Multi-path detection method for CDMA receivers

• US 7,440,493 B2
• Filed: 12/29/2004
• Issued: 10/21/2008
• Est. Priority Date: 12/29/2004
• Status: Active Grant

• Current Assignee: France Brevets SAS
• Original Assignee: Nokia Corporation
• Inventors: Valio, Harri, Pietilä, Samuli
• Primary Examiner(s): Kim; Kevin Y
• Application Number:
  US11/026,503
• Publication Number:
  US 20060140254A1
• Time in Patent Office: 1,392 Days
• Field of Search: 375/142, 375/144, 375/147, 375/150
• US Class Current: 375/150
• CPC Class Codes: G01S 19/22 Multipath-related issues
• CPC Class Codes: H04B 1/7075 with code phase acquisition
• CPC Class Codes: H04B 2201/70715 with application-specific features

Abstract

The present invention provides a method for a multi-path detection analysis and selectivity of CDMA signals using spread spectrum receivers using a correlation technique. The invention is based on determining by the spread spectrum receiver whether a distortion of a received radio frequency signal, caused by a multi-path component of said received signal, meets a predetermined condition using a pre-selected correlation analysis of said received signal. This invention is generally applicable to global navigation satellite system (GNSS) receivers and it is particularly useful in GNSS receivers, such as GPS (global positioning system) and Galileo receivers. The important goal of this invention is to provide a simple method for identifying signals that are corrupted by multi-path effects, and can be excluded from position calculation in the GNSS receivers.

Claims

1. A method, comprising:

receiving a radio frequency signal containing a multi-path component and converting said radio frequency signal to a digital signal; and

detecting said multi-path component and determining using at least two pairs of correlation signals, each pair being symmetrical relative to a prompt point, whether a distortion of said radio frequency signal caused by said multi-path component meets a predetermined condition using a correlation analysis of said digital signal with said at least two pairs of the correlation signals by maintaining equal the correlation signals of one pair of said two pairs and evaluating a difference between the correlation signals of another pair of said two pairs, for implementing a multi-path detection analysis of said radio frequency signal by said spread spectrum receiver which is configured to make a decision whether to further process the received radio frequency signal using results of said multi-path detection analysis.

2. The method of claim 1, wherein said determining is performed by a receiver processing block.

3. The method of claim 2, wherein said radio frequency signal is used for further processing beyond said receiver processing block after making said decision, only if said distortion meets said predetermined condition, for implementing a selective function of said multi-path detection operation of the spread spectrum receiver.

4. The method of claim 1, wherein said digital signal is generated by converting said radio frequency signal to a radio frequency electrical signal by an antenna of the spread spectrum receiver with subsequent converting said radio frequency electrical signal to a digital signal.

5. The method of claim 1, wherein said radio frequency signal is a code division multiple access signal.

6. The method of claim 1, wherein prior to said determining, said correlation analysis of said digital signal is performed by a receiving channel block of said spread spectrum receiver, and said analysis comprises:

generating a data intermediate signal by removing a residual carrier frequency from said digital signal using a phase-loop feedback and providing said data intermediate signal to each of K correlators of said receiving channel block, wherein K is an odd integer of at least a value of five;

providing a code signal indicative of a delay-loop feedback to a first delay module of said receiver processing block;

providing each of K consecutively delayed code signals to one corresponding correlator module of K correlator modules, wherein said each of said K delayed code signals is consecutively and individually delayed by pre-selected values relative to a previously delayed code signal of said K consecutively delayed code signals starting with said code signal provided by said receiver processing block; and

generating each of K correlation signals by a corresponding one of said K correlator modules using said data intermediate signal and said K delayed code signals and providing said K correlation signals to said receiver processing block for said determining, wherein said each of said K correlation signals contains an amplitude parameter or a phase parameter or both said amplitude parameter and said phase parameter.

7. The method of claim 6, wherein said distortion of said radio frequency signal caused by said multi-path component is evaluated in said receiver processing block using said predetermined condition by comparing said amplitude parameter of an Mth correlation signal of said K correlation signals generated using an Mth delayed code signal of said K consecutively delayed code signals, wherein M=1, or 2 . . . or (K−

1)/2, and said amplitude parameter of a corresponding Lth correlation signal of said K consecutively delayed code signals generated using a corresponding Lth delayed code signal of said K correlation signals, wherein L=K, or K−

1 . . . or (K+3)/2.

8. The method of claim 7, wherein said amplitude parameter of two correlation signals of said K correlation signals, generated by corresponding correlation modules using corresponding delayed code signals of said K consecutively delayed code signals delayed by (K−

1)/2 and (K+3)/2 times respectively, is maintained equal using a delay-locked loop of said spread spectrum receiver.

