This paper mainly deals with the channel diversity and the effect of spatial consistency parameters for different millimeter wave (mmWave) bands (28, 38 and 73 GHz) according to the channel parameters of the NYUSIM model. Statistical analyses are performed for various spatial consistency scenarios in an urban microcell (UMi) environment. Most of the recent analyses ignored the effect of adjusting the spatial consistency parameters on the 5G mmWave channel characteristics, including path loss (PL), received power, and path loss exponent (PLE). As a result, we have analyzed the effect of each parameter mentioned above for both directional power delay profile (DPDP) and omnidirectional power delay profile (OPDP). Numerical results illustrate how the characteristics of mmWave channels communication can be affected by changing the spatial consistency parameters.

This paper deals with analyzing a novel eddy current damper for an axially magnetized multi-ring permanent magnet thrust bearing (MPMTB). Initially, the bearing is optimized for maximum axial force by selecting three general parameters (air gap, outer diameter of stator, and length) using a generalized optimization procedure. Then, the axial force of an optimized bearing is validated with the mathematical model results. Finally, the novel and conventional eddy current dampers (ECDs) for an optimized MPMTB are analyzed for damping forces and coefficients using three-dimensional (3D) finite element transient analysis in ANSYS. Based on the analysis results, the proposed novel structure could be selected to replace the conventional one for providing damping to MPMTB effectively without affecting the radial air gap between the rotor and stator rings.

This paper proposes two low divergence angle orbital angular momentum (OAM) Fabry-Perot (F-P) antennas with nonuniform superstrates. There are two steps to design the proposed two F-P antennas. First, two primary array antennas (a slot array antenna and a patch array antenna) are designed. Both antennas can generate OAM vortex beams with a mode of -1. Second, two F-P resonator cavity antennas are formed by loading a nonuniform partially reflective surfaces (PRS) superstrates above the two primary antennas in order to increase the antenna gain and reduce the divergence angle. The PRS is designed non-uniform for increasing the aperture efficiency. The measured results indicate that the F-P OAM antennas can obviously improve the performance of primary OAM antennas: (1) for the slot array antenna, the divergence angle reduces from 27° to 18°, and the maximum gain increases from 5.2 dBi to 7.5 dBi; (2) for the patch array antenna, the divergence angle decreases from 30° to 18°, and the peak gain increases from 3.4 dBi to 7.2 dBi.

In this paper, a novel mechanical-flux-weakening interior permanent magnet (MFW-IPM) machine is proposed to improve flux-weakening ability. The key of the proposed machine is that the permanent magnet is rotatable, and a mechanical device is equipped on both sides of the rotor. The mechanical device can regulate the air-gap magnetic field by rotating PM to change the leakage flux and magnetization direction of PM. As a result, the flux-weakening ability is improved. The flux-weakening principle of the MFW-IPM machine is investigated in detail. In addition, a multi-objective optimization method is adopted to improve the performance of the proposed machine. Then, the electromagnetic performances of the original machine and optimized machine are compared by finite element analysis. Finally, both simulation results and experimental tests verify the effectiveness of the flux-weakening enhancement design and optimization method.

The engine of a fighter plane is one of the largest scattering centers of the entire aircraft. One possible way of reducing the radar cross section (RCS) of the engine is to use an S-shaped bending air inlet to avoid direct radar wave illumination and reflection. We evaluate the efficacy of an S-shaped air inlet on RCS reduction by simulating the boresight and ±15˚ bistatic RCS for a digital model of an engine located behind an S-shaped inlet, using a multi-level fast multipole method (MLFMM) code in the S and X bands. The results show that a curved S-type air inlet can reduce the engine boresight bistatic RCS by ~10-12 dBsm at 3 GHz, and ~16 dBsm at 10 GHz when radar wave is incident from boresight, but not to the level required by RF stealth standards. When the radar waves are incident from θ=105˚ φ=90˚ or θ=90˚ φ=345˚, the RCS reduction is less effective, which is the results of the bend direction of the S-type air inlet.

