Phase-noise compensated digital communication receiver and method therefor

• US 6,363,124 B1
• Filed: 10/06/2000
• Issued: 03/26/2002
• Est. Priority Date: 03/22/1999
• Status: Expired due to Fees

• Current Assignee: Intersil Americas LLC (Renesas Electronics Corporation)
• Original Assignee: SiCOM, Inc. (Renesas Electronics Corporation)
• Inventors: Cochran, Bruce A.
• Primary Examiner(s): TSE, YOUNG TOI
• Application Number:
  US09/680,877
• Time in Patent Office: 536 Days
• Field of Search: 375/232, 375/233, 375/324, 375/326, 375/327, 375/344, 375/346, 375/348, 375/230, 375/231, 329/307, 329/308
• US Class Current: 375/326
• CPC Class Codes: H04L 2027/0046 Open loops
• CPC Class Codes: H04L 27/0014 Carrier regulation of chaotic carriers H04L27/001; for multicarrier receivers H04L27/2657
• CPC Class Codes: H04L 5/06 the signals being represented by different frequencies combined with time-division multiplexing H04L5/26

Abstract

A phase-noise compensated digital communication receiver (40, 40′, 40″) includes a carrier tracking loop (56) which imposes a transport delay on a carrier tracking loop signal (60) before that signal (60) is fed back upon itself. The carrier tracking loop (56) includes a phase rotator (58) that rotates a down-converted digital communication signal (50) by a phase determined by a phase-conveying signal (72). A carrier tracking loop signal is obtained from the carrier tracking loop and delayed in a delay element (82) by a duration that compensates for the transport delay. A phase rotator (84) then rotates the delayed carrier tracking loop signal through a phase value determined by the phase-conveying signal (72) to obtain an open-loop phase signal (86) from which data are extracted. Different embodiments of the receiver (40, 40′, 40″) are provided to accommodate adaptive equalizer (54) issues.

Claims

1. A phase-noise-compensated receiver for digital communication comprising:

a carrier tracking loop having an input which receives a down-converted digital communication signal, having a first phase rotator with a first input adapted to receive said down-converted digital communication signal, having a first equalizer with an input coupled to an output of said first phase rotator and with first coefficients adaptively instantiated with values determined in response to received data, having a phase constellation error detector with an input coupled to an output of said first equalizer, having a loop filter with an input coupled to an output of said phase constellation error detector, having a phase integrator with an input coupled to an output of said loop filter and with an output coupled to a second input of said first phase rotator, said phase integrator output providing a phase-conveying signal;

a delay element having an input coupled to said carrier tracking loop to receive said down-converted digital communication signal and having an output;

a second phase rotator residing outside said carrier tracking loop, said second phase rotator having a first input coupled to said delay element output, a second input coupled to said phase integrator and having an output that provides a signal from which digital communication data are extracted; and

a second equalizer having an first input coupled to said second phase rotator output and a second input coupled to said first equalizer so that said second equalizer provides equalization determined by second coefficients which track said first coefficients.

2. A phase-noise-compensated receiver for digital communication comprising:

a carrier tracking loop having an input which receives a down-converted digital communication signal and having a phase integrator which generates a phase-conveying signal;

a delay element having an input coupled to said carrier tracking loop and having an output;

a phase rotator residing outside said carrier tracking loop, having a first input coupled to said delay element output, having a second input coupled to said phase integrator and having an output that provides a signal from which digital communication data are extracted; and

an equalizer having an input coupled to said phase rotator output.

3. A receiver as claimed in claim 2 wherein said delay element input couples to said carrier tracking loop to receive said down-converted digital communication signal.

4. A receiver as claimed in claim 2 wherein:

said equalizer is a first equalizer which provides equalization determined in response to a first set of filter coefficients; and

said carrier tracking loop includes a second equalizer having a second set of filter coefficients adaptively instantiated with values determined in response to data detected within said carrier tracking loop, said second equalizer being coupled to said first equalizer so that said first coefficients track said second coefficients.

