• 센서학회지
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• 제24권5호
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• pp.342-347
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• 2015

We introduce an indoor broadcasting system using light-emitting diode (LED) lamps coupled with a 220 V power line. Two couplers connected to the power line constitute a power line communication (PLC) link. The transmission path from an LED lamp to a photodetector forms a visible light communication (VLC) link in free space. When the LED lamp is coupled to the power line, a composite PLC-VLC link is formed, making it possible to transmit a VLC signal beyond line-of-sight. In experiments, a 4 kHz analog signal modulated with a 100 kHz carrier was sent to the power line by a PLC coupler, and LED lamps coupled to the power line detected the signal and radiated it to multiple VLC receivers in the room. This configuration is useful in expanding an indoor VLC sensor network to adjacent rooms or constructing a voice broadcasting system in a building or apartments with existing power lines.

• 한국전자파학회논문지
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• 제29권5호
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• pp.383-388
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• 2018

본 논문은 CMOS 공정을 이용하여 1.8 GHz 대역에서 임의의 부하 임피던스를 스위치 제어를 통해 가변 하는 6-포트 기반의 임피던스 변조기에 관한 연구이다. 1.8 GHz 대역 임피던스 변조기는 전력 분배기(Wilkinson power divider), $90^{\circ}$ 하이브리드 결합기(quadrature hybrid coupler), 그리고 각각의 서로 다른 부하 임피던스 선택을 위한 SP3T 스위치들로 구성하였다. 제안된 임피던스 변조기는 1.4~2.2 GHz에서 -13 dB 삽입손실과 10 dB 이상의 입/출력 반사손실 결과를 얻었다. 또한, 3.3 V의 안정적인 전원공급을 위한 LDO(Low Drop Output) 레귤레이터와 디지털 회로 제어가 간편하도록 SPI(Serial Peripheral Interface)를 집적화했으며, 칩 크기는 패드를 포함하여 $1.7{\times}1.8mm^2$이다.

• Journal of Advanced Marine Engineering and Technology
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• 제29권6호
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• pp.618-627
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• 2005

In this paper, we have compared and analyzed the performance of high amplifier using Doherty technique to improve linearity and efficiency of base station and repeater Power amplifier for WCDMA. This Doherty amplifier implements with 3dB branch line coupler and $90^{\circ}C$ transmission line The phase offset line is designed to maintain the high linearity and efficiency at the low efficiency Period of the power amplifier CW 1-tone experimental results at the WCDMA frequency $2.11{\sim}2.17GHz$ shows that Doherty amplifier which achieves power add efficiency(PAE) of 50% at 6dB back off the point from maximum output power 52.3 dBm, obtains higher efficiency of 13.3% than class AB Finding optimum bias Point after adjusted gate voltage, Doherty amplifier shows that $IMD_3$ improves 4dB.

• 한국마린엔지니어링학회:학술대회논문집
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• 한국마린엔지니어링학회 2005년도 전기학술대회논문집
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• pp.412-416
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• 2005

In this paper we propose low-impedance and miniaturized a wilkinson power divider on MMIC passive component which was fabricated by a novel microstrip line structure employing periodically perforated ground metal (PPGM). The novel microstrip line structure showed much lower impedance and shorter guided-wavelength than conventional one. Using the novel microstrip line with periodically perforated ground metal, a miniaturized 17 ${\Omega}$ power divider was fabricated. The line width of the power divider was 20 ${\mu}m$, and the size of it was 0.110 $mm^2$, which is 21 % of conventional one. The power divider exhibited good RF performances from 10 to 20 GHz.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제51권7호
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• pp.316-321
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• 2002

In this Paper, the channel characteristics of the medium voltage(22.9kV) power line to analysis the broadband power line communication in the frequency range up to 30MHz was measured. With the sideband electrical coupler in the operating frequency range from DC to 30MHz, we measured characteristic impedance, noise and attenuation of the medium voltage power line, and then characteristic impedance was measured at the state of unloaded medium voltage power line by Scattering parameter method of Vector Network Analyzer. As a measurement result, Channel impedance shows 100~380$\Omega$ at the less than 15MHz and 70~230$\Omega$ at the more than 15 MHz. Noise characteristics of power line shows -75dBm at 20MHz and Narrowband interference noise was from 3 MHz to 7MHz.

