• Journal of the Institute of Electronics Engineers of Korea TC
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• v.39 no.8
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• pp.14-25
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• 2002

In this paper, we propose a modified AFC algorithm which is suitable for the implementation of WCDMA reverse link receiver modem. To reduce the complexity, the modified CP-FDD algorithm named 'Normalized CP-FDD' is applied to the AFC loop. The proposed FDD algorithm overcomes the conventional CP-FDD's sensitivity to the variance of input signal amplitude and increases the linear range of S -curve. Therefore, offset frequency estimation using the proposed scheme can be more stable than the conventional method. Unlike IS-95, since pilot symbol in WCDMA is not transmitted continuously, we introduce a moving average filter at the FDD input to increase the number of cross-product. So, tracking speed and stability are improved. For more rapid frequency acquisition and tracking, we adopt a multi-stage tracking mode. Using NCO having ROM table structure, the frequency offset is compensated. We applied the proposed algorithm in the implementation of WCDMA base station modem successfully.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.42 no.9 s.339
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• pp.49-56
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• 2005

Memory effect, which influence the performance of Doherty amplifier, become more significant and critical in designing these circuits as the modulation signal bandwidth and operation power level increase. This paper reports on an attempt to investigate, model and quantity the contribution of the electrical nonlinearity effects and the thermal memory effects to a Doherty amplifier's distortion generation. Also this raper reports on the development of an accurate dynamic expression of the instantaneous junction temperature as a function of the instantaneous dissipated power. This expression has been used in the construction of an electrothermal model for the Doherty amplifier. Parameters for the nelv proposed behavior model were determined from the Doherty amplifier measurements obtained under different excitation conditions. This study led us to conclude that the effects of the transistor self-heating phenomenon are important for signals with wideband modulation bandwidth(ex. W-CDMA or UMTS signal). Doherty amplifier with electrothermal memory effect compensator enhanced ACLR performance about 20 dB than without electrothemal memory effect compensator. Experiment results were mesured by 60W LDMOS Doherty amplifier and electrothermal memory effect compensator was simulated by ADS.

• The Journal of the Korea Contents Association
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• v.6 no.2
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• pp.65-74
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• 2006

The MPEG-2 video compressed bitstream is very sensitive to transmission errors due to the complex coding structure of the MPEG-2 video coding standard. If one packet is lost or received with errors, not only the current frame will be corrupted, but also errors will propagate to succeeding frames within a group of pictures. Therefore, we employ various error resilient coding/decoding techniques to protect and reduce the transmission error effects. Error concealment technique is one of them. Error concealment technique exploits spatial and temporal redundancies of the correctly received video data to conceal the corrupted video data. Motion vector recovery and compensation with the estimated motion vector is good approach to conceal the corrupted data. In this paper, we propose various error concealment algorithms based on motion vector recovery, and compare their performance to those of conventional error concealment methods.

• The Journal of the Korea Contents Association
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• v.7 no.12
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• pp.303-310
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• 2007

Compressed video bitstreams are intended for real-time transmission over communication networks. Because video compression algorithms eliminate the temporal, spatial, and statistical redundancies, the coded video bitstreams are very sensitive to transmission errors. We propose an error resilient video coding technique to limit the effect of error propagation in low bit-rate video coding. The success of error resilient coding techniques relies on how accurately the transmission errors can be detected. To detect the transmission error, we propose a very simple error detection technique based on data hiding Next, we conceal the corrupted MB data using intra MB refresh and motion compensation with the estimated motion vector and compare the simulation results. This method will be useful in video communication in error Prone environment such as WCDMA networks.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.25 no.8B
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• pp.1383-1390
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• 2000

Pilot symbol-based coherent detection is used to increase the link capacity in CDMA systems. In order to detect data efficiently, data signals must be compensated with channel estimation values obtained by using pilot symbols. Many channel estimation schemes were published in previous literatures. However, most of these schemes have performance deterioration in fast fading because of using average vaules of several timeslots. In this paper, we propose an improved channel estimation scheme which is efficient in fast fading and also operates in slow fading satisfactorily. Through computer simulation we show that the proposed scheme has better performance than other schemes in terms of both MSE and BER in fast fading and show robustness for variation in Doppler frequencies.

• JOURNAL OF ELECTRICAL WORLD
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• s.360
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• pp.46-50
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• 2006

