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.

Electromagnetic Occlusion Algorithm Based on FPGA and Panel Grouping and Its Optimization

With the development of digital signal processing and advanced algorithms, real-time signal processing based on FPGA and DSP is suitable for high-speed radar signal processing. With the rapid development of science and technology, war has entered the information age guided by high technology, and advanced science and technology has played a vital role in the trend of war. In recent years in the modern war, many countries invest a lot of research effort on the stealth technology, and advanced stealth technology can use a variety of technical means to alter or weaken the feature information of the target, confuse the enemy radar detection system effectively, reduce the chance of being detected to the largest extent, and prolong the lifecycle of aircraft and weapons. This research mainly discusses the electromagnetic occlusion algorithm and its optimization based on FPGA and panel grouping. The FPGA model selected for this study is XC6VLX240T-1FF1156I. Because the amount of data processed here is not very large, the cache part directly uses the on-chip storage resources of the FPGA, and the AD device is used to perform analog-to-digital/digital-to-analog conversion on the signal and perform digital up-down conversion. For a facet, it is necessary to first verify whether it is a bright facet and set the flag to mark it, then the facet needs to be occluded with the triangular facet marked as a bright facet, and all bright facets that have been marked need to be traversed. Open MP parallelization of the occlusion algorithm is as follows: The physical optics method is used to calculate the target RCS, and the focus of parallelism is placed on the part with a large amount of calculation. When using Open MP to design a program on a multicore computer, each group is assigned a thread to give full play to the core computing power. The total field is scattered and superimposed by each surface element. This part uses the parallel processing mode of Open MP, which allows the panel judgment in the group to be carried out at the same time. This part requires schedule to allocate resources and use different parallel mechanisms for different calculations to optimize debugging. In the angular range where there is multiple scattering at 0 ° ≤ φ ≤ 90 ° , the calculation results and the measurement results are in good agreement, and when the two planes are simulated with 1820 triangular faces, the fast multiple scattering in this paper only needs 4 minutes. This research has realized the general radar signal processing method based on FPGA structure, and the design has important engineering realization significance.

SYNTHESIS POLYMER MATRIX COMPOSITE EPOXY FeNdB-Cu FOR RADAR ABSORBER COATING APPLICATION

SYNTHESIS POLYMER MATRIX COMPOSITE EPOXY FeNdB-Cu FOR RADAR ABSORBER COATING APPLICATION. Radar (Radio Detection and Ranging) is a technology using the principle of electromagnetic for detecting, measuring, and mapping target coordinates. So stealth technology was created to tackle these threats, one of which is the radar absorber coating method (RAC). This research aims to identify the effect addition of Cu to Fe-Nd-B radar absorber material as polymer matrix composite (PMC). The processes were done by powder metallurgy method, started by milling and mechanical alloying process using planetary ball mill for 60 minutes 1000 rpm, 25 kg/mm2 of compaction load, and sintering at the temperature 1000 oC for 3 hours. The coating process was carried out conventional method as much as 1 layer, the variation of resin and magnetic powder are (95:5), (90:10), and (85:5) with the addition of Cu 1%wt. Based on the characterization the lowest RL was obtained at the composition (85:15) with the value 32.08 dB at the frequency of 10.36 GHz, magnetic characterization after doping addition coercivity 0.096 kOe and Saturation 5.22 kG. PMC hardness was raising following to addition of magnetic powder with the 29.2 HD Shore D, and adhesivity value was decreased following to addition of magnetic powder to 0.5 MPa.

A Low Profile Asterick-Shaped Polarization Free Metamaterial-Inspired Absorber for Penta-Band Characteristics

A penta-band absorber is proposed and developed exhibiting ultra thin and polarization insensitive behavior. It has been designed to be operated in S, C and Ku bands with absorptions peaks at more than 95%. Proposed absorber is processed on a FR4 Glass Epoxy laminate with equivalent electrical thickness of 0.0108 λ0 where λ0 is the wavelength corresponding to the lowest frequency of operation. This confirms the ultra-thin nature of the structure. The absorption pattern of the proposed structure has been characterized under normal and oblique incidence followed by their experimental verification. Presented results demonstrate highly polarization-independent behavior of the proposed absorber due to its symmetric geometry. Also, the electromagnetic field distributions have been studied to acquire better insight of the absorption mechanism corresponding to distinct elements presented in the structure. Then the suggested structure is characterized in terms of its behavior as metamaterial, which ensures the miniaturization. The proposed absorber is suitable to be used in applications like radar cross section reduction, stealth technology, radio frequency identification and electromagnetic compatibility.

