• Transactions on Electrical and Electronic Materials
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• v.18 no.5
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• pp.250-252
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• 2017

High-performance full swing logic inverters were fabricated using amorphous 1 wt% Si doped indium-zinc-oxide (a-SIZO) thin films with different channel layer thicknesses. In the inverter configuration, the threshold voltage was adjusted by varying the thickness of the channel layer. The depletion mode (D-mode) device used a TFT with a channel layer thickness of 60 nm as it exhibited the most negative threshold voltage (-1.67 V). Inverters using enhancement mode (E-mode) devices were fabricated using TFTs with channel layer thicknesses of 20 or 40 nm with excellent subthreshold slope (S.S). Both the inverters exhibited high voltage gain values of 30.74 and 28.56, respectively at $V_{DD}=15V$. It was confirmed that the voltage gain can be improved by increasing the S.S value.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.5 no.5
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• pp.853-860
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• 2001

This paper presents the new two denoising methods using wavelet. One is new spatially selective noise filtration(NSSNF) using spatial correlation and the other is undecimated discrete wavelet transform (UDWT) threshold-based. NSSNF got the flexible gain special property of SNR adding new parameter at the existing SSNF and UDWT had superior denosing effect than orthogonal wavelet transform(OWT) applied soft-threshold by applied hard-threshold. We selected additive white gaussian noise(AWGN) in this test environment. Also we analyzed and compared ousting denoising method using SNR as standard of judgement of improvemental effect.

• The Journal of the Korea institute of electronic communication sciences
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• v.11 no.7
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• pp.665-670
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• 2016

In this paper, we suggest the design of OP-AMP using MOSFET in the operation of sub-threshold condition as a basic unit of an IoT. The sub-threshold operation of MOSFET is useful for an ultra low power consumption of sensor network system in the IoT, because it cause the supply voltage to be reduced. From the simulation result using 0.35 um CMOS process, the supply voltage, VDD can be reduced with 0.6 V, open-loop gain of 43 dB and the power consumption was evaluated with about $1.3{\mu}W$ and the active size for an integration was measured with $64{\mu}m{\times}105{\mu}m$. It is expected that the proposed circuit is applied to the low power sensor network for IoT.

• Journal of Korea Society of Industrial Information Systems
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• v.18 no.5
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• pp.1-8
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• 2013

This paper presents a variable gain amplifier(VGA) without passive devices. This VGA employes the architecture of current feedback amplifier and variable gain can be achieved by using the GM ratios of two trans-conductance(gm) circuits. To obtain linearity and high gain, it uses current division technique and source degeneration in feedback GM circuits. Input trans-conductance(GM) circuit was biased by using a tunable voltage controller to obtain variable gain. The prototype of the VGA is designed in $0.35{\mu}m$ CMOS technology and it is operating in sub-threshold region for low power consumption. The the gain of proposed VGA is varied from 23dB to 43dB, and current consumption is $2.82{\mu}A{\sim}3{\mu}A$ at 3.3V. The area of VGA is 1$120{\mu}m{\times}100{\mu}m$.

• The Journal of the Convergence on Culture Technology
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• v.6 no.4
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• pp.727-732
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• 2020

In this paper, when a refractive index grating and a gain grating were simultaneously present in a DFB laser having a wavelength of 1.55 ㎛, a dielectric film coating was applied so that reflection did not occur on the right mirror surface, so that 𝜌_r=0. In case of δL > 0, the threshold gain and the beam distribution in the longitudinal direction and the radiated power ratio P_l/P_r of the oscillation mode were compared for the cases of the phase of 𝜌_l=π and π/2. If the phase of 𝜌_l=π, in order to obtain a low threshold current and high frequency stability, κL should be greater than 8. In the case of the phase of 𝜌_l= π/2, when κL is larger than 4.0, the oscillation gain starts to be lower than when the phase of 𝜌_l=π. In order to lower the threshold current of a oscillation mode and enhance the frequency stability, κL should be greater than 8.

