Analysis of Nonlinear Transmission Line Metamaterials

Dr. Greg Milford

University of New South Wales, Canberra, Australia

Abstract:

The left-handed propagation characteristics of periodic transmission line structures offer an extra degree of freedom for the design of circuits and antennas. The inclusion of nonlinear components in the structure's unit cell produces effects such as harmonic generation, period doubling, and parametric amplification and oscillation. The parametric behaviour is particularly interesting, and arises as a result of nonlinear interactions between a strong input pump signal and either a spontaneously generated or a second input signal. This behaviour could be exploited in device design, particularly for signal processing at THz frequencies where the designer has few circuit component options. However the key to realising the potential of these structures is an accurate understanding of the energy exchange mechanisms between the pump and signal waves, and how these relate to the unit cell's internal passive and nonlinear circuitry, as well as the unit cell's interconnectivity.  In this talk we discuss some of the work undertaken at UNSW Canberra, aimed at gaining a better understanding of the fundamental principles of operation of these nonlinear periodic structures. This includes equivalent circuit modelling of the unit cell's passive circuit and nonlinear device components. Techniques for characterising the stability of the nonlinear transmission line structure formed by a cascade of unit cells will be reviewed, and extraction of the propagation coefficient and Bloch wave function envelope from scanned field data will be discussed.

Biography:

Greg has a Bachelor degree in Electrical Engineering from the University of Queensland (1979) and Master (1992) and PhD degrees from the University of New South Wales (2002). Since January 2000 he has been a member of academic staff in the School of Engineering & Information Technology, UNSW, at the Australian Defence Force Academy in Canberra. His research interests focus on analysis and design of metamaterial structures for circuit and antenna applications, and modelling and characterisation of antennas in conducting media. He teaches classes on circuit theory, electronics and engineering electromagnetics. He also has extensive experience working in industry on the design, development, maintenance and implementation of a range of RF circuits and systems.