• Proceedings of the Korea Electromagnetic Engineering Society Conference
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• 2001.11a
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• pp.337-340
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• 2001

We show that the microstrip ring with a narrow gap exhibits a photonic band gap (PBG) that is generally believed to be created by a periodic array. The discontinuity of impedance at the narrow gap induces the multiple reflections with fixed phase correlation necessary to make the PBG. We have also discussed the tuning of the PBG frequency by applying an external voltage on a varactor mounted on the gap and the applications of this PBG ring as a tunable bandstop filter and a microwave switch.

• Proceeding of EDISON Challenge
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• 2015.03a
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• pp.378-381
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• 2015

To produce low cost and efficient photovoltaic cells, inorganic-organic lead halide perovskite materials appear promising for most suitable solar cells owing to their high power conversion efficiency. Most recent research showes that formamidinium lead iodide ($FAPbI_3$) with methylammonium lead bromide ($MAPbBr_3$) improves the power conversion efficiency of the solar cell to more than 18 per cent under a standard illumination because incorporated $MAPbBr_3$ makes $FAPbI_3$-relatively unstable but comparatively narrow band gap-more stable composition. In respect to first principle study, we investigated band gap of $MAPbI_3$, $FAPbI_3$, $MAPbBr_3$, $(FAPbI_3)_{0.89}-(MAPbBr_3)_{0.11}$ and 0.615(eV), 0.466, 1.197, 0.518 respectively through EDISON DFT software. These results emphasize enhancing structure stability is important factor as well as finding narrow band gap.

• Proceedings of the KIEE Conference
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• 1992.07b
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• pp.813-815
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• 1992

Accurate Capacitance-Voltage characteristics of Metal-Insulator-Semiconductor (MIS) devices in narrow band-gap semiconductors are presented. The unique band structure of narrow band-gap semiconductors is taken into account such as non-parabolicity and degeneracy. Compensated and partially ionized impurities either in the bulk or the space charge region are also considered. HgCdTe is a defect semiconductor, so this approach is very important for characterization and analysis of MIS devices.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.43 no.3
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• pp.420-431
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• 1994

The HgCdTe material, which is II-VI compound semiconductor, is important materials for the fabrication of the infrared detectros. To suggest the model of accurate MIS C-V calculation for narrow band gap semiconductors such as HgCdTe, non-parabolicity from k.p theory and degeneracy effect are considered. And partially ionized effect and compensation effect which are material's properties are also considerd. Especially, degenerated material C-V characteristics from Fermi-Dirac statistics and exact charge theory are presented to get more accurate analysis of the experimental results. Also the comparison with calculation results between the general MIS theory from Boltzmann appoximation method and this model which is considered the narrow band gap semiconductor properties, show that this model is more useful theory to determination of accurate low and high frequency C-V characteristics.

• Journal of the Korean Institute of Telematics and Electronics D
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• v.36D no.6
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• pp.87-96
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• 1999

For analog optical transmission of narrow-band microwave signal, a novel all-optical linearization technique of electro-absorption (EA) optical modulator by using dual modulation scheme is proposed and theoretically investigated. By using the dual modulation scheme where the sub-modulator has a different length, DC bias and band-gap wavelength, the DC bias operation point where the third-order intermodulation products of ~30dB and the following increase of spurious free dynamic range (SFDR) of ~20dB wave achieved in sub-octave narrow band operation.

• Journal of IKEEE
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• v.24 no.4
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• pp.1122-1128
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• 2020

Bandwidth Extension refers to restoring and expanding a narrow band signal(NB) that is damaged or damaged in the encoding and decoding process due to the lack of channel capacity or the characteristics of the codec installed in the mobile communication device. It means converting to a wideband signal(WB). Bandwidth extension research mainly focuses on voice signals and converts high bands into frequency domains, such as SBR (Spectral Band Replication) and IGF (Intelligent Gap Filling), and restores disappeared or damaged high bands based on complex feature extraction processes. In this paper, we propose a model that outputs an bandwidth extended signal based on an autoencoder among deep learning models, using the residual connection of one-dimensional convolutional neural networks (CNN), the bandwidth is extended by inputting a time domain signal of a certain length without complicated pre-processing. In addition, it was confirmed that the damaged high band can be restored even by training on a dataset containing various types of sound sources including music that is not limited to the speech.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.12 no.3
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• pp.329-338
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• 2001

