Calculating impulse response from frequency response

Hi all,

I did next things regarding the FIR filter:

- Calculated filter coefficients (11)
- Calculated frequency response from filter coefficients by using freqz (512 points)
- I shifted frequency response for 0.5*pi

Do you know how I could get the filter coefficients from my shifted frequency response? I know there is the same operation I can do in time domain (that corresponds to shifting in frequency domain), but I don't wanna use that.

Thanks a lot