Exact Signal Measurements using FFT Analysis

This tutorial describes how to accurately measure signal power using the FFT. While it is easy to calculate powers in the time domain, this is not always applicable: If a signal contains several spectral components and broadband noise, considering the frequency domain allows to measure power of these components individually or to measure SNR (by separately considering signal and noise). However, obtaining accurate power numbers after having performed an FFT is not straightforward, because several e ects introduce errors during FFT processing, mostly due to windowing. This paper describes the di erent e ects and explains how they can be avoided or compensated. Finally, it will be explained how to do accurate measurements of signal and noise power using the FFT spectrum.