• Journal of the Korean Institute of Telematics and Electronics D
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• v.36D no.3
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• pp.75-84
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• 1999

Systematic studies for the effect of the linewidth enhancement factor, the confinement factor, the internal loss and the cavity length on the single mode gain difference and the frequency detuning are performed for $\lambda$/4 phase shifted DFB lasers above threshold. The above threshold characteristics are mainly determined by the linewidth enhancement factor, not by the confinement factor or the parameter defined by the product of the linewidth enhancement factor and the confinement factor. The normalized internal loss defined by the product of the internal loss and the cavity length mainly determines the above threshold characteristics compared to that of the internal loss or the cavity length alone. The effect of the cavity length on threshold characteristics is larger than that of the internal loss in the case of the same normalized internal loss. The above threshold characteristics of quantum well lasers are more resistant to the variations of the confinement factor and the normalized internal loss than those of bulk lasers due to the small linewidth enhancement factor.

• Korean Journal of Optics and Photonics
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• v.10 no.2
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• pp.89-94
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• 1999

The 1.54 ${\mu}{\textrm}{m}$ forward and backward stimulated Raman scattering (SRS) have been studied in CH$_4$pumped by 1.06 ${\mu}{\textrm}{m}$ Nd:YAG laser. The forward and backward SRS output energy in a single pass were measured at dufferent CH$_4$pressures. Under steady state conditions, the pump input threshold energies and Raman gains in forward and backward directions were for Raman conversion at various CH$_4$pressures for a tight focusing geometry. The forward and backward slope efficiency for Raman conversion were 18% and 34% respectively. The pump input threshold energy of the backward SRS was lower than that of the forward. In backward SRS, the experimental input laser threshold and Raman gain values were in good agreement with the calculated values at different pressures of CH$_4$. The retio of the backward to the forward SRS gain was appoximately 1.4 times above 1200 psi. We obtained that the backward Raman gain coefficient was 0.32 cm/GW, and the forward Raman gain coefficient 0.23cm/GW at 1400 psi. Asymmetry of the forward and backward Raman gain is caused by the interaction between different pump intensities of each direction duting the amplification of the Stokers. The backward Raman gain is proportional to the average pump intensity. However, the forward SRS output grows by depleting the local pump intensity.

• Journal of the Optical Society of Korea
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• v.8 no.4
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• pp.156-162
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• 2004

The spectroscopic model is proposed to analyze the gain bandwidth of a fiber Raman amplifier (FRA) with a multiple wavelength pumping scheme based on Raman gain theory. The oscillatory lineshape, which is the analytic function to analyze Raman gain spectra, allows us to estimate the gain bandwidth of the FRA. Based on the proposed theoretical modeling, we design and analyze the characteristics of the FRA using the combined multiwavelength pumping sources. We achieved the extended gain bandwidth of the FRA over 80 nm with the small gain ripple less than 0.5 dB. Threshold pumping power and effective noise figure for the FRA can be also analyzed by using the proposed model, which is also applicable for versatile fibers with other doping materials. The proposed analysis method can be useful for the design of FRA with the multiwavelength pumping scheme.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.33A no.7
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• pp.245-252
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• 1996

$\lambda$/4 phase-shifted DFB lasers with nonideal grating structure have been studied by using an effective-index transfer matrix method where material dispersion, vwaveguide dispersion and waveguide-structuredependent loss are taken into consideration. Nonideal grating structure in the center phase-shift region does not incur serous degradation of laser characteristics. Phase-shift error from the ideal shift of $\pi$ causes a decrease in the threshold gain difference and lasing wavelength shift and should be less than $\pi$/4 when residual facet reflectivity is 0.7%. also, positional error of the phase-shift should be less than 9% of the cavity length in order for the threshold gain difference to be decreased less than 10%.

• The Journal of the Acoustical Society of Korea
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• v.27 no.1E
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• pp.1-10
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• 2008

A noise suppression algorithm is proposed for nonstationary noisy environments. The proposed algorithm is different from the conventional approaches such as the spectral subtraction algorithm and the minimum statistics noise estimation algorithm in that it classifies speech and noise signals in time-frequency bins. It calculates the ratio of the variance of the noisy power spectrum in time-frequency bins to its normalized time-frequency average. If the ratio is greater than an adaptive threshold, speech is considered to be present. Our adaptive algorithm tracks the threshold and controls the trade-off between residual noise and distortion. The estimated clean speech power spectrum is obtained by a modified gain function and the updated noisy power spectrum of the time-frequency bin. This new algorithm has the advantages of simplicity and light computational load for estimating the noise. This algorithm reduces the residual noise significantly, and is superior to the conventional methods.