A rigorous radar cross section (RCS) analysis is carried out for two-dimensional rectangular and circular cavities with double-layer material loading by means of the Wiener-Hopf (WH) technique and the Riemann-Hilbert problem (RHP) technique, respectively. Both E and H polarizations are treated. The WH solution for the rectangular cavity and the RHP solution for the circular cavity involve numerical inversion of matrix equations. Since both methods take into account the edge condition explicitly, the convergence of the WH and RHP solutions is rapid and the final results are valid over a broad frequency range. Illustrative numerical examples on the monostatic and bistatic RCS are presented for various physical parameters and the far field scattering characteristics are discussed in detail. It is shown that the double-layer lossy meterial loading inside the cavities leads to the significant RCS reduction.

In the paper the well known ray method is generalized to the case of the inhomogeneous chiral electromagnetic media. The electromagnetic field decompose in a chiral medium into two components with different propagation velocities. In the paper each of these components are presented in the form of ray expantions. The coefficients of these expantions are calculated in the ray coordinates which are attributed to the characteristics of eikonal equations. The leading and admixed components of the electromagnetic vectors are investigated and the polarization effects for both field components are analysed.

A bicomplex representation for time-harmonic electromagnetic fields appearing in scattering and diffraction problems is given using two imaginary units i and j. Fieldsolution integral-expressions obtained in the high-frequency and low-frequency limits are shown to provide the new relation between high-frequency diffraction and low-frequency scattering. Simple examples for direct scattering problems are illustrated. It may also be possible to characterize electric or magnetic currents induced on the obstacle in terms of geometrical optics far-fields. This paper outlines some algebraic rules of bicomplex mathematics for diffraction or scattering fields and describes mathematical evidence of the solutions. Major discussions on the relationship between high-frequency and low-frequency fields are relegated to the companion paper which will be published in another journal.

In this paper an algorithm for numerical investigation of the transmission line having a generalized polygonal cross-section and open interface is proposed. Solution of the eigenmode problem is based on the method called the domain product technique, which employs a Mathieu function expansion and provides an efficient technique to the analysis of the structures with multiangular boundaries. An agreement at the obtained numerical results with existing data confirms the applicability of the theoretical analysis given in the paper.

Equivalence of physical optics (PO) and aperture field integration method (AFIM) in the full 360 observation angle is discussed for polyhedron approximate reflectors; the necessary conditions of integration surface in AFIM for the equivalence to PO are presented. In addition to the condition that complete equivalent currents consisting of both geometrical optics (GO) reflected fields from the reflector and direct incident fields from the feed source are used, the integration surface should cap the reflector perfectly and should be in the illuminated region of the GO reflected field. Validity of the conditions is numerically confirmed for a two-dimensional (2-D) strip reflector, 3-D corner reflectors and a 2-D polyhedron approximate reflector.

Gaussian beams constitute a very powerful tool to analyze radiation and scattering problems in high frequency regimes. The analysis of this kind of beams may be done by performing an analytical continuation of the real sources into the complex space. This is also a very powerful technique that arise, not only to this kind of solutions, but also to other solutions that may be very useful even for low frequency regimes. A complete parametrization of real propagation space in terms of the different type of complex beams solutions is presented in this paper. The analysis in the complex domain arises to different regions in the real space which may be anticipated and described through analytical transition regions. Some important conclusions may be derived from the results obtained, in particular the results related to the complex far field condition.

Three-dimensional (3-D) instrumentation using an image sequence is a promising instrumentation method for intelligent systems in which accurate 3-D information is required. However, real-time instrumentation is difficult since much computation time and a large memory bandwidth are required. In this paper, a 3-D instrumentation VLSI processor with a concurrent memory-access scheme is proposed. To reduce the access time, frequently used data are stored in a cache register array and are concurrently transferred to processing elements using simple interconnections to the 8-nearest neighbor registers. Based on a row and column memory access pattern, we propose a diagonally interleaved frame memory by which pixel values of a row and column are stored across memory modules. Based on the concurrent memory-access scheme, a 40 GOPS vprocessor is designed and the delay time for the instrumentation is estimated to be 42 ms for a 256256 images.

