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.

We have designed a demultiplexer (DMUX) with a simple structure, high-speed operation circuits and large bias margins. By using a binary-tree architecture and clock-driven circuits, multi-channel DMUXs can be constructed easily from the same elemental circuits, i.e., 1-to-2 DMUX, consisting of a T-FF and a 1-to-2 switch. By applying cell-level optimization and Monte Carlo simulation, bias margins and operation frequency of the circuits were enlarged. Logical operations of the 1-to-2 DMUX and a multi-channel DMUX, e.g., a 1-to-4 DMUX were experimentally confirmed. It was also confirmed that the large margins, 33% of the DMUX (1-to-2 switch) was kept up regardless the degree of integration, and that the 1-to-2 DMUX can operate up to 46 GHz by using measure of average voltages across Josephson junctions.

The major concern at a branch point in asynchronous transfer mode (ATM) networks for point-to-multipoint available bit rate (ABR) services is how to consolidate backward resource management (BRM) cells from each branch for a multicast connection. In this paper, we propose an efficient feedback consolidation algorithm based on an adaptive dynamic threshold (ADT) to eliminate consolidation noise and to reduce consolidation delay. The main idea of the ADT algorithm is that each branch point estimates the ABR traffic condition of the network through virtual queue estimation. Simulation results show that the proposed ADT algorithm can achieve a faster response in congestion status and a higher link utilization compared with the previous works.

An advanced center biased search algorithm for block motion estimation is proposed in this letter. It adopts an innovative center biased search strategy to get correct motion vector. The computational complexity is reduced by strict application of the unimodal error surface assumption and half stop technique. Experimental results show that proposed algorithm has improved performance as compared to the conventional block matching algorithms.

To the aim of developing industrializable low-cost electronic techniques for the compensation of non-linearities in Radio-over-Fibre networks, a semiconductor laser circuit model and a predistortion circuit configuration have been implemented and simulated. The CAD procedure illustrated indicates the steps to obtain a broadband compensation (0.4-2 GHz) of both second- and third-order distortions.

We have developed and demonstrated a novel technique for electrical inspection and electrical failure analysis, which can detect open, high-resistance, and short circuits without the need for electrical contact with the outside of the LSI chip or the board on which the LSI chip is mounted. The basic idea of the technique is the detection of the magnetic field produced by OBIC (optical beam induced current) or photo current. A DC-SQUID (superconducting quantum interference device) magnetometer is used to detect the magnetic field. This scanning laser-SQUID microscopy ("laser-SQUID" for short) has a spatial resolution of about 1.3 µm. It can be used to distinguish defective chips before bonding pad patterning or after bonding without pin-selection. It can localize any defective site in the chip to within a few square microns.

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-end telecommunication systems in the larger nationwide networks of the next decade will require routers having a packet switching throughput capacity of over 10 Tbps. In such future high-end routers, the packet switch, which is the biggest bottleneck of the router, will need higher processing speeds than semiconductor devices. We propose a high-end router system architecture using single flux quantum (SFQ) technology. This system consists of semiconductor line card units and an SFQ switch card unit. The features of this switch card architecture are (1) using internal speedup architecture to reduce effective loads in the network, (2) using a packet switch scheduler to attain non-blocking characteristics. This architecture can expand the switching capacity to a level greater than tens of Tbps scale, keeping with non-blocking characteristics.

Almost all land animals coordinate their behavior with circadian rhythms, matching their functions to the daily cycles of lightness and darkness that result from the rotation of the earth corresponding to 24 hours. Through external stimuli, such as dairy life activities or other sources from our environment may influence the internal rhythmicity of sleep and waking properties. However, the rhythms are regulated to keep their activity constant by homeostasis while fluctuating by incessant influences of external forces. A modeling study has been developed to identify homeostatic dynamics properties underlying a circadian rhythm activity of Sleep and Wake data measured from normal subjects, using an MA (Moving Average) model associated with Backpropagation (BP) algorithm. As results, we found that the neural network can capture the regularity and irregularity components included in the data. The order of MA neural network model depends on subjects behavior, the first two orders are usually dominant in the case of no strong external forces. The adaptive dynamic changes are evaluated by the change of weight vectors, a kind of internal representation of the trained network. The dynamic is kept in a steady state for more than 20 days at most. Identified properties reflect the subject's behavior, and hence may be useful for medical diagnoses of disorders related to circadian rhythms.

The size dependent properties of the intrinsic Josephson junctions in Bi2Sr2CaCu2Oy single crystal mesas in the external magnetic field are studied. The mesas of (1-140) µm long with 7-29 junctions were fabricated and their current-voltage characteristics were measured in external magnetic field applied parallel to the CuO2 layers up to 0.16 T. In zero magnetic field, multiple resistive branches with large hysteresis were observed in the current-voltage characteristics for the fabricated mesas. Almost identical critical currents were also observed for all the junctions in each mesa. With applied magnetic field, Ic of the longer mesas showed a complex magnetic field dependence as compared to that of the short mesas (of about 1 µm in length). It was observed that the lower critical magnetic field of the junctions decreased and approached a constant value with increasing number of junctions and also with increasing length of the junctions. Similar magnetic behavior was obtained by numerical simulations based on coupled sine-Gordon equations for such stacked junctions.

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.

