How to create ATAN function using LUT with 15 bit resolution

[paramesh]

ATAN creation using LUT

Hi all,

currently I am working on DDS.

How to create ATAN function using LUT with 15 bit resolution. with less memory.

I need to store the data and access faster rate.

thanks,

 

[fontp]

Re: ATAN creation using LUT

How to calculate trigonometric functions: **broken link removed**

Usually CORDIC is used for atan


Special approximations

static inline double arctg1 (double x)
//-------------------------------------------
// 2
// arctg(x) = A*x - B*x , if (x >= 0)
//
// 2
// arctg(x) = A*x + B*x , if (x < 0)
//
// error <= 0.004
//-------------------------------------------
{
if (x < 0) {
return x*(1.0597 + 0.27131*x);
}else {
return x*(1.0597 - 0.27131*x);
}
}/*arctan1*/


α=atan2(I,Q) (α in +- pi/4)
α = I*Q / (I^2 + 0,28125*Q^2)
error<0.045 radian (0.26 grad)

But If you use no operation, only LUT you should use linear quantization tables and correspondent restoration tables. The only posibility for making size less is to take into account range of argument or changing accuracy