This paper presents a fast inversion method for electromagnetic imaging of cylindrical dielectric objects with the optimal regularization parameter used in the Levenberg-Marquardt method. A novel procedure for choosing the optimal regularization parameter is proposed. The method of moments with pulse-basis functions and point matching is applied to discretize the equations for the scattered electric field and the total electric field inside the object. Then the inverse scattering problem is reduced to solving the matrix equation for the unknown expansion coefficients of a contrast function, which is represented as a function of the relative permittivity of the object. The matrix equation may be solved in the least-squares sense with the Levenberg-Marquardt method. Thus the contrast function can be reconstructed by the minimization of a functional, which is expressed as the sum of a standard error term on the scattered electric field and an additional regularization term. While a regularization parameter is usually chosen according to the generalized cross-validation (GCV) method, the optimal one is now determined by minimizing the absolute value of the radius of curvature of the GCV function. This scheme is quite different from the GCV method. Numerical results are presented for a circular cylinder and a stratified circular cylinder consisting of two concentric homogeneous layers. The convergence behaviors of the proposed method and the GCV method are compared with each other. It is confirmed from the numerical results that the proposed method provides successful reconstructions with the property of much faster convergence than the conventional GCV method.

For on-chip matching Si-MMIC fabricated on a conventional low resistivity Si substrate, the loss of on-chip inductors is quite high due to the dielectric loss of the substrate. In order to reduce the loss of on-chip matching circuit, the use of high resistivity Si substrate is quite effective. By using electro-magnetic simulation, the relationship between coplanar waveguide (CPW) transmission line characteristics and the resistivity of Si substrate is discussed. Based on the simulated results, the resistivity of Si substrate is designed to achieve lower dielectric loss than conductor loss. The effectiveness of high resistivity Si substrate is evaluated by the extraction of equivalent circuit model parameters of the fabricated on-chip spiral inductors and the measurement of the fabricated on-chip matching Si-MMIC LNA's.

This paper presents a novel concept of a Two-Dimensional (2-D) Finite-Difference Time-Domain (FDTD) formulation for the numerical analysis of electromagnetic fields. FDTD method proposed by Yee is widely used for such analysis, although it has an inherent problem that there exist half-cell-length and half-time-step distances between electric and magnetic field components. To dissolve such distances, we begin with the finite-difference approximation of the wave equation, not Maxwell's equations. Employing several approximation techniques, we develop a novel algorithm which can condense all field components to equidistant discrete nodes. The proposed algorithm is evaluated in comparison with several conventional algorithms by computer simulations.

The diffraction of a plane electromagnetic wave by an impedance wedge whose boundary is described in terms of the skew coordinate systems is treated by using the Wiener-Hopf technique. The problem is formulated in terms of the simultaneous Wiener-Hopf equations, which are then solved by using a factorization and decomposition procedure and introducing appropriate functions to satisfy the edge condition. The exact solution is expressed through the Maliuzhinets functions. By deforming the integration path of the Fourier inverse transform, which expresses the scattered field, the expressions of the reflected field, diffracted field and the surface wave are obtained. The numerical examples for these fields are given and the characteristics of the surface wave are discussed.

We propose the architecture of efficiently and flexibly extensible solver system for electromagnetic wave simulations, that can load multi kinds of schemes such as Finite-Difference Time-Domain (FDTD) scheme, Finite Element Method (FEM), and a circuit simulator, with various boundary conditions in the system. Object-oriented approach is a promising method for efficient development of the flexible simulator. The primary object in the architecture is found through our object-oriented analysis as decomposed "region" from whole the simulation space. The decomposed region is considered to be the stage on which the electromagnetic fields play under the local rules. Developers who will extend the functionality of the system can add new classes inherited from the abstract classes in our design depending on the grid structure, the scheme, or the boundary processing method.

Although Maxwell's equations have been known for over 100 years, it was not until the last decade that they have seen regular use in applied high frequency design. The availability of sufficient computer processing capability is only part of the reason Maxwell's equations now enjoy regular application. Other developments requiring considerable effort are needed as well. These include increased attention to robustness, software testing, ease of use, portability, integration with other tools, and support. These developments are detailed in this paper.

