int main() {
float r=sqrtf(19); // resampling rate (output/input)
unsigned int n=37; // number of input samples
float As=60.0f; // stop-band attenuation [dB]
unsigned int i;
// derived values: number of input, output samples (adjusted for filter delay)
unsigned int nx = 1.4*n;
unsigned int ny_alloc = (unsigned int) (2*(float)nx * r); // allocation for output
// allocate memory for arrays
float complex x[nx];
float complex y[ny_alloc];
// generate input signal (filter pulse with frequency offset)
float hf[n];
liquid_firdes_kaiser(n, 0.08f, 80.0f, 0, hf);
for (i=0; i<nx; i++)
x[i] = (i < n) ? hf[i]*cexpf(_Complex_I*1.17f*i) : 0.0f;
// create resampler
msresamp_crcf q = msresamp_crcf_create(r,As);
float delay = msresamp_crcf_get_delay(q);
// execute resampler, storing in output buffer
unsigned int ny;
msresamp_crcf_execute(q, x, nx, y, &ny);
// print basic results
printf("input samples : %u\n", nx);
printf("output samples : %u\n", ny);
printf("delay : %f samples\n", delay);
// clean up allocated objects
msresamp_crcf_destroy(q);
//
// export output files
//
FILE * fid;
//
// export time plot
//
fid = fopen(OUTPUT_FILENAME_TIME,"w");
fprintf(fid,"# %s: auto-generated file\n\n", OUTPUT_FILENAME_TIME);
fprintf(fid,"reset\n");
fprintf(fid,"set terminal postscript eps enhanced color solid rounded\n");
//fprintf(fid,"set xrange [0:%u];\n",n);
fprintf(fid,"set yrange [-1.2:1.2]\n");
fprintf(fid,"set size ratio 0.3\n");
fprintf(fid,"set xlabel 'Input Sample Index'\n");
fprintf(fid,"set key top right nobox\n");
fprintf(fid,"set ytics -5,1,5\n");
fprintf(fid,"set grid xtics ytics\n");
fprintf(fid,"set grid linetype 1 linecolor rgb '%s' lw 1\n", LIQUID_DOC_COLOR_GRID);
fprintf(fid,"set multiplot layout 2,1 scale 1.0,1.0\n");
fprintf(fid,"# real\n");
fprintf(fid,"set ylabel 'Real'\n");
fprintf(fid,"plot '-' using 1:2 with linespoints pointtype 6 pointsize 0.9 linetype 1 linewidth 1 linecolor rgb '#666666' title 'original',\\\n");
fprintf(fid," '-' using 1:2 with points pointtype 7 pointsize 0.6 linecolor rgb '#008000' title 'resampled'\n");
// export input signal
for (i=0; i<nx; i++)
fprintf(fid,"%12.4e %12.4e %12.4e\n", (float)i, crealf(x[i]), cimagf(x[i]));
fprintf(fid,"e\n");
// export output signal
for (i=0; i<ny; i++)
fprintf(fid,"%12.4e %12.4e %12.4e\n", (float)(i)/r - delay, crealf(y[i]), cimagf(y[i]));
fprintf(fid,"e\n");
fprintf(fid,"# imag\n");
fprintf(fid,"set ylabel 'Imag'\n");
fprintf(fid,"plot '-' using 1:3 with linespoints pointtype 6 pointsize 0.9 linetype 1 linewidth 1 linecolor rgb '#666666' title 'original',\\\n");
fprintf(fid," '-' using 1:3 with points pointtype 7 pointsize 0.6 linecolor rgb '#800000' title 'resampled'\n");
// export input signal
for (i=0; i<nx; i++)
fprintf(fid,"%12.4e %12.4e %12.4e\n", (float)i, crealf(x[i]), cimagf(x[i]));
fprintf(fid,"e\n");
// export output signal
for (i=0; i<ny; i++)
fprintf(fid,"%12.4e %12.4e %12.4e\n", (float)(i)/r - delay, crealf(y[i]), cimagf(y[i]));
