• 한국해양공학회:학술대회논문집
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• 한국해양공학회 2000년도 추계학술대회 논문집
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• pp.216-221
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• 2000

This paper deals with the Gain Control in the processing of the underwater acoustic image obtained from side scan sonar(SSS) system. At first, this paper describes the principles of SSS that is a surveying equipment for the underground of the rivers or dams as well as sea floor. Then this paper analyzes the cause and effects of the time varying intensity from the view point of transmission loss and beam pattern. At last, the time varying gain filter that is adopted by the towfish is introduced.

• 한국자동차공학회논문집
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• 제1권2호
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• pp.49-59
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• 1993

A new signal processing technique is applied to four-cylinder spark and compression ignition engines for the diagnosis of power faults inside the cylinders. This technique utilizes two-sided directional power spectra(예S) of complex vibration signals measured from engine blocks as the patterns for engine cylinder power faults. The dPSs feature that they give not only the frequency contents but also the directivity of the engine block motion. For the automatic detection/diagnosis of cylinder power faults, pattern recognition method using multi-layer neural networks is employed. Experimental results show that the sucess rate for diagnosis of cylinder power faults using dPSs is higher than that using the conventional one-sided power spectra. The proposed technique is also tested to check the robustness to the sensor position and the engine rotational speed.

• 소음진동
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• 제10권1호
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• pp.123-128
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• 2000

This paper describes the optimization of the hexagonal array transducer using finite element method. The transducer consists of the disc type sensors. Three dimensional beam patterns of each element and the array transducer are analysed using the finite element code ATILA. Beam patterns were analyzed for the disc type transducer. To optimize beam patterns of the array transducer, Chebyshev polynomial weight is applied to each element. In case of applying optimized weight, a 30 degree width beam pattern is presented at 10kHz. This paper also includes the effect of rubber filling material instead of using the water inside the transducer array.

• 한국위성정보통신학회논문지
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• 제8권4호
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• pp.30-36
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• 2013

최근 미디어 컨텐츠 산업의 세계화로 예술분야에 다양한 활동이 이루어지고 있으며, 이러한 예술분야의 하나인 음향에서 스피커의 중요성은 매우 높다. 스피커의 지향 특성은 음을 방사한 경우에 어느 특정 방향으로 방사되는 특성을 말하며, 공간에서 사용되는 스피커의 가장 중요한 특성중 하나이다. 현재 사용되고 있는 라우드스피커(loudspeaker, 이하 스피커)의 지향 특성을 모든 주파수에서 동일하게 유지되도록 설계하는 것은 음파의 길이와 혼(horn)이나 트랜스듀서(transducer)의 크기 때문에 어려운 문제이다. 이에 본 논문에서는 전기음향 설비에 있어서 실내 음향 특성에 영향을 미치는 전대역 스피커의 저주파수 지향 특성을 개선하기 위한 그레디언트 배열(gradient array) 방법을 제안하였다.

• 수산해양기술연구
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• 제41권3호
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• pp.207-212
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• 2005

Dual frequency acoustic pinger(AP) was manufactured to reduce study effect by long-term use of developed single frequency AP to prevent cetacean bycatch. Directivity characteristic of transducer was the omnidirectional pattern which showed less than ${\pm}3dB$ the change range of sensitivity on the beam pattern of right and left. Source power level(SPL) was 1384311pa with epoxy window before casing however after casing 1170B11Pa at sea. Dual frequency Af was tested to identify the avoidance behavior of bottlenose dolphin by its working. However the efficiency of dual frequency AP about the study effect was verified experiment repeatedly using single and dual frequency AP.

• 한국음향학회지
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• 제41권6호
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• pp.637-646
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• 2022

임의의 곡면 배열에서 단위 빔 형성에 사용되는 부배열은 조향 방위마다 기하학적 형상이 다르다. 이 때문에 조향 방위 별 부배열의 빔 패턴은 항상 균일하지 않다. 본 논문에서는 볼록 최적화를 이용한 빔 형성 기법을 곡면 배열에 적용하고, 조향 방위별 빔 성능의 균일성이 향상되는 것을 보였다. 시뮬레이션은 절단 구면 형상의 곡면 배열에 대해 수행되었다. 고각 3 dB 빔 폭의 표준 편차가 크게 감소하였으나 반대급부로 지향 지수도 감소하는 것을 관찰했다. 이를 완화시키기 위한 하나의 방법으로 쉐이딩 함수를 이용한 최적화 기법을 제안한다.

• 제어로봇시스템학회논문지
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• 제21권11호
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• pp.1050-1056
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• 2015

In this paper, we use the characteristics of electromagnetic waves underwater attenuation for estimating linear distance between a transmitting node and receiving node, and research underwater vertical plane attenuation model for constructing the underwater localization system. The underwater localization of 2 dimensional with the plane attenuation model in the horizontal plane (H-plane) was proposed previous research. But for the 3 dimensional underwater localization, the additional vertical plane (E-plane) model should be considered. Because the horizontal plane of omnidirectional antenna has the same attenuation tendency in x-y plane according to the distance, whereas in vertical plane shows an irregular pattern in x-z plane. For that reason, in the vertical plane environment, the attenuation should be changed by the position and inclination. Hence, in this paper the distance and angle between transmitting and receiving node are defined using spherical coordinate system and derive an antenna gain pattern using half power beam width (HPBW). The HPBW is called a term which defines antenna's performance between isotropic and other antennas. This paper derives omnidirectional antenna's maximum gain and attenuation pattern model and define vertical plane's gain pattern model using HPBW. Finally, experimental verifications for the proposed underwater vertical plane's attenuation model was executed.

• 한국항공우주학회지
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• 제48권8호
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• pp.641-651
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• 2020

본 논문은 무인헬기의 상부 및 하부에 탑재되는 전방향 안테나를 자동으로 선택하여, 비행 중에 데이터링크의 링크 마진을 0dB 이상으로 유지하도록 하는 안테나 선택로직을 구현한 내용으로, 비행체에 장착된 안테나의 방사 패턴을 시뮬레이션하고 분석하여 선택 기준을 도출하였으며, 비행체의 자세 및 비행체와 지상체와의 상대적 위치에 따라 비행체 안테나에서의 지향각이 분석된 방사 패턴의 어떤 지점을 향하는지를 함수로 유도하여 비행 중 실시간으로 최적의 안테나를 선택하도록 구현한 내용이다.

• 한국전자파학회논문지
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• 제11권4호
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• pp.619-626
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• 2000

본 논문에서는 $\infty$rrugation이 개구변에 수직인 환형 급전-혼 안테나의 전파반사를 FDTD 방법으로 해석하였 다. 동축선로로 혼 안테나가 급전할 때 thin wire 안테나 모델과 전계와 자계를 전압과 전류로 모댈렁한 1차원 F FDTD코딩방법을 이용하여 계산시간을 효율적으로 줄일 수 있었다. 중심주파수 11.8 GHz(X -band)에서 급천 동축선로의 특성임피던스를 50$\Omega$에서 20$\Omega$까지 lO$\Omega$씩 변화시켜 가며 계산한 결과 특성임피던스가 30$\Omega$인 경우 11 GHz-14 GHz의 넓은 주파수 영역에서 반사손실이 -25 dB 이상의 좋은 특성을 보인다. 또한 corrugation이 있을 때 방사패턴의 지향성이 개선되며 개구변에서의 위상오차가 감소됨을 확인하였다.

• 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.