Research On Microwave Dielectric Characteristics Of Typical Material Under High Power Level

Complex permittivity and permeability are the main properties of microwave materials.For non-magnetic materials,the complex permittivity determines the stability and reliability of the circuits and system,which is constructed by the materials.Once the microwave field intensity in the environment exceeds a certain threshold,the characteristics parameters of the material will develop to a serious nonlinear evolution,which will result in the enhancement of the nonlineariry of the device and system basing on the materials.Therefore,it is of great importance to obtain the microwave properties of materials under high power microwave accurately.In this dissertation,the microwave characteristics of typical microwave materials under strong microwave field,introduced by the high power microwave,are studied.It mainly includes the research on the interaction mechanism between high power microwave and materials,the evaluation technology on the evolution of microwave characteristics of typical materials under the strong field induced by high power microwave environment,the distinguishing extraction method of the main influence mechanism between microwave field and materials under the strong field induced by high power microwave.Firstly,the research situation and history on microwave properties of materials under high power microwave is studied and summarized at home and abroad.And a novel method for the characterization of microwave characteristics of small samples under high power microwave basing on the resonance method is proposed,which reduces the cost and improves the efficiency of the experimental research.Secondly,the interaction mechanism between high power microwave and materials,includes microwave thermal effect and microwave non-thermal effect was analyzed in detail,and the evolution of microwave characteristics of materials under the two interaction mechanism was studied.Then,basing on the resonance perturbation theory,the novel methods named single mode method and dual mode mehod are proposed for obtaining the evolution law of microwave characteristics of materials under high power microwave.The corresponding test systems are constructed and some typical materials such as window materials and semiconductor materials are tested.The experimental results are analyzed in detail,and the existence of the mechanism of high power microwave effect on the non-thermal properties of materials is preliminary verified.Finally,based on the theory of the interaction mechanism between microwave and materials,a novel technique for extracting the non-thermal effects of high microwave and materials by pulse method is proposed.Through the experimental test of the typical materials,the conclusion that the exists of microwave non-thermal effect is further verified,and the micwave non-thermal effect and thermal effect are distinguished.What's more,the evaluation characterization method and system can be used to characterize and measure the microwave characteristics of other low loss materials in high power application.The main research contents and contributions of this dissertation can be summarized as follows:1.The origination,research purpose and significance of this subject are expounded.Then,the application research progress of microwave materials under high power microwave is briefly be introduced.Such as the present situation and history of the microwave properties of typical window materials and the typical semiconductor materials under high power microwave,the research situation and history of common detection methods for getting microwave characteristics of materials,and so on.Finally,the existing problem in the research of the properties of the typical low loss materials under high power microwave,such as high cost and long study period,are summarized.2.Firstly,the interaction mechanism between microwave and materials is analyzed in detail,including the mechanism of material to microwave and the mechanism of microwave to material.Secondly,the research methods of the interaction between high power microwave and materials were studied,and the innovative method for characterization of microwave characteristics of small samples based on the resonance method under high power microwave is proposed.Finally,the overall research technology route of this dissertation is given from the theoretical research part,the system design part,and the experiment part,which points out the direction for the whole dissertation.3.The basic theory of resonant cavity is analyzed and the field intensities of different transmission structures and resonant structures are deduced and calculated theoretically,which are verified by the electromagnetic simulation soft.The structural design by locally compresing the regular resonant cavity and the processing method by loading capacitance are proposed,which make the field intensity in the local region of the resonant structure concentrated and improved greatly,and provide a theoretical basis for acquiring an equivalent high power microwave field by low power source.4.According to the theoretical study of microwave strong electromagnetic field,a novel method for the evaluation and characterization of high power microwave interaction with materials named single mode method and dual mode method basing on the principle of perturbation is proposed and the corresponding measurment system is constructed.Then,the evolution of the complex dielectric constant with the external field intensity of the several typical materials under the high power and strong field environment is completed using the measurment system.The temperature of the samples were acquired in real time and accurately under the single mode method and dual mode method experiment.The existence of microwave non-thermal mechanism was preliminarily verified by comparing the test results of the dielectric properties of samples under the action of high power microwave and the test results of dielectric temperature characteristics under the action of low power microwave.5.Due to the nonlinear behavior of the microwave characteristics of typical materials under high power microwave and the strong field,a novel pulsed method basing on the resonant cavity was established,which gives the extracting physical model of the non-thermal interaction mechanism between high power microwave and materials as well as the corresponding testing system.Finally,four kinds of sample were chosed to be tested and verified experimentally.The experimental results demonstrate that the proposed method could effectively extract and distinguish the microwave non-thermal effect from the microwave themal effect,which further proving that the evolution of microwave characteristics under the action of high power microwave was the results of the co-existence and synergistic influence of microwave thermal effect and non-thermal effect.The main technical indexes of the constructed system for characterizing the microwave dielectric performance under high microwave are as follow:?1?Field strength under measurement:>10⁵V/m;?2?Equivalent power density:>200MW/m²?characteristic impedance to 50??;?3?Measurement Frequency:S band;?4?Measurement range:dieletric?r:1.5?20;loss angle tan??<10^-2;...