• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.11 no.2
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• pp.186-196
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• 2000

In this paper, modified square loop frequency selective surface for dualband communication antenna systems is proposed, and the scattering characteristics is discussed. The analysis for the problem of scattering by periodic structures with a dielectric slab is formulated using the spectral-domain immittance approach and Floquet's theorem. The method of moments which uses rooftop subdomain basis function is employed to solve the equations. Numerical results include the comparison between the transmission characteristic of general square loop and that of modified square loop. Also, the transmission characteristics of modified square loop for arbitrary incident angle and polarization is presented. To verify analysis results, modified square loop frequency selective surface was fabricated and the calculated results were compared with the measured results. The measured results showed good agreement with the calculated results.

• The Journal of the Acoustical Society of Korea
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• v.20 no.2
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• pp.44-51
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• 2001

This Paper the practical echo signal synthesis model to predict the target strength and signal shape of a submarine for a valuable tool to active sonar engineer. It is based on UTAHID (Underwater TArget by Highlight Distribution) model which is relocated highlight points along to external hull for aspect angle, and synthesized echo signal by modified grouping highlights to internal scatter cloud. Proposed model is analyzed target strength characteristics on various incident pulse length, and synthesis signal signature, target time spreading loss, echo elongation effect and so on. Thus it can be efficiently used in various real systems related to underwater target echo signal synthesis, that is, active sonar, acoustic countermeasure and surveillance system.

• Journal of the Korea Computer Graphics Society
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• v.17 no.3
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• pp.21-31
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• 2011

This paper presents a practical method to estimate the directions of light sources in real environment, using a mirror sphere placed on a set of known natural features in augmented reality. For the stable result of static lighting, we take the multiple images around the sphere and estimate the principal light directions of the vector clusters for each light source in realtime. We also estimate the moving illuminant for changes of the scene illumination, and augment the virtual objects onto the real image with the proper highlighting and shadows. The proposed method of this paper can be applied to augmented reality visualization without any previous information respecting the environmental illuminations.

• The Proceeding of the Korean Institute of Electromagnetic Engineering and Science
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• v.6 no.1
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• pp.10-16
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• 1995

The E-polarized scattering problems by a perfect conductor strip grating are analyzed by the method of moments. For an E-polarization the induced surface current density is expected to blow up at the strip both edges. Then the induced surface current density on the strip is expanded in a series of multiplication of Ultraspherical ploynomials with zeroth order and functions with appropriate edge boundary condition. The numerical results for current density and reflection cofficient are compared with other functions, it is shown that numerical results better improves the convergence of the moment method soulutions with general incident angles than the existing several other functions. The sharp variation points in the magnitude of geometric-optical reflection coefficient can be moved by varying the incident angle, strip width, and strip spacing.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.20 no.2
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• pp.238-245
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• 2008

To evaluate wave reflection and transmission from buoyant flap-typed storm surge barriers, hydraulic experiments were performed by using regular and irregular wave conditions. Buoyant flap-typed storm surge barriers consist of buoyant main body connected with foundation structure in the seabed by hinge. The characteristics of wave reflection, transmission and dynamic response of the structure were investigated for 36 regular and 4 irregular wave conditions. It was also evaluated the usage of plain plate attached on the buoyant main body as one of alternatives to control wave reflection and transmission. From the hydraulic experiments, it was found that the case of plain plate attached on the offshore side is very effective to improve the wave transmission as well as reflection. But, the effect of the case on the harbor side might be negligible.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.274-274
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• 2016

