Analog circuit for fetal heart rate (FHR) detection application
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Date
2019-06
Authors
Low, Zhi Qian
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Abstract
This work presents the design of the analog circuit that is used for fetal heart rate (FHR) detection application. Heart rate is a measure for a human to examine his current body status. Heart rate monitoring plays crucial role in regulating the health of foetus as heart-related disease is top cause of death among the babies. In this research, electret microphone is used to detect the sound wave from surrounding and it is then amplified to increase the amplitude of weak signal for further filtering process. Next, bandpass filter will attenuate the frequency that is not in the range from 20Hz to 200Hz. The designed circuit was simulated using LTspice and then soldered on stripboard for further analysis by conducting experiment. Circuit designed is expected to provide the gain of 1016.38 and attenuates the signal outside the frequency range of 2.258Hz to 2080.5Hz. The simulation result provided the highest gain of 996.90 and had percentage difference from theoretical gain from 1.92% until 3.38%. For the frequency response, simulated result only provided the bandwidth of 1.988kHz. The experimental result provide the higher gain of 1005 but also higher percentage difference from theoretical gain of 4.07%. The upper cut-off frequency obtained from experiment was very weak in performance which in the range from 1026.06Hz until 1661.78Hz with 48.38% percentage error w.r.t. simulated result. The circuit is also able to detect heartbeat in the range of 36.24mVp-p to 59.76mVp-p. Overall, the circuit implemented is successfully because it able to provide high gain in the specified range of frequency.