An efficient hybrid MPI/OpenMP parallel implementation of an innovative approach that combines the Fast Fourier Transform (FFT) and the Multilevel Fast Multipole Algorithm (MLFMA) has been successfully used to solve an electromagnetic problem involving 620 millions of unknowns. The MLFMA-FFT method can deal with extremely large problems due to its high scalability and its reduced computational complexity. The former is provided by the use of the FFT in distributed calculations and the latter by the application of the MLFMA in shared computation.

The problem of imaging three-dimensional strong scatterers by means of a two-dimensional sliced tomographic reconstruction algorithm is dealt with. In particular, the focus of the paper is on the experimental validation of the involved inversion algorithm thanks to measurements collected in a controlled environment. A simple strategy exploiting reconstructions obtained at di®erent time instants in order to detect slowly moving scatterers is also experimentally validated.

An analysis is presented of a three-layer tapered core liquid crystal optical fiber (TLCF) having the outermost clad section made of radially anisotropic liquid crystal. TE mode propagation through TLCF is demonstrated with maximum distribution of power in the liquid crystal section under the situation that the TLCF core and the inner clad regions are constructed of homogeneous and isotropic dielectric materials. Such a propagation feature is attributed to the radial anisotropy of the liquid crystal outer region, and attracts useful applications of TLCFs in evanescent field optical sensing and other coupling devices primarily used in integrated optics.

Density is an important parameter to determine the strength of road, and it will ensure the safety of the use as well as maintaining the quality of road pavement. In this paper, the validation of GPR mixture model based on the microwave nondestructive free space method to determine the density of road pavement typed Hot Mix Asphalt (HMA) will be presented. The frequency range of operation used is 1.7-2.6 GHz. The attenuation is a major factor for gathering the density of road pavement predictably. The existing mixture model has been used to produce simulation data for determining the predicted complex permittivity and attenuation due to various densities of road pavement. The GPR laboratory measurement is performed where the measured attenuation due to various densities was obtained. The comparison results between measurement and simulation were investigated, and the relative errors in between were calculated to see the performance of the model. The best performance of mixture model was selected in the optimization technique due to the smallest mean error. An improved attenuation formula or optimized mixture model was obtained from the optimization technique to produce the better model. The finding from the optimization process suggested that three additional constant parameters which are volume factor, permittivity factor and attenuation factor need to be included to improve the existing mixture model. The optimized mixture model is introduced as GPR mixture model in this work. The validation process at field test had been conducted to evaluate the performance of optimized GPR model and produce the error range from 3.3% and 4.7%. At the end of this project, the GPR mixture model can be used as a calibration curve where the values of predicted density of a given real road pavement can be read directly once the attenuation values are known.

A wideband elliptical bowtie impulse antenna is proposed and investigated in this paper. Simulated results reveal that it can achieve an impedance bandwidth of 141% for S₁₁≤-10 dB, a broadside gain of 2.4-5.3 dB, and stable radiation pattern over the whole operating band. The measured reflection coefficient is less than -10 dB over the frequency from 1.30 to 6.65 GHz, and it agrees well with the simulated results. The characteristics of frequency-domain such as radiation pattern, phase center and time-domain behaviors are discussed. The antenna electrical dimension is 0.31λ₀, where λ₀ is the free-space wavelength at lower edge of the operating frequency band. Parameters are studied to optimize the antenna performance.

We present a new RADAR system able to perform Phase Conjugation experiments over the ultrawideband [2-4] GHz. The system is equipped with a transmit/receive linear array made of eight antennas connected to a 2-port Vector Network Analyzer through eight independent couples of digitally-controlled RF attenuators and phase shifters. Thus, each channel can selectively transmit or receive and can as well attenuate and phase shift the RF signal. For each frequency, either the Phase Conjugation or the Decomposition of the Time Reversal Operator (DORT) is applied to the received signal and the appropriate amplitude and phase law is coded into the prototype; the focusing wave is then experimentally re-emitted by the array. The quality of the achieved backpropagation is evaluated both in frequency and time domain: in this sense we can speak of Time Reversal. The excellent agreement between measured and theoretical results validates the potential of our system.

Strong interests are recently emerging for development of solid-state devices operating in the so-called "terahertz gap" region for possible application in radio astronomy, industry and defense. To fill the THz gap by using conventional electron approach or transit time devices seems to be very difficult due to the limitation that comes from the carrier transit time where extremely small feature sizes are required. One way to overcome this limitation is to employ the traveling wave type approach in semiconductors like classical traveling wave tubes (TWTs) where no transit time limitation is imposed. In this paper, the analysis method to analyze the properties of drifting plasma waves in semiconductor-insulator structure based on the transverse magnetic (TM) mode analysis is presented. Two waves components (quasi-lamellar wave and quasisolenoidal wave), electromagnetic fields (E_y, E_z and H_x) and ω-and k-dependent effective permittivity are derived where these parameters are the main parameters to explain the interaction between propagating electromagnetic waves and drifting carrier plasma waves in semiconductor. A method to determine the surface impedances in semiconductor-insulator multi-layered structure using equivalent transmission line representation method is also presented since multi-layered structure is also a promising structure for fabricating such a so-called plasma wave device.

