void gmskdem_demodulate(gmskdem _q,
float complex * _x,
unsigned int * _s)
{
// increment symbol counter
_q->num_symbols_demod++;
// run matched filter
unsigned int i;
float phi;
float d_hat;
for (i=0; i<_q->k; i++) {
// compute phase difference
phi = cargf( conjf(_q->x_prime)*_x[i] );
_q->x_prime = _x[i];
// run through matched filter
#if GMSKDEM_USE_EQUALIZER
eqlms_rrrf_push(_q->eq, phi);
#else
firfilt_rrrf_push(_q->filter, phi);
#endif
#if DEBUG_GMSKDEM
// compute output
float d_tmp;
# if GMSKDEM_USE_EQUALIZER
eqlms_rrrf_execute(_q->eq, &d_tmp);
# else
firfilt_rrrf_execute(_q->filter, &d_tmp);
# endif
windowf_push(_q->debug_mfout, d_tmp);
#endif
// decimate by k
if ( i != 0 ) continue;
#if GMSKDEM_USE_EQUALIZER
// compute filter/equalizer output
eqlms_rrrf_execute(_q->eq, &d_hat);
#else
// compute filter output
firfilt_rrrf_execute(_q->filter, &d_hat);
#endif
}
// make decision
*_s = d_hat > 0.0f ? 1 : 0;
#if GMSKDEM_USE_EQUALIZER
// update equalizer, after appropriate delay
if (_q->num_symbols_demod >= 2*_q->m) {
// compute expected output, scaling by samples/symbol
float d_prime = d_hat > 0 ? _q->k_inv : -_q->k_inv;
eqlms_rrrf_step(_q->eq, d_prime, d_hat);
}
#endif
}
int main() {
// options
unsigned int h_len=17; // filter length
float fc=0.2f; // filter cutoff
float As=30.0f; // stop-band attenuation [dB]
float mu=0.0f; // timing offset
unsigned int n=64; // number of random input samples
// derived values
unsigned int num_samples = n + h_len;
// arrays
float x[num_samples]; // filter input
float y[num_samples]; // filter output
unsigned int i;
float h[h_len];
liquid_firdes_kaiser(h_len,fc,As,mu,h);
firfilt_rrrf f = firfilt_rrrf_create(h,h_len);
firfilt_rrrf_print(f);
for (i=0; i<num_samples; i++) {
// generate noise
x[i] = (i<n) ? randnf()/sqrtf(n/2) : 0.0f;
firfilt_rrrf_push(f, x[i]);
firfilt_rrrf_execute(f, &y[i]);
printf("x[%4u] = %12.8f, y[%4u] = %12.8f;\n", i, x[i], i, y[i]);
}
// destroy filter object
firfilt_rrrf_destroy(f);
//
// export results
//
FILE*fid = fopen(OUTPUT_FILENAME,"w");
fprintf(fid,"%% firfilt_rrrf_example.m: auto-generated file\n\n");
fprintf(fid,"clear all;\nclose all;\n\n");
fprintf(fid,"h_len=%u;\nn=%u;\n", h_len, n);
for (i=0; i<h_len; i++)
fprintf(fid,"h(%4u) = %12.4e;\n", i+1, h[i]);
for (i=0; i<num_samples; i++)
fprintf(fid,"x(%4u) = %12.4e; y(%4u) = %12.4e;\n", i+1, x[i], i+1, y[i]);
fprintf(fid,"nfft=512;\n");
fprintf(fid,"H=20*log10(abs(fftshift(fft(h,nfft))));\n");
fprintf(fid,"X=20*log10(abs(fftshift(fft(x,nfft))));\n");
fprintf(fid,"Y=20*log10(abs(fftshift(fft(y,nfft))));\n");
fprintf(fid,"f=[0:(nfft-1)]/nfft-0.5;\n");
fprintf(fid,"figure;\n");
fprintf(fid,"plot(f,X,'Color',[0.3 0.3 0.3],...\n");
fprintf(fid," f,Y,'LineWidth',2,...\n");
fprintf(fid," f,H,'-b','LineWidth',2);\n");
fprintf(fid,"axis([-0.5 0.5 -80 40]);\n");
fprintf(fid,"grid on;\nxlabel('normalized frequency');\nylabel('PSD [dB]');\n");
fprintf(fid,"legend('noise','filtered noise','filter prototype',1);");
fclose(fid);
printf("results written to %s\n", OUTPUT_FILENAME);
printf("done.\n");
return 0;
}
int main(int argc, char*argv[])
{
// options
unsigned int h_len=19; // filter length
unsigned int p=5; // polynomial order
float fc=0.45f; // filter cutoff
float As=60.0f; // stop-band attenuation [dB]
float mu=0.1f; // fractional sample delay
unsigned int num_samples=60; // number of samples to evaluate
int verbose = 0; // verbose output?
