• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2002년도 International Meeting on Information Display
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• pp.1039-1040
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• 2002

For the I-V modeling of sharp tip arrays and nanostructured planar emitters, we propose a new and much practical I-V relation including tip height and radius by considering a statistical distribution of tip radius. Frequently observed nonlinearity of Fowler-Nordheim plot for sharp tip and tip arrays was successfully simulated and then, an application example was provided to extract relevant emission-governing parameters of sharp tip.

• Journal of Korean Vacuum Science & Technology
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• 제3권1호
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• pp.59-65
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• 1999

There has been an interest to develop an efficient, compact microwave device using field-emitter-arrays (FEA)-based cathode. Toe valuate the optimum device-efficiency in a compact size, the propagation properties of the premodulated electron beam for the FEA-based cathode is studied in detail by the computer simulation using a PIC code, MAGIC. For the premodulated electron beam whose phase of the energy leads the phase of the current by $\pi$/2, the amplitude of the downstream current modulation can be kept as high as the initial modulation level. Using the beam parameters with the beam voltage of 6kV and the current of 2.0A, 30% of efficiency is predicted when the quality factor of 800 is chosen. the device length is reduced about twice compared with that of the conventional device. The design of practical planar cathode is carried out to meet the minimum diameter of the electron beam as 0.5 mm.

• 한국재료학회:학술대회논문집
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• 한국재료학회 2012년도 춘계학술발표대회
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• pp.54.2-54.2
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• 2012

Solid-state dewetting of thin films is a process through which continuous solid films decay to form islands. Dewetting of thin films has long been a critical issue in microelectronics and much effort has been made to prevent the process and enhance the stability of films. On the other hand, dewetting has also been purposely induced to create arrays of particles and other structures for applications, including plasmonic structures and catalysts for growing nanotube and nanowire. We have investigated ways of producing regular structures via templated dewetting of thin films. Mainly, two different approaches have been used in our works to template dewetting of thin films: periodic topographical templating and planar patterning of epitaxially-grown films. Dewetting of topographically-patterned thin films results in the formation of nanoparticle arrays with spatial and crystallographic orders. Morphological evolution during templated-dewetting of single crystal films occurs in deterministic ways because of geometric and crystallographic constraints, and leads to the formation of regular structures with smaller sizes and more complex shapes than the initial patches. These results will be reviewed in this presentation.

• ETRI Journal
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• 제40권5호
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• pp.570-581
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• 2018

This work analyzes the performance of implementable detectors for the multiple-input multiple-output (MIMO) orthogonal frequency division multiplexing (OFDM) technique under specific and realistic operation system conditions, including antenna correlation and array configuration. A time-domain channel model was used to evaluate the system performance under realistic communication channel and system scenarios, including different channel correlation, modulation order, and antenna array configurations. Several MIMO-OFDM detectors were analyzed for the purpose of achieving high performance combined with high capacity systems and manageable computational complexity. Numerical Monte Carlo simulations demonstrate the channel selectivity effect, while the impact of the number of antennas, adoption of linear against heuristic-based detection schemes, and the spatial correlation effect under linear and planar antenna arrays are analyzed in the MIMO-OFDM context.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2000년도 ITC-CSCC -1
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• pp.163-166
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• 2000

The design, numerical simulation, and an experimental implementation of two-element cross-shaped microstrip line-fed printed slot array antenna for IMT-2000 at the 2.0 GHz band is presented in this paper. The proposed antenna with relative permittivity 4.3 and thickness 1.0mm is analyzed by the Finite-Difference Time-Domain (FDTD) method. It was shown that the measured 2.0 VSWR bandwidth of one-element microstrip slot antenna is from 1.42 GHz to 2.69 GHz, which is approximately 61.8% and that of two-element microstrip slot array antenna is from 1.42 GHz to 2.56 GHz, which is approximately 57.3% And it was shown that the measured gain of one-element microstrip slot antenna is 2.75 dBi and that of two-element microstrip slot antenna is 4.75 dEi. The antennas were fabricated and tested. The measured results are in good agreements with the FDTD results.

