void idft(std::vector<complex<float_type> >& y, int n) {
int j, l;
/* n inverse dft length */
std::vector<complex<float_type> > x(n + 1);
complex<float_type> mult;
/* calculate the w values recursively */
// complex<float_type> w_inc = expj(TWOPI/n);
// complex<float_type> w_x = complex<float_type>(1,0);
for (j = 0; j < n; j++) { x[j] = y[j]; }
/* start inverse fft */
for (l = 0; l < n; l++) {
y[l] = 0;
for (j = 0; j < n; j++) {
mult = x[j] * expj(TWOPI * l * j / (n));
y[l] += mult;
}
}
#define SCALEFFT
#ifdef SCALEFFT
int i;
/* scale all results by 1/n */
float_type scale = (float_type)(1.0 / n);
for (i = 0; i < n; i++) y[i] = scale * y[i];
#endif
}
template <> complex<int_s> vco<int_s>::clock() {
acc += new_fcw;
phase = acc >> (long)(32-phase_bits); // truncate
float arg = TWOPI*((float)phase)/phase_bits;
complex<float> x = ((float)amp)*expj(arg);
return(complex<int_s>(SPUC_TOLONG(real(x)),SPUC_TOLONG(imag(x))));
}
void dft(std::vector<complex<float_type> >& y, int n) {
int j, l;
/* n inverse dft length */
std::vector<complex<float_type> > x(n + 1);
for (j = 0; j < n; j++) x[j] = y[j];
/* start inverse fft */
for (l = 0; l < n; l++) {
y[l] = 0;
for (j = 0; j < n; j++) { y[l] += x[j] * expj(-TWOPI * j * l / n); }
}
}
void ifft(complex_t data[], int len)
{
int i;
double x;
complex_t temp[MAX_FFT_LEN];
/* A very slow and clunky FFT, that's just fine for filter design. */
for (i = 0; i < MAX_FFT_LEN/2; i++)
{
x = (2.0*3.1415926535*i)/(double) MAX_FFT_LEN;
circle[i] = expj(x);
}
fftx(data, temp, len);
}
SPAN_DECLARE(void) ifft(complex_t data[], int len)
{
int i;
double x;
complex_t temp[MAX_FFT_LEN];
/* A very slow and clunky FFT, that's just fine for tests. */
if (!icircle_init)
{
for (i = 0; i < MAX_FFT_LEN/2; i++)
{
x = (2.0*3.1415926535*i)/(double) MAX_FFT_LEN;
icircle[i] = expj(x);
}
icircle_init = true;
}
ifftx(data, temp, len);
}
/* *************************************************************************
fft - In-place radix 2 decimation in time inverse FFT
Requires pointer to complex array, x and power of 2 size of FFT, m
(size of FFT = 2**m). Places inverse FFT output on top of input
frequency domain COMPLEX array.
complex<float_type> fft(complex<float_type> *x, int m)
*************************************************************************/
void fft(std::vector<complex<float_type> >& y, int m) {
complex<float_type> u, temp, tm;
int wptr;
int i, j, k, l, le, windex;
/* n = 2**m = inverse fft length */
int n = 1 << m;
le = n / 2;
std::vector<complex<float_type> > w(n + 1);
std::vector<complex<float_type> > x(n + 1);
/* calculate the w values recursively */
complex<float_type> w_inc = expj(-TWOPI / n);
complex<float_type> w_x = w_inc;
for (j = 0; j < le; j++) {
w[j] = w_x;
w_x *= w_inc;
x[j] = y[j];
x[j + le] = y[j + le];
}
/* start inverse fft */
le = n;
windex = 1;
for (l = 0; l < m; l++) {
le = le / 2;
/* first iteration with no multiplies */
for (i = 0; i < n; i += 2 * le) {
temp = (x[i] + x[i + le]);
x[i + le] = (x[i] - x[i + le]);
x[i] = temp;
}
/* remaining iterations use stored w */
wptr = windex - 1;
for (j = 1; j < le; j++) {
for (i = j; i < n; i += 2 * le) {
temp = x[i] + x[i + le];
tm = x[i] - x[i + le];
x[i + le] = tm * w[wptr];
x[i] = temp;
}
wptr += windex;
}
windex = 2 * windex;
}
/* rearrange data by bit reversing */
j = 0;
for (i = 1; i < (n - 1); i++) {
k = n / 2;
while (k <= j) {
j = j - k;
k = k / 2;
}
j = j + k;
if (i < j) {
temp = x[j];
x[j] = x[i];
x[i] = temp;
}
}
for (i = 0; i < n; i++) y[i] = x[i];
}
