// compute filter coefficients and determine resulting ISI
//
// _k : filter over-sampling rate (samples/symbol)
// _m : filter delay (symbols)
// _beta : filter excess bandwidth factor (0,1)
// _dt : filter fractional sample delay
// _rho : transition bandwidth adjustment, 0 < _rho < 1
// _h : filter buffer [size: 2*_k*_m+1]
float liquid_firdes_rkaiser_internal_isi(unsigned int _k,
unsigned int _m,
float _beta,
float _dt,
float _rho,
float * _h)
{
// validate input
if (_rho < 0.0f) {
fprintf(stderr,"warning: liquid_firdes_rkaiser_internal_isi(), rho < 0\n");
} else if (_rho > 1.0f) {
fprintf(stderr,"warning: liquid_firdes_rkaiser_internal_isi(), rho > 1\n");
}
unsigned int n=2*_k*_m+1; // filter length
float kf = (float)_k; // samples/symbol (float)
float del = _beta*_rho / kf; // transition bandwidth
float As = estimate_req_filter_As(del, n); // stop-band suppression
float fc = 0.5f*(1 + _beta*(1.0f-_rho))/kf; // filter cutoff
// evaluate performance (ISI)
float isi_max;
float isi_rms;
// compute filter
liquid_firdes_kaiser(n,fc,As,_dt,_h);
// compute filter ISI
liquid_filter_isi(_h,_k,_m,&isi_rms,&isi_max);
// return RMS of ISI
return isi_rms;
}
// create FIR polyphase filterbank channelizer object with
// prototype filter based on windowed Kaiser design
// _type : channelizer type (LIQUID_ANALYZER | LIQUID_SYNTHESIZER)
// _M : number of channels
// _m : filter delay (symbols)
// _As : stop-band attentuation [dB]
FIRPFBCH() FIRPFBCH(_create_kaiser)(int _type,
unsigned int _M,
unsigned int _m,
float _As)
{
// validate input
if (_M == 0) {
fprintf(stderr,"error: firpfbch_%s_create_kaiser(), number of channels must be greater than 0\n", EXTENSION_FULL);
exit(1);
} else if (_m == 0) {
fprintf(stderr,"error: firpfbch_%s_create_kaiser(), invalid filter size (must be greater than 0)\n", EXTENSION_FULL);
exit(1);
}
_As = fabsf(_As);
// design filter
unsigned int h_len = 2*_M*_m + 1;
float h[h_len];
float fc = 0.5f / (float)_M; // TODO : check this value
liquid_firdes_kaiser(h_len, fc, _As, 0.0f, h);
// copy coefficients to type-specfic array
TC hc[h_len];
unsigned int i;
for (i=0; i<h_len; i++)
hc[i] = h[i];
// create filterbank object
unsigned int p = 2*_m;
FIRPFBCH() q = FIRPFBCH(_create)(_type, _M, p, hc);
// return filterbank object
return q;
}
// create LMS EQ initialized with low-pass filter
// _h_len : filter length
// _fc : filter cut-off, _fc in (0,0.5]
EQLMS() EQLMS(_create_lowpass)(unsigned int _h_len,
float _fc)
{
// validate input
if (_h_len == 0) {
fprintf(stderr,"error: eqlms_%s_create_lowpass(), filter length must be greater than 0\n", EXTENSION_FULL);
exit(1);
} else if (_fc <= 0.0f || _fc > 0.5f) {
fprintf(stderr,"error: eqlms_%s_create_rnyquist(), filter cutoff must be in (0,0.5]\n", EXTENSION_FULL);
exit(1);
}
// generate low-pass filter prototype
float h[_h_len];
liquid_firdes_kaiser(_h_len, _fc, 40.0f, 0.0f, h);
// copy coefficients to type-specific array (e.g. float complex)
unsigned int i;
T hc[_h_len];
for (i=0; i<_h_len; i++)
hc[i] = h[i];
// return equalizer object
return EQLMS(_create)(hc, _h_len);
}
// create decimator from prototype
// _M : decimolation factor
// _m : symbol delay
// _As : stop-band attenuation [dB]
FIRDECIM() FIRDECIM(_create_prototype)(unsigned int _M,
unsigned int _m,
float _As)
{
// validate input
if (_M < 2) {
fprintf(stderr,"error: decim_%s_create_prototype(), decim factor must be greater than 1\n", EXTENSION_FULL);
exit(1);
} else if (_m == 0) {
fprintf(stderr,"error: decim_%s_create_prototype(), filter delay must be greater than 0\n", EXTENSION_FULL);
exit(1);
} else if (_As < 0.0f) {
fprintf(stderr,"error: decim_%s_create_prototype(), stop-band attenuation must be positive\n", EXTENSION_FULL);
exit(1);
}
// compute filter coefficients (floating point precision)
unsigned int h_len = 2*_M*_m + 1;
float hf[h_len];
float fc = 0.5f / (float) (_M);
liquid_firdes_kaiser(h_len, fc, _As, 0.0f, hf);
// copy coefficients to type-specific array (e.g. float complex)
TC hc[h_len];
unsigned int i;
for (i=0; i<h_len; i++)
hc[i] = hf[i];
// return decimator object
return FIRDECIM(_create)(_M, hc, 2*_M*_m);
}
// create arbitrary resampler
// _rate : resampling rate
// _m : prototype filter semi-length
// _fc : prototype filter cutoff frequency, fc in (0, 0.5)
// _As : prototype filter stop-band attenuation [dB] (e.g. 60)
// _npfb : number of filters in polyphase filterbank
RESAMP() RESAMP(_create)(float _rate,
unsigned int _m,
float _fc,
float _As,
unsigned int _npfb)
{
// validate input
if (_rate <= 0) {
fprintf(stderr,"error: resamp_%s_create(), resampling rate must be greater than zero\n", EXTENSION_FULL);
exit(1);
} else if (_m == 0) {
fprintf(stderr,"error: resamp_%s_create(), filter semi-length must be greater than zero\n", EXTENSION_FULL);
exit(1);
} else if (_fc <= 0.0f || _fc >= 0.5f) {
fprintf(stderr,"error: resamp_%s_create(), filter cutoff must be in (0,0.5)\n", EXTENSION_FULL);
exit(1);
} else if (_As <= 0.0f) {
fprintf(stderr,"error: resamp_%s_create(), filter stop-band suppression must be greater than zero\n", EXTENSION_FULL);
exit(1);
} else if (_npfb == 0) {
fprintf(stderr,"error: resamp_%s_create(), number of filter banks must be greater than zero\n", EXTENSION_FULL);
exit(1);
}
// allocate memory for resampler
RESAMP() q = (RESAMP()) malloc(sizeof(struct RESAMP(_s)));
// set rate using formal method (specifies output stride
// value 'del')
RESAMP(_set_rate)(q, _rate);
// set properties
q->m = _m; // prototype filter semi-length
q->fc = _fc; // prototype filter cutoff frequency
q->As = _As; // prototype filter stop-band attenuation
q->npfb = _npfb; // number of filters in bank
// design filter
unsigned int n = 2*q->m*q->npfb+1;
float hf[n];
TC h[n];
liquid_firdes_kaiser(n,q->fc/((float)(q->npfb)),q->As,0.0f,hf);
// normalize filter coefficients by DC gain
unsigned int i;
float gain=0.0f;
for (i=0; i<n; i++)
gain += hf[i];
gain = (q->npfb)/(gain);
// copy to type-specific array, applying gain
for (i=0; i<n; i++)
h[i] = hf[i]*gain;
q->f = FIRPFB(_create)(q->npfb,h,n-1);
// reset object and return
RESAMP(_reset)(q);
return q;
}
ModemKit *ModemFMStereo::buildKit(long long sampleRate, int audioSampleRate) {
ModemKitFMStereo *kit = new ModemKitFMStereo;
kit->audioResampleRatio = double(audioSampleRate) / double(sampleRate);
kit->sampleRate = sampleRate;
kit->audioSampleRate = audioSampleRate;
float As = 60.0f; // stop-band attenuation [dB]
kit->audioResampler = msresamp_rrrf_create(kit->audioResampleRatio, As);
kit->stereoResampler = msresamp_rrrf_create(kit->audioResampleRatio, As);
// Stereo filters / shifters
double firStereoCutoff = 16000.0 / double(audioSampleRate);
// filter transition
float ft = 1000.0f / double(audioSampleRate);
// fractional timing offset
float mu = 0.0f;
if (firStereoCutoff < 0) {
firStereoCutoff = 0;
}
if (firStereoCutoff > 0.5) {
firStereoCutoff = 0.5;
