The concealment of aircraft from radar sources or stealth is achieved either through shaping, or radar absorbing coatings, or engineered materials, or plasma, etc. Plasma-based stealth is a radar cross-section (RCS) reduction technique associated with the reflection and absorption of incident electromagnetic (EM) wave by the plasma layer surrounding the structure. Plasma cloud covering the aircraft may give rise to other signatures such as thermal, acoustic, infrared, or visual. Thus it is a matter of concern that the RCS reduction by plasma enhances its detectability due to other signatures. This needs a careful approach toward the plasma generation and its EM wave interaction. This book presents a comprehensive review of the plasma-based stealth, covering the basics, methods, parametric analysis, and challenges toward the realization of the idea. The book starts with the basics of EM wave interactions with plasma, briefly discusses the methods used to analyze the propagation characteristics of plasma, and its generation. It presents the parametric analysis of propagation behavior of plasma, and the challenges in the implementation of plasma-based stealth technology. This review serves as a starting point for graduate and research students, scientists, and engineers working in the area of low-observables and stealth technology.

Plasma-based Radar Cross Section Reduction

An analytical technique referred to as the propagator ma- trix method (PMM) is presented to study the problem of electromag- netic (EM) waves interacting with the nonuniform magnetized plasma. In this method, the state vector is proposed to describe the characteris- tics of eigen waves in anisotropic medium, and state vectors at two dif- ferent locations are related with each other by the propagator matrix. This method can be used to deal with the phenomenon of the trans- formation of EM wave polarization induced by anisotropic magnetized plasma, besides the conventional propagation characteristics through plasma slab, which overcomes the drawback of other analytical meth- ods introduced in former studies. The EM problem model considered in this work is a steady-state, two-dimensional, nonuniform magne- tized plasma slab with arbitrary magnetic declination angle, which is composed of a number of subslabs. Each subslab has a flxed electron density, and the overall density proflle across the whole slab follows any practical distribution function. Based on PMM, a signiflcant feature of strong transformation of EM wave polarization is addressed when an incident wave normally projects on the slab, which leads to the re- ∞ected or transmitted waves containing two kinds of waves, i.e., the co-polarized wave and the cross-polarized wave. The efiects of vary- ing the plasma parameters on the re∞ected and transmitted powers of co-polarization and cross-polarization, as well as the absorptive power

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Analysis of propagation and polarization characteristics of electromagnetic waves through nonuniform magnetized plasma slab using propagator matrix method

Characteristics of electromagnetic wave propagation through a magnetized plasma slab with linear electron density proflle is analysed. In the numerical analysis, cold, weakly ionized, collisional and steady state plasma layer is divided into su-ciently thin, adjacent subslabs, in each of which plasma parameters are constant. Re∞ection and transmission coe-cients are calculated for discretised plasma by considering electron density proflle with positive and negative slopes. Wideband absorbtion characteristic is obtained with high collision frequency and high electron density combination in linearly decreasing proflle as well as wideband transmission characteristic is obtained for low collision frequency and low electron density combination in linearly increasing proflle of flnite length. The general results show that in steady state, plasma layer behaves as a frequency selective medium satisfying the major requirements of current shielding applications as the function of plasma parameters and the strength of external magnetic fleld excitation. Proposed plasma layer can be used in current shielding and stealth applications as a matching layer between the surface and the incident electromagnetic wave.

https://www.jpier.org/pierb/pierb21/19.10042205.pdf

Characteristics of Electromagnetic Wave Propagation through a Magnetised Plasma Slab with Linearly Varying Electron Density

Study on the influence of thin plasma thickness on electromagnetic wave attenuation

A novel multifrequency method is introduced in this paper for measuring the plasma produced by a $ \Phi 800$ -mm shock tube. The core of the measured object is a volume of relatively uniform plasma contained by the rectangular test section, and the dual-frequency or multifrequency configuration of the measuring system enables the coherent cancellation of measurement deviations. Based on the Lorentz model of plasma, the obvious correspondence exists between the plasma parameters and the transmittance variation with different frequencies of the electromagnetic wave; hence, the electron density $N_{e}$ and the collision frequency $\nu $ of the plasma could be retrieved according to the measured transmittance. A dual-frequency system is established as the verification of the proposed method. The measured values of the electron density by the proposed method are compared with those obtained by other means, and the results are in good agreement.

Multifrequency Method for Measuring Properties of Shock Tube Produced Plasma

Stealth characteristic of two dimensional cylinder plasma envelopes is studied. Three cases about plasma refraction efiect, re∞ection characteristic and attenuation by absorbing electromagnetic wave (EMW) are concerned synthetically. As for plasma refraction stealth, EMW traces equation in cylinder plasma is deduced; a novel concept of plasma refraction deviation angle is presented; the relation between refraction deviation angle and incidence angle of EMW is yielded; the relation between refraction deviation angle and plasma density distribution is made out. As for re∞ection stealth and attenuation stealth, re∞ection calculation of multi-layer plasma is presented flrst, and plasma collision frequency as well as corresponding collision absorption is taken into account simultaneously, then EMW re∞ectivity with double-path attenuation is obtained. It is shown that cylinder plasma envelopes considering the three cases above could make distinct stealth.

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Zhong Li

Papers

Analysis on the stealth characteristic of two dimensional cylinder plasma envelopes