• Korean Journal of Optics and Photonics
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• v.12 no.1
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• pp.40-47
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• 2001

The structural dependence of the performance of an 1.55 $1.55{\mu}m$ InGaAsPIInGaAsP MQW electro-absorption modulator for highspeed digital fiber communication was systematically investigated. The effects of n-doped SCH region length $t_n$ as well as the general structure parameters including quantum well number $N_w$, well-thickness $t_w$, detuning wavelength $\Delta\lambda$, and device length L were thoroughly analyzed. Thereby, a high-pelfoIDlance electro-absorption modulator with device length L of $100{\mu}m$ was successfully designed. The designed structure showed excellent characteristics that have residual loss less than -1.5 dB, operational voltage from 0 V to -2V, and extinction ratios of -2.92 dB at $V_{\alpha}$=-1 V and -10 dB at $V_{\alpha}$=-2V.X>=-2V.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.38 no.11
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• pp.19-29
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• 2001

The Pan-European Digital Audio Broadcasting(DAH) system's performance is characterized and improved with the aid of turbo codec. From the fact that the first bit among the four coded bits at the RCPC coding defined in the Eureka 147 DAD system is not. punctured and always transmitted, this paper proposes a new turbo coded DAB system model that replaces the existing RCPC codec by a turbo codec without modifying the puncturing procedure and puncturing vectors defined in the standard DAB system for compatibility. The performance of a new system is compared to that of the conventional system under the Rician fading channel and the Rayleigh fading channel in conjunction with DAD transmission mode I and III suitable for the terrestrial single frequency network and satellite broadcasting.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.49 no.1
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• pp.85-91
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• 2012

In this paper, we implemented a Ka-band frequency synthesizer for millimeter wave seeker. we designed for high frequency resolution and frequency hopping response time in the digital synthesis method which uses DDS(Direct Digital Synthesizer). but frequency bandwidth was limited low frequency because DDS output frequency was limited 1/2 by system clock. thus, frequency synthesizer was converted to Ka-band using the frequency multiplier ${\times}4$ and local oscillator. proposed frequency synthesizer was bandwidth 500MHz, frequency switching time was $0.7{\mu}s$, spurious level was suppressed below -52dBc. phase noise was -99dBc/Hz at offset 100kHz and flatness was ${\pm}1dB$.

• Journal of the Institute of Electronics and Information Engineers
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• v.49 no.10
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• pp.251-256
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• 2012

Expand the market because the size of the huge funds administered by the conversion of over-the-air digital TV broadcasts in the current situation is likely to be reduced due to the influence of the media over-the-air broadcasts new paid media, digital cable TV and IPTV new mobile TV as a new growth engineis required. Broadcasting system to increase the supply and demand of the module from the ATSC-M/H DMB business existing in the domestic over-the-air broadcasters, has seen significant achievements in sleep technology with the introduction is expected. ATSC-M/H does not require a separate frequency allocation for mobile services does not interfere with the existing ATSC system simulcast, which can be performed on Android mobile handsets American-style mobile broadcast reception module to develop should. This paper is to design the software modules in the broadcasting module embedded systems that are applied on the Android platform, broadcasting from mobile handsets to see.

• Journal of Broadcast Engineering
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• v.18 no.2
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• pp.297-310
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• 2013

In this paper, we present a model-based video bit rate estimation scheme for reducing the bit rate while maintaining a subjective quality in many video streaming services limited by network bandwidth, such as IPTV services. First, we extract major parameters which serve as an indirect measurement of frame's bits. Using those parameters, the proposed bit rate estimation scheme can extract candidate frames. Finally, the bit rate of each segment is estimated by statistical analysis and a mathematical model based on a given target quality. In experimental results, we show that the proposed scheme can reduce the bit rate on average by 43% in low-complexity video while maintaining the subjective quality. To find the appropriate bit rate based on video contents, the proposed schemes can estimate the bit rate with neither the repeated full encoding nor subjective quality test. On average, the bit rate can be automatically estimated by encoding the candidate frames of 4%.

• The Transactions of the Korean Institute of Power Electronics
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• v.9 no.2
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• pp.97-104
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• 2004

As a device that returns surplus energy, regenerated from trains to d.c. source, to a.c. system and reuses it, the thyristor Inverter has been widely used. Because the conventional thyristor inverter is a unidirectional phase-controlled device, it Is Impossible to control the power factor of its output. Moreover, harmonics emission is high and it needs to take a additional filter. In this paper, to solve the problems stated above, the inverter, which can control real and reactive power by adopting IGBT modules as switching elements and being controlled by means of space vector PWM, is developed. Considering high economical efficiency and reliability in order to apply to the system for commercial use, the developed inverter is equipped with fully digital control system and low pass filter, and reduces harmonics and has compact size. The detail description about the developed inverter is stated in various respects: design criteria, technical description, power circuits, control techniques, the developed system, test results, etc.

