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Radar cross section reduction metasurfaces based on phase gradient and chessboard structure
摘要： In this article, wideband radar cross section (RCS) reduction metasurface is proposed. The unit of the metasurface is consisted of a noncentral symmetry hexagon patch with 2 semi-circular slots at the symmetric corners. As a result, the unit has an anisotropic response for x- and y-polarized wave. The reflection phase is varied with the radius of slots. The range of phase variation is extended by rotation of the unit with 90°. According to the generalized Snell’s Law, 4 different phase gradient supercells with dual polarization characteristics and different gradient directions are obtained. To improve the RCS reduction, chessboard structure is used. By combining these 2 technological approaches, a wideband, polarization insensitive RCS reduction is designed, which can reflect the electromagnetic wave uniformly. Both numerical and measured results show that it enables to realize a 10 dB RCS reduction in a wideband from 8.5 to 13 GHz.
关键词： chessboard structure,metasurface,phase gradient,RCS reduction,phase variation
更新于2025-09-23 15:23:52
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Planar Phase Gradient Metasurface Antenna with Low RCS
摘要： A low radar cross section (RCS) planar antenna using phase gradient metasurface is proposed in this paper. The proposed antenna works in the X-band and is fed by a parallel plate waveguide power divider. The designed phase gradient metasurface is coplanar with the feeding structure and couples guided waves in the parallel plate waveguide power divider to radiation waves. According to the generalized reflection law, the proposed metasurface is a frequency scanning antenna and the beam direction can be steered slightly from 16.6° to 13°. The proposed antenna is linearly polarized, and however, the RCS is reduced significantly for arbitrary polarized incident waves. The antenna was simulated, fabricated, and measured. The measurement results confirm well with the simulation results.
关键词： frequency scanning,low profile,Phase gradient metasurface,RCS reduction
更新于2025-09-23 15:23:52
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The twisted solenoid RF phase gradient transmit coil for TRASE imaging
摘要： TRASE is an MRI k-space encoding method that uses radio-frequency (RF or B1) transmit phase gradient fields to achieve millimeter-level spatial resolution. Image quality is critically dependent upon the efficient generation of B1 fields with uniform magnitude and strong phase gradients. We present the design of a new family of phase gradient transmit coil based upon a solenoid twisted about a transverse axis. This design has many attractive geometric, electrical and magnetic characteristics, including the capability to spatially encode in the direction of the main static B0 field without obstructing access to the bore. Analytical, numerical simulation and experimental results are presented, including demonstration of 1-dimensional TRASE encoding without the use of PIN diode switches. Twisted solenoid coils significantly expand the capabilities of TRASE MRI.
关键词： Phase gradient,TRASE,k-space,RF coil
更新于2025-09-23 15:23:52
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Nonlinear Diffraction in Asymmetric Dielectric Metasurfaces
摘要： Metasurfaces provide new and promising mechanisms to control and manipulate light at the nanoscale. While most metasurfaces are designed to operate in the linear regime, it was recently shown that such metasurfaces may also generate nonlinear signal, by manipulating the higher order susceptibility terms. As such, metasurfaces can generate additional harmonics, without the need for light propagation, as typically occur in nonlinear crystals. While such demonstrations typically rely on the nonlinear properties of metals, we hereby report the design, fabrication and experimental characterization of a resonant dielectric metasurface made of amorphous silicon to create and manipulate second harmonic light and control its diffraction patterns. As shown in the paper, the second harmonic generation of light follows selection rules which rely on the asymmetry of the meta-atom. Given the fact that silicon crystals are centrosymmetric, the generation of second harmonic signal in amorphous silicon is intriguing. In fact, second harmonic signal is generated mostly from the surface of the meta atom. It is the use of nanostructures that increases the surface to volume ratio and enables second harmonic generation. Additionally, the meta atom is designed to exploit its spectral resonances in the principal and the second harmonic frequencies for providing electromagnetic field enhancement which assist in boosting up the generation of second harmonic signal.
关键词： Metasurfaces,Nonlinear optics,Dielectric metasurfaces,Phase gradient metasurfaces
更新于2025-09-23 15:23:52
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Noncanonical perfect vortex beams enabled via nonuniformly varying phase gradient
摘要： A method is proposed for generating noncanonical perfect vortex beams (PVBs) based on a theory deduced from the definition of topological charge. Varying the phase gradient of the light field in the region of the decomposed integral provides arbitrary control over the nonuniform phase distribution in the transverse plane. To correct the distorted beam shape, the traditional “perfect” method of controlling the global amplitude distribution is modified and used to adjust the local beam diameter and produce what are known as noncanonical scalar PVBs. Moreover, noncanonical vector PVBs with tunable azimuthal polarization can be obtained by combining two orthogonal circularly polarized scalar PVBs. The results of experiments and numerical simulations show that the structure of the inhomogeneous phase and polarization can be tuned arbitrarily.
