount and said digital receiver receiving the phase correction signal to phase align the received signals.

18. The transceiver according to claim 12 further comprising a phase accumulator, said phase accumulator being responsive to the phase difference from the combining system and a round trip time signal indicative of a round trip time between the transceiver and a satellite, said accumulation outputting a phase signal to the correction system.

19. A method of receiving and transmitting signals, said method comprising steps of:

arbitrarily arranging a plurality of antennas at a communications site, each of the antennas identifying a separate channel where one of the channels is a reference channel;

transmitting and receiving signals including the same data to and from each antenna;

generating a unique calibration signal that is transmitted by each channel;

receiving all of the calibration signals from all of the channels in each channel;

separately identifying the calibration signal for each channel;

determining an alignment error between the calibration signal for each channel and the calibration signal for the reference channel;

determining a phase difference between the calibration signal for each channel and the calibration signal for the reference channel; and

providing a time and phase correction for the calibration signal in each channel so that it is aligned with the calibration signal transmitted by the reference channel.

20. The method according to claim 19 further comprising the step of phase locking the calibration signals with a data signal transmitted by each channel.

21. The method according to claim 19 wherein the step of providing a time and phase correction includes delaying the transmission of the calibration signal in each channel so that it is aligned with the transmission of the reference channel.

22. The method according to claim 19 further comprising the step of determining a bit timing difference and a phase difference between signals received by the reference channel and signals received by the other channels, and providing a time alignment signal and a phase correction signal to align the data and carrier frequency of each signal received by each channel.