Study And Implementation Of A Signal Processing Algorithm For The Integrated Doppler Ultrasound Fetal Heart Monitor

Fetal heart rate is a key indicator in fetal monitoring.Ultrasound Doppler fetal heart monitor can detect fetal heart rate,so it can help pregnant woman to monitor the health of the fetus.Fetal heart signals are very weak,and there are multiple noise in fetal hear signals,so it often leads to low measurement sensitivity,small detection range,poor fetal heart sound,and howling phenomena in integrated ultrasound Doppler fetal heart monitor on the market.In order to solve those problems,this topic proposes a signal processing algorithm for an integrated ultrasound Doppler fetal heart monitor.The research contents of this article are as follows:1.Fetal heart signal denoising algorithm.The fetal heartbeat signal is denoised by an adaptive denoising algorithm based on spectral subtraction and a threshold denoising algorithm.First,the adaptive denoising algorithm based on the spectral subtraction identifies the noise signal through the endpoint detection algorithm,thereby realizing the update of the noise spectrum.The threshold denoising algorithm mainly performs clipping processing according to the relationship between the half-wave peak value of the signal and the amplitude threshold,and the threshold is adaptively adjusted according to the signal-to-noise ratio detection algorithm.This project uses the fetal heart rate simulator to generate simulated fetal heart signals to verify the effectiveness of the noise reduction algorithm2.Self-excitation howling suppression algorithm.According to the characteristics of amplitude and time distribution of the howling signal of the fetal heart monitor,a howling suppression algorithm based on signal amplitude and count detection was proposed and studied.This paper also researches howling suppression algorithm based on frequency shift,and determines the frequency shift direction and frequency range by combining the frequency response characteristics of the fetal heart rate speaker and the human ear's hearing characteristics.Based on this,the frequency domain is studied and realized.The frequency-shift method and time-domain frequency-shift method are compared comprehensively3.Equalization processing algorithm.A digital graphic equalizer was designed based on the frequency response characteristics of the fetal heart rate speaker and the human ear's hearing characteristics,and the method of reducing band aliasing in the equalizer was studied.The results of fetal heart simulation detection equipment and the actual measurement of pregnant women show that the fetal heart signal processing algorithm proposed in this paper can effectively improve the signal to noise ratio of the signal and can effectively solve the howling problem.The equalization processing algorithm has a certain effect on compensating the frequency response of the fetal heart monitor and improving the playback effect of the fetal heart monitor.