Design, Fabrication And Applications Of Some New Components Based On Electromagnetic Metamaterials

Electromagnetic metamaterials are broadly defined as artificial composite medium or structures which can guide or radiate the electromagnetic waves in some unusual manners. Quite recently, the so-called left-handed media becomes a famous representative of the metamaterials, which has inspired great research interesting in the microwave and optical communities. Generally speaking, all the artificial structures can be called metamaterials if they exert a special influence on the wave propagation, such as the photonic crystals, electromagnetic band-gap (EBG) materials, defected ground structures (DGS), left-handed media (LHM), composite right/left-handed (CRLH) structures and so on. In this thesis, the guiding characteristics of several kinds of metamaterials are deeply investigated to exploit their applications in e.g. modern communication devices and systems.The whole thesis consists of 6 chapters. The background of the thesis is introduced in chapter 1. In chapter2, we present both of the analytical networking parameters and full-wave numerical simulation methods for the designs in the thesis, such as the ABCD matrix, scattering parameters, the method of moment (MOM), finite element method (FEM) and finite differential time domain (FDTD). We also introduce a high-efficiency optimization algorithm - genetic algorithm (GA) and discuss how to use it to optimize a waveguide attenuator. In chapter 3 we introduce the applications of metamaterials in filter circuits. Firstly, we propose a one dimensional Bragg reflectors, which consists of the right-handed transmission line (RHTL) and left-handed transmission line (LHTL) alternative structures. Using the proposed circuits, the unusual transmission bands of the novel Bragg reflectors are illustrated and measured, which shows that the present devices can be well used in some narrow-band applications. Secondly, we propose a new EBG structure using the etched patterns on the coplanar waveguide (CPW), which can be used to fabricate the super compact low-pass filter with sharp stop band edge and very low loss. In chapter 4 we present the applications of metamaterials in signal power control circuits. Firstly, we propose a novel Wilkinson power splitter with broader isolation band and flatter pass band than its conventional counterparts. The novel device utilized a pure LHTL and its nonlinear dispersion property. Secondly, we propose a new CRLH structure to fabricate a transmission line (TL), using which a novel 2-way equal -division power splitter is implemented. Thirdly, utilizing the CRLH TL and its leaky wave characteristic, we fabricate a novel attenuator with about 11dB attenuation and lowvoltage stand wave ratio (VSWR). In chapter 5, we introduce the applications of metamaterials in phase shifter circuits. We present a novel 'dispersive' RHTL and a new CRLH structure with unusual dispersion properties. Using the novel RHTL and CRLH structure, we have designed and fabricated new broadband differential phase shifters with low loss and 90 degree phase shift. In the last, the chapter 6 concludes the whole thesis and outlines some future research topics.