A new hybrid formulation has been derived for analyzing biological electromagnetic compatibility (Bio-EMC) problems by combining the frequency-domain Method of Moments (MoM) and the Finite-Difference Time-Domain (FDTD) method. This hybrid form is different from, and more direct than, the method previously proposed by Mangoud et al. Some numerical examples are given for the human head exposure field due to a half wavelength dipole and a one-wavelength loop antenna. Our iterative method is found to have fast convergence. In addition, our method works well for cases when the radiation antenna wires are not aligned with the FDTD lattice.

This paper presents a new method to improve the resonant characteristics of a microstrip resonator. The improved characteristics have been achieved by inserting two dielectric rods between strip conductor and the ground plane. Dielectric rods to be inserted have higher relative permittivity than that of the substrate. Therefore, it is suitable to realize by Low-Temperature Cofired Ceramics (LTCC) technique. Several model of microstrip resonators employing the proposed method are analyzed by a Finite-Difference Time-Domain (FDTD) method, and their resonant characteristics are discussed. One of the advantages of the proposed method is that an attenuation pole (fl or fh) in each side of the fundamental resonant frequency (fr) and improved-spurious responses can be realized together by a capacitive-coupling tapped resonator loaded with dielectric rods. The proposed method is also effective to achieve sharp skirt characteristics and wide stopband of a direct-coupling tapped resonator which can be used either as a wideband lowpass filter or a band-elimination filter. Another interesting feature of the analyzed resonators is that about 60% reduction in resonator's length has been obtained compared to a basic half-wavelength (λ/2) microstrip resonator. Therefore, wide exploitation of the proposed method can be expected in the filter design based on the LTCC technique.

An image NRD guide-fed dielectric rod antenna, which is suitable for use at millimeter-wave frequencies, is presented in this paper. The antenna is composed of a linearly tapered dielectric rod connected to the image NRD guide. First, radiation characteristics of the dielectric rod antenna directly protruded from the end of the image NRD guide are investigated by FDTD analysis and measurements at 30 GHz band. For this case, the degradation of the radiation pattern and the decrease of the gain, which are due to the strong radiation from the guide-to-antenna discontinuity, are observed. In order to minimize this radiation and to realize reasonable radiation characteristics, a transition from the image NRD guide-to-rod antenna is proposed. A simple procedure to determine the optimum dimensions of the transition is described. This procedure is based on parametric study of the transition's dimensions, and is performed using FDTD analysis. Based on the results, the dielectric rod antenna having a length of 10 λ0 is designed, and its performance is analyzed and measured. The results show that radiation patterns with the half power beamwidth of 22, sidelobe level of -21 dB and reasonable gain of 18.5 dBi can be realized by employing the transition having the optimum dimensions.

A high permittivity LSE-NRD guide was applied to a planar antenna at 60 GHz. Emphasis was placed on compatibility between the high permittivity LSE-NRD guide and the conventionally used low permittivity LSM-NRD guide. Performance of the transition between two such types of NRD guides was optimized by using an electromagnetic simulator and the validity was experimentally demonstrated. A simple radiator, consisting of a tapered high permittivity LSE-NRD guide was fabricated and evaluated as to radiation characteristics. Since the radiator has a broad radiation pattern, it was employed in a primary radiator of a two-dimensional parabolic reflector to develop a new type of folded planar antenna at 60 GHz. This planar antenna has a double-layered structure. In the upper layer, a metalized dielectric substrate with a slotted array is excited by a rectangular-shaped oversized waveguide, and in the lower layer, an offset parabolic reflector is fed by the radiator. Measurement showed the half-power beam width of the fabricated antenna to be 2.5 degrees in the E and H planes, respectively, and the gain to be 35.3 dBi, thus indicating that a good pencil beam antenna was successfully developed in this manner.

In December 2001, the authors started two kinds of experiments on the meteor burst communication (MBC) in Antarctica to study the ability of MBC as a communication medium for data collection systems in that region. In the first experiment, a continuous tone signal is transmitted from Zhongshan Station. The signal received at Syowa Station (about 1,400 km apart) is recorded and analyzed. This experiment is aimed to study basic properties of the meteor burst channel in that high latitude region. On the other hand, the second experiment is designed to estimate data throughput of a commercial MBC system in that region. A remote station at Zhongshan Station tries to transfer data packets each consisting of 10 data words to the master station at Syowa Station. Data packets are generated with five minutes interval. In this paper, we explain the experiments, briefly examine the results of the first year (from April 2002 to March 2003), and put forward the plan for the experiments in the second and third year. From the data available thus far, we can see that 1) the sinusoidal daily variation in the meteor activity typical in middle and low latitude regions can not be clearly seen, 2) non-meteoric propagations frequently dominate the channel especially during night hours, 3) about 60% of the generated data packets are successfully transferred to the master station within two hours delay even though we are now operating the data transfer system only for five minutes in each ten minutes interval, etc.

