Periodic-signal analysis via correlation

• US 6,477,476 B1
• Filed: 12/06/1999
• Issued: 11/05/2002
• Est. Priority Date: 12/06/1999
• Status: Expired due to Fees

• Current Assignee: NXP B.V. (NXP Semiconductors NV)
• Original Assignee: Koninklijke Philips Electronics N.V. (Koninklijke Philips N.V.)
• Inventors: Wong-Lam, Ho Wai, Naley, Mark Douglas
• Primary Examiner(s): Hoff, Marc S.
• Assistant Examiner(s): Charioui, Mohamed
• Application Number:
  US09/455,126
• Time in Patent Office: 1,065 Days
• Field of Search: 702/66, 702/67, 702/70, 702/71, 702/73, 702/74, 702/75, 702/76, 702/79, 702/193, 600/300, 600/500, 600/517, 324/76.22
• US Class Current: 702/66
• CPC Class Codes: G06F 18/00 Pattern recognition
• CPC Class Codes: G06F 2218/08 Feature extraction

Abstract

The present invention is directed to systems and methods for analyzing and characterizing a time-limited waveform to avoid significant delays and miscalculations due to the presence of spurious transitions. In an example implementation, a processor is adapted to sense the signal and interpret various parameters of the waveform using a correlation method. In one application, the correlation method includes providing an autocorrelation function of a segment of the waveform that includes at least one period, and approximating a period of the waveform using peaks in the autocorrelation function. Other aspects of the invention involve approximating the period of the waveform by identifying a segment of the waveform having a steep slope magnitude that exceeds a certain threshold, and determining a polarity associated with the waveform.

Claims

1. A correlation method for analyzing the waveform of a time-limited signal having a plurality of periods, comprising:

providing an autocorrelation function of a segment of the waveform that includes at least one of the periods;

obtaining an approximate period of the waveform using peaks in the autocorrelation function;

providing data corresponding to a comparison waveform segment;

measuring a time difference between consecutive maximum and minimum levels of a segment of the time-limited signal; and

determining the polarity of the segment by cross-correlating the data corresponding to the comparison waveform segment and data corresponding to the segment of the time-limited signal.

2. A correlation method for analyzing the waveform of a time-limited signal, according to claim 1, wherein the autocorrelation function represents a measure of similarity of the segment of the waveform with a time-shifted version of the segment of the waveform.

3. A correlation method for analyzing the waveform of a time-limited signal, according to claim 2, wherein the measure of similarity is greatest where the segment of the waveform, relative to the time-shifted version, is shifted one complete period.

4. A correlation method for analyzing the waveform of a time-limited signal, according to claim 1, wherein the autocorrelation function represents a measure of dissimilarity of the segment of the waveform with a time-shifted version of the segment of the waveform.

5. A correlation method for analyzing the waveform of a time-limited signal, according to claim 4, wherein the measure of dissimilarity is greatest where the segment of the waveform, relative to the time-shifted version, is shifted by amount corresponding to a pulse width of the waveform.

6. A correlation method for analyzing the waveform of a time-limited signal, according to claim 1, wherein obtaining an approximate period of the waveform includes identifying a segment of the waveform having a steep slope magnitude that exceeds a certain threshold.

7. A correlation method for analyzing the waveform of a time-limited signal, according to claim 1, further including determining a polarity associated with the waveform.

8. A correlation method for analyzing the waveform of a time-limited signal, according to claim 1, wherein the autocorrelation function represents a measure of correspondence between the segment of the waveform with a time-shifted version of the segment of the waveform, and further including using a comparison waveform to determine a polarity associated with the period of the waveform.

9. A correlation apparatus adapted to analyze the waveform of a time-limited signal having a plurality of periods, comprising:

means for providing an autocorrelation function of a segment of the waveform that includes at least one of the periods;

means for obtaining an approximate period of the waveform using peaks in the autocorrelation function;

means for providing data corresponding to a comparison waveform segment;

means for measuring a time difference between consecutive maximum and minimum levels of a segment of the time-limited signal; and

means for determining the polarity of the segment by cross-correlating the data corresponding to the comparison waveform segment and data corresponding to the segment of the time-limited signal.

10. A correlation apparatus, according to claim 9, wherein at least one of said means is included as part of:

a test instrument and a data analysis package.

11. A correlation apparatus, according to claim 10, wherein the test instrument is an oscilloscope.

12. A correlation apparatus, according to claim 9, further comprising a programmable computer arrangement including at least one of said means.

13. A correlation apparatus adapted to analyze the waveform of a time-limited signal having a plurality of periods, comprising:

a signal receiver adapted to receive a waveform segment that includes at least one of the periods; and

a processor arrangement adapted to provide an autocorrelation function of the segment of the waveform, to obtain an approximate period of the waveform using peaks in the autocorrelation function, to provide data corresponding to a comparison waveform segment, to measure a time difference between consecutive maximum and minimum levels of a segment of the time-limited signal, and to determine the polarity of the segment by cross-correlating the data corresponding to the comparison waveform segment and data corresponding to the segment of the time-limited signal.

14. A correlation apparatus, according to claim 13, wherein the processor arrangement is further adapted to obtain an approximate period of the waveform by identifying a segment of the waveform having a steep slope magnitude that exceeds a certain threshold.

15. A correlation apparatus, according to claim 13, wherein the processor arrangement is further adapted to determine a polarity associated with the period of the waveform.

16. A correlation apparatus, according to claim 13, wherein the autocorrelation function represents a measure of correspondence between the segment of the waveform and a time-shifted version of the segment of the waveform.

17. A correlation method for analyzing the waveform of a time-limited signal having a plurality of periods, comprising:

providing an autocorrelation function of a segment of the waveform that includes at least one of the periods, wherein the autocorrelation function represents a measure of correspondence between the segment of the waveform with a time-shifted version of the segment of the waveform;

obtaining an approximate period of the waveform using peaks in the autocorrelation function; and

using a comparison waveform to determine a polarity associated with the period of the waveform.