RF mixers, or frequency mixers, are devices with three ports that are used to change the frequency of the two input signals. RF mixers are passive or active devices used for down converting or up converting signals. The characteristics are RF type, frequency, number of mixers, gain, noise figure, secondary attributes, current, and voltage. The frequency range is from 0 to 90 GHz with the number of mixers being 1, 2, 3, or 4.