A method for analyzing the scattering of electromagnetic waves by a general bianisotropic slab is presented by extending the author's previous approaches for anisotropic, chiral, and those periodic media. The analysis is formulated in a unified matrix form, so that scattering characteristics can be obtained by system matrix calculations. The method can be extended straightforwardly to multilayerd and periodic structures. The scattering efficiencies are obtained for the incidence of not only linearly polarized waves but also circularly polarized waves.

This paper deals with two different quantitative inversion algorithms for reconstructing the complex permittivity profile of bounded inhomogeneous objects from measured scattered field data. The first algorithm involves an imaging method with single frequency excitation and multiincidence illumination and the second algorithm involves a method with synthetic pulse (multifrequency mode) excitation for objects surrounded by freespace or buried in stratified half-space media. Transmission or reflection imaging protocols are considered depending on aimed applications: microwave imaging in free-space from far-field data for target identification, microwave imaging from near-field data for nondestructive testing (NDT), microwave tomography of buried objects for mine detection and localization, civil engineering and geophysical applications. And Edge-Preserving regularization scheme leading to a significant enhancement in the image reconstructions is also proposed. The methods are illustrated with synthetic and experimental data.

This paper deals with the scattering and diffraction of a plane wave by a randomly rough half-plane by three tools: the small perturbation method, the Wiener-Hopf technique and a group theoretic consideration based on the shift-invariance of a homogeneous random surface. For a slightly rough case, the scattered wavefield is obtained up to the second-order perturbation with respect to the small roughness parameter and represented by a sum of the Fresnel integrals with complex arguments, integrals along the steepest descent path and branch-cut integrals, which are evaluated numerically. For a Gaussian roughness spectrum, intensities of the coherent and incoherent waves are calculated in the region near the edge and illustrated in figures, in terms of which several characteristics of scattering and diffraction are discussed.

Investigated is a guided-wave device for dividing optical power into three equal parts. The device fundamentally consists of a three-waveguide tapered-velocity coupler which is designed to operate under the adiabatic condition. Field distributions of the local normal modes along the coupler explain basic principles of the device. Its performance is confirmed through numerical simulations by means of finite difference beam propagation method.

The present paper gives a new formulation for rough surface scattering in terms of a stochastic integral equation which can be dealt with by means of stochastic functional approach. The random surface is assumed to be infinite and a homogeneous Gaussian random process. The random wave field is represented in the stochastic Floquet form due to the homogeneity of the surface, and in the non-Rayleigh form consisting of both upward and downward going scattered waves, as well as in the extended Voronovich form based on the consideration of the level-shift invariance. The stochastic integral equations of the first and the second kind are derived for the unknown surface source function which is a functional of the derivative or the increment of the surface profile function. It is also shown that the inhomogeneous term of the stochastic integral equation of the second kind automatically gives the solution of the Kirchhoff approximation for infinite surface.

Coupling in time domain between two non-parallel transmission lines of finite length is analyzed by using a circuit concept. Coupling equations based on the Maxwell's equations for lossless transmission lines in a homogeneous medium are written by a set of non-homogeneous differential equations including distributed source terms produced by external electromagnetic fields. The forcing terms are expressed by vector potentials generated by currents in the line section and at the transitions. A set of solutions in frequency domain is obtained by a four-port network expression with regard to the terminal voltages and currents, and can be applied to estimation of the frequency-domain crosstalk. Utilizing the inverse fast Fourier transform (FFT), the crosstalk responses between the lines is studied in time domain. Comparison of theoretical and experimental results shows the validity of the method.

The main defficulty in recognizing 3-D objects from 2-D images is matching 2-D information to the 3-D object representation. The multiple-view approach makes this problem easy to solve by reducing the problem to 2-D to 2-D matching problem. This approach models each 3-D object by a collection of 2-D views from various viewing angles and recognizes an object in the image by finding a 2-D view that has the best match to the image. However, if the size of the model database becomes large, the approach requires long time for the recognition of objects. In this paper we present a 3-D object recognition algorithm based on multiple-view approach. To reduce the recognition time, the proposed algorithm uses the coarse-to-fine process previously proposed by the authors and a genetic algorithm-based search scheme for the selection of a best matched model in the database. And, we could verify from the results of the experiments that the algorithm proposed in this paper is useful to speed up the recognition process in multiple-view based object recognition systems.

