In this paper, materials frequently used in high-speed (HS) electrical machines are assessed. Highspeed permanent magnet synchronous machines with a special tooth-coil topology serve as an example for the assessment. The lamination and rotor sleeve materials are compared taking into account their price, per unit losses, resistivity, and other factors. The resulting tables provide the electrical machine designer with a means to enhance the HS machine performance at low costs.

We examine the effect of alignment errors on the performance of a frequency-diverse imaging system composed of metamaterial apertures. In a frequency-diverse imaging system, a sequence of distinct radiation patterns, indexed by frequency, provides measurements of the spatial content of a scene. This set of measurements can then be used to obtain a high-fidelity estimate of the scene using computational imaging techniques. As with any computational imaging system, realizing the full potential of the frequency-diverse system requires accurate characterization of the complex radiation patterns. This characterization entails precise knowledge of the locations and orientations of the transmitters and receivers; any discrepancy between the modeled and actual locations will introduce phase error and degrade the quality of image reconstructions. Here, we study the effect of various misalignment errors on the performance of a sparse, bistatic, frequency diverse imaging system and provide an estimate on the levels of error within which the frequency-diverse apertures can reconstruct high quality images. Depending on the misalignment type (i.e., displacement, rotation) and direction the phase error can change significantly. As a result, for instance, we show that the imaging system is significantly less sensitive to cross-range displacement errors than to range displacement errors. We also show that the displacement errors are reduced for larger systems comprising many sub-apertures, due to the reduced averaged phase error. We find the impact of rotational errors is small compared to that of the displacement errors. However, as the sub-aperture size increases, rotational errors become more pronounced, becoming severe for larger sub-apertures with multiple feeds.

A compact monopole antenna with broadband circular polarization for global navigation satellite system (GNSS) applications is presented in this paper. The proposed antenna comprises a simple tilted radiator fed by 50-Ohm microstrip line and an improved ground plane. By embedding two isosceles right triangular slits and introducing an isosceles right triangular perturbation in the ground plane, the circularly polarized (CP) performance can be improved significantly. The impedance and circular polarization characteristics are studied by simulation and measurement. With a compact size of 79×79×1.5 mm³ for the fabricated antenna, a measured 10-dB return loss bandwidth of 35.6% (1.13-1.62 GHz) and a 3-dB AR bandwidth of 35.4% (1.14-1.63 GHz) can be achieved.

This paper presents a novel, dual, three-stepped-trident, planar, monopole antenna for ultra-wideband applications. The planar trident type antenna is designed, simulated, and fabricated. Its impedance bandwidth, radiation pattern and gain performances were measured. This antenna operates in the ultra-wideband from 3.0 GHz to 12.15 GHz. The maximum gain of this antenna design is 5.5 dBi. Measurements confirm the simulated results over the frequency of operation.

Energy conservation is an important consideration in wave scattering and transmission from random rough surfaces and is particularly important in passive microwave remote sensing. In this paper, we study energy conservation in scattering from layered random rough surfaces using the second order small perturbation method (SPM2). SPM2 includes both first order incoherent scattering and a second order correction to the coherent fields. They are combined to compute the total reflected and transmitted powers, as a sum of integrations over wavenumber k_x, in which each integration includes the surface power spectra of a rough interface weighted by an emission kernel function (assuming the roughness of each interface is uncorrelated). We calculate the corresponding kernel functions which are the power spectral densities for one-dimensional (1D) surfaces in 2D scattering problems and examine numerical results for the cases of 2 rough interfaces and 51 rough interfaces. Because it is known that the SPM when evaluated to second order conserves energy, and it can be applied to second order for arbitrary surface power spectra, energy conservation can be shown to be satisfied for each value of k_x in the kernel functions. The numerical examples show that energy conservation is obeyed for any dielectric contrast, any layer configuration and interface, and for arbitrary roughness spectra. The values of reflected or transmitted powers predicted, however, are accurate only to second order in surface roughness.

