• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.9 no.6
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• pp.833-842
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• 1998

In this paper, a K-band oscillator which is composed of a hair-pin resonator, a GaAs MESFET, and a frequency doubler, is suggested, implemented by HMIC(Hybrid Microwave Integrated Circuits) form, and characterized for its microwave performance. A $\lambda_g$/4 open stub is used in frequency doubler to suppress the fundamental frequency of 9 GHz which is the output of the hair-pin resonator oscillator and output matching network is optimized for its second harmonic freuency of 18 HGz. For the oscillator, the output power of -0.83 dBm, the fundamental frequency suppression of -23 dBc, and phase noise of -86 dBc/Hz at 18.20 GHz are obtained.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.62 no.12
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• pp.1744-1749
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• 2013

Acoustic feedback is perceived as whistling or howling, which is a major complaint of hearing-aids users. Acoustic feedback cancellation is important in hearing-aids because acoustic feedback degrades performance of the hearing aid device by reducing maximum insertion gain. Adaptive systems for estimate acoustic feedback path and feedback suppression algorithms have been proposed in order to solve this problem. A typical feedback cancellation algorithm is LMS(least mean squares) because of its computational efficiency. However it has problem of convergence performance in high correlated input signal. In this paper, we propose a new variable step-size normalized LMS(least mean squares) algorithm using VAD(voice activity detection) to overcome the limitation of the LMS algorithm. The VAD algorithm is GSAP(global speech absence probability) and the feedback cancellation algorithm is normalized LMS. The proposed algorithm applies different step-size between voice and non-voice using VAD, for high stability, fast convergence speed and low misalignment when correlated inputs, such as speech. The result of simulation with white noise mixed speech signal, the proposed algorithm shows high performance then traditional algorithm in terms of stability, convergence speed and misalignment.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2012.10a
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• pp.221-224
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• 2012

This paper presents a CMOS interface circuit for MEMS acceleration sensor. It consists of a capacitance to voltage converter(CVC), a second-order switched-capacitor (SC) integrator and comparator. A bandgap reference(BGR) has been designed to supply a stable bias to the circuit and a ${\Sigma}{\Delta}$ Modulator with chopper - stabilization(CHS) has also been designed for more suppression of the low frequency noise and offset. As a result, the output of this ${\Sigma}{\Delta}$ Modulator increases about 10% duty cycle when the input voltage amplitude increases 100mV and the sensitivity is x, y-axis 0.45v/g, z-axis 0.28V/g. This work is designed and implemented in a 0.35um CMOS technology with a supply voltage of 3.3V and a sampling frequency of 3MHz sampling frequency. The size of the designed chip including PADs is $0.96mm{\times}0.85mm$.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.10A
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• pp.1031-1036
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• 2006

This paper proposes a novel BPF structure with less insertion loss and small size instead of the existing coupled line BPF for the output of the tripler using APDP (Anti-Parallel Diode Pair). This proposed BPF consists of the interdigital capacitor and spiral open stub. The proposed BPF has the insertion loss of less than 0.7dB within the band $(16.41{\sim}19.23GHz)$. The conversion loss of the tripler is about $16.6{\sim}18.5dB$ $(flatness<{\pm}1dB)$ at $5.72{\sim}6.28GHz$ of fundamental frequency. Its fundamental frequency and the fifth harmonic suppression characteristic at 6GHz are -32.16dBc and -44.6dBc, respectively And its phase noise attenuation characteristic is about 9.5dB at 100kHz.

• Journal of the Korean Society for Railway
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• v.15 no.5
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• pp.454-458
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• 2012

The CBTC(Communication based Train Control) and WPAN(Wireless Personal Area Network) systems employed on 2.4GHz ISM band wireless networks provide complementary service within the same environment. Coexistence between the networks will be impaired if the mutual packets are uncertainty associated the timing or gaussian distance. This paper analyzes the impact of the mutual interference and proposed method to minimize the effect of the WPAN system signals on CBTC system. The performance analysis is illustrated by examining the symbol error rate versus signal to noise interference ratio in terms of carrier frequency offset. The method contributes to reduce the symbol error rate drastically. However it can't be a fundamental solution for the impact on the interference problem. It may be needed for railway only frequency after checking the problems of the current railway frequency.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.46 no.6
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• pp.132-145
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• 2009

