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.

We present a new approach based on numerical constructions of testing functions for improving the accuracy of the magnetic-field integral equation (MFIE) and the combined-field integral equation (CFIE) with low-order discretizations. Considering numerical solutions, testing functions are designed by enforcing the compatibility of the MFIE systems with the accurate coefficients obtained by solving the electric-field integral equation (EFIE). We demonstrate the accuracy improvements on scattering problems, where the testing functions are designed at a single frequency and used in frequency ranges to benefit from the design procedure. The proposed approach is easy to implement by using existing codes, while it improves the accuracy of MFIE and CFIE without deteriorating the efficiency of iterative solutions.

Metamaterials have been previously loaded with diodes and other types of passive circuit elements. Transistors offer an alternative to these established loading elements to expand the possible capabilities of metamaterials. With embedded transistors, additional degrees of freedom are achieved and lay out the architecture for more complex electromagnetic metamaterial design. A mathematical analysis of transistor loaded SRR unit cells is described in which the transistor acts as a variable resistor. From the mathematical analysis, we calculate transmission coefficients for a single unit cell. We then experimentally measure two SRRs with tunable quality factors and thus tunable bandwidth based upon modulating the effective loading circuit resistance to confirm the calculations. From the agreement between the calculated and measured transmission coefficients, we expand the analysis to show that a slab of more densely packed unit cells can achieve negative permeability with varying degrees of dispersion.

A novel low radar cross section (RCS) microstrip patch antenna array (1×4) (MSPAA) is reported in this paper. A thin and wideband radar absorber (RA) based on a single octagonal loop (SOL) resistive frequency selective surface (FSS) is designed for realizing out-of-band RCS reduction of the MSPAA from 6.2 GHz to 18 GHz. The RA is designed for -15 dB reflectivity from 6.2 GHz to 18 GHz. Embedded Passives (EP) resistors are used for implementing the resistors as integral to the substrate with no soldering at all which results in a quantum improvement in reliability. Full wave analysis of the low RCS MSPAA with the RA is carried out using HFSS. RCS measurements are performed, and an RCS reduction of 6 to 18 dB is attained compared to the reference antenna array over a wide band from 6 GHz to 18 GHz, with no degradation in VSWR and gain of the antenna array. The thin and wideband RA with its low weight and flight worthy constituent materials can be applied independently as skins of a stealthy UAV configured primarily for low RCS with external shaping, and the proposed antenna array can be used without modifications, as a low RCS conformal antenna structure.

The simulation of multi-layer rough surfaces is an indispensable step in passive radiation imaging, to which little attention has been paid so far. Based on the existing model of brightness temperature tracing described in our recent works, diffused transmission of the bottom layer is taken into account in the improved model which is presented in this paper. Then, a method called multi-layer brightness temperature tracing method (MBTT) is established to obtain the brightness temperature of a rough surface, and the applied range of the simulation in passive millimeter-wave imaging (PMMW) is extended.

In fixed-receiver bistatic synthetic aperture radar (SAR), the spaceborne SAR is used as an illuminator. The direct-path signal and bistatic SAR raw data are sampled by the fixed-receiver which is placed on the top of a building or a hill. As the direct-path signal has high signal-tonoise ratio (SNR) advantage and almost the same synchronization error terms, it is used as the reference signal for the range matched filtering. Then the range compression can be realized with a time and frequency synchronization process. However, after range match filtering by the directpath signal, the range history of point target consists of three square-root terms, for which it is hard to use the Principle of Stationary Phase (POSP). Meanwhile, the two-dimensional (2-D) spatial variation of the target's 2-D frequency spectrum is serious. By combining azimuth preprocessing, directpath signal compensation and nonlinear Chirp Scaling (NLCS) imaging algorithm, a new focusing algorithm is presented in this paper. Simulation results of point targets are presented to validate the efficiency and feasibility of the proposed imaging algorithm. Finally, this algorithm is also validated by the measured data which is obtained using the HITCHHIKER system.

A new design of non-planar magneto-electric monopole antenna is proposed and presented. This antenna consists of a novel design of electric monopole with dual Ί shaped feed line design and possesses 61.5% impedance bandwidth, from 4.5 GHz-8.5 GHz. The antenna exhibits stable omnidirectional radiation pattern with almost identical E-plane and H-plane radiation patterns and also provides a peak gain of 7.4 dBi. Due to its good electrical characteristics and radiation parameters, the antenna has great capability to operate in C band, to overcome the challenges of multi-frequency applications.

This work investigates on the performance improvements in terms of sidelobe reduction provided by arrays organized into randomly overlapped subarrays (ROSAs) in comparison to other subarray arrangements such as contiguous and uniformly-overlapped modules. This configuration can be advantageous for applications that need to scan over a limited angular sector. The performance of the ROSA design is thoroughly analyzed for different degrees of overlapping in terms of scan losses, minimization of peak side lobe level, number of components and array size.