int fft (
COMPLEX *in,
unsigned n,
COMPLEX *out
)
{
unsigned i;
for (i = 0; i < n; i++)
c_conj (in [i]);
if (W_init (n) == -1)
return -1;
Fourier (in, n, out);
for (i = 0; i < n; i++) {
c_conj (out [i]);
c_realdiv (out [i], n);
}
return 0;
}
filterrep_t* create_resonator_representation( filter_t *f ) {
double theta, r, thm, th1, th2, phi;
int i, cvg;
complex_t z, g;
complex_t topco[MAXPZ+1], botco[MAXPZ+1];
filterrep_t *zrep;
// allocate memory for the filterrepresentation...
zrep = (filterrep_t*) calloc( 1, sizeof( filterrep_t) );
if ( ! zrep ) {
bpm_error( "Cannot allocate memory for resonator representation.", __FILE__, __LINE__ );
return NULL;
}
// for all :
zrep->nzeros = 2;
zrep->npoles = 2;
zrep->zero[0] = complex( 1., 0. );
zrep->zero[1] = complex( -1., 0. );
theta = 2.*PI*f->alpha1;
if ( f->Q <= 0. ) {
// negative Q, so assume infinte Q : pure oscillator, calculate the poles
z = c_exp( complex(0., theta) );
zrep->pole[0] = z;
zrep->pole[1] = c_conj( z );
} else {
// finite Q factor for the resonator, calculate the poles
_expand_complex_polynomial( zrep->zero, zrep->nzeros, topco);
r = exp(-theta / (2.0 * f->Q));
thm = theta;
th1 = 0.0;
th2 = PI;
cvg = 0;
for ( i=0; ( i<MAX_RESONATOR_ITER ) && ( cvg == 0 ); i++ ) {
z = complex( r*cos(thm), r*sin(thm));
zrep->pole[0] = z;
zrep->pole[1] = c_conj(z);
_expand_complex_polynomial( zrep->pole, zrep->npoles, botco);
g = c_div( _eval_complex_polynomial( topco, zrep->nzeros, complex(cos(theta),sin(theta))),
_eval_complex_polynomial( botco, zrep->npoles, complex(cos(theta),sin(theta))) );
phi = g.im / g.re;
if ( phi > 0.0 ) th2 = thm; else th1 = thm;
if ( fabs(phi) < FILT_EPS ) cvg = 1;
thm = 0.5 * ( th1 + th2 );
}
if ( ! cvg ) {
bpm_error( "Finite Q resonator failed to converge on pole/zero calculation.",
__FILE__, __LINE__ );
free(zrep);
return NULL;
}
}
// adjust the zeros for a bandstop resonator
if ( f->options & BANDSTOP ) {
theta = 2.*PI*f->alpha1;
z = complex( cos(theta), sin(theta) );
zrep->zero[0] = z;
zrep->zero[1] = c_conj( z );
}
// adjust the zeros for an allpas resonator
if ( f->options & ALLPASS ) {
zrep->zero[0] = _reflect( zrep->pole[0] );
zrep->zero[1] = _reflect( zrep->pole[1] );
}
return zrep;
}
