In this paper, we investigate electromagnetic problems for nanoscale antennas by using a boundary integral equation method with fast inverse Laplace transform. The antennas are designed for realizing ultrafast and high-density magnetic recording. Characteristics of nanoscale antennas are discussed in terms of eigenmodes and time domain responses of electric fields. Our computational method is highly efficient and the computational cost can be reduced by selecting coarse time step size and performing parallel computation.

A tunable electromagnetic-bangap (EBG) structure based on a double layer slotline using plasma is proposed. The plasma permittivity can be tuned by the electron density. The idea of integrating periodical plasma elements inside the slot to tune the stopband is investigated. An electron density and an electron collision frequency equal to 1.75 10¹³ cm^-3 and 10¹⁰ s^-1 respectively, are the plasma parameters selected in this study. The simulations reveal a shift rate of the second stopband equal to 6%. A new configuration of the structure is also proposed to adapt it better to the experimental requirements. Based on the simulation results, adding the plasma elements to the modified configuration shifts the stopband 4% and reduces its bandwidth by 43% (at -20 dB).

Bistatic forward-looking SAR (BF.SAR) has many potential applications, such as self-landing in bad weather and military detection. Therefore, BFSAR receives considerable attention recently. The imaging algorithms for BFSAR are the difficulties of the study. The original Loffeld's Bistatic Formula (LBF) can handle most general bistatic SAR configurations well. But in some complex bistatic geometries, such as high squint or forward-looking cases, the performance of LBF is degenerated. Some extended LBF (ELBF) methods have been developed, which improve the performance of LBF in some special geometries, but still not the forward-looking configuration. In this paper, we modify the LBF method and try to solve the instantaneous azimuth frequencies of transmitter and receiver directly. Then, we can obtain a bistatic point target reference spectrum (BPTRS), which is accurate enough for forward-looking configuration. A range Doppler algorithm (RDA) based on this BPTRS is derived. Finally, simulations validate the accuracy of the modified Loffeld's Bistatic Formula (MLBF) and effectiveness of imaging algorithm.

This paper presents a new approach for localizing mobile phone users using the promising technique of stratospheric platform (SP) flying at altitudes 17-22 km high and a suitable Direction-of-Arrival technique (DOA). The proposed technique provides information about accurate locations for mobile stations - through high resolution DOA technique - which is very important for traffic control and rescue operations at emergency situations. The DOA estimation in this technique defines the user location using MUSIC algorithm which provides good accuracy comparable to the Global Positioning System (GPS) techniques but without the need for GPS receivers. Several scenarios for users' locations determination are tested and examined to define the robustness of the proposed technique.

In this paper, a novel near zero refractive index metamaterial is designed and used as a superstrate of a microstrip antenna. In order to decrease the return loss, particle swarm optimization (PSO) is used to optimize the metamaterial structure. One of the important factors in the antenna designing, which influences the radiation efficiency, is to determine the accurate position of the feed, and PSO is used to find a precise location of the feed with minimum return loss. The simulation and fabrication of the microstrip antenna using the optimized metamaterial structure is also presented. The performance of the antenna is improved, and the gain is increased up to 4.5 dB. The directivity and radiation efficiency are significantly enhanced. Moreover, a very good agreement is observed between simulation and measurement results.

A volume-surface integral equation (VSIE) formulation is developed for determining the electromagnetic TM scattering by a two-dimensional conducting cylinder coated with an inhomogeneous dielectric/magnetic material. The electric field integral equations (EFIEs) are utilized to derive the VSIE. The surface EFIE is applied to the conducting surface, while the volume EFIE is applied to the coating region. By employing the surface and equivalence principles, the problem is reduced into a set of coupled integral equations in terms of equivalent electric and magnetic currents radiating into unbounded space. The moment method is used to solve the integral equations. Numerical results for the bistatic radar cross section for different structures are presented. The well-known exact series-solution for a conducting circular cylinder coated with multilayers of homogeneous materials is used along with the available published data to validate the results. The influence of using coatings with double-positive (DPS) and/or double-negative (DNG) materials on the radar cross section is investigated.

