Electroluminescence (EL) under alternating-current (ac) operation is first reported for n+-polysilicon/SiO2/p-Si MOS capacitors with 50 nm Si-implanted SiO2. Visible EL can be observed with the naked eye in the dark. The ac operation by pulse-wave distinctly enhances the EL intensity and its lifetime. The pulse frequency affects the EL spectrum and thus the EL color. A model of EL mechanism is proposed for the Si-implanted MOS EL device, which has a possibility of visible light emitting device.

Mobile terminals with Internet services such as i-mode are in wide use, and communication bandwidths are growing even further under 3G technology. However, displays of mobile terminals will remain small in view of their portable size and power consumption. In this paper, we propose a "ubiquitous display" that can be used in combination with mobile terminals. The user operates the mobile terminal and the ubiquitous display shows any content that requires a large screen space.

This paper describes a novel mobile video monitoring system. The receiver is a PDA (Personal Digital Assistant) with a PHS (Personal Handy Phone system) card. The sender is a PC-based video encoding system, which is connected to an ISDN line by ISDN-TA. Functions such as camera selection, remote camera control and high-resolution snap shot are implemented. In this paper, details of the system are explained and a practicability assessment is performed. An experiment was conducted to measure the upward and downward transmission delay. From the results, the system performs consistently to a theoretical behavior. Furthermore, the performance of this system is quite practical for mobile video monitoring.

As two simple relaxation oscillators are coupled by periodical and instantaneous switching, the system exhibits rich superstable synchronous phenomena. In order to analyze the phenomena, we derive a hybrid return map of real and binary variables; and give theoretical results for (1) superstability of the synchronous phenomena and (2) period of the synchronous phenomena as a function of the parameters. Using a simple test circuit, typical phenomena are verified in the laboratory.

MOSFETs can be used as capacitors, but its capacitance can vary by 5 to 7 times as its terminal voltage varies. To reduce the voltage dependence of the capacitance, this paper proposed two types of devices: one is called accumulation MOSFET (AMOS) and the other is formed by two conventional PMOS connected in anti-parallel. These two devices are readily available in the standard digital CMOS processes. The proposed capacitors were implemented in three different CMOS processes. The measured results show that the capacitances of both devices have less voltage dependence than a single PMOS. The voltage dependence of the AMOS capacitance can be as small as 17%. The minimum capacitance per unit area of the AMOS is 1.8 times that of the double-poly capacitor in an analog/mixed-mode CMOS process. To verify the usefulness of these two types of capacitors, they are used as compensation capacitors in a conventional two-stage amplifier. The measured results show that the amplifier compensated by the AMOS capacitor has little variation (6%) of the unity-gain frequency over the input common-mode range. Due to its smaller die area and cheaper digital process, AMOS can be used as compensation capacitor without resorting to more expensive analog process.

A new system, in which a real-time VLBI (very-long-baseline interferometer) is utilized, for real-time monitoring of atmospheric disturbances on a very-long baseline has been developed. In this system, beacon waves from geo-stationary satellites are used for received signals and public communication lines are used for data transmission. Connecting the system to the 6-m Kagoshima and the 10-m Mizusawa radio telescopes enables atmospheric disturbances to be observed. The cross-correlation phase was calculated from the received signals, and the Allan standard deviation of the phase was obtained. It was found that the Allan standard deviation across almost the whole region of the time interval reflects atmospheric disturbances.

In this paper, we propose a new coded orthogonal frequency division multiplex (COFDM)-based ubiquitous antenna system, which is composed of multiple radio base stations (RBSs) deployed over the service area and Radio-on-Fiber (RoF) link that connects RBSs to the central control station (CCS). The proposed system is capable of receiving multiple mobile terminals simultaneously operating at the same frequency by making effective use of joint detection. However, the propagation delay due to the RoF link could be a major problem for realizing the ubiquitous antenna system. In order to overcome this delay problem, we assume that the guard interval of COFDM is longer than the delay difference. Furthermore, in order to improve BER performance in a multipath Rayleigh fading channel, we also propose the MSE normalization scheme followed by the use of an MMSE-based joint detector. Computer simulation results show that the proposed system can improve the frequency utilization efficiency of the broadband wireless access system.

