Design And Algorithm For Doppler Fetal Heart Rate Detection System

The fetal heart rate is defined as the fetal heart beats per minute. It is an important evaluation of fetal health. The fetal heart rate which over160beats/min or less than120beats/min is called abnormal fetal heart rate, which indicating oxygen deficiency. Abnormal fetal heart rate will endanger the life of the fetus. In order to keep an eye to the state of the fetus, pregnant women should go to the hospital to have a basis prenatal care, furthermore, fetal heart rate self-monitoring is also necessary. The existing fetal heart rate equipments have lots of disadvantages such as lack of sensitivity, high prices, and high power consumption. We designed a set of fetal heart rate Doppler detection system, with low power consumption, high sensitivity, and high cost-performance ratio, to provide a new solution method of heart rate detection.In this paper, the fetal heart rate Doppler detection system is successfully achieved, and the fetal heart rate extraction algorithm is improved. This system is divided into two parts, the ultrasonic transmitter part and the receiving part. The transmitter part is different from the traditional instrument. DDS module is used in our system as a source of high-frequency ultrasound, and output signal of DDS is voltage-amplified by a high-frequency op-amp, and current-amplified by a push-pull amplifier and then through impedance matching network to drive the ultrasonic piezoelectric transducer. The input signal after the ultrasound sensor will be demodulated by an analog multiplier and a low-pass filter in the receiving part, to extract the low frequency signal from fetal heart beat, and then one way of signal will go through the frequency/voltage converter chip, another way of signal will go through the audio amplifier, to converted into sound for listener. The main controller is ultra-low power MCU chip MSP430F149, which take responsibility to write frequency word to DDS, A/D sampling, calculate fetal heart rate, control to display heart rate and other tasks.Compared with traditional fetal heart device, the fetal heart rate detection system designed in this paper have advantages of high sensitivity, low power consumption and high cost-performance ratio, which can help pregnant women to have a fetal examine in family, and to provide a guidance on status of fetus. This system will have a high market value and popularity.