Bistatic Radar Cross Section Reduction Research Articles

A Wideband Polarization-Insensitive Bistatic Radar Cross-Section Reduction Design Based on Hybrid Spherical Phase-Chessboard Metasurfaces

A wideband polarization-insensitive bistatic radar cross-section (RCS) reduction design under linear and circular polarization incidence is proposed based on spherical-chessboard metasurfaces. A new metasurface element with wideband characteristics was designed, including a double split-ring structure, single-layer media, and metal board. In the proposed RCS-reduction design, the Pancharatnam–Berry (P-B) phase theory is applied with the designed metasurface element to realize phase distribution mimicking the low-scattering sphere, and thus realizing RCS reduction. In addition, the chessboard configuration is combined with spherical phase distribution to further improve the performance of monostatic and bistatic RCS reduction. Finally, the proposed RCS reduction design can not only realize wideband RCS reduction but also exhibit polarization-insensitive characteristics. It realized 10 dB monostatic and bistatic RCS reduction in a frequency band ranging from 8.5 to 21 GHz (84.8% relative bandwidth) under linear polarization (LP) and circular polarization (CP) incidence. The straightforward and efficient design method of the hybrid spherical chessboard can effectively avoid the complex and time-consuming optimization process in RCS-reduction design.

Rapid design of hybrid mechanism metasurface with random coding for terahertz dual-band RCS reduction.

In this paper, a hybrid mechanism metasurface (HMM) employing 1-bit random coding is proposed to achieve polarization-insensitive and dual-wideband monostatic/bistatic radar cross section (RCS) reduction under a wide range of incident angles. The anisotropic unit cell is designed by the combination of the multi-objective particle swarm optimization (MOPSO) algorithm and Python-CST joint simulation, which facilitates the rapid acquisition of the desired unit cell with excellent dual-band absorption conversion capability. The unit cell and its mirrored version are used to represent the units "0" and "1", respectively. In addition, the array distribution with random coding of the units "0" and "1" is optimized under different incident angles, polarizations and frequencies, which enables better diffusion-like scattering. Simulation results demonstrate that the proposed coding HMM can effectively reduce the monostatic/bistatic RCS by over 10 dB within the dual-band frequency ranges of 2.07-3.02 THz and 3.78-4.71 THz. Furthermore, the specular and bistatic RCS reduction performances remain stable at oblique incident angles up to 45° for both TE and TM polarizations.

Bistatic RCS reduction caused by radionuclide layer for spherical object

Radar cross section (RCS) is one of the important research topics in recent decades and the use of Radionuclide Layer (RNL) is one of the methods for radar cross section reduction. In this paper, the RNL of Americium-241 is considered on the surface of the spherical body with a radius of 5 cm. The range of alpha particles emitted from RNL and the electron density of air at standard temperature and pressure (STP) conditions have been extracted by the SRIM and Geant4 computational codes. Finally using CST software and RF module, the radar cross-section of the conductive spherical body, without and with plasma induced by RNL are obtained in different activities. The radar cross-section reduction of about for the spherical body in the frequency range of 2 to 12 GHz is observed for the activity of .

Reduction of Radar Cross Section by Adopting Symmetrical Coding Metamaterial Design for Terahertz Frequency Applications.

This work focused on the novel and compact 1-bit symmetrical coding-based metamaterial for radar cross section reduction in terahertz frequencies. A couple of coding particles were constructed to impersonate the elements '0' and '1', which have phase differences of 180°. All the analytical simulations were performed by adopting Computer Simulation Technology Microwave Studio 2019 software. Moreover, the transmission coefficient of the element '1' was examined as well by adopting similar software and validated by a high-frequency structure simulator. Meanwhile, the frequency range from 0 to 3 THz was set in this work. The phase response properties of each element were examined before constructing various coding metamaterial designs in smaller and bigger lattices. The proposed unit cells exhibit phase responses at 0.84 THz and 1.54 THz, respectively. Meanwhile, the analysis of various coding sequences was carried out and they manifest interesting monostatic and bistatic radar cross section (RCS) reduction performances. The Coding Sequence 2 manifests the best bistatic RCS reduction values in smaller lattices, which reduced from -69.8 dBm2 to -65.5 dBm2 at 1.54 THz. On the other hand, the monostatic RCS values for all lattices have an inclined line until they reach a frequency of 1.0 THz from more than -60 dBm2. However, from the 1.0 THz to 3.0 THz frequency range the RCS values have moderate discrepancies among the horizontal line for each lattice. Furthermore, two parametric studies were performed to examine the RCS reduction behaviour, for instance, multi-layer structures and as well tilt positioning of the proposed coding metamaterial. Overall it indicates that the integration of coding-based metamaterial successfully reduced the RCS values.

