Rresearch On Design And Application Of Tunable Dielectric Metamaterials

Metamaterials are artificial composite materials and structures that have extraordinary properties.The specific electromagnetic response of metamatrial results from the artificial electromagnetic parameters.The metamaterial can control the phase,amplitude and polarization of incident electromagnetic waves.The traditional metamaterials have three main problems.First,the response of traditional metamaterials is decided by the artificial structure.So the operating frequency is fixed when the metamaterial structure is fixed.Second,for the metallic metamaterials,additional tunable elements are necessasy to fabricate the tunable devices.Third,the processed fabrication of the metamaterials in high frequency is complex.To solve the above problems,we proposed a method to design metamaterials and functional devices using dielectric materials.The electromagnetic properties of dielectric materials such as dielectric ceramic materials and ferrite materials are highly sensitive to some external fields and can be tuned without loading other components.These materials have intrinsic electromagnetic responses to incident electromagnetic waves.So the processing method is very simple.This research focuses on the design of metamaterials and devices,such as filters,sensors and absorbers.The metamaterials and devices are fabricated by dielectric materials and ferrite materials.1.Two tunable filters are designed and prepared.According to the influence of shape,size and external magnetic field of the converter on the ferrite,the broadband performance and magnetic tunable performance of the filter are realized.The first is a ferrite-based metamaterial filter,which mainly uses the transmission stop band caused by the intrinsic negative permeability of the ferrite to obtain the filtering performance.The size effect of the ferrite results in a wide filter band.The extraodinary transmission phenomenon has a passband at a specific frequency.Based on extraordinary transmission,the subwavelength aperture realizes the filtering performance.This waveguide filter has dual spectrum and magnetically tunable performance.2.Two microwave sensors have been designed and prepared,which have the characteristics of sharp resonance peak,high peak intensity and high sensitivity.A sensor based on dielectric resonator is used to detect cracks on metal surfaces.The measured results show that this sensor can detect cracks on the metal surface.This sensor can also characterize crack size.Another microwave sensor based on dielectric resonator is used for temperature detection.This temperature sensor can detect the temperature.At the same time,this temperature sensor integrates the resonance element and the sensing element,which solves the problem of the complex structure of the sensor based on the metamaterial unit and simplifies the structural design.3.A metamaterial absorber based on Mie resonance is designed to achieve the wideband absorption performance in the terahertz band.Using the Mie resonance of the dielectric particles under the incident electromagnetic waves,the electromagnetic energy can be dissipated and the electromagnetic waves are completely absorbed in a specific frequency band.It is important to combined four dielectric particles with various dielectric constants into the same metamaterial unit cell to achieve the widen bandwidth of the metamaterial absorber.The metamaterial absorber solves the problems of narrow band absorption of the current metamaterial absorber.