I am working on Time domain computation. I have S parameter results simulated, using these results I do the Inverse FFT to get results in time domain. I want to filter/window results using Hanning window. In frequency domain, I need to do the multiplication of the function of this filter in frequency and the S parameter results. So, I will loop on N:number of frequencies and multiply each results by the Hann window. How can I compute the length of the filter L??