Hi Group, I know my question may sound stupid. But I can not come up with a solution. So I post it here with the hope that someone could shed me some light. Thanks in advance! I am working on some image processing with FFT. It requires that the function to be FFTed into spatial frequency space. However, I found out that the result of FFT depends on the number of segments I choose. For example, %--------------code--------% N=200; t=linspace(-5,5,N); x=exp(-pi*t.^2); y=fftshift(fft(fftshift(x))); plot(abs(y)); %------------end------------% Here I wanted to do a Fourier transform of function exp(-t^2). When the parameter N is changed, for instance, from 100 to 200, the plot differs. It is understandable considering that the total DFT items increases by a factor of 2. However, isn't it true that the FFT of the function should be one single function exp(-pi*chi^2)? How can I normalize the resulted DFT function with N so that every set of result is consistent with each other? I have googled but still have not got a clue. Thank you! Regards, Doug

# FFT and normalization

Started by ●March 31, 2006