• Title/Summary/Keyword: selective reflection

Search Result 65, Processing Time 0.04 seconds

A Reflection Type Band-rejection Filter Using the Frequency Selective Loads (주파수 선택적 부하를 이용한 반사형 대역저지 필터)

  • 김윤조;정승환;황희용;정중성;박준석
    • Proceedings of the Korea Electromagnetic Engineering Society Conference
    • /
    • 2002.11a
    • /
    • pp.141-145
    • /
    • 2002
  • In this paper, we have implemented the reflection type band-rejection filter by employing the 3-㏈ hybrid and the frequency-selective loads. The frequency-selective loads have been achieved with the 3-pole bandpass filter terminated by a 50-ohm load. The reflection type band-rejection filter is less sensitive to unloaded Q-factor of resonator than the conventional one. Measurements and simulations on the presented band-rejection filter in this paper show the excellent performances in passband and rejection-band.

  • PDF

Deposition of Cermet Solar Selective Coatings for High Temperature Applications (고온용 서밋 태양선택흡수막의 증착)

  • Lee, Kil-Dong
    • Journal of the Korean Solar Energy Society
    • /
    • v.26 no.1
    • /
    • pp.57-64
    • /
    • 2006
  • Cr-CrO cermet solar selective coatings with a double cermets layer film structure were prepared using a special direct current (dc) magnetron sputtering technology. The typical films structures from surface to bottom substrate were measured to be an $Al_2O_3$ anti-reflection layer on a double Cr-CrO cermet layer on an Al metal infrared reflection layer. Optical properties of optimized Cr-CrO cermet solar selective coating were absorptance (${\alpha}$) = 0.95 and emittance (${\varepsilon}$) = 0.10 ($100^{\circ}C$). Atomic force microscopy (AFM) image showed that Cr-CrO cermet film was very smooth and their grain size was also very small The results of thermal stability test showed that the Cr-CrO cermet solar selective coatings were stable for use at temperature of $400^{\circ}C$.

Study on Planar Orientation and Selective Reflection of Cholesteric Liquid Crystals (콜레스테릭 액정의 Planar 배열과 선택 반사 특성에 관한 연구)

  • Jung, Gap-Ha;Seo, In-Seon;Lee, Mong-Ryong;Choi, Suk-Won;Song, Ki-Gook
    • Polymer(Korea)
    • /
    • v.34 no.3
    • /
    • pp.242-246
    • /
    • 2010
  • FTIR spectroscopy has been employed in order to quantitatively investigate the relationship between planar arrangements and selective reflectance of cholesteric liquid crystals. It was found that the selective reflection was enhanced as the amount of planar arrangements in cholesteric liquid crystals increased. Although the planar arrangements of cholesteric liquid crystals can be induced only by the shear force effect, it was more effective to use the alignment layer to obtain the perfect planar arrangements.

Deposition of Solar Selective Coatings for High Temperature Applications (고온용 태양 선택흡수막의 제작)

  • Lee, Kil-Dong
    • Journal of the Korean Solar Energy Society
    • /
    • v.28 no.1
    • /
    • pp.33-42
    • /
    • 2008
  • Zr-O ($Zr-ZrO_2$) cermets solar selective coatings with a double cermets layer film structure were prepared using a DC (direct current) magnetron sputtering method. The typical film structure from surface to bottom substrate were an $Al_2O_3$ anti-reflection layer on a double Zr-O cermets layer on an Al metal infrared reflection layer. Optical properties of optimized Zr-O cermets solar selective coating had an absorptance of ${\alpha}\;=\;0.95$ and thermal omittance of ${\epsilon}\;=\;0.10\;(100^{\circ}C)$. The absorbing layer of Zr-O cermets coatings on glass and silicon substrate was identified as being amorphous by using XRD. AFM showed that ZF-O cermets layers were very smooth and their surface roughness were approximately $0.1{\sim}0.2 nm$. The chemical analysis of the cermets coatings were determined by using XPS. Chemical shift of photoelectron binding energy was occurred due to the change of Zr-O cermets coating structure deposited with increase in oxygen flow rate. The result of thermal stability test showed that the Zr-O cermets solar selective coating was stable for use at temperature below $350^{\circ}C$.

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
    • /
    • v.9 no.1
    • /
    • pp.46-52
    • /
    • 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.

Design of Frequency-Selective Reflector for Large Reflecting Antennas using a Periodic Dielectric Layer (주기적인 유전체 층을 사용한 안테나용 주파수 선택 반사기의 설계)

  • Ho, Kwang-Chun
    • The Journal of the Institute of Internet, Broadcasting and Communication
    • /
    • v.10 no.1
    • /
    • pp.33-38
    • /
    • 2010
  • This paper examines the feasibility of using periodically varying dielectric layers with dielectric constant ${\epsilon}_1$ and ${\epsilon}_2$ at millimeter wave frequency for implementing the frequency-selective reflectors that permit feed separation in large aperture reflecting antenna systems. For oblique incidence, it is found that the total reflection can be obtained at different frequencies for proper choices of ${\epsilon}_1$, ${\epsilon}_2$ and the geometric parameters. In the frequency-selective reflector designed, the bandwidth for 90% reflection is always found to be much narrower than that for 90% transmission.

