Diff: notch.hpp

Revision:

0:5e2a4b964485

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/notch.hpp	Sat Dec 20 05:22:00 2014 +0000
@@ -0,0 +1,47 @@
+/*
+#include <stdio.h>
+#include <stdlib.h>
+#include <math.h>
+int main(){
+    int fs = 10000;
+    double  B0, a1, a2, b1, c0, F0, T;
+    F0 = 60;    // or 50
+    B0 = 100.;
+    T  = 1./fs;
+    a1 = 2. * exp(-M_PI * B0 * T) * cos(2. * M_PI * F0 * T);
+    a2 = -exp(-2. * M_PI * B0 * T);
+    b1 = -2. * cos(2. * M_PI * F0 * T);
+    c0 = (1-a1-a2)/(2+b1);
+    printf("a1 = %f\n", a1);
+    printf("a2 = %f\n", a2);
+    printf("b1 = %f\n", b1);
+    printf("c0 = %f\n", c0);
+    return 0;
+}
+60Hz
+    a1 = 1.936768
+    a2 = -0.939101
+    b1 = -1.998579
+    c0 = 1.642174
+50Hz
+    a1 = 1.937188
+    a2 = -0.939101
+    b1 = -1.999013
+    c0 = 1.938304
+*/
+
+float notch_filter1(float data){
+    y1[0] = data + a1*y1[1] + a2*y1[2];
+    float reault = y1[0] + b1*y1[1] + y1[2];
+    y1[2] = y1[1];
+    y1[1] = y1[0];
+    return(reault);
+}
+
+float notch_filter2(float data){
+    y2[0] = data + a1*y2[1] + a2*y2[2];
+    float reault = y2[0] + b1*y2[1] + y2[2];
+    y2[2] = y2[1];
+    y2[1] = y2[0];
+    return(reault);
+}