atan in a FPGA

[Andi]

Hi folks,

Could any one suggest me how to implemet an 'atan' function in a FPGA?
I've seen the Taylor polinomian but, is there any other way ?

rgds,

Bodhi

 

[Ralf Hildebrandt]

Hi Andi!

Could any one suggest me how to implemet an 'atan' function in a FPGA?
I've seen the Taylor polinomian but, is there any other way ?

What about a lookup-table (with linear/binomic/... interpolation)?

Ralf

 

[Acciduzzu]

Hi,

Another solution is to use a CORDIC rotator, working in the so-called
"vectoring mode". This allows you to get the phase and the amplitude
(polar coordinates) of an input vector specified in cartezian
coordinates (X and Y).
M = SQRT(X^2+Y^2);
A = ATAN(Y/X);
What you have to do now is to choose a convenient constant vaue for X
and use Y as your argument to ATAN.
Anyway, you cand find more info on the CORDIC algorithm on the net and
you will se you can do a lot more things with it than just compute
ATAN.
A pretty good example of synthesizable VHDL code can also be found on
www.opencores.org.

Hope this helps

Acciduzzu