This letter focuses on the design of a unified estimator for scheduled control in nonlinear systems with unknown parameter. An estimation law with a finite convergence time is formulated to compute the unknown scheduling parameter that drives a scheduled controller. This estimator can also be extended to the types of scheduled controllers addressed in the literature.

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 the capacity of the personal computer and workstation increase rapidly, many electromagnetic simulators are widely used. In this paper, Ansoft's High Frequency Structure Simulator (HFSS), which is a commercial software product, is applied to design a mode converter operating at 35 GHz is fabricated based on the simulation results. The numerical results are in good agreement with the measured data.

A low loss magnetic plate positioned near an antenna is proposed to increase radiation efficiency of cellular phones. This magnetic plate is used to control the nearby magnetic field around the cellular phone's antenna, and this field controlling is shown to be effective for the improvement of radiation efficiency and far-field pattern. As for the material design of the plate, a magnetic plate having high µr and low µr" (complex relative permeability: µr = µr - j µr") is found to be effective for achieving high performance. In our sample fabrication, a low loss magnetic sample with µr = 5.7 - j 0.7 at 900 MHz is realized. It is demonstrated that this low loss sample contributes to increased efficiency and improved far-field characteristics.

Magnetic random access memory (MRAM) possesses the attractive properties of non-volatility, radiation hardness, nondestructive readout, low voltage, high access speed, unlimited read and write endurance and high density. MRAM technology is described for the devices using giant magnetoresistance (GMR) and tunneling magnetoresistance (TMR) materials in this paper. The TMR type MRAM architectures using ferromagnetic tunneling junctions (MTJ) are more attractive for mainstream RAM applications than the GMR type, because the signal of the TMR type is larger than that of the GMR type. A MRAM device with an MTJ plus MOS transistor switch architecture, which can provide large signal-to noise ratio, is detailed. A design of the MTJ element is discussed and the requirements for the junction resistance and the TMR needed for the memory device are demonstrated based on the simple signal voltage calculations. The TMR significantly decreases with increasing bias voltage, which leads to the reduction of the signal voltage for the actual MRAM. A ferromagnetic double tunneling junction is proposed for the high density MRAM application demanding large signal voltage, because of the smaller degradation of the TMR for the bias voltage, compared with that of the conventional single junctions. Recent trials of MRAM fabrication are introduced, which demonstrates high-speed access time. Finally, challenges for the higher bit density MRAM above Gb are discussed, and it is noticed that higher signal voltage, lower power consumption for writing and novel cell designs are needed for the achievement.

We have developed a signal processing method that is appropriate for detecting electromagnetic radiation due to earthquake activities. The radiation is usually accompanied by a background noise that is mainly caused by atmospheric discharges in the tropical regions. Data representing the seismic radiation is presented as sound via the concept of sonification. This is useful for immediately finding out anomalous seismic radiations, which are often followed by a disastrous earthquake, from the massive data collected from over forty observation stations. It is illustrated that the auditory display is valuable for future earthquake prediction systems.

Fuzzy inference abilities were implemented to electromagnetic problems for the first time by the authors. After very successful results of applying the developed fuzzy modeling method to input impedance of a general monopole antenna, in this paper classifying the engineering electromagnetic problems simply, we apply the abilities of the proposed fuzzy inference method to make a qualitative model for transmission lines as a general example for a certain category of problems. The proposed approach starts from observing the problem through the window of human direct understandings and uses some parameters (as calculation base) evaluated basic for modeling process. It is shown that because of using this novel view point, a very simple fuzzy system based on new parameters may model the behavior of a transmission line in general form. The knowledge of each variable can be extracted and saved as simple curves individually, through continuing to make several models considering the desired variable as parameter. Finally, it is shown that the proposed method works even in highly nonuniform transmission line cases without changing in structure and complexity.

