Radar Cross Section Reduction Research Articles

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

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.

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.

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.

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

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.

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.

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.

Ultra-wideband radar cross section reduction achieved by an absorptive coding metasurface

An absorptive coding metasurface (ACM) is proposed to achieve radar cross section (RCS) reduction in this paper. In the design progress of the ACM, two different lossy coding elements are proposed at first, which can both be regarded as a composite composed of a two-layer resistive frequency selective surface (RFSS) and a polarization conversion metasurface (PCM). The two-layer RFSS has a certain wave-absorbing property due to ohmic loss. In addition, the PCM can achieve ultra-wideband linear polarization conversion, and the polarization-converted reflected waves in the two coding elements under the same incidence will differ by nearly 180° in phase because the sub-unit-cell structures in them are perpendicular to each other. Thus, based on the two lossy coding elements, the ACM is proposed, which can achieve ultra-wideband RCS reduction due to absorption and phase cancelation. Numerical simulations demonstrate that the RCS of the ACM under normal incidence can be reduced more than 10 dB in the ultra-wide frequency band from 6.9 to 41.2 GHz with a relative bandwidth of 142.6%. Moreover, it has the advantages of polarization-insensitivity and wide incident angle. Finally, one effective experimental verification is carried out, and a reasonable agreement is observed between the simulation and experimental results.

Multi-function digital THz-metasurfaces based on phase change materials

An effective and digitally tunable reflective multi-function metasurface in the THz band is proposed. The introduced planar structure consists of an array of a well-designed double-split SRR (DSSRR) utilizing phase-change materials (PCMs) in the gap regions, leading to the controllable function of the metasurface due to the tuning of the crystallization level of PCMs. According to Pancharatnam-Berry's principle, this effect creates different electromagnetic responses only by employing two types of unit cells (bit-0 and bit-1) based on the proper addressing of the PCMs in the structure. It is reported that by digitally changing the coding sequence of the metasurface, it is individually capable of performing different functions such as polarization rotation, beam steering, and RCS reduction. The computational results have been verified by appropriate analytical equivalent electric-circuit modeling and the theory of antenna-arrays. The studied planar-structure with its tunable and coding properties might be suggested for advanced applications in THz sensing, communications, and imaging systems.

Noninvasive inset-integrated meta-atom for achieving single-layer metasurface simultaneously with coded microwave reflectivity and digitalized infrared emissivity

Abstract With the rapid improvement of equipment integration technology, multi-spectrum detectors are integrated into compact volumes and widely used for object detection. Confront with this challenge, it is essential to propose a strategy to design a single-layer metasurface with multi-spectrum responses in microwave and infrared ranges. In this work, we proposed a method of designing meta-atoms, which is capable of achieving functional electromagnetic response at microwave and infrared individually. As a demonstration, a metasurface with four different occupation ratios and coding permutation features is designed, fabricated, and tested. In the microwave band, the pixel meta-atom is designed to realize highly efficient cross-polarization conversion between 5.0 and 10.0 GHz, which shows the metasurface can behave as ultra-low Radar Cross Section (RCS) reflectors in the working band; In the infrared band, different occupation ratio of meta-atoms are designed to realize the infrared emissivity from 0.60 to 0.80 in 3–14 μm, which can be used to exhibit digital infrared camouflage pattern. This work promotes the ability to use single-layer design to achieve digital infrared camouflage and microwave RCS reduction simultaneously. The one-layer design is simple in geometry, simplified in process, low cost in economy, and large scale in fabrication, which can promote practical use in compatible microwave stealth and infrared camouflage.

Ultra-thin wideband frequency tunable metamaterial absorber and its application for antenna radar cross section reduction

A metamaterial absorber (MMA) with broadband and efficient absorption performance based on ultra-thin dielectric layer is proposed. In this unique configuration, the absorption frequency of the MMA can be continuously and dynamically tuned across a wide frequency range by manipulating the reverse voltage of the central varactor diode. From both the equivalent circuit and field distribution perspectives, we analyze the mechanisms behind broadband tuning and superior absorption. Simulation and experimental results demonstrate that the absorption peak of MMA can be continuously tuned over a range of 5.16–8.16 GHz, with the absorption rate consistently exceeding 90%, and the thickness is only 0.5 mm. Integrating MMA array with a microstrip patch antenna in a suitable manner can dynamically mitigates the radar cross section (RCS) within the associated frequency range, with virtually negligible impact on the antenna’s radiation performance.

Reconfigurable water-based metamaterial with hybrid mechanism for backward-scattering reduction

A hybrid mechanism water-based metamaterial (HMWM) with polarization conversion, absorption and phase cancellation mechanisms is proposed in this paper. The absorption and polarization conversion mechanisms are integrated by combining the water layer with polarization conversion structure, and the absorption conversion rate reaches more than 90% in the dual band (4.0–4.7 GHz and 8.2–15.7 GHz). Based on the above mechanism, the phase cancellation mechanism makes use of the opposite phase between HMWM and its mirror structure for checkerboard configuration to reduce the wideband radar cross section (RCS) by 3–18 GHz, achieving wide-angle RCS reduction and polarization insensitivity. In addition, the model realizes stealth control by adjusting RCS reduction capability under different water layer conditions. The results of simulation and experiment agree well, which fully demonstrates that the HMWM has scattering suppression capability and has potential application in multifunctional metamaterial.

Magnetic media synergistic carbon fiber@Ni/NiO composites for high-efficiency electromagnetic wave absorption

Electromagnetic wave (EMW) absorbing materials have garnered significant attention for their potential applications in information security and military stealth fields. However, the development of highly efficient EMW absorbing materials possessing characteristics such as being “thin, lightweight, broadband and strong” remains a considerable challenge. Addressing this challenge involves the construction of low-dimensional composite material systems, which proves to be an effective approach. In this study, we developed a simple and innovative sol–gel strategy to fabricate carbon fiber (CF)@Ni/NiO composites. The results demonstrate that the incorporation of Ni/NiO particles into CF materials substantially enhances the ferromagnetic properties of CF@Ni/NiO composites. An optimum reflection loss (RL) of CF@Ni/NiO-3 is −55.58 dB at 15.4 GHz with a corresponding thickness of merely 1.7 mm. An effective absorption bandwidth (EAB) reaches a maximum of 6.0 GHz at a thickness of 1.8 mm. Meanwhile, the radar cross section (RCS) reduction value at 6 GHz reaches 29.92 dB m2. The uniform distribution of Ni/NiO nanoparticles not only establishes a magnetic coupling network but also creates abundant heterogeneous interfaces with CF, thereby enhancing interfacial polarization. The successful fabrication of CF@Ni/NiO composites will facilitate the development and broad application of advanced EMW absorption materials in the aviation and aerospace sectors.