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ABSTRACT: We present a potential of photonic technologies originally developed for fiber-optic communications for use in contemporary terahertz-wave applications and demonstrate several examples, including a high-precision time-continuous terahertz-wave signal and terahertz-wave band noise generators, sensing and imaging with CW and noise signals, and wireless communications. In addition, recent progress of uni-travelling photodiodes, key component of this work, is also presented.
General Assembly and Scientific Symposium, 2011 XXXth URSI; 09/2011
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ABSTRACT: A remote gas sensor based on a continuous-wave sub-terahertz spectrometer with an operation bandwidth between 200 and 500 GHz has been developed. The performance of the developed system was investigated in a full-scale fire. The measured transmission spectra of smoke show the existence of hydrogen cyanide (HCN) and water molecules, which were generated due to the combustion of a foam urethane block. The HCN content estimated from the absorption intensity agrees quite well with that obtained from the chemical analysis of gases sampled from the fire site. These results demonstrate the potential of the developed sensing system as a remote toxic gas sensor at disaster sites.
Microwave Symposium Digest (MTT), 2011 IEEE MTT-S International; 07/2011
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ABSTRACT: Increasing demand on the broadband wireless communication over Gigabits has focused renewed attention on 60 GHz millimeter wave. We developed a novel point-to-multipoint (P2MP) gigabit WLAN System on 60 GHz millimeter wave. The proposed system employed wide angle beams antenna overcomes the usability of the conventional system, covers larger areas. Maximum transmission rate was designed to be 1.2 Gigabit/sec. Orthogonal frequency division multiplex (OFDM) using 1024 points FFT and convolutional code were implemented with PHY layer of the WLAN equipments. Superframe for multiple beams and frame aggregation for high throughput were designed for MAC layer. All control channels for downlink such as broadcast, frame control and access feedback were aggregated to reduce overhead in addition to aggregation of data frame. Evaluated throughput using proposed frame aggregation was confirmed to be more than 800 Mbit/sec with developed prototype in the case of aggregation size of 10 Ã 1500 byte.
Consumer Communications and Networking Conference (CCNC), 2010 7th IEEE; 02/2010
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ABSTRACT: UWB is a short range (up to 10 m) wireless communication technology which provides high throughput with low transmission and high reliability. We developed a PHY prototype conformed to ECMA-368, one of UWB standards, and a network simulator for evaluating MAC throughput of ECMA-368. In this paper, we propose an evaluation method considering the characteristic of PHY, the channel model and the propagation loss derived from our PHY prototype. This enables throughput evaluation in various usage models. The evaluation result shows that an application that needed 200 Mbps throughput is available at range up to 2 m. The throughput is enough to transmit a HDTV stream about 50 Mbps up to about 6 m and to transmit two HDTV streams within 3 m.
Communications, 2009. APCC 2009. 15th Asia-Pacific Conference on; 11/2009
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ABSTRACT: Repetitive pulsed power generation by compact sources is being studied for industrial applications. The research efforts include pulse-compression concept exploration, electrical circuit design and optimization, switching device development and evaluation, and application demonstrations. The basic strategy is to take advantage of solid-state switching devices to achieve compactness, reliability, and high repetition rate of pulsed power systems operating in both capacitive and inductive energy-storage schemes. These solid-state switches include saturable inductors, saturable capacitors, photoconductive semiconductors, and other power semiconductor switching devices, such as MOSFET, IGBT, SiC-FET, and SI-Thyristor.
Pulsed Power Conference, 2009. PPC '09. IEEE; 08/2009
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ABSTRACT: We have demonstrated that a superconductor-insulator-superconductor (SIS) mixer is applicable for a power detector to evaluate the sideband noise radiated from a submillimeter-wave local oscillator (LO) under development. A simple analysis shows SIS mixers provide better resolution of LO noise than Schottky barrier diode mixers when the available LO power is less than ~ 0.4 mW. Systematic measurement of dependence of receiver noise temperature T <sub>RX</sub> on components and operational conditions of a photonic LO (Ph-LO) is carried out, which provides a guide to their optimization, e.g., source-laser power, photodiode drive current, use of an optical filter, and selection of an optical amplifier. Noise temperature of the Ph-LO estimated from experimental results ranges from ~ 1 times 10<sup>3</sup> K to ~ 5 times 10<sup>4</sup> K as a function of operational conditions and parameters.
