Investigations To The Properties And Applications Of Artificial Electromagnetic Metamaterials

Metamaterials have many kinds of properties which are totally different from the materials in nature and have gained much attention within the scientific community because of their potential applications to build the perfect lens, invisible cloaks and metamaterial antennas. In this thesis, we focus on the electromagnetic properties and applications of the metamaterials. The main contents and contributions are listed below:1. First of all, an effective method to obtain the constitutive parameters of metamaterials, the parameter retrieval algorithm, is investigated. Then, three novel designs for Left-Handed Medium (LHM) composed of single triangular open loop resonator plus wire structure, double triangular open loop resonator plus wire (TOLR-wire) structure and individual electric plus magnetic resonators are introduced. Finally, the parameter retrieval results, prism simulation results and transmission experiments in rectangular waveguide all validate the double negative property of double triangular open loop resonator plus wire structure.2. The novel parallel plate waveguide (PPW) measurement system, excited and received by two probes, is initially proposed. The PPW is especially designed to measure the transmission characteristic of metamaterials and the measurement results correspond very well with the simulation results. Besides, two effective methods, negative phase shift experiments and sub-wavelength imaging, are also adopted to validate the left-handed property of LHM composed of TOLR-wire structures.3. The triangular electromagnetic resonator (TER) and asymmetric triangular electromagnetic resonator (ATER) metamaterials, which have double and multi resonance properties, are studied. The parameter retrieval results, surface current distribution, analysis of critical parameter and transmission experiment in PPW system are also utilized to distinguish the electric and magnetic response for different resonance regime.4. A broad bandwidth and low loss LHM composed of TER-wire and composite left- and right-handed metamaterials composed of triangular left- and right-handed resonator (TLRR) are both presented. For the former, the parameter retrieval results, prism simulation and transmission experiment reveal that TER-wire structure has a broader left-handed passband and lower loss compared with the conventional SRR-wire structure. For the latter, the TLRR structure has a left-handed passband and right-handed passband through the validation of simulation and experiment.5. The TER applied to the design of microstrip patch antenna is discussed. Through arranging the covers composed of negative permeability and negative permittivity TER arrays covering the patch antenna, two kinds fo novel metamaterial antennas are proposed. The results show that the directional property, gain and the return loss of the two metamaterial antennas have been improved remarkably.