• Journal of electromagnetic engineering and science
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• 제10권3호
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• pp.132-137
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• 2010

We present results of room-temperature characterization of lithographically manufactured antenna-coupled NbN micro-bolometers. The bolometers are assembled together with a hyper-hemispherical Si lens to couple the incident radiation to the bolometer from the back-side of the substrate. The bolometers are designed to operate at 300~1,000 GHz and they are characterized at 321~782 GHz. Radiation patterns are measured at 321 GHz, 400 GHz, 654 GHz, and at 782 GHz. The frequency dependency of the beamwidth is studied with several azimuthal beam profile measurements at 321~500 GHz.

• 한국전기전자재료학회논문지
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• 제23권9호
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• pp.685-690
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• 2010

ZnO with the wide band gap near 3.37 eV is typically an n-type semiconductor in which deviation from stoichiometry is electrically active. It was known that the films with a resistivity of the order of $10^{-4}{\Omega}cm$ is not easy to obtain. In order to improve electrical characteristic of ZnO, we added 1, 3, 5 wt% Ga element in ZnO. The Ga-doped ZnO (GZO) was grown on a glass substrate by radio frequency (RF) magnetron sputtering at the temperature range from 100 to $500^{\circ}C$. X-ray diffraction (XRD) patterns of GZO films showed preferable crystal orientation of (002) plane. The lowest resistivity of the GZO films was $8.9{\times}10^{-4}{\Omega}cm$. GZO films significantly influenced by the working temperature. The average transmittance of the films was over 80% in the visible ranges.

• 한국정보통신학회:학술대회논문집
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• 한국해양정보통신학회 2007년도 춘계종합학술대회
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• pp.856-860
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• 2007

본 논문에서는 2.65GHz 위성 DMB 대역의 마이크로스트립 안테나를 설계 및 제작하고 이 특성을 바탕으로 단말기에 응용가능한 안테나를 설계하고 제작하였다. 2.65GHz 위성 DMB 대역의 마이크로 스트립 안테나를 CST Microwave Studio 프로그램으로 설계하고 시뮬레이션 특성을 기술하였다. 그리고 마이크로스트립 안테나를 이용하여 단말기에 이용될 수 있게 안테나를 설계 제작하였으며 실제 제작된 안테나의 성능을 측정하였다. 그 결과, 실제 상용화 되고 있는 안테나와 비슷한 성능이 나타났고 안테나가 이용될 수 있는 대역도 광대역의 특성을 보였다.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제54권6호
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• pp.286-292
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• 2005

Terahertz wave is a kind of electromagnetic radiation whose frequency lies in 0.1THz $\~$10THz range. In this paper, generation and detection characteristics of terahertz (THz) radiation by photoconductive antenna (PCA) method has been described. Using modern integrated circuit techniques, micron-sized dipole antenna has been fabricated on a low-temperature grown GaAs (LT-GaAs) wafer. A mode-locked Ti:Sapphire femtosecond laser beam is guided and focused onto photoconductive antennas (emitter and detector) to generate and measure THz pulses. Ultra-wide band THz radiation with frequencies between 0.1 THz and 3 THz was observed. Terahertz field amplitude variation with antenna bias voltage, pump laser power, pump laser wavelength and probe laser power was investigated. As a primary application example. a live clover leaf was imaged with the terahertz radiation.

• 제어로봇시스템학회논문지
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• 제10권11호
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• pp.1052-1057
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• 2004

Bluetooth technology is essentially a method for wireless connectivity of a diverse set of devices ranging from PDAs, mobile phone, notebook computers, to another equipments, The bluetooth system both point-to point connection and point-to multipoint connection. In point-to multipoint connection, the channel is shared among several bluetooth devices. Two or more devices sharing the same channel form a piconet. There one master device and up to seven active slave devices in a piconet. The radio operates in the unlicensed 2.45GHz ISM band. This allows users who travel world-wide to use bluetooth equipments anywhere. Since the link is based on frequency-hop spread spectrum, multiple channels can exist at the same time. The bluetooth standard ha s been suggested that bluetooth equipments can be used in the short-range, maximum 100 meters. It has been defined that the time takes to setup and establish a bluetooth connection among devices is 10 seconds. It is a long time and may be a cause to lose a chance of finding other non-fixed devices. We propose a routing protocols for scatternets which can be used to control a mobile units(MUs) in this network. The proposed routing protocol is composed of two kinds of bluetooth information, access point(AP) and MU.

