I am trying to generate a two sided FFT spectrum of a data array which itself is -22.5 to 22.5 in the steps on dt and this time domain signal i.e bandlimited one.
I am using four1 routine to generate the FFT output.But the problem is that I get only one side of the spectrum i.e from 0 to fc.
Now what I did , I divided the whole data into two parts -22.5 to 0 and 0 to 22.5 and took two separate FFT by calling four1 twice.Here I got the two sided spectrum but problem is that it is a sinc function and output looks like the one attached in the file.
I want a prefect sinc function and not the DC shifted sinc function,which is zero at the end of the spectrum.
In one sided spectum case I get proper output i.e a sinc fucntion with no DC shift.
What could be the reson of this? Please let me know.
Thank you.