Analysis of the THz Resonance Characteristics of H-shaped Metamaterials with Varying Width

류한철 한국광학회 2021 Current Optics and Photonics Vol.5 No.1

The resonance characteristics of H-shaped metamaterials, whose widths were varied while keeping the height constant, were investigated in the terahertz (THz) frequency range. The H-shaped metamaterials were numerically analyzed in two modes in which the polarization of the incident THz electric field was either parallel or perpendicular to the width of the H-shaped structure. The resonant frequency of the metamaterial changed stably in each mode, even if only the width of the H shape was changed. The resonant frequency of the metamaterial operating in the two modes increases without significant difference regardless of the polarization of the incident electromagnetic wave as the width of the Hshaped metamaterial increases. The electric field distribution and the surface current density induced in the metamaterial in the two modes were numerically analyzed by varying the structure ratio of the metamaterial. The numerical analysis clearly revealed the cause of the change in the resonance characteristics as the width of the H-shaped metamaterial changed. The efficacy of the numerical analysis was verified experimentally using the THz-TDS (time-domain spectroscopy) system. The experimental results are consistent with the simulations, clearly demonstrating the meaningfulness of the numerical analysis of the metamaterial. The analyzed resonance properties of the H-shaped metamaterial in the THz frequency range can be applied for designing THz-tunable metamaterials and improving the sensitivity of THz sensors.

Pendulum-type elastic metamaterial for reducing the vibration of a space tether

Yoon, Joo Young,Song, Weon Keun,Park, No-Cheol Elsevier 2019 Acta astronautica Vol.162 No.-

<P><B>Abstract</B></P> <P>In this paper, we present a pendulum-type elastic metamaterial that can be used to absorb the shock of a tether system. A tether system comprises a long and thin cable, so the resonant part of the elastic metamaterial should be attached to outside the cable. The unit cell of the elastic metamaterial consists of three strings and one ring, and strings are attached to the tether cable and reduces the shock transmitted to the satellite. We used modal analysis to find mode shapes of the unit cell of the elastic metamaterial that do not deform when in contact with the tether cable. A harmonic analysis on the properties of the strings confirmed the presence of bandgaps for the pendulum-type metamaterial because of the lateral resonance of the strings. The effect of the unit cell design parameters on the bandgaps were also investigated.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The pendulum-type elastic metamaterial for tether system is proposed. </LI> <LI> The bandgap mechanism of pendulum-type elastic metamaterial is presented. </LI> <LI> The effect of the unit cell design parameters on the bandgaps is investigated. </LI> <LI> The transverse vibration of the tether cable can be reduced due to the metamaterial. </LI> </UL> </P>

Characteristics of the Resonance and Impedance of Parallel Plates due to the Embedded Metamaterial Substrate

강승택(Sungtek Kahng) 대한전자공학회 2008 電子工學會論文誌-TC (Telecommunications) Vol.45 No.8

본 논문에서는 금속 평행평판에 일반 유전체 기판인 FR4 대신 Metamaterial을 삽입할 경우에 발생할 수 있는 전자기 공진 특성과 임피던스 변화에 대하여 연구하였다. 기판을 DPS는 물론 Metamaterial인 ENG, MNG, DNG 형으로 나눠, 투자율 함수를 위해 SRR 형식의 Lorentz 모델과, 유전율 함수를 위해 금속선 주기 배열 형식의 Drude 모델을 정확한 계산이 가능한 Full-wave 모드해석기법에 반영하여 평행평판이 가지는 공진모드들과 임피던스의 변화양상을 관측하였다. 관측을 통해 전자장비의 품질을 저하시키는 평행평판의 불요공진모드 억제를 위한 기판설계 가이드라인을 수립할 수 있었다. This paper conducts the research on the variation in the characteristics of the resonance and impedance of the metallic parallel plates due to the replacement of the normal dielectric substrate by the metamaterial. The ENG(ε<0), MNG (μ<0) and DNG(ε, μ<0) types of metamaterial as well as the DPS(Double Positive) material are taken into consideration a full-wave modal analysis method known for accurate computation, as the SRR-kind of Lorentz model for permittivity and metal wire-periodic array-kind of Drude model for permeability, and the behaviors of parallel plates' resonance mode and impedance are observed. Based upon the observation, the design guidelines for the substrate can be addressed regrading how to suppress the parallel plates' spurious resonance modes that degrade the quality of the electronic equipment.

