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//
// firinterp_crcf_example.c
//
// This example demonstrates the firinterp object (interpolator) interface.
// Data symbols are generated and then interpolated according to a
// finite impulse response Nyquist filter.
//
#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#include <getopt.h>
#include "liquid.h"
#define OUTPUT_FILENAME "firinterp_crcf_example.m"
// print usage/help message
void usage()
{
printf("firinterp_crcf_example:\n");
printf(" -h : print usage/help\n");
printf(" -k <s/sym> : samples/symbol (interp factor), k > 1, default: 4\n");
printf(" -m <delay> : filter delay (symbols), m > 0, default: 3\n");
printf(" -s <atten> : filter stop-band attenuation [dB], default: 60\n");
printf(" -n <num> : number of data symbols, default: 16\n");
}
int main(int argc, char*argv[]) {
// options
unsigned int k = 4; // samples/symbol
unsigned int m = 3; // filter delay
float As = 60.0f; // filter stop-band attenuation
unsigned int num_syms = 16; // number of data symbols
int dopt;
while ((dopt = getopt(argc,argv,"uhk:m:s:n:")) != EOF) {
switch (dopt) {
case 'u':
case 'h': usage(); return 0;
case 'k': k = atoi(optarg); break;
case 'm': m = atoi(optarg); break;
case 's': As = atof(optarg); break;
case 'n': num_syms = atoi(optarg); break;
default:
exit(1);
}
}
// validate options
if (k < 2) {
fprintf(stderr,"error: %s, interp factor must be greater than 1\n", argv[0]);
exit(1);
} else if (m < 1) {
fprintf(stderr,"error: %s, filter delay must be greater than 0\n", argv[0]);
exit(1);
} else if (num_syms < 1) {
fprintf(stderr,"error: %s, must have at least one data symbol\n", argv[0]);
usage();
return 1;
}
// derived values
unsigned int num_syms_total = num_syms + 2*m; // total symbols (w/ delay)
unsigned int num_samples = k*num_syms_total; // total samples
// create interpolator from prototype
firinterp_crcf q = firinterp_crcf_create_kaiser(k,m,As);
// generate input signal and interpolate
float complex x[num_syms_total]; // input symbols
float complex y[num_samples]; // output samples
unsigned int i;
for (i=0; i<num_syms; i++) {
x[i] = (rand() % 2 ? 1.0f : -1.0f) +
(rand() % 2 ? 1.0f : -1.0f) * _Complex_I;
}
// pad end of sequence with zeros
for (i=num_syms; i<num_syms_total; i++)
x[i] = 0.0f;
// interpolate symbols
for (i=0; i<num_syms_total; i++)
firinterp_crcf_execute(q, x[i], &y[k*i]);
// destroy interpolator object
firinterp_crcf_destroy(q);
// print results to screen
printf("x(t) :\n");
for (i=0; i<num_syms_total; i++)
printf(" x(%4u) = %8.4f + j*%8.4f;\n", i, crealf(x[i]), cimagf(x[i]));
printf("y(t) :\n");
for (i=0; i<num_samples; i++) {
printf(" y(%4u) = %8.4f + j*%8.4f;", i, crealf(y[i]), cimagf(y[i]));
if ( (i >= k*m) && ((i%k)==0))
printf(" **\n");
else
printf("\n");
}
//
// export output file
//
FILE * fid = fopen(OUTPUT_FILENAME,"w");
fprintf(fid,"%% %s: auto-generated file\n\n", OUTPUT_FILENAME);
fprintf(fid,"clear all;\n");
fprintf(fid,"close all;\n");
fprintf(fid,"k = %u;\n", k);
fprintf(fid,"m = %u;\n", m);
fprintf(fid,"num_syms_total = %u;\n", num_syms_total);
fprintf(fid,"num_samples = k*num_syms_total;\n");
fprintf(fid,"x = zeros(1,num_syms_total);\n");
fprintf(fid,"y = zeros(1,num_samples);\n");
for (i=0; i<num_syms_total; i++)
fprintf(fid,"x(%4u) = %12.4e + j*%12.4e;\n", i+1, crealf(x[i]), cimagf(x[i]));
for (i=0; i<num_samples; i++)
fprintf(fid,"y(%4u) = %12.4e + j*%12.4e;\n", i+1, crealf(y[i]), cimagf(y[i]));
fprintf(fid,"\n\n");
fprintf(fid,"tx = [0:(num_syms_total-1)];\n");
fprintf(fid,"ty = [0:(num_samples-1)]/k - m;\n");
fprintf(fid,"figure;\n");
fprintf(fid,"subplot(2,1,1);\n");
fprintf(fid," plot(ty,real(y),'-',tx,real(x),'s');\n");
fprintf(fid," xlabel('time');\n");
fprintf(fid," ylabel('real');\n");
fprintf(fid," grid on;\n");
fprintf(fid,"subplot(2,1,2);\n");
fprintf(fid," plot(ty,imag(y),'-',tx,imag(x),'s');\n");
fprintf(fid," xlabel('time');\n");
fprintf(fid," ylabel('imag');\n");
fprintf(fid," grid on;\n");
fclose(fid);
printf("results written to %s.\n",OUTPUT_FILENAME);
printf("done.\n");
return 0;
}
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