A tunable reflective frequency-selective absorber is proposed. It comprises a lossy array and a lossless array, and the resonant frequency of both can be tuned by controlling the reverse-biased voltage of embedded varactors. A pin-header-based bias network is introduced to provide both electrical connectivity and structural support across layers with minimal impact on electromagnetic (EM) performance. By carefully selecting varactors and designing the bias network, the required capacitance variations are effectively controlled. The structure demonstrates a sharp transition between the reflective and absorptive bands, achieving high selectivity alongside a flat reflective band and broadband absorption. Simulated and measured results exhibit great agreement, confirming the effectiveness of the proposed design. The reflective frequency-selective absorber achieves a voltage-controlled flat reflective band from 3.51-4.76GHz to 4.21-5.19 GHz. Outside the reflective band, the structure maintains a wideband absorption spanning 2.2-11.6 GHz.

An ultra-wideband reconfigurable reflectarray antenna based on liquid metal with beam scanning is proposed. The multi-layer unit cell, with its microfluidic channels, dielectrics, metal patterns and ground plane, is reconfigurable via liquid metal positioning. By filling gaps in the metal patterns, the liquid metal defines two distinct states, both of which achieve polarization conversion from linear polarization to its cross-polarization. Featuring a near-unity reflection magnitude and a 180° phase shift, the unit cell enables 1-bit phase control. When fed by a Vivaldi antenna, the 12×12 reflectarray built from these cells exhibits wide bandwidth, high gain, and high aperture efficiency. By reconfiguring the unit cell states at 4 GHz, beam scanning is achieved. The array has a 3 dB gain bandwidth of 3.05-5.2 GHz (52.12%). The peak gain and peak aperture efficiency reach 17.37 dBi and 31.2%, respectively. A prototype is fabricated, and the measurement results correlate well with simulations, confirming the design's accuracy.

Broadband and reconfigurable illusion camouflage remains a major challenge in electromagnetic wave manipulation, as it imposes concurrent demands for precise dispersion control together with reliable real-time switching across wide frequency ranges. Existing metasurface cloaks typically suffer from narrow bandwidths and limited adaptability, rendering them unsuitable for dynamic radar detection scenarios. Herein, we propose and experimentally demonstrate a Fluidic-Accessible Metasurface (FAM) that overcomes these limitations by enabling programmable electromagnetic illusions through focal-spot encoding. The supercells are designed with strong dispersion control and achromatic focusing capabilities, thereby generating stable scattering hotspots from the radar perspective. Through the assembly and fluidic reconfiguration of these supercells, the FAM dynamically reconstructs the illusionary contours of diverse targets, such as aircraft, drones, and tanks, within an ultrawide operational bandwidth of 9-14 GHz. Experimental near-field measurements, in agreement with full-wave simulations, verify reliable and repeatable illusion camouflage states without leakage or degradation during fluidic reconfiguration. This strategy, therefore, unifies broadband operation, dynamic programmability, high adaptability, and structural robustness, directly addressing the key limitations of existing metasurface cloaks. This work establishes a versatile platform for programmable electromagnetic illusions, enabling the practical deployment of next-generation intelligent metasurface camouflage systems.

This letter presents a high-gain Fabry-Pérot (F-P) antenna with reconfigurable scattering patterns, utilizing magnetically controlled (MC) switches. A novel magnetically controlled metamaterial (MCM) is employed, enabling the shared use of scattering reconfiguration and driving structures while maintaining stable radiation performance. By adjusting the MCM configuration, independent reconfiguration of dual-polarized scattering patterns is achieved. This layout modification is accomplished by manipulating the switch states at various positions within the MCM. The interaction between the switches and magnets enables modulation of the MC switches by adjusting the magnet positions. With the integrated design of the MCM and F-P cavity, the antenna maintains high and stable radiation performance while modulating scattering patterns. Both simulated and measured results demonstrate that the proposed antenna achieves a peak gain of 18.1 dBi at 10.1 GHz during scattering modulation. The 10 dB radar cross-section (RCS) reduction band spans from 8.7 to 14.3 GHz for both co-polarized and cross-polarized incident waves.

This paper proposes a fluidically reconfigurable metasurface unit cell based on the displacement of liquid metal (Galinstan) and sodium hydroxide (NaOH) solution for controllable polarization rotation and Radar Cross Section (RCS) reduction. The proposed meta-atom integrates a microfluidic channel within a multilayered structure. By switching the fluidic state from NaOH solution to liquid metal, the unit cell transforms from a simple dielectric-covered reflector into a high-efficiency polarization converter. Theoretical analysis based on the $u$and $v$-axis decomposition method is conducted to reveal the polarization conversion mechanism. Simulation results demonstrate that in the liquid metal state, the unit cell achieves a Polarization Conversion Ratio (PCR) exceeding 90% across a wide frequency range (e.g., X-band), effectively rotating the incident co-polarized wave into a cross-polarized wave. In contrast, the NaOH-filled state exhibits standard reflective characteristics, providing a significant switching dynamic for RCS control. This design offers a robust, high-power-handling solution for next-generation reconfigurable stealth surfaces.

