• 한국진공학회:학술대회논문집
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• 한국진공학회 2013년도 제44회 동계 정기학술대회 초록집
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• pp.694-694
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• 2013

With the growing need of more effective energy harvesting, solar energy has been sought as one of the prominent candidates among the eco-friendly methods. Although many types of solar cells have been developed, the electronic conversion efficiency is limited by the material's physical properties: solar cells can only harvest solar energy from limited range in solar energy spectrum. To overcome this physical limit, we approached by using the down conversion effect, transforming the high energy photons to low energy photons, to the range the designated solar cell can convert to electronic energy. In our study, we have fabricated GaAs single junction solar cells and applied CdSe quantum dots for down-conversion. We examine the effects of such application on the solar cell efficiancy, fill-factor, JSC, VOC, etc.

• JSTS:Journal of Semiconductor Technology and Science
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• 제6권2호
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• pp.114-118
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• 2006

In this paper, the effect of base and collector structures on DC, small signal characteristics of SiGe HBTs fabricated by RPCVD was investigated. The structure of SiGe HBTs was designed into four types as follows: SiGe HBT structures which are standard, apply extrinsic-base SEG selective epitaxial growth (SEG), apply selective collector implantation (SCI), and apply both extrinsic-base SEG and SCI. We verified the devices could be applied to the fabrication of RFIC chip through a fully integrated 2.4 GHz down-conversion mixer.

• 한국전기전자재료학회논문지
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• 제17권3호
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• pp.323-328
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• 2004

Down-conversion of Eu$^{3+}$ doped LiGdF$_4$ (LGF) for increasing the cell efficiency on dye-sensitized Ti $O_2$ solar cells has been studied. The dye sensitized solar cell (DSC) consisting of mesoporous Ti $O_2$ electrode deposited on transparent substrate, an electrolyte containing I$^{[-10]}$ /I$_3$$^{[-10]}$ redox couple, and Pt counter electrode is a promising alternative to the inorganic solar cell. The structure of DSC is basically a sandwich type, viz., FTO glass/Ru-red dye-absorbed Ti $O_2$/iodine electrolyte/sputtered Pt/FTO glass. The cell without down converter had open circuit potential of approximately 0.66 Volt, the short circuit photocurrent density of 1.632 mA/$\textrm{cm}^2$, and fill factor of about 50 ％ at the excitation wavelength of 550 nm. In addition, 5.6 mW/$\textrm{cm}^2$ incident light intensity beam was used as a light source. From this result, the calculated monochromatic efficiency at the wavelength of 550 nm of this cell was about 9.62 ％. The incident photon to current conversion efficiency (IPCE) of N3 used as a dye in this work is about 80 ％ at around 590 nm and 610 nm, which is the emission spectrum of Eu$^{3+}$ doped LGF, results in efficiency increasing of DSC.C.

• 한국광학회지
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• 제14권6호
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• pp.573-577
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• 2003

Hong-Ou-Handel 간섭계를 이용한 광자쌍의 4차 간섭실험에서 두 광자의 뭉침이 단일계수에 미치는 영향을 조사하였다. 검출기의 단일광자 시간 분해능보다 짧은 시간간격으로 두 광자가 검출기에 입사할 때 하나의 검출기에서 측정되는 단일계수가 현저하게 줄어드는 변화를 확인하였다.

• 한국정밀공학회지
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• 제25권11호
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• pp.83-89
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• 2008

The Effect of Space Velocity(SV) on NOx conversion rate was performed to develop NOx reduction after-treatment system. SV is calculated from engine exhaust gas volume and SCR catalyst volume. Found the Urea injection duty of maximum efficiency for NOx conversion if increase SV, NOx Conversion rate is down. Especially, when SV is more than $110,000h^{-1}$, NOx conversion rate decrease suddenly. Same case, if SV is lower than $40,000h^{-1}$, NOx conversion rate is down. Also, the characterization of Urea-SCR system was performed. Three candidate injectors for injecting Urea were tested in terms of 속 injection rate and NOx reduction rate. The performances of SCR catalytic converter on temperature were investigated. The performance of Urea-SCR system was estimated in the NEDC test cycle with and without EGR. It was found that nozzle type injector had high NOx conversion rate. SCR catalytic converter had the highest efficiency at the temperature of $350^{\circ}C$. EGR+Urea-SCR system achieved NOx reduction efficiency of 73% through the NEDC test cycle.

