Experimental Characterization of a Genetic Algorithm-Optimized Nonlinear Transmission Line for High Power RF Generation

A numerical model of a dispersive, discrete-element nonlinear transmission line (NLTL) employing saturable inductors is reported and demonstrated to qualitatively reproduce the experimentally measured output of an NLTL. This numerical model is used with a genetic algorithm (GA) to optimize RF output power by varying the number of turns on each inductor at each stage and capacitance at each stage of the NLTL. Based on these results, an NLTL with the GA-optimized component values is fabricated and tested. In testing, the optimized NLTL produced ~30% higher output power than the highest output power of a uniformly distributed NLTL. In selected cases, for identical bias conditions, the optimized NLTL generated nearly 80% higher output power. Notably, the optimized NLTL produced a nonnegligible higher output frequency while also generating higher output power.

I. Introduction

Nonlinear transmission lines (NLTLs) are a unique means of producing high-power RF and microwaves in a footprint that is considerably smaller than many other technologies. Moreover, NLTLs are free from many of the technological challenges of competing technologies, such as the vacuum and magnetic field requirements characteristic of vacuum electronic-based microwave sources [1]. Still, NLTLs generally produce considerably lower power than vacuum electronic sources and feature other drawbacks.