// convert discrete z/p/k form to transfer function form
// _zd : digital zeros (length: _n)
// _pd : digital poles (length: _n)
// _n : filter order
// _k : digital gain
// _b : output numerator (length: _n+1)
// _a : output denominator (length: _n+1)
void iirdes_dzpk2tff(float complex * _zd,
float complex * _pd,
unsigned int _n,
float complex _k,
float * _b,
float * _a)
{
unsigned int i;
float complex q[_n+1];
// expand poles
polycf_expandroots(_pd,_n,q);
for (i=0; i<=_n; i++)
_a[i] = crealf(q[_n-i]);
// expand zeros
polycf_expandroots(_zd, _n, q);
for (i=0; i<=_n; i++)
_b[i] = crealf(q[_n-i]*_k);
}
//
// AUTOTEST: polycf_findroots (random roots)
//
void xautotest_polycf_findroots_rand()
{
unsigned int n=5;
float tol=1e-4f;
float complex p[n];
float complex roots[n-1];
float complex p_hat[n];
unsigned int i;
for (i=0; i<n; i++)
p[i] = i == n-1 ? 1 : 3.0f * randnf();
polycf_findroots(p,n,roots);
float complex roots_hat[n-1];
// convert form...
for (i=0; i<n-1; i++)
roots_hat[i] = -roots[i];
polycf_expandroots(roots_hat,n-1,p_hat);
if (liquid_autotest_verbose) {
printf("poly:\n");
for (i=0; i<n; i++)
printf(" p[%3u] = %12.8f + j*%12.8f\n", i, crealf(p[i]), cimagf(p[i]));
printf("roots:\n");
for (i=0; i<n-1; i++)
printf(" r[%3u] = %12.8f + j*%12.8f\n", i, crealf(roots[i]), cimagf(roots[i]));
printf("poly (expanded roots):\n");
for (i=0; i<n; i++)
printf(" p[%3u] = %12.8f + j*%12.8f\n", i, crealf(p_hat[i]), cimagf(p_hat[i]));
}
for (i=0; i<n; i++) {
CONTEND_DELTA(crealf(p[i]), crealf(p_hat[i]), tol);
CONTEND_DELTA(cimagf(p[i]), cimagf(p_hat[i]), tol);
}
}
