| The fetal electrocardiogram(FECG) monitoring is an effective method to monitor the healthy condition and growth of fetusduring pregnancy. By analysising the waveform of fetal ECG and the change of fetal heart rate during contractions can provide people a lot of important information about the status of the fetus. The non-invasive method is usually used to collect the abdominal mixed signal from the maternal abdomen which is used for extracting FECG. While the abdominal mixed signal is very complex, so it is necessary to find a way to extract FECG clearly.The main content of this paper includes two parts: one is the research ofthe fetal ECG and contraction signal extraction method. On the other is the design of fetal ECG monitoring system and its implementation.First, the paper analyses the basic characteristics of mixed maternal abdominal signal.According to the signal frequency spectrum, a filter bank is applied to data preprocessing. The contraction signal is isolated from mixed signal, and and obtained abdominal mixed ECG signal without contraction signal. The next is to extract the fetal ECG from abdominal mixed ECG signals.Abdominal signal is a quasi-periodic time signal, and the sampling points exists some certain sequence relationship. The traditional independent component analysis(ICA) algorithm does not consider the temporal correlation in the process of separation, and the selection of mixed signal length has a certain effect on the separation effect in the process of signal extraction. To solve these problems, a novel method is proposed which combined self-correlation analysis with independent component analysis. The experiments are verified by clinical signals, the results show that the contraction signal is extracted by using filter bank and can determine the contraction interval effectively. The maternal component interference of the extracted fetal ECG is well suppressed by using the method proposed in this paper and the fetal ECG is clear.The separation is better than traditional Fast ICA.The fetal ECG monitoring system is constructed in this paper and the TMS320C6748 DSP is a core of the system.The system includes signal amplification filter circuit, A/D sampling circuit and C6748 core processing part. The real-time acquisition, storage and transmission of the abdominal signal are realized through the hardware debugging and software design. |
