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//
// firdes_kaiser_example.c
//
// This example demonstrates finite impulse response filter design
// using a Kaiser window.
// SEE ALSO: firdespm_example.c
//
#include <stdlib.h>
#include <stdio.h>
#include <getopt.h>
#include "liquid.h"
#define OUTPUT_FILENAME "firdes_kaiser_example.m"
// print usage/help message
void usage()
{
printf("firdes_kaiser_example:\n");
printf(" u/h : print usage/help\n");
printf(" f : filter cutoff frequency, 0 < f < 0.5, default: 0.2\n");
printf(" s : filter stop-band attenuation [dB], 0 < s, default: 60\n");
printf(" m : fractional sample delay, -0.5 < m < 0.5, default: 0\n");
printf(" n : filter length [taps], n > 1, default: 55\n");
}
int main(int argc, char*argv[]) {
// options
float fc=0.2f; // filter cutoff frequency
float As=60.0f; // stop-band attenuation [dB]
float mu=0.0f; // fractional timing offset
unsigned int h_len=55; // filter length
int dopt;
while ((dopt = getopt(argc,argv,"uhf:n:s:m:")) != EOF) {
switch (dopt) {
case 'u':
case 'h': usage(); return 0;
case 'f': fc = atof(optarg); break;
case 'n': h_len = atoi(optarg); break;
case 's': As = atof(optarg); break;
case 'm': mu = atof(optarg); break;
default:
exit(1);
}
}
// validate input
if ( fc <= 0.0f ) {
fprintf(stderr,"error: %s, filter cutoff frequency must be greater than zero\n", argv[0]);
exit(1);
} else if ( h_len == 0 ) {
fprintf(stderr,"error: %s, filter length must be greater than zero\n", argv[0]);
exit(1);
}
printf("filter design parameters\n");
printf(" cutoff frequency : %8.4f\n", fc);
printf(" stop-band attenuation [dB] : %8.4f\n", As);
printf(" fractional sample offset : %8.4f\n", mu);
printf(" filter length : %u\n", h_len);
// generate the filter
unsigned int i;
float h[h_len];
liquid_firdes_kaiser(h_len,fc,As,mu,h);
// print coefficients
for (i=0; i<h_len; i++)
printf("h(%4u) = %16.12f;\n", i+1, h[i]);
// output to file
FILE*fid = fopen(OUTPUT_FILENAME,"w");
fprintf(fid,"%% %s: auto-generated file\n\n", OUTPUT_FILENAME);
fprintf(fid,"clear all;\nclose all;\n\n");
fprintf(fid,"h_len=%u;\n",h_len);
fprintf(fid,"fc=%12.4e;\n",fc);
fprintf(fid,"As=%12.4e;\n",As);
for (i=0; i<h_len; i++)
fprintf(fid,"h(%4u) = %12.4e;\n", i+1, h[i]);
fprintf(fid,"nfft=1024;\n");
fprintf(fid,"H=20*log10(abs(fftshift(fft(h*2*fc,nfft))));\n");
fprintf(fid,"f=[0:(nfft-1)]/nfft-0.5;\n");
fprintf(fid,"figure; plot(f,H,'Color',[0 0.5 0.25],'LineWidth',2);\n");
fprintf(fid,"grid on;\n");
fprintf(fid,"xlabel('normalized frequency');\n");
fprintf(fid,"ylabel('PSD [dB]');\n");
fprintf(fid,"title(['Filter design/Kaiser window f_c: %f, S_L: %f, h: %u']);\n",
fc, -As, h_len);
fprintf(fid,"axis([-0.5 0.5 -As-40 10]);\n");
fclose(fid);
printf("results written to %s\n", OUTPUT_FILENAME);
printf("done.\n");
return 0;
}
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