}
unsigned int h_len = estimate_req_filter_len(ft, As);
float *h = new float[h_len];
liquid_firdes_kaiser(h_len, firStereoCutoff, As, mu, h);
kit->firStereoLeft = firfilt_rrrf_create(h, h_len);
kit->firStereoRight = firfilt_rrrf_create(h, h_len);
// stereo pilot filter
float bw = float(sampleRate);
if (bw < 100000.0) {
bw = 100000.0;
}
unsigned int order = 5; // filter order
float f0 = ((float) 19000 / bw);
float fc = ((float) 19500 / bw);
float Ap = 1.0f;
kit->iirStereoPilot = iirfilt_crcf_create_prototype(LIQUID_IIRDES_CHEBY2, LIQUID_IIRDES_BANDPASS, LIQUID_IIRDES_SOS, order, fc, f0, Ap, As);
kit->firStereoR2C = firhilbf_create(5, 60.0f);
kit->firStereoC2R = firhilbf_create(5, 60.0f);
kit->stereoPilot = nco_crcf_create(LIQUID_VCO);
nco_crcf_reset(kit->stereoPilot);
nco_crcf_pll_set_bandwidth(kit->stereoPilot, 0.25f);
return kit;
}
// create firhilb object
// _m : filter semi-length (delay: 2*m+1)
// _As : stop-band attenuation [dB]
FIRHILB() FIRHILB(_create)(unsigned int _m,
float _As)
{
// validate firhilb inputs
if (_m < 2) {
fprintf(stderr,"error: firhilb_create(), filter semi-length (m) must be at least 2\n");
exit(1);
}
// allocate memory for main object
FIRHILB() q = (FIRHILB()) malloc(sizeof(struct FIRHILB(_s)));
q->m = _m; // filter semi-length
q->As = fabsf(_As); // stop-band attenuation
// set filter length and allocate memory for coefficients
q->h_len = 4*(q->m) + 1;
q->h = (T *) malloc((q->h_len)*sizeof(T));
q->hc = (T complex *) malloc((q->h_len)*sizeof(T complex));
// allocate memory for quadrature filter component
q->hq_len = 2*(q->m);
q->hq = (T *) malloc((q->hq_len)*sizeof(T));
// compute filter coefficients for half-band filter
liquid_firdes_kaiser(q->h_len, 0.25f, q->As, 0.0f, q->h);
// alternate sign of non-zero elements
unsigned int i;
for (i=0; i<q->h_len; i++) {
float t = (float)i - (float)(q->h_len-1)/2.0f;
q->hc[i] = q->h[i] * cexpf(_Complex_I*0.5f*M_PI*t);
q->h[i] = cimagf(q->hc[i]);
}
// resample, reverse direction
unsigned int j=0;
for (i=1; i<q->h_len; i+=2)
q->hq[j++] = q->h[q->h_len - i - 1];
// create windows for upper and lower polyphase filter branches
q->w1 = WINDOW(_create)(2*(q->m));
q->w0 = WINDOW(_create)(2*(q->m));
WINDOW(_clear)(q->w0);
WINDOW(_clear)(q->w1);
// create internal dot product object
q->dpq = DOTPROD(_create)(q->hq, q->hq_len);
// reset internal state and return object
FIRHILB(_reset)(q);
return q;
}
void DemodulatorPreThread::initialize() {
initialized = false;
iqResampleRatio = (double) (params.bandwidth) / (double) params.sampleRate;
audioResampleRatio = (double) (params.audioSampleRate) / (double) params.bandwidth;
float As = 120.0f; // stop-band attenuation [dB]
iqResampler = msresamp_crcf_create(iqResampleRatio, As);
audioResampler = msresamp_rrrf_create(audioResampleRatio, As);
stereoResampler = msresamp_rrrf_create(audioResampleRatio, As);
// Stereo filters / shifters
double firStereoCutoff = ((double) 16000 / (double) params.audioSampleRate);
float ft = ((double) 1000 / (double) params.audioSampleRate); // filter transition
float mu = 0.0f; // fractional timing offset
if (firStereoCutoff < 0) {
firStereoCutoff = 0;
}
if (firStereoCutoff > 0.5) {
firStereoCutoff = 0.5;
}
unsigned int h_len = estimate_req_filter_len(ft, As);
float *h = new float[h_len];
liquid_firdes_kaiser(h_len, firStereoCutoff, As, mu, h);
firStereoLeft = firfilt_rrrf_create(h, h_len);
firStereoRight = firfilt_rrrf_create(h, h_len);
// stereo pilot filter
float bw = params.bandwidth;
if (bw < 100000.0) {
bw = 100000.0;
}
unsigned int order = 5; // filter order
float f0 = ((double) 19000 / bw);
float fc = ((double) 19500 / bw);
float Ap = 1.0f;
As = 60.0f;
iirStereoPilot = iirfilt_crcf_create_prototype(LIQUID_IIRDES_CHEBY2, LIQUID_IIRDES_BANDPASS, LIQUID_IIRDES_SOS, order, fc, f0, Ap, As);
initialized = true;
lastParams = params;
}
// create symsync using Kaiser filter interpolator; useful
// when the input signal has matched filter applied already
// _k : input samples/symbol
// _m : symbol delay
// _beta : rolloff factor, beta in (0,1]
// _M : number of filters in the bank
SYMSYNC() SYMSYNC(_create_kaiser)(unsigned int _k,
unsigned int _m,
float _beta,
unsigned int _M)
{
// validate input
if (_k < 2) {
fprintf(stderr,"error: symsync_%s_create_kaiser(), samples/symbol must be at least 2\n", EXTENSION_FULL);
exit(1);
} else if (_m == 0) {
fprintf(stderr,"error: symsync_%s_create_kaiser(), filter delay (m) must be greater than zero\n", EXTENSION_FULL);
exit(1);
} else if (_beta < 0.0f || _beta > 1.0f) {
fprintf(stderr,"error: symsync_%s_create_kaiser(), filter excess bandwidth must be in [0,1]\n", EXTENSION_FULL);
exit(1);
}
// allocate memory for filter coefficients
unsigned int H_len = 2*_M*_k*_m + 1;
float Hf[H_len];
// design interpolating filter whose bandwidth is outside the cut-off
// frequency of input signal
// TODO: use _beta to compute more accurate cut-off frequency
float fc = 0.75f; // filter cut-off frequency (nominal)
float As = 40.0f; // filter stop-band attenuation
liquid_firdes_kaiser(H_len, fc / (float)(_k*_M), As, 0.0f, Hf);
// copy coefficients to type-specific array, adjusting to relative
// filter gain
unsigned int i;
TC H[H_len];
for (i=0; i<H_len; i++)
H[i] = Hf[i] * 2.0f * fc;
// create object and return
return SYMSYNC(_create)(_k, _M, H, H_len);
}
// create filter using Kaiser-Bessel windowed sinc method
// _n : filter length, _n > 0
// _fc : cutoff frequency, 0 < _fc < 0.5
// _As : stop-band attenuation [dB], _As > 0
// _mu : fractional sample offset, -0.5 < _mu < 0.5
FIRFILT() FIRFILT(_create_kaiser)(unsigned int _n,
float _fc,
float _As,
float _mu)
{
// validate input
if (_n == 0) {
fprintf(stderr,"error: firfilt_%s_create_kaiser(), filter length must be greater than zero\n", EXTENSION_FULL);
exit(1);
}
// compute temporary array for holding coefficients
float hf[_n];
liquid_firdes_kaiser(_n, _fc, _As, _mu, hf);
// copy coefficients to type-specific array
TC h[_n];
unsigned int i;
for (i=0; i<_n; i++)
h[i] = (TC) hf[i];
//
return FIRFILT(_create)(h, _n);
}
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;
}
RESAMP() RESAMP(_create)(float _r,
unsigned int _h_len,
float _fc,
float _As,
unsigned int _npfb)
{
// validate input
if (_r <= 0) {
fprintf(stderr,"error: resamp_%s_create(), resampling rate must be greater than zero\n", EXTENSION_FULL);
exit(1);
} else if (_h_len == 0) {
fprintf(stderr,"error: resamp_%s_create(), filter length must be greater than zero\n", EXTENSION_FULL);
exit(1);
} else if (_npfb == 0) {
fprintf(stderr,"error: resamp_%s_create(), number of filter banks must be greater than zero\n", EXTENSION_FULL);
exit(1);
} else if (_fc <= 0.0f || _fc >= 0.5f) {
fprintf(stderr,"error: resamp_%s_create(), filter cutoff must be in (0,0.5)\n", EXTENSION_FULL);
exit(1);
} else if (_As <= 0.0f) {