This article presents a method for accurately and rapidly evaluating the far-field radiation characteristics of large-scale phased arrays by measuring only a small subset of typical elements at near-field distances. The measured element fields, which inherently include mutual coupling effects, are then synthesized via vector superposition to reconstruct the full-array pattern. Unlike conventional far-field measurement, which requires impractical distances satisfying R >= 2D(2)/lambda for the full array, the proposed method only requires the far-field distance of individual elements, reducing the measurement range by several orders of magnitude. The accuracy and efficiency of the proposed method are validated through simulations and measurements on arrays of various sizes and configurations, including linear, planar, triangular-lattice, and irregular arrays. Furthermore, it enables accurate beam scanning prediction for any scan angle up to 60 degrees with only a single set of typical element measurements, drastically reducing the time required for full-space scanning. By transforming array testing from "measure-the-whole" to "measure-typical-and-predict," this work addresses the fundamental challenges of full-space scanning and far-field measurement for large-scale phased arrays. It thereby offers significant engineering value for industrial applications where far-field chamber facilities are constrained.

This paper proposes a low-scattering array antenna designed to suppress the total Radar Cross Section (RCS) by manipulating the antenna mode scattering to cancel the structural mode scattering. A monopole antenna is integrated at the center of a circularly polarized (CP) array as a dummy element. By loading a specific impedance at the monopole terminal, the amplitude and phase of its antenna mode scattering field are precisely tuned to achieve destructive interference with the structural mode scattering field of the overall array. Due to the omnidirectional radiation characteristics of the monopole antenna, the proposed method enables the array to maintain low-scattering performance across a full 360° azimuthal range by optimizing the port impedance.

Achieving wide-angle muti-polarized radar cross section (RCS) reduction without degrading radiation performance is challenging for existing methods. To address this, a low-profile omnidirectional microstrip antenna integrated with three tailored absorbing structures (ASs) is proposed. The ASs are strategically embedded to efficiently dissipate incident wave energy, leading to significant reduction in both monostatic and bistatic RCS over the upper hemisphere. Equivalence theorem analysis reveals that the equivalent radiation current of the antenna and the scattering currents captured by the ASs are spatially orthogonal, thereby preserving good radiation performance. The proposed antenna operates at 3 GHz and has a diameter of 0.7λ₀ and an profile of 0.02λ₀. It achieves average monostatic RCS reductions of 15.41 dB (ϕ‑LP), 14.55 dB (θ‑LP), 11.09 dB(LHCP) and 11.08 dB(RHCP) and within the angular range of 0° to 90°, together with effective wide-angle dual-LP and CP bistatic RCS suppression. Measured results agree well with simulations. The design maintains the same low profile as the reference antenna with only 0.31 dB gain loss, offering a combination of superior muti-polarized, wide-angle, and high-level RCS reduction, making it well suited for stealth airborne applications.

In this paper, a wide-angle scattering reconfigurable antenna array based on time-division multiplexing and antenna mode scattering regulation is proposed. The radiation and scattering paths are separated through PIN diode switching, enabling independent regulation of both performances. Each element integrates a tunable reflection phase modulator, realizing dynamic modulation of scattering field phases. By programming the element phases into selected configurations, the proposed antenna array achieves flexible, frequency-agile monostatic RCS reduction across the 4 GHz to 5.6 GHz. Furthermore, by employing multi-bit phase coding, the scattered main beam can be dynamically steered within ±60° under both normal and oblique incidence up to ±60°. To validate the effectiveness of the proposed design, a prototype antenna array is fabricated and measured. The measured results show good consistency with the simulation ones.

