Period measurement system
First Claim
1. A period measurement system for measuring the period of a biosignal, said period having a minimum value, comprising:
- data memory means for storing sampled input biosignal data and for shifting the stored biosignal data when new biosignal data is entered;
autocorrelation function computation means for computing an autocorrelation function A (τ
) of the sampled input biosignal data, given by the equation ##EQU4## wherein a phase difference variable τ
is specified over each computation cycle corresponding to k=1 to n, said variable τ
being set to essentially the minimum value of the biosignal period being measured for an initial computation cycle, and thereafter incremented by a certain value in advance of each successive computation cycle of the autocorrelation function;
peak detection means for detecting a peak by comparing the autocorrelation function value previously computed by said function computation means with the autocorrelation function value most recently computed by said function computation means;
means for continuing the computation of the autocorrelation function for a fixed period of time following the detection by said peak detection means of a certain peak;
means for confirming that no peak larger than said certain peak exists in said fixed period of time, whereby said certain peak is determined to be a true peak; and
period computation means for computing the period of the biosignal based on the phase difference variable for which a peak is detected by said peak detection means.
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Accused Products
Abstract
A period measurement system adapted to sample a biosignal at a predetermined sampling period, find an autocorrelation function for a variable τ from the sampled biosignal, and then find an autocorrelation function corresponding to the value of a phase difference variable obtained by changing the variable τ along a time axis. An autocorrelation function found in this manner is stored in memory and then compared with a subsequent-found autocorrelation function. The comparison operation is repeated for successive autocorrelation functions, thereby to find a peak of autocorrelation functions to measure the period of the biosignal.
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Citations
7 Claims
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1. A period measurement system for measuring the period of a biosignal, said period having a minimum value, comprising:
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data memory means for storing sampled input biosignal data and for shifting the stored biosignal data when new biosignal data is entered; autocorrelation function computation means for computing an autocorrelation function A (τ
) of the sampled input biosignal data, given by the equation ##EQU4## wherein a phase difference variable τ
is specified over each computation cycle corresponding to k=1 to n, said variable τ
being set to essentially the minimum value of the biosignal period being measured for an initial computation cycle, and thereafter incremented by a certain value in advance of each successive computation cycle of the autocorrelation function;peak detection means for detecting a peak by comparing the autocorrelation function value previously computed by said function computation means with the autocorrelation function value most recently computed by said function computation means; means for continuing the computation of the autocorrelation function for a fixed period of time following the detection by said peak detection means of a certain peak; means for confirming that no peak larger than said certain peak exists in said fixed period of time, whereby said certain peak is determined to be a true peak; and period computation means for computing the period of the biosignal based on the phase difference variable for which a peak is detected by said peak detection means. - View Dependent Claims (2)
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3. A period measurement system for measuring the period of a biosignal, said period having a minimum value, comprising:
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means for extracting a biosignal; autocorrelation function computation means coupled to said extracting means for computing an autocorrelation function of the biosignal wherein said autocorrelation function varies according to position along a correlation axis; peak detection means coupled to said function computation means for detecting peak from the autocorrelation function; period computation means coupled to said peak detection means for computing a period of the biosignal from that position on the correlation axis at which a peak is detected by said peak detection means; means for continuing the computation of the autocorrelation function for an interval corresponding essentially to the minimum value of the period of the measured signal, which interval begins with detection of a certain peak by said peak detection means; and means for confirming that no peak larger than said certain peak exists in said interval which corresponds to said minimum value and which begins with the detection of said certain peak, whereby said certain peak is determined to be a true peak. - View Dependent Claims (4)
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5. A method of measuring the period of a biosignal, comprising the steps of:
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obtaining biosignal data corresponding to a biosignal the period of which is to be measured; repeatedly computing an autocorrelation function of the biosignal data including setting a minimum phase difference, deriving pairs of values of the biosignal data by selecting the data according to the minimum phase difference, summing the products of the derived pairs of values thereby providing a computed output, and incrementally advancing the phase difference between the selected data for each successive computing step; detecting a peak in the computed output provided by said computing step; and determining the period of the biosignal according to the total phase difference between the selected biosignal data for which a peak in the computed output is detected. - View Dependent Claims (6, 7)
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Specification