IEEE Transactions on Appiled Superconductivity 07/2009; · 1.04 Impact Factor
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ABSTRACT: Increasing demand on the broadband wireless communication over Gigabits has focused renewed attention on 60 GHz millimeter wave. We developed a novel point-to-multipoint (P2MP) Gigabit WLAN System on 60 GHz millimeter wave. The proposed system employed wide angle beams antenna overcomes the usability of the conventional system, covers larger areas. Maximum transmission rate was designed to be 1.2 Gigabit/sec. Orthogonal frequency division multiplex (OFDM) using 1024 points FFT, and convolutional code were implemented with PHY layer of the WLAN equipments. Superframe for multiple beams and frame aggregation for high throughput were designed for MAC layer. All control channels for downlink such as broadcast, frame control and access feedback were aggregated to reduce overhead in addition to aggregation of data frame. Maximum improvement of throughput due to control channel aggregation was evaluated to be 200% compared with individual transmission. Evaluated throughput using proposed frame aggregation was confirmed to be more than 852 Mbit/sec in the case of aggregation size of 16 times 1500byte.
Consumer Communications and Networking Conference, 2009. CCNC 2009. 6th IEEE; 02/2009
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ABSTRACT: In this paper, we present a microwave photonic technique to produce a noise signal from the microwave to sub-terahertz region with an optical amplified spontaneous emission noise, optical filter, and photodetector. With this scheme, it is easy to control the noise level by simply controlling the input optical noise power. In addition, the output noise spectral density with this scheme can be accurately estimated from the well-known spectral shape of an optical filter. For the demonstration of this scheme as a noise source, noise figure measurements for commercial devices such as amplifiers and a mixer, were performed in the frequency range from 0.1-20 to 293-357 GHz and the results were compared to those with conventional techniques.
IEEE Transactions on Microwave Theory and Techniques 01/2009; · 1.85 Impact Factor
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ABSTRACT: We present a photonic technique for generating sub-terahertz noise with an optical amplifier, arrayed waveguide grating (AWG), and uni-travelling carrier photodiode (UTC-PD). This scheme provides a high noise level and good controllability of the noise level and frequency band. The power density of the generated sub-terahertz noise is approximately -130.1 dBm/Hz at 350 GHz, which is 43.9 dB higher than the thermal noise (-174 dBm/Hz). Utilizing the implemented sub-terahertz noise generator with an UTC-PD module, we measured the absorption lines of N<sub>2</sub>O in the frequency range approximately 280~390 GHz and compared them with simulations.
Microwave Conference, 2008. EuMC 2008. 38th European; 12/2008
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ABSTRACT: The degraded region is formed even at low voltage almost equal to electroluminescence (EL) starting voltage, and then tree channel grows from the degraded region. This paper reports the relation between the progress of polymer degradation and EL intensity, and discusses the process at the very early stage of tree initiation including the formation of tree channel without gas discharge.
Electrical Insulation and Dielectric Phenomena, 2008. CEIDP 2008. Annual Report Conference on; 11/2008
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ABSTRACT: This paper presents a design technique for digital filter design using Pascal matrix operation for s-z transformation. The s-z transformation that used is bilinear transformation, so the obtained Pascal matrix called bilinear Pascal matrix for s-z transformation. The standard analog transfer functions of biquad filter prototype are used to idea of proposed design. The proposed design technique can give various frequency characteristic of the obtained digital filter transfer function without any frequency transformation by s variables, only some setting of parameters that called biquad-parametric technique. This technique can reduce the computational complexity, which occurs from frequency transformation matrix in previous design method.