fprintf(stderr,"error: resamp_%s_create(), filter stop-band suppression must be greater than zero\n", EXTENSION_FULL);
exit(1);
}
RESAMP() q = (RESAMP()) malloc(sizeof(struct RESAMP(_s)));
q->r = _r;
q->As = _As;
q->fc = _fc;
q->h_len = _h_len;
q->b = 0;
q->del = 1.0f / q->r;
#if RESAMP_USE_FIXED_POINT_PHASE
q->num_bits_npfb = liquid_nextpow2(_npfb);
q->npfb = 1<<q->num_bits_npfb;
q->num_bits_phase = 20;
q->max_phase = 1 << q->num_bits_phase;
q->num_shift_bits = q->num_bits_phase - q->num_bits_npfb;
q->theta = 0;
q->d_theta = (unsigned int)( q->max_phase * q->del );
#else
q->npfb = _npfb;
q->tau = 0.0f;
q->bf = 0.0f;
#endif
// design filter
unsigned int n = 2*_h_len*q->npfb+1;
float hf[n];
TC h[n];
liquid_firdes_kaiser(n,q->fc/((float)(q->npfb)),q->As,0.0f,hf);
// normalize filter coefficients by DC gain
unsigned int i;
float gain=0.0f;
for (i=0; i<n; i++)
gain += hf[i];
gain = (q->npfb)/(gain);
// copy to type-specific array
for (i=0; i<n; i++)
h[i] = hf[i]*gain;
q->f = FIRPFB(_create)(q->npfb,h,n-1);
//for (i=0; i<n; i++)
// PRINTVAL_TC(h[i],%12.8f);
//exit(0);
return q;
}
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;
}
firpfbch firpfbch_create(unsigned int _num_channels,
unsigned int _m,
float _beta,
float _dt,
int _nyquist,
int _gradient)
{
firpfbch c = (firpfbch) malloc(sizeof(struct firpfbch_s));
c->num_channels = _num_channels;
c->m = _m;
c->beta = _beta;
c->dt = _dt;
c->nyquist = _nyquist;
// validate inputs
if (_m < 1) {
printf("error: firpfbch_create(), invalid filter delay (must be greater than 0)\n");
exit(1);
}
// create bank of filters
c->dp = (DOTPROD()*) malloc((c->num_channels)*sizeof(DOTPROD()));
c->w = (WINDOW()*) malloc((c->num_channels)*sizeof(WINDOW()));
// design filter
// TODO: use filter prototype object
c->h_len = 2*(c->m)*(c->num_channels);
c->h = (float*) malloc((c->h_len+1)*sizeof(float));
if (c->nyquist == FIRPFBCH_NYQUIST) {
float fc = 0.5f/(float)(c->num_channels); // cutoff frequency
liquid_firdes_kaiser(c->h_len+1, fc, c->beta, 0.0f, c->h);
} else if (c->nyquist == FIRPFBCH_ROOTNYQUIST) {
design_rkaiser_filter(c->num_channels, c->m, c->beta, c->dt, c->h);
} else {
printf("error: firpfbch_create(), unsupported nyquist flag: %d\n", _nyquist);
exit(1);
}
unsigned int i;
if (_gradient) {
float dh[c->h_len];
for (i=0; i<c->h_len; i++) {
if (i==0) {
dh[i] = c->h[i+1] - c->h[c->h_len-1];
} else if (i==c->h_len-1) {
dh[i] = c->h[0] - c->h[i-1];
} else {
dh[i] = c->h[i+1] - c->h[i-1];
}
}
memmove(c->h, dh, (c->h_len)*sizeof(float));
}
// generate bank of sub-samped filters
unsigned int n;
unsigned int h_sub_len = 2*(c->m); // length of each sub-sampled filter
float h_sub[h_sub_len];
for (i=0; i<c->num_channels; i++) {
// sub-sample prototype filter, loading coefficients in reverse order
for (n=0; n<h_sub_len; n++) {
h_sub[h_sub_len-n-1] = c->h[i + n*(c->num_channels)];
}
// create window buffer and dotprod object (coefficients
// loaded in reverse order)
c->dp[i] = DOTPROD(_create)(h_sub,h_sub_len);
c->w[i] = WINDOW(_create)(h_sub_len);
#if DEBUG_FIRPFBCH_PRINT
printf("h_sub[%u] :\n", i);
for (n=0; n<h_sub_len; n++)
printf(" h[%3u] = %8.4f\n", n, h_sub[n]);
#endif
}
#if DEBUG_FIRPFBCH_PRINT
for (i=0; i<c->h_len+1; i++)
printf("h(%4u) = %12.4e;\n", i+1, c->h[i]);
#endif
// allocate memory for buffers
// TODO : use fftw_malloc if HAVE_FFTW3_H
c->x = (float complex*) malloc((c->num_channels)*sizeof(float complex));
c->X = (float complex*) malloc((c->num_channels)*sizeof(float complex));
c->X_prime = (float complex*) malloc((c->num_channels)*sizeof(float complex));
firpfbch_clear(c);
// create fft plan
c->fft = FFT_CREATE_PLAN(c->num_channels, c->X, c->x, FFT_DIR_BACKWARD, FFT_METHOD);
return c;
}
int main(int argc, char*argv[])
{
// options
float mod_index = 0.5f; // modulation index (bandwidth)
float fc = 0.0f; // FM carrier
liquid_freqmodem_type type = LIQUID_FREQMODEM_DELAYCONJ;
unsigned int num_samples = 256; // number of samples
float SNRdB = 30.0f; // signal-to-noise ratio [dB]
int dopt;
while ((dopt = getopt(argc,argv,"hn:S:f:m:t:")) != EOF) {
switch (dopt) {
case 'h': usage(); return 0;
case 'n': num_samples = atoi(optarg); break;
case 'S': SNRdB = atof(optarg); break;
case 'f': fc = atof(optarg); break;
case 'm': mod_index = atof(optarg); break;
case 't':
if (strcmp(optarg,"delayconj")==0) {
type = LIQUID_FREQMODEM_DELAYCONJ;
} else if (strcmp(optarg,"pll")==0) {
type = LIQUID_FREQMODEM_PLL;
} else {
fprintf(stderr,"error: %s, invalid FM type: %s\n", argv[0], optarg);
exit(1);
}
break;
default:
exit(1);
}
}
// create mod/demod objects
freqmodem mod = freqmodem_create(mod_index,fc,type);
freqmodem demod = freqmodem_create(mod_index,fc,type);
freqmodem_print(mod);
unsigned int i;
float x[num_samples];
float complex y[num_samples];
float z[num_samples];
// generate un-modulated signal (band-limited pulse)
liquid_firdes_kaiser(num_samples, 0.05f, -40.0f, 0.0f, x);
// modulate signal
for (i=0; i<num_samples; i++)
freqmodem_modulate(mod, x[i], &y[i]);
// add channel impairments
float nstd = powf(10.0f,-SNRdB/20.0f);
for (i=0; i<num_samples; i++)
y[i] += nstd*( randnf() + _Complex_I*randnf() ) * M_SQRT1_2;
// demodulate signal
for (i=0; i<num_samples; i++)
freqmodem_demodulate(demod, y[i], &z[i]);
// write results to 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=%u;\n",num_samples);
for (i=0; i<num_samples; i++) {
fprintf(fid,"x(%3u) = %12.4e;\n", i+1, x[i]);
fprintf(fid,"y(%3u) = %12.4e + j*%12.4e;\n", i+1, crealf(y[i]), cimagf(y[i]));
fprintf(fid,"z(%3u) = %12.4e;\n", i+1, z[i]);
}
// plot results
fprintf(fid,"t=0:(n-1);\n");
fprintf(fid,"figure;\n");
fprintf(fid,"plot(t,x,t,z);\n");
fprintf(fid,"axis([0 n -1.2 1.2]);\n");
// spectrum
fprintf(fid,"nfft=1024;\n");
fprintf(fid,"f=[0:(nfft-1)]/nfft - 0.5;\n");
fprintf(fid,"Y = 20*log10(abs(fftshift(fft(y/n,nfft))));\n");
fprintf(fid,"figure;\n");
fprintf(fid,"plot(f,Y);\n");
fprintf(fid,"axis([-0.5 0.5 -60 20]);\n");
fprintf(fid,"grid on;\n");
fclose(fid);
printf("results written to %s\n", OUTPUT_FILENAME);
freqmodem_destroy(mod);
freqmodem_destroy(demod);
return 0;
}
int main(int argc, char*argv[])
{
// options
unsigned int num_channels=16; // number of channels
unsigned int m = 5; // filter semi-length (symbols)
unsigned int num_symbols=25; // number of symbols
float As = 80.0f; // filter stop-band attenuation
int dopt;
while ((dopt = getopt(argc,argv,"hM:m:s:n:")) != EOF) {
switch (dopt) {
case 'h': usage(); return 0;
case 'M': num_channels = atoi(optarg); break;
case 'm': m = atoi(optarg); break;
case 's': As = atof(optarg); break;
case 'n': num_symbols = atof(optarg); break;
default:
exit(1);
}
}
unsigned int i;
// validate input
if (num_channels < 2 || num_channels % 2) {
fprintf(stderr,"error: %s, number of channels must be greater than 2 and even\n", argv[0]);
exit(1);
} else if (m == 0) {
fprintf(stderr,"error: %s, filter semi-length must be greater than zero\n", argv[0]);
exit(1);
