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To investigate the parameters distribution and electromagnetic scattering characteristics by plasma sources is the basis to develop plasma stealth technology of radar. In this paper, a radome inductively coupled plasma (ICP) source is designed. The fluid model of ICP discharge is established by COMSOL. The Boltzmann equation solver is introduced to correct the inaccuracy of the electron energy distribution function (EEDF) in the fluid model. The distribution of electron density (Ne) and electron temperature (Te) in ICP under different external conditions is obtained, and the Ne is diagnosed by microwave interference method. Then the Ne and Te under steady-state are introduced into the Z-transform finite difference time-domain model to simulate the propagation characteristics of electromagnetic waves. The results indicate that the amplitude and spatial distribution of ICP parameters change significantly under different external conditions (i.e., the pressure, the gas electronegativity, and the power). Moreover, the frequency bands of wave attenuation are adjusted over a broader range by control the discharge conditions. Additionally, the wave vector gradient of ICP induced the reflected wave to form the pseudo point source in the high Ne region.

In this article, an inductively coupled plasma (ICP) source with planar transparent cavity is designed, and the active control of ICP on the attenuation effect of electromagnetic wave is studied. The scattering parameters calculation model of ICP is established based on the COMSOL fluid model combined with Z transform finite-difference time domain (ZT-FDTD) method. A point wave source composed of continuous reflection waves in the plasma is observed through the numerical simulation of the model, and the location of the wave source depends on the spatial distribution of the peak electron density. The effects of different pressure (10 mtorr–1 torr), working gas (Ar and O2), and power (200–600 W) on the electromagnetic scattering characteristics are compared through numerical calculation and experimental measurement. The results show that the attenuation frequency band and amplitude can be actively controlled by changing external factors of ICP, such as gas pressure, working medium gas, and power. With the increase of power, the attenuation peak moves to the high-frequency band. With the increase of pressure, the fluctuation of attenuation curve is enhanced, and the attenuation bandwidth is increased. The O2-ICP is more capable of absorbing wave power of the low band below 6 GHz, while the Ar-ICP is more effective in 6–14 GHz. The research results broaden the active stealth mode of aircraft in complex electromagnetic environment.

In this article, a multiple diffuse coding metasurface (MDCM) of independent polarization is designed to control the propagation direction of diffuse reflections under different polarizations and to improve the monostatic and bistatic RCS (radar cross section) reduction effect. First, a method for controlling the distribution range and propagation direction of the diffuse field is studied, and the diffuse field distribution of the random phase metasurface is optimized by a genetic algorithm to improve the uniformity of the diffuse scattering distribution. Then, the random phase distribution is superimposed on the periodic gradient phase distributions of the linear and hedge types in the orthogonal direction so that the main propagation direction of the diffuse metasurface deviates from the specular reflection region under different polarizations, showing single and two diffuse beams. Finally, the anisotropic unit cell with a rectangle inside and an improved Jerusalem cross on the outside is employed as the basic coding element of the MDCM due to its independent polarization phase response. The numerical and experimental results show that the MDCM features multiple diffuse scattering, independent polarization and angle insensitivity and can efficiently improve the monostatic and bistatic RCS reduction effect simultaneously. Because the scattered energies are redirected away from the specular reflection direction, the specular scattering reduction effect is better than the isotropic diffuse metasurface. The proposed method increases the difficulty of detection by single or netted radar and has the potential for the applications of stealth techniques.

Desired by sparse subset learning, in this paper, a hyperspectral band selection method via pairwise band agreement with spatial-spectral graph regularier, referred as Regularized Band Selection via Learned Pairwise Agreement (RBS-LPA), was proposed. The process was formulated as a graph-regularized row-sparse constrained optimization problem, which select a few representative bands to code the all bands based on the learned pairwise band agreement. In RBS-LPA, a spatial-spectral informative graph, constructed by spatial-spectral neighbor relationship, is incorporated to encode both the spatial and spectral geometrical structure. By combining the learning procedure with graph regularizer jointly, the graph regularizer can adaptively change with the sparse representative bands, which ensures that the selected bands can well preserve the local manifold structure. Experimental results on three real urban hyperspectral data demonstrate the efficiency of the proposed RBS-LPA and achieve convincing performance.

With the development of artificial intelligence, multiagent algorithms have been applied to many real-time strategy games. Making plans on the human being is gradually passing away, especially in combat scenarios. Cognitive electronic warfare (CEW) is a complex and challenging work due to the sensitivity of the data sources. There are few studies on CEW. In the past, wargame simulations depended on differential equations and war theory, which resulted in high time and human resource costs. In the future, as other artificial intelligence theories are developed, artificial intelligence will play a more critical role in wargames. The capabilities of multiagent modeling to describe complex systems and predict actions in dynamic environments are superior to those of traditional methods. In this paper, we use a 3D wargame engine from China Aerospace System Simulation Technology Co., Ltd. (Beijing) named All Domain Simulation (ACS), which supports land, sea, and air combat scenarios, to simulate combat. In the simulations, there are several unmanned air vehicles (UAVs) as attackers and several radar stations as defenders, and both have the ability to detect the others. In the game, several UAVs need to learn to detect targets and track targets separately, and we train the UAV's behavior by well-designed reward shaping and multiagent reinforcement learning (MARL) with LSTM. We improved the RDPG algorithm and merged the MADDPG and RDPG algorithms. From the experimental results, we can see that the effectiveness and accuracy of the algorithm have been greatly improved.

A novel hybrid finite-element time-domain (FETD) algorithm is proposed to solve electromagnetic modeling with fine structures. This algorithm is based on the unconditionally stable FETD (US-FETD) and the traditional FETD methods. The US-FETD is used in the subdomain containing all fine grids and parts of coarse grids adjacent to the fine grids. The traditional FETD is applied in the other subdomain. A compensation and correction scheme is used to update the fields on the subdomain boundary. The hybrid FETD can make the explicit time marching unconditionally stable with a uniform time step determined by the coarse grids in the entire computational domain. In addition, the unstable modes of the entire system in the hybrid FETD can be effectively obtained by solving the partial solutions of the eigenvalue problem in the US-FETD subdomain. In comparison with the US-FETD in the entire computational domain, the eigenvalue analysis costs less memory and time. Numerical results certify the high efficiency of the hybrid FETD.

For this paper, an experiment of low-pressure Argon inductively coupled plasma (ICP) was conducted in a closed chamber. Obvious $E$ – $H$ mode transition could be observed in the experiment. To solve the problem that microwave interference diagnosis can only measure the average electron density along the transmission path of the microwave, a new microwave interference diagnosis method based on fluid dynamics modeling is put forward to gain an accurate distribution of electron density. Using this new method, the spatial resolution of electron density could be improved. Finally, the electron density of low-pressure ICP was diagnosed both with this method and the Langmuir probe. The results revealed that the electron density increased with power and the peak value reached $7.8\times 10^{17}\text{m}^{-3}$ at the radio frequency power of 700 W. The consistency in the distribution trend of electron density that resulted from two different methods illustrates that the new method can provide a relatively accurate spatial distribution detail of electron density. The electron temperature was measured via the Langmuir probe and the results show that the temperature declines with power.