Search Results (188)

Addressing the insufficient sensitivity of typical Archimedean spiral antennas for detecting partial discharge (PD) in electrical equipment, this paper proposes a high-sensitivity regulation technique for PD Archimedean antennas based on rotating unit-cell reflective metasurfaces. First, a finite element model of the ultra-high-frequency Archimedean antenna was constructed. Then, employing metasurface electromagnetic wave reflection technology and phase compensation principles, a rotating-unit reflective metasurface was designed to optimize its full-bandwidth gain. A multi-parameter joint optimization method was used to obtain the optimal data for the antenna and metasurface parameters. Finally, simulations and experimental analyses of the super-surface-controlled Archimedean antenna revealed the following: The gain of the Archimedean antenna controlled by the rotating-unit super-surface increases by up to 15.61 dB in the 0.3–1.5 GHz band, with an average full-band gain enhancement of 3.42 dB. During electrostatic discharge (ESD), the amplitude of UHF signals detected by the Archimedean antenna increases by approximately 88.9%, and the amplitude detection of UHF signals during GIS discharges increases by approximately 138.6–150%. These results demonstrate that the metasurface significantly enhances the antenna’s gain performance, providing a reference for highly sensitive control technologies in detecting discharges in electrical equipment. Full article

Metasurfaces provide a compact and powerful means of tailoring electromagnetic wavefronts through spatially varying phase manipulation. This review presents a unified, mechanism-centered perspective on phase control in metasurfaces, tracing their evolution from static designs to actively reconfigurable and space–time-modulated platforms. Beginning with the theoretical basis of generalized Snell’s law, phase-control strategies are categorized into resonance-based, PB phase, and propagation-phase mechanisms, with emphasis on their underlying physics, bandwidth, efficiency, and polarization characteristics. These static approaches are then extended to active metasurfaces that enable post-fabrication reconfiguration through liquid-crystal tuning, electro-optic, phase-change materials, and mechanical deformation. Beyond quasi-static tuning, space–time modulation is introduced as a distinct paradigm that exploits temporal phase gradients to achieve frequency conversion, nonreciprocity, and waveform synthesis. By organizing diverse implementations around their physical phase-control mechanisms and experimentally reported performance trends, this review provides practical guidance for selecting metasurface architectures across frequency regimes and application requirements. Full article

Dynamic wavefront control plays a crucial role in advancing terahertz (THz) high-precision non-destructive testing, wireless communication and high-resolution imaging. However, existing approaches to THz dynamic wavefront control suffer from inherent limitations, such complex structures, narrow operational bandwidth, and the ability to tune only a single function, significantly restricting their practical applications. To overcome these challenges, we propose a dynamic reflective THz metasurface based on nested split-ring unit cells. The nested unit cell consists of an outer double-split VO₂ ring resonator and an inner single-split aluminum ring deposited on a central VO₂ circular patch. By, respectively, rotating the inner and outer rings in the insulator and metal states of VO₂, independent full 2π phase coverage at 1.07 THz can be achieved in both VO₂ states while maintaining high polarization-conversion efficiency with a PCR exceeding 0.98, thereby enabling efficient dynamic wavefront control. Using these unit cells, we constructed three distinct reflective metasurfaces that, respectively, generate broadband focusing beams with tunable focal lengths, broadband vortex beams with different topological charges, and a broadband beam that can be switched between focusing and vortex modes by changing the state of VO₂. The design offers considerable flexibility for developing compact, multifunctional THz devices, with promising potential for integrated THz systems, high-capacity communications, and high-resolution imaging. Full article

