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Two-negative feedback loop PLL with frequency voltage converter loop
문대현,최영식 한국과학기술원 반도체설계교육센터 2019 IDEC Journal of Integrated Circuits and Systems Vol.5 No.4
- To reduce the phase noise and jitter of the conventional PLL, the proposed PLL uses frequency voltage converter (FVC). The inner negative feedback loop consisting of a voltage controlled oscillator (VCO) and a frequency voltage converter is nested inside a conventional outer PLL loop. When the output voltage (VCO input voltage) of the loop filter changes, the output voltage of the FVC changes in the opposite direction at a much higher sampling frequency in the negative feedback looped VCO. Thus, whenever the VCO output frequency varies, the FVC works as a compensator and it results in VCO noise reduction. It improves the phase noise characteristic and the stability of PLL. It has been simulated and proved by HSPICE in a CMOS 0.18μm 1.8V process. Measurement result of the two-negative feedback loop PLL fabricated in a one-poly six-metal 0.18μm CMOS process shows approximately 20dB improvement at 1MHz offset from 1GHz carrier frequency.
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문대현 단국대학교 인문과학대학 영어영문학과 1996 Lucifer Vol.- No.13
Joan Didion's Play It As It Lays reveals the destructive nature of Hollywood by presenting how Maria, a young actress and model, is driven into an isolated world of her own, suffering from a series of misfortunes such as divorce, a traumatic abortion and her retarded daughter's hopeless future. But Hollywood's destructiveness becomes clear in BZ's tragic suicide resulted from finding no meaning in his filmmaking business, his unwanted marriage and his wife's affaire with his filmmaker friend Cater, Maria's husband Maria's and BZ's lives have a similarity that after their painful experience of life, both end up escaping from the degenerating Hollywood, the world in which they have been deeply involved, into total different realms in which no one can touch them any longer. However, unlike BZ who chose to kill himself to complete his separation from everything he gets tired of,
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문대현,Arti Murnandari,Omotayo Salawu,이찬우,이원희,김영은,박기태,이지은,Jun Eo,정순관,윤민혜 한국화학공학회 2020 Korean Journal of Chemical Engineering Vol.37 No.10
The single process CO2 capture-mineralization approach integrates methods of CO2 absorption using aqueous solvents and mineral carbonation technology to not only remove carbon dioxide quickly, but also to simultaneously produce precipitated calcium carbonate (PCC). To develop a more sustainable process, it is important to extract calcium from inexpensive raw materials such as industrial by-products. The extractant has a significant effect on the quality of the calcium carbonate produced because it determines the anion paired with the calcium cation. In this work, several calcium sources with different anions (Propionate, Acetate, Nitrate and Chloride) were applied in the single process CO2 capture-mineralization method, and their influence on the polymorph of the obtained CaCO3 was investigated. The CaCO3 produced with inorganic calcium sources predominantly exhibited a calcite structure, while the CaCO3 produced with organic calcium sources had a structure in which vaterite and calcite coexist. This result was in good agreement with our DFT calculations, which indicated the adsorption energy of the organic anions (Propionate and Acetate) were lower than the inorganic anions on the surface of vaterite. Except for chloride with its non-polar nature, in most cases, there was a strong correlation between the polymorph and the adsorption energy calculated for each surface. A mechanism for the polymorph CaCO3 formation in our single process CO2 capture-mineralization method was proposed after observing crystal formation at low concentration.
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두 개의 입력을 가진 VCO를 이용하여 루프필터와 스퍼 크기를 줄인 위상고정루프
최영식,문대현,Choi, Young-Shig,Moon, Dae-Hyun 한국정보통신학회 2018 한국정보통신학회논문지 Vol.22 No.8
본 논문에서는 위상고정 상태에 따라 활성화 되는 루프가 다르게 설정하고, 두 개의 입력을 가지는 전압제어발진기를 사용하여 스퍼를 억제함과 동시에 루프필터의 크기를 줄이는 위상고정루프를 제안하였다. 동작 상태에 따른 안정도 분석을 통하여 위상고정 후에는 위상고정루프가 안정적으로 동작되게 설계하였다. 일반적으로 루프 필터의 커패시터는 위상고정루프에서 큰 면적을 차지한다. 두 개의 전하펌프에 의한 동시 충 방전 동작을 통해 커패시터의 유효커패시턴스를 증가시켜 루프필터 크기를 줄일 수 있으며, 서로 반대 위상으로 동작하는 두 개의 신호를 입력으로 가지는 전압제어발진기로 스퍼의 크기를 억제할 수 있었다. 위상고정 상태를 알려주는 LSI(Locking Status Indicator)를 사용하여 위상고정 시간은 $80{\mu}s$가 되도록 하였다. 제안된 위상고정루프는 1.8V의 공급전압과 $0.18{\mu}m$ CMOS공정을 사용하여 설계하였다. In this paper, a novel PLL has been proposed that reduces the size of the loop filter while suppressing spur by using a VCO with two inputs. Through the stability analysis according to the operating status, the PLL is designed to operate stably after the phase fixing. The capacitor of loop filter usually occupies larger area of PLL. It is a VCO that can reduce the size of the loop filter by increasing the effective capacitance of the capacitor through the simultaneous charge and discharge operation by two charge pumps and has two signals operating in opposite phases. The settling time of set to $80{\mu}s$ approximately by using a LSI(Locking Status Indicator) indicating the phase locking status. The proposed PLL is designed using a supply voltage of 1.8V and a $0.18{\mu}m$ CMOS process.
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