• 제목/요약/키워드: Microwave reflection

검색결과 177건 처리시간 0.023초

규칙적 또는 불규칙적 구조를 가지는 빌딩벽면에서의 전자파 산란 특성 (Scattering Characteristic from Building Walls with Periodic and Random Surface)

  • 윤광렬
    • 한국전자파학회논문지
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    • 제15권4호
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    • pp.428-435
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    • 2004
  • 최근 이동단말기의 급속한 보급과 발전에 의하여, 통상의 시가지에서의 전자파전파의 특성을 해명해야할 뿐만 아니라, 시가지, 산림, 계곡 등의 외부 공간과 실내 공간 등의 종래에는 전파불감지대로 불려오던 공간에 있어서도 안정적으로 통신을 이용할 수 있는 무선통신환경 개선의 중요성이 높게 요구되고 있다. 더욱이, 이동통신의 디지털화와 더불어 건물 등에 의한 반사에 의해서 생기는 멀티패스에 기인하는 수신펄스의 시간지연이 고속디지털통신의 장해가 되고 있다. 이러한 도심 시가지에 대한 전자파전파의 특성을 보다 정도 높게 추정하기 위해서는 건물 벽면의 구조 및 간판 등의 영향도 고려 대상으로 포함시킬 필요성이 있다. 본 연구에서는, 먼저 무선통신환경에서의 시가지, 산림, 해면, 빌딩 벽면 등의 문제를 규칙적 및 불규칙조면(random rough surface)에 의한 산란문제로 취급하여 그 특성을 상세히 파악하고자 한다. 실제 문제에 있어서도 간판과 같은 빌딩의 부착물, 창, 테라스 등과 같은 규칙적 벽면 구조 또는 불규칙적 벽면 구조를 가지고 있는 경우가 일반화되어 있는 실정이다. 따라서 본 논문에서는 FVTD(finite volume time domain)법을 적용하여 기초적인 자료 보완을 위하여 3분류에 의한, 즉 주기적 구조에 의한 산란 특성, 불규칙적 구조에 의한 산란 특성, 주기적 및 불규칙의 복합형구조에 의한 2차원 전파환경 모델들에 대한 산란 특성을 조사하였다. 특히 주기적 벽면구조에 대한 Bragg reflection의 영향을 조사하였다.

마이크로웨이브 방사형 전력 결합기 설계 (The design of a microwave radial power combiner)

  • 임재욱;강원태;이상호;장익수
    • 전자공학회논문지D
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    • 제34D권8호
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    • pp.1-7
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    • 1997
  • In ahigh power amplifier design, power combiner/divider is used to connect low power amplifiers in parallel. The raidal structure of the powe combiner/divider has not only a good characteristics of port-to-port isolation but also an advantage of giving a redundancy to the structure itself by using RF switches. The parastics of a power resistor, that would be a problem in design process, are removed by both slot lines and cavity resonators, and the comon node in the circuit is rdesigned as a planar topology, and thus a new type of 4-way radial power combiner/divider is accomplished at 1840 ~ 1870 MH PCS frequency band. The insertion loss, reflection, and isolation characteristics of 40way radial power combiner/divider which can be adaptable to PCS system in this thesis are -0.3dB, -24dB,a dn -27dB respectively.

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$20 mm\phi$ 동축관을 이용한 전파흡수체의 특성측정법에 관한 연구 (A Study on the Measurement Technique of the Characteristics of Electromagnetic Wave Absorber Using $20 mm\phi$ Coaxial Tube)

  • 김동일;정중식;백명숙;안영섭;정세모
    • 한국전자파학회지:전자파기술
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    • 제4권2호
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    • pp.17-23
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    • 1993
  • 본 논문은 종단단락형 $20 mm\phi$ 동축관을 이용하여 전자파흡수체로 제작된 샘플들의 반사감쇠량과 재료 정수를 측정하는 것이 목적이다. 저자는 One port method에 의한 재료정수의 산출 알고리즘을 제안하고, 슬 에 의한 실험치와 계산치가 잘 일치함을 보임으로써 제안한 측정법의 타당성을 입증하였다. 이 측정법은 전파흡수체 설계와 특성평가에 유효하게 사용될 것이다.용될 것이다.

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초고주파 구형도파로를 이용한 엔진 오일의 유전율 측정 (Microwave Rectangular Waveguide Measurement of the Engine Oil Dielectric Constant)

  • 김기훈;김영주
    • Tribology and Lubricants
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    • 제27권3호
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    • pp.156-161
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    • 2011
  • The rectangular waveguide technique can be used to measure the complex permittivity of dielectric material of various thickness and cross section. This paper presents the analysis system of engine oil permittivity at which deterioration of engine oil is measured at the X-band(8-12.5 GHz). The middle of the rectangular waveguide has engine oil case and is connected with VNA(Vector Network Analyzer) for the measurement of the transmission$(S_{21})$ and reflection$(S_11)$ and then the permittivity is extracted. The deterioration of engine oil is proved by the comparison with both the extracted data and reference data. As the additional research, This paper suggest that an accurate permittivity is considered by not only the wave guide length but the air gap between oil case and the waveguide.

Electromagnetic Interference Reflectivity of Nanostructured Manganese Ferrite Reinforced Polypyrrole Composites

  • Chakraborty, Himel;Chabri, Sumit;Bhowmik, Nandagopal
    • Transactions on Electrical and Electronic Materials
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    • 제14권6호
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    • pp.295-298
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    • 2013
  • Nano-size manganese ferrite reinforced conductive polypyrrole composites reveal a core-shell structure by in situ polymerization, in the presence of dodecyl benzene sulfonic acid as the surfactant and dopant, and iron chloride as the oxidant. The structure and magnetic properties of manganese ferrite nano-fillers were measured, by using X-ray diffraction and vibrating sample magnetometer. The morphology, microstructure, and conductivity of the composite were characterized by transmission electron microscopy, Fourier transform infrared spectroscopy, and four-wire technique. The microwave-absorbing properties of composites reinforcement dispersed in resin coating with the coating thickness of 1.2 nm were investigated, by using vector network analyzers, in the frequency range of 8~12 GHz. A reflection loss of -8 dB was observed at 10.5 GHz.

