Radar Cross Section Reduction Research Articles

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.

Realization of an ultra-thin absorber based on magnetic metamaterial working at L-band

In this paper, at the L-band, we design and verify an ultra-thin easy-realized absorber (LUTA) based on metasurface and magnetic material. The absorptivity achieves over 90% at 1–2.51 GHz (86.04% fractional bandwidth), covering the whole L-band (1–2 GHz) and the partial S-band (2–4 GHz). The total thickness of the LUTA is as low as 3.7 mm, corresponding to 0.012λ0 at the lowest operating frequency, which greatly breaks through the Rozanov limit. The excellent performance is achieved through analyzing the transmission line model of a basic absorber and then designing the metasurface layer with required impedance characteristics to make the impedance of the LUTA match with the air at the designed frequency band. The simulated absorption, power loss density, and the surface current distributions of the LUTA verify the design method, while the measured results demonstrate that the LUTA has the superiority of easy-fabrication, polarization independent, wide angle incidence, and high absorption at the whole L-band. The LUTA has great application potentials in the fields of L-band electromagnetic stealth and radar cross section reduction.

RCS reduction of wide-band, high-gain antenna array based on asymmetric transmission metasurfaces

In this paper, an ultra-wideband stealth antenna with high gain on the basis of asymmetric transmission metasurface (ATMS) is proposed. ATMS can convert an incident y-polarised sphere wave into an x-polarised plane wave at the front side and controls the scattering of the incident y-polarised wave to the back side. Excitation of ATMS via a horn antenna, a low radar cross-section (RCS) and wideband antenna system is designed. Furthermore, through design of the meta-atoms and optimization of the macrosequencing, broadband RCS reduction is achieved. The experimental data indicated the reduction of the RCS of the antenna system by up to 10 dB and more than 20 dB in the frequency range of 10.1 GHz to 18 GHz (relative bandwidth is 56.2%) and 13.9 GHz to 18 GHz (relative bandwidth is 25.7%), respectively. In addition, a 3 dB gain relative bandwidth of 57.4% is achieved between 10 and 18 GHz, with a peak gain of 28.2 dB. It is noteworthy that the high gain and low scattering performance of the antenna are achieved in the same spectral range (10–18 GHz), and there is no interference between the scattering performance and radiation performance of the antenna, which could be controlled separately.

Analysis of the Dihedral Corner Reflector’s RCS Features in Multi-Resource SAR

Artificial corner reflectors are widely used in the vegetated landslide for time series InSAR monitoring due to their permanent scattering features. This paper investigated the RCS features of a novel dihedral CR under multi-resource SAR datasets. An RCS reduction model for the novel dihedral corner reflector has been proposed to evaluate the energy loss caused by the deviation between the SAR incident angle and the CR’s axis. On the Huangtupo slope, Badong county, Hubei province, tens of dihedral CRs had been installed and the TSX–spotlight and Sentinel-TOPS data had been collected. Based on the observation results of CRs with more than ten deviation angles, the proposed reduction model was tested with preferable consistency under a real dataset, while 2 dBsm of systematic bias was verified in those datasets. The maximum incident angle deviation in the Sentinel data overlapping area is over 12°, which leads to a 2.4 dBsm RCS decrease for horizontally placed dihedral CRs estimated by the proposed model, which has also been testified by the observed results. The testing results from the Sentinel data show that in high, vegetation-covered mountain areas like the Huangtupo slope, the dihedral CRs with a 0.4 m slide length can be achieve 1 mm precision accuracy, while a side length of 0.2 m can achieve the same accuracy under TSX–spotlight data.

