Method for performing reacquisition in a positioning receiver, and an electronic device

• US 20030118086A1
• Filed: 12/20/2002
• Published: 06/26/2003
• Est. Priority Date: 12/21/2001
• Status: Active Grant

• Current Assignee: RPX Corporation
• Original Assignee: Nokia Corporation
• Inventors: Valio, Harri, Pietila, Samuli
• Granted Patent: US 7,447,258 B2
• Time in Patent Office: Days
• US Class Current: 375/150
• CPC Class Codes: G01S 19/30 code related G01S19/246 takes precedence
• CPC Class Codes: H04B 1/7115 Constructive combining of multi-path signals, i.e. RAKE receivers

Abstract

The invention relates to a method for performing reacquisition in a positioning receiver (PR), in which at least one spread spectrum modulated signal is received. In the positioning receiver (PR), a reference signal is formed by using a reference code corresponding to the code used in the modulation of the signal to be received, and a correlation is made between the received signal and the reference signal. Said correlation is made in at least a first and a second part, and different correlation times are used in said first part and in said second part. The invention also relates to an electronic device (ED) comprising a positioning receiver (PR). The positioning receiver (PR) comprises means (1-6) for receiving at least one spread spectrum modulated signal, means (13, 14, 15) for forming a reference code corresponding to the code used in the modulation of the signal to be received, and means (8) for performing a correlation between the received signal and the reference signal for reacquisition of the signal to be received. Said means (8) for making the correlation comprise at least first correlating means (20a, 20b; 22a, 22b; 24a, 24b; 26a, 26b) and second correlating means (21a, 21b; 23a, 23b; 25a, 25b; 27a, 27b) for making the correlation in at least first and second parts, and means (20a, 21a; 20b, 21b) for using different correlation times in said at least first and second parts.

Claims

1. A method for performing reacquisition in a positioning receiver, in which at least one spread spectrum modulated signal is received, a reference signal is formed by using a reference code corresponding to the code used in the modulation of the signal to be received, and a correlation is made between the received signal and the reference signal, wherein said correlation is performed in at least a first and a second part, and different correlation times are used in said first part and in said second part.

2. The method according to claim 1, wherein two signals with different phases are formed from the received signal, for which correlation is performed in said at least first and second parts.

3. The method according to claim 1, wherein at least the following steps are taken in the correlation:

a first combining step to combine the signal for a time substantially corresponding to the length of the code used in the modulation,

a second combining step to perform the coherent combining of the signals formed in the first step,

a magnitude determining step to determine the value proportional to the magnitude of the coherently combined signals,

a filtering step to filter said values proportional to the magnitude of the signals for a given filtering time, and

a comparing step to compare said filtered values, proportional to the magnitude of the signals, with a given threshold value, to determine the signal acquisition on the basis of the comparison.

4. The method according to claim 3, wherein in the second combining step to be taken in the first part of the correlation, a shorter time is used than in the second combining step to be taken in the second part of the correlation.

5. The method according to claim 3, wherein in the filtering step to be taken in the first part of the correlation, a higher limit frequency is used than in the filtering step to be taken in the second part of the correlation.

6. The method according to claim 3, wherein code phase information related to the signal to be received is stored, wherein for reacquisition of the signal to be received, the code phase is estimated on the basis of the code phase information stored.

7. The method according to claim 3, wherein the reacquisition of the signal can be performed, when the comparison made at the comparison step of one part indicates that said value, proportional to the magnitude of the signals, exceeds said threshold value.

8. An electronic device comprising a positioning receiver with means for receiving at least one spread spectrum modulated signal, means for forming a reference code corresponding to the code used in the modulation of the signal to be received, and means for performing a correlation between the received signal and the reference signal for reacquisition of the signal to be received, wherein said means for performing a correlation comprise at least first correlating means and second correlating means for making the correlation in at least first and second parts, and means for using different correlation times in said at least first and second parts.

9. The electronic device according to claim 8, wherein it comprises means for forming two signals with different phases from the received signal.

10. The electronic device according to claim 8, wherein said first and second correlating means comprise:

first combining means for combining samples formed from the signal for a time substantially corresponding to the length of the code used in the modulation,

second combining means for performing coherent combination of the signals formed in the first step,

magnitude determining means for determining a value proportional to the magnitude of the coherently combined signals,

filtering means for filtering said values proportional to the magnitude of the signals for a given filtering time,

comparing means for comparing said filtered values, proportional to the magnitude of the signals, with a given threshold value, and

determining means for determining the acquisition of the signal on the basis of the comparison.

11. The electronic device according to claim 10, wherein a shorter coherent combining time is arranged to be used in the second combining means of the first correlating means than in the second combining means of the second correlating means.

12. The electronic device according to claim 10, wherein a higher limit frequency is arranged to be used in the filtering means of the first correlating means than in the filtering means of the second correlating means.

13. The electronic device according to claim 10, wherein it comprises means for storing code phase information related to the signal to be received, and means for estimating the code phase on the basis of stored code phase information, to perform reacquisition of the signal to be received.

14. The method according to claim 10, wherein it comprises means for performing reacquisition of the signal, after the comparison made at the comparison step of one part has indicated that said value proportional to the magnitude of the signals exceeds said threshold value.

15. The electronic device according to claim 10, wherein it comprises at least a first and a second correlation branch containing said at least first and second correlating means.

16. The electronic device according to claim 15, wherein it comprises means for transferring the reference code in a different phase to each correlator branch.

17. A mobile station comprising a positioning receiver with means for receiving at least one spread spectrum modulated signal, means for forming a reference code corresponding to the code used in the modulation of the signal to be received, and means for performing a correlation between the received signal and the reference signal for reacquisition of the signal to be received, wherein said means for performing a correlation comprise at least first correlating means and second correlating means for making the correlation in at least first and second parts, and means for using different correlation times in said at least first and second parts.

18. The mobile station according to claim 17, wherein said first and second correlating means comprise:

first combining means for combining samples formed from the signal for a time substantially corresponding to the length of the code used in the modulation,

second combining means for performing coherent combination of the signals formed in the first step,

magnitude determining means for determining a value proportional to the magnitude of the coherently combined signals,

filtering means for filtering said values proportional to the magnitude of the signals for a given filtering time,

comparing means for comparing said filtered values, proportional to the magnitude of the signals, with a given threshold value, and

determining means for determining the acquisition of the signal on the basis of the comparison.