Electromagnetic scattering by conducting bodies of revolution (BOR) coated with homogeneous chiral media above a lossy half-space is formulated in terms of the Poggio-Miller-Chang-Harrington-Wu surface integral equation combined with combined field integral equation. A field decomposition scheme is utilized to split a chiral media into two equivalent homogeneous media. The spatial domain half-space Green's functions are obtained via the discrete complex image method. Due to the rotational symmetry property of BOR, the method of moment for BOR (BORMoM) is applied to the linear system solved by the multifrontal direct solver. Numerical results are presented to demonstrate the accuracy and efficiency of the proposed method.

Characteristics of electromagnetic wave propagation through a magnetized plasma slab with linear electron density profile is analysed. In the numerical analysis, cold, weakly ionized, collisional and steady state plasma layer is divided into sufficiently thin, adjacent subslabs, in each of which plasma parameters are constant. Reflection and transmission coe±cients are calculated for discretised plasma by considering electron density profile with positive and negative slopes. Wideband absorbtion characteristic is obtained with high collision frequency and high electron density combination in linearly decreasing profile as well as wideband transmission characteristic is obtained for low collision frequency and low electron density combination in linearly increasing profile of finite length. The general results show that in steady state, plasma layer behaves as a frequency selective medium satisfying the major requirements of current shielding applications as the function of plasma parameters and the strength of external magnetic field excitation. Proposed plasma layer can be used in current shielding and stealth applications as a matching layer between the surface and the incident electromagnetic wave.

In this paper, a directional slot antenna with parasitic patch and windowed superstrate is presented. Through this composition, high-gain property can easily be obtained by this proposed antenna. The proposed antenna has a measured impedance bandwidth of 2.41-2.49 GHz for S11<-10 dB, which can cover the 2.4-2.484 GHz frequency band of WLAN application. Simulated and measured results show that high-gain features up to 11.50 dBi across the corresponding impedance band are achieved. Details of the proposed slot antenna configurations and design procedures are given; the experimental results are also given and discussed.

A novel rectangular slot antenna with embedded self-similar strips is proposed for wireless local area network (WLAN) applications. The proposed antenna comprises a T-shaped monopole and inverted self-similar strips embedded in the rectangular slot etched on the ground plane. The measured results of the fabricated antenna show that the impedance bandwidths (VSWR<2) are 180 MHz from 2.36 to 2.54 GHz and 920 MHz from 5.05 to 5.97 GHz, which cover all the 2.4/5.2/5.8 GHz WLAN operating bands. And the radiation patterns are almost omni-directional in the azimuthal plane within the lower operating bands.

In this paper, we apply the parallel method of moments (MOM) to solve the Electric and Magnetic Current Combined Field Integral Equation (JMCFIE) for scattering by large, three-dimensional (3-D), arbitrarily shaped, homogeneous dielectric objects. We first derive the JMCFIE formulation which produces well-conditioned matrix equation when the MOM with Galerkin's type testing and Rao- Wilton-Glisson (RWG) functions is applied. We then develop a parallel conjugate gradient (CG) method on personal computer (PC) clusters using message passing interface (MPI) for solving the matrix equation obtained with JMCFIE. The matrix is decomposed by the row and stored in distributed memory of the node. Several numerical results are presented to demonstrate the accuracy and capability of the proposed method.

An efficient method is presented for rigorous description of three-dimensional electromagnetic diffraction fields in slot systems containing several parallel plane interfaces between dielectrics and conductors. For such structures, the method employs the representation of spatial field components in terms of two complex scalar functions. They specify two field polarizations, which reflect and refract on all parallel dielectric interfaces independently, one from the other, which essentially simplify the total solution of diffraction problem. As an example, the application of eigen-function expansions and mode-matching technique solves the specific problem of three-dimensional diffraction of a plane electromagnetic wave by a slot in a thin conducting screen located ahead of a half-infinite dielectric.