fprintf(fid,"e\n");
fprintf(fid,"unset multiplot\n");
// close output file
fclose(fid);
//
// export spectrum plot
//
fid = fopen(OUTPUT_FILENAME_FREQ,"w");
unsigned int nfft = 512;
float complex X[nfft];
float complex Y[nfft];
liquid_doc_compute_psdcf(x, nx, X, nfft, LIQUID_DOC_PSDWINDOW_NONE, 1);
liquid_doc_compute_psdcf(y, ny, Y, nfft, LIQUID_DOC_PSDWINDOW_NONE, 1);
fft_shift(X,nfft);
fft_shift(Y,nfft);
fprintf(fid,"# %s: auto-generated file\n\n", OUTPUT_FILENAME_FREQ);
fprintf(fid,"reset\n");
fprintf(fid,"set terminal postscript eps enhanced color solid rounded\n");
fprintf(fid,"set xrange [-0.5:0.5];\n");
fprintf(fid,"set yrange [-120:20]\n");
fprintf(fid,"set size ratio 0.6\n");
fprintf(fid,"set xlabel 'Normalized Output Frequency'\n");
fprintf(fid,"set ylabel 'Power Spectral Density [dB]'\n");
fprintf(fid,"set key top right nobox\n");
fprintf(fid,"set grid xtics ytics\n");
fprintf(fid,"set pointsize 0.6\n");
fprintf(fid,"set grid linetype 1 linecolor rgb '%s' lw 1\n",LIQUID_DOC_COLOR_GRID);
fprintf(fid,"# real\n");
fprintf(fid,"plot '-' using 1:2 with lines linetype 1 linewidth 4 linecolor rgb '#999999' title 'original',\\\n");
fprintf(fid," '-' using 1:2 with lines linetype 1 linewidth 4 linecolor rgb '#004080' title 'resampled'\n");
// export output
for (i=0; i<nfft; i++) {
float fx = ((float)(i) / (float)nfft - 0.5f) / r;
fprintf(fid,"%12.8f %12.4e\n", fx, 20*log10f(cabsf(X[i])));
}
fprintf(fid,"e\n");
for (i=0; i<nfft; i++) {
float fy = ((float)(i) / (float)nfft - 0.5f);
fprintf(fid,"%12.8f %12.4e\n", fy, 20*log10f(cabsf(Y[i])));
}
fprintf(fid,"e\n");
fclose(fid);
printf("done.\n");
return 0;
}
int main(int argc, char*argv[])
{
// options
float r=1.2f; // resampling rate (output/input)
float As=80.0f; // resampling filter stop-band attenuation [dB]
unsigned int nx=400; // number of input samples
float fc=0.40f; // complex sinusoid frequency
int dopt;
while ((dopt = getopt(argc,argv,"hr:s:n:")) != EOF) {
switch (dopt) {
case 'h': usage(); return 0;
case 'r': r = atof(optarg); break;
case 's': As = atof(optarg); break;
case 'n': nx = atoi(optarg); break;
default:
exit(1);
}
}
// validate input
if (nx == 0) {
fprintf(stderr,"error: %s, number of input samples must be greater than zero\n", argv[0]);
exit(1);
} else if (r <= 0.0f) {
fprintf(stderr,"error: %s, resampling rate must be greater than zero\n", argv[0]);
exit(1);
} else if ( fabsf(log2f(r)) > 10 ) {
fprintf(stderr,"error: %s, resampling rate unreasonable\n", argv[0]);
exit(1);
}
unsigned int i;
// derived values
unsigned int ny_alloc = (unsigned int) (2*(float)nx * r); // allocation for output
// allocate memory for arrays
float complex x[nx];
float complex y[ny_alloc];
// generate input
unsigned int window_len = (3*nx)/4;
for (i=0; i<nx; i++)
x[i] = i < window_len ? cexpf(_Complex_I*2*M_PI*fc*i) * kaiser(i,window_len,10.0f,0.0f) : 0.0f;
// create multi-stage arbitrary resampler object
msresamp_crcf q = msresamp_crcf_create(r,As);