} else if (num_symbols == 0) {
fprintf(stderr,"error: %s, number of symbols must be greater than zero", argv[0]);
exit(1);
}
// derived values
unsigned int num_samples = num_channels * num_symbols;
// allocate arrays
float complex x[num_samples];
float complex y[num_samples];
// generate input signal
unsigned int w_len = (unsigned int)(0.4*num_samples);
for (i=0; i<num_samples; i++) {
//x[i] = (i==0) ? 1.0f : 0.0f;
//x[i] = cexpf( (-0.05f + 0.07f*_Complex_I)*i ); // decaying complex exponential
x[i] = cexpf( _Complex_I * (1.3f*i - 0.007f*i*i) );
x[i] *= i < w_len ? hamming(i,w_len) : 0.0f;
//x[i] = (i==0) ? 1.0f : 0.0f;
}
// create filterbank objects from prototype
firpfbch2_crcf qa = firpfbch2_crcf_create_kaiser(LIQUID_ANALYZER, num_channels, m, As);
firpfbch2_crcf qs = firpfbch2_crcf_create_kaiser(LIQUID_SYNTHESIZER, num_channels, m, As);
firpfbch2_crcf_print(qa);
firpfbch2_crcf_print(qs);
// run channelizer
float complex Y[num_channels];
for (i=0; i<num_samples; i+=num_channels/2) {
// run analysis filterbank
firpfbch2_crcf_execute(qa, &x[i], Y);
// run synthesis filterbank
firpfbch2_crcf_execute(qs, Y, &y[i]);
}
// destroy fiterbank objects
firpfbch2_crcf_destroy(qa); // analysis fitlerbank
firpfbch2_crcf_destroy(qs); // synthesis filterbank
// print output
for (i=0; i<num_samples; i++)
printf("%4u : %12.8f + %12.8fj\n", i, crealf(y[i]), cimagf(y[i]));
// compute RMSE
float rmse = 0.0f;
unsigned int delay = 2*num_channels*m - num_channels/2 + 1;
for (i=0; i<num_samples; i++) {
float complex err = y[i] - (i < delay ? 0.0f : x[i-delay]);
rmse += crealf( err*conjf(err) );
}
rmse = sqrtf( rmse/(float)num_samples );
printf("rmse : %12.4e\n", rmse);
//
// EXPORT DATA TO FILES
//
FILE * fid = NULL;
fid = fopen(OUTPUT_FILENAME_TIME,"w");
fprintf(fid,"# %s: auto-generated file\n", OUTPUT_FILENAME_TIME);
fprintf(fid,"#\n");
fprintf(fid,"# %8s %12s %12s %12s %12s %12s %12s\n",
"time", "real(x)", "imag(x)", "real(y)", "imag(y)", "real(e)", "imag(e)");
// save input and output arrays
for (i=0; i<num_samples; i++) {
float complex e = (i < delay) ? 0.0f : y[i] - x[i-delay];
fprintf(fid," %8.1f %12.4e %12.4e %12.4e %12.4e %12.4e %12.4e\n",
(float)i,
crealf(x[i]), cimagf(x[i]),
crealf(y[i]), cimagf(y[i]),
crealf(e), cimagf(e));
}
fclose(fid);
printf("results written to '%s'\n", OUTPUT_FILENAME_TIME);
//
// export frequency data
//
unsigned int nfft = 2048;
float complex y_time[nfft];
float complex y_freq[nfft];
for (i=0; i<nfft; i++)
y_time[i] = i < num_samples ? y[i] : 0.0f;
fft_run(nfft, y_time, y_freq, LIQUID_FFT_FORWARD, 0);
// filter spectrum
unsigned int h_len = 2*num_channels*m+1;
float h[h_len];
float fc = 0.5f/(float)num_channels;
liquid_firdes_kaiser(h_len, fc, As, 0.0f, h);
float complex h_time[nfft];
float complex h_freq[nfft];
for (i=0; i<nfft; i++)
h_time[i] = i < h_len ? 2*h[i]*fc : 0.0f;
fft_run(nfft, h_time, h_freq, LIQUID_FFT_FORWARD, 0);
// error spectrum
float complex e_time[nfft];
float complex e_freq[nfft];
for (i=0; i<nfft; i++)
e_time[i] = i < delay || i > num_samples ? 0.0f : y[i] - x[i-delay];
fft_run(nfft, e_time, e_freq, LIQUID_FFT_FORWARD, 0);
fid = fopen(OUTPUT_FILENAME_FREQ,"w");
fprintf(fid,"# %s: auto-generated file\n", OUTPUT_FILENAME_FREQ);
fprintf(fid,"#\n");
fprintf(fid,"# nfft = %u\n", nfft);
fprintf(fid,"# %12s %12s %12s %12s\n", "freq", "PSD [dB]", "filter [dB]", "error [dB]");
// save input and output arrays
for (i=0; i<nfft; i++) {
float f = (float)i/(float)nfft - 0.5f;
unsigned int k = (i + nfft/2)%nfft;
fprintf(fid," %12.8f %12.8f %12.8f %12.8f\n",
f,
20*log10f(cabsf(y_freq[k])),
20*log10f(cabsf(h_freq[k])),
20*log10f(cabsf(e_freq[k])));
}
fclose(fid);
printf("results written to '%s'\n", OUTPUT_FILENAME_FREQ);
printf("done.\n");
return 0;
}
void DemodulatorWorkerThread::threadMain() {
std::cout << "Demodulator worker thread started.." << std::endl;
while (!terminated) {
bool filterChanged = false;
DemodulatorWorkerThreadCommand filterCommand;
DemodulatorWorkerThreadCommand command;
bool done = false;
while (!done) {
commandQueue->pop(command);
switch (command.cmd) {
case DemodulatorWorkerThreadCommand::DEMOD_WORKER_THREAD_CMD_BUILD_FILTERS:
filterChanged = true;
filterCommand = command;
break;
default:
break;
}
done = commandQueue->empty();
}
if (filterChanged && !terminated) {
DemodulatorWorkerThreadResult result(DemodulatorWorkerThreadResult::DEMOD_WORKER_THREAD_RESULT_FILTERS);
float As = 60.0f; // stop-band attenuation [dB]
if (filterCommand.sampleRate && filterCommand.bandwidth) {
result.iqResampleRatio = (double) (filterCommand.bandwidth) / (double) filterCommand.sampleRate;
result.iqResampler = msresamp_crcf_create(result.iqResampleRatio, As);
}
if (filterCommand.bandwidth && filterCommand.audioSampleRate) {
result.audioResamplerRatio = (double) (filterCommand.audioSampleRate) / (double) filterCommand.bandwidth;
result.audioResampler = msresamp_rrrf_create(result.audioResamplerRatio, As);
result.stereoResampler = msresamp_rrrf_create(result.audioResamplerRatio, As);
result.audioSampleRate = filterCommand.audioSampleRate;
// Stereo filters / shifters
double firStereoCutoff = ((double) 16000 / (double) filterCommand.audioSampleRate);
float ft = ((double) 1000 / (double) filterCommand.audioSampleRate); // filter transition
float mu = 0.0f; // fractional timing offset
if (firStereoCutoff < 0) {
firStereoCutoff = 0;
}
if (firStereoCutoff > 0.5) {
firStereoCutoff = 0.5;
}
unsigned int h_len = estimate_req_filter_len(ft, As);
float *h = new float[h_len];
liquid_firdes_kaiser(h_len, firStereoCutoff, As, mu, h);
result.firStereoLeft = firfilt_rrrf_create(h, h_len);
result.firStereoRight = firfilt_rrrf_create(h, h_len);
float bw = filterCommand.bandwidth;
if (bw < 100000.0) {
bw = 100000.0;
}
// stereo pilot filter
unsigned int order = 5; // filter order
float f0 = ((double) 19000 / bw);
float fc = ((double) 19500 / bw);
float Ap = 1.0f;
As = 60.0f;
result.iirStereoPilot = iirfilt_crcf_create_prototype(LIQUID_IIRDES_CHEBY2, LIQUID_IIRDES_BANDPASS, LIQUID_IIRDES_SOS, order, fc, f0, Ap, As);
}
if (filterCommand.bandwidth) {
result.bandwidth = filterCommand.bandwidth;
}
if (filterCommand.sampleRate) {
result.sampleRate = filterCommand.sampleRate;
}
resultQueue->push(result);
}
}
std::cout << "Demodulator worker thread done." << std::endl;
}
int main(int argc, char*argv[]) {
// options
unsigned int k=4; // samples/symbol
unsigned int m=3; // filter delay [symbols]
float BT = 0.3f; // bandwidth-time product
// read properties from command line
int dopt;
while ((dopt = getopt(argc,argv,"uhk:m:b:")) != EOF) {
switch (dopt) {
case 'u':
case 'h': usage(); return 0;
case 'k': k = atoi(optarg); break;
case 'm': m = atoi(optarg); break;
case 'b': BT = atof(optarg); break;
default:
exit(1);
}
}
// validate input
if (k < 2) {
fprintf(stderr,"error: %s, k must be at least 2\n", argv[0]);
exit(1);
} else if (m < 1) {