Synthetic aperture radar (SAR) imagery technology is one of most important advances in space-borne microwave remote sensing during recent decades. Completely polarimetric scattering from complex terrain surfaces can be measured. Polarimetric SAR (POLSAR), and its relevant technologies, such as POL-interferometric SA (POLINSAR), bistatic SAR (POL-BISAR), high resolution (in m and dm resolution) SAR, inverse SAR (ISAR) etc., have been providing rich all-weather, all-time and high resolution data and images of active miscrowave remote sensing. Fully understanding and retrieving information from polarimetric scattering signatures of natural media and SAR images have become a key issue for the SAR remote sensing and its broad applications. Many researches on polarimetric scattering and SAR imagery technology have been carried out (e.g., [1-6]). This paper presents a review of the research works in Fudan University (FDU) during recent years on theoretical modeling of the terrain surface for polarimetric scattering simulation and Mueller matrix solution, mono-static and bistatic SAR image simulation, new parameters for unsupervised surface classification, DEM inversion, change detection from multi-temporal SAR images, and reconstructions of buildings from multi-aspect SAR images, etc. [7-46]. Some applications are briefly reported.

We study the characteristics of nano-optical antenna made of two gold nano-particles by three dimensional numerical calculations in visible and near infrared bands. To carry the computational burden and guarantee the precision and speed of a three dimensional FDTD calculation, adaptive mesh refinement technology is used. In this paper, we first highlight the concrete way of controlling the emitter position and orientation to fulfill the requirements of larger spontaneous emission enhancement. Then, we analyze the far field distribution and find that the far fied directivity is strongly influenced by surface plasmon polaritons (SPPs). Choosing the incident wavelength of 600 nm, we compute the decay rates and radiant efficiency as a function of antenna geometry limitations. Next, the particle aspect ratio is optimized, and we obtain that L/R = 4 is the best for our optical-antenna. Furthermore, we present a spectrum analysis. Around 5000 fold spontaneous emission enhancement is successfully achieved. Finally, we find a piecewise linearity relationship between the particle length and resonant wavelength.

The feasibility of using a capacitive sensor to sense the proximity of an external load, especially a finger, to a mobile terminal antenna was experimentally studied using a PIFA-type antenna as one of the sensor's electrodes. It was found that with the proposed arrangement it is possible to detect objects with permittivity close to that of body tissue or the conductivity level of aluminium and the size of a human finger at distances up to 15 mm.

Rotating coils constitute a type of electrical transformers used to produce alternating voltage pulses exploiting the phenomenon of electromagnetic induction. In this study, we investigate the influence of the electromagnetic scattering from a metallic obstacle located inside the moving component. In particular, a perfectly conducting spherical core is positioned eccentrically inside a thin circular ring, rotating around an arbitrary axis passing through its own center, under plane wave excitation. Methods and formulas implemented in scattering and induction problems have been utilized for the derivation of the developed potential difference around the loop. Several graphs of the voltage output versus the geometrical characteristics of the conguration, are shown and explained.

This paper presents a phase-resolved optical coherence tomography (OCT) system that uses the polarization quadrature encoding method in a two-channel Mach-Zehnder interferometer. OCT is a powerful optical signal acquisition method that can capture depth-resolved micrometer-resolution images. In our method, a complex signal is optically generated, and its real and imaginary components are encoded in the orthogonal polarization states of one sample beam; absolute phase information can then be acquired instantaneously. Neither phase modulation nor numerical Fourier or Hilbert transformation to extract phase information is required, thereby decreasing data acquisition rates and processing time. We conducted signal post-processing to select data from the instabilities of reference scanning delay lines; the measured phase sensitivity was as low as 0.23°, and the corresponding path-difference resolution was 265 pm. A localized surface profile measurement of a chromium-coated layer deposited on a commercial resolution target surface was conducted. The results confirmed that successful images can be obtained even with very small optical path differences using the proposed method.

Design of array antennas for satellite applications is always a trade-off between physical constrains and pattern requirements. In this paper, the focus is on the design of a large array antenna for earth coverage applications using spot beams. The array antenna has a diameter of 1 m and consists of circular polarized horn antennas positioned in a non-uniform grid. By using a binary coded genetic algorithm (BCGA) the desired element positions and their excitations are optimized to fulfill the pattern requirements. In addition thinning has been used to study the possibility of maintaining good antenna performance when reducing the number of elements. The proposed antenna design has robust side lobe level, beam width and gain; all remain virtually unchanged under a change of operating frequency ±7% and under lobe steering over earth ±8.8^o.

This work presents an accurate and realistic positioning approach for indoor environments based on fingerprinting and ray-tracing techniques. Fading caused by multipath seriously degrades the performance of communication systems operating inside buildings. For this reason, the proposed localization method considers multipath effects due to reflections and diffraction from walls, roof and floor. However, fading in indoor environments can also be caused by the movement of people or the presence of furniture. Because people are the primary absorption agents in indoor channels, their influence on the radio propagation channel must be considered. The proposed localization method takes into account the effects of human body shadowing to provide a realistic estimation of the mobile station position. Numerical calculations in real indoor scenarios show reasonable results.