• Journal of electromagnetic engineering and science
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• 제16권1호
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• pp.35-43
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• 2016

A compact ultra-wide band antenna with a quadruple band-notched characteristic is proposed. The proposed antenna consists of a slotted trapezoid patch radiator, an inverted U-shaped band stop filter, a pair of C-shaped band stop filters, and a rectangular ground plane. To realize the quadruple notch-band characteristic, a U-shaped slot, a complementary split ring resonator, an inverted U-shaped band stop filter, and two C-shaped band stop filters are utilized in this antenna. The antenna satisfies the -10 dB reflection coefficient bandwidth requirement in the frequency band of 2.88-12.67 GHz, with a band-rejection characteristic in the WiMAX (3.43-3.85 GHz), WLAN (5.26-6.01 GHz), X-band satellite communication (7.05-7.68 GHz), and ITU 8 GHz (8.08-8.87 GHz) signal bands. In addition, the proposed antenna has a compact volume of $30mm{\times}33.5mm{\times}0.8mm$ while maintaining omnidirectional patterns in the H-plane. The experimental and simulated results of the proposed antenna are shown to be in good agreement.

• 한국인터넷방송통신학회논문지
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• 제21권2호
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• pp.151-156
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• 2021

고유치 문제에 기초한 모드 전송선로 이론 (Modal Transmission-Line Theory: MTLT)을 이용하여 비대칭 정방형 격자로 구성된 광 도파로의 누설특성과 Bragg 조건들을 정확하게 분석하였다. 비대칭 정방형 격자로 구성된 광도파로는 Bragg 조건들에서 leaky-wave stop-band가 나타났으며, Bragg 조건 근처에서 Rayleigh-Wood 조건에 기인한 anomalies 현상이 발생함을 보였다. 또한, 주기적인 격자구조의 특성 임피던스에 기초한 종 방향 등가 전송선로를 구성하여 광 도파로의 DFB 특성을 Bragg 조건에서 분석하였다. 분석 결과, leaky-wave stop-band가 발생하는 Bragg 조건 근처에서 DFB 도파로의 반사전력이 최대가 되는 filtering 특성이 활성화되는 것을 확인하였다.

• 전기전자학회논문지
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• 제22권3호
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• pp.793-799
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• 2018

An improved design of Ultra Wide Band(UWB) Bow-Tie antenna, which can control an enhanced wide stop-band, is presented. The mutually coupled slot-pair improves and controls the rejection band. The UWB antenna is composed of an electromagnetically coupled Bow-Tie patch and a parasitic ground patch, whose working frequency is extended to full UWB range in this work. By adding slot-pairs on the main patch and optimizing, they can give any requested wide rejection bands and sharp skirt characteristics, as is often required for UWB antennas and multi-band antennas. All the parameters are precisely calculated by an adequate optimization method. The Particle Swarm Optimization(PSO) technique is appropriately adopted. The proposed design and method is proved to give and control the sharp-skirt wide stop-band to UWB Bow-Tie antennas.

• 한국전자파학회논문지
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• 제16권2호
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• pp.194-198
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• 2005

UNII(Unlicensed National Information Infrastructure) 밴드에서 대 역 저지 특성을 갖는 새로운 형태의 UWB 통신용 마이크로스트립 급전 원형 패치 안테나를 제안한다. 안테나의 대역 저지 특성은 inverted-U 슬랏을 이용하여 구현한다. 제안한 안테나는 inverted-U 슬랏의 길이를 변화시켜 대역 저지 주파수 범위를 결정한다. 측정된 안테나의 대역폭은 VSWR<2를 기준으로 $2.9\~12.1GHz$에 걸쳐 광대역 특성을 만족하며 $4.9\~6GHz$ 부근에서 대역저지 특성을 갖는다 안테나의 복사 패턴은 모포폴과 비슷한 전 방향성 특성을 나타내며 전 동작 주파수 대역에 걸쳐 균일한 이득 특성을 갖는다.

• ETRI Journal
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• 제30권5호
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• pp.735-737
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• 2008

We propose a novel spatial multi-band-stop filter using modified multiple loop array elements to block electromagnetic waves or signals of mobile phones in public facilities. It operates at the following frequency bands: Korean cellular (824 MHz to 894 MHz), Personal Communication Service (PCS) (1.75 GHz to 1.87 GHz), and IMT-2000 (1.92 GHz to 2.17 GHz). Two frequency selective surfaces with modified multiple-loop elements are printed on the top and bottom of a pair-glass pane, which is a pair of glass panes with an air gap between them. A modified multiple-loop element with a meander line is used to make the size of the filter compact. The simulated and measured results show good agreement, which confirms the usefulness of the proposed tri-band spatial filter.

