Stress Mechanism about Field Lightning Surge of High Voltage BJT Based Line Driver for ADSL System

In this paper, we have verified stress root caused by lightning surge in High voltage BJT based line driver of ADSL telecommunication and created failure mechanism. To reproduce damages in Line driver, we have applied STD surge waveform in operating condition, which is specified in IEC-6000-4-5, to component and board level. Visual isolation for Damage root was conducted with Real-time Electrical Stress Analysis (RTESA) utilizing Photon Emission Microscopy (PEM). The surge made with input of Tx output created junction breakdown of amplifier, which is made of HVBJT cells, and also caused current crowding from Vcc (supply voltage). In case of Positive pulse, current crowding was observed from between Collector and Vcc (+)12V. For negative pulse, at between Emitter and Vee (−)12V, current crowding was found. For both cases, device damage level was the same. All of these could be considered as transient latchup phenomenon created in BJT cell. Applying temporary clamping diode to line driver Tx, we have conducted Board level surge injection test. As a result, with the correlation between surge level from component level reproduction test and the one from system level, we have decided field lightning surge damage level and set up line driver protection margin.     

Fabrication of micro heaters on polycrystalline 3C-SiC suspended membranes for gas sensors and their characteristics

This paper describes the design, fabrication, and characteristics of micro heaters mad on AlN (0.1 μm)/3C-SiC (1 μm) suspended membranes using surface micromachining technology. 3C-SiC and AlN thin films, which have a large energy band gap and very low lattice mismatch, were used for high-temperature environments. A Pt thin film was used as micro heaters and temperature sensor materials. The resistance of the temperature detector (RTD) and the power consumption of the micro heater were measured and calculated. The heater is designed for an operating temperature up to about 800 °C and can be operated at about 500 °C with a power of 312 mW. The thermal coefficient of the resistance (TCR) of fabricated Pt RTD’s is 3174.64 ppm/°C. The thermal distribution measured by IR thermovision is uniform across the membrane surface.     

A Multi‐Strategic Concept‐Spotting Approach for Robust Understanding of Spoken Korean

We propose a multi‐strategic concept‐spotting approach for robust spoken language understanding of conversational Korean in a hostile recognition environment such as in‐car navigation and telebanking services. Our concept‐spotting method adopts a partial semantic understanding strategy within a given specific domain since the method tries to directly extract pre‐defined meaning representation slot values from spoken language inputs. In spite of partial understanding, we can efficiently acquire the necessary information to compose interesting applications because the meaning representation slots are properly designed for specific domain‐oriented understanding tasks. We also propose a multi‐strategic method based on this concept‐spotting approach such as a voting method. We present experiments conducted to verify the feasibility of these methods using a variety of spoken Korean data.     

Profit Aware Circuit Design Under Process Variations Considering Speed Binning

In this paper, a profit-aware design metric is proposed to consider the overall merit of a design in terms of power and performance. A statistical design methodology is then developed to improve the economic merit of a design considering frequency binning and product price profile. A low-complexity sensitivity-based gate sizing algorithm is developed to improve economic gain of a design over its initial yield-optimized design. Finally, we present an integrated design methodology for simultaneous sizing and bin boundary determination to enhance profit under an area constraint. Experiments on a set of ISCAS'85 benchmarks show in average 19% improvement in profit for simultaneous sizing and bin boundary determination, considering both leakage power dissipation and delay bounds compared to a design initially optimized for 90% yield at iso-area in 70-nm bulk CMOS technology.     

Digital Laser Micropainting for Reprogrammable Optoelectronic Applications

Structural coloration is closely related to the progress of innovative optoelectronic applications, but the absence of direct, on-demand, and rewritable coloration schemes has impeded advances in the relevant area, particularly including the development of customized, reprogrammable optoelectronic devices. To overcome these limitations, a digital laser micropainting technique, based on controlled thin-film interference, is proposed through direct growth of the absorbing metal oxide layer on a metallic reflector in the solution environment via a laser. A continuous-wave laser simultaneously performs two functions—a photothermal reaction for site-selective metal oxide layer growth and in situ real-time monitoring of its thickness—while the reflection spectrum is tuned in a broad visible spectrum according to the laser fluence. The scalability and controllability of the proposed scheme is verified by laser-printed painting, while altering the thickness via supplementary irradiation of the identical laser in the homogeneous and heterogeneous solutions facilitates the modification of the original coloration. Finally, the proof-of-concept bolometer device verifies that specific wavelength-dependent photoresponsivity can be assigned, erased, and reassigned by the successive application of the proposed digital laser micropainting technique, which substantiates its potential to offer a new route for reprogrammable optoelectronic applications.     

