Electric Surface Currents Research Articles

Circular-ring tied arc loaded excellent metamaterial absorber for EMI shielding of Wi-Fi signal and impurity sensing of cooking oil

This paper demonstrates a unique symmetric structure excellent metamaterial absorber (MMA) loaded with circular-ring tied arcs. The FR4 substrate-based MMA can accomplish 98.88 % and 99.81 % absorption maximums at the Wi-Fi and 5G frequencies of 2.4 GHz and 5.0 GHz respectively. The unit cell dimension of 0.16λ0×0.16λ0×0.0128λ0 is considered where the wavelength, λ0 is calculated at 2.4 GHz. The performance of the absorber is analyzed through the electric field, magnetic field, surface current, and effective parameters. The dimensions are optimized through the parametric analysis of the developed model in CST software. The model exhibits stability up to 60° for Transverse electric and magnetic polarizations. During electromagnetic interference (EMI) shielding demonstration, it can achieve a high shielding effectiveness (SE) of 54.34 dB at 2.4 GHz and 77.96 dB at 5.0 GHz. For sensing operation, it can attain a quality factor (Q-factor) of 25.61, a sensitivity of 3.30 %, and a figure of merit (FoM) of 84.51. The prototype measurements of the MMA for EMI shielding and impurity sensing of oil samples have a strong correlation with the simulation performance. Because of the high SE, Q-factor, sensitivity, and FoM, the developed MMA can be a competitive candidate in EMI shielding and oil impurity sensing applications.

Modelling and analysis of a triple-band metamaterial absorber for early-stage cervical cancer HeLa cell detection

The paper introduces a unique design and analysis of a terahertz metamaterial absorber (MMA) that can be used for early detection of cervical cancer by employing microwave imaging techniques. Computer Simulation Technology (CST) is used to design and analyze the proposed absorber. The MMA operates in the frequency range of 6–8 THz and can absorb energy in three specific spectral bands: 6.606 THz, 6.824 THz, and 7.426 THz, with absorption peaks of 99.75 %, 99.87 %, and 99.73 % correspondingly. The working principle of the absorber is described using the impedance matching and interference theory. The electric field (E), magnetic field (H), and surface current of the MMA are also examined. Finally, detecting cancerous HeLa cells is also being investigated by analyzing the E-field and H-field using microwave imaging. The suggested biosensor features a high-quality factor of 494.3, a frequency shifts per refractive index of 1.08 THz/RIU, and a figure of merit (FOM) of 42. The suggested MMA-based sensor has numerous advantages and can be utilized for early-stage cervical cancer detection.

Low profile wide band high gain transmitarray antenna for Ku band applications

A wideband transmissive surface with identical slots on 15 × 15 unit cells proposes in this article. The high gain transmitarray antenna presents using Huygens' principle at 15 GHz. The transmitarray surface consists of trilayer H-shaped slots on the middle of four symmetric slots on the edges of the unit cells. The placed slots induce Huygens’ resonances at three frequencies, 13.5 GHz, 15 GHz and 16.7 GHz which is caused by electric and magnetic surface currents on the transmitarray surface. This makes a wide bandwidth for the antenna performance. 360° phase distribution is obtained by increasing the H-shaped slots legs. Since no dielectric substrate used between layers, the transmission coefficient is near 1 (0 dB) through the whole range. For experimental results, the trilayer artificial metallic surfaces with substrateless conductive slotted unit cells is fabricated. The test results presented the transmitarray antenna peak gain is measured 28.6 dB at operating frequency, 15 GHz. Ultra wide band antenna with 3 dB gain bandwidth of 30% and high aperture efficiency of 42.66%.

Conversion and Active Control between BIC and Absorber in Terahertz Metasurface

A multifunctional switchable metamaterial device based on graphene, a gold layer, polyimide, vanadiµm dioxide (VO2), and the sapphire substrate is designed in this paper. The top layer consists of a gold wire, graphene, and two split-ring resonators with the same parameters. By adjusting the Fermi level of graphene, the regulation of BIC and quasi-BIC is realized, and the conversion between BIC and absorber is realized by adjusting the conductivity of VO2. When the device is converted into a wave-absorbing device with single-band absorption characteristics, the Fermi level of graphene at this time is 0.001 eV, the absorption peak at 0.820 THz is higher than 99.5%, and when the Fermi level of regulated graphene is 1 eV, the absorption peak at 0.667 THz is also higher than 99.5%. The peak frequency of the device is 0.640 THz when it converts to quasi-BIC. To the best of our knowledge, this is the first time that the conversion and regulation of BIC and absorber have been achieved using these two phase change materials. Moreover, by adjusting the parameters of the metamaterial structure, the working efficiency and frequency of BIC and absorber can be dynamically adjusted. The electric field distribution and surface current of metamaterials are further studied, and the physical mechanism of effective absorption and BIC is discussed. These results show that the metamaterials proposed in this paper have many advantages, such as terahertz absorption, BIC, and active device control, and are of great significance for developing terahertz multifunctional devices.