• 한국인터넷방송통신학회논문지
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• 제20권2호
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• pp.195-200
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• 2020

고유치 문제에 기초한 모드 전송선로 이론 (Modal Transmission-Line Theory: MTLT)을 이용하여 blazed 격자로 구성된 광 도파로의 누설특성과 Bragg 조건들을 정확하게 분석하였다. 대칭형, 톱니형, 비대칭형으로 분류한 blazed 격자형 광 도파로는 Bragg 조건들에서 leaky-wave stop-band가 나타났으며, Bragg 조건 근처에서 Rayleigh 조건에 기인한 anomalies 현상이 발생함을 보였다. 또한, 주기적인 격자구조의 특성 임피던스에 기초한 종 방향 등가 전송선로를 구성하여 광 도파로의 DFB 특성을 Bragg 조건에서 분석하였다. 분석 결과, leaky-wave stop-band가 발생하는 Bragg 조건에서 DFB 도파로의 반사전력이 최대가 되는 것을 확인하였다.

• Advances in aircraft and spacecraft science
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• 제4권4호
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• pp.353-369
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• 2017

Flutter is a dangerous phenomenon encountered in flexible structures subjected to aerodynamic forces. This includes aircraft, buildings and bridges. Flutter occurs as a result of interactions between aerodynamic, stiffness, and inertia forces on a structure. In an aircraft, as the speed of the flow increases, there may be a point at which the structural damping is insufficient to damp out the motion which is increasing due to aerodynamic energy being added to the structure. This vibration can cause structural failure, and therefore considering flutter characteristics is an essential part of designing an aircraft. Scientists and engineers studied flutter and developed theories and mathematical tools to analyze the phenomenon. Strip theory aerodynamics, beam structural models, unsteady lifting surface methods (e.g., Doublet-Lattice) and finite element models expanded analysis capabilities. Periodic Structures have been in the focus of research for their useful characteristics and ability to attenuate vibration in frequency bands called "stop-bands". A periodic structure consists of cells which differ in material or geometry. As vibration waves travel along the structure and face the cell boundaries, some waves pass and some are reflected back, which may cause destructive interference with the succeeding waves. This may reduce the vibration level of the structure, and hence improve its dynamic performance. In this paper, for the first time, we analyze the flutter characteristics of a wing with a periodic change in its sandwich construction. The new technique preserves the external geometry of the wing structure and depends on changing the material of the sandwich core. The periodic analysis and the vibration response characteristics of the model are investigated using a finite element model for the wing. Previous studies investigating the dynamic bending response of a periodic sandwich beam in the absence of flow have shown promising results.

• 한국정보통신학회:학술대회논문집
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• 한국해양정보통신학회 2011년도 춘계학술대회
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• pp.43-46
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• 2011

A novel circuit structure of dual-band bandstop filters is proposed in this paper. This structure comprises two shunt-connected tri-section stepped impedance resonators with a transmission line in between. Theoretical analysis from the equivalent circuit and design procedures are described. We represented graphs for filter design from the derived synthesis equations by resonance condition of circuits. Notably, advantages of the proposed filter structure are compact size in design, wide range of realizable resonance frequency ratio, and more realizable impedances.

• 한국전자파학회논문지
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• 제30권1호
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• pp.1-7
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• 2019

본 논문에서는 bypass capacitor를 이용하여 Band Stop Matching Circuit(BSMC)을 적용한 Inverted-F Antenna(IFA)의 효율을 향상 기법을 제안한다. 본 논문에서 설계한 안테나의 동작주파수는 LTE band 26과 5(814~894 MHz) 대역이다. BSMC의 임피던스 변화를 이용하여 IFA의 대역폭을 -6 dB 기준 823~886 MHz에서 800~888 MHz로 확장하였다. 확장된 주파수 대역에서 안테나의 효율을 향상시키기 위해 BSMC가 적용된 IFA에 bypass capacitor를 적용하였다. Bypass capacitor는 BSMC가 적용된 IFA의 전류 변화량를 감소시켜 안테나의 효율을 향상시켜주는 역할을 한다. Bypass capacitor를 적용시켰을 때 대역폭은 804~895 MHz이며 확장된 주파수 대역에서 안테나 효율은 10 % 이상 증가하였다.

• 조명전기설비학회논문지
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• 제27권12호
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• pp.10-15
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• 2013

In this paper, we propose a Lyot-type optical fiber comb filter based on a polarization-diversity loop structure (PDLS), which has flat-top pass bands and multiwavelength switching capability. Generally, the PDLS can remove the dependency of the filter on input polarization. The proposed filter is composed of a polarization beam splitter, two half-wave plates (HWPs), and two polarization-maintaining fiber loops concatenated with a $60^{\circ}$ offset between their principal axes. By controlling two HWPs, it can operate in a flat-top band mode or a lossy flat-top band mode with an inherent insertion loss of ~3.49dB. In particular, flat-top bands can be interleaved in both modes, which cannot be realized in a Lyot-Sagnac comb filter based on a fiber coupler. Compared with Solc-type high-order comb filters with the same order, the proposed filter shows sharper transition between pass and stop bands.