A simulation tool for analyzing circuit characteristics of microstrip-type MIC (Microwave Integrated Circuit) passive elements is presented. The major part of this tool is the electromagnetic wave analysis based on the FD-TD (Finite-Difference Time-Domain) method combined with the mode expansion theory. Although the element structures which can be treated in this tool are limited to only less than ten fundamental structures in the present stage, its extension to the more versatile tool applicable to other various element types is rather straightforward and simple in principle. When using this tool, we first choose the element configuration to be calculated and give, on a panel, necessary parameter values related to calculation range and mesh division scheme. Given these values, the first step calculation starts to obtain the characteristic impedance, cross sectional field distribution of the propagating mode, etc. of the basic microstrip line. Field distributions around the element configulation are calculated next with the mode field oscillation being given. Through this process the field distributions on a closed rectangular parallelepiped surface enclosing the element configuration are stored in files, from which S parameter and radiated fields are calculated by invoking the reaction integral with propagation modes and radiation modes, respectively. The results obtained in these three steps can be expressed, at our discretion, as line drawings or two-dimensional density plots.

The microwave coagulation therapy has been used mainly for the treatment of hepatocellular carcinoma (small size tumor in the liver). In the treatment, a thin microwave antenna is inserted into the tumor, and the microwave energy heats up the tumor to produce the coagulated region including the cancer cells. At present, a problem occurs: the size of the coagulated region is insufficient, especially in the perpendicular direction of the antenna axis. In order to overcome this problem without increasing the physical load of the patient, the authors introduced a new type of array applicator composed of two coaxial-slot antennas. However, we cannot estimate heating characteristics of this array applicator precisely by using the FDTD calculation, because the use of staircasing approximation, which employs rectangular parallelepiped cells, is unsuitable for the analysis. Therefore, in this paper, we introduce the finite element method (FEM), which employs tetrahedral cells, to estimate the heating characteristics of the array applicator.

This paper describes an improved nonlinear GaAs FET model and its parameter extraction procedure for almost all operating conditions such as the small-signal condition, the power saturated condition, and the controlled-resistance condition. The model is capable of modeling the gate voltage dependent drain current and its derivatives in the saturated region as well as the drain voltage dependent drain current and its derivatives in the linear region. The model can take into account the frequency dispersion effects of both transconductance and output conductance. The model describes forward conduction and reverse conduction currents. Deriving the capacitance part of the model from unique charge equations satisfies charge conservation. The model accurately predicts voltage-dependent S-parameters, spurious response in an active condition and inter-modulation response in the controlled-resistance condition of a GaAs FET.

The genetic algorithm is used to reconstruct the shapes of multiple perfectly conducting cylinders. Based on the boundary condition and the measured scattered field, a set of nonlinear integral equations is derived and the imaging problem is reformulated into an optimization problem. The genetic algorithm is then employed to find out the global extreme solution of the object function. Numerical examples are given to demonstrate the capability of the inverse algorithm. Good reconstruction is obtained even when the multiple scattering between two conductors is serious. In addition, the effect of Gaussian noise on the reconstruction results is investigated.

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.

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.

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.

Making up a microwave simulator is tried, which has an analysis method based on the finite-element method as a solver and commercial tools as a pre- and post-processor of a graphical user interface. The platform of this simulator is Windows, but, since the codes and configuration files to be created are common on Windows, Unix, and Linux, the simulator running on any platform may be made up at the same time, except a document on which all the commands of the simulator are embedded and executable. Using the simulator, the transmission properties of a 2- and 3-D waveguide discontinuity in a microwave circuit and eigenmodes of a 2- and 3-D waveguide are analyzed, and the computed results are presented in graphs of S parameters and plots of the electric field distribution.

In addition to their intended role in design and optimization of microwave circuits, subsystems and systems; network and field simulators serve a key role in design-oriented education and continuing education. This paper brings out how these simulators are currently used in university education, and how this educational role of simulators will be further emphasized in currently changing scenario for higher education. A generic model is proposed for learning tools that combine computer-based tutorials with microwave circuit and field simulators.

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.

In this letter, we present a coarse frequency-offset synchronization technique for Eureka-147 DAB receiver. The proposed frequency-offset synchronization algorithm using two defined correlation functions is shown to have high robustness against a large range of symbol timing offset with a moderate implementational complexity.

