User:Nimur/Sandbox

Nimur Sandbox

Test 2

A frequency spectrum plot showing intermodulation between two injected signals at 270 and 275 MHz (the large spikes). Visible intermodulation products are seen as small spurs, identified by arrows, at 280 MHz and 265 MHz.

Intermodulation or intermodulation distortion (IMD), or intermod for short, is the result of two or more signals of different frequencies being mixed together, forming additional signals at frequencies that are not, in general, at harmonic frequencies (integer multiples) of either.

Intermodulation is caused by non-linear behaviour of the signal processing being used. The theoretical outcome of these non-linearities can be calculated by conducting a Volterra series of the characteristic, while the usual approximation of those non-linearities is obtained by conducting a Taylor series.

Intermodulation is rarely desirable in radio or audio processing, as it essentially creates spurious emissions, which can create minor to severe interference to other operations on the signal. Intermodulation should not be confused with general harmonic distortion (which does have widespread use in audio effects processing). Intermodulation specifically creates non-harmonic tones ("off-key" notes, in the audio case) due to unwanted mixing of closely spaced frequencies.