• Title/Summary/Keyword: Metamaterial surface

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Design and SAR Analysis of Wearable Antenna on Various Parts of Human Body, Using Conventional and Artificial Ground Planes

  • Ali, Usman;Ullah, Sadiq;Khan, Jalal;Shafi, Muhammad;Kamal, Babar;Basir, Abdul;Flint, James A;Seager, Rob D.
    • Journal of Electrical Engineering and Technology
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    • v.12 no.1
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    • pp.317-328
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    • 2017
  • This paper presents design and specific absorption rate analysis of a 2.4 GHz wearable patch antenna on a conventional and electromagnetic bandgap (EBG) ground planes, under normal and bent conditions. Wearable materials are used in the design of the antenna and EBG surfaces. A woven fabric (Zelt) is used as a conductive material and a 3 mm thicker Wash Cotton is used as a substrate. The dielectric constant and tangent loss of the substrate are 1.51 and 0.02 respectively. The volume of the proposed antenna is $113{\times}96.4{\times}3mm^3$. The metamaterial surface is used as a high impedance surface which shields the body from the hazards of electromagnetic radiations to reduce the Specific Absorption Rate (SAR). For on-body analysis a three layer model (containing skin, fats and muscles) of human arm is used. Antenna employing the EBG ground plane gives safe value of SAR (i.e. 1.77W/kg<2W/kg), when worn on human arm. This value is obtained using the safe limit of 2 W/kg, averaged over 10g of tissue, specified by the International Commission of Non Ionization Radiation Protection (ICNIRP). The SAR is reduced by 83.82 % as compare to the conventional antenna (8.16 W/kg>2W/kg). The efficiency of the EBG based antenna is improved from 52 to 74 %, relative to the conventional counterpart. The proposed antenna can be used in wearable electronics and smart clothing.

Analysis on Infrared Stealth Performance of Metal Nano-coating on Radome Surface (레이돔 표면에 금속 나노코팅을 적용한 적외선 저피탐 성능특성 연구)

  • Lee, Yongwoo;Chang, Injoong;Nam, Juyeong;Bae, Hyung Mo;Cho, Hyung Hee
    • Journal of the Korea Institute of Military Science and Technology
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    • v.25 no.3
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    • pp.251-258
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    • 2022
  • Infrared stealth technology used in aircraft is applied to reduce the infrared signal by controlling surface temperature and emissivity using internal heat sink, low emissivity material or metamaterial. However, there is one part of the aircraft where the use of this technology is limited, and that is the radome. Especially, radome should have transmittance for the specific radio frequency, therefore, common stealth technology such as emissivity control surfaces cannot be applied to radome surface. In this study, we developed metal nano-coating for infrared stealth which is applicable to radome surface. We designed slot-type pattern for frequency selective transmission in X-band, and also controlled thickness of metal nano-coating for long wavelength infrared emissivity control. As a result, our infrared stealth surface for radome has 93.2 % transmittance in X-band and various infrared emissivities from 0.17 to 0.57 according to nano-coatings thickness. Also, we analyzed infrared signature of radome through numerical simulation, and finally reduced contrast radiant intensity by 97.57 % compared to polyurethane surface.

Study on Wave Absorption of 1D-/2D-Periodic EBG Structures and/or Metamaterial Layered Media as Frequency Selective Surfaces

  • Kahng, Sung-Tek
    • Journal of electromagnetic engineering and science
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    • v.9 no.1
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    • pp.46-52
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    • 2009
  • This paper conducts a study on the frequency-dependent filtering and blocking effects of a variety of periodic structures, dubbed frequency selective surface(FSS). The periodic structures of interest are 1D and 2D repeated patterns of metal patches or slots sitting on the interface between the two different regions in the layered media which will show the capacitive or inductive behaviors and incorporated with the electromagnetic bandgap(EBG) geometry as another stratified media. Besides the normal substances so called double positive(DPS)-type in the layered media, metamaterials of double negative(DNG) are considered as layering components on the purpose of investigating the unusual electromagnetic phenomena. Frequency responses of transmission(absorption in terms of scattering) and reflection will be calculated by a numerical analysis which can be validated by the comparison with the open literature and demonstrated for the periodic structures embedding metamaterials or not. Most importantly, numerous examples of FSS will present the useful guidelines to have absorption or reflection properties in the frequency domain.

