Phase error correction using despread signals

• US 20030223479A1
• Filed: 10/31/2002
• Published: 12/04/2003
• Est. Priority Date: 05/31/2002
• Status: Active Grant

• Current Assignee: GlobalFoundries, Inc.
• Original Assignee: Advanced Micro Devices, Inc.
• Inventors: Sachse, Eric, Hanusch, Thomas, Mennenga, Menno
• Granted Patent: US 7,190,713 B2
• Time in Patent Office: Days
• US Class Current: 375/152
• CPC Class Codes: H04B 1/7093 Matched filter type
• CPC Class Codes: H04L 2027/003 at baseband only
• CPC Class Codes: H04L 2027/0057 quadrature phase
• 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: H04W 84/12 WLAN [Wireless Local Area Networks]
• CPC Class Codes: H04W 88/02 Terminal devices

Abstract

A phase error correction technique in receivers such as WLAN receivers is provided. Such receivers comprise a phase error correction unit connected to receive an input signal having a phase error and adapted to generate an output signal having a corrected phase error. Further, the receiver comprises a despreader which is adapted to despread a data signal. The despreader is connected to the phase error correction unit to provide the despread data signal to the phase error correction unit. The phase error correction unit is arranged for correcting the phase error dependent on the despread data signal. The despreader may be a Barker matched filter or a CCK matched filter, and there may be provided a multiplexer for selecting one of the filters.

Claims

1. A WLAN (Wireless Local Area Network) receiver comprising:

a phase error correction unit connected to receive an input signal having a phase error and adapted to generate an output signal having a corrected phase error; and

a despreader adapted to despread a data signal;

wherein said despreader is connected to said phase error correction unit to provide the despread data signal to said phase error correction unit, and

said phase error correction unit is arranged for correcting the phase error dependent on said despread data signal.

2. The WLAN receiver of claim 1, wherein said phase error correction unit comprises:

an error measurement module connected to receive said despread data signal and adapted to generate an error signal indicative of the current phase error; and

an error correction module connected to receive said error signal and adapted to generate said output signal.

3. The WLAN receiver of claim 2, wherein said error measurement module is adapted to integrate said despread data signal over time to generate said error signal.

4. The WLAN receiver of claim 1, wherein said despreader is connected to said phase error correction unit to receive said output signal as said data signal.

5. The WLAN receiver of claim 1, wherein said despreader is a Barker matched filter.

6. The WLAN receiver of claim 1, wherein said despreader is a CCK (Complementary Code Keying) matched filter.

7. The WLAN receiver of claim 6, wherein said CCK matched filter is implemented using a Walsh tree.

8. The WLAN receiver of claim 6, wherein said CCK matched filter comprises a CCK decorrelator to provide a phase output of said CCK decorrelator to said phase error correction unit.

9. The WLAN receiver of claim 1, wherein said despreader comprises:

a Barker matched filter;

a CCK (Complementary Code Keying) matched filter; and

a selection unit connected to said Barker matched filter and said CCK matched filter,

wherein said selection unit is adapted to select one of said Barker matched filter and said CCK matched filter to provide an output of the selected filter to said phase error correction unit.

10. The WLAN receiver of claim 9, wherein said selection unit is connected to receive a selection signal indicating which one of said Barker matched filter and said CCK matched filter is to be selected.

11. The WLAN receiver of claim 10, further comprising:

a controller adapted to generate said selection signal dependent on a data transfer mode relating to a signal currently received by said WLAN receiver.

12. The WLAN receiver of claim 11, wherein said controller is adapted to keep track of the currently used data transfer mode, and is capable of switching the selection signal in case the data transfer mode changes.

13. The WLAN receiver of claim 10, further comprising:

a controller adapted to generate said selection signal dependent on the data rate of said data signal to be despread.

14. The WLAN receiver of claim 13, wherein said controller is adapted to generate said selection signal to instruct said selection unit to select said Barker matched filter in case of a 1 Mbps or 2 Mbps data rate.

15. The WLAN receiver of claim 13, wherein said controller is adapted to generate said selection signal to instruct said selection unit to select said CCK matched filter in case of a 5.5 Mbps or 11 Mbps data rate.

