Periodic-signal analysis via correlation

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.

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.