Full-wave Analysis Research Articles

Моделирование резонансной спиральной электрически малой антенны

Currently, the development of methods and means of data transmission through absorbing media and shielding obstacles for organizing wireless communication and remote control of technological equipment and industrial robots, including those in the mining industry, is an urgent area of research. As experimental studies in mine workings have shown, radio systems with high-quality tuned resonant antennas from hundreds of kHz to several of MHz with a narrow operating frequency band suitable for transmitting low-speed signals turned out to be promising. In this article, a model of a resonant helical electrically small antenna (ESA) with an electrical size of 0.025 is considered. An equivalent circuit of this antenna is presented using an analytical description of its components. The results of a full-wave finite element analysis of a helical ESA using finite conductivity boundary are presented. Graphs are constructed that explain the resonant increase in the efficiency of the antenna. The obtained values of the efficiency of the spiral ESA are sufficient to create means of data transmission through absorbing media and imperfectly shielding obstacles.

Broadband Chiral-Type Linear to Linear Reflecting Polarizer With Minimal Bandwidth Reduction at Higher Oblique Angles for Satellite Applications

This work presents a broadband linear–cross polarizer for K- and Ka-band applications. The design consists of a simple asymmetric width-based meander-line metasurface printed on a thin FR-4 grounded dielectric substrate. Normal incidence demonstrates 90% polarization conversion ratio (PCR) bandwidth (BW) of 20.64 GHz from 18.31 to 38.95 GHz with 72.1% fractional BW (FBW). Due to the destructive interference involved at greater oblique angles, reflective polarizers experience severe degradation of 90% PCR BW response. The proposed polarizer’s performance is obliquely stable up to 43° for transverse electric (TE) and 45° for transverse magnetic (TM) incidence with minimal 90% PCR BW reduction of only 13.95% (TE) and 15.25% (TM) compared with normal incidence. For the first time, transfer matrix method (TMM)-based equivalent surface impedance technique is modeled for oblique incidence analytically, closely resembling the full-wave analysis. The design is compact with a periodicity of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\lambda \text{o}$ </tex-math></inline-formula> /5.98 and a thickness of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\lambda \text{o}$ </tex-math></inline-formula> /13.69. The surface current patterns at resonant frequencies illustrate the reason behind broadband behavior. Bistatic radar cross section (RCS) analysis of the proposed converter is studied with reference to PEC. To the best of the author’s knowledge, this structure demonstrates broadband response with wide angular stability with less than 90% PCR BW reduction at higher oblique angles reported so far.

Improved Beamforming in 3D Space Applied to Realistic Planar Antenna Arrays by Using the Embedded Element Patterns

Most of beamforming methods rely on the proper estimation of the steering vectors of the incoming signals in order to calculate appropriate array feeding weights. However, this estimation is often performed on a theoretical basis, since most methods assume that the array elements radiate like isotropic sources and consider only the phase differences between them due to their different spatial positions. This is a rough estimation as it ignores both the non-isotropic radiation pattern of the array elements and the mutual coupling between them. To overcome these limitations, we use a different approach for the construction of steering vectors based on the embedded patterns of the array elements, extracted through full-wave analysis. This approach is used in this paper to modify two well-known beamforming methods, namely the null steering beamforming and the minimum variance distortionless response method. Both modified methods are applied to a realistic model of a microstrip planar antenna array, and thus, both the azimuth and polar angles of the main lobe and nulls directions are controlled (beamforming in 3D space). Extensive statistical analyses are performed by implementing several scenarios of escalating difficulty, in order to examine the performance and temporal response of the modified beamforming methods in comparison to the respective conventional methods and also in comparison to beamforming methods based on evolutionary techniques.

Wide-band full-wave electromagnetic modal analysis of the coupling between dark-matter axions and photons in microwave resonators

The electromagnetic coupling axion-photon in a microwave cavity is revisited with the Boundary Integral - Resonant Mode Expansion (BI-RME) 3D technique. Such full-wave modal technique has been applied for the rigorous analysis of the excitation of a microwave cavity with an axion field. In this scenario, the electromagnetic field generated by the axion-photon coupling can be assumed to be driven by equivalent electrical charge and current densities. These densities have been inserted in the general BI-RME 3D equations, which express the RF electromagnetic field existing within a cavity as an integral involving the Dyadic Green functions of the cavity (under Coulomb gauge) as well as such densities. This method is able to take into account any arbitrary spatial and temporal variation of both magnitude and phase of the axion field. Next, we have obtained a simple network driven by the axion current source, which represents the coupling between the axion field and the resonant modes of the cavity. With this approach, it is possible to calculate the extracted and dissipated RF power as a function of frequency along a broad band and without Cauchy-Lorentz approximations, obtaining the spectrum of the electromagnetic field generated in the cavity, and dealing with modes relatively close to the axion resonant mode. Moreover, with this technique we have a complete knowledge of the signal extracted from the cavity, not only in magnitude but also in phase. This can be an interesting issue for future analysis where the axion phase is an important parameter.