16. The WLAN receiver of claim 13, wherein said controller is adapted to keep track of the currently used data rate, and is capable of switching the selection signal in case the data rate changes.

17. The WLAN receiver of claim 1, further comprising:

a frequency error correction unit adapted to correct a frequency error in a received signal;

wherein said input signal of said phase error correction unit is a signal having a corrected frequency error.

18. The WLAN receiver of claim 1, being IEEE 802.11b compliant.

19. A receiver in a spread spectrum communications system, comprising:

a phase error correction unit connected to receive an input signal having a phase error and adapted to generate an output signal having a corrected phase error; and

a despreader adapted to despread a data signal;

wherein said despreader is connected to said phase error correction unit to provide the despread data signal to said phase error correction unit, and

said phase error correction unit is arranged for correcting the phase error dependent on said despread data signal.

20. An integrated circuit chip for processing spread spectrum data signals, comprising:

phase error correction circuitry adapted to correct a phase error in an input signal; and

despreader circuitry adapted to despread a data signal;

wherein said despreader circuitry is connected to said phase error correction circuitry to provide the despread data signal to said phase error correction circuitry, and

said phase error correction circuitry is arranged for correcting the phase error dependent on said despread data signal.

21. A method of operating a WLAN (Wireless Local Area Network) receiver, the method comprising:

correcting a phase error in an input signal; and

despreading a data signal;

wherein the phase error correction is performed dependent on the despread data signal.

22. The method of claim 21, wherein correcting the phase error comprises:

generating an error signal based on said despread data signal, the error signal being indicative of the current phase error; and

generating a corrected output signal based on said error signal.

23. The method of claim 22, wherein generating the error signal comprises:

integrating said despread data signal over time.

24. The method of claim 21, wherein said data signal is a signal generated by correcting the phase error of said input signal.

25. The method of claim 21, wherein despreading the data signal comprises:

operating a Barker matched filter.

26. The method of claim 21, wherein despreading the data signal comprises:

operating a CCK (Complementary Code Keying) matched filter.

27. The method of claim 26, wherein said CCK matched filter is implemented using a Walsh tree.

28. The method of claim 26, wherein said CCK matched filter comprises a CCK decorrelator to provide a phase output of said CCK decorrelator, the phase error correction being performed dependent on said phase output.

29. The method of claim 21, wherein despreading the data signal comprises:

operating a Barker matched filter;

operating a CCK (Complementary Code Keying) matched filter; and

selecting one of said Barker matched filter and said CCK matched filter,

wherein the phase error correction is performed dependent on an output of the selected filter.

30. The method of claim 29, wherein selecting one of the filters comprising:

receiving a selection signal from a controller, the selection signal indicating which one of said Barker matched filter and said CCK matched filter is to be selected.

31. The method of claim 30, further comprising:

operating said controller to generate said selection signal dependent on a data transfer mode relating to a signal currently received by said WLAN receiver.

32. The method of claim 31, wherein operating said controller comprises:

keeping track of the currently used data transfer mode; and

switching the selection signal in case the data transfer mode changes.

33. The method of claim 30, further comprising:

operating said controller to generate said selection signal dependent on the data rate of said data signal to be despread.

34. The method of claim 33, wherein operating said controller comprises:

generating said selection signal to select said Barker matched filter in case of a 1 Mbps or 2 Mbps data rate.

35. The method of claim 33, wherein operating said controller comprises:

generating said selection signal to select said CCK matched filter in case of a 5.5 Mbps or 11 Mbps data rate.

36. The method of claim 33, wherein operating said controller comprises:

keeping track of the currently used data rate; and

switching the selection signal in case the data rate changes.

37. The method of claim 21, further comprising:

correcting a frequency error in a received signal;

wherein said input signal is a signal having a corrected frequency error.

38. The method of claim 21, adapted for operating an IEEE 802.11b compliant WLAN receiver.

39. A method of operating a receiver in a spread spectrum communications system, the method comprising:

correcting a phase error in an input signal; and

despreading a data signal;

wherein the phase error correction is performed dependent on the despread data signal.