Frequency conversion by means of a nonlinear admittance

This paper gives a mathematical analysis of a heterodyne conversion transducer in which the nonlinear element is made up of a nonlinear resistor and a nonlinear capacitor in parallel. Curves are given showing the change in admittance and gain as the characteristics of the nonlinear elements are varied. The case where a conjugate match exists at the terminals is treated. It is shown that when the output frequency is greater than the input frequency, modulators having substantial gain and bandwidth are possible, but when the output frequency is less than the input frequency, the converter loss is greater than unity and is little affected by the nonlinear capacitor. The conditions under which a conjugate match is possible are specified and it is concluded that a nonlinear capacitor alone is the preferred element for modulators and that a nonlinear resistor alone gives the best performance in converters.