The excitation of surface plasmon on a metallic grating can be observed by varying the polar angle, accompanied by the absorption of incident light. The absorption occurs at a resonance angle which is sensitive to the refractive index of the liquid coated on the surface of the grating. As a result, an application in index sensing is developed. However, the sensitivity by varying the polar angle is almost at the same level as a conventional prism couple-based sensor through angular detection. In our new setup, we propose two methods to improve the sensitivity to refractive index change using an index sensor. Our first method is a slight modification of the conventional setup by varying the azimuth angle instead of the polar angle. Absorption of the incident is also observed while scanning the azimuth angle. The second method is to utilize phase detection to realize high resolution in finding the refractive index of liquids. In the phase detection, a good linearity is observed in the experimental results, with a resolution 10 times higher than that of a conventional setup.

In this paper, an efficient volume surface integral equation (VSIE) method with nonconformal discretization is developed for the analysis of electromagnetic scattering from composite metallic and dielectric (CMD) structures. This VSIE scheme utilizes curved tetrahedral (triangular) elements for volume (surface) modeling and the associated CRWG (CSWG) basis functions for volume current (surface) current modeling. Further, a discontinuous Galerkin (DG) volume integral equation (VIE) method and a DG surface integral equation (SIE) approach are adopted for dielectric and metallic parts, respectively, which allow both conformal and nonconformal volume/surface discretization improving meshing flexibility considerably. Numerical results are provided to demonstrate the accuracy, efficiency, and flexibility of our scheme.

In this paper a staircase fractal curve is applied on a microstrip line fed truncated corner square patch antenna to achieve Super Wide Band (SWB) operation. The proposed antenna exhibits an impedance bandwidth from 0.1 GHz to 30 GHz with a ratio impedance bandwidth of 300:1 for S₁₁ ≤ -10 dB. The bandwidth enhancement of the proposed antenna structure due to the fractal curve is shown in a step by step manner. The Bandwidth Dimension Ratio (BDR) of the proposed antenna design is obtained as 496675. Relatively stable omnidirectional radiation pattern and satisfactory value of gain are obtained over the operation band. Time domain analysis has also been performed to check the applicability of the proposed design as SWB antenna.

Since electromagnetic compatibility studies intend to predict the compliance with electromagnetic standards, an accurate computation of both common and differential mode conducted noises is necessary. Modern networks-such as in automobiles that are known for supplying many electrical actuators-include many power converters and long cables (conductors) to efficiently manage power transfer. However, the presence of both converters and cables creates new electromagnetic compatibility issues. For example, the interaction between cables and converters becomes a noise source. For this reason, electromagnetic compatibility study becomes more complex. Therefore, the purpose of this paper is an attempt to propose an analytical model that computes noise sources by generating conducted signals within the network at any site, meaning all along the cable according to the CISPR16 standard. Our approach primarily consists of modeling conducted noise sources generated by converters connected to the DC-network, which are extracted and identified in both frequency and time domains. The electromagnetic compatibility modelling of converter's behaviour is performed by defining a mathematical switching function. The model is assessed with time domain simulations and identified by experimental measurements. Secondly, the extracted converter's model, based on equivalent noise sources, is used to predict the conducted noise inside a defined network at any location of the cable. The process of the network's modelling is realised through using the Multi-Transmission Line Method of lossless lines. This network's model is crucial for EMC analysis in order to evaluate the interaction degree between noise sources and cable parameters.

A surface wave antenna operating in the 2.4 GHz band and efficient for launching surface electromagnetic waves at metal/dielectric interfaces is presented. Theantennaoperation is based on the strong field enhancement at the antenna tip, which results in efficient excitation of surface waves propagating along nearby metal surfaces. Since surface electromagnetic waves may efficiently tunnel through deep subwavelength channels from inner to outer metal/dielectric interface of a metal enclosure,this antenna is useful for broadband radio communication through various conductive enclosures, such as typical commercial Faraday cages.

