Radar Absorbing Materials (RAM) for Aircraft

Aircraft design with reduced radar visibility and improved aerodynamics. The aircraft has an air intake, duct, and engine with a curved shape that allows pressure changes as air flows. Radar absorbing panels are inside the duct. The panels have regions with pressure decreasing, then increasing, as air flows. The curved duct shape and pressure variations optimize aerodynamics. The panels absorb radar waves inside the duct.

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The growing demand for stealth technology in military and aerospace applications has driven the development of advanced radar-absorbing structures. In particular, honeycomb absorbing structures (HASs) have shown promise due to their unique properties. In order to enhance the absorption characteristics of HASs and evaluate its application effect on aircraft, firstly, the mechanism of enhancing the electromagnetic (EM) absorption capacity of honeycomb structures by using a gradient design for the impregnation material is studied. Secondly, a multi-layer gradient honeycomb absorbing structure (MGHAS) with top skin and intermediate bonding layers is proposed. The influence of the type and arrangement of impregnation materials on reflectivity is analyzed to obtain design strategies that can enhance the absorption performance of the MGHAS. An improved particle swarm optimization (PSO) algorithm is proposed to optimize the EM absorption performance of the MGHAS. The optimized MGHAS achieves broadband absorption below 10 dB in a 2-18 GHz range, and the reflectivity even reaches 30 dB near ... Read More

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RCS reduction has become prominent in the field of stealth technology. The primary design criterion for aircraft design is to increase survivability by decreasing detectability. The radar cross section (RCS) of a target is the equivalent area seen by radar. The RCS value indicates how easily an object will be detected by the radar. RCS has been reduced using approaches such as shaping, radar absorbent material (RAM), passive cancellation, and active cancellation. Because of the low RCS, the sidelobe level rises due to radiation from higher-order harmonics. This study describes an overview of current passive RCSR techniques for a variety of applications including frequency selective surface (FSS), electronic bandgap materials (EBG), split ring resonator (SRR), and complementary split ring resonator (CSRR). An extensive comparison chart is obtained based on antenna size, RCSR, gain, and the operating band for different types of techniques. Challenges and the scope of future research are also proposed in this review.

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Radar Absorbing Structures (RAS) are widely used in defense applications in order to reduce the electromagnetic reflections from predominant hotspots. With majority of military radars operating in X-band, thin frequency selective absorbers catering to this frequency range are the need of the hour especially for airborne platforms. In this regard, a novel ultra-thin Frequency Selective Surface (FSS) based RAS with superior absorption performance in the frequency range of 8GHz to 12GHz is presented. The absorption characteristics and radar cross-section (RCS) of the RAS has been analysed using commercially available EM simulation software. Further, the ultra-thin RAS, with a thickness of 0.053l at the centre frequency, has been fabricated and the performance parameters have been measured. The measurement results show that the percentage of power absorbed by the proposed RAS is greater than 90% over majority of X-band. In addition, it provides atleast 8dB RCS reduction (RCSR) in monostatic as well as bistatic modes of operation in comparison with its metallic counterpart of identical di... Read More

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The so-called aircraft stealth refers to coating or pasting absorbing materials on the relevant parts of the aircraft, reasonably designing the aircraft shape and layout, so that the enemy detection system (such as radio radar, infrared radar, lidar, etc.) can only receive the greatly weakened aircraft reflection signal. In this way, the possibility of aircraft being found or tracked is reduced. The basic research of stealth technology includes designing the absorbing material into a reasonable shape to maximize its efficiency. Its achievements can be applied not only to military equipment such as aircraft, ships and tanks, but also to other scientific and technological fields. Although the mathematical and physical problems composed of Maxwell equations and corresponding boundary conditions can be analyzed and calculated strictly in theory, the model is complex and the calculation is complicated. Focusing on the problem of radiation absorption, the microwave absorption performance of wedge shaped absorber is studied in this paper. Simulation results show the effectiveness of the res... Read More

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A radar-absorbing structure for reducing radar cross-section in aircraft, comprising a composite material layer with anisotropic electrical conductivity, comprising carbon fiber reinforced fibers and a binding agent, and a barrier coating with rods disposed at predetermined angles to redirect incident radio waves. The structure's conductivity is adjusted by varying the density and length of the rods, with higher density and length near the aircraft's interior. The structure also incorporates transition metal particles for enhanced adhesion and iron-based nanoparticles for improved absorption.