To enhance the anti-jamming performance and operational reliability of drones, this paper presents the design, fabrication, and measurement of a novel polarization-reconfigurable metasurface antenna that meets these demands. The design process is guided systematically by characteristic mode analysis, in which the modal significance coefficient is used as a key tool to predict resonant frequencies and optimize bandwidth. A major innovation lies in the mechanical rotation mechanism, which enables the antenna to switch between left-hand circular polarization, linear polarization, and right-hand circular polarization, thereby avoiding losses associated with active electronic components. The antenna features a compact geometry of 0.49λ × 0.49λ and delivers strong performance across all polarization states. Impedance bandwidth exceeds 29.9%, average gain ranges from 5.1 to 6.0 dBi, and high polarization purity is achieved with an axial ratio bandwidth > 10% in circular polarization modes and cross-polarization discrimination >23 dB in the linear polarization state. Simulated and measured results are in good agreement, confirming the effectiveness and robustness of the proposed design for modern sub-6 GHz 5G drone terminals. Full article

In response to the significant challenges posed by the rapid progress of multi-spectral detection technologies to traditional stealth techniques, this paper presents a flexible transparent metasurface structure that is compatible with radar and infrared stealth. It consists of multi-layer functional patterned indium tin oxide (ITO) films and a flexible polydimethylsiloxane (PDMS) substrate. The metasurface uses a high-duty-cycle multi-scale circular ring to achieve a microwave absorption bandwidth of 30 GHz and low infrared emissivity of 0.33 in an optimized ultra-thin 2.65 mm thickness system. The simulation results show that the metasurface achieves absorption exceeding 90% in the frequency range of 10.8–40.8 GHz, which covers common radar bands like X, Ku, K, and Ka. Furthermore, the structure exhibits polarization insensitivity and sustains stable absorption in a wide range of 60 degrees of transverse magnetic (TM) fields. Meanwhile, it decreases the radar cross-section (RCS) by more than 10 dB over a wide angular range even when bent. This study presents a feasible metasurface with ultra-thin, flexible, transparent, and multi-spectral compatibility for the next generation of stealth systems. Full article

This paper proposes a compact, low-profile slot antenna integrated with a metasurface (MS) layer to realize wideband circular polarization and maintain a consistently high gain for IoT applications. The antenna element uses a C-shaped slot in the ground plane, excited by a microstrip feed to generate the circularly polarized waves. The metasurface layer incorporates mushroom-shaped outer cells and centrally placed slanted-slot elements to broaden the axial-ratio (AR) bandwidth and to maintain a consistently high gain. The metasurface consists of twelve adjacent cells arranged in a mushroom-shaped configuration, with a 45° slanted rectangular slots on four central cells. The simulated and measured results demonstrate strong agreement; the impedance-matching bandwidth is 26.7%, and the axial-ratio bandwidth is 15.7% at a central frequency of 6.8 GHz. Finally, the antenna consistently demonstrates a measurement gain exceeding 8 dBic across the AR bandwidth, with a peak measured gain of 9.6 dBic. Full article

In fields such as noise control, medical ultrasound, and acoustic communication, the flexible regulation of reflected sound waves has significant application value. In this work, a dual-band acoustic metasurface was designed using a split hollow cuboid with an open-hole plate (OPSHC) structure, which simultaneously achieves the direction control of reflected sound waves in both frequency bands. An OPSHC is a series structural unit, and the two center frequencies are mainly controlled by the diameters of the two openings in the structure and the position of the open-hole plate. Through finite element simulation, the influence of the center frequency of the metasurface and the position of the open-hole plate on the bandwidth of the anomalous reflection was studied. The results show that when the low-frequency center frequency is fixed, the low-frequency bandwidth of the metasurface increases with the increase in the high-frequency center frequency. When the position of the plate is moved, the low-frequency bandwidth increases and the high-frequency bandwidth decreases. This type of metasurface provides a new technical approach for broadband acoustic metasurface applications in noise control and underwater detection systems. Full article