This letter proposes a design methodology of a capacitor for a switched capacitor filter. The capacitor design method makes the capacitor accurate to the capacitance ratio and insensitive to the process deviation. The SCF designed is used for the PCM CODEC filter and the deviation of the frequency characteristic is below 0.05 dB for a process deviation 0.5 µm in 5 µm CMOS process.

A new test structure to specify accurately the position of gate oxide breakdown is proposed, which simply consists of a conventional polycrystalline Si gate MOS capacitor and Al dots array diagonally lined-up on the capacitor. Optical beam induced current microscope was used to discriminate the breakdown spot. Layout of the discriminated spot among the Al dot array accurately determined the breakdown position. A 5-nm-thick gate oxide breakdown spot determined by this method has been successfully investigated by cross-sectional transmission electron microscopy (XTEM). A series of site-specified XTEM studies reveal local melting of anode Si during the intrinsic dielectric breakdown. This test structure is practically useful for site-specified XTEM studies on process-induced degradation phenomena of thin gate oxides.

We have developed a distributed optical fiber strain sensor for detecting the collapse of river embankments. The sensor uses a Brillouin optical time domain reflectometer (BOTDR) and consists of an optical fiber cable and pieces of nonwoven cloth. Pieces of cloth are fixed to the cable at 1.5-meter intervals and it is then embedded in a U-shaped configuration in a river embankment. The pieces of cloth are displaced when there is movement of the soil in which they are embedded. If one of two adjacent pieces of cloth remains stationary while the other moves, the optical fiber between the two pieces is stretched. The collapse of an embankment can be detected by using a BOTDR to monitor any such stretching in the 1.5-m lengths of fiber. The developed sensor operates at a sensitivity of 0.025%/kgf, which is equivalent to 0.067%/mm, and is thus capable of detecting soil movements of a few mm in river embankments. The sensor is also able to provide effective advance warning of the collapse of a river embankment resulting from water penetration. We subjected the sensor system to field tests that demonstrated the effectiveness of its construction and its long-term stability. The developed sensor system is an effective tool for use in river management systems of the very near future.

This article addresses the problem of designing and implementing multigigabit post-detection filters for application in optical communication systems using optical soliton pulses. The designed filters have the main advantages of full integration, electrically adjustable frequency response and active input and output impedance match.

The initial phase alternation of RZ pulses having duty cycle beyond 50% in dispersion-managed-link is found to help stabilize DM solitons transmissions. The stable soliton propagation of such wide RZ pulses should ease the difficulties designing soliton-based DWDM systems due to less spectral occupancy/channel. For the proof of concept, 40 Gbit/s WDM transmissions are numerically investigated and the initial phase alternation improved the transmission distance by the factor of 2 in the soliton-soliton interaction limited regime. The advantage of this concept has also been verified by conducting 40 Gbit/s single and 8 channels WDM transmission experiments using OTDM techniques with initial phase alternation.

A traitor tracing scheme is a broadcast encryption scheme in which a provider can trace malicious authorized users who illegally gave their personal keys to unauthorized users. The conventional schemes have some problems; one of them is that there exists an upper bound on the sizes of keys to certify the security of the scheme against a collusion attack by many traitors, and so that the size of the header increases according to the increase of the bound. We shall propose a new traitor tracing scheme where the header size is independent of the number of traitors.

This paper describes the design concept and realized functions of the first Optical Transport Network (OTN) based 43 Gbit/s line terminal. The system requirements of new generation networks are provided, and the functions needed in this line terminal are obtained from the requirements. The line terminal deploys Time Division Multiplexing (TDM) to handle client signals, and provides transparent high quality multiple services such as SONET/SDH and Gigabit Ethernet. The configuration and features of the actually fabricated system are described.

