It is a fundamental problem to construct a virtual path layout minimizing the hop number as a function of the congestion for a communication network. It is known that we can construct a virtual path layout with asymptotically optimal hop number for a mesh of trees network, butterfly network, cube-connected-cycles network, de Bruijn network, shuffle-exchange network, and complete binary tree network. The paper shows a virtual path layout with minimum hop number for a complete binary tree network. A generalization to complete k-ary tree networks is also mentioned.

As a center of mobile multimedia of the 21st century, it is very much looking forward to explosion of R&D and business of the next generation of mobile communication systems and the ITS (Intelligent Transport Systems) because ITS will enable information-oriented in the field of the road, traffic and vehicles, by using the most advanced technologies of mobile communications and devices, for the various purposes such as decrease of the traffic accident, the reduction of traffic jam, the increase in efficiency of the logistics and the harmony with the earth environment. This invited paper will first briefly introduce evolution of mobile communications and ITS in ministries, industries and academia in Japan. Then core communication technologies for ITS will be overviewed such as spread spectrum CDMA, adaptive antenna array, and software radio or software defined radio. Demands of SoC (System on a Chip) to carry out the core technologies will be addressed.

The full wave TTL method is used to calculate the complex resonance frequency of the rectangular finline resonator. In this direct and concise method, the Maxwell's equations in Fourier transform domain, are used to obtain the electromagnetic fields in terms of the transversal electromagnetic fields. The complex resonant frequency is obtained by setting the determinant of the system matrix equal to zero and results in 3D using Fortran PowerStation programs are presented for different parameters including substrate thickness, permittivity and width of the slot resonator.

In the field of computer graphics (CG), some adaptive methods have been proposed in order to make CG images more real in relatively low computational cost. As one of such adaptive methods, in this paper, an adaptive method will be proposed for detection of edges and approximation of surfaces in the use of the so-called automatic differentiation. In the proposed method a CG image with high quality can be generated in suitable computational cost. In this paper, three cases will be considered. The first is an adaptive distributed ray tracing which can adaptively generate anti-aliased CG images in suitable computational cost. The second is a high quality triangular meshing, which guarantees accuracy of the generated meshes according to shape of given surface in suitable computational cost. The last case is used in the so-called radiosity method.

This paper presents novel flooding schemes for wireless mobile ad hoc networks. Clustering of nodes is assumed as a basic ad hoc network structure. GWF (Gateway Forwarding) and SGF (Selected Gateway Forwarding) are presented based on clustering. A new protocol, termed FGS (Flooding Gateway Selection) protocol, between a cluster head and its gateways to realize SGF is presented. It is shown that SGF significantly improves the packet delivery performance in ad hoc networks by reducing flooding traffic.

A coaxial cable measurement system applicable up to 60 GHz in the cryogenic temperature is developed by using V-connectors. In this system, the fine location of coupling loop antennas can be adjusted by three-dimensional mechanical stages in the low temperature region. In order to verify usefulness of this system, the temperature dependence of surface resistance (Rs) of Y-Ba-Cu-O (YBCO) films was measured at 30 GHz by the two-dielectric resonator method using TE011- and TE013- mode sapphire rod resonators. The measured result of Rs was 0.5 mΩ at 30 GHz and 20 K, which was 1/40, compared with those of copper plates.

In this paper, we review the progress in BiSrCaCuO-2212 Intrinsic Josephson junctions (IJJs) by summarizing our recent results in fabrication and high frequency experiments. Using a double-side fabrication process, a well defined number of intrinsic Josephson junctions in a well defined geometry can be fabricated. The junctions in the stack are quite homogeneous, and the power distribution of external irradiation among the junctions is even. Shapiro steps are clearly observed up to 2.5 THz, and the general condition for the occurrence of Shapiro steps at frequency frf is that it should be much greater than the plasma frequency fpl. Under certain conditions the Shapiro steps are zero-crossing, making some applications possible, such as quantum voltage standard etc.

