void SpectrogramComponent::processWindow()
{
//Calculate spectrogram, fftshift and accumulate
spgram_push(sp_, &window_[0], windowLength_x);
spgram_execute(sp_, &spec_[0]);
for(int i=0;i<nFft_x;i++)
{
Cplx c = spec_[(i+nFft_x/2)%nFft_x];
psd_[i] += real(c*conj(c));
}
//Clear containers
CplxVec temp = window_;
window_.assign(temp.begin()+delay_x,temp.end());
spec_.assign(nFft_x, Cplx(0,0));
//We've accumulated enough windows, normalize, convert to dB and output
if(++n_ >= nWindows_x)
{
FloatVecIt it = psd_.begin();
for(;it!=psd_.end();++it)
*it = (10*log10(*it/nWindows_x));
outputPsd();
psd_.assign(nFft_x, 0.0);
n_ = 0;
}
}
int main() {
// spectral periodogram options
unsigned int nfft=256; // spectral periodogram FFT size
unsigned int num_samples = 2001; // number of samples
float beta = 10.0f; // Kaiser-Bessel window parameter
// allocate memory for data arrays
float complex x[num_samples]; // input signal
float complex X[nfft]; // output spectrum
float psd[nfft]; // power spectral density
unsigned int ramp = num_samples/20 < 10 ? 10 : num_samples/20;
// create spectral periodogram
unsigned int window_size = nfft/2; // spgram window size
unsigned int delay = nfft/8; // samples between transforms
spgram q = spgram_create_kaiser(nfft, window_size, beta);
unsigned int i;
// generate signal
nco_crcf nco = nco_crcf_create(LIQUID_VCO);
for (i=0; i<num_samples; i++) {
nco_crcf_set_frequency(nco, 0.1f*(1.2f+sinf(0.007f*i)) );
nco_crcf_cexpf(nco, &x[i]);
nco_crcf_step(nco);
}
nco_crcf_destroy(nco);
// add soft ramping functions
for (i=0; i<ramp; i++) {
x[i] *= 0.5f - 0.5f*cosf(M_PI*(float)i / (float)ramp);
x[num_samples-ramp+i-1] *= 0.5f - 0.5f*cosf(M_PI*(float)(ramp-i-1) / (float)ramp);
}
//
// export output file(s)
//
FILE * fid;
//
// export time-doman data
//
fid = fopen(OUTPUT_FILENAME_TIME,"w");
fprintf(fid,"# %s : auto-generated file\n", OUTPUT_FILENAME_TIME);
for (i=0; i<num_samples; i++)
fprintf(fid,"%12u %12.8f %12.8f\n", i, crealf(x[i]), cimagf(x[i]));
fclose(fid);
printf("results written to %s.\n", OUTPUT_FILENAME_TIME);
//
// export freq-doman data
//
fid = fopen(OUTPUT_FILENAME_FREQ,"w");
fprintf(fid,"# %s : auto-generated file\n", OUTPUT_FILENAME_FREQ);
unsigned int t=0;
for (i=0; i<num_samples; i++) {
// push sample into periodogram
spgram_push(q, &x[i], 1);
if ( ((i+1)%delay)==0 ) {
// compute spectral periodogram output
spgram_execute(q, X);
unsigned int k;
// compute PSD and FFT shift
for (k=0; k<nfft; k++)
psd[k] = 20*log10f( cabsf(X[(k+nfft/2)%nfft]) );
#if 1
for (k=0; k<nfft; k++)
fprintf(fid,"%12u %12.8f %12.8f\n", t, (float)k/(float)nfft - 0.5f, psd[k]);
#else
for (k=0; k<nfft; k++)
fprintf(fid,"%12.8f ", psd[k]);
#endif
fprintf(fid,"\n");
t++;
}
}
// destroy spectral periodogram object
spgram_destroy(q);
fclose(fid);
printf("results written to %s.\n", OUTPUT_FILENAME_FREQ);
printf("done.\n");
return 0;
}
int main() {
// spectral periodogram options
unsigned int nfft=512; // spectral periodogram FFT size
unsigned int num_samples = 4000; // number of samples
float beta = 10.0f; // Kaiser-Bessel window parameter
float noise_floor = -60.0f; // noise floor [dB]
unsigned int i;
// derived values
float nstd = powf(10.0f, noise_floor/20.0f);
// allocate memory for data arrays
float complex X[nfft]; // output spectrum
float psd[nfft]; // power spectral density
// initialize PSD estimate
for (i=0; i<nfft; i++)
psd[i] = 0.0f;
// create spectral periodogram
unsigned int window_size = nfft/2; // spgram window size
unsigned int delay = nfft/8; // samples between transforms
spgram q = spgram_create_kaiser(nfft, window_size, beta);
// generate signal (interpolated symbols with noise)
unsigned int k = 4; // interpolation rate
unsigned int m = 7; // filter delay (symbols)
firinterp_crcf interp = firinterp_crcf_create_rnyquist(LIQUID_RNYQUIST_RKAISER, k, m, 0.3f, 0.0f);
int spgram_timer = nfft;
unsigned int n=0;
float complex x[k]; // interpolator output
unsigned int num_transforms = 0;
while (n < num_samples) {
// generate random symbol
float complex s = ( rand() % 2 ? 0.707f : -0.707f ) +
( rand() % 2 ? 0.707f : -0.707f ) * _Complex_I;
// interpolate
firinterp_crcf_execute(interp, s, x);
// add noise
for (i=0; i<k; i++)
x[i] += nstd * ( randnf() + _Complex_I*randnf() ) * M_SQRT1_2;
// push resulting samples through spgram
spgram_push(q, x, k);
//
spgram_timer -= k;
n += k;
//
if (spgram_timer <= 0) {
// update timer, counter
spgram_timer += delay;
num_transforms++;
// run spectral periodogram
spgram_execute(q, X);
// accumulate PSD and FFT shift
for (i=0; i<nfft; i++) {
float complex X0 = X[(i+nfft/2)%nfft];
psd[i] += crealf(X0*conjf(X0));
}
}
}
// destroy objects
firinterp_crcf_destroy(interp);
spgram_destroy(q);
// normalize result
printf("computed %u transforms\n", num_transforms);
// TODO: ensure at least one transform was taken
for (i=0; i<nfft; i++)
psd[i] = 10*log10f( psd[i] / (float)(num_transforms) );
//
// export 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\n");
fprintf(fid,"nfft = %u;\n", nfft);
fprintf(fid,"f = [0:(nfft-1)]/nfft - 0.5;\n");
fprintf(fid,"H = zeros(1,nfft);\n");
fprintf(fid,"noise_floor = %12.6f;\n", noise_floor);
for (i=0; i<nfft; i++)
fprintf(fid,"H(%6u) = %12.4e;\n", i+1, psd[i]);
fprintf(fid,"figure;\n");
fprintf(fid,"plot(f, H, '-', 'LineWidth',1.5);\n");
fprintf(fid,"xlabel('Normalized Frequency [f/F_s]');\n");
fprintf(fid,"ylabel('Power Spectral Density [dB]');\n");
fprintf(fid,"grid on;\n");
fprintf(fid,"ymin = 10*floor([noise_floor-20]/10);\n");
fprintf(fid,"ymax = 10*floor([noise_floor+80]/10);\n");
fprintf(fid,"axis([-0.5 0.5 ymin ymax]);\n");
fclose(fid);
printf("results written to %s.\n", OUTPUT_FILENAME);
printf("done.\n");
return 0;
}
