In this paper, we study a class of modified incomplete Cholesky factorization preconditioners LL^T with two control parameters including dropping rules. Before computing preconditioners, the modified incomplete Cholesky factorization algorithm allows to decide the sparsity of incomplete factorization preconditioners by two fillin control parameters: (1) p, the number of the largest number p of nonzero entries in each row; (2) dropping tolerance. With RCM reordering scheme as a crucial operation for incomplete factorization preconditioners, our numerical results show that both the number of PCOCG and PCG iterations and the total computing time are reduced evidently for appropriate fill-in control parameters. Numerical tests on harmonic analysis for 2D and 3D scattering problems show the efficiency of our method.

In this paper, design of the RII triple-clad structure as a dispersion flattened optical fiber including small pulse broadening factor as well as small dispersion and its slope applicable in broadband and fast communication is considered. The proposed optimization technique is based on the Genetic Algorithms (GA) consisting suitable fitness function for each application. The putting forward design method introduces the pulse broadening factor (?/?₀) about 1.0016 after 200 Km propagation at the zero dispersion wavelength that is so excellent compared to the structure (1.2794) reported in [2] recently. Meanwhile, the proposed structure provides high bit rate (more than 197.8 Gb/Sec at 100 km), large dispersion length (larger than 17400 km), uniform dispersion slope ([0.04,-0.08] ps/km/nm²) and broad bandwidths as well as small and uniform dispersion (smaller than 2.02 ps/km/nm) at [1.55-1.7] μm wavelength interval even for core diameter larger than 4.62 μm. Another important thing discussed in this paper is a proposal for optimization of the broadening factor on large wavelength duration, which is necessary for large bandwidth applications. The suggested technique is capable to minimize the pulse broadening factor over duration of wavelengths that is necessary for large bandwidth applications such as dense wavelength division multiplexing (DWDM) and optical time division multiplexing (OTDM). Our calculation for extracting optical properties of the proposed structure is evaluated analytically. For this purpose modal analysis of these fibers for obtaining possible wave vectors for given system parameters are done using Transfer Matrix Method (TMM) in cylindrical coordinate.

This paper presents the exact 3D calculation of the magnetic field produced by a tile permanent magnet whose polarization is both tangential and uniform. Such a calculation is useful for optimizing magnetic couplings or for calculating the magnetic field produced by alternate magnet structures. For example, our 3D expressions can be used for calculating the magnetic field produced by a Halbach structure. All our expressions are determined by using the coulombian model. This exact analytical approach has always proved its accuracy and its usefulness. As a consequence, the tile permanent magnet considered is represented by using the fictitious magnetic pole densities that are located on the faces of the magnet. In addition, no simplifying assumptions are taken into account for calculating the three magnetic field components. Moreover, it is emphasized that the magnetic field expressions are fully three-dimensional. Consequently, the expressions obtained are valid inside and outside of the tile permanent magnet, whatever its dimensions. Such an approach allows us to realize easily parametric studies.

A new design of feed for radial line slot antenna (RLSA) is presented. For better impedance match to the waveguide the effect of the various feed parameters is analyzed and their design sensitivity is studied. This paper emphasizes the advantages of using feed with a funnel below the connector entry and a conical segment over the entering probe.

A system level integration of simulation methods for high data-rate transmission circuit design applications is developed in this paper. While the elementary circuit theory was responsible for designing the circuits to meet the required performance specifications, three dimensional full-wave electromagnetic simulation technique was adopted to characterize the off-chip parasitic effects induce from the packages. The developed technique was applied for the design of optical Pick-Up Head (PUH) driver circuitry and a data transmission rate up to 640Mega bits per second (Mb/s) was achieved with standard 0.35 μm CMOS technology, showing the promising feature of applying such technique in successful design for high data-rate transmission circuits.

A novel set of boundary conditions requiring vanishing of the normal components of the D and B vectors at the boundary surface was introduced recently and labeled as the DB-boundary conditions. Basic properties of a resonator structure defined by the spherical DB boundary are studied in this paper. It is shown that the resonance modes polarized TE and TM with respect to the radial direction coincide with those of the respective PEC and PMC resonators. Modes in the DB resonator show higher degree of degeneracy than those of the PEC resonator which may find application in materials research.