This paper presents a new integro-differential coupling between partial equivalent electrical circuits (PEEC) and finite difference method (FDM) taking into account the magnetization effect. This coupling is intended for thin plates having simultaneously significant conductive and magnetic properties in presence of exciting coils of complex topologies. These cases exist in eddy current nondestructive testing (ECNDT), eddy current separation, induction or levitation melting devices and more other applications. The choice of FDM, is in relation with rectangular surfaces generated by numerical meshes leading to mathematical integrations of magnetic and electrical quantities with independent variables, unlike more complicated forms of surfaces generated by finite element method (FEM) or others. Fully successful analytical expressions have been realized and implemented in overall coupling process. The PEEC method is mainly used to calculate the magnetic field applied to the nodes of the plate from different inclined polygonal coils. The results of magnetic field and eddy current distributions on thin plates are presented, and parts of them are compared with those realized by Flux 3D software.

Due to low power density, it is difficult for a single-band rectenna to harvest enough power for IoT devices like wireless sensors. Thus to supply these consuming devices, harvesting RF energy from multiple frequencies is a solution to enhance the amount of harvested DC power. In this work, we introduce a triple-band rectenna, working at 900 MHz, 1.8 GHz and 2.1 GHz, three readily available bands in the ambience, for energy harvesting application. The proposed rectenna consists of three monoband rectifiers connected to a multi-band receiving antenna via a highly efficient triplexer. The antenna is made by superposing two concentric rings and manipulating their radii to achieve the desirable operating frequencies, with antenna gains of respectively 2.5 dBi, 4.5 dBi, and 4 dBi. The contiguous triplexer is made by connecting open stubs band-reject filters and optimizing their positions, resulting in the triplexing efficiency higher than 75%. The measured RF-DC efficiency under -10 dBm triple-tone input power is 40%.

This paper explores the effects of extended exposure to salt water fog on the microwave absorption properties of unidirectional carbon-fiber reinforced polymer (CFRP) circuit analog absorbers (CAA). Single-layer CFRP CAAs were fabricated using a wet-layup technique and were then subjected to a controlled salt water fog chamber following B117 standards. A total of ten samples using 305 g/m² areal-weight unidirectional CFRP were fabricated. Three samples were withdrawn from the salt water environment at ten-day intervals and tested, with the final samples being withdrawn after 30 days. The mass of each sample was measured immediately after removal to measure mass-accumulation and after a five-day interval to measure mass-loss. A free-space microwave reflection measurement system was implemented to track and quantify changes to the absorption capabilities of the CAA. A physically-based electromagnetic model was developed to characterize the changes caused by salt water absorption, and good agreement was observed with measured data.

This paper proposes a zero-forcing beamforming design for the energy efficiency optimization of the magnetic resonance based wireless power transfer system with multiple transmitter coils, which aims to secure energy transfer control. A scheme based on beamforming technology is proposed to prevent unauthorized users from accessing the system, which builds a beamforming model consisting of multiple transmitter coils, a target receiver, and a non-target receiver to simulate the actual system. Then to optimize the proposed system's energy efficiency while constraining the target receiver's energy, spectral efficiency, and transmitter's power, the proposed beamforming model is constructed as an optimization problem. To solve this non-convex nonlinear fractional programming problem, the Dinkelbach algorithm is used for fractional conversion, and then the zero-forcing constraints are equivalently replaced. Finally, two solutions of the nonlinear solution and closed-form solution are derived. The simulation results show that the energy efficiency optimization strategies of zero-forcing beamforming with the two derived solutions can satisfy the design requirements.

A dual-band two port MIMO antenna with very high isolation is proposed for 5G/WLAN application. The overall size of the MIMO antenna is (18 × 44× 0.8) mm³. The unequal arm of the Inverted-F Antenna (IFA) is the reason for the dual bands. Bending and extending one of the arms with the staircase shape is responsible for the proposed dual-bands having resonant frequency at 3.45 GHz (3.3 GHz-3.65 GHz) and 5.1 GHz (4.8 GHz-5.5 GHz) respectively with percentage impedance bandwidth of 10% and 13.6% respectively. The proposed antenna uses a simple decoupling structure based on a wide inverted T-shaped slot to achieve good isolation (better than 18 dB and 34 dB respectively for the dual-bands) between the ports. The envelope correlation coefficient (ECC) and channel capacity loss (CCL) are within the acceptable limits.

