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Dry etching of ferroelectric Bi$_{4-x}$Eu$_x$Ti$_3$O$_{12}$(BET) thin films
KyuTae Lim,김창일,김경태,김동표 한국물리학회 2004 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.44 No.52
Bi4Bi4xEuxTi3O12 (BET) thin lms were etched by using a inductively coupled Cl2/Ar plasma. We obtained a maximum etch rate of 69 nm/min at a gas mixing ratio of Cl2 (20 %)/Ar (80 %). This result suggests that an eective method for BET etching is chemically assisted physical etching. With increasing coil RF power, the plasma density increases so that the increased reactive free radicals and ions enhance the etch rates of BET, Pt, and SiO2. As the dc-bias voltage is increased, the increased ion energy leads to an increased etch rate of BET lms. From X-ray photoelectron spectroscopy, the intensities of the Bi-O, the Eu-O, and the Ti-O peaks change with increasing Cl2 concentration. For a pure Ar plasma, the peak associated with the oxygen-metal (O-M: TiO2, Bi2O3, Eu2O3) bond seems to disappear while the pure oxygen peak does not appear. After the BET thin lms is etched by using a Cl2/Ar plasma, the peak associated with the O-M bond increases slowly, but more quickly than the peak associated with pure oxygen atoms, due to a decrease in the Ar-ion bombardment. These results seem to indicate that Bi and Eu react little with Cl atoms and are removed predominantly by argon-ion bombardment. Also, Ti reacts little with Cl radicals and is mainly removed by chemically assisted physical etching. Bi4xEuxTi3O12 (BET) thin lms were etched by using a inductively coupled Cl2/Ar plasma. We obtained a maximum etch rate of 69 nm/min at a gas mixing ratio of Cl2 (20 %)/Ar (80 %). This result suggests that an eective method for BET etching is chemically assisted physical etching. With increasing coil RF power, the plasma density increases so that the increased reactive free radicals and ions enhance the etch rates of BET, Pt, and SiO2. As the dc-bias voltage is increased, the increased ion energy leads to an increased etch rate of BET lms. From X-ray photoelectron spectroscopy, the intensities of the Bi-O, the Eu-O, and the Ti-O peaks change with increasing Cl2 concentration. For a pure Ar plasma, the peak associated with the oxygen-metal (O-M: TiO2, Bi2O3, Eu2O3) bond seems to disappear while the pure oxygen peak does not appear. After the BET thin lms is etched by using a Cl2/Ar plasma, the peak associated with the O-M bond increases slowly, but more quickly than the peak associated with pure oxygen atoms, due to a decrease in the Ar-ion bombardment. These results seem to indicate that Bi and Eu react little with Cl atoms and are removed predominantly by argon-ion bombardment. Also, Ti reacts little with Cl radicals and is mainly removed by chemically assisted physical etching.
김관우,Kyutae Lim,Joonhoi Hu,Jae Joon Kim,변상진,변영재,Chang-Ho Lee 에스케이텔레콤 (주) 2010 Telecommunications Review Vol.20 No.5
There have been many efforts to improve efficiency of transmitter while meeting stringent linearity requirement of modern communication system. Among the technology to enhance efficiency of linear transmitter, the out-phasing technology, also called the linear amplification with nonlinear components (LINC), is considered as promising technology. LINC has been studied long time, since it provides excellent linearity with high efficiency by allowing adopt higg efficient switch-mode power amplifiers. In this paper, various state-of-art techniques for multi-level digital LINC transmitters are presented. For their all-digital implementation, flexible digital phase modulators (DPMs) are used to realize two RF phase input signals in LINC systems. An unbalanced phase calibration technique compensates amplitude/phase mismatches between two parallel paths in the LINC system, and an uneven multi-level LINC structure improves the overall power efficiency. The performance of multi-level LINC technology was experimentally verified for WiMAX signals.