The problem of the shielding evaluation of an infinitesimally thin perfectly conducting circular disk against a vertical magnetic dipole is here addressed. The problem is reduced to a set of dual integral equations and solved in an exact form through the application of the Galerkin method in the Hankel transform domain. It is shown that a second-kind Fredholm infinite matrix-operator equation can be obtained by selecting a complete set of orthogonal eigenfunctions of the static part of the integral operator as expansion basis. A static solution is finally extracted in a closed form which is shown to be accurate up to remarkably high frequencies.

Cables and electronic devices typically employ electromagnetic shields to prevent coupling from external radiation. The imperfect nature of these shields allows external electric and magnetic fields to induce unwanted currents and voltages on the inner conductor by penetrating into the interior regions of the cable. In this paper, we verify a circuit model tool using a previously proposed analytic model [1], by evaluating induced currents and voltages on the inner conductor of the shielded cable. Comparisons with experiments are also provided, aimed to validate the proposed circuit model. We foresee that this circuit model will enable coupling between electromagnetic and circuit simulations.

In this paper, a control strategy based on second-order sliding mode is proposed for a permanent magnet synchronous motor (PMSM) drive system applying direct torque control with space vector modulation (DTC-SVM). This control strategy combines the principles of super-twisting algorithms, direct torque control, and space vector modulation, designed to overcome some obvious shortcomings, such as the large ripple of flux linkage and torque in traditional DTC, the poor robustness of traditional PI controllers, and the chattering of traditional sliding mode control. It gives the system good steady state and dynamic performance. The results show that the proposed method effectively solves the above shortcomings. Meanwhile, the control strategy effectively accelerates the dynamic response ability of the system and improves the robustness to parameter perturbation.

This study explores the variability in the electric field, plasma number density, and plasma velocity driven by high-frequency (HF) radio wave injected into the vertically stratified ionosphere at a millisecond time scale after switch-on of the radio transmitter. It was found that the modeconversion process of electromagnetic (EM) waves took place at the reflection heights of both the R-X (right-circularly polarized extraordinary wave, R-X) and L-O (left-circularly polarized ordinary wave, L-O) modes. The ionospheric electron number density was remarkably oscillatory. A depletion of ionospheric ion number density at the L-O mode turning point and two ion number density peaks on each side of the O-mode reflection region were discovered. The turbulent layer of the ion density peak at the bottom of the critical height shifted downwards, which qualitatively conforms to the observations made at the Areciboand the EISCAT. The vertical electron velocity oscillated near the L-O mode reflection point. The vertical ion velocity remained positive above the reflection height of the L-O mode and remained negative below this height. These results, which were derived using realistic length scales, ion masses, pump waves, and other plasma parameters, are consistent with theoretical predictions and prior experimental observations, and should thus be useful for understanding the linear and nonlinear interactions between the HF EM wave and the ionospheric plasma at the initial stage.

An electrically small Asymmetric Co-planar Strip (ACS)-fed MIMO antenna for USB wireless applications is proposed. MIMO antenna consists of two electrically small antennas inserted inside a 3D-printed USB prototype. Electrically small ACS-fed antenna consists of an F-shaped monopole radiator with a U-shaped slot inserted into it. The proposed antenna is compact with dimensions 11 × 20 × 0.508 mm³. The proposed MIMO antenna has dual bands which caters to WiMAX-3.5/5.5 GHz, WLAN-5.8 GHz, and C-band-6.3 GHz. The proposed architecture attains reasonable gain for the available aperture. Also, ACS-fed antenna achieves fractional bandwidth of 22% and 20% in the lower and upper bands respectively complying with the theoretical bandwidth as defined by Chu's limit. Isolation between the radiators is greater than 15 dB in both the operating bands. Radiation patterns have high integrity, and actual USB deployment is presented. Simulation and measurement results are presented.