This work presents a polarization-independent, broadband reconfigurable electromagnetic metasurface based on liquid metal microfluidics that can simultaneously achieve wavefront scattering amplitude and frequency control. The metasurface features a cross-shaped unit cell design, where pressure-driven liquid metal flow through symmetrical microchannels permits dynamic reconfiguration at both individual cell and coding subarray levels, achieving continuous phase modulation exceeding 200 degrees across 6-11 GHz. Fabricated on a highly elastic polymer substrate, the modular subarray design facilitates large-scale metasurface implementation while maintaining structural integrity. Experimental results show that each subarray achieves continuous reconfiguration through single-port control with non-volatile state retention, while the symmetric microfluidic network ensures precisely synchronized liquid metal flow with excellent reversibility, spatial uniformity, and symmetry during operation. Full-wave simulations and electromagnetic reflection measurements demonstrate the metasurface's exceptional dynamic control capabilities, including continuous amplitude modulation from-0.88 dB to-18.75 dB across 5.8-11 GHz (88% fractional bandwidth), near real-time coding sequence reconfiguration, and dynamic tuning of both operational bandwidth and resonant frequencies. The design maintains polarization-insensitive operation across orthogonal polarizations and enables continuous transitions between metal reflection and diffuse scattering states. These advances establish a new paradigm for developing low-cost, high-agility, wideband multifunctional electromagnetic systems.

A left-handed circularly polarized (LHCP) and frequency reconfigurable Fabry-Pérot cavity antenna (FPCA) is proposed using mechanically reconfigurable Fabry-Pérot cavity (FPC). By using chiral metasurfaces as the top and bottom boundaries of the FPC, LHCP waves can be multiply reflected within the cavity while preserving the same handedness. Moreover, the resonant frequency is directly dependent on its twist angle. Hence, the antenna can realize frequency reconfiguration by rotating the chiral partially reflective surface (PRS). The chiral bottom reflector is designed with low polarization loss. Additionally, a chiral PRS is designed to achieve both chiral reflection and polarization-stable transmission during the rotation of the PRS, ensuring stable LHCP radiation during reconfiguration. Finally, a Fabry-Pérot cavity antenna is obtained under the excitation of an LHCP source antenna. It achieves narrowband performance in terms of gain and axial ratio bandwidth with a high directionality. Moreover, a wide and continuous frequency reconfiguration range of peak gain is realized from 5 to 6.02 GHz. The maximum peak gain of 19.98 dBic with a variation of less than 1.9 dB is realized. Maximum aperture efficiency reaches 55.55%. A prototype has been fabricated and measured for verification. Both simulation and measurement results show good agreement, confirming the feasibility of the proposed design method.

A polarization rotation reflective surface (PRRS) with a dynamic polarization rotation (PR) null is proposed. The working mechanism of PRRS is analyzed based on even-odd-mode theory. Hence, a bottom-integrated reflector approach can be proposed to create the PR null. The PR null can be independently and dynamically modulated by this approach. Building upon this method, an electrically reconfigurable PRRS is further developed, enabling dynamic manipulation of the PR null for the first time. Simulation results demonstrate that the proposed reconfigurable PRRS unit cell achieves wideband PR performance from 3.2 to 12.9 GHz, with a dynamically tunable PR null ranging between 4.7 and 10 GHz. A prototype consisting of 11 & times; 11 unit cells was fabricated, and radar cross section (RCS) measurements were conducted to validate its performance. Experimental results confirm the feasibility of dynamically adjusting the PR null.

In this article, a novel method for generating quasi-nondiffractive beams with steerable nondiffracting regions and scanning angles is proposed. For the first time, the starting point of the nondiffracting region is made steerable, rather than fixed on the antenna aperture. The feasibility of the proposed method has been validated through numerical electromagnetic simulations. Five quasi-nondiffractive beams antennas are designed, simulated, fabricated, and measured. The measured results are in agreement with both the numerical electromagnetic simulations and full-wave simulations results. The scan angle and nondiffracting region of each beam can be controlled independently. This advancement will greatly improve the flexibility and applicability of quasi-nondiffractive beams, with potential applications in areas such as multitarget wireless power transfer (WPT) and indoor signal enhancement.

A broadband active polarization rotation reflective surface (PRRS) featuring 1-bit reconfiguration capability is proposed in this letter. The unit cell can realize 1-bit reconfiguration within the frequency range of 6.15 GHz to 23 GHz, achieving polarization rotation while maintaining cross-polarized coefficients above -1 dB. The electromagnetic waves can be rotated by 90 degrees and reflected with a 180 degrees relative phase difference by the active PRRS in both states. The active polarization rotation performance is initially realized through the use of metal strips integrated with p-i-n diodes. The vertical interconnect access is reused to realize dc bias and enhance the unit's RF performance, introducing an additional resonance. The active PRRS is applied to radar cross section (RCS) reduction to validate its performance. Simulation results demonstrate that the directions of the RCS peaks can be dynamically controlled. A monostatic RCS reduction exceeding 10 dB is achieved across the frequency range of 6.1 GHz to 23 GHz, compared to an equal-sized metal plate. A prototype comprising a 12 x 12 array of elements has been fabricated for experimental verification.

