lp_filter_odd.cpp

c语言版各种fir滤波器的实现

/**********************************************
* Filename : LP_filter_odd.CPP                *
* Function : realization of LP FIR filter with*
             direct structure,n is odd        *
*Parameter : (h) the coefficients of H(z)     *
			 (z) the inner state variables    *
			 (x) the input data               *
			 (y) the output data              *
			 (n) the number of h[]            *
			 (m) the number of input data     *
**********************************************/

void LP_filter_odd(float h[],float z[],float x[],float y[],int n,int m)
{
	int i,j;
	for(i=0;i<m;i++)
	{
		y[i]=(x[i]+z[n-2])*h[0]+z[(n-3)/2]*h[(n-1)/2];
		for(j=0;j<((n-3)/2);j++)
		{
			y[i]=y[i]+(z[j]+z[n-3-j])*h[j+1];
		}
		for(j=(n-2);j>0;j--)
		{
			z[j]=z[j-1];
		}
		z[0]=x[i];
	}
}