Ultra-short pulse is a promising technology for achieving ultra-high data rate transmission which is required to follow the increased demand of data transport over an optical communication system. Therefore, the propagation of such type of pulses and the effects that it may suffer during its transmission through an optical waveguide have received a great deal of attention in the recent years. Our goal in this paper is to study the propagation characteristics of that pulse in a nonlinear optical fiber. In analyzing these characteristics, the nonlinear effects along with the dispersion are taking into account. Additionally, the considered nonlinear effects include self phase modulation (SPM) and stimulated Raman scattering (SRS). The problem to be processed is modeled using the finite difference time domain (FDTD) technique which represents an efficient tool in achieving the required purpose. Because of the symmetrical structure of the optical waveguide, the FDTD modeling of bodies of revolution (BOR) in cylindrical coordinates is the most preferable algorithm in analyzing our problem. The FDTD treatment of dispersion and nonlinearity of the optical waveguide is accomplished through the direct integration method. In addition, the Lorentzian model is chosen to represent the dielectric properties of the optical fiber. The azimuthal symmetry of optical fiber enables us to use a two-dimensional difference lattice through the projection of the three-dimensional coordinates (r, φ, z) into the (r, z) plane. Extensive numerical results have been obtained for various cavity structures.

We study the influence of the resistivity frequency dispersion effects on the magnetotelluric (MT) response. Impedivity is the term used to indicate the frequency dependent resistivity in rocks. The impedivity functions, used in this paper, have been derived from the general solution of the motion equation of a charge carrier, discussed in a previous paper. A 1D three-layered earth section, with the second layer assumed to be dispersive, is considered to analyze the distortions due to dispersion on the modulus and phase of the MT responses on the earth's free surface. The MT responses of the section, where the dispersive layer is attributed an impedivity function describing at first a positive, then a negative and finally a resonant dispersion model, are computed for various combines of the dispersion parameters. A general conclusion is that the dispersion effects can strongly influence the MT response either in recognizable or in subtle forms. In the former case, the distortions appear as either steeply rising and/or descending curve branches or spike-like deltas, not compatible with a dispersion-free section. In the latter case, instead, the MT curves preserve the typical behavior for a dispersion-free section, and may thus erroneously be modeled by a section, where the dispersive layer is totally suppressed. In both case, disregarding the distortion effects may lead to misleading conclusions as to the physical properties of the surveyed structures.

A planar Dual Exponentially Tapered Slot Antenna(DETSA) is presented in this paper. The DETSA is simulated and designed with the sofware Ansoft HFSS. The dimensions of the antennas and the exponential functions of tapered slot are also described. To verify the design, the DETSA is fabricated and measured, good impedance matching over a very wide bandwidth is achieved, measured radiation patterns of the proposed antenna is compared with the simulated one, good agreement is observed.

A novel composite right/left handed transmission line is presented which is synthesized by etching Koch fractal shape slot in the ground plane and series capacitive gap in the conductor strip. Unlike the structures loaded with complementary split ring resonators (CSRRs), the proposed structure can operate at very wide band and is used to design an ultra-wideband (UWB) filter. The UWB filter is fabricated and tested. The relative bandwidth of the -10 dB return loss is 128% and the insertion loss is larger than -1.5 dB except at high frequencies. The equivalent circuit model of the proposed structure is presented and the electrical parameters are also extracted. The circuit model results are compared with the simulation and measurement results which verify that not only the extracted parameters are exact but also the equivalent circuit model is reasonable.

A multifunctional meander line polarizer is described. The polarizer is capable of effecting conversions between linear and circular polarization and between left-hand and right-hand circular polarization. It can also cause arbitrary rotation of linear polarization, including converting a wave from horizontal polarization to vertical. The polarizer is analyzed by the spectral domain approach.

Plane-wave reflection from and transmission through a slab of uniaxial anisotropic medium is studied and the concept of ZAP (Zero-Axial-Parameter) medium sheet is defined as the limiting case when the axial parameters and the thickness of the slab vanish simultaneously. It is shown that the ZAP sheet may act as a spatial filter for the incident waves with transmission in a narrow cone around normal direction. Such a sheet may find application in narrowing the radiation beam and reducing sidelobes of an antenna or as a computer privacy filter in optical frequencies.

The case where the background material of a cloak possesses magnetoelectric coupling is investigated in this paper, for examples, the base medium is bianisotropic or an isotropic medium moving with uniform speed which may be comparable with that of light. The specifically proposed constitutive parameters for such kind of cloak show more complicated bianisotropic property, which can not be simply produced by an isotropic medium in a uniform-velocity motion.

