// create from square-root Nyquist prototype
// _type : filter type (e.g. LIQUID_RNYQUIST_RRC)
// _k : nominal samples/symbol, _k > 1
// _m : filter delay [symbols], _m > 0
// _beta : rolloff factor, 0 < beta <= 1
// _mu : fractional sample offset,-0.5 < _mu < 0.5
FIRFILT() FIRFILT(_create_rnyquist)(int _type,
unsigned int _k,
unsigned int _m,
float _beta,
float _mu)
{
// validate input
if (_k < 2) {
fprintf(stderr,"error: firfilt_%s_create_rnyquist(), filter samples/symbol must be greater than 1\n", EXTENSION_FULL);
exit(1);
} else if (_m == 0) {
fprintf(stderr,"error: firfilt_%s_create_rnyquist(), filter delay must be greater than 0\n", EXTENSION_FULL);
exit(1);
} else if (_beta < 0.0f || _beta > 1.0f) {
fprintf(stderr,"error: firfilt_%s_create_rnyquist(), filter excess bandwidth factor must be in [0,1]\n", EXTENSION_FULL);
exit(1);
}
// generate square-root Nyquist filter
unsigned int h_len = 2*_k*_m + 1;
float hf[h_len];
liquid_firdes_rnyquist(_type,_k,_m,_beta,_mu,hf);
// copy coefficients to type-specific array (e.g. float complex)
unsigned int i;
TC hc[h_len];
for (i=0; i<h_len; i++)
hc[i] = hf[i];
// return filterbank object
return FIRFILT(_create)(hc, h_len);
}
// create firfilt object
// _h : coefficients (filter taps) [size: _n x 1]
// _n : filter length
FIRFILT() FIRFILT(_create)(TC * _h,
unsigned int _n)
{
// validate input
if (_n == 0) {
fprintf(stderr,"error: firfilt_%s_create(), filter length must be greater than zero\n", EXTENSION_FULL);
exit(1);
}
// create filter object and initialize
FIRFILT() q = (FIRFILT()) malloc(sizeof(struct FIRFILT(_s)));
q->h_len = _n;
q->h = (TC *) malloc((q->h_len)*sizeof(TC));
#if LIQUID_FIRFILT_USE_WINDOW
// create window (internal buffer)
q->w = WINDOW(_create)(q->h_len);
#else
// initialize array for buffering
q->w_len = 1<<liquid_msb_index(q->h_len); // effectively 2^{floor(log2(len))+1}
q->w_mask = q->w_len - 1;
q->w = (TI *) malloc((q->w_len + q->h_len + 1)*sizeof(TI));
q->w_index = 0;
#endif
// load filter in reverse order
unsigned int i;
for (i=_n; i>0; i--)
q->h[i-1] = _h[_n-i];
// create dot product object
q->dp = DOTPROD(_create)(q->h, q->h_len);
// set default scaling
q->scale = 1;
// reset filter state (clear buffer)
FIRFILT(_reset)(q);
return q;
}
// create rectangular filter prototype
FIRFILT() FIRFILT(_create_rect)(unsigned int _n)
{
// validate input
if (_n == 0 || _n > 1024) {
fprintf(stderr,"error: firfilt_%s_create_rect(), filter length must be in [1,1024]\n", EXTENSION_FULL);
exit(1);
}
// create float array coefficients
float hf[_n];
unsigned int i;
for (i=0; i<_n; i++)
hf[i] = 1.0f;
// copy coefficients to type-specific array
TC h[_n];
for (i=0; i<_n; i++)
h[i] = (TC) hf[i];
// return filter object and return
return FIRFILT(_create)(h, _n);
}
// 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);
}
// copy coefficients to type-specific array (e.g. float complex)
unsigned int i;
TC hc[h_len];
for (i=0; i<h_len; i++)
hc[i] = hf[i];
// return filterbank object
return FIRFILT(_create)(hc, h_len);
}
// re-create firfilt object
// _q : original firfilt object
// _h : new coefficients [size: _n x 1]
// _n : new filter length
FIRFILT() FIRFILT(_recreate)(FIRFILT() _q,
TC * _h,
unsigned int _n)
{
unsigned int i;
// reallocate memory array if filter length has changed
if (_n != _q->h_len) {
// reallocate memory
_q->h_len = _n;
_q->h = (TC*) realloc(_q->h, (_q->h_len)*sizeof(TC));
#if LIQUID_FIRFILT_USE_WINDOW
// recreate window object, preserving internal state
_q->w = WINDOW(_recreate)(_q->w, _q->h_len);
#else
