• Title/Summary/Keyword: Electromagnetic absorber

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A Study on the Evaluation of the Characteristics of Semi-Anechoic Chamber Constructed by the Cross-Shaped Type Electromagnetic Absorbers (십자돌기형 전파흡수체로 구성된 전파암실의 특성평가)

  • 김민석;김동일;전상엽;민경식
    • Journal of the Korea Institute of Information and Communication Engineering
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    • v.3 no.1
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    • pp.51-58
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    • 1999
  • In this Paper, the Performance of the semi-anechoic chamber which is to be constructed by the cross-shaped ferrite absorbers with broadband frequency characteristics, has been evaluated by the image method. As a result it was confirmed that the cross-shaped absorber has excellent performance over the frequency range from 30 MHz to 3,000 MHz, while the tile and the gird-type ferrite absorbers have the bandwidth of 30 - 1,000 MHz.

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An Analysis of Natural Lacquer Characteristics and EM Absorber's Absorption Characteristics Using Natural Lacquer by Binder (옻의 특징과 옻을 지지재로 사용한 전자파 흡수체의 두께에 따른 흡수 특성 분석)

  • 최동한;김동일;김기만
    • Proceedings of the Korean Institute of Navigation and Port Research Conference
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    • 2004.04a
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    • pp.29-34
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    • 2004
  • Generally, a silicone rubber and a chloride polyethylene(CPE) have been used for the development of high-performance composite EM(ElectroMagnetic) wave absorbers. In this study, the EM wave absorption abilities for natural lacquer which is newly suggested in this study as a binder for composite EM wave absorbers were investigated to develop an improved EM wave absorbers. In addition, MnZn ferrite composite EM wave absorbers mixed with the natural lacquer were prepared and their absorption ability was also investigated. MnZn ferrite composite EM wave absorbers which employs the natural lacquer as a binder showed an improved EM wave absorption characteristics in comparison with the conventional binder such as a silicone rubber and a chloride polyethylene(CPE). The matching frequency and the absorption ability of EM wave absorbers mixed with natural lacquer can be controled the change of the thickness of them.

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Design and Fabrication of Semi-cylindrical Radar Absorbing Structure using Fiber-reinforced Composites (섬유강화 복합재료를 이용한 반원통형 전자파 흡수구조의 설계 및 제작)

  • Jang, Hong-Kyu;Shin, Jae-Hwan;Kim, Chun-Gon;Shin, Sang-Hun;Kim, Jin-Bong
    • Composites Research
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    • v.23 no.2
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    • pp.17-23
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    • 2010
  • The stealth technology can increase the survivability of aircrafts or warships and enhance the capability of mission completion in hostile territory. The purpose of this paper is to present the low observable structure with curved surfaces made by fiber-reinforced composites and to show the possibility of developing omnidirectional stealth platforms for military applications. In this study, we developed a radar absorbing structures(RAS) based on a circuit analog absorber to reduce the radar cross section(RCS) of an object with curved surfaces. Firstly, the RAS with a periodic square patterned conducting polymer layer was designed and simulated using a commercial 3-D electromagnetic field analysis program. Secondly, the designed semi-cylindrical structure with low RCS was fabricated using fiber-reinforced composites and conducting polymer. To make the periodic pattern layer, acts as resistive sheet, the intrinsic conducting polymer paste containing PEDOT with a polyurethane binder was used. Finally, the radar cross section was measured to evaluate the radar absorbing performances of the fabricated RAS by the compact range facility in POSTECH.

Absorption Properties of Thin Permalloy-Rubber Absorbers in Mobile Telecommunication Frequency Bands (Permalloy를 이용한 이동통신주파수 대역용 박형 전파흡수체의 제조 및 특성 연구)

  • Kim, Moon-Suk;Min, Eui-Hong;Koh, Jae-Gui
    • Journal of the Korean Magnetics Society
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    • v.18 no.3
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    • pp.115-119
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    • 2008
  • The raw materials of permalloy were processed the ball-mill for 30 hours and the shape of permalloy particles was changed from sphere to flake type, which was observed using scanning electron microscope. The complex permittivity and permeability spectra and reflection loss of permalloy-rubber composite was measured using Network Analyzer in order to investigate the relationship between the microwave absorption and the material constants. The flake type permalloy-rubber composite showed high reflection loss, which was due to the high complex permittivity and permeability. Also, the matching frequency shifted toward lower frequency range with microwave absorber thickness, and the maximum reflection loss of -6.1 dB was observed in $1.65\;GHz{\sim}1.86\;GHz$ for a 1.3 mm thickness.

Design and Properties of Microwave Absorbing Structures Composed of Fiber Reinforced Composites (섬유강화 복합재료로 구성된 전파흡수구조재의 설계 및 특성)

  • 김상영;김성수
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.12 no.6
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    • pp.1002-1008
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    • 2001
  • The absorbing structure composed of multi-layered fiber reinforced composite materials was designed and microwave absorbing properties are investigated. On the basis of transmission line theory, the theoretical equations to predict the reflection loss and the appropriate composite material for each functional layer are suggested. The most significant result of this study is the successful design and fabrication of triple-layered composite laminates which has the superior microwave absorbing porperties (more than 10 dB in 4∼12 GHz range), without using the ferrite filler in the impedance transforming layer. In the two-layered composite laminate (absorber/substrate), however, the use of ferrite filler (about 40 wt %) in the absorbing layer is necessary to obtain the certain level of microwave absorbance. By combining the glass-fiber composite with ferrite filler and carbon-fiber composite substrate, the microwave absorbing properties more than 10 dB in 4∼12 GHz frequencies than be obtained.