• 한국음향학회지
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• 제22권6호
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• pp.496-504
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• 2003

본 논문에서는 유전자 알고리즘을 이용하여 빔 패턴 오차의 허용범위를 만족하는 개별소자의 허용오차를 분석하였다. 기존의 수치적 통계방법은 배열소자의 개수증가에 따라 계산량이 증가하는 문제점이 있고 이를 보완하기 위해 제안된 Monte-Carlo 방법은 낮은 정밀도와 빔 패턴 합성으로의 확장이 어렵다는 한계점을 가지고 있어 본 논문에서는 이러한 단점을 극복하기 위해 유전자 알고리즘을 이용한 소나 배열 소자의 허용오차 분석법을 제안하였다. 제안된 알고리즘을 이용하여 1차원과 2차원 배열에서 주어진 빔 패턴 오차 허용범위를 만족하는 각 소자별 허용오차 범위를 분석하였고 모의실험을 통하여 소나 배열 소자의 허용오차 범위가 타당함을 검증하였다.

• 전기전자학회논문지
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• 제26권1호
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• pp.129-132
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• 2022

본 논문에서는 위상배열안테나의 부엽레벨을 최소화할 수 있는 부배열 시스템 구조의 최적화에 관한 기술을 제안하였다. 제안된 배열안테나 구조의 최적화는 6개의 육각배열을 한 개의 부배열과 육각 부배열의 육각형 배열 구조를 이용하여, 부배열의 배열간격과 부배열 사이의 배열 간격을 조절하여, 전체 위상배열안테나 시스템의 방사패턴을 최적화하였다. 제안된 기술은 2차원 평명배열안테나 시스템에 비하여, 24.3 dBi의 이득과 8.46도의 반치각은 변화없이 유지하며, 오직 x축과 y축 방향으로 각각 -3.4 dB와 -6.5 dB를 감소시켰다.

• ETRI Journal
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• 제27권3호
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• pp.250-256
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• 2005

A novel planar polarization-agile microstrip subarray is proposed and its performance assessed by a thorough numerical investigation. The subarray consists of five square patches with a central element, directly coupled to a pair of microstrip feed lines by a cross-shaped aperture, which spreads the power outwards to the other patches through a network of suitable connections. By properly exciting the antenna at its input ports, any kind of polarization of the radiated field can be accomplished with fairly low cross-polarization levels. Moreover, since only two feed lines are required to drive the whole subarray, polarization agility is simply and attractively achieved by a single phase-shift circuit. The design concept is described and the results of the analyses and simulations performed by two completely independent full-wave approaches are presented and discussed.

• Coupled systems mechanics
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• 제8권6호
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• pp.537-553
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• 2019

In this paper we present geometrically exact Kirchhoff's initially curved planar beam model. The theoretical formulation of the proposed model is based upon Reissner's geometrically exact beam formulation presented in classical works as a starting point, but with imposed Kirchhoff's constraint in the rotated strain measure. Such constraint imposes that shear deformation becomes negligible, and as a result, curvature depends on the second derivative of displacements. The constitutive law is plasticity with linear hardening, defined separately for axial and bending response. We construct discrete approximation by using Hermite's polynomials, for both position vector and displacements, and present the finite element arrays and details of numerical implementation. Several numerical examples are presented in order to illustrate an excellent performance of the proposed beam model.

• 대한전자공학회논문지
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• 제23권6호
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• pp.936-943
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• 1986

The lasing wavelengths and gain characteristics of the array modes of channel-substrate planar(CSP) lasers are presented. The gain values of array modes are determined from the complex coupling coefficients calculated using the fields of neighborig elements of the array. The computations show that for index guided lasers which have fields that are almost real valued, or have only slight phase curvature, the highest order array mode will have preferred oscillation. The inphase or fundamental mode, which produces only one major lobe in the far-field radiation pattern, will have the lowest modal gain of all array modes. Some of the devices discussed have modal gain differences of less than 10 cm**-1 between the highest and fundamental modes. For optical field confinement factors of about 20%, this gain difference corresponds to avtive layer gains of approximately 50**-1.