I have implemented Jens Joergen Nielsen FFT code in my windows program
that converts V(t) to V(f). I am using 2500 Hz sampling with N=8192 point
FFT.
I am plotting the FFT amplitude as sqrt(Re^2 + Im^2)/N. Im getting the
correct peak frequency after FFT, however, I am getting only about 1/2 of
the peak amplitude (of the input sine wave input amplitude) with
rectangular window. (If my input wave is 20.0*sin(omega*t) the FFT gives
~10 for peak height at omega).
Using various windows (Hamming, Bartlett, etc) the V(f) peak amplitude
becomes even smaller.
Any suggestion why do I get 1/2 peak heights?
What correction factors should I use for the spectrum height for various
window types?
Appreciate all help.
Peter