fprintf(stderr,"error: %s, m must be at least 1\n", argv[0]);
exit(1);
} else if (BT <= 0.0f || BT >= 1.0f) {
fprintf(stderr,"error: %s, BT must be in (0,1)\n", argv[0]);
exit(1);
}
unsigned int i;
// derived values
unsigned int h_len = 2*k*m+1; // filter length
// arrays
float ht[h_len]; // transmit filter coefficients
float hr[h_len]; // recieve filter coefficients
// design transmit filter
liquid_firdes_gmsktx(k,m,BT,0.0f,ht);
// print results to screen
printf("gmsk transmit filter:\n");
for (i=0; i<h_len; i++)
printf(" ht(%3u) = %12.8f;\n", i+1, ht[i]);
//
// start of filter design procedure
//
float beta = BT; // prototype filter cut-off
float delta = 1e-2f; // filter design correction factor
// temporary arrays
float h_primef[h_len]; // temporary buffer for real coefficients
float g_primef[h_len]; //
float complex h_tx[h_len]; // impulse response of transmit filter
float complex h_prime[h_len]; // impulse response of 'prototype' filter
float complex g_prime[h_len]; // impulse response of 'gain' filter
float complex h_hat[h_len]; // impulse response of receive filter
float complex H_tx[h_len]; // frequency response of transmit filter
float complex H_prime[h_len]; // frequency response of 'prototype' filter
float complex G_prime[h_len]; // frequency response of 'gain' filter
float complex H_hat[h_len]; // frequency response of receive filter
// create 'prototype' matched filter
// for now use raised-cosine
liquid_firdes_nyquist(LIQUID_NYQUIST_RCOS,k,m,beta,0.0f,h_primef);
// create 'gain' filter to improve stop-band rejection
float fc = (0.7f + 0.1*beta) / (float)k;
float As = 60.0f;
liquid_firdes_kaiser(h_len, fc, As, 0.0f, g_primef);
// copy to fft input buffer, shifting appropriately
for (i=0; i<h_len; i++) {
h_prime[i] = h_primef[ (i+k*m)%h_len ];
g_prime[i] = g_primef[ (i+k*m)%h_len ];
h_tx[i] = ht[ (i+k*m)%h_len ];
}
// run ffts
fft_run(h_len, h_prime, H_prime, FFT_FORWARD, 0);
fft_run(h_len, g_prime, G_prime, FFT_FORWARD, 0);
fft_run(h_len, h_tx, H_tx, FFT_FORWARD, 0);
#if 0
// print results
for (i=0; i<h_len; i++)
printf("Ht(%3u) = %12.8f + j*%12.8f;\n", i+1, crealf(H_tx[i]), cimagf(H_tx[i]));
for (i=0; i<h_len; i++)
printf("H_prime(%3u) = %12.8f + j*%12.8f;\n", i+1, crealf(H_prime[i]), cimagf(H_prime[i]));
for (i=0; i<h_len; i++)
printf("G_prime(%3u) = %12.8f + j*%12.8f;\n", i+1, crealf(G_prime[i]), cimagf(G_prime[i]));
#endif
// find minimum of reponses
float H_tx_min = 0.0f;
float H_prime_min = 0.0f;
float G_prime_min = 0.0f;
for (i=0; i<h_len; i++) {
if (i==0 || crealf(H_tx[i]) < H_tx_min) H_tx_min = crealf(H_tx[i]);
if (i==0 || crealf(H_prime[i]) < H_prime_min) H_prime_min = crealf(H_prime[i]);
if (i==0 || crealf(G_prime[i]) < G_prime_min) G_prime_min = crealf(G_prime[i]);
}
// compute 'prototype' response, removing minima, and add correction factor
for (i=0; i<h_len; i++) {
// compute response necessary to yeild prototype response (not exact, but close)
H_hat[i] = crealf(H_prime[i] - H_prime_min + delta) / crealf(H_tx[i] - H_tx_min + delta);
// include additional term to add stop-band suppression
H_hat[i] *= crealf(G_prime[i] - G_prime_min) / crealf(G_prime[0]);
}
// compute ifft and copy response
fft_run(h_len, H_hat, h_hat, FFT_REVERSE, 0);
for (i=0; i<h_len; i++)
hr[i] = crealf( h_hat[(i+k*m+1)%h_len] ) / (float)(k*h_len);
//
// end of filter design procedure
//
// print results to screen
printf("gmsk receive filter:\n");
for (i=0; i<h_len; i++)
printf(" hr(%3u) = %12.8f;\n", i+1, hr[i]);
// compute isi
float rxy0 = liquid_filter_crosscorr(ht,h_len, hr,h_len, 0);
float isi_rms = 0.0f;
for (i=1; i<2*m; i++) {
float e = liquid_filter_crosscorr(ht,h_len, hr,h_len, i*k) / rxy0;
isi_rms += e*e;
}
isi_rms = sqrtf(isi_rms / (float)(2*m-1));
printf("\n");
printf("ISI (RMS) = %12.8f dB\n", 20*log10f(isi_rms));
//
// 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");
fprintf(fid,"\n\n");
fprintf(fid,"k = %u;\n", k);
fprintf(fid,"m = %u;\n", m);
fprintf(fid,"beta = %f;\n", BT);
fprintf(fid,"h_len = 2*k*m+1;\n");
fprintf(fid,"nfft = 1024;\n");
fprintf(fid,"ht = zeros(1,h_len);\n");
fprintf(fid,"hp = zeros(1,h_len);\n");
fprintf(fid,"hr = zeros(1,h_len);\n");
// print results
for (i=0; i<h_len; i++) fprintf(fid,"ht(%3u) = %12.4e;\n", i+1, ht[i] / k);
for (i=0; i<h_len; i++) fprintf(fid,"hr(%3u) = %12.4e;\n", i+1, hr[i] * k);
for (i=0; i<h_len; i++) fprintf(fid,"hp(%3u) = %12.4e;\n", i+1, h_primef[i]);
fprintf(fid,"hc = k*conv(ht,hr);\n");
// plot results
fprintf(fid,"f = [0:(nfft-1)]/nfft - 0.5;\n");
fprintf(fid,"Ht = 20*log10(abs(fftshift(fft(ht, nfft))));\n");
fprintf(fid,"Hp = 20*log10(abs(fftshift(fft(hp/k,nfft))));\n");
fprintf(fid,"Hr = 20*log10(abs(fftshift(fft(hr, nfft))));\n");
fprintf(fid,"Hc = 20*log10(abs(fftshift(fft(hc/k,nfft))));\n");
fprintf(fid,"\n");
fprintf(fid,"figure;\n");
fprintf(fid,"plot(f,Ht,'LineWidth',1,'Color',[0.00 0.25 0.50],...\n");
fprintf(fid," f,Hp,'LineWidth',1,'Color',[0.80 0.80 0.80],...\n");
fprintf(fid," f,Hr,'LineWidth',1,'Color',[0.00 0.50 0.25],...\n");
fprintf(fid," f,Hc,'LineWidth',2,'Color',[0.50 0.00 0.00],...\n");
fprintf(fid," [-0.5/k 0.5/k], [1 1]*20*log10(0.5),'or');\n");
fprintf(fid,"legend('transmit','prototype','receive','composite','alias points',1);\n");
fprintf(fid,"xlabel('Normalized Frequency');\n");
fprintf(fid,"ylabel('PSD');\n");
fprintf(fid,"grid on;\n");
fprintf(fid,"axis([-0.5 0.5 -100 20]);\n");
fprintf(fid,"\n");
fprintf(fid,"figure;\n");
fprintf(fid,"tr = [ -k*m:k*m]/k;\n");
fprintf(fid,"tc = [-2*k*m:2*k*m]/k;\n");
fprintf(fid,"ic = [0:k:(4*k*m)]+1;\n");
fprintf(fid,"subplot(2,1,1);\n");
fprintf(fid," plot(tr,ht,'-x', tr,hr,'-x');\n");
fprintf(fid," legend('transmit','receive',1);\n");
fprintf(fid," xlabel('Time');\n");
fprintf(fid," ylabel('GMSK Tx/Rx Filters');\n");
fprintf(fid," grid on;\n");
fprintf(fid," axis([-2*m 2*m floor(5*min([hr ht]))/5 ceil(5*max([hr ht]))/5]);\n");
fprintf(fid,"subplot(2,1,2);\n");
fprintf(fid," plot(tc,hc,'-x', tc(ic),hc(ic),'or');\n");
fprintf(fid," xlabel('Time');\n");
fprintf(fid," ylabel('GMSK Composite Response');\n");
fprintf(fid," grid on;\n");
fprintf(fid," axis([-2*m 2*m -0.2 1.2]);\n");
fprintf(fid," axis([-2*m 2*m floor(5*min(hc))/5 ceil(5*max(hc))/5]);\n");
fclose(fid);
printf("results written to %s.\n", OUTPUT_FILENAME);
return 0;
}
int main() {
// options
unsigned int num_channels=8; // number of channels
unsigned int m=4; // filter delay
float As=60; // stop-band attenuation
unsigned int num_frames=25; // number of frames
//
unsigned int i;
unsigned int k;
// derived values
unsigned int num_samples = num_frames * num_channels;
// data arrays
float complex x[num_samples]; // time-domain input [size: num_samples x 1 ]
float complex y[num_samples]; // channelized output [size: num_channels x num_frames]
// initialize input with zeros
for (i=0; i<num_samples; i++)
x[i] = 0.0f;
// generate input signal(s)