Electromagnetic camouflage has attracted significant academic interest and extensive discussion. Compared to transformation optics cloaks, metasurface cloaks have become the prevailing approach due to their superior ability to manipulate electromagnetic waves and their ease of fabrication. However, existing dynamic camouflage active cloaks are constrained by narrow bandwidths resulting from the nonlinear effects of lumped elements, presenting significant challenges for effective concealment under broadband detection systems. To overcome this challenge, a novel quasi-3D microfluidic dynamic camouflage cloak based on multi-physical field analysis and integration of solid and liquid metals is proposed, which can not only camouflage different real objects in the broadband range but also achieve complete filling and fast switching of large-scale two-phase microfluidics. The electromagnetic and fluidic properties of the designed cloak are validated by experiments, which agree very well with numerical simulations. This work presents a feasible broadband dynamic camouflage strategy, which is closer to practical applications, and provides unprecedented potential for near-field and far-field regulation of broadband electromagnetic waves.

In this article, a novel programmable meta surface(PM) is proposed, characterized by simple structure, high-level integration, multiple polarization modes (including dual-linearand dual-circular polarizations), wide scanning angle, and low scanning loss. Equivalent circuit theory is employed, making it convenient to design a 2-bit unit cell with simplified structure. The proposed unit cell has only two substrates, five radio frequency(RF) electronic components, and five metalized vias, which, tothe best of our knowledge, represent the fewest components reported for 2-bit dual-polarized unit cells. A 12x12 scale meta surface is designed, fabricated, and measured. The direct current (dc) control circuit is ingeniously integrated behind the meta surface, resulting in a total thickness of just 5.34 mm for both the meta surface and the control circuit. This highly integrated control scheme eliminates the need for at least one substrate, two metal layers, and hundreds of external wires, significantly reducing both the complexity and cost of the PM. The measurements show good agreement with the simulations. The proposed meta surface can steer beams with multiple polarization modes within a range of +/- 60 degrees, requiring only a single linearly polarized feed source. The antenna achieves a maximum a per ture efficiency (AE) of 35.35% in linearly polarized modes and 32.02%in circularly polarized modes. The proposed meta surface has potential in various fields, including satellite communication, radar detection, wireless power transmission, and re configurable intelligent surface (RIS)-assisted communication

In this article, a novel method named mode filtering and subarray expansion (MF-SAE) for accurate and rapid evaluation of large-scale phased array scattering is proposed. Unlike traditional methods, this approach transforms the evaluation of large-scale array scattering into the total scattered field of a small subarray. The scattered field of the element in the array environment can be analytically separated from the total scattered field of the subarray based on spherical wave expansion (SWE) and mode filtering. The calculated element fields include coupling effects. Subsequently, the element field of the large array can be regarded as equivalent to the subarray element field under a similar coupling environment. This method solves the problem that the scattered field of the elements in an array cannot be directly obtained by measurement or simulation software. The MF-SAE method significantly reduces time consumption and memory requirements while maintaining high accuracy. The computational problem of a large-scale array is transformed into that of a $1\times 7$ or $7\times 7$ subarray. The amount of computation does not increase with the size of the large-scale array. The effectiveness of this method has been verified through the simulation and measurement of different array models. The radar cross section (RCS) error is below 1.5 dB in simulation and reaches 2.3 dB in measurement.

In this paper, an innovative approach is proposed for the co-polarized dual-port slot antenna with isolation improved. Firstly, the half-wavelength mode (model) and one-wavelength mode (mode2) of the slot antenna have been deeply investigated, and we have bent asymmetric distribution of the electric field successfully. As such, it could relocate the E-field cancellation point to the unexcited port of the slot antenna, while maintaining the maximum electric field at the excited port. Then, the resonant frequencies of modes1 and 2 are tuning by loading the short-ended bridges and shorted-ended branch. It makes the modes1 and 2 can be combined at 4.75 GHz. Based on this principle, we have combined three modes for the antenna for mutual coupling reduction. Finally, we machine and measure the antenna, which proves that the $\vert S_{12}\vert$ is better than 22dB and the $\vert S_{11}\vert$ is 21.5% from 4.57GHz to 5.68GHz, representing a great improvement. In addition, the bidirectional radiation patterns are successfully gained.

An different planar band-notched characteristics antennas is presented in this paper. Consisting of a radiation patch that has an improved (sic)-shape slot, M-shape slot, and two mirror images of each other C-shape slots embedded in reference ground. it will have band-notched characteristics in the WiMAX band, which range from 3.3 to 3.6 GHz, lower WLAN (which frequency is close to 5.2 GHz), higher WLAN (which frequency is close to 5.8 GHz) bands. The antenna proposed is successfully simulated and designed, which will satisfy the fundamental condition including widely frequency band match, stably antenna patterns.