• The Journal of Korean Institute of Communications and Information Sciences
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• v.13 no.2
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• pp.182-191
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• 1988

A log periodic microstrip array antenna using direct coupling feeder is designed at the frequency 7.2-12.4GHz. Transmission line analysis method was used for the design of each antenna element in consideration of the effects of dielectric and conductor loss and the discontinuity, also the optimized feeding points were obtained for the impedance matching between a main transmission line and each antenna element. It is shown that the measured VSWR was less that 2.4 at the frequency 7.2-12.4GHz, and 53% bandwidth was achived.

• Proceedings of the KIEE Conference
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• 2001.07c
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• pp.1858-1860
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• 2001

최근에 특정 주파수 대역에서 전자기파의 전파를 억제하는 주기 구조인 PBG(Photonic Band Gap) 구조에 대한 연구가 활발히 이루어지고 있다. 본 논문에서는 마이크로스트립 선로에서 사용될 수 있는 새로운 PBG cell을 제안하였다. 제안된 구조는 단일 cell 만으로도 대역저지 특성을 얻을 수 있고, cell의 치수를 조절하여 저지대역을 조절할 수 있다. 또한, 방사 효과 등으로 인한 손실을 고려하여 정확한 등가 모델링을 할 수 있다. 본 논문에서는 제안된 구조를 마이크로스트립 패치안테나의 하모닉 억제를 위해 사용하여 그 유용성을 입증하였다.

• Proceedings of the KIEE Conference
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• 2015.07a
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• pp.1032-1033
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• 2015

차세대 친환경 송전기술로 세계적으로 주목되고 있는 HVDC는 유전체 손실이 없으며 안정도가 좋아 송전용량이 크고 송전효율이 높으며 선로의 절연계급이 낮으므로 경제적이고, 주파수가 다른 계통과 비동기 연계가 가능하여 고효율 녹색기술로 크게 각광받고 있다. 본 논문에서는 HVDC 송전선로의 핵심 절연물인 가공절연디바이스에 대한 직류 절연 설계 및 평가기술을 연구개발하고, 이를 바탕으로 핵심 절연물인 HVDC 500kV 급 폴리머애자를 개발한 시제품에 대한 공인시험기관의 개발시험을 통하여 성능평가를 완료한 다음, HVDC 500kV가 실제로 가압되는 실증선로에서 1년간의 실증시험을 수행하고, 실증을 완료한 시료에 대하여 성능확인을 통한 신뢰성 확보를 목표로 개발을 진행하여 성공적인 결과를 거둔 내용에 대하여 설명하고자 한다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.18 no.11
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• pp.1663-1668
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• 1993

An X-band contiguous band diplexer is realized by using asymmetrical coupled microstrip lines. The design is based on the singly terminated low pass prototype filter and optimized by using SuperCompack. The designed channel 1 and channel 2 bandwidth is 22%, and 18% respectively, where the center frequency is 9,11 GHz. The measured results of the fabricated diplexer are in good agreement with the designed ones, but the measured insertion loss is slightly highier(0.5dB) than those of the designed value.

• Journal of Energy Engineering
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• v.11 no.4
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• pp.291-298
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• 2002

This paper presents a practical methodology that can analysis power flow and marginal factors based on optimal power flow (OPF) of power systems under restructuring environment. First of all, to evaluate useful marginal factors, nonlinear optimization problems of minimum fuel cost and minimum transmission loss are formulated and solved by nonlinear primal-dual interior point method. Here, physical constraints considered in the optimization problems are the limits of bus voltage. line overloading, and real & reactive power generation. Also, an evaluation method of marginal price and marginal transmission loss is presented based on sensitivities calculated by the two OPF problems. Especially, to reflect the cost related to transmission losses in the competitive electricity market, an analysis method of MLF (marginal loss factor) is pro-posed. Numerical results on IEEE RTS 24 show that the proposed algorithm is effective and useful for analysis of power market price.

