Radar Cross Section Reduction Research Articles

MOF Derivatives with Gradient Structure Anchored on Carbon Foam for High-Performance Electromagnetic Wave Absorption.

The impedance matching and high loss capabilities of composites with homogeneous distribution are limited owing to high addition and lack of structural design. Developing composites with heterogeneous distribution can achieve strong and wide electromagnetic (EM) wave absorption. However, challenges such as complex design and unclear absorption mechanisms still exist. Herein, a novel composite with a heterogeneous distribution gradient is successfully constructed via MOF derivatives Co@ nitrogen-doped carbon (Co@NC) anchored on carbon foam (CF) matrix (MDCF). Notably, the concentration of MOF can easily control the gradient structure. In particular, the morphologies of MOF derivatives on the surface of CF undergo a transition from the collapse of the inner layer to the integrity of the outer layer, accompanied by a continuous reduction in the size of Co nanoparticles. Correspondingly, enhanced interface polarization from the core-shell of Co@NC and good impedance matching of MDCF can be obtained. The optimized MDCF exhibits the minimum reflection loss of -68.18dB at 2.01mm and effective absorption bandwidth covering the entire X-band. Moreover, MDCF exhibits lightweight characteristics, excellent compressive strength, and low radar cross-section reduction. This work highlights the immense potential of composites with heterogeneous distribution for achieving high-performance EM wave absorption.

Graphene-based optically transparent metasurface for microwave and terahertz cross-band stealth utilizing multiple stealth strategies

Stealth, as a miraculous physical phenomenon, has received widespread attention from the scientific and engineering communities for a long time. Optically transparent stealth devices are of significant importance for the stealth capabilities of aircraft windshields and solar panels. However, the current stealth implementations are limited to a single frequency band due to the strong dispersion of passive materials so that cross-band stealth still remains challenging. In this paper, a novel cross-wavelength stealth strategy is proposed based on multi-layer graphene transparent metasurface, which achieves stealth both in microwave and terahertz frequency bands. Strong resonance is designed to achieve high absorption in the microwave band and diffuse scattering is employed for RCS reduction in the terahertz band. Materials such as graphene and ITO are employed to achieve optical transparency and flexibility of the metasurface. The above design is implemented using numerical simulations and experiments, and the results are in good agreements. This design method that integrates multiple stealth strategies opens up a new approach for cross-band stealth, with potential applications in countering advanced electromagnetic detection.

A coding based metasurface absorber with triple circular ring resonator for broadband RCS reduction and high EMI shielding effectiveness

In this paper, a novel coding-based metasurface absorber (CMA) featuring a triple circular ring resonator is introduced for broadband radar cross-section (RCS) reduction and high electromagnetic interference (EMI) shielding effectiveness. The coding element comprises a triple circular ring resonator generating a 1-bit coding scheme (‘0’ and ‘1’ element) with a reflection phase difference of 180° ± 45° across the frequency range of 7.5 GHz–15.5 GHz by employing varying dimensions for the outer circular ring. A most affordable FR-4 substrate with 1.6 mm thickness is used to design the CMA structure. Binary Particle Swarm Optimization (BPSO) algorithm combined with array theory is employed to strategically position unit cells within the subarray. Simulations demonstrate a significant RCS reduction of −10 dBsm across the entire 7.5 GHz–15.5 GHz band. Furthermore, the 2D and 3D scattering patterns observed at 8.26 GHz, 10.56 GHz, and 13.30 GHz serve as additional proof of the remarkable effectiveness of the optimized pattern in reducing bi-static RCS. The optimized CMA structure also exhibits absorption levels exceeding 80 % at different resonance frequency while maintaining high shielding effectiveness. To validate these findings, a prototype of the optimized CMA structure is fabricated, and experimental investigations are conducted. The measured results closely align with the simulated outcomes, with minor discrepancies observed outside the designated frequency band. Based on comprehensive simulation and experimental analyses, the optimized CMA structure emerges as a promising choice for achieving broadband RCS reduction and high EMI shielding effectiveness in practical applications.

