Yoichi Nagashima
/
CQ_nagasm_08_notch_test
add 60Hz/50Hz notch filter
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notch.hpp
00001 /* 00002 #include <stdio.h> 00003 #include <stdlib.h> 00004 #include <math.h> 00005 int main(){ 00006 int fs = 10000; 00007 double B0, a1, a2, b1, c0, F0, T; 00008 F0 = 60; // or 50 00009 B0 = 100.; 00010 T = 1./fs; 00011 a1 = 2. * exp(-M_PI * B0 * T) * cos(2. * M_PI * F0 * T); 00012 a2 = -exp(-2. * M_PI * B0 * T); 00013 b1 = -2. * cos(2. * M_PI * F0 * T); 00014 c0 = (1-a1-a2)/(2+b1); 00015 printf("a1 = %f\n", a1); 00016 printf("a2 = %f\n", a2); 00017 printf("b1 = %f\n", b1); 00018 printf("c0 = %f\n", c0); 00019 return 0; 00020 } 00021 60Hz 00022 a1 = 1.936768 00023 a2 = -0.939101 00024 b1 = -1.998579 00025 c0 = 1.642174 00026 50Hz 00027 a1 = 1.937188 00028 a2 = -0.939101 00029 b1 = -1.999013 00030 c0 = 1.938304 00031 */ 00032 00033 const float _60Hz_a1 = 1.936768, _60Hz_a2 = -0.939101, _60Hz_b1 = -1.998579, _60Hz_c0 = 1.642174; 00034 const float _50Hz_a1 = 1.937188, _50Hz_a2 = -0.939101, _50Hz_b1 = -1.999013, _50Hz_c0 = 1.938304; 00035 float a1, a2, b1, c0; 00036 float y1[3], y2[3]; 00037 int notch_1, notch_2; 00038 00039 void coef_set(int herz){ 00040 if(herz < 55){ 00041 a1 = _50Hz_a1; 00042 a2 = _50Hz_a2; 00043 b1 = _50Hz_b1; 00044 c0 = _50Hz_c0; 00045 } 00046 else{ 00047 a1 = _60Hz_a1; 00048 a2 = _60Hz_a2; 00049 b1 = _60Hz_b1; 00050 c0 = _60Hz_c0; 00051 } 00052 for (int i=0; i<3; i++) y1[i] = y2[i] = 0; 00053 } 00054 00055 float notch_filter1(float data){ 00056 y1[0] = data + a1*y1[1] + a2*y1[2]; 00057 float reault = y1[0] + b1*y1[1] + y1[2]; 00058 y1[2] = y1[1]; 00059 y1[1] = y1[0]; 00060 return(reault); 00061 } 00062 00063 float notch_filter2(float data){ 00064 y2[0] = data + a1*y2[1] + a2*y2[2]; 00065 float reault = y2[0] + b1*y2[1] + y2[2]; 00066 y2[2] = y2[1]; 00067 y2[1] = y2[0]; 00068 return(reault); 00069 }
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