• Journal of Advanced Navigation Technology
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• v.6 no.4
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• pp.279-290
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• 2002

In this paper, tapered shape of multiport power divider/combiner modified for 2 GHz range from the model published by [10] is proposed. Parameters determining electrical property of the circuit structure have been analyzed by HFSS simulation. For input matching, balance of output signals and phase linearity at each output port, one circular hole has been etched out on the circuit surface. 1:2 and 1:3 power dividers/combiners designed by this study have been compared with the same circuits designed by the method of [10] in terms of S-parameters. As a result, it has been found that the modified structure of power divider/combiner have improved return loss more than 20 dB and another 18 dB, respectively, at 2 GHz.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.21 no.4
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• pp.417-426
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• 2010

This paper describes the 6-way power divider to be used as a feeding structure of the waveguide array antenna generating the plane wave at the near distance. The SMA connector has been connected at the center of the power divider in order to feed the radiating element. The six output ports made of waveguide are positioned on the peripheral of the divider. This paper proposes the method utilizing the inductive post in order to decrease the return loss. The height of the feeding pin, the diameter of the inductive post, and the distance between the feeding pin and inductive post have been investigated, and as a result, the power divider has been optimized. The simulated and measured results show the low return loss of about -40 dB. The calculated and measured transmission coefficients are -7.78 dB and -8.06 dB, respectively. The output power of the six waveguide port show equal-amplitude and equal-phase distribution. Since the power divider proposed in this paper can be expanded to the divider having several output ports, it could be easily applied to the various array antennas.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.16 no.4
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• pp.21-26
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• 2016

In this paper we proposed a new structure of spatial combining power amplifier working in 60GHz global unlicensed band(56-64GHz) for the backhaul in the 5 generation mobile systems. The proposed structure is suitable to realize an antipodal finline transition in millimeter wave band, in which the size of cross section of waveguide becomes about a few mm ${\times}$ a few mm, due to its compact structure of the transition and shows effective heat sinking characteristics because its ground plane can contact to the body metal. However, the HFSS simulation results showed the return loss improvement by 1.27dB and the same insertion loss of -1.65dB compared with the conventional structure, which said nevertheless the advantages, there was no deterioration in the performance.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.41 no.11
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• pp.1528-1538
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• 2016

Common data link systems are designed to transmit the imaginary and signal intelligence data at long distance air-ground line of sight(LOS) link. In this paper, we analyze the received power variation according to the communication distance of the common data link using curved earth 2-Ray model suitable for received signal power analysis of long distance air-ground wireless channel. We propose optimal elevation angle control method of the receiving antenna to reduce a power variation caused by ground-reflected wave. Proposed method can get additional link margin compared to the conventional method without any additional hardware performance enhancement.

• Proceedings of the Korea Water Resources Association Conference
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• 2009.05a
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• pp.1832-1836
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• 2009

우리나라 수위관측소에 설치되어 있는 수위표는 야간 시인성 부족으로 야간이나 우천시 수위관측을 수행하는데 있어 많은 어려움이 있다. 특히 유량측정 전후 수위관측이 반드시 필요하지만 야간일 경우 눈으로 확인하는 것이 쉽지 않다. 야간 수위관측시 시인성을 높이기 위해 일부 관측소에서 야광도료를 이용하거나 빛의 반사효과를 높인 수위표를 설치하는 등의 노력을 하고 있으나 그 효과는 크지 않다. 이에 본 연구에서는 야간 수위관측시 수위 식별이 어려운 문제를 해결하기 위해 첨단 소자인 LED(Light Emitting Diode)를 이용한 수위표를 개발하고 동시에 전류식 수위센서를 이용하여 자동 수위측정이 가능한 수위표를 개발하였다. 이는 기존의 눈으로 확인하는 수위표와 로거에 저장되는 수위측정장치를 하나로 통합한 것이며 주야간을 가리지 않는 탁월한 시인성과 정확한 수위측정 및 수위자료의 저장이 특징이다. LED는 최근 각광받고 있는 첨단 소자로서 각종 전광판 등에 다양하게 활용되고 있으며 전력을 크게 소비하지 않는 것이 특징이다. 또한 전기장치를 수중에 설치하는 것이므로 방수를 위해 실리콘을 이용하여 완벽 방수구조를 갖추었으며 홍수시 하천 유하물에 의한 파손을 방지하기 위해 내구성을 갖춘 구조로 설계 제작하였다. LED를 이용한 수위표는 야간이나 홍수시 수위관측을 수행할 때 많은 장점이 있을 것으로 판단되며 저전력 구조로 상용전원을 이용할 수 없는 위치에서 태양열 전지판을 이용한 배터리 기반 시스템으로 구성할 수 있으므로 측정의 정확도, 활용도 측면뿐만 아니라 설치의 편리성 문제도 큰 장점을 가질 것으로 판단된다.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.24 no.2
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• pp.86-91
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• 2010

We constructed a quasi-distributed fiber-optic sensor network for the safety monitoring in power systems. It is possible to construct many of FBG sensors in a line and to be immune from electromagnetic noise. For demodulation analysis of reflected wavelength from FBG sensor, we proposed a simple and fast system using a InGaAs photo-diode array and a holographic diffraction grating. For accuracy improvement of the proposed demodulation system, we applied a Gaussian line-fitting algorithm. We obtained about 4[pm] of wavelength resolution and stability.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.20 no.5
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• pp.64-71
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• 2006

We developed a fiber-optic temperature sensor system, with 10 fiber Bragg gratings, for abnormal high-temperature monitoring in power systems. We used Gaussian line-fitting algorithm to compensate the spectrum distortion in the wavelength-scanned Farby-Perot filter demodulation scheme. Compared with highest-peak-detection method, the proposed algorithm substantially reduced measurement errors. The overall measurement error was less than 1[%] compared with the reference thermocouple and the linearity error was 0.37[%].

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.14 no.12
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• pp.1335-1340
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• 2003

In this paper, a single balanced diode Mixer for the homodyne FMCW radar to detect distance and velocity of a vehicle target is designed and implemented using a microstrip line and two schottky barrier beam lead diodes. This mixer is optimally designed to have less a conversion loss within the 100 MHz bandwidth with a little LO injection power and a higher LO isolation as soon as possible through the embedded electrical length of microsrtrip line placed between the coupler and diode matching, considering together LO matching condition. The measured results show 6 dB of conversion loss, 23 dB LO/RF isolation and 3 dBm of input 1l dB, respectively.

• Journal of the Korean Institute of Telematics and Electronics
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• v.27 no.2
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• pp.39-46
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• 1990

In this paper, Rectangular microstrip patch array antenna. relative current of which is distributed to 1:2:2:1, is designed and fabricated by using Tschebyscheff's polynominal expression and is verified by theoretical analysis and experiment. Seeking for more accurate resonant frequency, an equivlent network, which is consisted including feed line and power distribution line, is analyzed by using the analysis method of transmission line mode. As a result of their comparison and examination, such as resonant frequency by fringing effects, by return loss, by experiment, it is conformed that errors are not barely and agreed with each other. is also agreed with a measured values.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.38 no.1
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• pp.30-36
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• 2001

0.35 ${\mu}{\textrm}{m}$-gate AlGaAs/InGaAs PHEMTs have been fabricated using electron beam lithography. DC and AC characteristics of PHEMTs having different gate widths and number of fingers were measured at various bias conditions. An MIMIC power amplifier operating at 35 GHz has been designed and fabricated using passive element library. The power amplifier showed gain and input reflection coefficient of 7.9 ㏈ and -15 ㏈, respectively, at 27.6 GHz.