Radar Cross Section Reduction Research Articles

Ultra-Wide-Band and Polarization-Insensitive Metamaterial Absorber With Resistive Ink Sheet for RCS Reduction Applications

Ultra-Wide-Band and Polarization-Insensitive Metamaterial Absorber With Resistive Ink Sheet for RCS Reduction Applications

Facile synthesis of hierarchical Fe–S co-doped carbon-based composites with superior microwave absorption

Difficulty of multi-component coupling and hierarchical pore structure preparation make it challenging to manufacture highly efficient microwave absorption materials (MAMs). Herein, hierarchical porous carbon composites anchored with various types of iron sulfides are successfully fabricated using a simply feasible heating-induced self-assembly approach. Controllable electromagnetic parameters and impedance matching features of FexSy/AC (amorphous carbon) composites are obtained by varying carbonization temperature. Besides, AC and FexSy provide dielectric and magnetic losses, while defect-rich AC can effectively disperse FexSy nanoparticles, exhibiting high sintering resistance and high-density interfaces, which contributes to polarization losses. Moreover, the unique hierarchical porous structure not only offers better impedance matching, but also enhances microwave loss. The thorough investigation indicates that FexSy/AC nanocomposites exhibit outstanding microwave absorption performance by the joint effect of unique hierarchical porous structure and coupling loss of multi-components. The optimal sample (FSC-700) shows a strongest reflection loss value of up to −78.96 dB with a matching thickness of 2.85 mm, an effective absorption bandwidth (EAB, RL<−10 dB) of 6.98 GHz (11.02–18.0 GHz, spanning Ku-band), and a radar cross section (RCS) reduction value of 21.75 dBm2. In addition, the EAB can reach 13.8 GHz with the simulated thickness varies from 1.0 to 5.5 mm, covering 86 % of the measured frequency range. The in-depth research of the multi-component system with hierarchical porous structure offers an innovative and practical method for high-performance MAMs.

Resistive ink based polarization and incident angle independent wideband absorber for RCS reduction at KU and K band

In this paper, a thin, single layered, wideband, polarization-insensitive, frequency selective surface absorber for radar cross section reduction (RCS) at KU and K bands has been studied analytically and experimentally. The lossy resistive patterns on unit cell is printed using resistive ink and arranged periodically over a low-cost metal-backed FR-4 dielectric substrate. Through appropriate design and optimization, the proposed absorber demonstrates above 90 % absorption for broadband ranging from 15 GHz to 26.6 GHz, with multi-absorption peaks at 15.7, 18.5, and 22.9 GHz. The structure shows a high absorptivity of 96.8 % in the KU band and 95.7 %, and 99.3 % in the K band at the above mentioned frequencies. A fractional bandwidth of 55.8 % has been obtained at the expense of a thickness of 0.0835 λ1 (λ1 being the wavelength associated with the lower absorbing frequency). The absorption mechanism has been described with the help of surface current distribution, induced electric field, and equivalent circuit. Further, for both TE and TM waves, analysis of various polarization angles and oblique incidence angles have been investigated. It shows polarization insensitivity to normal incidence and a stable response up to 60° for oblique incidence to TM wave. The proposed absorber’s novelty comes through its thin, single-layered structure with wide band response at the KU and K frequency bands via a unique resistive ink pattern on a low cost FR-4. A prototype of the absorber has been fabricated and measured results have been validated with simulated results. A proposed single layered, wideband, thin, polarization, and angular stable absorber using resistive ink is commercially viable for RCS reduction applications at the KU and K band.

Structure Design And Optimization Approach For Low RCS Screws

With the rapid development of radar stealth and detection technology, large numbers of screws and rivets have become a major factor that affecting the aircraft’s invisibility. This is because these components have a significant impact on the overall radar cross section of the aircraft, when the electromagnetic scattering characteristic of strong scattering sources is greatly reduced. By analyzing the scattering contribution of the head and body to the screw, it has been obtained that the geometric structure of the head plays a primary role in influencing the overall radar cross section of the screw. According to the scattering mechanism and stealth principle, a shape design method for the low RCS screw is proposed, and then we investigated the scattering characteristic of the octagonal, hexadecagonal, and circular head screws respectively. Furthermore, a structure optimization approach for low RCS screws is introduced which takes the angle of the incident wave into account. This has resulted in the development of a corresponding triangular screw with low detection capabilities. The simulation results show that within the operating frequency band of radar, the triangular head screw has a maximum RCS reduction of approximately 30.1dB compared to a traditional round head screw in [-90°,90°]. On average, there is a reduction of 12.6dB. The simulated results demonstrate the effectiveness and feasibility of the proposed design and optimization method for low RCS screw structures

