I have been acquiring data through ADC and into memory, the input signal are square waves that step down in frequency as time goes by. Due to memory, I have a fixed maximum number of samples per FFT. But I would like to compare their magnitudes, and phase along side each other. The max length of FFT is good enough for frequency resolution, I am just wondering if I have a bunch of data that's been processed through FFT, can I sort of just add them to combine their total magnitude and phase? or will the addition cause bias and distortion?
Also, I was wondering since I noticed that at low frequencies, the flicker noise seems to increase the noise floor, is it possible to have a magnitude correction filter or equalizer to push the rest of the signals up such that I can have a common noise floor when I go through all my input signals?