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Ultrabroadband Linear Power Amplifier Using a Frequency-Selective Analog Predistorter
Mincheol Seo,Kyungwon Kim,Minsu Kim,Hyungchul Kim,Jeongbae Jeon,Myung-Kyu Park,Hyojoon Lim,Youngoo Yang IEEE 2011 IEEE Transactions on Circuits and Systems II: Expr Vol.58 No.5
<P>This brief presents an ultrabroadband (2- to 600-MHz band) linear power amplifier using a compact frequency-selective analog predistorter, which includes a capacitor having an optimized capacitance and a biased Schottky diode connected in series. It is shunted at the input of the main amplifier and has a frequency-selective third-order intermodulation generation capability using its optimized capacitance. A two-stage push-pull power amplifier, which has an ultrabroadband operation range from 2 to 600 MHz, was implemented and linearized using the proposed analog predistorter. It exhibited high 1-dB compression point (P1 dB) and power-added efficiency characteristics of over 43 dBm and 32% at each P1 dB for the entire operating band, respectively. At an average output power level of 36 dBm for the two-tone signal input, which has a tone spacing of 1 MHz, its third-order intermodulation distortion over the entire band is no higher than -39.1 dBc after linearization, as compared with -34.2 dBc before linearization.</P>
Hagyoul Bae,Hyojoon Seo,Sungwoo Jun,Hyunjun Choi,Jaeyeop Ahn,Junseok Hwang,Jungmin Lee,Oh, Saeroonter,Jong-Uk Bae,Sung-Jin Choi,Dae Hwan Kim,Dong Myong Kim IEEE 2014 IEEE transactions on electron devices Vol.61 No.10
<P>A sub-bandgap optoelectronic differential ideality factor technique is proposed for extraction of the intrinsic density-of-states (DOS) over the bandgap in amorphous semiconductor thin-film transistors (TFTs). In the proposed technique, the gate bias-dependent differential change in the difference of ideality factors (dAη(V<SUB>GS</SUB>)/dV<SUB>GS</SUB>) between dark and sub-bandgap photonic excitation condition is employed. With the sub-bandgap photons (hν <; E<SUB>g</SUB>), the photonic excitation of electrons is confined only from the localized DOS over the bandgap. We applied the proposed technique to a-InGaZnO TFTs with W/L = 50/25 μm/μm and extracted the energy distribution of the intrinsic DOS for the localized states over the bandgap.</P>
다중 사용자 환경에서 개인 데이터 보안을 위한 개인 폴더 관리 시스템의 설계 및 구현
박용훈(Yonghun Park),박형순(Hyeongsoon Park),김학철(Hakchul Kim),이효준(Hyojoon Lee),장용진(Yongjin Jang),임종태(Jongtae Lim),장수민(Sumin Jang),서원석(Wonseok Seo),유재수(Jaesoo Yoo) 한국콘텐츠학회 2010 한국콘텐츠학회논문지 Vol.10 No.5
최근에 세계적으로 다중사용자시스템(Multi-User System, MUS)에 대한 수요가 꾸준히 증가하고 있다. 다중사용자시스템은 한대의 컴퓨터본체에 여러 개의 디스플레이어와 키보드, 마우스 등 입출력장치들을 연결하여 여러 명의 사용자가 동시에 이용할 수 있게 하는 시스템이다. 다중 사용자 시스템에서 보안은 해결해야 할 중요한 문제 중의 하나이다. 본 연구에서는 다중 사용자 환경에서 사용자 편의성 중심의 설계와 다양한 보안 기능을 제공하는 시스템을 제안한다. 시스템은 마이크로소프트사에서 개발된 NTFS 파일 시스템 기반에서 작동하며 NTFS 파일 시스템의 복잡한 보안 설정 기능을 단순화 하여 사용자 편의성을 높인다. 기본적으로 윈도우즈 시스템과 같이 중요한 폴더에 대해서는 개인 폴더 설정이 안 되고 다른 사용자간에 개인 폴더 설정의 충돌을 방지하기 위한 다양한 정책을 제안한다. 접근 금지 폴더를 지정하여 아무도 개인 폴더로 지정할 수 없는 공간을 설정하는 기능도 제공한다. In recent, the interests of multi-user systems have been increased. Multi-user systems allow a number of users to access the system simultaneously. Security is one of the key issues to be addressed in a multi-user environment. We propose a solution based on the NTFS file system that provides the personal data security and considers the convenience of users. The system increases the convenience of users by simplifying the complexity of the security setting on NTFS. We also propose a variety of policies that prevent from the conflicts incurring when different users set up the personal folders simultaneously and do not set up the important folders such as the window system folders as personal folders. In addition, our system supports the function of setting up the prohibition folder lists so that no one can not set the folder to their personal folders.
Euiyoun Hong,Daeyoun Yun,Hagyoul Bae,Hyunjun Choi,Won Hee Lee,Mihee Uhm,Hyojoon Seo,Jieun Lee,Jaeman Jang,Dae Hwan Kim,Dong Myong Kim IEEE 2012 IEEE electron device letters Vol.33 No.7
<P>A distribution of interface states (<I>D</I><SUB>it</SUB>) in SOI MOSFETs has been characterized by a subbandgap optical differential body-factor (SODBoF) technique. We adopted a subbandgap (<I>E</I><SUB>ph</SUB> <; <I>E</I><SUB>g</SUB>) optical source as a virtual gate on the body-contactless SOI MOSFETs under the subthreshold (<I>V</I><SUB>GS</SUB> <; <I>V</I><SUB>T</SUB>) current-voltage characteristics. Employing a differentiation to the body factor, any possible error from the threshold voltage is also suppressed. We applied the SODBoF technique to n- and p-channel SOI MOSFETs on the same wafer and verified the result. Extracted traps over the bandgap ranges <I>D</I><SUB>it</SUB> = 10<SUP>10</SUP> - 10<SUP>11</SUP> cm<SUP>-2</SUP>·eV<SUP>-1</SUP> with a typical U-shape.</P>
Hagyoul Bae,Sungwoo Jun,Choon Hyeong Jo,Hyunjun Choi,Jaewook Lee,Yun Hyeok Kim,Seonwook Hwang,Hyun Kwang Jeong,Inseok Hur,Woojoon Kim,Daeyoun Yun,Euiyeon Hong,Hyojoon Seo,Dae Hwan Kim,Dong Myong Kim IEEE 2012 IEEE electron device letters Vol.33 No.8
<P>We propose a modified conductance method for extraction of the subgap density of states (DOS) in amorphous indium-gallium-zinc oxide thin-film transistors by using the measured capacitance and conductance through the capacitance-voltage (C-V) measurement. In the proposed method, the subgap DOS [g<SUB>A</SUB>(E)] is extracted from the frequency-dispersive C-V characteristics by localized traps in the active channel region. The extracted g<SUB>A</SUB>(E) shows a superposition of the exponential tail states and the exponential deep states over the bandgap (N<SUB>TA</SUB> = 3 × 10<SUP>18</SUP> cm<SUP>-3</SUP> · eV<SUB>-1</SUB>, N<SUB>DA</SUB> = 2.8 × 10<SUP>17</SUP> cm<SUP>-3</SUP> · eV-1, kT<SUB>TA</SUB> = 0.04 eV, and kT<SUB>DA</SUB> = 0.77 eV). We note that the gate-bias-dependent Cfree by free electron charges can be separated from C<SUB>loc</SUB> by localized trap charges through the proposed method.</P>