양규태(Kyutae Yang),백승권(Seungkwon Beack),이봉호(Bongho Lee),임형수(Hyoungsoo Lim) 한국방송·미디어공학회 2015 한국방송공학회 학술발표대회 논문집 Vol.2015 No.7
본 논문에서는 음성 및 음악 모두에 대해 최고의 품질을 제공하는 최신 오디오 코덱인 USAC 을 DAB+에 적용하기 위한 전송 방안을 제안한다. 기존 DAB+는 AAC+ v2 로 불리는 HE-AAC v2 (High Efficiency Advanced Audio Coding version 2) 오디오 코덱을 사용하였다. 하지만 AAC+ v2 는 낮은 데이터 전송률에서 음악에서는 좋은 품질을 제공하나 음성에서는 상대적으로 품질이 떨어지는 단점이 있다. 반면 USAC 은 낮은 데이터 전송률에서 음악 및 음성에 모두 좋은 품질과 높은 압축 성능을 제공할 수 있는 최신 오디오 코덱기술이다. USAC 의 성능을 최대한 보장하기 위해서는 DAB+와 달리 VBR 을 적용하는 효과적이다. 따라서 본 논문에서는 USAC VBR 스트림을 DAB+에 전송하는 방안을 제안한다. 제안된 전송 방안을 적용할 경우 최적의 음악 및 음성 품질을 효율적으로 제공할 수가 있다.
Cross-Layer Dynamic Spectrum Map Management Framework for White Space Applications
Yoon, Seungil,Lim, Kyutae,Kim, Jongman Hindawi Publishing Corporation 2010 EURASIP journal on wireless communications and net Vol.2010 No.-
<P>White space, unused TV spectrum, will be allowed for unlicensed use by wireless communication devices “the so called white space applications (WSAs).” WSAs retrieve a location-based spectrum map, a list of open white space channels, from a spectrum map server and can select one on the list as their operating channel for the broadband Internet access. However, since not only primary users such as TV broadcasting services use white space shortly or longly but also neighboring WSAs do, WSAs need to perform spectrum sensing that determines the occupancy status, either occupied or unoccupied, of white space channels and select one among the unoccupied channels according to the spectrum sensing results. In a conventional spectrum sensing, they can execute unnecessary spectrum sensing on the already occupied channels. This paper proposes a dynamic management framework of white space that extends a spectrum map to contain occupancy information with the assistance of WSAs. Our framework enables WSAs to avoid unnecessary spectrum sensing on the channels that are marked as occupied according to the extended spectrum map. In return for the provision of the spectrum map, a spectrum map server obtains the spectrum sensing results of associated WSAs to update the extended spectrum map about the channel occupancy status. Theoretical analysis indicates that the proposed framework can contribute to shortening the total spectrum sensing time of WSAs by up to 50%.</P>
하이브리드 라디오 환경에서의 Service Following 에 관한 연구
이봉호(Bongho Lee),양규태(Kyutae Yang),임형수(Hyoungsoo Lim),허남호(Namho Hur) 한국방송·미디어공학회 2016 한국방송공학회 학술발표대회 논문집 Vol.2016 No.6
디지털 라디오 수신 환경에서 권역을 이동하거나 수신 신호가 미약한 구간 특히 실내로 이동을 하고자 할 경우 서비스를 자동으로 연계해 줄 수 있는 서비스 연계(service following) 기술이 필요하다. 본 논문에서는 하이브리드 라디오 환경에서 자동으로 서비스 연계가 가능한 방법을 제안하고자 한다. 구체적으로는 서비스 연계 이벤트가 발생할 경우 연계 대상을 단말에서 결정하는 것이 아니라 인터넷 상에 이를 처리할 수 있는 서버를 두어 청취자로부터 전달되는 위치 좌표를 포함한 관련 방송 파라미터를 제공받아 가장 적합한 연계 대상을 식별한 후 이를 다시 단말에 제공하는 방식이다.