BSPII-ch3-filtering-time-2008

Blent ylmaz b bme402 biomedical signal processing ii

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Unformatted text preview: 02: Biomedical Signal Processing-II Processing- 23 Three-point central-difference operator • Average of two successive • • • • • output values y3[n]=(1/2) [y[n]+y[n-1]] [y[n]+y[ny3[n]=(1/2T) [x[n]-x[n-2]] [x[n]- x[nH(z)=(1/2T) (1-z-2) (1-1) (1/2) (1+z-1) =(1/T) (1-z (1First-order-diff operator + First- order2-point MA filter Bandpass filter Dr. Bülent Yılmaz Bü BME402: Biomedical Signal Processing-II Processing- 24 12 Illustration of Application: Removal of LF noise First-order difference operator Three-point-central-difference operator Dr. Bülent Yılmaz Bü BME402: Biomedical Signal Processing-II Processing25 Problem • How could we improve the performance of the basic first-order difference operator as a filter to remove LF noise or baseline wander w/o distorting the QRS complexes? • We would like the gain of the filter to be close to unity after a certain frequency. Dr. Bülent Yılmaz Bü BME402: Biomedical Signal Processing-II Processing- 26 13 Solution • To obtain high gain in the low frequencies • • • place a pole on the real axis (zero) frequency at z=0.995 pole H(z)=(1/T)[(1-z-1)/(1-0.995z-1)] H(z)=(1/T)[(z-1)/(z-0.995)] y[n]=(1/T)(x[n]-x[n-1])+0.995y[n-1] Dr. Bülent Yılmaz Bü BME402: Biomedical Signal Processing-II Processing- 27 Magnitude and phase response Dr. Bülent Yılmaz Bü BME402: Biomedical Signal Processing-II Processing- 28 14 Removal of wander Dr. Bülent Yılmaz Bü BME402: Biomedical Signal Processing-II Processing- 29 15...
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