关键词： scalar PVBs,noncanonical perfect vortex beams,vector PVBs,topological charge,phase gradient
更新于2025-09-23 15:21:01
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[IEEE 2019 Photonics & Electromagnetics Research Symposium - Fall (PIERS - Fall) - Xiamen, China (2019.12.17-2019.12.20)] 2019 Photonics & Electromagnetics Research Symposium - Fall (PIERS - Fall) - A Novel Coding Phase Gradient Metasurface for Wideband RCS Reduction
摘要： In this letter, a new design of metasurface based on coding phase gradient metasurface for wideband radar cross section (RCS) reduction is proposed. The unit cell of the metasurface is composed of a Jerusalem structure and a central circular ring. In order to reduce the burden of the computation time and to optimize design procedure, we use the genetic algorithm and nonlinear fitting method to determine the unit cell geometer. By changing and selecting the parameter of each unit, it is found that the reflection phase of the unit can achieve a stable distribution of phase gradient of the cell among the frequency range of 7.5–26 GHz. In our design, both the random coding sequences and gradient phases in the coding elements are combined to manipulate the EM waves. Four kinds of super-cells with different gradient directions are obtained according to the generalized Snell’s Law, serving as the coding element. A coding metasurface composed of 6 × 6 supercells with random arrangement is designed to improve its RCS reduction. By coding four types of linear-phase gradients in a random pattern, reflected wave can be uniformly diffused. Moreover, the manipulation of waves will be more flexible compared with other designs. The simulated results show that a 10 dB RCS reduction is realized over broadband ranging from 7.5 to 26 GHz.
关键词： nonlinear fitting,coding phase gradient,metasurface,genetic algorithm,RCS reduction
更新于2025-09-19 17:13:59
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Analysis and design of a multi-function metasurface
摘要： In this paper, based on phase gradient principle, a multi-function dual-layer reflective metasurface is proposed for linear-to-circular (LTC) polarization conversion, beam control and gain improvement. The rotation of reflected circularly polarized wave is switched by the electric field direction of incident linearly polarized waves. At the same time, the reflective circularly polarized wave emerges anomalous refraction (45.6°). The maximum gain of the reflected wave is increased by 3.6dB (70%). The measured results and simulation results are in a reasonable agreement. The presented multi-function metasurface may offer unprecedented potentials for real-time, fast polarization conversion and beam control.
关键词： switch,phase gradient,metasurface,anomalous reflection
更新于2025-09-04 15:30:14
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[IEEE 2018 International Conference on Microwave and Millimeter Wave Technology (ICMMT) - Chengdu, China (2018.5.7-2018.5.11)] 2018 International Conference on Microwave and Millimeter Wave Technology (ICMMT) - A Reconfigurable Electromagnetic Metasurface with Bifunctional Illusions
摘要： A planar dynamically bifunctional metasurface is proposed to rebuild its scattering field as a convex or a concave mirror illusion. Generalized Snell’s law and phase compensation principle are used to analyze the proposed metasurface. A novel unit cell, with controlled reflection phase, is used to design the metasurface and transform electromagnetic illusion. The illusion performance of the presented metasurface is verified with simulation results. With the advantages of reconfigurability, low profile, and easy integration, the proposed metasurface can be widely used in the fields of electromagnetic metamaterials and scattering regulation.
关键词： phase gradient,electromagnetic illusion,scattering regulation,metasurface,reconfigurable
更新于2025-09-04 15:30:14
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High-Gain Fabry-Perot Antennas with Wideband Low Monostatic RCS Using Phase Gradient Metasurface
摘要： The design of two high-gain Fabry-Perot (F-P) antennas with wideband low monostatic radar cross section (RCS) is presented in this paper. Firstly, a phase gradient metasurface (PGM) without lossy layer is used to realize in-band RCS reduction and high aperture efficiency simultaneously. The simulated results show that its peak gain is 19.2 dBi and a high aperture efficiency of 58.6% is achieved. By utilizing the PGM structure, the monostatic RCS is reduced from 7GHz to 11GHz and the in-band co-polarization RCS is reduced by 13.1 dB. After that, a PGM with metamaterial absorber (MA) is designed to broaden the bandwidth of RCS reduction. A prototype antenna is fabricated and measured. The peak gain of 17.9 dBi is obtained and the monostatic RCS is reduced in a wider frequency band of 7GHz to 15GHz.
关键词： radar cross section reduction (RCSR),Fabry-Perot antenna,phase gradient metasurface (PGM),high gain,in-band RCSR
更新于2025-09-04 15:30:14