Detection and Identification of System Level Soft Failure Induced by Radio Frequency Interference in Small UAV System

A system level methodology is presented for soft failure detection and analysis in small unmanned aerial vehicle (UAV) system, induced by radio frequency interference (RFI). This method includes a radio frequency test system based on the equivalent dynamic test method, and soft failure detection and identification method based on ground control station observation records and system log analysis. By designing signal forwarding system for global positioning system, the equivalent dynamic flight state of the UAV is realized. Through the application of standard radiated susceptibility test methods, the effects of RFI with multiple interference levels covering the frequency range from 2 MHz to 3 GHz on small UAV systems have been investigated. RFI is coupled into the UAV system through the antenna coupling and cable coupling. Soft failure modes are classified and failure analysis is mainly carried out through system log analysis, combined with full-wave simulation analysis, the root cause of the soft failure is determined. The understanding of the soft failure mode and susceptibility is beneficial to the design of UAV system, improving the robustness of software and hardware.

Multifunctional resonant graphene four-port for THz and far IR regions

A new multifunctional resonant device for THz and far-infrared regions based on surface plasmon-polariton graphene resonator and waveguides is suggested and analyzed in this paper. The device consists of a circular graphene resonator and four nanoribbons serving as waveguides. Every waveguide is front-coupled to the resonator with a small gap between them. The waveguides are oriented with the angle 90∘ between them. The graphene elements are deposited on a dielectric substrate. The Fermi energy of graphene can be dynamically varied by applying an electrical potential difference between the graphene and a thin polysilicon layer which acts as an electrode. The resonator can work with dipole and quadrupole resonant modes. They are used to provide the functions of tunable band-pass filter, tunable power divider and switch. Using the scattering matrix description of the four-port, the circuit theory representation and full-wave analysis, we show that for the central frequency 14.52 THz the parameters of the developed device are as follows: the Q-factor due to use of resonant structure is (6÷8), the matching in the pass-band with return loss of − 17 dB and low insertion loss of about − 1.0 dB. The component provides a tunability of the central frequency and the power ratio between the three output ports can be projected in a wide range. In the OFF regime, the transmission coefficients to output ports are lower than − 42 dB.

On the modularized analysis method for ceramic‐filled waveguide cavity filters

This article makes a systematic study on an analysis method called modularized analysis method (MAM) for both inline and cross-coupled ceramic-filled waveguide cavity filters (WCFs). Compared with full-wave numerical analysis method, equivalent circuit model method (ECMM) and mode-matching (MM) method, MAM achieves a good balance between accuracy and running speed. First, the network analysis principles of MAM through cumulative product of transfer matrices for inline WCFs and generalized connection method for cross-coupled WCFs are presented. Second, the determination of split planes in process of module decomposition, the key factor affecting MAM for ceramic-filled WCFs, is well examined. It is shown that setting split planes at chamfer ends is beneficial for improving the accuracy of MAM. Moreover, for cross-coupled ceramic-filled WCFs, an unequal-chamfer scheme needs to be adopted in order to set split planes correctly. Third, three analysis examples are given to verify the effectiveness of MAM for both inline and cross-coupled ceramic-filled WCFs. Finally, the practicability of MAM in design of cross-coupled ceramic-filled WCFs is demonstrated by combining it with space mapping algorithm.

