• Journal of the Institute of Electronics and Information Engineers
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• v.49 no.9
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• pp.287-292
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• 2012

In this paper, design of a conductivity detector using a synchronous demodulation is presented to detect the electric conductivity of liquids with low noise. For the purpose, the detector is constructed by the combination of a carrier generator, conductivity detecting cell, and synchronous demodulator. The signal-to-noise ratio(SNR) of the detector is improved by adjusting the frequency bandwidth of the demodulator, whereby infinitesimal conductivity signals can easily be measured under various noise environments. As an application example, a conductivity detector, which is applied to the air monitoring in a fabrication process of semiconductor chips, is designed using the synchronous demodulation. The validity of the design technique is verified by experiments. Since experimental results are shown to approach the design performance of the detector, the synchronous demodulation proves to be useful to the design of a conductivity detector for measuring the infinitesimal electric conductivity of liquids.

• Journal of electromagnetic engineering and science
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• v.4 no.4
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• pp.156-161
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• 2004

The MMIC cascode VCO is designed, fabricated, and measured for Ku-band Low Noise Blcok(LNB) system using InGaP/GaAs HBT technology. The phase noise of -116.4 dBc/Hz at 1 MHz offset with output power of 1.3 dBm is obtained at 11.526 GHz by applying 3 V and 11 mA, which is comparatively better characteristics than compared with the different configuration VCOs fabricated with other technologies. The simulated results of oscillation frequency and second harmonic suppression agree with the measured results. The phase noise is improved due to the use of the smallest value of inductor in frequency determining network and the InGaP ledge function of the technology. The chip size of $830\time781\;{\mu}m^2$ is also achieved.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.54 no.10
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• pp.455-460
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• 2005

A simple construction and low cost, fault tolerant power electronic drive has made the switched reluctance drive a strong contender for many applications. But, switched reluctance drive does exhibit higher levels of vibration and acoustic noise than that of most competing drives. The main source of vibration in the switched reluctance drive is generated by rapid change of radial magnetic force when phase current is extinguished during commutation action. In this paper,2 excitation method is proposed and compared to reduce vibration and acoustic noise of the switched reluctance drive. The excitation strategies considered this research are 1-phase, 2-phase and hybrid excitation method. 1-phase method is a conventional and 2-phase method is excited 2 phases simultaneously. The hybrid excitation has 2-phase excitation by long dwell angle as well as conventional 1-phase excitation. The vibration and acoustic noise are compared and tested. Suggested 2-phase and hybrid strategies reduce acoustic noise because the scheme reduces abrupt change of excitation level by distributed and balanced excitation.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.43 no.3 s.345
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• pp.68-77
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• 2006

This paper presents a new Design-for-Testability (DfT) circuit for 4.5-5.5GHz low noise amplifiers (LNAs). The DfT circuit measures gain, noise figure, input impedance, input return loss, and output signal-to-noise ratio for the LNA without external expensive equipment. The DfT circuit is designed using 0.18m SiGe technology. The circuit utilizes input impedance matching and DC output voltage measurements. The technique is simple and inexpensive.

• 한국정보통신설비학회:학술대회논문집
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• 2006.08a
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• pp.215-218
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• 2006

In this paper, a small size, $7{\times}6mm^2$, Low Noise Amplifier(LNA) using LTCC process was fabricated with multi-layer structure for 2.4GHz wireless LAN. The measured results demonstrate that the bandwidth is 130 MHz, and the operating frequency is from 2.39GHz to 2.52GHz. The power gain is above 7.3 dB in the operating frequency range and the gain flatness is 0.5 dB. The maximum S11 is -4 dB and the maximum S22 is -7.5 dB. The noise figure is less than 1.83 dB. The measured power gain, S11 and S22 were had poorer performance than the simulation results. The reason for this discrepancy is that the input and output matching was not performed exactly. However, the noise figure of the LTCC low noise amplifier is better than simulation result. It is found that it is possible to fabricate a LTCC low noise amplifier in a small size.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.8 no.11
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• pp.4170-4188
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• 2014