9. The method of claim 8, wherein said distortion of said radio frequency signal caused by said multi-path component is evaluated in said receiver processing block by comparing amplitude parameter of a first of said K correlation signals, generated using a first delayed code signal of said K consecutively delayed code signals and a last of said K correlation signals generated using a last delayed code signal of said K consecutively delayed code signals using said predetermined criterion.

10. The method of claim 9, wherein K=5.

11. The method of claim 6, wherein said phase parameter of one correlation signal of said K correlation signals, generated by a corresponding correlation module using a corresponding delayed code signal of said K consecutively delayed code signals delayed by (K+1)/2 times, is maintained to be zero using a phase-locked loop, and wherein phase parameters of said K correlation signals are provided to said receiver processing block for said determining.

12. The method of claim 6, wherein said code signal is generated by a code generating block of said receiving channel block in response to a code control signal indicative of said delay-loop feedback from said receiver processing block as a part of a delay-locked loop.

13. The method of claim 6, wherein said data intermediate signal is generated by a residual carrier removing block of said receiving channel block in response to a frequency control signal indicative of said phase-loop feedback from said receiver processing block.

14. A computer program product comprising:

a computer readable storage structure embodying computer program code thereon for execution by a computer processor with said computer program code, wherein said computer program code comprises instructions for performing the method of claim 1, indicated as being performed by a component or a combination of components of a spread spectrum receiver, or a terminal containing said spread spectrum receiver.

31. The method of claim 1, wherein said spread spectrum receiver is configured to track to substantially zero an early-minus-late signal of one of said at least two pairs of the correlation signals and to use a further early-minus-late signal of another of said at least two pairs of the correlation signals for said determining.

15. A spread spectrum receiver, comprising:

a receiving module, for performing a correlation analysis of a digital signal generated from a radio frequency signal comprising a multi-path component using at least two pairs of correlation signals, each pair being symmetrical relative to a prompt point, by maintaining equal the correlation signals of one pair of said two pairs and evaluating a difference between the correlation signals of another pair of said two pairs; and

a receiver processing block, for detecting said multi-path component and determining whether a distortion of said radio frequency signal caused by said multi-path component meets a predetermined condition using said correlation analysis of said digital signal, and for making a decision whether to further process the received radio frequency signal using results of said multi-path detection analysis for implementing a multi-path detection analysis of said radio frequency signal by said spread spectrum receiver.

16. The spread spectrum receiver of claim 15, wherein said radio frequency signal is used by said spread spectrum receiver for further processing beyond said receiver processing block after making said decision, only if said distortion meets said predetermined condition, for implementing a selective function of said multi-path detection operation of the spread spectrum receiver.

17. The spread spectrum receiver of claim 15, wherein said radio frequency signal is a code division multiple access signal.

18. The spread spectrum receiver of claim 15, wherein said receiving module comprises N receiving channel blocks, N being an integer of at least a value of one, and each of said N receiving channel blocks, comprises:

residual carrier removing block, for generating a data intermediate signal by removing a residual carrier frequency from said digital signal using a phase-loop feedback;

code generating block, for generating a code signal indicative of a delay-loop feedback;

K correlator modules, wherein K is an odd integer of at least a value of five, for generating each of K correlation signals by a corresponding one of said K correlator modules using said data intermediate signal and K delayed code signals and for providing said K correlation signals to said receiver processing block for said determining whether a distortion of said radio frequency signal caused by said multi-path component meets a predetermined condition using a correlation analysis of said digital signal, wherein said each of said K correlation signals contains an amplitude parameter or a phase parameter or both said amplitude parameter and said phase parameter; and

K delay modules, for providing each of K consecutively delayed code signals to one corresponding correlator module of said K correlator modules, wherein said each of said K delayed code signals is consecutively and individually delayed by pre-selected values relative to a previously delayed code signal of said K consecutively delayed code signals starting with said code signal provided to a first delay module out of said K delay modules by said receiver processing block.

19. The spread spectrum receiver of claim 18, wherein said distortion of said radio frequency signal caused by said multi-path component is evaluated in said receiver processing block using said predetermined condition by comparing said amplitude parameter of an Mth correlation signal of said K correlation signals generated using an Mth delayed code signal of said K consecutively delayed code signals, wherein M=1, or 2 . . . or (K−

1)/2, and said amplitude parameter of a corresponding Lth correlation signal of said K consecutively delayed code signals generated using a corresponding Lth delayed code signal of said K correlation signals, wherein L=K, or K−

1 . . . or (K+3)/2.

