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°.

Photoacoustic tomography (PAT) is an emerging imaging modality that shows great potential for preclinical research and clinical practice. As a hybrid technique, PAT is based on the acoustic detection of optical absorption from either endogenous chromophores, such as oxy-hemoglobin and deoxy-hemoglobin, or exogenous contrast agents, such as organic dyes and nanoparticles. Because ultrasound scatters much less than light in tissue, PAT generates high-resolution images in both the optical ballistic and diffusive regimes. Over the past decade, the photoacoustic technique has been evolving rapidly, leading to a variety of exciting discoveries and applications. This review covers the basic principles of PAT and its different implementations. Strengths of PAT are highlighted, along with the most recent imaging results.

Element failure distorts the main-lobe pattern and increases side-lobe power level, which is almost impossible to be corrected artificially for space-borne array. It might be solved by redistributing the excitations of the left functional elements; however, this is a nonlinear, non-convex, and NP-hard problem. In this paper, two effective approaches are proposed for failure correction, which is performed for space-borne hexagonal array using digital beamforming (DBF). One method, a modified real-code genetic algorithm (RCGA), is employed that uses reinsertion and worst-elimination schemes, but it pays the high computation complexity. The other approach based on convex optimization chooses the excitations synthesized by RCGA as the initial points, and skillfully transforms the non-convex problem into a sequence of second-order cone programming (SOCP) problem, which is solved iteratively by efficient optimization tool. Numerical results confirm that after the correction based on iterative convex optimization, the average root-mean-square error (RMSE) is reduced by 36%, and the relative side-lobe level (RSLL) is improved by 6.7 dB, with respect to the RCGA-based correction pattern.

This paper presents a hybrid scheme for fast calculation on the bistatic composite scattering from electrically very large ship-sea geometry at high frequencies. Based on the Kirchhoff approximation (KA), we try to break the large-scale sea surface into myriads of plane facets, then derive the Kirchhoff integration analytically on each individual discretized facet. The analytical expression obtained, so-called the ``facet-based Kirchhoff approximation (FBKA)'', is suitable for a quick scattering calculation on the electrically very large sea surface, since it is beyond the intensively refined meshes as the usual Monte Carlo implementation does. Meanwhile, combined with graphical electromagnetic computing method (GRECO) to extract the illuminated and shadow facets in accordance with the incident direction, the conventional physical optics method (PO) is improved by employing current marching technique (CMT) to calculate the currents in the shadow region. The shadow-corrected GRECO is presented in this hybrid model to solve the bistatic scattering from complex and very electrically large perfectly electric conducting (PEC) objects. The accuracy of the shadow-corrected GRECO is confirmed well by exact numerical methods, especially at large scattering angles. The electromagnetic interactions between the ship and sea surface are estimated by the famous ``four-path model'', which has been proved to be valid for ship scattering at relatively calm sea state. Several numerical examples have been presented to demonstrate the efficiency and accuracy of the proposed hybrid method.

A novel dual frequency microstrip antenna with low radar cross section (RCS) is proposed in thispaper. Compared with the traditional microstrip antenna, the novelmicrostrip antenna loaded complementary split-ring resonators (CSRRs) has a low RCS. The novel and traditional dual-frequency microstrip antennas with the center frequency of 3.4 GHz and 5 GHz are designed and fabricated. The results demonstrate that the monostatic RCS of the proposed antenna has beenwell reduced. The RCS reduction at 5 GHz is as much as 17 dB. Besides,in the case of the φ-polarized incident wave, the RCS reduction can be achieved in the angular ranges of -90°≤θ≤+90° in xoz-plane and yoz-plane. At the same time, the CSRRs cause no obvious deterioration in radiation performance.

