Side bands are produced during the process of modulation. During modulation, the audio frequency modulating signal wave is superimposed on a high frequency wave called carrier wave. Any form of modulation produces frequencies that are the sum and difference of the carrier and modulating frequencies.

How are sidebands generated?

Sideband. A FREQUENCY component in a SPECTRUM produced by a MODULATION of the original SIGNAL. In the case of amplitude and frequency modulation, sidebands occur in pairs on either side of the CARRIER frequency at a distance equal to the modulating frequency.

Where do sidebands come from?

When the signal is modulated onto the carrier in the electromagnetic spectrum, that signal occupies the small portion of the spectrum surrounding the carrier frequency. It also cause sidebands to be generated at frequencies above and below the carrier frequency.