This paper presents a miniaturized, polarization-insensitive frequency-selective metasurface (FSMS) with stopband behavior for RF shielding applications. The FSMS is designed to suppress communication at 10 GHz frequency in the X-band. The design comprises a circular metallic patch with a staircase slot engraved in the center. The FSMS achieves an attenuation of 38.5 dB at the resonant frequency with a 10 dB suppression fractional bandwidth of more than 46%. The physical geometry of the unit cell makes it polarization-independent, and the angle of incidence has no effect on the stopband. The FSMS cell has overall dimensions of 0.3λ_o × 0.3λ_o × 0.05λ_o, where λ_o is free-space wavelength at the resonant frequency. Moreover, an equivalent circuit model (ECM) of the FSMS filter is developed to analyze its operation principle. An FSMS prototype is fabricated and tested for its performance, and the simulated and measured results show good agreement, making it suitable for selective electromagnetic interference (EMI) shielding applications. Full article

An efficient deep-learning-based framework for optimization-based inverse design of electromagnetic metasurface design is proposed in this paper. A novel unit-cell parameterization strategy generates 16-element structures via symmetry operations governed by ten geometric parameters, overcoming the inefficiencies of pixel-based representations. A dataset of 16,000 parameter–reflection phase pairs is constructed, and a hybrid model combining Convolutional Neural Network (CNN), attention mechanisms, and the Kolmogorov–Arnold Network (KAN) is developed for broadband response prediction. The coefficient of determination (R²) of the proposed model is 0.8837 in the 2–18 GHz band, which is 44.87% higher than the R² without KAN. The proposed chessboard metasurface achieves a 10 dB monostatic radar cross-section (RCS) reduction under normal incidence over a wide frequency band from 7.4 to 15.2 GHz, corresponding to a relative bandwidth of 69%. This approach provides a generalizable, data-efficient solution for intelligent metasurface design. Full article

This study proposes design and fabrication methods for an electromagnetic metasurface absorber (MA) that absorbs electromagnetic waves using a metasticker attached on a dielectric substrate blocked by a copper sheet. To guarantee a high design freedom as well as make the absorption bandwidth (BW) as broad as possible, a square-fractal ring is chosen as the metapattern, and its design is optimized using a genetic algorithm. To fabricate the square-fractal rings in a simple manner, an indium-tin-oxide film is cut by using a laser-cutting machine. Then, the metasticker is fabricated by assembling the metapatterns on a double-sided adhesive film which could be attached on the dielectric substrate using the opposite side of the film. From measured results of the finalized MA of which damaged regions caused by the laser-cutting process are compensated in the design process, a broad $-10$ dB reflectance BW is confirmed from 4.39 to 7.51 GHz of which the fractional BW is 52.44% for the normal incidence. Moreover, a fractional BW of 4.35% is measured in a wide incident angle range from $0°$ to $60°$ for both the transverse electric and the transverse magnetic polarizations simultaneously. Full article

Wearable antennas for wireless sensor network (WSN) applications require circularly polarized (CP) radiation to maintain stable communication link under human body movement and complex environments. However, many existing wearable CP antennas rely on either linearly polarized (LP) or CP radiator with a single axial ratio (AR) mode combined with external polarization conversion structures, which limit the achievable axial ratio bandwidth (ARBW). In this work, an all-textile wideband CP antenna with a square-ring notched slot radiator, a 50 Ω microstrip line, and a 3 × 3 nonuniform metasurface (MTS) is proposed for 5.85 GHz WSN applications. Unlike conventional CP generation approaches, the square-ring notched slot, analyzed using characteristic mode analysis (CMA), directly excites three distinct AR modes, enabling potential wideband CP radiation. The nonuniform MTS further improves IBW performance by exciting additional surface wave resonances. Moreover, the nonuniform MTS further enhances ARBW by redirecting the incident wave into an orthogonal direction with equivalent amplitude and a 90° phase difference at higher frequency region. The proposed antenna is composed of conductive textile and felt substrates, offering flexibility for wearable applications. The proposed antenna is measured in free space, on human bodies, and fresh pork in an anechoic chamber. The measured results show a broad IBW and ARBW of 84.52% and 43.56%, respectively. The measured gain and radiation efficiency are 4.47 dBic and 68%, respectively. The simulated specific absorption rates (SARs) satisfy both US and EU standards. Full article

