Hetrodyne

In telecommunications, physics, and radio astronomy, heterodyning is the generation of new frequencies by mixing two or more signals in a nonlinear device such as a vacuum tube, transistor, diode mixer, Josephson junction, or bolometer. Mixing two frequencies creates two new frequencies, one at the sum of the two frequencies mixed, and the other at their difference. A heterodyne receiver is a telecommunication receiver which uses this effect to produce frequency shifts.