最近在做FFT，发几个用到的三角函数计算程序
#define DSP32_Q(x) ((int) ((x)*(((unsigned) (1 << (20))))))
const int atanLUT[20] = {
DSP32_Q(0.78539816340),
DSP32_Q(0.46364760900),
DSP32_Q(0.24497866313),
DSP32_Q(0.12435499455),
DSP32_Q(0.06241881000),
DSP32_Q(0.03123983343),
DSP32_Q(0.01562372862),
DSP32_Q(0.00781234106),
DSP32_Q(0.00390623013),
DSP32_Q(0.00195312252),
DSP32_Q(0.00097656219),
DSP32_Q(0.00048828121),
DSP32_Q(0.00024414062),
DSP32_Q(0.00012207031),
DSP32_Q(0.00006103516),
DSP32_Q(0.00003051758),
DSP32_Q(0.00001525879),
DSP32_Q(0.00000762939),
DSP32_Q(0.00000381470),
DSP32_Q(0.00000190735)
};
int MySin(int zi)
{
int x, y, z, x_new;
int i, sign;
x = DSP32_Q(0.60725293500888);
y = 0;
z = zi;
for(i=0; i<20; i++)
{
if(z >= 0)
{
sign = 1;
}
else
{
sign = -1;
}
x_new = x - ((sign*y)>>i);
y = y + ((sign*x)>>i);
x = x_new;
z = z - sign*atanLUT[i];
}
return (y);
}
int MyCos(int zi)
{
int x, y, z, x_new;
int i, sign;
x = DSP32_Q(0.60725293500888);
y = 0;
z = zi;
for(i=0; i<20; i++)
{
if(z >= 0)
{
sign = 1;
}
else
{
sign = -1;
}
x_new = x - ((sign*y)>>i);
y = y + ((sign*x)>>i);
x = x_new;
z = z - sign*atanLUT[i];
}
return (x);
}
int MyArctan2(int xi, int yi)
{
int x, y, z, x_new;
int i, sign;
x = xi;
y = yi;
z = 0;
for(i=0; i<20; i++)
{
if(y >= 0)
{
sign = -1;
}
else
{
sign = 1;
}
x_new = x - ((sign*y)>>i);
y = y + ((sign*x)>>i);
x = x_new;
z = z - sign*atanLUT[i];
}
return (z);
} |
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