In this work, we propose to use a type of periodic structures, the soft surfaces in their planar version, to reduce the back radiation of patch antennas. A key aspect of these surfaces when compared to other periodic structures is their anisotropy which provides different behaviour for different field polarization (horizontal or vertical). This make them especially convenient for this application, as the soft surfaces force the field intensity for any polarization to be zero on the surface for waves propagating along the surface. In this paper, a design example is presented and the back radiation reduction by using planar soft surfaces is demonstrated.

The shimming method used for producing high field homogeneity of the open permanent main magnet for magnetic resonance imaging (MRI) is researched in this paper. The central shimming method based on integer programming is proposed, which fulfills the combination of optimal theory and the practical manual shimming. The formulation of shimming is solved by using Lingo software and the numerical analysis method is used to compute the contribution of small shim arrays. The homogeneity of imaging region is eventually advanced nearly by 50%.The validity of the method is validated by using simulation test of shimming. The efficiency of shimming is improved through experiment corporated with the manufacturing enterprise.

Perfect electromagnetic conductor (PEMC) is a medium where certain linear combinations of electromagnetic fields are required to vanish. Since PMC has found important applications in antenna design, one may expect that PEMC will also have potential for similar applications; therefore it is important to investigate its radiation properties. In this paper, dyadic Green functions in integral forms have been derived for a structure with a dielectric layer on a PEMC plane. Whereas electric and magnetic dyadic Green functions is required to satisfy the dyadic mixed boundary condition on PEMC surface, a new classification of the electric and magnetic dyadic Green functions has been introduced based on parameter M of PEMC boundary. This classification is general and contains classes of dyadic Green functions which satisfy Dirichlet and Neumann boundary conditions.

In classical antenna books, the field radiated by a filamentary antenna is calculated integrating the electrical current induced over the wires as if it was a primary (impressed) source. This is no technically incorrect, but is not rigorous. In this paper some formal steps are added to the classical procedure to do it more rigorous.

The ambiguity function of a kind of chaotic signal radar using Colpitts oscillator is investigated and compared in several aspects. The Colpitts oscillator with specific value of capacitance, inductance and resistance can generate chaotic signal with frequency band from direct current to several gigahertz. The chaotic signal is obtained from simulation and experiment. The auto-ambiguity functions of the chaotic signal show that the chaotic signal of such oscillator is ideal for radar application with both high range and range rate resolution. The cross-ambiguity function also indicates the chaotic signal has excellent capabilities in the electronic countercountermeasures (ECCM).We also present the resolution of range with the spectrum from experiment.

A broadband method is introduced to measure the effective constitutive parameters of artificial magnetic materials. The method is based on the microstrip line topology, thus making it easy to retrieve the constitutive parameters over a wide band of frequencies. To demonstrate the effectiveness of this method, artificial magnetic materials with Fractal Hilbert inclusions are fabricated and characterized. Good agreement between the experimental and numerical simulation results verifies the accuracy of the proposed method.

To efficiently solve large dense complex linear system arising from electric field integral equations (EFIE) formulation of electromagnetic scattering problems, the multilevel fast multipole method (MLFMM) is used to accelerate the matrix-vector product operations. The inner-outer flexible generalized minimum residual method (FGMRES) is combined with the symmetric successive overrelaxation (SSOR) preconditioner based on the near-part matrix of the EFIE in the inner iteration of FGMRES to speed up the convergence rate of iterative methods. Numerical experiments with a few electromagnetic scattering problems for open structures are given to demonstrate the efficiency of the proposed method.

The shadowing relationship between facet elements can be determined rapidly through analytical expressions. On the basis of modeling using curved surfaces, an effective shadowing processing algorithm is proposed which is in combination with that used in the shadowing judgement of facet elements. Firstly several sampling points are taken on the ergodic curved surface element to construct a group of facet elements, which can replace the curved surface element. Then the shadowing processing between the stationary phase point and the ergodic curved surface element is converted to that between the stationary phase point and several facet elements, thus avoiding utilizing optimization method and can increase the computation speed. Similarly, the shadowing processing between the stationary phase segment and the ergodic curved surface element is converted to that between the stationary phase segment and several facet elements. And the trimming algorithm is used to accurately find the visible part of the stationary phase segment, which gets rid of the rough shadowing processing technique that determines the visibility of the whole stationary phase segment through the visibility of the center of the stationary phase segment. Therefore, the computation precision is greatly improved. When there exists a huge number of curved surfaces, maximum-minimum preprocessing is utilized to increase the computation speed. Examples show that this novel algorithm is superior to the traditional one in both computation speed and precision.