In this paper, characteristics of a digital system dedicated to the fast execution of the FDTD algorithm, widely used for electromagnetic simulation, are presented. Such system is conceived as a module communicating with a host personal computer via a PCI bus, and is based on a VLSI ASIC, which implements the "field-update" engine. The system structure is defined by means of a hardware description language, allowing to keep high-level system specification independent of the actual fabrication technology. A virtual implementation of the system has been carried out, by mapping such description in a standard-cell style on a commercial 0.35 µm technology. Simulations show that significant speed-up can be achieved, with respect to state-of-the-art software implementations of the same algorithm.

Achieving optimal performance with minimal complexity are conflicting problems encountered in constructing receivers. In this paper, to solve the problem, we propose sector beamed space hopping which utilizes a Viterbi equalizing receiver. Reduction of the number of RF circuit sets, system complexity and decreasing the computational burden of the Viterbi equalizer through the use of sector beamed space hopping is presented. This is achieved using a sector beamed antenna which limits the number of paths in the multipath channel environment. This paper describes each key component which comprises the system and discusses the application of FH-SS communication. The channel is assumed to be an industrial indoor propagation channel, such as those found in a factory, where high reliability is required and many complex multipaths exist. We confirm through simulation that Viterbi equalization using less computational complexity can be obtained. It is found that there exists a trade off between system complexity and performance. Through the discussion of power consumption, cost and BER performance, we show that the proposed system achieves acceptable performance while having a low system complexity.

We report the measurements on the ramp-edge type Josephson and quasiparticle tunnel junctions with the different interface angle geometry using high-Tc YBa2Cu3O7-y (YBCO) electrodes. The YBCO/I/Ag tunnel junctions with different crystal-interface boundary angles are fabricated for the investigation of zero bias conductance peak. The angle dependent zero bias conductance peak typical to a dx2-y2-wave superconductor is observable. For Josephson junctions, YBCO ramp-edge junctions with different ab-plane electrodes relatively rotated by 45are fabricated using a CeO2 seed-layer technique. The temperature dependence of the maximum Josephson current for YBCO/PBCO/YBCO junctions (PBCO: PrBa2Cu3O7-y) exhibits angle-dependent behavior, qualitatively different from the Ambegaokar-Baratoff prediction. Under microwave irradiation of 9 GHz, the Shapiro steps appear at integer and/or half integer multiples of the voltage satisfying Josephson voltage-frequency relation, whose behavior depends on the sample angle geometry. The results are reasonably interpreted by the dx2-y2-wave theory by taking the zero energy state into account.

Scaled models for an anatomical head model and a simple head model are used to investigate the effects of head size on SAR characteristics for a cellular phone exposure at 835 MHz. From the results, we can see that a larger head produces a higher localized SAR and a lower whole-head averaged SAR.

High-Tc superconductors convincingly showed that these materials are essentially natural arrays of Josephson junctions formed in atomic scale. In this paper, in-plane aligned a-axis-oriented YBa2Cu3O7-δ (YBCO) thin films were successfully grown on LaSrGaO4(LSGO) (100) substrates which were cleaned by ion-beam. Voltage jumps with hysteresis implying intrinsic Josephson effects are observed in c-axis direction. This result suggest that it is possible to achieve planar intrinsic Josephson devices which have applications in high frequency electronics, such as voltage standards, Josephson masers and so on.

We propose the new and highly accurate design theory of the high Tc superconducting (HTS) miniaturized coplanar waveguide (CPW) bandpass filters (BPFs) with highly packed meanderlines. BPFs are designed using the external quality factor (Qe) and coupling constant (k) (Q-k method). These parameters are estimated from the transmission coefficient obtained by the 2.5-dimensional electromagnetic field simulator. Moreover, the Q-k method is compared with the J-b method (designed using admittance inverter and susceptance slope parameter) presented previously; in this way we confirmed that the Q-k method has higher accuracy than the J-b method. We realized the design of a the highly packed meanderline CPW BPF (5 pole, center frequency = 2 GHz, fractional band width = 15 MHz, ripple = 0.1 dB) in a 3.5 mm 8 mm substrate.

This paper proposes a maneuvering target tracking algorithm using multiple model filters. This filtering algorithm is discussed in terms of tracking performance, tracking success rate and tracking accuracies for short sampling interval as compared with other conventional methodology. Through several simulations, validity of this algorithm has been confirmed.

