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Topic: Meaning of the phase angle from FFT
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Nina

Posts: 3
Registered: 11/6/12
Meaning of the phase angle from FFT
Posted: Feb 12, 2013 11:35 AM
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Hello everyone,
Basically I am forcing a system by a sinusoidal forcing function, which means it has a phase of pi/2. I get a response sinusoidal in nature and need to find the phase lag between it and the input forcing function. I use fft on the output and get a phase lag of pi/2. Now here is what is confusing me:
the phase lag of pi/2, is it the same as the phase of the original input forcing function? so the input and output are in phase? so is the actual phase lag 0?
Or, the phase lag of pi/2 is a lag between the original input forcing function and the output? so they are out of phase by pi/2?
I am really confused. Could someone please point me in the right direction?
Thank you so much in advance...



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