Method and apparatus for performing signal correlation using historical correlation data

• US 6,819,707 B2
• Filed: 09/26/2001
• Issued: 11/16/2004
• Est. Priority Date: 05/18/2001
• Status: Expired due to Term

• Current Assignee: Avago Technologies International Sales Pte Limited (Broadcom, Inc.)
• Original Assignee: Global Locate Incorporated (Broadcom, Inc.)
• Inventors: Abraham, Charles, van Diggelen, Frank
• Primary Examiner(s): Ha, Dac V.
• Application Number:
  US09/963,345
• Publication Number:
  US 20020172306A1
• Time in Patent Office: 1,147 Days
• Field of Search: 375/142, 375/143, 375/150, 375/152, 375/259-261, 375/343, 375/365-367, 370/514, 370/515, 370/320, 370/335, 370/342, 370/441, 370/479
• US Class Current: 375/142
• CPC Class Codes: G01S 19/23 Testing, monitoring, correcting or calibrating of receiver elements
• CPC Class Codes: G01S 19/29 carrier including Doppler, related G01S19/246 takes precedence
• CPC Class Codes: G01S 19/30 code related G01S19/246 takes precedence
• CPC Class Codes: G01S 19/37 Hardware or software details of the signal processing chain
• CPC Class Codes: G06F 17/15 Correlation function computation including computation of convolution operations arithmetic circuits for sum of products per se, e.g. multiply-accumulators G06F7/5443; digital filters, e.g. FIR, IIR, adaptive filters H03H17/00
• CPC Class Codes: H04B 1/707 using direct sequence modulation
• CPC Class Codes: H04B 1/70752 Partial correlation
• CPC Class Codes: H04B 1/7077 Multi-step acquisition, e.g. multi-dwell, coarse-fine or validation
• CPC Class Codes: H04B 2201/70715 with application-specific features

Abstract

A method and apparatus for computing a convolution between an input GPS signal and a reference code by generating the convolution result in real time without storing unprocessed signal samples. The apparatus comprises a vector multiplier running at high speed to achieve the same result as a vector multiplier sized to process an entire epoch. Additionally, historical correlation data is used to correct frequency and timing errors.

Claims

1. In a satellite positioning receiver, a method for estimating a receiver parameter comprising:

a) selecting a relative time delay between a signal received from a satellite and a reference signal;

b) generating a correlation history comprising a sequence of correlation results for the relative time delay; and

c) estimating at least one receiver parameter from the correlation history.

2. The method of claim 1 further comprising:

d) using the at least one receiver parameter when performing further correlations.

3. The method of claim 2 wherein the further correlations are performed on different signals from a different satellite than said signal received from the satellite.

4. The method of claim 2 wherein the further correlations are performed using a standard correlation mode.

5. The method of claim 1 wherein the at least one receiver parameter comprises a frequency of a receiver oscillator.

6. The method of claim 1 wherein the at least one receiver parameter comprises a receiver timing error.

7. The method of claim 6 wherein the receiver timing error is a modulo 20 millisecond estimate of an offset of a receiver clock with respect to a satellite reference time.

8. The method of claim 6 wherein the at least one receiver parameter further comprises a frequency of a receiver oscillator.

10. The method of claim 1 further comprising:

dividing the received signal into in-phase and quadrature components; and

separately performing steps b) and c) on the in-phase and quadrature components.

11. The method of claim 1 further comprising generating navigation data bits from the correlation history.

12. The method of claim 1 wherein step c) comprises:

applying the correlation history to a sequential estimation algorithm to estimate at least one of signal frequency and bit timing.

13. The method of claim 1, further comprising:

repeating steps a) and b) for at least one additional signal received from a respective at least one additional satellite to generate a respective at least one additional correlation history;

wherein the at least one receiver parameter is further estimated from the at least one additional correlation history.

14. The method of claim 1, further comprising:

repeating steps a) and b) for at least one additional relative time delay between the signal and the reference signal to generate a respective at least one additional correlation history;

wherein the at least one receiver parameter is further estimated from the at least one additional correlation history.

9. In a satellite positioning receiver, a method for estimating a receiver Parameter comprising:

a generating a correlation history comprising a sequence of correlation results for a signal received from at least one satellite, said generating comprising;

(a1) dividing a pseudorandom reference code into a plurality of code segments;

(a2) selecting a code segment;

(a3) forming an inner product between said selected code segment and a set of digital signal samples to produce a partial correlation;

(a4) repeating steps (a2) and (a3) to produce a plurality of partial correlations; and

(a5) summing the plurality of partial correlations as each partial correlation is produced to form a plurality of correlations; and

b) estimating at least one receiver parameter from the correlation history.