In the last few years analog adaptive filters have been a subject of active research because they have the ability to handle in real time much higher frequencies, with a smaller size and lower power consumption that their digital counterparts. During this time several analog adaptive filter algorithms have been reported in the literature, almost all of them use the continuous time version of the least mean square (LMS) algorithm. However the continuous time LMS algorithm presents the same limitations than its digital counterpart, when operates in noisy environments, although their convergence rate may be faster than the digital versions. This fact suggests the necessity of develop analog versions of recursive least square (RLS) algorithm, which in known to have a very low sensitivity to additive noise. However a direct implementation of the RLS in analog way would require a considerable effort. To overcome this problem, we propose an analog RLS algorithm in which the adaptive filter coefficients vector is estimated by using a fully connected network that resembles a Hopfield network. Theoretical and simulations results are given which show that the proposed and conventional RLS algorithms have quite similar convergence properties when they operate with the same sampling rate and signal-to-noise ratio.

This paper proposes a new speech codec based on CELP for PHS multimedia communication. PHS portable terminals should consume as little power as possible, and the codec used in them has to be robust against channel errors. Therefore, the proposed codec operates with low computational complexity while reducing the deterioration in speech quality due to channel errors. This codec uses two new schemes to reduce computational complexity. One is moving average scalar quantization for the filter coefficients of the synthesis filter. This scheme requires 90% less complexity to quantize synthesis filter coefficients compared to the widely used vector quantization. The other is pre-selection for selecting an algebraic codebook used as random excitation source. An orthogonalization scheme is used for stable pre-selection. Deterioration of speech quality is suppressed by using CRC and parameter estimation for error protection. Two types of codec are proposed: a 10-ms frame type that transmits 160 bits every 10-ms and a 15-ms frame type that transmits 160 bits every 15 ms. The computational complexity of these codecs is less than 5 MOPS. In a nochannel error environment, the speech quality is equal to that of ITU-TG.726 at 32.0 kbit/s. With 0.3% channel error, both codecs offer more comfortable conversation than G.726. Moreover, at 1.0% channel error, the 10-ms frame type still provides comfortable conversation.

This paper presents a salient method to find an optimal bandwidth for low noise phase-locked loop (PLL) applications by analyzing a discrete-time model of charge-pump PLLs based on ring oscillator VCOs. The analysis shows that the timing jitter of the PLL system depends on the jitter in the ring oscillator and an accumulation factor which is inversely proportional to the bandwidth of the PLL. Further analysis shows that the timing jitter of the PLL system, however, proportionally depends on the bandwidth of the PLL when an external jitter source is applied. The analysis of the PLL timing jitter of both cases gives the clue to the optimal bandwidth design for low noise PLL applications, Simulation results using a C-language PLL model are compared with the theoretical predictions and show good agreement.

A non-isothermal device simulation, consisting of solving heat flow equation three-dimensionally together with other semiconductor equations two-dimensionally, is reported for various arrangements of a pluralty of transistors mounted on a single chip. These arrangements are intended to simulate the real situation in an IC chip whereas a three-dimensional solution of the heat flow equation is aimed at accurately determining the thermal interdependence among individual transistors. As a result, the drain current versus drain voltage characteristics of a miniaturized transistor is found to exhibit a heat-induced negative resistance region.

We present theoretical results on the convergence of iterative methods for the solution of linear differential-algebraic equations arising form circuit simulation. The iterative methods considered include the continuous-time and discretetime waveform relaxation methods and the Krylov subspace methods in function space. The waveform generalized minimal residual method for solving linear differential-algebraic equations in function space is developed, which is one of the waveform Krylov subspace methods. Some new criteria for convergence of these iterative methods are derived. Examples are given to verify the convergence conditions.

Nonuniform transmission lines are crucial in integrated circuits and printed circuit boards, because these circuits have complex geometries and layout between the multi layers, and most of the transmission lines possess nonuniform characteristics. In this article, an efficient numerical method for analyzing nonuniform transmission lines has been presented by using the Chebyshev expansion method and moment techniques. Efficiency on computational cost is demonstrated by numerical example.