1-PORT METHOD에 의한 전파흡수체의 재료정수 및 전파흡수능 측정기법연구 (A Study on the Measurement Teachnique of the Meterial Constants And Propagation Absorbing Ability of Electromagnetic Wave Absorber By One Port Method)

  • 김동일;백명숙;정중식
    • 한국항해항만학회:학술대회논문집
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    • 한국항해항만학회 1993년도 춘계학술발표회
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    • pp.53-64
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    • 1993
  • This study aims to measure the reflection loss and the material constants of the fabricated samples for electromagnectic wave absorber precisely and easily by using 20mm$\Phi$coaxial tube with the end-short-type. The authors have estabilished the extraction algorithm of material constants by one port method and proved that the results of the experiments coincided with the calculated ones. On the basis of the above results the validity of the proposed measuring method is confirmed. This measurement method could be used effectively for the design of microwave absorbe and for its evaluation.

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니켈-아연 페라이트 소결체와 복합체의 전파흡수특성 (The Characteristics of Electromagnetic Wave Absorption in Sintered and Composite Ni-Zn Ferrites)

  • 조성백;오재희
    • 한국세라믹학회지
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    • 제32권1호
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    • pp.25-30
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    • 1995
  • The frequenc dependence of magnetic permeability($\mu$r) and dielectric constant($\varepsilon$r) in MHz-GHz frequency range and their relationships with microwave absorbing properties were investigated in sintered and composite Ni-Zn ferrites, respectively. It was confirmed that zero reflection condition was required the real parts of permeability and permittivity in sintered specimen, and the complex permeability, permittivity and dielectric loss tangent in composite specimen. The real part of permittivity varied with the replacement of nickel by manganese in sintered Ni-Zn ferrite. Therefore, we could control the matching frequency and matching thickness.

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나노탄소섬유와 나노카바이드섬유를 이용한 복합재의 제조와 활용에 관한 연구 (Preparation and Application of Fiber Composites made of Carbon Nanofibers and Carbide Nanofibers)

  • 임연수;김기덕;이재춘;김명수;김성수
    • 한국세라믹학회지
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    • 제37권6호
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    • pp.569-575
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    • 2000
  • Fabrication of carbon fiber reinforced composites was carried out by hand lay-up method. Carbon nanofibers and SiC nanofibers were used as filler in the composites fabrication. Carbon nanofibers, one of the new carbon materials, have 5∼500 nm in diameter and 5-10 nm in length. SiC nanofibers were modified by silicon monoxide vapor with carbon nanofibers. The composites were carbonized at 1000$^{\circ}C$ in a nitrogen atmosphere, and then densified by molten pitches impregnated in vacuum. Multiple cycles of liquid pitch impregnation and carbonization were carried out to obtain a desired density. The composites were characterized by density, microstructure. The inter-laminar shear strength (ILSS) test was performed for mechanical properties. For the new application, the microwave reflective proeprty of composites was investigated. Dielectric constant and permeability spectrum were measured in 12∼18 GHz frequency ranges. On the basis of the wave propagation theory in a lossy media, the reflection loss from the composite inter-layer was predict as a function of frequency.

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휴대전화 단말기용 전파흡수체의 개발에 관한 연구 (A Study on Development of EM Wave Absorbers for Mobile Phones)

  • 정재현;김동일
    • 한국마린엔지니어링학회:학술대회논문집
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    • 한국마린엔지니어링학회 2005년도 후기학술대회논문집
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    • pp.67-68
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    • 2005
  • This thesis is concerned with basic research for development of EM wave absorbers in sheet type for mobile phones. By controlling the sendust ratio, the $Al(OH)_3$ coating, the thickness, the kind of binders, EM wave absorbers were prepared and examined. Centeral frequency shifts toward lower with increasing thickness of the absorber, and absorption ability controlled to adjust Sendust amount. The absorption band of the EM wave absorber coated with $Al(OH)_3$ becomes larger than that of non-coated one. Sendust composite microwave absorbers mixed with CPE were prepared at $70^{\circ}C$ in temperature. The fabricated EM wave absorbers show a reflection coefficient 5.56 dB at 1.8 GHz in thickness of 0.85 mm.

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MIC화 PIN다이오드 하이브리드형 이상기의 설계에 관한 연구 (A Study on the Design of Hybrid MIC Phase Shifter Using PIN Dioid)

  • 김태회;박의준;박정기
    • 한국통신학회논문지
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    • 제12권4호
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    • pp.325-334
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    • 1987
  • PIN 다이오드를 利用한 反射形 移相器는 4端子網 임피던스 變換回路로 構成될 수 있는데 원하는 移相量을 얻기위한 設計方程式 誘導에 假想 임피던스法을 적용하였다. 실제로 2-bit($22.5^{\circ}$$45^{\circ}$)하이브리드 移相器를 設計 具現하여 中心周波數(10GHz)에서 $22.5^{\circ}$bit는 $0.5^{\circ}$, $45^{\circ}$bit는 $0^{\circ}$의 移相量 誤差의 것을 얻었으며 main beam 制御用 phased-array안테나를 위한 移相器設計에 이 方法을 사용할 수 있음을 立證하였다.

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