• KIEE International Transactions on Electrophysics and Applications
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• 제2C권5호
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• pp.273-278
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• 2002

Even though the modulating signal frequency of the light is too high to detect directly, the signal can be extracted by frequency conversion at the same time as the detection by means of the non-linearity of the APD. An analysis is presented for super-high-speed optical demodulation by an APD with electronic mixing. A normalized gain is defined to evaluate the performance of the frequency conversion demodulation. The nonlinear effect of the internal capacitance was included in the small signal circuit analysis. We showed theoretically and experimentally that the normalized gain is dependent on the down converted difference frequency component. In the experiment, the down converted different frequency outputs became larger than the directly detected original signal for the applied local signal of 20㏈m.

• 한국통신학회논문지
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• 제1권1호
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• pp.23-31
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• 1976

VHF 및 UHF 챠넬의 TV 信號는 映像 및 音聲을 포함한 6MHz의 대역폭으로 챠넬變換 된후 直線增幅器를 통해 재 送信될 때 搬送波付近의 兩側波帶傳送領域에서 出力振幅周波數特性에 不自然스러운 變化가 생겨 화질에 影響을 주는수가 있다. 이러한 現像은 發振器로 부터의 不要信號로 因한 不要下側帶波의 發生등 問題가 되는 要因인 트랜지스터 直線增幅器의 非直線性, MIXER 회로에서의 상호변조 歪 AM-PM 變換 및 envelope delay 特性 등을 고려하여 出力特性을 구한 결과 主原因은 非直線性에 의한 것이였으며 實驗結果로서는 非直線性의 主因으로 Bias 조건의 불합리 및 發振器로 부터의 不要周波數의 發生이 가장 큰 原因으로 나타났다. 특히 인접信號에 對한 相互變調歪 및 不要信號發生은 Up conversion의 경우가 Down Conversion의 경우보다 현저히 감소됨을 확인하였고 發振器로부터의 spurious가 system에 영향을 주지 않는 方案을 모색하였다.

• 한국통신학회논문지
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• 제31권8C호
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• pp.806-815
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• 2006

디지털 변복조 장치에는 디지털 신호의 표본화 속도를 변환시키는 표본화 속도 변환기(SRC: sample rate converter)가 필요한데, 여기에 사용되는 저역필터의 구현 문제를 연구하였다. 표본화 속도 변환율이 클 경우에는 저역필터의 신호처리 연산량이 많아져서 구현에 부담이 되므로 연산량을 감소시키는 방안이 중요하다. 본 논문에서는 이 필터를 2 단의 직렬 필터로 분할하여 구현하는 설계 방법을 제시하였고, 1 단 구조의 단일 필터로 구현하였을 경우에 비교하여 신호처리 연산량이 감소되는 것을 확인하였다. 표본화 속도 변환율이 증가할수록 2 단분할 방안에 의한 연산량 감소 효과는 증가하며, 변환율이 32 에서는 72 %까지 감소되는 것을 확인하였다. 변환율을 2 단으로 분할함에 있어서도 인수의 조합에 따라서 감소 효과가 다르게 나타났으므로, 여러 변환율에 대하여 최적 성능의 분할율을 조사하였다. 저역필터는 다상 필터 구조를 갖는 FIR 필터를 대상으로 하였으며, 필터계수의 설계는 Parks-McCllelan 알고리즘을 이용하였다.

• 한국광학회지
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• 제14권2호
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• pp.130-134
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• 2003

매개하향변환과정에서 발생한 광자쌍과 Hong-Ou-Handel 간섭계를 이용한 4차 간섭실험에서 두 광자가 빔분할기에 동시에 입사할 때 빔분할기의 한 쪽 출구로만 두 광자가 쌍을 이루어 빠져나가는 두-광자의 공간적인 뭉침 효과를 관측하였다. 또한 검출기의 단일광자 시간 분해능보다 짧은 시간에 두 광자가 쌍으로 입사할 때 하나의 검출기에 의한 단일계수와 비교하였다.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2005년도 추계종합학술대회
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• pp.261-264
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• 2005

This paper presents the design of a down-conversion mixer with built-in active balun integrated in a $0.25\;{\mu}m$ pHEMT process. The active balun consists of series-connected common-gate FET and common-source FET. The designed balun achieved broadband characteristics by optimizing gate-width and bias condition for the reduction in parasitic effect. From DC to more than 6GHz, the active balun shows the phase error of less than 3 degree and the gain error of less than 0.4 dB. A single-balanced down-conversion mixer with built-in broadband active balun has been designed with optimum width, load resistor and bias for conversion gain and without any matching component for broadband operating. The designed mixer whose size of including on-chip bias circuit is $1\;mm{\times}1\;mm$ shows the conversion gain of better than 7 dB from 2 GHz to 6 GHz and $P_{1dB}$ of -10 dBm at 5.8 GHz