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Achieving high electromagnetic (EM) wave transmission with excellent angular stability is crucial for communication, detection, and guidance but remains challenging, especially when integrating other functions like out-of-band radar cross-section (RCS) reduction, which often degrades transmission. In this work, we propose to solve this problem by utilizing the longitudinal design freedom of metasurface. To this end, a typical longitudinally-coupled structure is proposed as the meta-atom for designing metasurfaces, which is composed of one layer of metallic meshes and one layer of metallic patch. By leveraging the synergistic effect of the plasma oscillation of the metallic mesh and the Lorentz resonance effect of the metal patch within meta-atom, we obtain a dual-polarization angle stable EM window (0°–80°) within the operating band. On this basis, without altering the structural parameters of the meta-atom, we utilize the longitudinal dimension to encode the reflection phases of out-of-band EM waves by flipping the meta-atom structure longitudinally, which can integrate out-of-band radar cross-section (RCS) reduction function without affecting the in-band transmission performance. To demonstrate this idea, prototypes were designed, fabricated and measured. Fabricated prototypes show good agreement between measurements and simulations, validating the method. This opens new paths for multifunctional EM windows in next-gen communication and radar systems.

Diffusion‐like scattering along multiple directions based on coding metasurface (CM) is proposed for both mono‐static and bi‐static radar cross section (RCS) reduction in this work. Different from the previous CMs achieving diffusion‐like scattering only in one direction, the proposed CMs can realize diffusion‐like scattering along multiple directions via designing the phase spatial distributions of the consisted coding elements. The multiple diffusion‐like scattering CMs were designed by using the co‐polarization reflection resonators under circularly polarized wave incidence based on Pancharatnam–Berry (PB) phase. By elaborately arranging the phase spatial distribution of coding elements, two, three, and four beams of diffusion‐like scattering were realized. The bi‐static RCS reduction was improved with increasing number of the backward diffusion‐like scattering beams. The measured results agree well with the simulations, and both demonstrated the excellent performance on mono‐static and bi‐static RCS reduction. Our strategy can help realize stealth applications under bi‐static detections. Diffusion‐like scattering along multiple directions based on coding metasurface (CM) is proposed for both mono‐static and bi‐static radar cross section (RCS) reduction in this work. Different from the previous CMs achieving diffusion‐like scattering only in one direction, the proposed CMs can realize diffusion‐like scattering along multiple directions. This strategy can help realize stealth applications under bi‐static detections.

In this paper, a new coating structure is proposed for broadband radar cross section (RCS) reduction using 1‐bit metasurfaces. The designed structure consists of two types of unit cell, arranged in concentric square rings. The substrate of unit cells is different, FR4 and Ultralum‐2000 with thicknesses of 2.4 and 0.762 mm, respectively. The proposed structure shows an ultrawideband property to reduce the RCS, less than −10 dB, in the frequency range of 14–45 GHz. This range covers part of Ku‐band (14–18 GHz), K‐band (18–27 GHz), and Ka‐band (27–40 GHz) and part of millimeter‐wave band (40–45 GHz). To validate the designed work and simulation results, a prototype with the dimension of 84 × 84 mm 2 is fabricated and tested. Also, the RCS reduction is determined analytically and presented. The measured results verify well the analytical and simulation results. In short, this work includes three new points: (1) the use of two substrates with different thickness and dielectric constant to design unit cells, (2) a new arrangement of array cells in the form of concentric square rings, and (3) achieving a great bandwidth to reduce RCS.

Traditional stealth technologies all have their problems such as high cost and large thickness. To solve the problems, we used novelty checkerboard metasurface in stealth technology. Checkerboard metasurface does not have as high conversion efficiency as radiation converters, but it has many advantages such as small thickness and low cost. So it is expected to overcome the problems of traditional stealth technologies. Unlike other checkerboard metasurfaces, we improved it further by using two types of polarization converter units to be arranged in turn to form a hybrid checkerboard metasurface. Because the checkerboard metasurface composed of one type of polarization converter units can have a relatively wide radar cross-section (RCS) reduction in bandwidth when two types of polarization converter units are arranged in turn to form a hybrid checkerboard metasurface and mutual compensation of the two polarization converter units can broaden RCS reduction band further. Therefore, by designing the metasurface to be independent from the polarization, the effect of RCS reduction can be insensitive to the polarization of the incoming EM waves. The experiment and simulation results showed the value of this proposed hybrid checkerboard metasurface for RCS reduction. Mutual compensation of the units is a new attempt in the field of checkerboard metasurfaces for stealth technology and proved to be effective.

