Cutoff frequencies and the modal fields in hollow conducting waveguides of arbitrary cross section are frequently calculated by the method of solving integral equations. This paper presents some improvements for the method by the integral equations. The improved method can calculate the cutoff frequencies and the modal fields only by using the real number, and this method can remove extraneous roots when calculating the cutoff frequencies. The former method calculates the cutoff frequency and the fields only at the cutoff frequency, but the improved method can calculate the fields at arbitrary phase constants.

The use of the homomorphic filter technique is described in order to enhance the contrast in the mammographic images, which is adopted to the dyadic wavelet transform. The proposed method has employed the nonlinear enhancement in homomorphic filtering as well as denoising method in the wavelet domains. Experimental results show that the homomorphic filtering method improves the contrast in breast tumor images such that the contrast improvement index is increased by two fold compared to the conventional wavelet-based enhancement technique.

For several years, more and more people are joining the Internet and various kind of packets (so called transaction-, block-, and stream-types) have been transmitted in the same network, so that poor network conditions cause loss of the stream-type data packets, such as voices, which request smaller transmission delay time than others. We consider a switching node (router) in a network as an N-series M/G/1-type queueing model and have mainly evaluated the fluctuation of packet delay time and end-to-end delay time, using the two moments matching method with initial value, then define the delay jitter D of a network which consists of jointed N switching nodes. It is clarified that this network is not suitable for voice packets transmission media without measures.

In this paper, we propose an algorithm to calculate the higher moments of the busy period length of a discrete-time M/G/1 type queue with finite buffer. The queueing model has a level-dependent transition probability matrix. Our algorithm is given as a set of recursive formulas which are derived from the relationship among the generating function matrices of the fundamental period. As an example of our algorithm, we provide an approximate analysis of a HOL (Head Of Line) priority control queue.

This paper shows a comparison between several procedures to represent the Physical Optics (PO) current density into a hybrid Moment-Method-Physical-Optics (MM-PO) code. Some numerical results demonstrate that a set of basis functions suitable for the Method of Moments (MM) may be inappropriate to model the PO currents. A new evaluation of the PO operator is proposed. The radiation can be analytically determined and, since it includes a linear interpolation of the phase, it can be applied over large triangular domains. This allows a drastic reduction of the computational cost, maintaining or even improving the level of accuracy.

This paper deals with the radiation phenomenon from bent transmission lines numerically and experimentally. At first, the radiation loss for different types of bent transmission lines has been estimated by using the method of moments (MoM), in order to suggest the most optimal design for a bent line in terms of a radiation loss. So, the simplest line with a right-angle bend is recommended. Then, the radiation patterns from such a right-angle bent transmission line have been numerically calculated, which may indicate that the radiation is originated mainly at the bend, but other parts are also found to contribute to the overall pattern with many extra lobes. All of the numerical results were confirmed by the corresponding experiment.

In this letter, a new scheme of designing multilevel BTC coding is proposed. The optimal quantization can obtain by selecting the quantization threshold with an exhaustive search. However, it requires an enormous amount of computation and is thus impractical while we take an exhaustive search for the multilevel BTC. A two-steps searching method is applied to reduce the computational complexity. Comparisons of results with various methods have verified that the proposed method approach to the optimal quantization with little computation complexity.

As the capacity of a personal computer and workstation increases rapidly, many electromagnetic simulators solving antenna problems are widely used. In this paper, the IE3D electromagnetic simulator, which is a commercial software product, is applied to the analysis of handset antennas in the vicinity of the human body. Firstly, basic characteristics of popular handset antennas such as whip and planar inverted-F antennas are obtained by the IE3D electromagnetic simulator and calculated results are compared with measured results quoted from the referenced paper. Secondly, on the basis of newly considered design concept for a handset antenna, a loop antenna system for the handset, which we have proposed in order to reduce the influence of human body, is taken as an example of a balance-fed antenna and is analyzed theoretically and experimentally including the influence of the human body. In a result, calculated results by the IE3D electromagnetic simulator are in good agreement with measured results and it is confirmed that the simulator is very effective in analyzing the handset antenna in the vicinity of the human body.