Chiral-assisted geometric phase metasurfaces: Manipulating orbital angular momentum for efficient and stable microwave attenuation

Chiral wave-absorbing metamaterials can enhance microwave attenuation performance by converting linearly polarized waves into circularly polarized waves. However, the mechanism for transforming incident waves into vortex waves to overcome the angular momentum mismatch to satisfy broadband stealth is unclear. This work proposes a chiral-assisted geometrically phase (CAGP) metasurfaces that utilizes the Pancharatnam-Berry (PB) phase concept to convert incident plane waves into reflected vortex waves. Such metamaterials demonstrate adaptive transformation capabilities under the incidence of electromagnetic (EM) waves with multi-polarization modes, providing an effective absorption bandwidth (≥90 % absorptivity, reflection loss ≤ −10 dB) reaches 6.92 GHz (9.16–16.08 GHz) at a thickness of 2.48 mm. Based on an orbital angular momentum (OAM) phase and amplitude analysis, the mode purity of the generated vortex waves is discussed in detail, and the mechanisms are analyzed and verified by simulation models to confirm their effectiveness and practicability. Additionally, the metamaterials exhibit excellent radar cross-section (RCS) reduction properties and stable polarization insensitivity properties. In short, this work presents a tailorable metasurface to manipulate the OAM spectrum and achieve broadband microwave attenuation, which holds great potential for various applications in chiral wave-absorbing metamaterials.

Absorptive metasurface with optical transparency for broadband RCS reduction.

Here, we introduce an optically transparent and flexible metasurface designed for effective absorption within the microwave spectrum. Indium tin oxide (ITO) films with varying square resistances fabricate a metasurface ground layer and a lossy pattern layers. Polydimethylsiloxane (PDMS) with a low refractive index, high transparency, and high flexibility is chosen as the dielectric layer. The proposed structure exhibits a reflection band of less than -10 dB with a fractional bandwidth of 167% in the range of 3.0-33.8 GHz under vertical incident electromagnetic waves. The metasurface designed based on this unit allows for the attainment of a radar cross section (RCS) reduction bandwidth of 8.75-31.1 GHz with a 10 dB reduction and a fractional bandwidth of 112%. The metasurface can maintain a broadband RCS reduction over a range of 45° incidence angles. In addition, due to the flexibility of the structure, we analyzed its RCS reduction capability when non-planar by wrapping the structure around a cylinder. The integration of simulation and testing has demonstrated that the structure exhibits excellent performance in the field of electromagnetic stealth. It has potential practical applications in electromagnetic shielding windows and the windows or domes of airplanes or satellites.

Constructing and optimizing epoxy resin-based carbon Nanotube/Barium ferrite microwave absorbing coating system

High-performance microwave absorbing coatings are highly indispensable for protecting human health and enhancing military strength. A single- and double-layer wave-absorbing coating system that employs complex microwave absorbers composed of the helical carbon nanotubes/doped barium ferrite composite with epoxy resin as the matrix was developed. The concentration and thickness of the coating were optimized by the numerical simulation and the adaptive genetic algorithm. The developed helical carbon nanotubes/doped barium ferrite wave-absorbing composites have a porous reticular structure, with abundant microscopic cavities and an adequately conductive network. The coatings are characterized by a flat surface, good uniformity, and high density. The reflectivity measured by the arch method is similar to that obtained through the finite element simulation, where the absorption bands of all the developed coatings are distributed in the range of 10–18 GHz. The optimized wave-absorbing coating exhibits the most uniform scattering pattern, the largest radar cross section (RCS) reduction, the smallest input reflection coefficient, and the highest absorptivity. Thus, it exhibits the best comprehensive microwave-absorption performance with a minimum reflection loss of −17.22 dB at 16.66 GHz. In particular, the absorption bandwidth of the coating can reach 9.16 GHz, which is attributable to its multiple synergistic electromagnetic attenuation mechanisms and its excellent characteristics of interference-cancellation and impedance-matching characteristics. Generally, helical carbon nanotubes/doped barium ferrite wave-absorbing coatings are promising candidates for applications in Ku-band microwave absorption.