Graphene‐Based Flexible Optically Transparent Dual‐Tunable Metasurface

AbstractDynamically tunable flexible metasurfaces with optical transparency are essentially useful in stealth, electromagnetic sensing, and camouflage while keeping continuous optical observation and communication. In this paper, a dual‐tunable graphene‐based metasurface is designed based on patterned graphene sandwich structures, showing independent dynamic control of reflection amplitude and resonance frequency, excellent optical transparency, and outstanding flexibility. Both the simulated and measured results demonstrate that the transition from dual band absorption at 12 and 24.8 GHz to broad band absorption from 10 to 25.7 GHz, and the absorption amplitude can be tuned between −5 and −15 dB on average in each case dynamically and independently by applying bias voltage to graphene layers. Lastly, the distributions of the induced electric field and surface currents, as well as an equivalent circuit model, are provided to illustrate the tunable electromagnetic absorption mechanism. The designed metasurface has potential applications that are speculated in the fields of electromagnetic tune and electromagnetic stealth.

Dual-wideband radiating surface using interleaved electric and magnetic currents: Underlying physics and experimental verification

Unlike popular multiband antenna array radiation based on either electric or magnetic surface currents, the use of mutually interleaved and tightly coupled electric and magnetic currents results in an aperture-reuse space-efficient multiband radiating surface for highly integrated antenna-frontend architecture and spatial power combining design scenarios. In this work, slot and dipole modes corresponding to magnetic and electric currents are effectively interleaved and excited in a surface to develop a space-efficient dual-wideband aperture-shared radiating surface. In this case, due to an effective reuse of the antenna aperture over both frequency bands, a high aperture-reuse efficiency is achieved. First, we devise a planar magneto-electric (ME)-dipole-alike antenna and analyze it in both the frequency and time domain. The antenna is then studied by the characteristic mode theory and the findings are validated using full-wave simulations. The developed planar ME-dipole-alike antenna is used to realize a dual-wideband radiating surface in which electric and magnetic currents are mutually coupled and interlaced, which is excited by properly oriented and distributed sources on the antenna's surface. Eventually, a highly isolated dual-wideband prototype was developed and fabricated using a cost-effective multi-layer Printed Circuit Board (PCB) process that operates in the Ku-band with both impedance and gain bandwidth of approximately 42% and in the Ka-band with respective impedance and gain bandwidth of 29% and 16.32%.

Huygens' surface excitation for the finite element method applied to Maxwell's equations – A construction based on Nitsche's method

We present a Huygens' surface for the finite element method applied to Maxwell's equations, where the equivalent electric and magnetic surface currents are incorporated in the weak form by means of Nitsche's method. The proposed method preserves the reciprocity of Maxwell's equations and it allows for the computation of the total field inside the Huygens' surface, whereas on its outside only the scattered field is computed. The equivalent magnetic surface current at the Huygens' surface requires a double representation of the discontinuous tangential component of the electric field and we demonstrate that it can be efficiently combined with a previously presented higher-order brick-tetrahedron hybridization. Also, it is demonstrated that the near-to-far-field transformation can be evaluated in an accurate manner if collocated with the Huygens' surface, which allows for a compact computational domain and a reduction in the required computational resources. The proposed Huygens' surface is tested on two scattering problems with perfect electric conductor scatterers: (i) a sphere that demonstrates second-order convergence towards the analytical result for a piecewise linear approximation of the electric field; and (ii) a double ogive with two sharp tips which gives a computed monostatic radar cross section that compares well with measurements and computations in the open literature for both polarizations.

