Distortion (electrical engineering)

Distortion of the output variable compared to the input variable in the non-linear part of the characteristic of a field effect transistor ${\displaystyle I_{\mathrm {D} }}$ ${\displaystyle U_{\mathrm {GS} }}$

In electrical engineering, a distortion is a predominantly undesirable change in shape in the course of a time-varying variable . It is mainly observed with periodic signals; But even a single impulse can be changed in its form, even distorted. The distortion contrasts with the modulation as a desired change.

In acoustics, there is also deliberate distortion to achieve certain sound effects .

A distinction is made between “linear distortions” and “non-linear distortions”.

The non-linear distortion caused by a non-linear system is preferably significant when there is a deviation from an originally sinusoidal signal curve. Their main causes are semiconductor components and magnetic components ( chokes , transformers ) with non-linear characteristics , and also overdrive .

This type of distortion can be described in such a way that additional sinusoidal oscillations develop, which are referred to as harmonics to the original fundamental oscillation . Their share in the overall signal can be specified by the distortion factor . The harmonics have integer frequencies that are many times higher than the fundamental frequency. Mathematically, the distorted oscillation is represented by a Fourier series . - Furthermore, additional frequencies can arise through intermodulation .

Different distortions of a square pulse - depending on how far the high or all harmonics are missing

The linear distortion arises in linear networks through their frequency response , when amplifiers and transmission paths behave linearly but dependent on frequency, e.g. B. suppress parts with high frequencies.

This type of distortion cannot occur with a pure sine wave signal. But in the case of a non-sinusoidal oscillation up to and including a pulse , if the signal can be viewed as a superimposition of sinusoidal oscillations from the start, the proportion of harmonics in the overall signal can change due to linear distortion, which changes the shape.

literature

• Heinrich Schröder: Electrical communications engineering. Volume 1: Basics, theory and calculation of passive transmission networks. Verlag für Radio-Foto-Kinotechnik, Berlin-Borsigwalde 1966.