• The Journal of the Korea institute of electronic communication sciences
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• v.16 no.1
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• pp.9-18
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• 2021

The 5G communication system employs the millimeter wave with the extremely high frequency. Since the high frequency signal has the strong straightness, the beamforming technology based on the multiple base stations is required for services covering wide range. The beamformer needs the angle-of-arrival(AOA) information of the signal incident to the antenna, and it is generally estimated through the high resolution AOA estimation algorithm such as Multiple Signal Classification (MUSIC) or Estimation of Signal Parameters via Rotational Invariacne Technique (ESPRIT). Although various antenna array shapes can be employed for the beamformer, a single shape (square, circle, or hexagonal) is typically utilized. In this paper, we introduce a transmitting/receiving beamforming system based on the combined array antenna with square and circular shapes, which is proper to various frequency signals, and evaluate its performance. For evaluating the performance of the proposed beamforming system based on the combined array antenna, we implement the computer simulation employing various scenarios.

• Proceedings of the Optical Society of Korea Conference
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• 2009.02a
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• pp.329-330
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• 2009

• Proceedings of the Korea Crystallographic Association Conference
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• 2002.11a
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• pp.37-37
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• 2002

반도체 소자의 집적도는 지난 수십년간 끊임없이 증가해 왔다. 이러한 추세가 계속 된다면 앞으로 수년 이내에 100 nm 이하의 선폭을 갖는 집적회로가 출현하게 될 것이다. 수-수십나노 미터 크기의 구조가 이와같이 제품에 실제로 응용되려면 수 나노미터의 길이에 대한 표준 측정 기술이 확보되어야 하고 이 측정 기술을 서로 비교 평가 할 수 있는 표준 물질이 필요하다. 본 연구에서는 표준 물질로 사용될 수 있는 1차원 나노 구조를 제작하였다. 제작된 1차원 나노 구조는 선폭이 90 nm인 네모난 산과 네모난 우물들이 반복적으로 나타나는 형태를 갖는다. 나노 구조가 제작된 총영역은 0.1 ㎜ × 0.1 ㎜의 정사각형 영역이다. 1차원 나노 구조는 전자빔 석판 기술을 이용하여 제작하였다. 균일한 구조를 만들기 위해 전자 빔의 도즈량 최적화, 전자 빔의 비대칭성의 영향 최소화, 에칭 공정 변수 최적화 등 공정 조건을 선별하는 연구를 하였다. 본 연구에서 제작된 1차원 나노구조는 전자현미경의 배율 보정, Scanning Probe Microscope의 이미지 보정 등에 사용될 수 있을 것이다.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.441-441
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• 2010

Hyperthermal neutral beam (HNB)은 박막 성장에 필요한 에너지와 반응 입자들을 동시에 공급할 수 있기 때문에 특히, 저온에서 박막을 성장시킬 때 매우 유용하다. 이와 같은 목적으로 race track 형태의 자기장 구조를 갖고 있는 2.45 GHz electron cyclotron resonance (ECR) plasma를 이용한 HNB 소스를 개발하였다. HNB 소스에서 인출되는 입자들은 중성 입자 뿐만 아니라 이온이나 전자와 같은 하전 입자들로 구성되어 있다. 그러나 양질의 HNB를 얻기 위해서는 하전 입자들의 구성 비율을 최소화해야 한다. HNB 소스는 하전 입자의 구성 비율을 1 % ($1{\mu}A/cm^2$) 이하가 되도록 설계되었다. 이것을 위해서 영구 자석의 자기장을 이용한 plasma limiter를 설계하였다. 대부분의 전자는 limiter 앞에 형성된 자기장의 구조와 반응하여 주로 gradient B drift와 curvature drift를 통하여 차단되고, 이온은 로렌츠 힘을 받아 빔 축으로 부터 벗어나도록 하였다. Limiter의 특성을 연구하기 위해서 정전탐침을 limiter에서 빔 축 방향으로 이동시키면서 I-V 곡선과 이온 포화 전류 및 전자 포화 전류를 측정하였다. 측정 결과를 바탕으로 plasma limiter의 성능을 검증하였고 문제점을 논의하였다.