A Study on Resonance Properties of a Terahertz Asymmetric Split-Loop Resonator Type Metamaterial for High Quality Factor (테라헤르츠 비대칭 분리고리공진기 메타물질의 높은 품질인자를 위한 공진 특성에 관한 연구)

  • Park, Dae-Jun;Ryu, Han-Cheol
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.17 no.11
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    • pp.663-669
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    • 2016
  • A terahertz asymmetric split-loop resonator (ASLR) was analyzed for use in high-sensitivity sensing applications. Its structural asymmetricity induces an asymmetric Fano resonance which has a high quality factor compared to the symmetric eigen-resonance. The variations of the resonant frequency, transmission coefficient, and quality factor of the ASLR in the eigen and Fano resonances are analyzed as a function of its structural asymmetricity. Also, the surface current densities on the ASLR in both resonances are calculated to analyze the main cause of the variations of its transmission characteristics. The surface current of the ASLR in the eigen resonance shows a dipole resonance, which increases the radiation loss and reduces the quality factor. On the other hand, the surface current of the ASLR in the Fano resonance shows a trapped or quadrupole mode which has a low radiation loss. Therefore, the ASLR operated in the Fano resonance has a high quality factor. Terahertz, high-performance filters and high sensitivity sensors can be developed based on our analysis results of the ASLR having a high quality factor. These high-performance devices based on terahertz metamaterials could increase the adoption of terahertz industrial applications.

Study on Improvement of the Array Antenna Performance by Isolation Enhancement (격리도 향상을 통한 배열안테나의 성능개선 연구)

  • Park, Minseo;Lee, Jae-Gon;Lee, Jeong-Hae
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.27 no.3
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    • pp.229-238
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    • 2016
  • In this paper, we have studied isolation enhancement using a suppression of surface wave to improve performance of array antenna. To reduce isolation between elements of array antenna, perfect magnetic conductor(PMC) and SOFT-surface is designed and located at center of ground plane, isolation and gain is simulated by commercial full wave simulator(HFSS). As a result, isolation of more than 40 dB and gain improvement of 2.2 dBi are obtained at E-plane array in case of both PMC and SOFT-surface. At H-plane array, air coupling is dominant compared to coupling by surface wave. It is conclude that this study is useful for design of compact array antenna and performance improvement of array antenna.

Design of Metamaterial-Inspired FSS Sub-Reflector for a Dual-Band Offset Cassegrain Reflector Antenna (이중대역 오프셋 카세그레인 반사판 안테나용 메타재질구조 모사 주파수 선택표면 부반사판 설계)

  • Kim, Hyeonsu;Kahng, Sungtek;Khattak, M. Kamran;Jeon, Jinsu;Park, Jeong-hoon
    • Journal of Satellite, Information and Communications
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    • v.10 no.2
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    • pp.34-39
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    • 2015
  • In this paper, a design of an offset Cassegrain antenna is proposed for Ku and Ka dual-band without increasing the antenna size. For Efficiency of computation and implementation, the frequency selectivity surface (FSS) of reflecting the Ka-band signal and passing the Ku-band is provided for the sub-reflector instead of the main reflector. The proposed FSS hyperboloid sub-reflector is the periodic structure of a unit cell comprising octagon metal rings embedded in the multiple layers. The proposed design is verified for 19 GHz and 45 GHz bands by the use of precise electromagneitc-field simulations.

Realization of High Impedance Surface Characteristics Using a Periodically Transformed Artificial Magnetic Conductor Structure and Reduction Technique of Specific Absorption Rate

  • Lee, Seungwoo;Rhee, Seung-Yeop;Kim, Pan-Yeol;Kim, Nam
    • Journal of electromagnetic engineering and science
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    • v.13 no.2
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    • pp.113-119
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    • 2013
  • We developed a transformed, symmetrical, mushroom-like surface without via holes in cells focused on a 2.4-GHz WLAN band. Each slot in the novel type structure plays a key role in modeling at the desired frequencies. The designed artificial magnetic conductor (AMC) has several advantages, including a small size, a wider bandwidth, a short reflecting distance to the antenna, and easy fabrication because there are no via holes. Overall dimensions of the AMC cell are 21 mm $(Width){\times}21mm$ $(Height){\times}2.6mm$ (Thickness), and the bandwidth is about three times wider (11.7%) compared to that of a conventional AMC (4.0%). For evaluating the performance of the proposed structure, a reflector, which periodically consists of the designed AMC cells, was developed. The antenna with the investigated AMC reflector not only works within a quarter of the wavelength because of the extremely high wave impedance generated by the AMC cells on the surface of the structure but also reduces the specific absorption rate (SAR). Electromagnetic field (EMF) exposure to a human phantom was analyzed by applying the designed reflector to the 2.4-GHz dipole antenna in a tablet PC. The calculated peak SAR averaged over 1 g was 0.125 W/kg when the input power was 1 W and the antenna was located at 20 cm from the human phantom. However, the SAR value was only 0.002 W/kg (i.e., 98.4% blocked) when the designed reflector was inserted in front of the antenna.