A novel miniaturized design of UWB monopole antenna is presented and investigated for oil pipeline imaging. In the proposed antenna, an annular-ring shaped radiating patch, slotted ground plane and a feed-line embedded with a semicircular stub are used to enhance the bandwidth. The slotted ground-plane has two extended rectangular strips on its two sides to excite the lower frequency resonance. The proposed antenna design exhibits an enhanced bandwidth of 22 GHz from 3 to 25 GHz (for return loss <10 dB) which provides a wide usable fractional bandwidth of more than 157% with a compact size of 15 mm×12 mm. Simulated and measured results are discussed to validate the proposed antenna design with enhanced wide bandwidth performance.

This paper presents a comprehensive analysis of the roadway powering system for electric vehicles (EVs) and proposes a design from the perspective of power track design, integration, and powering control strategy, aiming to ensure the charging power and persistence, enhance the control flexibility, and reduce the construction cost. 1) A novel design scheme is first proposed to determine the length and number of turns for power tracks by investigating the power supply-and-demand and the loss. 2) A novel evaluation index, namely the magnetic distribution variance, is proposed to determine the gap between adjacent tracks, which can effectively produce evenly-distributed energy field, thus improving the dynamic charging performance for EVs. 3) A sectional powering control strategy is proposed to implement a cost-saving and flexible roadway powering system. Lastly, the simulated and experimental results show that the exemplified prototype can achieve the transmission power 50W over the distance of 200 mm, which verifies the proposed EV dynamic charging system with the salient advantages of the constant energization, flexible power control, and cost saving.

Applications of metallic metamaterials have generated significant interest in recent years. Electromagnetic behavior of metamaterials in the optical range is usually characterized by a local-linear response. In this article, we develop a finite-difference time-domain (FDTD) solution of the hydrodynamic model that describes a free electron gas in metals. Extending beyond the local-linear response, the hydrodynamic model enables numerical investigation of nonlocal and nonlinear interactions between electromagnetic waves and metallic metamaterials. By explicitly imposing the current continuity constraint, the proposed model is solved in a self-consistent manner. Charge, energy and angular momentum conservation laws of high-order harmonic generation have been demonstrated for the first time by the Maxwell-hydrodynamic FDTD model. The model yields nonlinear optical responses for complex metallic metamaterials irradiated by a variety of waveforms. Consequently, the multiphysics model opens up unique opportunities for characterizing and designing nonlinear nano devices.

In this paper, a single layer 4×4 U-slot patch antenna array based on differential feed was developed to achieve a wide bandwidth and low cross polarization with a simple feeding network. A U-slot was cut on a radiation patch to realize a wideband performance, and a microstrip-line fed structure was adopted to make the patch and feed network placed in a single layer. In order to reduce extra cross-polarization level in the H-plane caused by cutting U-slot, differential feed is adopted, which also makes it easily integrated with differential devices (such as differential amplifier) directly without baluns. A single layer U-slot patch array based on differential feed and an array having the same structure but based on normal feed were made and compared with each other. The designed differentially-fed patch array has more than 12% measured impedance bandwidth and stable gain at 18-19 dBi across the operating band from 5.2 to 5.88 GHz. The measured result shows that a better asymmetry of radiation pattern in the E-plane and a lower than -40 dB cross-polarization level in the H-plane can be achieved compared with normally-feed array.

Integral equation domain decomposition method (IE-DDM) with an efficient higher-order method for the analysis of electromagnetic scattering from arbitrary three-dimensional conducting objects in a half-space is conducted in this letter. The original objects are decomposed into several closed subdomains. Due to the flexibility of DDM, it allows different basis functions and fast solvers to be used in different subdomains based on the property of each subdomain. Here, the higher-order vector basis functions defined on curvilinear triangular patches are used in each subdomain with the flexibility of order selection, which significantly reduces the number of unknowns. Then a novel hybrid solver is introduced where the adaptive cross approximation (ACA) and the half-space multilevel fast multipole algorithm (HS-MLFMA) are integrated seamlessly in the framework of IE-DDM. The hybrid solver enhances the capability of IE-DDM and realizes efficient solution for objects above, below, or even straddling the interface of a half-space. Numerical results are presented to validate the efficiency and accuracy of this method.