“전자계는 커피 정도의 위험도 밖에는 되지 않습니다. 그러나 전력설비에서 발생하는 전자계에 대해서는 사람들이 민감하게 반응합니다.” 이는 전자계 분야에서 세계적인 권위자로 알려진 Repacholi 박사(WHO International EMF Project 위원장)가 지난 17일 서울 삼성동 그랜드 인터콘티넨탈 호텔에서 열린‘전자계 안전성에 관한 세미나’에 초청강사로 참석해 밝힌 말이다. 이처럼 일반인들은 전자레인지, 헤어드라이기 등 전자계를 훨씬 더 많이 발생하는 전자제품은 아무런 의심없이 사용하면서도 발생량이 훨씬 적고, 또 인체 유무해성에 대해 아직 과학적으로 증명이 되지 않은 전력설비 전자계에 대해서만큼은 매우 인색하다. 그런데 Repacholi 박사가 강조하는 것을 보면 이러한 현상은 비단 우리나라에서만 국한된 문제는 아닌가 보다. 이러한 전자계 민원이 발생하는 것은 여러 가지 이유가 있겠지만, 가장 큰 요인 두 가지를 꼽으라면 바로 보상을 위해 전자계를 이용하고 있다는 점과 홍보의 부족으로 일반인들이 전력설비에서 발생하는 전자계에 대해 막연한 불안감을 갖고 있다는 점이다. 이러한 원인을 해결하기 위한 다양한 방법들이 동원되고 있지만 설상 현실에서는 쉽게 적용되지 못하는 면도 있다. 그러나 정작 중요한 것은 늘어나는 전력수요를 감당하기 위해서는 전력설비가 꾸준히 건설되고 운영돼야 한다는 점이다. 즉 이는 전자계 민원을 예방하고, 해결하기 위한 현실적인 방안을 찾아야 함을 의미한다. 현재 추진되고 있는 전자계 민원 예방 및 해결을 위한 방안과, 향후 함께 고려해봐야 할 방안들을 종합적으로 정리해봤다.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.45 no.2
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• pp.21-27
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• 2008

This paper describes a CMOS 16:1 binary-tree multiplexer(MUX) using $0.18-{\mu}m$ technology. To provide immunity for wide frequency range and process-and-temperature variations, the MUX adopts several delay compensation techniques. Simulation results show that the proposed MUX maintains the setup margins and hold margins close to the optimal value, i.e., 0.5UI, in wide frequency-range and in wide process-and-temperature variations, with standard deviation of 0.05UI approximately. These results represent that these proposed delay compensations are effective and the reliability is much improved although CMOS logic circuits are sensitive to those variations. The MUX is fabricated using $0.18-{\mu}m$ CMOS process, and tested with a test board. At power supply voltage of 1.8-V, maximum data-rate and area of the MUX is 1.65-Gb/s and 0.858 $mm^2$, respectively. The MUX dissipates a power of 24.12 mW, and output eye opening is 272.53 mV, 266.55 ps at 1.65-Gb/s operation.

• Resources Recycling
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• v.21 no.1
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• pp.49-59
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• 2012

One of the world's top resource-rich countries, the Democratic Republic of the Congo has ample reserves of cobalt, iron ore, copper and diamond in particular. Importing most of major mineral resources, the Republic of Korea has examined-together with the Congo government since 2008-the possibility of a project where it supports port construction in the Democratic Republic of the Congo and acquires useful minerals such as zinc, cobalt and copper in exchange through slag reprocessing in the local city of Lubumbashi. This study conducted feasibility analysis on the slag reprocessing project in Lubumbashi, Congo and found that the project's payback period stands at 6.7 years, net present value(NPV) at 34 million dollars and internal rate of return(IRR) at 17.4%. According to sensitivity analysis that takes into account uncertainties concerning taxation, fixed cost, operational cost and resource prices, the NPV of the project ranges from -24.8 million dollars to 92.7 million dollars.

• Journal of Korean Society of societal Security
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• v.1 no.3
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• pp.77-81
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• 2008

In this paper, we introduce a multi purpose environmental monitoring system developed as a commercially available standard using the technique of hetero-core spliced fiber optic sensor. The monitoring system has been tested and evaluated in a possible outdoor condition in view of the full scaled operation at actual sites to be monitored. Additionally, the developed system in this work conveniently provides us with various options of sensor modules intended for monitoring such physical quantities as displacement, distortion, pressure, binary states, and liquid adhesion. Two channels of optical fiber line were monitored, in each of which three displacement sensor modules were connected in series, in order to examine the performance to a pseudo-cracking experiment in the outdoor situation, and to clarify temperature influences to the system in terms of the coupling of optical connectors and the OTDR stability. The pseudo-cracking experiment successfully observed the actually given cracks by means of calculation based on the detected displacement values and their geometrical arrangement of the used sensor modules. And the robustness to the temperature is verified in the various temperature change.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.22 no.3
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• pp.627-632
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• 2021

ITL (information-theoretic learning) has been applied successfully to adaptive signal processing and machine learning applications, but there are difficulties in deciding the kernel size, which has a great impact on the system performance. The correntropy algorithm, one of the ITL methods, has superior properties of impulsive-noise robustness and channel-distortion compensation. On the other hand, it is also sensitive to the kernel sizes that can lead to system instability. In this paper, considering the sensitivity of the kernel size cubed in the denominator of the cost function slope, a new adaptive kernel estimation method using the rate of change in error power in respect to the kernel size variation is proposed for the correntropy algorithm. In a distortion-compensation experiment for impulsive-noise and multipath-distorted channel, the performance of the proposed kernel-adjusted correntropy algorithm was examined. The proposed method shows a two times faster convergence speed than the conventional algorithm with a fixed kernel size. In addition, the proposed algorithm converged appropriately for kernel sizes ranging from 2.0 to 6.0. Hence, the proposed method has a wide acceptable margin of initial kernel sizes.