We developed a compact rf receiver subsystem using a high-Tc superconducting sharp skirt band-pass filter with a center frequency tuning function. A 24-pole hairpin-type 2 GHz microstrip-line filter was fabricated with YBa2Cu3Oy thin films deposited on a LaAlO3 substrate. Attenuation characteristics were more than 30 dB at 1 MHz apart from both the lower and the higher pass-band edges. For center frequency tuning, a 1-mm-thick dielectric sapphire plate was stacked on the filter, and the filtering characteristics were tuned by moving the plate using a piezoelectric bending actuator. The range of the center frequency modulation was more than 12 MHz with no degradation of the low-loss and sharp-skirt characteristics.

Scalabilities of bit rate and coding format in coded multimedia contents have become very important for the efficient use of network bandwidth and storage capacity with the recent availability of a wide variety of bandwidth and storage media. However, the conventional approach uses decompression and recompression processes to realize the above scalabilities, which require very expensive computations. In addition, a very large cache space is required for storing the decoded audio-video data. This paper describes three fast scalability methods for MPEG audio and video data, MPEG audio/video bit rate conversion and MPEG format conversion, in order to address these problems. As for the first scalability, MPEG audio coding bit rate conversions, we describe subband domain conversion using bandwidth limitation, requantization and a requantization reflecting phychoacoustic model. Four types of MPEG video bit rate conversion are described that use bandwidth limitation, out-loop requantization, in-loop requantization, and hybrid requantization. As for the format conversion, the fast baseband domain format conversion is performed using coding information such as motion vectors and coding types extracted from input coded video. The experimental results of several comparisons with the above scalabilities and conventional transcoding methods are also shown.

In this paper, the iterative decoding of BCH product codes also called Block Turbo Codes (BTC) is evaluated for the HIPERLAN/2 OFDM system. Simulations show that expurgated BCH codes should be chosen as constituent codes in order to outperform the specified convolutional code. We also show that the bit-by-bit frequency interleaver has a big impact on the behaviour of the turbo decoding process and that increasing its size together with time diversity lead to good performance when compared to the convolutional code.

The electronically steerable passive array radiator (ESPAR) antenna performs analog aerial beamforming that has only a single-port output and none of the signals on its passive elements can be observed. This fact and one that is more important--the highly nonlinear dependence of the output of the antenna from adjustable reactances--makes the problem substantially new and not resolvable by means of conventional adaptive array beamforming techniques. A novel approach based on stochastic approximation theory is proposed for the adaptive beamforming of the ESPAR antenna as a nonlinear spatial filter by variable parameters, thus forming both beam and nulls. Our theoretic study, simulation results and performance analysis show that the ESPAR antenna can be controlled effectively, has strong potential for use in mobile terminals and seems to be very perspective.

We have fabricated and characterized two types of high-Tc planar SQUID gradiometers having different line width of pickup loops. The device worked in flux-locked loop (FLL) operation even in laboratory environment without any shielding. A magnetic field gradient resolution of a parallel-type device in a lightly shielded room was about 0.5 pT/cmHz1/2 at 1 kHz and 2 pT/cmHz1/2 at 1 Hz. The device was possible to record magnetocardiograms in a shielded room. QRS-complex peaks of about 10 pT PP/4mm are clearly observed. For a mesh-type device, the increase of low frequency noise in the open laboratory environment was less than that for a parallel-type.

A flash analog-to-digital converter (ADC) that uses resonant-tunneling complex gates is proposed. The ternary quantizers, consisting of monostable-to-multistable transition logic (MML) circuits, convert the analog input signal into the ternary thermometer code. This code is then converted into the binary Gray-code output by a multiple-valued multiple-input monostable-bistable transition logic element (M2-MOBILE). By assuming InP-based resonant-tunneling diode (RTD) and heterojunction field-effect transistor technology, we have carried out SPICE simulation that demonstrates a 4-bit, 10-GS/s ADC operation. The input bandwidth, defined as a frequency at which the effective number of bit decreases by 0.5 LSB, was also estimated to be 500 MHz. Compact circuit configuration, which is due to the combination of MML and M2-MOBILE, reduces the device count and power dissipation by a factor of two compared with previous RTD-based ADCs.