Analyzing the traditional auto-correlation algorithms

an improved method is presented

where the adaptive control is adopted to realize a real-time adjustment for control factor

thus the attenuation of auto-correlation function at any time extension varies with different fetal heart rate. It consistently ensures that the largest cycle peak is in the first cycle of correlation function to effectively eliminate the misjudgments due to doubling and halving in the detection of Doppler fetal heart rate with the traditional methods. In the optimized algorithm

the computation is reduced to 18% of the original

and the computing rate is accelerated 6 times. Simultaneously

the influence of interference signals on heart rate is greatly weakened by removing the un-corresponding values.