On radar cross section reduction effect by filamentary discharge in a dielectric barrier discharge

On radar cross section reduction effect by filamentary discharge in a dielectric barrier discharge

Multi-heterointerface integration in nitrogen-doped Ti3C2Tx@Fe3O4 nanocomposites for superior microwave absorption

Engineering a lightweight and thin microwave absorber through the design of multiple heterogeneous interfaces represents a significant challenge. Here, we synthesized a nitrogen (N)-doped Ti3C2Tx@Fe3O4 (N–Ti3C2Tx@Fe3O4) nanocomposite with a sandwich-like structure through a solvothermal approach using hydrazine hydrate as the N donor. The numerous Ti3C2Tx electron transfer pathways of Ti3C2Tx enable the realization of a hierarchical conduction network within N–Ti3C2Tx@Fe3O4. The introduction of defects through N doping and the integration of Fe3O4 with Ti3C2Tx are pivotal for enhancing the dipole polarization. The heterogeneous interfaces in N–Ti3C2Tx@Fe3O4, coupled with Fe3O4 components, substantially boost the electromagnetic wave (EMW) absorption performance of the composite. An optimal N integration and the loading of Fe3O4 in Ti3C2Tx result in an improved impedance matching of N–Ti3C2Tx@Fe3O4. The synergistic effect of the improved impedance matching and the strong EMW attenuation capability endow N–Ti3C2Tx@Fe3O4 with enhanced microwave absorption (MA) properties. Specifically, at a thickness of 1.04 mm, the composite exhibits the effective absorption bandwidth (3.92 GHz; 14.08–18.00 GHz), surpassing that of Ti3C2Tx. At a thickness of 0.98 mm, it exhibits a maximum reflection loss of −40.28 dB at 17.25 GHz, which substantially exceeds that of Ti3C2Tx. Furthermore, it shows a maximum Radar Cross Section reduction of 21.32 dB cm2. A cotton fabric was coated with N–Ti3C2Tx@Fe3O4, and it was found to exhibit enhanced heat conduction and dissipation, at rates 3.83 and 4.64 times greater than those of uncoated cotton, respectively. These results highlight the considerable potential of N–Ti3C2Tx@Fe3O4 nanocomposites for use in far-field applications. It is envisaged that the exceptional MA and thermal management properties of N–Ti3C2Tx@Fe3O4 nanocomposites will provide a novel avenue for crafting lightweight and thin EMW absorbing materials.

Frequency selective rasorber based on cross bend resonators for wideband transmission and absorption

The wideband absorption and transmission of frequency-selective rasorber (FSR) remain a persistent challenge in the application of radar devices. In this article, a novel high performance wideband FSR design based on cross bend resonators was proposed. The FSR consists of an upper absorption lossy layer, which offers broad absorption and transmission bands, and a lower bandpass frequency-selective surface that enables a highly selective transmission of incident electromagnetic wave. Full wave simulation results showed that this novel design achieves an absorption bandwidth of 83.7% with more than 90% absorptivity in the frequency range of 5.2–12.7 GHz. Furthermore, the passband’s fractional bandwidth for the insertion loss (IL) less than −3 dB is 33.9%, ranging from 14.9 to 21 GHz, with the minimum IL recorded at 0.69 dB at 17.7 GHz. To further verify the proposed method, a prototype FSR with 10 × 10 units of 120 mm × 120 mm was fabricated and the performance of the FSR was tested. The experiment results were in good agreement with the simulated results, and it showed a significant monostatic radar cross-section reduction in the frequency range of 5.3 GHz to 18.3 GHz compared with a metallic plane of the same size.

An absorptive coding metasurface for ultra-wideband radar cross-section reduction