The research and development of microwave-tunable equipment has promoted the advancement of electronic countermeasures and electronic surveillance in the field of military communications. The research of fully tunable filters is a hotspot in the field of tunable filter research. Parameters such as center frequency (CF), absolute bandwidth (ABW), and transmission zero (TZ) are important indicators of fully tunable filters. In this paper, a high-performance fully tunable substrate integrated waveguide filter is designed and fabricated to achieve constant ABW (100 MHz) and TZ (1.59 GHz) with CF tunable, and the adjustable range is 1.1-1.3 GHz. Meanwhile, the constant CF (1.15 GHz) is achieved with the ABW tunable, and the adjustable range is 70-120 MHz. Also the constant ABW (100 MHz) and CF (1.14 GHz) are achieved with the TZ tunable, and the adjustable range is 1.59-1.89 GHz. The measured results show that the insertion loss of the tunable filter is lower than 2.04 dB, and the return loss is greater than 20 dB.

The possibility to achieve a continuous tuning of the spectral properties in the case of two types of planar metamaterials based on the moire effect is demonstrated both experimentally and numerically. Tuning spectral characteristics are provided by changing geometric parameters of above-mentioned metamaterials. It is shown that for a one-dimensional moire metamaterial obtained by superposition of two microstrip photonic crystals with close periods, the position of the stopband in the spectrum can be controlled by changing these periods. We also consider the two-dimensional moire metamaterial formed by two identical periodic crossed structures with hexagonal symmetry. The ability to control the frequency of surface state mode by changing the crossing angle of these structures relative to each other has been shown experimentally and numerically. It is numerically demonstrated that, if the moire metamaterial is irradiated by the horn antenna, a surface wave propagating in the metamaterial plane appears in all directions beginning from its intersection point with the axis of the incident wave beam. In practice, moire metamaterials of this type can be considered as a promising prototype of microwave filters, whose spectral properties can be continuously and smoothly mechanically rearranged.

The purpose of this work is to miniaturize a rectangular patch antenna which resonates at 2.4 GHz. To achieve this, we present a new geometry of a pi-shaped slot with three annular rings as a Defected Ground Structure (DGS). DGS is a periodic etched structure or a periodic sequence of configurations, and it has been used to switch the resonance frequency from starting value 13 GHz to an ending value at 2.4 GHz without any changes in the areas of the actual rectangular microstrip patch antenna (RMPA). The proposed antenna is structured on an FR-4 substrate with thickness 1.6 mm and permittivity 4.4. The general size of the ground plane is 34 × 34 mm². Using the optimal position and dimension of the pi-shaped slot on the ground, the resonant frequency is reduced to 2.4 GHz, which signifies an 81.53% decrease. Proposed antennas with and without DGS are simulated by using High-Frequency Structure Simulator (HFSS) and Advanced Digital System (ADS) Agilent technology, fabricated, and measured for Wireless Local Area Network (WLAN) application.

This paper proposes a wearable antenna for Wireless Body Area Network (WBAN) that operates at the 2.45 GHz medical band. The antenna is enabled by coplanar waveguide, and the impedance bandwidth of the antenna is expanded by combining a circular slot with asymmetric slots. In order to reduce the radiation of the antenna back lobe and improve the antenna gain, a new 2×2 Artificial Magnetic Conductor (AMC) is designed and loaded under the monopole antenna. The radiation of antenna back lobe is effectively reduced due to the addition of AMC reflector. Also, the front-to-back ratio of the demonstrated antenna is higher than 20 dB, achieving a forward gain of 7.47 dBi and Specific Absorption Rate (SAR) lower than 0.15 W/kg, in the ISM band.For further research, the antenna is fabricated and tested, showing a strong agreement between simulation and measurement. Meanwhile, the antenna has stable performance under the bending condition, meeting the practical application requirements of wearable equipment.

In this paper, the outage probability performance of energy harvesting based partial relay selection aided non-orthogonal multiple access (NOMA) system under outdated channel state information is studied. The source to relays link is assumed to follow Rayleigh fading distribution while the relay nodes to users are subjected to Nakagami-m distribution. The relay nodes employ an energy harvesting power splitting-based relaying protocol to transmit the source information to the users.At the destination, each user is equipped with multiple antennas, and maximum ratio combining is considered for signal reception. In order to evaluate the system performance, the outage probability closed-form expression for the concerned system is derived. The results demonstrate the significant impact of system and channel parameters on the system performance. In addition, the advantage of NOMA over the conventional orthogonal multiple access is also presented. Finally, the accuracy of the derived outage expression is validated through the Monte-Carlo simulation.