• JSTS:Journal of Semiconductor Technology and Science
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• 제17권4호
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• pp.499-504
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• 2017

A UHF CMOS variable gain low-noise amplifier (LNA) is designed for mobile digital TV tuners. The proposed LNA adopts a feedback topology to cover a wide frequency range from 474 to 868 MHz, and it supports the notch filter function for the interoperability with the GSM terminal. In order to handle harmonic distortion by strong interferers, the gain of the proposed LNA is step-controlled while keeping almost the same input impedance. The proposed LNA is implemented in a $0.11{\mu}m$ CMOS process and consumes 6 mA at a 1.5 V supply voltage. In the measurement, it shows the power gain of greater than 16 dB, NF of less than 1.7 dB, and IIP3 of greater than -1.7 dBm for the UHF band.

• 한국결정성장학회:학술대회논문집
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• 한국결정성장학회 1999년도 PROCEEDINGS OF 99 INTERNATIONAL CONFERENCE OF THE KACG AND 6TH KOREA·JAPAN EMG SYMPOSIUM (ELECTRONIC MATERIALS GROWTH SYMPOSIUM), HANYANG UNIVERSITY, SEOUL, 06월 09일 JUNE 1999
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• pp.253-269
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• 1999

The development of telecommunication and information technology requires to develop new piezoelectric materials with small size, low impedance, wide pass band width and high thermal stability of frequency. Langasite (La3Ga5SiO14) single crystal has been researched substitute of quartz and LiNbO3 for the applications of SAW filter, BAW filter and resonator. Its single crystal growth has been carried out by Czochralski Method. So, in order to get single crystal with higher quality, in this study, lnagasite (La3Ga5SiO14) single crystal was grown by using Floating Zone (FZ) method and characterized. For the growth of langasite single crystals, the langasite powder was synthesized at 135$0^{\circ}C$ for 5hrs and the feed rod was sintered at 135$0^{\circ}C$ for 5hrs. The growing rate was 1.5mm/h and the rotation speed was 15 rpm for an upper rotation and 13 rpm for a lower rotation. In order to prevent the evaporation of gallium oxide, Ar and O2 gas mixture was flowed. The growth direction was analyzed by Laue back-scattered analysis. The composition of grown crystal was analyzed suing XRD and WDS. The electrical properties of grown crystal at various frequencies and temperature were discussed.

• 한국통신학회논문지
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• 제27권2B호
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• pp.145-150
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• 2002

본 연구에서는 PCS 사업자 기지국의 RF부와 안테나를 통합한 하나의 통합 기지국으로 PCS 3사의 서비스를 제공할 수 있는 PCS 통합 기지국 시스템의 구현방안을 제안하였다. 본 연구에서 PCS 통합 기지국을 구현하기 위해 다중 채널 결합기(multi-channel combiner), 듀플렉서, LNA, 전력 분배기(power divider), 전송라인(feeder line), 통합 안테나 등으로 이루어진 기지국 통합 모듈을 설계·제작하여 PCS 사업자 기지국에 적용하였다. 통합 모듈은 최대 300W의 입력을 처리할 수 있도록 설계하였고 광대역용임에도 불구하고 삽입손실, isolation 등 전기적 특성을 크게 개선하였다. PCS 통합 기지국의 성능 평가를 위한 실험에서, 통합모듈을 설치했을 때 각 PCS 3사의 커버리지 및 신호 품질이 설치를 하지 알았을 때의 PCS 3사 기지국의 커버리지 및 신호 품질과 동등하다는 것을 확인하였다.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제51권7호
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• pp.387-398
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• 2002

In this paper, a new Three-Phase Lead-Lag Random Pulse Position PWM(LL-RPWM) scheme is proposed and implemented for decreasing audible acoustic noise of motor drives. In the proposed RPWM(Random PWM), each of three phase pulses is located randomly in each switching interval. Based on the space vector modulation technique, the duty ratio of the pulses is calculated. Along with the randomization of the PWM pulses, we can obtain the effects of spread spectra of voltage, current as in the case of randomly changed switching frequency. To verify the validity of the proposed LL-RPWM, the simulation and experimental study was tried. Along with the randomization PWM pulses, the space vector modulation is also executed in the C167 micro-controller. The simulation and experimental results show that the voltage and current harmonics are spread to a wide band area and that the audible acoustic noise is reduced by the proposed RPWM method.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2008년도 하계종합학술대회
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• pp.411-412
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• 2008

The high performance 94 GHz MMIC(Monolithic Micro-wave Integrated Circuit) single balanced mixer was designed and fabricated, using MHEMT structure based diodes and a CPW(Coplanar Waveguide) tandem coupler. A novel single-balanced structure of diode mixer is proposed in this work, where a 3-dB tandem coupler with two section of parallel-coupled line. Implemented air-bridge crossover structures achieve wide frequency operation and the fabricated mixer exhibits excellent LO-RF isolation, larger than 30 dB, in the 5 GHz bandwidth of 91-96 GHz. A good conversion loss of 7.4 dB is measured at 94 GHz. The proposed MHEMT-based diode mixer shows superior LO-RF isolation and conversion loss to those of the W-band mixers reported to date.