• The Transactions of the Korean Institute of Electrical Engineers
• /
• v.43 no.6
• /
• pp.951-957
• /
• 1994

We present a new model for the series resistance of inverted-staggered amorphous silicon (a-Si) thin film transistors (TFT's) by employing the current spreading under the source and the drain contacts as well as the space charge limited current model. The calculated results based on our model have been in good agreements with the measured data over a wide range of applied voltage, gate-to-source and gate-to-drain overlap length, channel length, and operating temperature. Our model shows that the contribution of the series resistances to the current-voltage (I-V) characteristics of the a-Si TFT in the linear regime is more significant at low drain and high gate voltages, for short channel and small overlap length, and at low operating temperature, which have been verified successfully by the experimental measurements.

• 한국정보통신설비학회:학술대회논문집
• /
• 2008.08a
• /
• pp.398-402
• /
• 2008

Cyclic prefix (CP) is one of the most important technique to OFDM system and is reducing inter-symbol interference (ISI) effects in high speed wireless mobile communication system. At the time varying channel condition, however, fixed CP length is not only increasing power consumption but also reducing data transmission rate. So in this paper, we propose the system that has adaptive CP length for high speed data transmission system. We don't control CP length of every symbol but adjust symbol interval depending on channel condition to CP reconstruction.

• Proceedings of the Korea Multimedia Society Conference
• /
• 2003.05b
• /
• pp.49-52
• /
• 2003

OFDM(Orthogonal Frequency Division Multiplexing) scheme can compensate for distortions caused by multipath delay spread and reduce the burst errors caused by the Doppler effect since OFDM signals have long symbol durations. However, OFDM is required to be improved for high speed data transmission and large capacity. Therefore, coding schemes should be combined with OFDM. In this paper, it was studied that the performance of OFDM transmission scheme was improved in mobile communication channel by applying TCM, which has advantages of error correction and bandwidth efficiency. Simulation was carried out for two TCM models with different code efficient length. By mapping two models to square 16QAM, the model with the code efficient length of 2 achieved 3dB better than the other for the BER of 10/sub -3/. In conclusion, if we want to achieve a better performance with TCNA in OFDM applications, we should select a TCM with larger code efficient length.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.24 no.5
• /
• pp.359-363
• /
• 2011

To integrate the sensor driver and logic circuits, fabricating down scaled transistors has been main issue. At this research, short channel effects were analyzed after n channel polycrystalline silicon thin film transistor was fabricated at high temperature. As a result, on current, on/off current ratio and transconductance were increased but threshold voltage, electron mobility and s-slope were reduced with a decrease of channel length. When carriers that develop at grain boundary in activated polycrystalline silicon have no gate biased, on current was increased with punch through by drain current. Also, due to BJT effect (parallel bipolar effect) that developed under region of channel by increase of gate voltage on current was rapidly increased.

• Journal of the Korean Institute of Telematics and Electronics
• /
• v.22 no.4
• /
• pp.1-7
• /
• 1985

In this paper, a more improved threshold voltage model dependent on drain voltage and substrate bias for short - channel enhancement - mode IGFET is presented. Especially, compared with the several recently published models, the error is sufficiently reduced with the precise analysis on the correction factor for short-channel effect and the calculated values using this model are also agreed well with the experimental data about 1$\mu$m - channel length device.

• ETRI Journal
• /
• v.39 no.2
• /
• pp.284-291
• /
• 2017

Drain-induced barrier lowering (DIBL) is one of the main parameters employed to indicate the short-channel effect for nano metal-oxide semiconductor field-effect transistors (MOSFETs). We propose a new physical model of the DIBL effect under two-dimensional approximations based on the energy-conservation equation for channel electrons in FETs, which is different from the former field-penetration model. The DIBL is caused by lowering of the effective potential barrier height seen by the channel electrons because a lateral channel electric field results in an increase in the average kinetic energy of the channel electrons. The channel length, temperature, and doping concentration-dependent DIBL effects predicted by the proposed physical model agree well with the experimental data and simulation results reported in Nature and other journals.

