There are many ways to obtain FHR signal

and the most common way is to use ultrasonic sensor.However

it is a challenge to quickly and accurately extract pure fetal heart signal from Doppler fetal heart echo signal which has a lot of noise interference in embedded real time system. Considering the difficulty

a new kind of denoising method based on empirical mode decomposition（ EMD） and lifting wavelet transform is constructed.Then use the Hilbert transform to extract envelope of signal and get fetal heart rate through autocorrelation operation. The experimental results show that the algorithm can effectively extract fetal heart rate signal

greatly reduce heart rate calculation time and improved veracity of calculation.