This work demonstrates an efficient and simple PML absorbing boundary conditions (ABCs) implementation for the highorder extended-stencil M24 FDTD algorithm. To accomplish this objective, the integral forms of the PML split-field formulations were derived and discretized using the same M24 weighted multiple-loop approach, resulting in ABC performances that match the standard FDTD-based PML formulations. This proposed approach eliminates the impedance mismatches caused by switching from M24 to regular FDTD update equations within the PML regions and the necessary cumbersome subgridding implementations needed to minimize the effects of these mismatches. It also eliminates the need to use large separations between the scatterers and the PML regions as a simpler though more costly alternative. This achievement coupled with the recent effective resolution of the PEC modeling issue finally eliminates the last hurdles hindering the wide adoption of the M24 algorithm and its three-dimensional counterpart, the FV24 algorithm, as a viable option for accurate and computationally efficient modeling of electrically large structures.

A novel technique for the amplification and the compression of an optical pulse is proposed.Based on cascaded a semiconductor optical amplifier (SOA) and a nonlinear optical loop mirror (NOLM), the chirping effect induced by the SOA and the cross phase modulation effect between the signal pulse and control pulse can be utilized to shape the pulse.The picosecond pulse amplification and compression are demonstrated in this paper.A good theoretical model is designed with optimal parameters.Results show that the output signal pulse with high peak power, narrow pulse width, and low pedestal can be obtained using the designed model, which is suited for furture 640 Gbps optical communications.

This paper is devoted to the forward radar propagation over clean and contaminated seas, using the Ament model and by taking the shadowing effect into account. The well-known Rayleigh parameter, which characterizes the degree of roughness of a corrugated surface for the case of reflection on a rough surface, is presented. Then, it is extended to the transmission through a rough surface, and to the reflection on a layer of two rough interfaces. This extended Rayleigh parameter allows then to calculate the forward radar propagation over oil slicks on sea surfaces, using the Ament model. Moreover, the model is improved by taking the shadowing effect into account. Numerical results of contaminated seas are presented, and compared to that of clean seas.

Various electromagnetic scattering approximations beyond the Born assumption have been published during the recent years. This paper introduces a simple framework of analyses and investigates in a systematic way the fundamentals of the proposed theories. Our main focus is to demonstrate the link and similarities between the different scattering approximations employing a common physical basis. Based on analogies established we try to bridge the apparent gap between existing theories as well as introducing possible extensions and refinements.

A detailed study of surface TM modes at the interface between an isotropic medium and a uniaxial plasma is presented. Four cases for the isotropic medium, including normal, Left-handed, magnetic, and metallic media, are considered. The conditions for the existence of surface modes in each case are analyzed, showing that the existence is determined by the parameters of media, working frequency, and the direction of the principle axis. The Poynting vector along the propagating direction is also calculated. Depending on the media parameters and the frequency, the surface mode can have time-average Poynting vector in the opposite direction of the mode phase velocity.

The rain attenuation in the 12-GHz band and one-minuterain rate were measured at four satellite beacons located in South East Asia countries over a three-year period (2002-2004). The cumulative distribution of rain rate obtained as well as cumulative distribution of rain attenuation obtained are presented and compared with the rain prediction models. Most of the rain prediction models showed noticeable deviation to the measured values above the existence of the breakpoint (the point at which the slope changes). The results can be employed to guide the design and application of slant-path communication systems, especially in South East Asia countries.

A new computationally efficient algorithm for reconstruction of lossy and inhomogeneous 1-D media by using inverse scattering method in time domain is proposed. In this algorithm, cosine Fourier series expansion is utilized in conjunction with finite difference time domain (FDTD) and particle swarm optimization (PSO) methods. The performance of the proposed algorithm is studied for several 1-D permittivity and conductivity profile reconstruction cases. Various types of regularization terms are examined and compared with each other in the presented method. It is shown that the number of unknowns in optimization routine is reduced to about 1/3 as compared with conventional methods which leads to a considerable reduction in the amount of computations, while the precision of the solutions would not be affected significantly. Another advantage of the proposed expansion method is that, since only a limited number of terms are taken in the expansion, the divergence of the algorithm is far less likely to occur. Sensitivity analysis of the suggested method to the number of expansion terms in the algorithm is studied, as well.