Analysis of Infinite Periodic Frequency Selective Surface using Method of Moment (모멘트법을 이용한 주기적 배열을 갖는 무한 크기의 주파수선택 표면(FSS) 해석)

  • 강봉수;강부식;김흥수
    • Proceedings of the IEEK Conference
    • /
    • 2003.07a
    • /
    • pp.290-293
    • /
    • 2003
  • In this paper, infinite frequency selective surface comprised with rectangular plates which are arranged periodically is analyzed using Method of Moment based on Galerkin's method. In analysis, it is assumed that the plates are infinite thin perfect conductors. Based on this assumption, the reflection characteristics of the FSS is compared according to the polarization of plane-wave and the direction of incidence. In the results, the variation of reflection characteristics of the FSS highly depends on the direction of incidence when the polarization of the plane-wave is parallel to the plane of incidence, but the variation is nearly independent upon direction of incidence when the polarization of the plane-wave is perpendicular to the plane of incidence.

  • PDF

Selective Emitter Effect of porous silicon AR Coatings formed on single crystalline silicon solar cells (단결정 실리콘 태양전지에 형성한 다공성실리콘 반사방지막의 선택적 에미터 특성 연구)

  • Lee, Hyun-Woo;Kim, Do-Wan;Lee, Eun-Joo;Lee, Soo-Hong
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
    • /
    • 2006.11a
    • /
    • pp.116-117
    • /
    • 2006
  • We investigated selective emitter effect of Porous Silicon (PSI) as antireflection coatings (ARC). The thin PSi layer, less than 100nm, was electrochemically formed by electrochemical method in about $3{\mu}m$ thick $n^+$ emitter on single crystalline silicon wafer (sc-Si). The appropriate PSi formations for selective emitter effect were carried out a two steps. A first set of samples allowed to be etched after metal-contact processing and a second one to evaporate Ag front-side metallization on PSi layer, by evaluating the I-V features The PSi has reflectance less than 20% in wavelength for 450-1000nm and porosity is about 60%. The cell made after front-contact has improved cell efficiency of about in comparison with the one made after PSi. The observed increase of efficiency for samples with PSi coating could be explained not only by the reduction of the reflection loss and surface recombination but also by the increased short-circuit current (Isc) within selective emitter. The assumption was confirmed by numerical modeling. The obtained results point out that it would be possible to prepare a solar cell over 15% efficiency by the proposed simple technology.

  • PDF

Growth and Characteristics of Al2O3/AlCrNO/Al Solar Selective Absorbers with Gas Mixtures

  • Park, Soo-Young;Han, Sang-Uk;Kim, Hyun-Hoo;Jang, Gun-Eik;Lee, Yong-Jun
    • Transactions on Electrical and Electronic Materials
    • /
    • v.16 no.5
    • /
    • pp.264-267
    • /
    • 2015
  • AlCrNO cermet films were prepared on aluminum substrates using a DC-reactive magnetron sputtering method and a water-cooled Al:Cr target. The Al2O3/AlCrNO (LMVF)/AlCrNO (MMVF)/AlCrNO (HMVF)/Al/substrate of the 5 multi-layers was prepared according to the Ar and (N2 + O2) gas-mixture rates. The Al2O3 of the top layer is the anti-reflection layer of triple AlCrNO (LMVF)/AlCrNO (MMVF)/AlCrNO (HMVF) layers, and an Al metal forms the infrared reflection layer. In this study, the crystallinity and surface properties of the AlCrNO thin films were estimated using X-ray diffraction (XRD) and field-emission scanning electron microscopy (FESEM), while the composition of the thin films was systematically investigated using Auger electron spectroscopy (AES). The optical properties of the wavelength spectrum were recorded using UH4150 spectrophotometry (UV-Vis-NIR) at a range of 0.3 μm to 2.5 μm.

Reduction of viewing-angle dependent color shift in a reflective type cholesteric liquid crystal color filter

  • Jang, Won-Gun;Beom, Tae-Won;Cui, Hao;Park, Jong-Rak;Hwang, Seong-Jin;Lim, Young-Jin;Lee, Seung-Hee
    • 한국정보디스플레이학회:학술대회논문집
    • /
    • 2008.10a
    • /
    • pp.1656-1659
    • /
    • 2008
  • The reflective type color filter for the liquid crystal displays (LCD) was produced using cholesteric liquid crystal monomers whose phase is characterized by the unique optical features of selective reflection. Periodic micrometer scale hemi-spherical photoresist (PR) patterns were formed on glass substrates by thermal reflow method after photolithography. Cholesteric color filter films for red, green and blue light reflections were then produced and the viewing angle dependence was investigated and compared with that of reflected light on the non-patterned substrates.

  • PDF