As a solver in a simulator, advantages of use of a wavelet function were investigated for analysis of a dipole antenna using the Moment Method. Realization of a sparse matrix due to orthogonality and due to inherent nature of the wavelet is confirmed by observing an impedance matrix using each Daubechies' wavelet. Calculated results of the input impedance, the impedance matrix, and the current distribution are compared in variation of the wavelet in two integral equations for a dipole antenna. Use of the Daubechies' wavelet of the high number with a small matrix and a threshold in the Hallen's Integral Equation is suitable for the reduction of the matrix size and of the calculation cost.

The transmission S-parameter, S21, between dipole elements on a rectangular finite ground plane is calculated by the MoM with planar-segments in the horizontally and vertically polarized configurations. Supposed a 1/10 scaling, the frequency range is selected 0.15-0.8 GHz. The size of the finite ground plane is 40 cm 100 cm. The dipole-element length is 18.8 cm (half-wavelength at 0.8 GHz). The distance between dipole elements is 30 cm. The results are compared to the calculated results with the conventional MoM-GTD hybrid method and also the measured results with a TRL-calibrated network analyzer. It makes clear that the MoM-GTD hybrid method is not applicable to a small ground plane in the vertically polarized configuration. The results calculated by the MoM with planar-segments agree well to the measured results both in the horizontal and vertical polarizations. The results show that the size of the finite ground plane for the vertical polarization should be much larger than for the horizontal polarization.

A signal processing approach is discussed which has the potential for imaging strongly scattering objects from a series of scattering experiments. The method is based on a linear spectral estimation technique to replace the filtered backpropagation for limited discrete data and a subsequent nonlinear signal processing step to remove the contribution of multiple scattering my means of homomorphic filtering. Details of this approach are discussed and illustrated by applying the imaging algorithm to both simulated and real data.

An inverse scattering problem in three dimensional two layered media is investigated. The shape and the location of the acoustic scatterer buried in one half-space are determined. With some a priori information, it becomes possible to solve this problem in three dimensions. Using the moment method, the scattered field is obtained for the estimated scatterer. An iterative procedure based on the Newton's method for the nonlinear least square problem is able to solve the inverse scattering problem. Some numerical results are presented.

First order line seach optimization techniques gained essential practical importance over second order optimization techniques due to their computational simplicity and low memory requirements. The computational excess of second order methods becomes unbearable for large optimization tasks. The only applicable optimization techniques in such cases are variations of first order approaches. This article presents one such variation of first order line search optimization technique. The presented algorithm has substantially simplified a line search subproblem into a single step calculation of the appropriate value of step length. This remarkably simplifies the implementation and computational complexity of the line search subproblem and yet does not harm the stability of the method. The algorithm is theoretically proven convergent, with superlinear convergence rates, and exactly classified within the formerly proposed classification framework for first order optimization. Performance of the proposed algorithm is practically evaluated on five data sets and compared to the relevant standard first order optimization technique. The results indicate superior performance of the presented algorithm over the standard first order method.

We present two estimation methods for camera rotation from two images obtained by the active camera before and after rotation. Based on the representation of the projected rotation group, quasi moment features are constructed. Camera rotation can be estimated by applying the singular value decomposition (SVD) or Newton's method to tensor quasi moment features. In both cases, we can estimate 3D rotation of the active camera from only two projected images. We also give some experiments for the estimation of the actual active camera rotation to show the effectiveness of these methods.

