System and method for making correlation measurements utilizing pulse shape measurements

• US 20060215739A1
• Filed: 03/24/2005
• Published: 09/28/2006
• Est. Priority Date: 03/24/2005
• Status: Active Grant

• Current Assignee: Novatel Incorporated (Hexagon AB)
• Original Assignee: Novatel Incorporated (Hexagon AB)
• Inventors: Williamson, Ian, Brown, David
• Granted Patent: US 7,738,606 B2
• Time in Patent Office: Days
• US Class Current: 375/149
• CPC Class Codes: H04B 1/7085 using a code tracking loop, e.g. a delay-locked loop

Abstract

A receiver utilizes an array of complex accumulation registers to form an image of the average chip shape or, as appropriate, chip edge shape, of the received signal over a specified period of time as a time series of complex power measurements. The receiver divides the length of the chip into a plurality of ranges, or “bins, and, as appropriate, extends the bins to cover additional chips or portions thereof.” When a sample is taken, the receiver enables the respective registers that are associated with the corresponding bin or bins, and the respective registers then accumulates the associated power measurement. The receiver uses the accumulated measurements from selected registers and/or selected groups of registers, to produce the correlation values that are needed to perform one or more correlation techniques and/or one or more multipath mitigation techniques. As appropriate, the sizes and/or starting points of the bins, and/or the selections of the bins for the various groupings may be altered, to change the spacings, locations, and so forth to which correlation values correspond.

Claims

1. A correlation subsystem for a receiver that receives spread-spectrum signals, including:

an array of complex accumulation registers that over multiple code chips accumulate correlation measurements that correspond to samples of the received signal, the complex accumulators being associated with code chip ranges that span all or a portion of one or more code chips;

a code phase decoder that controls the complex accumulation registers to direct respective correlation measurements to the complex accumulation registers that are associated with the code chip ranges from which the samples are taken, the code phase decoder decoding values that correspond to estimated code phase times of the samples; and

a processor for selectively combining the accumulated values from two or more accumulation registers to produce correlation values for use in one or more correlation techniques, multipath mitigation techniques or both.

2. The correlation subsystem of claim 1, wherein the code chip ranges over which the accumulated values are combined are selected to produce one set or multiple sets of early and late correlation values.

3. The correlation subsystem of claim 2, wherein the code chip ranges are adjustable to provide one or more desired delay spacings.

4. The correlation subsystem of claim 2 wherein one or all of the sizes, numbers and starting points of the code chip ranges are selectively varied to provide one or more desired delay spacings.

5. The correlation subsystem of claim 2 wherein the processor further manipulates the correlation values to produce early minus late code tracking discriminator information.

6. The correlation subsystem of claim 4 wherein the number of code chip ranges selected for combining is reduced to narrow one or more of the delay spacings.

7. The correlation subsystem of claim 4 wherein the number of code chip ranges selected for combining is increased to widen one or more of the delay spacings.

8. The correlation subsystem of claim 1 wherein a given code range that is associated with a code tracking point and a number of ranges both before and after the given range are selected for combining to determine a punctual correlation value.

9. The correlation subsystem of claim 8 wherein a code error is determined as:

$C_{\mathrm{error}}=\frac{I_P<br><br>I_{E-L}+Q_P<br><br>Q_{E-L}}{I_P^2+Q_P^2}\times <br><br>\mathrm{chipsize}$

where I and Q are the inphase and quadrature components of the complex values.

10. The correlation subsystem of claim 1 wherein the array further includes a non-transition complex accumulation register that accumulates correlation measurements associated with a code chip when the code does not transition at a chip time.

11. The correlation subsystem of claim 10 wherein a phase error is determined as:

$\mathrm{Phase}<br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{Error}=\arctan <br><br>\text{\hspace{1em}<br><br>}\left[\frac{{\left(\underset{k=p+1}{\overset{N}{\sum <br><br>}}<br><br>I_k-\underset{k=1}{\overset{p}{\sum <br><br>}}<br><br>I_k+I_{\mathrm{NT}}\right)}^2}{{\left(\underset{k=p+1}{\overset{N}{\sum <br><br>}}<br><br>Q_k-\underset{k=1}{\overset{p}{\sum <br><br>}}<br><br>Q_k+Q_{\mathrm{NT}}\right)}^2}\right]$

12. The correlation subsystem of claim 10 wherein the punctual correlation value is determined as:

$P_p=\underset{k=p+1}{\overset{N}{\sum <br><br>}}<br><br>A_k-\underset{k=1}{\overset{p}{\sum <br><br>}}<br><br>A_k+A_{\mathrm{NT}}$

where p is the bin that is associated with the code tracking point.

13. A receiver for receiving spread-spectrum signals, the receiver including:

a local code generator that produces a version of a code that is included in the received signal;

a code phase generator that produces chip edge signals and phase angles that correspond to an estimated code phase;

a carrier phase generator that produces phase angles that correspond to an estimated carrier phase;

a code tracking delay lock loop that produces code error signals that are used to control the code rate of the code generator;

a carrier tracking phase lock loop that produces phase error signals that are used to control the carrier phase generator;

a correlation subsystem that includes

an array of complex accumulation registers that collect measurements that correspond to samples of the received signal, the accumulators being associated with code chip ranges that span all or a portion of one or more code chips;

a code phase decoder that controls the complex accumulators to direct the measurements to the respective complex accumulators that are associated with the code chip ranges from which the associated samples are taken, the code phase decoder decoding values that correspond to the estimated phase angles of the samples; and

a processor that selectively combines the accumulated values from two or more accumulation registers to produce code tracking discriminator information for the code tracking delay lock loop.

14. The receiver of claim 13 wherein the processor further selectively combines the accumulated values from various code chip ranges and manipulates the results to produce phase error information for use in the carrier tracking phase lock loop.

15. The receiver of claim 13 further including

a multipath mitigation sub-system for producing multipath mitigation information for use in code tracking, carrier tracking, or both, and

the processor selectively combines the accumulated values from two or more accumulation registers to produce correlation values for the multipath mitigation subsystem.

16. A computer generated method for tracking a spread spectrum signal the method including the steps of:

accumulating correlation measurements that are associated with samples of a received signal over multiple code chips to produce complex accumulated values that correspond to code chip ranges that span all or a portion of one or more code chips;

selectively combining the complex accumulated values associated with two or more code chip ranges to produce correlation values for use in one or more correlation techniques, one or more multipath mitigation techniques, or both.

17. The method of claim 16 further including in the step of selectively combining the complex accumulated values the step of selecting the complex accumulated values that combine to produce one or more early correlation values and one or more late correlation values associated with one or more desired delay spacings.

18. The method of claim 17 further including in the step of producing early and late correlation values the step of combining the early and late correlation values to produce early minus late discriminator information.

19. The method of claim 18 further including in the step of selectively combining the complex accumulated values the step of selectively varying numbers of ranges that are combined, sizes of the ranges that are combined, or both.

20. The method of claim 16 further including in the step of selectively combining the complex accumulated values the step of selecting the complex accumulated values that combine to produce correlation values that are used to produce code tracking discriminator information.

21. The method of claim 16 further including

in the step of accumulating, mathematically manipulating the accumulated values to determine intermediate values that correspond to ranges that are between the ranges associated with the accumulated values, and

in the step of selectively combining the accumulated values, combining the inter-mediate values instead of or in addition to the accumulated values.