• Composites Research
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• v.24 no.1
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• pp.37-44
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• 2011

In this paper, Particle Swarm Optimization(PSO) is applied to the design of the Frequency Selective Surface(FSS) and residual stresses of hybrid radome is predicted. An equivalent circuit model with Square Loops arrays was derived and then PSO was applied for acquiring the optimized geometrical parameters with proper resonant frequency. Residual stresses occur in the FSS embedded composite structures after cocuring and have a great influence on the strength of the FSS embedded composite structures. They also effect transmission quality because of delamination. Therefore, the thermal residual stresses of FSS embedded composite structures were analyzed using finite element analysis with considering the effects of FSS pattern, and composite stacking sequence.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.26 no.6
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• pp.475-481
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• 2013

The residual stresses occur in the Frequency Selective Surface(FSS) embedded hybrid composite structures after co-curing due to mismatch among the coefficient of thermal expansions and stiffness values between the FSS and composite materials. The spring backs occur due to these residual stresses. Therefore, in this paper, the spring-backs caused by residual stresses in FSS embedded composite structures were studied with considering effect of symmetric and unsymmetric stacking sequence of composite laminates.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.26 no.2
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• pp.123-130
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• 2013

In this paper, the delamination and failures in frequency selected surface(FSS) caused by residual stresses in the FSS embedded hybrid composites due to the difference between the coefficients of thermal expansion of components and the transmission characteristic changes due to deformation of FSS patterns by residual stresses were studied. FSS may have different electromagnetic characteristics depending on the type of element, design variables, and arrangement. Design variables of dipole FSS were determined using PSO(Particle Swarm Optimization) to obtain the transmission characteristic for the target resonant frequency. Subsequently, the design variables of other types of N-pole(tripole, cross dipole, and Jerusalem cross) were determined based on the dimensions of the dipole for the comparisons of residual stresses of FSS embedded composite structures and transmission characteristics. In addition, effects of FSS pattern, and stacking sequence of composite laminates were considered.

• Composites Research
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• v.26 no.5
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• pp.279-288
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• 2013

In this paper, the delamination and deformed FSS caused by residual stresses in the Loop type FSS embedded composites and the transmission characteristic changes due to deformation of FSS by residual stresses were studied. FSS may have different electromagnetic characteristics depending on the type of element, design variables, and array. Therefore, design variables of square loop FSS embedded composites structures were determined to obtain the transmission characteristic for X-band (8~12 GHz). Then the design variables of other types of loops (triangular loop and circular loop) were determined based on the dimensions of square loop. Thereafter, the residual stresses and transmission characteristics of FSS embedded composite structures with various single and double loop FSS's, and stacking sequence of composite laminates were compared.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.14 no.10
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• pp.1060-1070
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• 2003

The frequency selective surface for use in Ka/Ku band parabolic antenna of domestic satellite communications is proposed. The frequency selective surface structure consists of the infinite periodic arrays of the triple square loop slot element with narrow width on the honeycomb structure of multi-layered dielectric. The frequency selective surface is fabricated and measured. The good agreement is obtained between theory and experiment. It is demonstrated that the frequency selective surface passes 14/12 GHz band wave while reflecting 30/20 GHz band wave as required.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.27 no.9
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• pp.791-799
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• 2016

This paper presents the design of reconfigurable frequency selective surfaces for X-band bandpass operation with improved isolation. The proposed reconfigurable FSS is composed of a four-legged loaded element, a inductive stub and a bias grid. The PIN diode is located between the four-legged loaded element and the stub, which can control the frequency response of reconfigurable FSS by ON/OFF state. By adjusting the length of the stub, the desired bandpass frequency and the improved isolation between ON and OFF state can be obtained. For validation of simulated results, we have carried out transmission characteristic measurements using rectangular waveguide of WR-90. The measured results are in good agreements with the simulated results.

• 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.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.30 no.4
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• pp.261-269
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• 2019

This study investigates a method of designing pixel-type frequency selective surfaces(FSS) with flexibility while considering factors, such as polarization and incident angle. Among the various methods used to solve the discrete space problem when designing a pixel-type FSS, the binary particle swarm optimization(BPSO) algorithm is one of the most applicable techniques to determine the periodic structure pattern of an FSS. Therefore, a method of efficiently designing FSS with roll-off band pass characteristics using an improved BPSO algorithm is proposed. To solve the convergence problem in the fitness function design to induce particles in the desired solution, FSS with desired roll-off wave characteristics can be easily obtained by applying a fitness function using "slope" as an input parameter.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.06a
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• pp.231-231
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• 2008

최근 인터넷의 보급과 함께 고화질 및 양방향 TV, VOD 방송, 화상 전화 등의 멀티미디어 시대가 열리면서 초고속 통신 시스템에 대한 관심이 증가되고 있다. 특히 화상이나 동영상 같은 대량의 정보가 졸은 품질 및 빠른 속도로 전달될 수 있는 통신 시스템의 필요성이 대두됨에 따라 가장 효율적인 고속 전송 수단으로 광통신이 이용되고 있으며 그에 따른 광통신 능 수동 소자 개발에 관한 연구도 활발히 이루어지고 있다. 이러한 광통신 소자 중 원하는 빛을 선택적으로 투과하고 반사할 수 있는 flat-band pass(FP) filter의 역할이 중요한 부분을 차지하고 있다. 본 논문에서는 IR 영역에서 투과성이 우수한 칼코게나이드 물질을 이용해 l 차원 광자결정구조의 FP-filter를 설계, 제작하고 그에 대한 특성을 평가하였다. 시료는 5N의 순도를 갖는 As, Se, Te 물질을 준비하고 $As_xSe_yTe_z$를 조성비에 맞추어서 석영관에 진공 봉입한 후 용융 혼합하여 $As_{33}Se_{67}$과 $As_{40}Se_{25}Te_{35}$ 조성의 두 가지 비정질 벌크를 제작하였다. 제작된 시료의 굴절률은 ellipsometer을 사용하여 측정하였고, 본 연구진이 자체 개발한 계산툴에 따라 다중층막 구조를 설계하였다. 열 증착법을 이용하여 설계된 구조에 맞게 기판에 올리는 방법으로 1차원 광자결정 구조의 다중층막 샘플을 제작하였고 UV-Vis-IR Spectroscopy를 사용하여 반사도와 투과도를 측정하였다. 광통신용 L/C 밴드 주파수 범위에서 투과성이 우수한 칼코게나이드 박막의 1차원 광자결정 구조는 FP-filter등의 소자로써 유용하게 사용될 수 있다.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.28 no.1
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• pp.80-83
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• 2017

In this paper, the X-band reconfigurable frequency selective surface having flexible geometry was proposed. The proposed RFSS is composed of patterns of cross-shaped loop with inductive stub, which can control the frequency response for C-Band and X-band by ON/OFF state of PIN diode. To minimize the parasitic effect and to obtain the high level of isolation between the unit cell of FSS and the bias circuit, we designed the grid type bias line on bottom layer through via hole. The measured transmission characteristics show good agreement with the simulation results and good stability of frequency response for different incident angles and curvatures of surface.