• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.14 no.5
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• pp.472-478
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• 2003

In this paper, a near zero If mixer was designed in cascode structure by using two single-gate FETs. Since it is driven by the second order harmonic of LO signal, a sub-harmonic cascode FET mixer has good LO-RF port isolation characteristic. In order to solve DC offset of a homodyne system, near zero If is used instead of zero If and the mixer is driven by sub-harmonic of LO signal. As RF input power was -30 dBm and LO power was 6 dBm, the designed mixer had 6.7 dB conversion gain, 8.4 dB noise figure, 31.5 dB LO-RF port isolation, -1.9 dBm lIP3 and -2.8 dBm IIP2.

• The Journal of the Korea institute of electronic communication sciences
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• v.9 no.2
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• pp.161-166
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• 2014

This Electromagnetic metal piece detection sensor, having high sensitivity even under high humidity and dust density, using LVDT was investigated. Metal detection characteristics using phase detection method, for 3 frequencies covering ELF and LF band, were experimentally measured. It was found that the sensitivity for metal and animal food, in which metal piece was included, was exponentially increased as frequency increased. Reducing cutoff frequency of LPF after PD was found to be effective to proportionally increase sensitivity. Also the sensitivity of metal piece detection was enhanced by optimizing BPF bandwidth and SNR. Metal piece detection limit using available ferrous test samples was found to be 0.7mm diameter from the experiment using 50kHz, in ELF band, which was known to have better selectivity to animal food. is an example of ABSTRACT format.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2003.05a
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• pp.59-263
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• 2003

정보통신의 비약적인 발전에 힘입어 멀티미디어 데이터는 언제 어디서든 전송 받거나 공유할 수 있게 되었다. 아날로그 형태에서 디지털의 아날로그를 형태로 빠르게 대체되고 있으며, 디지털로 신호를 표현하는 방법은 기존 사용하여 표현하는 방법에 비해 많은 장점을 가지고 있다. 하지만 디지털로 된 데이터는 언제 어디서든 대단위 복제가 가능하다. 즉, 저작권 침해, 불법 복제 및 배포, 손쉽게 위조할 수 있다는 점이 그것이다. 디지털 컨텐츠의 불법 복제와 유통은 저작자의 창작 의욕과 수입원을 차단하는 매우 중요한 문제이며, 이를 방지하기 위해서 멀티미디어 데이터의 저작권을 가진 소유자가 원하는 정보를 삽입함으로써 데이터의 저작권 보호와 복사 방지 및 불법적인 유통을 막고자 하는 기술이 개발되고 있다. 디지털 영상 정보의 보호를 위해 디지털 영상의 불법적인 내용 조작을 막고, 영상의 소유권을 보장할 수 있는 방법으로 디지털 워터마크(Digital Watermark)가 있다. 디지털 워터마크는 공개키 알고리즘이나 방화벽 등으로 해독된 영상에 대하여 부가적인 보호를 제공한다. 디지털 영상에 대한 저작권 정보, 배포자 정보 그리고 사용자 정보를 영상에 삽입함으로써 훗날 법적인 문제가 발생하였을 때 해결책을 제시할 수 있다. 본 논문에서는 디지털 영상 데이터의 정보 보호를 위해 주파수 영역에서의 웨이브릿 변환(Wavelet Transform)을 이용한 이미지 적응 디지털 워터마킹(Image-Adaptive Digital Watermarking) 방법을 제안한다. 이미지 적응 웨이브릿(Image-Adaptive Wavelet)은 영상을 주파수적으로 분해하면서 각 대역들의 공간 영역에서의 정보를 함께 지니고 JND(Just noticeable difference)을 포함한다. 이미지 적응 웨이브릿의 이러한 특성을 이용하여 다해상도 분해하고, 손실 압축(toss Compression) 이나 필터링(Filtering), 잡음(Noise) 등에 크게 영향받는 저주파 성분과 인간의 시각적으로 큰 의미를 갖는 고주파 성분의 특성을 이용하여 워터마크를 삽입한다.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.344-344
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• 2013

칩의 크기가 감소함에 따라 RC (Resistance, Capacitance) 지연, 전력소비증가 및 신호잡음 등이 문제가 되어왔다. RC지연 문제는 배선에 알루미늄 보다 비저항이 낮은 구리를 사용하고 절연막으로 유전상수가 낮은 물질을 사용하여 개선될 수 있다. 이와 같은 맥락에서 점차 저유전상수 박막의 필요성은 증가하고 있다. 그러므로 이를 개선하기 위해 저 유전상수 값을 가지는 물질을 개발 혹은, UV나 플라즈마 그리고 열을 이용하여 처리하는 연구가 절실히 요구되고 있으며, 현재 많은 연구가 진행되고 있다. 이 논문에서 저유전박막은 HDP-CVD (High Density Plasma Chemical Vapor Deposition) 시스템에서 (CyOz)-SiHx와 O2의 비율을 각각 변화시키면서 증착 되었다. (CyOz)-SiHx와 O2의 비율은 60/150, 60/180, 60/210, 60/240로 증가하면서 증착하였다. 그리고 surface profilometer을 이용하여 박막의 증착율을 측정하고 LCR meter를 이용하여 정전용량을 측정하여 유전상수 값을 얻었다. 박막의 화학적 조성과 구조는 FTIR (Fourier Transform Infrared Spectroscopy)로 측정하였다. 박막의 유동 특성은 SEM (Scanning electron microscope) 이미지로 살펴보았다.