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Electromagnetic wave absorbing foam-based sandwich composite for aircraft with a lightning protection metal layer that maintains load bearing and electromagnetic wave absorption performance even after being struck by lightning. The composite comprises a dielectric fiber, plated dielectric fiber, foam core, and metal layer with a periodic circular pattern applied to reduce radar cross-section and protect against lightning strikes. The metal layer is designed to exhibit high electrical conductivity and electromagnetic wave absorption performance, while the foam core provides structural integrity and electromagnetic wave absorption.

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Stealth or lower visibility is an inevitable feature of future-generation aircraft. A stealth aircraft is coated with a special type of material called radar absorbing material (RAM), which makes the aircraft invisible to radar. Stealth technology is a great threat to the Radar surveillance system. Anti-stealth radar can be built using low-frequency signals that are efficient in detecting stealth aircraft. The variation of radar cross section (RCS) under low frequency radar system is studied here also designed an antenna for low frequency radar.

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A radar-absorbing material with a honeycomb sandwich structure for stealth applications, comprising a core layer of hexagonal units formed from metal-coated dielectric fibers and skin layers on top and bottom surfaces. The material achieves broadband electromagnetic wave absorption through the electromagnetic properties of the metal-coated fibers, and can be used in aircraft structures to reduce radar cross-section.

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For at least four decades, scientists have been working on Radar Absorbing Materials (RAMs). The effectiveness of a system has been the primary criterion for evaluating military aircraft. The designer's objective is thus to optimise the efficiency of the system. Presented article describes a preliminary study of employing Radar Absorbing Shield (RAS) to reduce Radar Cross Section (RCS) on air channels. To begin, a three-dimensional model of a single and twin air channel has been generated through using the software "Computer Aided Three-Dimensional Interactive Application" (CATIA) for numerical computation. Following that, the possible applications of Radar absorbing shield (RAS) on the surface of the both air channel were assessed in order to lower their Radar Cross Section (RCS). The outcomes were then evaluated to see the feasibility of Radar absorbing shield (RAS).

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Radar absorbing structure for air and space vehicles that combines impedance matching and destructive interference to effectively dampen electromagnetic waves. The structure comprises an aerodynamic surface, a resistive layer, and multiple films with electroactive polymers and graphene, which are cured together to create a composite material. The films are arranged to provide both impedance matching and destructive interference, while also incorporating sensors and control units to enable active cancellation and spoofing capabilities.

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The paper presents the results of a study of the radar technique for aircraft with an artificially reduced radar cross section (RCS) under the condition of using a resonant electromagnetic field. It is shown that the detection and tracking of air objects under conditions of artificially reduced RCS is carried out using radar information with resonant excitation of their radar absorbing coating. It is proposed to carry out tracking and detection of aircraft by a complex combination of an active radar channel with the formation of a resonant radio signal and a passive radar capable of receiving signals formed by an excited surface. It has been determined that by increasing the power level of the irradiating signal to 20-30%, it is possible to increase the area of the local conduction region of the dielectric by 10 times, which means that it will simplify the technical implementation of the method of locating aircraft. The proposed control methods make it possible to provide the necessary probability of detection accompanied by a radar target in a difficult jamming environment and thus ... Read More

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Abstract Multilayer radar absorbing materials with light weight, strong absorption, and wide absorption bandwidth are urgently demanded with the increase of electromagnetic pollution. However, the current design methods with only simulation operation or optimization strategy are not comprehensive. Here, a simulation-optimization approach including electromagnetic simulation and numerical calculation is proposed based on the interaction between different software, in which the homogeneous medium substitution method is presented to simplify the complicated structures. Besides, return loss and impedance matching of different layer structures are investigated. From the simulated results, it can be found that the structures with better impedance matching have superior absorbing performance. The optimal method shows the advantages of fast and efficient, which has tremendous potential for various applications, such as military stealth and electromagnetic wave elimination.

