Harmonic distortion - definition
Harmonic distortion - definition
Harmonic distortion (Total Harmonic Distortion. Total Harmonic Distortion, THD) is a measure of the non-linearity of an electrical signal, which describes the proportion of higher order harmonics in relation to the fundamental. Ideally, a sinusoidal signal contains only one frequency - the fundamental. In real electronic systems, especially in amplifying systems, however, additional harmonics may occur, which are multiples of the fundamental frequency, which introduce distortions into the output signal. THD determines, to what extent these harmonics distort the original signal.
The THD value is usually expressed in percent or decibels (dB) and calculated as the ratio of the root of the sum of the squares of the amplitudes of all harmonics to the amplitude of the fundamental component. The lower the THD, the more faithful the reproduction of the signal and the higher the processing quality. This parameter is of particular importance in audio systems, signal transmission, switching power supplies and frequency converters, where maintaining the integrity of the waveform is critical to the quality of the device's performance.
Harmonic distortion can result from non-linear characteristics of active components, such as transistors or Operational amplifiers, as well as system response to overloads, saturation or improper impedance matching. In power engineering, this phenomenon concerns the power supply of electronic devices with non-linear current consumption, leading to deterioration of power quality, increased losses and electromagnetic interference.
In laboratory measurements and equipment certification, harmonic analysers are used, which allow the THD value for a specific frequency band to be accurately determined. In high-quality systems, such as audiophile amplifiers or medical Measuring Instruments, a THD of less than 0,01%, while in less critical applications higher values are acceptable, depending on the specific application.
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