The Direction of Arrival Location Deception Model Counter Duel Baseline Phase Interferometer Based on Frequency Diverse Array

With the emergence and development of the passive localization, the radiation source is more visible for the location system which endangers their survival. Therefore, there is an urgent demand for the radio frequency (RF) stealth technology. An effective method to realize RF stealth is location deception, therefore, for the passive localization system, this paper proposes a direction of arrival (DOA) location deception method using the frequency diverse array (FDA) against the dual baseline phase interferometer. Since the direction-finding of the dual baseline phase interferometer is based on the received signal with fixed frequency, the FDA signal has a deception effect on the interferometer owing to the introduction of the small frequency increment. Considering the influence of the frequency increment sequence on the deception effect, we derive the optimizations of the DOA location deception via the average location deviation for the sampling time in the case of no noise and noise, respectively. Besides, considering the time dependency of the beam, we investigate the average SNR (ASNR) and the corresponding CRLB to verify the proposed method. Numerical examples and simulations show that the proposed method can counter the interferometer by realizing location deception.

ANALYSIS OF SENSITIVITY OF TARGET TRACKING SYSTEMS TO EXTERNAL INTERFERENCE IN MULTICHANNEL RADARS WITH FIXED PARAMETERS

The multichannel and fixed parameters radars for tracking targets with the phased array antennas are widely used in modern military surveillance systems. The modular integration of a phased antenna array with digital processors allows to realize the command and control functions of antenna patterns for tracking multiple targets in the time resolution modes. Tracking of the air targets in range, radial speed and angular coordinates of evaluations and azimuth is provided by means of the multichannel radars without adaptation modes to the characteristics of external influences. Thus, adjusting the algorithms of tracking systems to the maximum maneuverability of the air targets can lead to a significant reduction in the accuracy of surveillance in comparison with the potentially achievable accuracy for such radars of tracking the linear flight targets in the long duration of time. In the case of adjusting the algorithms of tracking systems to either low intensity of flying targets, or lack of the aircraft maneuvering, it is possible to significantly increase the error of the aircraft flying information, and as a result to have a disruption of tracking the air targets. The increase in the parameters of the tracking error in relation to the influence of external interference were obtained as a result of the study. As a result of research, it is possible to assess the feasibility of adapting to certain characteristics of external influences, and provide recommendations for selecting and fixing the parameters of algorithms of tracking systems to ensure their versatility to surveillance targets with both high maneuverability, and implementing the stealth technology.

Anisotropic metamaterial with the ε-near-μ property in the entire angular domain enables broadband all-angle transmissions

Epsilon-near-mu metamaterials play a significant role in many fields such as radar, communication, and stealth technology, due to their ideal transmission responses. However, when electromagnetic (EM) waves illuminate such metamaterials at large angles, undesired reflectance occurs that greatly restricts the applications. Here, we propose a theoretical approach that can fundamentally eliminate the adverse effects of the incident angle on the transmission response of an anisotropic ε-near-μ material by adjusting the structural permittivity and permeability tensors. We take advantages of the nonresonance regions of electric and magnetic resonators so that the material parameters can attain the desired values in a wide frequency band. This allows us to design a nonreflective material with broadband all-angle transmissions from 0° to almost 90°, which is further verified by experiments with good performance. This work opens up a new route for the design of ultrawide-angle transmission-type metamaterials with high-efficiency and wideband properties, reaching significant applications in antenna radomes.

All-silicon terahertz metamaterials absorber and pesticides sensing

Perfect absorption based on metamaterials at terahertz frequencies range has attracted a great deal of interest in the field of sensing, imaging, bolometers and stealth technology. This review is focused on presenting several recently developed absorbers based on all-silicon metamaterials, such as single-band, dual-band, multi-band and broadband absorbers. The partial physical mechanisms and optical tunability corresponding to the absorption are also reported. Furthermore, the presented absorbers can be used to detect the concentration of trace pesticides, and a good linear regression coefficient was obtained between the absorption amplitude and the concentration. Notably, the presented all-silicon metamaterials perfect absorbers are compatible with COMS processing which is beneficial to promote the development of terahertz functional devices.

Research Progress of Bionic Adaptive Camouflage Materials

Bionic adaptive camouflage material is a new artificial functional material, whose surface color can change adaptively according to the optical environments. Therefore, how to reduce the visual detectability of this material becomes a research hotspot of digital camouflage stealth technology. In order to clarify the limitations and opportunities of the bionic adaptive camouflage materials in the field of visual stealth, we summarize the applications of current adaptive camouflage materials and carry out a prospect of next-generation photonic crystal infrared camouflage material in this review. It is expected to provide a solution for the demand of digital camouflage adaptive materials in the modern battle field.