A new miniaturized microstrip lowpass filter with ultra-wide stopband performance using trapezoid patch resonators is investigated. To achieve compact design and ultra-wide band rejection, trapezoid patch resonators are employed in the filter. To further reduce the circuit size of the filter, a meander transmission line is also introduced in the design. A demonstration filter with 3 dB cutoff frequency at 0.50 GHz has been designed, fabricated, and measured. Results indicate that the proposed filter is able to suppress the 26th harmonic response referred to a suppression degree of 15 dB. Furthermore, the proposed filter exhibits a small size of 0.122λ_g×0.109λ_g, where λ_g is the guided wavelength at 0.50 GHz.

The goal of this study is to analyze the effect of tri-band antennas in 2.45, 3.6, 3.8, 4.56 and 6 GHz frequencies, which cover Wi-Fi and some of the future 5G frequencies for wearable smart glasses applications. The latter 4 frequencies are studied for the first time for smart glasses. In order to provide a thorough analysis, first a simulation study for the head model with the proposed antennas is performed, then a realistic experiment by using a semi-liquid gel phantom head model with the infrared thermography method is conducted, and also 4 male subjects are included to analyze temperature rise effects on the skin. The phantom prepared for this study is also validated for its robustness and matching parameters. The SAR values and temperature rise due to the usage of smart glasses calculated by simulation modeling, bio-heat analytical solution, and infrared thermography technique are in good agreement. The temperature rise of the skin regions gets monotonically increased in the duration of usage. The simulations for all indicated frequencies are performed. Also, to provide comparable and practical results, the phantom study is compared with simulations for 2.45 GHz. According to the quantitative data obtained on the liquid-gel head phantom and on the subjects, the temperature increase is below 1ºC, and its compliance with safety standards is determined. The results show that tri-band antennas for these frequencies can be safely used; however, a limiting behavior for the power is necessary for lower frequencies due to the increasing SAR values and temperature rise.

An algorithm named MUSIC-like algorithm was previously proposed as an alternative method to the MUltiple SIgnal Classification (MUSIC) algorithm for direction-of-arrival (DOA) estimation. Without requiring explicit model order estimation, it was shown to have robust performance particularly in low signal-to-noise ratio (SNR) scenarios. In this letter, the working principle of a relaxation parameter β, a parameter which was introduced into the formulation of the MUSIC-like algorithm, is provided based on geometrical interpretation. To illustrate its robustness, the algorithm will be examined under symmetric α-stable distributed noise environment. An adaptive framework is then developed and proposed in this letter to further optimize the algorithm. The proposed adaptive framework is compared with the original MUSIC-like, MUSIC, FLOM-MUSIC, and SSCM-MUSIC algorithms. A notable improvement in terms of targets resolvability of the proposed method is observed under different impulse noise scenarios as well as different SNR levels.

In a MIMO system, scattering is always an important problem since it is closely related to the channel capacity of system. In most of previous works, scattering was usually neglected so as to simplify the process of analysis. Therefore, it is really necessary to investigate and understand the scattering effect on capacity. To this end, scattering is taken into consideration in terms of channel capacity in this paper. From the antenna point of view, antenna element layout can be viewed as an optimization problem. To resolve this problem, a binary whale optimization algorithm (BWOA) is proposed. We investigate the effect of scattering environment on the capacity of a MIMO system and make comparison with an existing method in performance. The simulated results demonstrate that the nonuniform sampling method is able to efficiently improve the capacity of system even for poor scattering environment.

Wideband digital beamforming (WDBF) technology is a key for the rapidly developing wideband digital array radar (WDAR). In this paper,by comprehensively considering the characteristics of WDAR and the current hardware and software capabilities for radar in engineering, several practical WDBF technologies based on accurate digital true time delay (TTD) are studied. WDBF technology at radio frequency (RF) is applied and tested on a WDAR test-bed. Besides, WDBF technologies at baseband by implementing fractional delay filers at element level and subarray level are presented and simulated.