Infinite impulse response filter
IIR.h
- Committer:
- benson516
- Date:
- 2016-07-29
- Revision:
- 1:3d8226c5abfe
- Parent:
- 0:a7405ea45d27
- Child:
- 2:0bae37b297f4
File content as of revision 1:3d8226c5abfe:
#include <vector> using std::vector; /*-----------------------------*/ // // y gain*( sum(i from 0 to m) b[i]*x[k-i] ) // --- = -------------------------------------------- // u 1 + sum( i from 1 to n) a[i]*y[k-i] // // y[k] = gain*( sum(i from 0 to m) b[i]*x[k-i] ) - sum( i from 1 to n) a[i]*y[k-i] // // Compatible with the coefficient generated by Matlab fdatool // // by C.F. Huang from LDSC /*-----------------------------*/ class Circular_buffer{ private: vector<float> A; // vector<float>::iterator it; int ind; // The index of the newest element public: Circular_buffer(){ ind = 0; } Circular_buffer(int n){ A.resize(n); for (size_t i=0; i< A.size(); i++) A[i] = 0; ind = 0; } void Init(int n){ // Input: buffer size A.resize(n); for (size_t i=0; i< A.size(); i++) A[i] = 0; ind = 0; } float Get(int i){ // Get the value of the (t-i)th element, where t stands for the current sample int ind_e = ind-i; while (ind_e < 0){ ind_e += A.size(); } return A[ind_e]; } void Insert(float x_new){ // Pop the oldest element and push a new element ind++; while (ind >= A.size()){ ind -= A.size(); } A[ind] = x_new; } }; class IIR{ private: int m; // the order of numerator int n; // the order of denominator Circular_buffer x,y; vector<float> b; // parameters of numerator, highest order --> lowest order (newest -> oldest) vector<float> a; // parameters of denominator, highest order --> lowest order (newest -> oldest) float gain; public: IIR(int m, int n): m(m),n(n) { x.Init(m+1); y.Init(n); } void Assign_parameters(float b_in[], float a_in[], float gain_in){ //b.assign(b_in,b_in+m+1); // a.assign(a_in,a_in+n); b.resize(m+1); a.resize(n); for (size_t i = 0; i < n; i++){ a[i] = a_in[i+1]; } gain = gain_in; for (size_t i = 0; i < b.size(); i++){ b[i] = gain*b_in[i]; } } float Iterate_once(float x_in){ x.Insert(x_in); float y_new = 0; // Numerator for (int i = 0; i <= m; i++ ){ y_new += b[i]*x.Get(i); } // Denominator for (int i = 0; i < n; i++){ y_new -= a[i]*y.Get(i); } y.Insert(y_new); return y_new; } };