An output load VSWR (voltage standing wave ratio) protection circuit for SiGe power amplifiers (PA) is presented by using the relatively low collector-emitter avalanche breakdown characteristic of SiGe HBT. Unlike the conventional diode-type switch, the new protection circuit completely eliminates the undesirable dc leakage current during the normal operation of the PA. Simulations and measurements show the proposed protection circuit enhances the ruggedness of the PA at harsh operating condition while it imposes only minor performance degradation at normal operating condition.

In this paper, we present the interlaced fast Fourier transform (FFT) method to parallelize the adaptive integral method (AIM) algorithm for the radar cross-section (RCS) computation of large scattering objects in free space. It is noted that the function obtained after convolution is smoother as compared to the original functions. Utilizing this concept, it is possible to interlace the grid current and charge sources in AIM and compute the potentials on each set of interlaced grid independently using FFT. Since the potentials on each interlaced grid are smooth functions in space, we can then interpolate the potentials to every other nodes on the original grid. The final solution of the potentials on the original grid is obtained by summing the total contributions of all the computed and interpolated potentials from every individual interlaced grid. Since the potentials of each interlaced grid can be computed independently without much communication overheads between the processes, such an algorithm is suitable for parallelizing the AIM solver to run on distributed parallel computer clusters. It is shown that the overall computation complexity of the newly proposed interlaced FFT scheme is still of O(N log N).

This paper analyzes program and erase mechanisms for Floating Channel type Surrounding Gate Transistor (FC-SGT) Flash memory cells for the first time. In FC-SGT Flash memory cell, control gate, floating gate, drain and source is arranged vertically on the substrate. The body region is isolated from the substrate by the bottom source region. The cell is programmed by applying a high positive voltage to the control gate electrode with drain and source electrodes grounded. Erasing is performed by applying a high positive voltage to the drain and source electrodes with the control gate electrode grounded. The physical models for program and erase operations in FC-SGT Flash memory cell are developed. Program and erase operations based on the developed physical models are simulated by utilizing a device simulator. Program and erase characteristics obtained from the device simulation agree well with the results of analytical models. The FC-SGT Flash memory cell can realize program and erase operation with a floating body structure.

Point-to-point optical and millimeter wave communication has recently been of interest, especially in urban areas. Its benefits include simpler and easier installation compared with a land-based line. However, this technology suffers when adverse weather conditions are present, such as rain, fog and clouds, which induce scattering and absorption of the optical wave. The effects of scattering and absorption degrade the quality of the communication link resulting in increase of bit-error-rate. Therefore, there exists a need for accurate channel characterization in order to understand and mitigate the problem. In this paper, radiative transfer theory is employed to study the behavior of amplitude modulated signal propagating through a random medium. We show the effect of the medium to a modulated signal and relate the outcome on the quality of the communication link.

For future high-speed wireless communications using orthogonal frequency division multiplexing (OFDM), two major system requirements will emerge: throughput improvement and rich interference elimination. Because of its broadband nature and limited frequency allocations worldwide, interference from co-located wireless LAN's operating in the same frequency band will become a serious deployment issue. Adaptive array antenna can enhance the performance by suppressing the co-channel interference even when interference may have a large amount of multipath and also have similar received power to the desired signal. There are typically two types of adaptive array architecture for OFDM systems, whose signal processing is carried out before or after FFT (Fast Fourier Transform). In general, the pre-FFT array processing has low complexity, but in rich multipath and interference environments, the performance will deteriorate drastically. In contrast, the post-FFT array processing can provide the optimum performance even in such severe environments at the cost of complexity. Therefore, complexity-reduction techniques combined with the achievement of high system performance will be a key issue for adaptive array antenna applications. This paper proposes novel adaptive array architecture, which is a complexity-reduction technique using subcarrier clustering for post-FFT adaptive array. In the proposed scheme, plural subcarriers can be clustered into a group with the same spatial weight. Simulation results show that the proposed architecture is a promising candidate for real implementation, since it can achieve high performance with much lower complexity even in a rich multipath environment with low signal to noise plus interference ratio (SNIR).