15. In a satellite positioning receiver, a method for estimating at least one receiver parameter from a correlation history comprising:

a) determining, in response to the correlation history, a plurality of estimates of signal level using a receiver frequency and bit timing hypothesis;

b) determining, in response to signal level estimates, estimates of at least one receiver parameter that provides a frequency and bit timing for the receiver that substantially maximizes signal level.

16. The method of claim 15 further comprising:

(c) frequency correcting the correlation history;

(d) integrating the correlation history over a navigation bit period;

(e) computing a signal level for the signal within the navigation bit period;

(f) summing a plurality of successive signal level values to form an integrated signal level value as the signal level to be maximized.

17. The method of claim 16 wherein said signal level is at least one of signal power and signal magnitude.

18. The method of claim 15 wherein said signal level is at least one of signal power and signal magnitude.

19. The method of claim 15 further comprising:

searching over frequency to determine a maxima in signal level.

20. The method of claim 19 wherein searching comprises a downhill simplex method.

21. The method of claim 15 further comprising:

searching over bit timing to determine a maxima in signal level.

22. The method of claim 15 further comprising:

searching over frequency and bit timing to determine a maxima in signal level.

23. Apparatus for estimating at least one receiver parameter in a satellite positioning receiver comprising:

a) means for selecting a relative time delay between a signal received from a satellite and a reference signal;

b) means for generating a correlation history comprising a sequence of correlation results for the relative time delay; and

c) means for estimating at least one receiver parameter from the correlation history.

24. The apparatus of claim 23 further comprising:

(d) a correlator for using the receiver parameter when performing further correlations.

25. The apparatus of claim 24 wherein the further correlations are performed on different signals from a different satellite than said signal received from at the satellite.

26. The apparatus of claim 23 wherein the at least one receiver parameter comprises a frequency of a receiver oscillator.

27. The apparatus of claim 23 wherein the at least one receiver parameter comprises a receiver timing error.

28. The apparatus of claim 27 wherein the receiver parameter further comprises a frequency of a receiver oscillator.

29. The apparatus of claim 27 wherein the receiver timing error is a modulo 20 millisecond estimate of an offset of a receiver clock with respect to a satellite reference time.

31. The apparatus of claim 23 further comprising:

means for dividing the received signal into in-phase and quadrature components; and

separately processing the in-phase and quadrature components.

32. The apparatus of claim 23 further comprising means for generating navigation data bits from the correlation history.

33. The apparatus of claim 23 further comprising:

means for determining an estimate relating to a signal level at a frequency and bit timing hypothesis.

30. Apparatus for estimating at least one receiver parameter in a satellite positioning receiver comprising:

a) means for generating a correlation history comprising a sequence of correlation results from signals received from at least one satellite, said means for generating comprising;

(a1) means for dividing a pseudorandom reference code into a plurality of code segments;

(a2) means for selecting a code segment;

(a3) means for forming an inner product between said selected code segment and a set of digital signal samples to produce a partial correlation;

(a4) means for repeatedly operating means (a2) and (a3) to produce a plurality of partial correlations; and

(a5) means for summing the plurality of partial correlations as each partial correlation is produced to form a plurality of correlations; and

b) means for estimating at least one receiver parameter from the correlation history.

34. A computer readable medium storing software that, when executed by a processor, causes a satellite positioning receiver to perform a method for estimating at least one receiver parameter from a correlation history comprising:

a) determining, in response to the correlation history, a plurality of estimates of signal level, using a receiver frequency and bit timing hypothesis;

b) determining, in response to the signal level estimates, estimates of at least one receiver parameter that provides a frequency and bit timing for the receiver that substantially maximizes signal level.

35. The method of claim 34 further comprising:

(c) frequency correcting the correlation history;

(d) integrating the correlation history over a navigation bit period;

(e) computing a signal level for the signal within the navigation bit period;

(f) summing a plurality of successive signal level values to form an integrated signal level value as the signal level to be maximized.

36. The method of claim 35 wherein said signal level is at least one of signal power and signal magnitude.

37. The method of claim 35 further comprising:

searching over frequency to determine a maxima in signal level.

38. The method of claim 35 further comprising:

searching over bit timing to determine a maxima in signal level.

39. The method of claim 34 wherein said signal level is at least one of signal power and signal magnitude.

40. The method of claim 34 further comprising:

searching over frequency and bit timing to determine a maxima in signal level.

41. The method of claim 40 wherein searching comprises a downhill simplex method.

42. In a satellite positioning receiver, a method for estimating a receiver parameter, comprising:

producing a plurality of correlation results between a signal received from at least one satellite and a reference signal;

storing each correlation result of the plurality of correlation results as each correlation result is produced to generate a correlation history; and

estimating at least one receiver parameter from the correlation history.