A High-Gain Wideband Fabry-Pérot Antenna Employing a Water-Based Frequency Selective Surface for Polarization- and RCS-Reconfigurability

A Fabry-Pérot (FP) antenna with wideband dual-polarization and radar cross section- (RCS-) reconfigurability adopting water-based frequency selective surface (FSS) is presented. The feed antenna is designed to switch between horizontal polarization (HP) and vertical polarization (VP) by controlling the on/off states of two PIN diodes. By optimizing the height of the FP resonant cavity, the proposed FP antenna achieves wideband and high-gain properties. In addition, the incident wave can be absorbed when the polymethyl methacrylate (PMMA) container is filled with water, which reduces the monostatic RCS. This design can be selected to be in stealth mode or radiation mode by injecting water into or extracting water from the water container. The measured results indicate that in stealth mode, the 10-dB RCS reduction band is from 4.5 GHz to 6.4 GHz, and the peak RCS reduction is 31.5 dB at 5.2 GHz. In the radiation mode, the realized gains of the FP antenna in both HP and VP at 5.2 GHz reach 16.6 dBi. Simulated and measured results verify the realizability and operational concept of the designed FP antenna.

Transparent conformal metasurface absorber for ultrawideband radar cross section reduction

Flexible metasurface (MS) based absorbers have gained significant importance in recent years due to their possible use in non-planar radar stealth applications, however, their narrow bandwidth and insensitivity to incidence angles limit their potential use. In this work, we present an ultrawideband and angular insensitive MS absorber based on indium tin oxide (ITO), polyethylene-terephthalate, and polyvinyl chloride, that is both transparent and flexible. Broad-spectrum absorption can be maximized by using ITO with modest sheet resistance upon interaction with electromagnetic (EM) waves. To further validate the absorption performance, the radar cross section (RCS) characteristics are investigated. The results indicate that over 10 dB RCS reduction is realized across an ultra-wide frequency range of 13.30–39.76 GHz, with relative bandwidth up to 100% for planar MS under linearly and circularly polarized incidence EM waves. Furthermore, the RCS reduction performance of an MS is well maintained in the abovementioned frequency band when it is bent with various bending angles. The proposed MS is a promising contender for practical applications in microwave stealth technology due to its additional advantages of visible transparency, mechanical flexibility, low profile, wide-angle stability, and polarization insensitivity.

A polarization conversion metasurface for reducing radar cross section and enhancing radiation performance of circularly polarized array antennas

In this paper, we present a metasurface for ultra-wideband polarization conversion. The unit structure of the PCM consists of a metallic pattern layer, an air layer, and a grounded dielectric layer, which can achieve a polarization conversion bandwidth (PCR) from 6.17 GHz to 19.5 GHz (103.9%). According to the phase cancellation principle, the PCM cells and their mirror cells are arranged in a checkerboard fashion to form a metasurface. Applying it to a circularly polarized patch array antenna for RCS reduction. With the addition of PCM, the impedance matching (S11) bandwidth of the antenna is broadened from 7.2 to 8.3 GHz (14.2%) to 6.2–8.4 GHz (30.1%), the axial ratio (AR) bandwidth is broadened from 6.9 to 8.25 GHz (17.8%) to 6.75–8.32 GHz (20.1%), the peak gain to 11.1 dBi and the antenna's monostatic RCS achieves more than 5 dB reduction from 6.4 to 18.6 GHz (97.6%) under x- and y-polarized plane wave irradiation.The current distribution of the antenna is used to explain the gain improvement. Finally, we fabricated and tested a prototype of the proposed metasurface antenna.

Broadband Metamaterial Surface for Antenna RCS Reduction and Gain Enhancement

This paper presents a broadband metamaterial surface with low radar cross section (RCS) and introduces its application on antenna. The metamaterial surface is composed of polarization-dependent artificial magnetic conductors (PDAMCs), which are orthogonal arranged in chessboard-like configuration for backscatter cancellation. By optimizing the PDAMC cell, effective phase difference is obtained in wideband and the surface achieves 10dB RCS reduction over the bandwidth of 32%. As a potential application, the metamaterial surface is employed to replace the metallic ground of a slot antenna. Illustrated by detecting wave, the novel antenna shows low RCS at boresight. While the antenna operates, the gain gets enhanced as a result of parasitic radiation of the surface. Full wave simulations and measurements validate that the novel antenna achieves both broadband low RCS and high gain compared with the slot antenna installed on a same-size metallic plate.