Multifunctional and multispectral polarization converter and checkerboard metasurface design with low infrared emissivity

With the continuous development of detection technology, single detection technologies such as radar and infrared (IR) can no longer meet the current detection needs. The design of metamaterials is gradually moving towards multispectral compatible design. In this work, a polarization converter with low IR emissivity and a checkerboard metasurface with radar-IR bi-stealth were proposed. The filling rate of indium-tin-oxide(ITO) is increased to reduce the IR emissivity without affecting the polarization conversion efficiency. In addition, based on the radar cross section (RCS) reduction theory of the checkerboard composed of polarization conversion units, a broadband RCS reduction radar-IR bi-stealth structure is designed and analyzed. A sample was fabricated and the IR and microwave characteristics of the metasurface were measured. The numerical simulation results are in good agreement with the measurement results. The results show that the polarization conversion rate (PCR) is higher than 90% in the frequency range of 7.98-12.02 GHz, and the axial ratio (AR) is between 0.5 and 2 in the frequency range of 6.92-7.56 GHz and 12.48-15.78 GHz for the proposed polarization converter. The RCS reduction of the checkerboard metasurface exceeded 10 dB in the frequency range of 7.7-11.8 GHz. Meanwhile, the IR emissivity is less than 0.3 in 8-14 µm and the structure exhibits good optical transparency. This indicates the potential application of the proposed structure in multifunctional and multispectral compatible materials.

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

Reducing out-of-band radar cross-section of metasurface-based radome composites via beam-scattering mechanism

In this work, a metasurface-based radome composite (MRC) with customized electromagnetic (EM) functions is proposed. By employing a beam-scattering mechanism, high transmission at 2–4 GHz and significant radar cross-section (RCS) reduction at 8–18 GHz are achieved. The MRC prototype features a sandwiched construction and is fabricated using quartz fiber-reinforced composite (QFRC) skins, polymethacrylimide (PMI) foam cores, and silver-based frequency selective surface (FSS) screens. The calculation, simulation, and measured results demonstrated that the transmission of the planar specimen is larger than −1 dB at 2–4 GHz and the RCS reduction is less than −10 dB at 8–18 GHz. The measured results also verified that in the HH and VV polarizations, the mono-static RCS of a square pyramid (SP) specimen at specific directions from 8 GHz to 12 GHz is significantly reduced. It is believed that our finding has great application potential in stealth radome technology.

A spatiotemporal encoding metasurface design for manipulation of integrated radiation-scattering characteristic

This paper presents a spatiotemporal encoding metasurface design to independently achieve the good radiation and the low scattering performances in the same frequency band. The proposed metasurface unit cell is composed of a square patch and two orthogonally placed I-shaped strips. By switching the operating states of the PIN diode inserted into each I-shaped strip between ON state and OFF state, a phase difference of 180° can be obtained in the band of 7.6–7.95 GHz for two orthogonally polarized incident waves. When a coaxial probe is introduced at the diagonal line of the square patch, the dual-polarized radiation capability is achieved within the frequency range of 7.6–7.95 GHz. With the proposed metasurface unit cell, the manipulation of the radiating wave and the scattering wave has no influence on each other. By controlling the PIN operating states by the field programmable gate array in real time, the power of the scattering wave is transferred to some higher order harmonics, thus realizing radar cross section (RCS) reduction. With optimized spatial and temporal encoding layouts, the proposed metasurface realizes the RCS reduction over 10 dB within the range of 7.3–8 GHz, with the maximum RCS reduction of 35.6 dB, while maintaining good radiation capability.

High Q ultra-thin nona-band polarization insensitive homogeneous single layer metasurface for electronics and space industry with electromagnetic interference and antenna radar cross section reduction

In this article, a nona-band metasurface with unit cell dimensions of 0.038λo×0.038λo×0.019λo (20×20×1.0 mm3) is designed on a FR-4 substrate (Dielectric constant εr = 4.4 and loss tangent = 0.02) of 1.0 mm thickness with 35 µm copper (Conductivity = 5.8×107 S/m) cladding with unit cell periodicity is 20 mm. 10×10 metasurface array size is 200×200×1.0 mm3. In TE/TM mode, the absorbance is greater than 99 % at the intended frequency bands (i.e., 5.76, 8.6, 12.68, 14.38, 17.05, 17.94, 19.20, 20.88, 22.62, and 23.62 GHz), and its reflectivity is almost zero. Results indicated that the metasurface is found to extremely independent on the angles of polarization of the incident wave and the absorber is almost insensitive to the incident angle (0° – 90°) for TE/TM modes. The unit cell of metasurface is having negative permittivity, near zero permeability and negative refractive index at all intended bands which confirm exotic properties of the metasurface. The metasurface is having high quality-factor (Q = 72) at 5.76 GHz frequency therefore, this metasurface is also useful for dielectric sensing application in intended bands. The metasurfaces unparalleled properties make it suitable for EMI shielding, sensing applications in the C, X, and Ku-bands, the reduction of mono-static RCS, the improvement of isolation in MIMO antennas, and the reduction of unintended noise produced by copper components used in satellite and RADAR communication.