A new type of antenna named as compound box-horn antenna is designed and analyzed for its radiation pattern. The present analysis is based on plane wave spectra for three-dimensional fields. The compound box-horn antenna is obtained by combining modified box-horn and pyramidal horn antennas, in which modified box-horn is coupled to pyramidal horn to excite TE₁₀- and TE₃₀- modes at the input of pyramidal horn. Thus, the compound boxhorn antenna has properties and advantages of both the modified box-horn and pyramidal horn antennas. The radiation patterns and corresponding half-power beam widths (HPBWs) of compound boxhorn antenna in free-space are computed at 10 GHz and compared for different flare angles in E- and H-planes of larger size pyramidal horn section of the compound box-horn. The results for HPBWs in Eand H-planes demonstrate that the radiation patterns in E- and Hplanes for compound box-horn can be made narrower by decreasing the flare angles in both E- and H-planes of larger size pyramidal horn section of the compound box-horn. The radiation patterns of compound box-horn are also compared with those for TE10-mode pyramidal horn of same aperture size and it found that the former horn is narrower in E- as well as H-plane than the latter. The analysis has been validated against the experimental results available in the literature. The work presented here can provide useful design guidelines for development of prototypes of compound box-horn which may find potential application as a high-directivity transmitting horn for antenna measurements in the laboratory or as a range illuminator, or in microwave communication etc.

Maxwell's equations are solved to determine transient electromagnetic fields inside as well as outside a large conducting plate of an arbitrary thickness. The plate is carrying a uniformly distributed excitation winding on its surfaces. Transient fields are produced due to sudden interruption of the d.c. current in the excitation winding. On the basis of a linear treatment of this initial value problem it is concluded that the transient fields may decay at a faster rate for plates with smaller value of relaxation time. It is also shown that the energy dissipated in the eddy current loss may exceed the energy stored in the initial magnetic field.

Awideband E-shaped microstrip patch antenna has been designed for high-speed wireless local area networks (IEEE 802.11a standard) and other wireless communication systems covering the 5.15-5.825 GHz frequency band. Two parallel slots are incorporated to perturb the surface current path, introducing local inductive effect that is responsible for the excitation of the second resonant mode. The length of the center arm can be trimmed to tune the frequency of the second resonant mode without affecting the fundamental resonant mode. Acomprehensiv e parametric study has been carried out to understand the effects of various dimensional parameters and to optimize the performance of the antenna. Asubstrate of low dielectric constant is selected to obtain a compact radiating structure that meets the demanding bandwidth specification. The reflection coefficient at the input of the optimized E-shaped microstrip patch antenna is below -10 dB over the entire frequency band. The measurement results are in excellent agreement with the HFSS simulation results.

Fractional curl operator is utilized to construct the solutions corresponding to fractional dual rectangular waveguides. Fractional dual rectangular waveguides may be considered as intermediate of two given waveguides, where both waveguides are related through principle of duality. Characteristic impedance of fractional waveguide is determined. Behavior of field lines in transverse plane is also investigated.

This paper presents a complete ray-tracing based model which takes into account scattering from rough surfaces in indoor environments. The proposed model relies on a combination between computer graphics and radar techniques. The paths between the transmitter and the receiver are found thanks to a Bi-Directional Path-Tracing algorithm, and the scattering field after each interaction between the electromagnetic wave and the environment is computed according to the Kirchhoff Approximation. This propagation model is implemented as a plug-in in an existing full 3-D ray-tracing software. Thus, we compare the results of classical ray-tracing with those of our model to study the influence of the scattering phenomenon on the wave propagation in typical indoor environments.

In this paper a novel intelligent method to identify an unknown medium (type of apodization and chirping) is developed. Our consideration is concentrated on complex fiber Bragg Gratings. For realization of the idea the Genetic Algorithms (GAs) is used. So, GAs is used to solve inverse scattering problem for reconstruction of nonuniform or complex fiber Brag gratings. In this method, the reflection coefficient measured in practice is inserted to a suitable algorithm. According to the proposed method, first medium discrimination is performed between predefined large classes of mediums and then the whole and necessary parameters for reconstruction of the medium are extracted. Full numerical method is used for compare of the results obtained from the presented algorithm. Our simulation shows good agreement between them. So, a novel method for identification and discrimination of optical mediums especially complex Bragg Gratings is presented. Finally the presented method can be used to identify optical mediums and complex Bragg Gratings systems.