We have developed a simple method to calculate the axial force between concentric thin walled solenoids. To achieve this, we mapped the force between them as a function of their geometrical relations based on separation to diameter ratios. This resulted in an equation and a set of data. We used them together to calculate the axial forces between two coaxial thin walled solenoids. With this method, direct evaluation of elliptical integrals was circumvented, and the forces were obtained with a simple expression. The results were validated against existing semi-analytical solutions and measurements of force between high coercivity permanent magnets.

The problem of the shift and broadening of the normal modes of electromagnetic oscillations in a cylindrical cavity resonator with axisymmetric interior and ideally conducting walls with a circular hole at the base is solved. It is shown that the existence of the hole perturbs the normal frequencies, and this perturbation is calculated. The method of solution is based on the Rayleigh-Schrodinger perturbation theory. It is found that the frequency shift depends on the value of the perturbed electric field at the hole. This field is calculated using the quasistatic approximation, which involves the solution of a mixed boundary value problem for the potential. An expression for the frequency shift and broadening is obtained.

In this paper, a band-notched UWB filtering antenna with defected ground structure (DGS) is presented. This defected ground structure as a lowpass filter (LPF) plays a role in filtering unwanted band. The DGS is applied to suppress the upper passband spectrum of the proposed antenna. A U-shaped slot line etched in the feeding line creates a single band-notched characteristic in 3.3-3.83 GHz for WIMAX to avoid potential interference with the existing system. The measured return loss has a wide fractional bandwidth up to 127.6%, which covers a range of 2.43-11 GHz, with the return loss higher than 10 dB except notch band and less than 2 dB up to 16 GHz. The measured and simulated results reveal that the antenna has good upper stopband performance and consistent quasi-omnidirectional radiation pattern within the UWB frequency range.

Electrical cables of all types are subject to aggressive operational environments that can be source of defects or accelerated aging. Reflectometry-based methods are among the best ones for the detection and location of hard defects, but cannot easily provide efficient unambiguous diagnosis for complex topology networks, such as bus or star-shaped wired networks. This paper introduces the use of a new method, called transferometry, as an additional tool for the diagnosis of complex topology networks and shows that it presents many advantages compared to reflectometry, both in terms of implementation and data processing. Based on the fusion of the analysis results of several transmitted signals, it can provide a better diagnosis with fewer sensors than distributed reflectometry, with a simpler electronic architecture.

This article describes the operational principle of the satellite-based Chinese Area Positioning System (CAPS) and proposes a monopole antenna for a large anchored buoy platform in harsh marine environment. The proposed antenna is highly omnidirectional with sufficiently wide half-power beamwidth (HPBW) greater than 40˚ (i.e., not less than ±20° swing) by using a conical ground plane, taking into account the geostationary satellite position, link budget, sea conditions, volume and cost. The impedance bandwidth defined by 10 dB return loss is 750 MHz (5.60-6.35 GHz), and the main lobe direction and the half-power beamwidth are about 46° and 43° at the operating frequency 5.885 GHz, respectively. The antenna prototype has been installed on-site to test its performance in sea. The results confirm that the proposed antenna is a suitable candidate for a variety of CAPS applications in China.