An Optically Transparent Hybrid Mechanism Metasurface for Wideband, Wide-Angle and Omnidirectional Scattering Suppression

Metasurface provides an efficient method to regulate wave propagation in multiphysics fields ranging from light waves, electromagnetic (EM) waves, and acoustic waves. Considering the versatile demands in practical scenarios, the essential challenge is to design the metasurface with spectral compatibility to satisfy the various applications. Here, we proposed an optically transparent hybrid mechanism metasurface (HMM) incorporating absorption, polarization conversion, and phase cancellation mechanisms for wideband, wide-angle, and omnidirectional scattering suppression performance. The unit cell integrates absorption and polarization conversion capabilities by etching the indium tin oxide (ITO) film into the specific structure, exhibiting wideband ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$7.44-31.31$ </tex-math></inline-formula> GHz), wide-angle ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\!&lt; 45^{\circ }$ </tex-math></inline-formula> ), high-efficiency ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\!\ge 90$ </tex-math></inline-formula> %), and omnidirectional co-polarized scattering suppression performance. Moreover, the phase cancellation mechanism is implemented by distributing the unit cell and its mirror structure in the chessboard configuration, which provides cross-polarized reflection reduction capability for the HMM. Therefore, the HMM achieves a significant total radar cross section (RCS) reduction by integrating multiple scattering suppression mechanisms. Eventually, the simulated and measured results indicate that the proposed HMM can realize more than 10 dB total monostatic and bistatic RCS reduction within 7.49-32.23 and 7.46-30.55 GHz, respectively. In addition, good specular and omnidirectional RCS reduction capabilities are also obtained. Furthermore, the HMM also presents good optical transparency, which is attributed to the high transmittance of the polyethylene terephthalate (PET) substrates and the ITO films. The proposed strategy has potential application in the multifunctional stealth design of stealth platforms.

Frequency-Selective Rasorber Based on High-Q Minkowski Fractal-Shaped Resonator for Realizing a Low Radar Cross-Section Radiating System

In this article, a novel design of compact frequency-selective rasorber exhibiting absorption–transmission–absorption characteristics and having high passband selectivity has been proposed. A square-loop resonator with mounted lossy elements serves as the elemental broadband absorber from 4 to 12 GHz. The transmission frequency at 8.4 GHz is realized by printing a Minkowski fractal-shaped resonator with a high-Q factor on the resistive layer, which provides a transmission pole at the frequency corresponding to the passband of a double-cross-slot-shaped bandpass layer. The functioning of the proposed frequency-selective rasorbers (FSR) is explained by a corresponding equivalent circuit model. The proposed FSR exhibits higher selectivity at the passband, thus making it a suitable candidate for shielding the narrowband radiating system. Measurements performed on the fabricated prototype of a 17 × 17 unit cell array provides experimental validation. Further, a low radar cross-section antenna is realized by integrating a patch antenna with the proposed FSR, which achieves an average out-of-band monostatic radar cross-section (RCS) reduction of 11.92 and 5.04 dB in the lower (4–7.5 GHz) and upper (9.2–10.8 GHz) absorption bands, respectively, while maintaining the other antenna parameters. Furthermore, the bistatic total RCS reduction of 77% and 60% are achieved in the lower and upper frequency bands, respectively.

