Tham khảo tài liệu 'adaptive filtering applications part 6', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 142 Adaptive Filtering Applications comparison with other modalities. Continuous wave near infrared NIR spectroscopy has been applied to trans-abdominal fetal pulse oximetry Ramanujam et al. 2000 Chance 2005 Zourabian et al. 2000 Nioka et al. 2005 Vintzileos et al. 2005 . The system consists of NIR sources halogen lamps and a photomultiplier as detection unit Ramanujam et al. 2000 Chance 2005 . The generated heat was justified by using cooling fans for the halogen lamps. Recently trans-abdominal oxygen saturation SpCh in animal Nioka et al. 2005 and human fetuses were successfully obtained in the laboratory Vintzileos et al. 2005 . However the proposed techniques require high power a total of 80 w optical power and a relatively expensive detection unit photo-multiplier . In this project we propose to design and develop a low-power optical FHR monitor. The signal of interest is the photoplethysmogram PPG which is generated when a beam of light is modulated by blood pulsations. PPG is a noninvasive technique for detecting blood volume changes in living tissue by optical means consisting of a light emitting diode LED and a photo-detector. One of the potential applications of the PPG technology is non-invasive fetal heart rate detection through the maternal abdomen. In this application the light intensity is modulated by the mother as well as fetal blood circulation producing a combined signal which needs to be separated via digital signal processing DSP techniques. The design of a fixed filter would not be adequate as the frequency spectrum of the noise maternal PPG overlaps with the desired signal fetal PPG . The adaptive filter will automatically adjust its coefficients therefore achieve the high degree of noise rejection. Such an approach - based on adaptive noise cancellation ANC - has been evaluated for extraction of the fetal heart-rate using PPG signals from the maternal abdomen. A simple optical model has been proposed in which the maternal and fetal blood .