msresamp_crcf_print(q);
float delay = msresamp_crcf_get_delay(q);
// run resampler
unsigned int ny;
msresamp_crcf_execute(q, x, nx, y, &ny);
// print basic results
printf("input samples : %u\n", nx);
printf("output samples : %u\n", ny);
printf("delay : %f samples\n", delay);
// clean up allocated objects
msresamp_crcf_destroy(q);
//
// export output
//
// open/initialize output file
FILE*fid = fopen(OUTPUT_FILENAME,"w");
fprintf(fid,"%% %s: auto-generated file\n",OUTPUT_FILENAME);
fprintf(fid,"clear all;\n");
fprintf(fid,"close all;\n");
fprintf(fid,"\n");
fprintf(fid,"r=%12.8f;\n", r);
fprintf(fid,"delay = %f;\n", delay);
// save input series
fprintf(fid,"nx = %u;\n", nx);
fprintf(fid,"x = zeros(1,nx);\n");
for (i=0; i<nx; i++)
fprintf(fid,"x(%6u) = %12.4e + j*%12.4e;\n", i+1, crealf(x[i]), cimagf(x[i]));
// save output series
fprintf(fid,"ny = %u;\n", ny);
fprintf(fid,"y = zeros(1,ny);\n");
for (i=0; i<ny; i++)
fprintf(fid,"y(%6u) = %12.4e + j*%12.4e;\n", i+1, crealf(y[i]), cimagf(y[i]));
// output results
fprintf(fid,"\n\n");
fprintf(fid,"%% plot frequency-domain result\n");
fprintf(fid,"nfft=1024;\n");
fprintf(fid,"%% estimate PSD, normalize by array length\n");
fprintf(fid,"X=20*log10(abs(fftshift(fft(x,nfft)/length(x))));\n");
fprintf(fid,"Y=20*log10(abs(fftshift(fft(y,nfft)/length(y))));\n");
fprintf(fid,"G = max(X);\n");
fprintf(fid,"X = X - G;\n");
fprintf(fid,"Y = Y - G;\n");
fprintf(fid,"f=[0:(nfft-1)]/nfft-0.5;\n");
fprintf(fid,"figure;\n");
fprintf(fid,"if r>1, fx = f/r; fy = f; %% interpolated\n");
fprintf(fid,"else, fx = f; fy = f*r; %% decimated\n");
fprintf(fid,"end;\n");
fprintf(fid,"plot(fx,X,'Color',[0.5 0.5 0.5],fy,Y,'LineWidth',2);\n");
fprintf(fid,"grid on;\n\n");
fprintf(fid,"xlabel('normalized frequency');\n");
fprintf(fid,"ylabel('PSD [dB]');\n");
fprintf(fid,"legend('original','resampled','location','northeast');");
fprintf(fid,"axis([-0.5 0.5 -120 10]);\n");
fprintf(fid,"\n\n");
fprintf(fid,"%% plot time-domain result\n");
fprintf(fid,"tx=[0:(length(x)-1)];\n");
fprintf(fid,"ty=[0:(length(y)-1)]/r-delay;\n");
fprintf(fid,"figure;\n");
fprintf(fid,"subplot(2,1,1);\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], 'MarkerSize',1);\n");
fprintf(fid," legend('original','resampled','location','northeast');");
fprintf(fid," xlabel('time');\n");
fprintf(fid," ylabel('real');\n");
fprintf(fid," grid on;\n\n");
fprintf(fid,"subplot(2,1,2);\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 0.5 0], 'MarkerSize',1);\n");
fprintf(fid," legend('original','resampled','location','northeast');");
fprintf(fid," xlabel('time');\n");
fprintf(fid," ylabel('imag');\n");
fprintf(fid," grid on;\n\n");
fclose(fid);
printf("results written to %s\n",OUTPUT_FILENAME);
printf("done.\n");
return 0;
}
int main(int argc, char*argv[])
{
// options
float r=0.23175f; // resampling rate (output/input)
float As=60.0f; // resampling filter stop-band attenuation [dB]
unsigned int n=400; // number of input samples