ПРИБЛИЖЕННЫЕ АСИМПТОТИЧЕСКИЕ ВЫРАЖЕНИЯ ЭЛЕКТРОМАГНИТНОГО ПОЛЯ ИСТОЧНИКОВ ВБЛИЗИ ГЛАДКОЙ ВЫПУКЛОЙ ПРОВОДЯЩЕЙ ПОВЕРХНОСТИ ВРАЩЕНИЯ

Approximate asymptotic solution is developed for the electromagnetic field due of a surface magnetic and electric currents located near an arbitrary smooth convex conducting surface of rotation of large size. The expressions of field are valid in a near-surface layer with a thickness of the order of the wavelength and have the form of a sum of a series of azimuthal harmonics and an integral over a continuous spectrum of eigenfunctions of the field. The coefficients of the series are expressed by integrals from the product of a given distribution of sources with eigenfunctions. For eigenfunctions, both general integral representations and closed expressions in terms of Airy functions are obtained, which are uniformly valid along surface of a rotation for the case of one pole by the parabolic equation method. The field expressions take into account the inseparability of the field by the sum in term of E- and H-type fields, are uniformly valid in the near-surface layer, excluding the vicinity of the poles of the rotation surface, and have no discontinuities on the caustics of surface rays. The expressions obtained were used to calculate the mutual admittances between two annular slots on a semi-infinite and smoothly truncated conical surface. Numerical results obtained by the proposed and rigorous methods for a semi-infinite cone were compared. It is shown that in the case of in-phase annular slots in a semi-infinite cone, the obtained asymptotic expression for mutual admittance coincides with the main term of the asymptotic of a strict solution based on the method of eigenfunctions.

Broadband metamaterial absorbers based on magnetic composites

The thickness and absorption width of electromagnetic wave-absorbing- materials remain a considerable challenge. This paper proposed a new design method for metamaterial absorbers. The absorber is composed of magnetic composites with a periodic structure. The effective absorption bandwidth (reflection loss <−10 dB) achieves 13.4 GHz, from 4.6 GHz to 18 GHz with 3.5 mm thickness (0.05 λmax). There are two absorption peaks at 6.1 GHz and 10.8 GHz, the reflection loss reaches −20 dB and −15.6 dB, respectively. The loss mechanism is analyzed by analyzing the electric field distribution and surface current. Actual samples were prepared, their reflection losses were measured, and the test results verified the simulation results.

Self-isolated MIMO antenna using mixed coupling by close coupling technique

A self-isolated multiple-input-multiple-output (MIMO) antenna in a compact shared ground structure is proposed for 5G systems. The proposed MIMO antenna consists of customized M-pattern, closely coupled members. It benefits to attain good isolation of the targeted bandwidth transversely without additional de-coupling structures. It is discovered that the arm of M-pattern antenna members can cancel out the coupling on the system and achieve sound isolation among antenna members. A relevant matching circuit model is discussed to show how the suggested theory works in principle. The mixed couplings among antenna members neutralize by modifying the antenna shape with the help of electric and magnetic coupling and surface currents. The proposed self-isolated 2-member MIMO antenna demonstrates sound isolation superior to 15 dB transversely in the frequency bands dedicated to 5G NR: n48/n78 and long-term evolution (LTE) band 42/43/48/52 (3.2–3.98 GHz). Moreover, the proposed 2-member design structure has a scalability advantage. It is extended into an 8-members structure, where a pair of antennas located at each side of the frame offers orthogonality. The proposed 8-members M-pattern MIMO is validated using fabricated and simulated measurements. The investigational results show that the 8-members MIMO (M-shaped) system is effective in higher order MIMO antenna design and offers more than 20 dB isolation transversely in the frequency band 5G NR n48 and LTE band 42/43/52(3.29–3.66 GHz).

Numerical analysis of scattering fields by a multiple plane grating using shadow theory.

In the shadow theory, a new description of electromagnetic fields using scattering factors has been employed. This paper presents a new numerical method based on scattering factors for the scattering problem of a composite dielectric grating embedded with conducting strips. The scattering factors for the primary fields, which are based on the assumption of conducting strips being removed completely and those for the secondary fields generated by the surface electric currents on conducting strips, are introduced. The presented method is formulated to obtain scattering factors for the total fields and Joule losses for propagating wave and evanescent wave incidences from the currents determined by using the Galerkin procedure. Numerical examples are given for an asymmetric multiple plane grating consisting of conducting strips. The scattering properties and the normalized Joule losses are calculated for propagating wave and evanescent wave incidences. It is shown that the diffraction efficiencies and scattering factors hold the symmetries on the reciprocity in the case of resistive plane gratings.

