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Medical Instrumentation 학습노트 9

Medical Instrumentation 학습노트 9. 생체의공학과 2010103805 이규락. QRS Detection. ECG Signal. Band pass Filtering. 미분. Thresholding. 제곱 ( 전파정류 ). 적분. QRS Detection. 1) L PF. Int QRS_LPF( int x) { static int y1=0, y2=0, x[26], p=12; int y; x[p]=x[p+13]=x;

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Medical Instrumentation 학습노트 9

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  1. Medical Instrumentation학습노트9 생체의공학과 2010103805 이규락

  2. QRS Detection ECG Signal Band pass Filtering 미분 Thresholding 제곱 (전파정류) 적분

  3. QRS Detection 1) LPF Int QRS_LPF(int x) { static int y1=0, y2=0, x[26], p=12; int y; x[p]=x[p+13]=x; y=x[p]-(x[p+6]<<1)+x[p+12]+(y1<<1)-y2; y2=y1; y1=y; if(--p<0) p=12; return (y>>5); } LPF필터의 이득(32배)을 없애주기 위해 나눠준다. ‘Ring Buffer’ Arr[13] Arr[25] Arr[0] Arr[12] Arr[12],Arr[25]가 최신 데이터면 Arr[11], Arr[24]가 가장 오래된 데이터이다.

  4. QRS Detection 2) HPF LPF Int QRS_HPF(int x) { static int l1=0, x[66], p=32; int l; x[p]=x[p+33]=x; l=l1+x[p]-x[p+32]; l1=l; if(--p<0) p=32; return (x[p+16]-(l>>5)); } Delay가 15.5 sample 정도 생겨서 16만큼 당겨준다.

  5. QRS Detection 3) 미분 Int QRS_Denivative(int x) { static int x1=0; int y; y=x-x1; x1=x; return (y); } Int QRS_Denivative(int x) { static int x1, x2, x3, x4; int y; y=((x<<1)+x1-x3-(x4<<1))>>3; x4=x3; x3=x2; x2=x1; x1=x; return (y); } 현재와 바로 전의 차만 구함. 시간적 경향을 볼 수 있다.

  6. QRS Detection 4) Square(제곱) IntQRS_Square(int x) {return (x*x); } 곱셈이 얼마나 걸리는지 datasheet를 참조하여 전체가 Realtime이 되는지를 확인해줘야 한다. 4) 절대값 IntQRS_Abs(int x) { if(x<0) return (-x); else return (x); } 곱셈이 없으므로 속도가 빠르다.

  7. QRS Detection 5) 적분 IntQRS_MWI(int x) { static int x[32], p=0; static long sum; long ly; int y; if(++p=32) p=0; sum-=x[p]; sum+=x; x[p]=x; ly=(xum>>5); if(ly>32400) y=32400; else y=(int) ly; return (y); } Moving window integral =>최근 들어온 n개의 data를 더한다. QRS의 폭을 고려하여 Window폭을 설정해야 한다. Return type이 int형이므로 int의 범위가 넘었는지 파악해준다.

  8. QRS Detection • 주의할 점 d1=Getdatach1(); d2=Getdatach2(); -------------------------------------------------- int MyLPF1(int x) { static int x1,x2,x3,x4; x4=x3; x3=x2; x2=x1, x1=x; return y; } intMyLPF2(intx) { static int x1,x2,x3,x4; x4=x3; x3=x2; x2=x1, x1=x; return y; } --------------------------------------------------- l1=MyLPF1(d1); l2=MyLPF2(d2); d1=Getdatach1(); d2=Getdatach2(); -------------------------------------------------- intMyLPF(int x) { static int x1,x2,x3,x4; ∙∙∙ x4=x3; x3=x2; x2=x1, x1=x; ∙∙∙ return y; } --------------------------------------------------- l1=MyLPF(d1); l2=MyLPF(d2); Static변수들을 두 데이터가 공통으로 사용하므로값들이 섞인다.

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