Control, Automation and Systems, 2008. ICCAS 2008. International Conference on; 11/2008
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ABSTRACT: We present active gas sensing with a sub-terahertz (THz) spectrometer. The transmitter and receiver of the system are composed of a photonic-base source and a Schottky barrier detector, respectively, and their arrangement is monostatic. From the intensity of the absorption peak of the received sub-THz signal, the density of the sample gas (N<sub>2</sub>O) can be successfully obtained.
Infrared, Millimeter and Terahertz Waves, 2008. IRMMW-THz 2008. 33rd International Conference on; 10/2008
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ABSTRACT: Electroluminescence (EL) occurs in initiation phase of electrical tree and is considered to be a probe of the degradation of polymer insulating materials. We consider that EL is caused by electron impact; namely, electrons injected from electrode are accelerated in micro cavity of sub-micron size and causes bond scission and excitation of luminescence center. Under existence of water, water treeing takes place when subjected to a high electric field. Water tree provides a starting point of electrical tree, and therefore is responsible for the final breakdown of power cables with polymeric insulation. But the relation between EL and degradation in water-treed region is still unclear. We studied the EL properties of cross-linked polyethylene (XLPE) with a water-treed region after drying process. Wepsilall discuss the relation between EL properties and progress of material degradation in water treed region.
Electrical Insulating Materials, 2008. (ISEIM 2008). International Symposium on; 10/2008
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ABSTRACT: We have developed a sensitivity-stabilized fiber-mounted electrooptic (EO) probe for electric field mapping. In this probe, a polarization-rotated reflection method is used to cancel out the phase difference between the lights transmitted on the fast and slow axes of a polarized maintaining fiber (PMF) in a round trip since a Faraday rotator (FR) on the tip of the PMF rotates the polarization plane of the transmitted light orthogonally. Consequently, the sensitivity of the EO probe is stable against PMF bending and changes in temperature. The sensitivity degradation caused by PMF bending with a radius larger than 4 mm is less than 0.5 dB. The sensitivity fluctuation caused by a temperature change of 50degC to 100degC is suppressed to less than 1 dB. Since the PMF connecting the EO probe to the polarization control module is 5-m long, we can avoid any disturbance from the region around the probe tip. We demonstrate precise near-field measurements for a dipole antenna in a 20 cm x 10 cm scanning area. This result means that the EO probe can be used for calibrating antennas fixed in practical fields.
Journal of Lightwave Technology 09/2008; · 2.78 Impact Factor
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ABSTRACT: The aim of this study was to isolate single-chain variable fragments (scFvs) against human insulin-like growth factor I receptor (IGFIR) from a phage library displaying human scFvs. Isolated scFvs-displaying phages showed affinity for IGF-IR in comparison to the control. Expression of scFv proteins in Escherichia coli for further characterization, however, proved extremely difficult. Alternatively, the scFv protein was expressed as a fusion protein with a maltose-binding protein (MBP) that is a highly soluble E. coli protein. The MBPscFv fusion protein expressed in a soluble form in E. coli was purified to homogeneity by two-step affinity chromatography. The resulting MBP-scFv exhibited affinity for IGF-IR and structurally-related insulin receptor (IR). These results suggest both that MBPscFv fusion proteins are practical alternatives to isolating scFv proteins for further characterization and that successful isolation of human scFvs against a specific protein of interest requires vigorous screening in the early stages. Such screening is accomplished by using two independent screening methods such as measuring binding to IGF-IR but not to IR by ELISA or measuring competitive binding by IGF-I in addition to binding to IGF-IR alone.
Drug discoveries & therapeutics. 08/2008; 2(4):245-53.
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ABSTRACT: A photonic sub-terahertz wave generation technique that utilizes an optical comb generator, a J-band UTC-PD module as a photomixer, and commercial optical components such as arrayed waveguide gratings (AWGs), optical switch units (OSWs), and couplers is presented. The proposed scheme offers broadband frequency tunability with high spectral resolution, high signal purity, and narrow linewidth. The proposed photonic sub-terahertz wave generator is utilized to successfully demonstrate a simple spectroscopic measurement of N<sub>2</sub>O gas.
