, the term heterodyne
has the following meanings:
1. To generate new frequencies by mixing two or more signals in a nonlinear device such as a vacuum tube, transistor, or diode mixer.
Note: A superheterodyne receiver converts any selected incoming frequency by heterodyne action to a common intermediate frequency where amplification and selectivity (filtering) are provided.
2. A frequency produced by mixing two or more signals in a nonlinear device.
Source: from Federal Standard 1037C and from MIL-STD-188