An Etymological Dictionary of Astronomy and Astrophysics
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In the → superheterodyne technique, the electronic component that lowers the frequency of the input signal and combines it with the signal coming from the → local oscillator to produce the → intermediate frequency signal. The lowered frequency, when amplified, has little chance to escape back into the antenna and produce feedback. Moreover, it is easier to make efficient amplifiers, filters, and other components for lower frequencies.

Agent noun from → mix.

In a → superheterodyne receiver, a → mixer which consists of a sandwich structure of two superconducting leads separated by a thin isolator. SIS mixers give a good noise performance especially for → millimeter wavelengths.

SIS, acronym for Superconductor-Insulator-Superconductor; → mixer.