Investigation into wideband electromagnetic stealth device based on plasma array and radar-absorbing materials

Manipulation of electromagnetic waves is essential to various microwave applications,and absorbing devices composed of low-pressure gas discharge tubes and radar-absorbing materials(RAM)can bring new solutions to broadband electromagnetic stealth.The microwave transmission method is used to measure the physical parameters of the plasma unit.The designed structure exhibits superior absorption performance and radar cross-section(RCS)reduction capability in the 2–18 GHz band,with unique absorption advantage in the S and C frequency bands.It is found that the combination of the plasma and the RAM can significantly broaden the absorption frequency band and improve the absorption performance with excellent synergistic stealth capability.Experimental and simulation results present that broadband,wide-angle,tunable electromagnetic wave absorption and RCS reduction can be achieved by adjusting the spatial layout of the combined plasma layer and the type of RAMs,which creates opportunities for microwave transmission and selective stealth of equipment.Therefore,the wave manipulation by combined plasma array and RAM provides a valuable reference for developing numerous applications,including radar antenna stealth,spatial filter,and high power microwave shielding.

Study of plasma-based stable and ultrawideband electromagnetic wave absorption for stealth application

A plasma-based stable,ultra-wideband electromagnetic（EM） wave absorber structure is studied in this paper for stealth applications.The stability is maintained by a multi-layer structure with several plasma layers and dielectric layers distributed alternately.The plasma in each plasma layer is designed to be uniform,whereas it has a discrete nonuniform distribution from the overall view of the structure.The nonuniform distribution of the plasma is the key to obtaining ultra-wideband wave absorption.A discrete Epstein distribution model is put forward to constrain the nonuniform electron density of the plasma layers,by which the wave absorption range is extended to the ultra-wideband.Then,the scattering matrix method（SMM） is employed to analyze the electromagnetic reflection and absorption of the absorber structure.In the simulation,the validation of the proposed structure and model in ultra-wideband EM wave absorption is first illustrated by comparing the nonuniform plasma model with the uniform case.Then,the influence of various parameters on the EM wave reflection of the plasma are simulated and analyzed in detail,verifying the EM wave absorption performance of the absorber.The proposed structure and model are expected to be superior in some realistic applications,such as supersonic aircraft.

FDTD Analysis of Reflection of Electromagnetic Wave From a Conductive Plane Covered with Inhomogeneous Time-Varying Plasma

A finite-difference time-domain (FDTD) algorithm is applied to study the electromagnetic reflection of conduction plane covered with inhomogeneous time-varying plasma, homogeneous plasma and inhomogeneous plasma. The collision frequency of plasma is a function of electron density and plasma temperature. The number density profile follows a parabolic function. A discussion on the effect of various plasma parameters on the reflection coefficient is presented. Under the one-dimensional case, transient electromagnetic propagation through various plasmas has been obtained, and the reflection coefficients of EM wave through various plasmas are calculated under different conditions. The results illustrate that a plasma cloaking system can successfully absorb the incident EM wave.

Numerical and Experimental Investigation on Electromagnetic Attenuation by Semi-Ellipsoidal Shaped Plasma

Some reports presented that the radar cross section （RCS） from the radar antenna of military airplanes can be reduced by using a low-temperature plasma screen. This paper gives a numerical and experimental analysis of this RCS-reduction method. The shape of the plasma screen was designed as a semi-ellipsoid in order to make full use of the space in the radar dome. In simulations, we discussed the scattering of the electromagnetic （EM） wave by a perfect electric conductor （PEC） covered with this plasma screen using the finite-difference-time-domain （FDTD） method. The variations of their return loss as a function of wave frequency, plasma density profile, and collision frequency were presented. In the experiments, a semi-ellipsoidal shaped plasma screen was produced. Electromagnetic attenuation of 1.5 GHz EM wave was measured for a radio frequency （RF） power of 5 kW at an argon pressure of 200-1150 Pa. A good agreement is found between simulated and experimental results. It can be confirmed that the plasma screen is useful in applications for stealth of radar antenna.

Experimental Investigation on Electromagnetic Attenuation by Low Pressure Radio-Frequency Plasma for Cavity Structure

This paper reports on an experiment designed to test electromagnetic（EM）attenuation by radio-frequency（RF）plasma for cavity structures.A plasma reactor,in the shape of a hollow cylinder,filled with argon gas at low pressure,driven by a RF power source,was produced by wave-transmitting material.The detailed attenuations of EM waves were investigated under different conditions：the incident frequency is 1-4 GHz,the RF power supply is 13.56 MHz and1.6（-3） k W,and the argon pressure is 75-200 Pa.The experimental results indicate that 5-15 d B return loss can be obtained.From a first estimation,the electron density in the experiment is approximately（1.5-2.2）×1016m（-3）and the collision frequency is about 11（-3）0 GHz.The return loss of EM waves was calculated using a finite-difference time-domain（FDTD）method and it was found that it has a similar development with measurement.It can be confirmed that RF plasma is useful in the stealth of cavity structures such as jet-engine inlet.