Lasers and Electro-Optics Society, 2007. LEOS 2007. The 20th Annual Meeting of the IEEE; 11/2007
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ABSTRACT: This paper describes a CW terahertz-wave source with narrow spectral linewidth and high frequency accuracy. This source uses a photonic millimeter-wave generation as a primary source of radiation. We succeeded in observing a rotational transition line of N<sub>2</sub>O gas molecules with the source. This proves that the source has the high frequency accuracy and narrow linewidth required for the spectroscopic applications.
Infrared and Millimeter Waves, 2007 and the 2007 15th International Conference on Terahertz Electronics. IRMMW-THz. Joint 32nd International Conference on; 10/2007
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ABSTRACT: In recent years, biomaterials have attracted attention in various fields in response to environmental problems. We pay attention to bamboo because it is naturally decomposed and characterized by its excellent elasticity and water absorption properties. We had proposed a bamboo-ice composite system as a substitute for glass fiber reinforced plastics (GFRP) for electrical insulation systems at cryogenic temperatures. In this paper we will report the AC breakdown properties of a bamboo pulp-ice composite system at liquid nitrogen temperature. The bamboo pulp-ice composite system had an AC breakdown strength comparable with GFRP, and can be easily molded in various shapes. We consider that the bamboo pulp-ice composite system is promising as a substitute for GFRP for electrical insulating systems at cryogenic temperatures
Electrical Insulation, 2006. Conference Record of the 2006 IEEE International Symposium on; 07/2006
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ABSTRACT: Power semiconductor devices have been used in development of various pulsed power generators for industrial applications. A repetitive pulsed high-voltage modulator using power MOSFETs has been developed for accelerator applications. It is capable of high-speed switching of 2kV at repetition rate of 1 MHz. This modulator, operating in continuous mode at average power level of 30 kW, has played an important role in the experimental demonstration of Induction Synchrotron. In the same time, SIThy is also tested for the same application since it has higher power capability than MOSFET. Initial experiments have demonstrated 1-MHz operation of SIThy at 2kV in burst mode. A pulsed high-voltage generator using SIThy has been developed for applications in flue-gas treatment. This generator uses a newly developed inductive-energy-storage circuit to achieve both output-voltage multiplication and pulse-width compression. It is very compact and it needs a 12-V (DC) battery as the only power supply to give output of 12 kV with pulse width of 100 ns at repetition rate of 2 kHz in continuous mode. A pulsed high-current modulator has been developed for extreme-ultraviolet generation. It uses IGBTs as the main switch and employs magnetic-pulse-compression to achieve pulsed high current. The output reaches 40 kA with pulse width of 240 ns while operating at repetition rate of 1 kHz in burst mode. This modulator is used in light source development for next-generation lithography. Semiconductor opening switches (SOS) are used in pulsed power generators for excimer laser pumping and flue-gas treatment. These developments are mostly international collaboration with Russian scientists, while efforts are being made to develop SOS devices in Japan.
Pulsed Power Conference, 2005 IEEE; 07/2005
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ABSTRACT: When a liquid droplet is placed on a surface acoustic wave (SAW) propagation surface, a longitudinal wave is radiated into the liquid and the liquid begins to stream, jet, and atomize. This phenomenon is known as SAW streaming. We describe experimental results concerning the temperature of a thin liquid layer and liquid droplet during SAW generation. The results reveal that the temperature of the liquid is a function of the SAW amplitude, which is determined by the applied voltage. This means that the liquid temperature can be controlled by the applied voltage. Rapid rise and fall times are realized by the SAW. The influence of viscosity with respect to temperature is also discussed. Due to viscous damping of the radiated longitudinal wave, temperature of a high-viscosity liquid is higher than that of at low-viscosity liquid at the same applied voltage. We conclude that a novel micro-liquid heating system can be realized using the SAW device.
Ultrasonics Symposium, 2004 IEEE; 09/2004
