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

In this paper, a current density convolution finite-difference time-domain method is extended to study the electromagnetic wave propagation and absorption in inhomogeneous magnetized plasmas. First of all, we analyze the wave propagation in homogeneous magnetized plasmas for arbitrary magnetic inclination angle. Then, we studied three types of plasma absorption, including plasma resonance, electron cyclotron resonance, and upper hybrid resonance in homogeneous and inhomogeneous magnetized plasmas. This model is applied to simulate the heating mechanism during ionospheric modification experiments by high-power high-frequency radio waves. These results have important implications for the interpretation of physical mechanisms for the interaction of high power radio waves with magnetized ionospheric plasmas and design of future experiments.

FDTD Analysis of Propagation and Absorption in Nonuniform Anisotropic Magnetized Plasma Slab

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

In this paper, a recently improved SO-FDTD (shift- operator flnite difierence time-domain) method is proposed and applied to the numerical analysis of the anisotropic magnetized plasma with arbitrary magnetic declination. By using the constitutive relation between polarized current density vector J and electric vector E and bringing the shift operators, the difierence iteration equations of fleld components for Maxwell equations are derived in detail. Furthermore, the memory requirement is decreased signiflcantly through incorporating a memory-minimized algorithm into the FDTD iterative cycles. The re∞ection and transmission coe-cients of electromagnetic wave through a magnetized plasma layer are calculated by using this method. It is shown that the new method not only improves accuracy but also produces speed and memory advantages over the SO-FDTD method in kDB coordinates system proposed in the recent reference. In addition, the recursion formulae of the improved SO-FDTD method are deduced and programmed easily and they involve no complex variables, so the computations for the magnetized plasma become very simple.

/pdf/improved-shift-operator-fdtd-method-for-anisotropic-4jn7sa53si.pdf

Improved Shift-Operator FDTD Method for Anisotropic Magnetized COLD Plasmas with Arbitrary Magnetic Field Declination

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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Analysis on the stealth characteristic of two dimensional cylinder plasma envelopes

Electromagnetic (EM) problem model for anisotropic plasma in kDB coordinates system is set up. And the model includes almost all the respects of EM-problems for anisotropic plasma. Based on shift-operator flnite difierence time-domain (SO-FDTD) method, Maxwell equations and EM-fleld constitutive equations are solved and discrete difierence scheme of each EM-fleld component is obtained. Then the propagation characteristics of eigen wave are expressed by the two components of electric displacement vector as well. Lastly, three typical examples are calculated by SO-FDTD method, and the results verify the efiectiveness and exactness of SO-FDTD method in kDB coordinates system.

/pdf/shift-operator-fdtd-method-for-anisotropic-plasma-in-kdb-50zicyh9oa.pdf

SHIFT-OPERATOR FDTD METHOD FOR ANISOTROPIC PLASMA IN kDB COORDINATES SYSTEM

The purpose of this paper is to study the time-domain complex electric field distribution caused by partial discharge (PD) in switchgear, using LOLA-Voronoi adaptive sampling and compressed sensing technology based on curvelet transform. The possible discharge position in the switchgear is briefly described and the time-domain electric field distribution characteristics generated by the discharge at this position are analyzed, which provides a reference for the later research and optimization of the installation of UHF PD detection sensor in the switchgear.

Application of Time-Domain Electric Field Distribution in Switchgear Based on LOLA-Voronoi and Curvelet Transform

A broad-band isotropic electric-field probe which can be printed on PCB is proposed. Loaded with patched resistors, the dipole will obtain traveling-wave characteristics to measure broad-band electric fields. Two columns of high resistance patch resistors are used as high resistance transmission lines which are effectively transparent to RF and microwave fields. Three identical probes are placed in a special way where three dipoles are orthogonal to each other to achieve an isotropic frequency response. Benefited from using patched resistors, the probe can be printed on PCB and easily made. Software simulation results indicate that the probe has a flat voltage frequency response within ±1.5 dB from DC to 10 GHz and a stable isotropic response within ±0.2 dB.

A Broad-Band PCB Isotropic Electric-Field Probe with Resistance Loaded Dipoles

An innovative strategy for the reconstruction of indoor electromagnetic radiation field power distribution using LOVA-Voronoi adaptive sampling is proposed. By using the compressed sensing technology which based on curvelet transform, the reconstruction renderings are obtained by setting different sampling rates. When the sampling ratio is 18%, the vast majority of areas can be reconstructed.

Chen-Xin Zhang

Papers

Analysis on the stealth characteristic of two dimensional cylinder plasma envelopes

SHIFT-OPERATOR FDTD METHOD FOR ANISOTROPIC PLASMA IN kDB COORDINATES SYSTEM

Application of Time-Domain Electric Field Distribution in Switchgear Based on LOLA-Voronoi and Curvelet Transform

A Broad-Band PCB Isotropic Electric-Field Probe with Resistance Loaded Dipoles

Reconstruction of Indoor Electromagnetic Radiation Field Power Distribution under Different Sampling Rates