A high Tc superconducting quantum interference device (SQUID) magnetometer system is developed for the application to biological immunoassay. In this application, magnetic nanoparticles are used as magnetic markers to perform immunoassay, i.e., to detect binding reaction between an antigen and its antibody. The antibody is labeled with γ-Fe2O3 nanoparticles, and the binding reaction can be magnetically detected by measuring the magnetic field from the nanoparticles. Design and set up of the system is described, and the sensitivity of the system is studied in terms of detectable number of the magnetic markers. At present, we can detect 4106 markers when the diameter of the marker is 50 nm. Total weight of the magnetic nanoparticles becomes 520 pg in this case. An experiment is also conducted to measure antigen-antibody reaction with the present system. It is shown that the sensitivity of the present system is 10 times better than that of the conventional method using an optical marker. A one order of magnitude improvement of sensitivity will be realized by the sophistication of the present system.

We have developed a measuring system for high-Tc superconducting single-flux quantum circuits and evaluated its performance in terms of bit error rate (BER) measurement for given signal voltage levels. The system includes magnetic shields and a high-frequency test fixture mounted on a closed-cycle cooler. The test fixture is made of non-magnetic material. The transmission characteristics of the measuring system were evaluated by using a vector network analyzer at frequencies ranging from 40 MHz to 20 GHz. The operating temperature of the measuring system ranges from 20 K to room temperature. We connected a 12-GHz wideband pulse amplifier to the system and evaluated its high-speed transmission characteristics. We used a standard 50-Ω microstrip line as an impedance-matched sample. The signal used in the experiment was a 215-1 pseudo random bit signal (PRBS) at 3 Gbps. As a result, the output voltage required for an output driver under the experimental condition was 18.8 mV in order to obtain a resolution of BER measurement of 10-12.

In this paper we report the results of a study regarding the backscattering from wind-roughened water surfaces. The reference profile data has been deducted by an experiment held at the University of Heidelberg circular wave tank facility. The scattering theory is based on a fractal description of the surface and a combined use of the Kirchhoff approximation and the small perturbation method (SPM). The scattering results are tested versus the ones obtained via the periodic-surface moment method. The study shows the reliability of the novel approach.

A method for determination of the location, shape, and material properties of a 3D object from measurements of the scattered field, when the object is successively illuminated by a number of incident fields is presented. This work extends the method previously developed for reconstructions of 2D permittivity and conductivity from electromagnetic measurements to the more complicated full-vector 3D electromagnetic inversion. Furthermore, a frequency hopping strategy to improve the resolution of the unknown objects when the frequency is raised, is underlined. Results of numerical experiments are presented to illustrate both strengths and weaknesses of the method.

The micro positioning systems using magnetic suspension technique, which is one of precision actuating method, have been suggested. Utilizing the various potentials such as the exclusion of a mechanical friction, they are being applied broadly to multi degrees of freedom (d.o.f) system requesting high accuracy or hybrid system requesting to be controlled position and force simultaneously. This paper presents the entire development procedure of a novel six d.o.f micro positioning system using mag-netic levitation, with a repulsive force mechanism covering the all d.o.f. First, the interactions between magnetic elements are modeled and the system design flow by an optimal location of the elements is given. A kinematic relationship between the measuring instruments and the levitated object is derived, and dynamic characteristics are identified by the narrow gap principles. And the main issues for control are discussed.

In this paper, the electromagnetic scattering from a cylinder with a computer-generated random rough surface is analyzed by a numerical simulation method. The validity of the proposed numerical method is confirmed by comparing the present numerical results with those calculated by the perturbation method to second order and its Pade approximation. It is shown that the present proposed method can be applied to the case where the surface roughness becomes relatively large.

We study the electromagnetic wave propagation in three-dimensional (3-D) dense random discrete media containing dielectric spheroidal scatterers. We employ a Monte Carlo method in conjunction with the Method of Moments to solve the volume integral equation for the electric field. We calculate the effective permittivity of the random medium through a coherent-field approach and compare our results with a classical mixing formula. A parametric study on the dependence of the effective permittivity on particle elongation and fractional volume is included.