Plasma characteristics and broadband electromagnetic wave absorption in argon and helium capacitively coupled plasma

A one-dimensional self-consistent calculation model of capacitively coupled plasma(CCP)discharge and electromagnetic wave propagation is developed to solve the plasma characteristics and electromagnetic wave transmission attenuation.Numerical simulation results show that the peak electron number density of argon is about 12 times higher than that of helium,and that the electron number density increases with the augment of pressure,radio frequency(RF)power,and RF frequency.However,the electron number density first increases and then decreases as the discharge gap increases.The transmission attenuation of electromagnetic wave in argon discharge plasma is 8.5-dB higher than that of helium.At the same time,the transmission attenuation increases with the augment of the RF power and RF frequency,but it does not increase or decrease monotonically with the increase of gas pressure and discharge gap.The electromagnetic wave absorption frequency band of the argon discharge plasma under the optimal parameters in this paper can reach the Ku band.It is concluded that the argon CCP discharge under the optimal discharge parameters has great potential applications in plasma stealth.

An electromagnetic wave attenuation superposition structure for thin-layer plasma

This work proposes a new plasma super-phase gradient metasurfaces(PS-PGMs)structure,owing to the limitations of the thin-layer plasma for electromagnetic wave attenuation.Based on the cross-shaped surface unit configuration,we have designed the X-band absorbing structure through the dispersion control method.By setting up the Drude dispersion model in the computer simulation technology,the designed phase gradient metasurfaces structure is superposed over the plasma,and the PS-PGMs structure is constructed.The electromagnetic scattering characteristics of the new structure have been simulated,and the reflectance measurement has been carried out to verify the absorbing effect.The results demonstrate that the attenuation effect of the new structure is superior to that of the pure plasma structure,which invokes an improved attenuation effect from the thin layer plasma,thus enhancing the feasibility of applying the plasma stealth technology to the local stealth of the strong scattering part of a combat aircraft.

Attenuation characteristics of electromagnetic waves in plasma generated by coating radionuclide on surface structures

Stealth technology plays an important role in modern military conflicts, especially when used in fighter jets. Since airfoil structures have a leading edge, inlet, and surface bulge that are easily detected by radar, it is necessary to study the stealth of these structures. In this study,we investigate structures coated with radionuclides to generate plasma. Using simulation and calculation methods, the attenuation of 0.1–10 GHz electromagnetic waves propagating in plasma was studied. The results showed that the attenuation of low-frequency electromagnetic waves is greater than that of high-frequency electromagnetic waves.The attenuation of 0.1–1 GHz electromagnetic waves is found to be less than-2.7 d B,-3.0 d B, and-15.6 d B at the airfoil leading edge, inlet, and surface bulge structures, respectively. We also found that the attenuation of electromagnetic waves with 0°-incidence is greater than that of waves with 10°, 20°, and 30° incidence angles.Additionally, the attenuation of electromagnetic waves decreases gradually as the incident angle increases.

Numerical and Experimental Investigation on the Attenuation of Electromagnetic Waves in Unmagnetized Plasmas Using Inductively Coupled Plasma Actuator

The attenuation of electromagnetic （EM） waves in unmagnetized plasma generated by an inductively coupled plasma （ICP） actuator has been investigated both theoretically and experimentally. A numerical study is conducted to investigate the propagation of EM waves in multilayer plasma structures which cover a square fiat plate. Experimentally, an ICP actuator with dimensions of 20 cm×20 cm×4 cm is designed to produce a steady plasma slab. The attenuation of EM waves in the plasma generated by the ICP actuator is measured by a reflectivity arch test method at incident waves of 2.3 GHz and 10.1 GHz, respectively. A contrastive analysis of calculated and measured results of these incident wave frequencies is presented, which suggests that the experiment accords well with our theory. As expected, the plasma slab generated by the ICP actuator can effectively attenuate the EM waves, which may have great potential application prospects in aircraft stealth.

