The sensitivities of an aluminum gallium arsenide Al_0.7Ga_0.3As based surface plasmon resonance (SPR) sensor with gold (Au) and silver (Ag) layers are numerically analyzed and compared at 633 nm wavelength for different thicknesses of the Al_0.7Ga_0.3As. As the thickness of Al_0.7Ga_0.3As increases, the sensitivity of aluminum gallium arsenide Al_0.7Ga_0.3As with a specific metal (Au or Ag) layer increases. Our calculations show that the sensitivities of the proposed sensors are 80.55% (Au film) and 34.74% (Ag film) higher than the conventional Au and Ag sensors successively. The aluminum gallium arsenide Al_0.7Ga_0.3As based SPR sensor has the advantages of high angular sensitivity, narrow resonance widths, and low minimum reflectance, making it a much better choice for biosensing applications.

Estimation of soil moisture using Synthetic Aperture Radar (SAR) backscatter values, over agricultural area, is still difficult. SAR backscatter is sensitive to the surface properties like roughness, crop cover, and soil type, along with its strong sensitivity to the soil moisture. Hence, to develop a methodology for agricultural area soil moisture estimation using SAR, it is necessary to incorporate the effects of crop cover and soil texture in the soil moisture retrieval model. A field experiment was conducted by the authors and used along with Sentinel 1A SAR data to estimate the soil moisture in the paddy agricultural fields. Generally, water used for irrigation in the study region was obtained from ground water. As in the hot climate conditions ground water level would be reduced, and the water for irrigation must be supplied optimally. Hence, available soil moisture in the field was estimated from SAR data on the day of satellite passing the crop fields and utilized for deciding the amount of water to be supplied. The soil moisture values of soil samples that are collected from the agricultural field are calculated with the laboratory experiments. A soil moisture retrieval model is derived and proposed in this paper after a comparative analysis of experimental soil moisture values and satellite values. The feasibility of above model for paddy agricultural fields is validated using the field measurements.

In this paper, the performance of a concentric hexagonal antenna array (CHAA) is investigated with the exploitation of a robust variable diagonal loading (VDL) technique in the presence of direction of arrival (DOA) mismatch. The performance of minimum variance distortionless response (MVDR) based CHAA is compared with the performance of existing MVDR based concentric circular antenna arrays (CCAAs), and it is found that the proposed MVDR based CHAA provides 25.54% narrow half-power beamwidth (HPBW) and lower side lobe level than the existing MVDR based CCAAs. When DOA mismatch occurs between main beam steering direction and actual signal-of-interest (SOI) direction, the performance of MVDR based CHAA is deteriorated. In the case of DOA mismatch, to ameliorate the performance of CHAA, this paper proposes VDL technique for the CHAA processor and compare the performance of proposed robust CHAA with existing robust CHAAs. The proposed VDL based robust CHAA delivers 88.37% and 78.56% higher output power for 2˚ DOA mismatch than existing fixed diagonal loading (FDL) and optimal diagonal loading (ODL) based CHAAs, respectively. Several tapering window functions are proposed to reduce the side lobe level of CHAA. Performance of the proposed beamformer is analyzed utilizing MATLAB environment in various scenarios.

This paper presents the design of flexible parasitic element patch (FPEP) antenna with defects on ground plane at ISM band for biomedical application. The antenna resonates at 2.46 GHz frequency with reflection coefficient of -16.8 GHz in free space and at 2.45 GHz frequency when being placed on cotton and the single layer skin tissue of human body. The proposed parasitic element patch antenna is used to measure the body temperature, and the specific absorption rate (SAR) of the proposed antennas is 1.0 W/kg. The measurement data with respect to reflection coefficient, and radiation pattern are presented.

This paper proposes an improved method for calculating static capacitance between two conductors with circular cross-sections in inductor windings. It considers the effects of electric field coupling and energy distribution on static capacitance. In this paper, the capacitance between two conductors in inductor windings is calculated by the improved calculation method and the finite-element method (FEM), respectively. The relative error of the improved calculation method is between 0.11% and 4.51% compared to the FEM. In order to verify the effectiveness of this method for inductor winding, the orthogonal stacking winding and staggered stacking winding are chosen as calculation examples to accurately predict the static capacitance of multi-layer circular-section induction coils. Finite element models for the two types of windings are built to determine the capacitances for our 3×3 array arrangement winding. The results show that the improved calculation method proposed in this paper highly conforms to FEM. Finally, we adopt an air-cored cylindrical inductor winding for experimental verification, and the improved calculation method is proved to be correct.