A Liquid Metal Based Multimodal Sensor and Haptic Feedback Device for Thermal and Tactile Sensation Generation in Virtual Reality

Virtual reality (VR) has been widely used for training, gaming, and entertainment, and the value of VR is continually increasing as a contact-free technology. For an immersive VR experience, measuring finger movements and providing appropriate feedback to the hand are as important as visual information, given the necessity of the hands for activities in daily life. Thus, a hand-worn VR device with motion sensors and haptic feedback is desirable. In this paper, a multimodal sensing and feedback glove is developed with soft, stretchable, lightweight, and compact sensor and heater sheets manufactured by direct ink writing (DIW) of liquid metal, eutectic gallium-indium (eGaIn). In the sensor sheet, ten sensors and three vibrators are embedded to measure finger movements and provide vibro-haptic feedback. The other heater sheet provides thermo-haptic sensation in accurate and rapid manner via model-based feedback control even under stretched conditions. The multimodal sensing and feedback glove allows users to feel the contact status and discriminate materials with different temperature. Performance of the proposed multimodal glove is verified under VR environments including touching and pushing two blocks of different materials and grabbing a heated metal ball submerged in hot water.     

Dissolution Behaviors and Applications of Silicon Oxides and Nitrides in Transient Electronics

Silicon oxides and nitrides are key materials for dielectrics and encapsulation layers in a class of silicon‐based high performance electronics that has ability to completely dissolve in a controlled fashion with programmable rates, when submerged in bio‐fluids and/or relevant solutions. This type of technology, referred to as “transient electronics”, has potential applications in biomedical implants, environmental sensors, and other envisioned areas. The results presented here provide comprehensive studies of transient behaviors of thin films of silicon oxides and nitrides in diverse aqueous solutions at different pH scales and temperatures. The kinetics of hydrolysis of these materials depends not only on pH levels/ion concentrations of solutions and temperatures, but also on the morphology and chemistry of the films, as determined by the deposition methods and conditions. Encapsulation strategies with a combination of layers demonstrate enhancement of the lifetime of transient electronic devices, by reducing water/vapor permeation through the defects.     

Variable length signal detection framework for cognitive radio systems

The cognitive radio (CR) system opportunistically utilizes the frequency bands temporally unoccupied by the primary user. In the CR system, the energy or cyclostationary detector is used to detect the primary user signal. For protecting the primary user tightly, the signal detection time can be very long, which leads to inefficiency in the CR system. Thus, we propose a novel signal detector that greatly reduces the average detection time. The proposed detector periodically decides whether it terminates the detection process or receives more input signal for more information. Therefore, the proposed detector has variable detection time. We will call the proposed detector the variable length signal detector (VLSD). The VLSD is designed by using a partially observable Markov decision process framework for optimal performance. We present the numerical results showing that the VLSD requires much smaller average detection time compared with the traditional fixed length signal detector to achieve a given detection error probability. Copyright © 2012 John Wiley & Sons, Ltd.     

Analysis of large-signal dynamic characteristics of 10-Gb/s tunable distributed Bragg reflector lasers integrated with electroabsorption modulator and semiconductor optical amplifier based on the time-dependent transfer matrix method

We investigate large-signal dynamic characteristics of tunable distributed Bragg reflector (DBR) lasers with different structures. Because of high chirp and complex structures of tunable DBR lasers, it is difficult to accurately analyze large signal chirp and output pulse shapes with analytical models. Therefore, we apply a numerical model based on the time-dependent transfer matrix method to tunable DBR lasers integrated with electroabsorption modulator (EAM) and semiconductor optical amplifier (SOA). Using this model, we find a suitable /spl alpha/-parameter range in the Bragg grating section (/spl alpha//sub Bragg/-parameter) that produces the tolerable wavelength chirp while maintaining a proper tuning range. To employ the tunable lasers in wavelength division multiplexed networks and improve flexibility of the networks, the tunable lasers should have high output power and low wavelength chirp. According to our simulation results, the EAM section had better be located in between SOA and DBR laser sections to obtain high output power and low wavelength chirp.     

Experimental demonstration of enhancing pump absorption rate in cladding-pumped ytterbium-doped fiber lasers using pump-coupling long-period fiber gratings

A long-period fiber grating (LPFG) was inscribed in a single-mode fiber and was spliced with a ytterbium (Yb)-doped double-clad fiber in order to couple pump radiation of the inner cladding into the core in a cladding-pumped fiber laser. The use of an LPFG permits a partial core-pumping scheme in a cladding-pumping fiber laser because a portion of the pump radiation can be coupled to the core by LPFG. The enhancement of the pump absorption of a Yb-doped cladding-pumped fiber laser as the result of pump coupling by LPFG was 35%, and the maximal output power increased by up to 55% when a 20-W pump source is used.