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Topic: FFT and amplitude plots
Replies: 1   Last Post: Jul 8, 1996 9:24 AM

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Johan Carlson

Posts: 39
Registered: 12/7/04
FFT and amplitude plots
Posted: Jul 5, 1996 8:43 AM
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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...

--
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Johan Carlson e-mail: d93-jcn@sm.luth.se
M.Sc. Student www: http://jota.sm.luth.se/~d93-jcn
Lulea University
Sweden
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