We have developed a new torque magnetometer on the basis of a 4-K refrigerator. The system temperature can be lowered down to 1.5 K by pumping liquefied helium from a top loading sample space. A piezoresistor bridge on a Si cantilever is used to detect torque acting on a sample. A transverse magnetic field is supplied by a variable-field permanent magnet up to 10 kG. We find that a sensitivity of our torque magnetometer is Δ τ 10-10 Nm.

We have fabricated a prototype of interface devices between SFQ and CMOS circuits using HTS quasi-particle injection devices. By the injection of quasi-particles, the bridge area becomes resistive and high voltage appears at the drain electrode. As a test of device operation, we applied the signal of a function generator to the gate electrode and observed that the device successfully repeated on/off operation. We also succeeded in explaining the device characteristics by considering the thermal effects.

The Fundamental Law of Science and Technology and the Basic Plan of Science and Technology were established in Japan in 1995 and 1996, respectively and the second Basic Plan for Science and Technology R&D was established in April, 2001. In addition, as a part of Japanese government administrative reform, the Council for Science and Technology Policy was organized in the Cabinet Office and the most of the national research laboratories including the Communications Research Laboratory (CRL) have been restructured to the Independent Administrative Institution (IAI). This paper introduces first the relationship between the info-communications R&D and the national science and technology policy in Japan. Second, the R&D of CRL, IAI is introduced. Third, as a typical example of the wireless communications R&D, the research of wireless communication in CRL is shown in more detail in terms of terrestrial wireless/mobile communication system and satellite communication system. Finally the future prospect of such an R&D is shown briefly.

Two novel linearization processes in electro-absorption-modulator (EAM) are proposed and demonstrated. These two modulation schemes are used to compensate the nonlinear component of the EAM by controlling the DC bias voltages of the each EAM separately. The simulations on the nonlinearity of EAM and linearization process are performed in both time and frequency domains. From a serially cascaded modulation simulation, a reduction of 16 dB in IMD3, 45 dB in IMD5 and the following increase of 15 dB in linear dynamic rage (LDR) are achieved. In dual-parallel modulation experiment at 8 GHz, a reduction of 23 dB in IMD3 and the following increase of 15.1 dB in LDR of are achieved compared to those of a single EAM operation.

New bandpass filters (BPFs) with stub resonators are proposed for creating multiple attenuation poles. Firstly, the stub-dependent characteristics of the distributed-element stubs are examined theoretically. Secondly, the new BPFs with resonators of combined stubs are proposed. An advantage of these filters is the possibility of controlling the number of attenuation poles. The design of the proposed filter is carried out based on the general filter design with the narrow-band approximation technique. The transmission and reflection characteristics of the proposed BPFs are also examined theoretically and experimentally. The miniaturization of the filters is also carried out using the resonator with loaded-element stubs. The discussions lead us to the conclusion that the proposed design method of the filters are useful for controlling the number of attenuation poles of the BPF.

We present a design framework of a high-end server based on Single-Flux-Quantum (SFQ) circuit technologies. The server proposed here has multiple microprocessors and memories, which are mounted on a single board or package and are connected each other by SFQ interconnection switches. The extremely large bandwidth up to 100 Gbps/channel in the interconnection will be realized because of high throughput nature of the SFQ circuits. SFQ memories or Josephson-CMOS hybrid memories are employed as the shared memory of the multiprocessor. The SFQ microprocessors are constructed based on the complexity-reduced (CORE) architecture, in which complexity of the system is eased in exchange for using a high clock rate of the SFQ circuits. The processor is so-called Java-processor that directly executes the Java Byte Codes. Assuming a proper advancement of the Nb/AlOx/Nb integrated circuit process technology, we have estimated that the power consumption of the server system including a cryocooler is reduced by a factor of twenty as compared to the future CMOS system with the same processor performance, while the SFQ system has 100 times of magnitude larger memory-processor bandwidth.

We present measurements of kilohertz and megahertz sine waves synthesized using a Josephson arbitrary waveform synthesizer. A 4.8 kHz sine wave synthesized using an ac-coupled bias technique is shown to have a stable 121 mV peak voltage and harmonic distortion 101 dB below the fundamental (-101 dBc (carrier)). We also present results of our first phase-noise measurement. A 5.0 MHz sine wave was found to have distortion 33 dB lower than the same signal synthesized using a semiconductor digital code generator. The white-noise floor of the Josephson synthesized signal is -132 dBc/Hz and is limited by the noise floor of the preamplifier.

Lymph-node detection system using a high Tc SQUID and ultra-small particles was proposed. Pseudo lymph nodes containing small iron particles were made and the magnetic signal was measured. The SQUID signal was proportional to the weight of the iron in the fluid. At the distance of 20 mm, the detectable minimum weight of the iron was 40 µg. We demonstrated that the possibility of the application of the system to the human body.

We have designed the Half Adder (HA) circuit and the Carry Save Serial Adder (CSSA) circuit based on pipeline architecture. Our HA has the structure of a two-stage pipeline and consists of 160 Josephson Junctions (JJs). Our CSSA has the structure of a four-stage pipeline with a feedback loop and consists of 360 JJs. These circuits were fabricated by the NEC standard process. There are two issues which should be considered in the design. One is parameter spreads generated by the fabrication process and the other is leakage currents between the gates. We have introduced a parameter optimization method to deal with the parameter spreads. We have also inserted three stages of JTLs to reduce leakage currents. We have experimentally confirmed the correct operations of these circuits. The obtained bias margins were 33.1% for the HA and 24.6% for the CSSA.