Period measurement system

摘要

An autocorrelation function is computed for a value of a phase difference variable over a range determined by a set minimum period and a set maximum periods of one beat, corresponding to a maximum heart rate and a minimum heart rate, respectively. The maximum and minimum rates are estimated from a latest computed heart rate obtained from a preceding measurement of a heartbeat signal, by way of sampling the heartbeat signal at a predetermined sampling period and then using the data obtained from the sampling operation. The period of the heartbeat signal is computed from the computed autocorrelation function, and the sampling period is decided from the computed heartbeat signal period.