### The Nebula tip of the month (#43 - December 2012)

Posted:

**Wed Nov 14, 2012 8:08 pm****Non lineal distortion and inter modulation distortion**

Transfer function and also known as the system function or network function is a mathematical representation, in terms of spatial or temporal frequency of the relation between the input and output. If the relationship or ratio 1:1 no distortion is present. Distortion is the alteration of the original shape or characteristic waveform or signal and is usually unwanted. Nonlinear distortion is a term used in fields such as electronics, audio and telecommunications to describe the phenomenon of a non-linear relationship between the input and output signals that happens. when nonlinear distortion is applied to a superposition of two signals at different frequencies causes the circuit to act as a frequency mixer, creating inter modulation distortion. These phenomena occur constantly in the analog domain.

The easiest way to explain how it behaves nonlinear distortion is as follows: we have two simple sinusoidal signals, F1 of 1000 Hz and F2 of 1200 Hz. If we introduce F1 in an equipment with nonlinear distortion, the harmonics generated will be at 2000 Hz, 3000 Hz, and so on. If we introduce F2 on the same equipment with the same nonlinear distortion, harmonics generated will be at 2400 Hz, 3600 Hz, and so on. Then if we mix those signal we will have two pure sinusoidal signals and the harmonics of each one. But if we first mix F1 with F2 and then send to the same equipment with the nonlinear distortion the result will be different, will appear an harmonic frequency of F2-F1 that is called modulation distortion.