• Proceedings of the KAIS Fall Conference
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• 2002.11a
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• pp.197-200
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• 2002

본 논문에서는 IMT-2000용 AB급 대전력 증폭기를 설계 및 제작하였다. 전력증폭기의 주파수 대역은 IMT-2000용 순방향 주파수인 2110MHz-2170MHz에서 AB급으로 동작하도록 하였고, 고효율성과 우수한 선형성 소자인 LDMOSFET를 사용하였다. 설계 특성에 맞는 최적부하를 찾아 마이크로 스트립 회로로 입력 및 출력 정합 회로를 구현하였다 임피던스 정합 방법으로는 소자를 실제 측정상태에서 입력단과 출력단에 튜너를 삽입하고 기본 주파수에서 최대 출력상태를 만족하는 임피던스를 튜너로 구현한 후, 튜너를 제거하고 튜너의 입력 임피던스를 Network Analyzer로 측정하여 최적 부하 임피던스를 추출하는 로드풀 방법을 사용하였다. 대전력 증폭기의 측정결과로는 2-톤 인가시 40.57dBm의 출력결과를 얻을 수 있었고 30.61dBc의 상호 혼변조 특성을 확인하였으며, 원신호의 하모닉(Hamonic) 주파수 성분과는 21.46dBc의 차이를 보였다.

• Digital Contents
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• no.10 s.125
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• pp.63-65
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• 2003

정보통신부와 한국소프트웨어진흥원은 지난달 17일과 18일 양일간에 거쳐 '제1회 IT오퍼튜너티(Opportunity) 2003' 전략세미나와 디지털콘텐츠 분야 '1대1 해외비즈니스 수출 상담회'를 성황리에 개최했다. IBM, HP, NTT동일본, AOL등 해외 대기업들이 대거 참여해 국내기업에 호감을 보였다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.25 no.4B
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• pp.613-623
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• 2000

Digital TV tuner for 8-VSB modulation was developed with satisfying the requirements of ATSC. The double frequency conversion and the active tracking filter in the front-end were used to reduce interference of the adjacent channels and multi-channels, which suppress If beat and image band. However, it was impossible to get frequency mapping between tracking filter and first VCO(Voltage Controlled Oscillator) in the double conversion digital TV tuner differing from conventional NTSC tuner. This paper, therefore, suggests the available structure and a new method for automatic frequency selection by obtaining the mapping of frequency characteristic over tracking voltage and the combined hardware which compose of Micro-controller, EEPROM, D/A(Digital-to-Analog Converter), OP amp and switch driver to solve above problems.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.18 no.7
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• pp.698-703
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• 2007

In this paper, a novel impedance tuner using a directional coupler is proposed. The design topology is analyzed by signal flow graph(SFG) and shows advantages compared with conventional single and double stub methods from the view points of easy implementation and wide tuning range, respectively. This impedance tuner consists of ten switches and its $2^{10}$ tuning points are distributed uniformly on the whole Smith chart. The measured maximum magnitude of the reflection coefficient is 0.9. And the fabricated impedance tuner has a wide bandwidth from 1.8 to 2.2 GHz. Using this impedance tuner, we did a load-pull measurement of a power transistor.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.2 no.2 s.3
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• pp.1-12
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• 2003

DAB(Digital audio broadcasting) is a next generation radio broadcasting system which provides CD quality audio, various data services and superior reception ability when moving. Also, it can show traffic informations and news literally or graphically. In this paper, we design and fabricate the DAB tuner for ITS service that follows Eureka-147 and ETSI 300 401 specifications. This small-sized tuner can be adopted to mny electronic equipments such as a Hi-Fi audio, DVD player, car audio system etc.. The overall performance of the tuner depends on a phase noise of VCO and the sensitivity of the receiving system is influenced by LNA, image rejection filter and channel selection filter. All our measurement results satisfy the specification for a DAB system with the return loss of 9dB, the noise figure of 6dB for both Band 111 and L-band and the sensitivity of -97dBm.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.21 no.4
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• pp.443-451
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• 2010

This paper describes a fully integrated CMOS low-IF mobile-TV RF tuner for Band-III T-DMB/DAB applications. All functional blocks such as low noise amplifier, mixers, variable gain amplifiers, channel filter, phase locked loop, voltage controlled oscillator and PLL loop filter are integrated. The gain of LNA can be controlled from -10 dB to +15 dB with 4-step resolutions. This provides a high signal-to-noise ratio and high linearity performance at a certain power level of RF input because LNA has a small gain variance. For further improving the linearity and noise performance we have proposed the RF VGA exploiting Schmoock's technique and the mixer with current bleeding, which injects directly the charges to the transconductance stage. The chip is fabricated in a 0.18 um mixed signal CMOS process. The measured gain range of the receiver is -25~+88 dB, the overall noise figure(NF) is 4.02~5.13 dB over the whole T-DMB band of 174~240 MHz, and the measured IIP3 is +2.3 dBm at low gain mode. The tuner rejects the image signal over maximum 63.4 dB. The power consumption is 54 mW at 1.8 V supply voltage. The chip area is $3.0{\times}2.5mm^2$.

• Photonics industry news
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• s.14
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• pp.50-55
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• 2003

• Journal of Korean Electronics
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• v.4 no.7
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• pp.10-14
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• 1984

• Proceedings of the Korean Institute of Communication Sciences Conference
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• 1996.06a
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• pp.226-229
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• 1996

• Journal of Korean Electronics
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• v.24 no.5
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• pp.6-7
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• 2004