• Journal of Communications and Networks
• /
• v.16 no.2
• /
• pp.209-216
• /
• 2014

Cognitive radio (CR) has been proposed to solve the spectrum utilization problem by dynamically exploiting the unused spectrum. In CR networks, a spectrum selection scheme is an important process to efficiently exploit the spectrum holes, and an efficient channel allocation scheme must be designed to minimize interference to the primary network as well as to achieve better spectrum utilization. In this paper, we propose a multichannel selection algorithm that uses spectrum hole prediction to limit the interference to the primary network and to exploit channel characteristics in order to enhance channel utilization. The proposed scheme considers both the interference length and the channel capacity to limit the interference to primary users and to enhance system performance. By using the proposed scheme, channel utilization is improved whereas the system limits the collision rate of the CR packets.

• Journal of the Institute of Electronics Engineers of Korea SD
• /
• v.42 no.1
• /
• pp.25-32
• /
• 2005

In this paper, it is attempted to provide a unified explanation for typical short channel GaAs MESFET’s and SOI-structured Si JFET's behaviors such as: i) drain voltage-induced threshold voltage roll-off, ii) finite output ac resistance beyond the saturation, and iii) weak dependence of the drain saturation current on the channel length. Replacing the conventional GCA with a new assumption that is suggested in order to include the longitudinal field variation, and taking into account the channel current continuity and the field-dependent mobility, we can derive the two-dimensional potential in both depletion region and undepleted conducting channel. Obtained expressions for the threshold voltage and the drain current will be considerably accurate over the entire operating region. Moreover, in comparison with the conventional channel length shortening models, our model seems to be more reasonable in explaining the Early effect.

• International Journal of Naval Architecture and Ocean Engineering
• /
• v.8 no.1
• /
• pp.102-109
• /
• 2016

The hydrodynamic interaction between two large vessels can't be neglected when two large vessels are closed to each other in restricted waterways such as in a harbor or narrow channel. This paper is mainly concerned with the ship maneuvering motion based on the hydrodynamic interaction effects between two large vessels moving each other in curved narrow channel. In this research, the characteristic features of the hydrodynamic interaction forces between two large vessels are described and illustrated, and the effects of velocity ratio and the spacing between two vessels are summarized and discussed. Also, the Inchon outer harbor area through the PALMI island channel in Korea was selected, and the ship maneuvering simulation was carried out to propose an appropriate safe speed and distance between two ships, which is required to avoid sea accident in confined waters. From the inspection of this investigation, it indicates the following result. Under the condition of $SP_{12}{\leq}0:5L$, it may encounter a dangerous tendency of grounding or collision due to the combined effect of the interaction between ships and external forces. Also considering the interaction and wind effect as a parameter, an overtaken and overtaking vessel in narrow channel can navigate while keeping its own original course under the following conditions; the lateral separation between two ships is about kept at 0.6 times of ship length and 15 degrees of range in maximum rudder angle. On the other hand, two ships while overtaking in curved narrow channel such as Inchon outer harbor in Korea should be navigated under the following conditions; $SP_{12}$ is about kept at 1.0 times of ship length and the wind velocity should not be stronger than 10 m/s.

• JSTS:Journal of Semiconductor Technology and Science
• /
• v.13 no.4
• /
• pp.367-380
• /
• 2013

In this paper, an analytical threshold voltage model is developed for a short-channel double-material-gate (DMG) strained-silicon (s-Si) on silicon-germanium ($Si_{1-X}Ge_X$) MOSFET structure. The proposed threshold voltage model is based on the so called virtual-cathode potential formulation. The virtual-cathode potential is taken as minimum channel potential along the transverse direction of the channel and is derived from two-dimensional (2D) potential distribution of channel region. The 2D channel potential is formulated by solving the 2D Poisson's equation with suitable boundary conditions in both the strained-Si layer and relaxed $Si_{1-X}Ge_X$ layer. The effects of a number of device parameters like the Ge mole fraction, Si film thickness and gate-length ratio have been considered on threshold voltage. Further, the drain induced barrier lowering (DIBL) has also been analyzed for gate-length ratio and amount of strain variations. The validity of the present 2D analytical model is verified with ATLAS$^{TM}$, a 2D device simulator from Silvaco Inc.