Doubly negative isotropic elastic metamaterial for sub-wavelength focusing: Design and realization

Oh, Joo Hwan,Seung, Hong Min,Kim, Yoon Young Elsevier 2017 Journal of sound and vibration Vol.410 No.-

<P><B>Abstract</B></P> <P>In spite of much progress in elastic metamaterials, tuning the effective density and stiffness to desired values ranging from negatives to large positives is still difficult. In particular, simultaneous realization of double negativity and isotropy, critical in sub-wavelength focusing, is very challenging since anisotropy is usually unavoidable in resonance-based metamaterials. The main difficulty is that there is no established systematic design method for simultaneous achieving of double negativity and isotropy. Thus, we propose a unique elastic metamaterial unit cell with which simultaneous realization can be achieved by an explicit step-by-step approach. The unit cell of the proposed metamaterial can be accurately modeled as an equivalent mass-spring system so that the effective properties can be easily controlled with the design parameters. The actual realization was carried out by acquiring the desired properties in sequential steps which is in detail. The specific application for this study is on sub-wavelength focusing, which will be demonstrated by waves from a single point source focused on a region smaller than half the wavelength. Actual experiments were performed on an aluminum plate where the designed metamaterial flat lens was imbedded. The results acquired through simulations and experiments suggest potential applications of the proposed metamaterial and the systematic design approach in advanced acoustic surgery or non-destructive testing.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Doubly negative and isotropic elastic metamaterials are realized. </LI> <LI> An explicit step-by-step design method is proposed. </LI> <LI> The sub-wavelength focusing of S0 waves is realized and validated by experiment. </LI> </UL> </P>

Design and Analysis of Metamaterial Antenna Using Double Square Rings

Tong Huang 보안공학연구지원센터 2016 International Journal of Signal Processing, Image Vol.9 No.7

In this paper, the design and the analysis of the double square ring (DSR) metamaterial is presented, which is based on the equivalent circuit theory and the analysis of the distribution of the electromagnetic field. Based on the retrieval algorithm, the effect of the structural parameters on the effective permittivity and the effective permeability are proposed. The effective permittivity and the effective permeability of the designed DSR metamaterial are simultaneously negative in the range from 4.8GHz to 5.65GHz. A conventional microstrip antenna is designed as comparison, and the analysis of the microstrip antenna is not written in this paper for brevity. The superstrate is composed of an 44 array of the DSR metamaterial, and the novel antenna is consist of the conventional microstrip antenna and the superstrate. The effect of the distance between the superstrate and the antenna are simulated by HFSS software, and the novel antenna is proposed according to the analysis of the distance. The simulation results show that the gain of the novel antenna increased by 1.1dB, and the half power beam width decreased by 40.9°. Therefore, it is concluded that the performance of microstrip antenna can be improved by using DSR metamaterials.

Metamaterials and Their Applications in Patch Antenna : A Review

Rakhi Rani,Preet Kaur,Neha Verma 보안공학연구지원센터 2015 International Journal of Hybrid Information Techno Vol.8 No.11

Metamaterial is the arrangement of "artificial" elements in a periodic manner providing unusual electromagnetic properties. This unusual property has made it an area of interest for last few decades. It has wide applications in antennas. Gain, directivity, bandwidth, efficiency, and many other parameters of microstrip patch antenna can be improved using metamaterials. In this review paper, we first overview the metamaterials, its types and then the application of metamaterials in Microstrip patch antennas over the last 13-15 years.

Acoustic metamaterial design for noise reduction in vacuum cleaner

안기용,권호진,장준영,Kyung-Jun Song 대한기계학회 2022 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.36 No.11

In this study, we investigate the acoustic metamaterial (AMM) design for flow noise reduction when using a vacuum cleaner. The AMM was based on the principle of Helmholtz resonators, and metamaterial design variables were defined to reduce noise to approximately 1.5 and 2.5 kHz bands. An acoustic simulation was performed considering the thermoviscous effect using the designed AMM, and a transmission loss in the simulation results was calculated using the four-microphone method. Finally, noise experiments were performed on a vacuum cleaner equipped with metamaterial. Through this, the noise reduction performance of metamaterial predicted through simulations was verified, thereby showing the selective implementation of noise reduction in the desired frequency band.