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A lot of airstrikes are being reported and other operations are done by the defense sector using modern aircraft that are not detected by radar in which this technology is named as stealth technology. Radar Absorbing Materials (RAM) is a type of stealth application process in aircraft that are composites that absorbs electromagnetic radiation from the source radar. In this work, the radar absorption material properties were analyzed by using High-Frequency Selective Surface (HFSS) software in ANSYS electronics desktop, and two different materials at different thickness 1 mm, 1.5 mm, 2mm, 2.5 mm&3mm are analyzed for the comparison of the input properties such as Permittivity, Permeability, Reflection loss, tan loss and bulk conductivity for impedance matching and reflection loss to analyze their absorbing properties. From which the efficient material is found out from the analysis for stealth application.

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Abstract There is some kind of materials widely used in microwave engineering that known as radar absorbers. Whether it is the aircraft coating, the anechoic chamber interior or waveguide feed load. Anechoic chamber absorbers are typically characterized by reflectivity at normal incidence of electromagnetic wave. The study of the angular dependence of reflectivity for several absorber samples and the appraising of the impact of their combination on the anechoic chamber performance are the main aims of present work. For this purpose the experimental studies were carried out in an antenna measuring and computing complex based on the anechoic chamber. Obtained results may be useful in the anechoic chamber design and construction stages as well as the modernization of existing ones. It can also be used for modelling of the internal electromagnetic field distribution of indoor field test ranges.

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The application of absorbing materials on military aircraft has greatly improved the aircrafts survivability and operational effectiveness on the battlefield. The coating method of absorbing materials affects the stealth performance of the aircraft. Therefore, a zoning coating method for absorbing materials is proposed in this paper, and it reduces the amount of the absorbing materials and achieves purpose of reducing the aircrafts cost and weight by reducing the coating thickness of the weak scattering source. In this paper, CAD software is used to build a stealth aircraft model. Then through calculating and analyzing the surface current distribution characteristics of the aircraft under different electromagnetic wave irradiation angles, the aircrafts zoning coating design scheme is determined. Later, the electromagnetic scattering characteristics of the aircraft are simulated by the Multi Level Fast Multipole Method (MLFMM) under the circumstance that the electromagnetic wave horizontal illumination azimuth angle is 045 and the frequency is 3 GHz and 8 GHz. At the same time, t... Read More

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Radar absorbers are one among the promising technologies toward radar cross section reduction at microwave frequencies. Hence, the key role of radar absorber is emerging in military aviation platform. Although the research on radar absorbers are continuing since decades using multilayer concept, viz., ferrite-based radar absorbers, they are narrow band in nature. Recently artificially engineered materials widely known as metamaterials are playing an important role toward performance enhancement of radar absorbers. This chapter provides a systematic review of the advances in metamaterial-based radar absorbers in conjunction with graphene and conducting polymer.

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Radar absorbing structures with multiple resistive frequency selective surfaces (FSSs) are of great potential in the aerospace and marine fields. However, reliable theoretical prediction models of multilayer circuit-analog (CA) absorbers together with proper optimizing programs have not yet well been established despite the large number of reported investigations. Herein, a precise and comprehensive optimization method was proposed for the design of lightweight and broadband absorbing structures based on improved genetic algorithm. To this end, the spatial scale effect of the entire structures and interlayer interference effects between FSS films were firstly considered. Several absorbing sandwich structures composed of fiber-reinforced epoxy facesheets, polyvinyl chloride (PVC) foam and FSS films with square patterns of various periods were then fabricated. The environmental adaptabilities of the as-obtained absorbing structures were assessed through electromagnetic and load-bearing experimental tests under different ambient temperatures and marine corrosion durations. The optimized... Read More

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A multi-functional heating sandwich composite for large wing structures, comprising a face skin and a honeycomb core. The face skin absorbs electromagnetic waves, while the honeycomb core, made of metal electroless plated dielectric fibers, converts electromagnetic wave power loss into thermal energy. The composite enables selective heating and high-speed temperature control through electromagnetic wave absorption technology.