Design of a 2-Bit wide-angle coding metasurface for bistatic RCS reduction

A 2-bit wide-angle coding metasurface is proposed to decrease the bistatic radar cross section (RCS) in this study. Each meta-atom of the designed coding metasurface is composed of a wide-beamwidth microstrip antenna whose feeding port is loaded with an open stub. There are globally four phase-coding states, namely, “00,” “01,” “10,” and “11,” which are achieved in a wide-angle range through an elaborate design of the lengths of the open stubs. Simulation results indicate that, for each meta-atom, the reflective amplitude is above −1 dB, and the reflective phase difference between two adjacent coding states is limited in the range of 90° ± 25° at 8 GHz at incident angles, 0°, 20°, 40°, and 60°. In addition, the generalized Rudin–Shapiro (RS) polynomial is applied to design the coding sequence of the metasurface array to reduce bistatic RCS. A 16 × 16 metasurface array is simulated, manufactured, and measured to validate the bistatic RCS reduction. The simulated results perfectly agree with the experimental results when the incidence angle of the 8 GHz plane wave is within 60°, which shows that the coding metasurface is practical and valid.

Wideband Radar Cross Section Reduction of Microstrip Patch Antenna using Polarization Converter Metasurface

Antenna is the key device of communication on stealth platform. It is the greatest contributor to the overall RCS. So, it is desired to reduce the radar signature of the antenna. In this paper, a novel antenna is designed using polarization converter metasurface. The polarization converter metasurface converts the polarization of the incident wave into its orthogonal component. This PCM structure is loaded around patch antenna to reduce the RCS of the antenna over wide frequency range. With this novel design, the overall RCS reduction bandwidth of 140.57% is obtained for the frequency range of 3.49 GHz – 20 GHz. In addition to this, the 10 dB RCS reduction bandwidth is obtained for the frequency ranges of 8.84 GHz – 10.42 GHz (16.41%) and 16.99 GHz – 17.81 GHz (4.71%). The design shows excellent angular stability for both TE and TM polarization. Discernible Bistatic Radar Cross Section reduction is obtained over a wide frequency range. Simulation and experimental results show that there is no degradation in antenna radiation pattern and other parameters. So, with this novel design the problem of obtaining wideband RCS reduction of a microstrip patch antenna is addressed without degradation in radiation pattern along with excellent angular stability for both the polarization modes.

A compact transparent polarization-insensitive metasurface with broadband monostatic and bistatic radar cross-section reduction of millimeter-waves

This paper proposes an optimized optically transparent metasurface (OTM) which achieves broadband monostatic and bistatic radar cross-section (RCS) reduction with polarization and angle insensitivity. Through employing (a) theoretical formulation involving both monostatic and bistatic RCS and (b) unit cell placement optimization using the particle swarm optimization approach, we achieve monostatic and bistatic RCS reduction over a broad bandwidth with a single-layer, ultra-thin metasurface featuring only two types of unit cells. The proposed metasurface has high optical transparency and electrically small size compared to counterparts with similar performances. Simulation and experimental measurement show that the metasurface achieves more than 10 dB monostatic and bistatic RCS reduction from 18 to 34 GHz, which completely covers the 5G mm-wave spectrum. The proposed optically transparent metasurface can find use in many areas, including mm-wave applications, invisible glass technology, and vehicle windshield systems.

Ultrabroadband RCS Reduction Design by Exploiting Characteristic Complementary Polarization Conversion Metasurfaces

