Research On The Fetal Heart Rate Detecting Algorithm

Fetal heart rate monitoring is an important parameter of fetal’s health in the womb. There are many ways to obtain the FHR, and the most common way is to use the ultrasonic signal of Doppler because of its advantages such as high sensitivity, no damage, strong direction, long cycle, simplicity of operator and so on. However, there are various kinds of interference and noise in ultrasound Doppler echo signal, how to extract the pure fetal heart signal to increase the calculating accuracy of fetal heart rate has become a difficult problem to study. To overcome the problem, this paper launches an in-depth research on how to improve the accuracy of fetal heart rate detection algorithms, and the main work is as follows:Firstly, the processing method of fetal heart signal based on wavelet analysis is studied. Because of the multiresolution characteristic and local feature representation ability, Wavelet transform is widely used in the field of signal processing. After the study of the basic theory of wavelet, an appropriate wavelet base and decomposition number is selected according to the properties of fetal heart signal, and a new bivariate threshold function is put forward to remove the noises in the womb. Simulation experiments show that the denoising effect of this method, compared with traditional threshold functions is better.Secondly, because of that the wavelet transform does not have the capacity of adaptive decomposition and occupies system resources, this paper puts forward a fusion method, which conbines the adaptive decompodition characteristic of empirical mode decomposition and fast calculation characteristic of wavelet transform. Simulation experiments show that applying this algorithm to fetal heart signal processing can obtain a more pure heart signal, in addition, the signal-to-noise ratio and smoothness can be greatly enhanced.Finally, this paper applies the fusion algorithm to the fetal heart signal denoising, then uses the Hilbert transform to extract the envelope of the signal, and extract the fetal heart signal rate by autocorrelation algorithm. Simulation experiments show that the double heart rate frequency and half frequency problems can be solved by this fusion algorithm, compared with the band-pass filter and wavelet algorithm, the algorithm proposed in this paper can reach the maximum calculation accuracy.