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FFT and amplitude plots
Posted:
Jul 5, 1996 8:43 AM


Hi!
I want to plot the amplitude of a Fourier transformed signal The FFT seems to affect the amplitude in a way that I haven't been able to figure out. I'm working on a program where I need to make the signals look "continuous". Therefore I must compensate for the FFT's effect on the transfomed vector's amplitude.
For example: let the signal be
x = sin(2*pi*f*t)
The continuous Fourier transform of this should be two impulses (I know I'll get shifted sincs due to the finite sequence) with amplitude 1/2 located at +f In the discrete Fourier transform the transform depends of the number of samples in some way.
How do I compensate for this? Does it depend on the sampling frequency as well, and if so; How?
I'm trying to visualize the properties of the continuous and discrete Fourier transforms, and therefor it's very important to get the correct scaling of the axes...
Thanks in advance...
  Johan Carlson email: d93jcn@sm.luth.se M.Sc. Student www: http://jota.sm.luth.se/~d93jcn Lulea University Sweden 