Low-RCS electromagnetic metasurface antenna based on shared-aperture technique

In this paper, a novel shared-aperture method of electromagnetic metasurface and antenna is proposed to obtain low radar-cross-section (RCS) performance. This method first designs low-RCS metasurface and conventional antenna independently, and then obtains novel low-RCS antenna by combining this metasurface with conventional antenna based on shared-aperture technique. Besides, current analysis and consequent local structure modification are also conducted to guarantee the antenna’s good radiation performance and broadband RCS reduction in the meantime. Using this method, a dual-layer polarization rotation unit cell is first proposed and its broadband working principle is investigated by both theoretical analysis and numerical comparison. Based on this unit cell, a broadband low-RCS metasurface is constructed. Then an initial shared-aperture metasurface antenna is obtained by substituting the middle cells in the metasurface with conventional patch antenna directly. Through careful analysis of surface current in radiation mode, the gain decrease of this metasurface antenna is revealed. On this basis, a limited removing strategy is put forward and some metasurface cells in the antenna is removed with the aid of current analysis. Consequently, an improved shared-aperture metasurface antenna is proposed. (The design flow of this metasurface antenna is displayed in the following Fig. 1) This improved antenna works from 6.3 GHz to 7.48 GHz, which is a bit wider than conventional patch antenna. Its gain is also higher than conventional antenna with the maximum improvement of 1 dB. Meanwhile, apparent RCS reduction is obtained from 6 GHz to 16 GHz for any polarized incident wave, and the reduction peak is larger than 20 dB. Fabrications and measurements are finally conducted. The good agreements of measured results and numerical calculations are achieved. The well-behaved radiation performance and broadband low-RCS property of this metasurface antenna verify the effectiveness of the proposed method. Different from most reported design method of low-RCS antenna directly from conventional antenna, the proposed method adopts a reverse thinking and converts the scattering optimization to radiation optimization, realizing the integration of metasurface and antenna, and making the design of low-RCS antenna easier and faster.

Design of broadband gradient resistive film metamaterial absorber based on genetic algorithm

In recent years, electromagnetic (EM) wave absorbing devices based on metamaterials have attracted widespread attention, due to their advantages such as broadband, easy preparation, and flexibility to tailor EM waves. Nevertheless, a review of the existing research reveals that the inherent sub-wavelength characteristics of metamaterials and metasurfaces impose certain constraints on their applications in low-frequency ranges. In order to achieve low detectability that takes into account both low-frequency and broadband absorbing performance, this work, presents a metamaterial absorber based on 5-layer gradient resistance film and dielectric composite structure, as shown in <xref ref-type="fig" rid="FigureAbstract">Fig. (a)</xref>. To begin with, we introduce the structural design of the initial element, and based on this, the transmission line theory and impedance matching principle are used to analyze the strong wave absorption conditions of the absorber element. In terms of the element structure optimization, the genetic algorithm is adopted to globally search for the optimal solution in the multi-variable domain, resulting in the rapid determination of metamaterial elements’ configurations and resistance parameters that meet the design goals. In the simulation, the wave absorption performance and mechanism of the designed absorbing element are also investigated in an in-depth manner. Simulation results show that the designed metamaterial absorber can achieve more than 90% EM wave absorption in a frequency range of 1.62–19.16 GHz (with a relative bandwidth of 168.8%) under normal incidence of linearly polarized plane waves, which effectively expands the absorption bandwidth to the L band and K band. In addition, the simulations for oblique incidence at different polarizations provide strong evidence for the device’s insensitivity to both polarization and angle. The radar cross section (RCS) curves obtained by the time domain (TD) simulation illustrate that the novel structure can achieve more than 10 dB RCS reduction in a frequency range of 1.7–20 GHz. In the device's performance verification process, a metamaterial absorber with 20 × 20 elements and dimensions of 1.566<inline-formula><tex-math id="M1">\begin{document}$ {\lambda }_{l} $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="7-20231781_M1.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="7-20231781_M1.png"/></alternatives></inline-formula>×1.566<inline-formula><tex-math id="M2">\begin{document}$ {\lambda }_{l} $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="7-20231781_M2.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="7-20231781_M2.png"/></alternatives></inline-formula>× 0.113<inline-formula><tex-math id="M3">\begin{document}$ {\lambda }_{l} $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="7-20231781_M3.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="7-20231781_M3.png"/></alternatives></inline-formula> is fabricated and tested by using the bow method reflectivity test system. The absorptivity curves under 5° oblique incidence of different polarizations, show that the proposed metamaterial absorber can realize more than 80% EM absorption in an entire frequency range from 2 to 18 GHz, the test results of different polarizations are basically consistent. The test results at oblique incidence (<i>θ</i> ≥ 30°) show that although the measured and simulated curves exhibit discrepancies in certain frequency bands due to human error or material dispersion characteristics, the overall experimental results are consistent with our expectations, which fully proves that the designed metamaterial absorber has potential application value in the field of low-frequency and broadband EM absorption.