We introduce an equal-phase method to design the polarization-insensitive metasurface lens, composed of subwavelength nano-holes etched into a silver film. By calculating the intensity distribution under linearly, circularly, and elliptically polarized light illumination, we demonstrate that the designed metasurface lens can effectively focus incident light with different polarization states. Moreover, we confirm that this polarization-insensitive property of the designed lens maintains stable focus ability across the entire visible light bandwidth, exhibiting a broadband performance. It is important to note that the metasurface lens design based on the equal-phase method is not limited by specific nanostructure units and exhibits considerable flexibility. For some complex application conditions, we also explore the design of polarization-insensitive lenses capable of generating longitudinal and transverse dual focal spots. The metasurface lenses and the design method proposed in this paper may provide a reference for the development and application of polarization-independent components in integrated photonic devices. Full article

Photodetectors are critical components in a wide range of applications, including military, communications, medical, and aerospace fields. With ongoing advancements in optoelectronics, the strategy of integrating multiple optical structures with photodetectors has led to substantial improvements in detection performance. This review summarizes recent research progress in optically coupled photodetectors, providing a systematic analysis of the operational mechanisms and performance characteristics of five key coupling configurations: optical waveguides, surface plasmon resonance structures, microcavities, gratings, and integrated metasurfaces. Furthermore, the main limitations of current coupling technologies and challenges facing the development of future coupled devices are discussed. Recent studies indicate that heterogeneous integration, multi-physical field coupling, and automated fabrication processes are paving the way for high-performance photodetectors with enhanced bandwidth, sensitivity, functional integration, and spectral control capabilities. Full article

High-gain linear polarized antennas are widely used in wireless communications. However, the insertion loss of the feed network increases, limiting the potential for enhancing antenna gain. In this paper, a high-gain linear polarized Fabry–Perot (FP) antenna based on a fractal structure, which consisted of a metasurface and 2 × 2 array antenna structure, was designed. The spacing between the metasurface structure and array antenna was a free space half-wavelength, forming an FP antenna with a high gain. The self-similarity of the fractal structure allowed miniaturization of the structure. The proposed antenna and metasurface structural units comprised a first-order Minkowski fractal structure. The antenna unit was further miniaturized by including a square gap structure in its unit structure, while its gain was improved by using an air dielectric layer as the dielectric substrate of the antenna unit. The antenna unit formed a 2 × 2 array antenna through a 1–4 feeding network. The reliability of the array antenna performance was verified by processing and measuring the antenna structure. Experimental results showed that the −10 dB working bandwidth of the antenna is 5.71–5.89 GHz, while at 5.8 GHz its gain is 16.5 dBi. The radiation efficiency is over 90%. The experimental results were consistent with the simulation results. The proposed antenna exhibits high gain and is suitable for short-distance wireless communication systems and other fields. Full article

Although the elitist genetic algorithm (EGA) is an approach for the optimal design of pixelated metasurfaces, it is necessary to convert a two-dimensional (2D) metasurface to a one-dimensional array. This ignores the effects of the mutation on neighboring data in 2D metasurfaces, and hinders the rapid convergence of the algorithms. Therefore, we propose the 2D mutation-based EGA (2DM-EGA) to optimally design the linear-to-circular (LTC) polarization conversion metasurface (PCM). Compared with EGA, 2DM-EGA can significantly improve the convergence rate. Furthermore, combined with the proposed intuitive reward-based fitness function and circular polarization discrimination pertaining to an ellipticity angle β, 2DM-EGA, programmed in Python (2023 version), is used to accomplish optimal targets. Finally, the simulated operating band of the optimized metasurface varies from 8.16 GHz to 11.5 GHz with a reduced ellipticity angle β/π ≥ 0.15 and a relative bandwidth of 33.5%, which suggests that the optimized metasurface realizes the broadband LTC polarization conversion. The measured results are in excellent accord with the simulations validating 2DM-EGA for the optimal design of transmission-type wideband LTC PCMs. Additionally, the physical mechanism of the design is expounded. Full article