the diodes are commonly Schottky types. Such mixers are widely used because of their low feedthrough, broad frequency range, and good large-signal performance.

Bell System research in the late 1920s examined double-balanced mixers using copper-oxide rectifiers for voice modulation. By 1931 they were reported as serious competitors to vacuum-tube modulators, and by 1939 they were used in many telephony carrier systems. These circuits translated voice channels to higher carrier frequencies so that