int dopt;
while ((dopt = getopt(argc,argv,"hvt:")) != EOF) {
switch (dopt) {
case 'h': usage(); return 0;
case 'v': verbose = 1; break;
case 't': mu = atof(optarg); break;
default:
exit(1);
}
}
// data arrays
float x[num_samples]; // input data array
float y[num_samples]; // output data array
// create and initialize Farrow filter object
firfarrow_rrrf f = firfarrow_rrrf_create(h_len, p, fc, As);
firfarrow_rrrf_set_delay(f, mu);
unsigned int i;
// generate input (filtered noise)
float hx[21];
liquid_firdes_kaiser(15, 0.1, 60, 0, hx);
firfilt_rrrf fx = firfilt_rrrf_create(hx, 15);
for (i=0; i<num_samples; i++) {
firfilt_rrrf_push(fx, i < 40 ? randnf() : 0.0f);
firfilt_rrrf_execute(fx, &x[i]);
}
firfilt_rrrf_destroy(fx);
// push input through filter
for (i=0; i<num_samples; i++) {
firfarrow_rrrf_push(f, x[i]);
firfarrow_rrrf_execute(f, &y[i]);
}
// destroy Farrow filter object
firfarrow_rrrf_destroy(f);
FILE*fid = fopen(OUTPUT_FILENAME,"w");
fprintf(fid,"%% %s : auto-generated file\n\n", OUTPUT_FILENAME);
fprintf(fid,"clear all;\nclose all;\n\n");
fprintf(fid,"h_len = %u;\n", h_len);
fprintf(fid,"mu = %f;\n", mu);
fprintf(fid,"num_samples = %u;\n", num_samples);
for (i=0; i<num_samples; i++) {
fprintf(fid,"x(%4u) = %12.4e; y(%4u) = %12.4e;\n", i+1, x[i], i+1, y[i]);
}
// plot the results
fprintf(fid,"\n\n");
fprintf(fid,"figure;\n");
fprintf(fid,"tx = 0:(num_samples-1); %% input time scale\n");
fprintf(fid,"ty = tx - (h_len-1)/2 + mu; %% output time scale\n");
fprintf(fid,"plot(tx, x,'-s','MarkerSize',3, ...\n");
fprintf(fid," ty, y,'-s','MarkerSize',3);\n");
fprintf(fid,"legend('input','output',0);\n");
fclose(fid);
printf("results written to %s\n", OUTPUT_FILENAME);
printf("done.\n");
return 0;
}
int main() {
// spectral periodogram options
unsigned int nfft = 1024; // 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]
float alpha = 0.1f; // PSD estimate bandwidth
unsigned int i;
// derived values
float nstd = powf(10.0f, noise_floor/20.0f);
// create spectral periodogram
unsigned int window_size = nfft/2; // spgramf window size
spgramf q = spgramf_create_kaiser(nfft, window_size, beta);
// generate signal (filter with frequency offset)
unsigned int h_len = 91; // filter length
float fc = 0.07f; // filter cut-off frequency
float f0 = 0.20f; // filter center frequency
float As = 60.0f; // filter stop-band attenuation
float h[h_len]; // filter coefficients
liquid_firdes_kaiser(h_len, fc, As, 0, h);
// add frequency offset
for (i=0; i<h_len; i++)
h[i] *= cosf(2*M_PI*f0*i);
firfilt_rrrf filter = firfilt_rrrf_create(h, h_len);
firfilt_rrrf_set_scale(filter, 2.0f*fc);
for (i=0; i<num_samples; i++) {
// generate random sample
float x = randnf();
// filter
float y = 0;
firfilt_rrrf_push(filter, x);
firfilt_rrrf_execute(filter, &y);
// add noise
y += nstd * randnf();
// push resulting sample through periodogram
spgramf_accumulate_psd(q, &y, alpha, 1);
}
// compute power spectral density output
float psd[nfft];
spgramf_write_accumulation(q, psd);
// destroy objects
firfilt_rrrf_destroy(filter);
spgramf_destroy(q);
//
// 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;
}
void ModemFMStereo::demodulate(ModemKit *kit, ModemIQData *input, AudioThreadInput *audioOut) {
ModemKitFMStereo *fmkit = (ModemKitFMStereo *)kit;
