Esempio n. 1
0
        public complex EE(complex b1, complex b2)   //旋转因子
        {
            complex b3 = new complex();

            b3.real = b1.real * b2.real - b1.imag * b2.imag;
            b3.imag = b1.real * b2.imag + b1.imag * b2.real;
            return(b3);
        }
Esempio n. 2
0
        public void FFT(complex[] xin, int N)      //*xin为需要FFT变换的数组,N为转换的点数
        {
            int     f, m, LH, nm, i, k, j, L;
            double  p, ps;
            int     le, B, ip;
            float   pi;
            complex w = new complex();
            complex t = new complex();

            LH = N >> 1;
            f  = N;
            for (m = 1; (f = f >> 1) != 1; m++)
            {
                ;
            }
            nm = N - 2;
            j  = N >> 1;

            for (i = 1; i <= nm; i++)        //  变址运算
            {
                if (i < j)
                {
                    t = xin[j]; xin[j] = xin[i]; xin[i] = t;
                }
                k = LH;
                while (j >= k)
                {
                    j = j - k; k = k / 2;
                }
                j = j + k;
            }

            for (L = 1; L <= m; L++)       //实现蝶形运算
            {
                le = (int)Math.Pow(2, L);
                B  = le >> 1;
                pi = 3.14159f;
                for (j = 0; j <= B - 1; j++)
                {
                    p      = Math.Pow(2, m - L) * j;
                    ps     = 2 * pi / N * p;
                    w.real = Math.Cos(ps);
                    w.imag = -Math.Sin(ps);
                    for (i = j; i <= N - 1; i = i + le)
                    {
                        ip           = i + B;
                        t            = EE(xin[ip], w);
                        xin[ip].real = xin[i].real - t.real;
                        xin[ip].imag = xin[i].imag - t.imag;
                        xin[i].real  = xin[i].real + t.real;
                        xin[i].imag  = xin[i].imag + t.imag;
                    }
                }
            }
        }