Optimizing and Quantifying Gold Nanospheres Based on LSPR Label-Free Biosensor for Dengue Diagnosis

The localized surface plasmon resonance (LSPR) due to light–particle interaction and its dependence on the surrounding medium have been widely manipulated for sensing applications. The sensing efficiency is governed by the refractive index-based sensitivity () and the full width half maximum (FWHM) of the LSPR spectra. Thereby, a sensor with high precision must possess both requisites: an effective and a narrow FWHM of plasmon spectrum. Moreover, complex nanostructures are used for molecular sensing applications due to their good values but without considering the wide-band nature of the LSPR spectrum, which decreases the detection limit of the plasmonic sensor. In this article, a novel, facile and label-free solution-based LSPR immunosensor was elaborated based upon LSPR features such as extinction spectrum and localized field enhancement. We used a 3D full-wave field analysis to evaluate the optical properties and to optimize the appropriate size of spherical-shaped gold nanoparticles (Au NPs). We found a change in Au NPs’ radius from 5 nm to 50 nm, and an increase in spectral resonance peak depicted as a red-shift from 520 nm to 552 nm. Using this fact, important parameters that can be attributed to the LSPR sensor performance, namely the molecular sensitivity, FWHM, , and figure of merit (FoM), were evaluated. Moreover, computational simulations were used to assess the optimized size (radius = 30 nm) of Au NPs with high FoM (2.3) and sharp FWHM (44 nm). On the evaluation of the platform as a label-free molecular sensor, Campbell’s model was performed, indicating an effective peak shift in the adsorption of the dielectric layer around the Au NP surface. For practical realization, we present an LSPR sensor platform for the identification of dengue NS1 antigens. The results present the system’s ability to identify dengue NS1 antigen concentrations with the limit of quantification measured to be 0.07 μg/mL (1.50 nM), evidence that the optimization approach used for the solution-based LSPR sensor provides a new paradigm for engineering immunosensor platforms.

High efficiency coupling to metal-insulator-metal plasmonic waveguides.

A periodic array of dual-Vivaldi antennas integrated with metal-insulator-metal (MIM) plasmonic waveguides was designed and investigated for its infrared light absorbance efficiency. Full-wave analysis was used to optimize MIM waveguides compatible with parallel and series connected DC leads without sacrificing radiation efficiency. Free-space to MIM waveguide in-coupling efficiency as high as 41% has been obtained in a sub-wavelength unit cell geometry at a wavelength of 1373 nm. Higher efficiency, up to 85%, is predicted with a modified design including a backplane reflector. A nanofabrication process was developed to realize test devices and far-field optical spectroscopy was used as experimental evidence for antenna-waveguide matching.

Terahertz waveguide-based pulse-shaper system analysis and modeling

In this paper, the transfer function (TF) of a passive waveguide-based terahertz (THz) pulse shaper is calculated using the time domain data provided by the full-wave simulation of the structure. The fractional order of the TF is determined based on the time response resulting from an arbitrary excitation of the proposed pulse shaper. Full-wave electromagnetic numerical analyses are applied to attain the time-domain output data of the helical gold-ribbon dielectric-lined waveguide as the terahertz pulse shaper. To verify the simulation results, the proposed device has been examined using two different numerical methods including the Finite Element Method (FEM) and the Finite Integral Technique (FIT). A good agreement was found between the results of the FIT and the FEM. The use of the system transfer function to analyze the structure is preferable to the full-wave simulation due to execution time savings. Once the TF is determined, one could apply it to subsequent time-domain analyses of the pulse shaper with various inputs.

Equivalent circuit model of tower based on full-wave analysis

The tower model is very important for the assessment of lightning protection for transmission line. The parameters of tower model mainly rely on the impulse experiments of tower. There is a difference between the current channel of the experiments and the lightning strikes, which will result in different impulse responses of the towers. Based on FDTD method, the insulator voltage and current distribution of the tower were calculated when impulse current injected into tower along the lightning strike channel. The parameters of the equivalent model of the tower were determined which can reproduce the insulator voltage, the current flowing into the tower and the current flowing into ground wire.