식각된 VO 2 박막을 이용한 밴드-전환형 테라헤르츠파 메타물질

류한철 한국광학회 2020 한국광학회지 Vol.31 No.1

We propose a band-switchable terahertz metamaterial based on an etched vanadium dioxide (VO 2 ) thin film. A line of etched VO 2 thin film was placed in the center gap of the split square-loop shape for the tunability of the metamaterial. The resonance frequency of the metamaterial can be switched from the 1.4 THz band to the 0.7 THz band, according to the insulator-metal phase transition in the VO 2 thin film. The absolute difference in the transmittance of the metamaterial was 78.5% and 65.8% at 0.7 THz and 1.4 THz respectively, according to the band switching. The differential phase shift was around 90°, and the transmittance was stably maintained between 40% and 60% in the middle band of the two switchable resonance-frequency bands.

Topology optimization of anisotropic metamaterials tracing the target EFC and field polarization

Ahn, Byungseong,Lee, Hyung Jin,Kim, Yoon Young Elsevier 2018 Computer methods in applied mechanics and engineer Vol.333 No.-

<P><B>Abstract</B></P> <P>Equi-frequency contours (EFCs) can be used to predict certain intrinsic wave behaviors of a metamaterial, and are therefore frequently used for analysis and design. However, information about field polarization (FP) dictating whether particle motion along an EFC is longitudinal, shear, or longitudinal–shear coupled should also be considered to accurately predict the actual wave phenomena of a metamaterial. For instance, anomalous polarization can be used to create mode converters characterized only when both EFCs and FPs are simultaneously considered. In this work, we aim to develop a topology optimization method to design anisotropic metamaterials that trace target EFCs and FPs. Earlier studies on the topology optimization method have considered EFCs or dispersion curves; however, there is no topology optimization that considers the EFC and FP simultaneously. As a means to trace the FP, we introduce a scalar measure equivalent to the modal assurance criterion and derive its sensitivity with respect to density design variables. We present various case studies to design metamaterial unit cells to trace target EFCs and FPs corresponding to anomalous polarization. Furthermore, mode converters made of the metamaterials designed by the developed topology optimization method are created and their performance in converting a longitudinal wave mode to a transverse wave mode is evaluated.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Topology optimization of anisotropic metamaterials performed. </LI> <LI> Simultaneous consideration of Equi-frequency contour and field polarization. </LI> <LI> Polarization anomaly realized by designed metamaterials. </LI> <LI> Applications to mode converters. </LI> </UL> </P>

CRLH 전송선로를 이용한 공통 모드 억압 평형 필터

김영 ( Young Kim ),윤정호 ( Jeong Ho Yun ),윤영철 ( Young Chul Yoon ) 한국항행학회 2011 韓國航行學會論文誌 Vol.15 No.4

본 논문은 차동 모드로 동작하는 메타 재질 구조를 바탕으로 평형 필터 설계를 제안한 것이다. 이 메타 재질 구조는 차동 모드 동작에서는 Composite Right/Left-Handed(CRLH) 메타 재질로 동작하여 필터 특성을 갖지만, 공통 모드에서는 통과대역이 차단되는 성질을 갖는 평형 CRLH 단위 셀로 구성되었다. 이러한 차동모드 특성을 갖는 단위 셀을 직렬로 4단을 연결하여 필터를 구성하였으며, 제안된 메타 재질의 특성은 차동 모드 평형 필터로 동작하고, 공통 모드에서는 차단되는 특성을 실험 결과를 통하여 확인하였다. 메타 재질을 이용한 평형 필터는 대역폭이 960 MHz~1000 MHz, 4.1dB의 삽입손실을 갖는 특성을 얻었다. This paper presents a novel balanced filter design based on a metamaterial structure applicable to differential-mode excitation. The metamaterial structure is based on a unit-cell which under a differential-mode excitation behaves like composite right/left-handed(CRLH) metamaterial with filter characteristics. In contrast, the metamaterial unit-cell is below cut-off under a common-mode excitation. Experimental results are used to verify the proposed metamaterial`s differential-mode characteristics. The metamaterial is fabricated with a balanced filter design resulting in an operating frequency range of 960~1000 MHz with a insertion loss of 4.1 dB.