Spurious free dynamic range (SFDR) and total harmonic distortion (THD) are easily explained by this picture. SFDR is the distance between the signal of interest and the highest spur, including harmonics. THD is the distance relative to the signal of interest and the RMS sum of a defined set of harmonics. SNR is the distance (ratio) from the signal of interest to the RMS sum of the noise components in the Nyquist bandwidth (excluding harmonics).