We demonstrated variable dispersion compensation using the Virtually Imaged Phased Array (VIPA) for a 40-Gbit/s dense-WDM transmission system. The large tunable range from -800 to +800 ps/nm in the entire C-band wavelength range and the high tunable resolution of 1 ps/nm was achieved by using a 3-dimensional mirror equipped with a stepping motor that we developed. We adopted the dispersion monitor of 40-GHz intensity extracted from the received 40-Gbit/s baseband signals, and verified that this dispersion monitoring method is applicable to nonlinear transmission by detecting the monitor peak. Using the VIPA variable dispersion compensator and the dispersion monitor, we demonstrated 1.28-Tbit/s (40-Gbit/s 32 ch) automatic dispersion compensation. As a result, we confirmed that only two VIPAs and one fixed dispersion compensating fiber (DCF) are needed to make our method applicable to the entire C-band for dense WDM 40-Gbit/s systems having a large transmission range of 80 km.

A novel sensor system of denture base type was developed for simultaneous monitoring of salivary pH and tissue temperature in the oral cavity. Fundamental components of the monitoring system, sensor devices and sensor configuration are showed in this paper. The sensor units consist of IrO2 electrode and thermistor circuit implanted in the denture base that is tightly fixed in the oral cavity. The signals are transmitted by PFM-FM telemeter system that can be used for health care of the aged people without restraint of their daily behavior while at work, sleeping and even at exercise. Some of results concerning the basic characteristics of the sensor system and continuously monitored physiological data were obtained from the preliminary experiments. Availability of the whole system and monitoring method was discussed.

Spatial dynamic pattern formations or trails by organisms attract us, which remind us chaos and fractal. They seem to show the emergence of co-operation, job separation, or division of territories when genetic programming controls the reproduction, mutation, crossing over of the organisms. Recent research in social insect behavior suggests that swarm intelligence comes from pheromone or chemical trails, and models based on self-organization can help explain how colony-level behavior emerges out of interactions among individual insects. We try to explain the co-operative behaviors of social insect by means of density of organisms and their interaction with environment in simple simulations. We also study that MDL-based fitness evaluation is effective for improvement of generalization of genetic programming. At last, interspecific and intraspecific mathematical models are examined to expand our research into interspecific evolution.

We review recent progresses in our studies on the fiber-optic soliton compression and related subjects with special emphasis on dispersion-flattened fibers (DFFs). As for the ultimately short pulse generation, it has been demonstrated to compress 5 ps laser diode pulses down to 20 fs with a 15.1 m-long single-stage step-like dispersion profiled fiber employed. The compression was brought about through a series of the higher order soliton processes in conjunction with a single and ordinary erbium-doped fiber preamplifier, and DFFs contained at its end played a major role. We have performed intensive investigations on the DFF compression mechanisms in the 100-20 fs range. A fairly reliable model was developed for the higher order soliton propagation along a DFF in the temporal range from 100 down to 30 fs by taking into consideration the higher order nonlinear and dispersion effects as well as incident pulse shape dependence. Through the simulation, parametric spectrum generation originating from the modulation instability gain was pointed out at frequencies apart from the pump wave frequency, which agrees with the experimental observation. Its possible application is also discussed.

In this paper, we review recent developments in the field of optical regeneration for both ultra long-haul transmission and terrestrial networking applications. Different techniques (2R/3R) using nonlinear properties of materials and/or devices are proposed such as saturable absorber or InP based interferometer structures showing regenerative capabilities. Principles of operation as well as system experiments are described.

This paper addresses the problem of designing an unconditionally secure conference system that fulfills the requirements of both traceability and dynamic sender. In a so-called conference system, a common key is shared among all authorized users, and messages are encrypted using the shared key. It is known that a straightforward implementation of such a system may present a number of security weaknesses. Our particular concern lies in the possibility that unauthorized users may be able to acquire the shared key by illegal means, say from one or more authorized but dishonest users (called traitors). An unauthorized user who has successfully obtained the shared key can now decrypt scrambled messages without leaving any evidence on who the traitors were. To solve this problem, in this paper we propose a conference system that admits dynamic sender traceability. The new solution can detect traitors, even if the sender of a message is dynamically determined after a shared key is distributed to authorized users. We also prove that this scheme is unconditionally secure.