Double balanced diode mixer with high output third order intercept point

A double balanced mixer consisting of an RF balun, a local oscillator balun and a diode "quad" bridge circuit connected between the two baluns and where the IF output is taken at the center tap of the RF balun secondary transformer. A second harmonic termination consisting of an RLC resonant circuit is coupled across the diode bridge at the RF side. Each arm of the diode bridge, moreover, includes three series connected diodes. The mixer is in the form of a microminiature integrated circuit (MMIC) using HBT emitter-based junction diodes fabricated on a gallium arsenide (GaAs) substrate.