Artificial material has the feature to realize a controllable effective permittivity, which leads to many potential applications in the RF and optical fields. In this study, an artificial material is proposed for a Resonant Cavity antenna (RCA) to enhance the gain of patch antenna. The artificial material is made of a lot of circular conducting patches in a uniform size hosted in an FR-4 substrate. The fabricated artificial material is in a square shape with a length and width of 52 mm × 52 mm and a thickness of 1.2 mm. The artificial material is set in front of a patch antenna to construct an RCA, and the gain property of the proposed RCA is evaluated with the simulation and measurement methods. The results by both the simulation and measurement methods prove that the gain is enhanced by the proposed artificial material. The maximum gains are 14.5 dBi in simulation and 12.8 dBi in measurement at 15 GHz for the RCA with on slab of the artificial material. The gain is improved compared to the gain of a patch antenna without the artificial material.

Multilayer grid polarizers for millimeter waves produced with photolithographic technology have been simulated. Polarizers have spectral bands of enhanced performance where polarization extinction ratio in decibels grows in proportion to the number of layers. Full-wave modeling is compared with three asymptotic models for subwavelength gratings using adjusted grating parameters. Random variations of interlayer spacings reduce the enhancement of polarizing performance, yet the latter continues to grow in proportion to the number of layers. Broadband signal detection is also considered.

A package-board co-design method was applied for a Narrowband Internet-of-Things (NB-IoT) SiP module. The electromagnetic interference (EMI) generated by the module was studied by improving the transmission quality of radio frequency (RF) signal. The SiP models of the initial design and the optimized design were simulated separately to show that the optimized design significantly increased effective transmission power of the RF signal and suppressed near-field electromagnetic radiation intensity to a certain extent. In addition, the optimized design model was verified by measurement. The measured results show good agreement with the simulated ones and demonstrate that the package-board co-design method can improve the electromagnetic compatibility (EMC) of NB-IoT applications.

A low-profile half-mode substrate integrated waveguide (HMSIW) filtering antenna with high frequency selectivity is proposed in this letter. The proposed antenna with a height of 0.014λ₀ (λ₀ is the free-space wavelength) consists of a slot-loaded HMSIW cavity, two parasitic patches, and five shorting pins. An upper-edge radiation null is generated by the interaction between the HMSIW cavity and parasitic patches. A rectangular slot etched on the HMSIW cavity is adopted to generate another null to improve the filtering performances at the upper stopband. Besides, the radiation in the lower stopband is suppressed by two nulls which emerge due to placing shorting pins under two parasitic patches. Thus, four radiation nulls can be obtained to enhance the frequency selectivity. The measured results illustrate that the proposed antenna provides an impedance bandwidth of 4.3% ranging from 2.74 to 2.86 GHz and a peak gain of 6.76 dBi during the operating frequency band. Moreover, four radiation nulls appear at 2.34, 2.56, 3, and 3.24 GHz in the lower and upper stopbands.

This paper proposes a novel bandpass filter for L-band based on CRLH TL, which is mainly formed by coupling a high-pass characteristic module with a low-pass characteristic module in a cascade. The high-pass module consists of an interdigitated coupled line and a grounding via, owning to its singular characteristics, which the miniaturization is realized. The low-pass module is composed of a C-type resonator with high-low impedance lines, which can realize great sideband attenuation characteristics. To further improve its out-of-band rejection characteristics, a complementary split-ring resonator (CSRR) defective ground structure with single-pole attenuation characteristics is loaded, and a transmission zero is introduced at 2.5f₀ out-of-band. The test results are in great agreement with the simulation ones, and the dimensions are only 0.20λ_g*0.22λ_g. Compared with other similar types, the filter proposed in this paper has miniaturization, great passband selection characteristics, stopband characteristics, and the advantage of low insertion loss.

