【作者】 张辉彬；

【导师】 邓龙江；

【作者基本信息】 电子科技大学 ， 电子信息材料与元器件， 2013， 博士

【摘要】 雷达吸波材料是指能够有效吸收衰减入射电磁波的一类材料，其核心是在薄的厚度下获得宽频段高强度吸收。然而，任何厚度的吸波材料都存在一个对应的使用频段，而通过提高磁导率或进行多层吸波材料设计拓展带宽的传统方法已经远远不能满足当前需求，特别是在L、S波段。因此，拓展吸收带宽、突破低频吸收瓶颈成为当前电磁波吸波技术领域亟需解决的核心问题。与传统吸波材料不同，周期吸波结构侧重于利用人工结构聚集入射的电磁场，再通过介质损耗吸收被聚集的能量。由于这种特别的吸波方式，周期吸波结构有望解决上述宽频吸收难题。本文以电阻膜、磁性吸波涂层或磁性薄膜构成的周期吸波结构为研究对象，通过分析电磁场及其能量损耗分布，建立等效电路模型，构建吸收性能与等效集总参数、结构参数之间的关系，解决吸波材料的宽频及低频吸收难题，取得了以下主要成果：1.采用等效电路理论，建立了周期吸波结构宽频吸收的约束方程，发现了常规图案在宽频吸收中的不足。（1）对电阻膜周期吸波结构的等效电路理论进行反演计算，得出宽频吸收的约束方程，方程定量揭示了吸收峰与等效参数之间的关系，并给出了实现吸收峰所需的理想电阻曲线。（2）将约束方程用于分析长方形、正方形和方环形等电阻膜吸波结构的吸收特点，研究了这些结构的低频单谐振吸收缺陷，发现单一表面电流分布是造成该缺陷的原因。2.基于约束方程进行多谐振设计，提高了电阻膜吸波结构的低频宽频吸收性能。（1）根据约束方程中吸收峰与等效参数之间的关系，提出了一种低频双谐振吸收的梯形耦合型周期吸波结构，理论分析、数值计算以及实验证明了这种结构可以将单元内外内的耦合作用有机结合在一起，实现了表面电流的频散分布，拓展了低频吸收带宽。（2）根据约束方程中的理想电阻曲线，提出了基于非均匀表面电阻设计的多谐振型周期吸波结构，并建立相应的设计方法，这种设计理念兼容了空间电荷引起的相对近场作用以及表面电流引起的相对远场作用，从而引入多谐振机制，拓展了低频吸收频带。3.通过周期结构的多谐振设计，拓展了磁性吸波涂层的吸收带宽。（1）针对具有频散电磁参数的磁性吸波涂层，通过局域场作用调节谐振特性，设计了一种低频双谐振吸收的针尖耦合型周期吸波结构，与传统的非磁性周期吸波结构不同，这种结构的能量耗散包含磁损耗和介电损耗，多损耗机制进一步拓展了周期吸波结构的吸收带宽。（2）通过在磁性吸波涂层内部嵌入金属阵列，激发频散的电磁相互作用，不仅在中高频段提高常规的干涉吸收能力，而且在低频段引入尺寸谐振吸收，进一步增加了吸收带宽。4.创新性地提出了金属磁性薄膜型周期吸波结构。（1）结合金属磁性薄膜的电磁特性与周期结构设计理论，提出了磁场定向型吸波结构，发现薄膜阵列对入射磁场的重定向作用，使磁场被薄膜的高磁损耗吸收掉，克服了磁性薄膜中高电导率导致的阻抗严重失配问题。（2）结合不同薄膜的电磁特性与磁场定向作用，进行多谐振设计，发现薄膜导电性决定了电磁响应形式，高导电性薄膜起重定向作用，低导电性薄膜起损耗吸收作用，为多谐振宽频结构设计提供了新思路。更多还原

【Abstract】 The aim of the radar absorbing material, a class of materials used to effectivelyabsorb incident electromagnetic waves, is to obtain the highest absorption within thewidest operating waveband in the least thickness. However, any traditional absorbingmaterial with a certain thickness operates only in a limited frequency band. Thetraditional methods to expand the absorption bandwidth, such as increasing materialpermeability and carrying out multilayer design, have no longer met the challenge ofmilitary and civil application. As a result, to expand the absorption bandwidth andimprove the absorption at low frequency becomes fatal problems in the field ofelectromagnetic wave absorption.Different from traditional radar absorbing material, periodic absorbing structures(PAS) utilize the ability of controlling incident electromagnetic fields to introduce highabsorption. Due to the special ability, PAS are promising broadband absorbing material.In this thesis, the design of PAS consisting of resistive film, magnetic coating materialor magnetic film is studied. Based on the electromagnetic field and surface currentdistribution, an equivalent circuit model is built to analyze the relationships ofabsorption, equivalent circuit parameters and structure parameters. The aim is to expandabsorption bandwidth, especially the absorption bandwidth in the low frequency band.1. According to the equivalent circuit theory, constraint equations of broadbandabsorption are built, and defects of PAS with common pattern are presented.(1) Based on the equivalent circuit theory, the constraint equations of broadbandabsorption are obtained by the inverse calculation method. The equations reveal therelationship between absorption and equivalent parameters. The equations also calculatethe ideal equivalent resistance for high absorption.(2) By analyzing the absorption characteristics of resistive-type periodic absorbingstructures with rectangle, square and square ring pattern, defects of sole resonantabsorption in low frequency band are found. The reason turns out to be thenon-dispersive surface current distribution.2. According to the constraint equations, multi-resonances are designed to improvethe absorption of resistive-type PAS in low frequency band.(1) A resistive-type PAS with trapezoids-coupling pattern is proposed to deal with the constraint condition between absorption and equivalent parameters. Theoreticalanalysis, mathematical calculation and experiment show that the couplings between andwithin unit cells realize the dispersive distribution of surface current to excite doubleresonances in the structure. The designed structure effectively improves absorption inlow frequency band.(2) A resistive-type PAS with non-homogeneous sheet resistances is proposed todeal with the constraint condition of equivalent resistance. The structure excites threeresonances by introducing relative near-field interaction and relative far-field interaction.These resonances effectively expand the absorption bandwidth in low frequency band.3. By loading periodic structures, multi-resonances are designed to improve theabsorption of magnetic-type PAS in low frequency band.(1) Through partly adjusting resonant characteristics in the magnetic coatingmaterial of dispersive electromagnetic parameters, magnetic-type PAS with needle-pointpattern is proposed to realize double-resonance absorption in low frequency band.Different from traditional non-magnetic PAS, the magnetic-type PAS achievesbroadband absorption by both dielectric and magnetic loss.(2) Through exciting dispersive electromagnetic responses, metal array which isembedded in the magnetic layer can further expand the absorption bandwidth. The arrayimprove the usual interference absorption in high frequency band while introducedimensional resonant absorption in low frequency band.3. Some unique PASs consisting of metal magnetic film arrays are innovativelyproposed.(1) Combining the PAS design theory and the electromagnetic characteristic ofmagnetic film, magnetic-field-controlling structure is proposed. It is found that themagnetic field is re-oriented by the film array, and then absorbed through the highpermeability of the film. The design solves the impedance-mismatching problemcausing by the high conductivity.(2) Combining the different electromagnetic characteristic and re-oriented effect ofdifferent films, a multi-resonance structure is proposed. In the design, theelectromagnetic responses can be determined by the conductivity. The film of highconductivity re-orients the direction of magnetic field while the film of low conductivity.The design provides new method for design of multiband absorber.更多还原