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A radar absorber comprising a water-filled cavity between two dielectric layers, where the cavity dimensions are optimized to absorb a wide range of radar frequencies. The absorber can be manufactured by assembling the dielectric layers and frame, injecting water into the cavity, and applying a waterproof coating. The design enables efficient absorption of radar waves across multiple frequency bands without the need for expensive or specialized materials.

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A stealth structure that selectively controls infrared emissivity to emit infrared radiation through atmospheric absorption windows while absorbing microwave radiation. The structure comprises a radar absorption unit, a low-frequency transmission filter unit, and an infrared radiation unit. The radar absorption unit absorbs broadband microwaves, while the low-frequency transmission filter unit absorbs microwaves in the 2-4 GHz range. An infrared radiation unit emits infrared radiation through atmospheric absorption windows. This configuration enables the structure to selectively emit infrared radiation while absorbing microwave radiation, providing effective infrared stealth through both radar and infrared detection windows.

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Due to the large size of grounded aircraft and the difficulty in using shielding cloth to completely cover the aircraft, it is necessary to study efficient RCS shielding schemes for grounded aircraft to ensure that they can quickly hide on the spot. By covering key parts, the RCS of the aircraft can be reduced, the probability of being detected by radar can be reduced, and the survival rate of the aircraft can be improved. The geometric model of the aircraft is established using SolidWorks, and the RCS distribution of the electromagnetic model is determined by FEKO simulation calculation. Suitable shielding materials are selected to design the shielding scheme, and the radar characteristics of the shielding model are simulated and calculated. The effectiveness of the shielding scheme is evaluated by comparing the RCS distribution with the numerical change results. The study found that using magnetic absorbers combined with high-toughness epoxy resin materials reduced the average RCS by 10.757 dBm² at a frequency of 9.14 GHz after coating the aircraft model, providing a the... Read More

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A radio-wave anti-reflection sheet for reducing radar wave reflections from multilayer substrates, particularly in automotive applications. The sheet features a lower-density foam layer facing the substrate and a higher-density foam layer facing away from the substrate, which together create destructive interference patterns to suppress reflections. The sheet is particularly effective in reducing reflections from multilayer substrates used in vehicle body components, enabling improved radar detection of pedestrians and small vehicles.

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A radar-absorbing structure for air and space vehicles that combines impedance matching and destructive interference to effectively dampen electromagnetic waves. The structure comprises an aerodynamic surface, a resistive layer, and multiple films with electroactive polymers and graphene, which are cured together to provide both impedance matching and destructive interference properties. The structure can also incorporate sensors and a control unit to detect changes in the electroactive polymer films and transmit spoofing signals to the radar source.

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An air vehicle with a structure for absorbing electromagnetic waves, comprising a cylindrical air duct with panels positioned to absorb electromagnetic waves while maintaining aerodynamic performance. The panels are arranged in an "S" shape with varying distances between them, creating a flat surface against low-frequency electromagnetic waves. The structure provides both low radar frequency (RF) visibility and passive flow control by developing minimum drag resistance against the flow.

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Radar-absorbing materials (RAMs) covering the exterior surfaces of installed parts and assembled devices are crucial in absorbing most incident electromagnetic (EM) waves. This absorption minimizes reflected energy, thereby enhancing pilot safety and the stability of operating electronic devices without interference. Particularly, active stealth aircraft require effective protection from near- and far-field EM radiation across a wide spectrum of frequencies from both highly integrated electronic components and advanced enemy radars. Studies of RAMs often prioritize absorption over crucial tunability in frequency selectivity, revealing a research gap. In this study, we propose smart RAMs with frequency-selective absorption capabilities. Our approach involves incorporating two types of core-shell spheres in a polymer matrix, which feature shells of either wave-diffuse reflecting metal or wave-absorbing graphene. The key innovation lies in the ability to tailor absorption frequencies in the X-band range (8.2-12.4 GHz) by adjusting the interstitial spaces between the metallic spheres whi... Read More