20. The spread spectrum receiver of claim 19, wherein said amplitude parameter of two correlation signals of said K correlation signals, generated by corresponding correlation modules using corresponding delayed code signals of said K consecutively delayed code signals delayed by (K−

1)/2 and (K+3)/2 times respectively, is maintained equal using a delay-locked loop of said spread spectrum receiver.

21. The spread spectrum receiver of claim 20, wherein said distortion of said radio frequency signal caused by said multi-path component is evaluated in said receiver processing block by comparing amplitude parameter of a first of said K correlation signals generated using a first delayed code signal of said K consecutively delayed code signals and a last of said K correlation signals generated using a last delayed code signal of said K consecutively delayed code signals using said predetermined criterion.

22. The spread spectrum receiver of claim 21, wherein K=5.

23. The spread spectrum receiver of claim 18, wherein said phase parameter of one correlation signal of said K correlation signals, generated by a corresponding correlator module of said K correlator modules using a corresponding delayed code signal of said K consecutively delayed code signals delayed by (K+1)/2times, is maintained to be zero using a phase-locked loop of said spread spectrum receiver, and wherein phase parameters of said K correlation signals are provided to said receiver processing block for said determining.

24. The spread spectrum receiver of claim 18, wherein said receiving channel block comprises a code generating block, for generating said code signal in response to a code control signal indicative of said delay-loop feedback from said receiver processing block as a part of a delay-locked loop.

25. The spread spectrum receiver of claim 18, wherein said receiving channel block comprises a residual carrier removing bloc for generating said data intermediate signal in response to a frequency control signal indicative of said phase-loop feedback from said receiver processing block.

26. The spread spectrum receiver of claim 15, further comprising:

an antenna, responsive to the radio frequency signal containing said multi-path component, for providing a radio frequency electrical signal; and

a preprocessor, responsive to the radio frequency electrical signal, for providing the digital signal.

32. The spread spectrum receiver of claim 15, wherein said spread spectrum receiver is configured to track to substantially zero an early-minus-late signal of one of said at least two pairs of the correlation signals and to use a further early-minus-late signal of another of said at least two pairs of the correlation signals for said determining.

27. A system, comprising:

a satellite, for providing a radio frequency signal;

a base station, for providing a further radio frequency signal used for mobile communications; and

a terminal, responsive to said radio frequency signal or to said further radio frequency signal, both containing a multi-path component, wherein said terminal comprises a spread spectrum receiver which is;

for providing a digital signal in response to the radio frequency electrical signal or to the further radio frequency signal,

for performing a correlation analysis of said digital signal using at least two pairs of correlation signals, each pair being symmetrical relative to a prompt point, by maintaining equal the correlation signals of one pair of said two pairs and evaluating a difference between the correlation signals of another pair of said two pairs, and

for detecting said multi-path component and determining whether a distortion of said radio frequency signal caused by said multi-path component meets a predetermined condition using said correlation analysis of said digital signal, and for making a decision whether to further process the received radio frequency signal using results of said multi-path detection analysis for implementing a multi-path detection analysis of said radio frequency signal or said further radio frequency signal by said spread spectrum receiver.

29. The system of claim 27, wherein said spread spectrum receiver is a global navigation satellite system receiver, a global positioning system receiver or a Galileo receiver.

28. A receiving module of a spread spectrum receiver, comprising:

at least one receiving channel block, for performing a correlation analysis of a digital signal generated from a radio frequency signal comprising a multipath component using at least two pairs of correlation signals, each pair being symmetrical relative to a prompt point, by maintaining equal the correlation signals of one pair of said two pairs and evaluating a difference between the correlation signals of another pair of said two pairs, for determining by said spread spectrum receiver whether a distortion of said radio frequency signal caused by said multi-path component meets a predetermined condition using said correlation analysis of said digital signal for implementing a multi-path detection analysis of said radio frequency signal by said spread spectrum receiver, wherein said receiving module is removable from said spread spectrum receiver.

30. The receiving module of claim 28, wherein said radio frequency signal is a code division multiple access signal.

33. A spread spectrum receiver, comprising:

means for performing a correlation analysis of a digital signal using at least two pairs of correlation signals, each pair being symmetrical relative to a prompt point, by maintaining equal the correlation signals of one pair of said two pairs and evaluating a difference between the correlation signals of another pair of said two pairs; and

means for detecting said multi-path component and determining whether a distortion of said radio frequency signal caused by said multi-path component meets a predetermined condition using said correlation analysis of said digital signal, and for making a decision whether to further process the received radio frequency signal using results of said multi-path detection analysis for implementing a multi-path detection analysis of said radio frequency signal by said spread spectrum receiver.

34. The spread spectrum receiver of claim 33, wherein said radio frequency signal is a code division multiple access signal.