unsigned int num_signals = 4;
float fc[4] = {0.0f, 0.25f, 0.375f, -0.375f}; // center frequencies
float bw[4] = {0.035f, 0.035f, 0.035f, 0.035f}; // bandwidths
unsigned int pulse_len = 137;
float pulse[pulse_len];
for (i=0; i<num_signals; i++) {
// create pulse
liquid_firdes_kaiser(pulse_len, bw[i], 50.0f, 0.0f, pulse);
// add pulse to input signal with carrier offset
for (k=0; k<pulse_len; k++)
x[k] += pulse[k] * cexpf(_Complex_I*2*M_PI*fc[i]*k) * bw[i];
}
// create prototype filter
unsigned int h_len = 2*num_channels*m + 1;
float h[h_len];
liquid_firdes_kaiser(h_len, 0.5f/(float)num_channels, As, 0.0f, h);
#if 0
// create filterbank channelizer object using internal method for filter
firpfbch_crcf q = firpfbch_crcf_create_kaiser(LIQUID_ANALYZER, num_channels, m, As);
#else
// create filterbank channelizer object using external filter coefficients
firpfbch_crcf q = firpfbch_crcf_create(LIQUID_ANALYZER, num_channels, 2*m, h);
#endif
// channelize input data
for (i=0; i<num_frames; i++) {
// execute analysis filter bank
firpfbch_crcf_analyzer_execute(q, &x[i*num_channels], &y[i*num_channels]);
}
// destroy channelizer object
firpfbch_crcf_destroy(q);
//
// export results to file
//
FILE * fid = fopen(OUTPUT_FILENAME,"w");
fprintf(fid,"%% %s: auto-generated file\n\n", OUTPUT_FILENAME);
fprintf(fid,"clear all;\n");
fprintf(fid,"close all;\n");
fprintf(fid,"num_channels = %u;\n", num_channels);
fprintf(fid,"m = %u;\n", m);
fprintf(fid,"num_frames = %u;\n", num_frames);
fprintf(fid,"h_len = 2*num_channels*m+1;\n");
fprintf(fid,"num_samples = num_frames*num_channels;\n");
fprintf(fid,"h = zeros(1,h_len);\n");
fprintf(fid,"x = zeros(1,num_samples);\n");
fprintf(fid,"y = zeros(num_channels, num_frames);\n");
// save prototype filter
for (i=0; i<h_len; i++)
fprintf(fid," h(%6u) = %12.4e;\n", i+1, h[i]);
// save input signal
for (i=0; i<num_samples; i++)
fprintf(fid," x(%6u) = %12.4e + 1i*%12.4e;\n", i+1, crealf(x[i]), cimagf(x[i]));
// save channelized output signals
for (i=0; i<num_frames; i++) {
for (k=0; k<num_channels; k++) {
float complex v = y[i*num_channels + k];
fprintf(fid," y(%3u,%6u) = %12.4e + 1i*%12.4e;\n", k+1, i+1, crealf(v), cimagf(v));
}
}
// plot results
fprintf(fid,"\n");
fprintf(fid,"nfft = 1024;\n"); // TODO: use nextpow2
fprintf(fid,"f = [0:(nfft-1)]/nfft - 0.5;\n");
fprintf(fid,"H = 20*log10(abs(fftshift(fft(h/num_channels,nfft))));\n");
fprintf(fid,"X = 20*log10(abs(fftshift(fft(x,nfft))));\n");
fprintf(fid,"figure;\n");
fprintf(fid,"subplot(2,1,1);\n");
fprintf(fid," plot(f, H, 'Color', [0 0.5 0.25], 'LineWidth', 2);\n");
fprintf(fid," axis([-0.5 0.5 -100 10]);\n");
fprintf(fid," grid on;\n");
fprintf(fid," xlabel('Normalized Frequency [f/F_s]');\n");
fprintf(fid," ylabel('Prototype Filter PSD');\n");
fprintf(fid,"subplot(2,1,2);\n");
fprintf(fid," plot(f, X, 'Color', [0 0.25 0.5], 'LineWidth', 2);\n");
fprintf(fid," axis([-0.5 0.5 -100 0]);\n");
fprintf(fid," grid on;\n");
fprintf(fid," xlabel('Normalized Frequency [f/F_s]');\n");
fprintf(fid," ylabel('Input PSD');\n");
// compute the PSD of each output and plot results on a square grid
fprintf(fid,"n = ceil(sqrt(num_channels));\n");
fprintf(fid,"figure;\n");
fprintf(fid,"for i=1:num_channels,\n");
fprintf(fid," Y = 20*log10(abs(fftshift(fft(y(i,:),nfft))));\n");
fprintf(fid," subplot(n,n,i);\n");
fprintf(fid," plot(f, Y, 'Color', [0.25 0 0.25], 'LineWidth', 1.5);\n");
fprintf(fid," axis([-0.5 0.5 -120 20]);\n");
fprintf(fid," grid on;\n");
fprintf(fid," title(num2str(i-1));\n");
fprintf(fid,"end;\n");
fclose(fid);
printf("results written to %s\n", OUTPUT_FILENAME);
printf("done.\n");
return 0;
}
// Design (root-)Nyquist filter from prototype
// _type : filter type (e.g. LIQUID_FIRFILT_RRRC)
// _k : samples/symbol
// _m : symbol delay
// _beta : excess bandwidth factor, _beta in [0,1]
// _dt : fractional sample delay
// _h : output coefficient buffer (length: 2*k*m+1)
void liquid_firdes_prototype(liquid_firfilt_type _type,
unsigned int _k,
unsigned int _m,
float _beta,
float _dt,
float * _h)
{
// compute filter parameters
unsigned int h_len = 2*_k*_m + 1; // length
float fc = 0.5f / (float)_k; // cut-off frequency
float df = _beta / (float)_k; // transition bandwidth
float As = estimate_req_filter_As(df,h_len); // stop-band attenuation
// Parks-McClellan algorithm parameters
float bands[6] = { 0.0f, fc-0.5f*df,
fc, fc,
fc+0.5f*df, 0.5f};
float des[3] = { (float)_k, 0.5f*_k, 0.0f };
float weights[3] = {1.0f, 1.0f, 1.0f};
liquid_firdespm_wtype wtype[3] = { LIQUID_FIRDESPM_FLATWEIGHT,
LIQUID_FIRDESPM_FLATWEIGHT,
LIQUID_FIRDESPM_FLATWEIGHT};
switch (_type) {
// Nyquist filter prototypes
case LIQUID_FIRFILT_KAISER:
liquid_firdes_kaiser(h_len, fc, As, _dt, _h);
break;
case LIQUID_FIRFILT_PM:
// WARNING: input timing offset is ignored here
firdespm_run(h_len, 3, bands, des, weights, wtype, LIQUID_FIRDESPM_BANDPASS, _h);
break;
case LIQUID_FIRFILT_RCOS:
liquid_firdes_rcos(_k, _m, _beta, _dt, _h);
break;
case LIQUID_FIRFILT_FEXP:
liquid_firdes_fexp(_k, _m, _beta, _dt, _h);
break;
case LIQUID_FIRFILT_FSECH:
liquid_firdes_fsech(_k, _m, _beta, _dt, _h);
break;
case LIQUID_FIRFILT_FARCSECH:
liquid_firdes_farcsech(_k, _m, _beta, _dt, _h);
break;
// root-Nyquist filter prototypes
case LIQUID_FIRFILT_ARKAISER:
liquid_firdes_arkaiser(_k, _m, _beta, _dt, _h);
break;
case LIQUID_FIRFILT_RKAISER:
liquid_firdes_rkaiser(_k, _m, _beta, _dt, _h);
break;
case LIQUID_FIRFILT_RRC:
liquid_firdes_rrcos(_k, _m, _beta, _dt, _h);
break;
case LIQUID_FIRFILT_hM3:
liquid_firdes_hM3(_k, _m, _beta, _dt, _h);
break;
case LIQUID_FIRFILT_GMSKTX:
liquid_firdes_gmsktx(_k, _m, _beta, _dt, _h);
break;
case LIQUID_FIRFILT_GMSKRX:
liquid_firdes_gmskrx(_k, _m, _beta, _dt, _h);
break;
case LIQUID_FIRFILT_RFEXP:
liquid_firdes_rfexp(_k, _m, _beta, _dt, _h);
break;
case LIQUID_FIRFILT_RFSECH:
liquid_firdes_rfsech(_k, _m, _beta, _dt, _h);
break;
case LIQUID_FIRFILT_RFARCSECH:
liquid_firdes_rfarcsech(_k, _m, _beta, _dt, _h);
break;
default:
fprintf(stderr,"error: liquid_firdes_prototype(), invalid root-Nyquist filter type '%d'\n", _type);
exit(1);
}
}
int main() {
// options
unsigned int num_channels = 16; // number of channels
unsigned int m = 5; // filter delay
float As = 60; // stop-band attenuation
unsigned int num_frames = 25; // number of frames
//
unsigned int i;
unsigned int k;
// derived values
unsigned int num_samples = num_frames * num_channels;
// data arrays
float complex x[num_channels][num_frames]; // channelized input
float complex y[num_samples]; // time-domain output [size: num_samples x 1]
// create narrow-band pulse
unsigned int pulse_len = 17; // pulse length [samples]
float bw = 0.30f; // pulse width (bandwidth)
float pulse[pulse_len]; // buffer
liquid_firdes_kaiser(pulse_len, bw, 50.0f, 0.0f, pulse);
// generate input signal(s)
int enabled[num_channels]; // signal enabled?
