A novel and simple analytical technique referred to as transmission line analogy is developed modified study the properties of perpendicular polarized wave parallel obliquely incident on reentry plasma sheath. Based coefficients, effects sheath polarization property electromagnetic (EM) waves are studied. Taking GPS navigation right hand circularly an example, influences angle parameters, including electron density collision frequency EM wave's Numerical results indicate that larger lower...

Linear-based low-rank and sparse models (LRSM) nonlinear-based deep autoencoder (DAE) have been proven to be effective for the task of anomaly detection (AD) in hyperspectral images (HSIs). The linear-based LRSM is self-explainable, while it may not characterize complex scenes well. In contrast, DAE able extract discriminative features between background scenes, whereas self-explainable. To effectively combine advantages both, a dynamic priors-constrained DAEs (DLRSPs-DAEs) AD (HAD), this...

The plasma sheath communication blackout issue for hypersonic or reentry vehicles is addressed from a channel characteristic perspective.Different previous research, this paper emphasizes the importance of in study blackout, and discussion on transmission phase shift their effect performance was made with detail.A mathematical model proposed following roadmap about how to obtain parameter given.Flow field simulation blunt conical body physical made, electron density collision frequency...

Radar high-resolution range profiles (HRRPs) are typical high-dimensional, non-Gaussian and interdimension dependently distributed data, the statistical modelling of which is a challenging task for HRRP based target recognition. Assuming data follow dependent Gaussian distribution, factor analysis (FA) was recently applied to describe radar HRRPs two-phase procedure used model selection, showing promising recognition results. Besides interdimensional dependence, this paper further models...

Channel modeling of a plasma sheath for hypersonic reentry vehicles is important in addressing communication blackout issues. Given that the time-varying property transmission medium caused by physical factors such as large-scale flight conditions variation, especially angle attack, and small-scale fluid turbulence, new adaptive multistate Markov channel method proposed to present dynamic effects sheaths on wireless channels. First, quasi-Gaussian function mathematical model electron density...

ABSTRACT By studying the impedance characteristics of horizontal half‐wave dipole near metal reflector, we find that antenna input decreases when distance between and reflector is reduced. Therefore, a folded with high considered to replace reduce profile. The developed here occupies two connected dipoles different widths, which conducive obtaining higher resistance, in other words, lower In rectangular area enclosed by dipole, coupling branch added extend bandwidth. can cover 2.3–2.62 GHz...

During reentry, plasma sheath is affected by many flight factors, such as trajectory, velocity, angle of attack, and fluid turbulence. As a result, the parameters are time-varied nonstationary. The nonstationary effects reentry on electromagnetic (EM) wave propagation investigated in this paper. First, factors that affect analyzed, variation divided into three scales. A multiscale electron density model established. compatible modeling method proposed, proven effective. Finally, we analyze...

Channel capacity is the prerequisite and basis for design of a communication system. To assess impact harsh plasma environment on system reentry vehicles, Shannon's information theory used to evaluate channel through estimation results signal-to-noise ratio obtained by link budget method. First, attenuation caused sheath calculated with stratified medium finite-difference time-domain method typical S, C Ka telemetry frequencies in environment. Thereafter, transceiver parameters are...

During hypersonic flight, the communication link is affected by multipath effect and plasma sheath. As a result, envelopes phases of wireless signals fluctuate with time. In this paper, an integrated channel model proposed based on geometric propagation theory. The statistical characteristics sheath are carefully studied. probability density functions, correlation coefficient between envelope phase, autocorrelation function, level-crossing rate, average fade duration derived detailed...

A 3-D total-field/scattered-field (TF/SF) plane-wave source was developed for the analysis of plane wave propagation characteristics in reentry plasma sheath. Owing to dynamic variation surrounding flow field, sheath during process presents various inhomogeneous structures, such as turbulence and considerable metal ablation particles. The proposed model can be efficiently applied simulate scattering effects structures on electro-magnetic (EM) signals. utilizes a TF/SF boundary introduce into...

AbstractA plasma sheath generated around a hypersonic vehicle can be serious obstacle to fixed-frequency communications, especially navigation systems. This paper studies the effects of on Beidou circular microstrip patch antenna. The dynamic stratified medium model method, which is based gradient electron density profile curve, employed nonuniform sheath. Using algorithm calculation time-domain finite integration, antenna radiation pattern property obtained, along with changes in reflection...