Neural network inverse model for multi-band unequal Wilkinson power divider

PurposeThe purpose of this paper is to build a neural network (NN) inverse model for the multi-band unequal-power Wilkinson power divider (WPD). Because closed-form expressions of the inverse input–output relationship do not exist, the NN becomes an appropriate choice, because it can be trained to learn from the data in inverse modeling. The design parameters of WPD are the characteristic impedances, lengths of the transmission line sections and the isolation resistors. The design equations used to train the NN inverse model are based on the even–odd mode analysis.Design/methodology/approachAn inverse model of a multi-band unequal WPD using NNs is presented. In inverse modeling of a microwave component, the inputs to the model are the required electrical parameters such as reflection coefficients, and the outputs of the model are the geometrical or the physical parameters.FindingsFor verification purposes, a quad-band WPD and a penta-band WPD are designed. The results of the full-wave simulations verify the validity of the design procedure. The resulting NN model outperforms traditional time-consuming optimization procedures in terms of computation time with acceptable accuracy. The designed WPDs using NN are implemented by microstrip lines and verified by using full-wave analysis based on high-frequency structure simulator (HFSS). The results of the microstrip WPDs have good agreements with the corresponding results obtained by using ideal transmission line sections.Originality/valueThe associated time-consuming procedure and computational burden in realizing WPD through optimization are major disadvantages; needless to mention the substantial increase in optimization time because of the multi-band design. NNs are one of the best candidates in addressing the abovementioned challenges, owing to their ability to process the interrelation between electrical and geometrical/physical characteristics of the WPD in a superfast manner.

FILTER BASED ON SPLIT RING RESONATOR

This paper presents a novel wideband bandpass filter making use of split ring resonator (SRR) as the basic ring resonant unit. The resonant characteristic of SRR is carefully studied through full wave analysis. The coupling of SRR structure is very effective that can be used to realize wideband filter with small insertion loss. A filter with center frequency at 2.4GHz, passband 1.8GHz to 3.4GHz is designed using FR4 dielectric substrate with 1.6mm thickness. The simulated results are good consistent.

Active focusing and manipulation of light beam through Ag grating covered by graphene

An electrically controllable focal length is proposed for the visible wavelength range. The proposed structure is composed of a graphene sheet placed on a silver grating. The effect of the chemical potential variation of the graphene sheet on the light wave deflection, and hence the focal length of the structure, is investigated. The results of the full-wave simulation analysis based on the finite difference time domain (FDTD) method show that the focal length of the structure varies by approximately 7.82λ through changing the chemical potential of graphene from 0.1 to 1 eV. In addition, a generalized equivalent circuit model is introduced for the analysis of the proposed tunable graphene structure. The achieved results based on the circuit model match well with those based on the FDTD method. The proposed structure has the potential to be used in imaging devices and optical sensors.

Radial GRIN Lenses Based on the Solution of a Regularized Ray Congruence Equation

We introduce a novel formulation for flat radial GRadient INdex (GRIN) lenses allowing for the optimal lens design through closed-form expressions. The validity of the proposed formulation covers a very large range of GRIN lens design parameters (focal distance, lens thickness, and maximum refractive index). The formulation is based on the derivation of a new form of nonlinear integral equation representing the equalization of all the optical ray-path lengths, denoted as regularized ray congruence (RRC) equation, and on its closed-form solution. An analytical form of aperture efficiency is given for standard feed patterns. The application of the formulas presented here allows for an instantaneous design for medium/high gain antennas with controllable total aperture efficiency till 80&#x0025;. The accuracy of the formulation is tested by a full-wave analysis and compared with other formulations available in the literature. We found that the new formulation proposed here significantly reduces the phase error in a wide range of the lens parameters, thus allowing for a more efficient, accurate, and flexible design for GRIN lenses. As a proof of concept, a thin GRIN lens antenna for operation in E-band (60&#x2013;90 GHz) is designed, demonstrating high aperture efficiency (63&#x0025;) across a wide frequency range.

Harmonic Balance/Full-Wave Analysis of Wearable Harmonic Transponder for IoT Applications

The article presents a novel design of a compact wearable harmonic transponder with double-plane symmetry, composed of a dual-band patch-type antenna loaded by an HSMS-2820 Schottky diode, operated as a proof of concept at ISM UHF 869 and 1734 MHz frequencies. The antenna is analyzed and optimized for a minimum ground plate size by means of the CST Microwave Studio electromagnetic simulator, and its reflection coefficient is incorporated into the equivalent circuit model for a combined harmonic balance (HB) and full-wave analysis using the AWR Microwave Office commercial simulator. The transponder performance, including the complex input impedance matching and conversion loss (CL) between the fundamental and second harmonic frequencies on the diode, was evaluated both in free space and when attached to a human muscle phantom. The total harmonic transponder CL, including diode CL, antenna transponder gains, and impedance mismatching, is 6.2 dB for an excitation power of −25 dBm at the antenna–diode interface. The measured reading distances are 9.0 and 8.8 m for equivalent isotropically radiated power (EIRP) <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$=20$ </tex-math></inline-formula> dBm when the transponder is placed in free space and on the human body, respectively. As a means of machine-to-person communication, the transponder is suitable for the Internet of Things (IoT) concept, e.g., for the identification of pedestrians in traffic, i.e., in a complex environment with unwanted radiation clutter and multipath fading.