r exploring the possibility of dual frequency response, a higher order mode frequency response in the air suspended design of a wideband E-shape microstrip antenna is studied, by appropriately decreasing the air gap.The decrease in the air gap realizes the impedance matching at higher order TM12 mode which along with the fundamental TM10 mode,gives dual frequency response. On an air suspended FR4 substrate with total thickness of 0.043λg, optimized single patch configuration yields dual band response at 2427 and 5730 MHz giving frequency ratio of 1:2.36. It yields impedance bandwidths of 6.6 % and 4.8% at two frequencies with respective broadside gains of 6.8 and 2.1dBi. The proposed configuration satisfies the requirements of 2.4/5.8 GHz WLAN applications. Parametric formulations are proposed for various antenna dimensions. The MSAs redesigned using them at given fundamental mode frequency yield a similar dual band response.

With a constantly increasing number of cars equipped with 77 GHz automotive radar, the performance degrading effects of crosstalk are becoming a rising threat to radar-enabled automated driving functions. Since interference is sensitive to slight changes of temporal and spatial conditions of the scenario, meaningful measurements are hard to conduct which is why simulations are an important supplement. In this paper, a simulation model is introduced that estimates the distribution of the reduction of the detection range of automotive radars due to multiple interferers focusing on stochastic temporal conditions. The underlying system model calculates the direction- and timing-dependent influence of one single interferer on the detection range of the host radar. The model is kept simple, making it suitable for Monte Carlo methods, which allow the indispensable statistical evaluation of the broadly spread results. Finally, a method is presented that transfers multiple statistics regarding single interferers into a single environment. The computing time of the simulation grows linearly with the number of interfering radars, so the effects of vast numbers of interferers can be studied using this simulation model. Statistical evaluations of the detection performance degradation of a front-mounted radar in sample highway scenarios, containing up to ten interfering radar sensors, are performed in this paper.

A new wideband dual-polarized patch antenna using substrate-integrated waveguide (SIW) technology is proposed in this paper. The antenna is composed of a patch radiator and a square SIW cavity. The square patch is internally embedded in the square SIW cavity with a surrounded slot. A pair of L-shaped probes are used for the excitation of the orthogonal linearly-polarized signals. The dominant resonant mode of the square patch resonator (TM010) and the modes of the SIW cavity (TE110 and TE120/TE210) are employed to achieve a wide impedance bandwidth under these resonances. By introducing two shorting pins, the isolation between two feeding ports can be enhanced to more than 21 dB. The resonant properties of these modes are investigated based on the cavity model theory. Then, their resonant frequencies are discussed to provide information for designing and optimizing such an antenna. For demonstration, a prototype is fabricated and measured. The measured results show that the proposed antenna achieves a wide impedance bandwidth of about 66.7% (3.71-7.43 GHz) and 70.9% (3.58-7.52 GHz) for horizontal and vertical polarizations, respectively. A stable gain in the range of 7.15 to 8.03 dBi is obtained within the operating band. Due to the SIW cavity-backed structure, the antenna shows unidirectional radiation patterns and low back-lobe radiation at the resonant frequencies. Thus, the antenna is highly suitable for the base station antenna that is required to cover the bandwidth of 5.5 GHz WiMAX and 5.2/5.8 GHz WLAN systems.

Wireless power transfer (WPT) via coupled magnetic resonance is anencouraging technology to be applied in many fields. In this paper, a method using a circular coil spiral inductor structure to wirelessly transfer energy is proposed. It represents the characteristic of six parallel air core inductor mutually coupled in the free space for wireless power transfer system. Based on the analytical model and circuit theory, the relationship between the coil design parameters and the system performance is deduced, and the effects of the outer radius, inner radius, channel width and coil turns are thoroughly studied to improve the system performance at different axial distances and in lateral misalignment. Also, an elimination method for transmission efficiency dead-zone (TEDZ) is proposed. The proposed method utilizes angular rotation of the receiver (Px) to eliminate the zero-coupling point which causes TEDZ and boosts the coupling coefficient such that the TEDZ is eliminated, and the high efficiency region is extended.

A novel balanced bandpass reconfigurable microstrip filter is presented, where in differential mode, the filter operates in seven different bands, and each inductor LM represents a state of frequency. The common mode rejection ration (CMRR) is better than 30 dB for all the states. The central frequency of the filter is changed by liquid metal droplets flowing along a microfluidic channel placed at the middle of the inductors LM. For demonstration, a third-order filter is designed, simulated, and fabricated, operating in the S-band. Good agreement between simulation and measurement is presented.