Single-event burnout hardening evaluation with current and electric field redistribution of high voltage LDMOS transistors based on TCAD Simulations

—A single-event burnout (SEB) hardened design based on high voltage lateral double-diffused metal-oxide-silicon (LDMOS) devices with an optimal partial buried oxide (BOX) layer and a N-buffer layer is firstly proposed in this paper. By analyzing the response of surface electric field and transient current, the optimal parameters of hardened layers are selected. Simulation results reveal that an optimal buffer layer can suppress the peak electric field from 4.5 MV/cm to 2 MV/cm, recreate the position of peak electric field and an optimal BOX layer can reconstruct the path of electron and hole currents, reducing the risk of parasitic bipolar-junction-transistor (BJT). By contrast, the SEB triggering voltage can be improved from 197 V to 396 V, with an increase of 100%. And the ratio of safe operating area (SOA) with SEB to breakdown voltage (BV) can be increased from 30% to 69%. In the case of heavy-ions with different energies, the SEB hardened LDMOS also has better performance than the conventional one.

Discontinuous Galerkin integral equation method for light scattering from complex nanoparticle assemblies.

This paper presents a discontinuous Galerkin (DG) integral equation (IE) method for the electromagnetic analysis of arbitrarily-shaped plasmonic assemblies. The use of nonconformal meshes provides improved flexibility for CAD prototyping and tessellation of the input geometry. The formulation can readily address nonconformal multi-material junctions (where three or more material regions meet), allowing to set very different mesh sizes depending on the material properties of the different subsystems. It also enables the use of h-refinement techniques to improve accuracy without burdening the computational cost. The continuity of the equivalent electric and magnetic surface currents across the junction contours is enforced by a combination of boundary conditions and local, weakly imposed, interior penalties within the junction regions. A comprehensive study is made to compare the performance of different IE-DG alternatives applied to plasmonics. The numerical experiments conducted validate the accuracy and versatility of this formulation for the resolution of complex nanoparticle assemblies.

Inverse MoM Approach to Near-Field Prediction and RFI Estimation in Electronic Devices With Multiple Radiating Elements

An inverse method of moments (MoM) approach is developed to estimate the equivalent electric/magnetic current sources to predict radio frequency interference (RFI) in electronic devices. The proposed method is designed to reconstruct the noise sources in electronic devices containing multiple radiating elements by using a finite metal object carrying electric surface currents. The surface current elements are further applied to calculate the electromagnetic fields on arbitrary observation planes near the device under test (DUT). The method is validated through numerical simulation examples, including electric-type CPU noise, magnetic-type non-planar HDMI connector noise, printed circuit board (PCB) with Wi-Fi and PIFA antennas, and heat sink embedded in the DUT. The results confirm less than 0.4 dB difference in the predicted pattern at the antenna operating frequency when a triangular segmentation is applied in the vicinity of the noise source area, and the equivalent surface current is calculated at the edges of the Rao-Wilton-Glisson (RWG) meshes. The proposed method is a promising ’source reconstruction’ candidate for predicting the near-field radiation characteristics of electronic devices with multiple peaks and nulls in the near-field radiation pattern. The method helps estimate the level of RFI by summing up the contributions of all the dipoles of the equivalent noise source derived by solving forward and inverse problems. The RFI results based on the inverse MoM approach are validated by comparing them with those obtained from CST simulation, and good agreement is achieved between the two.

Wave Diffraction by Metamaterial-Coated Wedges: The UAPO Solution for Skew Incidence

The interaction between an electromagnetic plane wave and a metallic wedge coated with a uniform layer made of a double-negative metamaterial is studied by means of the uniform asymptotic physical optics method in the high-frequency range, e.g., at microwave and optical frequencies. The apex angle of the structure is arbitrarily chosen, and the wave is at a skew incidence with respect to the external edge, which is formed by the metamaterial layers covering the wedge faces. The proposed method is built on the scattering integral involving electric and magnetic surface currents as physical optics equivalent sources, and it takes advantage of analytic evaluations. The last step uses a uniform asymptotic procedure to obtain a closed form expression of the diffracted field to be added to the geometrical optics one for computing the total field at the observation point in the neighboring free space. The study also includes a numerical validation of the method.

