public static complex[] dft(double[] signal, int n) //(信号，信号长度)
{
int i, j;
complex w1;
w1 = omega(n);
complex[] w = new complex[n];
for (i = 0; i < n; i++)
{
w[i] = complex.powcc(w1, i);
}
complex[] f = new complex[n];
complex temp; //w[i]的次方
complex temp1; //f中单项的值
for (i = 0; i < n; i++)
{
f[i].a = 0;
f[i].b = 0;
for (j = 0; j < n; j++)
{
temp = complex.powcc(w[i], j);
temp1 = complex.commul(signal[j], temp);
f[i] = complex.comsum(f[i], temp1);
}
}
return(f);
}
public static complex decrease(complex x, complex y)
{
complex c = new complex();
c.a = x.a * y.a - x.b * y.b;
c.b = x.a * y.b + x.b * y.a;
return(c);
}
public static complex comsum1(double x, complex y)
{
complex c = new complex();
c.a = x + y.a;
c.b = y.b;
return(c);
}
public static complex comsum(complex x, complex y)
{
complex c = new complex();
c.a = x.a + y.a;
c.b = x.b + y.b;
return(c);
}
public static complex commul(double x, complex y)
{
complex c = new complex();
c.a = x * y.a;
c.b = x * y.b;
return(c);
}
public static complex powcc(complex x, double n)
{
int k;
complex xout;
xout.a = 1;
xout.b = 0;
for (k = 1; k <= n; k++)
{
xout = complex.commulcc(xout, x);
}
return(xout);
}
private void show_ADCdata_fft()
{
ZoomToggle(chart4, true);
float Fs = 1 / float.Parse(dtADC.Rows[1]["Time(s)"].ToString());
double[] x = get_data_colomn(dtADC, "ADC(V)").ToArray();
int n = x.Length;
double[] freqs = new Double[n / 2];
for (int i = 0; i < freqs.Length; i++)
{
freqs[i] = Fs * i * 0.5 / freqs.Length;
}
complex[] y = new complex[n]; //接收复数结果的数组
double[] z = new Double[n]; //接收幅值结果的数组
y = airthm.dft(x, n);
z = airthm.amplitude(y, n);
double[] z_half = new Double[n / 2];
Array.ConstrainedCopy(z, 0, z_half, 0, n / 2);
chart4.Series["Series1"].Points.DataBindXY(freqs, z_half);
}