I am really new to FFT and signal processing. I am doing an analysis of square waves with FFT and I am trying to understand why the FFT output on the frequency domain has a downward slope for square waves. Specifically:
- Why in FFT output for a square wave, bin 0 has the highest amplitude and bin 1 has the second highest amplitudes no matter what the original frequency of the input signal in the time series domain representation is.
- I read that bin 0 has to do with the ADC and that is the sum of the whole signal and that is why it is 0Hz. What does that mean?
- What does amplitude represent in FFT output like below?