Signal processes in transistor mixer circuits at high frequencies

The signal performance of transistor mixers at high frequencies is investigated by treating the basic nonlinear differential equations of the transistor. These equations have been solved in normalised form on a digital computer, and the results have been obtained as normalised graphs, which allow rapid prediction of the conversion transconductance at higher frequencies. Transistor parameters and operating conditions for maximum conversion gain at high frequencies are readily determined from these results. The transistor-mixer input impedance is also investigated in detail, and it is shown, in general, to be higher than the corresponding amplifier input impedance. Although calculable, the precise input impedance cannot be predicted as simply as the conversion transconductance.