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Abstract The iterative upgrading of the means of warfare has promoted the development of detection technology, and military activities are increasingly demanding target stealth. In this paper, a multifunctional metamaterial absorber is recommended, which simultaneously realizes the integrated stealth functions of ultra-wideband radar wave absorption, low infrared emission, and optically transparent. The structure is composed of an infrared shield, a radar-absorbing layer, and a reflective layer. Simulation results indicate that the absorption bandwidth in the radar band (1.8120.4 GHz) is more than 90%, and the infrared emissivity is as low as 0.271 in the IR band (314 m). Moreover, it has the features of flexibility, angle stability (045), polarization insensitivity (090), and so on. Furthermore, the electric field current distribution and equivalent circuit model of the structure are analyzed, and a 180 mm*180 mm sample is built and tested; the results show that the simulated and actual measurements are in agreement, and it is expected that such absorbers will be used in are... Read More

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A modular lightning protection system for composite aircraft structures, comprising a barrier coating made of MXene-based transition metal alloy layers with controlled nitrogen and carbon atom density. The coating is applied in multiple layers, with nitrogen atom density decreasing and carbon atom density increasing from the outermost layer to the innermost layer, providing impedance matching and electromagnetic wave absorption. The MXene-based coating is compatible with composite materials, corrosion-resistant, and can be applied using spray coating or other methods.

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This chapter discusses the importance of functional paints and coatings. The types of materials used, their processing, and different methods of testing of the final products are discussed. The range of applications is immense and especially important for strategic applications in defence and aerospace systems and platforms. Some specific functional applications include camouflage and stealth coatings; thermal imaging coatings; anti-static coatings; thermal insulating paints; high performance anti-corrosion coatings; anti-skid coatings; antifouling coatings; self-healing and self-cleaning coatings. Over the years DMSRDE, Kanpur, has made considerable efforts to develop specialized paints and coatings. In this chapter particular attention is paid to DMSRDE-developed camouflage and stealth coatings.

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Electromagnetic wave absorbing material (EWAM) plays an essential role in manufacturing stealth aircraft, which can achieve the electromagnetic stealth (ES) by reducing the strength of the signal reflected back to the radar system. However, the stealth performance is limited by the coating thickness, incident wave angles, and working frequencies. To tackle these limitations, we propose a new intelligent reflecting surface (IRS)-aided ES system where an IRS is deployed at the target to synergize with EWAM for effectively mitigating the echo signal and thus reducing the radar detection probability. Considering the monotonic relationship between the detection probability and the received signal-to-noise-ratio (SNR) at the radar, we formulate an optimization problem that minimizes the SNR under the reflection constraint of each IRS element, and a semi-closed-form solution is derived by using Karush-Kuhn-Tucker (KKT) conditions. Simulation results validate the superiority of the proposed IRS-aided ES system compared to various benchmarks.

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A radar-compatible coating for vehicle parts that achieves a silver-metallic appearance without using metal pigments. The coating consists of two layers: a base layer containing absorbent pigments and a top layer containing flake-form effect pigments with absorbent properties. The base layer is designed to have minimal color difference between coated black and white backgrounds, while the top layer provides the desired metallic appearance. The coating is free from metal pigments and achieves radar transparency while maintaining high hiding power and lightness flop.

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Abstract. The article presents the characteristics of modern reconnaissance systems in the radar range and camouflage methods for this range. Two absorbers of electromagnetic radiation in the 4-18 GHz range were tested, measuring their attenuation properties. Carbonyl iron and thin-walled hollow microspheres based on soda-lime-borosilicate glass were tested, on the basis of which paint coatings with different shares of absorbers and different coating thicknesses were produced. The attenuation properties of both absorbers were determined and attention was paid to the maximum values and frequencies for which they occur. Further directions of research were also proposed in order to obtain varnish coatings that are an effective camouflage agent in radiolocation.

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The paper proposes a theoretical and numerical study of the quality criteria of radar absorbing layer. Simple analytical expressions for the minimum of the reflection coefficient of a homogeneous absorbing layer are obtained. It is shown that this quantity is not a correct characteristic of absorption. To describe the quality of an absorber, other quality criteria are needed, such as relative bandwidth of operating waveband or the ratio of the operating waveband to the layer thickness. The first of these values may be useful in obtaining a broadband absorber, and the second, in obtaining a small thickness of an absorber.