In this paper, we propose a stochastic approach for the analytical analysis of the multicarrier multipactor discharge occurring in high-power vacuum microwave devices, in which electric fields are not homogeneously distributed. We indicate that the statistical behavior of large amount of secondary electrons in the process of a multipactor discharge can be well described by the probabilistic random walk and Levy walk theory. Based on the derived probability density of the lateral diffusion of secondary electrons in homogeneous fields, the multicarrier multipaction in inhomogeneous fields can be analytically computed with significantly enhanced efficiency. As a demonstration, the accumulation of secondary electrons of a multicarrier multipaction in a rectangular waveguide supporting TE₁₀ mode is given. The theoretical results comply well with the results achieved by the time-consuming particle simulation, the slope difference of which is less than 0.8%, while only costs one-order less computational time. To the best of our knowledge, this is the first time that the probability density of the lateral diffusion of secondary electrons during a multipaction is theoretically derived. This density depicts the physical picture of the statistical movement of secondary electrons during the process of a multicarrier multipactor, which can be widely used in the areas of high-power electronics and electromagnetism.

This paper introduces a novel structure of 4×4 multiple beam forming antenna system using substrate integrated folded waveguide technology. For high speed wireless communication it is necessary to minimize the interferences and multipath fading. Multiple beam forming antenna system is a good solution to these problems. The substrate integrated folded waveguide (SIFW) technology reduces the width of substrate integrated waveguide (SIW) by half. All the basic building blocks required for the antenna array system are designed and simulated individually. They are then combined to form the butler matrix fed antenna array system. The SIFW technology reduces the total width of butler matrix. The radiation performance of the multiple beam forming antenna system is realized by integrating the H-plane SIFW horn antennas with the output ports of the butler matrix. The system is practically realized and good directive multiple beams with symmetric gain (5.8 dB, 5.63 dB, 5.31 dB and 5.9 dB for the beams 1R, 2L, 2R and 1L) have been achieved.

This paper concerns with the interaction of electromagnetic waves with a moving slab. Consider a homogeneous isotropic slab moving uniformly in an arbitrary direction surrounded by an isotropic medium (free space). In this paper a new simple and systematic method is proposed for analyzing reflection and transmission of obliquely incident electromagnetic waves by a moving slab based on the concept of propagators. In the previous works complex relations were arrived but using this novel method those complexities will not appear thus the method may be extended to more complex structures. In this method, first, electric and magnetic fields are decomposed into their tangential and normal components then each constitutive dyadic is decomposed into a two-dimensional dyadic in transverse plane and two two-dimensional vectors in this plane. Substituting these dyadics into Maxwell's equations gives a first order differential equation which contains fundamental dyadic of the medium. From the solution of this equation, fields inside the slab may be expressed in terms of fields at the front surface of the slab and the propagator matrix which is an exponential function of fundamental dyadic. Using this method the up-going and down-going tangential electromagnetic fields may be obtained at the same time. As a limiting case a slab with vanishing velocity is discussed using this method, and reflection and transmission coefficients of this slab are derived, which ends in Fresnel's equations. At last, several typical examples are provided to exemplify the applicability of the proposed method. Moreover, the results are compared with the method of Lorentz transformation. A good agreement is observed between the results which verifies the validity of the proposed method.

A compact printed dipole antenna with wide impedance bandwidth is proposed in this paper. This antenna consists of a pair of radiation metal arms and a microstrip-to-slotline transition structure. At the end of the feeding slotted line, a beveled slot with stepped connection structure is designed to realize an offset feeding structure for feeding the dipole antenna. By using the beveled offset feeding structure, the bandwidth of the dipole antenna is significantly improved. The microstrip-to-slotline transition is used as an integrated balun to realize a balanced feeding for the dipole antenna. To demonstrate the effectiveness of the proposed design, a prototype of the designed antenna is fabricated and measured. The measured results show that the designed dipole antenna achieves a gain of 2.2-4.4 dBi across a wide impedance bandwidth from 2.65 GHz to 17.5 GHz with a compact size (33 mm×16 mm). The performance of the proposed dipole antenna is also compared with some similar printed dipole antennas with respect to overall size, substrate dielectric constant, impedance bandwidth and antenna gain.