• Journal of Korea Multimedia Society
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• v.4 no.4
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• pp.333-338
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• 2001

In this paper, fuzzy-ARTMAP equalizer is developed mainly for overcoming the obstacles, such as complexity and long training, in implementing the previously developed neural-basis equalizers. The proposed fuzzy-ARTMAP equalizer is fast and easy to train and includes capabilities not found in other neural network approaches a small number of parameters, no requirements for the choice of initial weights, no risk of getting trapped in local minima, and capability of adding new data without retraining previously trained data. In simulation studies, binary signals were generated at random from linear channel with Gaussian noise. The performance of the proposed equalizer is compared with other neural net basis equalizers, such as MLP and RBF equalizers. The fuzzy ARTMAP equalizer combines relatively simple structure and fast processing speed; it gives accurate results for nonlinear problems that cannot be solved with a linear equalizer.

• Journal of Advanced Navigation Technology
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• v.15 no.3
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• pp.386-391
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• 2011

CRU (contiguous resource unit) composed of adjacent OFDMA subcarriers is popularly adopted for recently developed cellular communication standards, e.g. IEEE 802.16e/m. If multiple CRUs having different SNR are assigned to a mobile station, and multiple packet streams are independently transmitted by using H-ARQ transmission, an achievable data rate can be varied according to the channel allocation method of re-transmission packets and new transmission packets. In this paper, the optimum channel allocation method for the above stated problem, and several sub-optimum channel allocation methods to reduce the computational complexity of the optimum allocation method are proposed. According to the simulation results, a sub-optimum allocation method assigning a CRU having good SNR to new transmission packet shows marginal performance loss compared with optimum method, however, the computational complexity can be significantly reduced.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.11B
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• pp.965-971
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• 2003

This paper suggests a low-complexity frame timing synchronization system for IEEE802.11a wireless LAN systems. The proposed timing synchronization scheme has been implemented by correlating the received OFDM preamble with quantized coefficients composed of ｛0, ${\pm}$2$^{0}$ , ${\pm}$2$^1$‥‥‥ ${\pm}$2$^{i}$ ), where i is an integer number. The 2$^{i}$ -valued coefficients enable the multipliers in the correlation system to be simplified to i-bit shifters. So we can design the correlation system using shifters instead of multipliers. We estimate the performance of the proposed scheme in comparison with conventional systems under the AWGN and Rayleigh fading channels. In this paper we show that the complexity can be reduced by 90% while still maintaining a performance comparable to that of the conventional system.

• Journal of the Korean Magnetics Society
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• v.3 no.3
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• pp.229-233
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• 1993

The effects of differential partial pressures of oxygen during sputtering on the magnetic and recording characteristics of magneto-optical disks were investigated. Different flows of oxygen were deliberately introduced into the sputtering chamber to have a variety of partial pressures of oxygen during sputtering. A residual gas analyzer was employed to monitor the oxygen peak before, during, and after sputtering and to estimate the reacted oxygen amount. Most of the oxygen introduced into the chamaber was reacted during sputtering. As the partial pressure of oxygen increased, the oxygen content of the TbFeCoCr film increased also. The oxygen appeared to be bound as Tb-O, effectively decreasing the magnetically active Tb content of the film The coercivity decreased but the squareness of the Kerr hysteresis loops was still excellent. The perpendicular anisotropy was not significantly affected by oxygen amount. The carrier-to-noise ratio, includi!1g the write power sensitivity and bias field sensitivity did not change too much with oxygen content in the film The disks sputtered with oxygen showed better bias field sensitivity with lower write power threshold than the disk sputtered without oxygen, due to high demagnetization during domain formation. No significant degradation of coercivity for the disk sputtered oxygen was observed during an accelerated aging test.

• Journal of the Microelectronics and Packaging Society
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• v.27 no.3
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• pp.61-67
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• 2020

In this paper, we calculated the warpage of bare substrates and chip attached substrates by using FEM (Finite Element Method), and compared and analyzed the effect of the chips' attachment on warpage. Also, the effects of layer thickness of substrates for reducing warpage were analyzed and the conditions of layer thickness were analyzed by signal-to-noise ratio of Taguchi method. According to the analysis results, the direction of warpage pattern in substrates can change when chips are attached. Also, the warpage decreases as the difference in the CTE (coefficient of thermal expansion) between the top and bottom of the package decreases and the stiffness of the package increases after chips are loaded. In addition, according to the impact analysis of design parameters on substrates where chips are not attached, in order to reduce warpage, the inner layers of the circuit layer Cu1 and Cu4 has be controlled first, and then concentrated on the thickness of the solder resist on the bottom side and the thickness of the prepreg layer between Cu1 and Cu2.

• Geophysics and Geophysical Exploration
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• v.14 no.2
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• pp.152-157
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• 2011

The small-loop electromagnetic (EM) method is one of the rapid and non-destructive geophysical methods and has been used widely for many geophysical investigations, particularly for shallow engineering and environmental surveys. Especially in the shallow marine environment, the small-loop EM technique is very effective because of rapid and convenient data acquisition, large signal and low noise level. However, the method has been rarely applied in the very conductive marine environment since it's penetration or investigation depth might be considered too low. In this study, we demonstrated that the small-loop EM method can be effectively applied in the extremely conductive marine environment through the analysis of 1D small-loop EM data. Furthermore, we confirmed that the resistivity distribution under the sea bottom can be quantitatively predicted from the 1D inversion results of synthetic and field data.