public static double[] GetDataWindow(DataWindowType type, int size)
{
double[] Table = new double[size];
Table = new double[size];
double h = 2 * Math.PI / (size - 1);
switch (type)
{
case DataWindowType.Box:
for (int i = size; --i >= 0;)
{
Table[i] = 1;
}
break;
case DataWindowType.Hanning:
for (int i = size; --i >= 0;)
{
Table[i] = 0.50 - 0.50 * Math.Cos(h * i);
}
break;
case DataWindowType.Hamming:
for (int i = size; --i >= 0;)
{
Table[i] = 0.54 - 0.46 * Math.Cos(h * i);
}
break;
case DataWindowType.Blackman:
for (int i = size; --i >= 0;)
{
Table[i] = 0.42 - 0.50 * Math.Cos(h * i) + 0.08 * Math.Cos(2 * h * i);
}
break;
case DataWindowType.Parzen:
for (int i = size; --i >= 0;)
{
Table[i] = 1.0 - Math.Abs((i * 2 - (size - 1)) / (double)(size + 1));
}
break;
case DataWindowType.Welch:
for (int i = size; --i >= 0;)
{
Table[i] = 1.0 - Mt.Sq((i * 2 - (size - 1)) / (double)(size + 1));
}
break;
}
//double c = Math.Sqrt(n / Table.Sum(x => Sq(x)));
//for (int i = n; --i >= 0; ) Table[i] *= c;
return(Table);
}
// Power Spectral Densityを求めたい。nの増加に伴いそれぞれの周波数カラムの幅(Δf)は狭くなるため、結果のData値は増加する
// ΣResult != 単位時間辺りのpower
// ∫Result df = 単位時間辺りのpower
// y=a*sin(x) の結果は、a*a*n/2 振幅はa/2でパワーはa*a/4、one-sidedなので2倍してa*a/2、nは上記
// これは (1/n)*Σ(y*y) の結果と一致する
// y=a の結果は a*a*n
public static double[] PowerSpectrumFFT(double[] data, double amplitude)
{
Complex[] Freq = RealFastFourierTransform(data, Math.Sqrt(2 * amplitude / data.Length));
double[] Powr = new double[Freq.Length];
for (int i = Powr.Length; --i >= 0;)
{
Powr[i] = Mt.Sq(Freq[i].Real) + Mt.Sq(Freq[i].Imaginary);
}
Powr[0] /= 2;
Powr[Powr.Length - 1] /= 2;
return(Powr);
}
public static Complex[] PowerPhaseSpectrumFFT(double[] data, double amplitude)
{
Complex[] Freq = RealFastFourierTransform(data, Math.Sqrt(2 * amplitude / data.Length));
Complex[] Powr = new Complex[Freq.Length];
for (int i = Powr.Length; --i >= 0;)
{
Powr[i] = new Complex(Mt.Sq(Freq[i].Real) + Mt.Sq(Freq[i].Imaginary), Freq[i].Phase);
}
var a = Powr[0]; Powr[0] = new Complex(a.Real / 2, a.Imaginary);
var b = Powr[Powr.Length - 1]; Powr[Powr.Length - 1] = new Complex(b.Real / 2, b.Imaginary);
return(Powr);
}
