Research On The Key Techniques Of Electromagnetic Metamaterials Synthesizing Mechanisms And Applications

Electromagnetic metamaterial (EMM) is a kind of artificial material which cannot be found in nature and can exhibit some novel electromagnetic phenomena. There are many applications and research meanings for the EMM in the electromagnetism, optics, material, and wireless communication, electrical/electronic engineering. Since the first realization of the EMM at microwave frequency band in 2000, it has excited much research attentation. And in the past 15 years, there are three main achievement structures, including metallic resonator structure, planar transmission structure, and all dielectric structure, etc. However, most of the researches on the EMMs focused on the bulk period structures and also most of the novel electromagnetic properties are based on the bulk structures. There are only a few reports focused on the interactions within the EMM units, and/or between the adjacent units. Therefore, in the research area of EMM design and applications, we have to further take deep considerations on the coupling mechanism within the EMM unit and/or between the units.This dissertation investigated the methods to control such coupling mechanism, and finally understand the properties and advantageous of EMM, and enrich the engineering applications. Based on the fully understanding of the basic EMM unit, the dissertation discussed and analyzed systemically the complex coupling properties between split ring resonators, and found applications on the controllable band notched rectangular waveguide filter, designed a super compact planar metamaterial absorber (MMA) and single, dual, multi-band MMAs based on a snowflake resonator, and the tunable multiband EMM based on the ferrite. The research details and achievements are shown as bellows.1. By using the equivalent circuit method and imaging theory, this dissertation analyzed interactions and couplings within the resonators, between the original resonators and its images. Based on the numerical simulations and experimental demonstrations, the resonance properties of the single, dual and multi twist resonators in the rectangular waveguide, and the frequency shift properties of these resonators when changing the split directions were analyzed in details. This thesis designed the single-and dual-band tunable rectangular waveguide band-notched filter based on the twist split ring resonators, by controlling the interactions and couplings within the resonators, between the original resonators and its images, and between the resonators. The results show that 7.5% relative notching frequency shift can be obtained by changing the number of the resonators, and rotating and shifting these resonators. This design method has advantages such as simple realization and low power consumption, and can be used widely in the microwave and mm wave systems.2. This dissertation analyzed the interactions within/between resonators by using the equivalent circuit method. Based on the step by step method, the dissertation realized a super compact planar MMA based on conventional EMM units and FR4 dielectric substrate, and the minimum electrical size of λ/37 was obtained. The obtained MMA had more than 93% absorptivity for the wide angles incident waves. Such super compact MMA can be used to reduce the coupling in the adjacent antenna elements and microwave integrated systems.3. This dissertation also analyzed the interactions among the different main and sub branches within the snowflake shaped resonators, discussed the effects of the branches on the absorbing frequencies, the parameter conditions of realizing single, dual, multi-band absorbing modes. By using rectangular waveguide measurement system, the dissertation demonstrated that the absorbing modes can be controlled by simply changing the length of the main branches of the snowflake shaped resonators.4. This dissertation analyzed the effective permeability of ferrite under different DC biases, and the interaction between conventional EMM units and the ferrite, based on the effective media theory. And finally a tunable multiband EMM was discussed and analyzed. The analyzed results indicate that the designed EMM exhibit three tunable negative permeability band. And such EMM can be used to further design tunable multiband absorber, cloak, antenna, etc.After the deeply investigations on the coupling mechanisms and effects within/between the resonators, this dissertation obtained and found method to control the interactions within/between the resonators, and have obtained the band-notched filter, super compact MMA, mode-controllable MMA, and multiband tunable EMM. These achievements have very important contributions for popularizing the EMM in the communication and electronic engineering areas.