Rational design and fabrication of optically transparent broadband microwave absorber with multilayer structure based on indium tin oxide

A multilayer metamaterial absorber (MMA) with optically transparent and broadband microwave absorption characteristics based on Indium Tin Oxide ( ITO) and polymethyl methacrylate (PMMA) was designed and fabricated. The microwave absorption properties can be regulated by the resistance of ITO and the structural parameters of the unit cell. In the frequency range of 2.64–18 GHz, more than 90 % microwave absorption can be achieved. The microwave attenuation mechanism was investigated through equivalent electromagnetic parameters, impedance matching, electric and magnetic field distribution, power loss density and layer electric current at special frequencies. The microwave absorption performance at different incident angles under TE and TM polarization models was investigated to explore the angle-sensitive properties. The average transmittance of the absorber in the visible light wavelength range (400–800 nm) was also measured. The experimental and simulated microwave absorption rates are in accordance, indicating the potential application of the proposed absorber in the field of transparent microwave absorption. • Visible light transparent metamaterial absorber is fabricated. • The microwave absorbance over 90 % can be achieved within 2.64–18 GHz. • The metamaterial absorber has polarization insensitive and wide-angle stability properties. • Microwave attenuation mechanisms were investigated by surface electric current.

Ultra-broadband origami absorber with large angle stability in the THz region

A three-dimensional origami-structured absorber based on V O 2 is designed. The unit structures of the origami absorber are folded from both sides to the middle, and a cavity is formed. After simulation, it is found that this absorber possesses insensitivity to polarized electromagnetic waves and stability at large incident angles. In addition, the origami absorber exhibits good absorption performance at low frequencies. An absorption band with absorptivity over 0.9 at 0.61–6.5 THz can be formed in TE mode. The coverage of the absorption band exceeds 10 octaves, and the relative bandwidth is 165.7%. In TM mode, the absorption band is located at 0.68–6.5 THz, which exceeds 9.5 octaves, and the relative bandwidth is 162.1%. We demonstrate the absorption mechanism by analyzing the electric field, surface current, and magnetic field distribution.

Coherent Asymmetric Absorbers

Most applications of metasurfaces require excitation and control of both electric and magnetic surface currents. For such purposes, the metasurface must have a finite thickness to handle magnetic surface currents. For metasurface sheets of negligible thickness that offer only electric response, coherent illumination can compensate the need to create discontinuities of the tangential electric field component using magnetic surface currents. Most of the known coherent metasurfaces are space uniform and can control only plane-wave absorption and specular reflection. However, it is also known that periodical space-modulated (inhomogeneous) metasurfaces can be used to realize anomalous reflection, refraction, and other useful effects. In this paper, we propose the concept of a coherently illuminated space-modulated metasurface that functions as a coherent asymmetric absorber. We study its behavior under nonideal illumination and suggest applications related to sensing.

Расчет двузеркальной антенны по методу физической оптики с учетом многократных переотражений.

Calculation of a double reflector Cassegrain antenna by physical optics method with taking into account multiple reflections between the reflector and the subreflector was performed. It was shown that the convergence of antenna characteristics (gain, antenna efficiency, side-lobe level) with the increase of accounting reflections is observed. To check the method of multiple reflections the same Cassegrain antenna was calculated by the method of electric field integral equation with the unknown surface electric currents on the reflector and the sub-reflector. The comparison showed the coincidence of the result obtained by two different methods. The calculation of gain and efficiency of a Cassegrain antenna in frequency range from 1 to 10 GHz was performed by physical optics method with multiple reflections.

High-confinement ultra-wideband bandpass filter using compact folded slotline spoof surface plasmon polaritons

A novel bandpass filter (BPF) based on spoof surface plasmon polaritons (SSPPs) using a compact folded slotline structure is proposed and experimentally demonstrated. The proposed novel SSPPs structure compared with a conventional plasmonic waveguide with slot line SSPPs unit structure at the same size, the considerable advantages in much lower asymptotic frequency with tight field confinement, which enable the proposed filter to be more miniaturization. A high-efficient mode conversion structure is designed to transition from TE-mode to SSPPs-mode by gradient slotline lengths. The low-frequency stop-band can be committed with microstrip to slotline evolution on both sides of the dielectric, while the high-frequency cutoff band is realized by the proposed SSPPs structure. The influence of dispersion relation, electric field distribution, surface current, and structural parameters on the transmission characteristics of the proposed BPF are analyzed by finite difference time domain (FDTD). To validate the design concept, the prototype of the miniaturized SSPPs BPF has been manufactured and measured. The experimental results show high performance of the fabricated sample, in which the working in a range of 0.9 GHz–5.2 GHz with the relative bandwidth is 142%, the insertion loss less than 0.5 dB, the reflection coefficient less than −10 dB, and the group delay is less than one ns. This works provides a mirror for realizing the miniaturization of waveguides, and the application and development of high-confinement SSPPs functional devices in the microwave and THz regimes.