Method and device for determination of fetal heartbeat frequency, using ultra-sonic sensor containing ultrasonic Doppler-signal

摘要

The method for the determination of the fetal heartbeat frequency is based on the information recorded over a certain period by an ultrasonic sensor containing an ultrasonic Doppler-signal. In a first step the coefficient of the frequency of a harmonic analysis of the signal at a certain time is calculated for several periods. In a second step an auto-correlation function of the coefficients determined by the previous calculation is made. In the third step the fetal heartbeat frequency is calculated from the position of the maximum of the auto-correlation function obtained in the second step.