An experiment on the propagation of electromagnetic (EM) signals in continuous time-varying plasma is designed to establish nonlinear mirror between electron density and transmission coefficient. The nonlinearity confirmed from theoretical experimental results. amplitude phase can be considered functions when complex interaction EM waves ignored. Results show that distributions are asymmetrical follows symmetric distribution. skewness positive, whereas negative. degree closely related ratio...

To meet the increasing demand for practicality and rapidity of optical components in aircraft folding systems, an aluminum mirror preparation method based on additive manufacturing (AM) technology is proposed. From perspective special processing AM, a process chain additively manufactured mirrors proposed to address limitations design such as size, support, connectivity constraints. First, deposited by AM prepared. Second, metal densified hot isostatic pressing process. Then, computer...

Most of the existing anomaly detection (AD) approaches for hyperspectral images (HSIs) usually achieve high accuracy at cost computational complexity. To meet needs actual scenarios (efficiency, robustness, and accuracy), this letter introduces a fast robust AD algorithm via subfeatures grouping binary accumulation (SFBA) HSIs. We propose spatial–spectral scoring strategy to improve accuracy. A number spectral HSI are selected divided into <inline-formula...

Time-varying plasma sheath likely causes a parasitic phase modulation effect on communication signals. It is essential to understand the of tracking telemetry and command (TT&C) systems for blackout mitigation. This paper comprehensively investigates impact TT&C system Ka band signals, especially single-frequency phase-modulated A fluctuant electron density model in space-time domain initially established. The noise caused by time-varying then obtained through wave impedance numerical...

Due to the severe impact of plasma turbulence on electromagnetic waves, dynamic sheath can degrade communication quality, even resulting in blackouts. This article studies effect different frequency bands and two typical telemetry modulation methods signals under a time-varying channel. First, considering dynamics scales, reentry channel response is simulated analyzed. Then, average bit error rate (BER) capacity <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML"...

Abstract The scattering of waves in the ion cyclotron range by plasma density perturbations edge has been previously studied Zhang et al with help antenna code RAPLICASOL (2020, Nucl. Fusion , 60 096001). further interesting question is whether have an effect on resonance heating (ICRH) core. In this paper, finite element method based 2D full wave integrating core used to study issue. analytical are applied influence field distribution, power deposition, coupling, partition among different...

An analytical method is proposed in this paper to study the effect of time-varying reentry plasma sheath on instantaneous polarization statistic property electromagnetic (EM) waves. Based disturbance hypersonic fluid, spatial-temporal model established. technique referred as transmission line analogy developed calculate coefficient EM wave propagation plasma. Then, theory developed. Taking S-band telemetry right hand circularly polarized an example, effects incident angle and parameters,...

The simulation of the electromagnetic wave propagation plays an important role in solving communication blackout issue. Finite element analysis software package COMSOL is employed by us to model presence non-uniform reentry plasma sheath this paper. characteristics are analyzed observation field distributions. with s polarization begins attenuate as exponential function at cut-off position. mode conversion takes place for p when real part permittivity close 0. reflection, transmission, and...

Exhaust-plume-induced plasma from solid rocket engines absorbs electromagnetic (EM) waves and may cause communication interruptions. Previous articles have proposed both physical phenomena propagation models for this problem, but few analyzed random fluctuations of EM propagating through plumes a communications perspective. This article attempts to attach these fluctuations, which are caused by the plume-induced turbulent spread medium, channel characteristics. A multi-parameter stochastic...

The reentry plasma sheath propagation environment is nonstationary and has high-dynamic characteristics. communication signal suffers serious parasitic modulation effect since the time-varying degree of channel on same order as telemetry symbol rate. This paper proposes an effective transmission scheme to cancel (PSC) distortion by utilizing short spreading adaptive equalization technology. proposed spreads inserts a small number pilot signals determine whether state changed amplitude...

The randomness of turbulent reentry plasma sheaths can affect the propagation and scattering properties electromagnetic waves. This paper developed algorithms to estimate influences. With typical data, influences GPS frequency Ka are studied respectively. Results show that, in terms wave scattering, loss caused by sheath increases with increase ensemble average electron density, collision frequency, density fluctuation turbulence integral scale Also is much smaller than dielectric loss. less...

Space-based spectral radiation detection is one of the most effective approaches for detecting hypersonic vehicles. However, due to complex characteristics plasma sheath that generated by aerodynamic thermal effect and envelopes vehicle, space-based still confronted with great challenges. Based on mechanisms transmission, we establish a model conduct optimal selection wavebands vehicle. Through using established model, obtain plasma-sheath-enveloped vehicles (RAM-CII HTV2) under different...