A new design method for ultrabroadband radar cross section (RCS) reduction by exploiting characteristic complementary polarization conversion metasurfaces (PCMs) is proposed and validated. The proposed method lifts the conventional bandwidth limitation enforced by the performance of a single PCM and expands the RCS reduction bandwidth. A systematic strategy for ultrabroadband RCS reduction design is developed and an effective reflection coefficient amplitude of the composite surface ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\Gamma _{ {eff}}$ </tex-math></inline-formula> ) is derived as a new RCS reduction indicator. Based on this indicator, complete polarization conversion (CPC) frequency points of PCM are identified as important characteristics, and PCM pairs with interleaved CPC points, termed as initial PCM (I-PCM) and complementary PCM (C-PCM), are designed to compensate each other for ultrabroadband RCS reduction. A scaling-and-tuning two-step method for designing the C-PCM of a specific I-PCM is developed and validated. To further improve RCS reduction performance, taking the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${\Gamma _{ {eff}}}$ </tex-math></inline-formula> as an indicator, the particle swarm optimization (PSO) algorithm is used to select the optimal I-PCMs, C-PCMs, and their area ratios. Finally, an ultrabroadband RCS reduction surface is designed, fabricated, measured, and validated. It realizes 10-dB monostatic RCS reduction ranging from 7.6 to 26.2 GHz (110.7% relative bandwidth) which exceeds the polarization conversion bandwidth of each individual PCM. Besides, good polarization insensitivity and bistatic RCS reduction performance are also obtained. The proposed method provides a new route for designing broadband RCS reduction surface based on PCMs with unsatisfactory characteristics and greatly alleviates the performance requirement for PCMs.

Broadband polarization insensitive wide angular stable dual‐split square ring circuit analog absorber for radar cross section and electromagnetic interference shielding applications

This work presents a simple broadband polarization-insensitive circuit analog absorber (CAA) with wide angular stability. It comprises of dual-cut square loop resonator loaded with eight lumped resistors as top patch and an inductive grid. The normal incidence reveals a 90% absorption bandwidth of 20.51 GHz (110% fractional bandwidth) covering the entire X to K-band with a minimum flat absorption rate of 92.82%. Equivalent circuit analysis is carried out, and responses are validated with full-wave simulations. The proposed prototype is insensitive to different polarization angles under normal incidence and stable with 45° in transverse electric (TE) and transverse magnetic (TM) incidences. The design's novelty lies in using two resistors on each side of the square ring, which improves the absorptivity performance. The inductive grid enhances TM mode's angular stability. The proposed absorber is fabricated, and the measured results are in good agreement. In-band bistatic radar cross section reduction of 12.97 dBsm is obtained with the absorber using an X-band antenna. The temperature profile of the prototype is illustrated using near-in-lock infrared thermography, and 2.1°F of temperature rise is noticed in the absorption band. The proposed structure possesses a low profile, broad bandwidth, polarization insensitivity, and wide angular stability to the best of the author's knowledge.

Design of Broadband Wide-Angle Scatterer Surface Using Artificial Dielectric Layers

In this letter, the reflection elements based on artificial dielectric layers (ADLs) are proposed for broadband wide-angle bistatic radar cross section (RCS) reduction. ADLs are introduced to improve the interference cancellation bandwidth of the reflection elements, and avoid the dilemma of mixing multiple dielectric mediums. The reflection elements achieve an approximate 180° phase difference over the frequency range of 4.8–17.5 GHz (113.9%) under normal incidence, and the bandwidth under TE 40° incidence and TM 55° is 113.9% and 100%, respectively. To validate this design, a coding scatterer surface is simulated and fabricated. Measured results show that the proposed coding scatterer surface achieves a 10 dB bistatic RCS reduction from 5 to 17.5 GHz under normal incidence for both polarizations. Bistatic RCS reduction under oblique incidence is analyzed and presented as well.

Design, development and characterization of wide incidence angle and polarization insensitive metasurface absorber based on resistive-ink for X and Ku band RCS reduction