A segmented conformal surface for ultrawideband monostatic and bistatic RCS reductions

In this paper, a segmented cylindrical metal surface based on an optimal arrangement is proposed to achieve ultrawideband and wide-angle radar cross section (RCS) reduction. Firstly, a multi-stage semi-cylindrical surface that uses the difference in radius between each cylinder to achieve phase cancellation is designed. The PSO algorithm is used to obtain the best length of each cylinder. Then, each semi-cylinder is equally divided into a certain number of sub-surfaces. Subsequently, in the axial direction, the sequence of these sub-surfaces with different radii is disrupted according to the optimal arrangement to form discontinuous surface reflection phases. A 10-dB RCS reduction under normal incidence is achieved from 4.36 to 20.6 GHz, and the bandwidth ratio reaches 4.72:1. The theoretical analysis and simulated results are in good agreement with the measured results, and the design has an important reference value for ultrawideband monostatic and bistatic RCS reductions for cylinder-like targets.

Metasurface loaded dual port circularly polarized dielectric resonator antenna with reduced RADAR cross section and mutual coupling features

The design of dual port radiator with a polarization diversity technique and reduced radar cross section (RCS) is described in this study. Cross slot is used to stimulate cylindrical ceramic for generating circular polarization features. Mirror orientation of aperture between port-1 and port-2 improves the isolation level by 25 dB. To suppress the antenna’s monostatic RCS, split ring resonator (SRR) based frequency selective surface is positioned between and around the dual ports. Experimental outcomes confirm the designed radiator operates from 4.11–5.24 GHz along with 3-dB axial ratio in between 4.15–4.92 GHz. The value of monostatic RCS is reduced by 15 dBsm in between the operating band. Broadsided radiation characteristics and good value of diversity parameter makes the designed radiator applicable for C-band Radar applications.

An Efficient Method for the RCS Reduction of Cavities in the Ground Plane

An Efficient Method for the RCS Reduction of Cavities in the Ground Plane

Ultra-wideband RCS reduction based on reflection cancellation and tunable absorption

Ultra-wideband RCS reduction based on reflection cancellation and tunable absorption

Wideband RCS Reduction Metasurface Based on Printing Resistive Graphene Ink

Wideband RCS Reduction Metasurface Based on Printing Resistive Graphene Ink

Wideband monostatic and bistatic radar cross‐section reductions using polarization conversion metasurface

AbstractA high‐efficiency polarization conversion metasurface (PCM) is proposed and applied to radar cross section (RCS) reduction. The PCM can achieve cross‐polarization conversion with a polarization conversion ratio of over 97% from 13.9 to 30.3 GHz, covering K‐band. The low‐RCS antenna is designed from a circularly polarized patch antenna loading with the PCM. The antennas with and without PCM are fabricated and measured. The results show that the radiation performance is well preserved and the scattering performance is greatly improved. The average monostatic RCS reduction value reaches 14.6 dB in an ultra‐wideband from 12.2 to 30.2 GHz under normal incidence. What's more important, bistatic RCS is researched in detail and evident RCS reduction is achieved at different incidence angles. This research has potential applications in the field of stealth platform.

Terahertz RCS reduction employing reconfigurable graphene-based AMC structures

Recently, modern technology has towards stealth technology, especially in military applications so, this paper presents a terahertz radar cross-section (RCS) reduction utilizing reconfigurable graphene-based artificial magnetic conductor (AMC) arrays. The AMC unit cell has a Vivaldi shape with circular slots etched in the radiator to reduce the RCS from metallic surfaces at THz bands. The AMC cells affect the surface impedance of the metallic objects which reduces the reflected EM waves from them. The RCS reduction bandwidth is achieved and controlled by varying the voltage applied to graphene cells which varies its chemical potential (µc). The effect of changing the graphene conductivity on the RCS reduction is investigated. Different arrangements to obtain maximum RCS reduction are presented. A 12 × 12 hybrid arrangement of the graphene-based AMC structures achieved maximum RCS reduction from 1.5 to 4 THz with 22 dB greater than the unloaded metallic surface. The CST simulator is employed in the simulation.

