Transmission line metamaterials - a novel approach to dispersion extraction of composite right-handed/left-handed transmission line using near-field scanning S-parameter measurements

摘要

This thesis proposes a novel approach to dispersion extraction of an N-stage composite right-handed/left-handed transmission line (CRLH TL) using near-field scanning S-parameter measurements, which is elaborated in chapters 3 and 4. The data obtained from the measurements is proportional to the electromagnetic field produced by the N-stage CRLH TL, so that a mathematical model for a synthesized field can be built based on the Bloch-wave function which introduces unknown wave amplitudes and propagation constants. By applying Particle Swarm Optimization, the solutions for wave amplitudes and propagation constants of the known field (simulated or measured) are found by minimizing the discrepancy between the reconstructed E-field and the known field. The extracted dispersion characteristics show general agreement with other well-known methods except at high frequencies. The method also provides information about the wave behaviour within the interior structure of the periodic unit cells. An interesting outcome is the structure behaving as 10-stage rather than 20-stage circuit as designed.In addition, this thesis investigates parametric oscillation of the nonlinear CRLH TL when it is excited with a large signal, which is described in a short chapter, chapter 5, as a brief exploration of the nonlinearity of CRLH TL during my research. The analysis of phase-matching with the single-pair and multi-pair frequency generation shows the three-wave mixing model applies only over limited frequency range pass-band of the structure.