for (i=0; i<num_channels; i++) {
// pseudo-random channel enabled flag
enabled[i] = ((i*37)%101)%2;
if (enabled[i]) {
// move pulse to input buffer
for (k=0; k<num_frames; k++)
x[i][k] = k < pulse_len ? bw*pulse[k] : 0.0f;
} else {
// channel disabled; set as nearly zero (-100 dB impulse)
for (k=0; k<num_frames; k++)
x[i][k] = (k == 0) ? 1e-5f : 0.0f;
}
}
// create prototype filter
unsigned int h_len = 2*num_channels*m + 1;
float h[h_len];
liquid_firdes_kaiser(h_len, 0.5f/(float)num_channels, As, 0.0f, h);
#if 0
// create filterbank channelizer object using internal method for filter
firpfbch_crcf q = firpfbch_crcf_create_kaiser(LIQUID_SYNTHESIZER, num_channels, m, As);
#else
// create filterbank channelizer object using external filter coefficients
firpfbch_crcf q = firpfbch_crcf_create(LIQUID_SYNTHESIZER, num_channels, 2*m, h);
#endif
// channelize input data
float complex v[num_channels];
for (i=0; i<num_frames; i++) {
// assemble input vector
for (k=0; k<num_channels; k++)
v[k] = x[k][i];
// execute synthesis filter bank
firpfbch_crcf_synthesizer_execute(q, v, &y[i*num_channels]);
}
// destroy channelizer object
firpfbch_crcf_destroy(q);
//
// export results to file
//
FILE * fid = fopen(OUTPUT_FILENAME,"w");
fprintf(fid,"%% %s: auto-generated file\n\n", OUTPUT_FILENAME);
fprintf(fid,"clear all;\n");
fprintf(fid,"close all;\n");
fprintf(fid,"num_channels = %u;\n", num_channels);
fprintf(fid,"m = %u;\n", m);
fprintf(fid,"num_frames = %u;\n", num_frames);
fprintf(fid,"h_len = 2*num_channels*m+1;\n");
fprintf(fid,"num_samples = num_frames*num_channels;\n");
fprintf(fid,"h = zeros(1,h_len);\n");
fprintf(fid,"x = zeros(num_channels, num_frames);\n");
fprintf(fid,"y = zeros(1,num_samples);\n");
// save prototype filter
for (i=0; i<h_len; i++)
fprintf(fid," h(%6u) = %12.4e;\n", i+1, h[i]);
// save channelized input signals
for (i=0; i<num_frames; i++) {
for (k=0; k<num_channels; k++) {
float complex v = x[k][i];
fprintf(fid," x(%3u,%6u) = %12.4e + 1i*%12.4e;\n", k+1, i+1, crealf(v), cimagf(v));
}
}
// save output time signal
for (i=0; i<num_samples; i++)
fprintf(fid," y(%6u) = %12.4e + 1i*%12.4e;\n", i+1, crealf(y[i]), cimagf(y[i]));
// compute the PSD of each input and plot results on a square grid
fprintf(fid,"nfft = 1024;\n"); // TODO: use nextpow2
fprintf(fid,"f = [0:(nfft-1)]/nfft - 0.5;\n");
fprintf(fid,"n = ceil(sqrt(num_channels));\n");
fprintf(fid,"figure;\n");
fprintf(fid,"for i=1:num_channels,\n");
fprintf(fid," X = 20*log10(abs(fftshift(fft(x(i,:),nfft))));\n");
fprintf(fid," subplot(n,n,i);\n");
fprintf(fid," plot(f, X, 'Color', [0.25 0 0.25], 'LineWidth', 1.5);\n");
fprintf(fid," axis([-0.5 0.5 -120 20]);\n");
fprintf(fid," grid on;\n");
fprintf(fid," title(num2str(i-1));\n");
fprintf(fid,"end;\n");
// plot results
fprintf(fid,"\n");
fprintf(fid,"H = 20*log10(abs(fftshift(fft(h/num_channels,nfft))));\n");
fprintf(fid,"Y = 20*log10(abs(fftshift(fft(y/num_channels,nfft))));\n");
fprintf(fid,"figure;\n");
fprintf(fid,"subplot(2,1,1);\n");
fprintf(fid," plot(f, H, 'Color', [0 0.5 0.25], 'LineWidth', 2);\n");
fprintf(fid," axis([-0.5 0.5 -100 10]);\n");
fprintf(fid," grid on;\n");
fprintf(fid," xlabel('Normalized Frequency [f/F_s]');\n");
fprintf(fid," ylabel('Prototype Filter PSD');\n");
fprintf(fid,"subplot(2,1,2);\n");
fprintf(fid," plot(f, Y, 'Color', [0 0.25 0.5], 'LineWidth', 2);\n");
fprintf(fid," axis([-0.5 0.5 -100 0]);\n");
fprintf(fid," grid on;\n");
fprintf(fid," xlabel('Normalized Frequency [f/F_s]');\n");
fprintf(fid," ylabel('Output PSD');\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;
}
// Design frequency-shifted root-Nyquist filter based on
// the Kaiser-windowed sinc using approximation for rho.
//
// _k : filter over-sampling rate (samples/symbol)
// _m : filter delay (symbols)
// _beta : filter excess bandwidth factor (0,1)
// _dt : filter fractional sample delay
// _h : resulting filter [size: 2*_k*_m+1]
void liquid_firdes_arkaiser(unsigned int _k,
unsigned int _m,
float _beta,
float _dt,
float * _h)
{
// validate input
if (_k < 2) {
fprintf(stderr,"error: liquid_firdes_arkaiser(), k must be at least 2\n");
exit(1);
} else if (_m < 1) {
fprintf(stderr,"error: liquid_firdes_arkaiser(), m must be at least 1\n");
exit(1);
} else if (_beta <= 0.0f || _beta >= 1.0f) {
fprintf(stderr,"error: liquid_firdes_arkaiser(), beta must be in (0,1)\n");
exit(1);
} else if (_dt < -1.0f || _dt > 1.0f) {
fprintf(stderr,"error: liquid_firdes_arkaiser(), dt must be in [-1,1]\n");
exit(1);
}
#if 0
// compute bandwidth adjustment estimate
float rho_hat = rkaiser_approximate_rho(_m,_beta); // bandwidth correction factor
#else
// rho ~ c0 + c1*log(_beta) + c2*log^2(_beta)
// c0 ~ 0.762886 + 0.067663*log(m)
// c1 ~ 0.065515
// c2 ~ log( 1 - 0.088*m^-1.6 )
float c0 = 0.762886 + 0.067663*logf(_m);
float c1 = 0.065515;
float c2 = logf( 1 - 0.088*powf(_m,-1.6 ) );
float log_beta = logf(_beta);
float rho_hat = c0 + c1*log_beta + c2*log_beta*log_beta;
// ensure range is valid
if (rho_hat <= 0.0f || rho_hat >= 1.0f)
rho_hat = rkaiser_approximate_rho(_m,_beta);
#endif
unsigned int n=2*_k*_m+1; // filter length
float kf = (float)_k; // samples/symbol (float)
float del = _beta*rho_hat / kf; // transition bandwidth
float As = estimate_req_filter_As(del, n); // stop-band suppression
float fc = 0.5f*(1 + _beta*(1.0f-rho_hat))/kf; // filter cutoff
#if DEBUG_RKAISER
printf("rho-hat : %12.8f (compare to %12.8f)\n", rho_hat, rkaiser_approximate_rho(_m,_beta));
printf("fc : %12.8f\n", fc);
printf("delta-f : %12.8f\n", del);
printf("As : %12.8f dB\n", As);
printf("alpha : %12.8f\n", kaiser_beta_As(As));
#endif
// compute filter coefficients
liquid_firdes_kaiser(n,fc,As,_dt,_h);
// normalize coefficients
float e2 = 0.0f;
unsigned int i;
for (i=0; i<n; i++) e2 += _h[i]*_h[i];
for (i=0; i<n; i++) _h[i] *= sqrtf(_k/e2);
}
// Design GMSK receive filter
// _k : samples/symbol
// _m : symbol delay
// _beta : rolloff factor (0 < beta <= 1)
// _dt : fractional sample delay
// _h : output coefficient buffer (length: 2*k*m+1)
void liquid_firdes_gmskrx(unsigned int _k,
unsigned int _m,
float _beta,
float _dt,
float * _h)
{
// validate input
if ( _k < 1 ) {
fprintf(stderr,"error: liquid_firdes_gmskrx(): k must be greater than 0\n");
exit(1);
} else if ( _m < 1 ) {
fprintf(stderr,"error: liquid_firdes_gmskrx(): m must be greater than 0\n");
exit(1);
} else if ( (_beta < 0.0f) || (_beta > 1.0f) ) {
fprintf(stderr,"error: liquid_firdes_gmskrx(): beta must be in [0,1]\n");
exit(1);
} else;
unsigned int k = _k;
unsigned int m = _m;
float BT = _beta;
// internal options
float beta = BT; // prototype filter cut-off
float delta = 1e-3f; // filter design correction factor
liquid_firfilt_type prototype = LIQUID_FIRFILT_KAISER; // Nyquist prototype
unsigned int i;
// derived values
unsigned int h_len = 2*k*m+1; // filter length
// arrays
float ht[h_len]; // transmit filter coefficients
float hr[h_len]; // recieve filter coefficients
// design transmit filter
liquid_firdes_gmsktx(k,m,BT,0.0f,ht);
//
// start of filter design procedure
//
// 'internal' arrays
float h_primef[h_len]; // temporary buffer for real 'prototype' coefficients
float g_primef[h_len]; // temporary buffer for real 'gain' coefficient
float complex h_tx[h_len]; // impulse response of transmit filter
float complex h_prime[h_len]; // impulse response of 'prototype' filter
float complex g_prime[h_len]; // impulse response of 'gain' filter
float complex h_hat[h_len]; // impulse response of receive filter
float complex H_tx[h_len]; // frequency response of transmit filter
float complex H_prime[h_len]; // frequency response of 'prototype' filter
float complex G_prime[h_len]; // frequency response of 'gain' filter
float complex H_hat[h_len]; // frequency response of receive filter
// create 'prototype' matched filter
liquid_firdes_nyquist(prototype,k,m,beta,0.0f,h_primef);
// create 'gain' filter to improve stop-band rejection
