Abstract :
The types of 3-frequency parametric upconvertors that have useful amounts of gain whilst being conjugately matched at both input and output terminals are reviewed. A detailed analysis is undertaken of 4-frequency upconvertors having similar properties. It is shown to be necessary for all such 4-frequency convertors, under high-gain conditions, to have certain properties in common. In all cases, the admittance looking into the idler terminals will have a negative-conductance component, which will approach in magnitude to the conductance of the idler termination as the gain of the convertor is increased. The admittances looking into the input and output terminals, on the other hand, are independent of any increase in gain obtained by varying the idler termination. Possible circuits of this type are discussed, and it is shown that convertors using both nonlinear inductance and capacitance, and also convertors using a double-pumped nonlinear capacitor, are both, in principle, realisable.