Malignant melanoma is a skin cancer that can be mistaken as a harmless mole in the early stages and is curable only in these early stages. Therefore, dermatologists use a microscope that shows the pigment structures of the skin to classify suspicious skin lesions as malignant or benign. This microscope is called "dermoscope." However, even when using a dermoscope a malignant skin lesion can be mistaken as benign or vice versa. Therefore, it seems desirable to analyze dermoscopic images by computer to classify the skin lesion. Before a dermoscopic image can be classified, it should be segmented into regions of the same color. For this purpose, we propose a segmentation method that automatically determines the number of colors by optimizing a cluster validity index. Cluster validity indices can be used to determine how accurately a partition represents the "natural" clusters of a data set. Therefore, cluster validity indices can also be applied to evaluate how accurately a color image is segmented. First the RGB image is transformed into the L*u*v* color space, in which Euclidean vector distances correspond to differences of visible colors. The pixels of the L*u*v* image are used to train a self-organizing map. After completion of the training a genetic algorithm groups the neurons of the self-organizing map into clusters using fuzzy c-means. The genetic algorithm searches for a partition that optimizes a fuzzy cluster validity index. The image is segmented by assigning each pixel of the L*u*v* image to the nearest neighbor among the cluster centers found by the genetic algorithm. A set of dermoscopic images is segmented using the method proposed in this research and the images are classified based on color statistics and textural features. The results indicate that the method proposed in this research is effective for the segmentation of dermoscopic images.

Even in embedded processors, the accuracy in a branch prediction significantly affects the performance. In designing a branch predictor, in addition to accuracy, microarchitects should consider area, delay and power consumption. We propose two techniques to reduce the power consumption; these techniques do not requires any additional storage arrays, do not incur additional delay (except just one MUX delay) and never deteriorate accuracy. One is to look up two predictions at a time by increasing the width (decreasing the depth) of the PHT (Prediction History Table). The other is to reduce unnecessary accesses to the BTB (Branch Target Buffer) by accessing the PHT in advance. Analysis results with Samsung Memory Compiler show that the proposed techniques reduce the power consumption of the branch predictor by 15-52%.

This paper proposes two types of network architectures using UMTS Release 5 architecture and wireless LAN suitable for context-aware information delivery and personal communication services, and it reports on preliminary evaluations of their performance. The first type of network architecture is the NCA (network-centric architecture) and the second is the ECA (end-user-centric architecture). The two architectures are modeled with a queuing network and their response times are compared through theoretical analysis and simulation. The results indicate that with low-performance servers, the response times of the ECA are generally shorter or almost the same as those of the NCA. However with high-performance servers, the response times of the NCA are generally shorter except during high server utilization.

The single path routing protocol, known as the Ad Hoc On-demand Distance Vector, has been widely studied for use in mobile ad hoc networks. AODV requires a new route discovery whenever a path breaks. Such frequent route discoveries cause a delay due to route discovery latency. To avoid such inefficiency, a multipath routing protocol has been proposed that attempts to find link-disjoint paths in a route discovery. However, when there are two or more common intermediate nodes on the path, the protocol can not find a pair of link-disjoint paths even if the paths actually exist. To reduce this route discovery latency, it is necessary to increase the opportunities for finding a pair of link-disjoint paths. In this paper, we focus on AODV and propose an AODV-based new multipath routing protocol for mobile ad hoc networks. The proposed routing protocol uses a new method to find a pair of link-disjoint paths by selecting a route having a small number of common intermediate nodes on its path. Using simulation models, we evaluate the proposed routing protocol and compare it with AODV and the existing multipath routing protocol. Results show that the proposed routing protocol achieves better performance in terms of delay than other protocols because it increases the number of cases where a pair of link-disjoint paths can be established.

