Apparatus for and method of making pulse-shape measurements

• US 8,442,097 B2
• Filed: 04/28/2010
• Issued: 05/14/2013
• Est. Priority Date: 04/15/2003
• Status: Active Grant

• Current Assignee: Novatel Incorporated (Hexagon AB)
• Original Assignee: Novatel Incorporated (Hexagon AB)
• Inventors: Fenton, Patrick C., Williamson, Ian, Brown, David
• Primary Examiner(s): NGUYEN, LEON VIET Q
• Application Number:
  US12/769,260
• Publication Number:
  US 20100246645A1
• Time in Patent Office: 1,112 Days
• Field of Search: 342/352, 342/357.37, 342/357.61, 375/130, 375/149, 375/150, 375/343, 375/347, 375/354
• US Class Current: 375/150
• CPC Class Codes: G01S 19/21 Interference related issues ; Issues related to cross-correlation, spoofing or other methods of denial of service
• CPC Class Codes: G01S 19/22 Multipath-related issues
• CPC Class Codes: G01S 19/30 code related G01S19/246 takes precedence
• CPC Class Codes: H04B 1/7075 with code phase acquisition
• CPC Class Codes: H04B 1/7085 using a code tracking loop, e.g. a delay-locked loop
• CPC Class Codes: H04B 2201/70715 with application-specific features

Abstract

A receiver includes a pre-correlation filter that forms an image of the average chip shape of a received signal over a specified period of time. The filter includes an array of complex accumulation registers that accumulate measurements that are associated with signal samples from specific ranges of locations, or code chip phase angles, along a spread-spectrum chip. Using the accumulated measurements, the receiver estimates the location of the chip transitions in a direct path signal component. The receiver may thereafter change the starting points, sizes and numbers of ranges, such that the accumulation registers accumulate more detail from the chip edges. The receiver in addition may use 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 taken at times that are asynchronous to code rate, the complex accumulators being associated with code chip ranges that span all or a portion of a code chip;

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 angles 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 changed to narrow one or more of the delay spacings.

7. The correlation subsystem of claim 1 wherein the array further includes an accumulation register that is selectively enabled to accumulate correlation measurements associated with a code chip when the code does not transition at a chip time.

8. 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 taken at times that are asynchronous to code rate, the accumulators being associated with code chip ranges that span all or a portion of a code chip;

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.

9. The receiver of claim 8 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.

10. The receiver of claim 8 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.

11. 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 taken at times that are asynchronous to code rate over multiple code chips to produce complex accumulated values that correspond to code chip ranges that are associated with code phase angles and each span a portion of a code chip;

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

12. The method of claim 11 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.

13. The method of claim 12 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.

14. The method of claim 13 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.

15. The method of claim 14 wherein the number of code chip ranges selected for combining is changed to narrow one or more of the delay spacings.

16. The method of claim 11 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.

17. The method of claim 11 wherein the step of accumulating includes the step of separately accumulating correlation measurements that correspond to sequential I and Q samples.

18. The method of claim 11 wherein

the step of accumulating includes the step of separately accumulating correlation measurements that correspond to code chips in which no transition occurred at the corresponding chip times to produce a non-transition complex accumulation value, and

the step of selectively combining includes a step of selectively including in a combination the non-transition complex accumulation value.