Research On The Key Technology Of Reconfigurable Windowing-metamaterial And Its Application

As an advancing paradigm of materials,the metamaterial has been widely researched since the last century.Due to its low profile,excellent performance and low fabricating cost,it can be applied to the fields including antenna camouflage,electromagnetic(EM)compatibility and satellite communications,etc.Recently,the reconfigurable windowingmetamaterial(RWM)with much more flexibility has attracted a great deal of research interest.RWM is the metamaterial with transmission windows in its response,e.g.,reconfigurable frequency selective surface(FSS),reconfigurable rasorber and active multifunctional metamaterial(AMM),etc.RWM can be applied to more complex scenarios since it has integrated dual or multiple functions in one piece.This dissertation has researched the theory and design methodology of several key issues about the RWM and can be summarized as four aspects listed below:(1)This dissertation proposes the design methodology of the dual-band FSS with independently switchable characteristics.Based on the theory of equivalent circuit model(ECM),the synthesizing method of the FSS with a first-order response has been presented.In addition,a unit cell(UC)with Jerusalem cross structure has been realized through the aforementioned method.To improve the frequency selectivity,the methodology of the dual-band FSS with a second-order response and independently switchable characteristic has been developed based on the first-order one.A rotational symmetric antenna-filterantenna UC configuration has achieved a dual-polarization property.The switching operations of the FSSs are both realized by the loaded PIN diodes.The proposed FSSs are both validated by the ECM and full-wave simulation.In addition,the prototype of the second-order FSS has been fabricated and experimentally verified as well.(2)This dissertation proposes the design methodology of a switchable rasorber with high roll-off and polarization selection characteristics.A corresponding UC structure has been realized based on the proposed methodology.The device can be switched between rasorber,polarization selection,and absorber modes.It is composed of two resistive layers(a passive and an active resistive layer)and an FSS.Transmission zeros(TZs)are introduced in the FSS design to improve the roll-off characteristic of its transmission band.The PIN diodes on the active resistive layer and FSS can be independently controlled in the orthogonal polarizations to realize the polarization selectivity.In addition,a prototype is fabricated and measured,and the experimental results have matched the simulated ones well.(3)This dissertation proposes the design methodology of an RWM with multiple functions.The UC configuration with four operating modes has been realized based on the proposed methodology.The device can be electronically switched between reflective linear-to-linear polarization converter(RLTL-PC),absorber,FSS and transmissive linearto-circular PC(TLTC-PC)modes.Further,the UC structure consists of a resistive layer and a double-layer FSS.The operating mode is controlled by electronically tuning the states of PIN diodes loaded on each layer.A prototype of the proposed device is also fabricated and experimentally tested to validate the full-wave simulation.(4)This dissertation investigates the theory and paradigm of the RWM with spatial coding and the RWM applying for the time-varying metamaterial,respectively.The UC structure of the RWM with spatial coding,as well as the UC structure of the RWM that can be used in the time-varying metamaterial,have been proposed respectively.The discussed RWMs can both operate under FSS and RLTL-PC modes.For the RWM with spatial coding,a phase difference can be introduced by rotating the UC under its RLTL-PC modes,and the incidence EM wave will be diffused based on the spatially coding UC array.The latter RWM has rotated its UC by electronically controlling the biasing state of the PIN diode? such a characteristic can be applied in the time-varying metamaterial that requires the dynamic manipulation of the reflective state.Finally,the resistive layers are both inserted to the above devices to achieve out-band absorption.