터치스크린패널로 응용하기 위하여 80%이상의 높은 투과도와 낮은 저항이 요구된다. 그 중에서도 무반사 효과 (anti-reflective, AR) 를 크게하여 투과도를 향상시키는 방법으로 나노구조물, 증착시 경사각, 다층박막 방법 등이 연구 개발되고 있다. 단일 박막을 이용하여 무반사 코팅을 하는 경우, 정밀한 굴절률 조절이 어려우며 낮은 반사율 영역의 선폭이 좁은 단점이 있다. 반면, 저/고굴절률 다층박막의 경우 비교적 굴절률 조절이 용이하고 가시광영역 전반적으로 높은 투과도를 가질 수 있다. plasma enhanced chemical vapor deposition (PECVD) 증착법을 이용하여 무반사 효과를 증대시키기 위해 저/고굴절률 다층구조의 박막을 두께조합에 따라 평가하였으며, 가장 널리 사용되고 있는 Sputtering증착법과 비교하여 연구하였다. 제작된 다층박막의 구조는 glass(sub.)/SiN/SiO2/ITO 이며, 무반사 코팅층인 SiN/SiO2층은 각각 PECVD와 Sputtering 증착법을 통해 성장되었고, ITO는 스퍼터링 증착법을 이용하여 동일하게 성장하였다. 그 결과 PECVD 증착법이 Sputtering 증착법에 비하여 가시광영역(400~800nm)에서 더 높은 투과도를 얻게 되었다. 결과의 차이에 대해서 PECVD 증착법과 Sputtering 증착법으로 성장된 SiN, SiO2 박막의 광학적 특성과 물리적 특성의 변화를 spectroscopic ellipsometry (SE), Rutherford backscattering (RBS), atomic force microscopy (AFM) 을 이용하여 비교, 분석하였다.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.11 no.7
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• pp.1139-1146
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• 2000

In this paper, circular-polarized dipole antenna with a novel structure is designed, simulated and fabricated for PCS or IMT-2000 base station at an arbitrary test frequency(1.575 GHz). Its radiation pattern is analyzed by means of physical optics(PO). The designed antenna is made up of a horizontal and a vertical dipole elements at a height of λ/4 above an reflector. One of λ/4 length vertical dipole element is located at a height of λ/8 above an reflector. In this case, circularly polarized radiation pattern is obtained by making impedance difference due to adjusting the length of each element. The characteristic of antenna measured from this study is that return loss is 18.4 dB, -10 dB bandwidth is 360 MHz(22.8%), 2 dB axial ratio bandwidth is 30 MHz, -3 dB beamwidth is 76$^{\circ}$, 2 dB axial ratio beamwidth is 58$^{\circ}$, axial ratio is 1.7 dB at 1.575 GHz. Radiation pattern is in well agreement with the result of PO.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.22 no.10
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• pp.966-980
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• 2011

Radar receiving echo signal provides target information - range, velocity and position by signal magnitude and Doppler shift, which are determined by target reflection characteristics and target maneuver. Target angle error is extracted from the magnitude ratio of difference channel to sum channel. In this paper, we introduce a radar Return Signal Simulation Equipment(RSSE) which is implemented for the purpose of performance analysis and evaluation of phased array multi-function radar(MFR). It generates multi-target environment with jamming signals using MC-DDS (Multi-Channel Direct Digital Synthesis), and has scalability by using the efficient hardware configuration. The performance of the developed RSSE has been evaluated under various test environments. Especially, we proved that required target detection performance is achieved by RSP(Radar Signal Processor) interfaced RSSE configuration.

• Journal of the Korean Institute of Telematics and Electronics
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• v.11 no.1
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• pp.1-7
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• 1974

This paper discribes the reflector type ultrasonic concentrator which makes hghintencity of ultrasonic field. This was made by rotating parabolic surface which only using total reflection aria, that makes boundary by the critical angle of reflection of sound. I made two binds of concentrator acording to the type of ultrasonic transduser: one is internal surface reflector type concentrator, which is available for disc type transducer, and the other is external surface reflector type concentrator which is available cylinderical transduser. In the mony aspects the reflector tripe concentrator is supel'ier to the reflection type concentrator as plastics lens; It is more durable in high temperature and high intencity ultrasonicfield then refrector type concentrator because of it is made by glass or metal, and it has higher. efficiency because of it wasts made by only total reflection aria that is without absoption lose. I think this is useful ultrasonic concentrator in mony industrial field, in which high intencitr of ultrasonic energy was used.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.12 no.1
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• pp.25-32
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• 2008

This paper presents the reflection and transmission measurements conducted at the 60GHz suitable to provide a high speed wide band service. Mean received power and standard deviation are calculated and used to compare the characteristics of radio wave propagation to the various obstacles between transmitting and receiving antennas at the frequency. The results show that the transmitted signal strength by the steel door and copper plate are about 40dB lower than in free space, those by the rubber plate, glass and styroform are about 3dB lower than in free space. Also, the re(looted signal strengths at the 60 degree grazing angle show that in case by the partition is about 23dB lower, by the surface of a wall is about 6dB lower than by the copper plate. The presented results can be used for the design of 60 GHz picocell communication network that the reflected and transmitted waves affect to the service area.