I'm a noobie to DSP, and recently I'm learning DSP for an urgent assignment. There's a problem that has been confused me for days. I hope anybody could shed some light on it, although it might seem to be silly.
The assignment asks me to filter a signal so that it's in $20-800$Hz. After I spent several days to learn DSP, I finally get some idea about frequency domain, DTFT, FIR, IIR, etc. But I still have no idea about how to proceed. Furthermore, I have a huge confusion about frequency: in the frequency domain, we always talk about the radian $\omega$ which is always less than $\pi$, how can I connect this $\omega$ to the physical frequency? Is it right to use $\omega/2\pi$?