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//
// resamp2_crcf_interp_example.c
//
// Halfband interpolator. This example demonstrates the interface to the
// interpolating halfband resampler. A low-frequency input sinusoid is
// generated and fed into the interpolator one sample at a time,
// producing two outputs at each iteration. The results are written to
// an output file.
//
// SEE ALSO: resamp2_crcf_interp_example.c
// interp_crcf_example.c
//
#include <stdio.h>
#include <stdlib.h>
#include <getopt.h>
#include <complex.h>
#include <math.h>
#include "liquid.h"
#define OUTPUT_FILENAME "resamp2_crcf_interp_example.m"
// print usage/help message
void usage()
{
printf("%s [options]\n", __FILE__);
printf(" h : print help\n");
printf(" m : filter semi-length, default: 5\n");
printf(" s : filter stop-band attenuation, default: 60 dB\n");
printf(" w : pulse bandwidth, default: 0.4\n");
}
int main(int argc, char*argv[])
{
unsigned int m = 12; // filter semi-length
float As = 60.0f; // stop-band attenuation [dB]
float bw = 0.2f; // pulse bandwidth
int dopt;
while ((dopt = getopt(argc,argv,"hm:s:w:")) != EOF) {
switch (dopt) {
case 'h': usage(); return 0;
case 'm': m = atoi(optarg); break;
case 's': As = atof(optarg); break;
case 'w': bw = atof(optarg); break;
default:
exit(1);
}
}
unsigned int i;
// allocate arrays
unsigned int w_len = 37; // pulse length
unsigned int num_samples = w_len + 2*m;
float complex x[ num_samples]; // input array
float complex y[2*num_samples]; // output array
// generate input
float w[w_len];
liquid_firdes_kaiser(w_len,bw,60.0f,0.0f,w);
for (i=0; i<num_samples; i++)
x[i] = i < w_len ? w[i] : 0.0f;
// create/print the half-band resampler
resamp2_crcf q = resamp2_crcf_create(m,0,As);
resamp2_crcf_print(q);
unsigned int delay = resamp2_crcf_get_delay(q);
// run the resampler
for (i=0; i<num_samples; i++) {
// execute the interpolator
resamp2_crcf_interp_execute(q, x[i], &y[2*i]);
// print results to screen
printf("y(%3u) = %8.4f + j*%8.4f;\n", i+1, crealf(y[i]), cimagf(y[i]));
}
// destroy half-band resampler
resamp2_crcf_destroy(q);
// export results
FILE*fid = fopen(OUTPUT_FILENAME,"w");
fprintf(fid,"%% %s : auto-generated file\n", OUTPUT_FILENAME);
fprintf(fid,"clear all;\nclose all;\n\n");
fprintf(fid,"num_samples=%u;\n", num_samples);
fprintf(fid,"delay =%u;\n", delay);
fprintf(fid,"bw =%12.8f;\n", bw);
for (i=0; i<num_samples; i++) {
// save results to output file
fprintf(fid,"x(%3u) = %12.8f + j*%12.8f;\n", i+1, crealf(x[i ]), cimagf(x[i ]));
fprintf(fid,"y(%3u) = %12.8f + j*%12.8f;\n", 2*i+1, crealf(y[2*i+0]), cimagf(y[2*i+0]));
fprintf(fid,"y(%3u) = %12.8f + j*%12.8f;\n", 2*i+2, crealf(y[2*i+1]), cimagf(y[2*i+1]));
}
// plot time series
fprintf(fid,"tx = 0:( num_samples-1);\n");
fprintf(fid,"ty = [0:(2*num_samples-1)]/2 - (delay+1)/2;\n");
fprintf(fid,"figure('position',[100 100 720 720]);\n");
fprintf(fid,"subplot(4,1,1);\n");
fprintf(fid," plot(tx,real(x),'-s','Color',[0.5 0.5 0.5],'MarkerSize',1,...\n");
fprintf(fid," ty,real(y),'-s','Color',[0.5 0.0 0.0],'MarkerSize',1);\n");
fprintf(fid," legend('original','interpolated','location','northeast');");
fprintf(fid," axis([-delay num_samples -1.2 1.2]);\n");
fprintf(fid," grid on;\n");
fprintf(fid," xlabel('Normalized Time [t/T_s]');\n");
fprintf(fid," ylabel('real');\n");
fprintf(fid,"subplot(4,1,2);\n");
fprintf(fid," plot(tx,imag(x),'-s','Color',[0.5 0.5 0.5],'MarkerSize',1,...\n");
fprintf(fid," ty,imag(y),'-s','Color',[0.0 0.5 0.0],'MarkerSize',1);\n");
fprintf(fid," legend('original','interpolated','location','northeast');");
fprintf(fid," axis([-delay num_samples -1.2 1.2]);\n");
fprintf(fid," grid on;\n");
fprintf(fid," xlabel('Normalized Time [t/T_s]');\n");
fprintf(fid," ylabel('imag');\n");
// plot spectrum
fprintf(fid,"nfft=max([1024, 2^(1+nextpow2(num_samples))]);\n");
fprintf(fid,"g = 2*bw;\n");
fprintf(fid,"X=20*log10(abs(fftshift(fft(x*g, nfft))));\n");
fprintf(fid,"Y=20*log10(abs(fftshift(fft(y*g/2,nfft))));\n");
fprintf(fid,"f=[0:(nfft-1)]/nfft-0.5;\n");
fprintf(fid,"subplot(4,1,3:4);\n");
fprintf(fid," plot( f,X,'LineWidth',1, 'Color',[0.5 0.5 0.5],...\n");
fprintf(fid," 2*f,Y,'LineWidth',1.5,'Color',[0.1 0.3 0.5]);\n");
fprintf(fid," grid on;\n");
fprintf(fid," xlabel('Normalized Frequency [f/F_s]');\n");
fprintf(fid," ylabel('PSD [dB]');\n");
fprintf(fid," legend('original','interpolated','location','northeast');");
fprintf(fid," axis([-1 1 -100 10]);\n");
fclose(fid);
printf("results written to %s\n", OUTPUT_FILENAME);
printf("done.\n");
return 0;
}
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