I can't wrap my head around why fft transform of
complex signal produces a complex output. After all the output
reflects the amount of energy per frequency bin and frequency bins
and energy are both real numbers, no?
I'm trying to write a python script to analyze the energy across
frequency bins but I don't know where to insert a complex to mag
block. I think if I can understand the fft I will know to put the
complex to mag.
The output of an FFT is complex because it contains magnitude _and_
phase. If the output is I,Q (cartesian coordinates) then the
magnitude is the length of the vector from 0,0 to I,Q or sqrt(i^2 +
q^2). The phase of the signal is atan2(Q,I).
Note that the FFT transforms Voltage samples into Voltages per
frequency bin. When you say "energy" you may mean power which is
the magnitude squared or (i^2 + q^2).
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