samer@0: /*
samer@0:  *	Copyright (c) 2000, Samer Abdallah, King's College London.
samer@0:  *	All rights reserved.
samer@0:  *
samer@0:  *	This software is provided AS iS and WITHOUT ANY WARRANTY; 
samer@0:  *	without even the implied warranty of MERCHANTABILITY or 
samer@0:  *	FITNESS FOR A PARTICULAR PURPOSE.
samer@0:  */
samer@0: 
samer@0: package samer.units;
samer@0: import  samer.core.*;
samer@0: import  samer.maths.*;
samer@0: import  samer.tools.*;
samer@0: import  java.util.*;
samer@0: 
samer@0: public class FIRFilter implements Filter
samer@0: {
samer@0: 	int		N;			// order of filter
samer@0: 	double	A[];	// coefficients
samer@0: 	double	u[];		// circular buffer of previous values
samer@0: 	int		k;    		// current position in u buffer
samer@0: 
samer@0: 	public FIRFilter( int n)
samer@0: 	{
samer@0: 		N=n;
samer@0: 		u=new double[n];
samer@0: 		A=new double[n];
samer@0: 		reset();
samer@0: 	}
samer@0: 
samer@0: 	public FIRFilter( double [] A)
samer@0: 	{
samer@0: 		N=A.length;
samer@0: 		u=new double[N];
samer@0: 		this.A=A;
samer@0: 		reset();
samer@0: 	}
samer@0: 
samer@0: 	public void dispose() {}
samer@0: 	public void reset() { Mathx.zero(u); k=0; }
samer@0: 
samer@0: 	/** FIR filter using array of filter coefficients */
samer@0: 	public final double filter( double z)
samer@0: 	{
samer@0: 		if (k==0) k=N-1; else k--;
samer@0: 		double	y=0;
samer@0: 		u[k]=z;
samer@0: 
samer@0: 		int i=0, j;
samer@0: 		for (j=k; j<N; j++) y += u[j]*A[i++];
samer@0: 		for (j=0; j<k; j++) y += u[j]*A[i++];
samer@0: 
samer@0: 		return y;
samer@0: 	}
samer@0: }
samer@0: