Electromagnetic Structure Research Articles

Frequency insensitive electromagnetic absorption core-shell sandwich structure with excellent electromagnetic damage tolerance

The compatibility of broadband electromagnetic absorption and electromagnetic damage tolerance poses challenges to the regulation of electromagnetic response characteristics, which are typically restricted by the intrinsic dispersion of materials and strong resonant features of unit cell structures. In this work, triply-periodic-minimal-surfaces (TPMS) based gradient core-shell sandwich structure is proposed to address this challenge for its mathematical defined unique conductive pore structure. The reflection loss-frequency curve is less than −10 dB in 2–18 GHz frequency band, accompanied by two separate resonant absorption peaks at 2.4 GHz and 17.5 GHz. The reflection loss curve is insensitive to frequency in a wide frequency band of 4–14 GHz, using merely three kinds of absorbing materials. When the damage proportion is less than 40 %, effective electromagnetic absorption can be maintained in panel damage, core damage and penetrating damage modes, thanks to the extraordinary conduction-dissipation effect. Our study provides valuable insights for the design of damage tolerant electromagnetic absorption structures.

Origami multifunctional metagrating for a mechanically controlled electromagnetic wavefront

Metasurface or artificial electromagnetic (EM) structures offer viable options for manipulating EM waves with compact periodic structures. Tunable metasurfaces are ideal for many engineering and scientific applications because they can manipulate EM wavefronts. However, it is challenging to implement tunable metasurfaces that can achieve multiple functions for integration. In addition, integrated multifunctional metasurfaces are often structurally complicated and bulky. This paper proposes a simple spatial modulation mechanism that uses Miura origami reconfigurable one-dimensional metagrating to achieve multiple control of EM wavefront. Theoretical predictions, numerical simulations, and experiments confirm and validate the basic concepts. In particular, the continuous geometric deformation of the Miura-ori lattice is a promising method for compensating the dispersion of characters in gradient metasurfaces. Considering origami structures’ outstanding mechanical properties and strong deformation abilities, this discovery opens up another avenue for lightweight and deployable meta-devices.

Progress on Single-Feed Quality Wideband Linear Wire Array

This paper presents the latest developments regarding the single-feed Quality Wideband Linear (QWL) wire array antenna, known for its broadband and high-gain electromagnetic characteristics and robust design. A systematic review of recent advances in relation to the QWL antenna is provided, covering its driven element, director, reflector, low common-mode current interference connector, and array series-feed configuration. For the first time, an analytical expression and a quick design formula for the input impedance of the QWL antenna’s driven element, the linear Wideband High-gain Electromagnetic Structure (WHEMS) antenna, are presented. Theoretical analysis demonstrates the potential for broadband performance using the WHEMS antenna. The rugged design of the QWL array antenna offers engineering advantages such as simple feeding, low wind resistance, a lightweight construction, low cost, and structural robustness. The QWL antenna has already found applications in various industrial sectors, with potential for broader use in the future, contributing to further advancements in antenna technology.

Efficient linear analysis of coupled-cavity traveling-wave tubes using minimum number of dispersion frequency points

Coupled-cavity traveling-wave tubes (CCTWTs) are high-power amplifiers operating in the microwave and millimeter-wave regions of the spectrum, utilizing beam-wave coupling within an electromagnetic slow-wave structure (SWS). The linear (small-signal) analysis of these amplifiers is a crucial initial step in their electromagnetic design. This paper presents and evaluates a method for analyzing these structures in the linear regime using only three frequency points from the SWS. The results obtained from this method are compared with full-wave particle-in-cell simulations, demonstrating satisfactory agreement. This approach offers a rapid analysis method for examining CCTWTs in the linear state, eliminating the need for lumped circuit modeling and detailed knowledge of the SWS dispersion characteristics.

Electromagnetic field compensation to attenuate energy leakage in TM020 mode damped cavity

This paper discusses the TM020 mode Higher-order Mode (HOM) damped cavity, which has a higher quality factor and lower characteristic impedance than the conventional TM010 mode. The unique electromagnetic field (EMF) distribution of the TM020 mode allows for an absorber to be placed at the magnetic field wave node, protecting the working mode while suppressing the HOMs. However, the introduction of high power input couplers and other structures can cause an asymmetrical EMF distribution, leading to operating mode leakage.To address this, EMF compensation methods are applied to the high power input coupler to achieve symmetrical EMF distribution, reducing operating mode loss. Overcoupling of the high power input coupler and the resonant cavity can significantly affect local EMF distribution, causing TM020 mode asymmetry. A tab structure at the coupler port are used to compensate for coupler-induced perturbations, attenuating EMF leakage.The paper proposes electromagnetic compensation structure schemes to mitigate working mode EMF leakage. The reliability of the scheme is demonstrated by the analysis of radiofrequency performance and other aspects through simulation software.

A fully integrated GaAs HBT power amplifier for WLAN 802.11ax applications

AbstractA fully integrated gallium arsenide (GaAs) heterojunction bipolar transistor (HBT) power amplifier (PA) for wireless local area network 802.11ax applications is presented in this paper. The structure consists of two‐stage power cells. To satisfy the high linearity requirements of IEEE 802.11ax, we analyzed the distortion of amplitude‐to‐amplitude and amplitude‐to‐phase. Due to the thermal and voltage sensitivity of GaAs HBT, an adaptive bias circuit is designed to ensure linearity. Moreover, an efficient passive output matching network is designed by analyzing the efficiency of the passive network. The design electromagnetic structure is fabricated in a 2‐μm GaAs HBT process. Under continuous wave testing, the output power reaches 27.2 dBm and the maximum efficiency of 28% at 2.4 GHz. Under the excitation of a 40 MHz 1024‐quadratic amplitude modulation signal, the output power meeting error vector magnitude of −35 dB reaches 16.8–17.2 dBm from 2.4 to 2.5 GHz.

Au Nanorings/TiO2 NPs@MXene-Based Metasurfaces with a Magnetic Mirror-Modulated ECL Strategy for Extracellular Vesicle Detection.

A metasurface as an artificial electromagnetic structure can concentrate optical energy into nanometric volumes to strongly enhance the light-matter interaction, which has been becoming a powerful platform for optical sensing, nonlinear effects, and quantum optics. Herein, we developed a novel hybrid plasmonic-dielectric metasurface consisting of Au nanorings (Au NRs) and TiO2 nanoparticles derived from MXene (TiO2 NPs@MXene). The hybrid metasurface simultaneously benefited from the high near-field enhancement effect of plasmonic materials and the low loss of dielectric materials. Furthermore, the optical modulation efficiency of the hybrid metasurface can be regulated by a magnetic mirror configuration. The magnetic mirror acted like a mirror, confining the electrons to a limited region and increasing the density of the surface plasmon. Moreover, the electrochemiluminescence (ECL) of the Cu2BDC metal-organic framework (Cu2BDC-MOF) served as a light source for the Au NRs/TiO2 NPs@MXene metasurface. Due to the exceptional light manipulation capability of the hybrid metasurface and the coordination of the magnetic mirror, the isotropic ECL signal can be dynamically amplified and converted into polarized emission. Finally, a metasurface-regulated ECL (MECL)-based biosensor with a dual-positive membrane protein recognition strategy was developed for the accurate identification of gastric cancer-derived extracellular vesicles. The novel MECL research opened up a new route in the realization of dynamically tunable metasurfaces for optical sensing and novel nanophotonic devices.

A Polyimide Composite-Based Electromagnetic Cantilever Structure for Smart Grid Current Sensing.

Polyimides (PIs) have been extensively used in thin film and micro-electromechanical system (MEMS) processes based on their excellent thermal and mechanical stability and high glass transition temperature. This research explores the development of a novel multilayer and multifunctional polymer composite electro-piezomagnetic device that can function as an energy harvester or sensor for current-carrying wires or magnetic field sensing. The devices consist of four layers of composite materials with a polyimide matrix. The composites have various nanoparticles to alter the functionality of each layer. Nanoparticles of Ag were used to increase the electrical conductivity of polyimide and act as electrodes; lead zirconate titanate was used to make the piezoelectric composite layer; and either neodymium iron boron (NdFeB) or Terfenol-D was used to make the magnetic and magnetostrictive composite layer, which was used as the proof mass. A novel all-polymer multifunctional polyimide composite cantilever was developed to operate at low frequencies. This paper compares the performance of the different magnetic masses, shapes, and concentrations, as well as the development of an all-magnetostrictive device to detect voltage or current changes when coupled to the magnetic field from a current-carrying wire. The PI/PZT cantilever with the PI/NdFeB proof mass demonstrated higher voltage output compared to the PI/Terfenol-D proof mass device. However, the magnetostrictive composite film could be operated without a piezoelectric film based on the Villari effect, which consisted of a single PI-Terfenol-D film. The paper illustrates the potential to develop an all-polymer composite MEMS device capable of acting as a magnetic field or current sensor.

Controlling Plasmonic Catalysis via Strong Coupling with Electromagnetic Resonators.

Plasmonic excitations decay within femtoseconds, leaving nonthermal (often referred to as "hot") charge carriers behind that can be injected into molecular structures to trigger chemical reactions that are otherwise out of reach─a process known as plasmonic catalysis. In this Letter, we demonstrate that strong coupling between resonator structures and plasmonic nanoparticles can be used to control the spectral overlap between the plasmonic excitation energy and the charge injection energy into nearby molecules. Our atomistic description couples real-time density-functional theory self-consistently to an electromagnetic resonator structure via the radiation-reaction potential. Control over the resonator provides then an additional knob for nonintrusively enhancing plasmonic catalysis, here more than 6-fold, and dynamically reacting to deterioration of the catalyst─a new facet of modern catalysis.

From waste to resource: Transforming Kraft black liquor into sustainable porous carbon fillers for radome applications

The study addresses environmental and commercial challenges posed by weak black liquor (WBL) generated through the Kraft process in the paper industry. WBL, a toxic waste, annually reaches a staggering 1.3 billion tonnes globally. Currently, it is either incinerated for energy production or subjected to costly and complex chemical treatments to extract valuable compounds. Despite efforts to develop a scalable value-added material, the existing methods are inefficient in fully reusing WBL. Here, we report a simple chemical synthesis process that reuses 100 % of WBL without generating any waste materials; even salts recovered during the process might be reintegrated into the industry as chemical byproducts. Furthermore, given the simplicity and efficiency of the proposed synthesis methodology to transform WBL into a novel and sustainable porous carbon material, the carbon Kraft (CK). The process can also be scaled by using the right synthesis proportions and within a circular economy. CK exhibited desirable characteristics with a renewable content of 65 wt%, including a turbostratic graphitic-like structure (48.8 % graphitized), carbon content of 85 wt%, large specific surface area of 234.0 m2∙g−1, nanoporosity of 0.13 cm3∙g−1, and density of 1.92 g∙(cm3)-1. Moreover, CK showed electrical and thermal insulating characteristics, essential for use as fillers for elastomeric composite in electromagnetic transparent radome structures used to protect antennas and radars of unmanned aerial vehicles (UAV) from harsh environmental effects. Radomes were designed through the electromagnetic impedance match theory of half-wavelength calculations over specific frequencies of 1.3, 10, 15, 20, and 30 GHz. Results showed excellent transmission loss between −0.41 and −1.48 dB, representing 90.8 % and 70.5 % of transmittance, respectively.

Electromagnetic effects on solitons propagation of the (3+1)-dimensional extended Zakharov-Kuznetsov dynamical model with applications

This paper investigates wave solutions and electromagnetic wave phenomena governed by the (3+1)-dimensional extended Zakharov-Kuznetsov equation (EZKE) utilizing the Sardar sub-equation method. With a focus on electromagnetic wave generation and propagation, we rigorously analyze fundamental properties, soliton solutions, and dynamic behaviors of the EZKE. Through this analytical technique, we unravel the complex interplay among various wave types, including solitary waves and electromagnetic structures, elucidating their formation mechanisms and interaction dynamics. Furthermore, we delve into the stability characteristics of the EZKE, enhancing our understanding of its mathematical and physical implications. Our findings not only contribute to theoretical insights into nonlinear wave phenomena in (3+1)-dimensional space but also hold practical significance in plasma physics, nonlinear optics, and electromagnetic wave propagation. This study advances the development of innovative wave manipulation and control techniques, with applications ranging from plasma confinement in fusion devices to the design of advanced photonic devices for telecommunications and sensing purposes.

Enhancing electromagnetic shielding property and absorption coefficients via constructing electromagnetic rings in janus composites

Polymer based electromagnetic wave (EMW) shielding materials with high conductivity have excellent electromagnetic shielding properties, but also exhibit high reflection of EMWs, resulting in inevitable secondary electromagnetic pollution. EMW shielding materials with low reflection have extensive potential applications in the next generation of anti-EMW equipment. Herein, a production strategy combining three dimensional (3D) printing technology and solution casting method was proposed to prepare polylactic acid (PLA)@multi-walled carbon nanotubes (MWCNT)/polydimethylsiloxane (PDMS)@carbonyl iron powder (CIP) absorptive electromagnetic shielding Janus composites with a ring-shaped electromagnetic synergistic structure (spiral rings or concentric circular rings). By utilizing PLA and MWCNTs as primary components, a 3D integrated framework that combines a highly conductive reflector and a ring inductance structure can achieve significant EMW shielding performance with low reflection. With PDMS as a matrix and magnetic CIP as functional fillers, a strong magnetic permeability network is provided around the ring inductance frame. The magnetic loss resulting from electromagnetic cooperative ring structure further enhances microwave absorption capacity. The composite materials, benefiting from the synergistic interaction between the electromagnetic rings and the reflector, demonstrate excellent impedance matching and efficient EMW shielding capabilities. Specifically, the PLA@MWCNT/PDMS@CIP Janus composites with ring structure exhibit a notable EMW shielding effectiveness (SE) of 31 dB and a reflection coefficient as minimal as 0.3. Therefore, this study presents a powerful approach to the development of low-reflective materials with high EMW SE, promising potential applications in the next-generation intelligent electronic devices.

Generalized Huygens' Condition as the Fulcrum of Planar Nonlocal Omnidirectional Transparency: From Meta‐Atoms to Metasurfaces

AbstractFresnel reflection has been known for centuries to fundamentally impede efficient transmittance across planar interfaces, especially at grazing incidence. In this work, the generalized Huygens' condition (GHC) is introduced to resolve such intricacies in metasurface (MS) designs and allow omnidirectional transparency. Compared to common numerical metamaterial approaches, the analytical framework herein yields surprisingly simple closed‐form conditions, carefully leveraging the natural nonlocal mechanisms endowed in planar electromagnetic structures. At the meta‐atom level, the GHC is met by balancing traditional tangential susceptibilities of Huygens' MSs with their unconventional normal counterparts; the latter facilitates the key requisite of vanishing backscattering at the challenging grazing incidence scenario. At the MS level, this central insight is sheerly utilized to engineer realistic all‐angle transparent printed‐circuit‐board (PCB) cascaded admittance sheets. Thoroughly validated in simulation and experiment, this universal GHC demonstrates a resourceful venue for practical implementation of advanced nonlocal devices, e.g., flat optical components, optical analog computers, and spaceplates.

Chipless RFID Sensor for Measuring Time-Varying Electric Fields Using a Contactless Air-Filled Substrate-Integrated Waveguide Resonator.

This paper presents a wireless chipless resonator-based sensor for measuring the absolute value of an external time-varying electric field. The sensor is developed using contactless air-filled substrate-integrated waveguide (CLAF-SIW) technology. The sensor employs a low-impedance electromagnetic band gap structure to confine the electric field within the sensor's air cavity. The air cavity is loaded with varactor diodes whose reverse bias voltage is modified by the to-be-measured external electric field. Variation in the external electric field results in a variation of the sensor's resonant frequency. The CLAF-SIW sensor offers a high unloaded quality factor, which is required for a long-distance ringback-based interrogation system. A prototype of the proposed sensor is fabricated and tested. It can measure a time-varying external electric field up to 6.9 kV/m, has a sensitivity of 1.86 (kHz)/(V/m), and can be interrogated from a distance of 80 cm. The feasible maximum bandwidth of the external electric field is 25 kHz. The proposed sensor offers a compact planar multilayer structure that can easily be incorporated with a planar antenna and its size can be reduced by selecting a higher operating frequency without an increase in dielectric loss.

Injection Process of Pickup Ion Acceleration at an Oblique Heliospheric Termination Shock

The injection process of pickup ion acceleration at a heliospheric termination shock is investigated. Using two-dimensional fully kinetic particle-in-cell simulation, accelerated pickup ions are self-consistently reproduced by tracking long time evolution of shocks with an unprecedentedly large system size in the shock normal direction. Reflected pickup ions drive upstream large-amplitude waves through resonant instabilities. Convection of the large-amplitude waves causes shock surface reformation and alters the downstream electromagnetic structure. A part of pickup ions are accelerated to tens of upstream flow energy in the timescale of ∼100 times inverse ion gyrofrequency. The initial acceleration occurs through the shock surfing acceleration (SSA) mechanism followed by the shock drift acceleration mechanism. Large electrostatic potential accompanied by the upstream waves enables the SSA to occur.

Level set methods for gradient-free optimization of metasurface arrays

Global optimization techniques are increasingly preferred over human-driven methods in the design of electromagnetic structures such as metasurfaces, and careful construction and parameterization of the physical structure is critical in ensuring computational efficiency and convergence of the optimization algorithm to a globally optimal solution. While many design variables in physical systems take discrete values, optimization algorithms often benefit from a continuous design space. This work demonstrates the use of level set functions as a continuous basis for designing material distributions for metasurface arrays and introduces an improved parameterization which is termed the periodic level set function. We explore the use of alternate norms in the definition of the level set function and define a new pseudo-inverse technique for upsampling basis coefficients with these norms. The level set method is compared to the fragmented parameterization and shows improved electromagnetic responses for two dissimilar cost functions: a narrowband objective and a broadband objective. Finally, we manufacture an optimized level set metasurface and measure its scattering parameters to demonstrate real-world performance.

High performance and compact antenna with new scheme for broadband circular polarisation applications

ABSTRACT In this research paper, the authors propose a unique broad-band circularly polarised antenna design with a sequentially rotated feed network intended for applications in the WiMAX IEEE 802.16, C-band, and ITU-R F386.9 bands. A sequential feeding approach utilising transmission lines with varying impedance properties and lengths has been utilised to properly stimulate the amplitude and phase distribution of each radiation element. To facilitate the rotation of the surface current distribution on the ground plane and further improve impedance matching, four L-shaped slits have been inserted into each corner of the ground plane along with a pair of mirrored slits of identical geometry within the antenna ground plane. The individual antenna element achieves an impedance bandwidth between 5–6.8 GHz and a 3 dB axial ratio bandwidth from 5.1–6.6 GHz. To additionally advance the radiation performance, the elements are configured into a 2 × 2 antenna and are interconnected utilising a sequentially rotated feeding network to attain broader axial ratio and impedance bandwidths. A key benefit of the implemented feed network is the minimisation of coupling effects between elements. To significantly increase the performance metrics of the antenna with limited increase to its physical size, electromagnetic band gap structures were incorporated as a one-dimensional lattice between the radiating elements. For the resulting antenna, an axial ratio bandwidth from 4.19 to 6.8 GHz (48%) and an impedance bandwidth spanning 2.9 to 9.8 GHz (102%) are achieved. The peak gain of the antenna is 11.2 dBic.

An Adaptive Elastic Support Seat-Based Magnetorheological Elastomer for Human Body Vibration Reduction.

This paper introduces an electromagnetic structure utilizing the controllable mechanical properties of magnetorheological elastomer (MRE) materials through magnetic flux. An adaptive elastic foundation composed of these materials is explored for vibration reduction and frequency modulation. This study investigates these effects using both a single-mass model and a coupled human-seat model. For objects supported by the adaptive elastic foundation, increasing the magnetic flux enhances the stiffness and damping, thereby significantly reducing the peak response while slightly increasing the resonance frequency. Strategies such as increasing the magnetic flux, reducing the object mass, and minimizing the system's degrees of freedom and internal damping contribute to enhancing the vibration reduction and frequency modulation in the adaptive elastic foundation. The simulation results indicate that for a seated human (weighing between 72.4 kg and 88.4 kg), the adaptive elastic foundation reduces the head peak response by approximately 15.7% and increases the resonance frequency by approximately 3.4% at a magnetic flux of 138 mT.

Analysis of Parasitic Parameters and Winding Loss Characteristics of High-Frequency Transformer under Different Winding Structures

Abstract With the development of the smart grid and the increasing access of renewable energy to the distribution grid, the traditional AC power grid puts forward an urgent demand for power electronic transformer (PET). The high-frequency transformer (HFT) serves as the core equipment of PET, and its electromagnetic structure and parasitic parameters are the hot spot of study in the field of power electronics. In this paper, the parasitic parameters, winding loss, and leakage magnetic field characteristics of the 20 kHz, 20 kVA HFT are investigated under different winding structures. The results show that the higher the degree of crossover of HFT winding, the lower the leakage magnetic field. The cross winding reduces winding loss and leakage inductance, and also attenuates the impact of frequency variations. The higher the winding height, the lower the leakage inductance. As the insulation thickness increases, the leakage inductance rises. The distribution capacitance varies opposite to the leakage inductance. Based on the analysis of winding loss and parasitic parameters, as well as the consideration of insulation, the final winding layout, the height of winding and the thickness of insulation of the HFT are determined.

Low‐cost and easy‐to‐embed 7‐bit 360° phase shifter with transitions for large‐scale phased arrays

AbstractIn this letter, a low‐cost and easy‐to‐embed 7‐bit 360° phase shifter with transitions is presented for applications to beamforming in the large‐scale phased array. In the proposed 360° phase shifter, the topology of the reflection‐type phase shifter (RTPS) is employed, composed of a 3‐dB branchline coupler terminated with two tunable parallel L–C loads. First, a two‐step phase extraction process for RTPS is applied to design the RTPS rapidly with competitive performance, including 360° phase range and low insertion loss. A huge amount of parameter sweep is reduced in the design and test. Meanwhile, the parameter of inductors in the tunable loads is investigated effectively, to achieve the minimal phase step. Second, aiming at the enhanced performance of beamforming and improved flexibility of integration, the stripline is adopted in the design of the phase shifter, avoiding the interference on antenna radiation effectively. To facilitate the integration with antenna and radio frequency connectors of the input and output signals, a stripline‐to‐microstrip line transition with electromagnetic bandgap structures is adopted. By this means, the complexity and cost of fabrication are decreased. Finally, fabricated in the low‐cost printed circuit board technology, our proof‐of‐concept design operated from 2.4 to 2.5 GHz is measured and achieves a 386.8° phase shift range with an insertion loss of 2.21 ± 0.82 dB at 2.45 GHz.