• 한국소음진동공학회논문집
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• 제24권2호
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• pp.93-101
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• 2014

Underwater radiated noise is the key in acoustic stealth performance of modern naval ships. The underwater radiated noise predicted by the hull vibration with radiation efficiency cannot always give the information of radiation pattern which is essential to analyze of detection probability by enemy and to improve the operational performance of the naval ship. The radiation pattern of underwater radiated noise is able to be obtained with radiation efficiency and radiation directional coefficient. In this paper, a new method to extract the radiation efficiency and radiation directional coefficient is suggested and proved with the simulation and experiment by using cylindrical shell of 70 cm diameter in air.

• 한국산업융합학회 논문집
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• 제4권1호
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• pp.35-40
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• 2001

A spectral measurement system for reflection and transmission properties by using an optical fiber and an ellipsoidal mirror was newly developed. The hemispherical reflectance and transmittance spectra of several heating resisting ceramics materials were measured from visible to middle infrared region. The directional characteristics of reflection and transmission were also investigated in consideration of the absorptance. The measured data were analyzed by using a four flux model of radiation transfer, The radiation properties could be estimated by the obtained scattering and absorption coefficient spectra.

• Journal of electromagnetic engineering and science
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• 제19권1호
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• pp.20-30
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• 2019

A wide-band multiple-input multiple-output (MIMO) antenna with dual-band (2.4 and 5 GHz) operation is proposed for premium indoor access points (IAPs). Typically, an omni-directional pattern is used for dipole antennas and a directional radiation pattern is used for patch antennas. In this paper, both antenna types were used to compare their performance with that of the proposed $2{\times}2$ MIMO antenna. We simulated and measured the performance of the MIMO antenna, including the isolation, envelope correlation coefficient (ECC), mean effective gain (MEG) for the IAPs, and the throughput, in order to determine its communication quality. The performance of the antennas was analyzed according to the ECC and MEG. The proposed antenna has sufficient performance and excellent characteristics, making it suitable for IAPs. We analyzed the communication performance of wireless networks using the throughput data of a typical office environment. The network throughput of an 802.11n device was used for the comparison and was conducted according to the antenna type. The results showed that the values of the ECC, MEG, and the throughput have unique characteristics in terms of their directivity, antenna gains, isolation, etc. This paper also discusses the communication performance of various aspects of MIMO in multipath situations.

• 대한조선학회논문집
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• 제53권4호
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• pp.275-281
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• 2016

One of the most important things for quality to meet ship-production schedule is an accuracy control. A ship is assembled by welding through whole production process, so it is important that loss by correction will not happen as much as possible by using some engineering skills like reverse design, reverse setting and margin for thermal shrinkage. These efforts are a quite effective in fabrication stages, but not in erection stages. If a ship block which consists of common steel is exposed to directional solar radiation, its dimensional accuracy will change high as time by its thermal expansion coefficient. Therefore, the measuring work would be often done at dawn or evening even with having a very accurate device. In this study, an FE analysis method is developed to solve this problem. It can change measured data affected by solar thermal distortion to ones not, even though ship-block is measured at an arbitrary time. It will use the time when measuring, the direction of block and the weather record by satellites. It is confirmed by a comparison between measured data of a ship-block and the result by suggested analysis method. Furthermore, a pre-processing system is also developed for fast application of the suggested analysis method.

• 한국정보통신학회논문지
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• 제20권4호
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• pp.691-697
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• 2016

본 논문에서는 UWB 통신 시스템에 적합한 안테나를 제안하였으며, 특정 구간에서 위치 인식에 적합한 특성을 만족하였다. 제안된 테이퍼드 슬롯 안테나는 Ansys사의 HFSS 시뮬레이션 툴을 통하여 최적화 설계되었으며, 유전율 4.5, 손실 탄젠트 0.0035, 두께 1.62 mm를 갖는 Taconic TRF-45 기판으로 제작되었다. 테이퍼드 슬롯 안테나는 주파수 영역에서의 반사계수 및 정재파비, 방사패턴 등을 분석하였다. 제작된 테이퍼드 슬롯 안테나의 임피던스 대역폭은 3.8 ~ 8.9 GHz 대역에서 5.1 GHz 대역폭을 보였으며, 안테나의 E-평면과 H-평면에서 방사패턴은 특정 구간에서 실내 외 위치 인식에 적합한 지향성의 특성을 만족하였다. 안테나 이득은 시뮬레이션에서 6 GHz 대역에서 7.4 dBi이며, 측정 결과는 6 GHz 대역에서 7.6 dBi의 최대 이득을 보인다. 제안된 테이퍼드 슬롯 안테나는 시뮬레이션과 측정 결과는 다소 차이가 있지만 UWB 통신 시스템의 규정을 만족하였다.

• 전자공학회논문지
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• 제54권3호
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• pp.10-14
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• 2017

빠른 측정시간과 간단한 조작 기능의 장점 때문에 전자파 잔향실이 무선기기 성능 측정에 널리 쓰이고 있다. 본 논문에서는 전자파 잔향실 송수신용 및 보정용으로 쓰일 수 있는 10:1 광대역 역원뿔형(inverse conical) 안테나를 제안한다. 기존 전자파 잔향실에서 주로 사용하는 디스콘 안테나는 대역폭 제한으로 인해 복수의 디스콘 안테나를 대역 별로 교체해 가며 측정해야 하는 번거로움이 있다. 제안된 안테나는 빗변에 따라 임피던스가 선형적으로 변하는 역원뿔 구조를 방사체로, 전자파 잔향실의 금속 벽면 구조를 접지면으로 활용해 광대역 임피던스 매칭 및 전방향성 방사 특성을 갖는다. 3차원 전파 시뮬레이션 소프트웨어로 최적화된 안테나 모델을 3차원 프린터를 이용해 제작하여 측정한 결과, 목표 동작주파수 대역인 0.65~7 GHz에서 반사계수가 -10dB 이하, 방사효율이 70% 이상임을 확인할 수 있었다.