Research On The Ultrasonic Doppler Fetal Heart Rate Detecting Algorithm

Fetal heart rate which has become as an indispensable mean of routine examination is an important parameter of fetal health in perinatal period. Because of the safety, health and noninvasive of doppler method, it has become the principal means of acquisition fetal heart rate signal. However, because of maternal blood flow, breathing, heartbeat and orther factors interference, it makes the acquisition fetal heart rate signal, accurate extraction fetal heart rate signal and detection fetal heart rate as a big problem, which also are the main research contents of this study.In the extraction field the fetal heart rate signal, this study researches the principle, methods and shortcomings of wavelet and wavelet packet hard threshold and soft threshold function. This article deeply studys the characteristic of doppler fetal heart rate signal from the angle of entropy, and puts forward wavelet packet mixed node threshold value method based on the maximum entropy principle for the fetal heart rate signal extraction. In addition, contraposing the shortcoming of traditional hard and soft threshold function, this article puts forward a new threshold function. Through the experiments it shows that the method is able to more pure extract fetal heart rate signal.In the inspection field of the fetal heart rate, this study researches the principle and shortcomings of traditional autocorrelation algorithm, and puts forward the generalized kernel related algorithm based on kernel function for fetal heart rate signal cycles inspection. In addition, contraposing the problem how to seek the first peak, this study puts forward the rapid interpolation envelope method. Experiments prove that tthis study’s method can accurately detect fetal heartbeats cycle. At the same time, from the view of the whole system, this study takes some comprehensive tests for the acquisition circuit, digital circuit, extraction algorithm and cycle detection algorithm.In the acquisition field of the fetal heart rate signal, this study designs the fetal heart rate signal acquisition circui including ultrasonic launching and receiving circuit, synchronous demodulation circuit, band-pass filter circuit, amplifying circuit, envelope detection circuit, the digital processing circuit based on DSP and realizes the fetal heart rate signal accurately acquisition. At the same time, from the view of the whole system, this study takes some comprehensive tests for the acquisition circuit, digital circuit, extraction algorithm and cycle detection algorithm.Finally, the paper summarizes the research work of fetal heart rate detection and looks to the future of the method of fetal heart rate detection.