This article deals with the design, development and characterization of a broadband, wide incidence angle and polarization-insensitive metasurface, which consists of periodic resistive-ink pattern printed on top of FR-4 dielectric substrate as a RADAR absorber. Geometrical dimensions of the proposed unit cell have been optimized numerically using CST-Microwave Studio to achieve 99% absorptivity for X and Ku frequency spectrum (8–18 GHz) under the normal angle of incidence and to achieve almost 90% absorptivity under the oblique angle of incidence up to 50° within X-Band to Ku-Band spectrum. Furthermore, it is reported that by having fourfold rotation symmetry, the designed structure is insensitive to the polarization of the incident wave. An equivalent circuit analytical modeling has also been performed to understand and verify numerical findings that are nearly in agreement. The designed absorber is fabricated and characterized using ABmm VNA and free space measurement method, for both normal and oblique angle of incidence, and it is found that measured characteristics are in agreement with numerical-analytical findings. Furthermore, the monostatic and bistatic Radar Cross Section reduction capability of the designed absorbing structure for both planar and curved surface (cylinder) is studied extensively to assess its potential application in X-Band to Ku-Band Spectrum.

Compact, broadband, wide angular stable circuit analog absorber at sub‐6 GHz for radar cross section reduction

AbstractThis work presents a compact broadband wide angular stable polarization‐insensitive circuit analog absorber at sub 6 GHz. It shows almost 95% absorption from 2.26 to 5.76 GHz over the entire operating range. A transmission line equivalent circuit is modeled, and the response is validated. The design is obliquely stable up to 45° for both transverse electric and transverse magnetic incidences. The analysis of surface current distributions at two resonant frequencies confirming magnetic resonances' role in near‐unity absorption. It is compact with a periodicity of 0.1 λL and thickness of 0.08 λL. Finally, bistatic radar cross section reduction of the proposed absorber attached with an antenna is measured.

Magnetoelectric Dipole-Fed Fabry–Perot Antenna With Wideband RCS Reduction Based on Multilayer Metasurface

This letter presents a novel superstrate composed of multilayer metasurface (MM), which is characterized by wideband monostatic and bistatic radar cross section reduction (RCSR) for Fabry-Perot (FP) antenna with magnetoelectric (ME) dipole-fed. The proposed MM consists of four layers, the top three layers form a polarization-selective absorber (PSA), and the bottom layer is a polarization conversion metasurface (PCM). The copolarized incident waves are absorbed by the PSA, while the cross-polarized waves pass through with a low insertion loss. Then, it is reflected by the PCM with 90° polarization rotation and absorbed by the upper PSA. Additionally, the bottom layer of the PCM unit is an improved pattern instead of the ground plane. It is capable of polarization conversion and partial reflection. Therefore, the MM and ME dipole are respectively utilized as the partially reflecting surface (PRS) and the primary source to construct an FP antenna. Simulation and measurement results show that the bandwidth of monostatic RCSR is more than 80%. The FP antenna also achieves a high aperture efficiency of 51%, which is due to the benefit from the widebeam characteristics of the ME dipole.

Wideband and wide-angle radar cross section reduction using a hybrid mechanism metasurface.

In this paper, a hybrid mechanism metasurface (HMM) that incorporates absorption, polarization conversion and phase cancellation mechanisms is proposed for wideband and wide-angle radar cross section (RCS) reduction. The polarization conversion absorber (PCA) is proposed by embedding the lumped resistors into the polarization conversion structure, which integrates the absorption and polarization conversion mechanisms. Then, the phase cancellation mechanism is employed to redirect the scattering energy to the non-incident directions through the chessboard configuration, which exploits the opposite phase between the PCA and its mirror structure. Unlike previous HMMs that depended on nested or cascaded structures, the proposed strategy integrates the absorption and polarization conversion mechanisms in the same structure, and the two mechanisms are complementary to each other. Through the integration of multiple mechanisms, the HMM can achieve more than a 10 dB monostatic and bistatic RCS reduction in 8.7-32.5 GHz and 8.6-31.2 GHz, respectively. Furthermore, the specular and bistatic RCS reduction performances under oblique incident waves are also studied, and the stable scattering suppression performances are determined. The proposed hybrid mechanism strategy exhibits significant scattering suppression capability through the incorporation of multiple mechanisms, which have potential applications in the multifunctional metasurface.