Electromagnetic Backscattering Mechanisms of Frequency Selective Surfaces for Effective Analysis of Radar Cross Section by the First-Order Approximation of Floquet Modes

Full-wave analysis of finite but electrically large frequency selective surfaces (FSSs) substrates for the radar cross section (RCS) estimation is too time-consuming and unbearable for practical applications. Such FSS substrates can be either absorbing or reflective types and are widely used as radomes of antennas for stealth applications, where the electromagnetic (EM) backscattering is of much concern. This large EM problem is simplified by applying Floquet mode decomposition on the scattering fields, where the Kirchhoff approximation is employed to find the backscattering fields for RCS estimation. The resulted formula allows one to explore the scattering mechanism for RCS enhancement or reduction. Besides, the approximation is used to resemble the FSS radome by equivalent substrates. Thus, the transmission and reflection coefficients of the equivalent dielectric substrates are similar to those from FSS elements under an infinite array assumption. Afterward, the resulting EM problems of antenna radiations and scattering can be easily analyzed using the equivalent substrates of EM materials. Numerical examples of planar FSSs to form radomes demonstrate the feasibility of numerical simulations’ proposed work. The presented work can also be directly applied for fast analysis of EM shielding effectiveness by FSS substrates.

Dual-band multifunctional coding metasurface with a mingled anisotropic aperture for polarized manipulation in full space

Integrated metasurfaces with diversified functionalities have demonstrated promising prospects for comprehensive implementations in compact 5G/6G communication systems by flexibly manipulating electromagnetic (EM) waves. Increasingly emerged multifunctional metasurfaces have successfully revealed integrated wavefront manipulations via phase gradient arrays, coding apertures, independent polarization control, asymmetric transmission/reflection, etc. However, multifunctional metasurfaces with more degrees of freedom in terms of multi-band/broadband operation frequencies, full-space coverage, and computable array factors are still in dire demand. As a step forward in extending manipulation dimensions, we propose and corroborate a dual-band multifunctional coding metasurface for anomalous reflection, radar cross-section reduction, and vortex beam generation through full-wave analysis and experiment. Our tri-layer meta-device comprises a shared coding aperture of split-ring and cross-shaped resonators sandwiched between two layers of orthogonal wire gratings. With an approach of independent control of a reflection–transmission wavefront under orthogonal polarization states and Fabry–Perot-like constructive interference, the low-cross-talk shared coding aperture features a smooth phase shift and high efficiency for 3-bit coding in the K-band and 1-bit coding in the Ka-band. Both numerical and measured results verify that the proposed coding metasurface can effectively realize full-space EM control and improve the capacity of the information channel, which could be developed for potential applications in multifunctional devices and integrated systems.

Parallel full-wave electromagnetic field analysis based on domain decomposition method

Parallel full-wave electromagnetic field analysis based on domain decomposition method

Transistor Laser Antenna: Electromagnetic Model in Transmit and Receive Modes

Transistor laser can drive recent innovative technologies like optical antennas and rectennas. To this end, this semiconductor device requires an accurate electromagnetic model capable of determining the antenna characteristics like radiation pattern, directivity, gain, bandwidth, and polarization. Nonetheless, the current semiconductor models of transistor laser describe the absorption and emission of light mainly by simplified expressions and circuit models. These models usually overlook the actual physical geometry and full-wave light-emitting analysis of the device. In this article, a comprehensive computational electromagnetic modeling and characterization is presented for transistor laser. The existing semiconductor and electromagnetic equations are reorganized in a systematic fashion, coupled, and solved numerically to get the electromagnetic field components emitted or absorbed by the device. These fields determine the radiation pattern, directivity, gain, bandwidth, and polarization of transistor laser in transmit and receive modes. The equations involved in the above electromagnetic model are the Poisson and continuity equations incorporating radiative and non-radiative recombination rates, the vector magnetic potential equation interacting with the Hamiltonian operator of electrons in valance and conduction bands, the equation of the dielectric properties fluctuations of semiconductor layers, and the Poynting vector determining the power flow. The constructed model demonstrates agreement with the general performance of the device in experimental reports.