float fc = (0.7f + 0.1*beta) / (float)k;
float As = 60.0f;
liquid_firdes_kaiser(h_len, fc, As, 0.0f, g_primef);
// copy to fft input buffer, shifting appropriately
for (i=0; i<h_len; i++) {
h_prime[i] = h_primef[ (i+k*m)%h_len ];
g_prime[i] = g_primef[ (i+k*m)%h_len ];
h_tx[i] = ht[ (i+k*m)%h_len ];
}
// run ffts
fft_run(h_len, h_prime, H_prime, LIQUID_FFT_FORWARD, 0);
fft_run(h_len, g_prime, G_prime, LIQUID_FFT_FORWARD, 0);
fft_run(h_len, h_tx, H_tx, LIQUID_FFT_FORWARD, 0);
// find minimum of reponses
float H_tx_min = 0.0f;
float H_prime_min = 0.0f;
float G_prime_min = 0.0f;
for (i=0; i<h_len; i++) {
if (i==0 || crealf(H_tx[i]) < H_tx_min) H_tx_min = crealf(H_tx[i]);
if (i==0 || crealf(H_prime[i]) < H_prime_min) H_prime_min = crealf(H_prime[i]);
if (i==0 || crealf(G_prime[i]) < G_prime_min) G_prime_min = crealf(G_prime[i]);
}
// compute 'prototype' response, removing minima, and add correction factor
for (i=0; i<h_len; i++) {
// compute response necessary to yeild prototype response (not exact, but close)
H_hat[i] = crealf(H_prime[i] - H_prime_min + delta) / crealf(H_tx[i] - H_tx_min + delta);
// include additional term to add stop-band suppression
H_hat[i] *= crealf(G_prime[i] - G_prime_min) / crealf(G_prime[0]);
}
// compute ifft and copy response
fft_run(h_len, H_hat, h_hat, LIQUID_FFT_BACKWARD, 0);
for (i=0; i<h_len; i++)
hr[i] = crealf( h_hat[(i+k*m+1)%h_len] ) / (float)(k*h_len);
// copy result, scaling by (samples/symbol)^2
for (i=0; i<h_len; i++)
_h[i] = hr[i]*_k*_k;
}
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(int argc, char*argv[])
{
// options
unsigned int num_channels=6; // number of channels (must be even)
unsigned int m=4; // filter delay
unsigned int num_symbols=4*m; // number of symbols
// validate input
if (num_channels%2) {
fprintf(stderr,"error: %s, number of channels must be even\n", argv[0]);
exit(1);
}
// derived values
unsigned int num_samples = num_channels * num_symbols;
unsigned int i;
unsigned int j;
// generate filter
// NOTE : these coefficients can be random; the purpose of this
// exercise is to demonstrate mathematical equivalence
#if 0
unsigned int h_len = 2*m*num_channels;
float h[h_len];
for (i=0; i<h_len; i++) h[i] = randnf();
#else
unsigned int h_len = 2*m*num_channels+1;
float h[h_len];
// NOTE: 81.29528 dB > beta = 8.00000 (6 channels, m=4)
liquid_firdes_kaiser(h_len, 1.0f/(float)num_channels, 81.29528f, 0.0f, h);
#endif
// normalize
float hsum = 0.0f;
for (i=0; i<h_len; i++) hsum += h[i];
for (i=0; i<h_len; i++) h[i] = h[i] * num_channels / hsum;
// sub-sampled filters for M=6 channels, m=4, beta=8.0
// -3.2069e-19 -6.7542e-04 -1.3201e-03 2.2878e-18 3.7613e-03 5.8033e-03
// -7.2899e-18 -1.2305e-02 -1.7147e-02 1.6510e-17 3.1187e-02 4.0974e-02
// -3.0032e-17 -6.8026e-02 -8.6399e-02 4.6273e-17 1.3732e-01 1.7307e-01
// -6.2097e-17 -2.8265e-01 -3.7403e-01 7.3699e-17 8.0663e-01 1.6438e+00
// 2.0001e+00 1.6438e+00 8.0663e-01 7.3699e-17 -3.7403e-01 -2.8265e-01
// -6.2097e-17 1.7307e-01 1.3732e-01 4.6273e-17 -8.6399e-02 -6.8026e-02
// -3.0032e-17 4.0974e-02 3.1187e-02 1.6510e-17 -1.7147e-02 -1.2305e-02
// -7.2899e-18 5.8033e-03 3.7613e-03 2.2878e-18 -1.3201e-03 -6.7542e-04
// create filterbank manually
dotprod_crcf dp[num_channels]; // vector dot products
windowcf w[num_channels]; // window buffers
#if DEBUG
// print coefficients
printf("h_prototype:\n");
for (i=0; i<h_len; i++)
printf(" h[%3u] = %12.8f\n", i, h[i]);
#endif
// create objects
unsigned int h_sub_len = 2*m;
float h_sub[h_sub_len];
for (i=0; i<num_channels; i++) {
// sub-sample prototype filter
#if 0
for (j=0; j<h_sub_len; j++)
h_sub[j] = h[j*num_channels+i];
#else
// load coefficients in reverse order
for (j=0; j<h_sub_len; j++)
h_sub[h_sub_len-j-1] = h[j*num_channels+i];
#endif
// create window buffer and dotprod objects
dp[i] = dotprod_crcf_create(h_sub, h_sub_len);
w[i] = windowcf_create(h_sub_len);
#if DEBUG
printf("h_sub[%u] : \n", i);
for (j=0; j<h_sub_len; j++)
printf(" h[%3u] = %12.8f\n", j, h_sub[j]);
#endif
}
// generate DFT object
float complex x[num_channels]; // time-domain buffer
float complex X[num_channels]; // freq-domain buffer
#if 1
fftplan fft = fft_create_plan(num_channels, X, x, LIQUID_FFT_BACKWARD, 0);
#else
fftplan fft = fft_create_plan(num_channels, X, x, LIQUID_FFT_FORWARD, 0);
#endif
float complex y[num_samples]; // time-domain input
float complex Y0[2*num_symbols][num_channels]; // channelizer output
float complex Y1[2*num_symbols][num_channels]; // conventional output
// generate input sequence
for (i=0; i<num_samples; i++) {
//y[i] = randnf() * cexpf(_Complex_I*randf()*2*M_PI);
y[i] = (i==0) ? 1.0f : 0.0f;
y[i] = cexpf(_Complex_I*sqrtf(2.0f)*i*i);
printf("y[%3u] = %12.8f + %12.8fj\n", i, crealf(y[i]), cimagf(y[i]));
}
//
// run analysis filter bank
//
#if 0
unsigned int filter_index = 0;
#else
unsigned int filter_index = num_channels/2-1;
#endif
float complex y_hat; // input sample
float complex * r; // buffer read pointer
int toggle = 0; // flag indicating buffer/filter alignment
//
for (i=0; i<2*num_symbols; i++) {
// load buffers in blocks of num_channels/2
for (j=0; j<num_channels/2; j++) {
// grab sample
y_hat = y[i*num_channels/2 + j];
// push sample into buffer at filter index
windowcf_push(w[filter_index], y_hat);
// decrement filter index
filter_index = (filter_index + num_channels - 1) % num_channels;
//filter_index = (filter_index + 1) % num_channels;
}
// execute filter outputs
// reversing order of output (not sure why this is necessary)
unsigned int offset = toggle ? num_channels/2 : 0;
toggle = 1-toggle;
for (j=0; j<num_channels; j++) {
unsigned int buffer_index = (offset+j)%num_channels;
unsigned int dotprod_index = j;
windowcf_read(w[buffer_index], &r);
//dotprod_crcf_execute(dp[dotprod_index], r, &X[num_channels-j-1]);
dotprod_crcf_execute(dp[dotprod_index], r, &X[buffer_index]);
}
printf("***** i = %u\n", i);
for (j=0; j<num_channels; j++)
printf(" v2[%4u] = %12.8f + %12.8fj\n", j, crealf(X[j]), cimagf(X[j]));
// execute DFT, store result in buffer 'x'
fft_execute(fft);
// scale fft output
for (j=0; j<num_channels; j++)
x[j] *= 1.0f / (num_channels);
// move to output array
for (j=0; j<num_channels; j++)
Y0[i][j] = x[j];
}
// destroy objects
for (i=0; i<num_channels; i++) {
dotprod_crcf_destroy(dp[i]);
windowcf_destroy(w[i]);
}
fft_destroy_plan(fft);
//
// run traditional down-converter (inefficient)
//
// generate filter object
firfilt_crcf f = firfilt_crcf_create(h, h_len);
float dphi; // carrier frequency
unsigned int n=0;
for (i=0; i<num_channels; i++) {
// reset filter
firfilt_crcf_clear(f);
// set center frequency
dphi = 2.0f * M_PI * (float)i / (float)num_channels;
// reset symbol counter
n=0;
for (j=0; j<num_samples; j++) {
// push down-converted sample into filter
firfilt_crcf_push(f, y[j]*cexpf(-_Complex_I*j*dphi));
// compute output at the appropriate sample time
assert(n<2*num_symbols);
if ( ((j+1)%(num_channels/2))==0 ) {
firfilt_crcf_execute(f, &Y1[n][i]);
n++;
}
}
assert(n==2*num_symbols);
}
firfilt_crcf_destroy(f);
// print filterbank channelizer
printf("\n");
printf("filterbank channelizer:\n");
for (i=0; i<2*num_symbols; i++) {
printf("%2u:", i);
for (j=0; j<num_channels; j++) {
printf("%6.3f+%6.3fj, ", crealf(Y0[i][j]), cimagf(Y0[i][j]));
}
printf("\n");
}
#if 0
// print traditional channelizer
printf("\n");
printf("traditional channelizer:\n");
for (i=0; i<2*num_symbols; i++) {
printf("%2u:", i);
for (j=0; j<num_channels; j++) {
printf("%6.3f+%6.3fj, ", crealf(Y1[i][j]), cimagf(Y1[i][j]));
}
printf("\n");
}
//
// compare results
//
float mse[num_channels];
float complex d;
for (i=0; i<num_channels; i++) {
mse[i] = 0.0f;
for (j=0; j<2*num_symbols; j++) {
d = Y0[j][i] - Y1[j][i];
mse[i] += crealf(d*conjf(d));
}
mse[i] /= num_symbols;
}
printf("\n");
printf(" e:");
for (i=0; i<num_channels; i++)
printf("%12.4e ", sqrt(mse[i]));
printf("\n");
#endif
printf("done.\n");
return 0;
}