size_t bufSize = input->data.size();
liquid_float_complex u, v, w, x, y;
double audio_resample_ratio = fmkit->audioResampleRatio;
if (demodOutputData.size() != bufSize) {
if (demodOutputData.capacity() < bufSize) {
demodOutputData.reserve(bufSize);
}
demodOutputData.resize(bufSize);
}
size_t audio_out_size = (size_t)ceil((double) (bufSize) * audio_resample_ratio) + 512;
freqdem_demodulate_block(demodFM, &input->data[0], bufSize, &demodOutputData[0]);
if (resampledOutputData.size() != audio_out_size) {
if (resampledOutputData.capacity() < audio_out_size) {
resampledOutputData.reserve(audio_out_size);
}
resampledOutputData.resize(audio_out_size);
}
unsigned int numAudioWritten;
msresamp_rrrf_execute(fmkit->audioResampler, &demodOutputData[0], bufSize, &resampledOutputData[0], &numAudioWritten);
if (demodStereoData.size() != bufSize) {
if (demodStereoData.capacity() < bufSize) {
demodStereoData.reserve(bufSize);
}
demodStereoData.resize(bufSize);
}
float phase_error = 0;
for (size_t i = 0; i < bufSize; i++) {
// real -> complex
firhilbf_r2c_execute(fmkit->firStereoR2C, demodOutputData[i], &x);
// 19khz pilot band-pass
iirfilt_crcf_execute(fmkit->iirStereoPilot, x, &v);
nco_crcf_cexpf(fmkit->stereoPilot, &w);
w.imag = -w.imag; // conjf(w)
// multiply u = v * conjf(w)
u.real = v.real * w.real - v.imag * w.imag;
u.imag = v.real * w.imag + v.imag * w.real;
// cargf(u)
phase_error = atan2f(u.imag,u.real);
// step pll
nco_crcf_pll_step(fmkit->stereoPilot, phase_error);
nco_crcf_step(fmkit->stereoPilot);
// 38khz down-mix
nco_crcf_mix_down(fmkit->stereoPilot, x, &y);
nco_crcf_mix_down(fmkit->stereoPilot, y, &x);
// complex -> real
firhilbf_c2r_execute(fmkit->firStereoC2R, x, &demodStereoData[i]);
}
// std::cout << "[PLL] phase error: " << phase_error;
// std::cout << " freq:" << (((nco_crcf_get_frequency(stereoPilot) / (2.0 * M_PI)) * inp->sampleRate)) << std::endl;
if (audio_out_size != resampledStereoData.size()) {
if (resampledStereoData.capacity() < audio_out_size) {
resampledStereoData.reserve(audio_out_size);
}
resampledStereoData.resize(audio_out_size);
}
msresamp_rrrf_execute(fmkit->stereoResampler, &demodStereoData[0], bufSize, &resampledStereoData[0], &numAudioWritten);
audioOut->channels = 2;
if (audioOut->data.capacity() < (numAudioWritten * 2)) {
audioOut->data.reserve(numAudioWritten * 2);
}
audioOut->data.resize(numAudioWritten * 2);
for (size_t i = 0; i < numAudioWritten; i++) {
float l, r;
float ld, rd;
if (fmkit->demph) {
iirfilt_rrrf_execute(fmkit->iirDemphL, 0.568f * (resampledOutputData[i] - (resampledStereoData[i])), &ld);
iirfilt_rrrf_execute(fmkit->iirDemphR, 0.568f * (resampledOutputData[i] + (resampledStereoData[i])), &rd);
firfilt_rrrf_push(fmkit->firStereoLeft, ld);
firfilt_rrrf_execute(fmkit->firStereoLeft, &l);
firfilt_rrrf_push(fmkit->firStereoRight, rd);
firfilt_rrrf_execute(fmkit->firStereoRight, &r);
} else {
firfilt_rrrf_push(fmkit->firStereoLeft, 0.568f * (resampledOutputData[i] - (resampledStereoData[i])));
firfilt_rrrf_execute(fmkit->firStereoLeft, &l);
firfilt_rrrf_push(fmkit->firStereoRight, 0.568f * (resampledOutputData[i] + (resampledStereoData[i])));
firfilt_rrrf_execute(fmkit->firStereoRight, &r);
}
audioOut->data[i * 2] = l;
audioOut->data[i * 2 + 1] = r;
}
}