In this paper, we propose an optimization method based on real-coded genetic algorithm (GA) with elitist strategy for thinning a large linear array of uniformly excited isotropic antennas to yield the maximum relative sidelobe level (SLL) equal to or below a fixed level. The percentage of thinning is always kept equal to or above a fixed value. Two examples have been proposed and solved with different objectives and with different value of percentage of thinning that will produce nearly the same sidelobe level. Directivities of the thinned arrays are found out and simulation results of different problems are also compared with published results to illustrate the effectiveness of the proposed method.

This paper investigates the scattering of electromagnetic plane wave from an impedance strip. Both E- and H-polarizations are considered. The method of analysis is Kobayashi potential, which uses the discontinuous properties of Weber-Schafheitlin's integrals. Imposition of boundary conditions result in dual integral equations. Using the projection, equations reduces to matrix equations. The elements are given in terms of infinite integrals that contains the poles for particular values of surface impedance and these integrals are computed numerically. Far diffracted fields in the upper half space for different angles of incident are computed. To check the validity of the results, we have derived the physical optics (PO) approximate solutions. Numerical results for both the methods are compared. The agreement is good. Current distribution on the strip is also presented.

It is well known that a left-handed-medium (LHM) slab with negative permittivity −ε₀ and negative permeability −μ₀ can be made as a perfect lens for its negative refraction. In this paper, we show that such two semi-infinite lossless LHM slabs can realize electromagnetic energy localization completely through an accurate analysis. If two current sources with the same amplitude and opposite direction are placed at the right edge of the left LHM slab and the perfect-imaging point of the right LHM slab separately, we have demonstrated that all electromagnetic waves are completely confined in a region between the two sources and there is no power radiating outwards the region.

A compact dual-band bandpass filter using equal-length split-ring resonators (SRRs) is proposed in this paper. The tworesonance frequency response of equal-length split-ring resonator is described in detail. A cross-coupled dual-band filter with four equallength split-ring resonators is designed. Several finite out-of-band attenuation poles are realized to improve the selectivity of the proposed filter. The measurement of the filter is in good agreement with the simulation.

Cognitive Ultra Wideband Radio is proposed to exploit the advantages of combining Cognitive Radio with Ultra Wideband technologies, so as to solve the problems of coexistence and compatibility between UWB and other existing narrowband wireless systems. A novel adaptive UWB pulse shaping algorithm with low complexity, instead of notch filter, is presented for producing the expected spectral notches right in the frequency band occupied by the nearby wireless devices. Simulation results show that the proposed UWB waveform has better single-link BER performances in AWGN channel and stronger anti-jamming ability than other conventional waveforms such as Scholtz's monocycle, etc. Besides, the power spectral density of UWB pulse does not need to be reduced over the whole frequency band. Therefore, it is possible to expand the communication range of UWB systems by increasing the transmitted power of UWB pulse.

This work investigates the unique numerical dispersion behavior of the Compact-FDTD method for waveguide analysis, especially when the waveguide dimensions are much larger than the operating wavelength as in high-frequency EMC analysis or radio-wave propagation in tunnels. The divergence of this dispersion behavior from the standard FDTD algorithm is quantified and a major source of dispersion error is isolated and effectively eliminated. Optimized modeling parameters in terms of appropriate spatial and temporal resolutions are generated for computationally efficient and error-free numerical simulations of electrically large waveguiding structures.

Apractical problem in the reflection method for dielectric constant measurement is the difficulty to ensure the sample is placed exactly at the waveguide flange. Asmall position offset of the dielectric sample will give rise to some errors in calculating the dielectric constant, especially when a thin sample is used. To circumvent this problem, a method to determine the dielectric constant by measuring the transmission coefficient of the thin slab placed in a waveguide has been developed. Slab position offset from the measurement reference plane has no effect on the measurement accuracy. An explicit expression for the dielectric constant is obtained in terms of the transmission coefficient by simplifying the exact solution for transmission through a thin dielectric slab. The method is verified with measurement on Teflon of 0.5-mm thickness. The measured dielectric constant of Teflon shows excellent agreement of both ε' and ε'' with published data. Subsequently, the dielectric constant of a vegetation leaf was measured.