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//
// resamp2_crcf_filter_example.c
//
// Halfband filter example.
//
// SEE ALSO: resamp2_crcf_decim_example.c
// resamp2_crcf_interp_example.c
//
#include <stdio.h>
#include <complex.h>
#include <math.h>
#include "liquid.h"
#define OUTPUT_FILENAME "resamp2_crcf_filter_example.m"
int main() {
unsigned int m=9; // filter semi-length
unsigned int num_samples=128; // number of input samples
float As=60.0f; // stop-band attenuation [dB]
// derived values
unsigned int h_len = 4*m+1; // half-band filter length
unsigned int N = num_samples + h_len;
// arrays
float complex x[N]; // input time series
float complex y0[N]; // output time series (lower band)
float complex y1[N]; // output time series (upper band)
// generate input sequence
unsigned int i;
for (i=0; i<N; i++) {
//x[i] = randnf() * cexpf(_Complex_I*M_PI*randf());
x[i] = cexpf(_Complex_I*2*M_PI*0.072f*i) + 0.6f*cexpf(_Complex_I*2*M_PI*0.37f*i);
x[i] *= (i < num_samples) ? liquid_hamming(i,num_samples) : 0.0f;
}
// create/print the half-band filter with a specified
// stop-band attenuation
resamp2_crcf q = resamp2_crcf_create(m,0.0f,As);
resamp2_crcf_print(q);
for (i=0; i<N; i++) {
// run the filter
resamp2_crcf_filter_execute(q, x[i], &y0[i], &y1[i]);
//printf("y(%3u) = %8.4f + j*%8.4f;\n", i+1, crealf(y), cimagf(y));
}
// clean up allocated objects
resamp2_crcf_destroy(q);
//
// export output file
//
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,"m = %u;\n", m);
fprintf(fid,"num_samples = %u;\n", num_samples);
fprintf(fid,"N = %u;\n", N);
fprintf(fid,"t = 0:(N-1);\n");
// save results to output file
for (i=0; i<N; i++) {
fprintf(fid,"x(%3u) = %12.4e + j*%12.4e;\n", i+1, crealf(x[i]), cimagf(x[i]));
fprintf(fid,"y0(%3u) = %12.4e + j*%12.4e;\n", i+1, crealf(y0[i]), cimagf(y0[i]));
fprintf(fid,"y1(%3u) = %12.4e + j*%12.4e;\n", i+1, crealf(y1[i]), cimagf(y1[i]));
}
fprintf(fid,"figure;\n");
fprintf(fid,"subplot(2,1,1);\n");
fprintf(fid," plot(t, real(x), 'LineWidth',2,'Color',[0.50 0.50 0.50],...\n");
fprintf(fid," t-2*m,real(y0),'LineWidth',1,'Color',[0.00 0.25 0.50],...\n");
fprintf(fid," t-2*m,real(y1),'LineWidth',1,'Color',[0.00 0.50 0.25]);\n");
fprintf(fid," xlabel('time');\n");
fprintf(fid," ylabel('real');\n");
fprintf(fid," legend('original','lower band','upper band',1);");
fprintf(fid,"subplot(2,1,2);\n");
fprintf(fid," plot(t, imag(x), 'LineWidth',2,'Color',[0.50 0.50 0.50],...\n");
fprintf(fid," t-2*m,imag(y0),'LineWidth',1,'Color',[0.00 0.25 0.50],...\n");
fprintf(fid," t-2*m,imag(y1),'LineWidth',1,'Color',[0.00 0.50 0.25]);\n");
fprintf(fid," xlabel('time');\n");
fprintf(fid," ylabel('imag');\n");
fprintf(fid," legend('original','lower band','upper band',1);");
fprintf(fid,"nfft=512;\n");
fprintf(fid,"g = 1 / sqrt( real(x*x') );\n");
fprintf(fid,"X =20*log10(abs(fftshift(fft(x*g, nfft))));\n");
fprintf(fid,"Y0=20*log10(abs(fftshift(fft(y0*g,nfft))));\n");
fprintf(fid,"Y1=20*log10(abs(fftshift(fft(y1*g,nfft))));\n");
fprintf(fid,"f=[0:(nfft-1)]/nfft-0.5;\n");
fprintf(fid,"figure;\n");
fprintf(fid,"plot(f,X, 'LineWidth',2,'Color',[0.50 0.50 0.50],...\n");
fprintf(fid," f,Y0,'LineWidth',1,'Color',[0.00 0.25 0.50],...\n");
fprintf(fid," f,Y1,'LineWidth',1,'Color',[0.00 0.50 0.25]);\n");
fprintf(fid,"grid on;\n");
fprintf(fid,"xlabel('normalized frequency');\n");
fprintf(fid,"ylabel('PSD [dB]');\n");
fprintf(fid,"legend('original','lower band','upper band',2);");
fprintf(fid,"axis([-0.5 0.5 -80 20]);\n");
fclose(fid);
printf("results written to %s\n", OUTPUT_FILENAME);
printf("done.\n");
return 0;
}
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