Hybrid frequency selective surface phase cancelation structure based broadband switchable radar cross section reduction

In this paper, a switchable radar cross section (RCS) reduction between the two broadbands' (1-7 GHz and 4-10 GHz) has been achieved by just considering the integration of hybrid frequency selective surface (FSS) based phase cancelation structure (PCS) with a modified ground square patch antenna operating at 2.4 GHz. The full metallic ground plane of the conventional microstrip antenna (MSA) is replaced by a 2 × 2 array of band-stop FSS having the same frequency as that of the MSA. This ground plane modification helps to increase the maximum out-of-band RCS reduction from 16.4 dB to 20 dB. The ground modified MSA without any PCS exhibits both in-band and out-of-band maximum RCS reduction of 20 dB over a wideband (1-7 GHz). A new approach is adopted to form the PCS. It is formed by placing two non-overlapping hybrid FSSs at different heights above the MSA. The MSA with FSS based ground plane along with the hybrid FSS based PCS exhibits good monostatic and bistatic RCS reduction across 4 to 10 GHz without affecting the radiation characteristics of the conventional MSA. The measured results show a close resemblance to the simulated ones.

A Low Cost, Low in-Band RCS Microstrip Phased-Array Antenna With Integrated 2-bit Phase Shifter

In this article, we present a low-cost microstrip phased-array antenna, which is composed of electronically reconfigurable elements. The p-i-n diodes' integrated elements have various functions, such as tunable polarization characteristics and adjustable radiation phases. The high sidelobe level (SLL) due to the 2-bit phase shifter can be reduced by a randomly rotated (RR) array element. It is shown that the array can realize electronic beam-steering capabilities and keep -10 to -14 dB sidelobes without tapering. To verify the above theory, an eight-element linear array prototype working at 3 GHz was designed, fabricated, and tested. Numerical simulations and experimental results show that, by controlling the “ON” and “OFF” states of p-i-n diodes, the radiation beam can be controlled to steer in a circular polarization (CP) mode, wherein the scanning angle is up to ±45°. Furthermore, the principle of suppressing the vector scattering field by the opposite phasing cancellation method can achieve in-band radar cross section (RCS) reduction. Simulation results show that approximately 15 dB in-band RCS reduction can be realized for both bistatic and monostatic RCS reduction with an 8×8 array.

Ultra-Wideband RCS Reduction Based on Non-Planar Coding Diffusive Metasurface

A novel non-planar coding metasurface optimized by discrete particle swarm algorithm (DPSO) is proposed in terms of the property of wideband radar cross-section (RCS) and diffuse scattering. The design consists of two unit cells, “0” and “1”, which have a 180° ± 37° phase difference for phase interference cancellation. The 10 dB monostatic RCS reduction frequency range of the metasurface is from 6.4 to 29.6 GHz, and its bandwidth ratio is 4.62:1, under normal incidence of the two polarizations. Compared to the planar surface, the non-planar surface has a greater bandwidth with respect to the monostatic and bistatic RCS reduction. The results declare its properties of ultra-wideband, angle insensitivity, and polarization insensitivity. Finally, the theoretical analysis, simulation, and experimental results match perfectly, indicating that the metasurface can be used in the RCS reduction or other microwave applications with wider RCS reduction and diffuse scattering.

Wideband Angular Stable Absorber Based on Spoof Surface Plasmon Polariton for RCS Reduction

A wideband absorber with high angular stability based on spoof surface plasmon polariton (SSPP) is proposed in this letter. The absorber consists of a metal ground and an SSPP structure that comprises nine incurved metallic strips loading lumped resistors. It realizes wideband absorption in the range of 6.95−17.4 GHz (factional bandwidth of 85.8%) for the normal incident wave and maintains high absorptivity when the incident angle tilts to 60° and 65° for transverse electronic (TE) and transverse magnetic (TM) waves, respectively. As a reflector of a Vivaldi antenna, the proposed absorber reduces the bistatic radar cross section (RCS) effectively and does not decrease the performance of the antenna. Prototypes of the absorber and antenna are fabricated and measured. The simulated and measured results have a good agreement, which verifies the wide-angle absorption of the proposed absorber and its good work in bistatic RCS reduction.