High power pulse burst generation by soliton-type oscillation on Nonlinear Lumped Element Transmission Lines

Nonlinear lumped element transmission line (NLETL) technology has potential value as a source of high power RF pulse burst waveforms. Recent work by the pulsed power & plasma physics group at the University of Oxford has provided a comprehensive analysis of key trends relevant to the design of such lines, and an enhanced understanding of the phenomenon by which the input pulse to a suitable NLETL may break into a train of high frequency oscillations. The nonlinear-dispersive Korteweg de Vries (KdV) equation has on occasion been associated with electrical transmission lines incorporating capacitive nonlinearity, and the individual pulses in the past identified as soliton waves accordingly. The type of oscillation under consideration has been found here to be directly reliant upon the discrete nature of the transmission line, and mathematically distinct from other continuous soliton solutions. There are, however, strong indications that the combination of spatial discreteness and nonlinearity leads to wave trains of a solitonic nature, most closely related to the discrete breathers arising from certain theoretical models of nonlinear lattices. This paper reports on the continuing work in this area alongside the latest high power experimental results. Whilst good quality oscillation has been demonstrated on a range of lines, it is also important to overcome the problems associated with extracting RF energy to typical load impedances. Experimental work presented focuses on a special `asymmetric parallel' (ASP) two-line configuration for effective extraction of high power soliton-type pulse burst waveforms, and also investigates the incorporation of propagating antenna components directly into the transmission line structure.