An efficient algorithm based on high-order cumulant is addressed for the scenarios where both far-field and near-field narrow-band signals may exist synchronously. The first matrix built by four-order cumulant is utilized to estimate the two dimensional direction-of-arrivals (DOAs) using the orthogonal projection matrix of the signal subspace and the virtual steering matrix. Then, the second matrix built by four-order cumulant is decomposed to get the noise subspace using the eigen decomposition. Meanwhile, a virtual steering matrix is used to distinguish far-field signals (FFSs) from near-field signals (NFSs). And one-dimensional MUSIC algorithm is used to estimate the range of the NFSs. Compared to the TSMUSIC, the proposed algorithm can provide high resolution for the DOAs. In addition, there is higher accuracy for the DOA of NFS in the proposed algorithm than that in TSMUSIC and in TSMD. Simulation results are carried out to certify the performance of the proposed algorithm.

The effect of a substantial increase of the Faraday rotation angle has been investigated in a symmetrical resonator structure, which is represented by a one-dimensional photonic crystal with dielectric Bragg mirrors and a magnetically active layer placed between mirrors. In the numerical analysis, the parameters of a pure yttrium iron garnet at two wavelengths - 1.15 μm and 1.3 μm have been used. The increase in the Faraday rotation angle is caused by not only an increase of the magnetic layer thickness, but also a symmetrical increase in the number of Bragg mirrors periods.

In this paper, we introduce an efficient algorithm to analyze metamaterials, which can be finite periodic structures with tightly coupling between nearby cells. Firstly, the algorithm, based on method of moments (MoM), uses hybrid volume-surface integral equation (VSIE) to analyze composite dielectric-conductor objects. Then, the characteristic basis function method (CBFM) and precorrected-fast Fourier transform (p-FFT) algorithm are combined to accelerate the calculation of equations, based on which, metamaterials composed of connected periodic cells can be analyzed efficiently.

Multipactor effect is studied in a hollow elliptical waveguide carrying two orthogonal polarization modes, i.e., the fundamental (TE_c11) and the second (TE_s11) elliptical waveguide modes. The introduction of a modal equivalent voltage allows defining the standard axial ratio, which characterizes each polarization state of the problem. The RF breakdown threshold is determined as a function of the axial ratio for various amplitudes and phases of the two elliptical modes. In particular, the effect of the second mode on the RF breakdown threshold of the fundamental mode is studied. The simulations are carried out for different values of the eccentricity of the ellipse eccentricity.

This paper presents a design of wideband and low-profile linear array of H-plane horn antennas. In order to construct the linear array in H-plane, the aperture size of the horn antenna in the H-plane should be comparable with one wavelength in the free space, which leads to a poor impedance matching especially in the lower frequency range. The approach to the problem is removing the side walls of the flare part of the antennas. The array is fed by a wideband 4-way ridged SIW power divider. The designed array operates from 5.6 GHz to 18 GHz for VSWR 2.5 and exhibits stable radiation beam with a narrow beam-width in H plane over the same frequency rang while retaining the antenna array height of only 4 mm (0.17λ₀ at the center frequency). The designed array is fabricated and tested. It is observed that measured results agree well with simulated ones.

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.