An effective design of a novel, compact, single feed, dual patch frequency reconfigurable Microstrip Patch Antenna (MPA) for wireless communication systems is proposed and studied in this paper. Fundamental structure of the antenna consists of a rectangular patch and a U-shaped patch. This antenna occupies a compact volume of 86.3 mm × 50 mm × 1.5875 mm (6850.6 mm³) including ground plane. Switching among four different frequencies is obtained by varying effective length of antenna. Effective length is changed by placing three PIN diodes at different positions in the slot present between two patches of the antenna. Variations in effective length perturb the surface current paths and hence change current density on the conducting patches. By changing states of PIN diodes, the proposed antenna could be switched to 1.87 GHz, 3.55 GHz, 3.67 GHz and 5.6 GHz frequencies. Antenna is simulated in High Frequency Structure Simulator (HFSS) Version 13.0, and a prototype of the simulated antenna with DC biasing circuit is fabricated on a flame retardant (FR-4) Epoxy substrate. The antenna is fed by an inset microstrip line which provides impedance matching. The prototype is tested for its performance analysis. A good agreement is obtained between measured and simulated results. Simulated and measured results show that the antenna provides return loss less than -10 dB assuring good match in absence of any matching network at all frequencies. Effect of changing the position of PIN diodes on resonance frequencies is also studied. The proposed antenna provides benefits such as multifunction operation and symmetry of radiation pattern upon switching between different frequencies.

In this study, new closed-form solutions are presented for deriving inductance and capacitance elements of the extended-composite right/left-handed transmission line (E-CRLH TL) unit cell from the cutoff frequencies of right-handed (RH) and left-handed (LH) bands. The characteristics of the E-CRLH TL are investigated. The dispersion diagram, Bloch impedance, S-parameters are analyzed by the TL, circuit theories and the Bloch-Floquet theorem. Lastly, the usefulness of our method has been shown in detail by designing the desired characteristics for various cases.

This paper investigates the cogging torque and torque ripple in high pole number interior permanent magnet generators, designed for direct-drive applications. Two interior permanent magnet rotor topologies --- flat-shaped and V-shaped were considered with distributed wound and fractional slot concentrated wound stators. A comparison of torque performances was made between distributed wound and fractional-slot concentrated wound generators. Cogging torque was minimized by finding an optimum magnet pole arc length and torque ripples were minimized by finding optimum slotopening and flux barrier shape. Design analysis was carried out in finite element models. It was found that flat-shaped rotor topology in the fractional slot concentrated wound stator can provide the best torque performance regarding low cogging torque and torque ripple. This finding was verified in constructed prototype machine.

This paper presents the modeling and simulation of a new rectangular ferrite-loaded waveguide based on left-handed metamaterial (LHM) unit cells at K_u-band. The structure has an 8×8 unit cell configuration, whose negative permittivity and negative permeability are achieved by metallic wires array and ferrite medium, respectively. The equivalent circuit model and transmission parameter matrix for the unit cell are presented based on microwave two-port network theory. The operating frequency is in the TE₁₀ single mode range at 12.97-15.90 GHz where magnetic and electric resonances are coupled simultaneously. The finite-element method (FEM) based simulation software HFSS has been used to set original model and optimized model with vacuum layers for decoupling. Analysis of 3D electromagnetic waves propagation and scattering parameters demonstrate the backward wave property of the optimized waveguide. Negative propagation constant and negative index of refraction are calculated based ona method for extracting effective parameters of LHM. The proposed structure has scalability, double negative, and broad-band operation characteristics in the electromagnetic paradigm.

In this paper, a new analytically regularizing method, based on Helmholtz decomposition and Galerkin method, for the analysis of the electromagnetic scattering by a hollow finite-length perfectly electrically conducting (PEC) circular cylinder is presented. After expanding the involved functions in cylindrical harmonics, the problem is formulated as an electric field integral equation (EFIE) in a suitable vector transform (VT) domain such that the VT of the surface curl-free and divergence-free contributions of the surface current density, adopted as new unknowns, are scalar functions. A fast convergent second-kind Fredholm infinite matrix-operator equation is obtained by means of Galerkin method with suitable expansion functions reconstructing the expected physical behaviour of the unknowns. Moreover, the elements of the scattering matrix are efficiently evaluated by means of analytical asymptotic acceleration technique.