An emitter-injected mixer with improved conversion gain, efficiency

Traditional emitter-injected mixers use an inductor placed between the emitter and ground to produce voltage feedback to the transistor for mixing purpose. This configuration provides good port-isolation but low conversion gain due to the presence of the feedback impedance between emitter and ground which reduces the gain of the transistor. It is observed that by replacing the inductor with a diode and choosing suitable bias points for both the transistor and the diode, an improvement in the conversion gain of a few dB and a better collector efficiency can be achieved. The conversion gain of this kind of mixer is analytically predictable