float fc=0.017f; // complex sinusoid frequency
int dopt;
while ((dopt = getopt(argc,argv,"hr:s:n:f:")) != EOF) {
switch (dopt) {
case 'h': usage(); return 0;
case 'r': r = atof(optarg); break;
case 's': As = atof(optarg); break;
case 'n': n = atoi(optarg); break;
case 'f': fc = atof(optarg); break;
default:
exit(1);
}
}
// validate input
if (n == 0) {
fprintf(stderr,"error: %s, number of input samples must be greater than zero\n", argv[0]);
exit(1);
} else if (r <= 0.0f) {
fprintf(stderr,"error: %s, resampling rate must be greater than zero\n", argv[0]);
exit(1);
} else if ( fabsf(log2f(r)) > 10 ) {
fprintf(stderr,"error: %s, resampling rate unreasonable\n", argv[0]);
exit(1);
}
unsigned int i;
// create multi-stage arbitrary resampler object
msresamp_crcf q = msresamp_crcf_create(r,As);
msresamp_crcf_print(q);
float delay = msresamp_crcf_get_delay(q);
// number of input samples (zero-padded)
unsigned int nx = n + (int)ceilf(delay) + 10;
// output buffer with extra padding for good measure
unsigned int ny_alloc = (unsigned int) (2*(float)nx * r); // allocation for output
// allocate memory for arrays
float complex x[nx];
float complex y[ny_alloc];
// generate input signal
float wsum = 0.0f;
for (i=0; i<nx; i++) {
// compute window
float w = i < n ? kaiser(i, n, 10.0f, 0.0f) : 0.0f;
// apply window to complex sinusoid
x[i] = cexpf(_Complex_I*2*M_PI*fc*i) * w;
// accumulate window
wsum += w;
}
// run resampler
unsigned int ny;
msresamp_crcf_execute(q, x, nx, y, &ny);
// clean up allocated objects
msresamp_crcf_destroy(q);
//
// analyze resulting signal
//
// check that the actual resampling rate is close to the target
float r_actual = (float)ny / (float)nx;
float fy = fc / r; // expected output frequency
// run FFT and ensure that carrier has moved and that image
// frequencies and distortion have been adequately suppressed
unsigned int nfft = 1 << liquid_nextpow2(ny);
float complex yfft[nfft]; // fft input
float complex Yfft[nfft]; // fft output
for (i=0; i<nfft; i++)
yfft[i] = i < ny ? y[i] : 0.0f;
fft_run(nfft, yfft, Yfft, LIQUID_FFT_FORWARD, 0);
fft_shift(Yfft, nfft); // run FFT shift
// find peak frequency
float Ypeak = 0.0f;
float fpeak = 0.0f;
float max_sidelobe = -1e9f; // maximum side-lobe [dB]
float main_lobe_width = 0.07f; // TODO: figure this out from Kaiser's equations
for (i=0; i<nfft; i++) {
// normalized output frequency
float f = (float)i/(float)nfft - 0.5f;
// scale FFT output appropriately
float Ymag = 20*log10f( cabsf(Yfft[i] / (r * wsum)) );
// find frequency location of maximum magnitude
if (Ymag > Ypeak || i==0) {
Ypeak = Ymag;
fpeak = f;
}
// find peak side-lobe value, ignoring frequencies
// within a certain range of signal frequency
if ( fabsf(f-fy) > main_lobe_width )
max_sidelobe = Ymag > max_sidelobe ? Ymag : max_sidelobe;
}
// print results and check frequency location
printf("output results:\n");
printf(" output delay : %12.8f samples\n", delay);
