public static double[] FFT(double[] daten)
{
int samples = daten.Length;
daten = Hanning(daten);
komplex[] data = new komplex[samples];
for (int i = 0; i < samples; i++)
{
data[i].re = daten[i];
data[i].im = 0.0;
}
data = FFT(data, samples);
double[] OutPut = new double[samples / 2];
if (Statics.dB == true)
{
for (int i = 0; i < samples / 2; i++)
{
OutPut[i] = Statics.dB_factor * Math.Log10(Math.Sqrt(data[i].re * data[i].re + data[i].im * data[i].im));
}
}
else
{
for (int i = 0; i < samples / 2; i++)
{
OutPut[i] = Math.Sqrt(data[i].re * data[i].re + data[i].im * data[i].im);
}
}
return OutPut;
}
public static double[] FFT(double[] daten)
{
int samples = daten.Length;
daten = Hanning(daten);
komplex[] data = new komplex[samples];
for (int i = 0; i < samples; i++)
{
data[i].re = daten[i];
data[i].im = 0.0;
}
data = FFT(data, samples);
double[] OutPut = new double[samples / 2];
if (Statics.dB == true)
{
for (int i = 0; i < samples / 2; i++)
{
OutPut[i] = Statics.dB_factor * Math.Log10(Math.Sqrt(data[i].re * data[i].re + data[i].im * data[i].im));
}
}
else
{
for (int i = 0; i < samples / 2; i++)
{
OutPut[i] = Math.Sqrt(data[i].re * data[i].re + data[i].im * data[i].im);
}
}
return(OutPut);
}
/// <summary>
/// Methode FFT aus dem Buch :
///
/// "Praktische Informationstechnik mit C#", Oliver Kluge
/// Springer Verlag
///
/// </summary>
private static komplex[] FFT(komplex[] data, int samples)
{
double tempr = 0; // für Tausch bei Bit-Umkehr
double tempi = 0; // für Tausch bei Bit-Umkehr
double wreal = 0; // Drehfaktor (Realteil)
double wimag = 0; // Drehfaktor (Imaginärteil)
double real1 = 0; // Hilfsvariable
double imag1 = 0; // Hilfsvariable
double real2 = 0; // Hilfsvariable
double imag2 = 0; // Hilfsvariable
int i = 0;
int j = 0;
int k = 0;
int stufen = 0;
int sprung = 0;
int schritt = 0;
int element = 0;
// Bit-Umkehr
for (j = 0; j < samples - 1; j++)
{
if (j < i)
{
tempr = data[j].re;
tempi = data[j].im;
data[j].re = data[i].re;
data[j].im = data[i].im;
data[i].re = tempr;
data[i].im = tempi;
}
k = samples / 2;
while (k <= i)
{
i -= k;
k /= 2;
}
i += k;
}
stufen = (int)(Math.Log10((double)samples) /
Math.Log10((double)2));
sprung = 2;
for (i = 0; i < stufen; i++)
{
// jede Iterationsstufe startet mit dem 1. Wert
element = 0;
for (j = samples / sprung; j >= 1; j--)
{
schritt = sprung / 2;
for (k = 0; k < schritt; k++)
{
// 1. Zweig des Butterfly
wreal = Math.Cos(k * 2.0 * Math.PI / sprung);
wimag = Math.Sin(k * 2.0 * Math.PI / sprung);
real1 = data[element + k].re + (wreal * data[element + k + schritt].re - wimag * data[element + k + schritt].im);
imag1 = data[element + k].im + (wreal * data[element + k + schritt].im + wimag * data[element + k + schritt].re);
// 2. Zweig des Butterfly
wreal *= -1.0;
wimag *= -1.0;
real2 = data[element + k].re + (wreal * data[element + k + schritt].re - wimag * data[element + k + schritt].im);
imag2 = data[element + k].im + (wreal * data[element + k + schritt].im + wimag * data[element + k + schritt].re);
// Ergebnisse übernehemen
data[element + k].re = real1;
data[element + k].im = imag1;
data[element + k + schritt].re = real2;
data[element + k + schritt].im = imag2;
}
element += sprung;
}
sprung *= 2;
}
return data;
}