A dual-beam microstrip array antenna based on conical beam elements is proposed in this paper. Circular patch operating at the TM₀₁ mode is used to achieve conical beam pattern. Grating lobes of the array is used to obtain dual-beam patterns with large elevation angle and high gain. Detailed analysis and design have been presented. A 4x4 antenna prototype has been fabricated and measured. Experimental results show that the antenna array has the return loss better than 10 dB over 12.26 GHz-12.88 GHz and exhibits two symmetric radiation beams, directed at ±49.4° with 16.6 dBi gain at 12.5 GHz. Good agreement between the simulated and measured results is observed. Compared with the previous scheme, the alternative proposal possesses the advantages of being easy to form a planar array with low cross-polarization and having relatively high aperture efficiency simultaneously.

The Radar Cross Section(RCS) of moving targets varies dramatically with aspect or time. The accuracy of simulated dynamic RCS is very important for radar system simulation. A novel simulation approach of aircraft's dynamic RCS is proposed in this paper. Firstly, the electromagnetic (EM) model of aircraft is built and the all-space mono-static RCS database calculated. Secondly, the aspect angles (azimuth and elevation) in target coordinate system are calculated from flight path by coordinate transformation. Then dynamic RCS is obtained based on database and aspect angles by linear interpolation method. Account for the influence results from aircraft vibration in target motion, we use a white Gaussian distributed random series to modify the simulated results. The statistical characteristics of three kinds of dynamic RCS values are investigated, and the desirable agreement of results between modification and measurement shows the applicability of this simulation approach.

In this paper, an analytical model of permanent magnet electrodynamic suspension systems (PEDSs) is proposed. Horizontal and vertical magnetic fields of a permanent magnet (PM) are affectively approximated by sinusoidal functions. By this means, closed form solutions are obtained for lift and drag forces of PEDS for the first time. The suspension system is modelled by finite element method (FEM). The analytical values of lift and drag forces are compared with the FEM results. Also, the analytical results are evaluated by experimental results. As so, the accuracy of the analytical model is validated by FEM and experimental measurements.

We provide a critical account of the dynamics of laser induced refractive index changing mechanisms in nematic liquid crystals which may be useful for all-optical switching and modulation applications in the visible as well as the Terahertz and long-wavelength regime. In particular, the magnitude and response times of optical Kerr effects associated with director axis reorientation, thermal and order parameter changes, coupled flow-reorientation effects and individual molecular electronic responses are thoroughly investigated and documented, along with exemplary experimental demonstrations. Emphases are placed on identifying parameter sets that will enable all-optical switching with much faster response times compared to their conventional electro-optics counterparts.

The generic foundry approach will lead to a revolution in micro and nanophotonics, just as it did in microelectronics thirty years ago. Generic integration leads to a drastic reduction in the entry costs for developing Photonic Integrated Circuits. Integrated circuits using generic integration open up a whole new range of applications including data communications, fiber-to-the-home, fiber sensors, gas sensing, medical diagnostics, metrology and consumer photonics. Present status and prospects of InP-based photonic foundry technology are reviewed.

The idea of transformation inside a null-space region is introduced for the first time, and used to design a novel DC magnetic compressor that concentrates DC magnetic flux greatly and behaves as a DC magnetic funnel. The proposed device can be used as a passive DC magnetic lens to achieve an enhanced DC magnetic field (e.g. 7.9 times or more depending on the size and other parameters of the compressor) with a large gradient (e.g. 400T/m or more) in free space. After some theoretical approximation, the proposed device can be easily constructed by using a combination of superconductors and ferromagnetic materials. Numerical simulations are given to verify the performance of our device. The proposed method (use a null-space region as the reference space) can be extended to reduce the material requirement when designing other devices with transformation optics.

We present a broadband microwave metamaterial (MM) absorber, the unit cell of which consists of a lumped-resistor-loaded electric-inductive-capacitive (ELC) resonator and a cut-wire on the same side of a flexible polyimide substrate. In contrast to the common MM absorber, the metallic pattern layer of the proposed structure is placed parallel to the direction of propagation of the incident wave in order to reduce the radar cross-section (RCS) at frequencies other than the targeted frequency bands. Our experiments show that the proposed absorber exhibits a peak absorption rate of 92% and 93% at 8.6 GHz and 13.4 GHz, respectively, and 88% of the full-width at half-maximum (FWHM) bandwidth is achieved.