• JSTS:Journal of Semiconductor Technology and Science
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• 제6권4호
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• pp.275-280
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• 2006

We propose Doherty power amplifier structure which can be integrated in Silicon RF ICs. Doherty power amplifiers are widely used in RF transmitters, because of their high Power Added Efficiency (PAE) and good linearity. In this paper, it is proposed that a method to replace the quarter wavelength coupler with IQ up-conversion mixers to achieve 90 degree phase shift, which allows on-chip Doherty amplifier. This idea is implemented and manufactured in CMOS 5 GHz band direct-conversion RF transmitter. We measured a 3dB improvement output RF power and linearity.

• Current Optics and Photonics
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• 제2권5호
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• pp.443-447
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• 2018

We propose a diode-pumped cesium laser using frequency locking of a pump laser that can effectively increase the maximum output power of the cesium laser. We simultaneously monitored the absorption spectrum of cesium and the laser output power, and the frequency of pump laser was locked at the center of the $D_2$ absorption line of the cesium atom to obtain an effective gain enhancement. Using this scheme, we have achieved output power increase of ~0.1 W compared to when frequency locking was not applied. Furthermore, by optimizing the temperature of the cesium cell and the reflectivity of the output coupler, we successfully achieved an output power of 1.4 W using the pump power of 2.9 W, providing a slope efficiency of 61.5% and optical-to-optical efficiency of 49%.

• 동력기계공학회지
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• 제20권3호
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• pp.22-28
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• 2016

Energy consumption rapidly increases with industrial development. therefore an interest in the efficiency of various power converters is increasing. Especially, the field of high-efficiency small motors widely distributed for industrial and family use is considered a very important field in terms of efficient energy usage, and accordingly, in the field of small electric equipment, the use of BLDC that allows high-efficiency drive in an inductor gradually increases. However, for the BLDC drive, information on the position of the rotor is essential. Both methods using a magnetic encoder and an optical encoder to detect the information on the position of the rotor obtain the information by three position sensitive devices, and if any one of these position sensitive devices fails to function, no positional information can be obtained, so there is a limitation in implementing a position sensor with high reliability. In the paper, proposes a new type of encoder that can obtain the positional information on the position of the rotor using a single position sensor in order to overcome the issues that it has to use numerous signal flows and that the reliability is reduced for the acquisition of positional information generated by using multiple position detectors. The encoder in the proposed method replaced the function of generating positional information from multiple sensors with the shape of the encoder plate and the capture function of MICOM. In order to verify the validity of the position detection technique by the proposed encoder, a prototype was produced, and an experiment using the capture function of DSP was conducted through this.

• 한국통신학회논문지
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• 제19권11호
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• pp.2228-2237
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• 1994

This paper describes the development of a Ku-band ($12.25GHz\sim12.75GHz$) SSPA intended as a replacement for TWTAs used in communication satelite transponder. The power stage of the amplifier consists of tow intrmally matched 8W FET divices combined using the branch-line coupler. To operate this stage, the drive stage has been designed with intermally matched 2W, 4W, 8W FET and two medium power FETs. The entire amplifier is made up by a aluminum chassis housing both the RF circuit and the bias circuitry. A regrlator/sequencing circuitry is used for FET biasing. The amplifier results implemented in this way show $41\pm0.3dB$ small-signal gain, 15W saturation power, a typical two tone $IM_3=-21.5dBc$ with single carrier backed off 5dB from saturation, $2^*/dBmax$ AM/PM conversion, and $3.47\pm0.25nsec$ group delay.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2005년도 제36회 하계학술대회 논문집 D
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• pp.3040-3042
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• 2005

During the last several years, interest in broad-band power line communications (PLC) has been grown over medium voltage(MV) power distribution lines as well as low voltage lines. This paper introduces a medium voltage PLC test field that is set up in the suburbs of Euiwang city in Korea. This test field could be used not only for the measurement of communication channel environment but also for internet service. This paper shows the configuration of medium voltage test field with network devices like MV signal coupler and the results of channel environment like noise and impulse response. It also shows the service performance of PLC access network through network management system.