Feed-forward carrier recovery system and method

• US 8,792,592 B2
• Filed: 05/28/2010
• Issued: 07/29/2014
• Est. Priority Date: 05/29/2009
• Status: Expired due to Fees

• Current Assignee: Magnolia Licensing LLC (IP Edge LLC)
• Original Assignee: Thomson Licensing (Vantiva SA)
• Inventors: Schmitt, Dirk, Gao, Wen, Knutson, Paul Gothard
• Primary Examiner(s): Nguyen, Leon-Viet
• Assistant Examiner(s): Hassan, Sarah
• Application Number:
  US13/138,953
• Publication Number:
  US 20120045028A1
• Time in Patent Office: 1,523 Days
• Field of Search: 375/326, 375/354, 327/236
• US Class Current: 375/326
• CPC Class Codes: H04H 40/90 specially adapted for satellite broadcast receiving
• CPC Class Codes: H04L 2027/0053 Closed loops
• CPC Class Codes: H04L 2027/0067 Phase error detectors
• CPC Class Codes: H04L 27/0014 Carrier regulation of chaotic carriers H04L27/001; for multicarrier receivers H04L27/2657
• CPC Class Codes: H04L 27/2656 Frame synchronisation, e.g. packet synchronisation, time division duplex [TDD] switching point detection or subframe synchronisation
• CPC Class Codes: H04L 27/2678 using cyclostationarities, e.g. cyclic prefix or postfix
• CPC Class Codes: H04L 27/2679 Decision-aided
• CPC Class Codes: H04L 7/0062 detection of error based on data decision error, e.g. Mueller type detection
• CPC Class Codes: H04L 7/042 Detectors therefor, e.g. correlators, state machines digital correlators in general G06F17/15
• CPC Class Codes: H04L 7/10 Arrangements for initial synchronisation
• CPC Class Codes: H04W 56/005 compensating for timing error by adjustment in the receiver

Abstract

A method of feedforward phase recovery on a data stream is described. Phase estimation base points are calculated, at a phase detector, for each block of the received data stream. A current phase, at a phase interpolator, between two phase estimation base points. Data stream delays within the phase detector are matched with delays within the phase interpolator.

Claims

1. A method of feedforward phase recovery on a data stream, wherein the data stream includes data frames segmented into data blocks comprising:

calculating phase estimation base points, at a phase detector, for each block of the received data stream, comprising;

calculating one of;

a number of sync symbols and a number of pilot symbols in each block;

processing each sync symbol or pilot symbol, at a matched filter; and

calculating a carrier phase offset, at the phase detector, over a block of sync symbols or pilot symbols.

setting a current phase, at a phase interpolator, between two phase estimation base points; and

matching data stream delays within the phase detector with delays within the phase interpolator, wherein the number of said data blocks is calculated by the equation

2. A method of feedforward phase recovery on a data stream, comprising:

calculating phase estimation base points, at a phase detector, for each block of the received data stream;

setting a current phase, at a phase interpolator, between two phase estimation base points; and

matching data stream delays within the phase detector with delays within the phase interpolator, wherein calculating the two phase estimation base points is performed at a sawtooth device, and wherein the sawtooth device uses the equation θ

″

(i)=θ

″

(i−

1)+SAW(θ

′

(i)−

θ

″

(i−

1)), where θ

′

(i−

1),θ

′

(i) denotes the estimate of the phase offset in the (i−

1)-th and the i-th blocks and where θ

″

(i−

1),θ

″

(i) denotes the corresponding un-wrapping values, and

detecting and tracking out phase variations, at a post-processing block,

wherein detecting and tracking out phase variations is calculated using the equation;

θ

″

(i)=θ

″

(i−

1)+α

·

SAW(θ

′

(i)−

θ

′

(i−

1)) with α

≦

1.0.

3. The method of claim 2, further comprising estimating the frequency of the output of said sawtooth device at a frequency estimation block.

7. The method of claim 3, wherein the convergence speed of the frequency estimation block is adjusted by a β

parameter, wherein the value of said β

depends on he delay between an outer frequency correction circuit fed by said frequency estimation block and said post processing block.

8. The method of claim 7, wherein the values of α

and β

are switched from acquisition values to tracking values.

9. The method of claim 8, wherein the values of α

tracking values is smaller than the α

acquisition value.

10. The method of claim 9, wherein the values of β

tracking values is smaller than the β

acquisition value.

11. The method of claim 8, wherein switching from acquisition to tracking values is based on a threshold detector.

12. The method of claim 11, wherein said threshold detector is based on the value of the sawtooth output.

13. The method of claim 12, wherein said threshold switching from acquisition to tracking value if the sawtooth output is below a certain value for a period of time.

4. An apparatus that performs feedforward phase recovery on a data stream, comprising:

a phase detector, that calculates phase estimation base points for each block of the received data stream;

a phase interpolator, that sets a current phase between two phase estimation base points;

a delay line, that matches data stream delays within the phase detector with delays within the phase interpolatorl; and

a matched filter that calculates one of;

a number of sync symbols and a number of pilot symbols in each block and processes each sync symbol or pilot symbol,

wherein the phase detector calculates the two phase estimation base points over a block of sync symbols or pilot symbols, and wherein the number of said blocks is calculated by the equation

5. An apparatus that performs feedforward phase recovery on a data stream, comprising:

a phase detector, that calculates phase estimation base points for each block of the received data stream;

a phase interpolator, that sets a current phase between two phase estimation base points;

a delay line, that matches data stream delays within the phase detector with delays within the phase interpolatorl;

a sawtooth device that calculates the two phase estimation base points, wherein the sawtooth device uses the equation θ

″

(i)=θ

″

(i−

1)+SAW(θ

′

(i)−

θ

″

(i−

1)), where θ

′

(i−

1), θ

′

(i) denotes the estimate of the phase offset in the (i−

1)-th and the i-th blocks and where θ

″

(i−

1), θ

″

(i) denotes the corresponding un-wrapping values; and

a post-processing block, that detects and tracks out phase variations from the output of the sawtooth device, wherein the post-processing block uses the equation;

θ

″

(i)=θ

″

(i−

1)+α

·

SAW(θ

′

(i)−

θ

′

(i−

1)), with α

≦

1.0.

6. The apparatus of claim 5, further comprising a frequency estimation block, that estimates the frequency of the output from the sawtooth device.

14. The apparatus of claim 6, wherein the convergence speed of the frequency estimation block is adjusted by β

parameter, wherein the value of said β

depends on the delay between an outer frequency correction circuit fed 1by said frequency estimation block and said post processing block.

15. The apparatus of claim 14, wherein the values of α

and β

are switched from acquisition values to tracking values.

16. The apparatus of claim 15, wherein the α

tracking values is smaller than the α

acquisition value.

17. The apparatus of claim 15, wherein the β

tracking values is smaller than the β

acquisition value.

18. The apparatus of claim 15, further comprising a threshold detector for performing the switch from acquisition to tracking values.

19. The method of claim 18, wherein said threshold detector performs the switch based on the value of the sawtooth output.

20. The method of claim 19, wherein said threshold detector switches from acquisition to tracking value if the sawtooth output is below a certain value for a period of time.