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A dynamic camouflage system for aircraft and spacecraft that rapidly adapts its appearance through controlled manipulation of microscopic structure. The system employs an active coating with integrated, wavelength-dependent microscopic structures that can be precisely arranged to produce selective diffraction patterns. By varying the structure's arrangement, the system can dynamically change its appearance to evade detection, particularly in the infrared range. The system's control mechanism can be programmed to achieve specific camouflage patterns through electrical signals, enabling rapid adaptation to changing environmental conditions.

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A shielding device for protecting an optical imaging system from electromagnetic interference (EMI) emitted by a radar system within a common housing. The device captures and dissipates EMI signals reflected from a radome, while maintaining optimal radar performance. The shielding device is attached to the radar antenna assembly and features angular surfaces to reflect EMI signals away from the radar, and a capture surface to absorb signals directed towards the optical system.

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A method for manufacturing radar-absorbing composite materials with improved mechanical properties, comprising a three-block laminate structure. The second and third blocks form the active electromagnetic component, with the second block manufactured by superimposing layers of dry fiber sprayed with graphene nanoplatelets, interspersed with untreated dry fiber fabrics. The number of untreated fabrics is inversely proportional to the central frequency of the absorption band. The blocks are solidified through resin infusion and curing, enabling broadband radar absorption while maintaining mechanical properties comparable to the first block.

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The paper presents an analysis of the functional operational properties of multilayer coatings for use in military technology in the field of masking. The developed coating systems are characterized by operational innovation due to their small thickness when compared to those currently used by global defence contractors while maintaining the re-emission coefficient required for camouflage to be effective in the optical range. Their service life and durability were assessed in terms of functional properties based on measurements of attenuation coefficients, surface geometric structure, adhesion, specular gloss and colour parameters. The tests were carried out for coating systems fabricated in five variants: a two-layer paint system (SP1), a threelayer paint system (SP2), a laser-modified three-layer paint system (SP3) and a four-layer paint system in two variants (SP4 and SP5), with the former being modified with carbon nanotubes and the later with spherical iron. Coating systems are characterized by low roughness and good adhesion and have appropriate attenuation coefficients for r... Read More

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Abstract Implementation of stealth features on advanced airborne platforms (aircrafts, unmanned air vehicles, missiles, etc.) has become a compulsion for each country, for denial/delay detection of these objects from enemy radars, during tactical missions. Apart from the shaping of the airframe, implementation of microwave-absorbing materials (MAMs) on identified locations of airborne vehicles is the only viable solution to reduce their radar cross-section (RCS) and eventually attain stealth capabilities. Numerous dielectric and magnetic class materials have been developed over the last few decades to fulfil the requirement for RCS reduction against various radars operating in different frequency ranges. In this review, a detailed representation of almost the entire range of materials used as MAMs has been provided along with their possible microwave (MW) loss mechanism to fill the gap that existed for a systematic insight on MAMs till now. The current limitations and future aspects are also discussed for the development of future stealth materials.

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The signature of radar target is an important aspect in military war. The demands for low signature targets have been increased to achieve the critical mission successes in defence. Worldwide scientists and engineers are incessant working on it. This paper presents the data analysis of radar absorbing material (RAM) suitable for attaining of low signature applications for small air vehicles such as sUAV, UAV, drones, hexcopter, spy birds etc. In this paper, the polyethylene (PE) and their composites characteristics and data analysis are presented, for applications in small air vehicles to attain the lower value of their target signatures. This is achieved in terms of EM measurement parameters of RAM material such as reflection loss, transmission loss, absorption loss, shielding effectiveness (SE), radar cross section (RCS) etc. The obtained values of reflection loss are 29.49 dB, - 36.91 dB and 23.94 dB; then, the transmission loss are 133.18 dB, - 128.70 dB and 0.19 dB for PE, polyethylene terephthalate (PET) and PET + conductive paint (PETCP) respectively for materials b... Read More

