Harmonic distortion is a measure of the amount of power contained in the harmonics of a fundamental signal compared to the power of the fundamental signal.

Harmonic distortion is inherent to devices and systems that possess nonlinear characteristics. The more nonlinear the device, the greater its harmonic distortion.

Harmonic distortion can be expressed as a power ratio or as a percentage. Use the following formula to express it as a power ratio:

P HD = Pfund–Pharm(dBc)

where

  • P HD is the power of the harmonic distortion in dBc
  • P fund is the fundamental signal power in dB or dBm
  • P harm is the power of the harmonic of interest in dB or dBm

Convert power to voltage and use the following equation to express harmonic distortion as a percentage ratio:

Percentage of Distortion   = V h a r m V f u n d × 100 % Percentage of Distortion   = V h a r m V f u n d × 100 %