• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.27 no.7
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• pp.612-619
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• 2016

In this paper, a dual band electrical beam tilting array antenna with bi-directional directivity is designed. Radiating element operates at dual-resonance frequencies and is designed as planar dipole using PCB. In order to tilt the main beam, the phase delay line is designed by use of only the phase shifting line of a $50\Omega$ microstrip line for broadband. The designed antenna has tilting angle of $0^{\circ}$ to ${\pm}8^{\circ}$. For validation of the designed antenna specification, the array antenna is fabricated and the performances are measured. Comparison between theory and experiment shows good agreement.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.38 no.1
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• pp.34-42
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• 2001

The new periodic array structure or frequency selective surface with polarizers characteristic is proposed. The present structure is constructed with two sheets or FSS material, spaced about one-eight wavelength apart, the dipole element orientations of the two sheets being almost perpendicular to each other. The methods of the spectral domain immittance and MoM are used to analyze electromagnetic scattering from this periodic array structure. To confirm the validity of the polrizer's functions or the new periodic array structure, frequency selective surfaces are fabricated, calculated values for the frequency response of the reflection and transmission loss are compared with measured values. Good correspondence has been observed between them. Good axial ratio has been also observed to be achieved in the proposed structure.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.15 no.5
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• pp.1171-1176
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• 2011

This paper describes an analysis on the relationship between elemental image size and object locations in the computational integral imaging reconstruction and in the pickup using a periodically-distributed lenslet array. A sparse sampling effect arises from a periodically-distributed lenslet array in the pickup of 3D objects. The relationship between elemental image size and object location is also reported. Based on the analysis, a method to eliminate the sparse sampling is proposed. To show the effectiveness of the proposed method, experimental results are carried out. It turns out that the theory works.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.10 no.3
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• pp.220-224
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• 2017

In this paper, a method of feeding for the near field beam scanning array antenna with three dimensional focal point has been studied. The conventional array antenna theory is mostly about the far field points. The basic idea is to feed the transmitted signal so that it is in phase at the desired point. In this study, a method is proposed to compensate the phase to have the maximum received power at the point where the measurement point distance is near to the array antenna size. In the proposed method, 11 point source antennas are arrayed in three ways in free space. And the contour map is plotted by calculating the radiation patterns in the three dimensional space and the received signal intensities in the plane within the near space. As a result, it was confirmed that 3 dimensional beam scanning is possible also in the near field of the array antenna.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.14 no.7
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• pp.721-726
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• 2003

This paper present a waveguide slot 16${\times}$16 assay antenna with diaphragms for 38 GHz frequency band. Diaphragms are used to control the impedance and to minimize the return loss of the structure. A 20 dB Chebyshev array of 16 waveguide slots has been designed by optimizing the positions and sizes of the diaphragms. A serial feeding system with $\pi$- and T-junction power dividers has also designed to get a 20 dB Chebyshev power distribution. A 16${\times}$16 slot array was designed for a Fixed Wireless Access System at 38 GHz frequency band, manufactured using a computer controlled milling technique, and measured for the return -19 dB and the frequency band of 740 MHz.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.26 no.8
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• pp.758-764
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• 2015

This paper describes the pattern synthesis of array antenna which conforms to a metallic curved surface formed by the rotation of a quadratic function by using EAGA(Enhanced Adaptive Genetic Algorithm). Three rotated-type conformal surfaces are realized by changing the coefficient of the quadratic function and the pattern of each conformal array antenna is synthesized. In order to reduce the overall time of pattern synthesis, the transformed active element pattern obtained by the active element pattern of the 2-dimensional planar array using Euler angles rotation is utilized instead of the active element pattern of the 3-dimensional conformal array antenna itself. To verify validity of the proposed synthesis procedure, the synthesized patterns using EAGA are compared with those obtained by MWS.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.2 no.2
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• pp.69-77
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• 2009

Small size and low profile antenna for mobile vehicular-top-mounted is needed in satellite communication services such as DBS, Satellite Internet and VSAT. In middle latitudes, the development of an array antenna which has the conformal, low profile and 45 degree beam tilted configuration, and has the high gain with sharp beamwidth, low sidelobe and low loss is required for Ka band satellite communication. In this paper, in order to meet with these performances, an array antenna consisting of the vertical polarized waveguide longitudinal slots based on the leaky-wave mode of traveling wave antenna is proposed. Especially, for the lower sidelobe level the radiation power control using a design method of the different slot width is proposed. An array antenna consisting of 32 leakywave elements is showing 34.4 dBi of gain, 3.6 degree of beamwidth, below than -25 dB of sidelobe level, 43 degree of beam tilt angle in center frequency 20.0 GHz. Feed network designed by waveguide cooperated feed shows good performance of wideband and low loss.

• Journal for History of Mathematics
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• v.15 no.1
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• pp.147-168
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• 2002

In this paper, we introduce the arrangement of hyperplanes and the graph theory. In particular, we explain how to study the 4-color problem by using characteristic polynomials of the arrangement of hyperplanes. The 4-color problem was appeared in 1852 at first and Appel and Haken proved it by using computer in 1976. The arrangement of hyperplanes induced from a graph is called a graphic arrangement. Graphic arrangement is a subarrangement of Braid arrangement. Thus the chromatic function of a graph is equal to the characteristic polynomial of a graphic arrangement. If we use this result, we can apply the theory of the arrangement of hyperplanes to the study for the chromatic functions.

• Proceedings of the Acoustical Society of Korea Conference
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• 1997.06a
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• pp.53-56
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• 1997

Tonpilz 압전변환기에 관하여 유한요소법을 사용하여 공기중의 동특성 해석과 수중의 방사임피던스를 해석하였다. 공기중에서 트랜스듀서의 구조를 변화시키면서 입력 어드미턴스 특성과 진동모드를 해석하여 압전변환기를 모델링하였다. 음향 윈도우를 압전변환기 전면에 부착한 후 유한요소법(FEM)에 의하여 매질의 영향을 고려한 입력어드미턴스 특성을 해석하였으며, 또한 방사임피던스 계산 루틴을 추가하여 무한 배플의 경계조건하에서 방사 임피던스를 해석하였다. 공기중과 수중에서의 해석을 통하여 Tonpilz 압전변환기 단일 소자의 구조 변경 및 기계 부재의 추가등에 따라 변동하는 변환기의 특성 및 방사 임피던스를 해석하므로서 평면 배열형 음향 트랜스듀서의 설계에 필요한 파라메터를 구할 수있다.

• Journal of the Korean Institute of Intelligent Systems
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• v.9 no.4
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• pp.396-403
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• 1999

본 논문에서는 새로운 블록기반 신경망을 제안하고 블록기반 신경망의 패턴류 성능을 확인하였다. 블록기반 신경망은 4개의 가변 입출력을 가지는 블록을 기본 구성요소로하고 있으며 블록들의 2차원배열 형태로 이루어진다. 블록기반 신경망은 재구성가능 하드웨어에 의하여 구현이 용이하고 구조 및 가중치의 최적화에 진화 알고리즘을 적용시킬수 있는 새로운 신경망 모델이다. 블록 기반 신경망의 구조와 가중치를 재고성 가능 하드웨어(FPGA)의 비트열에 대응시키고 유전자 알고리즘에 의하여 전역최적화를 하여 구조와 가중치를 최적화한다. 유전 알고리즘에 의하여 설계된 블록기반 신경망을 비선형 결정평면을 가지는 여러 학습패턴에 적용하여 패턴분류 성능을 확인하였다.