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Radar is a sensitive detection tool that uses electromagnetic radio waves to determine the position and motion of objects. Since its development, the methods for reducing radar wave reflections have been explored to improve stealth technology. One of the methods for reducing radar reflection is coating the aircraft using radar absorbing metamaterialMetamaterials. This research studies the radar absorption properties of a metamaterialMetamaterials honeycomb structureHoneycomb structure which has gradient protruded inner walls that are made of a radar absorbing material fabricated of Carbon Nanotube (CNT) Iron Oxide composite. The CNT Iron Oxide material was first prepared, then EMI measurement was conducted to obtain the permeability and permittivity values of the material. Then, the effect of changing the geometrical parameters of the honeycomb structureHoneycomb structure (size, height, thickness, and tilted angle) on the radar absorption properties has been simulated using Multi-Physics COMSOL. Simulation results showed that the optimum structure can absorb more than 90% of the rad... Read More

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Abstract Stealth performance plays an increasingly important role in the evaluation of aircraft performance, while achieving excellent stealth performance in multiple frequency bands simultaneously remains a crucial challenge. Herein, a visible transparent wideband microwave absorber with infrared camouflage function is theoretically presented and experimentally demonstrated. The sample is composed of two radar absorption layers (RALs) and an infrared shielding layer (IRSL). In addition, the magnetic resonance model and the ohmic loss model are employed to strengthen the absorption of the designed RALs >90% in a broadband frequency range of 723 GHz with a relative bandwidth of 106.7%, and an average visible transmittance of 60%. Furthermore, IRSL is achieved by a designable digital frequency selective surface (FSS), which promotes a compatible design between infrared camouflaged emissivity and microwave absorption. These peculiar properties not only verify the feasibility of the proposed strategy for achieving suitable artificially designed IR digital camouflage patterns to meet... Read More

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Microwave absorbent materials (MAMs) are significant in a extensive range of civil and military applications, including national defense security, healthcare, electronic reliability, and anti-radar detection of war fighters, as information technology advances quickly, and recent years have seen an explosion in the investigation of nanomaterials for use in microwave absorption applications. Therefore, the creation of high-performance MAMs with thin thickness, low density, wide bandwidth, and robust absorption has attracted a lot of attention. MAMs nanocomposites are also used to make radar-absorbing materials (RAMs) for stealth aircraft. By combining RAMs with geometry, stealth technology (ST) reduces the reflection of electromagnetic waves back to a radar system. In this article, we discuss the fundamental theory, components, and mechanism of electromagnetic microwave absorption. It will be detailed how to improve the microwave absorbent materials' (MAMs') absorption characteristics. Metal-based composites often show significant efficacy in achieving desired magnetic and dielectric p... Read More

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Multispectral compatible stealth technology, such as radar-infrared, infraredvisible, and radar-infraredvisible stealth, has been applied in the military field for better defensive capability than single-band technology. Developing low radar cross-section, low infrared radiation energy, and optical transparency compatible stealth materials is promising for the large-scale application of military. In this review, a deep analysis about multispectral compatible stealth technology is presented to understand the various types, the mechanisms and the design principles of different waveband absorbers. Subsequently, recent advances of compatible stealth materials are discussed in detail. Finally, current challenges and future opportunities in this promising field are also proposed and predicted.

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Low observable techniques for stealth applications have become the need of the hour. RCS analysis for airborne platforms in military bands is the stringent requirement. Techniques such as shaping of aircrafts and use of absorbers suppresses radar echoes. This paper discusses about the use of special absorber techniques such as multi-layered Radar Absorbing Techniques with and without FSS to cater the reduction of echoes in the X-Band. The RCS analysis with and without absorber for Unmanned Combat Aerial Vehicle has been compared and analysed. The target tracking for the UCAV has also been covered in hostile environment condition using Altair Feko.

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Radar cross section (RCS) reduction is thoroughly studied among electrical engineers so as to attain stealth capabilities of any object of interest. One particular kind of absorber which is in high demand is of the transparent and flexible kind. Transparent absorbers find their applications in various defence related applications such as in wind shield of aircraft and vehicles. Manufacturing of transparent metamaterial absorbers is a challenge as it is always a trade off between electrical performance and maintaining optical transparency. In this paper the authors present a technique of optimizing the electrical and optical performance of transparent absorber manufactured with commercially available Polyethylene Terephthalate (PET) coated Indium Tin Oxide (ITO) sheets.