printf(" desired resampling rate : %12.8f\n", r);
printf(" measured resampling rate : %12.8f (%u/%u)\n", r_actual, ny, nx);
printf(" peak spectrum : %12.8f dB (expected 0.0 dB)\n", Ypeak);
printf(" peak frequency : %12.8f (expected %-12.8f)\n", fpeak, fy);
printf(" max sidelobe : %12.8f dB (expected at least %.2f dB)\n", max_sidelobe, -As);
//
// export results
//
FILE * fid = fopen(OUTPUT_FILENAME,"w");
fprintf(fid,"%% %s: auto-generated file\n",OUTPUT_FILENAME);
fprintf(fid,"clear all;\n");
fprintf(fid,"close all;\n");
fprintf(fid,"delay=%f;\n", delay);
fprintf(fid,"r=%12.8f;\n", r);
fprintf(fid,"nx = %u;\n", nx);
fprintf(fid,"x = zeros(1,nx);\n");
for (i=0; i<nx; i++)
fprintf(fid,"x(%3u) = %12.4e + j*%12.4e;\n", i+1, crealf(x[i]), cimagf(x[i]));
fprintf(fid,"ny = %u;\n", ny);
fprintf(fid,"y = zeros(1,ny);\n");
for (i=0; i<ny; i++)
fprintf(fid,"y(%3u) = %12.4e + j*%12.4e;\n", i+1, crealf(y[i]), cimagf(y[i]));
// time-domain results
fprintf(fid,"\n");
fprintf(fid,"%% plot time-domain result\n");
fprintf(fid,"tx=[0:(length(x)-1)];\n");
fprintf(fid,"ty=[0:(length(y)-1)]/r-delay;\n");
fprintf(fid,"tmin = min(tx(1), ty(1) );\n");
fprintf(fid,"tmax = max(tx(end),ty(end));\n");
fprintf(fid,"figure;\n");
fprintf(fid,"subplot(2,1,1);\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], 'MarkerSize',1);\n");
fprintf(fid," legend('original','resampled','location','northeast');");
fprintf(fid," axis([tmin tmax -1.2 1.2]);\n");
fprintf(fid," grid on;\n");
fprintf(fid," xlabel('time');\n");
fprintf(fid," ylabel('real');\n");
fprintf(fid,"subplot(2,1,2);\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 0.5 0], 'MarkerSize',1);\n");
fprintf(fid," legend('original','resampled','location','northeast');");
fprintf(fid," axis([tmin tmax -1.2 1.2]);\n");
fprintf(fid," grid on;\n");
fprintf(fid," xlabel('time');\n");
fprintf(fid," ylabel('imag');\n");
// frequency-domain results
fprintf(fid,"\n\n");
fprintf(fid,"%% plot frequency-domain result\n");
fprintf(fid,"nfft=2^nextpow2(max(nx,ny));\n");
fprintf(fid,"%% estimate PSD, normalize by array length\n");
fprintf(fid,"X=20*log10(abs(fftshift(fft(x,nfft)/length(x))));\n");
fprintf(fid,"Y=20*log10(abs(fftshift(fft(y,nfft)/length(y))));\n");
fprintf(fid,"G=max(X);\n");
fprintf(fid,"X=X-G;\n");
fprintf(fid,"Y=Y-G;\n");
fprintf(fid,"f=[0:(nfft-1)]/nfft-0.5;\n");
fprintf(fid,"figure;\n");
fprintf(fid,"if r>1, fx = f/r; fy = f; %% interpolated\n");
fprintf(fid,"else, fx = f; fy = f*r; %% decimated\n");
fprintf(fid,"end;\n");
fprintf(fid,"plot(fx,X,'LineWidth',1, 'Color',[0.5 0.5 0.5],...\n");
fprintf(fid," fy,Y,'LineWidth',1.5,'Color',[0.1 0.3 0.5]);\n");
fprintf(fid,"grid on;\n");
fprintf(fid,"xlabel('normalized frequency');\n");
fprintf(fid,"ylabel('PSD [dB]');\n");
fprintf(fid,"legend('original','resampled','location','northeast');");
fprintf(fid,"axis([-0.5 0.5 -120 20]);\n");
fclose(fid);
printf("results written to %s\n",OUTPUT_FILENAME);
printf("done.\n");
return 0;
}