We propose a new end-to-end transport protocol called Multi-path Transmission Control Protocol (M/TCP) and its two robust acknowledgement (ACK) schemes. Our protocol is designed as an alternative TCP option to improve reliability and performance of the Internet. The M/TCP sender simultaneously transmits data via multiple controlled paths to the receiver. Our protocol requires no modification in IP layer. Two M/TCP endpoints establish multiple paths between them by subscribing to multiple ISPs. The two robust ACK schemes proposed in this paper aim at improving M/TCP performance over the Internet with high packet loss in ACK channels. Performances between our protocol and TCP Reno are compared in terms of throughput and fairness by using ns2 simulator. Simulation results indicate that M/TCP achieves higher throughput than TCP Reno in situation of random drop and burst traffic with small buffer size. When there is network congestion on reverse path, M/TCP with the proposed robust ACK schemes performs better than M/TCP with the conventional immediate ACK scheme.

Digital watermarks on pictures must have the ability to survive various image processing operations while not causing degradation of picture quality. Random geometric distortion is one of the most difficult kinds of image processing for a watermark to survive, and this problem has become a central issue in watermarking research. Previous methods for dealing with random geometric distortion have been based on searches, special watermark patterns, learning, or additional data such as original pictures. Their use, however, is accompanied by large computational overhead or by operational inconvenience. This paper therefore proposes a method based on embedding watermark patterns in two of the three color planes constituting a color picture so that these two planes have a specific covariance. The detection of the embedded information is based on the covariance between these two planes. Random geometric distortion distorts all the constituent color planes of a picture in the same way and thus does not affect the covariance between any two. The covariance-based detection is therefore immune to the distortion. The paper clarifies that detection error would occur whenever the inherent covariance (the covariance in the original picture) overrides the covariance made by watermarking. The two constituent planes having the minimum inherent covariance are therefore selected and their inherent covariance is reduced by shifting one of them and using a noise-reduction preprocess. Experimental evaluations using StirMark confirmed that 64 bits embedded in 256256-pixel pictures can be correctly detected without using searches, special patterns, learning, or additional data.

First we introduce the high-frequency equivalent circuit model of the Fine Pitched Ball Grid Array (FPBGA) bonding for frequencies up to 20 GHz. The lumped circuit model of the FPBGA bonding was extracted based on S-parameters measurement and subsequent fitting of the model parameters. The test packages, which contain probing pads, coplanar waveguides and FPBGA ball bonding, were fabricated and measured. The suggested π-model of the FPBGA bonding consists of self-inductor, self-capacitor, and self-resistor components. From the extracted model, a solder ball of 350 µm diameter and 800 µm ball pitch has less than 0.08 nH self-inductance, 0.40 pF self capacitance, and about 10 mΩ self-resistance. In addition, the mutual capacitance caused by the presence of the adjacent bonding balls is included in the model. The FPBGA solder ball bonding has less than 1.5 dB insertion loss up to 20 GHz, and it causes negligible delay time in digital signal transmission. The extracted circuit model of FPBGA bonding is useful in design and performance simulation of advanced packages, which use FPBGA bonding.

Using daily infection data for Hong Kong we explore the validity of a variety of models of disease propagation when applied to the SARS epidemic. Surrogate data methods show that simple random models are insufficient and that the standard epidemic susceptible-infected-removed model does not fully account for the underlying variability in the observed data. As an alternative, we consider a more complex small world network model and show that such a structure can be applied to reliably produce simulations quantitative similar to the true data. The small world network model not only captures the apparently random fluctuation in the reported data, but can also reproduce mini-outbreaks such as those caused by so-called "super-spreaders" and in the Hong Kong housing estate of Amoy Gardens.

Integrated implementation of RF front-end components has been shown to posses many benefits. Furthermore, it presents a new way of approaching RF design. This paper will discuss the recent developments by the author's group in the field of RF front-end technology. This will include stand-alone RF front-end components such as a self-heterodyne mixer as well as more functional front-end circuitry such as digital beamformer arrays, retrodirective arrays and an array error calibration scheme.

In this study, a CG animation tool was designed that allows interpolation and extrapolation of two types of repeated motions including finger actions, for quantitative analyses of the relationship between features of human motions and subjective impressions. Three-dimensional human motions are measured with a magnetic motion capture and a pair of data gloves, and then relatively accurate time-series joint data are generated utilizing statistical characteristics. Based on the data thus obtained, time-series angular data of each joint for two dancing motions is transformed into frequency domain by Fourier transform, and spectral shape of each dancing action is interpolated. The interpolation and extrapolation of two motions can be synthesized with simple manner by changing an weight parameter while keeping good harmony of actions. Using this CG animation tool as a motion synthesizer, repeated human motions such as a dancing action that gives particular impressions on the observers can be quantitatively measured and analyzed by the synthesis of actions.