It is not rare case that a floated metal plate exists nearby high speed circuit traces. Heatsink placed on a IC chip nearby circuit traces, metal enclosure or circuit traces in a compact designed product may be a good example. It may be also seen such structure for a shield box and circuit traces confined. It is generally known that such metal plate as placing nearby circuit trace may change circuit trace parameters and then resonance frequency associated with the circuit trace. In this study, we clarified resonance frequency variation with comprehensive observation of input impedance of microstrip line that is an essential model of circuit traces on a printed circuit board. Since such structure is created in various cases in product designs, we believe that the results shown in this study may be useful for EMC design as well as signal integrity. For computation, method of moment was used.

The features of the method of moment (MoM) and the finite difference time domain (FDTD) method for numerical analysis of the electromagnetic scattering problem are presented. First, the integral equations for the conducting wire, conducting plane and the dielectric materials are described. Importance to ensure the condition of the continuity of the current of the scatterers is emphasized and numerical examples for a conducting structure involving a junction of wire segment and planar segment is presented. Finally, the advantages and the disadvantages of the FDTD method are discussed.

An accurate and efficient numerical solution is presented for a two-dimensional electromagnetic wave scattering from a multilayered resistive strip grating embedded in a dielectric slab. Both E- and H-waves are treated. The problem is formulated into a set of integral equations, which is solved by the moment method accompanied by a regularization procedure. The resultant set of linear algebraic equations has the form of the Fredholm second kind, and therefore yields stable and accurate numerical solutions. The power distribution is computed for several grating parameters. Attention is paid to seek a set of parameters that maximizes absorption in the strips. The low frequency approximate formulas are also derived. This analysis would be useful in designing electromagnetic wave absorbers.

Hallen's integral equation for cylindrical antennas is modified to deal with finite gap excitation. Because it is based on more realistic modeling, the solution is more accurate, and the convergence is guaranteed. The new equation is written with a new excitation function dependent on the gap width. The moment method analysis is presented where the piecewise sinusoidal surface current functions are used in Galerkin's procedure. Total, external and internal current distributions can be determined. Numerical results for cylindrical antennas with wide variety of gap width and radius are shown, and are compared with the numerical results by the Pocklington type integral equation and those by measurement.

In this paper, we apply the discrete wavelet transform (DWT) and the discrete wavelet packet transform (DWPT) with the Daubechies wavelet of order 16 to effectively solve for the electromagnetic scattering from a one-dimensional inhomogeneous slab. Methods based on the excitation vector and the [Z] matrix are utilized to sparsify an MoM matrix. As we observed, there are no much high frequency components of the field in the dielectric region, hence the wavelet coefficients of the small scales components (high frequency components) are very small and negligible. This is different from the case of two-dimensional scattering from perfect conducting objects. In the excitation-vector-based method, a modified excitation vector is introduced to extract dominant terms and achieve a better compression ratio of the matrix. However, a smaller compression ratio and a tiny relative error are not obtained simultaneously owing to their deletion of interaction between different scales. Hence, it is inferior to the [Z]-matrix-based methods. For the [Z]-marix-based methods, our numerical results show the column-tree-based DWPT method is a better choice to sparsify the MoM matrix than DWT-based and other DWPT-based methods. The cost of a matrix-vector multiplication for the wavelet-domain sparse matrix is reduced by a factor of 10, compared with that of the original dense matrix.

The wavelet matrix transform approach, in combination with the method of moments (MoM), is applied to solve the electromagnetic scattering problem of an array of metal strips. The problem is first discretized by the conventional MoM to obtain a dense impedance matrix, then the wavelet matrix transform is applied to produce a sparse matrix. This approach avoids a great number of integral computations existing in the wavelet basis expansion method and provides fast approach to solution for the scattering problem. Daubechies' wavelet is chosen as the mother wavelet to construct a sparse wavelet matrix so that the matrix-matrix multiplications occurring in the transform cost only O(N2) with N unknowns. Numerical tests show that the computation cost necessary for solving the resultant sparse matrix is only O(N log N). An appropriate choice of the number of vanishing moments of wavelets is suggested from consideration of total computation cost and accuracy of solutions.