According to the Coarse Wavelength Division Multiplexing (CWDM) wavelength dependent transmission characteristics, a wide range fiber Bragg grating (FBG) demodulation method is proposed and experimentally demonstrated in this paper. The relationship between system input and output is obtained through analysis, and verified experimentally. Particularly the influence of light source power on demodulation precision and calibration value is analyzed. The wavelength demodulation range of the system is about 10 nm, which can realize the measurement of 8000με; The precision can be 3~5 pm. Since the system is compact, low cost and passive, it is able to be integrated as a portable demodulation module.

An externally modulated NTSC 77-channel erbium-doped fiber amplifier (EDFA)-repeated system employing Fabry-Perot (FP) etalon at the receiving site to improve system performance was proposed and demonstrated. In comparison with conventional externally modulated fiber optical CATV transport systems, good performance of carrier-to-noise ratio (CNR), composite second order (CSO), and composite triple beat (CTB) were achieved for the full channel band over a 100-km single-mode fiber (SMF) transmission. Our proposed systems are suitable for the long-haul fiber optical CATV transport systems.

A bidirectional high gain four-element printed dipole array for WLAN (2.4/5.8 GHz) applications is analyzed and successfully implemented in this paper. Each element used is a double-side printed dipole fed with a balance twin-lead transmission line. A wide-band balun is implemented for the dipole array. Both simulated and measured data are pretty matched. According to the measured results, the bandwidth with return loss less than -10 dB is about 280 MHz (2250-2530 MHz) and 510 MHz (5470-5980 MHz) in the two operating bands, the measured gain for 2.4 GHz band is between 4.5 and 5.9 dB, and 6.1-8.9 dB for 5.8 GHz respectively. Good shaped patterns have also been attained by tuning parameters of the dipole array.

Based on composite right/left-handed (CRLH) transmission line (TL),a novel series feed network for microstrip arrays is proposed and its theoretical analysis and experimental results are presented. In the present structure,p ower dividers and open-ended stubs are employed to even the amplitude distributions among different output ports,while CRLH TLs and short meandering lines are used to compensate the phase delay caused by the different lengths of righthanded (RH) TLs. Finally,an X-band series feed network is designed and fabricated as an example. The simulated and measured results indicate that the present design can achieve even amplitude and phase distributions among different output ports in the range of 8.8-9.6 GHz. And it has other advantages such as a compact size of 350mm×50mm and good return loss which is higher than 22 dB in the operation frequency.

The solution to the problem of far field radiation from an arbitrarily oriented Hertzian dipole in an electrically gyrotropic medium is found with the application of dyadic Green's function (DGF) technique. The form of the DGF, which is expressed as the sum of two single dyads, simplifies the derivation of the far fields significantly in comparison to the existing methods. The far field integral is evaluated analytically using the method of steepest descent. The numerical results for the radiation fields are presented in different frequency bandwidth using Clemmow-Mually-Allis (CMA) diagram. It is shown that the operational frequency bandwidth and the orientation of the antenna, which give the highest directivity and gain, can be determined when the CMA diagram is employed. Our analytical results are compared with the existing ones which were obtained using different techniques. Agreement is observed on all of them. The results presented in this paper can be used for radiation problems involving space exploration, radio astronomy or laboratory plasmas.

In this letter, we use two embedded isolation moats which have different size to obtain the wide stopband elimination performance. The proposed structure is realized by embedding the double isolation moats between power and ground planes. The suppression frequency range of the proposed structures is from 1.2 to 7.2 GHz and the peak noise improvement in time domain is 36%. Furthermore, the proposed structure uses two elimination cells to avoid the parasitic effect generated in the frequency range of several hundred MHz.