Study On Key Technologies Of Nonlinear Electromagnetic Meta-materials And Its Antennas

With the rapid developments of communication technologies,some traditional device design methods are difficult to satisfy the requirements of communication components for the performance improvements and more functional integration.Since the electromagnetic metamaterial has many novel characteristics,the electromagnetic metamaterial provides a new design and realization method for the new-generation communication devices in the tuning controllable,broadband,nonlinear and quantum directions.Among them,the frequency conversion function of nonlinear device has a wide range of applications in communication systems.Based on the property of that the microscopic size of the electromagnetic material in response to changes in the electric field and magnetic field strength is more significant than in the macroscopic field,a new method for designing nonlinear electromagnetic metamaterials can be developed.And the achievement will significantly promote the development of nonlinear electromagnetic metamaterials in application of communication system,such as the mixers and frequency multipliers.However,at present,the research of nonlinear electromagnetic metamaterials mostly focuses at optical frequency band.This thesis will explore in-depth the coupling mechanism,design method and electromagnetic characteristics of a magnetostrictive nonlinear electromagnetic metamaterial that works in the microwave frequency range.The nonlinear shifting feature of the resonant frequency for the ptoposed nonlinear metamaterial will be demonstrated experimentally,and an antenna power protection cover based on the magnetostrictive nonlinear electromagnetic material will be proposed.The main research work and innovation contributions of this thesis are shown as follows:1.Based on the electromagnetic-mechanical force coupling model,the coupling mechanism,nonlinear characteristics and steady-states of magnetostrictive electromagnetic metamaterials were studied with detailed theoretical analysis,electromagnetic simulation and experimental verification.The define and determine method of steady state,critical-stable state,and unreachable steady state of the metamaterial are provided.Two influential factors,the intensity and frequency of incident electromagnetic waves,that affect the electromagnetic characteristics of magnetostrictive nonlinear electromagnetic materials are investigated in depth.In experiments,when the magnetic field strength H₀ of the electromagnetic wave is enhanced to 0.182 A/m,the resonance frequency shift of nearly 50 MHz occurs in the electromagnetic metamaterial,which verifies the correctness of the theoretical analysis.2.A nonlinear electromagnetic metamaterial design method in liquid environment is proposed.The dynamic process of the structural change of this electromagnetic metamaterial unit after irradiation by electromagnetic waves in a low Reynolds number fluid medium is studied.Two important physical parameters,electromagnetic wave intensity and metal material,which affect the electromagnetic properties of nonlinear electromagnetic metamaterials based on liquid media,are pointed out.In experiments,when the magnetic field strength H₀ of the electromagnetic wave is enhanced to 0.407A/m,the electromagnetic metamaterial in the dimethyl silicone oil with a viscosity coefficient of 100 CST can obtain a resonance frequency deviation of nearly 300 MHz.The experimental results and theoretical analysis are in a good aggrement.3.A power protection radome based on the nonlinear characteristics of magnetostrictive nonlinear electromagnetic metamaterials is proposed.A antenna covered by the metamaterial protection radome was simulated and experimentally analyzed.The results showed that the antenna protection radome,exhibited a resonant frequency of 13 GHz at low power and 12.5 GHz at high power conditions,had a 4 d B more reflection effect when the external electromagnetic wave power is high.So it can protect the antenna and the communication components after the antenna.The designed and obtained nonlinear metamaterial and the power protection radome can be widly used in the areas of microwave communication components and electromagnetic protection devices.