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Compact S-Band Antenna Hat for RF Compatibility Testing of Launch Vehicle (발사체의 RF 호환성 시험을 위한 소형 S-밴드 안테나 햇)

  • Kim, Sung-Wan;Park, Dong-Chul
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.26 no.2
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    • pp.148-157
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    • 2015
  • In this paper, we propose a compact antenna hat to perform RF compatibility testing efficiently between the launch vehicle and ground stations. The proposed structure implements a small size and low loss using the conductive shield instead of the conventional RF absorber. The S-band antenna hat, which is fabricated for an inverted-F onboard antenna with the size of $74mm{\times}13mm{\times}16mm$, has the small enclosure of $88mm{\times}35mm{\times}44mm$, the return loss of 25.6 dB, the insertion loss of 0.26 dB, and the leakage loss of 49.4 dB at the center frequency of 2.25 GHz. The simulated and measured results show a good agreement.

Isolation Improvement in Vivaldi Antennas Using DSRR (DSRR을 이용한 비발디 안테나 소자 간 격리도 향상)

  • Yun, Juho;Park, Daesung;Jang, Donghyeok;Hwang, Keum Cheol
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.29 no.10
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    • pp.739-744
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    • 2018
  • In this paper, a double split-ring resonator(DSRR) is proposed to improve the isolation between Vivaldi antenna elements. The DSRR was designed using a unit cell simulation and applied to a $1{\times}2$ Vivaldi antenna array to confirm the improvement in the isolation. The unit cell size of the proposed DSRR is $5mm{\times}5mm{\times}1.52mm$ and six unit cells are used. To verify the performance of the proposed DSRR, $1{\times}2$ Vivaldi antenna arrays with and without the DSRR were fabricated and measured. The results show an isolation improvement of 20 dB in the Vivaldi antennas with the DSRR when compared to the Vivaldi antennas without the DSRR.

Multi-Functional Microstrip Spiral Antenna : Dual-Band Operation and Multi-Pattern Control (다양한 복사패턴을 가지는 이중대역용 다기능 마이크로스트립 스파이럴 안테나)

  • 김명기;오대영;박익모
    • Journal of the Institute of Electronics Engineers of Korea TC
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    • v.40 no.11
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    • pp.77-84
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    • 2003
  • This paper presents a multi-functional microstrip spital antenna that operates in dual frequency bands. Several types of beam shape can be selected by controlling the phase difference of two spiral arms with the phase shifters located on each feed line. It has a normal beam at the lower frequency band, and four different patterns at the higher frequency band: normal beam, conical beam and two types of tilted beam. The antenna exhibits more than 10% of bandwidth at each band. The antenna is fabricated with conductor backed electromagnetic absorber in order to attain unidirectional radiation pattern and confirmed the multi-functionality by measurements.

The Micro Coil Production through Research on the Additive Conditions of Electrochemical Metal 3D Printer (전기화학적 금속 3D 프린터의 적층 조건 연구를 통한 마이크로 코일 제작)

  • Kim, Young-Kuk;Kang, Donghwa;Kim, Sung-Bin;Yoo, Bongyoung
    • Journal of the Korean institute of surface engineering
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    • v.53 no.4
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    • pp.138-143
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    • 2020
  • In this study, we produced a coil of micro-pattern that can be used for electromagnetic wave absorber, heating material, wireless charging, sensor, antenna, etc. by using electrochemical additive manufacturing method. Currently, it contains research contents for manufacturing a micro pattern coil having practicality through control of process control variables such as applied voltage, distance between electrode, and nozzle injection. Circulation of the electrolyte through the nozzle injection control can significantly contribute to improving the surface characteristics of the coil because of minimizing voltage fluctuations that may occur during the additive manufacturing process. In addition, by applying the pulse method in the application of voltage, the lamination characteristics of the plated body were improved, which showed that the formation of a fine line width plays an important role in the production of a micro pattern coil. By applying the pulse signal to the voltage application, the additive manufacturing characteristics of the produced product were improved, and it was shown that the formation of a fine line width plays an important role in the production of a micro pattern coil.

W-type hexaferrite-epoxy composites for wide-band radar absorption (광대역 레이다 흡수용 W-type 육방정 페라이트-에폭시 복합 소재)

  • Su-Mi Lee;Tae-Woo Lee;Young-Min Kang;Hyemin Kim
    • Journal of Aerospace System Engineering
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    • v.17 no.1
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    • pp.42-50
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    • 2023
  • In this study, hexagonal ferrite powder with chemical formula SrZn2-xCoxFe16O27 was synthesized by a solid-state reaction method and its electromagnetic (EM) wave absorption characteristics were evaluated in the frequency range of 0.1-18 GHz with absorber thickness range of 0 - 10 mm. Reflection loss (RL) affecting electromagnetic wave absorption performance was calculated based on the transmission line theory using measured complex permeabilities and permittivities. RL spectra were also directly measured for some samples. They were well matched with calculated results. High-frequency complex permeability characteristics were changed gradually according to the amount of Co substitution (x). The EM wave absorption frequency band could be tuned accordingly. Hexaferrite samples with x = 1.0, 1.25, and 1.5 exhibited remarkable maximum electromagnetic wave absorption performances with minimum RL (RLmin) lowered than -50 dB. They also showed a very broad frequency band (Δf > 10 GHz) in which more than 90% of the EM wave energy absorption occurred (RL ≤ -10 dB).