Mobile communication channels always suffer serious frequency-selective fading due to multipath effect. Traditional spreading codes are characterized by the fact that their time-domain orthogonality is based on fixed chip width across a code period. They often fail to perform well under frequency-selective fading. This paper proposes a new class of CDMA codes, wavelet-packet orthogonal codes capable to retain time-domain orthogonality as well as to offer intra-code subband diversity to mitigate frequency-selective fading. The new codes are constructed by congregating several wavelets with various dilations and shifts. The combination of the wavelets in different nodes in a wavelet-packet full binary tree enables frequency diversity capability. Owing to the even code length, they can be easily used in mobile communications for multi-rate streaming and multi-code spreading. The performance study is carried out using correlation statistics distribution convolution algorithm and the results reveal that wavelet-packet codes, combined with RAKE receiver, perform better than traditional spreading codes in frequency-selective fading channels.

Fingerprint recognition is a well-researched problem, and there are several highly accurate systems commercially available. However, this biometric technology still suffers from problems with the handling of bad quality prints. Recent research has begun to tackle the problems of poor quality data. This paper takes a new approach to one problem besetting fingerprints--that of distortion. Previous attempts have been made to ensure that acquired prints are not distorted, but the novel approach presented here corrects distortions in fingerprints that have already been acquired. This correction is a completely automatic and unsupervised operation. The distortion modelling and correction are explained, and results are presented demonstrating significant improvements in matching accuracy through the application of the technique.

A symbol timing synchronization method is proposed for the realization of a multi-mode and multi-service software radio receiver. The method enables an accurate search for the optimum symbol timing without any redundant hardware such as sampling rate conversion devices, when the system clock is non-integer times for the target systems' symbol rates. Accordingly, a multimode and multi-service receiver can set an arbitrary system clock for the target systems' symbol rates, and the number of A/D converters can be reduced to the minimum. Also, it may lead to a reduction of the implementation time for digital signal processing hardware, and reduce the burden on the memory in a multi-mode and multi-service software radio receiver, since no sampling rate conversion is needed. The effectiveness of the proposed method for use with a multi-mode and multi-service software radio receiver for future ITS services, which are GPS (Global Positioning System), ETC (Electric Toll Collection system), and Japanese PHS (Personal Handy-phone System) is assumed, and the supposed system is evaluated by computer simulation. The jitter performance under an AWGN (Additive White Gaussian Noise) environment is first simulated, and the necessary number of over-samples and observation symbols are defined by the value of jitter which gives a theoretical value of the BER, respectively. Moreover, the bit error rate performance under a fading environment condition where the attenuation of a signal level fluctuates more rapidly than in a noise environment is calculated, and it is shown that the proposed method enables an accurate search for the optimum synchronization timing caused by a cycle slip even if the signal level is quite low, and allows one handset to adopt a system clock for several systems.

This paper proposes a 2.6 GHz low cost DBF array antenna system and reports its evaluation based on our experimental results. The proposed system is partially constructed by digital devices for the simplification of hardware, and employs some techniques for improving the resolution. The system is evaluated through the DOA estimation by the MUSIC algorithm inside a radio anechoic chamber. As a result, we found that the proposed system estimates the DOA with the highest accuracy at which MUSIC algorithm can perform. Moreover, this paper discusses the estimation errors. We also found that the estimation error is particularly affected from the inaccurate element interval.

Currently, the most popular model in data compression theory is that of stationary ergodic sources. But there do exist sequences each of which is not emitted from any stationary ergodic source but can be compressed sufficiently by a certain algorithm. We estimate the size of the set of such sequences in terms of Hausdorff dimension.

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.

Recently, biometrics such as a person's fingerprint, face, and voice has come to be used for personal authentication. At present, most biometrics authentication systems depend on verification (one-to-one matching) because such verification takes a short period of time and is expected to provide a quick response. In these systems, however, every single user has to enter an ID number for each authentication session and might feel incovenienced as a result. To improve the operation efficiency, identification (one-to-many matching) is required, but identification is currently assumed to require much more time than verification (i.e., the response time is not practical). After probing these problems, we developed a new method to achieve identification in a short period of time. This method shortens the response time by using a matching score matrix, which is constructed in the enrollment phase. The proposed method is shown to need only about 45 one-to-one matchings to identify data in a database with two thousand fingerprints, a count much less than by conventional methods.

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.

PID control schemes based on the classical control theory, have been widely used for various real control systems. However, in practice, since it is considerably difficult to determine the PID parameters suitably, lots of researches have been reported with respect to tuning schemes of PID parameters. Furthermore, several self-tuning and auto-tuning techniques in the PID control have been reported for systems with unknown or slowly time-varying parameters. On the other hand, so-called a generalized predictive control (GPC) scheme has been reported as a useful self-tuning control technique for unknown and/or time variant delay systems. In this paper, a new self-tuning predictive PID control algorithm based on a GPC criterion is proposed.