Circuit modeling of nonlinear lumped element transmission lines

A nonlinear lumped element transmission line (NLETL) that consists of an LC-ladder network can be used to convert a rectangular input pump pulse to a series of RF oscillations at the output. The discreteness of the LC-sections in the network contributes to the line dispersion while the nonlinearity of the LC-elements produces the nonlinear characteristics of the line. Both of these properties combine to produce wave trains of high frequency. This paper describes a NLETL circuit model that is used to simulate RF generation for a given input pump pulse. The circuit model is used to study a NLETL with nonlinear capacitance (nonlinear C but linear L), and a NLETL with nonlinear inductance (nonlinear L but linear C). With the goal of better matching to a resistive load, an hybrid line that comprises both nonlinear elements L and C was also investigated using the circuit model. Parametric studies were carried out for the various NLETLs to understand the behaviour and characteristics of these lines.