• Journal of KIISE:Information Networking
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• v.31 no.3
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• pp.314-326
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• 2004

Bluetooth has been reputed as a wireless ad-hoc networking technology supplying scalable and extensible networks between digital devices. For that kind of networks, scatternet is a most essential part in bluetooth. But past researches on bluetooth scatternet has proposed only possibilities of scatternet algorithm based on simulation results. And many of the researches failed in guaranteeing extensibility and flexibility and had many difficulties in real hardware implementation. In this paper, we proposed node ring scatternet(NRS) algorithm guaranteeing extensible and flexible networks. NRS algorithm is designed for hardware implementation using real commercial bluetooth module. That algorithm is divided into initial formation and reformation. For initial formation, we proposed limited SEEK/SCAN algorithm. For reformation, we proposed DIAC algorithm and Reserved Recovery Node algorithm. And we proposed SFMP(Scatternet Formation ＆ Management Protocol) in protocol stack for real implementation. NRS algorithm is operated in SFMP. Finally, we performed real hardware experiments and evaluated the proposed algorithm. In that experiments, we succeeded in forming scatternet up to 20 nodes. In comparison with other similar algorithm, proposed algorithm have the improvement in scatternet formation delay and success rate.

• Journal of KIISE:Computer Systems and Theory
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• v.34 no.3
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• pp.124-131
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• 2007

Research field on crowd animation can be classified into two major categories. One is to offer realism of the crowd motion and the other is to improve speed of the animation. For the last decade, a lot of research on realism and behavior of crowd have been presented. But lately, research on improving speed seems like more interesting. Therefore, in this paper, we conducted an experiment to analyze what is the main bottleneck of crowd animation. As the result, we find out one of the most important bottleneck is the number of joints transformed in each animation frame. In order to resolve this problem we propose a novel level-of-detail technique 'motion level-of-detail', which is a joint-reduction technique operated in the pre-processing time. We used a non-linear optimization, SQP (sequential quadric programming), to generate the low detailed motions.

• 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.

• Proceedings of the KAIS Fall Conference
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• 2010.05b
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• pp.610-613
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• 2010

본 과제를 통하여 기술적으로는 로봇 개발에 있어 기존 기술을 최대한 활용하고 새로운 기능을 추가하는 형태로 발전해 갈 수 있도록, 각 요소별 기능을 표준화 모듈화 하여 새로운 제품의 개발이 손쉽게 이루어 질 수 있는 기본 platform으로의 역할이 가능해졌다. 구동부 제작 및 설계, 금형 비용 등을 절감하기 위한 다목적 완구로봇 플랫폼을 확보할 수 있었다. 로봇이 복잡한 환경을 인식하고, 자율적으로 작업을 수행하며, 예측하지 못한 문제에 적절한 대처를 할 수 있도록 하기 위한 핵심 기술을 제공하게 될 것으로 생각된다. 로봇 개발에 있어 전문지식이 없는 초보자들이 직접 제작 구동해 볼 수 있는 비주얼한 개발환경을 지원할 뿐만 아니라 GUI 개발환경 및 TEXT Programming 으로 상호 전환이 가능한 코딩 방법을 지원(MSRS와의 차별화를 시도하였다. 기존 하드웨어 지식과 소프트웨어지식이 없는 상태에서도 제작자의 창의력에 따라 다양한 형태의 로봇을 제작 적용이 용의 하며 초보자들에 대한 로봇개발에 흥미를 유발할 수 있도록 하였다. 고급사용자를 위한 별도의 다운로딩 포트를 제공하였다. 로봇공학의 기본지식을 습득(아날로그/디지털 회로를 이해하고, 각종 센서의 이해하며, 스템/서보/DC모터의 제어기술, 펌웨어개발능력, 기본수준의 소프트웨어개발 능력) 활용할 수 있다. 또한, 경제 및 산업적 측면으로는 다음과 같은 장점이 있다. 기존 기술들의 장점을 취합하여 추가적인 기술을 적용할 수 있는 Base형태의 로봇을 개발할 경우 이를 활용한 제품 개발 및 Base자체로도 충분한 시장을 형성 할 수 있을 것으로 기대된다. 인터넷기반 로봇 제어 기술의 확보로 로봇시스템의 생산비용을 낮추고 TTM (Time-to-Market) 제약을 해결시켜 준다. 다른 응용 시스템에 쉽게 적용이 가능하고 지식기반 로봇 서비스의 요소기술 개발은 멀티미디어 콘텐츠분야(교육/게임/오락 등)의 활성화가 가능하기 때문에 타 IT산업에의 파급효과가 예상된다. B2B를 통한 실질적인 판매를 통한 동종기업의 연구 개발비 및 개발 기간의 단축이 예상된다.