| 摘要 |
<p>PURPOSE:To shorten a calculation time and to perform processing within a real time without being affected by noise by a method wherein the change range of the phase difference variable in the next calculation of an autocorrelation function is controlled according to the newest detected cycle so as to become the cycle range corresponding to a range exerting effect on a calculated cycle. CONSTITUTION:A transducer 2 is arranged on the abdomen W of a woman and detects the heartbeat signal of the embryo to generate an electric signal which is, in turn, sampled by a sampling circuit 4 to be stored in a data memory 6. A calculation range setting circuit 24 receives a signal showing a heart rate of + or -20BPM from a heart rate calculation circuit 18 to calculate the corresponding time and outputs a signal to a multiplier 8. The multiplier 8 reads two sampling data separated by a value of the phase difference variable gamma shown by the signal from the data memory 6 to multiply the same. An adder 10 reads the autocorrelation function calculated value relating to the phase difference variable gamma from a correlation memory 12 to add the calculated data thereto to again store the calculated value in the correlation memory 12. A cycle calculation circuit 16 calculates the cycle of the heart rate signal shown by a time corresponding to the phase difference variable gamma and the heart rate calculation circuit 18 calculates a heart rate.</p> |
