• Proceedings of the Korea Electromagnetic Engineering Society Conference
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• 2001.11a
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• pp.213-217
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• 2001

본 논문에서는 CPW 구조를 이용하여 60 GHz 무선 시스템 응용을 위한 V-band용 하향 주파수 혼합기를 설계 및 제작하였다. 하향 주파수 혼합기의 설계 및 제작에 있어서 GaAs PHEMT(Pseudomorphic high electron mobility transistor)를 기반으로 하였으며, 회로설계를 위해 coplanar waveguide(CPW) 라이브러리를 구축하여 이용하였다. 제작된 하향 주파수 혼합기의 변환이득은 국부발진주파수(LO) 입력이 8 dBm일 때 -8.5 dB의 최대 변환이득 특성을 얻었으며 Pl dB는 -3.3 dBm을 얻었다. 제작된 회로의 칩 크기는 1.6$\times$l.6 $\textrm{mm}^2$ 이다.

• Journal of the Korean Institute of Navigation
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• v.19 no.2
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• pp.107-113
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• 1995

Since the most of the mal-functions in the industrial equipments controlled by processors have been occured by the Electrical Fast Transient(EFT), the International Electrotechnical Commision(IEC) prepare the dummy signal to test the immunity level of the equipments controlled by processors and recommend it for the measuring. In this paper, the defined dummy EFT signal by IEC are analyzed by the spectrum analyzer in the frequency domain and studied the developed countermeasuring parts. The new developed parts are consist of the feedthrough capacitors ( $C_y$ type ) in the input and materials with high permeaility which was wound or inserted in the second layer of the Power Cable in order to increase Common Mode inductance. And it is compared inserted Permalloy to material with high permeability increasing Common Mode inductance. We could gotten a excellent insertion loss on the wide band against EFT signal. Especially, we confirm that countermeasuring Power Cable have been an excellent dynamic characteristics in computer system above the 3.6Kv. This new parts could be effectively used for industrial, MIL, and medical equipments to reduce a mal-functions on the site. Furthermore, these parts also have a good characteristics for EMI countermeasuring over the 60MHz up to several GHz band, they are also expected to be used for all kind of EMS test with IEC801-2, 3, 5 and 6 on the power distributed line.

• Information and Communications Magazine
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• v.25 no.3
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• pp.60-63
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• 2008

WiBro 기술이 IEEE 802.16e 표준으로 채택되기까지의 과정은 크게, 국내표준이 우선되던 단계(2002. 11$\sim$2004. 6.)와 IEEE 802.16을 중심으로 국제표준에 힘쓰던 단계(2004. 7.$\sim$2005. 12.)으로 나누어서 볼 수 있다. 첫 번째 단계는 정부에 의한 비활성화된 2.3-2.4 GHz WLL용 주파수 대역의 회수 및 활용을 위한 WiBro 개념의 도입부터, ETRI를 중심으로 한 연구개발 프로젝트의 추진, TTA 내의 PG302 프로젝트그룹의 결성 및 적극적 국내표준화 활동을 통한 표준초안의 개발까지의 과정에 해당된다. 이 과정에서 개념의 창출부터, 요구사항의 정의, 방식의 선정, 규격 초안의 개발까지의 과정을 독자적으로 수행하였으며, 독자 기술에 의한 국내 기술의 개발 및 표준화를 바탕으로 국제표준화를 추진하기 위한 꿈과 도전의 시기였다고 할 수 있다. 두 번째 단계는 규모의 경제의 실현 및 국제표준의 중요성에 대한 인식에 따른 IEEE 802.16e를 중심으로 한 국제표준화의 추진을 통한 표준 IPR의 확보 및 시험 규격 등 제반 규격의 정비 등 세계 최초 상용화를 위한 표준선도의 시기였다고 할 수 있다. 나름 아쉬움이 없는 것은 아니나, 우리 힘으로 여러 난관들을 극복하고 상용화 및 IMT-2000 국제표준채택을 통한 세계화의 실현 등을 위한 성숙의 시기였다고 할수 있다. 이제 4세대 이동통신 표준화에서도 대한민국이 주도적인 역할을 수행해야 할 때이다. 좀 더 우리의 역량을 결집하고 발휘할 수 있도록 지혜를 발휘하여야 한다.

• Proceedings of the KSRS Conference
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• 2007.10a
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• pp.633-636
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• 2007

The objective of this study is to measure backscattering coefficients of paddy rice using L, C, X-bands scatterometer system during a rice growth period. The measurement was conducted at an experimental field located in National Institute of Agricultural Science and Technology (NIAST), Suwon, Korea. The rice cultivar was a kind of Japonica type, called Chuchung. The scatterometer system consists of dual-polarimetric square horn antennas, HP8720D vector network analyzer (20MHz ${\sim}$ 20GHz), RF cables, and a personal computer that controls frequency, polarization and data storage. The scatterometer system is calibrated using a calibration kit (3.5mm, 85052D). The backscattering coefficients were calculated by applying radar equation for the measured at incidence angles between $20^{\circ}$ and $60^{\circ}$ for four polarization (HR, VV, HV, VH), respectively, and compared with rice growth data such as plant height, stem number, biomass, dry weight and LAI that were collected at time of each scatterometer measurement simultaneously.

