/*
* COPYRIGHT
*
* tdlpf - time domain lowpass filter coefficient calculator.
* Copyright (C) 2003, 2004, 2005, 2006 Exstrom Laboratories LLC
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* A copy of the GNU General Public License is available on the internet at:
*
* http://www.gnu.org/copyleft/gpl.html
*
* or you can write to:
*
* The Free Software Foundation, Inc.
* 675 Mass Ave
* Cambridge, MA 02139, USA
*
* You can contact Exstrom Laboratories LLC via Email at:
*
* info(AT)exstrom.com
*
* or you can write to:
*
* Exstrom Laboratories LLC
* P.O. Box 7651
* Longmont, CO 80501, USA
*
*/
#include
#include
#include
#include
#define MAXLINESIZE 128
int main( int argc, char *argv[] )
{
FILE *fp;
int i, nc, nz;
double d1, d2;
double fc, h;
if( argc < 3 )
{
printf("\ntdlpf creates a file of low pass filter coefficients.\n");
printf("\nUsage: tdlpf outfile fc nc nz\n");
printf(" outfile = output file\n");
printf(" fc = cutoff frequency as a fraction of PI [0,1]\n");
printf(" nc = number of coefficients\n");
printf(" nz = number of zeros to pad\n");
return(-1);
}
fp = fopen(argv[1], "w");
if( fp == 0 )
{
perror( "Unable to open outfile" );
return(-1);
}
fc = atof( argv[2] ) * M_PI;
nc = atoi( argv[3] );
nz = atoi( argv[4] );
printf( "\nCreating file\n" );
fprintf( fp, "# Time domain low pass filter coefficients\n" );
fprintf( fp, "# %5d : number of coefficients\n", nc );
fprintf( fp, "# %5d : number of zeros padded on end\n", nz );
d1 = ((double)nc - 1.0)/2.0;
for( i = 0; i < nc; ++i )
{
d2 = (double)i - d1;
h = d2 == 0 ? fc / M_PI : sin( fc * d2 ) / ( M_PI * d2 );
fprintf( fp, "%1.15lf\n", h );
}
for( i = 0; i < nz; ++i )
fprintf( fp, "0.0\n" );
fclose( fp );
}