The Gain Estimation of a Fabry-Perot Cavity (FPC) Antenna with a Finite Dimension

  • Kwon, Taek-Sun;Lee, Jae-Gon;Lee, Jeong-Hae
    • Journal of electromagnetic engineering and science
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    • v.17 no.4
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    • pp.241-243
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    • 2017
  • In this paper, we have presented an equation for estimating the gain of a Fabry-Perot cavity (FPC) antenna with a finite dimension. When an FPC antenna has an infinite dimension and its height is half of a wavelength, the maximum gain of that FPC antenna can be obtained theoretically. If the FPC antenna does not have a dimension sufficient for multiple reflections between a partially reflective surface (PRS) and the ground, its gain must be less than that of an FPC antenna that has an infinite dimension. In addition, the gain of an FPC antenna increases as the dimension of a PRS increases and becomes saturated from a specific dimension. The specific dimension where the gain starts to saturate also gets larger as the reflection magnitude of the PRS becomes closer to one. Thus, it would be convenient to have a gain equation when considering the dimension of an FPC antenna in order to estimate the exact gain of the FPC antenna with a specific dimension. A gain versus the dimension of the FPC antenna for various reflection magnitudes of PRS has been simulated, and the modified gain equation is produced through the curve fitting of the full-wave simulation results. The resulting empirical gain equation of an FPC antenna whose PRS dimension is larger than $1.5{\lambda}_0$ has been obtained.

Flexible Zeroth-Order Resonant(ZOR) Antenna Independent of Curvature Diameter (곡률에 독립적인 플렉서블 기판 위에 설계된 영차 공진 안테나)

  • Lim, In-Seop;Chung, Tony J.;Lim, Sung-Joon
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.23 no.1
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    • pp.21-28
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    • 2012
  • In this paper, we propose a flexible zeroth-order resonant(ZOR) antenna. Its zero phase constant ensures that the antenna performance is independent of substrate deformation. A composite right/left-handed transmission line is designed based on coplanar waveguide technology to realize the zeroth-order resonance phenomenon. The CRLH is an implementation of metamaterial(left handed material) which is composed of shunt inductance and series capacitance. In order to yield additional circuital parameter, chip inductor and gap capacitor is added, respectively. The proposed ZOR antenna provides good performances: reasonable bandwidth(6.5 %) and peak gain(0.69~1.39 dBi). Simulated and measured results show that the antenna's resonant frequencies and radiation patterns are almost unchanged at different curvature diameters of 30, 50, 70 mm, as well as for a flat surface.

Improved photoresponsivity of AlGaN UV photodiode using antireflective nanostructure (반사방지 나노 구조체를 이용한 AlGaN UV 광다이오드의 광반응도 향상)

  • Dac, Duc Chu;Choi, June-Heang;Kim, Jeong-Jin;Cha, Ho-Young
    • Journal of the Korea Institute of Information and Communication Engineering
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    • v.24 no.10
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    • pp.1306-1311
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    • 2020
  • In this study, we proposed an anti-reflective nano-structure to improve the photoresponsivity of AlGaN UV photodiode that can be used as a receiver in a solar blind UV optical communication system. The anti-reflective nano-structure was fabricated by forming Ni nano-clusters on SiO2 film followed by etching the underneath SiO2 film. A sample with the anti-reflective nano-structure exhibited lower surface reflection along with less dependency on the wavelength in comparison with a sample without the nano-structure. Finally, a UV photodiode was fabricated by applying an anti-reflective structure produced by heat-treating a 2 nm-thick Ni layer. The photodiode fabricated with the proposed nano-structure exhibited noticeable improvement in the photoresponsivity at the wavelength range from 240 nm to 270 nm in comparison with the same photodiode with a SiO2 film without the nano-structure.