We present the framework for JND based Illumination and Color Restoration Using Edge-preserving filter for restoring distorted images taken under the arbitrary lighting conditions. The proposed method is effective for appropriate illumination compensation, vivid color restoration, artifacts suppression, automatic parameter estimation, and low computation cost for HW implementation. We show the efficiency of the mean shift filter and sigma filter for illumination compensation with small spread parameter while considering the processing time and removing the artifacts such as HALO and noise amplification. The suggested CRF (color restoration filter) can restore the natural color and correct color distortion artifact more perceptually compared with current solutions. For the automatic processing, the image statistics analysis finds suitable parameter using JND and all constants are pre-defined. We also introduce the ROI-based parameter estimation dealing with small shadow area against spacious well-exposed background in an image for the touch-screen camera. The object evaluation is performed by CMC, CIEde2000, PSNR, SSIM, and 3D CIELAB gamut with state-of-the-art research and existing commercial solutions.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.12 no.3
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• pp.401-408
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• 2001

This paper shows the design, fabrication and performance analysis of VCO which plays a major role in 5.8 GHz RF module for ITS. The design specifications of the VCO are determined on the basis of 5.8 GHz RF modul performance requirements. The design parameters are optimized through ADS simulation tool. The operating characteristic and performance analysis of the implemented VCO based on the design parameters are accomplished. The frequency variations according to the voltage change(0 ~5 V) of varactor diode are from 5.42 GHz to 5.518 GHz and the power level is 6.5 dBm. The second harmonic suppression are -21.5 dBc at 5.51 GHz and the phase noise characteristics are -83.81 dBc at 10 kHz offset frequency. The implemented VCO is available to not only DSRC and also, 5.8 GHz other systems.

• Proceedings of the SAREK Conference
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• 2007.11a
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• pp.606-611
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• 2007

Pulsation is an inherent phenomenon in reciprocating compressors. It interacts with piping to cause vibrations and performance problems. Indiscriminately connecting to a compressor can be dangerous and cost money in the form of broken equipment and piping, poor performance, inaccurate metering, unwanted vibration, and sometimes noise. Piping connected to a compressor can materially affect the performance and response. To minimize these detrimental effects, reciprocating compressor system should be equipped by pulsation suppression system. This study discusses pressure pulsation phenomena occurred in a reciprocating compressor system. An experiment applied air compressor unit, as pulsating pressure generator, has been done. The compressor was connected sequentially to a snubber model and pressure tank. Sensor probes were placed on the inlet and outlet pipes of snubber. Compressor was driven by a motor controlled by a frequency regulator. The experiment was conducted by adjusting the regulator at 40Hz. General information about an internal gas flow can be achieved by numerical analysis approach. Information of the velocity, pressure and turbulence kinetic energy distribution are presented in this paper. Based on this result, the design improvement might be done.

• Korean Journal of Optics and Photonics
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• v.21 no.2
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• pp.74-81
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• 2010

A modeling methodology for the analysis of injection-locked Fabry-Perot laser diodes (FP-LDs), promising for cost-effective WDM-PON sources, is proposed. The time-domain large-signal model that is used is found to provide quite similar results to some experimental ones. With our methodology, we model characteristics of FP-LDs, such as influence of reflectivity at a facet and detuning on injection-locking. The eye diagram characteristics are also investigated. It is observed that the facet reflectivity at the injection side should be lower than 1% to provide stable operation in terms of good side-mode suppression ratio and independence from detuning between narrow-band injection noise and LD modes. It is also observed that good eye opening can be obtained for 155 Mbps modulation while the parameters such as the active region thickness should be properly optimized to obtain reasonable eye opening at 1.25 Gbps.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2006.05a
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• pp.607-610
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• 2006

The Digital Frequency Synthesizer(DFS) that generates the wideband signal with hish speed frequency hopping rate and high frequency resolution characteristics was implemented in this paper. The DFS was applied as local oscillator for direct frequency conversion IF modules of DVB-RCS, which directly generates the transmission immediate frequency signal by using DDS and wideband PLL technologies. The DDS technology provides high speed frequency hopping rate and high frequency resolution characteristics, which ate also the DVB-RCS requirement. The wideband PLL technology also provides the wideband signal generation, which is a necessity for direct frequency conversion modules. The implemented DFS provide the spurious suppression characteristic of -50 dBc, frequency resolution of 0.233 Hz and frequency hopping rate of 125 ns, respectively. Also the DFS represent the amplitude flatness of 3 dB and less in the pass-band and phase noise characteristic of -75 dBc/Hz at 1 kHz frequency offset.