This graph shows a Fourier Transform of a signal. The various parts of the diagram are marked with letters that denote the different AC parameters. “A” denotes the signal amplitude. This is the magnitude of the signal. “B” shows the spurious free dynamic range, or SFDR. This, again, is the difference between the input signal amplitude and its second harmonic frequency. “C” shows the average noise floor. This is the difference between the signal amplitude and the median of the noise amplitude. “D” denotes the RMS noise level average, and “E” is the RMS signal-to-noise ratio. This ratio is a key indicator of how much of the real signal is noise, and higher values are more desirable.