In this paper, we designed microstrip patch antenna to enhance the weak point of general microstrip patch antenna that has narrow bandwidth and analyzed that. To reduce reactance in probe feed antenna, capacitive gap added to the patch. Using single patch and auxiliary wire, makes dual frequency resonant. So bandwidth is improved and gain also becomes higher. To verify with experiment, PCS band antenna is designed, fabricated. For PCS band antenna, bandwidth is 180 MHz in VSWR<1.5 and gain is 8.6 dBi.

• Journal of electromagnetic engineering and science
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• v.5 no.1
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• pp.43-47
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• 2005

Microwave or optical photonic band-gap(PBG) structures are conventionally realized by cascading distributive elements in a periodic pattern. However, the frequency bandwidth obtained through such plainly periodic arrangement is typically narrow, corporate with a relatively high rejection side-lobe band. To alleviate such problems, a design involving a chirping and tapering technique is hence introduced and employed. The design has been applied in both a planar stratified dielectric medium as well as a strip-line transmission line structure, and results are validated when compared with the corresponding conventional PBG structure.

• Bulletin of the Korean Chemical Society
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• v.35 no.2
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• pp.505-512
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• 2014

A new donor-accepter-donor-accepter-donor (D-A-D-A-D) type 2,1,3-benzothiadiazole-thiophene-based acceptor unit 2,5-di(4-(5-bromo-4-octylthiophen-2-yl)-2,1,3-benzothiadiazol-7-yl)thiophene ($DTBTTBr_2$) was synthesized. Copolymerized with fluorene and indeno[1,2-b]fluorene electron-rich moieties, two alternating narrow band gap (NBG) copolymers PF-DTBTT and PIF-DTBTT were prepared. And two copolymers exhibit broad and strong absorption in the range of 300-700 nm with optical band gap of about 1.75 eV. The highest occupied molecular orbital (HOMO) energy levels vary between -5.43 and -5.52 eV and the lowest unoccupied molecular orbital (LUMO) energy levels range from -3.64 to -3.77 eV. Potential applications of the copolymers as electron donor material and $PC_{71}BM$ ([6,6]-phenyl-$C_{71}$ butyric acid methyl ester) as electron acceptors were investigated for photovoltaic solar cells (PSCs). Photovoltaic performances based on the blend of PF-DTBTT/$PC_{71}BM$ (w:w; 1:2) and PIF-DTBTT/$PC_{71}BM$ (w:w; 1:2) with devices configuration as ITO/PEDOT: PSS/blend/Ca/Al, show an incident photon-to-current conversion efficiency (IPCE) of 2.34% and 2.56% with the open circuit voltage ($V_{oc}$) of 0.87 V and 0.90 V, short circuit current density ($J_{sc}$) of $6.02mA/cm^2$ and $6.12mA/cm^2$ under an AM1.5 simulator ($100mA/cm^2$). The photocurrent responses exhibit the onset wavelength extending up to 720 nm. These results indicate that the resulted narrow band gap copolymers are viable electron donor materials for polymer solar cells.

• Proceedings of the Korean Magnestics Society Conference
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• 2002.12a
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• pp.32-33
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• 2002

최근 세계적 주목을 받고 있는 spin FET[1] 소자의 구현은 강자성 물질에 의하여 반도체에 주입된 spin 편향된 전자가 반도체 계면에 유도된 전기장의 영향을 받아 spin-orbit interaction을 하는 mechanism(Rashbar effect)이 근간을 이루고 있다. 작은 band gap을 가지는 반도체(narrow gap 반도체)는 작은 유효질량의 전자에 의해서 이러한 Rashbar effect[2]를 크게 할 수 있는 물질로서, spin FET 구현을 위한 강력한 후보이며, 요즘 한창 연구되고 있는 주제이기도 하다[3]. (중략)