• 전자공학회논문지C
• /
• 제34C권11호
• /
• pp.76-85
• /
• 1997

Charge-pump loop filter was designed using GaAs MESFET for GHz-range PLL system applications. Characteristics of charge-pump loop filter and stability of charge-pump PLL, system were analyzed. Performance specifications were defined and a charge-pump loop filter was designed that satisfies these specifications.

• 한국대기환경학회지
• /
• 제28권6호
• /
• pp.644-655
• /
• 2012

As soon as a new air filter is applied to an air purification process, the filter gets loaded with dust particles. Thus, the study on the particle loading characteristics of air filter is very essential in order to understand the real filtration phenomena during filter use. In this study, we investigated the effect of particle and filter charge on the particle loading property of air filter. Charged filter and uncharged filter prepared by discharging the charged filter by isopropyl alcohol were used as test samples, and three types of particle having different charge states were supplied to filters tested. For neutralized particles there was a big difference in areal mass loading rates between charged and uncharged filters due to the very small amount of particle charge, on the other hand the difference was diminished for atomized particle and finally almost vanished for corona charged particles. The pressure drop of filter loaded with corona charged particles was only half of those for neutralized and atomized particles at the same areal mass loading because of the porous structure of particle deposit formed on filter fibers, caused by the space charge effect between particles.

• 대한설비공학회:학술대회논문집
• /
• 대한설비공학회 2008년도 하계학술발표대회 논문집
• /
• pp.1134-1138
• /
• 2008

Electret filter media are used in general ventilation filters, disposable respirators, vehicle cabin filters, vacuum cleaners and room air cleaners. There are basic mechanisms of interception, inertial impaction, diffusion, gravitational settling, electrostatic attraction by which an aerosol particle can be deposited onto a fiber in a filter. The ability of fine particle removal strongly depends on the electrostatic forces between particles and polarized fibers. Thus, the stability of the fiber polarization is a major factor in the reliability of electret filters. In this study, electrical properties and filtration performance of electrospun filter media are quantitatively investigated. Electrical properties of electrospun filters have been studied on surface charge potential and surface charge density. Also the filtration performance of the electret filters are evaluated on collection efficiency. Electrospun filters show same collection efficiency with low pressure drop compare to commercialized HEPA filters. Surface charge potential and surface charge density of electrospun filters are increased with increasing applied voltage. Also collection efficiency of electrospun filters is increased with increasing surface charge potential and surface charge density.

• 한국입자에어로졸학회지
• /
• 제5권2호
• /
• pp.71-81
• /
• 2009

In this study, Nylon 6,6 electrospun (ES) nanofiber filter media were prepared at various spinning conditions. The ES filters tested had no intrinsic electrical charges. The ES filters were triboelectrically charged in the course of filter sample handling, and the charge was drastically decayed in a few hours. On the other hand, the corona charged melt blown filter media showed a permanent electrical charge. The electrical charge state of the ES filters was also examined by comparing collection efficiencies of ES filters for uncharged and charged aerosol particles.

• 대한기계학회논문집B
• /
• 제26권8호
• /
• pp.1102-1114
• /
• 2002

An electret filter is composed of permanently charged electret fibers and is widely used in applications requiring high collection efficiency and low-pressure drop. In this work, the collection efficiency of the filter media used in manufacturing cabin air filters was investigated by using poly-disperse particles when submicron particles were loaded. Long-term experiments were conducted by applying two different charging states, which were spray electrification and charge equilibrium by bipolar ionization. In order to investigate the effect of particle loading in filter media, NaCl particles were generated from 0.1% and 1% solutions by an atomizer. Liquid DOS particles were used to evaluate the effect of liquid particles on the collection efficiency of an electret filter. The results show significant effect of charge amount and size distribution of loading particles on the collection performance of a filter media in submicron region. Smaller particles loaded in electret fibers cause a more rapid degradation in collection efficiency and have lower minimum efficiency with time. The pressure drop of a filter media do rarely increase when the collection efficiency decreases to the minimum value. For the larger particles charged by spray electrification, which have charge amounts more than that of Boltzmann equilibrium charge distribution, the pressure drop of a filter media slowly increases in comparison with that of equilibrium charged particles. For DOS particles it is shown that the charging level of an electret filter severely decreases and the collection efficiency is below 10% in some particle size range.