A wideband high gain three-layer hemispherical dielectric resonator antenna (HDRA) that operates at TE₅₁₁ and TE₇₁₁ higher order modes is proposed. The HDRA is composed of three layers, which has permittivities of 20, 10 and 3.5. The multilayer structure has been chosen in order to reduce the Q-factor and achieve a wider impedance bandwidth. Cross slot feeding mechanism has been utilized taking into account the excited higher order modes for gain enhancement. The proposed antenna provides an impedance bandwidth of 35.8% over a frequency range of 20.8 to 29.9 GHz in conjunction with a high gain of ~9.5 dBi. The proposed DRA represents the first attempt in utilizing a mm-wave hemispherical DRA.

A CPW-fed printed square slot antenna (PSSA) based on characteristic modes (CMs) theory is investigated for broadband circular polarization (CP). It consists of an I-shaped patch and CPW ground plane loaded with a rectangular stub, a pair of asymmetric inverted-L grounded strips, and a spiral slot to get CP radiation over a wide-angle range. CMs of this strip and slot loaded PSSA show that the entire structure takes participation to excite magnetic and electric modes to provide broadband performance. First six characteristic modes are excited using CPW feeding to find resonating frequencies and radiating behavior. The proposed antenna is fabricated over RO-3003 substrate material with a floor area of 20×20 mm². Experimental results showcase the broadband CP performance with wide 3-dB ARBW of 56 % (6.6-11.8 GHz) and impedance bandwidth (IBW) (|S11| ≤-10dB) about 115 % (4-11 GHz) which make it suitable for C-band and X-band wireless and satellite communication applications. The antenna has a peak gain about 5.5 dBi with good LHCP radiations in the broadside direction.

In this article, a novel dual-band omnidirectional antenna for WiFi applications is presented and investigated. The proposed antenna is mainly composed of two pairs of half-wavelength dipoles with different lengths. It is fed by a microstrip balun, which provides a good impedance matching for desired dual-band operation. The dimension of the proposed antenna is only 50 mm × 10 mm × 1 mm (0.4λ₀ × 0.08λ₀ × 0.008λ₀, and λ₀ is the wavelength of 2.4 GHz). The performance study of this dual-band omnidirectional antenna with different geometric parameters has been conducted. The final design is fabricated and measured, and the results exhibit a good impedance bandwidth of approximately 19.2% for |S₁₁| ≤ -10 dB ranging from 2.24 to 2.70 GHz centered at 2.4 GHz, and over 17.4% for |S₁₁| ≤ -10 dB ranging from 4.73 to 5.6 GHz centered at 5.0 GHz. This antenna also has a stable gain of 2.09~2.87 dBi and omnidirectional radiation patterns over the whole operating band. Dual-band coverage, stable omnidirectional radiation performance, simple structure, and miniaturized dimension make this antenna an excellent candidate for WiFi applications.

This article presents the design and optimization of multi-ring permanent magnet thrust bearing (PMTB) with an axial air gap between successive axial stacks. Larger air gap due to the inclusion of conductive materials needs to be critically analysed in permanent magnet bearings with eddy current damper. High conductivity materials can be filled in an axial air gap instead of a radial air gap to increase the required amount of damping. Three-dimensional (3D) mathematical model for load-carrying capacity for the said configuration is presented using the Coulombain model. The significance of an axial air gap between successive ring pairs in the configuration concerning maximization in the bearing characteristics is presented. Variables such as the number of axial stacks, an axial air gap between the successive rings, an inside radius of rotor ring magnets, and an inside radius of stator ring magnets are optimized at different air gap values for maximizing the load-carrying capacity and stiffness. A significant increase in the values of bearing characteristics is observed in the optimized configuration as compared to bearing with a single permanent magnet ring pair. Optimized PMTB with comparable load carrying capacity and stiffness values can be used to replace conventional bearings used in high-speed applications to improve system efficiency.

In this paper, a new cross section configuration of partially dielectric-filled rectangular waveguide (PDF-RW) is proposed and analyzed. It may beused when substrate integrated waveguides (SIWs) are designed such as to maximize the frequency bandwidth for insertion losses as low as possible. Imposing the boundary conditions for the electromagnetic field components, the equations for the cutoff frequencies and propagation constants are developed for the TE_m0 modes. It is shown that the cutoff frequency equations developed in this paper may also be used to analyze particular cases investigated by other authors. The ratio between the cutoff frequencies of the TE₂₀ and TE₁₀ modes is computed and represented graphically for different geometric dimensions of the proposed PDF-RW configuration. The conductor and dielectric losses for the TE₁₀ mode are computed as well, based on the results provided by the equations developed in this paper. The results obtained by using the proposed approach are compared to the HFSS (High-Frequency Structure Simulator) results, and very good agreement is observed between them.

