微波吸波材料在太赫兹、红外段反射谱测量研究

Study on the Measurement of Reflection Spectra of Microwave Absorbing Materials in the Terahertz and Infrared Regions

吸波材料是外形隐身技术的有效补充技术,电磁波进入到吸波材料内部后,应该被迅速地最大限度的衰减掉,因此,在设计吸波材料的电磁参数时,一方面要考虑阻抗匹配,使电磁波最大限度地进入到材料内部,另一方面,要确保进入到材料内部的电磁波尽可能被全部衰减掉。对吸波材料来说,也就是材料要有较大的介电常数虚部和磁导率的虚部,它们会引起电磁波能量的衰减。传统的吸波材料主要针对于微波,随着技术的发展,太赫兹雷达已投入使用,传统的微波吸波材料能否对太赫兹频段、乃至红外段有效衰减,以及这些吸波材料在太赫兹频段的评估成为了有必要研究和探讨的问题。分别基于矢量网络分析仪的微波暗室测量系统、太赫兹时域光谱测量系统、以及傅里叶变换光谱系统对2种微波段吸波材料板开展深入测量研究,在微波段反射率测量基础上,拓展到太赫兹、红外波段,测量了这些材料1 GHz~180 THz的雷达吸波材料反射率。测量结果表明,随着频率的升高,吸波材料表面形态、粗糙度对反射率形成了一定的影响,并针对这种影响在太赫兹、红外波段进一步开展了吸波材料反射特性随角度的变化的研究;为了弄清吸波材料在太赫兹、红外频段的吸波原理,将吸波涂层从金属衬板上剥离后进行了测量,获得了该吸波涂层2~180 THz的反射率、透射率,并基于Kamers-Kronig关系计算了该复合吸波材料等效的介电参数,测试结果证明,微波波段的吸波材料在太赫兹、远红外频段仍具备一定的吸波能力,太赫兹、红外不足以穿透该吸波材料的反射涂层到达金属衬板,其吸收主要来自反射吸收和吸波材料表面的散射。

Absorbing materials are an effective supplement to external stealth technology.After electromagnetic waves enter the interior of absorbing materials,they should be rapidly and maximally attenuated.Therefore,when we design the electromagnetic parameters of absorbing materials,impedance matching should be considered to maximize the entry of electromagnetic waves into the material.On the other hand,it is necessary to ensure that all electromagnetic waves entering the material are attenuated as much as possible.For absorbing materials,it means that the material must have a large imaginary part of the dielectric constant and magnetic permeability,which can cause attenuation of electromagnetic wave energy.Traditional microwave-absorbing materials mainly focus on microwaves.With the development of technology,terahertz radar has been put into use.It is necessary to study and explore whether traditional microwave absorbing materials can effectively attenuate in the terahertz and even infrared frequency bands and evaluate these absorbing materials in the terahertz frequency band.Two types of absorbing material plates are studied in-depth by the terahertz time-domain spectrum,Fourier transform spectral system,and microwave anechoic chamber measurement system based on a vector network analyzer.The microwave,terahertz,and infrared bands measured the reflectivity of radar-absorbing materials from 1 GHz to 180 THz.The measurement results indicate that as the frequency increases,the surface morphology and roughness of the absorbing material have a certain impact on the reflectivity.Further research has been conducted on the changes in the reflection characteristics of the absorbing material with angles in the terahertz and infrared bands.To further study the absorption principle of the absorbing material in the terahertz and infrared frequency bands,the absorbing layer was peeled off from the metal lining plate and measured.The reflectivity and transmittance of the absorbing coating at 2~180 THz were obtained,and the equivalent dielectric parameters of the composite absorbing material were calculated based on the Kamers-Kronig relation.The test results showed that the absorbing material still has a certain absorption ability in the terahertz and infrared.Infrared is not sufficient to penetrate the reflective coating of the absorbing material to reach the metal lining plate,and its absorption mainly comes from reflection absorption and scattering from the surface of the absorbing material.