• 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 Illuminating and Electrical Installation Engineers
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• v.17 no.6
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• pp.31-38
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• 2003

Among mitigation techniques for electric and magnetic field (EMF) from an overhead transmission line a passive loop is a way that can be cheap and easily installed on the existing towers and have a satisfactory effect as well. However current induced in the passive loop causes transmission power loss and the phase imbalance increases since geometrical asymmetry of the transmission lines becomes larger. So in order to evaluate the power loss and the phase imbalance due to a passive loop, this paper represent a 345[kV] 1-circuit flat type transmission line as asymmetrical 3-phase distributed parameter line model where the effect of a passive loop is embedded in the line parameters, and then formulates differential equations. By solving these equations voltages and currents of each phase at receiving end become known. We find out that power losses occur differently at each phase and positive sequence component decreases at receiving end while negative sequence component increase. In general phase imbalance due to a passive loop is slight, but it increases in proportional to the induced current and length of section where the passive loop is installed. Thus the phase imbalance should be included in terms of cost for introducing a passive loop.

• Journal of the Institute of Electronics and Information Engineers
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• v.50 no.1
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• pp.174-179
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• 2013

This paper presents a capacitor loaded tunable bandpass chip filter using multiple split ring resonators (MSRRs) with two transmission zeros. To obtain high selectivity and minimize the chip size, asymmetric feed lines are adopted to make a pair of transmission zeros located on each side of passband. Compared with conventional filters using cross-coupling or source-load coupling techniques, the proposed filter uses only two resonators to achieve high selectivity through a pair of transmission zeros. In order to optimize selectivity and sensitivity (insertion loss) of the filter, the effect of the position of asymmetric feed line on transmission zeros and insertion loss is analyzed. The SOI-CMOS switched capacitor composed of metal-insulator-metal (MIM) capacitor and stacked-FETs is loaded at outer rings of MSRRs to tune passband frequency and handle high power signal up to +30 dBm. By turning on or off the gate of the transistors, the passband frequency can be shifted from 4GH to 5GHz. The proposed on-chip filter is implemented in 0.18-${\mu}m$ SOI CMOS technology that makes it possible to integrate high-Q passive devices and stacked-FETs. The designed filter shows miniaturized size of only $4mm{\times}2mm$ (i.e., $0.177{\lambda}g{\times}0.088{\lambda}g$), where ${\lambda}g$ denotes the guided wave length of the $50{\Omega}$ microstrip line at center frequency. The measured insertion loss (S21)is about 5.1dB and 6.9dB at 5.4GHz and 4.5GHz, respectively. The designed filter shows out-of-band rejection greater than 20dB at 500MHz offset from center frequency.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.17 no.3 s.106
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• pp.249-258
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• 2006

In this letter, we propose a novel printed helix antenna for RFID reader in UHF band. The printed strip line of the antenna is first wound up outside a polygonal shaped layer and then the winding continues on an inner layer to control the overall gain and the radiation pattern. In addition, the winding pitch angles on each layer have either negative or positive values resulting in the broad CP bandwidth. The detail structure of the antenna was optimized using Pareto genetic algorithm(GA), so as to obtain excellent performances for RFID reader antennas. The optimized two-layered polygonal helix was fabricated on the cardboard of a flexible substrate and the performances were measured and compared with the simulations. The fabricated antenna was made up of copper tape which can adhere to a flexible cardboard and had 21.4 % matching bandwidth, 31.9 % CP bandwidth, readable range of $5.5m^2$ with kr=3.2. Also based on the current distribution of the strip line of the antenna and sensitivity of the antenna bents points, we confirmed that the antenna has the quarter-wave transformer near the feed for the broad matching bandwidth and radiates the traveling wave for the broad CP bandwidth using the bent strip line.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.18 no.7
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• pp.796-808
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• 2007

In this paper, two novel compact microstrip bandstop filters using complimentary split ring resonators(CSRRs) and spiral resonators is proposed. The first one is the bandstop filter using an array of CSRRs etched on the center line of a microstrip. The bandstop is due to the presence of negative effective permittivity and positive permeability near resonant frequency which prevent the wave propagation. The second on is the bandstop filter using an array of spiral resonators etched on the center line of a microstrip. The bandstop is due to the self-resonance of spiral circuit. We have achieved controllable resonance frequency and bandwidth, super compact dimension, low insertion losses in the passband and high level of rejection in the stopband with sharp cutoff. The electrical sizes of two proposed filter are very small. Additionally, they can be easily fabricated and compatible with MMIC or PCB technology.