A compact printed dipole antenna for UHF RFID reader is presented. The proposed antenna occupies a volume of 65*30*2 mm3 and the radiator is composed of two rectangular patches etched with folded slit. The radiation element of the dipole antenna is fed by 50 Ω coaxial line. Measured results indicate that the proposed antenna has a good impedance matching characteristic at 905-935.5 MHz (return loss less than 10 dB). In addition, the effect of some parameters on the performance of the proposed antenna is also discussed in this article. This printed dipole antenna will be applicable for future RFID systems.

An outdoor crop-bed was prepared to observe scatterometer response in the angular range of 20^ο to 70^ο at VV- and HHpolarization. The soil moisture and crop variables like plant height, leaf area index and biomass of crop ladyfinger were measured at different growth stages of the crop ladyfinger. Temporal variation in scattering coefficient was found highly dependent on crop variables and observed to increase with the increase of leaf area index and biomass for both polarizations. In this paper, a novel approach is proposed for the retrieval of soil moisture and crop variables using ground truth microwave scatterometer data and artificial neural network (ANN). Two different variants of radial basis function neural network (RBFNN) algorithms were used to approximate the function described by the input output relationship between the scattering coefficient and corresponding measured values of the soil moisture and crop variables. The new model proposed in this paper gives near perfect approximation for all three target parameters namely soil moisture, biomass and leaf area index. The retrieval with minimal error obtained with the test data confirms the efficacy of the proposed model. The generalized regression network was observed to give minimal system error at a much lower spread constant.

The design of an optimized Wideband Electronically Steerable Passive Array Radiator (W-ESPAR) antenna, for Terrestrial Digital Video Broadcasting (DVB-T) reception, is proposed. A genetic algorithm is used in order to calculate the positions and lengths of antenna elements (structural parameters) and loading conditions (control parameters). A nine-element W-ESPAR antenna with one element active and eight passive can have one directive beam per channel, with mean gain of 9 dBi, reflection factor less than 0.2 and input impedance around 75 Ohms. Computer simulations have shown that one main lobe may be achieved in the same direction and for all UHF channels, from 470MHz to 890 MHz. The analytical results for the design are provided, and they show that the proposed W-ESPAR antenna is suitable for portable DVB-T reception.

This paper presents an analysis with the aim of characterizing the electromagnetic properties of an arbitrary linear, bianisotropic material inside a metallic waveguide. The result is that if the number of propagating modes is the same inside and outside the material under test, it is possible to determine the propagation constants of the modes inside the material by using scattering data from two samples with different lengths. Some information can also be obtained on the cross-sectional shape of the modes, but it remains an open question if this information can be used to characterize the material. The method is illustrated by numerical examples, determining the complex permittivity for lossy isotropic and anisotropic materials.

The broadband wavelength conversion based on four-wave mixing in a silicon nanowire waveguide is theoretically investigated by taking into account the influence of the waveguide loss and free-carrier absorption on the phase-matched condition. The lossy wavelength conversion is compared with the lossless one in terms of conversion efficiency and bandwidth. The size of the silicon-oninsulator nanowire waveguide is optimized to be 400nm × 269nm for broadband wavelength conversion by realizing a flattened dispersion. The pump wavelength is also optimized to 1538.7nm in order to further enhance the conversion bandwidth. A 3-dB conversion bandwidth of over 280nm is achieved in the optimized waveguide with the optimized pump wavelength.

The modal dispersion relation of electromagnetic waves in a Bragg fiber having plasma in the cladding regions is investigated analytically. The proposed Bragg fiber consists of a low index central region having air surrounded by a large number of periodic cladding layers of alternating high and low refractive indices of dielectric and plasma respectively. The modal dispersion relation is obtained by solving Maxwell wave equations using a simple boundary matching method. The analysis shows that the normalized frequency parameter (also called V -number) is frequency independent. This indicates that the proposed Bragg fiber may be used for single mode operation without high frequency limitation as well as with little loss of energy compared to the conventional dielectric waveguide.