• Korean Journal of Optics and Photonics
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• v.24 no.5
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• pp.224-230
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• 2013

Laser Lift-Off (LLO) is a process that removes a GaN or AIN thin layer from a sapphire wafer to manufacture vertical-type LEDs. It consists of a light source, an attenuator, a mask, a projection lens and a beam homogenizer. In this paper, we design an attenuator and a projection lens. We use the 'ZEMAX' optical design software for analysis of depth of focus and for a projection lens design which makes $7{\times}7mm^2$ beam size by projecting a beam on a wafer. Using the 'LightTools' lighting design software, we analyze the size and uniformity of the beam projected by the projection lens on the wafer. The performance analysis found that the size of the square-shaped beam is $6.97{\times}6.96mm^2$, with 91.8 % uniformity and ${\pm}30{\mu}m$ focus depth. In addition, this study performs dielectric coating using the 'Essential Macleod' to increase the transmittance of an attenuator. As a result, for 23 layers of thin films, the transmittance total has 10-96% at angle of incidence $45-60^{\circ}$ in S-polarization.

• The Journal of the Acoustical Society of Korea
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• v.18 no.7
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• pp.75-79
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• 1999

The beam patterns of source array and changes in the far-field signatures are compared and analyzed each other in order to identify the seismic capability affected by the misfired source at the multi-channel seismic source array. In the primary pulse amplitude of far-field signature, the 66% of seismic capacity are sustained if approximately 40% of source are misfired among whole gun volume. When the sources with the same distances are misfired at the 154㎐, the beam width of the long- and wide-array which is identical regardless of arraying pattern. The beam width has a tendency to narrow now from 41 to 34 according to increase the volume of misfired source at the long-array beam pattern. Therefore, the source array of small volume are suitable for the shallow seismic survey because of producing adequate beam patterns with narrow beam width.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.29 no.1
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• pp.32-35
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• 2018

Massive multiple-input multiple-output (MIMO) transmission is an essential technique for achieving the high bandwidth efficiency required in 5G mobile communication systems. Various forms of arrays can be used as the number of antenna elements increases for massive MIMO transmission. In this letter, we propose a beamforming algorithm applicable to multiuser MIMO transmission using uniform circular arrays. By employing quasi-orthogonal beam pairs obtained from the inter-beam correlation information, we minimize inter-user interference and evaluate the resulting performance gain.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.4A
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• pp.318-324
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• 2011

In this paper, three coordinated random beamforming (CRBF) schemes are analyzed in a two-cell symmetric interference channel. A simple partial coordination of RBF with base station selection (BSS) is shown to achieve the same average sum rate performance of CRBF with joint encoding (JE). To improve the sum rate performance further, we also propose a transmission mode selection (TMS) between the BSS and JE which is shown to have additional sum rate gain for the large number of users. Simulation results verify the eectiveness of the proposed CRBF schemes and accuracy of the proposed analysis.

• Korean Journal of Optics and Photonics
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• v.16 no.5
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• pp.450-455
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• 2005

We have studied on operational characteristics of the nitrogen laser with sliding discharge and longitudinal excitation. We could observe radiation of nitrogen laser excited by a sliding discharge along the surface of a dielectric. The shape of the beam was a ring type which had 2 mm or 4mm in diameter depending on the sliding discharge tube shape. In this experiment, We show the possibilities to make other shapes of laser beam, for example, rectangle, ellipse, and to excite another gas laser system like an excimer laser.

• The Journal of the Convergence on Culture Technology
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• v.5 no.2
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• pp.381-388
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• 2019

In this paper, we propose a new wireless transport network, which is named as Mobile Xhaul Network(MXN), that is enable to bring cost efficiency of fronthaul, midhaul and backhaul and to make easy installation of 5G Radio Access Network(RAN). For this purpose, we design XDU discovery and xhaul link setup mechanism with MXN architecture and operational procedure. Especially, in this paper, we propose various types of beam discovery mechanisms for mmWave based radio access on XDU and evaluate proposed schemes. The Simulation result shows that threshold based scheme and information based scheme have less than about 50% beam discovery latency compared to full search scheme.