Generating oscillating pulses using nonlinear capacitive transmission lines

A nonlinear lumped element transmission line (NLETL) that consists of a series cascading network of linear inductors and parallel nonlinear capacitors can be used to produce oscillating pulses. This paper describes the implementation of such high voltage nonlinear capacitive lines (NLCL) using commercial-off-the-shelf (COTS) components. Instead of using complex pulse forming networks or pulse forming lines, a storage capacitor and a fast semiconductor switch are used to provide an input pulse onto the cascading LC-elements of the NLCL with good approximation for a rectangular pulse-shape. The design of the NLCL is based on the NLETL circuit model that has been developed in-house. Experimental results are compared with simulations predicted by the NLETL model. The voltage modulation and the frequency content of the output pulses are analyzed. The conventional single NLCL produces a signal with a DC offset and a decoupling capacitor is needed at the end of the line to extract the AC component before injecting into a load such as an antenna. A novel method of directly extracting the AC component without the use of a decoupling capacitor is proposed and investigated. Results of this direct AC extraction, which show the possibility of better performance, are discussed.