Based on message passing interface (MPI) of the PC Clusters, the parallel method of moment (MOM) is applied to the electromagnetic (EM) scattering from one dimensional (1-D) large scale PEC Gaussian rough surface with two dimensional (2-D) PEC cylinder above it with low grazing incidence. The conjugate gradient method (CGM) for solving MOM matrix equation is parallelized according to the property of MPI in this work. The parallel computational efficiency and validity are shown by several numerical simulations, in which it is proved that the proposed method supplies a novel technique for solving the problem of the composite EM scattering for a 2-D target above 1-D large scale rough surface. Finally, the influences of root mean square (rms) height, the correlation length of the Gaussian surface, the size and the altitude of the cylinder, the polarization on the bistatic scattering coefficient (BSC) for low grazing incidence are also discussed in detail.

The electromagnetic field distributions in the waveguide of a 915 MHz single-mode microwave sintering applicator equipped with a loading pressure system were simulated using a JMAG-Studio program. The disturbance in the magnetic field as well as in electric field was caused by the insertion of the alumina loading pressure system due to reflection effect of alumina. However, the separated magnetic field and electric field maxima can be obtained by adjusting position of the alumina loading pressure system in the waveguide. The simulation results were evaluated by comparison with experimental measurement.

Based on the improvements of both Genetic Algorithm and Particle Swarm Optimization, a novel IGA-edsPSO (Improved Genetic Algorithm-extremum disturbed simple Particle Swarm Optimization) Hybrid algorithm is proposed in this paper. An improved performance of GA is achieved by reducing the array space. By discarding the particle velocity vector in the PSO evolutionary equation, the sPSO (simple PSO) can avoid the problem of slow later convergence velocity and low precision caused by determining the maximal velocity vector factitiously. And the edsPSO can overstep local extremum point more effectively with the help of the extremum disturbed factor. The proposed IGA-edsPSO Hybrid algorithm is used in the design of the sparse arrays with minimum element spacing constraint. Given the array aperture and the number of the array elements, the suppression of the peak sidelobe level (PSLL) with a certain half power beamwidth (HPBW) restriction is implemented with a high efficiency by optimizing the HPBW and PSLL synchronously. The simulation results show that faster convergence velocity (which means less computation time) and lower sidelobe level are obtained using IGA-edsPSO compared to IGA, standard PSO, GA-PSO and GA-sPSO.

Detailed procedure for Green's function derivation of an annular waveguide is presented in this paper for the first time. The proper components of the electromagnetic fields along with their corresponding Green's functions will be derived in a useful and applicable form. Based on the derived Green's functions, proper set of integral equations are derived in a novel general form which their MoM solution will lead to complete slot field distribution in the annular waveguide slot antenna (AWSA). The proposed theory would be found of high value in circuit modelling and array design of such novel antenna structures in the future.

The rigorous numerical formulation for TE-scattering from a conducting wedge with concaved edge is presented and numerical computations for scattered fields are shown. The radial mode matching technique is used to obtain the scattering field in a series form. The accuracy of the present method is checked with existing solutions of a semi-circular channel and sharp wedge, which are special case of the general geometry of a conducting wedge with concaved edge.

A hybrid method is developed to compute the radiation pattern of antennas on large complex three-dimension carriers. The hybrid method involves computing the radiation fields of the antenna in free space with FEM, characterizing the reflection and diffraction of the carrier to the radiation fields with CRE (Complex Ray Expansion) and UTD (Uniform Theory of Diffraction). The ray technique of SBR using traditional hybrid method is employed by CRE. The shortcomings of the SBR, such as great number of ray trace, distortion and partly shadowing of the rays etc., are overcome by the use of CRE, and the time consuming physical-optics-type integration is replaced by the paraxial approximation of the complex rays. A dipole placed on different carriers are taken as the examples to show the validity of the hybrid method, and the radiation patterns computed by the proposed method are in good agreement with those by FEM. By using the proposed method, the computation of the three dimension radiation pattern of an antenna in a large ship is finished by a PC in 1671.20 seconds.

The diffraction by a terminated, semi-infinite parallelplate waveguide with four-layer material loading is rigorously analyzed for the H-polarized plane wave incidence by means of the Wiener-Hopf technique. Introducing the Fourier transform for the unknown scattered field and applying boundary conditions in the transform domain, the problem is formulated in terms of the simultaneous Wiener-Hopf equations. The Wiener-Hopf equations are solved via the factorization and decomposition procedure together with the use of the edge condition leading to exact and approximate solutions. The scattered field inside and outside the waveguide is evaluated by taking the inverse Fourier transform and applying the saddle point method. Numerical examples on the radar cross section (RCS) are presented for various physical parameters, and the backscattering characteristics of the waveguide are discussed.