A highly efficient and multi-functional butterfly polarization conversion metasurface is proposed for the Ku-Ka frequency range, designed to reduce the radar cross-section. The suggested converter enables dual frequency bands linear-to-cross (LX) and linear-to-circular (LC) polarization transformations. The efficiency of cross-polarization conversion exceeds 90% over the frequency ranges of 14.57–16.30 GHz and 25.70–37.03 GHz, with relative bandwidths of 11% and 36%, respectively. Reflections of left-hand (LHCP) and right-hand circularly polarized (RHCP) waves are realized within the frequency ranges of 17.78–25.31 GHz and 37.38–37.73 GHz, with relative bandwidths of 35% and 0.9%. The oblique incidence significantly affects the metasurface conversion performance, and the proposed model manifests angular robustness up to 60°. Additionally, the butterfly metasurfaces are deployed in a triangular chessboard configuration to achieve radar cross section (RCS) reduction spanning the frequency bands of 14–15.17 GHz, 24.60–35.20 GHz, and 36.30–38 GHz. Drawing from simulation results and test-based validation data, the proposed converter holds promising applications in wireless communication, antenna engineering, and radar stealth.

This research reports the design of a polarization converter based non-uniform metasurface in which the unit cells have been arranged in such a manner that both co and cross polarized reflections are minimized which results in mitigation of radar cross-section (RCS). The propounded metasurface has been integrated with an antipodal Vivaldi antenna for facilitating it’s wideband RCS reduction from 14 to 36 GHz. Maximum monostatic RCS reduction across 84.6% frequency bandwidth is 30 dB for both x-polarized and y-polarized incident waves. Bistatic angular view of the antenna with metasurface is 70 ⁰ at 27 GHz. A high bistatic angular view ensures that the metasurface integrated antenna exhibits similar electromagnetic performance like reflection and radiation characteristics even when the incident or observation angle changes significantly. The specific property conveyed is angular stability, which refers to the ability of the structure to maintain its resonant frequency and electromagnetic characteristics (reflection/transmission/gain) when the incident angle varies. The antenna’s radiation and scattering characteristics remain nearly constant even when the direction of incoming or outgoing waves changes since the metasurface comprises periodic unit cells with sub-wavelength dimensions, which exhibit high angular stability. An equivalent circuit model has been proposed for the polarization converter-based unit cell which exhibits negative permittivity and zero refractive index. The radiation characteristics of the antenna are not affected adversely by the incorporation of the polarization converter based metasurface. Peak gain of the antenna is 9.3 dBi. Measured results of the fabricated non-uniform metasurface and Vivaldi antenna closely match the simulations.

In this study, we introduce a strategy for constructing an absorptive metasurface, which integrates the absorption and phase cancellation mechanisms. Through topological optimization and the synthesis of a checkerboard metasurface array, we achieve a significant reduction in ultra-wideband RCS. A prototype of the suggested design is produced and tested to confirm the effectiveness of the absorptive coding metasurface. When compared to a metallic plate of the same dimensions, a notable decrease in reflection is observed within the 4.0–12.0 GHz range. The RCS reduction exceeds 15 dB within the same frequency range (the fractional bandwidth is 100%). The proposed methods of phase and amplitude control, along with topological optimization, prove to be efficient strategies for wideband RCS reduction applications.

This paper presents a dual-mechanism method to design a single-layer absorptive metasurface with wideband 20 dB RCS reduction by simultaneously combining the absorption and phase cancellation mechanisms. The metasurface comprises two kinds of absorbing unit cells with 10 dB absorption performance but different reflection phases. The impedance condition for 20 dB RCS reduction is theoretically analyzed considering both the absorption and the phase cancellation based on the two unit cells, and the relationship between the surface impedance and the reflection phase/amplitude is revealed. According to these analyses, two unit cells with absorption performance and different reflection phases are designed and utilized to realize the absorptive metasurface. Numerical and experimental results show that the single-layer absorptive metasurface features wideband 20 dB RCS within 11.5–16 GHz with a thickness of only 3 mm.

A class of linear polarization conversion coding metasurfaces (MSs) based on a metal cut-wire structure is proposed, which can be applied to the reduction properties of radar cross section (RCS). We firstly present a hypothesis based on the principle of planar array theory, and then verify the RCS reduction characteristics using linear polarization conversion coding MSs by simulations and experiments. The simulated results show that in the frequency range of 6–14 GHz, the linear polarization conversion ratio reaches a maximum value of 90%, which is in good agreement with the theoretical predictions. For normal incident x- and y-polarized waves, RCS reduction of designed coding MSs 01/01 and 01/10 is essentially more than 10 dB in the above-mentioned frequency range. We prepare and measure the 01/10 coding MS sample, and find that the experimental results in terms of reflectance and RCS reduction are in good agreement with the simulated ones under normal incidence. In addition, under oblique incidence, RCS reduction is suppressed as the angle of incidence increases, but still exhibits RCS reduction effects in a certain frequency range. The designed MS is expected to have valuable potential in applications for stealth field technology.