• Journal of electromagnetic engineering and science
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• v.6 no.3
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• pp.189-195
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• 2006

In this paper, the derivation of the protection ratio for the digital microwave system with diversity is newly suggested for a basic guidance of initial planning for frequency coordination, and computational results are presented for an actual radio frequency band. The net filter discrimination has been also examined to see the effect of the adjacent channel protection ratio caused by adjacent channel interference. In addition, the protection ratios for the space or frequency diversity system are analyzed in terms of diversity improvement factors to find out an equivalent allowable noise-to-interference ratio (N/I) from degraded fade margin. According to results for 6.2 GHz system, with the space diversity of 25 m distance between antennas or the frequency diversity of ${\Delta}f/f=0.05$, under 64-QAM and 60 km at BER $10^{-6}$, the protection ratio can be greatly reduced in comparison to the non-diversity system. So, assuming that only the same protection ratio as the non-diversity system is kept, it is shown that the system with diversity may get more interference level of N/I allowing from 9.0 to - 5.9 dB or from 6.0 to - 4.3 dB for the space or frequency diversity. In consequence, it is concluded that the diversity system is more robust or tolerable for interferences or fades, which may play an important role in overcoming N/I to some extent.

• Journal of electromagnetic engineering and science
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• v.14 no.2
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• pp.54-60
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• 2014

A systematic design for asymmetric coupled-section Marchand baluns is presented. Asymmetrically coupled transmission lines in multilayer configuration are exploited for constructing Marchand baluns. Design equations for characteristic impedance and electrical length of asymmetrical coupled transmission lines are derived for establishing a systematic design procedure. Novel Marchand balun based on these design equations is composed of two identical asymmetrical coupled transmission lines. However, contrary to the general conventional design approach where ranges for characteristic impedances of coupled lines are ambiguously capitalized, values for characteristic impedance and length are explicitly expressed. Our approach is fundamentally different from the design method using coupling coefficients where solution for coupling coefficient is inherently restricted. To verify the proposed method, one design example is performed for wideband Marchand balun in multilayer configuration, and is fabricated for verifying the design procedure proposed. Maintaining the return loss more than 10 dB, the bandwidth is measured from 0.43 to 1.0 GHz, where $S_{21}$ and $S_{31}$ show better than -4 dB. The measured phase and amplitude imbalances illustrate 0.5 dB and ${\pm}5^{\circ}$, respectively.

• Journal of Ocean Engineering and Technology
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• v.20 no.4 s.71
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• pp.76-82
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• 2006

The large-eddy simulation(LES) technique, based an a message passing interface method(MPI), was applied to investigate the turbulent flaw phenomena around a ship. The Smagorinski model was used in the present LES simulation to simulate the turbulent flaw around a ship. The SPMD(sidsngle program multiple data) technique was used for parallelization of the program using MPI. All computations were performed an a 24-node PC cluster parallel machine, composed of 2.6 GHz CPU, which had been installed in the Advanced Ship Engineering Research Center(ASERC). Numerical simulations were performed for the Wigley hull, and the Series 60 hull(CB=0.6) using 1/4-, 1/2-, 1- and 2-million grid systems and the computational results had been compared to the experimental ones.

• ETRI Journal
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• v.36 no.6
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• pp.924-930
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• 2014

This paper presents a $0.13{\mu}m$ CMOS 3-level envelope delta-sigma modulation (EDSM) RF signal generator, which synthesizes a 2.6 GHz-centered fully symmetrical 3-level EDSM signal for high-efficiency power amplifier architectures. It consists of an I-Q phase modulator, a Class B wideband buffer, an up-conversion mixer, a D2S, and a Class AB wideband drive amplifier. To preserve fast phase transition in the 3-state envelope level, the wideband buffer has an RLC load and the driver amplifier uses a second-order BPF as its load to provide enough bandwidth. To achieve an accurate 3-state envelope level in the up-mixer output, the LO bias level is optimized. The I-Q phase modulator adopts a modified quadrature passive mixer topology and mitigates the I-Q crosstalk problem using a 50% duty cycle in LO clocks. The fabricated chip provides an average output power of -1.5 dBm and an error vector magnitude (EVM) of 3.89% for 3GPP LTE 64 QAM input signals with a channel bandwidth of 10/20 MHz, as well as consuming 60 mW for both channels from a 1.2 V/2.5 V supply voltage.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.11 no.6
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• pp.169-174
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• 2012

Electromagnetic interference(EMI) shielding effectiveness(SE) was investigated in of woven fabric made of epoxy/copper-nickel fabrics and nickel coated carbon fiber reinforced acrylonitrile-butadiene-styrene(ABS) composites. The coaxial transmission line method was used to measure the EMI shielding effectiveness of the composites. We designed and constructed a measuring system, consisting of a network analyzer and a device that plays the serves as a sample holder and at the same time as a transmission medium of the incident electromagnetic wave. The measurement of SE were carried out frequency range from 100MHz to 2GHz. It is observed that the SE of the composits is the frequency dependent increase with the increase in nickel coated carbon fibre volume fraction. The nickel coating with 20wt% ABS composite was shown to exhibit up to 60dB of SE. The result that nickel coated carbon fibre ABS composite can be used for the purpose of EMI shielding as well as for some microwave applications.

• Journal of electromagnetic engineering and science
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• v.17 no.2
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• pp.65-70
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• 2017

The design and implementation aspects of a new single-balanced mixer for ultra-wideband (UWB) applications are presented in this study. The proposed mixer utilizes a miniaturized UWB ring coupler as a balun, consisting of a pair of in-phase and inverted-phase transitional structures. The well-balanced UWB performance of the ring coupler, aside from the optimized diode matching, results in improved conversion loss and inter-port isolations for a wide bandwidth. The size of the implemented single-balanced diode mixer is reduced to about 60% of the area of the conventional single-balanced ring diode mixer. The measured results of the proposed mixer exhibit an average conversion loss of 7.5 dB (minimum 6.7 dB) and a port-to-port isolation of greater than 18 dB over a UWB frequency range of 3.1-10.6 GHz. The measured results agree well with the simulated results.