Absorptive frequency-selective transmission/reflection metamaterials with angular-insensitive and switchable octave absorption

Absorptive frequency-selective transmission/reflection (AFST/AFSR) metamaterials (MMs) embedded with yttrium-iron-garnet are proposed, capable of achieving angular-insensitive and switchable octave absorption. The season optimization algorithm is utilized to optimize the structural parameters of the MM, thus achieving exceptional angular stability. By adjusting the discrete decreasing magnetic field applied to the MM, it can freely switch between double, triple, quadruple, and fivefold octave absorptions. Incorporating reflection layers into two symmetrical AFST MMs, which individually handle electromagnetic waves in forward and backward incidence cases, the Janus feature is realized. This accomplishment led to the achievement of the Janus AFSR MM, enabling angular-insensitive and switchable octave absorption. AFST and AFSR MMs demonstrate stable performance for TE waves under various oblique incidence angles up to 53°. The AFST/AFSR MMs showcase a novel approach to achieving angular-insensitive and switchable octave absorption, and hold significant application value in fields such as electromagnetic computing, RCS reduction, and information processing.

A Complementary Overview and Challenges in Radar Cross Section Modeling of Phased Array Antennas

The radar cross-section (RCS) is a critical factor in the design and performance of modern airborne weapon systems. These systems utilize phased array antennas due to their low profile, advanced beamforming, and angle measurement capabilities. The effect of phased array antennas on platform RCS can be crucial. Addressing the RCS of phased array antennas involves solving both structural and antenna mode scattering. Each component presents different challenges for computation and requires specific RCS reduction techniques. This short review delves into various existing methods for computing antenna and structural mode RCS and offers insights into their application. Simulating the RCS of large array antennas presents significant challenges due to the high demands on computing resources. Additionally, this review highlights existing solutions aimed at reducing the simulation times and memory usage in RCS modeling while maintaining accurate results. However, further advancements are necessary to simulate large scale array antennas more efficiently and accurately.

An ultra-wideband magnetic composite metamaterial microwave absorber embedded with multilayered graphene FSS

Nowadays, it is still challenging to develop high-efficiency broadband microwave absorption materials for electronic equipment and communication facilities. Herein, an ultra-wideband metamaterial microwave absorber (MMA) composed of CoNi@CNH/epoxy composite absorption substrates and the multilayered graphene frequency selective surface (FSS) is designed and fabricated. Thanks to the effective synergies of the multilayered graphene FSS with impressive tunable frequency features and magnetic absorption substrates with distinguished broadband absorption capacity, the obtained MMA showcases an effective absorption bandwidth from 4.5 GHz to 18 GHz. Meanwhile, an equivalent circuit model is proposed to explain its physical absorption mechanism. The designed MMA exhibits the insensitivity to both polarization modes and oblique incidences, and a significant radar cross-section reduction. The experimental results of the as-fabricated sample match well with the simulation values. Furthermore, the as-designed MMA possesses a simple fabrication process and an ultralight feature of 2.7 kg/m2. All these excellent properties make this MMA a high application prospect in both military stealth and civil fields.

Reconfigurable metasurface array for diverse retrodirective reflections and radar cross section reduction

Abstract Retroreflectors can scatter the arbitrarily incident wave back to incoming direction, demonstrating great potential in wireless communication. However, there are limitations in adaptive retroreflection and polarization modulation with the existing retroreflectors. In this paper, a novel metasurface array with a reconfigurable transmission line (TL) network has been proposed to flexibly achieve multiple manipulation functions of electromagnetic wave including upper half-space cross-polarized retroreflection and circularly polarized retroreflection in the diagonal planes and radar cross section (RCS) reduction. To accomplish these capabilities, a novel transmission mode for ferrite circulators has been developed, enabling precise phase control of the TL. By adjusting the operation states of the circulators, multiple phase differences between forward and reverse transmission directions including ±90° and ±180° are generated. With the obtained phase differences, the metasurface array can flexibly achieve the adaptive retroreflection fields with multiple polarization characteristics based on the spatial field superposition and the RCS reduction based on the phase cancellation. To validate the concept and feasibility of the proposed reconfigurable retrodirective metasurface, an X-band prototype has been fabricated and measured. Good agreement between the simulation and the experiment is observed to verify the effectiveness of our retrodirective design in upper half-space wave manipulation.