5. A receiver as claimed in claim 2 wherein said phase rotator is a first phase rotator and said carrier tracking loop comprises:

a second phase rotator having a first input adapted to receive said down-converted digital communication signal, a second input and an output;

a phase constellation error detector having an input coupled to said output of said second phase rotator and having an output;

a loop filter having an input coupled to said phase constellation error detector output and having an output; and

said phase integrator having an input coupled to said loop filter output and having an output coupled to said second input of said second phase rotator, said phase integrator output providing said phase-conveying signal.

6. A receiver as claimed in claim 5 wherein:

said delay element input couples to said carrier tracking loop to receive said down-converted digital communication signal;

said equalizer is a first equalizer configured to provide equalization determined by first coefficients; and

said carrier tracking loop additionally comprises a second equalizer coupled between said second phase rotator and said phase constellation error detector, said second equalizer having second coefficients adaptively instantiated with values determined in response to received data, and said second equalizer being coupled to said first equalizer so that said first coefficients track said second coefficients.

7. A receiver as claimed in claim 2 wherein said delay element provides a delay in the range of 2-80 unit intervals.

8. A receiver as claimed in claim 2 wherein said carrier tracking loop includes a phase constellation error detector which detects phase constellation errors in accordance with a modulation order wherein data are communicated at greater than or equal to four bits per unit interval.

9. A receiver as claimed in claim 2 wherein:

said carrier tracking loop is configured so that said phase-conveying signal experiences a group delay plus an implementation delay relative to said down-converted digital communication signal; and

said delay element provides a delay sufficient to substantially compensate for said group delay plus said implementation delay.

10. A receiver as claimed in claim 2 wherein said receiver additionally comprises:

a variable frequency oscillation circuit configured to generate an oscillation signal which exhibits an amount of phase noise; and

a mixer adapted to receive a communication signal and said oscillation signal, said mixer being coupled to said carrier tracking loop in order to supply said down-converted digital communication signal.

11. A receiver as claimed in claim 2 additionally comprising a decoder having an input coupled to said phase rotator output.

12. A method of compensating for phase noise in a digital communication receiver comprising the steps of:

altering a phase-conveying signal generated by a phase integrator in a carrier tracking loop, said phase-conveying signal being altered to minimize a phase-constellation error signal generated in said carrier tracking loop;

obtaining a down-converted digital communication signal from said carrier tracking loop;

delaying said down-converted digital communication signal to generate a delayed carrier tracking loop signal, said delayed carrier tracking loop signal being external to said carrier tracking loop;

rotating said delayed carrier tracking loop signal in response to said phase-conveying signal to generate an open-loop phase signal;

equalizing said open-loop phase signal to generate an equalized open-loop phase signal; and

extracting communicated data from said equalized open-loop phase signal.

13. A method as claimed in claim 12 wherein:

said equalizing step is a first equalizing step;

said first equalizing step provides equalization determined in response to a first set of filter coefficients;

said altering step comprises a second equalizing step which causes said phase-conveying signal to be altered in response to a second set of filter coefficients that are adaptively instantiated with values determined in response to data detected in said carrier tracking loop; and

said first set of filter coefficients track said second set of filter coefficients.

14. A method as claimed in claim 12 wherein said delaying step delays said signal extracted from said carrier tracking loop by a duration in the range of 2-80 unit intervals.

15. A method as claimed in claim 12 wherein said phase-constellation error signal is determined in accordance with a modulation order wherein data are communicated at greater than or equal to four bits per unit interval.

16. A method as claimed in claim 12 additionally comprising the steps of:

generating an oscillation signal which exhibits an amount of phase noise; and

down-converting a received signal in response to said oscillation signal to generate said down-converted digital communication signal, wherein said down-converted digital communication signal is influenced by said amount of phase noise.

17. A method as claimed in claim 12 wherein said extracting step comprises the step of decoding said equalized open-loop phase signal.