Adaptive correlation

• US 8,064,552 B2
• Filed: 06/02/2008
• Issued: 11/22/2011
• Est. Priority Date: 06/02/2008
• Status: Active Grant

• Current Assignee: Harris Corporation (L3Harris Technologies, Inc.)
• Original Assignee: Harris Corporation (L3Harris Technologies, Inc.)
• Inventors: Michaels, Alan J., Chester, David B.
• Primary Examiner(s): Payne; David C.
• Assistant Examiner(s): Cadeau; Wednel
• Application Number:
  US12/131,386
• Publication Number:
  US 20090296860A1
• Time in Patent Office: 1,268 Days
• Field of Search: 375/343
• US Class Current: 375/343
• 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 1/70752 Partial correlation
• CPC Class Codes: H04L 7/042 Detectors therefor, e.g. correlators, state machines digital correlators in general G06F17/15

Abstract

A method is provided for correlating samples of a received signal and samples of an internally generated/stored sample sequence (“IGSSS”). The method involves performing a first iteration of a first-resolution correlation state. The first-resolution correlation state involves: selecting a first N sets of samples from the received signal; selecting a first set of samples from the IGSSS; and concurrently comparing each of the N sets of samples with the first set of samples to determine if a correlation exists between the same. If it is determined that a correlation does not exist between one of the N sets of samples and the first set of samples, then a second iteration of the first-resolution correlation state is performed. If it is determined that a correlation exists between one of the N sets of samples and the first set of samples, then a first iteration of a second-resolution correlation state is performed.

Claims

1. A method for correlating samples of a received signal and samples of an internally generated or stored sample sequence, comprising:

performing, by at least one electronic circuit, a first iteration of a low-resolution correlation, said low-resolution correlation including the steps of;

selecting a first N sets of received signal samples from a received signal;

selecting a first set of reference samples from an internally generated or stored sample sequence;

concurrently comparing each of said first N sets of received signal samples with said first set of reference samples to determine if a sufficient correlation exists between the same, wherein a sufficient correlation exists when a correlation peak value associated with a respective one of said first N sets of received signal samples exceeds a pre-defined threshold value;

performing a second iteration of said low-resolution correlation if it is determined that a sufficient correlation does not exist between said first N sets of received signal samples and said first set of reference samples; and

performing, by at least one electronic circuit, a first iteration of a higher-resolution correlation if it is determined that a sufficient correlation exists between at least one of said first N sets of received signal samples and said first set of reference samples, and said higher-resolution correlation comprising obtaining a plurality of correlation values by comparing each of a second N sets of received signal samples with a second set of reference samples;

wherein said first N sets of received signal samples and said first set of reference samples comprise the same number of samples, and each of said second N sets of received signal samples comprises a larger number of samples than each of said first N sets of received signal samples.

2. The method according to claim 1, wherein said higher-resolution correlation comprises the steps of (a) selecting said second N sets of received signal samples from a received signal and (b) selecting said second set of reference samples from said internally generated or stored sample sequence, wherein said second N sets of received signal samples and said second set of reference samples comprise the same number of samples.

3. The method according to claim 1, wherein said second N sets of received signal samples comprise samples that are delayed in time as compared to samples contained in said first N sets of received signal samples.

4. The method according to claim 1, wherein said second set of reference samples comprises samples that are delayed in time as compared to samples contained in said first set of reference samples.

5. The method according to claim 2, wherein said higher-resolution correlation further comprises the step of concurrently comparing each of said second N sets of received signal samples with said second set of reference samples to determine if a sufficient correlation exists between the same.

6. The method according to claim 5, further comprising computing, by said electronic circuit, a correlation index value if it is determined that a sufficient correlation exists between at least one of said second N sets of received signal samples and said second set of reference samples.

7. The method according to claim 1, wherein said higher-resolution correlation operates on independent sets of samples with the same relative delays as said samples of said first set of reference samples with a correlation peak to compute a correlation verification or an independent correlation measure.

8. The method according to claim 1, wherein said second iteration of said low-resolution correlation comprises the step of selecting a second N sets of received signal samples from said received signal and a second set of reference samples from said internally generated or stored sample sequence, wherein said second N sets of received signal samples and said second set of reference samples comprise the same number of samples.

9. The method according to claim 8, wherein said second N sets of received signal samples comprise the same number of samples as said first N sets of received signal samples.

10. The method according to claim 8, wherein said second N sets of received signal samples comprise samples that are delayed in time as compared to samples contained in said first N sets of received signal samples.

11. A method for correlating samples of a received signal and samples of an internally generated or stored sample sequence, comprising:

performing, by at least one electronic circuit, a first iteration of a first-resolution correlation state, said first-resolution correlation state comprising the steps of;

selecting a first N sets of received signal samples from a received signal;

selecting a first set of reference samples from an internally generated or stored sample sequence;

concurrently comparing each of said first N sets of received signal samples with said first set of reference samples to determine if a sufficient correlation exists between the same, wherein a sufficient correlation exists when a correlation peak value associated with a respective one of said first N sets of received signal samples exceeds a pre-defined threshold value;

performing, by said electronic circuit, a second iteration of said first-resolution correlation state if it is determined that a sufficient correlation does not exist between at least one of said first N sets of received signal samples and said first set of reference samples; and

performing, by said electronic circuit, a first iteration of a second-resolution correlation state if it is determined that a sufficient correlation exists between at least one of said first N sets of received signal samples and said first set of reference samples, said second-resolution correlation state comprising obtaining a plurality of correlation values by comparing each of a second N sets of received signal samples with a second set of reference samples, wherein each of said second N sets of received signal samples comprises a larger number of samples than each of said first N sets of received signal samples.

12. The method according to claim 11, wherein said first N sets of received signal samples and said first set of reference samples comprise the same number of samples.

13. The method according to claim 11, wherein said second-resolution correlation state comprises the steps of (a) selecting said second N sets of received signal samples from a received signal and (b) selecting said second set of reference samples from said internally generated or stored sample sequence, wherein said second N sets of received signal samples and said second set of reference samples comprise the same number of samples.

14. The method according to claim 11, wherein said second N sets of received signal samples comprise samples that are delayed in time as compared to samples contained in said first N sets of received signal samples.

15. The method according to claim 11, wherein said second set of reference samples comprises samples that are delayed in time as compared to samples contained in said first set of reference samples.

16. The method according to claim 13, wherein said second-resolution correlation state further comprises the step of concurrently comparing each of said second N sets of received signal samples with said second set of reference samples to determine if a sufficient correlation exists between the same.

17. The method according to claim 16, further comprising computing, by said electronic circuit, a correlation index value if it is determined that a sufficient correlation exists between at least one of said second N sets of received signal samples and said second set of reference samples.