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Stealth technology is widely implemented in modern military aircraft in order to reduce radar cross section (RCS) which in turn avoid detection by enemy radars. Multilayered radar absorbing structures (RAS) are used in this respect to get wide absorption bandwidth with minimal thickness. In this regard, a lossy frequency selective surface (FSS) based multi-layered RAS model, having a total thickness of 5.84mm, is proposed in the present paper. The full wave simulation results as well as the equivalent circuit model (ECM) of the proposed design show that the reflection coefficient is below -10dB in the frequency range from 2GHz to 24GHz for wide range of incident angles for both perpendicular as well as parallel polarizations. This in turn implies that the percentage of power absorbed is greater than 90%. Further, RCS analysis of the planar RAS model presents an average RCS reduction (RCSR) of around 12dB.

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The survivability and mission of a military aircraft is often designed with minimum radar cross section (RCS) to ensure its long-term operation and maintainability. To reduce aircrafts RCS, a specially formulated Radar Absorbing Structures (RAS) is primarily applied to its external skins. A Ni-coated glass/epoxy composite is a recent RAS material system designed for decreasing the RCS for the X-band (8.2 12.4 GHz), while maintaining efficient and reliable structural performance to function as the skin of an aircraft. Experimentally measured and computationally predicted radar responses (i.e., return loss responses in specific frequency ranges) of multi-layered RASs are expensive and labor-intensive. Solving their inverse problems for optimal RAS design is also challenging due to their complex configuration and physical phenomena. An artificial neural network (ANN) is a machine learning method that uses existing data from experimental results and validated models (i.e., transfer learning) to predict complex behavior. Training an ANN can be computationally expensive; however, traini... Read More

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Stealth technology, a kind of low observable technology, is a military tactic that has created a jolt since World War II (19391945) in order to invade enemies' territory without leaving any signature of its invasion like radar, acoustic and smoke. Radars use electromagnetic radiation in order to detect and observe the target even from a longer distance. The electromagnetic radiation from radars strikes on the target object and they are reflected, or absorbed, or transmitted by the object. The number of reflected waves depends on radar cross section (RCS). The trajectories of research done on stealth technology through Wesch, Jaumann, Halpern Anti-Radiation Paint, MX-410, etc., influenced the researchers to look forward towards more developments in the field and immense effort enabled the target object to pass the radar without getting detected by reducing the radar cross section with the selective spectral signatures. The conglomerate effect of size, shape, materials coated on the surface, radar frequencies, angle and orientation of stealth aircraft, or submarine results in better i... Read More

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Stealth Technology so as to avoid detection by using combination of features so that Aircraft can interfere with RADAR and also reduce the visibility in radio frequency (RF) spectrum, audio and infrared visual. During the last decades, stealth technology has proven to be one of the most effective approaches as far as the Endeavour to hide from radar systems is concerned. Stealth means to avoid the detection or try to hide, for airplanes, hiding from radar meant stealth. The concept used in the stealth technology is not so difficult. It uses the principle to absorb and reflect the radar waves. Aircraft deflects the radar waves in various directions and minimizes the radar waves which return backs to radar. This paper reviews about the different aspects in stealth technology

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The article explores methods for detecting and tracking air targets in radar with an artificially reduced radar cross-section (RCS). A technique for control the radar antenna system using an adaptive method is presented, which is based on adapting the system to the conditions of information uncertainty due to fluctuations in the excitation signal of the radar target's radar-absorbing coating. Known methods of radar aircraft (active and passive, which do not take into account the structure of the coating of the aircraft) do not allow obtaining information about an air target with an artificially reduced RCS. The main contribution of this article is the development of radar and control methods based on the resonant frequency-phase interaction of the microwave electromagnetic field with the crystal structure of the radar absorbing coating of the aircraft. The stages of antenna system control based on the "frequency-phase detection method", "passive-active" tracking method, and "adaptive method" of antenna control have been studied. To test the proposed methods, an experiment was conduct... Read More

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