• 설비공학논문집
• /
• 제20권12호
• /
• pp.820-824
• /
• 2008

Electret filter media are used in general ventilation filters, disposable respirators, vehicle cabin filters, vacuum cleaners and room air cleaners. There are basic mechanisms of interception, inertial impaction, diffusion, gravitational settling, electrostatic attraction by which an aerosol particle can be deposited onto a fiber in a filter. The ability of fine particle removal strongly depends on the electrostatic forces between particles and polarized fibers. Thus, the stability of the fiber polarization is a major factor in the reliability of electret filters. In this study, the electret filter is made by electrospinning process using Polystyrene which is dissolved by 5 : 5 of Tetrahydrofuran (THF) and Dimethylformamide (DMF). Also the electrical properties and the filtration performances of electrospun filter media are Quantitatively investigated. Electrical properties of electrospun filters have been studied on surface charge potential and surface charge density. Also the filtration performance of the electret filters are evaluated on collection efficiency. The surface charge potential and the surface charge density of electrospun PS filters are increased with increasing applied voltage and saturated at 30 kV of applied voltage. Also collection efficiency of electro spun filters is increased with increasing surface charge potential and surface charge density. But the surface charge potential is decreased by natural decay and it causes deterioration of particle collection efficiency.

• Journal of electromagnetic engineering and science
• /
• 제11권2호
• /
• pp.105-112
• /
• 2011

In phase-locked frequency synthesizers, a fast-lock technique is frequently employed to overcome the trade-off between a lock-time and a spurious response. The function of fast-lock in a conventional PLL (Phased Lock Loop) IC (Integrated Circuit) is limited by a factor of 16, which is usually implemented by a scaling of charge pumper, and consequently a lock time improvement of a factor of 4 is possible using the conventional PLL IC. In this paper, we propose a novel external active fast-lock loop filter. The proposed loop filter provides, conceptually, an unlimited scaling of charge pumper current, and can overcome conventional trade-off between lock-time and spur suppression. To demonstrate the validity of our proposed loop-filter, we fabricated an X-band frequency synthesizer using the proposed loop filter. The loop filter in the synthesizer is designed to have a loop bandwidth of 100 kHz in the fast-lock mode and a loop bandwidth of 5 kHz in the normal mode, which corresponds to a charge pumper current change ratio of 400. The X-band synthesizer shows successful performance of a lock-time of below 10 ${\mu}sec$ and reference spur suppression below -64 dBc.

• 한국지능시스템학회논문지
• /
• 제20권2호
• /
• pp.214-219
• /
• 2010

본 논문은 리튬폴리머 배터리의 잔존충전용량 추정을 위한 비선형 퍼지 $H_{\infty}$ 필터의 설계 방법을 제시한다. 배터리 셀의 동적방정식을 T-S 퍼지시스템으로 모델하고 선형행렬 부등식의 해를 이용하여 퍼지필터를 설계한다. 제시한 퍼지 $H_{\infty}$ 필터의 성능을 입증하기 위하여 UDDS 전류 프로파일을 사용한 실험 데이터를 이용하여 모의실험을 수행하였다.

• 한국정보통신학회논문지
• /
• 제16권11호
• /
• pp.2495-2502
• /
• 2012

이 논문은 전하펌프를 추가하여 루프필터에서 공정에 따라 값이 크게 변하는 저항을 없앤 새로운 구조의 위상고정루프를 보여준다. 두 번째 전하펌프가 기존의 루프 필터 저항 역할을 하도록 하였다. 두 개의 전하펌프 출력은 공정 변화에 같은 방향으로 움직이므로 위상고정루프의 동작이 공정 변화 영향을 적게 받게 된다. 공정 조건(SS/TT/FF)에 따른 시뮬레이션 결과는 제안된 구조가 공정 변화에 무관하게 동작함을 보여주고 있다. 제안된 구조는 1.8V $0.18{\mu}m$ CMOS 공정의 파라미터를 이용하여 HSPICE로 시뮬레이션을 수행하였고 회로의 동작을 검증하였다.

• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2001년도 추계학술대회논문집B
• /
• pp.71-76
• /
• 2001

An electret filter is composed of permanently charged electet fibers and is widely used in applications requiring high collection efficiency and low-pressure drop. In this work, the collection efficiency of the filter media used in manufacturing cabin air filters was investigated by using poly-disperse particles when submicron particles are loaded. Long-term experiments were conducted by applying different charging states, which are spray electrification and charge equilibrium by bipolar ionization. In order to investigate on the effect of particle loading in filter media, NaCl particles were generated from 0.1% and 1% solutions by an atomizer. In NaCl 0.1%, the collection efficiency of electret filter decreased and then did not change in equilibrium state. In the case of relative larger particles of NaCl 1%, collection efficiency for the equilibrium charged particles increases due to the particle loading on the filter fibers. Particles charged by spray electrification are small in collection efficiency after equilibrium state and increase of filter media's pressure drop was very low in comparison of the equilibrium charged particles.