涂覆型雷达吸波材料研究进展

雷达吸波材料是隐身技术的关键材料,雷达吸波材料的研究越来越受到世界各国的高度重视。较详细地介绍了磁性吸收材料、高温吸波材料、纤维吸收材料、手征吸波材料、高分子材料吸收体、等离子体吸波材料、纳米吸收体等涂覆型吸收材料研究状况和吸波机理。

等离子体隐身机理研究

等离子体隐身技术作为一种全新的隐身概念 ,日益受到人们的关注。本文首先简要介绍等离子体隐身的发展现状 ;然后分别从折射效应和吸收衰减两方面详细论述等离子体隐身的基本原理 ,说明等离子体隐身是一种很有前途的隐身方法。

不均匀磁等离子体的隐身机理——圆极化电磁波的碰撞吸收

研究了圆极化电磁波在不均匀磁等离子体的传播和吸收。讨论了不均匀磁化等离子体片对平行于磁场方向传播的左、右旋圆极化电磁波的碰撞吸收 ,计算了不同条件下衰减率。计算表明 ,当电磁波的频率接近电子碰撞频率时 ,磁等离子体对电磁波的吸收达到最大值。当入射电磁波的频率很低时 ,不均匀磁化等离子体中碰撞对雷达波的吸收非常小。当入射电磁波频率较高时 。

国外隐身材料研究进展

简单回顾了从二次世界大战至今几十年间 ,国外隐身材料的发展历程 ;系统综述了国外在陶瓷材料、导电高分子材料、晶须材料、纳米材料、手征材料等新型隐身材料研究方面所取得的进展 ;从耐高温隐身材料、智能隐身材料、等离子体隐身三个方面入手 ,重点介绍了国外近年来在隐身材料领域的最新进展 ;

不均匀等离子体球的电磁波轨迹及其应用

分析了非均匀等离子体球对电磁波的折射隐身。用变分法给出了电磁波在等离子体球中的轨迹 ,讨论了等离子体自由电子密度分布与电磁波的返转点、目标的 RCS缩减的关系。分析发现 ,等离子体的电子密度变化对目标隐身效果影响很大 。

闭式等离子体隐身技术及等离子体参数的优化

提出了一种等离子体隐身技术,即闭式等离子体隐身技术,从而解决了开放式的等离子体隐身技术的诸多问题。通过计算入射到覆盖闭式等离子体的金属平板上的电磁波的反射率,得出了在低温下,提高等离子体密度和温度,有利于更好的吸收电磁波结论。最后计算了未覆盖与覆盖闭式等离子体导体圆锥的雷达散射截面,结果表明:采用闭式等离子隐身技术有很好的隐身效果。

等离子体隐身技术在SAR对抗中的应用

通过对合成孔径雷达(SAR)基本原理以及等离子隐身机制的分析,研究了采用等离子体隐身技术对抗SAR从而保护地面静止目标的方法。利用研制的SAR对抗数字仿真系统开展了不同衰减特性等离子体对抗机载SAR的仿真实验,定量评估了SAR干扰效果,仿真实验结果说明了等离子体隐身技术用于SAR对抗的有效性。最后,结合工程应用分析了采用等离子体隐身技术对抗SAR所面临的实际问题。

非磁化等离子体密度与目标雷达隐身的关系

对不均匀非磁化等离子体密度与目标隐身的关系进行了研究。给出了等离子体电子密度线性分布和指数分布时 ,雷达电磁波的频率、电子碰撞频率、等离子体密度对电磁波衰减的影响。研究发现 ,等离子体的自由电子密度越高 ,电磁波的能量衰减越快。

非均匀等离子体覆盖目标隐身研究

推导了各向同性等离子体中的 FDTD分段线性递归卷积 ( PLRC)计算式 ,首次将 PLRC FD2 TD方法用于仿真电磁波与等离子体的相互作用 ,对垂直入射的非均匀等离子体简化隐身模型进行了时域和频域研究。数值结果表明 。

低气压闭式等离子体放电实验及光谱诊断

闭式等离子体可以克服等离子体隐身技术在开放环境中等离子体难以维持及能耗过大的问题。针对等离子体隐身应用，设计了一种封闭式的等离子体发生装置，选用微秒脉冲电源，以氩气为工质气体，在低气压环境下进行了放电实验。采用发射光谱法，测量了密闭腔体内部厚度方向上的Ar谱线强度，并将碰撞-辐射模型用于分析等离子体参数的分布规律。当放电参数确定时，给定电子温度和电子密度，可通过碰撞-辐射模型计算得到2p能级上的布居分布比值，将其与从光谱数据中得到的布居分布比值进行比较，当差异值最小时，即可确定相应的等离子体参数。通过对电子温度在1～5 eV 范围内的2p9和2p1能级布居分布比值进行计算，分析了碰撞-辐射模型计算可能存在的误差。实验结果表明，在厚度方向上，封闭式腔体中的等离子体电子密度达到1011 cm^-3量级且呈一定的梯度分布，但变化幅度不大，其分布情况有利于等离子体隐身技术的应用。

浅谈等离子体隐身技术在武器装备上的应用

等离子隐身体技术作为一种全新的隐身技术,是通过等离子体与电磁波的相互作用实现隐身的。文章介绍了等离子体的组成、分类以及生成方法,论述了等离子体隐身的机理和在军事上的应用,并结合现状,展望了其未来的发展趋势。