This paper presents a star-shaped compact dielectric resonator antenna for wideband and multiband wireless applications. The slots in the dielectric slab have been created to achieve wider bandwidth. The star-shaped alumina dielectric is placed on a low cost FR-4 substrate and fed using a microstrip line. The electrical dimensions of the proposed dielectric resonator antenna are 0.86λ₀×0.86λ₀×0.13λ₀. The proposed design resonates at multiple frequency bands of 5.04-6.13 GHz, 6.87-7.97 GHz, and 8.58-9.63 GHz having the fractional bandwidths of 20.76%, 15.3%, and 11.4%, with peak gains of 3.71 dBi, 6.20 dBi, and 8.10 dBi, respectively. The design was fabricated to validate the simulation results. Good agreement can be seen between the measured and simulated results.

An efficient analysis and optimization method is proposed to compensate the influence of asymmetric radome on an antenna by correcting amplitude and phase of the excitations. The asymmetrical and heteromorphic radomes are inevitable for the radar on high-speed aircraft. Many previous researches focused on the optimization of the radome structure and thickness to reduce the influence of radomes. However, the influence of complex streamlined radome cannot be compensated by merely optimizing the structure and thickness of the radome. Therefore, an alternative optimization method, optimizing amplitude and phase of feeds, is used in this paper. This paper adopts the active element pattern (AEP) technique, utilizing full-wave simulation method to extract the AEP for each antenna element and computing radiation patterns of array antenna by using vector composition of AEP. In combination with hybrid genetic algorithm-particle swarm optimization (HGAPSO), the antenna radiation characteristics can be obtained by updating excitations, which avoid the repeated full-wave simulation in the optimization process. Furthermore, the speed updating formula of PSO algorithm is improved combined with prior information, and the convergence speed is further increased. Finally, a 64 elements array antenna-radome system was optimized as an example in the cases of continuously adjustable phase and digital discrete phase.

The electromagnetic characterization of layered materials is applicable to many different applications. In previous work it has been shown that reflection-only techniques - which vary the underlying structure of the sample stack to obtain two independent measurements - are a variation of a single unifying scheme such that there is a single set of closed-form unifying extraction equations for the electric permittivity and magnetic permeability. In this paper, the error propagation method is applied to this single set of closed-form extraction equations in order to derive an accompanying set of closed-form equations to predict the measurement uncertainty of electric permittivity and magnetic permeability. An error analysis is performed on the layer-shift method, and results are compared to a Monte Carlo simulation to prove the viability of the general error analysis equations.

A simple, compact, contactless, and high sensitivity metamaterial-inspired sensorhas been developed to detect and classify precious transition metals in the S- and C-band regime, using reflection coefficients. A multi-band metamaterial, quadruple concentric circular split ring resonator, is specifically designed as a sensing enhancer, where the additional bands can effectively trigger the electromagnetic properties, as well as enhance the differentiation between the testing metal samples. The proposed sensor was tested on precious transition metals, silver, platinum and gold thin slabs of various thicknesses, from 0.5 μm to 3 mm. Five resonances were established in the frequency range of 2-8 GHz. Distinguishable frequency responses generated from different metal samples at those five resonances specify the capability of classifying the metal contents and thicknesses.

A new compact nonuniform leaky-wave antenna (LWA) with left-handed elliptical polarization (LHEP), based on composite right/left-handed (CRLH) metamaterial operating in the range of 7-10.2 GHz is presented in the work. The nonuniform structure of a CRLH transmission line (TL) is realized by the placement of different configurations of inter-digital capacitor (IDC) in the form of sinusoid (SIN-IDC), on the top of metal wall of a half-mode substrate integrated waveguide (HMSIW). Balanced condition of the unit cells is provided by the change in slit width, amplitude and the number of SIN-IDC periods, as well as by relocation of two additional transition apertures arranged by both sides of SIN-IDC. Based on the known Hensen-Woodyard criterion, the optimal number of the unit cells was determined, when the gain coefficient varied from 7.5 to 9.8 dB in all of the operational range of antenna. The developed prototype of nonuniform CRLH LWA has the size of 8.1x115.2 mm. It is characterized by a continuous scan angle range equal to 117°. The maximum angle of rotation radiation pattern is -66° for backward radiation and +51° for direct radiation. The maximum efficiency of the antenna radiation is 85%, while the total one is 68%.