This paper presents a low-cost strip-to-bilateral-slotline transition with operating bandwidth from 0.53 to 6 GHz. The low-cost design concept is realized by utilizing conventional cheap FR-4 substrate and wide slotline with large slot width. By virtue of the low price of FR-4, less strict fabrication tolerance of wide slotline and the avoidance of metallic vias, the fabrication cost is reduced significantly compared to schemes using expensive Rogers RT laminates, extremely narrow slotline with strict fabrication tolerance and metallic vias. The broadband impedance matching difficulty caused by the high characteristic impedance of wide slotline is solved by three means. Firstly, bilateral structure is used to lower the characteristic impedance of the slotline. Then an elliptic slotline stub and an innovative half-elliptic strip stub are proposed to provide good impedance matching. Finally, multi-section stepped impedance transformers are used to match the transition from high impedance to standard 50 Ohm. The validity of the design methods is verified through experiments.

A compact millimeter-wave (MMW) wideband high-gain antenna is proposed and implemented. The development is based on the design principle of wideband Fabry-Perot resonator antennas (FPRAs). The antenna consists of three dielectric slabs and a PEC ground, and it is fed by a rectangular waveguide. All slabs are used to form the superstrate that exhibits the increasing reflection phase at the designed frequency band. Size reduction of the superstrate is carried out to enhance the bandwidth of the antenna. The effect of ground size and resonant frequency shift due to size reduction of the superstrate were studied. A wide bandwidth of over 30% was finally obtained, and measurements of the fabricated prototype validate the theory and simulation results.

A novel rotational motion compensation algorithm for high-resolution inverse synthetic aperture radar (ISAR) imaging based on golden section search (GSS) method is presented. This paper focuses on the migration through cross-range resolution cells (MTCRRC) compensation, which requires rotation angle and center as priori information. The method is nonparametric and uses entropy criterion to estimate rotation angle and rotation center, which are used for rotational motion compensation. Experimental results show that the rotational motion in ISAR imaging can be effectively compensated. Moreover, the proposed method is robust and computationally more efficient compared to the parametric methods.

This paper proposes an ecient method to obtain ISAR images of multiple targets ying in formation. The proposed method improves the coarse alignment and segmentation of the existing method. The improved coarse alignment method models the ight trajectory using a combination of a polynomial and Gaussian basis functions, and the optimum parameter of the trajectory is found using particle swarm optimization. In the improved segmentation, the binary image of the bulk ISAR image that contains all targets is constructed using a two-dimensional constant false alarm detector, then the image closing method is applied to the binary image. Finally, the connected set of binary pixels is used to segment each target from the bulk image. Simulations using three targets composed of point scattering centers and the measured data of the Boeing747 aircraft prove the eectiveness of the proposed method to segment three targets ying in formation.

This paper proposes a new modal analysis based on Floquet's theorem which is needful for the study of a 1-D periodic phased array antenna excited by arbitrary located sources. This analysis requires an accurate estimation for calculation of the mutual coupling parameters (for example: mutual impedances or admittances...) between the array elements and their effects integrating a large planar radiating structure. Two different formulations are suggested, in spectral and spatial domains, to solve the problem and to calculate the coupling coefficients between the neighbouring elements in a periodic environment. Important gain in the running time and used memory is obtained using Floquet analysis. One numerical method is used for modeling the proposed structures: the moment method combined with Generalized Equivalent Circuit (MoM-GEC).

Based on Faraday's law of electromagnetic induction and the existence condition of non-trivial solution to a homogeneous and linear differential system of equations, the equivalent self-inductance of N coupled parallel coils has been derived by uing some algebraic techniques. It can be expressed as the ratio of the determinants of two matrices, with ranks of N and N-1, respectively, and constructed with the self and mutual inductance of those coils. In addition, special conclusions are deduced and/or discussed in detail for three particular cases: 1, the completely uncoupled case, 2, the identical and symmetrical case, and 3, the completely coupled case, which are coincident with the existing results in the references.

The selection of matching method is critical to the scene matching navigation system, as it determines the accuracy of navigation. A coarse-to-fine matching method, which combines the area-based and feature-based matching method, is presented to meet the requirements of navigation, including the real-time performance, the sub-pixel accuracy and the robustness. In the coarse matching stage, the real-time performance is achieved by a pyramid multi-resolution technique, and the robustness is improved by multi-scale circular template fusion. In the precise matching stage, an improved SIFT method is introduced to calculate the matching position and the rotation angle. To validate the method, some experiments are completed. The results show that the proposed method can achieve the sub-pixel matching accuracy and improve the angle accuracy to 0.1°.