Experimental And Application Study Of Microwave Band Left-handed Material

Left-handed materials have recently attracted great interests in scientific community. This dissertation addresses experiments that verify their basic properties and other relevant physical phenomenon and their potential applications in microwave coupler, periodic structures as well as antennas.In the first part of this dissertation (chapter 3), a backward waveguide coupler partially filled with a left-handed material is realized and measured. The electromagnetic wave propagates in the primary branch of the coupler which is filled with the left-handed material and is backward edge-coupled into the secondary waveguide, filled with a right-handed material, so as to satisfy phase matching conditions at the interface between the two media. Experimental results verify that EM power is backward coupled between left-handed material and right-handed material, and that Poynting vector and wave vector are anti-parallel within the left-handed material.In the second part of this dissertation (chapter 4), using a metamaterial sample which has been verified to possess a left-handed property over a wide frequency band, a series of transmission experiments are performed on various one-dimensional LHM-RHM layered stacks to verify the existence of zero order bandgap in such structures and its unique property. This special bandgap occurs due to zero volume-averaged refractive index of the periodic structure, and unlike conventional photonic band gap, the frequency corresponding to the zero order gap remains unchanged when the periodicity is altered.A highly directive antenna based on anisotropic metamaterials is presented theoretically and experimentally in the third part of this dissertation (chapter 5). The condition for highly directive radiation based on anisotropic medium is presented, and is confirmed by FDTD simulation results. Ideal half-power beamwidth of the antenna is obtained, and effects of various factors on the performance of the antenna arefurther discussed. The theoretical predictions are confirmed by experiments.