This article discusses the effect of sectorization technique in hemispherical dielectric resonator antennas (HDRA) for the first time with its significant effects on electromagnetic modes and various antenna parameters. The sector angle (β) forms an additional framework for better optimization of HDRA. The resonance frequency, impedance bandwidth, co-cross polarization characteristics have been investigated in new sectored HDRA geometries excited at their TE₁₁₁ and TM₁₀₁ modes. Further, examination of circular polarization (CP) is carried out by detuning of degenerate orthogonal modes in HDRAs, and β = 180° has been particularly examined in details for CP. Based on the results, appropriate values of `β' and probe position (P_r) are chosen followed by modelling a prototype and experimental.

Vertically- and horizontally-polarized antennas were investigated for on-body to on-body (OB2OB), in-body to in-body (IB2IB), and on-body to in-body (OB2IB) wireless propagations at frequencies of 915 MHz and 2.45 GHz. Theoretical formulations, simulations, and measurements were employed to study the effect of source antenna orientation on the attenuation of the radio frequency (RF) wave as it propagates around, inside, and through the body near the torso region. The results show that the vertical polarization is preferred for OB2OB communication, and the horizontal polarization is better for IB2IB communication. Furthermore, the dominant propagation mechanism and optimum antenna excitation for OB2IB communication are identified to be distance-dependent. The horizontally-polarized dipole is preferred at a shorter distance while the vertically-polarized dipole is preferred at a larger distance away from the source. The observed results were explained using the estimated attenuation rates of the different propagation mechanisms.

When a high voltage direct current (HVDC) system works at single line operation mode, a big current will flow into the earth through the grounding system directly. Then the large current can cause damage to surrounding equipment and the environment. Therefore, it is significant to study the current dispersion characteristics of HVDC grounding system. Firstly, a ±800 kV HVDC model operated at single line mode is built. The grounding current can be seen as the equivalent current source injecting to the grounding system. Secondly, the current dispersion characteristics of horizontal, cross and ring electrodes are investigated. It proves that the ring grounding electrode shows better current dispersion characteristic. And the double-ring grounding electrode whose ratio of inner and outer rings is controlled at 0.7 to 0.75 can get a better current dispersion characteristic. In addition, a dynamic seasonal frozen soil resistivity changing model is built to study the effects of season on the grounding electrodes. The frozen soil would not only increase the ESP, the resistance to ground, and step voltage, but also reduce the current density and electrical field. When the frozen soil is melting, the current dispersion characteristics are the best. The results provide meaningful reference for the design of the grounding system in extremely cold regions.

The aim of this research is to propose a new efficient and reliable approach on the field of Non Destructive Testing (NDT), for the characterization of cracks in non-ferromagnetic material by Electromagnetic Acoustic Transducer (EMAT). EMAT is an ultrasonic technique that generates and detects ultrasonic waves in the conductive material without physical contact. The research goes through two principal phases. The first, which is a forward model, is based on Finite Element Method (FEM). The FEM is applied to simulate the EMAT response (output voltage) to the material under test in order to build a database for the inversion tool. The second is the inverse model and depends on the Partial Least Square Regression (PLSR) method, as it is a fast, simple, and accurate inversion tool, in order to estimate the depth and width of the cracks on the surface of non-ferromagnetic materials. PLSR is a dimensionality reduction method which aims to model the relationship between the matrix of independent variables (predictors) (X) and the matrix of dependent variables (response) (Y). The purpose of PLSR is to find the Latent Variables (LV) that have a higher ability of prediction by projecting original predictors into a new space of reduced dimensions.

In general, a single beam reflection can be realized by 2-bit coding metasurfaces. In order to obtain multi-beam reflection, a design method for coding sequence based on 2-bit coding metasurfaces is proposed, which can manipulate the direction of reflected beams by 2-bit addition rule and control the number of reflected beams by addition theorem on complex codes. This method simplifies the design process of coding sequence, and the direction and number of multi-beams can be flexibly designed. In this paper, the design of dual-beam reflection is taken as an example to illustrate the design process of coding sequence. Both simulation and measurement results show that the designed metasurface realizes the dual-beam reflection, and the direction of reflected beams is consistent with expectations. The proposed method is of great significance for the design of multi-beam reflection based on coding metasurfaces.