Broadband AMC Metasurface and Its Application for Radar Cross Section Reduction of a Microstrip Antenna

Broadband AMC Metasurface and Its Application for Radar Cross Section Reduction of a Microstrip Antenna

Wideband Radar Cross Section Reduction of a Coding Metasurface Combined With an Inhomogeneous Plasma

Wideband Radar Cross Section Reduction of a Coding Metasurface Combined With an Inhomogeneous Plasma

RCS Reduction of Eight-Port Multilayer MIMO Antenna Based on Linear-to-Circular Polarization Converter With Pattern Diversity Mechanism

RCS Reduction of Eight-Port Multilayer MIMO Antenna Based on Linear-to-Circular Polarization Converter With Pattern Diversity Mechanism

Wideband RCS Reduction of Fabry-Perot Resonator Antenna Based on Diffuse Scattering Method

Wideband RCS Reduction of Fabry-Perot Resonator Antenna Based on Diffuse Scattering Method

Design of Polarization-Insensitive and Angularly Stable Metasurfaces With Symmetric Cubic Phase Distribution for Broadband RCS Reduction

Design of Polarization-Insensitive and Angularly Stable Metasurfaces With Symmetric Cubic Phase Distribution for Broadband RCS Reduction

A 2-bit Coded Transparent Metasurface with Polarization Conversion, Absorption and Scattering Functions for RCS Reduction

A 2-bit Coded Transparent Metasurface with Polarization Conversion, Absorption and Scattering Functions for RCS Reduction

Transparent and Flexible Chessboard Metasurface Based on Optimized Multielement Phase Cancellation for Wideband RCS Reduction

Transparent and Flexible Chessboard Metasurface Based on Optimized Multielement Phase Cancellation for Wideband RCS Reduction

Hierarchical porous carbon frameworks derived from Juncus effusus biomass with robust electromagnetic wave absorption properties

A biomass-derived electromagnetic absorber was developed using Juncus effusus (JE), achieving low RL value and broad EAB (−40.4 dB, 3.48 GHz), and the maximum RCS reduction value of 32.4 dB m2.

Wideband RCS Reduction Metasurface Based on Printing Resistive Graphene Ink

Wideband RCS Reduction Metasurface Based on Printing Resistive Graphene Ink

BALANIS’ ADVANCED ENGINEERING ELECTROMAGNETICS, 3RD EDITION [BOOK REVIEW

The third edition of "Balanis’ Advanced Engineering Electromagnetics" marks a significant advancement in the field of electromagnetics education and research. This edition not only retains the foundational theories of its predecessors but also introduces cutting-edge topics like artificial impedance surfaces, offering a comprehensive overview of contemporary electromagnetic technologies. With its detailed coverage of advanced topics such as metasurfaces, radar cross-section reduction, and optimization of antenna parameters, the book stands as an indispensable resource for students and professionals in electrical engineering. It bridges theoretical concepts with practical applications, making it an essential tool for both teaching and research.

Identification of Control Parameters Using Taguchi Method for Hybrid Real-Binary Differential Evolution Algorithm and Its Applications in Electromagnetic Optimization

The hybrid real-binary differential evolution (HDE) algorithm has been proficient in addressing electromagnetic optimization problems (EOPs) involving both real and binary variables. However, its optimization performance on different control parameter (CP) settings is not further studied, and the method to determine the values of CPs is more likely to use the trial-and-error method, which lacks universality on both unimodal and multimodal benchmarks. To completely account for the effect of CPs in HDE, the Taguchi method is utilized to identify the values of each CP. The orthogonal experiment result is the average rank of the mean values of 23 benchmark functions obtained by HDE and other classic optimization algorithms. Based on the analysis of variance results, three CPs that have a major effect on the performance of HDE are selected, and each of them is changed from level 1 to level 5 to further obtain the best combination of CPs, which is indicated as HDEN1. To further enhance the local search ability of HDEN1 for the global best, a modified algorithm (HDEN2) is proposed based on a novel mutation strategy selection method, and the simulation results demonstrate that the minimum values obtained by HDEN2 are smaller than those obtained by HDEN1. Two EOPs, including planar microwave absorber and Yagi-Uda antenna designs, are solved to validate the performance of HDEN1 and HDEN2. The results reveal that the HDEN1 and HDEN2 outperform HDE, demonstrating the efficacy of the proposed method for identifying the CPs of HDE. In the end, a low profile and wideband RCS reduction pixelated checkboard metasurface is optimized utilizing the HDEN2, proving that the proposed algorithm can be a good candidate for hybrid real-binary electromagnetic problems.