In this paper, an absorptive coding metasurface (ACM) is proposed for ultra-wideband radar cross section (RCS) reduction, the design process is presented in detail, in which a lossy polarization conversion metasurface (PCM) is proposed at first. The lossy PCM is an anisotropic resistive structure with both polarization conversion and absorption performances, so that its co-polarization reflection coefficients under u- and v-polarized incidences can be kept at less than − 10 dB in magnitude in the frequency range from 7.5 to 45.2 GHz. Though the magnitude of the cross-polarization reflection coefficient cannot be very small only due to the absorption, its phase will be changed by nearly 180° when the unit-cell structure of the lossy PCM is rotated by 90°. Thus, the lossy PCM can be used as one of the two types of lossy coding elements for an ACM when its unit-cell structure is rotated by 90° or not. Based on the lossy PCM, an ACM is proposed. The simulation and experimental results show that the ACM has an excellent RCS reduction performance under arbitrary polarized incidence, it can achieve effective RCS reduction under normal incidence in the ultra-wide frequency band from 7.4 to 45.5 GHz with a ratio bandwidth (fH/fL) of 6.15:1; moreover, an ultra-wideband RCS reduction can still be achieved when the incident angle is increased to 45°, which indicates that the ACM has good stealth performance under the detection of various radars working in X, Ku, K and Ka bands, it is very practical.

Wideband radar cross-section reduction by a double-layer-plasma-based metasurface

Reduction of the radar cross-section (RCS) is the key to stealth technology. To improve the RCS reduction effect of the designed checkerboard metasurface and overcome the limitation of thin-layer plasma in RCS reduction technology, a double-layer-plasma-based metasurface—composed of a checkerboard metasurface, a double-layer plasma and an air gap between them—was investigated. Based on the principle of backscattering cancellation, we designed a checkerboard metasurface composed of different artificial magnetic conductor units; the checkerboard metasurface can reflect vertically incident electromagnetic (EM) waves in four different inclined directions to reduce the RCS. Full-wave simulations confirm that the double-layer-plasma-based metasurface can improve the RCS reduction effect of the metasurface and the plasma. This is because in a band lower than the working band of the metasurface, the RCS reduction effect is mainly improved by the plasma layer. In the working band of the metasurface, impedance mismatching between the air gap and first plasma layer and between first and second plasma layers cause the scattered waves to become more dispersed, so the propagation path of the EM waves in the plasma becomes longer, increasing the absorption of the EM waves by the plasma. Thus, the RCS reduction effect is enhanced. The double-layer-plasma-based metasurface can be insensitive to the polarization of the incoming EM waves, and can also maintain a satisfactory RCS reduction band when the incident waves are oblique.

Terahertz VO2-Based Dynamic Coding Metasurface for Dual-Polarized, Dual-Band, and Wide-Angle RCS Reduction.

With the rapid development of terahertz radar technology, the electromagnetic device for terahertz radar cross-section (RCS) reduction is worth investigating. However, the existing research concentrates on the RCS reduction metasurface with fixed performance working in the microwave band. This paper proposes a terahertz dynamic coding metasurface integrated with vanadium dioxide (VO2) for dual-polarized, dual-band, and wide-angle RCS reduction. The simulation result indicates that by switching the state of the VO2 between insulator and metal, the metasurface can realize the effective RCS reduction at 0.18 THz to 0.24 THz and 0.21 THz to 0.39 THz under the left-handed and right-handed circularly polarized incident waves. When the polar and azimuth angles of the incident wave vary from 0° to 40° and 0° to 360° respectively, this metasurface can maintain a 10 dB RCS reduction. This work has potential value in the terahertz stealth field.

RCS-reduced patch antenna with wide frequency tuning range based on absorbing metasurface

A frequency-tunable patch antenna with reduced radar cross section (RCS) based on absorbing metamaterial is proposed. By controlling the external voltage of the varactor diodes, the working frequency of the patch can be adjusted. Through an investigation of the composite structure of the patch and absorbing metamaterial, RCS reduction is achieved over the entire wide tunable frequency range of the antenna. Measured results illustrate that the proposed patch antenna can dynamically operate in the range from 2.28 to 3.6 GHz with a gain variation of 7.1–8.7 dBi. Meanwhile, the RCS can be reduced by at least 7 dB and up to 20 dB in a fractional bandwidth of 44.9% of the antenna under a normal incidence. In comparison to conventional RCS-reduced antennas, the proposed one features a broader frequency tuning range and has potential value in wideband radar systems under complex electromagnetic interference environments.