In this study, we present a denoising algorithm for high-frame-rate videos in an ultra-low illumination environment on the basis of Kalman filtering model and a new motion segmentation scheme. The Kalman filter removes temporal noise from signals by propagating error covariance statistics. Regarded as the process noise for imaging, motion is important in Kalman filtering. We propose a new motion estimation scheme that is suitable for serious noise. This scheme employs the small motion vector characteristic of high-frame-rate videos. Small changing patches are intentionally neglected because distinguishing details from large-scale noise is difficult and unimportant. Finally, a spatial bilateral filter is used to improve denoising capability in the motion area. Experiments are performed on videos with both synthetic and real noises. Results show that the proposed algorithm outperforms other state-of-the-art methods in both peak signal-to-noise ratio objective evaluation and visual quality.

• ETRI Journal
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• v.18 no.3
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• pp.171-179
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• 1996

Fully passivated low noise AlGaAs/InGaAs/GaAs pseudomorphic (PM) HEMT with wide head T-shaped gates were fabricated by dose split electron beam lithography (DSL). The dimensions of gate head and footprint were optimized by controlling the splitted pattern size, dose, and spaces of each pattern. We obtained stable T-shaped gate of $0.15{\mu}m$ gate length with $1.35{\mu}m-wide$ head. The maximum extrinsic transconductance was 560 mS/mm. The minimum noise figure measured at 18 GHz at $V_{ds}=2V andI_{ds}=17mA$ was 0.41 dB with associated gain of 8.19 dB. At 12 GHz, the minimum noise figure and an associated gain were 0.26 and 10.25 dB, respectively. These noise figures are the lowest values ever reported for GaAs-based HEMTs. These results are attributed to the extremely low gate resistance of wide head T-shaped gate having a ratio of the head to footprint dimensions larger than 9.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.45 no.7
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• pp.77-80
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• 2008

In this paper, low phase noise VCO using novel compact microstrip spiral resonator is proposed. A spiral resonator has super compact dimension, low insertion losses in the passband and high level of rejection in the stopband with sharp cutoff and a large coupling coefficient value, which makes a high Q value, and has reduced the phase noise. To increase the tuning range of VCO, varactor diode has been connected at the tunable negative resistance in VCO. This VCO has presented the oscillation frequency of $5.686{\sim}5.841GHz$, harmonics -29.83 dBc and phase noise of $-115.16{\sim}-115.17dBc/Hz$ at the offset frequency of 100 KHz.

• Journal of Korean Society of Environmental Engineers
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• v.27 no.11
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• pp.1193-1197
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• 2005

The low frequency noise below 200 Hz, including inaudible infra-sound, is known to affect human physiology ; circulation, respiration, nerve, endocrine, etc. Legislation has been introduced in several countries regarding evaluation guideline and measurement method of low frequency noise. In this work, low frequency characteristics of the Seoul subway transportation system was investigated in terms of the noise level and spectrum in the interior of running passenger car and the subway station. The interior sound pressure level of the passenger car was between 60 and 105 dB in the frequency range of $1{\sim}200\;Hz$ and varied with car speed. The marked sound pressure level peak at 8 Hz, infra-sound, observed for the most of Lines is shown to correspond to the resonance frequency of passenger car. The level of station platform noise was lower than the interior noise of running car because of the lower speed at arriving/departure. The results indicated that the interior noise level of running passenger car was inside the oppressive feeling region, proposed by Ochiai, in the frequency range of $20{\sim}80\;Hz$ which makes a little concern.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2000.06a
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• pp.407-412
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• 2000

Response surface method is employed in optimizing the acoustic performance of automotive engine-cooling axial fans. The effects of modifications in blade geometry on noise reduction are investigated. Taking the far-field noise level as the objective, a quadratic response surface is constructed utilizing D-Optimality condition as the candidate-points selection criteria. It is shown that the quadratic model exhibits an excellent fitting capability resulting in the blade design with low far-field noise level.