1. The problem statement, all variables and given/known data See Attachment 2. Relevant equations 3. The attempt at a solution Ok so in a previous question I worked out fd = e-ipd*2*sinc(pa)/√(2∏), also worked out its fourier transform if that helps. Now I really am stuck on the question, any guidance would be appreciated, I don't understand how the function fd is summed over from -N to N, like I say any help to just send me in the right direction would be great.